Electrolytes are key custom lithium battery pack components that transfer charge carrying particles (i.e., ions) back and forth between two electrodes, ultimately allowing batteries to repeatedly charge and discharge. Engineering and identifying promising electrolytes can help to improve the performance and properties of batteries, allowing them to better support the needs of the electronics industry.
Lithium-metal batteries (LMBs) are a promising class of batteries that have been found to have numerous advantageous properties, including longer battery use per single charge. However, electrodes in these batteries are prone to become corroded when exposed to some chemicals, which makes the design of suitable liquid electrolytes for these batteries challenging.
Researchers at the Korea Advanced Institute of Science and Technology (KAIST) and LG Energy Solution in South Korea recently engineered a new liquid electrolyte for LMBs based on lean borate-pyran. Their paper, published in Nature Energy, shows that this electrolyte could minimize corrosion in LMBs, while retaining their performance.
“Lithium metal batteries are undergoing development with the aim of maximizing battery energy density,” Hee-Tak Kim, one of the researchers who carried out the study, told Tech Xplore. “However, the current obstacle lies in the electrolyte, which currently represents the second-highest weight fraction in the battery. To effectively implement high energy density, it is imperative to reduce the amount of electrolyte used.”
The recent work by Kim and his colleagues draws inspiration from an earlier paper by a research team at Stanford University, published in Science. The authors of this paper found that the swelling of the solid electrolyte interphase (SEI), a protective layer created on the surface of anodes in lithium batteries, ultimately prompts the reversibility of Li metal electrodes.
“Motivated by the finding, we tried to devise a strategy to build a SEI with minimal liquid electrolyte swelling and consequently minimal Li corrosion,” Kim said. “To make Li-metal batteries work, two requirements should be met, namely uniform Li plating/stripping and minimal Li corrosion. Our electrolyte design achieves both requirements by inducing the densely packed, nanocrystalline, and inorganic-rich SEI.”
The borate-pyran based electrolyte engineered by this team of researchers produces the anti-Oswald ripening of LiF crystallites in the SEI. This process in turn prompts the formation of the SEI, while also reducing the protective layers’ swelling and thus minimizing the electrodes’ corrosion.
In the future, the new promising liquid electrolyte identified by Kim and his colleagues could be tested in further experiments and integrated in other LMBs with varying designs. In addition, this recent work could inform the engineering of additional electrolytes, thus contributing to ongoing efforts aimed at introducing better performing battery designs.
“Our recent paper emphasizes the critical role of the microstructure of SEI in addressing the problem of Li corrosion,” Kim added. “Furthermore, the microstructure can be strategically restructured by the unique design of the electrolyte. The ultimate goal of Li metal battery technology is to achieve an anode-free lithium metal battery and to enable high-rate charging. Our efforts are dedicated to resolving the pivotal challenges associated with making these cutting-edge technologies a reality.”
More information: Hyeokjin Kwon et al, Borate–pyran lean electrolyte-based Li-metal batteries with minimal Li corrosion, Nature Energy (2023). DOI: 10.1038/s41560-023-01405-6
Journal information: Science , Nature Energy
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IFR26650 lithium battery has a rated capacity of 3000-5000mAh, and 18650 lithium ion battery pack has a rated capacity of 2200~3200mAh.
The sizes are different:
the diameter of IFR26650 is 26 mm, and the diameter of IFR18650 is 18 mm.
The weight is different:
the weight of IFR26650 lithium battery is 94 grams, and the weight of IFR18650 lithium battery is 45 grams.
The capacities are different:
the 26650 battery capacity is larger than the 18650 battery capacity. Assuming that the 26650 battery using ternary materials is used, the capacity is generally around 5200mAh; while the capacity of the 18650 battery is mostly around 2600mAh.
Different application environments:
18650 lithium batteries are widely used in lighting fixtures, industrial accessories, power tools, electric bicycles, power lithium battery packs, etc.; while 26650 lithium batteries are widely used in power tools, lighting, wind and solar energy storage, electric vehicles, toys, instrumentation, UPS backup power supply, communication equipment, medical equipment and lights.
When the battery compartment space is relatively small and you want a larger capacity, it is recommended to use 26650 batteries.
Himax focus on 18650 lithium ion battery pack and 26650 Lithium Ion battery pack manufacturing for over 12 years. We can provide all kinds of custom lithium battery pack for customers. Please get in touch with us if you need a power solution to your device.
HIMAX can make all kinds of custom lithium battery pack and 12v Lead Acid Replacement Battery for our customers. We have full of confidence to meet your quality level. Looking forward to build a long term business with you and we wait for your kind respond
Contact Himax now to unlock your exclusive battery customization options, Himax offers a wide range of options and flexible customization services to meet the needs of different users.
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A team headed by business chemist Prof. Stephan von Delft from the University of Münster has concluded that China will be the first country worldwide to become independent of the need to mine the raw materials that are essential for custom lithium battery pack. They have also established that this development could be accelerated in all the regions they looked at—including Europe and the U.S.
With the increase in the production of batteries for electric vehicles, demand is also rising for the necessary raw materials. In view of risks to the supply chain, environmental problems and precarious working conditions which are all associated with the mining and transportation of these materials, the recycling of battery materials has become an important issue in research, politics and industry.
Prof. Stephan von Delft from the University of Münster heads a team of researchers from the fields of science and the automotive and battery industries who have therefore been investigating when the demand for the three most important raw materials for batteries—lithium, cobalt and nickel—can be met entirely through recycling in Europe, the U.S. and China; in other words, when a completely circular economy will be possible in these regions. The team’s conclusion is that China will achieve this first, followed by Europe and the U.S.
In detail, the results published in Resources, Conservation and Recycling show that China is expected to be able to employ recycling to meet its own demand for primary lithium for electric vehicles, obtained through mining, from 2059 onwards; in Europe and the U.S., this will not happen until after 2070. As far as cobalt is concerned, recycling is expected to ensure that China will be able to meet its needs after 2045, at the earliest; in Europe this will happen in 2052 and in the U.S. not until 2056. As regards nickel: China can probably meet demand through recycling in 2046 at the earliest, with Europe following in 2058 and the U.S. from 2064 onwards.
Although earlier research looked at the supply of recycled raw materials for batteries and the demand for them, it had not so far been clear when complete circularity would be achieved, with supply and demand being equal (“break-even point”). The team of researchers also looked at the question of whether there are any possibilities of achieving equilibrium sooner than is predicted by current developments.
“Yes, there are,” says Stephan von Delft. “Our research shows that, in particular, a faster rate of electrification in the automotive industry, as is currently being discussed in the EU, will play a role in the process. The reason is that the faster electric vehicles spread throughout the automotive market, the sooner there will be sufficient quantities of batteries available for recycling.”
As Ph.D. student Jannis Wesselkämper adds, “The demand for raw materials could also be met much earlier by recycling as a result of a reduction in custom lithium battery pack size and by avoiding a so-called ‘second life’ for batteries—for example as stationary storage units for solar power.”
The researchers made use of a so-called dynamic material flow analysis to calculate both future demand and the recyclable raw materials then available. The data basis the team used consisted of data from current research work and market forecasts regarding developments in custom lithium battery pack production and sales and the associated demand for raw materials.
More information: Jannis Wesselkämper et al, A battery value chain independent of primary raw materials: Towards circularity in China, Europe and the US, Resources, Conservation and Recycling (2023). DOI: 10.1016/j.resconrec.2023.107218
Provided by University of Münster
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The price of a custom lithium battery pack is mainly composed of three major components: battery cell, PCM, and casing. At the same time, due to the current of the electrical appliances, the material of the connecting piece between the cells (conventional nickel sheet, formed nickel sheet, copper-nickel composite sheet, jumper sheet, etc.) or selection, different connectors (such as Special plugs, ranging from tens to thousands of dollars) may also have a greater impact on the cost. In addition, different PACK manufacturing processes will also affect the cost.
Battery cell selection
Depending on the cathode material, custom lithium battery pack include lithium manganate (3.6V), lithium cobalt oxide (3.7V/3.8V), lithium nickel cobalt manganate (commonly known as ternary, 3.6V), and lithium iron phosphate (3.2V). , lithium titanate (2.3V/2.4V) and other battery cores of various material systems. Batteries made of different materials have different voltage platforms, safety factors, number of cycles, energy density, operating temperatures, etc.
Requirements and design of custom lithium battery pack PCM
PCM design can be divided into: basic protection, communication, BMS
Basic protection: Basic protection includes overcharge, over-discharge, over-current and short-circuit protection. Over-temperature protection can be added according to product needs.
Communication: Communication protocols can be divided into I2C, RS485, RS232, CANBUS, HDQ, SMBUS, etc. There is also a simple power display, which can be indicated by a power meter using LED.
BMS: Mainly to intelligently manage and maintain each battery unit, prevent the battery from overcharging and over-discharging, extend the service life of the battery, and monitor the status of the battery. Its main functions include: real-time monitoring of battery physical parameters; battery status estimation; online diagnosis and early warning; charge, discharge and precharge control; equalization management and thermal management, etc. Subsystems are mostly used in electric vehicle batteries.
What kind of outer shell packaging form is used mainly depends on the specific needs of the customer’s product. It can be mainly divided into: PVC heat shrink film, plastic shell, metal shell
PVC heat shrink film: generally suitable for battery packs with a small number of cells in series and in parallel and a light overall weight. However, for battery packs with a relatively large overall weight, fixed brackets can be added between the cells, and fiberglass boards are added to the periphery for protection, and then PVC heat sealing is used. PVC heat shrink film is also the most economical packaging method.
Plastic case: Mainly because after different battery packs are finalized, the cases involved may need to be molded. The mold cost is a large expense. If the product is not finalized in the early stage of development, a prototype shell can be used for proofing. Different material and process requirements for the shell will also affect the cost.
Metal casel: The metal case is the same as the plastic case. Before the product is finalized or the quantity demand is not large, it is recommended to use sheet metal sample preparation, which mainly shortens the sample preparation and delivery time. If the order quantity is large, it is recommended to open a mold. There are waterproof level requirements for metal casings, which will also greatly affect the cost. Metal casings made of special materials (such as titanium alloy, etc.) will also increase the cost.
At the same time, due to different product technical difficulty, procurement volume, and defective rate requirements, lithium battery prices will vary greatly!
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With the increase in solar panels on houses and plug-in cars patrolling the roads, custom lithium battery pack is going to be ever more important in the coming years.
Technology has shown the way to harnessing power from the sun and other sources in nature, but what to do with that power once harvested? Researchers and students from Chico State are going to be among a group coming up with a better battery.
Most parts of California, for example, enjoy more than 280 days of sunshine per year—a real bounty for capturing solar energy. However, the substantial challenge is storing that power for use at night or on overcast days.
Members of Chico State’s faculty will work to overcome this problem and they have money to help them do it—a three-year,$2.25 million grant from the federal Department of Energy’s Office of Electricity and the Office of Basic Energy Services. The university will receive half of that money—funding a collaborative research project to maximize the storage capacity of low-cost batteries.
San Jose State and the Lawrence Livermore National Laboratory are the other participants in the project and will receive the other half of the funding.
Monica So, principal investigator and associate professor in Chico State’s Department of Chemistry and Biochemistry, joins Kathleen Meehan, co-principal investigator and professor in the Department of Electrical and Computer Engineering, to help coordinate this project. The other principal investigators involved are Philip Dirlam from San Jose State and Liwen Wan from Lawrence Livermore.
The center of this effort is the lithium-sulfur battery—much like a watch battery—that is lighter that its current “king of the hill” model, the lithium ion unit.
“We’re actually trying to enhance the storage cap of lithium-sulfur batteries. They’re potentially a safer alternative to custom lithium battery pack and the storage capacity is higher,” So explained. “We’re trying to enhance performance by modifying the materials that make up certain components.”
Batteries typically have two electrodes. “We’re trying to create materials to improve the anode, then we’re going to put them in a lithium-sulfur coin cell”—about the diameter of a dime.
That won’t be the final size the researchers will strive to create.
“The overall size of prototype is like a watch battery, which we can scale up to a car battery, storing energy generated at a house or solar farm,” Meehan said.
“The weight and size will be smaller than what’s needed for a lithium-ion battery. We will halve its size. That will allow the battery to drive its car longer because it won’t need as much to make the wheels move” due to its reduced weight.
It’s no easy undertaking and the process is slow, Meehan said.
“The time to market hasn’t changed that much over the decades,” she said. “With lithium-sulfur batteries, we expect about 10 years to have some on the market. Historically, it has taken 20 years to move something from advanced research to manufacture.
“That length of time hasn’t moved that much. Nothing ever goes from small scale to large scale completely smoothly.”
The project began in August. The grant will enable Chico State and San Jose State to purchase state-of-the-art equipment, provide research materials and supplies to be used in the development and characterization of the lithium-sulfur batteries and fund travel to conferences where the investigators and participants can discuss their research findings with other researchers in the field.
“Ideally, in three years we’ll have a working prototype,” So said.
Principal investigators will also contribute the research training and professional development of the 22 students and two postdoctoral scholars, creating a local pool of talented scientists and engineers who can continue to develop technologies for a more sustainable energy future, a Chico State press release said.
So said she and Meehan found out about the grant opportunity in January and had four months to formulate a proposal. They submitted the proposal to the Department of Energy in May.
Federal officials will make sure the three institutions involved are making good use of the funds.
“The DOE does care about deliverables and the quality of work. I just met with them two weeks ago,” So said. “They do care that we make progress on this, and that we publish academic papers.
“They also expect we’ll recruit and retain participants—22 students from Butte County and Santa Clara County, plus two early-career scientists. They’ll track development.”
She added that the investigators will recruit undergraduate students from Butte College and other area community colleges.
Meehan said increasing the ranks of groups not historically represented in electrical engineering and chemistry is also an objective.
“One of our goals is to recruit people who are typically not in this discipline—women, Latinos, African-Americans and Native Americans,” she said.
Referring to herself and So, as females, Meehan said,”We’re outliers in our field—there are only about 10% of women in electrical enginnering. Blacks make up about 3%. So it doesn’t match the general population.
“The more we can pull in, it would be good. It creates a fuller idea of what a product should be and how we should be doing our research.”
Having more underrepresented groups also makes products like improved batteries more widely available in the long run, as there will be a larger group offering suggestions on how to make the custom lithium battery pack better. The grant is part of a $70 million package through the Department of Energy’s RENEW Initiative, which aims to support research by historically underrepresented groups in science, technology, engineering and mathematics.
“They can contribute more fully to the development, and also make sure the product serves as many people as possible,” Meehan said.
(c)2023 Chico Enterprise-Record, Calif Distributed by Tribune Content Agency, LLC.
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Let’s talk about some details of the tin-based tandem electrocatalyst for the synthesis of ethanol via CO₂ reduction and li ion customized battery manufacturing process.
The electrochemical reduction of carbon dioxide (CO2) into various multi-carbon products is highly desirable, as it could help to easily produce useful chemicals for a wide range of applications. Most existing catalysts to facilitate CO2 reduction are based on copper (Cu), yet the processes underpinning their action remain poorly understood.
Researchers at the Chinese Academy of Sciences, City University of Hong Kong, and other institutes in China have recently set out to design more efficient Cu-free electrochemical catalysts for the reduction of CO2 Their paper, published in Nature Energy, introduces a new catalyst based on Tin (Sn), which was found to reduce CO2 to ethanol (CH3CH2OH) with a selectivity of 80%.
“The discovery of C-C coupling over the Sn1-O3G catalyst was not accidental, but instead built on our earlier works on understanding the CO2RR behavior of transition metal single-atom catalysts,” Prof. Bin Liu, co-author of the paper, told Tech Xplore.
“Specifically, we conducted preliminary experiments involving structural and electrochemical characterizations of various Sn-based CO2RR catalysts, including metallic Sn nanoparticles, SnS2 nanosheets, SnS2 on nitrogen-doped graphene, single Sn atoms on nitrogen-doped graphene (Sn-4N) and single Sn atoms on O-rich graphene (Sn1-O3G).”
In their preliminary experiments, the researchers found that both Sn1-4N and Sn1-O3G catalysts could reduce CO2 to CO with KHCO3, as a proton donor in a CO2RR solution. However, these catalysts displayed different behavior in the presence of the acid formate, with only Sn1-O3G ultimately producing ethanol.
“These observations led us to believe that the difference in CO2RR between the Sn1-4N and Sn1-3OG catalysts could result from the different coordination environments of Sn,” Prof. Liu said. “Thereafter, we focused our efforts on understanding the C-C coupling mechanism on O-coordinated Sn catalytic sites and constructed a tandem catalyst to realize selective CO2RR to ethanol.”
Prof. Liu and his colleagues fabricated their new Sn-based electrocatalyst by eliciting a solvothermal reaction between SnBr2 and thiourea on a three-dimensional (3D) carbon foam. They subsequently examined their catalyst to characterize its structure.
Their examinations suggest that their catalyst is made up of SnS2 nanosheets and atomically dispersed Sn atoms. These components are coordinated on the 3D O-rich carbon by binding with three O atoms (Sn1-O3G).
“The electrochemical performance of the SnS2/Sn1-O3G catalyst for CO2RR was evaluated using chronoamperometry in an H-type cell containing CO2-saturated 0.5-M KHCO3,” Prof. Liu said. “Our catalyst can reproducibly yield ethanol with a Faradaic efficiency (FE) of up to 82.5% at -0.9 VRHE and a geometric current density of 17.8 mA cm–2. Additionally, the FE for ethanol production could be maintained at above 70% over the potential window from -0.6 to -1.1 VRHE.”
In initial evaluations, the catalyst developed by the researchers achieved highly promising results, successfully producing ethanol from a CO2RR solution with a high selectivity. In addition, the catalyst was found to be stable, maintaining 97% of its initial activity after 100 h of operation.
“The dual active centers of Sn and O atoms in Sn1-O3G serve to adsorb different C-based intermediates, which effectively lowers the C-C coupling energy between *CO(OH) and *CHO,” Prof. Liu explained. “Our tandem catalyst enables a formyl-bicarbonate coupling pathway, which not only provides a platform for C-C bond formation during ethanol synthesis and overcomes the restrictions of Cu-based catalysts but also offers a strategy for manipulating CO2 reduction pathways towards desired products.”
The recent work by this team of researchers introduces an alternative Cu-free catalyst for eliciting the C-C bond formation and enabling the reduction of CO2 to ethanol. In the future, their proposed approach could be used to produce ethanol more reliably and could potentially also be applied to the synthesis of other desired chemical products via the CO2 reduction reaction.
“The search for more efficient catalysts with dual active sites should be pursued through high-throughput experiments and theoretical calculations,” Prof. Liu added. “The rate and selectivity of a catalytic reaction are also closely related to the coverage of reaction intermediates on the catalyst‘s surface.
“Therefore, an in-depth study of factors that affect the residence time of intermediates, such as the pore structure of the support for the Sn1-O3G dual-active sites, would help to deepen understanding of the C-C coupling process. We envisage that tandem catalysis based on the concept of dual-active sites could be extendable to C-X (X = N or S) coupling to prepare other chemicals, such as urea and alanine.”
More information: Jie Ding et al, A tin-based tandem electrocatalyst for CO2 reduction to ethanol with 80% selectivity, Nature Energy (2023). DOI: 10.1038/s41560-023-01389-3
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The product consistency and safety of cylindrical lithium-ion battery are better. Cylindrical li ion customized battery packs are the earliest mature industrial lithium-ion battery products. The 18650 lithium-ion battery was first launched by Sony Corporation of Japan in 1992. At that time, the important application direction was 3C digital products. After more than two decades of development, cylindrical custom lithium battery pack have a mature production process, high production efficiency and relatively low cost, so the packaging cost is also relatively low. The yield of 18650 lithium ion battery pack is higher than that of prismatic lithium-ion batteries and LiPO li ion customized battery packs.
Cylindrical lithium-ion batteries have better heat dissipation performance than prismatic batteries due to their large heat dissipation area; cylindrical batteries are easy to combine into various forms and are suitable for full-layout electric vehicle space design. Based on these advantages, most domestic companies choose cylindrical batteries in the power supply field.
Prismatic lithium-ion battery:
Prismatic lithium-ion battery casings are mostly made of aluminum alloy, stainless steel, etc. The internal winding or lamination technology protects the battery better than soft batteries, and the safety of the battery is greatly improved compared to cylindrical batteries. At present, prismatic batteries are still developing towards high-hardness shells and lightweight technology, which will also provide the market with li ion customized battery packs products with better performance.
LiPO battery:
Small thickness, light weight, large capacity and good safety performance.
Li-PO batteries can be arbitrarily changed in size according to customer requirements. The structure of Li-PO batteries uses aluminum-plastic soft packaging, which is different from the metal casing of liquid batteries. Once a safety hazard occurs, the Li-PO batteries will only swell but not explode.
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When designing custom lithium battery pack, it is very important to correctly calculate the reasonable ratio of positive and negative electrode capacities. For traditional graphite negative electrode lithium-ion batteries, the main shortcomings of battery charge and discharge cycle failure mainly occur in lithium deposition and dead zone problems on the negative electrode side, so the solution of excess negative electrode is usually used. In this case, the battery capacity is limited by the capacity of the positive electrode, and the ratio of negative electrode capacity/positive electrode capacity is greater than 1.0 (i.e. N/P ratio >1.0).
If there are too many positive electrodes, excess lithium ions from the positive electrode cannot enter the negative electrode during charging, and lithium will be deposited on the surface of the negative electrode, leading to the formation of dendrites, thus affecting the cycle performance of the battery. Therefore, generally speaking, the graphite negative electrode in custom lithium battery pack will have slightly more than the positive electrode, but not too much. Too much negative electrode will consume the lithium in the positive electrode. In addition, this will also cause waste of negative electrodes, reduce battery energy density, and increase battery costs.
For lithium titanate anode batteries, due to the relatively stable LTO anode structure, high voltage platform, excellent cycle performance, and no lithium deposition, battery cycle failure mainly occurs on the cathode side. The preferred solution for battery system design is to use excess positive and negative capacity limits (N/P ratio <1.0), which can alleviate electrolyte decomposition problems due to high positive electrode potential when the battery is near or fully charged.
N/P ratio refers to the ratio of negative electrode capacity to positive electrode capacity. Actually, there is another way of saying it, called CB (Battery Balancing). Generally speaking, the ratio of positive and negative electrodes in a battery is mainly determined by the following factors:
Efficiency of positive and negative electrode materials: All reactive substances should be considered, including conductive agents, binders, current collectors, separators and electrolytes.
Coating accuracy of the equipment: Now the ideal coating accuracy can reach 100%. This factor needs to be considered if the coating accuracy is not high.
Cyclic decay rate of positive and negative electrodes: If the positive electrode decays faster, then the N/P ratio is lower than the design value, leaving the positive electrode in a shallow charge and discharge state. On the other hand, if the negative electrode decays quickly and the N/P ratio is high, the negative electrode will be in a shallow state of charge and discharge.
The rate capability the battery needs to achieve. The calculation formula of N/P is: N/P = negative electrode area density × active material ratio × active material discharge specific capacity / positive electrode area density × active material ratio × active material discharge specific capacity. For example: in the voltage range of 4.2 ~ 3.0V, at 25°C, the first round charge and discharge efficiency of LiCoO2 is about 95%, and the first round charge and discharge efficiency of ternary materials is between 86% and 90%. Table 1 shows the mass specific capacity of commercial NCM111 under 1C discharge for the first three charge-discharge cycles.
Before using material ratios, calculations can be made based on first-round efficiency data provided by the material manufacturer. If the manufacturer does not provide these data, it is best to test the first-run efficiency of the material using a button half cell in order to calculate the ratio of positive to negative electrodes. The ratio of positive and negative electrodes in graphite negative electrode lithium batteries can be calculated based on the empirical formula N/P = 1.08, where N and P are the mass specific capacities of the active materials of the negative electrode and positive electrode respectively.
The calculation formulas are as follows (1) and (2). Excess negative electrode helps prevent lithium from depositing on the surface of the negative electrode when the battery is overcharged, and helps improve the cycle life and safety of the battery. N = Negative electrode area density × active material ratio × active material discharge specific capacity (1); P = positive electrode area density × active material ratio × active material discharge specific capacity (2).
Assuming that the positive electrode area density is 200 mg/cm2, the active material ratio is 90%, and the specific discharge capacity is 145 mAh/g, then P = 200 mg/cm2 × 0.9 × 145 mAh/g = 26.1 mA hour/cm2. Assuming that the active material ratio of the negative electrode is 95% and the specific discharge capacity is 320 mAh/g, it is more appropriate to design the areal density of the negative electrode to 93 mg/cm2. At this time, N = 93 mg/cm2 × 0.95 × 320 millimeter Ampere-hour/gram = 28.3 mA-hour/cm2, N/P = 1.084.
Because the irreversible capacity of the custom lithium battery pack material in the first round will also affect the ratio of positive and negative electrodes, the above calculation should also be verified with the first round charging capacity. According to Table 2, the first round charge and discharge efficiency of LiCoO2 is 95%, the first round charge and discharge efficiency of NCM111 is 86%, and the first round charge and discharge efficiency of the negative electrode is 90%. Their charging capacities are 153 mAh/g, 169 mAh/g and 355 mAh/g respectively.
PLCO=27.54 mA·h·cm–2
N=31.36 mA·h·cm–2
N/PLCO=1.138
P111=30.42mA·h·cm–2
N/P111=1.03
Generally speaking, the N/P ratio calculated based on charging capacity should be greater than 1.03. If it is lower than 1.03, you need to fine-tune the ratio of positive and negative electrodes again. For example, when the first-round efficiency of the positive electrode is 80%, the above-mentioned positive charging capacity is 181 mAh/g, then P = 32.58 mAh/cm2, N/P = 0.96. At this time, the surface density of the positive and negative electrodes should be adjusted so that N/P is greater than 1, preferably around 1.03. For mixed cathode materials, calculations also need to be performed according to the above method.
Effects of different N/P ratios on the performance of lithium titanate negative electrode custom lithium battery pack
The impact of different N/P ratios on custom lithium battery pack capacity
In this study, a flexible packaging lithium-ion battery was prepared using ternary NCM as the positive electrode material and lithium titanate LTO as the negative electrode material; the experimental plan was to keep the positive electrode capacity unchanged and change the negative electrode capacity, that is, set the positive electrode capacity to 100 , and then designed the negative electrode capacities of 87, 96, 99 and 102 respectively, as shown in Figure 2. When the N/P ratio is less than 1.0, the negative electrode capacity is insufficient, the positive electrode capacity is too much relative to the negative electrode capacity, and the battery capacity is limited by the negative electrode capacity;
When the negative electrode capacity is high, that is, when the N/P ratio increases, the battery capacity increases accordingly; when N/P is greater than 1.0, the cathode capacity is insufficient relative to the negative electrode capacity, and the battery capacity is limited by the positive electrode capacity. Even if the negative electrode capacity is increased, the battery capacity will not change. It can be seen that under this experimental scheme, as the N/P ratio increases, the battery capacity also increases.
The full custom lithium battery pack capacity test also verified the above analysis. As shown in Figure 3(a), as the N/P ratio increases, the full battery capacity increases from 2430 mA h to 2793 mA h. By calculating the gram capacity of the positive and negative electrode materials, the changing trend of the gram capacity with the N/P ratio can be obtained. As shown in Figure 3(b), it can be seen that increasing the N/P ratio can increase the gram capacity of the cathode material and the battery capacity.
Effects of different N/P ratios on battery high-temperature storage performance
The high temperature storage (60°C, 100% SOC) test is to charge at 1.0C to 2.8V/0.1C cut-off, leave it for 5 minutes, charge at 1.0C to 1.5V, cycle 3 times, and select the one with the highest capacity as the initial capacity; then , test the full charging voltage, internal resistance and thickness of the battery before storage, and record these values;
After storing the battery at 60°C for 7 days, measure the full charge voltage, internal resistance and fully charged thickness of the corresponding battery. Then discharge the battery to 1.5V at 1.0C, record the remaining capacity, charge at 1.0C to 2.8V/0.1C cutoff, leave it for 5 minutes, and discharge at 1.0C to 1.5V. The discharge capacity after 3 cycles was recorded as the recovery capacity, and the test results are shown in Figure 3(a).
Effects of different N/P ratios on battery cycle performance
NCM/LTO system batteries with three different N/P ratios (0.87/0.99/1.02) were used for 3C charging and 3C discharge cycle tests. The voltage range was 2.8 to 1.5V. Cycle capacity retention rates under the three N/P ratios As shown in Figure 5(a). As can be seen from the figure, the battery with an N/P ratio of 0.87 has the best cycle performance, with a capacity retention rate of 97% after 1,600 cycles. However, when the N/P ratio increases to 0.96 and 1.02, the cycle capacity retention rate decreases significantly.
The change rate of internal resistance during the cycle is shown in Figure 5(b). When the N/P ratio is 0.87, the internal resistance increase rate is the smallest. After 1800 cycles, the internal resistance increased by 7.6%. When the N/P ratio increases to 1.02, the internal resistance increases sharply to 34% after 1800 cycles. It can be seen that the N/P ratio design of the battery has a great impact on the cycle performance, and a lower N/P ratio is more beneficial to the cycle performance of the battery.
Three-electrode test with different N/P ratios
Three-electrode tests were performed on cells with different N/P ratios. The test conditions are 3C constant current charging to 2.8V, 0.1C cutoff, 30 minutes of sleep, and 3C discharge to 1.5V. The test results are shown in Figure 6.
The positive electrode potential of the battery with an N/P ratio of 0.87 dropped from 4.325 V at the beginning of constant voltage charging to 4.295 V at the end of constant voltage charging, and then continued to drop to 4.215 V during the 30-minute rest period. The positive electrode potential of the battery with an N/P ratio of 1.00 remained basically unchanged during the constant voltage charging stage, and only dropped to 4.321 V during 30 minutes of rest.
The negative electrode potential of the battery with an N/P ratio of 0.87 dropped from 1.56 V to 1.50 V, while the negative electrode potential of the battery with an N/P ratio of 1.00 remained basically unchanged, only decreasing from 1.56 V to 1.54 V. The battery voltage of the battery with an N/P ratio of 0.87 dropped from 2.8 V to 2.69 V during 30 minutes of rest, while the voltage of the battery with an N/P ratio of 1.00 remained basically unchanged, only dropping from 2.8 V to 2.77 V.
It can be seen that the battery with lower N/P has a larger positive electrode potential drop during the constant voltage charging stage and subsequent resting process. The positive electrode potential of a battery with an N/P of 0.87 is significantly lower than that of a battery with an N/P of 1.0. It can be seen from the three-electrode test results that for the LTO negative electrode, the voltage platform is around 1.55 V, and most electrolyte solvents have stable electrochemical performance on the lithium titanate negative electrode side.
However, the potential on the positive electrode side is higher, and the electrolyte is prone to oxidation reactions on the positive electrode side, especially when it is close to a fully charged state. Therefore, for a battery system with an N/P ratio less than 1 (LTO capacity is limited), when the battery is fully charged, the negative electrode potential will drop from 1.56 V to 1.50 V, and the positive electrode potential will drop from 4.325 V to 4.295 V, and then continues to drop to 4.215 V during the 30-minute sleep depolarization process;
For battery systems with an N/P ratio greater than 1 (positive electrode capacity is limited), there is too much LTO relative to the positive electrode, and the potential of LTO remains basically unchanged during the charging process, only decreasing from 1.56 V to 1.54 V. The positive electrode potential remains unchanged during constant voltage charging, which is 4.295 V higher than the positive electrode potential in batteries with a low N/P ratio. The higher positive electrode potential state makes side reactions such as oxidation between the electrolyte and the positive electrode more likely to occur, resulting in poor cycle performance and high-temperature storage performance.
Conclusion For lithium titanate negative electrode lithium-ion batteries, increasing the N/P ratio will help increase the positive electrode gram capacity of the battery and help increase the initial discharge capacity of the battery; however, increasing the N/P ratio will increase the positive electrode potential, The electrolyte is prone to oxidation reactions on the cathode side, especially when it is close to a fully charged state. The low N/P ratio can ensure that the positive electrode has a lower electrode potential, thereby reducing the internal side reactions of the battery during high-temperature storage and cycling, which helps to improve the high-temperature storage performance of the battery and the cycle performance of lithium batteries. When the energy density requirement is not high, in order to ensure long life cycle and good high temperature performance, the N/P ratio can be moderately reduced to between 0.85 and 0.9.
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The energy density of li ion customized battery packs is 48% higher than that of Ni-MH batteries. And its cycle life of charge and discharge times can reach more than 600 times.
Advantages of li ion customized battery packs: small self-discharge, no memory effect, small size, light weight, green and environmental protection.
Application fields: transportation power supply, energy storage power supply, mobile communication power supply, new energy energy storage power supply, aerospace special power supply, electric vehicle applications.
Ni-MH battery is a battery with excellent performance. As an important direction of hydrogen energy application, hydrogen energy has attracted more and more attention.
Advantages: low price, strong versatility, large current, strong reliability, good over-discharge performance, overcharge protection, high charge-discharge rate, no dendrite-formation, good low-temperature performance, no significant change in capacity at -10 °C.
In recent years, more and more Ni-MH batteries are used. The capacity is getting larger and larger, chargers are becoming more and more advanced, and the charging time is greatly shortened.
Uses: electric toys, electric bicycles, power tools, digital products.
Conclusion: In terms of daily charging, li ion customized battery packs have no memory effect and are easy to use. In addition, li ion customized battery packs are light in size and weight, making them easy to carry on mobile devices. The working voltage of the Ni-MH battery is 1.2V~1.5V, and the series voltage of the two batteries is 2.4V~3.0V. Most electrical appliances already have this operating voltage standard, such as walkman, radio, etc. Therefore, in the civil battery, lithium-ion batteries cannot replace Ni-MH batteries. However, in the later development of new electrical appliances, such as mobile phone batteries, camera batteries, mobile power supplies, etc., li-ion battery is more popular now.
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Name: Dawn Zeng (Director)
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We know the importance of li ion customized battery packs and solid-state batteries. Despite the importance of solid-state batteries, But in its publicity and boasting, there’s something less clear. This article lists ten topics to provide a clearer understanding of solid-state batteries, but we need to put these topics into the correct context and be alert to missing information.
Safety – Undoubtedly the most important factor Let’s start at the beginning, which is also the original and hopefully still the main reason for solid state batteries. The reason for this is safety, which is directly related to the temperature limits of the liquid electrolyte. We all know about thermal runaway in current li ion customized battery packs: rare, but unstoppable fires. When the battery is unable to discharge heat at the rate it is being produced, a chain reaction begins. Current li ion customized battery packs are kept operating within a safe temperature range, typically around 25-45°C, by cooling systems and battery management systems (BMS). Typically, a battery requires failure, defect, misuse, or accident to cause overheating. Unfortunately, with billions of batteries present in millions of electric vehicles and energy storage systems, these problems are statistically inevitable. Therefore, we should not pretend that risk can be eliminated by design, but rather that the sources of risk must be eliminated. Liquid electrolytes are discussed further below (#3) and lithium compatibility (#5), as well as new risks such as hydrogen sulfide (#8). Summary: Security remains a top concern, so we need to keep talking about it.
Pressure – An often overlooked issue People seem to think that solid electrolytes require a pressure system. Eminent scientists say the solid-state problem has been solved in the laboratory and now it’s up to engineers to design a pressure system. Indeed, it has been shown that lithium metal deposition can be enhanced by increasing pressure. But while some pressure can be easily integrated (e.g., vacuum on a vacuum-sealed bag), for many solid-state batteries the high voltages required remain impractical for practical applications. The high voltage is used to overcome interfacial resistance, especially for oxides and sulfides. Some solid-state polymers do not require pressure, but perhaps surprisingly, hybrid and semi-solid batteries require high voltages. If high voltage is required, the problem is compounded by changes in volume of the battery as it charges and discharges, heats and cools. There is a lack of transparency into this complex issue, as pressuring the system can add significant expense and quality. Quoting improved energy density is inappropriate without acknowledging additional pressure systems. QuantumScape recently provided energy density data “unpackaged” to give it some credit. Maybe a bit cryptic, but this suggests the battery needs more content to run. Summary: Operating pressure is often ignored in performance claims, but it has important implications for energy density, cost, and scalability. (See the next topic for information on scalability).
Liquid – Does a solid have to be a true solid? This topic is crucial because liquids can cause issues with safety and pressure (#1&2 above) as well as temperature range (#4 below). Many products are called solid state because the separator is a solid electrolyte. The inactive porous polymer separator is replaced by an active solid-state electrolyte that excels in both mechanical strength and ionic conductivity. It maintains electrode spacing, resists dendrites (see Topic #5) and transports lithium ions. But the cathode also requires an electrolyte (unless a very thin film cathode is used), and if this electrolyte is a liquid or gel, then we need to evaluate safety risks and performance issues. The risks of liquid electrolytes are explained in Topic #1. Topic #4 explains how liquids can limit temperature range and reduce cycle life. Additionally, if high pressure is required, the liquid will limit scalability. The airtight bag can be easily sealed under vacuum to incorporate 1 atmosphere of pressure, but if there is liquid to flow, then adding high pressure evenly throughout the battery will be problematic. This is a scalability barrier that cannot be easily solved with solid-state electrolytes. During processing, the ceramic needs to be sintered and the sulfide requires huge pressure (500 bar), which is possible for the separator but not for the positive electrolyte. In contrast, solid polymers can work simultaneously as separators and catholytes only if their ionic conductivity is comparable to that of conventional liquid electrolytes. Summary: Whether we call it solid, semi-solid, or hybrid, using any liquid electrolyte introduces the risk of thermal runaway, limits the temperature range, and inhibits scalability through high voltages.
Temperature range – is it clear enough? Solid-state batteries should offer higher temperature adaptability than liquid electrolyte batteries, that is, without the need for cooling systems. Liquid electrolyte becomes unstable above 40°C and accelerates the degradation of the positive electrode. If semi-solid or hybrid batteries require cooling systems, this will impact energy density and cost. A simple way to check is to test whether the data covers the range of 40°C to 80°C. 80°C is a useful benchmark because it is above surface temperatures on the hottest days. This means an electric car can be parked in the sun without draining the battery’s cooling system! Please check the data carefully, sometimes the high temperature statement may not include the entire battery for the separator electrolyte. Some solid polymer electrolytes have the opposite problem in that they must be heated before the ions can conduct electricity, usually between 50-80°C. This would also increase cost, reduce the energy density of the system, and be impractical for general use. Summary: Solid-state batteries should operate over a wide temperature range without the need for external systems that would otherwise be recognized in energy density and cost claims.
Lithium compatibility and dendrites in order to increase energy density, the electrolyte needs to work stably with lithium metal and high-energy cathode, otherwise the energy density improvement will be minimal. Developers of various solid-state batteries have experimented with lithium metal and then moved to graphite or silicon. This indicates incompatibility with lithium metal, although one company claims that lithium metal is unsafe, which could also be interpreted as being incompatible with their solid electrolytes. Another unresolved debate is the best solution to who owns the dendrites. Ceramics and sulfides are very hard, but have grain boundaries and are prone to brittleness. Polymers have been accused of being too weak, but some companies disagree. Cycle life and millions of tests will provide the answer, but as mentioned above, failure is statistically inevitable, so the debate once again turns to how to eliminate the possibility of thermal runaway. Summary: Highly stable and mechanically strong solid-state electrolytes are needed to increase energy density.
Layer Thickness – Often Not Mentioned High energy density requires a thin separator equivalent to current li ion customized battery packs, an even thinner anode, and a cathode at least as thick as current li ion customized battery packs. Taking actual numbers as an example: the separator is in the 20-30µm range, thin lithium is less than 40µm, and the cathode is at least 80µm. Why? If not, simple math proves that batteries can’t achieve higher energy densities. There are some innovative 3D technologies that developers may disagree with, but they also need to respond to scalability and processability issues (see Topic #10). Reasons why layer thickness is often not mentioned include that thin ceramic separators are very fragile, reducing thickness makes it difficult to extend the cycle life of lithium, and penetration of thick cathodes through solid electrolytes is often difficult, often requiring liquid. Summary: Higher energy density requires a thinner negative electrode and a thin separator to match the thick positive electrode.
Cycle Life and C-Rate – Battery Performance For many developers and original equipment manufacturers (OEMs), long battery life and fast charging are top topics as it promises longer range and shorter battery life for electric vehicles. parking time. It’s what everyone wants to hear and therefore becomes the target of propaganda. Long cycle life and high C rate can be achieved, but usually at the expense of each other, which is often not explained in detail. As mentioned above, layer thickness or pressure requirements may not be stated. Most readers have come to understand that, typically, long cycle life is typically achieved at low C rates, while high C rates often come at the expense of cycle life. Sometimes the fine print terms will qualify long life with a high C rate in cycles 1-10 or 1-30, while other cycles will go in with a low C rate. Solid-state batteries should eventually offer really long life and fast charging. One reason is the ability to operate stably at higher temperatures, thus accommodating faster power transfer, but this requires a highly stable solid-state electrolyte in the battery. Another reason is that charging speed is limited by the rate of intercalation reactions, a limitation that is eliminated when using lithium metal. Summary: Dramatic cycle life and C rates are closely publicized but are often opaque and further distract from the fact that the actual fundamentals are not achieved.
Risks introduced the primary goal is to improve safety, but some “solutions” reduce one risk and then increase another. It is important to remember that failures and accidents are inevitable, so we need to check whether the failure mode is “fail-safe” or not. Adding huge amounts of pressure means containing an unexpected release of energy. The use of certain liquid electrolytes retains the risk of thermal runaway. At least one company claims that using lithium metal is dangerous, but using ultra-thin lithium could mitigate this risk. Using sulfide introduces new hydrogen sulfide risks due to moisture sensitivity. Summary: The key to reducing risk is to have a highly stable solid electrolyte throughout the battery, allowing it to operate over a wide temperature range.
Packaging and Demonstration Cells Packaging has already been mentioned regarding pressure (Topic #2) and requires further analysis as this is one of the most opaque issues. Gorgeous pictures of giant display batteries have one thing in common – a real operating system that requires pressure, cooling, heating or contains risks such as hydrogen sulfide is never shown. Or, there are animations that show certain obvious advantages, but don’t show the whole story. Or there are some very realistic pictures without any mention that they are renderings.
Scalable Process – Tiny Wearables and Cost Every startup has an obligation to say “our technology is easily scalable”. Without specific figures and timetable, this statement is somewhat empty. Some companies have developed solid-state battery technology for the tiny wearables market, and then implicitly scalable it for the electric vehicle and renewable energy markets. Most tiny solid-state batteries are made of ceramic, but this is not easily scalable. Novel architectures and processes, such as 3D or printing, should not be put in the same context as JICA-scale lithium-ion batteries that took decades to develop. Solid-state batteries need to reduce costs to make electric vehicles and renewable energy affordable. New processes will not reduce costs until they have been developed for a decade. Adding external systems does not reduce costs. Ceramics need to be sintered. Sulfide requires large-scale pressure during its production. Hybrid batteries require “special protective coatings” to reduce risk. All of this adds to costs. The goal is to reduce costs. Processing should use standard R2R processes. It is widely accepted that solid polymer electrolytes are the simplest to manufacture and easiest to adapt to existing processes and cell structures. Summary: The standard R2R process combined with fewer product materials (no active separator, no cathode host, no liquid) provides cost reduction incentives. Summary Solid-state technology has made tremendous advances that will ultimately provide improved safety and higher performance at lower cost. But solid-state battery developers need to openly address these issues to launch viable products for the real world. Reduce risk, eliminate the need for external pressure systems, increase energy density and use existing R2R production to produce commercial-scale batteries. While there’s still a lot of work to be done, and of course I’m biased, I think Nuvvon is the only solid-state battery technology provider to date that can do it all.
Nuvvon:
Completely solid state, therefore reducing the risk of thermal runaway
Operates without external pressure system
Solid polymer as separator electrolyte and positive electrolyte – no liquid or gel particles
Wide temperature range (currently -10 to +80°C)
Compatible with thin lithium and has high mechanical strength to resist dendrites
The cycle life and C rate of thin lithium at C/4 are still a work in progress, with cycle life in the range of several hundred cycles
No new risks (no pressure, no liquids, no harmful ingredients)
Bare cells operate without external systems (pressure, heating, cooling)
Pouch cells using existing battery architecture and built on standard li ion customized battery packs processes.
Author Dr. Simon Madgwick of Nuvvon Inchttps://www.batterydesign.net
If you have any question, please feel free to contact us:
Name: Dawn Zeng (Director)
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