Custom lithium battery pack is mainly composed of electrolyte, separator, positive electrode material and negative electrode material. As one of the four key materials in lithium battery manufacturing, electrolyte is the medium for lithium ion migration and charge transfer, and is known as the “blood” of lithium batteries.

As an important component of custom lithium battery pack, electrolyte additives have a direct and significant impact on the performance of lithium batteries. Therefore, improving the functional role of electrolyte additives in lithium batteries is an important way to improve the performance of lithium batteries. 1. Electrolyte additive VC This additive has the characteristics of small dosage and significant effect. It can significantly improve the performance of lithium batteries without increasing production costs and changing the production process. In high-energy-density lithium iron phosphate batteries, electrolyte additives are used as auxiliary materials. They were previously added in small amounts and accounted for less than 8% of the electrolyte additive cost structure. The average market price of VC electrolyte additives fell.

The sharp increase in VC prices at the end of 2021 is due to the imbalance of supply and demand and the sudden increase in customer demand. As the capacity utilization rate of VC manufacturers increases, the supply side has increased. VC manufacturers may have stocked up before, but now they have shipped, so the price has dropped.

Electrolyte additive DTD

• Introduction to DTD (vinyl sulfate)

DTD (vinyl sulfate) is a film-forming additive for SEI. The addition ratio of iron lithium is less than 1%, and the ternary addition ratio is less than 3%. At present, the preparation of DTD mainly uses sulfoxide chloride and ethylene glycol as raw materials.

• Market size

Ternary batteries have higher energy density, but the disadvantage is poor thermal stability. DTD can improve the high-temperature cycle and high-temperature storage performance of the battery, and reduce battery expansion after being placed at high temperatures. Therefore, the research report believes that a higher proportion of DTD needs to be added to ternary batteries. DTD is a relatively new additive, mainly added to ternary lithium, but the proportion of lithium iron phosphate has exceeded that of ternary lithium. Therefore, the compound annual growth rate of DTD is still conservatively estimated at 20%.

• DTD market price

Since 2018, the market supply of vinyl sulfate has increased, so the price of vinyl sulfate has dropped accordingly. The current unit price is about 230,000 yuan/ton.

The study predicts unit prices will fall by 10% annually. The price of ethylene sulfate continues to decline from 2019 to 2021. The main reasons are:

Improve the vinyl sulfate production process and reduce costs.

The top five battery electrolyte companies continue to deploy upstream raw materials, driving the price of ethylene sulfate downward.

The price of ethylene sulfate rebounded from January to March 2022. The price increased mainly due to the boom in the downstream electric vehicle industry and the tight supply and demand of upstream raw materials.

 

Scale of electrolyte additive industry

Industry development status quo

The development of global electrolyte additives is deeply affected by the development of the custom lithium battery pack industry. Major lithium battery producing countries have been affected to varying degrees, resulting in a slowdown in the growth rate of lithium battery production, which in turn affects the market demand for electrolyte additives.

Power batteries are the largest downstream application area for electrolyte additives. Benefiting from the development of the electric vehicle industry, my country’s demand for power batteries continues to grow, driving the development of lithium battery electrolytes.

China’s lithium battery electrolyte market continues to grow. The market size of electrolyte is proportionally related to the production of lithium batteries. The increase in demand for lithium batteries has driven the market size of electrolyte additives to continue to rise.

With the continuous expansion of the scale of the lithium battery industry and electric vehicles and the improvement of battery safety, cycle life and energy density requirements, more requirements have been put forward for electrolyte additives. Charge protection, improved low-temperature performance, etc. will gradually be enhanced.

Supply side

The global output of electrolyte additives is growing steadily, and Chinese companies are the absolute main force in the additive industry. In the future, new additive production capacity will largely depend on the expansion of Chinese companies. Among battery companies, Guangzhou Tyker Energy is a professional lithium battery seller.

Electrolyte additives replace risk factors

① Hydrogen battery

A hydrogen fuel cell is a battery that uses hydrogen element to store energy. Its basic principle is the reverse reaction of water electrolysis. Compared with lithium batteries, hydrogen fuel cells have the following advantages: low energy conversion consumption.

The hydrogenation speed is faster than the charging speed, which is more in line with the needs of long-term efficient transportation. It has no pollution to the environment and basically achieves zero carbon emissions.

However, hydrogen fuel cells are still in the early stages of industrialization, and there are still many problems to be solved:

• The industrial chain is not yet mature and the cost is high.
• It is difficult to build hydrogen refueling stations.
• The construction cost of a hydrogen refueling station is generally more than three times that of a gas station, and is also higher than the construction cost of a charging station.
• Hydrogen is a dangerous, flammable and explosive gas. Early construction, safety management and later maintenance are difficult. It may also pose certain threats to vehicle safety during use.

Hydrogen fuel cells have the advantages of long cruising range and short charging time. It is one of the directions for the industrialization development of automobile companies.

It is expected that after the industrialization of hydrogen fuel cells in 2030, hydrogen fuel cells will coexist with other batteries, and a combination of hydrogen fuel cells and lithium batteries may occur.

②Solid-state lithium-ion battery

A solid-state lithium-ion battery is a battery that uses solid electrodes and solid electrolytes. Compared with lithium batteries, solid-state lithium-ion batteries have the following advantages:

• high energy density

Solid-state batteries directly use lithium metal as the negative electrode, which is light in weight and has high energy density, ensuring the durability of the vehicle.

• small size

Solid electrolyte additives replace the separator and electrolyte additives of traditional lithium batteries, making the battery thin, small, and light.

• High flexibility

The flexibility of solid-state batteries will also be significantly improved after thinning, ensuring that their performance does not decrease.

• High safety factor

Solid electrolyte additives are non-flammable and moisture-proof, and the battery safety factor is higher than traditional lithium batteries. As the core component of electric vehicles, the energy density and scale of batteries directly determine the cruising range of electric vehicles.

High energy density solid-state lithium batteries have broad application prospects, but solid-state lithium batteries still have the following development resistance:

• Low ionic conductivity

This blocks the movement of lithium ions between the positive and negative electrodes of the battery, resulting in reduced lithium ion transport speed and efficiency.

• Poor interface contact

The contact area between the solid electrolyte additive and the positive and negative electrodes is small, the interface impedance is large, and the battery cycle life and rate performance are poor, resulting in slow charging speed.

• expensive

Without a complete industrial chain to support commercialization, it is impossible to prepare large quantities of materials. Development is still relatively slow.

To sum up, hydrogen fuel cells and solid-state lithium-ion batteries have certain technical advantages. The world’s top 10 custom lithium battery pack companies and well-known car companies have made arrangements, and the development prospects are good. But it is limited by technical and cost pain points.

In the future, the battery industry is more likely to see technological parallelization. Consumer trends require future cars to be economical, safe and environmentally friendly. Both lithium batteries and fuel cells are deficient in their current supply. A combination of the two can complement each other.

Conclusion

Taken together, it is expected that the future market structure will be that liquid lithium-ion batteries coexist with other batteries, and each battery has its own application fields.

Liquid lithium-ion batteries are less likely to be replaced. Moreover, they are likely to maintain a considerable market space in the short term, and the market space for electrolyte additives such as VC and FEC will not be significantly compressed.

source:

https://www.tycorun.com/blogs/news/electrolyte-additive

If you have any question, please feel free to contact us:

• Name: Dawn Zeng (Director)
• E-mail address: sales@himaxelectronics.com

The use of li ion customized battery packs in low battery temperature environments is limited. In addition to the serious decline in discharge capacity, lithium batteries cannot be charged at low battery temperature. When charging at low battery temperature, the intercalation and lithium plating reactions of lithium ions on the graphite electrode of the battery exist simultaneously and compete with each other.

The diffusion of lithium ions in graphite is inhibited under low battery temperature conditions, and the conductivity of the electrolyte decreases, resulting in a decrease in the intercalation rate and the lithium plating reaction is more likely to occur on the graphite surface. The main reasons for the decline in the life of lithium-ion batteries when they are used at low battery temperature are the increase in internal impedance and the loss of capacity due to the precipitation of lithium ions.

1.Effect of low battery temperature on battery discharge capacity

Capacity is one of the most important parameters of lithium batteries, and its size varies with temperature. For AGM replacement battery, the charge end voltage is 3.65±0.05V, and the discharge end voltage is 2±0.05V. The two curves are the temperature capacity curves obtained by discharging the battery at different temperatures at 0.1C and 0.3C respectively.

2.Effect of low battery temperature on battery internal resistance

The relationship between li ion customized battery packs temperature and resistance is shown in the figure below. Different curves represent different charge levels of the battery itself. Under any charge, the internal resistance of the battery increases significantly as the temperature decreases. The lower the charge, the greater the internal resistance, and this trend remains unchanged as the temperature changes.

At low battery temperature, in the cathode and anode materials, the diffusion and movement ability of charged ions becomes poor, and it becomes difficult to pass through the passivation film between the electrode and the electrolyte. The speed of transfer in the electrolyte is also reduced, and a lot of heat is additionally generated during the transfer.

After lithium ions reach the anode, the diffusion inside the anode material also becomes unsmooth. During the whole process, the movement of charged ions becomes very difficult. From the outside, it means that the internal resistance of the battery cell has increased.

3. Effect of low battery temperature on battery charge and discharge efficiency

The lower curve is the curve of charging efficiency changing with temperature. We can observe that the charging efficiency at -20°C is only 65% of that at 15°C.

The low battery temperature brings about the changes in the various electrochemical performances described above, and the internal resistance increases significantly. During the discharge process, a large amount of electric energy is consumed on the internal resistance to generate heat.

4. Internal side reactions of lithium-ion batteries at low battery temperatures

The performance of li ion customized battery packs degrades severely at low battery temperatures, and some side reactions will occur during the charging and discharging process of lithium-ion batteries. These side reactions are mainly the irreversible reaction between lithium ions and the electrolyte, which will cause the capacity of the lithium battery to decline and further deteriorate the battery performance.

The consumption of conductive active material causes capacity fading. Considering the potentials of the cathode and anode in the battery, these side reactions are more likely to occur on the anode side than the cathode side. Because the potential of the anode material is much lower than that of the cathode material, the deposits of side reactions of ions and electrolyte solvents are deposited on the electrode surface, forming an SEI film. The impedance of the SEI film is one of the factors that cause the overpotential of the anode reaction.

When the battery is further cycled and aged, due to the continuous insertion and extraction of lithium ions on the anode during continuous cycles, the expansion and contraction of the electrode caused by the continuous cycle will cause the SEI film to rupture. The cracks after the rupture of the SEI film provide a direct contact channel between the electrolyte and the electrode, thereby forming a new SEI film to fill the crack and increase the thickness of the SEI film.

These reaction processes are constantly repeated as the battery is continuously charged and discharged, so that lithium ions are continuously reduced in the reaction, resulting in a decline in the discharge capacity of the lithium-ion battery.

During charging, deposits form on the surface of the active material, increasing the electrical resistance. The effective surface area of the active particles is reduced and the ionic resistance is increased. The usable capacity and energy of lithium batteries decline simultaneously. Lithium batteries are more prone to side reactions during charging.

At the beginning of lithium battery charging, lithium ions move to the anode through the electrolyte, so the potential difference between the electrode and the electrolyte decreases, making it easier for lithium ions to undergo irreversible side reactions with the substances in the electrolyte. The different electrode materials of lithium-ion batteries have different relationship curves between the potential and the lithium intercalation concentration fraction of the electrode material.

Lithium battery low temperature preheating technology

Faced with the limited use of lithium batteries at low battery temperature, the technicians found a countermeasure to charge and preheat. Although it is an expedient measure, it has a significant effect on improving the discharge capacity and long-term life of lithium batteries.

Before charging or using a lithium battery in a low battery temperature environment, the battery must be preheated. The way the battery management system (BMS) heats the battery can be roughly divided into two categories: external heating and internal heating.

Compared with external heating methods, internal heating avoids long-path heat conduction and the formation of local hot spots close to the heating device. Therefore, internal heating can heat the battery more uniformly for better heating with higher efficiency and is easier to implement.

At present, most of the research on the internal AC preheating scheme focuses on the heating speed and efficiency, and there is little clear consideration of the heating strategy to prevent the occurrence of side reactions such as lithium deposition.

In order to prevent the generation of lithium deposition during the preheating process, it is necessary for the BMS to estimate and control the conditions of lithium deposition in real time. A model-based controlled battery heating technique at low battery temperature is required to achieve the above functions.

With the development of new energy, the use of power li ion customized battery packs is also increasing day by day. The use of lithium batteries at low battery temperature urgently needs to solve the problem of battery warm-up. This is a field that is very close to practical applications. In addition, AC heating, mobilizing electrochemical substances to generate movement, and the impact on battery life have not yet been seen. It is also a problem worthy of continuous attention.

If you have any question, please feel free to contact us:

• Name: Dawn Zeng (Director)
• E-mail address: sales@himaxelectronics.com