On January 13, Zhaohe Automobile held its first announcement. In addition to automatic driving highlights, the largest highlight is a 100-km of battery life. To do this, the brand is propaganda is the battery’s silicon-donate supplement.
. In fact, these two months “Silicon-donate” appear in frequent car companies, battery companies and even CCTV news reports, but the law is different: on December 8 last year, CCTV “Economic Half-hour” mentioned Tianmu pilot nano-silica negative technology; January 8, 2021 The ET7 claims that pre-lithiuming, silicon carbon negative electrode technology; and the silicon-donate supplement of intellectual car. First of all, it is to be clear that the silicon and lithium is two technologies, and the negative electrode dry is to improve the energy density, and the lithium is to improve the life of the cycle.
. They all help to increase the performance of the power lithium battery, which has been widely used on higher energy density products..
1 silicon negative electrode: Application difficulty to increase battery energy density, positive electrode material and negative electrode material to improve. The positive extreme is generally high-nickel material. Everyone is familiar with 811; the negative electrode is a silicon-based negative electrode.
The reason why silicon is selected because the theoretical gram of silicon-based negative electrode material is 4200ah / g, which is 10 times the graphite negative electrode.. With the current technical level, the battery is to be 300Wh / kg, the silicon base is essential.
. (1) The expansion rate is highly divided into two categories, one is a silicone carbon negative electrode, i.e.
, nanoilabic and graphite blended, theoretical gram has exceeded 3000mAh / g, but actually exceeded 2000mAh / g; another It is a silicon oxygen negative electrode, and the silicon oxide dicing graphite is used as a negative electrode, and the substantially g is 1400-1800mAh / g.. At present, the two negative applications have different points.
. Lin Juli, the negative material technology of Guoxuan High-Tech Engineering Research Center, said that the reporter said that the domestic silicone carbon negative electrode is generally used in 3C products; the power lithium battery is generally used..
Therefore, whether it is 3C product or a power lithium battery, it is necessary to achieve higher energy density, silicon-negative is essential.. But silicon also has a lot of disadvantages, one of which is high expansion rate.
. Silicon negative charge and discharge expansion can reach around 300%, while ordinary graphite is only about 10%. Silicon and graphite are inconsistent when charging the lithium, the number of times the battery expansion shrinks is more, the structure will collapse, and lithium can not enter and exit.
. In other words, after silicon, although the gram capacity is increased, the cycle life is shortened..
For the sake of popular understanding, graphite and silicon can be imagined into two particles, and the particles have just started to stick together, but the expansion ratio of the two expansion contractions is large, and after multiple shrinkage expansion, it will break, the battery cycle life will decrease. Therefore, the silicon negative material in practical applications, the silicon content is very low..
Luofei, general manager of Tianmu, said that in the field of power lithium battery, 5% -10% of the silica and graphite will be used in combination.. It can be seen that the application difficulty of silicon negative electrode is very high.
. Can the application difficulty have such a high silicon-based negative electrode that can increase the energy density of the battery? Luofei told us that after nano-silicon, the battery energy density can be increased by 5% -10%..
“Don’t underestimate this 5%, in accordance with the law of traditional lithium-ion batteries, the increase in the energy density of lithium-ion batteries is about 2%, but now 2% is difficult to achieve, have arrived in the bottleneck.. “It can be seen that these 5% energy density improved more precious.
(2) Low production, cost high silicon-based negative electrode is not only difficult to apply, not much company is currently producing. According to the research of high-operated lithium electronics, only Better can be supplied in large quantities in China, and has entered the pneumatic supply chain, indirect supply TSLA, currently 3,000 tons of silicon-based negative yield. International, in the 1990s, it began to develop silicon materials to be applied to the negative electrode of lithium ion battery until 2013.
In 2014, the industrialization of silicon carbon negative electrode and silicon oxygen negative industrialization.. Overall, the true industrialization process of silicon base negatives is relatively short.
. In silicon-based negative electrode applications, international manufacturers are relatively leading. Panasonic has been applied to power lithium batteries in 2017, supplies TSLA.
Samsung, LG chemical silicon-based negative, currently important applications in consumer battery fields. Japan GS Soup is a lithium-ion battery of silicon-based negative material, applied to Mitsubishi. Overall, the silicon-based negative electrode is complex, no standardized process, high technical barriers, difficulty is the preparation process of silicon material nanochemical and silicone composites, belongs to the core technology of each company.
There is less yield, which means a single price. The national Sheng securities data show that the lowest end silicon base price is more than 100,000, the gross profit margin is more than 40%, unit price, profitability is higher than the current graphite negative material..
2 lithium: Safety and technical maturity are bottleneck biopsy technology is pre-lithiuming technology. The reason why the reason is to be lithium, this is important because the second largest disadvantage of silicon negative material – the first effect. (1) Lithium lithium prolonging cycle life, when charging the lithium-ion battery first, it will cause a large number of lithium losses, and it is irreversible.
. In order to ensure the capacity of the battery, it is necessary to make a loss of lithium back. This technology is pre-lithium, the purpose is to compensate for lithium loss, extend the cycle life, thereby reaching the use of attenuation.
After using silicon, the problem is low in the problem.. This is because silicon expansion is relatively large, and it is easy to cause the SEI film (solid electrolyte membrane) of the negative electrode surface to break, and the SEI film is reformated during the discharge process.
. Therefore, the SEI film of the silicon surface is always in the destroy-reconstructed dynamic process, eventually leading to the continuous increase in the thickness of the SEI membrane, the interface impedance is increased, the active material consumption, resulting in a capacity attenuation, and the first logging. Source: Universal Patent 201510029061.
5 Pre-Lithion Treatment Effect Tuchalang Negative Negative and Silicon Supplies The Lithium Loss of Charging Discharge Each is? The study found that the existing graphite material has 5% to 10% of the first non-lithium loss, and the high-capacity negative electrode material, the first lithium loss is even higher; the non-reversible capacity loss of silicon is 15% ~ 35%. (2) Bi lithium technology is not mature, and lithium technology is divided into positive supplements and negative lithium. An industry expert told the reporter that the positive supplement is relatively simple.
Taking the lithium iron phosphate ion battery as an example. By increasing the proportion of lithium in the positive electrode material to reach the pre-lithium-based purpose, the problem is to destroy the positive structure, the technical maturity is more Low. The above experts said that the company currently uses more negative lithium technology.
. For example, using electrochemical pre-lithiuming, direct contact with short circuit method is a simple and effective way, can effectively reduce high-capacity carbon material, alloy negative electrode, and the first irreversible loss of the conversion material, the advantage is that the pre-lithium amount is accurately controlled and stabilized. However, the environment is high, such as an oxygen, no water, dry environment, etc.
is the difficulty of mass application.. In addition, the use of metal lithium powder for pre-lithium is a negative pre-pre-lithium, and is also the most effective and direct method of commercialization.
. However, its requirements for the environmental production environment are very high, to develop a sealed mixed equipment to prevent high-speed mixing of combustion safety hazards such as electrode materials, conductive agents, etc., the risk of the process is very large.
Therefore, overall, pre-lithically difficult industrialization is very difficult. However, there are currently many companies to announce the techniques of silicon supplementation techniques. The industrialization of the two technologies should be solved some extent.
. Per allows battery products that use silicon-donate supplement techniques to be available in the past two years, and it is also the popularity of 300Wh / kg battery products..
Overall, silicon and lithium is based on optimization of the existing material technology route, not a complete replacement of materials.. No matter the triple or lithium iron phosphate, it can improve the energy density.
. It can have limited effect, but when the energy density of the material system is close to the bottleneck, it is very precious..
In terms of overseas leading power lithium batteries, it is already a technology that is already commercially available.. About domestic companies, they are still in the stage of starting production applications.
. It is finally applied to the whole vehicle, if it reaches the safety and reliability of the car level, it is of course able to bring a better life experience to consumers..
At present, the high-end ternary and lithium iron phosphate are used first, if the maturity is good, it is widely used, and the electric vehicle consumers at all levels will benefit.