The Challenges and Opportunities of Silicon-Based Negative Electrodes for Lithium-Ion Batteries

The silicon negative electrode is indeed like timely rain. Looking at the plan for 2023-2025, the energy density of the battery is required to be increased. At present, the most mature system that can increase the energy density is the existing lithium-ion battery system. The capacity of the existing lithium-ion battery system, and the energy density is related to the capacity of the government machine. As mentioned earlier, it is about 200 mA. If the energy of the negative electrode is increased from the current 300 to 1200 or 1500, the energy density of the battery will increase. If it is improved, the cruising range can be doubled. At this time, a silicon carbon negative electrode like timely rain appears. Silicon carbon negative electrode has high energy, relatively good density, and it is safe. But this thing also has many defects. It is 4.4 lithium combined with one silicon, resulting in a very large volume expansion, three to four hundred, continuous expansion and contraction, continuous formation and rupture, and the cycle is getting worse and worse, resulting in more and more sex. Bad because it’s a semiconductor.

Siloxane X is generally considered to be a composite of silicon and silicon dioxide. This material has obvious advantages when it is soaked in lithium ions. Its cycle mainly contains silicon dioxide, and lithium silicate is in the reaction process together. It is a Buffer body, so the material cycle performance is good, but the first effect is average. After the previous reaction is over, the process of forming silicon compounds is an irreversible process. At present, the first effect of silicon oxide in the industry is generally around 76%.

Performance improvement and industrialization of silicon-based negative electrodes

After working for so many years, what kind of things are people studying, and what is the status of industrialization? There are three major parts to improve the silicon-based negative electrode. This is a cliché. One is to reduce the size of the membrane; The idea is to give silicon space to expand, so that the SEI film will not break during the silicon expansion process. That’s still the case with silicon oxide, it’s a few microns now, and encapsulation, the binder is also very important.

At present, the most mainstream silicon preparation method is the mechanical grinding made by the industry leader, which is continuously ground; in recent years, there are CVD methods, using silicon as raw materials, and non-silicon as raw materials. We have a team in Wuhan to do reduction. Among these methods, the most industrialized one is our mechanical nanotechnology, grinding the membrane. I once calculated this process. Metallurgical silicon produced in the metallurgical process needs to be milled from the millimeter level to the micron level, and then to the nanometer level. This method was done very well in the early stage, and now it is the largest volume, but the retention is poor and the energy consumption is high. Many people in the CVD industry are doing it. Using silane, which contains silicon and carbon compounded together, there are indeed some problems at the beginning of the research. There will be two growth states of homogeneous nuclei and heterogeneous nuclei. These problems are now are slowly being resolved. The biggest problem is that everyone feels their own consciences about how much they sell, and how much it costs you to make it. As far as I know, the industry buys the most in the world. One of the biggest problems is that the price of this thing is not cheap. In the first half of last year, it cost 100 US dollars per kilogram. This thing is very scary. There is another problem. The industrialization of this method in the future requires particularly high requirements for factories. It is difficult to require Class A factory buildings, Class A warehouses, and chemical parks, and not everyone can do it. In terms of price, silane is the most common raw material for solar photovoltaics. Since lithium batteries have increased from 100,000 yuan at the beginning of the year, they have now increased a lot. Is it necessary to use these methods?

Cost reduction in the industry is fundamental. We have done a series of work and are now doing industrialization. It is very expensive to use the metallurgical method. The metallurgical method is the reduction method. The metallurgy is “stupid, big, stupid, and crude”. The metallurgical industry sells 10,000 tons of products, and 1 ton of products can earn 100-200 yuan. I am very happy, because the volume is large, we all have hundreds of thousands of tons, millions of tons. At present, Australia reported in March this year that silicon should be dried to the price of cabbage. In fact, I have already applied for this patent ten years ago. We use natural halloysite as raw material. Halloysite itself has a porous structure. Halloysite is used to make it, bare silicon, and nothing is needed. Do 1000 cycles, it gives silicon a good expansion space, and the energy will still be 840 after 1000 cycles. But halloysite is a mine and unstable. We make zinc and silicon together, and then control the boundary pores through the pore structure. After the material is made, silicon does not conduct electricity, but some alloys in silicon conduct electricity, and new materials are obtained. We cycled 1000 times without adding any carbon, and the energy remained at more than 00. I also made some structural changes, and I will communicate again when I have time. We doped non-metallic impurities to solve its cycle and further increase its magnification.

Silicon oxygen is a disproportionation reaction. This disproportionation reaction is the reaction of metal magnesium in metallurgy. I dry metal magnesium. Metal magnesium uses silicon as a reducing agent to reduce magnesium oxide. When we make silicon monoxide, we use silicon as a reducing agent. to reduce silicon monoxide, it is the same. Our metal magnesium is tens of thousands of tons per dry, and our silicon monoxide is 100 tons per dry. The biggest problem at present is the low production rate. At the beginning, there was a company in China that produced 10 kilograms per mine at first. Later, when they went out, one person produced 16 kilograms, and another equipment produced more than 100 kilograms. We are now producing 300 kilograms. To reduce energy consumption. The first effect is low. We have done a lot of work on these problems, including the first generation of carbon, pre-lithium, and pre-magnesium, including how to control the oxygen content in silicon and oxygen. We deal with it by etching to make the X of silicon and oxygen less than 1. To ensure its circularity, we are doing all these work. And we have done industrialization. We have bases in Hunan, Guangxi, and Yunnan. Recently, we have also set up bases in Inner Mongolia. Now we have a lot of them, and the volume is very large, but they have not yet reached full production capacity.

We have modified silicon-oxygen equipment. It is a good idea to use metallurgy to do this. What we are now pursuing is civilianization, popularization, and cost reduction. Silica is also being supplied to some at present, and after mutual matching, it can follow up to 100 tons per month. The first generation, second generation, and third generation of silicon carbon are made. The first generation is a very simple generation of silicon. Everyone is doing CVD, so we also do CVD, and the silicon is evenly distributed in it.

The question of the soul of the development of silicon-based anodes

This industry always fools others into it, but how does this industry work? We have been doing it for more than ten years. Why is the progress of large-scale mass production so slow? I think the first is that the performance defect is very obvious. Although silicon carbon and silicon oxygen have changed the cycle life of silicon oxygen, they are still not as good as carbon. At present, the amount of addition is very small, and it cannot be used alone. A few years ago, a company asked me to talk about graphene, saying that it would build a trillion tons of graphene. I poured cold water on him, and then he never invited me again. . Just like monosodium glutamate is a good thing on the table, but people can’t just eat monosodium glutamate, not everything needs silicon dioxide, we have to tell the truth. The second is that the application fields of silicon-oxygen negative electrodes and silicon-carbon negative electrodes are limited. Now the cylinder is the most practical, but it is almost impossible in the long-cycle field. It requires 10,000 cycles and 15,000 cycles. It is not bad if it can dry up to 3,000 cycles; the energy density requires high The oil market is a small power field, but this is a small field. The third is that cost performance is a stumbling block. Maybe no one will invite me to report after I finish this report, because I always tell the truth. Cost-effectiveness, in order to improve performance by 5% and increase cost by 10%, we will only do it as a last resort. In this place, we must take this into consideration. In 2021, I will go to Shenzhen for a meeting to pour cold water on the negative electrode materials.

Silicon oxide pre-aluminum or magnesium, is it necessary? The first-generation silicon-oxygen CVD method has a first effect of 46%, which is enough for some common fields. You go to reserve lithium, the cost is more expensive than silicon carbon, its raw material is metal lithium, cost reduction is the kingly way. My point of view is that the pre-lithium of silicon and oxygen has no prospect. If you intervene in lithium, you should calculate the price of pre-lithium yourself. The preservation of raw materials is a problem, and various risks will arise in this process. Of course, mine Opinion is not necessarily right. For this thing, you should ask the battery factory and several of our leading companies whether they are willing to use pre-lithium silicon oxygen or silicon carbon. You are a generation of silicon oxide, and it is OK to make the price of silicon oxide to the price of carrots. If you make it again, it will be embroidered on the burlap bag, which has little value.

Will the CVD method dominate the world? A certain company is saying that this method is the best in the world, but why does the best method sell the least amount? You feel your conscience and say, those who practice CVD method, how many products are sold, and whether life is good or not, only you know, and I also know whether it is good or not. How to deal with the price? Even if the price of the CVD method is less than 150,000, your capacity can still be as good as it is now. There is a market for this, but can you do it? It is very difficult. I think that we investors who enter this industry and do research, we must touch our conscience and tell the truth.