Lithium sulfide costs as low as 200000 yuan "analysis"

Since this year, the material system centered on sulfide-based solid electrolytes has been gradually established as the main technical route for the development of all-solid-state batteries. This aspect is influenced by the unanimous choice of top battery companies; On the other hand, academic circles believe that sulfides has outstanding advantages in ionic conductivity, which can promote the development of all-solid-state batteries in the short period of time. In this context, the market has begun to explore and track the progress of every detail of the sulfide industry chain, involving raw materials (pyrite), precursors (lithium sulfide, etc.), electrolytes, batteries, auxiliary materials and many other links.

Among them, the low-cost preparation of lithium sulfide is the focus of people. In particular, the multi-wave upsurge caused by lithium sulfide in the secondary market in the fourth quarter is more worthy of public attention. 

Industry companies have stated that their high-purity lithium sulfide is currently in the "small-scale trial stage after a certain breakthrough in research and development", and are cooperating with domestic and foreign customers for verification or small batch supply. Industry insiders revealed during institutional exchanges that the company's high-purity lithium sulfide shipments have reached the ton, and customers require it to "prepare" at least 100 ton of production capacity by 2025. By then, the cost of high-purity lithium sulfide is expected to drop to RMB 200000. What is the concept that the cost of high purity lithium sulfide is 200,000/ton? First of all, it needs to be clarified that the commercialization of lithium sulfide has begun to make progress, which was mainly used in lithium-sulfur batteries before. However, if lithium sulfide is used to prepare solid electrolytes, it still needs technical solutions to solve the problems of low purity and large particle size. 

The staff pointed out that the core requirements of downstream solid-state customers for lithium sulfide for electrolytes focused on purity, particle size (D 50), specific surface area, etc. Among them, the minimum purity should be "49s" (99.99%); The particle size needs to be adjustable, balancing small particle size and high conductivity; It is necessary to modify the specific surface area to reduce its reactivity and minimize the possibility of chemical reactions between sulfides and air or water. Purity is the core parameter, and the latter two are mainly used to provide choices for different technical specifications.

Secondly, in the cost composition of sulfide solid-state batteries, lithium sulfide is sold at a single ton price of 2.5-4 million yuan, accounting for nearly 70%. Solid-state battery enterprises point out that reducing the cost of lithium sulfide to 500000 yuan/ton is a key turning point for industrialization, and the cost of sulfide electrolytes is expected to drop to 300,000 yuan/ton. The cost of all-solid-state battery will also be reduced to 0.6 yuan/watt-hour. At present, the high-purity products of major suppliers of lithium sulfide are still in the stage of small-scale laboratory production. Therefore, most companies mainly use high-purity lithium salt (purification is a key technical difficulty) and sulfide raw materials to synthesize high-purity lithium sulfide through solid-state high-temperature synthesis. The process equipment investment is low, and the double expectations of lithium price reduction and mass production can reduce the cost per ton of high-purity lithium sulfide to 100,000-200,000 yuan. 

However, the problem is that the preparation process involves high temperatures, which will bring high energy consumption and high costs and increase the complexity of operating condition control.

Previously, some companies in the industry proposed that low temperature and liquid phase synthesis were more promising ways to reduce cost. Generally speaking, the preparation process of lithium sulfide can be divided into three main ways: solid phase, liquid phase and gas phase. Solid state method is the most common method, and specific methods include ball milling, high temperature sintering (Guanghua technology), carbothermal reduction and so on.

Carbothermal reduction is the mainstream method to synthesize lithium sulfide in industry at present. The key step is to reduce lithium salt by carbon or carbon-containing compounds at high temperatures. The operation is simple, the intermediate steps is convenient for the storage and transportation of crude products, and it is suitable for preparing lithium sulfide by one step method.

The production experience of lithium battery materials and separator enterprises in powder sintering, heat treatment of separator and other high-temperature processes laid the technical foundation for such enterprises to prepare lithium sulfide across borders. Among them, En Jie thinks that carbothermal reduction is a low-cost, large-scale and high-safety method for preparing high-purity lithium sulfide. En Jie, Hunan Province, said that the advantage of carbothermal reduction method are low and sufficient raw materials, which is conducive to large-scale production; Moreover, as long as the equipment and tail gas treatment methods are well controlled, it is still relatively environmentally friendly. The carbothermal reduction method reduces costs, but technically it still needs to meet strict requirements for some parameters, gas charging amount, temperature and environmental adaptability, and further improve the purity of lithium sulfide. Preparation of High Purity Lithium Sulfide by Liquid Phase Method. 

To sum up, lithium sulfide for solid electrolytes has attracted many chemical and lithium battery companies to make layout. It can only be said that there are differences in the layout of enterprises in terms of process selection and industrial base. In fact, it is still unknown who can realize the low-cost and large-scale preparation of high-purity lithium sulfide first. Next, it depends on the large-scale production level, advanced technology and the rhythm of market demand of enterprises.