Solid state electrolytes are the biggest uncertainty in the mass production process of solid-state batteries.

Gaogong Lithium Battery has noticed that the production capacity plans of several solid-state electrolyte enterprises have reached the level of thousands or even tens of thousands of tons. According to the 700-1000 tons of solid electrolyte corresponding to a single GWh solid-state battery, if all of the above production capacity is implemented, it can already support the preparation of several GWh solid-state batteries.

Moreover, higher value-added products corresponding to solid electrolytes, including solid electrolyte coated membranes and (pure) solid electrolyte membranes, are also accelerating their development.

However, based on the shipment situation, the sales of solid electrolyte products are still mainly based on sample delivery, and multiple solid electrolyte companies are expected to receive bulk orders and deliveries by the end of this year or next year.

The geometric distance between solid electrolyte production capacity planning and mass production still needs further understanding.

From November 20th to 22nd, 2024, the High Tech Lithium Battery Annual Conference will set up three special sessions on solid-state batteries. Invited solid-state enterprises will give keynote speeches and conduct in-depth discussions on promoting the mass production of solid-state batteries.

Observation of Solid State Electrolyte Production Capacity Layout

According to incomplete analysis, solid electrolyte enterprises in the industry generally plan to have a production capacity of thousands of tons, while the layout scale of top enterprises reaches tens of thousands of tons.

In terms of specific technical routes, solid electrolyte production projects mainly focus on oxides and polymers, while sulfide related production capacity is mostly in the stage of not being started yet.

From the perspective of product structure, the shipment forms include solid electrolyte powder, slurry/in-situ solid-state electrolyte, solid electrolyte composite separator, solid electrolyte membrane, etc.

In situ solid-state electrolyte refers to organic or polymer based solid-state electrolyte systems. Due to the fact that in-situ solidification actually occurs in the injection process of battery cell production, this type of electrolyte is mainly produced, packaged, stored, and sold in the form of electrolyte.

Companies with in-situ solid-state electrolyte production capacity include Blue Solid New Energy (50000 tons/year in Zibo, Shandong) and JuSheng Technology (3000 tons/year in Foshan, Guangdong).

Slurry and powder are the shipping forms of inorganic solid electrolytes such as sulfides and oxides. The powder can be partially used as raw material for slurry further processing or sold externally.

Solid electrolyte powders and slurries in nanoscale form are commonly used for modifying electrode sheets (including mixing, surface coating, and surface coating of electrode particles) or membrane coatings. Compared to common membrane coating materials such as alumina and boehmite, solid electrolyte slurry with ion conductivity as a coating can further improve the conductivity of the membrane.

If the nano powder is directly added, the dispersion is poor and the particles are easy to agglomerate; It is easier to obtain uniformly dispersed nanoparticle systems in the form of slurry, which is widely used in liquid batteries, solid-liquid hybrid batteries, and solid-state batteries in the industry.

On the oxide route, enterprises such as Blue Solid New Energy and Blue Chrome New Materials have planned a production capacity of 10000 tons of solid electrolyte slurry, including 20000 tons/year of Blue Solid in Liyang, Jiangsu and 10000 tons/year of Blue Chrome in Shaoxing, Zhejiang, all of which have passed environmental impact assessment approval.

Among them, Lanyue is a subsidiary and supplier of Weilan New Energy, with a production capacity of 10000 tons of solid electrolyte slurry, evenly distributed between water-based (using pure water as the solvent) and oil-based (using NMP as the solvent). The research and development capability includes an annual output of 500 kilograms of oxide electrolyte powder, mainly used for adjusting and improving the proportion of powdered materials added in the production line, without involving external sales.

The Nanmu Nano thousand ton oxide solid electrolyte production line has also recently completed acceptance, and the company's production capacity plan also includes a capacity of 30 million square meters to Timo.

On the sulfide route, the Zhongke Solid Energy (hundred ton level in Liyang, Jiangsu) and Ruigu New Materials (6000 tons/year in Quzhou, Zhejiang) projects are both in the stage of environmental impact assessment preparation and have not yet started construction.

Solid state material companies with a background in membrane research include Star Source Materials, Jiangsu Sanhe (a joint venture between Weilan New Energy, Tianmu Pioneer, and Enjie), Lanting New Energy, Ruizhi New Energy, and Rouhe New Energy. Their solid electrolyte product forms further include solid electrolyte composite/coated membranes (solid electrolytes or mixed with other materials as coatings), solid electrolyte membranes, etc.

For composite membranes, the industry currently mostly uses 7-9 μ m base film for solid electrolyte coating, with a coating thickness of 1-4 μ m.

For solid-state electrolyte membranes, some believe that the solid-state electrolyte layer, like the separator, plays two major roles in ion conduction and electronic insulation inside the battery cell. They tend to view the solid-state electrolyte membrane as the ultimate form of lithium battery separator iteration (while the composite separator is a transitional form).

Therefore, the development of solid-state electrolyte membrane products can also be measured by referring to the membrane evaluation system, which needs to consider its impact on battery internal resistance, cycling, capacity, and safety performance. Key parameters include thickness, mechanical strength, interface impedance, ion conductivity, thermal stability, chemical stability, etc.

Among them, the oxide and polymer solid electrolyte membranes developed by Xingyuan Material have already met the conditions for mass production preparation. The products have entered the certification or testing stage for multiple customers and have been supplied in small quantities to several well-known top customers.

Lanting New Energy Composite Diaphragm includes various materials such as solid electrolytes, functional polymers, and binders, which can improve ion conductivity (1.1-1.5 mS/cm) and electrochemical window (5.2 V), reduce electrolyte content, and enhance battery cycling performance.

In terms of sulfide solid electrolyte membranes, Hunan Enjie has recently achieved laboratory technology standardization of electrolyte membrane products based on sulfides. Its 8cm * 10cm ultra-thin independent self-supporting electrolyte membrane has a minimum thickness of less than 30 μ m and an ion conductivity of up to 2mS/cm at room temperature.

In theory, midstream material enterprises should develop upstream and downstream simultaneously in the early stages of industrial development, which can not only obtain higher value, but also strive for the discourse power of product definition and profit definition in the solid-state battery industry chain in advance.

In this sense, material companies related to sulfide solid electrolytes objectively need to reduce costs by mastering the mass production process of expensive raw materials (lithium sulfide), while also having the objective advantage of preparing them into film products. The potential for integrated development in the later stage is the highest.

The distance between production capacity and mass production

The challenges of preparing solid-state electrolytes through different routes have been explained in previous articles on advanced lithium-ion batteries. This article mainly supplements the production challenges of its product forms: pulp and film.

As mentioned earlier, there is a greater demand for inorganic solid electrolyte slurry in the market. However, due to gravity and particle interactions, such products are prone to solid electrolyte settling to the bottom within 24 hours, resulting in uneven particle size and unstable solid content in the upper and lower layers. They cannot be used as inventory reserves, and their current use will affect production efficiency; Entering the production process can also make it difficult to accurately determine the feeding value, ultimately affecting battery consistency.

In addition, if the solid content is too low or the solvent content is too high, it will bring about adverse effects such as increased raw material costs (solvents are the ineffective components that ultimately evaporate), increased transportation costs (solvent mass ratio is high), and increased safety risks (some organic solvents are flammable and explosive). Whether the upper limit of solid content can exceed 30% is a reference indicator.

The above challenges hinder the large-scale application of inorganic solid electrolytes. The solution requires both adjusting the material ratio (selection and combination of dispersants, solvents, etc.) and improving key processes such as dispersion and grinding. The goal is to meet the requirements of simple process, stable solid content, good redispersibility, low transportation cost, and no additives at the same time.

A patent suggests that using a grinding method that combines crushing and ultrasonic functions (crushing requires lower particle size of raw materials and has a simple process) instead of high-speed centrifugation and single ultrasonic dispersion can obtain slurries with more stable particle size and solid content. Related enterprises can build technical barriers by selecting grinding equipment, controlling grinding time and line speed, etc.

Currently, there is a company that can achieve a solid content of over 40% based on LATP oxide solid electrolyte, which can support a shelf life of 2 months from the date of production. The settling stability shows that the solid content change after 30 days is less than or equal to 1%, making it a representative of the industry with leading progress.

For solid electrolyte membranes, their preparation methods can also be divided into dry and wet methods.

Dry process film formation can be understood as the use of dry electrode technology to prepare solid electrolytes in the form of membranes. The adhesive fiber method mainly mixes electrolyte materials, binders (mainly PTFE), and lithium salts through high-speed shear dispersion, and then prepares solid electrolyte membranes through processes such as extrusion casting and roll pressing.

During the rolling process, due to the uneven distribution of stress and density caused by rigid molds and unidirectional compression, it is easy to result in low film density (difficult thickness control) and high porosity, ultimately leading to an increase in impedance and promoting lithium dendrite growth in solid-state batteries.

This puts forward higher requirements for the working pressure, rolling accuracy, and uniformity of the rolling equipment, or promotes the iteration of new rolling machines.

Rouhe New Energy has chosen Toyota's leading spraying route and achieved large-scale preparation of organic/inorganic composite solid electrolyte films based on innovation in air flow spinning and suspension spraying technology. The company received a multi million yuan angel round of financing in September this year.

The wet process route is based on electrolyte slurry and supports multiple film-forming methods such as mold support, positive electrode support, and skeleton support. It has high compatibility with existing lithium battery production line equipment and high film-forming efficiency.

According to the information publicly disclosed by Hunan Enjie, its recent breakthrough in the laboratory preparation of sulfide based solid electrolyte membranes uses a wet process. Due to the tendency of sulfides to react with some organic compounds, the selection of solvents, binders, etc. presents greater challenges. In addition, solvent drying and recycling will become challenges in the mass production stage.