Solid state batteries: ushering in a new revolution in battery technology with unlimited application prospects

As a new generation technology in the field of batteries, solid-state batteries have opened up vast application space with innovative design concepts. It completely bids farewell to the traditional liquid electrolyte and separator of liquid batteries, and uses solid electrolyte as the core component. The most significant feature is that ions are conducted through solid materials, forming a "solid solid interface" between the electrode and electrolyte. Its working principle revolves around the migration of lithium ions in solid electrolytes. Both the positive and negative electrodes are made of high-energy density materials such as lithium metal. The specific charging and discharging process is as follows: during discharge, lithium ions will start from the negative electrode and migrate to the positive electrode through the diffusion channel of the solid electrolyte. During this process, solid electrolytes perfectly avoid the problems of volatile and corrosive liquid electrolytes. At the same time, the positive electrode material undergoes an oxidation reaction to release electrons, which then pass through an external circuit to form a current and achieve electrical energy output. During charging, the external power source drives lithium ions to return from the positive electrode to the negative electrode. The negative electrode material undergoes a reduction reaction to receive electrons, completing energy storage. Throughout the process, the solid electrolyte consistently conducts ions stably

1.1 Safety, High Energy, and Long Life - Three Core Advantages Promote the Replacement of Liquid Batteries with Solid State Batteries

Compared to traditional liquid batteries, solid-state batteries have achieved significant improvements in multiple key performance indicators, becoming the core driving force for replacing liquid batteries

The significant upgrade in safety is the most prominent advantage of solid-state batteries. Due to the use of non flammable solid electrolytes, it eliminates the risk of fire from the root, even in a high temperature environment of 800 ℃, it can achieve no fire or explosion, completely solving the safety pain points of traditional batteries

The energy density has significantly increased. At present, the energy density of solid-state batteries has reached 400-500Wh/kg, while traditional liquid batteries can only reach a maximum of 200-300Wh/kg, which is close to the physical limit of lithium-ion batteries. Higher energy density means that solid-state batteries can store more electrical energy with the same volume or weight, providing stronger support for device endurance. In addition, solid-state batteries also have the characteristic of long cycle life, with a cycle count of over 5000 times, far exceeding traditional batteries; Stronger temperature adaptability, with a capacity retention rate of over 80% even in low temperature environments of -30 ℃; The charging speed has also significantly increased - according to the latest technological achievements of CATL, solid-state batteries can be charged to 80% in 15 minutes, with charging efficiency far exceeding traditional liquid power batteries.

According to the different contents of electrolyte liquid, batteries can be divided into four categories: liquid state batteries (with a liquid content of 25wt%), semi-solid state batteries (5-10wt%), quasi solid state batteries (0-5wt%), and all solid state batteries (0wt%). Among them, semi-solid, quasi solid, and all solid state batteries are collectively referred to as solid-state batteries due to their high dependence on liquid electrolytes. These two types of solid-state batteries are currently at different stages of development, demonstrating differentiated industrial rhythms.

Semi solid state batteries: have entered the industrialization stage, and commercialization is approaching

As the first technology route close to landing in solid-state batteries, semi-solid state batteries have completed a long period of technological accumulation and are standing at a key point of commercialization. Its development process can be traced back to the 1970s, and the real technological breakthrough occurred in 2011 when MIT scientist Ye Ming Chiang proposed the concept of "flow battery", using a suspension containing fine particles as the electrode to develop a "slurry electrode" semi-solid battery composed of lithium compound particles mixed with liquid electrolyte, laying an important theoretical and practical foundation for this technology.

The period from 2012 to 2016 was the start-up period for semi-solid state batteries, and technological exploration was mainly limited to the laboratory, focusing on basic principle verification and material performance optimization; From 2017 to 2022, we entered a period of rapid development, with substantial progress made in material research and development. Core indicators such as battery energy density and cycle life continued to improve. At the same time, the industry began to pay close attention to this track, with leading companies gradually laying out research and development and capacity planning; Since 2023, semi-solid state batteries have officially entered the industrialization stage, and some products have entered small-scale trial production or demonstration applications, just one step away from large-scale commercialization.

Solid state batteries: R&D breakthroughs continue to advance, and the dawn of mass production is gradually emerging

All solid state batteries are still in the research and development stage due to their complete elimination of liquid components, making them more technically challenging. However, the mass production process is accelerating. The starting point of its technological exploration can be traced back to earlier times: in early electrochemical research, British scientist Joseph Thomson prospectively proposed the idea of "using solid electrolytes to achieve stable cycling of batteries"; In the mid-19th century, the discovery of solid electrolyte materials such as silver sulfide and lead fluoride provided a key material basis for subsequent research.

In 1992, it became an important turning point in the development of all solid state batteries - the Oak Ridge National Laboratory in the United States developed inorganic solid-state electrolytes (LiPON) and successfully assembled solid-state batteries, verifying the feasibility of the all solid state route. Since then, various solid electrolyte materials have emerged continuously. Driven by market demand in the 21st century, core challenges such as electrolyte stability and electrode electrolyte interface compatibility have gradually been overcome, and the research and development focus has shifted from the laboratory to engineering implementation.

In 1992, it became an important turning point in the development of all solid state batteries - the Oak Ridge National Laboratory in the United States developed inorganic solid-state electrolytes (LiPON) and successfully assembled solid-state batteries, verifying the feasibility of the all solid state route. Since then, various solid electrolyte materials have emerged continuously. Driven by market demand in the 21st century, core challenges such as electrolyte stability and electrode electrolyte interface compatibility have gradually been overcome, and the research and development focus has shifted from the laboratory to engineering implementation.

Currently, countries around the world consider all solid state batteries as the core direction of next-generation battery technology. Multiple domestic and foreign companies have established production schedules and built trial production lines for process validation. With the improvement of material system maturity and the decrease of preparation costs, all solid state batteries are steadily moving from "laboratory samples" to "mass production products", and the commercialization dawn is becoming increasingly clear.

1.2 Positive and negative poles of solid-state batteries

Positive electrode: High energy density system is the development direction

The development goal of solid-state battery cathode materials is clearly aimed at high-energy density systems. The energy density of lithium-ion batteries is largely determined by the energy density of the positive electrode material, so it is necessary to develop high-energy density positive electrode materials to adapt to solid-state batteries. Currently, most semi-solid state batteries use existing ternary materials; In the long run, all solid state batteries are more likely to use high-voltage positive electrode materials such as high nickel, lithium cobalt oxide, and lithium rich manganese based materials.

The stable voltage window of traditional electrolyte is usually between 1.5-4.3V. When the positive voltage exceeds 4.3V, the electrolyte will be oxidized and decomposed, resulting in gas and interface facial mask, which will cause battery capacity degradation. The stable chemical window of solid-state electrolytes can reach above 5V, providing a safe operating environment for high-voltage positive electrode materials, making the application of high-voltage positive electrode materials such as high nickel, lithium cobalt oxide, and lithium rich manganese based in solid-state batteries a reality.

Negative electrode: from graphite negative electrode, silicon-based negative electrode to metal lithium negative electrode

To improve battery energy density, the negative electrode material needs to evolve from the current graphite negative electrode to silicon-based negative electrode. At present, graphite anode is the mainstream choice in the lithium battery market, and its various technologies are quite mature. However, in terms of capacity, it is close to the theoretical capacity of 372mAh/g. Silicon based negative electrodes are regarded as high-quality materials for the new generation of negative electrodes due to their extremely high theoretical specific capacity (3759mAh/g at room temperature and 4200mAh/g at high temperatures of 400-500 ℃), far exceeding graphite negative electrodes.

In addition to its capacity advantage, silicon-based negative electrodes also have a lower deintercalation potential, which can prevent surface lithium deposition during charging. However, there is a major issue with silicon-based negative electrodes, which is significant volume expansion during charging and discharging processes. Therefore, most current silicon-based negative electrodes are mixed with graphite materials, which can not only improve battery capacity but also ensure that other key performance meets standards.

Among various negative electrode materials, metallic lithium has a very high specific capacity (3860mAh/g) and an extremely low electrode potential (-3.04V, relative to the standard hydrogen electrode potential), making it a highly promising core negative electrode system in the field of energy materials. However, in lithium metal batteries, uneven deposition of lithium metal can cause lithium dendrite growth, increase interface side reactions, and exacerbate negative electrode volume expansion, thereby reducing the battery's charge and discharge efficiency and cycle life.

1.3 Application scenario upgrade, from replacing liquid batteries to creating new industries

The downstream application scenarios of solid-state batteries are rich and diverse, which is the driving force for their industrial development. In traditional battery fields such as new energy vehicles, energy storage systems, and consumer electronics, it can meet the needs of long range, multi cycle, and miniaturization; In emerging fields such as low altitude economy and humanoid robots, it can also serve as a viable source of energy and an important foundation for future high-tech industries.

On the one hand, solid-state batteries can solve pain points in traditional fields and promote industrial technological progress. In the field of new energy vehicles, solid-state batteries can solve pain points in terms of range and safety. Their energy density can theoretically reach 500Wh/kg and support vehicle range of over 1000 kilometers; In the field of consumer electronics, it can enable electronic products such as mobile phones to achieve thinner and lighter structures, while improving durability and service life.

On the other hand, solid-state batteries can lead the development of emerging fields and become the cornerstone of future industrial upgrading. EVTOL (electric vertical takeoff and landing aircraft) has a strict requirement for battery energy density, which needs to reach 400Wh/kg or above, and the achievement of this goal must rely on breakthroughs in semi-solid and all solid state battery technology; Solid state batteries are also one of the ideal energy sources for humanoid robots. They not only significantly extend the robot's endurance, but also have non flammable, non corrosive, and non-volatile characteristics, which can maximize the safety of the robot working indoors.

1.4 The three major solid electrolyte systems each have their own advantages and disadvantages, suitable for different scenarios

Solid electrolytes are mainly divided into three systems: polymer electrolytes, oxide electrolytes, and sulfide electrolytes. The advantages and disadvantages of each system determine their different application scenarios and development potential.

The polymer electrolyte system consists of a polymer matrix, lithium salt, and additives. Commonly used polymer matrices such as polyethylene oxide (PEO), polyacrylonitrile (PAN), etc. have good mechanical flexibility, are easy to handle and manufacture, and exhibit excellent mechanical properties and interfacial compatibility. This material can achieve thin film formation and is suitable for various battery structures. However, its low ionic conductivity at room temperature, poor thermal stability under high temperature conditions, easy aging, and narrow electrochemical stability window limit its application in high-performance batteries.

Oxide electrolytes are compounds containing lithium, oxygen, phosphorus, titanium, and other components. According to the electrolyte composition, it can be divided into crystalline and amorphous types. Crystalline oxide electrolytes have low manufacturing costs, can be used to prepare capacity batteries, and are easy to achieve large-scale production, mainly including GARNET (garnet) type, NASICON (fast ion conductor) type, etc. Oxide electrolytes have advantages such as high mechanical strength, strong physical and chemical stability, and good pressure resistance, and can still maintain high lithium-ion conductivity under high temperature conditions. However, its poor interface contact ability, low interface stability, complex preparation process, and high cost severely restrict its commercial application.

Sulfide electrolytes such as Li-Ge-P-S system have extremely high lithium ion conductivity, high mechanical strength, good compatibility with high-capacity sulfur cathode materials, and flexible structure, making them widely applicable. However, sulfide materials have high sensitivity to water and oxygen, potential flammability, complex manufacturing processes, and high costs, which hinder their large-scale commercialization process.

Overall, major domestic and foreign automotive and battery companies are focusing on sulfide solid-state batteries, and the mainstream development path is basically clear. Companies such as CATL, Toyota, and Samsung SDI are all focused on the research and development of sulfide electrolytes. Sulfide electrolytes, with their high ionic conductivity and good interfacial contact performance, are significantly superior to oxide and polymer routes. This material combination can achieve a battery energy density of 350-500Wh/kg, far exceeding the current upper limit of 300Wh/kg for liquid batteries. According to Academician Ouyang Minggao's speech at the 2nd China All Solid State Battery Innovation and Development Summit Forum, the development of all solid state batteries in 2025 will determine the main technological route.

More than 1.5 regulatory policies have been introduced to support the development of the solid-state battery industry

The country has continuously introduced multiple policies to encourage the development and innovation of solid-state batteries. In June 2022, the Ministry of Industry and Information Technology released the "Implementation Plan for Carbon Peak and Carbon Neutrality Supported by Technology (2022-2030)", which for the first time listed solid-state batteries as the development direction of high-efficiency energy storage technology; In January 2023, the Ministry of Industry and Information Technology and six other departments formulated the "Guiding Opinions on Promoting the Development of Energy Electronics Industry", which further refined the requirements for strengthening the research on the standard system of solid-state batteries; In December 2023, the Ministry of Industry and Information Technology proposed the "Implementation Opinions on Strengthening the Integration and Interaction between New Energy Vehicles and the Power Grid", which requires promoting the increase of the cycle life of power batteries to 3000 times or more, and overcoming battery safety prevention and control technologies under high-frequency bidirectional charging and discharging conditions; The "Lithium Battery Industry Standard Conditions (2024 Edition)" released in June 2024 further standardizes the performance requirements for solid-state single-cell battery products.

The "2025 Automotive Standardization Work Points" released in April 2025 propose to promote the development of a subsystem for solid-state battery standards, accelerate the research and development of standards for all solid state batteries, and provide policy guidance for the development of the solid-state battery industry. The "Determination and Testing Methods for All Solid State Batteries" to be released next month will for the first time clarify the definition of "all solid state batteries", requiring ion transfer to be completely achieved through solid electrolytes, forming a strict technical boundary with mixed solid-liquid electrolyte batteries, and promoting the development of the solid-state battery industry towards standardization.

1.6 Domestic and foreign manufacturers advance together, aiming for mass production by 2027

The all solid state batteries of overseas enterprises are expected to achieve mass production after 2026. Japanese, Korean, European and American companies have made early research layouts in this field and have a large R&D scale. From the perspective of technological routes, Japanese and Korean companies mainly focus on sulfide technology routes, while European and American companies have more diverse technological routes.

From the perspective of technology roadmap and planning, domestic enterprises focus on the high nickel ternary+carbon silicon negative electrode+sulfide route, and some enterprises also adopt diversified electrolyte layouts. The energy density of all solid state batteries is around 400Wh/kg, and it is expected to achieve mass production around 2027.

Process innovation drives manufacturing equipment upgrade

2.1. Changes in the production process of solid-state batteries

Traditional liquid battery production process

The traditional production process of lithium batteries mainly consists of three stages: the front stage, the middle stage, and the back stage. The front stage involves the manufacturing of electrode plates, which are often prepared using wet methods for positive and negative electrode plates. Uniformly coat the slurry of mixed conductive agent and adhesive on the positive and negative electrode sheets, then dry and combine with the current collector roller, and then cut the wide electrode sheet into narrow strips that meet the size of the battery cell through a slitting device to form the electrode sheet. The intermediate process focuses on battery cell assembly and requires liquid injection, welding, and sealing. The positive and negative electrode plates are combined with the diaphragm to form the main body of the battery cell through winding or laminating process. Then, the battery cell is placed in a metal or aluminum-plastic film shell and dried to remove residual moisture. After that, electrolyte is injected and finally sealed by welding. The subsequent process focuses on battery performance testing, with a particular emphasis on chemical conversion and capacity division. The process includes cleaning the residual electrolyte on the surface of the battery cell, drying and storing it to stabilize the electrolyte state, and screening the appearance, size, and electrical performance of the battery through testing equipment. Finally, the battery is activated through charging and discharging and its actual capacity is tested.

Solid state battery production process

The front-end process of solid-state batteries can adopt dry or wet methods. The wet process is basically the same as the traditional liquid pre-treatment process; Dry electrode is an emerging technology in recent years, which has the advantages of low cost, low energy consumption, and high performance. Dry electrode is a mixture of active material, conductive agent, and binder in a dry state, which is formed by dry coating and then compounded onto the surface of the current collector by roller pressing; Electrolyte membranes can also be prepared by dry/wet methods. Dry methods can form membranes through three methods: roll pressing, melt extrusion, and electrostatic spraying. In China, roll pressing is mainly used, followed by strip shaping. Cancel the diaphragm and liquid injection process in the middle section, and add rubber frame printing and isostatic pressing. After the shaping is completed by rolling and slitting, a rubber frame printing process is added before laminating. The resin sound is brushed to the edge of the electrode to form a circular frame, which plays a supporting and insulating role under pressure. Then, the electrode sheet and electrolyte layer are stacked by laminating. Before entering the later stage, an isostatic pressing process is usually added to enhance the density of the electrolyte and electrode plate, and optimize the interface contact; In semi-solid state, the diaphragm structure still needs to be retained and the injection volume is less, only infiltration is required. The subsequent process remains unchanged, and high-pressure chemical transformation is used instead. Part of the all solid state batteries apply high voltage to the cells through high-pressure forming equipment. The conventional battery requires a restraining pressure of 3-10t, while the solid-state battery generally requires a restraining pressure of 60-80t (10Mpa pressure/individual cell); Some will use pre lithiation technology.

Compared to traditional liquid lithium battery production, the manufacturing process changes of solid-state batteries mainly focus on the front and middle stages. Due to the tendency of solid-state battery materials to react with other substances such as water and air, the overall sealing and production assembly processes have been improved to varying degrees.

2.2. Previous steps: Dry electrode assisted cost reduction, innovative electrolyte film formation process

Previous step: The equipment for wet film production has little difference from traditional liquid batteries; If dry process technology is introduced, corresponding new dry electrodes, coating equipment, etc. need to be added. The core of dry process technology lies in film formation technology, which is regarded as the main trend of the future. Dry process is not only an effective means to reduce battery costs, but also suitable for the wafer production process of all solid state batteries. Compared with wet electrode process, it has higher load capacity and is less prone to cracking, making it more suitable for the characteristics of sulfide electrolytes.

Dry electrode equipment

The core advantage of dry electrodes lies in their low cost. From the perspective of the process flow of electrode preparation by dry method, compared with the traditional lithium-ion battery process, it greatly shortens the process, does not require the use of solvents and related evaporation, recovery and drying equipment, and significantly reduces energy consumption. Therefore, it has positive significance for reducing costs and increasing efficiency in battery manufacturing. According to American dry electrode equipment supplier AM Batteries, adopting their dry process equipment can save 40% of capital expenditures and 20% of operating expenses in electrode manufacturing, while also reducing energy consumption and carbon emissions by 40%. For silicon-based negative electrodes, dry electrode technology is also considered as an effective means to solve the bottleneck of their cycling and rate performance.

Dry electrode equipment is used to prepare positive and negative electrodes for solid-state batteries, replacing traditional wet coating processes. The dry process is a must-have for sulfide solid-state batteries. Due to the high sensitivity of sulfide solid-state electrolytes to air and moisture, the dry process has become a necessary condition for their mass production. At present, there are two development strategies for the preparation of dry electrodes: spraying and rolling.

Coating plant

The coating equipment uniformly coats the solid electrolyte on the surface of the electrode to form an ion conductive layer. The dry electrode coating machine adopts a solvent-free process to achieve high-energy density electrode preparation, ensuring the uniformity and consistency of electrode materials. The leading intelligent all solid state whole line solution covers the preparation of all solid state electrodes. In 2025, the solid-state dry electrode coating equipment customized by the company for top battery enterprise customers in South Korea has been successfully shipped to the customer's site. Yinghe Technology has launched the third generation of integrated equipment for dry mixing fiberization and dry film-forming processes.

Roller press equipment

Roll pressing is a key process in the film-forming process, and the requirements for dry process equipment have been raised. The core goal of roll pressing is to reduce the thickness of the film to meet the requirements of lamination or continuous winding, while increasing the tension and strength of the film to achieve industrial production. It is a key step to ensure uniform and consistent electrode thickness. The dry electrode process places higher demands on the performance of rolling equipment, especially in terms of working pressure, rolling accuracy, and uniformity. Due to the lack of wetting effect of liquid solvents in dry electrodes, the binding force between particles is weak. Therefore, greater external pressure is required during the rolling process to achieve tight compaction of particles. In addition, the precision of rolling and the uniformity of film thickness are crucial for the yield, energy density, and stability of battery performance of electrodes. The film-forming performance and production efficiency of the roller press are the core factors determining whether the dry process can achieve mass production. The speed and pressure of dry rolling directly affect the compaction density of the electrode. The industry-leading compaction density target is negative electrode compaction>1.6g/cm ³, ternary positive electrode compaction>3.5g/cm ³, and iron lithium positive electrode compaction>2.5g/cm ³. In terms of production efficiency, the speed and width of film formation are key factors. Qingyan Nako proposed that the negative electrode film formation speed should reach>80 meters/minute, the positive electrode film formation speed should be>50 meters/minute, the width should be>1000 millimeters, and multiple (6) manufacturing should be achieved in order to approach the production efficiency of wet electrodes (double-sided wet process speed can reach 160m/min) and meet the needs of large-scale production.

2.3. Intermediate stage: lamination+polar film frame printing+isostatic pressing technology

Intermediate stage: The lamination process is expected to become mainstream in the assembly process of solid-state batteries, and the precision requirements for supporting equipment will be greatly improved. It is necessary to replace traditional lamination and winding machinery with non diaphragm lamination machines; Add a rubber frame printing machine for structural stability; Newly added isostatic pressing equipment is used to enhance the contact effect between the interfaces of the components inside the battery cell. The densification ability of isostatic pressing materials can be transferred to solid-state batteries, improving the interface composite problem between porosity and electrodes and electrolytes.

Stacker: All solid state mainstream assembly process, with significantly improved precision requirements

Stacking process is the mainstream assembly solution for all solid state batteries. All solid state batteries require a tight fit between the solid electrolyte layer and the electrode layer in the absence of a liquid medium. Inorganic electrolytes, due to their poor toughness and ductility, are not suitable for the common winding process in traditional liquid state batteries. The stacking process can integrate various components of the battery through simple stacking of the positive electrode, solid electrolyte membrane, and negative electrode. From the perspectives of process maturity, cost, efficiency, etc., it is the most suitable assembly process for all solid state batteries. Currently, leading companies such as Toyota and Quantum Scape are promoting mass production of all solid state batteries with laminated technology as their core. Therefore, in the intermediate equipment of solid-state batteries, the laminating machine is expected to replace the winding machine and occupy the dominant position.

Solid state batteries impose strict requirements on laminated devices. On the one hand, the stacking pressure needs to be precisely controlled to ensure the adhesion between adjacent electrode sheets and avoid microcracks in the solid electrolyte, which can directly cause battery short circuits; On the other hand, during the lamination process, there is a tendency for relative displacement between the solid electrolyte membrane and the electrode membrane due to lateral forces, and during the lamination process, the positive and negative electrode edges are prone to bending and contact due to lamination, resulting in short circuits. Therefore, solid-state battery lamination equipment needs to have higher accuracy and stability.

Rubber frame overlay technology: improves the adhesion of solid-state battery pole pieces and avoids internal short circuit problems

In the field of solid-state battery manufacturing, there are still immature production processes. Specifically, a prominent issue in the process of compounding the cut electrode sheet material roll (single electrode sheet) with other electrode sheets to prepare solid-state battery cells is the difficulty in achieving high-precision bonding between adjacent electrode sheets. This poor bonding condition will ultimately cause damage to the quality of solid-state battery cells. In order to solve the key adhesion problem that affects the performance of battery cells, Liyuanheng has proposed a solid-state battery pole piece adhesive frame covering method in its publicly available patent. This patented technology can significantly enhance the adhesion between adjacent electrode pieces during the composite process, thereby ensuring the quality level of the produced solid-state battery cells.

Isostatic Pressure Equipment: Potential Solutions for Densification and Interface Problems

The development of solid-state battery devices focuses on high-voltage densification and electrode/electrolyte composites. In traditional liquid batteries, electrode pores form continuous ion transport channels through the infiltration of liquid electrolyte. However, the rigid characteristics of solid electrolyte in solid-state batteries make it difficult to fully fill the high pore structure. Therefore, the porosity in solid-state batteries needs to be controlled below 5% to ensure rapid conduction of lithium ions. Meanwhile, the physical contact quality of the electrode/electrolyte interface in solid-state batteries is much inferior to that in liquid systems, and interface impedance becomes the main limiting factor for performance. In order to solve the above problems, high-voltage densification process and electrolyte electrode composite process have become key processes in solid-state battery manufacturing. The focus of equipment development is on enhancing the tight composite of electrolyte/electrode and electrode densification, and improving interface uniformity. Isostatic pressure is an advanced material densification technology. Isostatic pressure technology is to place the powder of the workpiece in a high-pressure container, and use the incompressible and uniform pressure transmission properties of liquid or gas media to uniformly apply pressure to the workpiece from all directions, so that the powder is subjected to consistent pressure in all directions, thereby achieving high-density and high uniformity blank forming. In this process, the characteristics of the material are not related to size, shape, or sampling direction, but to the forming temperature and pressure of the material. Isostatic pressure technology itself is a mature technology that has been widely applied in fields such as ceramics and powder metallurgy. In solid-state batteries, traditional hot pressing and rolling schemes provide limited and uneven pressure, making it difficult to ensure consistent requirements for dense stacking, which in turn affects battery performance. And isostatic pressing technology can effectively eliminate the gaps inside the battery cell, improve the contact effect between the interfaces of the components inside the battery cell, thereby enhancing conductivity, increasing energy density, and reducing volume changes during operation.

According to the temperature during molding and solidification, isostatic presses are mainly divided into three categories: cold isostatic presses, warm isostatic presses, and hot isostatic presses. Cold isostatic pressing is currently the most commonly used isostatic pressing technology. Cold isostatic press operates at room temperature without the need for heating devices. It generally consists of a pressure station, cooling system, cylinder body (steel cylinder), frame, upper plug (top cover), control cabinet, etc. Usually, liquid (such as water, oil, or a mixture of ethylene glycol) is used as the pressure medium, and rubber and plastic are used as the packaging mold materials. Compared with hot isostatic pressing, higher pressure (100-630MPa) can be applied to the powder, which can provide a "green body" with sufficient strength for the next sintering, calcination, or hot isostatic pressing processes, and can be finely machined before sintering, significantly reducing the amount of processed products after sintering. In the field of solid-state battery applications, some researchers have used cold isostatic pressing technology to prepare ultra-thin flexible composite solid electrolyte membranes based on garnet, while others have used cold isostatic pressing high-temperature solid-phase method to prepare Li6.3Al0.15La3Zr1.75Ta0.25O12 solid electrolyte.

There are certain difficulties in regulating isothermal pressure, and overseas enterprises have made some arrangements. The isothermal static press uses liquid or gas as the working medium, and gradually pressurizes the processed object through a pressurization system in a closed container, so that the object is subjected to equal pressure on all surfaces, and completes the forming process under the limitation of the mold. Compared with cold isostatic presses, warm isostatic presses heat the medium or workpiece during operation to achieve specific temperature conditions, thereby promoting material densification, diffusion, or phase transformation processes. The working temperature generally does not exceed 500 ℃, and the pressure range can reach around 300MPa. However, the temperature and pressure of isostatic pressing have a significant impact on the product, making it difficult to achieve precise temperature control. At the same time, the temperature uniformity inside the working cylinder is also difficult to ensure. According to reports from Lithium Battery China and China Craft News Network, Samsung SDI used a warm isostatic press machine with water pressure and roll pressing technology in its solid-state battery production line testing. The QIB180 laboratory battery press machine invested by Swedish high-voltage equipment professional supplier Quintus Technologies in its battery application center is also a warm isostatic press machine.

Hot isostatic pressing has good applicability but high cost. A hot isostatic press requires the use of expensive inert gases such as argon, nitrogen, helium, or other mixed gases as pressure media to apply isotropic pressure (100-200MPa) to the product (powder or already formed sample) while using a heating furnace to apply a high temperature of 1000-2200 ℃ to the product, in order to sinter or densify the product. In the production of solid-state batteries, a hot isostatic press can ensure that the battery components are subjected to uniform pressure under high pressure and high temperature, thereby producing highly uniform materials and improving the overall performance of the battery; Strong controllability, by adjusting parameters such as pressure and temperature, the densification and interface contact process of solid-state batteries can be precisely controlled to meet the needs of different application scenarios; Widely applicable, the hot isostatic press is suitable for the production of solid-state batteries with different materials and structures, and has a wide range of applicability.

2.4. Subsequent stage: Addition of high-voltage chemical equipment

Post process: Solid state batteries require high pressure conversion, with a conversion pressure of 60-80 tons, resulting in a demand for high-voltage conversion and capacity separation equipment. Low voltage conversion is replaced by high-voltage conversion, and a high-voltage conversion and capacity separation machine is required to activate the performance of the solid state battery. The core reason why solid-state batteries require high-voltage transformation is their unique solid solid interface characteristics and ion conduction mechanism, which are fundamentally different from the transformation process of traditional liquid batteries. Solving the problem of solid solid interface contact: The solid electrolyte and electrode are in rigid contact, with microscopic gaps and poor contact. High voltage (usually 60-100MPa) compression is necessary to eliminate the interface gaps, increase the effective contact area, and promote the physical/chemical bonding between the solid electrolyte and the electrode. Activate ion conduction channel: Solid state electrolytes have low ion conductivity and require high voltage conversion to force lithium ions to penetrate the solid solid interface barrier, forming an ion conduction network at the interface and reducing interface impedance.

Drive downstream industry upgrading, eVTOL+humanoid robots open up incremental space

3.1. With the improvement of research and development capabilities, all solid state batteries will usher in a golden period of development

As of 2023, the top 5 countries and regions in terms of global solid-state battery patent applications are Japan, China, the United States, South Korea, and Europe. Japan ranks first in the world in terms of patent application volume, and has started early and accumulated rich research in the field of batteries. Japan is building a joint research and development system between car companies and battery factories, with government funding support exceeding 200 billion yen, striving to achieve commercialization of all solid state batteries by 2030. China ranks second in the world in terms of patent application volume, and since 2016, its patent application volume has jumped to the top of the world.

Since 2022, significant progress has been made in the research and industrialization of solid-state batteries, but they still face unresolved issues such as ion conductivity, solid solid interface, and cycling performance. It is expected that their industrialization will take place around 2030. According to data from the Forward looking Industry Research Institute, the market size of China's solid-state battery industry has reached 2 billion yuan in 2024, is expected to reach 8.6 billion yuan in 2025, and will further grow to 20.5 billion yuan in 2026. By 2030, the market size of China's solid-state battery industry will reach 116.3 billion yuan.

According to EV Tank data, the shipment volume of China's solid-state battery industry has reached 1GWh in 2023. It is expected that the shipment volume of solid-state batteries will reach 3.3GWh in 2024 and further increase to 11.1GWh in 2025. After the mass production of solid-state batteries is achieved, the shipment volume will further grow rapidly and enter a period of rapid growth. It is expected that the shipment volume will reach 614.1GWh in 2030. According to data from the China Academy of Commerce Industry Research, the current penetration rate of solid-state batteries is relatively low, with a penetration rate of less than 0.1% by 2023. With the development and mass production of solid-state batteries, the penetration rate is rapidly increasing, and it is expected that the penetration rate of solid-state batteries can reach 10% by 2030.

3.2. Solid state batteries perfectly match eVTOL

The eVTOL aircraft is mainly composed of body subsystems, navigation communication and flight control subsystems, power subsystems, and energy subsystems. The power system of eVTOL adopts Distributed Electric Propulsion (DEP), which enhances the safety redundancy of the power system, effectively reduces local noise (by about 10% to 15%), and maximizes the energy efficiency of the power system. For eVTOL aircraft, there are two key performance indicators of the battery that are closely related to the overall performance of eVTOL: energy density and power density. Comparatively speaking, battery power density (the discharge power per unit mass of battery) is a more critical performance indicator for eVTOL aircraft, as it determines whether eVTOL can safely take off and land. On the other hand, the energy density (the amount of electrical energy released by the average mass of the battery) roughly determines the range of eVTOL, and currently 300Wh/Kg can guarantee a range of 200-300 kilometers.

As the core component of eVTOL technology, the performance and safety of batteries directly determine the performance and market acceptance of eVTOL aircraft. In terms of energy density, eVTOL requires 10-15 times more power for vertical takeoff than ground travel, with a commercial threshold of up to 400Wh/kg, and future energy density requirements will reach 1000Wh/kg, far higher than the energy density of current vehicle power batteries; In terms of charging and discharging rates, the flight of eVTOL requires stages such as takeoff, cruise, and hover, among which the instantaneous charging and discharging rate of the battery is required to be above 5C during the takeoff and landing stage; In terms of safety performance and cycle life, eVTOL also has extremely strict requirements for batteries.

Guided by policies, eVTOL will become a driving force for the commercialization of solid-state batteries. On March 27, 2024, the Ministry of Industry and Information Technology and four other departments issued the "Implementation Plan for Innovative Applications of General Aviation Equipment (2024-2030)", which clearly proposed to promote the mass production of 400Wh/kg aviation lithium battery products and achieve the application verification of 500Wh/kg aviation lithium battery products. Given the energy density limitations of traditional liquid lithium batteries and the high performance requirements of eVTOL, solid-state batteries are expected to be the first to gain popularity in the eVTOL market.

In 2025, with the expansion and implementation of low altitude scenario applications, related battery companies will continue to receive orders and financing, and domestic battery companies will intensify their efforts in the low altitude economic track, including CATL, EVE Energy, Guoxuan High Tech, Changhong Energy, Zhuhai Guanyu, Funeng Technology, Xinwangda, Ganfeng Lithium, etc.

3.3. Solid State Battery: The Key Driver for Humanoid Robots to Breakthrough the 'Last Mile'

The urgent development of humanoid robots is essentially a reflection of human society's transition to a critical state of "human-machine symbiosis" civilization. As the labor gap continues to widen, AI technology becomes increasingly mature, breakthroughs are made in the energy revolution, and geopolitical competition becomes more intense, multiple factors overlap and resonate with each other, and the development of humanoid robots is no longer a multiple-choice question of "whether it is necessary", but a survival proposition of "how fast can it be achieved".

Currently, humanoid robots are facing three specific energy challenges. Firstly, the poor battery life of lithium batteries leads to frequent interruptions in operations, such as the Tesla Optimus only supporting a few hours of basic tasks; Secondly, the high proportion of battery volume and weight limits the breakthrough of robots in flexibility and lightweight design; Thirdly, in extreme temperature environments, battery performance deteriorates and there is a potential risk of thermal runaway, which hinders the application of humanoid robots in industrial, rescue, and other scenarios. And these shortcomings can perfectly complement the high energy density, fast charging and discharging ability, compact structure, and thermal stability of solid-state batteries.

When solid-state batteries are deeply integrated with humanoid robots, this' energy revolution 'will redefine the boundaries of robot capabilities. Batteries with higher energy density can support robots to perform autonomous operations around the clock, and ultra fast charging technology can make robots "charge and use" like humans. Its inherent safety features can also broaden the application range of robots in sensitive scenarios such as homes and medical care.

In 2025, with the continuous iteration of technology and the continuous expansion of application scenarios, solid-state batteries are expected to become the preferred energy system for humanoid robots in the future, mainly reflected in the following four aspects. Firstly, the energy density of traditional lithium batteries has approached the theoretical limit (about 300Wh/kg), while solid-state batteries can theoretically increase their energy density to over 500Wh/kg by replacing liquid electrolytes with solid electrolytes, providing more durable dynamic support for high-intensity operations of humanoid robots. Secondly, humanoid robots may encounter extreme environments such as collisions and high temperatures in industrial inspections, home services, and other scenarios. Liquid lithium batteries have the risk of leakage, short circuits, and even explosions, while solid-state electrolytes in solid-state batteries have higher thermal stability and can maintain structural integrity even under external impact. Thirdly, solid-state batteries are smaller in size and lighter in weight, which can significantly optimize the mechanical design of humanoid robots. For example, the iterative version of Tesla Optimus, which uses solid-state batteries, has reduced its overall weight by 15%, freeing up space for improving joint flexibility and sensor density. Fourthly, humanoid robots need to integrate more sensors and AI modules, which significantly increases energy consumption pressure. The high energy density and low self discharge rate of solid-state batteries can provide energy security for complex algorithms and multimodal interactions.

Tailored intelligent robots are expected to become an important driving force for the growth of lithium battery demand, while promoting the iterative upgrading of high energy density and high safety battery technology, reshaping the segmented market pattern.

According to the data of Gaogong Robot Industry Research Institute, it is estimated that the sales volume of humanoid robots in China will reach 7300 sets in 2025, and the market scale is expected to be close to 2.4 billion yuan; By 2030, sales will reach 162500 units and the market size will exceed 25 billion yuan; It is expected that by 2031, humanoid robots will enter a period of rapid growth; By 2035, the sales volume is expected to reach about 2 million sets, and the market size of Chinese humanoid robots is expected to be close to 140 billion yuan.

Summary:

From a technical perspective, solid-state batteries replace traditional liquid electrolytes with solid electrolytes, fundamentally solving the bottleneck of liquid batteries in core performance such as safety and energy density. Its high safety (no fire at 800 ℃), high energy density (currently 400-500Wh/kg, theoretically can exceed 500Wh/kg), long cycle life (over 5000 times), and wide temperature adaptability have become the core direction of the next generation battery technology. From the perspective of development stage, semi-solid state batteries have entered industrialization, while all solid state batteries are still in the research and development stage. However, with the breakthrough of electrolyte routes such as sulfides, the landing of trial production lines by domestic and foreign enterprises, and the improvement of policy standards, the dawn of mass production is becoming increasingly clear. It is expected to achieve large-scale production around 2027.

At the industrial application level, solid-state batteries are upgrading from "replacing liquid batteries" to "creating new demand". In the field of new energy vehicles, it will drive the range to exceed 1000 kilometers and solve safety pain points; In the field of consumer electronics, helping devices evolve towards slimness and long battery life. More importantly, it provides an "energy key" for emerging fields such as eVTOL and humanoid robots - the energy density of over 400Wh/kg required for eVTOL and the dual requirements of safety and endurance for humanoid robots both rely on the maturity of solid-state battery technology. According to estimates, the size of China's solid-state battery market will reach 116.3 billion yuan by 2030, and the explosion of downstream scenarios such as humanoid robots will open up incremental space.

From the perspective of the industrial chain, solid-state batteries not only drive the innovation of their own materials (high nickel positive electrode, silicon-based negative electrode, sulfide electrolyte) and processes (dry electrode, isostatic pressing, high-voltage conversion), but also reshape the equipment market pattern. With the clear technological roadmap, improved policy norms, and the simultaneous progress of domestic and foreign manufacturers, solid-state batteries are accelerating from a "technological concept" to an "industrial reality". In the future, they will not only rewrite the competitive landscape of the battery industry, but also become the core cornerstone supporting the integrated development of new energy and high-tech industries.