Lithium ion batteries have the advantages of high energy, long life, high cost performance and less pollution, and are widely used in new energy vehicles, consumer electronics, energy storage and other fields. Lithium ion batteries are mainly divided into liquid and solid batteries. Liquid lithium batteries include liquid batteries, gel electrolyte batteries, and solid lithium batteries include semi-solid, quasi solid, and all solid batteries. Among them, semi-solid lithium batteries (with a solid electrolyte content of 90-95% in the cell) have achieved safety, energy density, and economy by reducing the liquid electrolyte content and increasing the solid electrolyte coating, and are now ready for mass production; The proportion of solid electrolyte in the battery cells of quasi solid state lithium batteries is further increased (the solid electrolyte content is usually above 95%), which is the stage of transition from semi-solid lithium batteries to all solid batteries; All solid-state lithium battery cells are composed entirely of solid-state electrodes and solid-state electrolyte materials.

Overall, at present, solid-state lithium batteries contain some liquid electrolytes, and the technological path is gradually developing from solid-liquid hybrid batteries to all solid-state batteries. Compared with mainstream liquid lithium batteries, solid-state lithium batteries have two major advantages, making them mainstream. On the one hand, most solid electrolyte materials have non combustible properties (such as oxide solid electrolytes with thermal stability up to 1000 degrees), are non corrosive, non volatile, and do not have leakage problems, thus achieving high safety; On the other hand, solid-state batteries can be matched with high-energy positive electrodes and metal lithium negative electrodes, significantly improving the theoretical energy density.

1. Development history:

The development history of solid-state lithium-ion batteries can be mainly divided into the embryonic stage (1972-1999), the initial development stage (2000-2016), and the rapid development stage (2017 present). Since the use of Li1 as the electrolyte in solid-state lithium-ion batteries in 1972, solid-state electrolytes with high ion conductivity have been introduced, and various oxide, sulfide, and polymer solid-state electrolyte materials have been proposed successively; After 2000, the research and experimental development of solid-state batteries gradually accelerated, and multiple companies around the world announced the launch of research and development plans for solid-state batteries; The proposal of glassy dielectric technology in 2017 marked the completion of the first stage of research and development for solid-state batteries. In 2022, Weilan New Energy launched the construction of a 20GWh solid-state battery production line project, marking a further acceleration of China's solid-state battery industrialization process. Looking into the future, relevant manufacturers will focus on overcoming the low ion conductivity of solid electrolytes, the contact stability of solid-solid interfaces, the influence of space charge layers on ion transport, the impact of volume expansion during charging and discharging on battery safety performance, difficulties in the application of metal lithium negative electrodes, and high costs.

2. Development environment

Policy dividends continue to be released, promoting the prosperous development of the solid-state lithium battery market

As early as 1987, solid-state lithium batteries were included in the major theme of the "863" plan by the Chinese Ministry of Science and Technology. In recent years, the national level has intensively introduced policies around the top-level design of solid-state lithium batteries, encouraging and regulating the healthy and orderly development of the industry. The "Made in China 2025" and "Action Plan for Promoting the Development of the Automotive Power Battery Industry" released in 2015 and 2017 both proposed the establishment and improvement of the next generation lithium-ion power battery and new system power battery industry chains, including lithium-ion batteries with rich lithium oxide cathode materials/silicon-based alloy systems, all solid lithium-ion batteries, metal air batteries, lithium sulfur batteries, etc., to promote the capacity density of solid-state batteries to reach 500Wh/kg; Since 2020, the State Council has released the "Development Plan for the New Energy Vehicle Industry (2021-2035)", which for the first time includes solid-state batteries as a key development target in the industry and proposes to accelerate research and industrialization processes; Since the second half of 2022, solid-state batteries have been jointly recognized by multiple departments such as the Ministry of Industry and Information Technology, the Ministry of Science and Technology, and the Energy Bureau twice, proposing to accelerate the research and development of solid-state battery energy storage technology, strengthen the research of solid-state battery standard system, and strengthen support and guidance in application fields, laying the foundation for the positioning of solid-state batteries in the modern industry.

The booming new energy vehicle industry is driving the rapid expansion of demand in the solid-state battery industry

According to EV Sales data, global sales of new energy vehicles increased from 125000 units to 10.522 million units from 2012 to 2022, with a CAGR of 55.4% and penetration rate increasing from 0.2% to 13%. The strong growth in terminal sales has driven a rapid increase in the global installed capacity of power batteries, with the global installed capacity rising from 15GWh in 2015 to 517.9GWh in 2022. With the rapid development of the new energy vehicle industry, higher requirements have been put forward for the safety and energy density of power batteries. As the performance of liquid lithium batteries gradually reaches its upper limit, the research and application of solid-state lithium batteries with higher energy density have reached a consensus in the industry.

Traditional enterprises and emerging enterprises compete on the same stage to accelerate the research and development process of solid-state batteries

With continuous support from the national key research and development plan, China's solid-state battery research and development technology has made rapid progress. Not only have companies such as Weilan New Energy and Qingtao Energy emerged that focus on the research and industrialization of solid-state batteries as their main business, but traditional lithium-ion battery companies such as Ganfeng Lithium and Ningde Times have also entered the solid-state battery related business. Each enterprise continues to increase investment in solid-state battery research. At the same time, new energy vehicle companies such as NIO have begun to introduce solid-state battery models in the product side, promoting the acceleration of the industrialization process of solid-state batteries. According to the data of the China National Intellectual Property Administration, China's patent applications for solid state batteries have kept rising, increasing from 10 patent applications in 2013 to 305 patent applications in 2021, with a compound annual growth rate of 53.3%.

3. Development status

Industry chain structure: composed of three parts: upstream raw materials and equipment, midstream cell material manufacturing and solid-state battery manufacturing, and downstream application market

The upstream of the industrial chain consists of raw materials and equipment.

The main raw materials for solid-state batteries include lithium, cobalt, nickel, manganese, phosphorus, sulfur, etc. The reserves and distribution of these minerals have a significant impact on the cost and supply of solid-state batteries. China is the world's largest consumer of lithium resources, but its lithium resource reserves are relatively small, mainly relying on imports. At the same time, there is also a risk of insufficient supply of resources such as cobalt and nickel; The production equipment for solid-state batteries mainly includes mixers, laminating machines, coating machines, liquid injection machines, slitting machines, mixing equipment, and coiling machines. Compared with liquid lithium battery production equipment, such production equipment requires higher accuracy and stability. Currently, it has been basically localized, and the industry gross profit margin is between 30% and 35%.

The midstream of the industrial chain includes two major links: battery cell materials and solid-state battery manufacturing.

(1) The battery cell materials of solid-state/semi-solid batteries can partially use the existing liquid lithium battery material system, but it will cause certain impacts in terms of negative electrode materials and separators. From the perspective of positive electrode materials, semi-solid batteries can be matched with the positive electrode systems used in existing liquid lithium batteries (such as lithium iron phosphate, ternary, lithium manganese oxide, lithium cobalt oxide, etc.). All solid electrolytes can be compatible with the current positive electrode material system and can also match high voltage positive electrode materials (such as lithium rich manganese based, etc.); From the perspective of negative electrode materials, semi-solid batteries can be matched with the negative electrode systems used in existing liquid lithium batteries (such as graphite, lithium titanate, silicon carbon systems, etc.), but there are still many technical barriers to the nanoscale coating of solid electrolytes. However, in all solid state batteries, due to the absence of liquid electrolytes, metallic lithium is expected to become the mainstream negative electrode material; From the perspective of separator materials, semi-solid batteries can also use the current separator material system, and solid-state electrolytes can be used to coat the separator, while solid-state electrolytes may eliminate the separator.

(2) Solid state battery manufacturing includes four systems: polymer, oxide, sulfide, and halide. Although halide electrolytes have advantages such as low cost, environmental friendliness, and positive electrode stability, their ion conductivity, positive electrode material compatibility, and air/humid environment stability still need further improvement. Therefore, there are few participants in this route, and the market mainly focuses on the polymer, oxide, and sulfide routes.

Oxide system: Using oxides as the main solid electrolytes, including garnet type electrolytes, perovskite type electrolytes, NASICON type electrolytes, and LIPON type electrolytes, it has strong thermal stability, electrochemical stability, good mechanical properties, and high ion conductivity and low research and development costs. At present, the research focus is on improving room temperature ion conductivity and its compatibility with electrodes. At present, many leading solid-state battery companies in China, such as Beijing Weilan, Jiangsu Qingtao, and Taiwan Huineng, mainly adopt the solid-liquid mixing technology route based on oxide materials.

Sulfide system: Sulfide electrolytes such as lithium sulfide and phosphorus sulfide need to be synthesized under high pressure, which is difficult and costly to prepare. However, their high conductivity and excellent mechanical properties make them a hot research topic at present. This includes improving electrolyte stability, reducing production costs, and utilizing element doping to enhance the synergistic effect of various elements. At present, the main participating enterprises and institutions in the sulfide system are mainly concentrated in Japan, South Korea, and the United States, with domestic enterprises represented by CATL.

Polymer system: Due to its proximity to traditional liquid lithium batteries, polymer systems can be produced through modification of existing equipment, which has advantages such as simple process and low cost. However, due to low ion conductivity, energy density, and poor compatibility of high voltage positive and negative electrode materials, their application fields are limited. At present, the main participating enterprises and institutions in the polymer system are mainly concentrated in European and American countries.

The downstream application fields of solid-state batteries mainly include consumer electronics, energy storage, and new energy vehicles.

(1) Consumer electronics: Solid state batteries have become the first to be used as high safety portable power sources in consumer electronics products such as wearable devices and drones, which have high safety requirements and low cost sensitivity. For example, Huineng Technology has built a 40MWh semi-solid battery production line, and Weilan New Energy has built a 200MWh semi-solid production line for use in consumer electronics such as drones.

(2) Energy storage: Solid state batteries meet the requirements of high safety and high energy density for energy storage batteries, but their cycle life and cost-effectiveness are limited. Currently, their application is mainly focused on demonstration energy storage projects, which require technological breakthroughs and cost reduction before they can be widely commercialized.

(3) New energy vehicles: As the main downstream application market, solid-state batteries provide high safety and strong endurance for new energy vehicles, and are conducive to building high-voltage platforms, more efficient CTC technology, and thermal management systems. At present, China's top car companies are jointly promoting the industrialization process of solid-state batteries through self research or close cooperation with battery companies.

4. Development Trends and Prospects

The development of solid-state batteries is hindered and has a long way to go, and the technical and cost challenges urgently need to be overcome

Overall, the solid-state battery industry in China is still in its early stages. Solid electrolyte materials still face problems such as low ion conductivity, high interface impedance between solid electrolytes and electrodes, poor interface compatibility, and easy interface separation due to material volume expansion and contraction during charging and discharging, which directly affects the low-temperature performance, fast charging performance, energy density, and power density of batteries, restricting further development of the industry. The industry generally believes that the large-scale production of all solid-state batteries still needs 5-10 years. Prior to this, a large number of automotive companies announced that the expected installation time for semi-solid batteries was concentrated between 2024 and 2026. At that time, it is expected to be the first to usher in the industrialization wave of semi-solid batteries. With the increasing maturity of solid-state battery technology, technical and cost challenges are gradually overcome, and the future market size of the industry is expected to achieve leapfrog growth, with promising prospects for the industry. According to the research report, it is expected that the shipment volume of solid-state batteries in China is expected to exceed 250GWh by 2030, and the market space may reach 20 billion yuan by then.