Development trend and outlook of all solid state lithium battery technology

1. Development trend of all solid state lithium battery technology
   1. Solid-state electrolyte in all solid state lithium battery
   2. Challenges faced by all solid state lithium battery
   3. Future development trend of all solid state lithium battery
2. All solid state lithium battery technology patent application country
3. Prospects for all solid state lithium battery

Today, both lead-acid batteries and liquid lithium-ion batteries have entered a mature stage of commercial application. However, the current commercial lithium batteries all use liquid electrolytes or semi-solid electrolytes. When the ambient temperature is too low, the activity of lithium ions decreases, the battery capacity declines, and the output power decreases.

While solid-state lithium batteries (including solid-state lithium-ion batteries and solid-state lithium metal batteries) are still in the development stage of principle prototypes, all solid state lithium battery that replace traditional liquid or semi-solid electrolytes with solid-state electrolytes are regarded as the development of energy storage to medium and large-scale applications.

Development trend of all solid state lithium battery technology

Traditional lithium-ion batteries generally use organic electrolytes as electrolytes, but there are flammability problems, and there are great safety hazards when used for large-capacity storage. Solid electrolytes have the advantages of flame retardancy, easy encapsulation, etc., and have a wide electrochemical stability window, which can be used in conjunction with high-voltage electrode materials to improve the energy density of batteries.

In addition, the solid electrolyte has high mechanical strength, which can effectively inhibit the puncture of lithium dendrites in liquid lithium metal battery during cycling, making it possible to develop lithium metal batteries with high energy density. Therefore, all solid state lithium battery are the ideal development direction of lithium-ion batteries.

Solid-state electrolyte in all solid state lithium battery

According to the chemical composition, solid electrolytes can be divided into three types: inorganic type, polymer type and organic-inorganic composite type. Inorganic solid electrolytes usually include solid oxide electrolytes such as perovskite type, garnet type (Garnet), and NASICON type, and sulfide solid electrolytes.

Among various garnet-type solid electrolytes, Li7La3Zr2O12 (LLZO) solid electrolyte has high ionic conductivity and wide voltage window, has good stability to air, does not react with metallic lithium, and is an ideal electrolyte material for all solid state lithium battery. But scientists recommend focusing research on LLZO films with a thickness of 20-50 μm for commercial application as soon as possible.

Compared with oxide electrolytes, sulfide-type solid electrolytes have high ionic conductivity, low grain boundary resistance, and high oxidation potential. The polymer-based solid electrolyte (SPE) mainly embeds the lithium salt in the polymer matrix, and the Li-polar group coordination is formed between the two substances through the reaction of blending and cross-linking, and the ionic conductivity has been improved. above 10-4 S/cm.

Organic-inorganic composite solid electrolytes combine the advantages of inorganic solid electrolytes and polymer solid electrolytes, which not only have the flexibility and scale-up processability of polymer components, but also can obtain stronger Ionic conductivity and stability.

In recent years, organic-inorganic sapphire-type solid-state electrolytes with high performance have attracted attention.

Challenges faced by all solid state lithium battery

All solid state lithium battery face three major challenges:

1. Materials. Defects of lithium metal anode, failure of solid electrolyte interface in contact with metal lithium, and poor mechanical stability of active cathode materials and solid composite cathode materials;
2. Processing. Spend a lot of time and energy in the development of new and improved materials;
3. Design engineering. The use of 3D templates to increase the interface area and reduce the local current density of the interface is very promising, but it will face cost problems in the mass production process.

Among them, the electrolyte interface stability is crucial for the long cycle life of all solid state lithium battery. There is currently no electrolyte material with both a high oxidation limit and a low reduction limit.

In addition, for all solid state lithium battery using lithium metal as the negative electrode, the problem of lithium dendrite growth in the battery needs to be considered. Studies have shown that in some solid-state electrolytes with ultra-high mechanical strength, dendrite growth pierces the electrolyte faster than in liquid batteries.

Dendrite growth in solid-state electrolytes is more complex and diverse than that in liquid electrolytes, mixing different physical and chemical environments, and the exact mechanism is currently uncertain.

Future development trend of all solid state lithium battery

The future development directions of all solid state lithium battery include:

• Continuously improving battery safety performance and volumetric energy density of lithium ion battery;
• Continuously enhancing the stability of battery interface chemistry and mechanical properties while improving ionic conductivity;
• Exploring electrical conductivity and microstructure of solid electrolyte membranes and other factors on the formation mechanism of lithium dendrites, and explore methods to inhibit the growth of lithium dendrites;
• In the manufacturing process of all solid state lithium battery, develop a manufacturing method that keeps the interface in close contact, especially for pomegranate with strong mechanical properties Stone-type oxide solid electrolyte.

All solid state lithium battery technology patent application country

Generally speaking, patent applicants will first apply for patents in their own country or region, and then use the priority to apply for patents in other countries or regions within one year.

Therefore, the number of patent applications in priority countries or regions can be used to measure the development level and R&D strength of a country or region in related technologies to a certain extent.

Among them, there are 1,142 priority patents in Japan, accounting for about 40.20% of the world’s total solid-state lithium battery technology priority patents. Subsequently, the number of priority patents in China, the United States and South Korea was 1027, 397 and 79 respectively, accounting for 36.15%, 13.97% and 2.78% of the total number of priority patents in the world.

Japan, China and the United States have strong R&D capabilities and independent innovation capabilities in the field of all solid state lithium battery technology, and are the main R&D countries in this field. China has more than 1,000 patent applications in this field, and has strong research and development capabilities.

Prospects for all solid state lithium battery

In recent years, thanks to the rapid development of material synthesis technology, precision manufacturing technology and energy storage technology, the research and development of new high-efficiency all solid state lithium battery in the world is in a stage of rapid development.

Judging from the patent application situation of all solid state lithium battery technology in the world, Japan entered the field of all solid state lithium battery technology earlier, and the number of patent applications is far ahead of other countries, among which the number of patent applications for Toyota ranks first in the world.

China ranks second in the number of patent applications in the field of all solid state battery technology. In 2019, the number of new patent applications surpassed that of Japan, becoming the world’s largest patent applicant in this field. Among them, the number of patent applications by the Chinese Academy of Sciences ranked second in the world.

Among the world’s top ten patent holders in this field, China occupies four seats and has strong technology research and development capabilities. Patent applications for all solid state lithium battery technology mainly focus on the following directions:

• Development and manufacture of secondary batteries;
• Development of electrodes;
• Research and development of conductive materials;
• Development and manufacture of primary batteries;
• Production of special equipment for conducting materials R&D.

In short, with the continuous optimization of the performance of all solid state lithium battery electrolyte materials, the demand for all solid state lithium battery for energy storage devices such as new energy vehicles and smart grids is becoming more and more urgent.

In the future, high-energy density, low-cost, safe and stable all solid state batteries will play an important supporting role in the transformation of clean energy.

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