Four solid challenges in the development of all-solid-state lithium batteries

Recently, the development goals of the power battery proposed by the governments of China, Japan and the United States, from the technical indicators, the core indicator is the energy density, the higher the higher, from 300 watt-hours per kilogram to 500 watt-hours per kilogram, including the US DOE. There are special projects in China, and nanomaterials and genomes have set high requirements.

How to achieve these ultra-high energy density indicators, while also taking into account the safety, life and cost of the power battery, this is a problem faced by many developers.

From the technical analysis point of view, the main power battery is still the positive electrode material to match the negative electrode material such as artificial graphite. Next, the energy density is increased. It is very likely that the silicon negative electrode will be introduced. Volume expansion is a difficult problem to solve. The silicon negative electrode was replaced by metallic lithium. It has been developed since 1972 and lasted for more than 50 years. There are many challenges. The key problem is that most of the current research and development is still in organic solvents, the first problem in organic solvents. It is not like the graphite negative electrode lithium in and out, is a non-uniform precipitation. The second is spontaneous and electrolyte reaction, and the volume change is also relatively large. Gradually, the lithium-ion battery VCR film can not be stably existed, and the safety and self-discharge can not meet the demand. Many enterprises and R&D teams pin their hopes on all-solid lithium battery . Solid-state batteries and commercial batteries are also three-layer structures on the micro level. They just replace the current diaphragm electrolyte with a solid electrolyte. This is a typical photo. There is no essential difference. The core is that it is possible to use metallic lithium in the negative electrode. In the case of the positive electrode side, the original liquid can sufficiently wet the positive electrode particles and contact the positive electrode side, which is very difficult. From the advantages that everyone expects, if metal lithium is used, the liquid electrolyte that is now easy to burn and explode, and the service life will be prolonged, and the module configuration is expected. In practice, these data need to be further tested. In 2007, Japan's NEDO announced such a roadmap in 2008. In their view, in the long run of 2030, many battery forms appeared in all solid form, including lithium metal, lithium sulfur and lithium air batteries. These routes are constantly being revised, but generally the strategy to improve security is solid state.

In 2016, APER's US$20 million project supports all types of solid electrolyte development and solid electrolyte manufacturing technology. Now in China, the team that has been engaged in solid-state battery development has been promoted in the past two or three years. There are not many units to display, and there are small teams with capacity development. There are many R&D teams from south to north. The enterprises include Ningde Times New Energy, Suzhou Xintao and Qiwei Shares. I will not introduce them one by one.

At present, the development of all-solid-state lithium batteries faces four challenges. One is how to meet the positive and negative electrodes and the ion transport of solid electrolytes at the electrode level, especially during the cycle. The second is that the positive and negative materials cannot be recycled during the cycle. Maintain very good contact like a liquid. There is also a change in the volume of the lithium metal electrode and a change in lithium solids.

Next, in 2013, the Chinese Academy of Sciences decided to adopt the nano-leading special project. Here, the power battery for long-life is proposed. By increasing the energy density to extend the driving range of the electric vehicle , the index of 300 watt-hour per kilogram is proposed, which is consistent with the current national mission. This includes third-generation lithium-ion battery technology, including the current generation of solid-state batteries, lithium-sulfur and lithium-air batteries, including 12 research units, 24 PI, 400 people, has been in dynamic management.

Then briefly talk about the progress of the entire pilot project, and develop some high-energy density lithium ion, lithium space, lithium sulfur at the level of the sample, and also create a high-level diagnostic analysis platform, the introduction of inorganic lithium phosphate on the surface of metal lithium Doing this and improving its stability is done by Dr. Guo from the Institute of Chemistry. They have recently developed polyether acrylate which is a very important breakthrough.

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