Solid-state batteries are expected to lead the next wave of new energy technology progress

Solid-state batteries use solid electrolytes to replace the electrolyte and diaphragm of traditional lithium-ion batteries. Compared with traditional lithium-ion batteries, they have greatly improved in terms of safety, low-temperature reliability and energy density.

In terms of safety: Inorganic solid electrolytes reduce safety risks such as battery leakage and short circuit.

In terms of low temperature reliability: solid electrolyte solves the problem of increased viscosity and slow ion conduction speed of electrolyte at low temperature.

In terms of energy density: the amount of lithium used in solid batteries is about double that of traditional ternary or iron-lithium batteries, and the energy density can reach about 400Wh/kg.

There are still some technical difficulties in solid-state lithium batteries: one is the batch, low-cost, and stable synthesis of electrolytes; the other is the large internal resistance of the solid-solid interface; the third is that the equipment and process have not yet been finalized.

BYD: The company's main technical route from 2016 to 2019 is polymer solid electrolyte, and has tried polymer + inorganic solid electrolyte (perfluorosulfonimide ion as an anionic ionic liquid polymer), nanoparticle modified cross-linked copolymer electrolyte , Polymer + lithium salt + ionic liquid electrolyte. During this period, the company has also improved the positive electrode materials (MnO2 conductive matrix sheet and lithium-containing composite oxide sheet), and no additional conductive agent is needed. In 2020, the company's main technical route is oxide/sulfide composite solid-state electrolyte, while polymer solid-state batteries are also constantly iterating.

Ganfeng Lithium Group CO.,LTD.: The company's technical route is mainly based on oxide solid electrolytes. In 2020, the company has improved the diaphragm of solid-state batteries and looked for alternatives. The patent applied for in July 2020 is a quasi-solid-state battery without a diaphragm. The surface of the negative electrode is first coated with an inorganic solid electrolyte layer and then an organic polymer layer to replace the diaphragm. On the one hand, the electrical conductivity and mechanical strength are improved. On the one hand, the organic polymer layer melts and collapses at high temperature to isolate lithium ions, improving the safety of the battery. The patent applied for in September 2020 is a multi-phase electrolyte film whose main component is a lithium-containing active fast ion conductor or an inert inorganic non-metal, which has the advantages of high mechanical strength, simple process, and convenient industrial quantitative production.

Contemporary Amperex Technology Co. Limited: The company's main technical route from 2018 to 2019 is based on sulfide solid electrolytes. The patent discloses the recycling technology of sulfide solid-state batteries, and a kind of sulfide solid-state battery with endothermic phase change and added salt in the positive electrode. The heat generated by exothermic processes such as reactions reduces the risk of thermal runaway and improves the thermal safety and cycle stability of the sulfide solid-state battery system.