Electrolyte - solid state battery&jelly battery

　　On December 8 local time, QuantumScape, a start-up company supported by Volkswagen and Bill Gates, announced its latest solid-state battery and said that the battery would be put into production in 2024. Compared with the traditional lithium-ion battery, this kind of solid-state battery has a significant improvement: they can increase the range of electric vehicles by 80%. Let's discuss what solid state batteries are and what their benefits are.

　　While improving the energy density of the battery, the safety of the battery has to be considered. The fundamental elimination of the potential safety hazard of lithium ion batteries still lies in the improvement of the safety of battery materials. However, for positive materials, these two aspects are contradictory. For example, as mentioned earlier, increasing the nickel content can improve the energy density, but increasing the nickel content means reducing the safety. What other ways to enhance the safety of batteries, so as to improve the energy density more confidently? At this time, the electrolyte should be considered. A large number of studies have shown that liquid electrolyte participates in most of the reactions during the thermal runaway process of the battery, and greatly reduces the initial reaction temperature of the battery, which means that the threshold of thermal runaway becomes lower. Therefore, improving electrolyte safety is one of the most effective ways to achieve battery safety [3]. The physical characteristics of the liquid electrolyte determine that it cannot avoid leakage all the time, and it is also not conducive to reducing the battery volume and improving the energy density. Therefore, in order to improve the energy density and safety, the solid state of the electrolyte has become a trend. We call the battery whose electrode and electrolyte are solid state as solid state battery. The solid state battery cell does not contain liquid inside, which is not only safer, but also can realize series and parallel connection before assembly, reducing the packaging shell material, greatly simplifying the PACK design, which also improves the energy density of the battery after grouping.

　　Like traditional lithium batteries, solid state batteries are composed of positive electrodes, negative electrodes and electrolytes. Its structure is simpler than that of traditional lithium battery, and the solid electrolyte acts as the double functions of electrolyte and separator. There is no essential difference between cathode materials and traditional lithium batteries. The anode materials are lithium metal anode materials, carbon group anode materials and oxide anode materials. For solid state battery, the research and development of solid electrolyte is the most important. Its materials are various, mainly including oxides, sulfides, polymers and composite solid electrolytes.

　　In addition to the large-scale use of liquid lithium batteries and the solid-state batteries under research, a semi-solid battery - jelly battery - has entered people's vision. In December 2020, Honeycomb Energy took the lead in releasing jelly battery and accepted the reservation. Jelly battery is a kind of lithium battery using a new jelly like electrolyte. This gel type electrolyte can better fit with the surface of electrode materials, and has the characteristics of self-healing, flame retardant, etc. It can almost not reduce the conductivity while preventing thermal diffusion. Jelly battery is a transition from liquid battery to solid battery.

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