Application Advantages Of Solid Electrolyte

Solid electrolyte is a trend in the development of lithium battery electrolytes in the future, because solid electrolyte battery technology has developed to today. From a technical perspective, solid electrolytes can be divided into oxide electrolytes, sulfide electrolytes, organic polymer electrolytes, and LiPON electrolytes. It can be said that it is relatively mature, but it has also encountered a bottleneck. The birth of a new generation of technology is urgently needed, especially in the field of new energy. Solid-state batteries are expected to become the most appealing one among the next-generation power battery technologies. Because all-solid-state batteries not only have relatively high technological maturity, many domestic and foreign lithium-ion battery companies have also regarded all-solid-state battery technology as an important next-generation technology reserve.

In the early development of solid-state battery technology, due to the relatively low conductivity of solid electrolyte materials, the focus of research and development was mostly on improving the conductivity of solid electrolytes. Therefore, sulfide solid electrolytes and oxide solid electrolytes with high ionic conductivity have attracted a wide range of attention.

All-solid-state lithium-ion batteries use solid electrolytes instead of traditional organic liquid electrolytes, which can well solve battery safety issues and are ideal chemical power sources for electric vehicles and large-scale energy storage. The key is to prepare solid electrolytes with high room temperature conductivity and electrochemical stability, as well as high-energy electrode materials suitable for all solid-state lithium-ion batteries, and to improve the compatibility of the electrode/solid electrolyte interface.

Solid-state lithium batteries are developed based on lithium batteries. Compared with traditional lithium batteries, they mainly no longer use liquid or gel as the conductive material between the positive and negative electrodes, which greatly improves the safety of the car and the ability to withstand high temperatures. . It has the advantages of high safety, high energy density, long cycle life, and wide operating temperature range, among which the very core is the solid electrolyte.

Oxide solid electrolytes can be divided into crystalline and glassy (amorphous) according to the material structure. Crystalline electrolytes include perovskite type, NASICON type, LISICON type and garnet type, etc. The glassy oxide electrolyte The research hotspot is the LiPON type electrolyte used in thin film batteries.

The oxide crystalline solid electrolyte has high chemical stability and can exist stably in the atmosphere, which is beneficial to the large-scale production of all-solid-state batteries. The research focus is to improve the room temperature ionic conductivity and its compatibility with electrodes. At present, the methods to improve conductivity are mainly element replacement and heterovalent element doping, and compatibility with electrodes is also an important issue that restricts its application.

The most typical sulfide crystalline solid electrolyte is thio-LISICON, which was first discovered by Professor KANNO of Tokyo Institute of Technology in the Li2S-GeS2-P2S system. The chemical composition is Li4-xGe1-xPxS4, and the room temperature ion conductivity is as high as 2.2×10. -3S/cm (where x=0.75), and the electronic conductivity can be ignored. The general chemical formula of thio-LISICON is Li4-xGe1-xPxS4 (A=Ge, Si, etc., B=P, Al, Zn, etc.).

The sulfide glass solid electrolyte is usually composed of P2S5, SiS2, B2S3 and other network formers and network modifier Li2S. The system mainly includes Li2S-P2S5, Li2S-SiS2, Li2S-B2S3. The composition has a wide variation range, high room temperature ion conductivity, high thermal stability, good safety performance, and wide electrochemical stability window (up to 5V). It has outstanding advantages in high-power and high-low-temperature solid-state batteries and has great potential Of solid-state battery electrolyte materials.

The polymer solid electrolyte is composed of polymer matrix (such as polyester, polymerase and polyamine, etc.) and lithium salt (such as LiClO4, LiAsF4, LiPF6, LiBF4, etc.), because of its light weight, good viscoelasticity, and excellent mechanical processing performance And other characteristics have received widespread attention.

Common SPEs include polyethylene oxide (PEO), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polymethylmethacrylate (PMMA), polypropylene oxide (PPO), polyvinylidene chloride (PVDC) and single-ion polymer electrolyte systems.

At present, the mainstream SPE matrix is still the first proposed PEO and its derivatives, mainly due to the stability of PEO to metal lithium and its ability to better dissociate lithium salts.

The LiPON electrolyte is made by the Oak Ridge National Laboratory (ORNL) in the United States. The lithium phosphorus oxynitride (LiPON) electrolyte film was prepared by sputtering a high-purity Li3P04 target using a radio frequency magnetron sputtering device in a high-purity nitrogen atmosphere.

It is understood that the material has excellent comprehensive performance, room temperature ionic conductivity is 2.3×10-6S/cm, electrochemical window is 5.5V (http://vs.Li/Li+), thermal stability is good, and Positive electrodes such as LiCoO2, LiMn2O4, and negative electrodes such as lithium metal and lithium alloy have good compatibility. The ionic conductivity of the LiPON film depends on the amorphous structure and the N content in the film material. The increase of the N content can improve the ionic conductivity.