Lithium-ion solid electrolyte data, as the core component of
all-solid-state lithium-ion batteries, is the core data to achieve its high
functions, and it is also one of the bottlenecks affecting its practical
application. The development history of solid electrolytes has been more than
one hundred years, and there are hundreds of discussions on solid electrolyte
materials. As long as the conductivity of solid electrolytes at room temperature
or high temperature is greater than three s/cm, it can be used in
electrochemical power supply systems, and most of the conductivity The data
value is several orders of magnitude lower than the value, which makes few solid
electrolyte materials have practical application value.
2. Research progress of solid electrolytes
As an important part of the battery, the function of the electrolyte determines to a large extent the power density, cycle stability, safety performance, high and low temperature performance and service life of the battery. The evaluation indicators of electrolytes generally include:
(1) Ionic conductivity: Ionic conductivity will affect the volume resistance of assembled batteries. Regarding solid electrolytes, the ion conductivity is generally required to reach 10-4s/cm or more.
(2) Removal number: refers to the share of lithium ions in the current passing through the electrolyte. In an ideal state, the removal number is 1. If the removal rate is too low, negative ions will accumulate on the electrode surface, causing the polarization and resistance of the battery to increase.
(3) Electrochemical window: In the battery working voltage range, the electrolyte needs to have high electrochemical stability, otherwise it will be decomposed during the working process. Generally, the electrochemical window is required to be higher than 4.3v. 
The solid electrolytes currently studied mainly include oxide solid electrolytes, sulfide solid electrolytes, polymer solid electrolytes and composite solid electrolytes. The following is a detailed introduction to these solid electrolytes and their research progress.
Research progress of all solid-state lithium-ion batteries
2.1 Oxide solid electrolyte
Oxide solid electrolyte is divided into crystalline electrolyte and glassy (amorphous) electrolyte according to the material structure. Crystal electrolytes include garnet solid electrolytes, perovskite li3xla2/3-xTiO3 solid electrolytes, NASICONLi1+xalxti2-x(PO4)3 and Li1+xalxge2-x(PO4)3 solid electrolytes. The glassy electrolyte is composed of an anti-perovskite li3-2xmxhalo solid electrolyte and a lipid thin film solid electrolyte.
2.1.1 Garnet solid electrolyte
The traditional garnet electrolyte is Li7La3Zr2O12 (LLZO). The cubic phase garnet electrolyte has higher ionic conductivity at room temperature (10-3s/cm), and is more stable than other types of electrolytes when in contact with metallic lithium. It is a promising electrolyte.
Currently, garnet electrolyte faces two major problems:
1. The high lithium content makes the surface of the electrolyte easy to produce lithium hydroxide and lithium carbonate with water and carbon dioxide in the air, resulting in large interface impedance and poor battery function.
2. The garnet electrolyte has poor wetting ability to metal lithium, and lithium ions accumulate unevenly during the cycle, prone to dendrites, and pose serious safety risks.
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