Research progress of all-solid-state lithium -Lithium - Ion Battery Equipment

Research progress of all-solid-state lithium batteries -Lithium - Ion Battery Equipment

Since their introduction into the market in 1991, lithium-ion batteries have attracted much attention due to their high energy density and long lifespan. It has become an integral part of the energy economy in the 21st century. However, the application of lithium-ion batteries in large-scale battery fields such as automobiles and energy storage still has some safety issues that need to be solved urgently. The organic electrolytes of lithium-ion batteries are volatile, flammable and explosive. [1] The all-solid-state lithium-ion battery fundamentally solves this problem, and has the advantages of large capacity and light weight, and the research that can complete the industrialization of all-solid-state lithium-ion batteries is imminent.(Lithium - Ion Battery Equipment)

1. Overview of all solid-state lithium-ion batteries

All-solid-state lithium-ion batteries are related to liquid lithium-ion batteries, which refer to energy devices that do not contain liquid in the structure and all data are stored in solid state. Specifically, it is composed of positive data + negative data and electrolyte, while liquid lithium ion battery is composed of positive data + negative data + electrolyte and separator.

Research progress of all-solid-state lithium-ion batteries

Lithium-ion solid electrolyte data, as the core component of all-solid-state lithium-ion batteries, is the core data to achieve its high function, and it is also one of the bottlenecks affecting its practical application. The development history of solid-state electrolytes has been more than a hundred years, and there are hundreds of discussions on solid-state electrolyte materials. As long as the solid-state electrolyte has a conductivity greater than 3 s/cm at room temperature or high temperature, it can be used in electrochemical power systems. The data values ​​are orders of magnitude below the value, which makes few solid-state electrolyte materials of practical value. [2]

2. Research progress of solid electrolytes

As an important part of the battery, the function of the electrolyte largely determines the power density, cycle stability, safety performance, high and low temperature performance and service life of the battery. Electrolyte evaluation indicators generally include:

(1) Ionic conductivity: The ionic conductivity affects the volume resistance of the assembled battery. Regarding solid electrolytes, the ionic conductivity is generally required to reach more than 10-4s/cm.

(2) Removal number: refers to the share of lithium ions in the current passing through the electrolyte. Ideally, the removal number is 1. If the removal rate is too low, negative ions will accumulate on the electrode surface, resulting in increased polarization and resistance of the battery.

(3) Electrochemical window: Within the working voltage range of the battery, the electrolyte needs to have high electrochemical stability, otherwise it will decompose during the working process, and the electrochemical window is generally required to be higher than 4.3v. [3]

The solid electrolytes currently studied are mainly 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 electrolytes are classified into crystalline electrolytes and glassy (amorphous) electrolytes according to their material structure. Crystal electrolytes include garnet solid electrolytes, perovskite li3xla2/3-xTiO3 solid electrolytes, NASICON Li1+xalxti2-x(PO4)3 and Li1+xalxge2-x(PO4)3 solid electrolytes, etc. The glassy electrolyte consists of an anti-perovskite li3-2xmxhalo solid electrolyte and a lipid film solid electrolyte.

2.1.1 Garnet solid electrolyte [4]

The traditional garnet electrolyte is Li7La3Zr2O12 (LLZO). The cubic garnet electrolyte has high ionic conductivity at room temperature (10-3 s/cm) and is more stable than other types of electrolytes in contact with metallic lithium. It is a promising electrolyte.

Currently, garnet electrolytes face two major problems:

1. The high lithium content makes the surface of the electrolyte easy to form lithium hydroxide and lithium carbonate with water and carbon dioxide in the air, resulting in high interface impedance and poor battery function.

2. The garnet electrolyte has poor wetting ability to metal lithium, and the accumulation of lithium ions is uneven during the cycle process, which is prone to dendrites and poses serious safety hazards.



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