Negative Electrode-Solid Electrolyte Interlayer for Uniform Lithium Deposition
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Solution Overview
Problem
All-solid secondary batteries using lithium as a negative active material and solid electrolytes face issues with non-uniform lithium deposition leading to cracks in the solid electrolyte, which can cause short circuits and reduce safety and performance.
Innovation Solution
A negative electrode-solid electrolyte sub-assembly is designed with a first negative active material layer comprising a mixture of specific compounds, an interlayer, and a second negative active material layer, which includes lithium metal, to prevent short circuits and improve rate capability and lifespan by controlling lithium ion movement and volume expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium metal is used as a negative active material to increase energy density, then the specific capacity increases about 10 times compared to graphite, but non-uniform lithium deposition occurs during charging which induces cracks in the solid electrolyte
Solution Approach 1:
A buffer layer comprising a compound of formula Li2M1M2O3 (where M1 is a divalent metal and M2 is a trivalent metal) is introduced between the lithium metal negative active material and the solid electrolyte. This buffer layer acts as an intermediary that prevents direct contact and mechanical stress transmission, thereby preventing crack formation in the solid electrolyte while maintaining high capacity performance.
Solution Approach 2:
The negative electrode is designed as a composite structure with multiple layers: lithium metal particles, a buffer layer with specific spinel structure compounds, and conductive carbon materials. This composite structure distributes mechanical stress and prevents uniform crack propagation, resolving the contradiction between high capacity and electrolyte integrity.
2Quantity of substance
If lithium metal is used as a negative active material, then capacity is increased, but cracks in the solid electrolyte may induce short circuit
Solution Approach 1:
The buffer layer serves as a protective intermediary that physically separates the lithium metal from the solid electrolyte, preventing direct mechanical contact that would cause cracks and subsequent short circuits. The layer maintains ionic conductivity while providing mechanical protection.
Solution Approach 2:
The buffer layer is pre-formed before battery operation to cushion and absorb mechanical stresses that would otherwise transmit to the solid electrolyte during lithium deposition and volume expansion, preventing crack formation before it occurs.
3Reliability
If a buffer layer comprising a compound of formula Li2M1M2O3 is disposed between the negative active material and the solid electrolyte, then crack formation is prevented, but the device complexity increases
Solution Approach 1:
The buffer layer uses compounds with specific crystal structures (spinel structure Li2M1M2O3) where the atomic arrangement parameters are optimized to provide both mechanical protection and ionic conductivity. By controlling the metal composition ratios and crystal structure, the layer achieves multiple functions simultaneously, reducing the need for additional components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively prevents short circuits and enhances the safety and performance of all-solid secondary batteries by ensuring uniform lithium ion movement and reducing interfacial resistance, thereby improving the battery's rate capability and lifespan.
Implementation Method 1
the first negative active material layer comprises a mixture of a compound of Formula 1 and a compound of Formula 2... LixM1y wherein M1 is a first metal and is an element capable of forming a compound or an alloy with lithium and oxygen
Implementation Method 2
ensuring uniform lithium ion movement
Implementation Method 3
the interlayer comprises a third metal material, lithium oxide, or a combination thereof... electron conduction in the solid electrolyte may be prevented
Implementation Method 4
a solid electrolyte disposed on the interlayer and opposite the first negative active material layer
Implementation Method 5
improve rate capability and lifespan by controlling lithium ion movement and volume expansion
Data Source
AI summary
A negative electrode-solid electrolyte sub-assembly for an all-solid secondary battery, the negative electrode-solid electrolyte sub-assembly including: a negative electrode current collector, a first negative active material layer disposed on the negative electrode current collector, an interlayer disposed on the first negative active material layer and opposite the negative electrode current collector, and a solid electrolyte disposed on the interlayer and opposite the first negative active material layer, wherein the first negative active material layer may include a mixture of a compound of Formula 1 and a compound of Formula 2, a composite of the compound of Formula 1 and the compound of Formula 2, or a combination thereof, the interlayer comprises a third metal material, lithium oxide, or a combination thereof, and the third metal material comprises a third metal oxide, an oxide comprising a third metal and lithium, or a combination thereof,LixM1y, Formula 1M2aNb. Formula 2