Lithium Silicate Anode Gradient for Battery Cycle Stability
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Solution Overview
Problem
The non-uniform distribution of electrolyte liquid in the negative electrode of nonaqueous electrolyte secondary batteries due to stress generated during charge/discharge cycles leads to degraded cycle characteristics, as the electrolyte liquid is pushed out and fails to permeate uniformly, causing deficiency at the negative electrode collector side.
Innovation Solution
A nonaqueous electrolyte secondary battery design with a negative electrode mixture layer containing a lithium silicate phase with silicon particles, where the atomic ratio of oxygen to silicon (O/Si) is between 2 and 3, promoting increased surface roughness and affinity with the electrolyte liquid, and a dual-region structure with varying content of the lithium silicate phase to balance stress and maintain high capacity and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a negative electrode active material containing lithium silicate phase is used to achieve high theoretical capacity density, then energy density is improved, but non-uniform distribution of electrolyte liquid occurs leading to degraded cycle characteristics
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of lithium silicate phase particles within the negative electrode active material, with higher concentration at specific regions. This localized arrangement ensures that areas with better electrolyte access have more high-capacity material, compensating for the non-uniform electrolyte distribution and maintaining consistent electrochemical performance across cycles
Solution Approach 2:
The patent uses composite materials by combining lithium silicate phase particles with other negative electrode active materials in a specific ratio. This composite structure allows the battery to benefit from the high theoretical capacity density of lithium silicate while the other materials provide stable electrolyte interaction, thus improving both energy density and cycle characteristics
2Quantity of substance
If negative electrode active material is expanded during charge to occlude lithium ions, then capacity is improved, but stress is generated that pushes out electrolyte liquid, causing non-uniform distribution
Solution Approach 1:
The patent applies beforehand cushioning by pre-arranging the negative electrode active material with a specific composition and structure that can accommodate expansion stress. The controlled distribution of lithium silicate phase and other materials creates a buffer system that absorbs expansion forces during charge, preventing electrolyte liquid from being pushed out and maintaining uniform distribution throughout cycles
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 improved surface roughness and balanced stress distribution enhance electrolyte liquid permeation, leading to uniform distribution and improved cycle characteristics, maintaining high capacity and stability from initial to middle stages of cycles.
Implementation Method 1
promoting increased surface roughness and affinity with the electrolyte liquid
Implementation Method 2
a material containing silicone (Si) which forms an alloy with lithium
Implementation Method 3
When lithium ions are occluded in a negative electrode active material during charge, the negative electrode active material is expanded
Data Source
AI summary
A nonaqueous electrolyte secondary battery includes a positive electrode, a negative electrode, and an electrolyte liquid. The negative electrode includes a negative electrode mixture layer containing a first negative electrode active material and a negative electrode collector to which the negative electrode mixture layer is adhered. The first negative electrode active material contains a first lithium silicate phase containing lithium, silicon, and oxygen and first silicon particles dispersed in the first lithium silicate phase. An atomic ratio A1:O/Si of the oxygen to the silicon in the first lithium silicate phase satisfies a relationship of 2<A1≤3. At a surface side of the negative electrode, an existence ratio of the first negative electrode active material in the negative electrode mixture layer is high as compared to that at a negative electrode collector side of the negative electrode.