Silicon-Graphite Negative Electrode Porous Structure for Battery Swelling
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Solution Overview
Problem
The combined use of silicon-containing particles and graphite particles in non-aqueous electrolyte secondary batteries leads to deterioration of cycle characteristics due to large swelling of silicon-containing particles, causing damage to the electrode structure and disruption of electron conduction paths.
Innovation Solution
A non-aqueous electrolyte secondary battery design that includes a negative electrode mixture layer with a specific ratio of Log-differential pore volume at 2 μm to 0.2 μm, within the range of 10.5 to 33.1, to absorb swelling and maintain efficient electron conduction, achieved by forming pores in the negative electrode mixture layer using ethylene carbonate, fluoroethylene carbonate, or vinylene carbonate as solid materials in the electrolyte solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-containing particles are used as negative electrode active material, then specific capacity is improved, but cycle characteristics deteriorate due to large swelling
Solution Approach 1:
The invention introduces a porous structure in the negative electrode mixture layer with controlled pore size distribution (V2/V0.2 ratio of 10.5 to 33.1). The pores act as buffer spaces that absorb the volume expansion of silicon-containing particles during lithiation, preventing structural damage and maintaining electron conduction paths. This resolves the contradiction by providing a material structure that accommodates the inherent swelling of silicon while preserving cycle stability.
Solution Approach 2:
The invention creates a composite structure combining silicon-containing particles, graphite particles, and conductive material within a porous matrix. This composite approach leverages the high capacity of silicon, the structural stability of graphite, and the conductivity of conductive materials to achieve both high specific capacity and good cycle characteristics simultaneously.
2Reliability
If large pores are increased to absorb swelling, then cycle characteristics are improved, but electron conduction paths are disrupted
Solution Approach 1:
The invention optimizes the pore size distribution by controlling the V2/V0.2 ratio within a specific range (10.5 to 33.1). This parameter control ensures that pores are large enough to absorb silicon swelling but not so large as to disrupt electron conduction paths. The conductive material filling the pores maintains electrical connectivity while the pore structure provides swelling accommodation, resolving the contradiction between cycle stability and electron conduction.
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
This design improves cycle characteristics and increases the use efficiency of silicon-containing particles, leading to enhanced initial capacity and efficiency by maintaining a balanced proportion of large and small pores, thereby reducing structural damage and promoting efficient electron conduction.
Implementation Method 1
forming pores in the negative electrode mixture layer by dissolving the solid material in the electrolyte solution
Implementation Method 2
large swelling of the silicon-containing particles is absorbed by the pores
Implementation Method 3
disruption of electron conduction paths between the adjacent particles
Data Source
AI summary
A non-aqueous electrolyte secondary battery includes a negative electrode, a positive electrode, and an electrolyte solution. The electrolyte solution contains at least one selected from the group consisting of ethylene carbonate, fluoroethylene carbonate, and vinylene carbonate. The negative electrode includes a negative electrode mixture layer. The negative electrode mixture layer contains a silicon-containing particle and a graphite particle. In a Log-differential pore volume distribution of the negative electrode mixture layer, the ratio of a Log-differential pore volume at a pore diameter of 2 μm to a Log-differential pore volume at a pore diameter of 0.2 μm is within a range of 10.5 to 33.1.