Porous Positive Electrode Protection Layer for Li-Ion Rate Stability
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Solution Overview
Problem
Nonaqueous electrolyte rechargeable batteries, such as lithium-ion batteries, face issues with high-rate deterioration and delamination of the insulative protection layer, leading to uneven electrolyte concentration and potential short circuiting due to insufficient movement of the electrolyte and foreign matter penetration.
Innovation Solution
A positive electrode plate structure with an insulative protection layer having a specific thickness, porosity, and composition, including boehmite or alumina insulative particles and a binder, is implemented, along with a manufacturing method that involves simultaneous application and pressing of the insulative and positive electrode mixture layers to ensure effective insulation and electrolyte movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insulative protection layer is added to prevent short circuiting, then safety is improved, but electrolyte movement is hindered causing high-rate deterioration
Solution Approach 1:
The insulative protection layer is designed with a porous structure having a porosity of 30% to 70%, allowing the nonaqueous electrolyte to penetrate and move through the layer efficiently while maintaining its insulative function to prevent short circuiting between the positive electrode current collector and negative electrode mixture layer
Solution Approach 2:
The thickness of the insulative protection layer is controlled within a specific range of 1 μm to 50 μm, optimizing the balance between providing sufficient insulation to prevent short circuiting and maintaining adequate porosity to allow efficient electrolyte movement during high-rate charging and discharging
2Reliability
If the insulative protection layer is made thicker for better insulation, then short circuit prevention is improved, but delamination occurs
Solution Approach 1:
The thickness of the insulative protection layer is optimized to be within 1 μm to 50 μm, providing sufficient insulation effectiveness while maintaining strong adhesion to the positive electrode current collector through the binder, preventing delamination during battery operation
Solution Approach 2:
The insulative protection layer is formed as a composite material containing insulative particles (such as alumina or boehmite) and a binder in a controlled ratio, creating a structure that provides both effective insulation and strong adhesion to the current collector, preventing delamination while maintaining insulation properties
Data Source
AI summary
A nonaqueous electrolyte rechargeable battery includes a positive electrode plate, a negative electrode plate, a separator, and a nonaqueous electrolyte. The positive electrode plate includes a positive electrode current collector, a positive electrode mixture layer including positive electrode active material particles and a conductor, and an insulative protection layer including insulative particles and a binder. In the insulative protection layer, a value of (the insulative particles)/(the insulative particles+the binder) is between 75 wt % and 85 wt %, inclusive. A single-surface thickness TI of the insulative protection layer is between 3.0 μm and 15 μm, inclusive. A porosity PI of the insulative protection layer is between 42% and 55%, inclusive. A ratio of the single-surface thickness TI to a single-surface thickness TP of the positive electrode mixture layer is between 0.12 and 0.80, inclusive.