Non-Aqueous Battery Electrode Structure for Fast-Cycle Capacity Retention
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries with high-capacity positive electrodes face reduced durability due to increased BET specific surface area and decreased electrolyte permeability during rapid charge-discharge cycles, leading to capacity retention issues.
Innovation Solution
A nonaqueous electrolyte secondary battery design incorporating a positive electrode with first and second composite oxide particles of specific size distributions and nickel content, and a negative electrode with graphite particles of varying internal void percentages, optimized to enhance packing density and electrolyte permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If small particle size positive electrode active material is used to increase capacity, then the BET specific surface area increases and capacity is improved, but side reactions on the surface increase and durability is reduced
Solution Approach 1:
The patent applies parameter changes by precisely controlling the particle size distribution parameters (D10, D50, D90) of the positive electrode active material and the internal void percentage (P) of graphite particles. By optimizing these parameters within specific ranges, the patent achieves high capacity while controlling side reactions to maintain durability.
Solution Approach 2:
The patent applies local quality by creating different regions within the electrode structure with different properties. The positive electrode mixture layer has different composition and structure in different areas, and the graphite particles are distributed with varying internal void percentages to create localized regions that optimize both capacity and durability.
2Quantity of substance
If packing density of positive electrode active material is improved to increase capacity, then energy density is improved, but electrolyte permeability decreases and capacity retention rate is reduced
Solution Approach 1:
The patent applies porous materials by utilizing graphite particles with controlled internal void percentages (P ≥ 10%). These porous graphite particles maintain electrolyte permeability even when the positive electrode has high packing density, ensuring that ions can transport efficiently and capacity retention is maintained during rapid charge-discharge cycles.
Solution Approach 2:
The patent applies composite materials by combining positive electrode active material particles with graphite particles of specific internal void percentages. This composite structure allows the positive electrode to achieve high packing density while the porous graphite components maintain electrolyte pathways for efficient ion transport.
3Quantity of substance
If high capacity positive electrode is used to improve energy density, then output power is improved, but electrolyte permeability decreases and durability is reduced
Solution Approach 1:
The patent applies parameter changes by optimizing the particle size distribution parameters (D10, D50, D90) of the positive electrode active material and the internal void percentage (P) of graphite particles. By controlling these parameters within specific ranges, the patent achieves high energy density while maintaining durability through balanced electrochemical performance.
Solution Approach 2:
The patent applies local quality by creating heterogeneous regions within the electrode with varying graphite particle distributions and internal void percentages. This creates localized zones that facilitate electrolyte penetration and maintain durability even when the overall electrode has high capacity and energy density.
Data Source
AI summary
A nonaqueous electrolyte secondary battery having a positive electrode active material including first and second composite oxide particles each having a Ni proportion in metal elements other than Li of 50 at. % or more; the first and second composite oxide particles respectively have average particle diameters D1 and D2 satisfying 1 μm≤D1<6 μm and 8 μm≤D2≤μ20 m; a negative electrode active material includes a graphite material, and a Si-containing material; the graphite material includes first and second graphite particles having first and second internal void percentages P1 and P2, respectively, satisfying P1<P2; the first graphite particles are contained more in a first region of the negative electrode mixture layer than in a second region; and average values Pf (14% or less) and Ps of internal void percentages of the graphite material contained respectively in the first and second regions satisfy Pf<Ps.