Positive Electrode Composition for Conductivity-Active Material Balance
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Solution Overview
Problem
The existing positive electrode plates for non-aqueous electrolyte rechargeable batteries face challenges in achieving optimal performance due to the balance between the surface area of the active material and conductive material, with excessive conductive material reducing the percentage of active material and battery performance.
Innovation Solution
A positive electrode plate design with a specific surface area ratio of conductive to active material, optimized porosity, and aspect ratio of the conductive material, where the conductive material is distributed unevenly across the plate to enhance conductivity and porosity, allowing for a balanced mixture that maximizes battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of conductive material is increased to improve conductivity, then the conductivity between electrolyte and active material is improved, but the percentage of active material decreases and battery performance deteriorates
Solution Approach 1:
The conductive material is distributed non-uniformly in the positive electrode mixture layer, with higher concentration near the separator and lower concentration near the current collector. This local quality variation optimizes conductivity where needed (near electrolyte interface) while preserving active material percentage in the bulk, resolving the contradiction between conductivity and active material quantity.
Solution Approach 2:
The patent specifies a particular range for the ratio of conductive material surface area to active material surface area (0.05 to 0.50), and controls the porosity (40-55%). By changing these parameters within optimized ranges, the patent achieves sufficient conductivity without excessive conductive material addition, thereby maintaining high active material percentage.
2Productivity
If the surface area of positive electrode active material is increased to improve reaction amount, then the battery reaction capacity is improved, but the surface area available for conductive material decreases
Solution Approach 1:
The conductive material is concentrated in specific regions (near the separator) rather than uniformly distributed, allowing the majority of the electrode surface to be covered by active material for maximum reaction capacity, while still providing sufficient conductive pathways in the regions where they are most needed for electrolyte contact.
Solution Approach 2:
The positive electrode mixture layer is designed as a composite structure combining active material particles, conductive material particles, and binder in specific proportions and arrangements. This composite approach allows simultaneous optimization of reaction surface area (through active material packing) and conductivity (through conductive material distribution within the composite matrix).
Data Source
AI summary
A positive electrode plate for a non-aqueous electrolyte rechargeable battery includes a positive electrode mixture layer that is formed by a positive electrode mixture including a positive electrode active material and a conductive material. When RS=(RC×BC)/(RA×BA) is satisfied, where RC (mass %) represents a percentage of the conductive material, BC (m2/g) represents a specific surface area of the conductive material, RA (mass %) represents a percentage of the positive electrode active material, BA (m2/g) represents a specific surface area of the positive electrode active material, and RS represents a total surface area ratio, an aspect ratio AR of the conductive material is thirty or greater, the total surface area ratio RS is in a range of 0.20 to 1.93, and a porosity P (%) of the positive electrode mixture layer is in a range of 40% to 55%.