Graphite Anode Porosity and SBR Balance for Cycle-Stable Batteries
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries with graphite negative electrodes face deterioration in charging/discharging cyclic characteristics due to reduced contact with the electrolyte and poor particle binding, especially when using graphite particles with small porosity and high porosity voids between particles.
Innovation Solution
A non-aqueous electrolyte secondary battery design featuring a negative electrode active material layer with graphite particles having porosity due to closed pores of 1% to 5% and porosity due to voids between particles of 10% to 20%, along with a styrene-butadiene copolymer rubber (SBR) content of 1.5 to 3 mass %, ensuring adequate electrolyte retention and particle binding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If graphite particles with small porosity due to closed pores are used, then reliability is improved, but manufacturing precision deteriorates due to difficulty in controlling porosity within the specific range
Solution Approach 1:
The patent applies parameter changes by precisely controlling the porosity due to closed pores of graphite particles within the specific range of 1% to 5%, and controlling the porosity due to voids between particles within 10% to 20%. This quantitative parameter control resolves the contradiction by establishing exact manufacturing specifications that ensure both reliability improvement and manufacturing precision.
2Reliability
If porosity due to voids between particles is increased to improve electrolyte contact, then reliability deteriorates due to particle breakage and decomposition reactions
Solution Approach 1:
The patent resolves this contradiction by optimizing the porosity due to voids between particles to within 10% to 20%, which is sufficient for electrolyte contact but controlled low enough to prevent particle breakage and decomposition reactions. This precise parameter optimization balances electrolyte accessibility with structural integrity.
Solution Approach 2:
The patent uses a composite negative electrode active material layer combining graphite particles with specific porosity characteristics and SBR binder content (1.5 to 3 mass %). This composite structure provides both adequate electrolyte contact pathways and mechanical binding to prevent particle breakage during charging/discharging cycles.
3Reliability
If SBR content is increased to improve particle binding, then reliability improves, but manufacturing complexity increases due to precise content control requirements
Solution Approach 1:
The patent simplifies manufacturing complexity by establishing a clear quantitative parameter range for SBR content (1.5 to 3 mass % based on negative electrode active material mass). This specific parameter specification provides straightforward manufacturing guidance while ensuring adequate particle binding and reliability.
Data Source
AI summary
The purpose of the present disclosure is to provide a non-aqueous secondary battery that is able to suppress a decrease in charge-discharge cycle characteristics. The non-aqueous electrolyte secondary battery that is a mode of the present disclosure comprises a negative electrode having a negative electrode active material layer, wherein the negative electrode active material layer contains a negative electrode active material that contains graphite particles, and an SBR component selected from at least one of a styrene-butadiene copolymer rubber and a modified product thereof, the internal porosity of the graphite particles is 1% to 5%, the porosity due to voids between particles of the negative electrode active material layer is 10% to 20%, and the content of the SBR component is 1.5 mass % to 3 mass % with respect to the mass of the negative electrode active material.