Negative Electrode Plate with Embedded Silicon Oxide
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries using graphite and silicon oxide as negative electrode active materials face challenges in maintaining charge/discharge cycle characteristics due to the expansion and contraction of silicon oxide, leading to adhesion loss between graphite and silicon oxide particles, which deteriorates battery performance.
Innovation Solution
A negative electrode plate with a composite material layer containing graphite, amorphous carbon-coated graphite particles, and silicon oxide particles, where the silicon oxide is embedded within the graphite, providing a spring constant of 700 kN/mm to 3000 kN/mm and a density of 1.5 g/cm3 to enhance adhesion and rigidity, thereby improving charge/discharge cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon oxide is used as negative electrode active material to increase capacity, then specific capacity is improved, but charge/discharge cycle characteristics deteriorate due to expansion and contraction
Solution Approach 1:
Silicon oxide particles are embedded within graphite particles, creating a nested structure where the expanding silicon oxide is contained within the graphite matrix. This prevents adhesion loss between particles during charge/discharge cycles while maintaining the high capacity benefit of silicon oxide.
Solution Approach 2:
The invention uses a composite material system combining graphite and silicon oxide in specific proportions (2-10 mass% silicon oxide). The composite structure leverages the stability of graphite and the high capacity of silicon oxide, achieving both improved capacity and maintained cycle characteristics.
2Reliability
If the spring constant is increased to maintain rigidity and prevent deformation, then charge/discharge cycle characteristics are improved, but the binder may break easily
Solution Approach 1:
The invention optimizes the spring constant parameter to a specific range (700-3000 kN/mm) that balances rigidity and binder stress. This parameter optimization ensures the electrode plate is rigid enough to maintain particle adhesion during silicon oxide expansion/contraction, while not so rigid as to cause binder failure.
3Reliability
If the negative electrode composite material layer density is increased to improve adhesion, then charge/discharge cycle characteristics are improved, but manufacturing complexity increases
Solution Approach 1:
The invention specifies a density range (1.5 g/cm³ or more) for the negative electrode composite material layer that optimizes particle adhesion while remaining achievable through standard manufacturing processes. This parameter control ensures good contact between graphite and silicon oxide particles without requiring excessive manufacturing complexity.
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
The solution enhances the charge/discharge cycle characteristics and capacity retention of non-aqueous electrolyte secondary batteries by maintaining the adhesion between graphite and silicon oxide particles, allowing the battery to withstand expansion and contraction, and balancing capacity and cycle performance.
Implementation Method 1
The amorphous carbon material is coated on the surface of each graphite particle
Implementation Method 2
The negative electrode plate has a spring constant of 700 kN/mm or more, and thereby the negative electrode plate may have a rigidity (difficulty in deformation) to withstand the expansion and contraction of silicon oxide
Data Source
AI summary
The negative electrode plate includes at least a negative electrode composite material layer. The negative electrode composite material layer has a density of 1.5 g/cm3 or more. The negative electrode composite material layer contains at least first particles, second particles and a binder. The first particles contain graphite particles and an amorphous carbon material. The amorphous carbon material is coated on the surface of each graphite particle. The second particles are made of silicon oxide. The ratio of the second particles to the total amount of the first particles and the second particles is 2 mass % or more to 10 mass % or less. The negative electrode plate has a spring constant of 700 kN/mm or more to 3000 kN/mm or less.