Graphite Negative Electrode Tuning for Fast-Charging Secondary Batteries
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Solution Overview
Problem
Rechargeable batteries face challenges in achieving high energy density and fast charging capability without compromising safety and cycle life, as the design of the negative electrode plate affects both energy density and charging speed, leading to heat issues during fast charging.
Innovation Solution
A secondary battery design featuring a negative electrode plate with a specific negative active material, such as graphite, tested under controlled conditions to optimize capacity ratios and coating weights, combined with a positive electrode plate using materials like lithium nickel cobalt manganese oxide, to balance energy density and charging speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the weight of the active material coated on the unit area of the current collector is increased to obtain high energy density, then the energy density is improved, but the charging capability deteriorates
Solution Approach 1:
The patent changes the particle size parameter of the negative active material to D50=4μm~18μm and controls the coating weight CW to satisfy 0.05≤(A/X)×CW≤2.00, where A and X are capacity values obtained under specific discharge conditions. This parameter optimization enables the negative electrode to achieve both high energy density and fast charging capability by balancing the coating weight and particle size characteristics.
2Productivity
If the charging capability is improved by reducing the weight of the active material, then the charging capability is improved, but the energy density deteriorates
Solution Approach 1:
The patent optimizes the particle size distribution (D50=4μm~18μm) and controls the coating weight within a specific range (0.05≤(A/X)×CW≤2.00) to achieve the best balance between charging capability and energy density. This parameter optimization ensures that the negative electrode can deliver both fast charging performance and high energy density simultaneously.
3Speed
If fast charging is performed to improve charging speed, then the charging speed is improved, but heat generation increases affecting safety
Solution Approach 1:
The patent controls the particle size (D50=4μm~18μm) and coating weight parameters to optimize the negative electrode's electrochemical performance. This parameter optimization enables fast charging while controlling heat generation by ensuring uniform current distribution and reducing polarization effects during rapid charge/discharge cycles.
Solution Approach 2:
The patent uses graphite as the negative active material, which is a cost-effective and well-established material with good thermal stability. By optimizing the graphite particle size and coating weight, the patent achieves fast charging capability while maintaining safety through the inherent thermal stability of graphite.
Data Source
AI summary
The present invention provides a secondary battery. The negative active material comprises graphite, and the negative active material satisfies the following characteristics when the negative active material is tested in a button half battery: the button half battery is discharged to 5 mV at a constant current of 0.05 C, and the obtained capacity is recorded as X; then the button half battery is discharged to 5 mV at a constant current of 50 µA, and the obtained capacity is recorded as A; then the button half battery is discharged to 5 mV at a constant current of 10 µA, and the obtained capacity is recorded as B; and 0.02≤(A+B)/X≤0.50. In the present invention, by selecting an appropriate negative active material, a secondary battery having long cycle life, high energy density and fast charging capability at the same time is obtained.