Graphite Negative Electrode Tuning for Fast-Charging Li-Ion Batteries
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Solution Overview
Problem
Existing rechargeable batteries, particularly lithium-ion batteries, face challenges in achieving fast charging capabilities without compromising energy density and cycle life due to issues with the design of the negative active material and electrode plate, leading to lithium precipitation and safety hazards.
Innovation Solution
A secondary battery design that includes a negative electrode plate with a negative active material composed of graphite, where the graphitization degree, capacity excess ratio, and OI value of the negative film are optimized to satisfy specific relationships, enhancing energy density, dynamics performance, and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If lithium titanate or amorphous carbon is used as negative active material to achieve fast charging capability, then the rate performance is improved, but the energy density of the battery decreases
Solution Approach 1:
The patent changes the crystalline structure parameters of graphite by controlling the graphitization degree (0.2≤Δd002<0.0045) and lattice spacing, thereby improving lithium ion diffusion speed while maintaining high energy density. This resolves the contradiction by modifying material parameters rather than changing material composition.
Solution Approach 2:
The patent uses composite graphite material with specific crystalline structure characteristics (combining highly graphitized regions with controlled defects) to achieve both fast charging capability and high energy density, rather than using single-phase materials like lithium titanate or amorphous carbon.
2Productivity
If large charging rate is applied to charge the battery, then the charging speed is improved, but lithium metal precipitates on the negative electrode plate and side-products are generated, affecting cycle life and safety
Solution Approach 1:
The patent performs preliminary structural optimization on the graphite crystalline structure before charging, creating a pre-conditioned lattice structure with controlled defects and specific graphitization degree that facilitates smooth lithium ion insertion even at high charging rates, preventing lithium precipitation before it occurs.
Solution Approach 2:
By precisely controlling the graphitization degree parameter (0.2≤Δd002<0.0045) and lattice spacing of graphite, the patent creates optimal conditions for lithium ion diffusion that prevent kinetic limitations from causing lithium precipitation during fast charging, thereby maintaining reliability at high charging speeds.
3Quantity of substance
If conventional graphite with high graphitization degree is used to achieve high energy density, then the energy density is improved, but the lithium ion diffusion speed decreases, limiting fast charging capability
Solution Approach 1:
The patent optimizes the graphitization degree parameter to a specific range (0.2≤Δd002<0.0045) that balances crystalline order for high energy density with controlled lattice spacing for fast lithium ion diffusion, resolving the contradiction between density and speed through precise parameter control.
Solution Approach 2:
The patent creates local variations in crystalline structure quality within the graphite material, maintaining highly graphitized regions for energy density while introducing controlled local defects and lattice spacing variations to enhance lithium ion diffusion pathways, achieving both high density and fast charging capability.
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 optimized battery achieves high energy density, excellent dynamics performance, and long cycle life while supporting fast charging, minimizing lithium precipitation and safety hazards.
Implementation Method 1
a negative electrode plate, a separator and an electrolyte, the negative electrode plate comprises a negative current collector and a negative film
Implementation Method 2
how to improve the tranferring speed of the lithium ions between the positive electrode plate and the negative electrode plate
Data Source
AI summary
The present invention provides a secondary battery, the secondary battery comprises a positive electrode plate, a negative electrode plate, a separator and an electrolyte, the negative electrode plate comprises a negative current collector and a negative film, the negative film is provided on at least one surface of the negative current collector and comprises a negative active material. The secondary battery satisfies relationships 3.9≤G×3.5+2.8/CB≤6.2 and 1.23≤0.55/VOI+CB×1.2≤2.80 at the same time. The battery of the present invention has the characteristics of high energy density and excellent dynamics performance, and the battery of the present invention also has the characteristic of long cycle life while charged under a large rate and a fast speed.