Layered Graphite Negative Electrode for Fast-Charging Li Batteries
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving high-capacity and fast charge performance, particularly in maintaining low resistance and preventing decreases in fast charging characteristics.
Innovation Solution
A negative electrode for rechargeable lithium batteries is designed with a current collector having a first negative active material layer with a higher loading level than a second negative active material layer. The first layer includes a 1a layer contacting the current collector and a 1b layer, with the 1a layer containing natural or mixed graphite and the 1b layer containing artificial graphite, optimizing adhesion and reducing resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the loading level of the negative active material layer is increased to provide high capacity, then the capacity is improved, but the resistance increases and fast charge performance deteriorates
Solution Approach 1:
The negative active material layer is divided into multiple layers with different loading levels. The first negative active material layer has a higher loading level (10.0 to 20.0 mg/cm²) to provide high capacity, while the second negative active material layer has a lower loading level (5.0 to 15.0 mg/cm²) to maintain low resistance and fast charge performance. This segmentation allows each layer to optimize for its specific function.
Solution Approach 2:
Different regions of the negative electrode are assigned different loading levels to achieve different local functions. The first layer with higher loading level is positioned to maximize capacity contribution, while the second layer with lower loading level is positioned to maintain electrical conductivity and fast charge characteristics. This creates local quality variations that resolve the contradiction between capacity and fast charge performance.
2Device complexity
If a single-layer negative active material layer is used to simplify structure, then the device complexity is reduced, but the ability to simultaneously achieve high capacity and fast charge performance is compromised
Solution Approach 1:
The negative active material layer is segmented into a first layer and a second layer with different loading levels and material compositions. This segmentation enables the electrode to simultaneously achieve high capacity (through the first layer) and fast charge performance (through the second layer), resolving the contradiction between structural simplicity and performance requirements.
Solution Approach 2:
The patent uses composite material composition in the layers, where the first negative active material layer contains natural graphite or a mixture of natural and artificial graphite, while the second layer contains artificial graphite. This composite approach allows each layer to contribute different properties, achieving both high capacity and fast charge performance while managing structural complexity.
Data Source
AI summary
Disclosed are a negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same. The negative electrode includes a current collector, a first negative active material layer on a first side of the current collector; and a second negative active material layer on a second side of the current collector, wherein a loading level (A) of the first negative active material layer is larger than a loading level (B) of the second negative active material layer, the first negative active material layer includes a 1a layer contacting the current collector and a 1b layer on one side of the 1a layer, the 1a layer includes a 1a negative active material, the 1b layer includes a 1b negative active material, the 1a negative active material includes natural graphite, or a mixture of natural graphite and artificial graphite, the 1b negative active material includes artificial graphite, and the second negative active material layer is a single layer.