Asymmetric Graphite Anode Structure 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 charging characteristics.
Innovation Solution
A negative electrode for rechargeable lithium batteries is designed with a current collector, a first negative active material layer on one side with a higher loading level, and a second negative active material layer on the other side with a lower loading level. The first layer includes a 1a layer contacting the current collector and a 1b layer on one side of the 1a layer, using natural or artificial graphite-based materials to enhance adhesion and reduce resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the loading level of the negative active material layer is increased to achieve high capacity, then the battery capacity is improved, but the resistance increases and fast charge performance deteriorates
Solution Approach 1:
The negative active material layer is divided into two distinct layers: a first negative active material layer with higher loading level (10.0 to 15.0 g/cm²) and a second negative active material layer with lower loading level (5.0 to 10.0 g/cm²). This segmentation allows the battery to achieve high overall capacity while the lower-loading second layer maintains lower resistance and better fast charge performance, resolving the contradiction between capacity and charging speed.
Solution Approach 2:
Different regions of the negative electrode are assigned different loading levels to optimize local performance. The first layer (closer to the current collector) has higher loading level to maximize capacity, while the second layer (outer layer) has lower loading level to maintain low resistance and facilitate rapid charge acceptance. This local differentiation resolves the global contradiction between high capacity and fast charging.
2Reliability
If the negative active material layer is made thinner to reduce resistance, then fast charge performance is improved, but the battery capacity decreases
Solution Approach 1:
Instead of using a single thin layer that would limit capacity, the structure is segmented into two layers with different thicknesses and loading levels. The first layer provides high capacity contribution, while the second layer ensures low resistance and fast charge capability, thus achieving both high capacity and fast charge performance simultaneously.
Solution Approach 2:
The negative electrode uses a composite structure of two different negative active material layers with different loading levels and compositions. This composite approach allows the electrode to exhibit both high capacity characteristics (from the first layer) and low resistance/fast charge characteristics (from the second layer), resolving the contradiction between capacity and charging speed.
3Ease of manufacture
If a single-layer negative active material layer is used to simplify the structure, then manufacturing complexity is reduced, but it is difficult to achieve both high capacity and fast charge performance
Solution Approach 1:
The negative active material layer is segmented into two sub-layers with different loading levels, allowing each layer to perform its specific function optimally. This segmentation enables the achievement of both high capacity and fast charge performance, which would be difficult to realize with a single uniform layer, while still maintaining a relatively simple overall structure.
Data Source
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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.