Negative Electrode Layer Layout for Better Electrolyte Wetting
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Solution Overview
Problem
Existing lithium secondary batteries face issues with non-wetted areas in the negative electrode, leading to defects such as lithium precipitation and performance deterioration.
Innovation Solution
The negative electrode active material layer is designed with first and second layers having different specific capacities and densities, minimizing the non-wetted area by ensuring electrolyte penetration, using a silicon-carbon composite with varying silicon and carbon ratios in each layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform negative electrode active material layer is used, then the manufacturing process is simple, but non-wetted areas form leading to lithium precipitation and performance deterioration
Solution Approach 1:
The negative electrode active material layer is segmented into multiple sub-layers (first, second, and third layers) with different specific capacities. This segmentation allows each layer to serve different functions: the first layer provides high capacity, the second layer ensures electrolyte penetration, and the third layer maintains structural integrity, thereby preventing non-wetted areas and lithium precipitation while improving overall battery reliability
Solution Approach 2:
Different regions of the negative electrode active material layer are assigned different specific capacities to address local requirements. The first layer near the current collector has higher specific capacity for energy storage, while the second intermediate layer has lower specific capacity optimized for electrolyte penetration and wetting, and the third outer layer has specific capacity designed for structural stability. This local differentiation eliminates non-wetted areas without compromising overall performance
2Quantity of substance
If high specific capacity material is used throughout the layer, then energy density increases, but electrolyte penetration is insufficient causing non-wetted areas
Solution Approach 1:
The electrode layer is divided into multiple segments with different specific capacities. The first layer contains high specific capacity material for maximum lithium ion storage, while the second intermediate layer uses material with lower specific capacity specifically optimized for electrolyte penetration and complete wetting, ensuring that high capacity regions do not compromise electrolyte access
Solution Approach 2:
The specific capacity is locally optimized at different positions within the electrode layer. Regions closer to the current collector use high specific capacity material to maximize energy storage, while intermediate regions use material with tailored lower specific capacity to ensure adequate electrolyte penetration and wetting, thus maintaining both high lithium ion capacity and reliable electrolyte distribution
3Quantity of substance
If the negative electrode active material layer is made thicker to increase capacity, then energy storage increases, but non-wetted areas increase leading to defects
Solution Approach 1:
The thick negative electrode active material layer is segmented into multiple thinner sub-layers with different specific capacities. This segmentation reduces the thickness of each individual layer, enabling complete electrolyte penetration throughout the entire structure. The intermediate layer with lower specific capacity acts as a conduit for electrolyte distribution, preventing non-wetted areas even in thick overall structures, while maintaining high total lithium ion capacity
Solution Approach 2:
Different regions of the thick electrode layer are assigned different specific capacities to optimize both capacity and wetting. The intermediate regions use material with lower specific capacity specifically to facilitate electrolyte penetration and distribution throughout the thick structure, while surface and boundary regions maintain higher specific capacity for energy storage, thus eliminating non-wetted area defects while preserving high energy storage 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
This design reduces the non-wetted area, preventing defects and improving the electrical properties of the lithium secondary battery.
Implementation Method 1
the negative electrode active material layer includes first negative electrode active material layers spaced apart from each other in a second direction that crosses the first direction, and a second negative electrode active material layer between respective ones of the first negative electrode active material layers. A ratio of a specific capacity of the first negative electrode active material layer to a specific capacity of the second negative electrode active material layer is about 0.75 to about 0.95.
Data Source
AI summary
Disclosed are a negative electrode for a lithium secondary battery, a lithium secondary battery including the same, and a method for manufacturing the lithium secondary battery. A negative electrode active includes a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector, the negative electrode active material layer has a long axis in a first direction, the negative electrode active material layer includes first negative electrode active material layers spaced apart from each other in a second direction that crosses the first direction and a second negative electrode active material layer between respective ones of the first negative electrode active material layers, and a ratio of a specific capacity of the first negative electrode active material layer to a specific capacity of the second negative electrode active material layer is 0.75 to 0.95.