Segmented Lithium Battery Electrode with Carbon Gaps
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Solution Overview
Problem
Rechargeable lithium ion batteries face issues with active material delamination from the current collector due to volume changes during charge and discharge cycles, and deteriorated lithium ion conductivity leading to unsatisfactory cycle-life and capacity degradation.
Innovation Solution
The electrode design includes a current collector with active material patterns in a band shape and carbon layers between them, where the carbon layers have a gap of 1-10 mm, comprising materials like acetylene black, ketjen black, and carbon black, to enhance ion conductivity and reduce stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the active material is coated to be thick on the current collector to obtain high capacity, then the battery capacity is improved, but the active material easily delaminates from the current collector due to volume change stress
Solution Approach 1:
The active material layer is divided into multiple sub-layers with different thicknesses. The lower sub-layer (closer to current collector) has smaller thickness to reduce stress and prevent delamination, while the upper sub-layer has larger thickness to maintain high capacity. This segmentation resolves the contradiction between thick coating for capacity and thin coating for adhesion.
Solution Approach 2:
Different regions of the active material layer have different thicknesses tailored to their specific functions. The lower sub-layer near the current collector is thinner to accommodate volume changes and prevent delamination, while the upper sub-layer is thicker to maximize capacity. This local differentiation of quality allows each region to optimize for its specific requirement.
2Quantity of substance
If the active material layer is formed to be thick and highly densified to increase capacity, then the battery capacity is improved, but the lithium ion conductivity of the active material layer deteriorates
Solution Approach 1:
The thick active material layer is segmented into multiple sub-layers. The lower sub-layer has smaller thickness which maintains good lithium ion conductivity by reducing diffusion path length, while the upper sub-layer provides high capacity. This segmentation allows the overall layer to be thick for capacity while local regions maintain thinness for conductivity.
Solution Approach 2:
The thickness parameter of the active material layer is changed differently across different regions. The lower sub-layer has smaller thickness parameter to maintain ion conductivity, while the upper sub-layer has larger thickness parameter to increase capacity. This parameter differentiation resolves the contradiction between thickness for capacity and thinness for conductivity.
Data Source
AI summary
There is provided an electrode for a rechargeable lithium battery including a current collector, and an active material layer on the current collector, the active material layer including a plurality of active material patterns having a band shape and a plurality of carbon layers between the neighboring active material patterns, wherein neighboring ones of the carbon layers have a gap of greater than about 1 mm and less than about 10 mm.