Spirally Wound Battery Non-Uniform Cathode Thickness
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Solution Overview
Problem
High-capacity batteries with spirally wound electrode bodies face challenges in preventing cracks and breaks when the thickness of the cathode active material layer is increased, particularly with materials like tin and silicon, due to stress relaxation issues during winding.
Innovation Solution
A battery design where the spirally wound electrode body has a cathode with a thinner inner-face active material layer and a thicker outer-face active material layer, with an outer face active material region overlapping the lead on the center side to reduce stress and prevent cracks, and a similar configuration for the anode to optimize capacity and prevent breaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness of the cathode active material layer is increased to improve capacity, then the energy density is improved, but cracks and breaks are easily generated in the active material layer during spirally winding
Solution Approach 1:
The patent applies local quality by making the active material layer thickness non-uniform: the inner-face thickness is smaller than the outer-face thickness. This local variation in thickness allows the inner portion to better accommodate winding stress while the outer portion maintains high capacity, resolving the contradiction between overall thickness increase and crack prevention during spirally winding.
2Reliability
If the thickness of the inner-face cathode active material layer is reduced to prevent cracks during winding, then the stress relaxation is improved, but the capacity is insufficient
Solution Approach 1:
The patent makes different portions of the active material layer have different thicknesses: the inner-face (near the winding center) has smaller thickness to prevent cracks, while the outer-face (near the winding outer surface) has larger thickness to provide capacity. This local differentiation resolves the contradiction between crack prevention and capacity maintenance.
Solution Approach 2:
The patent introduces a radial dimension variation in thickness, transitioning from uniform thickness to radially varying thickness. This dimensional change allows the structure to simultaneously achieve stress relaxation at the inner radius and high capacity at the outer radius, resolving the contradiction between reliability and quantity of active material.
3Quantity of substance
If high capacity materials such as tin and silicon are used for the anode to increase capacity, then the energy density is improved, but the thickness of the cathode active material layer must be increased which causes cracks
Solution Approach 1:
The patent applies local quality by varying the cathode active material layer thickness radially, with the inner-face being thinner than the outer-face. This allows the use of high-capacity anode materials like tin and silicon while preventing cracks in the cathode during winding, as the thinner inner portion accommodates winding stress and the thicker outer portion maintains capacity.
Data Source
AI summary
A battery includes a spirally wound electrode body in which a cathode and an anode are layered with a separator in between and spirally wound. The spirally wound electrode body is attached with at least one lead on the spirally-winding center side. The cathode has a cathode current collector having a pair of opposed faces, an outer-face cathode active material layer provided on the spirally-winding outer face side of the cathode current collector, and an inner-face cathode active material layer provided on the spirally-winding inner face side thereof. A thickness of the inner-face cathode active material layer is smaller than a thickness of the outer-face cathode active material layer. An outer face active material region provided with only the outer-face cathode active material layer is formed to be overlapped with the lead on the spirally-winding center side of the cathode.