Cylindrical Battery Electrode Density Layout for Surface Pressure Balance
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Solution Overview
Problem
The expansion and contraction of the negative electrode in a wound-type electrode assembly lead to localized increases in surface pressure, causing uneven electrode reaction and electrolyte distribution, which affects battery characteristics.
Innovation Solution
A cylindrical battery design with a negative electrode wound ten times or more, featuring a low-density area at 25% to 35% of the total turns, and a high-density area at other turns, to prevent localized surface pressure increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the negative electrode is wound with uniform density throughout all turns, then the manufacturing process is simple, but the surface pressure locally increases due to expansion and contraction, causing uneven electrode reaction and electrolyte distribution
Solution Approach 1:
The negative electrode is designed with non-uniform density distribution, creating a low-density area at specific turns (25%-35% from the winding start) and high-density areas at other turns. This local variation in density compensates for the expansion and contraction effects during battery operation, preventing localized surface pressure increases and ensuring uniform electrode reaction and electrolyte distribution throughout the wound structure.
2Reliability
If the negative electrode has a low-density area at turns 25% to 35%, then the surface pressure distribution is improved, but the manufacturing precision requirement increases
Solution Approach 1:
The invention changes the density parameter of the negative electrode mixture layer at specific positions during the winding process. By controlling the density to be lower at turns 25%-35% and higher at other turns, the structure compensates for mechanical expansion and contraction, achieving more uniform surface pressure distribution while maintaining manufacturability through controlled parameter variation.
Data Source
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AI summary
This cylindrical battery comprises: an electrode body in which a long positive electrode, which has a positive electrode core body and a positive electrode mixture layer, and a long negative electrode (12), which has a negative electrode core body (12a) and a negative electrode mixture layer (12b), are wound with a separator therebetween; a bottomed tubular exterior can that houses the electrode body; and a sealing body that seals an opening in the exterior can. In a case where the number of windings of the negative electrode (12) is counted from the side where the winding starts on the basis of a range, of the negative electrode (12), opposing the positive electrode via the separator, the negative electrode (12) is wound ten or more times, and in the negative electrode mixture layer (12b), a first mixture layer region (15a), which is located in a winding 25% to 35% through the total number of windings of the negative electrode (12), has a low-density region (14b), in the negative electrode mixture layer (12b), which has a lower density than a second mixture layer region (15b) located on the outside of the first mixture layer region.