Wound Electrode Packing Density for Battery Cycle Life
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face a decrease in cycle characteristics due to electrolyte depletion in the flat part of the electrode body during charge/discharge, leading to liquid shortage and insufficient electrolyte for battery reactions.
Innovation Solution
A nonaqueous electrolyte secondary battery design with a wound electrode body having a flat part and curved parts, where the negative electrode mixture layer's packing density ratio between the curved and flat parts is optimized (0.75 to 0.95) and the sectional area ratio of curved to flat parts is controlled (0.28 to 0.32), allowing effective electrolyte stocking and redistribution during volume changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the electrode body is designed with a flat part and curved parts to suppress distortion, then the electrode plate distortion is reduced, but the electrolyte is pushed out from the flat part during expansion, causing electrolyte depletion and decreased cycle characteristics
Solution Approach 1:
The patent applies local quality by creating different packing densities in different regions of the negative electrode mixture layer. Specifically, the packing density in the curved parts is set to 0.75-0.95 times that of the flat part, making each region have optimized properties for its specific function: the flat part maintains structural stability while the curved parts act as electrolyte reservoirs.
Solution Approach 2:
The patent implements preliminary action by pre-positioning electrolyte in the curved parts of the electrode body before charge/discharge cycles begin. The curved parts are designed with specific packing densities to serve as advance-prepared electrolyte reservoirs that will automatically supply electrolyte to the flat part when needed during electrode expansion.
2Quantity of substance
If the packing density in curved parts is reduced to stock electrolyte, then electrolyte depletion is suppressed, but the electrode body structure becomes more complex with specific density ratios required
Solution Approach 1:
The patent applies parameter changes by optimizing specific numerical ranges for packing density ratios (0.75-0.95) and sectional area ratios (0.28-0.32). These parameter changes transform a complex structural problem into a controllable set of numerical specifications that can be achieved through standard manufacturing processes while ensuring electrolyte retention functionality.
3Quantity of substance
If the sectional area of curved parts is increased to provide electrolyte reservoir, then electrolyte pushing out is suppressed, but the overall electrode body volume increases
Solution Approach 1:
The patent uses parameter changes to optimize the sectional area ratio of curved parts to the flat part within the range of 0.28-0.32. This numerical optimization ensures that the curved parts provide sufficient electrolyte reservoir capacity while minimizing the volume occupied by curved structures, thus maintaining a compact overall electrode body design.
Data Source
AI summary
A nonaqueous electrolyte secondary battery according to an embodiment of the present disclosure includes a negative electrode mixture layer which contains a first region located in a flat part of an electrode body and second regions located in a pair of curved parts of the electrode body, the ratio (B/A) of the packing density (B) in each of the second regions to the packing density (A) in the first region being 0.75 or more and 0.95 or less. Further, in a section passing through the center in the axial direction of the electrode body and being perpendicular to the axial direction, the ratio (SB/SA) of the sectional area (SB) of the pair of curved parts to the sectional area (SA) of the flat part is 0.28 or more and 0.32 or less.