Wound Secondary Battery Structure to Prevent Separator Deformation
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Solution Overview
Problem
Lithium ion batteries of cylindrical shape face issues with internal short circuits due to metal powder from the positive electrode current collector coming into contact with the negative electrode, and structural deformation during the suction process, which compromises safety.
Innovation Solution
The battery design includes a positive electrode and negative electrode with uncovered parts that are bent towards the central axis to form flat surfaces, with grooves and thermal fusion bonding of separator layers to prevent metal powder contact and deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal powder removal process is applied to the electrode wound body, then safety is improved by preventing internal short circuits, but the separator may be deformed during the suction process
Solution Approach 1:
The separator layers are thermally fused together in advance before the metal powder removal process. This preliminary bonding action creates a rigid, integrated structure that resists deformation when subjected to the suction forces during metal powder removal, thus preventing separator deformation while maintaining safety
Solution Approach 2:
The physical state of the separator is changed from loose layers to a bonded, rigid structure through thermal fusion. This parameter change in the separator's mechanical properties (from flexible to rigid) enables it to withstand the suction process without deforming, resolving the contradiction between safety and shape maintenance
2Quantity of substance
If the electrode wound body is made compact to improve energy density, then space utilization is improved, but metal powder from the positive electrode current collector may come into contact with the negative electrode
Solution Approach 1:
A protective layer is introduced as an intermediary between the positive electrode current collector and the negative electrode. This protective layer prevents direct contact between metal powder from the positive electrode and the negative electrode, eliminating the internal short circuit risk while allowing the electrode wound body to maintain compact configuration for high energy density
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 configuration effectively suppresses internal short circuits and deformation, enhancing the safety and performance of the lithium ion battery by preventing metal powder contact with the innermost wind side negative electrode and maintaining separator integrity during the suction process.
Implementation Method 1
respective end parts of layers of the separator that are located at least on respective opposite sides of an innermost wind side negative electrode are coupled to each other
Data Source
AI summary
A positive electrode includes, on a positive electrode foil having a band shape, a positive electrode active material covered part covered with a positive electrode active material layer, and a positive electrode active material uncovered part. A negative electrode includes, on a negative electrode foil having a band shape, a negative electrode active material covered part covered with a negative electrode active material layer, and a negative electrode active material uncovered part extending at least in a longitudinal direction of the negative electrode foil. The positive electrode active material uncovered part is coupled to a positive electrode current collector at one end part of an electrode wound body. The negative electrode active material uncovered part is coupled to a negative electrode current collector at another end part of the electrode wound body. The electrode wound body has one or more flat surfaces, in which the positive electrode active material uncovered part, the negative electrode active material uncovered part, or both are bent toward a central axis of a wound structure to form the one or more flat surfaces, and a groove provided in each of the one or more flat surfaces. When at least a positive electrode side of the electrode wound body is viewed in a section taken along a plane including the central axis, respective end parts of layers of the separator that are located on at least respective opposite sides of an innermost wind side negative electrode are coupled to each other, the innermost wind side negative electrode being a part of the negative electrode that is located on a side of an innermost wind.