Lithium Ion Battery Electrode Winding Strain Reduction
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Solution Overview
Problem
The porous film in lithium ion secondary batteries lacks structural strength parallel to the electrode surface, leading to potential breakage and short-circuiting during the winding process due to strain from electrode edges and gaps.
Innovation Solution
A lithium ion secondary battery design featuring a porous film with a filler and binder on at least one electrode, where the active material layer is applied on one side of the core member on the initial winding side, and a recess in the winding core to reduce strain, optionally with a separator between the electrodes, and a lead welded to the region without active material to minimize gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a porous film is formed on the electrode surface to eliminate the separator, then the structure is simplified and short-circuit prevention is improved, but the film lacks structural strength and may break during winding
Solution Approach 1:
The patent applies composite materials by combining the porous film with a filler material to create a reinforced structure. The porous film alone lacks sufficient strength, but when combined with the filler in a composite configuration, the resulting structure maintains both the porosity needed for ion transport and the mechanical strength required to prevent breakage during winding and assembly.
2Ease of manufacture
If the porous film is integrated into the electrode without a separator, then manufacturing is simplified, but the film is susceptible to breakage from strain during winding
Solution Approach 1:
The patent implements beforehand cushioning by designing the electrode structure with sufficient margin and reinforcement before the winding process occurs. The porous film is integrated with the electrode and filler in advance to create a pre-reinforced structure that can withstand the strain and stress that will be applied during subsequent winding and assembly operations.
3Quantity of substance
If the active material layer is applied on both sides of the core member, then electrode capacity is maximized, but gaps at the edges create strain that breaks the porous film
Solution Approach 1:
The patent applies local quality by varying the application of the active material layer across different regions of the core member. Instead of uniformly applying the active material layer on both sides throughout, the configuration allows regions without active material layers, creating local variations that eliminate gap-induced strain at critical areas while preserving active material in regions where it is needed for capacity.
Data Source
AI summary
A lithium ion secondary battery having an electrode group that includes: a winding core, a positive electrode containing a positive electrode core member and a positive electrode active material layer, a negative electrode comprising a negative electrode core member and a negative electrode active material layer, and a porous film including a filler and a binder formed on at least one of the positive and negative electrodes which are wound around the winding core. The positive electrode and/or the negative electrode have/has, on the initial winding side, a region where the active material layer is carried on only one side of the core member and a region where the active material layer is carried on neither side of the core member, at a position closer to the initial winding position than the region where the active material layer is carried on only one side of the core member.