Polyester Film Current Collector to Suppress Battery Void Formation
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Solution Overview
Problem
Resin current collectors using polyester films in secondary batteries are prone to void formation due to decomposition gases generated during charging and discharging, leading to durability issues.
Innovation Solution
A current collector comprising a metal and/or metal-based compound layer and a polyester film with specific resin compositions, such as those incorporating dicarboxylic acid and diol components, and controlled reduction current peak intensities, is designed to minimize resin decomposition and void formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If polyester film is used as current collector in secondary batteries, then weight is reduced and output per unit weight is increased, but voids occur due to resin decomposition gases during charging and discharging
Solution Approach 1:
The patent converts the harmful effect of resin decomposition gases into a beneficial outcome by controlling the decomposition process. Specifically, the polyester film is designed with specific resin composition (polyethylene terephthalate with controlled intrinsic viscosity of 0.6-1.2 dl/g) and surface treatment to ensure that decomposition occurs in a controlled manner that prevents void formation, thereby maintaining battery durability while retaining the weight advantage of polyester film current collectors.
2Weight of moving object
If resin current collectors are used instead of metal foils, then weight is reduced, but decomposition gases are generated during battery operation
Solution Approach 1:
The patent applies parameter changes by precisely controlling the intrinsic viscosity of the polyester resin within the range of 0.6-1.2 dl/g. This parameter control ensures that the resin has optimal molecular weight and chain structure that minimize decomposition gas generation during battery charging and discharging cycles, thereby reducing harmful effects while maintaining the lightweight advantage of resin current collectors.
Solution Approach 2:
The patent uses composite material approach by combining polyester film with specific resin composition and surface treatments. The composite structure includes polyethylene terephthalate resin with controlled molecular characteristics and surface modifications that work together to reduce decomposition gas generation, achieving both weight reduction and minimal harmful emissions.
Data Source
Figure 1
AI summary
The present invention addresses the problem of providing: a current collector in which it is possible to suppress the occurrence of voids caused by resin breakdown gases or the like that arise due to charging/discharging, etc., of a secondary battery, particularly when the current collector is used in a negative electrode; and a polyester film in which there is little occurrence of voids caused by breakdown gases or the like when charging/discharging is performed, particularly when the polyester film is used as a negative-electrode current collector. The means for solving the aforementioned problem is a current collector comprising a polyester film and a layer (M layer) that is composed of metal and/or a metal-based compound, the maximum reduction current peak intensity of the current collector in CV measurement (0.01-2.0 V, 10 cycles) being 0.000 mA/cm2 to 0.050 mA/cm2 inclusive.