Battery Separator Creep Range for Cycle-Stable Energy Storage
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Solution Overview
Problem
Energy storage devices face a challenge in maintaining high capacity retention ratios after repeated charge-discharge cycles due to issues with the degradation of positive active materials and separators, leading to decreased electrolyte availability and electron conductivity.
Innovation Solution
An energy storage device design featuring a positive electrode with a positive active material layer using particles with an average size of 1.0 μm or more, combined with a separator that exhibits a creep strain of 11% to 28% after a 2 MPa load at 65°C for 24 hours, optimizing the balance between void reduction and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the positive active material has a small primary particle size (less than 1 μm), then the initial capacity is improved, but the capacity retention ratio after charge-discharge cycles decreases due to pulverization and cracking
Solution Approach 1:
The patent changes the particle size parameter of the positive active material from fine particles (less than 1 μm) to coarse particles (1 μm or more). This parameter change resolves the contradiction by sacrificing some initial capacity for significantly improved capacity retention ratio, as coarse particles are less susceptible to pulverization and cracking during repeated charge-discharge cycles.
2Quantity of substance
If the separator is made hard to reduce voids, then the electrolyte retention is improved, but the electron conductivity decreases
Solution Approach 1:
The patent changes the physical parameter of the separator by controlling its creep strain to be within a specific range (11% to 28%). This parameter change resolves the contradiction by finding an optimal balance point where the separator is soft enough to maintain electron conductivity through adequate void spaces, yet sufficiently rigid to retain electrolyte, achieving both requirements simultaneously.
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 enhances the capacity retention ratio by minimizing electrolyte depletion and maintaining electron conductivity, thereby improving the device's performance over charge-discharge cycles.
Implementation Method 1
a creep strain in the separator after a load of 2 MPa is held for 24 hours at a temperature of 65° C. is 11% or more and 28% or less
Data Source
AI summary
An energy storage device according to an aspect of the present invention includes: a positive electrode; a negative electrode; and a separator disposed between the positive electrode and the negative electrode, in which the positive electrode includes a positive active material layer containing a positive active material having an average primary particle size of 1.0 μm or more, and a creep strain in the separator after a load of 2 MPa is held for 24 hours at a temperature of 65° C. is 11% or more and 28% or less.