Separator Porosity Control for Battery Cycle Durability
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries, particularly those for electric vehicles, face challenges in maintaining cycle durability when capacity and size are increased, due to insufficient lithium ion conductivity and electro-current constriction caused by non-uniform porosity in the separator.
Innovation Solution
A non-aqueous electrolyte secondary battery with a separator having a porosity variation of 4.0% or less, a ratio of rated capacity to pore volume of 1.55 Ah/cc or more, and a battery area to rated capacity ratio of 4.0 cm2/Ah or more, which improves lithium ion conductivity and suppresses electro-current constriction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the capacity and size of the battery are increased, then the energy storage capability is improved, but the cycle durability deteriorates due to insufficient lithium ion conductivity and electro-current constriction
Solution Approach 1:
The patent applies local quality by controlling the porosity distribution within the separator to be highly uniform (variation of 4.0% or less). This ensures that lithium ion conductivity is consistent across different regions of the separator, preventing local electro-current constriction that would otherwise occur in high-capacity batteries. The uniform porosity creates optimal local conditions for lithium ion transport throughout the entire separator area.
Solution Approach 2:
The patent employs parameter changes by precisely controlling the porosity variation of the separator to be 4.0% or less. This parameter control optimizes lithium ion conductivity while maintaining the required battery capacity. By adjusting and constraining the porosity parameter within a narrow range, the patent resolves the contradiction between increased capacity and maintained cycle durability.
2Ease of manufacture
If the porosity variation in the separator is large, then the manufacturing process is simpler, but the lithium ion conductivity becomes non-uniform causing electro-current constriction
Solution Approach 1:
The patent applies homogeneity by ensuring the separator has uniform porosity throughout its structure with a variation of 4.0% or less. This homogeneous structure guarantees consistent lithium ion conductivity across the entire separator, preventing electro-current constriction. The homogeneity principle is achieved through controlled manufacturing processes that maintain uniform pore distribution and size throughout the separator material.
3Quantity of substance
If conventional separators are used in high-capacity batteries, then the battery capacity can be increased, but sufficient cycle durability cannot be obtained due to electro-current constriction
Solution Approach 1:
The patent applies parameter changes by controlling the porosity variation of the separator to be 4.0% or less. This precise parameter control optimizes lithium ion conductivity and prevents electro-current constriction, enabling high-capacity batteries to achieve sufficient cycle durability. The parameter change transforms the separator from a conventional component with variable porosity to a precisely controlled component with uniform porosity distribution.
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 cycle durability and capacity retention, allowing for longer cruising distances in electric vehicles by maintaining high lithium ion conductivity and preventing issues like electrolyte decomposition and electrode material degradation.
Implementation Method 1
charge and discharge reactions of a battery occur as ions such as lithium ions are absorbed into and desorbed from an electrode active material
Data Source
AI summary
A non-aqueous electrolyte secondary battery with improved cycle durability includes a power generating element including a positive electrode obtained by forming a positive electrode active material layer containing a positive electrode active material on a surface of a positive electrode current collector, a negative electrode obtained by forming a negative electrode active material layer containing a negative electrode active material on a surface of a negative electrode current collector, and a separator, a ratio of a rated capacity to a pore volume of the separator being 1.55 Ah/cc or more, a ratio of a battery area to a rated capacity being 4.0 cm2/Ah or more, and a rated capacity being 30 Ah or more, wherein a variation in porosity in the separator is 4.0% or less.