Lithium-Ion Battery Electrode Structure for Swelling-Induced Casing Stress
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Solution Overview
Problem
Lithium-ion batteries experience swelling of the negative electrode, leading to potential damage, safety hazards, and reduced cycle life due to microscopic internal stress and macroscopic thickness changes during charging and discharging.
Innovation Solution
A lithium-ion battery design that satisfies specific formulas controlling the tensile strength and thickness of the negative electrode current collector, puncture strength and thickness of the separator, and thickness and OI value of the negative electrode active layer, along with the mass percentage of silicon-based material, to mitigate the extrusion effect on the battery housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the negative electrode active material swells during charging and discharging, then lithium ion insertion and extraction is enabled, but extrusion effect on battery housing and potential damage occur
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of the negative electrode current collector (d1) and the puncture strength (m2) within specific ranges. These parameter adjustments enable the structure to accommodate the swelling of negative electrode active material during charging and discharging, thereby reducing the extrusion effect on the battery housing while maintaining charging and discharging capability.
Solution Approach 2:
The patent employs composite materials by combining the negative electrode current collector with the negative electrode active layer in a structured configuration. This composite structure allows the current collector to provide mechanical support and accommodate volume changes of the active material, effectively mitigating the harmful extrusion effects while preserving electrochemical performance.
2Stability of the object's composition
If the negative electrode current collector thickness is increased to reduce swelling, then structural stability improves, but battery energy density decreases
Solution Approach 1:
The patent applies parameter changes by optimizing the thickness of the negative electrode current collector (d1) within a specific range. This precise parameter control ensures sufficient structural stability to accommodate swelling while minimizing the thickness to preserve battery energy density, achieving a balance between mechanical support and electrochemical performance.
3Reliability
If the separator puncture strength is increased to prevent damage, then safety improves, but manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by specifying the puncture strength (m2) of the separator within a defined range. This parameter optimization ensures adequate safety performance to prevent damage during electrode swelling while maintaining manufacturability by avoiding excessively high strength requirements that would complicate the manufacturing process.
Data Source
AI summary
The disclosure provides a lithium-ion battery that satisfies the equation (2M+3)2(S+2)2/W≥20, where M=exp(m1/d1)+(d1−2)(m1−0.26). Wherein, m1 is the tensile strength of the negative electrode current collector in the length direction, and d1 is the thickness of the negative electrode current collector. Additionally, S=exp(m2/d2)+(d2−2)(m2−0.16), wherein m2 is the puncture strength of the separator, and d2 is the thickness of the substrate within the separator. Furthermore, W=(((exp(−10q))/(φ−6)+exp(10q))(d3−13.5)(ρ−3.5))/100. This disclosure effectively addresses the issue of pressure exerted on the battery casing due to volume swelling of the negative electrode material, thereby significantly enhancing the battery's cycle life and safety performance.