Battery Separator Surface Structure for Dendrite Shape Control
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Solution Overview
Problem
Lithium ion secondary batteries face issues with fibrous dendrite growth leading to micro short circuits, which reduce long-term reliability and voltage, as existing technologies do not effectively control the shape of dendrites.
Innovation Solution
A nonaqueous electrolyte secondary battery separator with controlled surface smoothness and rigidity, characterized by specific kurtosis and standard deviation of surface unevenness, and a laminated structure with a porous layer containing nitrogen-containing aromatic resin, such as aramid resin, to control dendrite shape and prevent penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the separator has high ion permeability to satisfy high output power demand, then the output power is improved, but fibrous dendrite growth occurs leading to micro short circuits and reduced reliability
Solution Approach 1:
The invention applies different surface roughness characteristics to different regions of the separator surface. Specifically, it controls the arithmetic mean roughness Ra to be within 0.5-5.0 μm and the maximum height of the profile Rz to be within 3-20 μm, creating an optimized local surface quality that prevents dendrite penetration while maintaining ion permeability for high power output
Solution Approach 2:
The invention changes the surface roughness parameters of the separator by controlling the arithmetic mean roughness Ra and maximum height of the profile Rz within specific ranges. This parameter optimization modifies the dendrite growth environment, preventing fibrous dendrite formation and micro short circuits while maintaining high ion permeability for improved output power and reliability
2Reliability
If the separator surface is made smoother to prevent dendrite penetration, then short circuit prevention is improved, but ion permeability may be reduced affecting output power
Solution Approach 1:
The invention optimizes surface roughness parameters within specific ranges (Ra: 0.5-5.0 μm, Rz: 3-20 μm) to achieve the balance between short circuit prevention and ion permeability. This controlled roughness prevents fibrous dendrite growth while maintaining sufficient ion transport pathways for high power output
3Reliability
If the separator rigidity is increased to control dendrite shape, then dendrite morphology control is improved, but manufacturing complexity increases
Solution Approach 1:
The invention controls the compressive elastic modulus within 10-500 MPa to achieve appropriate rigidity for dendrite shape control. This parameter optimization allows the separator to maintain structural integrity and guide dendrite morphology without requiring complex manufacturing processes
Solution Approach 2:
The invention uses a laminated structure combining a porous base layer with a polyolefin porous film layer. This composite structure provides the necessary rigidity for dendrite control while maintaining manufacturing feasibility through established lamination techniques
Data Source
AI summary
A nonaqueous electrolyte secondary battery separator has a short circuit prevention effect improved by controlling the shape of a dendrite. In the nonaqueous electrolyte secondary battery separator, when unevenness data of at least one surface of the separator is analyzed, kurtosis of a data group of heights from a reference level is not less than 5, and standard deviation of the data group of the heights from the reference level is not more than 12.