Battery Separator Laminate for Dendrite Shape Control
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Solution Overview
Problem
Existing lithium ion secondary batteries face issues with fibrous dendrite growth that can lead to micro short circuits, reducing long-term reliability and voltage, as existing methods do not effectively control the shape of dendrites.
Innovation Solution
A nonaqueous electrolyte secondary battery laminate is designed with a graphite negative electrode having a non-reactivity parameter of not less than 230% and a separator surface with an average void volume of not more than 0.015 μm³, incorporating a laminated separator with a porous layer and a polyolefin porous film to control dendrite shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a separator with high ion permeability is used to satisfy high output power demand, then output power is improved, but fibrous dendrite growth occurs leading to micro short circuits and reduced reliability
Solution Approach 1:
The invention applies local quality by creating a separator surface with non-uniform void distribution - a skin layer with smaller voids on the battery interior side and larger voids on the exterior side. This local variation in void size allows the separator to simultaneously support high ion permeability (through the larger voids) and prevent fibrous dendrite penetration (through the smaller voids in the skin layer), thus resolving the contradiction between power output and reliability
Solution Approach 2:
The invention uses a composite separator structure combining a porous base layer with a skin layer containing nitrogen-containing aromatic resin. This composite structure integrates the high ion permeability of the porous layer with the dendrite-blocking properties of the nitrogen-containing aromatic resin skin layer, enabling both high power output and long-term reliability
2Productivity
If the separator surface has larger voids for better ion permeability, then ion transport is improved, but fibrous dendrites can easily extend through the pores causing short circuits
Solution Approach 1:
The separator surface is designed with local quality variation - the skin layer contains smaller voids (average void volume ≤ 0.015 μm³) specifically at the battery interior side where dendrites originate, while the bulk separator maintains larger voids for ion transport. This local differentiation allows the separator to permit ion permeability while blocking dendrite extension
Solution Approach 2:
The skin layer with smaller voids acts as a preliminary barrier against dendrite extension before dendrites can penetrate deeper into the separator. By placing this protective layer at the dendrite origin side, the invention prevents harmful dendrite growth in advance while maintaining overall ion permeability through the larger voids in the bulk separator
Data Source
AI summary
A nonaqueous electrolyte secondary battery laminate is provided which has a short circuit prevention effect improved by controlling the shape of a dendrite. The nonaqueous electrolyte secondary battery laminate in accordance with an aspect of the disclosure includes a separator and a graphite negative electrode. The graphite negative electrode has a non-reactivity parameter of not less than 230%. The separator has a surface that faces the graphite negative electrode and has an average void volume, obtained by analyzing a microscopic image of the surface, of not more than 0.015 μm3.