Separator with biased inorganic particles for lithium ion battery
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Solution Overview
Problem
The use of electrode-integrated type separators in lithium ion secondary batteries faces challenges with internal short circuits due to the peeling of active material-containing layers, which can occur when the film thickness is reduced, leading to contact with the counter electrode.
Innovation Solution
The electrode structure incorporates a separator with a layer of organic fibers and inorganic solid particles, where the inorganic solid particles are biased to the surface side, reducing the likelihood of peeling and contact with the electrode, thereby preventing internal short circuits while allowing for a thinner separator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the film thickness of the separator is reduced to increase energy density, then the energy density is improved, but the active material-containing layer peels off and contacts the counter electrode causing internal short circuits
Solution Approach 1:
The separator is constructed as a composite material comprising organic fibers and inorganic solid particles. The organic fibers provide flexibility and conformability allowing thin film design, while the inorganic solid particles provide mechanical strength and structural stability preventing peeling even at reduced thickness. This composite structure enables the separator to maintain both thin profile for high energy density and sufficient integrity for reliable short circuit prevention.
Solution Approach 2:
The inorganic solid particles are selectively distributed within the organic fiber matrix, with higher concentration near the electrode interface where peeling stress is greatest. This non-uniform distribution provides enhanced local reinforcement at the critical peeling interface while maintaining overall thinness. The local quality enhancement ensures peeling resistance precisely where needed without compromising the thin-film design for energy density.
2Reliability
If a self-supporting film type separator is used to prevent short circuits, then the reliability is improved, but the film thickness cannot be decreased due to mechanical strength requirements
Solution Approach 1:
The composite of organic fibers and inorganic particles creates a structure where the organic phase provides flexibility enabling thin-film formation, while the inorganic phase embedded within provides the mechanical strength equivalent to self-supporting films. This allows achieving self-supporting level reliability at significantly reduced thickness compared to conventional self-supporting film separators.
Solution Approach 2:
The separator utilizes a porous structure formed by the organic fiber network with inorganic particles distributed within the pores and on the surface. This porous architecture provides high surface area and mechanical interlocking that enhances peeling resistance while maintaining thin profile. The porous structure allows ion transport while the embedded inorganic particles prevent pore collapse and maintain structural integrity at thin thickness.
Data Source
AI summary
According to one embodiment, an electrode structure is provided. The electrode structure includes an electrode and a separator. The electrode includes an active material-containing layer. The active material-containing layer contains active material particles. The separator includes a layer of organic fibers and inorganic solid particles. The layer of organic fibers is on the active material containing layer. The inorganic solid particles are on the layer of organic fibers. The inorganic solid particles are disposed so as to be biased to a surface side opposite to an electrode side of the separator.