Substrate-Free Battery Separator for High-Temperature Insulation Stability
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Solution Overview
Problem
Conventional separators for lithium secondary batteries with polyolefin substrates suffer from low adhesion force with electrodes, high temperature melting, and poor mechanical strength, leading to potential short circuits and dimensional instability.
Innovation Solution
A separator design without a polyolefin substrate, utilizing inorganic particles, a binder, and a crosslinking agent to form a three-dimensional net-shaped structure, enhancing electrical insulation, tensile strength, and dimensional stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyolefin separator substrate is used, then the separator provides basic separation function, but the adhesion force with electrodes is low and melting occurs at high temperature
Solution Approach 1:
The patent removes the polyolefin separator substrate entirely and replaces it with an inorganic coating layer containing inorganic particles (such as alumina, silica, or boehmite) dispersed in a binder polymer. This extraction of the problematic polyolefin component eliminates the melting issue while maintaining the separation function through the inorganic network structure.
Solution Approach 2:
The patent creates a composite inorganic coating layer by combining inorganic particles with a binder polymer (such as PVdF, PVdF-HFP, or PEO) to form a new material system. This composite structure provides both the mechanical integrity needed for separator function and the high-temperature stability of inorganic materials, achieving reliability without melting.
2Device complexity
If a polyolefin separator substrate is used, then the separator structure is simple, but the mechanical strength is insufficient and the separator is easily torn
Solution Approach 1:
The patent employs a composite structure where inorganic particles form a rigid framework that provides mechanical strength, while the binder polymer matrix provides flexibility and cohesion. This composite architecture enables the separator to resist tearing and maintain structural integrity without requiring a complex multi-layer polyolefin construction.
Solution Approach 2:
The inorganic coating layer is designed with a porous structure that allows ion permeation while the inorganic particle network provides mechanical reinforcement. The porous architecture prevents the separator from being easily torn by distributing stress across the rigid inorganic framework, enhancing tensile strength without compromising the simple overall structure.
3Ease of manufacture
If the separator structure is simplified without polyolefin substrate, then the manufacturing process is simplified, but the electrical insulation is very low and short circuit occurs easily
Solution Approach 1:
The patent designs the inorganic coating layer with controlled porosity that provides both ion permeability for battery operation and sufficient electrical insulation. The inorganic particles (particularly ceramic materials like alumina and silica) inherently provide high electrical resistance, maintaining insulation properties even in the simplified structure without polyolefin substrate.
Solution Approach 2:
The patent optimizes the local properties of the inorganic coating layer by controlling particle size distribution, binder content, and coating thickness to achieve adequate electrical insulation. The inorganic particles are strategically distributed to create tortuous paths for ion transport while maintaining electrical barrier properties, ensuring reliability in the simplified manufacturing structure.
4Temperature
If the separator uses inorganic coating layer alone without polyolefin substrate, then the high-temperature stability is improved, but the dimensional stability is poor and wrinkles are formed
Solution Approach 1:
The patent creates a composite where the inorganic particle network provides thermal stability and resistance to shrinkage at high temperatures, while the binder polymer matrix maintains flexibility and dimensional integrity during normal operation. This combination prevents wrinkle formation by balancing the rigid thermal-stable inorganic framework with the compliant polymer phase.
Solution Approach 2:
The patent adjusts key parameters including the ratio of inorganic particles to binder polymer, particle size distribution, and crosslinking density to optimize dimensional stability. By controlling these parameters, the separator maintains its flat configuration and prevents wrinkle formation while preserving high-temperature stability through the inorganic network structure.
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
The solution effectively prevents short circuits, improves mechanical strength, and maintains insulation, even under high temperatures, thereby enhancing the reliability and lifespan of lithium secondary batteries.
Implementation Method 1
a crosslinking agent configured to crosslink with the binder when a slurry is formed using the crosslinking agent, the binder, and inorganic particles
Implementation Method 2
a separator that does not include a polyolefin substrate, which is used as a separator substrate, and includes inorganic particles
Data Source
AI summary
Disclosed herein is a separator for electrochemical devices, configured to guarantee electrical insulation between a positive electrode and a negative electrode, wherein the separator includes no polyolefin substrate, and includes inorganic particles, a binder for coupling between the inorganic particles, and a crosslinking agent.