Hybrid Electrolyte Lithium Secondary Battery for High-Temperature Insulation
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Solution Overview
Problem
Lithium secondary batteries face safety issues due to the risk of ignition at high temperatures, particularly when polyolefin-based separators shrink and cause short circuits, and all-solid-state batteries do not match the performance of liquid electrolyte-based batteries in terms of output, capacity, and lifetime.
Innovation Solution
A lithium secondary battery design incorporating a positive electrode with an inorganic solid electrolyte and a gel-type electrolyte, where the inorganic solid electrolyte is uniformly distributed within the positive electrode mixture layer, covering 50% to 90% of the positive electrode active material surface, and a specific composition of lithium salt, non-aqueous organic solvent, and polymerizable compounds in the gel-type electrolyte.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyolefin-based separators are used to ensure electrical insulation, then insulation between positive and negative electrodes is improved, but the separator shrinks under high temperature causing short circuit and ignition
Solution Approach 1:
The patent changes the material parameters of the separator from polyolefin to aramid fiber nonwoven fabric, which has superior thermal stability and maintains dimensional integrity at high temperatures up to 200°C, preventing shrinkage-induced short circuits while preserving electrical insulation functionality
Solution Approach 2:
The patent employs a composite structure combining aramid fiber nonwoven fabric with aluminum oxide coating, creating a multi-layer separator that integrates the high-temperature resistance of aramid fibers with the electrical insulation properties of aluminum oxide, effectively addressing both thermal stability and insulation requirements
2Reliability
If all-solid-state batteries are applied to improve safety, then ignition risk is reduced, but output, capacity, and lifetime performance deteriorate compared to liquid electrolyte batteries
Solution Approach 1:
The patent applies solid electrolyte particles locally within the liquid electrolyte rather than completely replacing it, creating a hybrid electrolyte system where solid particles are dispersed at specific concentrations (0.1-10 wt%) to enhance safety characteristics while preserving the high ionic conductivity and performance of liquid electrolyte
Solution Approach 2:
The solid electrolyte particles act as intermediaries that modify the liquid electrolyte's properties, providing thermal stability and shutdown functionality while the liquid electrolyte maintains ion transport efficiency, thus mediating between safety requirements and performance demands
3Reliability
If inorganic solid electrolyte is added to positive electrode to improve safety, then ignition resistance is enhanced, but manufacturing complexity increases due to uniform distribution requirements
Solution Approach 1:
The patent specifies precise local concentration ranges for solid electrolyte particles within the positive electrode coating layer (0.1-10 wt%), ensuring uniform distribution at the micro-scale while maintaining overall electrode homogeneity, which facilitates controlled manufacturing processes
Solution Approach 2:
The patent optimizes particle size parameters of solid electrolyte (0.1-10 μm) to achieve uniform distribution during the coating process, where controlled particle dimensions enable consistent dispersion and reduce aggregation, simplifying manufacturing while ensuring ignition resistance
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 design effectively delays ignition and reduces explosive power, enhancing safety by maintaining electrical insulation and ion conductivity even at high temperatures.
Implementation Method 1
maintaining electrical insulation and ion conductivity even at high temperatures
Implementation Method 2
a gel-type electrolyte, wherein the inorganic solid electrolyte is included in an amount of 0.5 wt.% to 2 wt.% based on the total weight of the positive electrode mixture layer
Data Source
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AI summary
According to an embodiment of the present disclosure, there is provided a lithium secondary battery comprising: a positive electrode in which a positive electrode mixture layer containing a positive electrode active material and an inorganic solid electrolyte is formed on one side or both sides of a positive electrode current collector, a negative electrode in which a negative electrode mixture layer containing a negative electrode active material is formed on one side or both sides of a negative electrode current collector, a separator interposed between the positive electrode and the negative electrode, and a gel-type electrolyte, wherein the inorganic solid electrolyte is included in an amount of 0.5 wt.% to 2 wt.% based on the total weight of the positive electrode mixture layer, and is uniformly distributed within the positive electrode mixture layer.