Crosslinked Separation Membrane for Thin Low-Resistance Li-Ion Batteries
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Solution Overview
Problem
In lithium ion secondary batteries, there is a need for a separation membrane with a thin film thickness and low resistance value to prevent solvent mixing between the positive and negative electrodes, while maintaining lithium ion conductivity.
Innovation Solution
A lithium ion secondary battery configuration that includes a separation membrane made of a copolymer with a first monomer having two (meth)acryloyl groups and a second monomer with three or more (meth)acryloyl groups, along with a lithium salt and solvent, positioned between the positive and negative electrodes to ensure effective solvent separation and ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separation membrane is made thinner to reduce resistance, then resistance value decreases, but solvent separation performance deteriorates
Solution Approach 1:
The patent uses a composite gel polymer electrolyte containing both a crosslinkable polymer component and a lithium salt component. The crosslinking creates a three-dimensional network structure that provides physical separation barriers, while the lithium salt ensures ion conductivity. This composite structure enables effective solvent separation even in thin membranes.
Solution Approach 2:
The gel polymer electrolyte forms a porous three-dimensional crosslinked structure that acts as a physical barrier to solvent molecules while allowing lithium ion transport. The porous network provides channels for ion conduction while the crosslinked gel matrix prevents solvent mixing between electrodes.
2Reliability
If a separation membrane is made thinner to improve ion conductivity, then resistance value decreases, but membrane strength deteriorates
Solution Approach 1:
The crosslinked gel polymer structure provides mechanical strength through the three-dimensional network, while the incorporated lithium salt ensures high ion conductivity. The synergistic combination of crosslinked polymer matrix and lithium salt components enables both structural integrity and electrical performance in thin membranes.
Solution Approach 2:
The patent creates localized crosslinked regions within the gel polymer electrolyte that provide structural reinforcement. The crosslinking density can be controlled to optimize both mechanical strength and ion conductivity in different regions of the membrane 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 provides a separation membrane with a thin film thickness and low resistance value, effectively preventing solvent mixing and enhancing the performance of lithium ion secondary batteries by maintaining lithium ion conductivity.
Implementation Method 1
the separation membrane contains a polymer having lithium ion conductivity
Implementation Method 2
it is important that the solvent contained in the electrolyte is sufficiently separated without mixing between the positive electrode and the negative electrode
Implementation Method 3
the polymer is a copolymer comprising, as monomer units thereof, a first monomer that has two (meth)acryloyl groups and a second monomer that has three or more (meth)acryloyl groups
Data Source
AI summary
One aspect of the present invention provides a lithium ion secondary battery comprising a positive electrode mixture layer, a separation membrane, and a negative electrode mixture layer in the stated order, wherein: the positive electrode mixture layer contains a positive electrode active material, a first lithium salt, and a first solvent, the negative electrode mixture layer contains a negative electrode active material, a second lithium salt, and a second solvent different from the first solvent, the separation membrane contains a polymer having lithium ion conductivity, a third lithium salt, and a third solvent, and the polymer is a copolymer comprising, as monomer units thereof, a first monomer that has two (meth)acryloyl groups and a second monomer that has three or more (meth)acryloyl groups.