Lithium Ion Battery Porous Membrane Transition Metal Capture
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Solution Overview
Problem
Lithium ion secondary batteries with transition metal-containing positive electrode active materials face issues with transition metal ions, such as cobalt, eluting into the electrolyte solution and depositing on the negative electrode, leading to deterioration of battery life characteristics like cycle and expansion resistance.
Innovation Solution
A porous membrane composition using a binding material with a polymer A containing an aliphatic conjugated diene monomer unit in excess of 85% and a polymer B with a (meth)acrylic acid ester monomer unit in the range of 60-99%, in a specific mass ratio, is used to capture transition metal ions effectively while maintaining peel strength and heat contraction resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a transition metal-containing positive electrode active material is used to increase battery capacity, then battery capacity is improved, but transition metal ions elute into the electrolyte solution causing deterioration of cycle characteristics and expansion resistance
Solution Approach 1:
A porous membrane containing polymer particles with transition metal ion capturing functionality is introduced as an intermediary between the positive electrode and negative electrode. This membrane captures transition metal ions that elute from the positive electrode active material, preventing them from depositing on the negative electrode. The membrane thus mediates the harmful interaction while allowing the high-capacity positive electrode material to be used.
Solution Approach 2:
The invention converts the harmful elution of transition metal ions into a beneficial capturing process. The porous membrane is designed to specifically capture transition metal ions through polymer particles containing functional groups that bind to these ions. By capturing the harmful ions in the membrane structure, the system transforms a detrimental side reaction into a controlled and useful ion capture mechanism that protects the battery.
2Reliability
If a porous membrane with high transition metal capturing ability is designed, then transition metal deposition is prevented, but peel strength of the porous membrane may deteriorate
Solution Approach 1:
The porous membrane is designed with local quality differentiation: polymer particles with high transition metal capturing functionality are concentrated in specific regions of the membrane, while other regions maintain structural integrity and adhesion properties. This localized functional distribution allows the membrane to achieve high ion capturing ability without compromising overall peel strength.
Solution Approach 2:
The porous membrane is constructed as a composite material system combining polymer particles with transition metal capturing functionality, porous matrix material, and binding agents. This composite structure integrates multiple functions: the polymer particles provide ion capturing, the porous matrix provides structural framework and ion transport pathways, and the binding agents ensure adequate adhesion. The synergistic combination resolves the contradiction between capturing ability and peel strength.
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 proposed solution enables a lithium ion secondary battery with enhanced transition metal capturing ability, improved peel strength, and prolonged cycle characteristics by effectively preventing transition metal deposition on the negative electrode.
Implementation Method 1
a polymer A including an aliphatic conjugated diene monomer unit in a proportion of greater than 85 mass%... displays high transition metal capturing ability
Data Source
AI summary
Provided is a technique for capturing transition metal ions, such as cobalt ions, in a secondary battery that elute from a positive electrode active material and for preventing deposition of transition metal at a negative electrode. A composition for a lithium ion secondary battery porous membrane that contains non-conductive particles and a binding material is provided. The binding material includes a polymer A including an aliphatic conjugated diene monomer unit in a proportion of greater than 85 mass% and a polymer B including a (meth)acrylic acid ester monomer unit in a proportion of at least 60 mass%. A mass basis ratio of content of the polymer A relative to content of the polymer B is at least 0.2 and no greater than 9.0.