Cathode Particle Coating With Oxetane Copolymer for Lower Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lithium-ion battery cathode materials face challenges in improving input-output characteristics, and polymer coatings containing nitrile groups pose environmental concerns.
Innovation Solution
Coating lithium-transition metal oxide particles with a cross-linked acrylic polymer having an oxetane ring, specifically a copolymer of alkyl methacrylate and methacrylic acid ester with an oxetane ring, to form a coating layer that reduces internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a nitrile group-containing acrylic polymer is used to coat cathode active material particles, then cycle characteristics at high electric potential are improved, but environmental burden increases
Solution Approach 1:
The patent replaces the nitrile group-containing polymer with a copolymer containing oxetane rings and carboxyl groups. This chemical parameter change in the coating material eliminates the environmental burden associated with nitrile groups while maintaining the protective function that improves cycle characteristics at high electric potential.
Solution Approach 2:
The invention uses a composite copolymer structure combining oxetane rings (for cross-linking and protection) and carboxyl groups (for lithium ion conductivity). This composite material approach achieves both protective function for cycle life improvement and environmental compatibility by avoiding harmful nitrile groups.
2Stability of the object's composition
If the weight average molecular weight of the copolymer is increased, then coating stability is improved, but coating uniformity deteriorates
Solution Approach 1:
The patent specifies a precise molecular weight range (200,000 to 600,000) for the copolymer. This parameter optimization ensures that the polymer chains are long enough to provide stable cross-linked coating structure, yet not so long as to cause poor dispersion and uniformity issues during the coating process.
3Reliability
If the copolymer amount is increased, then protective effect is enhanced, but internal resistance increases
Solution Approach 1:
The patent optimizes the copolymer content to a specific range (0.7 to 5 mass %) relative to the lithium-transition metal oxide. This quantitative parameter control ensures sufficient protective coating for improved reliability while limiting the amount to prevent excessive internal resistance that would harm battery performance.
Solution Approach 2:
The cross-linked copolymer coating forms a porous or semi-permeable structure that allows lithium ion transport. This structure provides protective function at optimal thickness while maintaining ion conductivity, preventing the harmful effect of increased internal resistance even when protective effect is enhanced.
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 cross-linked polymer coating enhances the input-output characteristics of lithium-ion batteries by reducing internal resistance, thereby improving discharge capacity and efficiency.
Implementation Method 1
the copolymer is cross-linked by ring opening of an oxetane ring
Implementation Method 2
a step of heating a mixture containing lithium-transition metal oxide particles, a copolymer which is represented by the general formula (1) above and which has a weight average molecular weight of 200,000 to 600,000 and a polymerization initiator
Data Source
AI summary
The input-output characteristics of a lithium-ion battery are improved. In coated lithium-transition metal oxide particles, at least a part of the surfaces of lithium-transition metal oxide particles are coated with a copolymer which is represented by the formula (1) and which has a weight average molecular weight of 200,000 to 600,000, and the copolymer is cross-linked by ring opening of an oxetane ring. In the formula (1), m and n represent a number of one or more. R1 and R2 represent a hydrogen atom or a methyl group. R3 represents an alkyl group having one to five carbon atoms. R4 represents an alkanediyl group having one to five carbon atoms. R5 represents a hydrogen atom or an alkyl group having one to five carbon atoms.