Nonaqueous Battery Cathode Composition for HF Trapping Stability
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries using lithium nickel complex oxide as a positive electrode material experience capacity degradation due to high-temperature storage, as fluorine compounds decompose and generate hydrogen fluoride, leading to the dissolution of transition metals and reduced battery capacity.
Innovation Solution
Incorporating a positive electrode with complex oxides containing Li, Ni, and W, where the W content in one complex oxide is 5 mol% or more and 0.5 mol% or less in another, with a mass ratio of the first complex oxide being 0.002% to 0.1% relative to the total, effectively traps hydrogen fluoride and suppresses the dissolution of transition metals from the positive electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a nonaqueous electrolyte containing a fluorine compound is used, then battery output and energy density are improved, but hydrogen fluoride is generated during high-temperature storage, leading to dissolution of transition metals and capacity degradation
Solution Approach 1:
A small amount of complex oxide A containing 5 mol% or more tungsten is introduced as an intermediary substance that preferentially reacts with and traps hydrogen fluoride generated during high-temperature storage. This mediator protects the main positive electrode active material from HF attack, suppressing transition metal dissolution and capacity degradation while allowing the fluorine compound to continue providing high output and energy density benefits
Solution Approach 2:
The invention changes the chemical composition parameters of the positive electrode active material by controlling the tungsten content and mass ratio of complex oxides. By setting W content in complex oxide A to 5 mol% or more and the mass ratio of complex oxide A to total complex oxides to 0.002%-0.1%, the material achieves optimal HF trapping capability while maintaining electrochemical performance
2Ease of manufacture
If lithium nickel complex oxide is used as a positive electrode active material, then manufacturing cost is reduced and capacity is increased, but capacity degradation during high-temperature storage is more noticeable compared to other materials
Solution Approach 1:
The invention creates a composite positive electrode active material system consisting of complex oxide A (with high W content ≥5 mol%) and complex oxide B (with low W content ≤0.5 mol%). This composite structure combines the cost and capacity advantages of lithium nickel complex oxide with the high-temperature stability provided by tungsten-containing phases that trap hydrogen fluoride
Solution Approach 2:
The invention applies local quality by creating regions with different tungsten concentrations within the positive electrode active material. The complex oxide A with high tungsten content (≥5 mol%) is distributed at specific locations to provide localized HF trapping functionality, while the majority complex oxide B maintains the overall electrochemical performance and cost-effectiveness
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
This configuration efficiently traps hydrogen fluoride, minimizing the dissolution of transition metals and thereby maintaining battery capacity during high-temperature storage, while also stabilizing initial capacity.
Implementation Method 1
the positive electrode active materials include a complex oxide A containing Li, Ni, and W and a complex oxide B containing Li, Ni, and W as an optional element; W content in the complex oxide A is 5 mol % or more... efficiently traps hydrogen fluoride
Data Source
AI summary
An object of the present disclosure is to provide a nonaqueous electrolyte secondary battery that can suppress lowering in capacity due to high-temperature storage of the battery. The nonaqueous electrolyte secondary battery (10) includes: a positive electrode (11) containing one or more positive electrode active materials; a negative electrode (12); and a nonaqueous electrolyte containing a fluorine compound, where: the positive electrode active materials include a complex oxide A containing Li, Ni, and W and a complex oxide B containing Li, Ni, and W as an optional element; W content in the complex oxide A is 5 mol % or more; W content in the complex oxide B is 0.5 mol % or less; and a mass ratio of the complex oxide A is 0.002% or more and 0.1% or less relative to the total of the complex oxide A and the complex oxide B.