Cathode Active Material for Fluoride Ion Battery
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Solution Overview
Problem
The capacity maintenance rate of existing cathode active materials in fluoride ion batteries is low due to the aggregation of fine Cu particles, which degrades their function as active materials.
Innovation Solution
A cathode active material comprising a first active material with a composition of Pb2−xCu1+xF6 and a second active material containing a Bi element, where the second active material inhibits the coarsening of Cu particles, thereby maintaining high dispersion coefficients and capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If Pb2CuF6 is used as cathode active material, then high voltage and high energy density are achieved, but capacity maintenance rate deteriorates due to Cu particle aggregation
Solution Approach 1:
BiF3 is introduced as an intermediary substance that prevents direct contact and aggregation between Cu particles during charge-discharge cycles. The BiF3 forms a protective matrix around Cu particles, maintaining their dispersion while allowing electrochemical reactions to proceed, thus preserving capacity maintenance rate while utilizing the high energy density of Pb2CuF6
Solution Approach 2:
The invention creates a composite cathode active material consisting of Pb2CuF6, BiF3, and PbF2 phases. This composite structure combines the high energy density advantage of Pb2CuF6 with the particle-dispersion-stabilizing effect of BiF3, achieving both high power and good reliability simultaneously
2Quantity of substance
If Cu particles are used as active material, then high capacity is achieved, but particle aggregation occurs during cycling reducing effectiveness
Solution Approach 1:
BiF3 serves as a spacer and stabilizing matrix that maintains Cu particle dispersion throughout charge-discharge cycling. It prevents Cu particles from aggregating while allowing sufficient ionic and electronic transport for high capacity utilization
Solution Approach 2:
The cathode active material exhibits local quality variations with different phases serving different functions: Pb2CuF6 provides high capacity, BiF3 provides particle dispersion stability, and PbF2 provides ionic conductivity. This functional differentiation resolves the contradiction between maintaining high capacity and preventing particle aggregation
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 use of BiF3 in conjunction with Pb2CuF6 enhances the capacity maintenance rate by preventing Cu particle aggregation, allowing for efficient fluoride ion dispersion and maintaining high discharge capacity over multiple cycles.
Implementation Method 1
This cathode active material is an active material of which phase split into, during first discharge for example, PbF2 that functions as a solid electrolyte (ion conductor) and Cu that functions as an active material
Implementation Method 2
the second active material inhibits the coarsening of Cu particles, thereby maintaining high dispersion coefficients and capacity retention
Implementation Method 3
it is necessary that the fluoride ions are dispersed in Cu during charge
Data Source
AI summary
A main object of the present disclosure is to provide a cathode active material used for a fluoride ion battery, the cathode active material comprising: a first active material having a composition represented by Pb2−xCu1+xF6, wherein 0≤x<2; and a second active material containing a Bi element and a F element.