Positive Electrode Dielectric Particle Dispersion for Low Cell Resistance
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Solution Overview
Problem
Barium titanate particles with a particle size of 200 nm or less tend to aggregate, leading to insufficient dielectric polarization and increased initial cell resistance in lithium-ion secondary batteries.
Innovation Solution
A positive electrode comprising a current collector and a material mixture layer with a combination of ionically-conductive and non-ionically-conductive dielectric particles, which are dispersed to prevent aggregation and enhance dielectric polarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If barium titanate particles with a particle size of 200 nm or less are used to increase specific surface area, then the area of contact with electrolytic solution increases, but the particles aggregate which reduces the effective contact area and dielectric polarization
Solution Approach 1:
The patent uses a composite particle system combining barium titanate (dielectric) particles with lithium ionic-conductive particles. This composite structure allows the barium titanate particles to maintain their high dielectric properties while the lithium ionic-conductive particles prevent aggregation by providing ionic conductivity pathways and electrostatic stabilization, thus resolving the contradiction between maximizing contact area and maintaining dispersion stability.
2Reliability
If barium titanate particles are used to enhance dielectric polarization, then the dissociation degree of supporting salt increases, but aggregation reduces dielectric polarization effectiveness and increases initial cell resistance
Solution Approach 1:
The lithium ionic-conductive particles act as an intermediary between the barium titanate particles and the electrolytic solution. They prevent direct aggregation of barium titanate particles while facilitating ionic transport, thereby maintaining the dielectric polarization effectiveness of barium titanate and preventing the increase in initial cell resistance that would otherwise occur due to particle aggregation.
3Productivity
If positive electrode active material and electrolytic solution are used for battery operation, then energy storage function is achieved, but corrosion and decomposition occur which increase cell resistance after endurance test
Solution Approach 1:
The dielectric particles, particularly the lithium ionic-conductive particles, serve as a protective cushioning layer between the positive electrode active material and the electrolytic solution. This layer prevents direct corrosive interaction between these components before degradation can occur, thereby maintaining low cell resistance even after extended endurance testing while preserving the energy storage function.
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 dielectric particles with high relative permittivity and appropriate median diameters reduces initial cell resistance and maintains low resistance after an endurance test, improving the performance of lithium-ion secondary batteries.
Implementation Method 1
the dielectric polarization of the barium titanate particles will be insufficiently effective in increasing the dissociation degree of the supporting salt in the electrolytic solution
Implementation Method 2
the ionically-conductive particles may have a lithium-ionic conductivity of 1×10−7 S/cm or more at 25° C.
Data Source
AI summary
Provided is a positive electrode including: a positive electrode current collector; and a positive electrode material mixture layer including a positive electrode active material and dielectric particles, the dielectric particles including ionically-conductive particles and non-ionically-conductive particles. Also provided is an electricity storage device including: the positive electrode; a negative electrode; and an electrolytic solution.