Positive Electrode with Dual Mixture Layers for Thermal Stability
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Solution Overview
Problem
Secondary batteries using Li-containing compounds with high Ni content as positive electrode active materials face challenges in suppressing temperature increases during internal short circuits due to low heat stability, leading to insufficient thermal management.
Innovation Solution
A positive electrode structure comprising a first mixture layer with a Ni, Co, Al, and Li-containing compound A and a second mixture layer with a Li-containing compound B of lower specific capacity and smaller average particle size, where compound B has high heat stability, is used to prevent thermal decomposition and maintain battery temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a Li-containing compound with high Ni content is used as positive electrode active material, then battery capacity is improved, but heat stability deteriorates
Solution Approach 1:
The patent uses a composite structure consisting of a core region containing high Ni-content compound A and a shell region containing compound B with lower specific capacity but higher heat stability. This composite design allows the battery to achieve high capacity from compound A while compound B provides thermal stability protection, resolving the contradiction between capacity and heat stability.
2Use of energy by moving object
If high Ni-content compound is used without protective layer, then battery capacity increases, but temperature control during internal short circuit deteriorates
Solution Approach 1:
The patent implements a shell region of compound B surrounding the high Ni-content compound A before any thermal runaway occurs. This pre-established protective barrier acts as a cushion against heat propagation during internal short circuits, allowing the high-capacity compound A to function while preventing excessive temperature increases through the thermally stable compound B shell.
3Reliability
If compound A directly contacts current collector, then electrical conductivity is improved, but thermal runaway risk increases
Solution Approach 1:
The patent introduces compound B as an intermediary material between the high Ni-content compound A and the current collector. This intermediary shell maintains electrical connectivity while providing thermal stability, allowing compound A to be electrically connected to the current collector without direct contact, thereby reducing thermal runaway risk while preserving conductivity.
Data Source
AI summary
A positive electrode with a positive electrode current collector and a positive electrode mixture layer, and the positive electrode mixture layer has first and second positive electrode mixture layers. The first positive electrode mixture layer comprises a positive electrode active material composed of compound A that contains Ni, Co, Al and Li. The second positive electrode mixture layer is disposed between the first positive electrode mixture layer and the positive electrode current collector, and comprises a positive electrode active material including: said compound A; and a Li-containing compound B which is smaller in specific capacity (mAh/g) and average particle diameter than said compound A. In said compound A, a ratio of Ni to the total number of moles of the metal elements except Li is 82 mol % or more. The average particle diameter of said compound B is 55% or less of the average particle diameter of said compound A.