Layered Ni-Rich Cathode Material for Suppressing Battery Self-Heating
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Solution Overview
Problem
Cathode active materials with a high ratio of Ni to total metal elements other than Li in lithium-transition metal oxides exhibit low thermal stability, leading to self-heat-generation and potential short-circuiting in non-aqueous electrolyte secondary batteries.
Innovation Solution
A cathode active material with a layered structure containing Ni, Mn, and optionally Co, where the ratio of Ni is between 75 mol% and 95 mol%, Mn is greater than or equal to Co, and metal elements other than Li are present in specific ratios within the Li layer, enhancing structural stability and thermal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the ratio of Ni in lithium-transition metal oxide is increased to 75-95 mol% to achieve high charging/discharging capacity, then the battery capacity is improved, but the thermal stability deteriorates leading to self-heat-generation
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the particle interior maintains high Ni content (75-95 mol%) for high capacity, while the surface layer has modified composition with additional metal elements (Al, Ti, Zr, Nb, Ta, or Hf) to suppress oxygen release and improve thermal stability. This spatial differentiation of composition allows simultaneous achievement of high productivity and reliability.
Solution Approach 2:
The patent uses composite materials by combining Ni-rich lithium-transition metal oxide core with a surface-modified layer containing multiple metal elements. The composite structure integrates the high capacity advantage of Ni-rich materials with the thermal stability of multi-element surface layers, resolving the contradiction between productivity and reliability.
2Use of energy by moving object
If the ratio of Ni is increased to improve battery capacity, then energy density is improved, but the self-heat-generation starting temperature decreases
Solution Approach 1:
The patent implements local quality by maintaining high Ni concentration in the particle core to maximize energy density while creating a surface layer with thermally stable metal elements that raise the self-heat-generation starting temperature. The surface layer acts as a thermal barrier without significantly reducing the overall energy capacity.
Solution Approach 2:
The surface-modified layer with multiple metal elements serves as an intermediary between the high-energy Ni core and the external environment. This intermediary layer suppresses direct oxygen release reactions that cause self-heat-generation, thereby raising the starting temperature while preserving the high energy density of the core material.
3Productivity
If the ratio of Ni is increased to achieve high capacity, then the charging/discharging performance is improved, but the reactivity and oxygen release increase causing thermal runaway risk
Solution Approach 1:
The patent applies local quality by concentrating high Ni content in the particle interior for high charging/discharging performance while placing oxygen-suppressing metal elements (Al, Ti, Zr, Nb, Ta, or Hf) in the surface layer. This spatial separation allows the core to maintain high reactivity for performance while the surface suppresses harmful oxygen release.
Solution Approach 2:
The patent converts the potential harm of high Ni reactivity into benefit by using the surface layer to control and direct the reactivity. The metal elements in the surface layer modulate the oxygen release behavior, transforming the uncontrolled harmful reactivity of Ni-rich materials into a controlled process that maintains high performance while reducing thermal runaway risk.
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 described cathode active material improves thermal stability by suppressing oxygen release and reactivity, thereby increasing the self-heat-generation starting temperature and reducing the risk of thermal runaway in batteries.
Implementation Method 1
improving thermal stability of a cathode active material including a lithium-transition metal oxide
Implementation Method 2
a half-width n of a diffraction peak of a (208) plane of an X-ray diffraction pattern obtained by X-ray diffraction in the lithium-transition metal oxide
Data Source
AI summary
A positive electrode active material for non-aqueous electrolyte secondary batteries comprises a lithium transition metal oxide containing Ni, Mn, Co, and Al and having a layered structure, wherein the content ratio of Ni in the lithium transition metal oxide is 75 to 95 mol %, the content ratio of Mn in the lithium transition metal oxide is equal to or greater than the content ratio of Co in the lithium transition metal oxide, the content ratio of Co in the lithium transition metal oxide is 0.5 to 2 mol %, the content ratio of a metal element other than Li in an Li layer in the layered structure is 1 to 2.5 mol %, and, in the lithium transition metal oxide, the half width n of a diffraction peak for (208) plane of an X-ray diffraction pattern as measured by X-ray diffraction is as follows: 0.30°≤n≤0.50°.