Coated Ternary Cathode Material for Thermal Stability
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Solution Overview
Problem
Ternary positive electrode materials in lithium ion batteries suffer from low thermal safety, which is a critical concern for the widespread adoption and application of these batteries, particularly in electric vehicles where safety performance is stringent.
Innovation Solution
A positive electrode active material with a specific composition and structure, characterized by a low proportion of cracked secondary particles and an ionic conductor coating, is developed. The material has a general formula of Li1+a[NixCoyMzM1b]O2, with controlled doping elements and a particle size of 10-20 μm, which enhances thermal stability and reduces the risk of side reactions with the electrolyte solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If ternary positive electrode materials are used to achieve high discharge capacity and charging efficiency, then the energy density and electrochemical performance are improved, but the thermal safety deteriorates
Solution Approach 1:
An ionic conductor coating layer is introduced as an intermediary between the ternary positive electrode material and the electrolyte solution. This coating layer acts as a protective barrier that prevents direct contact and harmful side reactions, thereby improving thermal safety while maintaining the electrochemical performance of the underlying ternary material.
Solution Approach 2:
The positive electrode material is designed as a composite structure combining the ternary material (Li1+a[NixCoyMzM1b]O2) with an ionic conductor coating layer. This composite structure integrates the high capacity benefits of ternary materials with the thermal stability and safety benefits of the coating layer.
2Object-affected harmful factors
If the proportion of cracked secondary particles is reduced to improve thermal safety, then the risk of side reactions with electrolyte is decreased, but the electrochemical performance may be compromised
Solution Approach 1:
The ionic conductor coating layer is applied in advance to the surface of secondary particles before they can crack. This preliminary protective action ensures that even if cracking occurs during thermal events, the coating layer remains intact and prevents electrolyte contact with the cracked surfaces, thereby maintaining both safety and performance.
3Object-affected harmful factors
If a coating layer is added to improve thermal safety, then the protection against side reactions is enhanced, but the device complexity increases
Solution Approach 1:
The coating layer is designed with specific parameter ranges (thickness of 1-10 nm, specific ionic conductivity values) that optimize both protective function and manufacturing feasibility. By controlling these parameters within defined ranges, the coating provides effective protection without excessive complexity in fabrication or characterization.
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 proposed solution significantly improves the thermal safety of the positive electrode material by maintaining low cracking degrees of secondary particles, thereby reducing the risk of thermal runaway and enhancing the overall safety of lithium ion batteries.
Implementation Method 1
the ionic conductor layer is a metallic lithium compound or a non-metallic lithium compound... significantly improves the thermal safety of the positive electrode material
Implementation Method 2
reducing the risk of side reactions with the electrolyte solution
Data Source
AI summary
The present application relates to the technical field of batteries, in particular to a positive electrode active material, a positive electrode slurry, a positive electrode sheet and a secondary battery. In a DSC graph of the positive electrode active material, an exothermic peak is present between 200-250° C.; at an onset temperature t1 of the exothermic peak, the proportion of cracked secondary particles in the positive electrode active material is x1; and at a peak temperature T1 of the exothermic peak, the proportion of cracked secondary particles in the positive electrode active material is X1, where the proportion of cracked secondary particles is a ratio of the number of the cracked secondary particles to the number of all secondary particles in the positive electrode active material, 0%≤x1≤5%, 0%≤X1≤10%, 0%≤X1−x1≤5%.