Composite Cathode Material With Core-Shell Coating for Cycle Stability
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Solution Overview
Problem
Conventional positive electrode active materials in secondary batteries suffer from low cycling capacity retention rate, short cycle life, and safety concerns due to Li/Mn antisite defects and manganese dissolution during charge and discharge.
Innovation Solution
A composite positive electrode active material is developed, comprising a first material with a layered transition metal oxide structure and a second material with a core-shell structure, where the core is lithium manganese phosphate, coated with pyrophosphate and phosphate layers, and further coated with a carbon layer. This combination enhances lithium ion transport, electrical conductivity, and desolvation performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium manganese phosphate is used as positive electrode active material, then energy density is improved, but cycling performance and safety performance deteriorate due to Li/Mn antisite defects and manganese dissolution
Solution Approach 1:
The patent uses a composite structure consisting of lithium manganese phosphate core particles coated with lithium nickel cobalt manganese oxide shell layer. This composite material combines the high energy density advantage of lithium manganese phosphate with the superior cycling stability of lithium nickel cobalt manganese oxide, resolving the contradiction between energy density and cycling performance
Solution Approach 2:
The patent applies different material properties to different parts of the electrode structure: the core uses lithium manganese phosphate for high energy density while the shell uses lithium nickel cobalt manganese oxide for enhanced stability and protection against manganese dissolution, addressing both energy density and cycling performance requirements
2Use of energy by moving object
If lithium manganese phosphate is used as positive electrode active material, then energy density is improved, but safety performance deteriorates due to manganese dissolution
Solution Approach 1:
The patent applies a protective shell layer of lithium nickel cobalt manganese oxide on the surface of lithium manganese phosphate particles. This shell acts as a barrier that prevents manganese dissolution into the electrolyte while allowing lithium ion transport, thus maintaining high energy density while improving safety performance
Solution Approach 2:
The lithium nickel cobalt manganese oxide shell serves as an intermediary layer between the lithium manganese phosphate core and the electrolyte, preventing direct contact and harmful interactions while facilitating beneficial lithium ion exchange, thereby reducing manganese dissolution without compromising energy density
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 composite active material significantly improves the cycling capacity retention rate, extends the cycle life, and enhances the safety of secondary batteries by reducing manganese dissolution and oxygen activity, while maintaining high energy density and rate performance.
Implementation Method 1
the first coating layer includes pyrophosphate MaP2O7 and phosphate XnPO4
Implementation Method 2
the second coating layer includes carbon
Implementation Method 3
the core includes a compound Li1+xMn1−yAyP1−zRzO4, the first coating layer includes pyrophosphate MaP2O7 and phosphate XnPO4
Data Source
AI summary
This application provides a positive electrode active material, a method for preparing a positive electrode active material, a positive electrode plate, a secondary battery, a battery module, a battery pack, and an electric apparatus. The positive electrode active material includes a first positive electrode active material and a second positive electrode active material. The first positive electrode active material includes a compound LiNibCodMneM′fO2, and the second positive electrode active material includes a core, a first coating layer enveloping the core, and a second coating layer enveloping the first coating layer, where the core includes a compound Li1+xMn1−yAyP1−zRzO4, the first coating layer includes pyrophosphate MaP2O7 and phosphate XnPO4, and the second coating layer includes carbon.