Ammonium Phosphate Coated Cathode for Battery Cycle Life
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Solution Overview
Problem
Conventional cathode active materials in secondary batteries experience a significant decrease in discharge capacity retention ratio due to side reactions between lithium composite oxides and non-aqueous solvents, leading to poor cycle characteristics.
Innovation Solution
A cathode active material comprising lithium composite oxide particles coated with an ammonium phosphate compound containing metals like manganese, nickel, or cobalt, which suppresses the reduction and elution of transition metals and oxidative decomposition of the solvent, thereby maintaining discharge capacity and improving cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional cathode active material is used, then the secondary battery can operate, but the discharge capacity retention ratio significantly decreases along with charge/discharge cycle repetition
Solution Approach 1:
An ammonium phosphate compound coating layer is introduced as an intermediary between the lithium composite oxide particles and the non-aqueous electrolyte. This coating layer suppresses side reactions by acting as a protective barrier, preventing direct contact and chemical interaction between the cathode active material and the electrolyte solvent, thereby improving discharge capacity retention and cycle life.
Solution Approach 2:
The cathode active material is constructed as a composite structure consisting of lithium composite oxide particles coated with an ammonium phosphate compound layer. This composite material approach combines the high capacity properties of lithium composite oxides with the protective and stable properties of the ammonium phosphate coating, achieving both high performance and long cycle life.
2Reliability
If the cathode active material surface is coated to suppress side reactions, then the cycle characteristic improves, but the complexity of the material structure increases
Solution Approach 1:
The invention optimizes specific parameters of the ammonium phosphate compound coating, including the metal content (manganese, nickel, or cobalt), coating thickness (0.1-5 μm), and composition ratios, to achieve effective protection while maintaining manufacturing feasibility. By controlling these parameters within specific ranges, the patent balances performance improvement with structural simplicity.
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 coating layer effectively inhibits the reduction and elution of transition metals, reducing oxidative solvent decomposition and maintaining discharge capacity retention, thus enhancing the cycle characteristics and overall performance of secondary batteries.
Implementation Method 1
a coating layer containing an ammonium phosphate compound containing a metal other than lithium, wherein each of the particles is coated with the coating layer
Implementation Method 2
suppress a side reaction involving decomposition of the non-aqueous solvent
Data Source
AI summary
Provides is a cathode active material comprising particles each containing a lithium composite oxide, a coating layer containing an ammonium phosphate compound containing a metal other than lithium. The coating layer coats each of the particles. The metal other than lithium includes at least one selected from the group consisting of manganese, nickel, and cobalt.