Monoclinic Lithium Metal Oxide Coating for Cathode Stability
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Solution Overview
Problem
Lithium ion batteries experience capacity loss and poor cycling life due to irreversible changes in cathode active materials during charging and discharging cycles, primarily caused by reactions with organic solvents, which affect the stability and conductivity of the materials.
Innovation Solution
A cathode composite material is developed by coating a lithium metal oxide layer with a monoclinic crystal structure onto the surface of lithium transition metal oxide particles, using a method that involves forming a composite precursor and reacting it with a lithium source chemical compound to create a core-shell structure, enhancing the chemical and thermal stability and preventing unwanted reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cathode active material is left untreated, then the manufacturing process is simple, but the conductivity and cycling stability are poor
Solution Approach 1:
The patent applies composite materials by coating the cathode active material surface with a dual-layer structure consisting of an amorphous aluminum oxide layer and a crystalline alumina layer. This composite structure combines the high conductivity improvement of amorphous aluminum oxide with the thermal stability of crystalline alumina, resolving the contradiction between cycling stability and manufacturing complexity by providing a systematic surface treatment approach
Solution Approach 2:
The patent employs parameter changes by controlling the deposition conditions to form amorphous aluminum oxide initially, then transforming it to crystalline alumina through heat treatment at temperatures above 400°C. This parameter change approach allows optimization of both conductivity (amorphous phase) and thermal stability (crystalline phase), effectively addressing the cycling stability issue while maintaining manageable manufacturing complexity
2Duration of action of stationary object
If a coating layer is added to improve stability, then the cycling life is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent applies self-service by utilizing the cathode active material itself as the aluminum source for coating formation. The aluminum-containing cathode material undergoes surface transformation during battery assembly or initial charging cycles, forming the protective alumina coating in-situ. This eliminates the need for separate coating equipment and processes, significantly reducing manufacturing complexity while ensuring the coating is perfectly integrated with the substrate
Solution Approach 2:
The patent employs preliminary action by pre-introducing aluminum-containing compounds into the cathode active material before battery assembly. During the initial battery cycles or assembly process, these compounds automatically transform into the protective alumina coating layer, preparing the surface for optimal performance before the battery enters service. This preliminary coating formation simplifies the manufacturing process while ensuring long cycling life
3Object-generated harmful factors
If the cathode active material reacts with organic solvent, then the material shows high reactivity, but the capacity loss increases
Solution Approach 1:
The patent applies the intermediary principle by introducing an alumina coating layer as a mediator between the cathode active material and the organic electrolyte solvent. This coating layer is chemically inert and physically separates the reactive cathode material from the solvent, preventing unwanted chemical reactions and material dissolution. The intermediary layer allows ionic transport while blocking harmful chemical interactions, effectively reducing capacity loss from material degradation
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 cathode composite material improves the cycling stability and capacity retention of lithium ion batteries, maintaining discharge specific capacity even at high current rates, with the coating layer allowing lithium ion mobility while preventing electron migration and side reactions.
Implementation Method 1
the coating layer allowing lithium ion mobility while preventing electron migration and side reactions
Implementation Method 2
preventing unwanted reactions between the cathode active material and the organic solvent
Data Source
AI summary
A cathode composite material includes a cathode active material and a coating layer coated on a surface of the cathode active material. A material of the coating layer is a lithium metal oxide having a crystal structure belonging to C2/c space group of the monoclinic crystal system. The present disclosure also relates to a lithium ion battery including the cathode composite material.