Amorphous Cathode Coating for High-Voltage Lithium Battery Life
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Solution Overview
Problem
Lithium secondary batteries face rapid lifespan degradation due to electrolyte decomposition, active material deterioration, and increased internal resistance, especially in high-voltage and long-lifespan batteries, with existing surface treatment methods like aluminum-based coatings being non-uniform and boron-based coatings reacting with moisture.
Innovation Solution
A cathode active material with an amorphous coating layer composed of lithium oxide, tungsten oxide, boron oxide, and phosphorus oxide is applied to the surface of a lithium composite metal oxide core, forming a uniform and stable coating that reduces lithium byproducts and enhances high-voltage and low-temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminum-based surface treatment layer is formed on cathode active material, then stability at high voltage and in electrolyte is improved, but uniform coating is difficult and resistance increases
Solution Approach 1:
The invention changes the physical state parameter of the coating material from crystalline (aluminum-based) to amorphous (glassy). This parameter change enables uniform coating formation while maintaining stability at high voltage, as the amorphous structure can conform better to the substrate surface and reduce intrinsic resistance
Solution Approach 2:
The invention uses a composite coating layer containing multiple oxide components (WO3, B2O3, P2O5, Li2O) in amorphous phase. This composite approach combines the benefits of different materials: tungsten oxide for stability, boron oxide for glassy phase formation, phosphorus oxide for uniform distribution, and lithium oxide for lithium ion conductivity, achieving both uniform coating and high voltage stability
2Manufacturing precision
If boron-based coating is applied to cathode active material, then uniform coating in glassy state is achieved, but coating becomes incapable of acting as coating layer upon long-term reaction with electrolyte
Solution Approach 1:
The invention creates a composite coating system where boron oxide (providing glassy phase and uniform coating) is combined with tungsten oxide (providing long-term stability), phosphorus oxide (enhancing uniform distribution), and lithium oxide (maintaining lithium ion conductivity). This composite structure prevents the degradation issues of pure boron-based coatings while preserving the uniform coating advantage
Solution Approach 2:
The amorphous phase acts as an intermediary state that allows the coating to maintain uniform coverage while incorporating multiple functional components. The glassy matrix provides a stable framework that prevents direct contact and reaction between individual oxide components and the electrolyte, thereby improving long-term stability
3Temperature
If tungsten is used in cathode active material, then low-temperature characteristics are improved, but coating is not uniform and lithium byproducts remain on surface
Solution Approach 1:
The invention combines tungsten oxide with boron oxide, phosphorus oxide, and lithium oxide in an amorphous composite coating. This composite structure allows tungsten to provide low-temperature performance enhancement while the other components ensure uniform distribution and reduce lithium byproduct formation through the glassy phase formation process
Solution Approach 2:
The invention applies heat treatment to transform the coating from crystalline to amorphous phase, changing the physical state parameter. This parameter change enables uniform coating formation and reduces lithium byproducts while maintaining tungsten's beneficial effects on low-temperature characteristics
4Duration of action of stationary object
If surface treatment layer is formed to prevent active material deterioration, then lifespan is improved, but internal resistance increases
Solution Approach 1:
The invention changes the coating phase from crystalline to amorphous, which reduces intrinsic resistance while maintaining protective functions. The amorphous structure provides better contact with the substrate and reduces interface resistance, thereby extending lifespan without significantly increasing internal resistance
Solution Approach 2:
The composite coating containing lithium oxide provides lithium ion conductivity that compensates for any resistance introduced by the protective layer. The combination of multiple oxides creates a coating that both protects the active material and maintains efficient ion transport, achieving lifespan extension with minimal resistance penalty
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 amorphous coating layer significantly improves the lifespan, high-voltage characteristics, and low-temperature output of lithium secondary batteries by ensuring uniform coverage and reducing lithium byproducts, while maintaining stability and conductivity.
Implementation Method 1
a coating layer disposed on the core, containing a mixture of lithium oxide, tungsten oxide, boron oxide and phosphorus oxide, and having an amorphous phase
Data Source
AI summary
Disclosed are a cathode active material for a lithium secondary battery including a core containing lithium composite metal oxide, and a coating layer disposed on the core, containing a mixture of lithium oxide, tungsten oxide, boron oxide and phosphorus oxide, and having an amorphous phase, and a lithium secondary battery including the same.