Amorphous Lithium Tungsten Oxide Coating for Battery Cathodes
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Solution Overview
Problem
Conventional cathode active materials for lithium secondary batteries face challenges in achieving uniform coating and low-temperature characteristics due to crystalline tungsten-containing coating layers, which lead to inadequate discharge capacity and output characteristics.
Innovation Solution
A cathode active material with a coating layer comprising an amorphous phase of lithium oxide and tungsten oxide mixture is developed, ensuring uniform coating and improved low-temperature characteristics by adhering to the core at a low firing temperature, reducing charge transfer resistance, and enhancing lithium ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a crystalline tungsten-containing coating layer (LixWyOz) is used, then the coating material can be formed on the core surface, but the coating is not uniform and is separately present outside the core
Solution Approach 1:
The patent changes the phase state parameter of the coating material from crystalline to amorphous. By controlling the firing temperature to be below the crystallization temperature of lithium tungsten oxide, the coating layer maintains an amorphous phase that enables uniform distribution and adhesion to the core surface, preventing separate presence of coating material
Solution Approach 2:
The patent creates a composite coating layer containing both amorphous lithium tungsten oxide and amorphous tungsten oxide. This composite structure combines the benefits of both compounds while maintaining the amorphous phase, achieving both uniform coating and improved low-temperature discharge characteristics
2Ease of manufacture
If lithium tungsten oxide is formed by precipitating lithium and inducing chemical reaction, then the coating can be applied, but it forms as a crystallized phase rather than amorphous phase
Solution Approach 1:
The patent applies preliminary action by pre-coating the core surface with lithium compound before firing. This preliminary lithium layer reacts with tungsten compound during firing to form the desired amorphous lithium tungsten oxide coating, avoiding the need for direct precipitation while maintaining amorphous phase through controlled temperature processing
Solution Approach 2:
The patent controls the firing temperature parameter to remain below the crystallization temperature of lithium tungsten oxide. This parameter control ensures that the chemical reaction between lithium and tungsten compounds produces the coating in an amorphous phase rather than crystalline phase
3Ease of manufacture
If plasma or ion-sputtering method is used to spray element onto surface, then element can be deposited, but it is merely dotted on the surface rather than uniformly coated
Solution Approach 1:
The patent replaces the mechanical/physical deposition methods (plasma or ion-sputtering) with a chemical approach. By using solution-based coating followed by controlled firing, the patent achieves uniform distribution of elements through chemical reactions rather than physical deposition, eliminating the dotted surface pattern
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 phase coating significantly improves discharge capacity, output characteristics, and cycle life, particularly at low temperatures, by facilitating uniform adhesion and reducing resistance in lithium secondary batteries.
Implementation Method 1
a coating layer disposed on the core and comprising an amorphous phase, wherein the amorphous phase contains lithium oxide and tungsten oxide in a form of mixture
Implementation Method 2
the cathode active material includes an amorphous phase containing lithium oxide and tungsten oxide in a form of mixture
Implementation Method 3
enhancing lithium ion conductivity
Data Source
AI summary
Disclosed is 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 and having an amorphous phase, wherein the amorphous phase contains lithium oxide and tungsten oxide in a form of mixture.