Amorphous Oxide Coating on Lithium Composite Cathode
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Solution Overview
Problem
Lithium secondary batteries face rapid lifespan deterioration due to electrolyte decomposition and active material degradation, especially in high-voltage and long-life batteries, caused by moisture and increased internal resistance, which affects their cycle life and voltage stability.
Innovation Solution
A positive electrode active material with a surface treatment layer composed of an amorphous oxide including silicon, nitrogen, and specific metal elements, such as Group 1A, 2A, and 3B elements, is developed to enhance hardness, elasticity, chemical resistance, and fracture toughness, improving the structural stability and lifespan characteristics of the battery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an aluminum-based surface treatment layer is applied on a positive electrode active material, then stability in electrolyte and high voltage is improved, but uniform application on entire active material is difficult and resistance increases due to crystallinity
Solution Approach 1:
The invention changes the physical state parameter of the aluminum-based compound from crystalline to amorphous. This parameter change enables uniform coating on the entire active material surface while maintaining the desired stability in electrolyte and high voltage conditions, and reduces resistance compared to crystalline structures
Solution Approach 2:
The invention uses a composite structure consisting of a positive electrode active material core and an amorphous aluminum-based compound coating layer. This composite material combines the high capacity of the active material with the protective and stabilizing properties of the amorphous aluminum-based layer, achieving both uniform coverage and electrochemical stability
2Ease of operation
If a boron-based coating is uniformly coated in an amorphous state, then it does not interfere with lithium ion movement, but it reacts with moisture when reaction with electrolyte is prolonged
Solution Approach 1:
The invention introduces an amorphous aluminum-based compound as an intermediary protective layer between the positive electrode active material and the electrolyte. This intermediary layer provides chemical stability and moisture resistance while maintaining lithium ion conductivity, solving the problem of boron-based coating reacting with moisture
Solution Approach 2:
The invention changes the composition parameter from boron-based to aluminum-based compound, and maintains the amorphous state. This parameter change provides both uniform coating capability and enhanced chemical stability with moisture, while preserving lithium ion movement properties
3Use of energy by moving object
If charging and discharging are repeated in lithium secondary batteries, then energy storage function is maintained, but lifespan deteriorates rapidly due to electrolyte decomposition and active material degradation
Solution Approach 1:
The invention applies an amorphous aluminum-based compound coating layer beforehand on the positive electrode active material surface. This protective layer cushions and prevents direct contact between the active material and electrolyte, reducing decomposition and degradation during repeated charging and discharging cycles, thereby extending battery lifespan while maintaining energy storage function
Solution Approach 2:
The invention creates a composite structure with the positive electrode active material core and amorphous aluminum-based compound coating. This composite material provides both the energy storage capability of the active material and the protective, lifespan-extending properties of the coating layer, enabling sustained performance over many cycles
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 oxide layer effectively protects the core from electrolyte and hydrogen fluoride, reducing gas generation and improving the battery's lifespan, cycle, and high-voltage stability, while maintaining lithium ion conductivity and adhesion, thus enhancing the overall performance of lithium secondary batteries.
Implementation Method 1
a surface treatment layer located on a surface of the core and including an amorphous oxide... excellent chemical resistance
Implementation Method 2
a second process of forming a surface treatment layer including the amorphous oxide on a lithium composite metal oxide by mixing the amorphous oxide and the lithium composite metal oxide and performing a heat treatment
Data Source
AI summary
The present invention relates to a positive electrode active material for a secondary battery, which comprises a core including a lithium composite metal oxide, and a surface treatment layer located on a surface of the core and including an amorphous oxide, wherein the amorphous oxide including silicon (Si), nitrogen (N) and at least one metal element selected from the group consisting of a Group 1A element, a Group 2A element, and a Group 3B element, and a method for preparing the same.