Amorphous Oxide Surface Treatment for Lithium Battery Cathodes
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Solution Overview
Problem
Lithium secondary batteries face rapid lifetime degradation due to increased internal resistance and gas generation, particularly in high-voltage batteries, caused by degradation of positive electrode materials and reactions with moisture in the electrolyte.
Innovation Solution
A positive electrode active material is developed with a surface treatment layer composed of chemically bonded amorphous lithium, boron, and aluminum oxides, where the aluminum oxide content is greater than boron oxide, and a lithium by-product amount is less than 0.55 wt%, formed through a heat treatment process in an oxygen atmosphere, which reduces direct contact with the electrolyte and minimizes gas generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a crystalline aluminum-based surface treatment layer is coated on the positive electrode active material, then stability at high voltage and in electrolyte solution is improved, but resistance increases and uniform coating is difficult
Solution Approach 1:
The patent changes the physical state parameter of the aluminum-based surface treatment layer from crystalline to amorphous. This parameter change resolves the contradiction by eliminating the crystalline structure that causes high resistance while maintaining the protective function against electrolyte decomposition and moisture reaction, thus achieving both low resistance and high voltage stability.
2Manufacturing precision
If a boron-based coating is applied to the positive electrode active material, then uniform coating and lithium ion movement are improved, but gas generation increases due to reaction with moisture
Solution Approach 1:
The patent introduces an aluminum-based amorphous surface treatment layer as an intermediary between the positive electrode active material and the electrolyte. This intermediary layer prevents direct contact between the boron-based coating and moisture, thereby eliminating gas generation while preserving the uniform coating and lithium ion movement benefits.
Solution Approach 2:
The patent creates a composite surface treatment structure combining aluminum-based amorphous oxide as the primary protective layer with boron-based coating underneath. This composite material approach allows the boron layer to provide uniform coating and lithium ion conductivity while the aluminum amorphous layer prevents moisture reaction and gas generation.
3Duration of action of moving object
If the positive electrode material is used for long-term operation, then battery capacity is maintained, but internal resistance increases and lifetime decreases
Solution Approach 1:
The patent applies an aluminum-based amorphous surface treatment layer as a preliminary protective action before the positive electrode material contacts the electrolyte during long-term operation. This pre-formed protective barrier prevents electrolyte decomposition and material degradation that would otherwise increase internal resistance and reduce lifetime, enabling sustained battery performance.
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 solution results in improved lithium ion conductivity, reduced resistance, and extended battery life by preventing damage from the electrolyte and hydrogen fluoride, while minimizing gas generation, thus enhancing the battery's output characteristics and cycle stability.
Implementation Method 1
the lithium oxide, the boron oxide, and the aluminum oxide are chemically bonded to one another
Implementation Method 2
forming a surface treatment layer including an amorphous oxide on a core including the lithium composite metal oxide by performing a heat treatment on the mixture in an oxygen atmosphere
Data Source
AI summary
The present invention relates to a positive electrode active material for a secondary battery, which includes a core including a lithium composite metal oxide, and a surface treatment layer which is disposed on the core and includes an amorphous oxide containing a lithium (Li) oxide, a boron (B) oxide, and an aluminum (Al) oxide, wherein an amount of a lithium by-product present on a surface of the positive electrode active material is less than 0.55 wt % based on a total weight of the positive electrode active material, and a method of preparing the same.