Lithium Battery Cathode Coating for Gas Suppression
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving improved battery capacity, rate characteristics, and lifespan due to the reaction of excess lithium with water or CO2, leading to increased pressure and reduced performance.
Innovation Solution
A cathode active material is developed with a core capable of intercalating and deintercalating lithium ions, coated with a composite layer containing a metal oxide and phosphate compound, where the weight ratio of phosphate to metal oxide is greater than 0 to 1, enhancing ion conductivity and protecting the core from side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If excess lithium is used in the cathode active material, then battery capacity is improved, but side reactions with water or CO2 occur leading to gas generation and pressure increase
Solution Approach 1:
A coating layer comprising a metal oxide compound and a phosphate compound is applied to the surface of the core material. This coating layer acts as an intermediary barrier that prevents direct contact between excess lithium and harmful substances (water, CO2), thereby suppressing side reactions and gas generation while maintaining high battery capacity
Solution Approach 2:
The coating layer is formed as a composite material combining metal oxide compound and phosphate compound. This composite structure provides synergistic effects: the metal oxide compound suppresses side reactions with water/CO2, while the phosphate compound enhances lithium ion conductivity, collectively resolving the contradiction between high capacity and harmful gas generation
2Reliability
If a coating layer is applied to protect the core, then side reactions are suppressed, but ion conductivity may be reduced
Solution Approach 1:
The coating layer is designed as a composite of metal oxide compound and phosphate compound where each component contributes different functional properties. The phosphate compound specifically enhances lithium ion conductivity while the metal oxide compound provides protection against side reactions, thus achieving both suppression of side reactions and maintenance of high ion conductivity simultaneously
Solution Approach 2:
The weight ratio of phosphate compound to metal oxide compound is optimized within a specific range (0.01 to 2:1). By adjusting this compositional parameter, the coating layer achieves optimal balance between protective function and ion conductivity, resolving the contradiction between reliability and speed
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 improves battery capacity, rate characteristics, and lifespan by reducing lithium surface accumulation, suppressing side reactions, and minimizing gas generation, thereby enhancing overall battery performance.
Implementation Method 1
a core capable of intercalating and deintercalating lithium ions
Implementation Method 2
suppressing side reactions by reducing lithium surface accumulation
Data Source
AI summary
A cathode active material includes a core capable of intercalating and deintercalating lithium ions; and a coating layer on at least a portion of the core, wherein the coating layer includes a composite including a metal oxide compound and a phosphate compound, the metal oxide compound is at least one compound selected from a lithium metal oxide and a metal oxide, the phosphate compound is at least one compound selected from a lithium phosphate, a lithium metal phosphate, and a metal phosphate, and a weight ratio of the metal oxide compound to the phosphate compound is from greater than 0 to about 1.