Reduced Surface Metal Oxide Layer for Lithium Battery Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining high energy density and longevity, especially under high voltage and temperature conditions, due to electrolyte oxidation and element elution from the electrode active material, which existing surface coatings fail to adequately address.
Innovation Solution
A surface-treated electrode active material with a higher degree of reduction in the surface metal oxide layer compared to the bulk metal oxide layer, formed by adding a basic and/or reducing material to the electrode active material in a solvent, followed by stirring, filtering, cleaning, and drying, to create a layer that prevents electrolyte contact and element elution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a surface coating is applied to the electrode active material, then side reactions between electrolyte and electrode surface are prevented, but the coating material itself undergoes oxidation under high voltage conditions
Solution Approach 1:
The invention changes the chemical state parameter of the surface layer by creating a reduced metal oxide layer with lower oxygen content compared to the bulk material. This parameter change allows the surface layer to remain stable at high voltages without undergoing oxidation, while still providing protective functions.
Solution Approach 2:
The invention creates a surface layer with different chemical composition and properties than the bulk material. The surface layer has a lower degree of oxidation and different stoichiometry, providing localized protection against electrolyte decomposition while the bulk material maintains its high voltage electrochemical activity.
2Quantity of substance
If high voltage electrode materials are used to achieve high energy density, then energy storage capacity increases, but element elution from the electrode surface occurs
Solution Approach 1:
The invention modifies the surface composition parameter by creating a reduced metal oxide layer with different cation ratios and oxygen content. This surface modification prevents element elution while allowing the bulk material to maintain high voltage and high energy density characteristics.
3Productivity
If batteries operate at high temperature to improve performance, then charging/discharging rate increases, but lifetime decreases due to accelerated degradation
Solution Approach 1:
The invention creates a protective surface layer beforehand that cushions against thermal degradation. This reduced metal oxide surface layer acts as a stable interface that prevents harmful reactions between the electrode and electrolyte at elevated temperatures, thereby extending battery lifetime while allowing high-rate operation.
4Reliability
If a surface layer with lower degree of oxidation is created, then stability at high voltage and temperature is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The invention employs a self-service approach where the electrode material itself serves as the reducing agent. By controlling the atmosphere and heating conditions, the bulk material reduces its own surface layer, eliminating the need for separate coating processes or external reducing agents, thereby simplifying the manufacturing process.
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 surface-treated electrode active material exhibits improved lifetime characteristics and charging/discharging performance at high temperatures, effectively suppressing side reactions and element elution, enhancing the battery's operational stability and energy storage capacity.
Implementation Method 1
a surface metal oxide layer including the same n types of metal elements as those of the bulk metal oxide layer, wherein the degree of reduction of the metal element included in the surface metal oxide layer is higher than the degree of reduction of a corresponding metal element included in the bulk metal oxide layer
Data Source
AI summary
A surface-treated electrode active material, a method of surface treating an electrode active material, an electrode, and a lithium secondary battery. The surface-treated electrode active material includes a surface metal oxide layer having higher degree of reduction of a metal than that of a bulk metal oxide layer. The method includes: forming a mixture by adding an untreated electrode active material comprising a metal oxide, and at least one of a basic material and a reducing material to a solvent; and stirring the mixture.