Carbon-Coated Cathode Material Without High-Temperature Oxidation
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Solution Overview
Problem
Lithium nickel composite metal oxides used in lithium secondary batteries face issues with low thermal stability and vulnerability to moisture, leading to decomposition and ignition, while carbon coating methods require high-temperature heat treatment that alters the oxidation state of the electrode material, reducing performance.
Innovation Solution
A method involving surface treatment of lithium transition metal oxides with a carbon-based material of hollow structure to form a uniform carbon coating layer, maintaining the material's oxidation state and improving conductivity without high-temperature heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a carbon coating layer is formed using pitch and high-temperature heat treatment, then electrical conductivity is improved, but the oxidation number of the positive electrode material changes due to carbon-oxygen reaction, deteriorating performance
Solution Approach 1:
The invention changes the temperature parameter from high-temperature heat treatment to room temperature or low-temperature processing. The carbon coating is applied without high-temperature carbonization, preventing the carbon-oxygen reaction that would alter the oxidation number, while still achieving improved electrical conductivity through the carbon coating layer formation.
Solution Approach 2:
The invention replaces the thermal/chemical process (high-temperature heat treatment for carbonization) with a mechanical process (mechanical alloying or ball milling). This mechanical approach allows carbon to be incorporated into the coating layer without the thermal conditions that cause oxidation, thus maintaining the oxidation number while improving conductivity.
2Reliability
If cobalt is used in excess to improve thermal stability, then thermal stability is improved, but cost increases due to sharp increase in cobalt price
Solution Approach 1:
The invention applies local quality by creating a carbon coating layer on the surface of the positive electrode material particles. This surface modification provides the desired stability and conductivity properties locally at the particle surface without requiring bulk substitution of expensive cobalt, thus reducing overall cobalt content while maintaining performance.
Solution Approach 2:
The invention uses composite materials by combining the positive electrode active material with a carbon coating layer. This composite structure provides the thermal stability and electrical conductivity benefits of carbon while allowing the use of less expensive, lower-cobalt compositions in the bulk material, reducing overall cobalt content and cost.
3Shape
If high-temperature heat treatment is performed for carbonization, then carbon coating layer is formed, but carbon element on surface reacts with oxygen and reduces, causing oxidation number to greatly change
Solution Approach 1:
The invention changes the temperature parameter from high-temperature heat treatment to room temperature or low-temperature processing. The carbon coating is applied without high-temperature carbonization, preventing the carbon-oxygen reaction that would alter the oxidation number, while still achieving improved conductivity through the carbon coating layer formation.
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 method enhances electrical conductivity and lifespan properties of the positive electrode active material by forming a thin, uniform carbon coating layer, preventing oxidation number changes and side reactions, thus improving battery performance and safety.
Implementation Method 1
surface-treated in a mechanical manner with a carbon-based material of a hollow structure, so that a uniform carbon coating layer is formed on the surface
Implementation Method 2
when the high-temperature heat treatment is performed, a carbon element on a surface reacts with oxygen on the surface of a positive electrode material and reduced, which causes the oxidation number of the positive electrode material to greatly change
Data Source
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AI summary
The present invention relates to a method for producing a positive electrode active material, a positive electrode active material produced by the method, thereby having a BET specific surface area of 10 m2/g or less, a positive electrode including the positive electrode active material, and a lithium secondary battery, wherein the method includes preparing a lithium transition metal oxide in the form of a secondary particle in which primary particles are aggregated, mixing the lithium transition metal oxide and a carbon-based material of a hollow structure having a plurality of pores to form a mixture, and surface treating the mixture in a mechanical manner to form a carbon coating layer on the surface of the lithium transition metal oxide, wherein the carbon-based material of a hollow structure having a plurality of pores has a specific surface area of 200 m2/g or greater and a graphitization degree(ID/IG) of 0.5 or greater.