High-Nickel Cathode Coating to Reduce Swelling and Stability Loss
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Solution Overview
Problem
Conventional lithium cobalt oxide and nickel-based positive electrode active materials for lithium secondary batteries face issues with structural stability, chemical stability, and thermal stability due to high nickel content, leading to increased lithium by-products and swelling, which affect battery life and performance.
Innovation Solution
A method involving the preparation of a lithium complex transition metal oxide with high nickel content, followed by water washing to remove surface lithium by-products, and subsequent high-temperature heat treatment with cobalt and boron-containing materials to form a cobalt-rich surface coating and lithium boron oxide, enhancing structural and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the nickel content in the lithium complex transition metal oxide is increased to improve capacity characteristics, then the capacity increases, but the structural stability and chemical stability deteriorate
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the interior maintains high nickel content for capacity while the exterior develops a cobalt-rich surface layer for stability. This spatial differentiation allows the bulk material to provide high capacity (0.8-0.95 nickel content) while the surface layer (formed through heat treatment) provides structural and chemical stability, resolving the contradiction between capacity and stability.
Solution Approach 2:
The patent creates a composite structure consisting of the lithium complex transition metal oxide core with a cobalt-rich surface layer shell. This composite material approach combines the high-capacity nickel-based core with the stabilizing cobalt-rich surface layer, allowing simultaneous achievement of high capacity characteristics and improved structural/chemical stability through the synergistic combination of different material phases.
2Quantity of substance
If the nickel content is increased to improve capacity, then the capacity increases, but thermal stability rapidly deteriorates
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the interior maintains high nickel content for capacity while the exterior develops a cobalt-rich surface layer for stability. This spatial differentiation allows the bulk material to provide high capacity (0.8-0.95 nickel content) while the surface layer (formed through heat treatment) provides structural and chemical stability, resolving the contradiction between capacity and stability.
Solution Approach 2:
The patent creates a composite structure consisting of the lithium complex transition metal oxide core with a cobalt-rich surface layer shell. This composite material approach combines the high-capacity nickel-based core with the stabilizing cobalt-rich surface layer, allowing simultaneous achievement of high capacity characteristics and improved structural/chemical stability through the synergistic combination of different material phases.
3Quantity of substance
If the nickel content is increased to improve capacity, then the capacity increases, but the residual amount of lithium by-products increases causing gas generation and swelling
Solution Approach 1:
The patent applies the extraction principle by removing lithium by-products (LiOH and Li2CO3) from the surface of the positive electrode active material through water washing. This extraction of harmful substances from the high-nickel material surface reduces the residual lithium by-products that would otherwise cause gas generation and swelling, allowing the use of high-nickel content (0.8-0.95) for high capacity while mitigating the harmful by-product formation.
4Temperature
If a coating process is applied to overcome thermal stability problems, then thermal stability improves, but the production time and process cost increase
Solution Approach 1:
The patent applies the merging principle by combining the heat treatment step (performed at 600-900°C for 5-24 hours) to simultaneously achieve multiple objectives: improving thermal stability, forming the cobalt-rich surface layer, and reducing lithium by-products. This consolidation of functions into a single heat treatment step eliminates the need for separate coating processes, thereby improving thermal stability while avoiding additional production time and process cost.
Solution Approach 2:
The patent applies universality by designing the heat treatment process to perform multiple functions simultaneously: (1) improving thermal stability of the high-nickel material, (2) forming the protective cobalt-rich surface layer, and (3) reducing lithium by-products. This multi-functional approach allows a single process step to address multiple issues that would traditionally require separate treatments, reducing overall production time and complexity.
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 improves the stability and capacity of the positive electrode active material, reducing lithium by-products and simplifying the production process while increasing high-temperature life-time and output characteristics.
Implementation Method 1
removing lithium by-products present on a surface of the lithium complex transition metal oxide by washing the lithium complex transition metal oxide with water
Implementation Method 2
mixing the washed lithium complex transition metal oxide, a cobalt (Co)-containing raw material, and a boron (B)-containing raw material and performing high-temperature heat treatment at a temperature of 600° C. or higher
Implementation Method 3
mixing the washed lithium complex transition metal oxide, a cobalt (Co)-containing raw material, and a boron (B)-containing raw material and performing high-temperature heat treatment at a temperature of 600° C. or higher
Implementation Method 4
performing high-temperature heat treatment at a temperature of 600° C. or higher
Data Source
AI summary
A positive electrode active material for a secondary battery includes a lithium complex transition metal oxide and a surface coating portion. The lithium complex transition metal oxide includes nickel (Ni), cobalt (Co), and at least one selected from the group consisting of manganese (Mn) and aluminum (Al). The surface coating portion is formed on surfaces of the lithium complex transition metal oxide particles and the surface coating portion includes a cobalt-rich layer, which has a higher cobalt content than the lithium complex transition metal oxide, and a lithium boron oxide.