Lithium Cobalt Composite Cathode for High-Temperature Stability
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Solution Overview
Problem
Lithium cobalt oxide cathode active materials in lithium secondary batteries face challenges in achieving satisfactory load characteristics, low-temperature characteristics, and cycle characteristics, particularly at high temperatures, despite efforts to improve stability and performance through element substitution and coprecipitation techniques.
Innovation Solution
A cathode active material comprising lithium cobalt composite oxide with specific mole ratios of cobalt, aluminum, magnesium, titanium, and tin, where these elements are incorporated within predetermined ranges to enhance stability and conductivity, and exist as compounds in crystal grain boundaries, thereby improving load, low-temperature, and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If cobalt is replaced by other elements or additional elements are added to lithium cobalt oxide, then high-temperature stability is improved, but load characteristics and low-temperature characteristics deteriorate
Solution Approach 1:
The patent uses a composite material approach by combining lithium cobalt oxide with a core-shell structure where the core is lithium cobalt oxide and the shell is formed by coprecipitation of multiple metal elements (including aluminum, magnesium, titanium, zirconium, and tin) that provide both stability and conductivity. This composite structure allows the material to simultaneously achieve high-temperature stability from the shell and good load characteristics from the optimized core composition.
Solution Approach 2:
The patent applies local quality by creating a non-uniform distribution of elements within the cathode material structure. The coprecipitation process creates a specific spatial arrangement where certain elements concentrate in the shell region while maintaining appropriate composition in the core, allowing different regions to fulfill different functions - the shell provides stability while the core maintains conductivity and capacity.
2Stability of the object's composition
If cobalt is replaced by other elements or additional elements are added to lithium cobalt oxide, then high-temperature stability is improved, but low-temperature characteristics deteriorate
Solution Approach 1:
The composite lithium cobalt oxide with coprecipitated shell structure provides a solution where the shell composition is specifically designed to maintain structural integrity at high temperatures while the overall material composition is optimized to preserve ionic conductivity at low temperatures, thus simultaneously addressing both stability and low-temperature performance.
Solution Approach 2:
The patent employs parameter changes by carefully controlling the composition ratios of multiple metal elements in the coprecipitated shell and optimizing the particle size distribution of the cathode material. These parameter optimizations ensure that the material maintains appropriate structural stability at high temperatures while preserving sufficient ionic conductivity for low-temperature operation.
3Stability of the object's composition
If cobalt is replaced by other elements or additional elements are added to lithium cobalt oxide, then thermal stability is improved, but cycle characteristics deteriorate
Solution Approach 1:
The patent creates a composite structure where the coprecipitated shell of multiple metal elements provides thermal stability by forming a protective layer that prevents structural degradation, while the optimized core composition and controlled particle morphology maintain good cycle characteristics by facilitating stable lithium ion insertion and extraction over repeated cycles.
Solution Approach 2:
By creating a localized shell structure through coprecipitation with specific element distribution, the patent achieves thermal stability at the surface level while maintaining the electrochemical activity needed for good cycle characteristics in the bulk material, thus resolving the contradiction between thermal stability and cycle performance.
4Stability of the object's composition
If zirconium compound is coprecipitated and zirconium is allowed to exist on particle surface, then thermal stability is improved, but satisfactory load characteristics and low-temperature characteristics cannot be obtained
Solution Approach 1:
The patent extends the single-element zirconium surface coating approach to a multi-element coprecipitated composite shell structure. By incorporating zirconium along with aluminum, magnesium, titanium, and tin in specific ratios, the material achieves thermal stability from zirconium while the synergistic effects of other elements improve load characteristics and ionic conductivity that zirconium alone cannot provide.
Solution Approach 2:
The patent refines the local quality approach by creating a complex multi-element shell composition rather than a simple zirconium coating. This sophisticated local composition at the particle surface provides thermal stability while the specific arrangement and ratios of multiple elements maintain appropriate conductivity and reactivity for satisfactory load characteristics.
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 proposed cathode active material effectively stabilizes the crystalline structure, suppressing resistance increase during charging and discharging, and enhances load, low-temperature, and cycle characteristics at high temperatures, leading to improved battery performance.
Implementation Method 1
many trials for improving the characteristics by replacing cobalt in lithium cobalt acid by another element or by adding another element have been made
Implementation Method 2
lithium cobalt acid has a stratified structure which is advantageous to diffuse lithium ions
Implementation Method 3
when lithium cobalt acid is synthesized, a zirconium compound is coprecipitated and zirconium Zr is allowed to exist on a particle surface of lithium cobalt acid
Data Source
AI summary
A cathode contains: a lithium cobalt composite oxide expressed by LixCoaM1bM2cO2, where M1 denotes the first element; M2 indicates the second element; x, a, b, and c are set to values within ranges of 0.9≦x≦1.1, 0.9≦a≦1, 0.001≦b≦0.05, and 0.001≦c≦0.05; and a+b+c=1; a first sub-component element of at least one kind selected from a group containing Ti, Zr, and Hf, and a second sub-component element of at least one kind selected from a group containing Si, Ge, and Sn. 0.01 mol %≦(content of the first sub-component element)≦10 mol % as a ratio to cobalt in the lithium cobalt composite oxide. 0.01 mol %≦(content of the second sub-component element)≦10 mol % as a ratio to cobalt in the lithium cobalt composite oxide.