Core-Shell LiCoO2 Cathode and Electrolyte for High-Voltage Cycle Life
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Solution Overview
Problem
Lithium cobalt-based positive electrode active materials suffer from gas and cobalt dissolution at high voltages, leading to degraded life characteristics and high-temperature storability, limiting their use in batteries operating at 4.45V or higher.
Innovation Solution
A lithium secondary battery design featuring a positive electrode with a core-shell structure, where the core is a lithium cobalt-based oxide doped with specific elements (Al, Zr, Mg, Ti) and a shell with a different lithium cobalt-based oxide, combined with a non-aqueous electrolyte containing lithium difluorophosphate and a dinitrile-based compound, forms a stable film on the electrode surface, enhancing structural stability and preventing side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium cobalt-based oxide is used as positive electrode active material to achieve high energy density and operating voltage, then energy density and operating voltage are improved, but gas and cobalt dissolution occur rapidly at high voltage (4.45V or higher), degrading life characteristics and high-temperature storability
Solution Approach 1:
The patent applies parameter changes by precisely controlling the doping concentration of aluminum in the lithium cobalt-based oxide within the range of 0.01-0.06 atomic ratio. This specific parameter range optimizes the balance between maintaining high voltage operation capability and suppressing cobalt dissolution and gas generation, thereby improving both energy density and reliability simultaneously
Solution Approach 2:
The patent uses composite materials by combining lithium cobalt-based oxide with aluminum doping to create a modified positive electrode active material. The aluminum-doped lithium cobalt-based oxide forms a composite structure that enhances structural stability at high voltage while maintaining high energy density, preventing the harmful side reactions that occur with undoped materials
2Use of energy by moving object
If lithium cobalt-based oxide is used as positive electrode active material, then operating voltage is improved, but high-temperature storability is degraded due to side reactions with electrolyte solution
Solution Approach 1:
The patent applies parameter changes by optimizing the aluminum doping concentration to 0.01-0.06 atomic ratio, which fundamentally alters the material's chemical stability. This parameter optimization suppresses the side reactions between lithium cobalt-based oxide and electrolyte solution at high temperatures, enabling the material to maintain both high operating voltage and improved high-temperature storability
3Volume of stationary object
If large particle diameter active material is used to increase packing density, then packing density is improved, but surface area decreases, reducing rate capability and initial capacity
Solution Approach 1:
The patent applies local quality by introducing aluminum doping at specific locations within the lithium cobalt-based oxide crystal structure. This local modification enhances the bulk structural stability and lithium ion diffusion pathways throughout the particle, allowing large particles to maintain high packing density while the doped structure ensures adequate rate capability and initial capacity by improving internal transport properties
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 design improves high-temperature durability and cycle characteristics by minimizing interfacial resistance and preventing side reactions, making it suitable for high-voltage automotive applications.
Implementation Method 1
combined with a non-aqueous electrolyte containing lithium difluorophosphate and a dinitrile-based compound, forms a stable film on the electrode surface
Implementation Method 2
forms a stable film on the electrode surface, enhancing structural stability and preventing side reactions
Implementation Method 3
the core is a lithium cobalt-based oxide doped with specific elements (Al, Zr, Mg, Ti)
Implementation Method 4
doped with specific elements (Al, Zr, Mg, Ti) and a shell with a different lithium cobalt-based oxide, enhances structural stability
Data Source
AI summary
The present disclosure provides a lithium secondary battery capable of improving high-temperature durability and cycle characteristics during high-voltage operation. The lithium secondary battery includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte solution for a lithium secondary battery, wherein the positive electrode active material includes a core including a lithium cobalt-based oxide represented by Formula 1; and a shell including a lithium cobalt-based oxide represented by Formula 2 which is disposed on a surface of the core, wherein the core and the shell include at least one doping element selected from the group consisting of Al, Zr, Mg, and Ti, and the non-aqueous electrolyte solution may include a lithium salt, an organic solvent, lithium difluorophosphate, and a dinitrile-based compound represented by Formula 3.