Core-Shell Cathode Coating for Thermal-Stable Lithium-Ion Batteries
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Solution Overview
Problem
Existing cathode active materials, such as LiNiO2, face issues with structural collapse during charging and discharging due to low thermal stability and oxidation number problems, limiting their commercial use, while ternary NCM systems suffer from decreased thermal stability with increasing nickel content.
Innovation Solution
A cathode active material with a core-shell structure and a specific coating layer is developed, where the intensity ratio of XPS peaks satisfies 0.3 to 0.7, enhancing thermal stability and suppressing electrolyte decomposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If LiNiO2 is used as cathode active material to achieve high capacity, then battery capacity is improved, but thermal stability deteriorates due to structural collapse during charging and discharging
Solution Approach 1:
The patent uses a core-shell structure where the core is LiNiO2 (providing high capacity) and the shell is LiNi0.8Co0.1Mn0.1O2 (providing structural stability). This composite structure allows the high-capacity LiNiO2 to be protected by the more stable NCM shell, preventing structural collapse during charging and discharging while maintaining high battery capacity.
2Quantity of substance
If nickel content is increased to improve battery capacity, then energy density is improved, but thermal stability deteriorates
Solution Approach 1:
The patent applies local quality by having different nickel contents in different regions of the cathode material. The core region has high nickel content (0.9≤x<1.0 in Li1+xNiyCozMn1-y-zO2) for high capacity, while the shell region has lower nickel content (y=0.8) for structural stability. This spatial variation in composition allows simultaneous optimization of both energy density and thermal stability.
3Reliability
If ternary NCM system is used to substitute unstable Ni sites, then thermal stability is improved, but capacity decreases as Ni content is reduced
Solution Approach 1:
The patent uses a nested structure where the high-capacity LiNiO2 core is enclosed within the LiNi0.8Co0.1Mn0.1O2 shell. This nested arrangement allows the inner high-nickel core to provide maximum capacity while being protected and stabilized by the outer lower-nickel shell, effectively combining the advantages of both high-capacity and stable materials.
4Duration of action of stationary object
If coating layer is added to suppress electrolyte decomposition, then high-temperature lifespan is improved, but device complexity increases
Solution Approach 1:
The patent merges the protective coating function with the cathode active material structure itself by forming the LiNi0.8Co0.1Mn0.1O2 shell directly on the LiNiO2 core during the sintering process. This integrated approach provides electrolyte decomposition suppression and structural stabilization simultaneously without requiring separate coating steps, thus improving high-temperature lifespan while minimizing additional 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 core-shell structure with a controlled coating layer significantly improves high-temperature lifespan and thermal stability of lithium secondary batteries.
Implementation Method 1
it is possible to suppress a decomposition reaction on a surface of the cathode active material
Implementation Method 2
a structure of LiNiO2 easily collapses during charging and discharging
Data Source
AI summary
Embodiments of the present invention relate to a cathode active material, a method for manufacturing the same, and a lithium secondary battery including the same.According to an embodiment, a cathode active material can be provided, the cathode active material comprising: a lithium metal oxide including a core and a shell disposed on a surface of the core; and a coating layer disposed on a surface of the lithium metal oxide, wherein a c value that satisfies Equation 1 and is in a range of 0.3 to 0.7, and the core and the shell have a layered crystalline structure.c=b/a [Equation 1](in Equation 1, a is a peak at 530 to 533 eV and b is a peak at 528 to 531 eV in an XPS spectrum of the coating layer).