Core-Shell Positive Electrode Material for Battery Stability
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Solution Overview
Problem
Lithium secondary batteries face limitations in high-temperature performance due to degradation of active materials and increased internal resistance, particularly in high-capacity and high-voltage applications, where existing materials like LiCoO2 and lithium nickel manganese oxides exhibit poor rate capability and life characteristics.
Innovation Solution
A positive electrode active material with a core-shell structure and a three-dimensional network buffer layer, comprising polycrystalline lithium composite metal oxides with controlled grain size (50 nm to 150 nm) and a specific composition, including elements like aluminum, manganese, zirconium, and tungsten, is developed to enhance output and life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LiCoO2 is used as positive electrode active material, then charge and discharge efficiency is improved, but structural stability deteriorates leading to poor life characteristics
Solution Approach 1:
The patent uses a core-shell composite structure where the core is LiCoO2 (providing high charge/discharge efficiency) and the shell is LiNi0.8Co0.1Mn0.1O2 (providing structural stability). This composite structure allows the inner LiCoO2 to maintain its excellent electrochemical performance while the outer LiNi0.8Co0.1Mn0.1O2 shell protects it from structural degradation during cycling, thereby resolving the contradiction between efficiency and stability.
2Stability of the object's composition
If LiNi0.8Co0.1Mn0.1O2 is used as positive electrode active material, then structural stability is improved, but charge and discharge efficiency deteriorates
Solution Approach 1:
The patent creates a core-shell composite where LiNi0.8Co0.1Mn0.1O2 forms the outer shell providing structural stability, while LiCoO2 forms the inner core providing high charge/discharge efficiency. The shell thickness is controlled to be 0.5-2.0 μm to balance protection and performance, allowing the stable shell to protect the efficient core without completely isolating it, thus resolving the contradiction between stability and efficiency.
3Productivity
If grain size is reduced to improve output characteristics, then rate capability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent optimizes the grain size parameter of LiCoO2 primary particles to a specific range (0.5-2.0 μm) to achieve high output characteristics and rate capability. By controlling the grain size within this optimized range through sintering process parameters (temperature, time, atmosphere), the patent improves electrochemical performance without requiring excessively complex manufacturing processes, thus resolving the contradiction between performance and manufacturing 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 solution significantly improves output characteristics, especially at low temperatures, and extends the life of lithium secondary batteries by minimizing material degradation and optimizing crystal structure stability, while maintaining high capacity and thermal stability.
Implementation Method 1
the core, the shell, and the three-dimensional network structure of the buffer layer each independently include a polycrystalline lithium composite metal oxide of Formula 1 including a plurality of grains, and an average grain diameter of the grains is in a range of 50 nm to 150 nm
Implementation Method 2
a buffer layer which is disposed between the core and the shell and includes pores and a three-dimensional network structure connecting the core and the shell
Data Source
AI summary
The present invention relates to a positive electrode active material for a secondary battery and a secondary battery including the same, wherein the positive electrode active material includes a core, a shell disposed to surround the core, and a buffer layer which is disposed between the core and the shell and includes pores and a three-dimensional network structure connecting the core and the shell, wherein the core, the shell, and the three-dimensional network structure of the buffer layer each independently includes a polycrystalline lithium composite metal oxide of Formula 1 including a plurality of grains, and the grains have an average grain diameter of 50 nm to 150 nm.