Ni-rich Cathode Coating for Battery Stability
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Solution Overview
Problem
Current lithium secondary batteries face limitations in high energy density, capacity, and lifetime due to the use of Ni-rich cathode active materials, which suffer from micro-cracking and side reactions with the electrolyte, and single-crystal lithium cobalt oxide is restricted in high voltage applications.
Innovation Solution
A composite cathode active material is developed, comprising a lithium transition metal oxide with a layered crystalline phase and a cobalt hydroxide coating layer, which stabilizes the structure and reduces interfacial reactivity, enhancing charge/discharge characteristics and lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Ni-rich cathode active materials are used to increase capacity, then electrode capacity is improved, but micro-cracking occurs and lifetime characteristics deteriorate
Solution Approach 1:
The patent uses a composite structure with a Ni-rich core (LiNi0.8Co0.1Mn0.1O2) and a LiCoO2 coating layer. The core provides high capacity while the coating layer prevents micro-cracking and side reactions, resolving the contradiction between high capacity and long lifetime by combining materials with complementary properties.
Solution Approach 2:
The patent applies different material properties to different regions: the inner core uses Ni-rich material for high capacity, while the outer coating layer uses LiCoO2 for structural stability and protection. This local differentiation allows each region to perform its specific function optimally.
2Volume of stationary object
If single-crystal lithium cobalt oxide is used to achieve high electrode density, then electrode density is improved, but structural stability at high voltage deteriorates
Solution Approach 1:
The patent creates a composite where LiCoO2 serves dual purposes: as the coating layer providing structural stability at high voltage, and as the base material ensuring high electrode density. The Ni-doping further stabilizes the layered structure, resolving the contradiction between density and high-voltage stability.
3Ease of manufacture
If co-precipitation method is used to synthesize cathode active material, then manufacturing process is simplified, but secondary particle formation occurs and electrode density is limited
Solution Approach 1:
The patent performs preliminary doping of Ni into the LiCoO2 structure during the co-precipitation process, before final formation. This preliminary action allows the use of simple co-precipitation manufacturing while achieving the desired high-density single-crystal structure with improved electrochemical performance.
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 composite cathode active material improves structural stability and charge/discharge performance, inhibits gas generation, and maintains high electrode density, enabling better energy and cycle retention at high voltages.
Implementation Method 1
a coating layer on a surface of the core, wherein the coating layer is formed by a cobalt hydroxide (Co(OH) 2 )
Implementation Method 2
a charging and discharging mechanism is based on oxidation and reduction reactions of a transition metal in a transition metal oxide
Data Source
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AI summary
Provided is a composite cathode active material including: a core including a lithium transition metal oxide, the lithium transition metal oxide being doped with nickel (Ni) and at least one element selected from Group 4 to Group 13 elements and having a layered crystalline phase belonging to the Space Group R-3m; and a coating layer on a surface of the core, the coating layer including a cobalt compound.