Al-Coated Ni-Mn Cathode Particles for High-Voltage Cycle Stability
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Solution Overview
Problem
The demand for high-capacity, high-energy-density rechargeable lithium batteries is increasing, but the supply of cobalt, a rare and expensive metal, is limited, and existing cobalt-free positive electrode active materials face challenges in maintaining structural stability, resistance, and cycle-life characteristics under high-voltage and high-temperature conditions.
Innovation Solution
A positive electrode active material comprising a layered lithium nickel-manganese-based composite oxide with an aluminium coating layer on the surface of core particles, where the material is formed by agglomerating primary particles into secondary particles, and smaller single particles with a thinner aluminium coating, enhancing structural stability and reducing side reactions with electrolytes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If cobalt-free positive electrode active materials are used to reduce cost and supply dependency, then production cost decreases and supply security improves, but structural stability and performance under high-voltage and high-temperature conditions deteriorate
Solution Approach 1:
An aluminium coating layer is introduced as an intermediary substance between the cobalt-free positive electrode active material and the electrolyte. This coating layer mediates the interaction by providing structural support and protecting the underlying active material from degradation under high-voltage and high-temperature conditions, thereby improving reliability without compromising the cost benefits of cobalt-free composition
Solution Approach 2:
The invention creates a composite structure consisting of cobalt-free positive electrode active material combined with an aluminium coating layer. This composite material approach allows the system to benefit from the cost advantages of cobalt-free materials while the aluminium coating provides the necessary structural stability and performance characteristics under extreme operating conditions
2Reliability
If aluminium coating layer is applied to improve structural stability and reduce side reactions, then reliability and cycle-life characteristics improve, but manufacturing complexity increases
Solution Approach 1:
The invention optimizes specific parameters of the aluminium coating layer including thickness (5-50 nm), aluminium content (0.1-5 at%), and crystal structure to achieve the desired balance between reliability improvement and manufacturing complexity. By controlling these parameters within specific ranges, the coating provides effective protection while maintaining manufacturability
3Quantity of substance
If high energy density is achieved through optimized composition and structure, then capacity and energy density improve, but resistance to side reactions with electrolytes under high-voltage conditions worsens
Solution Approach 1:
The aluminium coating layer serves as a protective intermediary that prevents direct contact between the high-energy-density active material and the electrolyte. This intermediary layer blocks harmful side reactions while allowing the underlying material to maintain its high capacity and energy density characteristics
Solution Approach 2:
The aluminium coating layer acts as a sacrificial protective layer that can be consumed or degraded preferentially to protect the valuable high-energy-density active material. This approach allows the system to achieve high energy density while the coating absorbs the damage from side reactions with electrolytes
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 achieves high energy density, improved capacity, and extended cycle-life characteristics under high-voltage and high-temperature conditions while minimizing production costs by using a cobalt-free composition and optimizing the aluminium coating layer.
Implementation Method 1
an aluminium coating layer on the surface of the core particle
Implementation Method 2
layered lithium nickel-manganese-based composite oxide... maximize or increase capacity (e.g., electrical capacity)
Data Source
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AI summary
A positive electrode active material, a positive electrode, and a rechargeable lithium battery including the positive electrode are disclosed. The positive electrode active material includes a first positive electrode active material including a core particle in a form of secondary particles including a layered lithium nickel-manganese-based composite oxide and provided by agglomerating a plurality of primary particles and a second positive electrode active material including a core particle including a layered lithium nickel-manganese-based composite oxide and in a form of single particles. The first positive electrode active material and the second positive electrode active material each independently further include an aluminium coating layer on the surface of the core particle, and an average particle diameter (D50) of the second positive electrode active material is smaller than that of the first positive electrode active material.