Al/Mn-Coated Ni-Mn Cathode Material for Low-Cobalt Cycle Stability
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Solution Overview
Problem
The increasing demand for high-capacity, high-energy-density rechargeable lithium batteries has been hindered by the shortage of cobalt, a rare and expensive metal, which is essential for many existing positive electrode active materials.
Innovation Solution
A positive electrode active material is developed, comprising core particles of lithium nickel-manganese-based composite oxide with a first coating layer containing aluminum and a second coating layer containing manganese, which enhances capacity, efficiency, and cycle-life characteristics while reducing cobalt content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium nickel-based oxide is used to achieve high capacity, then energy density increases, but structural stability and cycle-life characteristics deteriorate
Solution Approach 1:
The patent introduces aluminum doping at specific locations within the crystal structure (substituting at nickel sites) to locally enhance structural stability without significantly reducing overall capacity. This localized modification of the material's chemical composition creates regions of enhanced stability that prevent structural degradation during cycling.
Solution Approach 2:
The patent creates a composite oxide structure combining multiple elements (Li, Ni, Mn, Al) in specific ratios and arrangements. This composite material approach allows the system to simultaneously achieve high capacity from the nickel component and structural stability from the manganese and aluminum components, resolving the contradiction between capacity and cycle-life.
2Quantity of substance
If high voltage operation is implemented to increase energy density, then capacity increases, but gas generation and safety issues worsen
Solution Approach 1:
The patent converts the potential harm of high-voltage operation (which typically causes gas generation and safety issues) into a benefit by designing a material composition that is inherently stable at high voltages. The specific Ni0.75Mn0.23Al0.02O2 composition with its optimized oxidation states and structural features prevents electrolyte decomposition and gas generation even at 4.45V, turning the high-voltage condition from a harmful factor into an opportunity for enhanced energy density.
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 proposed solution achieves high initial charge/discharge capacity and efficiency, along with long cycle-life characteristics, and effectively suppresses gas generation under high-voltage and high-temperature conditions, addressing the cobalt shortage and cost concerns.
Implementation Method 1
performing a first heat treatment to obtain a lithium nickel-manganese-based composite oxide
Implementation Method 2
mixing an Al raw material and the lithium nickel-manganese-based composite oxide with an aqueous solvent to prepare a first mixture
Implementation Method 3
drying the second mixture and performing a second heat treatment
Data Source
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AI summary
A positive electrode active material, a method of preparing the same, a positive electrode and a rechargeable lithium battery including the same are disclosed. The positive electrode active material includes core particles including a layered lithium nickel-manganese-based composite oxide, a first coating layer disposed on a surface of the core particles and containing Al, and a second coating layer disposed on the first coating layer and containing Mn.