Al-Mg Doped LiCoO2 Cathode Coating for High-Voltage Stability
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Solution Overview
Problem
Rechargeable lithium batteries using lithium cobalt oxide as a positive electrode material face challenges with capacity reduction due to phase transition and side reactions at high voltages, limiting their high energy density and structural stability.
Innovation Solution
A positive electrode active material is developed by doping lithium cobalt-based oxides with aluminium and magnesium, and applying aluminium coating layers to stabilize the structure, using a combination of large and small particles with controlled aluminium and magnesium content to enhance stability and cycle-life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium cobalt oxide is used as positive electrode material to achieve high theoretical capacity (274 mAh/g), then energy density is improved, but structural stability deteriorates due to phase transition at high voltages
Solution Approach 1:
An aluminum coating layer is applied as an intermediary between the lithium cobalt oxide particles and the electrolyte. This coating layer prevents direct contact and chemical reactions between the high-voltage electrode material and electrolyte, thereby maintaining structural stability while enabling high energy density operation
Solution Approach 2:
The positive electrode uses a composite structure combining lithium cobalt oxide core with aluminum oxide coating shell. This composite material approach allows the inner core to provide high capacity while the outer shell provides structural stability and protects against phase transition at high voltages
2Use of energy by moving object
If high voltage charging and discharging is implemented to achieve high energy density, then energy density is improved, but reliability deteriorates due to side reactions with electrolyte
Solution Approach 1:
The aluminum coating layer serves as a protective intermediary that blocks side reactions between the electrode and electrolyte during high-voltage charging and discharging cycles, thereby improving reliability and cycle-life characteristics while maintaining high energy density
Solution Approach 2:
The aluminum oxide coating creates an inert environment around the lithium cobalt oxide particles, preventing harmful chemical interactions with the electrolyte during high-voltage operation, which enhances both reliability and energy density performance
3Stability of the object's composition
If uniform aluminum coating is applied to all particles to maximize stability, then structural stability is improved, but manufacturing complexity increases due to different coating methods for different particle sizes
Solution Approach 1:
Different aluminum coating methods are applied to different particle size ranges: wet coating for smaller particles (D50 ≤ 10 μm) and dry coating for larger particles (D50 > 10 μm). This local quality approach optimizes coating effectiveness for each particle size while managing manufacturing complexity through standardized procedures for each category
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 provides high stability at high voltage, low resistance, and improved cycle-life characteristics, enhancing the battery's capacity and energy density while suppressing side reactions.
Implementation Method 1
a first positive electrode active material including a first lithium cobalt-based oxide doped with aluminium and magnesium
Implementation Method 2
the first positive electrode active material and the second positive electrode active material each include aluminium coating layers on particle surfaces
Implementation Method 3
removing an aqueous solvent from the mixed solution, drying the obtained product, and performing a heat treatment to obtain a first positive electrode active material including an aluminium coating layer
Implementation Method 4
adding aluminium sulfate to an aqueous solvent and mixing to prepare a coating solution; adding a first positive electrode active material into the coating solution and mixing to prepare a mixed solution
Implementation Method 5
removing an aqueous solvent from the mixed solution, drying the obtained product
Data Source
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AI summary
A positive electrode active material includes a first positive electrode active material including a first lithium cobalt-based oxide doped with aluminium and magnesium, and a second positive electrode active material including a second lithium cobalt-based oxide doped with aluminium and magnesium. An average particle diameter (D50) of the second positive electrode active material is less than an average particle diameter (D50) of the first positive electrode active material. The first positive electrode active material and the second positive electrode active material each include an aluminium coating layer on particle surfaces, with the aluminium coating layer of the first positive electrode active material being in a form of a shell that continuously surrounds the particle surfaces. An aluminium content based on 100 at% of cobalt and aluminium as measured by energy profiling energy dispersive spectroscopy (EP-EDS) on the surface of the first positive electrode active material is about 6 at% to about 10 at%.