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, leading to instability and reduced cycle-life characteristics.
Innovation Solution
A positive electrode active material is developed by doping lithium cobalt-based oxides with aluminum and magnesium, and applying an aluminum coating layer to stabilize the structure, with varying particle sizes and concentrations to enhance stability and capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium cobalt oxide is used as positive electrode material to achieve high theoretical capacity (274 mAh/g), then capacity is improved, but phase transition occurs at high voltages causing capacity reduction and stability deterioration
Solution Approach 1:
The patent applies composite materials by combining lithium cobalt oxide with aluminum and magnesium doping elements, creating a multi-component composite structure. The aluminum and magnesium atoms are incorporated into the lithium cobalt oxide lattice, forming a composite material that maintains the high capacity of lithium cobalt oxide while adding structural stability through the dopant elements, thereby resolving the contradiction between capacity and stability
Solution Approach 2:
The patent changes the chemical composition parameters of the positive electrode material by introducing aluminum and magnesium doping. This parameter change modifies the crystal structure and electronic properties of lithium cobalt oxide, enabling it to maintain structural integrity at high voltages while preserving high capacity, thus resolving the stability-capacity contradiction
2Use of energy by moving object
If high voltage charging and discharging is performed to achieve high energy density, then energy density is improved, but irreversible phase transition and side reactions with electrolyte occur
Solution Approach 1:
The patent applies preliminary action by pre-doping aluminum and magnesium into the lithium cobalt oxide structure before battery operation. This preliminary modification of the material structure prevents irreversible phase transitions and reduces side reactions with the electrolyte during subsequent high-voltage charging and discharging cycles, thereby maintaining both high energy density and long cycle-life
Solution Approach 2:
The aluminum and magnesium doping elements act as a protective cushioning mechanism that preemptively stabilizes the crystal structure against high-voltage stress. This beforehand cushioning prevents the harmful effects of irreversible phase transitions and electrolyte decomposition, allowing the battery to operate at high voltages for improved energy density without sacrificing cycle-life
3Reliability
If aluminum coating layer is applied to stabilize structure at high voltage, then stability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the doping and coating processes by incorporating aluminum and magnesium simultaneously during the synthesis of lithium cobalt oxide. This merging of functions eliminates the need for separate doping and coating manufacturing steps, reducing manufacturing complexity while achieving both structural stabilization and surface protection in a single integrated process
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, resulting in high-capacity and high-energy-density rechargeable lithium batteries.
Implementation Method 1
a first positive electrode active material including a first lithium cobalt-based oxide doped with aluminum and magnesium
Implementation Method 2
the first positive electrode active material and the second positive electrode active material each include aluminum coating layers on particle surfaces
Implementation Method 3
performing a heat treatment to obtain a first positive electrode active material including an aluminum coating layer
Data Source
AI summary
A positive electrode active material includes a first positive electrode active material including a first lithium cobalt-based oxide doped with aluminum and magnesium, and a second positive electrode active material including a second lithium cobalt-based oxide doped with aluminum 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 aluminum coating layer on particle surfaces, with the aluminum coating layer of the first positive electrode active material being in a form of a shell that continuously surrounds the particle surfaces. An aluminum content based on 100 at % of cobalt and aluminum 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 %.