Aluminum-Doped LiCoO2 Cathode Composition for High-Voltage Cycle Life
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Solution Overview
Problem
Lithium cobalt oxide-based positive electrode materials in rechargeable lithium batteries suffer from capacity reduction due to phase transition and irreversible reactions at high voltages, limiting their structural stability and cycle-life characteristics.
Innovation Solution
A positive electrode active material comprising a mixture of two lithium cobalt-based oxides doped with aluminum, where larger particles have a higher aluminum content and smaller particles have a lower aluminum content, enhancing structural stability and cycle-life characteristics while maintaining high capacity and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium cobalt oxide is used as positive electrode active material to achieve high theoretical capacity (274 mAh/g), then capacity is improved, but structural stability deteriorates due to phase transition at high voltages
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core region contains lithium cobalt oxide with high capacity characteristics, while the outer shell region contains lithium cobalt oxide doped with aluminum for enhanced structural stability. This spatial differentiation of material properties allows the electrode to simultaneously achieve high capacity from the core and structural stability from the shell during high-voltage charging and discharging cycles.
Solution Approach 2:
The patent employs composite materials by combining two distinct lithium cobalt oxide phases with different aluminum doping levels to form a composite electrode structure. The composite consists of a first lithium cobalt oxide component (core) with lower aluminum content for high capacity, and a second lithium cobalt oxide component (shell) with higher aluminum content for structural stability, thereby resolving the contradiction between capacity and stability.
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 cycle-life characteristics deteriorate due to irreversible phase transition and side reactions with electrolyte
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core region contains lithium cobalt oxide with high capacity characteristics, while the outer shell region contains lithium cobalt oxide doped with aluminum for enhanced structural stability. This spatial differentiation of material properties allows the electrode to simultaneously achieve high capacity from the core and structural stability from the shell during high-voltage charging and discharging cycles.
Solution Approach 2:
The patent applies preliminary action by pre-doping the lithium cobalt oxide with aluminum at specific concentrations before electrode fabrication. This pre-modification of the material structure creates a more stable crystal lattice that resists irreversible phase transitions during subsequent high-voltage cycling, thereby improving cycle-life characteristics before the degradation can occur.
3Stability of the object's composition
If aluminum doping amount is increased to improve structural stability, then structural stability is improved, but capacity is reduced due to substitution of lithium sites
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core region contains lithium cobalt oxide with high capacity characteristics, while the outer shell region contains lithium cobalt oxide doped with aluminum for enhanced structural stability. This spatial differentiation of material properties allows the electrode to simultaneously achieve high capacity from the core and structural stability from the shell during high-voltage charging and discharging cycles.
Solution Approach 2:
The patent applies parameter changes by precisely controlling the aluminum doping concentration as a gradient parameter - lower aluminum content in the core region to maintain capacity, and higher aluminum content in the shell region to enhance stability. This parametric variation across different spatial zones optimizes both capacity and structural stability simultaneously.
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 electrode material achieves high stability at high voltages with low resistance and improved cycle-life characteristics, supporting high capacity and energy density in rechargeable lithium batteries.
Implementation Method 1
a first positive electrode active material comprising a first lithium cobalt-based oxide doped with aluminum; and a second positive electrode active material comprising a second lithium cobalt-based oxide doped with aluminum
Implementation Method 2
only half of the capacity can be used due to the problem of capacity reduction caused by phase transition
Data Source
AI summary
Disclosed are a positive electrode active material for a rechargeable lithium battery, and a positive electrode including the positive electrode active material, a method of manufacturing positive electrode, and a rechargeable lithium battery. The first positive electrode active material includes a first lithium cobalt-based oxide doped with aluminum and a second positive electrode active material including a second lithium cobalt-based oxide doped with aluminum. An average particle diameter (D50) of the first positive electrode active material is greater than an average particle diameter (D50) of the second positive electrode active material. An amount of aluminum based on 100 wt % of a total metal amount in the second positive electrode active material excluding lithium is greater than an amount of aluminum based on 100 wt % of a total metal amount in the first positive electrode active material excluding lithium.