Al-Doped LiCoO2 Cathode Blend for High-Voltage Cycle Stability
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Solution Overview
Problem
Lithium cobalt oxide-based positive electrode active materials in rechargeable lithium batteries suffer from capacity reduction due to phase transition and irreversible reactions at high voltages, leading to instability and reduced cycle-life characteristics.
Innovation Solution
A positive electrode active material comprising a mixture of two lithium cobalt-based oxides doped with aluminium, where the first oxide has a larger particle size and higher aluminium content than the second, enhancing structural stability and capacity while maintaining low resistance.
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 parameter changes by doping lithium cobalt oxide with aluminium at specific concentrations (0.01 to 0.1 mole ratio of Al to total transition metals) to modify the crystal structure and electronic properties, thereby improving structural stability while maintaining high capacity at voltages above 4.3V
Solution Approach 2:
The patent creates a composite material system by combining lithium cobalt oxide with aluminium dopant, forming a modified cathode material that exhibits both high capacity and enhanced structural stability through the synergistic effect of the base material and dopant
2Use of energy by moving object
If charging and discharging at high voltages is performed to achieve high energy density, then energy density is improved, but reliability deteriorates due to irreversible phase transition and side reactions with electrolyte
Solution Approach 1:
The patent changes the electrochemical parameters by enabling operation at high voltages (4.3V to 4.6V) through aluminium doping, which shifts the phase transition behavior and reduces irreversible reactions, thereby achieving high energy density with improved reliability and cycle-life characteristics
Solution Approach 2:
The patent applies preliminary anti-action by pre-doping the lithium cobalt oxide with aluminium before battery operation, which proactively prevents irreversible phase transitions and side reactions with electrolyte that would otherwise occur during high-voltage charging and discharging cycles
3Stability of the object's composition
If aluminium doping is increased to improve structural stability at high voltage, then structural stability is improved, but manufacturing precision deteriorates due to difficulty in controlling doping amount and particle size distribution
Solution Approach 1:
The patent establishes specific parameter ranges for aluminium doping (0.01 to 0.1 mole ratio) and particle size (5 to 20 micrometers) that optimize both structural stability and manufacturability, making it easier to control doping amount and achieve consistent performance across production batches
Data Source
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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 aluminium and a second positive electrode active material including a second lithium cobalt-based oxide doped with aluminium. 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 aluminium based on 100 wt% of a total metal amount in the second positive electrode active material excluding lithium is greater than an amount of aluminium based on 100 wt% of a total metal amount in the first positive electrode active material excluding lithium.