LiCoO2 Cathode Doping for High-Voltage Cycle Stability
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Solution Overview
Problem
Lithium cobalt oxide-based positive electrode materials for rechargeable lithium batteries face challenges in maintaining structural stability and cycle life at high voltages due to instability and side reactions with electrolytes, leading to capacity degradation and potential combustion or swelling phenomena.
Innovation Solution
The method involves doping lithium cobalt oxide particles with Mg and Zr, where Zr is primarily included in the outer bulk and Mg in the inner bulk, forming a lithium trap or lithium dumbbell structure that stabilizes the crystalline structure by allowing dopant and lithium ion movement between octahedral and tetrahedral sites, suppressing structural changes and enhancing capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiCoO2 is used as positive electrode material, then high compression density and electrochemical characteristics are achieved, but charge and discharge current amount is low and cycle-life characteristic deteriorates at voltage greater than or equal to 4.3 V
Solution Approach 1:
The patent applies different doping elements (Mg, Zr, Nb, Ta, Mo, W, V) at specific concentrations (0.01-0.1 mol ratio of M/LiCoO2) to create local compositional variations that optimize both structural stability and electrochemical performance at different regions of the material
Solution Approach 2:
The patent modifies the chemical composition parameters of LiCoO2 by introducing dopant elements M, changing the stoichiometric ratios and oxidation states to achieve stable operation at high voltages (4.3-4.8V) while maintaining high capacity
2Quantity of substance
If high voltage is applied to develop high-capacity secondary battery, then capacity is increased, but surface and structure destabilize to generate gas due to side-reaction with electrolyte solution
Solution Approach 1:
The patent converts the harmful effect of high voltage-induced instability into a beneficial outcome by using controlled doping with elements M, which stabilizes the structure through modified electronic configuration and reduced Co3+ to Co4+ oxidation, thereby preventing harmful side reactions while maintaining high capacity
3Stability of the object's composition
If metal such as Al, Ti, Mg, or Zr is doped or coated on surface of LiCoO2, then structural stability is improved, but phase change may be generated or Li ion transfer is interrupted
Solution Approach 1:
The patent optimizes the dopant concentration parameter to a specific range (0.01-0.1 mol ratio of M/LiCoO2) to achieve structural stability without excessive doping that would cause phase changes or Li ion transfer interruption
Solution Approach 2:
The patent uses selective doping with specific elements (Mg, Zr, Nb, Ta, Mo, W, V) that provide structural stabilization through their electronic and ionic properties while minimizing adverse effects on Li ion conductivity
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
This approach achieves capacity retention of greater than 90% after 30 cycles at 45°C under 4.5 V, effectively preventing structural collapse and maintaining high voltage stability by suppressing side reactions and structural changes.
Implementation Method 1
the dopant and/or lithium ions move from octahedral sites to tetrahedral sites at the time of charge, thereby forming a lithium trap and/or a lithium dumbbell structure
Implementation Method 2
doping or coating a metal such as Al, Ti, Mg, or Zr on a surface of the LiCoO2
Implementation Method 3
in the case of a coating layer including the metal, it may interrupt Li ion transfer during the charge and discharge
Data Source
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AI summary
The present invention provides a positive active material for a rechargeable lithium battery, the active material including a dopant and having a crystalline structure in which metal oxide layers (MO layers) including metals and oxygen and reversible lithium layers are repeatedly stacked, wherein in a lattice configured by oxygen atoms of the MO layers adjacent to each other, the dopant time of charge, thereby forming a lithium trap and/or lithium dumbbell structure.