Lithium Cobalt Oxide Cathode Morphology for High-Voltage Stability
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Solution Overview
Problem
Existing lithium cobalt-based oxide cathode active materials for lithium-ion secondary batteries face challenges in achieving high volumetric energy density and structural stability at voltages above 4.5V, with conventional materials exhibiting capacity loss and instability.
Innovation Solution
A lithium cobalt-based oxide cathode active material powder with specific particle size, circularity, and aluminum distribution characteristics, including a median particle size of 20-45µm, averaged circularity of 0.85-1.00, and (018) diffraction peak asymmetry factor of 0.85-1.15, ensures uniform aluminum distribution and improved structural stability, enhancing volumetric capacity and capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the charge cutoff voltage is increased to improve volumetric energy density, then the volumetric energy density is improved, but the structural stability deteriorates
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core region contains high-voltage LCO material optimized for energy density, while the shell region contains aluminum-doped LCO material optimized for structural stability. This spatial differentiation of material properties allows the cathode to simultaneously achieve high volumetric energy density through the core material and structural stability through the protective shell material at high charge cutoff voltages.
Solution Approach 2:
The patent employs composite materials by combining two distinct LCO-based materials with different compositions and properties into a single cathode structure. The core uses LCO with specific doping elements for high capacity, while the shell uses aluminum-doped LCO for enhanced stability. This composite approach enables the system to achieve both high volumetric energy density and structural stability at voltages ≥4.5V, which neither material could achieve alone.
2Stability of the object's composition
If aluminum content is increased to improve structural stability, then the structural stability is improved, but the volumetric capacity decreases
Solution Approach 1:
The patent applies local quality by concentrating aluminum doping specifically in the shell region rather than uniformly throughout the entire cathode particles. This localized aluminum distribution provides structural stability exactly where needed (at the particle surface experiencing highest stress during cycling) while preserving the high-capacity composition in the core region, thereby maintaining high volumetric capacity.
Solution Approach 2:
The patent employs parameter changes by precisely controlling the aluminum concentration gradient from the core to the shell, with the aluminum content varying spatially within the particles. By optimizing this concentration parameter distribution and the shell thickness, the patent achieves sufficient crystal-structural stability to enable operation at high voltages while minimizing the volumetric capacity penalty associated with aluminum doping.
3Quantity of substance
If particle size is increased to improve volumetric capacity, then the volumetric capacity is improved, but the surface uniformity deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-forming particles with controlled size and morphology before the aluminum doping process. This ensures that particles of 20-45 µm with high circularity (0.85-1.00) are obtained before shell formation, maintaining surface uniformity and preventing aggregation during subsequent processing steps.
Solution Approach 2:
The patent employs parameter changes by optimizing the particle size distribution parameters (D50 between 20-45 µm) and circularity parameters (0.85-1.00) to achieve the desired balance between volumetric capacity and surface uniformity. These parameter specifications ensure that particles are large enough for high volumetric capacity but maintain sufficient surface uniformity for consistent electrochemical performance.
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 achieves a volumetric capacity of over 570mAh/cm³ and specific floating capacity below 80mAh/g, with improved structural stability and reduced capacity loss at high voltages, demonstrating enhanced performance in lithium-ion batteries.
Implementation Method 1
said diffraction peak asymmetry factor being obtained by a synchrotron XRD spectrum analysis with an emission wavelength λ value equal to 0.825Å
Data Source
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AI summary
A lithium cobalt-based oxide cathode active material powder comprising particles having a median particle size D50 of superior or equal to 20µm, preferably 25µm, and inferior or equal to 45µm, said particles having an averaged circularity of superior or equal to 0.85 and inferior or equal to 1.00, said particles having a general formula Li1+aCo1-x-y-zAlxM'yMezO2, wherein M' and Me comprise at least one element of the group consisting of: Ni, Mn, Nb, Ti, W, Zr, and Mg, with -0.01≤a≤0.01, 0.002≤x≤0.050, 0≤y≤0.020 and 0≤z≤0.050, said lithium cobalt-based oxide particles having a R-3m structure and (018) diffraction peak asymmetry factor AD(018) of superior or equal to 0.85 and inferior or equal to 1.15, said diffraction peak asymmetry factor being obtained by a synchrotron XRD spectrum analysis with an emission wavelength λ value equal to 0.825Å.