Surface-Doped Positive Electrode Material for High-Voltage Cycle Stability
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in maintaining charge and discharge capacity, cycle performance, reliability, safety, and cost due to progressive defects in positive electrode active materials during high-voltage and high-temperature charging and discharging.
Innovation Solution
A positive electrode active material with an additive element is formed, where the surface and inner portions are topotaxy aligned, reducing distortion in the crystal structure and inhibiting oxygen release, using lithium, cobalt, oxygen, and additives like nickel, aluminum, or magnesium to enhance stability and capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high voltage charging and discharging is performed to increase charge and discharge capacity, then the charge and discharge capacity is improved, but progressive defects are generated in the positive electrode active material leading to capacity degradation
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the surface portion contains an additive element (nickel, aluminum, or magnesium) at a concentration of 0.01-5% that is different from the inner portion. This localized modification of the surface region protects against defect generation during high-voltage charging while maintaining the overall high capacity of the bulk material. The additive element specifically addresses the surface degradation issue without compromising the bulk electrochemical performance.
Solution Approach 2:
The patent employs composite materials by combining the base positive electrode active material (such as lithium cobalt oxide) with an additive element to form a composite structure. The additive element is distributed in the surface portion to create a composite material that exhibits both high charge/discharge capacity and enhanced stability against progressive defects. This composite approach allows simultaneous optimization of capacity and reliability.
2Power
If high voltage charging is performed to increase charge and discharge capacity, then the charge and discharge capacity is improved, but the crystal structure becomes distorted and oxygen is released
Solution Approach 1:
The patent applies local quality by concentrating the additive element (nickel, aluminum, or magnesium) in the surface portion of the positive electrode active material. This localized surface modification creates a protective layer that stabilizes the crystal structure during high-voltage charging, preventing distortion and oxygen release. The bulk material maintains its high-capacity crystal structure while the surface provides structural stability.
Solution Approach 2:
The patent implements preliminary action by pre-distributing the additive element in the surface portion before the high-voltage charging process begins. This preliminary presence of the additive element prevents crystal structure distortion and oxygen release during subsequent high-voltage charging, rather than attempting to repair damage after it occurs. The additive element is positioned in advance to counteract the harmful effects of high-voltage charging.
3Power
If conventional positive electrode active materials are used to achieve high capacity, then charge and discharge capacity is improved, but cycle performance and reliability deteriorate due to progressive defects
Solution Approach 1:
The patent applies local quality by modifying only the surface portion of the positive electrode active material with an additive element, rather than uniformly modifying the entire material. This localized surface modification preserves the high-capacity properties of the bulk material while specifically addressing the cycle performance degradation issue that originates at the surface. The additive element in the surface portion prevents progressive defect formation during cycling.
Solution Approach 2:
The patent employs composite materials by creating a composite structure where the base positive electrode active material is combined with an additive element in the surface portion. This composite structure maintains the high charge/discharge capacity of the conventional material while adding the stabilizing effect of the additive element, thereby improving cycle performance and reliability without sacrificing power.
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 inhibits capacity degradation and structural breakdown, providing a highly reliable and safe lithium-ion secondary battery with improved charge and discharge performance.
Implementation Method 1
The surface portion and the inner portion are topotaxy
Implementation Method 2
by containing the additive element in the surface portion, shift of a layer structure formed of octahedrons of a transition metal M and oxygen can be inhibited and/or release of oxygen from the positive electrode active material can be inhibited
Data Source
AI summary
A positive electrode active material that is unlikely to generate defects even when charging and discharging at a high voltage and/or at a high temperature is provided. A positive electrode active material in which crystal structures are unlikely to collapse even when charging and discharging are repeated is also provided. The positive electrode active material contains lithium, cobalt, oxygen, and an additive element. The positive electrode active material includes a surface portion, an inner portion. The positive electrode active material contains the additive element in the surface portion. The surface portion is a region extending from a surface of the positive electrode active material to a depth of 10 nm or less toward the inner portion, and the surface portion and the inner portion are topotaxy. A degree of diffusion of the additive element vary between crystal planes of the surface portion, and the additive element is at least one or two or more selected from nickel, aluminum, and magnesium.