Coated Lithium-Rich Cathode Material for Capacity and Cycle Stability
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Solution Overview
Problem
Lithium-rich manganese-based positive electrode materials experience decreased cycling stability after washing with acid solutions, which are used to increase gram capacity, leading to performance degradation.
Innovation Solution
A two-step coating process is applied to the lithium-rich manganese-based positive electrode material, involving a primary coating before pickling with metal oxides or fluorides and a secondary coating after pickling with metal oxides or fluorides and borides, to form a positive electrode active material that meets specific microscopic indicators for improved gram capacity and cycling stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If acid solutions are used to wash the lithium-rich manganese-based positive electrode materials to increase gram capacity, then the gram capacity increases, but the cycling stability decreases
Solution Approach 1:
A coating layer comprising at least one of metal oxide and metal fluoride is introduced as an intermediary between the lithium-rich manganese-based positive electrode material and the acid washing solution. This coating layer allows the acid solution to effectively increase gram capacity while preventing direct harmful interaction between the acid and the electrode material, thereby maintaining cycling stability.
Solution Approach 2:
The coating layer is applied preliminarily before the acid washing process. By pre-coating the electrode material surface with a protective layer, the material is prepared in advance to withstand the acid washing treatment, enabling subsequent gram capacity enhancement without suffering from the stability-degrading effects of direct acid exposure.
2Reliability
If a coating layer is applied to protect cycling stability, then cycling stability improves, but gram capacity may be limited
Solution Approach 1:
The coating layer parameters (composition, thickness, material type) are optimized to achieve the right balance. By adjusting these parameters, the coating provides sufficient protection for cycling stability while maintaining adequate lithium ion transport capability to support high gram capacity 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 coated positive electrode material achieves a high gram capacity of at least 220 mAh/g with enhanced cycling stability and first-cycle efficiency, addressing the stability issues caused by acid washing.
Implementation Method 1
The positive electrode active material comprises a lithium-rich manganese-based positive electrode material and a coating layer distributed on at least a portion of the surface of the lithium-rich manganese-based positive electrode material. The coating layer comprises at least one of a metal oxide and a metal fluoride.
Implementation Method 2
in a Fourier infrared spectrum of the positive electrode active material, the M-O/Mn—O peak intensity ratio is 25-40
Implementation Method 3
in a refined result of an X-ray diffraction spectrum of the positive electrode active material, the oxygen defect indicator is greater than or equal to 2.12
Data Source
AI summary
A positive electrode active material comprises a lithium-rich manganese-based positive electrode material and a coating layer distributed on at least a portion of the surface of the lithium-rich manganese-based positive electrode material, wherein the coating layer comprises at least one of a metal oxide and a metal fluoride. The positive electrode active material has a gram capacity of greater than or equal to 220 mAh/g, and satisfies at least one of the following conditions: the oxygen defect indicator is greater than or equal to 2.12; the microscopic stress is 0.1%-1.5%; in a Fourier infrared spectrum, the M-O/Mn—O peak intensity ratio is 25-40; and the specific surface area is 0.9 m2/g-3.5 m2/g.