Lithium-Rich Manganese Cathode Surface Modification
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Solution Overview
Problem
Lithium-rich manganese-based positive electrode materials for lithium-ion batteries face challenges with low initial coulombic efficiency, poor rate performance, and cycle performance, limiting their large-scale application.
Innovation Solution
A lithium-rich manganese-based positive electrode material is developed with a specific composition and preparation method involving a lithium-removal reaction using a lithium remover, which creates lithium and oxygen vacancies without damaging the surface structure, enhancing initial coulombic efficiency, rate performance, and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If surface coating methods are used to improve initial coulombic efficiency, then initial efficiency is improved, but discharge capacity decreases
Solution Approach 1:
The patent removes Li2O from the surface of lithium-rich manganese-based positive electrode material through acid treatment, extracting the harmful component that causes low initial efficiency while preserving the bulk material's high discharge capacity. This extraction approach improves initial coulombic efficiency without sacrificing the material's inherent capacity.
Solution Approach 2:
The patent applies local modification only to the surface layer of the material through controlled acid treatment, creating lithium vacancies and oxygen vacancies specifically at the surface where they are most needed for improving initial efficiency, while leaving the bulk material structure intact to maintain high discharge capacity.
2Reliability
If strong acid treatment is used to improve initial efficiency, then initial efficiency is improved, but surface structure is damaged and cycle performance decreases
Solution Approach 1:
The patent optimizes the acid treatment parameters including acid concentration (0.1-2.0 M), treatment time (0.5-48 hours), and temperature (20-100°C) to achieve the desired surface modification without excessive damage. By carefully controlling these parameters, the patent creates beneficial lithium and oxygen vacancies while avoiding severe surface structure degradation.
Solution Approach 2:
The patent applies a controlled amount of acid treatment that is sufficient to create the necessary lithium and oxygen vacancies for improving initial efficiency, but not excessive enough to cause severe surface structure damage. The treatment is optimized to achieve just the right level of modification.
3Quantity of substance
If conventional positive electrode materials are used, then cost and safety are acceptable, but specific capacity is limited to less than 150 mAh/g
Solution Approach 1:
The patent uses acid treatment as an intermediary process that bridges the gap between conventional materials and high-capacity lithium-rich manganese-based materials. This simple chemical treatment enables the material to achieve high specific capacity (>300 mAh/g) while maintaining manufacturing simplicity and cost-effectiveness, avoiding the need for complex alternative materials.
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 material achieves an initial efficiency greater than 93% and a specific discharge capacity of 260 mAh/g at 1 C, with no significant decline in cycle performance after 100 cycles, demonstrating improved performance characteristics.
Implementation Method 1
mixing a lithium-rich manganese-based compound represented by formula (II) with a lithium remover, and carrying out a lithium-removal reaction to obtain the lithium-rich manganese-based positive electrode material represented by formula (I)
Data Source
AI summary
A lithium-rich manganese-based positive electrode material represented by formula (I). In an X-ray diffraction pattern of the lithium-rich manganese-based positive electrode material, a ratio of a diffraction peak intensity of a Bragg angle near 18.7° to a diffraction peak intensity of a Bragg angle near 44.6° is 1.10 to 1.24. A method for preparing the lithium-rich manganese-based positive electrode material comprises: mixing a lithium-rich manganese-based compound with a lithium remover; and under the effect of the lithium remover, removing part of Li2O from Li2MnO3 in the lithium-rich manganese-based compound, so as to obtain the lithium-rich manganese-based positive electrode material. Due to the reduction of the irreversible product Li2O, the initial coulombic efficiency is improved; because of existence of lithium vacancy and oxygen vacancy, the lithium-rich manganese-based positive electrode material has good rate performance and cycle performance.(x−y)Li2MnO3yMnO2 (1−x)Li(MaM′b)O2 (I)