Dual-Layer Coated Li-Mn-Ni Cathode for Stability
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Solution Overview
Problem
The existing cathode materials for Li-ion batteries, particularly spinel type lithium-manganese-nickel-containing composite oxides, face challenges such as unstable surface structures, manganese dissolution during cycling, and poor rate and cycle performance, which limit their large-scale application in electric vehicles.
Innovation Solution
A cathode material with a complex coating layer composed of Li7La3Zr2O12 and LiNbO3 is applied, where the first coating layer is formed through solid phase methods and the second layer via hydro-thermal reactions, enhancing electronic and lithium ion conductivity, thereby improving cycle stability and rate performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If spinel type lithium-manganese-nickel-containing composite oxide is used as cathode material, then high working voltage and low cost are achieved, but surface structure instability and manganese dissolution occur during cycling
Solution Approach 1:
The patent applies composite materials by coating the spinel cathode material surface with a dual-layer structure consisting of Li7La3Zr2O12 (LLZO) and LiNbO3. This composite coating combines the high ionic conductivity of LLZO with the structural stability and manganese dissolution resistance of LiNbO3, thereby maintaining high working voltage while improving surface structure stability and preventing manganese dissolution during cycling.
Solution Approach 2:
The patent applies local quality by creating a heterogeneous coating structure where different materials are positioned at different locations on the cathode surface. The LLZO layer provides ionic conductivity pathways, while the LiNbO3 layer specifically addresses surface instability and manganese dissolution at the electrode-electrolyte interface. This localized functional distribution resolves the contradiction between maintaining high voltage performance and improving structural stability.
2Ease of manufacture
If conventional coating materials (metal oxides or phosphates) are used, then manufacturing simplicity is maintained, but low electronic conductivity and lithium ion conductivity coefficient limit performance improvement
Solution Approach 1:
The patent applies parameter changes by selecting coating materials with fundamentally different conductivity characteristics from conventional options. Li7La3Zr2O12 exhibits ultra-high lithium ion conductivity (10^-3 to 10^-4 S/cm at room temperature), while LiNbO3 provides complementary electronic conductivity and structural stability. These parameter changes in material selection, combined with optimized coating thickness and composition ratios, resolve the contradiction between manufacturing simplicity and conductivity performance.
3Device complexity
If single-layer coating is applied, then manufacturing complexity is reduced, but insufficient protection against manganese dissolution and electrolyte decomposition occurs
Solution Approach 1:
The patent applies segmentation by dividing the protective coating into two distinct functional layers: an inner Li7La3Zr2O12 layer that provides high ionic conductivity and an outer LiNbO3 layer that specifically prevents manganese dissolution and electrolyte decomposition. This segmented structure allows each layer to optimize its specific function, achieving superior protection performance while maintaining reasonable manufacturing complexity through a systematic two-step coating process.
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 complex coating layer significantly enhances the cycle stability and rate performance of the cathode material, reducing manganese dissolution and electrolyte decomposition, making it suitable for large-scale industrial production with low manufacturing costs.
Implementation Method 1
A surface of spinel type lithium-manganese-nickel-containing composite oxide is coated with a first coating layer containing Li7La3Zr2O12 in a solid phase method
Implementation Method 2
A surface of the spinel type lithium-manganese-nickel-containing composite oxide coated with Li7La3Zr2O12 is further coated with a second coating layer containing LiNbO3 in a hydro-thermal method
Data Source
AI summary
The present invention relates to the field of the Li-ion battery and, particularly, relates to a cathode material for the Li-ion battery, a method for preparing the same and a Li-ion battery containing the same. A surface of the cathode material of spinel type lithium-manganese-nickel-containing composite oxide of the present invention is coated with a complex coating layer composed of a first coating layer containing Li7La3Zr2O12 and a second coating layer containing LiNbO3. The method includes: firstly coating the first coating layer containing Li7La3Zr2O12 on the surface of spinel type lithium-manganese-nickel-containing composite oxide in a solid phase method; and then coating the second coating layer containing LiNbO3 in a hydro-thermal method. The cathode material of the present invention improves cycle stability and rate performance of spinel type lithium-manganese-nickel-containing composite oxide, and meanwhile reduces dissolution and erosion effect of the electrolyte on the cathode material during charging or discharging.