Fluoride-Coated Ni-Rich NCM Cathodes for Thin CEI Layers
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Solution Overview
Problem
Existing technologies do not effectively modify the surface of highly nickel-based NCM-type composite oxides or disclose the specific configuration of the coating portion formed on the surface of these composite oxides, leading to limitations in improving the characteristics of lithium-ion secondary batteries.
Innovation Solution
Forming a fluoride layer on the surface or near the surface of a highly nickel-based NCM-type composite oxide to create a thinner solid electrolyte interface layer, which suppresses high resistance to lithium-ion transport and electron conduction, thereby enhancing the battery's capacity, cycle characteristics, and discharge characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating layer of water-repellent material is provided on the surface of electrode active material to suppress metal element elution, then battery deterioration is suppressed, but the capacity and cycle characteristics are not sufficiently improved
Solution Approach 1:
The invention changes the chemical composition parameter of the coating layer from conventional water-repellent materials to fluoride-containing coating material. This parameter change enables the coating to simultaneously suppress metal element elution and reduce resistance to lithium-ion transport, resolving the contradiction between reliability and productivity by achieving both battery deterioration suppression and improved capacity/cycle characteristics.
Solution Approach 2:
The invention uses a composite coating material containing fluoride and water-repellent components. This composite structure combines the benefits of fluoride (suppressing metal elution and reducing resistance) with water-repellent properties, enabling simultaneous achievement of durability and performance improvement that neither material alone could provide.
2Productivity
If the solid electrolyte interface layer is made thinner to reduce resistance to lithium-ion transport, then capacity and discharge characteristics are improved, but surface stabilization is compromised
Solution Approach 1:
The invention changes the chemical composition parameter of the coating material to include fluoride, which enables the formation of a thin CEI layer with low resistance to lithium-ion transport. This parameter change allows the coating to provide surface stabilization while simultaneously achieving high capacity and discharge characteristics, resolving the contradiction between productivity and reliability.
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 fluoride layer significantly improves the capacity, cycle characteristics, and discharge characteristics of lithium-ion secondary batteries while maintaining a low cost, by reducing the thickness of the solid electrolyte interface layer and stabilizing the surface of the active material.
Implementation Method 1
forming a fluoride of a highly nickel-based NCM-type composite oxide on the surface or near the surface of a positive-electrode active material for a lithium-ion secondary battery formed of the composite oxide makes it possible to make a solid electrolyte interface layer (also referred to below as a CEI layer) formed during charge/discharge cycles thinner
Data Source
AI summary
Provided is a positive-electrode active material for a lithium-ion secondary battery able to achieve an even higher capacity, improved cycle characteristics and discharge characteristics, and a low cost.The positive-electrode active material 11 for a lithium-ion secondary battery has a fluoride layer 11b which coats at least part of a core particle 11a and is formed of fluoride of the lithium metal composite oxide. The lithium metal composite oxide of the core particle 11a is represented by LiNikColMnmO2 (k+1+m=1, k≥0.6). In addition, the fluoride of the lithium metal composite oxide of the fluoride layer 11b is represented by Li1-zNikColMnmO2-xFx (k+1+m=1, k≥0.6, z≤0.62, 0<x≤1).