Mg-Doped Cathode Coating to Limit Li-Ion Impedance Growth
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Solution Overview
Problem
Conventional lithium ion secondary battery positive electrode materials face challenges in effectively improving cycle performance and reducing impedance increase, as existing methods either increase initial electrochemical reaction impedance or result in poor electron and ionic conduction performance.
Innovation Solution
A positive electrode composite material is developed, comprising a high-nickel positive electrode matrix material doped with Mg and featuring a fluoride layer, specifically MgF2, applied in a dotted form on the surface to enhance ionic conductivity and protect the material from electrolyte corrosion, while maintaining stable capacity and initial impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a positive electrode precursor is treated to cover one or more substances of Co2O3, B2O3, Al2O3 and Al(OH)3 on the surface of a matrix, then the surface is protected, but the initial electrochemical reaction impedance increases and high energy consumption is required
Solution Approach 1:
The invention changes the chemical composition parameters of the coating layer by incorporating fluorine-containing substances and specific metal elements (Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, W) in controlled amounts. This parameter optimization allows the coating to provide protection while maintaining lower processing temperatures and reducing initial electrochemical impedance compared to conventional coatings
Solution Approach 2:
The invention creates a composite coating layer combining fluorine-containing substances with multiple metal oxides/hydroxides/carbides/nitrides. This composite structure synergistically provides surface protection, maintains ionic conductivity, and reduces the energy required for processing while avoiding the high energy consumption associated with single-substance coatings
2Ease of manufacture
If conventional positive electrode materials are used, then manufacturing is simple, but cycle performance cannot be effectively improved and impedance increase cannot be ameliorated
Solution Approach 1:
The invention develops a composite positive electrode material consisting of a matrix (such as LiNi0.8Co0.1Mn0.1O2) combined with a fluorine-containing coating layer containing specific metal elements. This composite structure maintains manufacturing feasibility while dramatically improving cycle performance and reducing impedance increase compared to conventional uncoated or simply coated materials
Solution Approach 2:
The invention applies local quality enhancement by adding fluorine-containing substances with specific metal elements in optimized concentrations within the coating layer. This localized optimization of chemical composition improves cycle performance and impedance characteristics without requiring complete restructuring of the manufacturing 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 solution significantly improves cycle performance and reduces impedance increase in lithium ion secondary batteries without affecting capacity or initial impedance, ensuring better stability and safety by reserving more lithium ion channels and preventing electrolyte corrosion.
Implementation Method 1
the fluoride present on the surface of the positive electrode matrix material in a dotted form... preventing electrolyte corrosion
Implementation Method 2
a positive electrode matrix material doped with Mg element... the Mg element is distributed in a gradient manner within particles
Data Source
AI summary
The present invention provides a positive electrode composite material, a preparation method thereof, a positive electrode and a lithium ion secondary battery. The positive electrode composite material comprises: a positive electrode matrix material doped with Mg element; and a fluoride present on the surface of the positive electrode matrix material in a dotted form, the fluoride containing MgF2. By the positive electrode composite material, the method for preparing the positive electrode composite material, and the positive electrode and the lithium ion secondary battery which contain the positive electrode composite material in the present invention, the positive electrode matrix material in the lithium ion secondary battery can be effectively prevented from being corroded by an electrolyte, and more lithium ion channels can be reserved, thereby improving the cycle performance of the lithium ion secondary battery, and reducing the impedance increase of the lithium ion secondary battery while not affecting the capacity and initial impedance of the lithium ion secondary battery.