High-Nickel Core-Shell Cathode Precursor for Capacity and Cycle Life
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Solution Overview
Problem
Current high-nickel ternary layered oxide materials for lithium batteries face challenges with stability and cycle performance, limiting their application due to high Ni content, and the conventional co-precipitation method for core-shell precursors is cumbersome and costly.
Innovation Solution
A high-nickel ternary core-shell precursor with a chemical formula zNi(C4H7N2O2)–Nix-yM1yM21-x-y(OH)2 is prepared using a method involving metal salt solutions, dimethylglyoxime-ammonia water, and sodium hydroxide, allowing for a core-shell structure formation without altering the ternary solution ratio, simplifying the process and reducing equipment needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-nickel ternary layered oxide material is used to increase capacity, then specific capacity increases, but stability and cycle performance deteriorate
Solution Approach 1:
The precursor is segmented into core and shell regions with different nickel contents. The core region contains high nickel content (x≥0.6) for high capacity, while the shell region contains lower nickel content (x<0.6) for high stability. This spatial segmentation allows simultaneous achievement of high specific capacity and excellent cycle performance.
Solution Approach 2:
Different regions of the precursor are assigned different chemical compositions and properties. The core region has high nickel content providing high capacity, while the shell region has lower nickel content providing stability. This local differentiation of quality enables the material to simultaneously achieve high capacity and good cycle performance.
2Shape
If conventional co-precipitation method is used to prepare core-shell precursor, then core-shell structure can be formed, but process complexity and equipment costs increase
Solution Approach 1:
The patent merges the core formation and shell formation steps into a single co-precipitation process. By adding dimethylglyoxime-ammonia water to the metal salt solution, both core and shell regions form simultaneously in one reactor, eliminating the need for separate synthesis steps and reducing equipment complexity.
Solution Approach 2:
Dimethylglyoxime-ammonia water acts as an intermediary reagent that selectively reacts with nickel ions to form the core region, while the remaining metal ions form the shell region. This intermediary enables automatic phase separation and core-shell structure formation during a single co-precipitation 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 method achieves high capacity retention and excellent cycle performance for the positive electrode material, maintaining high capacity and stability while simplifying operations and reducing equipment costs.
Implementation Method 1
pumping the metal salt solution, the dimethylglyoxime-ammonia water composite solution, and the ammonia-water solution which are prepared in step (1) into the reaction kettle, maintaining pH of a reaction system at a range from 8.0 to 10.0, and reacting for 4 h to 20 h to obtain a sphere-like precursor core with a structural formula of Ni(C4H7N2O2)2
Data Source
AI summary
A high-nickel ternary core-shell precursor for a lithium battery, a positive electrode material and a preparation method therefor. The chemical structural formula of the precursor is zNi(C4H7N2O2)2—Nix-zM1yM21-x-y(OH)2, wherein M1 and M2 are two of cobalt, aluminum, and manganese. The preparation method comprises: pumping a prepared metal salt solution, a dimethylglyoxime-ammonia water composite solution, and an ammonia water solution into a reaction kettle, maintaining the pH of a reaction system, and controlling the reaction time to obtain a sphere-like precursor inner core with a structural formula of Ni(C4H7N2O2)2; pumping the metal salt solution and the ammonia water solution, stopping pumping the dimethylglyoxime-ammonia water composite solution, pumping a sodium hydroxide solution to obtain a sphere-like core-shell precursor, washing, drying, sieving and deironing the precursor, mixing with a lithium source, and calcining to prepare the positive electrode material. The material can keep high capacity and also has excellent cycle performance.