Lithium Battery Positive Electrode Surface Coating for Cycle Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining high capacity and cycle characteristics when using metal-based negative electrode materials, which lead to irreversible capacity and electrolyte solution dissolution issues, especially during repeated charging and discharging.
Innovation Solution
A positive electrode active material is developed with element M2 incorporated in the crystal structure of a complex oxide, specifically in the surface layer area, using a formula like Li1+a(MnbCocNi1−b−c)1−aM1dO2−e, where M2 differs from M1 and is selected from magnesium, calcium, titanium, and others, to enhance structural stability and prevent electrolyte interaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If metal-based negative electrode materials are used to achieve high capacity, then battery capacity is improved, but irreversible capacity occurs and electrolyte solution dissolution happens during repeated charging and discharging
Solution Approach 1:
A coating layer comprising at least one element selected from the group consisting of B, Si, P, S, and Ge is formed on the surface of the positive electrode active material. This coating layer acts as an intermediary between the positive electrode active material and the electrolyte solution, preventing direct harmful interactions while allowing lithium ion transport, thereby suppressing electrolyte solution dissolution and improving cycle characteristics without sacrificing battery capacity.
Solution Approach 2:
The invention changes the surface composition parameter of the positive electrode active material by introducing a coating layer with specific elements (B, Si, P, S, or Ge). This parameter change modifies the surface properties to enhance stability during charging-discharging cycles, reducing irreversible capacity and preventing electrolyte solution dissolution while maintaining high capacity performance.
2Duration of action of stationary object
If a coating of metal oxide is formed on the surface of positive electrode active material to improve charge-discharge cycle characteristics, then cycle life is improved, but capacity characteristics may be reduced
Solution Approach 1:
The invention changes the coating composition parameter from conventional metal oxides to a specific group of elements (B, Si, P, S, Ge), which have different chemical properties. These elements form coatings that are more effective at preventing electrolyte solution dissolution while maintaining better lithium ion conductivity, thus improving cycle life without significantly reducing capacity characteristics.
Solution Approach 2:
The coating layer is formed as a composite structure on the surface of the positive electrode active material. This composite material approach combines the positive electrode active material with a coating layer comprising specific elements (B, Si, P, S, or Ge), creating a synergistic structure that simultaneously improves cycle characteristics and maintains capacity characteristics by optimizing both protection and ion transport functions.
Data Source
AI summary
A lithium secondary battery includes a positive electrode, a negative electrode, and an electrolyte solution. The positive electrode contains a positive electrode active material including element M2 incorporated in a crystal structure in a surface layer area of a complex oxide, the oxide including the element M1 and being represented by the following formula (1), M2 being different from M1. The element M2 is at least one kind selected from the group consisting of magnesium Mg, calcium Ca, titanium Ti, zirconium Zr, sulfur S, fluorine F, iron Fe, copper Cu, boron B, aluminum Al, phosphorus P, carbon C, manganese Mn, nickel Ni, and cobalt Co.Li1+a(MnbCocNi1−b−c)1−aM1dO2−e (1)M1 is at least one kind of aluminum, magnesium, zirconium, titanium, barium Ba, boron, silicon Si, and iron, a satisfies 0<a<0.25, b satisfies 0.5≦b<0.7, c satisfies 0≦c<1−b, d satisfies 0.01≦d≦0.2, and e satisfies 0≦e≦1.