Fluorine-Adsorbed Cathode Material for Li-Ion Thermal Safety
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in thermal safety, particularly due to the risk of overheating and ignition, which can occur during internal short circuits, necessitating improved materials to enhance their thermal stability.
Innovation Solution
A positive electrode active material is developed containing nickel, manganese, and cobalt with fluorine adsorbed on its surface, which inhibits thermal decomposition of the electrolyte solution and improves thermal safety by maintaining a layered rock-salt crystal structure and facilitating lithium insertion and extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fluorine is contained in the positive electrode active material to improve thermal safety, then thermal stability is improved, but manufacturing complexity increases due to the need for surface treatment processes
Solution Approach 1:
Fluorine is adsorbed on the surface of the positive electrode active material before battery assembly through contact with a fluorine-containing gas or vapor in a controlled atmosphere. This preliminary surface treatment ensures thermal safety is built into the material structure before the battery is put together, avoiding the need for complex post-assembly modifications
Solution Approach 2:
The surface composition of the positive electrode active material is modified by changing the fluorine concentration on the surface while maintaining the bulk material composition. This parameter change at the surface level provides thermal protection without requiring fundamental changes to the overall manufacturing process or material synthesis
2Quantity of substance
If nickel content is increased to improve energy density, then discharge capacity is improved, but thermal stability deteriorates due to increased risk of thermal runaway
Solution Approach 1:
The positive electrode active material exhibits different compositional qualities at different locations: the bulk material contains high nickel content for high energy density and discharge capacity, while the surface layer contains fluorine adsorbed on it to provide thermal stability. This local differentiation allows the material to simultaneously achieve high energy density and thermal safety by optimizing each region for its specific function
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 fluorine-adsorbed positive electrode active material effectively reduces the risk of overheating and ignition, enhancing the thermal safety and stability of lithium-ion secondary batteries while maintaining high energy density and discharge capacity.
Implementation Method 1
fluorine is adsorbed on a surface of the positive electrode active material
Implementation Method 2
the adsorbed fluoro group can react with an electrolyte solution or the like near the fluoro group, leading to inhibition of thermal decomposition or the like of the electrolyte solution
Implementation Method 3
facilitating lithium insertion and extraction
Data Source
AI summary
One embodiment of the present invention further improves thermal safety of a lithium-ion secondary battery for stable power supply from the lithium-ion secondary battery. To improve thermal safety, fluorine is contained in a positive electrode active material or adsorbed on a surface portion of the positive electrode active material so that overheating or ignition of the lithium-ion secondary battery is inhibited. When fluorine is adsorbed on the surface of the positive electrode active material, the adsorbed fluorine can react with its vicinity electrolyte solution or the like, leading to inhibition of thermal decomposition or the like of the electrolyte solution.