Separator Coating Chemistry for High-Voltage Cathode Stability
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Solution Overview
Problem
High-energy density secondary batteries suffer from high-temperature performance deterioration, leading to safety issues and reduced stability.
Innovation Solution
A separator with a base film coated with an organic cyanide containing a functional group, such as cyano, isocyano, or melamine derivative, is used to stabilize positive electrode structures, reducing active oxygen release and preventing structural phase transitions during high-voltage charging and discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high-energy density secondary batteries are used to meet increasing energy demands, then energy density is improved, but high-temperature performance deteriorates and safety issues arise
Solution Approach 1:
An organic cyanide coating layer is introduced as an intermediary between the positive electrode material and the electrolyte. This coating layer mediates the interaction by stabilizing the surface structure of the positive electrode material, preventing direct harmful reactions while allowing ionic transport, thus resolving the contradiction between high energy density and high-temperature stability
Solution Approach 2:
The patent modifies the chemical composition and surface properties of the positive electrode material by coating it with organic cyanide compounds. This changes the surface chemistry parameters, creating a stable interface that maintains performance at high temperatures while preserving the high-capacity characteristics of the underlying material
2Use of energy by moving object
If charging voltage is increased to improve energy density, then capacity is improved, but structural phase transition occurs and safety performance declines
Solution Approach 1:
The organic cyanide coating is applied in advance to the positive electrode material surface before battery assembly and operation. This preliminary action pre-stabilizes the crystal structure and surface morphology, creating a protective layer that prevents structural degradation when high charging voltages are subsequently applied
Solution Approach 2:
The coating layer acts as a mediator that buffers the mechanical and chemical stresses induced by high charging voltages. It maintains the integrity of the positive electrode structure during voltage cycling, preventing phase transitions while allowing the battery to operate at higher voltages for improved energy density
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 separator improves thermal safety and high-temperature cycle performance by stabilizing positive electrode structures, enhancing the battery's stability and safety under high-temperature conditions.
Implementation Method 1
The organic cyanide diffuses and comes into contact with the surface of a positive electrode material, which can stabilize metal atoms and positive electrode crystal structures, reduce release of active oxygen, and restrain structural phase transition
Implementation Method 2
The organic cyanide diffuses and comes into contact with the surface of a positive electrode material
Data Source
AI summary
A separator includes a base film and a first coating disposed on a surface of the base film to face one side of a positive electrode. The first coating includes an organic cyanide with a first functional group. The first functional group includes at least one of a cyano group, an isocyano group, an isocyanate group, or a melamine compound. The first functional group of the first coating has a molar concentration of M fmol/μm3, where 0.1≤M≤30. The secondary battery provided by this application has a high energy density and also has good thermal safety, high-temperature cycle performance and high-temperature storage performance.