MOF-Coated Battery Separator for Polysulfide Shuttle Suppression
Solution Overview
Problem
Lithium-sulfur secondary batteries face poor cycle characteristics due to the shuttle phenomenon caused by polysulfide leaching from the positive electrode, which is not effectively suppressed by conventional separator manufacturing methods, leading to non-uniform and thick coatings that increase battery resistance.
Innovation Solution
A separator for lithium secondary batteries is developed with a porous substrate and a metal organic framework (MOF) layer formed on its surface using the Langmuir-Blodgett method, which prevents polysulfide leaching by having an amorphous structure and controlled pore size, enhancing cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional coating methods are used to form MOF coating on separator, then the separator can provide some polysulfide blocking effect, but the coating becomes non-uniform and thick, increasing battery resistance
Solution Approach 1:
The patent applies preliminary action by pre-forming MOF crystals and then coating them onto the separator surface. This allows the MOF layer to be formed in a controlled manner before battery assembly, ensuring uniform distribution and appropriate thickness while maintaining effective polysulfide blocking capability.
Solution Approach 2:
The patent changes the physical and chemical parameters of the MOF coating process, specifically controlling crystal size, coating concentration, and deposition conditions. By optimizing these parameters, the patent achieves a thin, uniform coating that effectively blocks polysulfides without increasing battery resistance.
2Reliability
If conventional coating methods are used to form MOF coating on separator, then the separator can provide some polysulfide blocking effect, but the coating thickness increases, acting as resistance during battery operation
Solution Approach 1:
The patent applies partial action by forming a thin MOF coating layer that is sufficient to block polysulfides but not excessively thick to cause resistance. The coating is applied only to the extent necessary to achieve the blocking function, maintaining optimal thickness for both polysulfide suppression and ion conductivity.
Solution Approach 2:
The patent optimizes coating parameters including MOF crystal size, coating solution concentration, and deposition conditions to achieve the minimum necessary thickness for effective polysulfide blocking. This controlled parameter adjustment ensures the coating is thin enough to minimize resistance while maintaining protective function.
3Ease of manufacture
If already grown crystals are used for coating, then the coating formation is determined by crystal spacing, but it is difficult to obtain the influence of the pore size of the crystal forming the coating
Solution Approach 1:
The patent applies preliminary action by pre-synthesizing MOF crystals with controlled pore sizes before coating. This allows precise control over the pore structure of the coating layer, enabling the MOF pores to effectively block polysulfides based on their size, while maintaining a simple coating 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 MOF layer effectively suppresses polysulfide permeation, improving the cycle stability and reducing battery resistance, as demonstrated by the enhanced long-term cycle performance of lithium-sulfur secondary batteries.
Implementation Method 1
the depositing the MOF molecular film is carried out by the Langmuir-Blodgett method
Implementation Method 2
the MOF layer includes one or more MOF molecular films and has an amorphous structure
Implementation Method 3
having an amorphous structure and controlled pore size
Data Source
AI summary
A separator for a lithium secondary battery and a manufacturing method thereof are provided. The separator comprises a metal organic framework (MOF) layer formed by Langmuir-Blodgett method, and prevents shuttle phenomenon caused by polysulfide leaching from a positive electrode which includes a sulfur-containing material, and thereby improving cycle stability of a lithium secondary battery.