Integrated Separator-Anode Structure for Polysulfide Shuttle Control
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Solution Overview
Problem
Conventional lithium-sulfur batteries face challenges such as the 'shuttle effect' caused by dissolved polysulfides and lithium dendrite formation, which affect capacity, stability, and coulombic efficiency.
Innovation Solution
An integrated separator-anode structure is developed using a bacterial cellulose membrane coated with an aqueous anode layer formed by cross-linking a sulfur-carbon nanotube composite, alginate, and calcium ions, enhancing mechanical strength and reducing polysulfide shuttle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional separator is used in lithium-sulfur batteries, then the battery structure is simple, but the shuttle effect caused by dissolved polysulfides reduces capacity and efficiency
Solution Approach 1:
The patent merges the separator and anode into a single integrated component. The bacterial cellulose membrane serves as both the separator that prevents polysulfide shuttle and the anode that enables lithium deposition, eliminating the need for separate components while solving both the shuttle effect and dendrite formation problems
Solution Approach 2:
The bacterial cellulose membrane performs multiple functions simultaneously: it acts as a physical barrier to prevent polysulfide diffusion, provides a substrate for uniform lithium deposition, and maintains structural integrity during cycling. This multi-functionality resolves the contradiction by making the separator itself capable of anode functions
2Use of energy by moving object
If lithium metal is used as anode, then the theoretical energy density is high, but lithium dendrite formation reduces stability and safety
Solution Approach 1:
The bacterial cellulose membrane provides locally optimized properties for lithium deposition. Its nanofiber structure and hydroxyl groups create specific local environments that guide uniform lithium ion distribution, preventing dendrite formation while maintaining high energy density
Solution Approach 2:
The bacterial cellulose membrane acts as an intermediary between the electrolyte and lithium metal. It mediates the lithium deposition process by providing a controlled interface that promotes uniform growth, thereby maintaining stability and safety while preserving high energy density
3Power
If polysulfide dissolution is allowed, then the electrochemical reaction is active, but the shuttle effect reduces coulombic efficiency
Solution Approach 1:
The patent converts the harmful shuttle effect into a beneficial process by using the bacterial cellulose membrane to selectively interact with polysulfides. The membrane allows controlled polysulfide dissolution for electrochemical activity while simultaneously preventing their harmful diffusion, thereby maintaining both reaction activity and coulombic efficiency
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 integrated separator-anode structure improves lithium-sulfur battery performance by ensuring uniform lithium deposition, reducing dendrite formation, and enhancing specific capacity and coulombic efficiency.
Implementation Method 1
an aqueous anode layer formed on a surface of the bacterial cellulose membrane by cross-linking, wherein the aqueous anode layer is formed from a cross-linking reaction of a polymerized colloid, an alginate, and calcium ions
Implementation Method 2
the sulfur-carbon nanotube composite exhibits better abilities in electrolyte solution absorption and holding
Implementation Method 3
the bacterial cellulose separator could promote the uniform deposition of lithium ions on the surface of lithium metal and prevent the formation of lithium dendrites
Implementation Method 4
the bacterial cellulose separator could promote the uniform deposition of lithium ions on the surface of lithium metal
Data Source
AI summary
The present disclosure provides an integrated separator-anode, including a bacterial cellulose membrane and an aqueous anode layer formed on a surface of the bacterial cellulose membrane by cross-linking via calcium ions. The aqueous anode layer is formed from a cross-linking reaction of a polymerized colloid, an alginate, and calcium ions in a presence of a sulfur-carbon nanotube composite, and the sulfur-carbon nanotube composite, the alginate, and the polymerized colloid have a concentration ratio of 1:0.06-0.33:0.16-1. The integrated separator-anode of the present disclosure is applicable for a lithium-sulfur battery which would exhibit a high discharge specific capacity, a high coulombic efficiency and a stable cycle performance.