Li-S Battery Electrolyte Additives for Polysulfide Shuttle Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-sulfur (Li-S) batteries face challenges in cycling stability due to the formation of highly soluble lithium polysulfide intermediates, which lead to active material loss and reduced Columbic efficiency.
Innovation Solution
The use of electrolyte additives such as fluorinated borates and lithium bis(nonafluorobutanesulfonyl)imide (LiNFBSI) to modulate lithium polysulfide conversion, facilitating solid-liquid-solid conversion and preventing active material loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If lithium polysulfide intermediates are formed during electrochemical reactions, then sulfur utilization is enhanced, but active material loss increases and cycling stability deteriorates
Solution Approach 1:
The patent introduces a solid electrolyte interphase (SEI) layer as an intermediary between the lithium polysulfide intermediates and the electrodes. This SEI layer acts as a mediator that allows ionic transport while blocking the harmful dissolution and shuttling of polysulfides, thus enabling sulfur utilization while preventing active material loss and improving cycling stability
Solution Approach 2:
The patent converts the harmful effect of lithium polysulfide intermediates (which cause dissolution and shuttling) into a beneficial process by controlling their conversion through the SEI layer. The SEI layer facilitates the desired solid-liquid-solid conversion while preventing the harmful dissolution pathway, thus turning the problematic polysulfide formation into a useful electrochemical reaction
2Productivity
If lithium polysulfide intermediates shuttle between cathode and anode, then electrochemical reactions proceed, but Columbic efficiency decreases and shelf life reduces
Solution Approach 1:
The SEI layer serves as a selective intermediary that permits ionic transport necessary for electrochemical reactions while blocking the shuttling of lithium polysulfide intermediates between electrodes. This selective mediation maintains reaction productivity while improving Columbic efficiency by preventing polysulfide loss
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 additives improve the cycling stability and energy density of Li-S batteries by reducing polysulfide shuttling, enhancing sulfur utilization, and forming protective passivation layers on the electrodes.
Implementation Method 1
The additives modulate lithium polysulfide intermediate conversion and facilitate solid-liquid-solid conversion to substantially prevent active material loss
Implementation Method 2
forming protective passivation layers on the electrodes
Implementation Method 3
highly soluble lithium polysulfide intermediates
Data Source
AI summary
A lithium-sulfur battery providing stable, high energy density includes a cathode including sulfur, an anode including lithium metal, and an electrolyte including non-aqueous solvent and an additive including a fluorinated borate or a fluorinated borane; and lithium bis(nonafluorobutanesulfonyl)imide (LiNFBSI).