Lithium-Sulfur Battery Sulfur Control to Limit Shuttle Reactions
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Solution Overview
Problem
Lithium-sulfur batteries exhibit lower specific capacity than theoretical due to the dissolution of lithium polysulfide in the electrolyte solution during charging and discharging, leading to shuttle reactions and rapid degradation.
Innovation Solution
A lithium-sulfur battery design with a sulfur-carbon composite positive electrode and a specific weight ratio of sulfur in the electrolyte solution to the positive electrode (WSE/WSP ≤ 0.15) to minimize sulfur loss and enhance capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium polysulfide dissolves in the electrolyte solution during charging and discharging, then the battery can undergo electrochemical reactions, but the specific capacity decreases due to shuttle reactions and rapid degradation
Solution Approach 1:
A lithium polysulfide catalyst is introduced as an intermediary substance in the electrolyte solution. This catalyst facilitates the conversion reaction between lithium ions and sulfur at the positive electrode while preventing the dissolution of lithium polysulfide into the electrolyte. The catalyst acts as a mediator that enables the electrochemical reaction to proceed efficiently without causing shuttle reactions, thereby maintaining high specific capacity and reducing sulfur loss.
Solution Approach 2:
The invention changes the chemical composition parameter of the electrolyte solution by adding a lithium polysulfide catalyst. This parameter change transforms the electrolyte from a passive medium to an active catalytic environment that promotes the desired conversion reaction while suppressing harmful dissolution. By adjusting the chemical parameters of the electrolyte system, the battery achieves both high reactivity and low material loss.
2Use of energy by moving object
If sulfur-based compounds are present in both the positive electrode and electrolyte solution, then electrochemical reactions can occur, but the energy density decreases due to sulfur distribution in the electrolyte
Solution Approach 1:
The invention extracts the harmful function of sulfur-based compounds from the electrolyte solution while retaining their beneficial electrochemical function. By introducing a lithium polysulfide catalyst, the system enables the necessary sulfur reactions to occur at the positive electrode without requiring dissolved lithium polysulfide in the electrolyte. This extraction of the harmful dissolution aspect while preserving the useful reaction aspect leads to higher energy density.
Solution Approach 2:
The invention creates a localized catalytic environment at the positive electrode interface where lithium polysulfide catalyst concentrates the electrochemical activity. Instead of having sulfur-based compounds distributed throughout the entire electrolyte volume, the reactive sulfur species are concentrated and controlled at the electrode surface where they are needed. This local quality enhancement improves energy density by reducing unnecessary sulfur distribution in the bulk electrolyte.
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 battery achieves a specific capacity of 1,000 mAh/g or more and energy density of 300 Wh/kg or more, approaching theoretical limits by controlling sulfur distribution and reducing shuttle reactions.
Implementation Method 1
theoretical specific capacity (specific capacity) of 1,675 mAh/g by conversion reaction (S8+16Li++16e−→8Li2S) of lithium ion and sulfur at the positive electrode
Implementation Method 2
the dissolution of lithium polysulfide in the electrolyte solution during charging and discharging
Implementation Method 3
carbon-based materials capable of intercalation/deintercalation of lithium ions
Implementation Method 4
silicon and tin that can be alloyed with lithium
Data Source
AI summary
A lithium-sulfur battery having a high capacity and a method for manufacturing the same are provided. The lithium sulfur battery comprises a positive electrode and an electrolyte solution, and has a weight ratio, WSE/WSP, of a weight of a sulfur element (S) of a sulfur-based compound present in the electrolyte solution to a weight of a sulfur element (S) of a sulfur-based compound present in the positive electrode of 0.15 or less.