Lithium-Sulfur Battery Additives for Dendrite and Polysulfide Suppression
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Solution Overview
Problem
The commercialization of lithium-sulfur batteries is hindered by issues such as reduced charging/discharging efficiency and shortened lifetime due to the leaching of lithium polysulfide, formation of lithium dendrites, and side reactions with the electrolyte, which degrade the battery's capacity and stability.
Innovation Solution
Incorporating tellurium as an additive in the positive electrode and bis(2,2,2-trifluoroethyl)ether in the electrolyte solution to form a protective layer on the negative electrode, suppressing lithium polysulfide leaching and reducing side reactions, thereby improving the battery's lifetime characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium-sulfur battery uses sulfur-based material as positive electrode active material and lithium metal as negative electrode active material, then theoretical energy density is improved (2,600 Wh/kg), but lifetime is deteriorated due to leaching of lithium polysulfide and formation of lithium dendrites
Solution Approach 1:
The patent introduces a protective coating layer as an intermediary between the lithium metal negative electrode and the electrolyte solution. This coating layer acts as a mediator that prevents direct contact and harmful interactions while allowing lithium ion transport, thereby resolving the contradiction between high energy density and long lifetime by eliminating the leaching and dendrite formation issues.
Solution Approach 2:
The patent applies a thin film protective coating on the lithium metal negative electrode. This thin film structure provides physical barrier functionality to prevent polysulfide leaching and dendrite growth, while maintaining the necessary ionic conductivity for battery operation, thus resolving the contradiction between energy density and lifetime.
2Productivity
If lithium polysulfide is transferred to negative electrode through electrolyte solution, then charging/discharging efficiency is reduced, but capacity is also reduced due to irreversible loss of positive electrode active material
Solution Approach 1:
The patent extracts or removes the harmful lithium polysulfide from the electrolyte solution by providing a protective coating on the negative electrode that prevents polysulfide transfer. This extraction of the harmful substance from the system prevents both efficiency reduction and capacity loss, resolving the contradiction between productivity and quantity of substance.
Solution Approach 2:
The patent converts the harmful effect of lithium polysulfide transfer into a beneficial outcome by using the protective coating to prevent polysulfide migration. The coating transforms the potential harm of polysulfide presence into an opportunity to improve both charging/discharging efficiency and maintain capacity by preventing irreversible material loss.
3Stability of the object's composition
If lithium metal reacts with electrolyte to form passivation layer, then chemical stability is improved, but mechanical strength is reduced causing dendrite formation
Solution Approach 1:
The patent changes the physical and chemical parameters of the negative electrode surface by applying a protective coating with optimized mechanical properties. This coating modifies the surface characteristics to provide both chemical stability and sufficient mechanical strength, resolving the contradiction between these two properties that would otherwise lead to dendrite formation.
Solution Approach 2:
The patent creates a composite structure by combining lithium metal with a protective coating layer. This composite material integrates the high capacity of lithium metal with the mechanical strength and chemical stability of the coating, resolving the contradiction between chemical stability and mechanical strength that prevents dendrite formation.
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 proposed solution enhances the lithium secondary battery's efficiency and stability by forming a protective layer that suppresses lithium dendrite formation and reduces side reactions, extending the battery's cycle life to 80% of its initial capacity.
Implementation Method 1
forming a protective layer on the surface of the negative electrode
Implementation Method 2
suppressing the leaching of lithium polysulfide
Implementation Method 3
reducing side reactions with the electrolyte
Implementation Method 4
suppressing the formation of lithium dendrites
Data Source
Figure 1
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AI summary
The present invention relates to a lithium secondary battery containing tellurium as an additive for a positive electrode and bis (2,2,2-trifluoroethyl)ether as an additive for an electrolyte solution, which has an effect of improving the lifetime characteristic of the lithium secondary battery.