Tin Fluoride Anode Layer for Lithium-Sulfur Battery Polysulfide Mitigation
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Solution Overview
Problem
Lithium-sulfur batteries face performance limitations due to polysulfide migration, which leads to capacity decay and cell failure, as polysulfides diffuse throughout the battery, interfering with lithium ion transport and causing unwanted chemical species formation.
Innovation Solution
A lithium-sulfur battery design incorporating a cathode with a ternary solvent package and protective sheaths formed from tri-functional epoxy and di-amine oligomer-based compounds, along with a polymeric network on the anode, to prevent polysulfide migration and dendrite formation, enhancing structural integrity and ion transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polysulfides are allowed to diffuse throughout the battery during operation, then lithium ion transport is interfered with and unwanted chemical species form, but the battery structure remains simple without additional protective layers
Solution Approach 1:
The battery is segmented into distinct functional zones by introducing a protective sheath layer on the cathode and a polymeric network on the anode. These layers create separate regions: a first region containing polysulfides confined to the cathode side, and a second region on the anode side substantially free of polysulfides, allowing independent optimization of each zone's function
Solution Approach 2:
The protective sheath and polymeric network act as intermediary barrier layers between the cathode and anode. These intermediaries selectively allow lithium ion transport while blocking polysulfide migration, thus mediating the interaction between electrodes and preventing direct contact between polysulfides and the anode
2Duration of action of stationary object
If protective sheaths and polymeric networks are added to prevent polysulfide migration, then battery performance is maintained and cycle life is extended, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The protective sheath and polymeric network are prepared and positioned in advance during battery assembly. The protective sheath is formed on the cathode before assembly, and the polymeric network is pre-formed with lithium fluoride particles distributed within it, allowing for controlled placement and reducing manufacturing complexity during final assembly
Solution Approach 2:
The invention uses composite material structures: the protective sheath combines epoxy and amine compounds to form a cross-linked network, while the anode protective layer combines polymeric network with lithium fluoride particles. These composite materials provide multiple functions (polysulfide blocking, ion transport, structural support) in single integrated components
3Strength
If the anode is made purely of lithium metal to maximize energy density, then dendrite formation occurs and structural integrity is compromised, but a composite anode structure with carbonaceous materials and polymeric networks reduces energy density
Solution Approach 1:
The anode structure uses local quality differentiation by creating distinct regions with different properties: a polymeric network region providing structural integrity and dendrite prevention, and lithium-containing regions providing electroactive material. This allows each local region to optimize for its specific function while contributing to overall anode performance
Solution Approach 2:
The anode employs a nested structure where lithium metal particles or lithium-containing compounds are embedded within the polymeric network matrix. The polymeric network forms the outer structure that provides mechanical strength, while lithium species are nested within this matrix, creating a hierarchical structure that combines structural and electrochemical functions
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 solution effectively reduces polysulfide shuttle effects, maintaining battery performance by preventing polysulfide migration and dendrite growth, thereby extending cycle life and enhancing energy density.
Implementation Method 1
The protective sheath may prevent polysulfide migration within the battery based on chemical binding between the protective sheath and one or more lithium-containing polysulfide intermediates
Implementation Method 2
the polymeric network may retain an alkali-metal containing fluoride, which in turn may suppress alkali metal dendrite formation associated with the anode
Implementation Method 3
The lithium fluoride layer may inhibit lithium-containing dendritic growth from the anode
Data Source
AI summary
A battery is disclosed that includes an anode, a graded interface layer disposed on the anode, a cathode positioned opposite to the anode, an electrolyte, and a separator. The anode may output lithium ions during cycling of the battery. A graded interface layer may be disposed on the anode and include a tin fluoride layer. A tin-lithium alloy region may form between the tin fluoride layer and the anode. The tin-lithium alloy region may produce a lithium fluoride uniformly dispersed between the anode and the tin fluoride layer during operational cycling of the battery. The electrolyte may disperse throughout the cathode and the anode. The separator may be positioned between the anode and cathode. In some aspects, the battery may also include lithium electrodeposited on one or more exposed surfaces of the anode.