Graphene Separator Layer for Alkali Metal-Selenium Battery
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Solution Overview
Problem
Lithium-selenium batteries face issues such as dendrite formation, capacity decay, and low cycle life due to selenium's high solubility and insulating nature, leading to internal shorting and reduced energy density, which hinders their widespread commercialization.
Innovation Solution
A rechargeable alkali metal-selenium battery design featuring a graphene separator layer that is permeable to lithium ions but impermeable to selenium or metal selenide, preventing the migration of dissolved species from the cathode to the anode and enhancing the utilization of electro-active cathode materials, thereby improving energy density and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium metal is used as anode to achieve high specific capacity, then energy density is improved, but dendrite formation occurs causing internal shorting and safety issues
Solution Approach 1:
A lithium phosphate coating layer is applied to the lithium metal anode surface, serving as an intermediary protective barrier. This coating layer prevents direct contact between lithium metal and electrolyte/separator, thereby blocking dendrite penetration pathways while maintaining lithium ion conductivity, thus resolving the contradiction between high capacity and safety
Solution Approach 2:
The anode system is transformed from pure lithium metal to a composite structure of lithium metal core with lithium phosphate coating shell. This composite material approach combines the high capacity advantage of lithium metal with the protective and stabilizing properties of lithium phosphate, achieving both high energy density and improved safety
2Use of energy by moving object
If lithium-selenium battery is designed to achieve high energy density, then specific energy is improved, but selenium solubility causes capacity decay and low cycle life
Solution Approach 1:
A graphene-based separator layer is introduced as an intermediary between the cathode and separator, specifically designed to trap dissolved selenium species. This graphene layer acts as a mediator that prevents selenium migration to the anode while maintaining lithium ion transport, thereby eliminating the shuttle effect and enabling long cycle life at high energy density
Solution Approach 2:
Graphene-based porous materials are utilized in the separator layer to provide selective transport pathways. The porous structure allows lithium ions to pass through while the specific pore size and surface chemistry of graphene adsorb and trap dissolved selenium species, preventing their migration and maintaining cathode capacity over extended cycling
3Reliability
If conventional separator is used to separate anode and cathode, then internal shorting is prevented, but selenium migration through separator causes shuttle effect and capacity loss
Solution Approach 1:
The separator system is enhanced by adding a graphene-based functional layer to the conventional separator, creating a composite structure. This composite separator maintains the electrical insulation properties of the base separator while the graphene component provides selective adsorption and blocking of selenium species, preventing their migration through the separator
Solution Approach 2:
The graphene-based layer in the separator utilizes its unique porous structure with specific pore sizes that allow lithium ions to pass through via diffusion while physically blocking and adsorbing larger dissolved selenium species. This selective porosity prevents selenium migration while maintaining ionic conductivity
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 implementation of a graphene separator layer significantly reduces the shuttle effect, enhances energy density, and prolongs cycle life, achieving specific energies greater than 300 Wh/kg and improving the overall performance of lithium-selenium batteries.
Implementation Method 1
a graphene separator layer containing a solid graphene foam, paper or fabric that is permeable to lithium ions but substantially non-permeable to selenium or metal selenide
Implementation Method 2
preventing the migration of dissolved species from the cathode to the anode
Data Source
AI summary
One embodiment of the invention is an alkali metal-selenium battery comprising an anode, a selenium cathode, an electrolyte, an electronically insulating porous separator, and an electronically conducting graphene separator layer comprising a solid graphene foam, paper or fabric that is permeable to lithium ions or sodium ions but is substantially non-permeable to selenium or metal selenide, wherein the graphene separator layer is disposed between the selenium cathode layer and the electronically insulating porous separator layer and the graphene separator layer contains pristine graphene sheets or non-pristine graphene sheets having 0.01% to 20% by weight of non-carbon elements, wherein the non-pristine graphene is selected from graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, boron-doped graphene, nitrogen-doped graphene, chemically functionalized graphene, or a combination thereof.