Pre-sulfurized cathode for alkali metal-sulfur secondary battery and production process

摘要

A method of producing a pre-sulfurized active cathode layer for a rechargeable alkali metal-sulfur cell; the method comprising: (a) Preparing an integral layer of porous graphene structure having a specific surface area greater than 100 m2/g; (b) Preparing an electrolyte comprising a solvent and a sulfur source; (c) Preparing an anode; and (d) Bringing the integral layer and the anode in ionic contact with the electrolyte and imposing an electric current between the anode and the integral layer (serving as a cathode) to electrochemically deposit nano-scaled sulfur particles or coating on the graphene surfaces. The sulfur particles or coating have a thickness or diameter smaller than 20 nm (preferably <10 nm, more preferably <5 nm or even <3 nm) and occupy a weight fraction of at least 70% (preferably >90% or even >95%).

主权项

1. An electrochemical method of producing a pre-sulfurized active cathode layer for a rechargeable alkali metal-sulfur cell, said method comprising:
(a) Preparing an integral layer of porous graphene structure having massive graphene surfaces with a specific surface area greater than 100 m2/g, wherein said graphene structure contains a graphene material or an exfoliated graphite material wherein the graphene material is selected from pristine graphene, 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 and wherein the exfoliated graphite material is selected from exfoliated graphite worms, expanded graphite flakes, or recompressed graphite worms or flakes, and wherein said graphene structure comprises multiple sheets of said graphene material or multiple flakes of said exfoliated graphite material that are intersected or interconnected to form said integral layer with or without a binder to bond said multiple sheets or flakes together and with or without a conductive filler included in said integral layer, and wherein said porous graphene structure contains optional 0-49% by weight of sulfur or sulfur-containing compound pre-loaded therein and an optional binder material of 0-10% by weight; (b) Preparing an electrolyte comprising a non-aqueous solvent and a sulfur source dissolved or dispersed in said solvent; (c) Preparing an anode; and (d) Bringing said integral layer of porous graphene structure and said anode in ionic contact with said electrolyte and imposing an electric current between said anode and said integral layer of porous graphene structure, serving as a cathode, with a sufficient current density for a sufficient period of time to electrochemically deposit nano-scaled sulfur particles or coating directly on said graphene surfaces to form said pre-sulfurized active cathode layer, wherein said particles or coating have a thickness or diameter smaller than 20 nm.