Manufacturing method for selenium preloaded mesoporous carbon cathode for alkali metal-selenium secondary battery
View Patent ↗A method of producing a pre-selenized (selenium-preloaded) active cathode layer for a rechargeable alkali metal-selenium cell; the method comprising: (a) preparing an integral layer of mesoporous structure having pore sizes from 0.5 nm to 50 nm (preferably from 0.5 nm to 5 nm) and a specific surface area from 100 to 3,200 m 2 /g; (b) preparing an electrolyte comprising a solvent and a selenium 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 nanoscaled selenium particles or coating on the graphene surfaces. The selenium particles or coating have a thickness or diameter smaller than 20 nm (preferably <10 nm, more preferably <5 nm or even <3 nm) and preferably occupy a weight fraction of at least 70% (preferably >90% or even >95%).
1. An electrochemical method of producing a pre-selenized active cathode layer for a rechargeable alkali metal-selenium cell, said method comprising:
(a) preparing an integral layer of a mesoporous structure of a carbon, graphite, metal, or conductive polymer, wherein said mesoporous structure has mesoscaled pores of 0.5-50 nm and a specific surface area greater than 100 m 2 /g and wherein said carbon, graphite, metal, or conductive polymer is selected from chemically etched or expanded soft carbon, chemically etched or expanded hard carbon, exfoliated activated carbon, chemically etched or expanded carbon black, chemically etched multi-walled carbon nanotube, nitrogen-doped carbon nanotube, boron-doped carbon nanotube, chemically doped carbon nanotube, ion-implanted carbon nanotube, chemically treated multi-walled carbon nanotube with an inter-planar separation no less than 0.5 nm, chemically expanded carbon nanofiber, chemically activated carbon nanotube, chemically treated carbon fiber, chemically activated graphite fiber, chemically activated carbonized polymer fiber, chemically treated coke, activated mesophase carbon, mesoporous carbon, electrospun conductive nanofiber, highly separated vapor-grown carbon or graphite nanofiber, highly separated carbon nanotube, carbon nanowire, metal nanowire, metal-coated nanowire or nanofiber, conductive polymer-coated nanowire or nanofiber, or a combination thereof;
(b) preparing an electrolyte comprising a non-aqueous solvent and a selenium source dissolved or dispersed in said solvent;
(c) preparing an anode; and
(d) bringing said integral layer of mesoporous structure and said anode in ionic contact with said electrolyte and imposing an electric current between said anode and said integral layer of mesoporous structure, serving as a cathode, with a sufficient current density for a sufficient period of time to electrochemically deposit nanoscaled selenium particles or coating directly on said graphene surfaces to form said pre-selenized active cathode layer, wherein said particles or coating have a thickness or diameter smaller than 20 nm.
2. The method of claim 1 , wherein said selenium source is selected from M x Se y , wherein x is an integer from 1 to 3 and y is an integer from 1 to 10, and M is a metal element selected from an alkali metal, an alkaline metal selected from Mg or Ca, a transition metal, a metal from groups 13 to 17 of the periodic table, or a combination thereof.
3. The method of claim 2 , wherein said metal element M is selected from Li, Na, K, Mg, Zn, Cu, Ti, Ni, Co, Fe, or Al.
4. The method of claim 2 , wherein said M x Se y is selected from Li 2 Se 6 , Li 2 Se 7 , Li 2 Se 8 , Li 2 Se 9 , Li 2 Se 10 , Na 2 Se 6 , Na 2 Se 7 , Na 2 Se 8 , Na 2 Se 9 , Na 2 Se 10 , K 2 Se 6 , K 2 Se 7 , K 2 Se 8 , K 2 Se 9 , K 2 Se 10 , or a combination thereof.
5. The method of claim 1 , wherein said anode comprises an anode active material selected from an alkali metal, an alkaline metal, a transition metal, a metal from groups 13 to 17 of the periodic table, or a combination thereof.
6. The method of claim 1 , further comprising a procedure of depositing an element Z to said porous graphene structure wherein said element Z is mixed with selenium or formed as discrete Z coating or particles having a dimension less than 100 nm and said Z element is selected from Sn, Sb, Bi, S, Te, or a combination thereof and the weight of element Z is less than the weight of selenium.
7. The method of claim 6 , wherein said procedure of depositing element Z includes electrochemical deposition, chemical deposition, or solution deposition.
8. The method of claim 1 , wherein said nanoscaled selenium particles or coating occupy a weight fraction of at least 70% based on the total weights of said selenium particles or coating and said carbon, graphite, metal or polymer material combined.
9. The method of claim 1 , wherein said electrolyte further comprises a metal salt selected from lithium perchlorate (LiClO 4 ), lithium hexafluorophosphate (LiPF 6 ), lithium borofluoride (LiBF 4 ), lithium hexafluoroarsenide (LiAsF 6 ), lithium trifluoro-metasulfonate (LiCF 3 SO 3 ), bis-trifluoromethyl sulfonylimide lithium (LiN(CF 3 SO 2 ) 2 ), lithium bis(oxalato)borate (LiBOB), lithium oxalyldifluoroborate (LiBF 2 C 2 O 4 ), lithium oxalyldifluoroborate (LiBF 2 C 2 O 4 ), lithium nitrate (LiNO 3 ), lithium-fluoroalkyl-phosphates (LiPF 3 (CF 2 CF 3 ) 3 ), lithium bisperfluoro-ethysulfonylimide (LiBETI), lithium bis(trifluoromethanesulphonyl)imide, lithium bis(fluorosulphonyl)imide, lithium trifluoromethanesulfonimide (LiTFSI), an ionic liquid-based lithium salt, sodium perchlorate (NaClO 4 ), potassium perchlorate (KClO 4 ), sodium hexafluorophosphate (NaPF 6 ), potassium hexafluorophosphate (KPF 6 ), sodium borofluoride (NaBF 4 ), potassium borofluoride (KBF 4 ), sodium hexafluoroarsenide, potassium hexafluoroarsenide, sodium trifluoro-metasulfonate (NaCF 3 SO 3 ), potassium trifluoro-metasulfonate (KCF 3 SO 3 ), bis-trifluoromethyl sulfonylimide sodium (NaN(CF 3 SO 2 ) 2 ), sodium trifluoromethanesulfonimide (NaTFSI), bis-trifluoromethyl sulfonylimide potassium (KN(CF 3 SO 2 ) 2 ), or a combination thereof.
10. The method of claim 1 , wherein said solvent is selected from 1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME), tetraethylene glycol dimethylether (TEGDME), poly(ethylene glycol) dimethyl ether (PEGDME), diethylene glycol dibutyl ether (DEGDBE), 2-ethoxyethyl ether (EEE), sulfone, sulfolane, ethylene carbonate (EC), dimethyl carbonate (DMC), methylethyl carbonate (MEC), diethyl carbonate (DEC), ethyl propionate, methyl propionate, propylene carbonate (PC), γ-butyrolactone (γ-BL), acetonitrile (AN), ethyl acetate (EA), propyl formate (PF), methyl formate (MF), toluene, xylene, methyl acetate (MA), fluoroethylene carbonate (FEC), vinylene carbonate (VC), allyl ethyl carbonate (AEC), a hydrofluoroether, a room temperature ionic liquid solvent, or a combination thereof.
11. The method of claim 1 , wherein said anode, said electrolyte, and said integral layer of mesoporous structure are disposed in an external container outside of a lithium-selenium cell and said step of electrochemically depositing nanoscaled selenium particles or coating in said mesoscaled pores is conducted outside said lithium-selenium cell and said method further includes a step of incorporating said pre-selenized active cathode layer in said lithium-selenium cell.
12. The method of claim 1 , wherein said anode, said electrolyte, and said integral layer of mesoporous structure are disposed inside a lithium-selenium cell and said step of electrochemically depositing nanoscaled selenium particles or coating in said mesoscaled pores is conducted after said lithium-selenium cell is produced.
13. The method of claim 1 , wherein said anode, said electrolyte, and said integral layer of mesoporous structure are part of a lithium-selenium cell and said step of electrochemically depositing nanoscaled selenium particles or coating in said mesoscaled pores occurs after said lithium-selenium cell is fabricated and is conducted during a first charge cycle of said cell.
14. The method of claim 1 , wherein said nanoscaled selenium particles or coating occupy a weight fraction of at least 80%.
15. The method of claim 1 , wherein said nanoscaled selenium particles or coating occupy a weight fraction of at least 90%.
16. The method of claim 1 , wherein said nanoscaled selenium particles or coating have a thickness or diameter smaller than 10 nm.
17. The method of claim 1 , wherein said nanoscaled selenium particles or coating have a thickness or diameter smaller than 5 nm.
18. The method of claim 1 , wherein said nanoscaled selenium particles or coating have a thickness or diameter smaller than 3 nm.
19. The method of claim 1 , wherein said method is conducted in an electrochemical chamber that is outside of an intended alkali metal-selenium cell and said method further contains a step of combining said pre-selenized active cathode layer, an alkali metal anode layer, and an electrolyte to form said alkali metal-selenium cell.
20. The method of claim 1 , wherein said method is conducted inside an intended alkali metal-selenium cell and during the first charge or discharge cycle of the cell.