Graphene-based Battery Electrodes Having Continuous Flow Paths

Abstract

Some batteries can exhibit greatly improved performance by utilizing electrodes having randomly arranged graphene nanosheets forming a network of channels defining continuous flow paths through the electrode. The network of channels can provide a diffusion pathway for the liquid electrolyte and/or for reactant gases. Metal-air batteries can benefit from such electrodes. In particular Li-air batteries show extremely high capacities, wherein the network of channels allow oxygen to diffuse through the electrode and mesopores in the electrode can store discharge products.

We claim: 
     
         1 . A metal-air battery having an air electrode comprising graphene, the air electrode characterized by randomly arranged graphene nanosheets forming a network of channels defining continuous flow paths through the air electrode and by oxygen diffusing through the channels. 
     
     
         2 . The metal-air battery of  claim 1 , further comprising a carbon material mixed with the graphene nanosheets, the carbon material having a mesopore volume greater than 1 cc/g. 
     
     
         3 . The metal -air battery of  claim 1 , wherein at least a portion of the air electrode comprises fluorinated graphene nanosheets (CF x , where 0.5 <x<1.5). 
     
     
         4 . The metal-air battery of  claim 1 , wherein the air electrode further comprises a catalyst deposited on surfaces of the electrode, the catalyst comprising a transition metal or transition metal oxide. 
     
     
         5 . The metal-air battery of  claim 1 , wherein the channels have average diameters between 0.1 and 10 μm. 
     
     
         6 . The metal-air battery of  claim 1 , wherein the metal comprises Zn, Na, Mg, Fe, Ca, or Al. 
     
     
         7 . The metal-air battery of  claim 1 , wherein the metal comprises Li. 
     
     
         8 . The metal-air battery of  claim 1 , having a specific capacity greater than or equal to 5000 mAh/g graphene/carbon. 
     
     
         9 . The metal-air battery of  claim 1 , further comprising an electrolyte comprising ethers, glymes, or combinations thereof. 
     
     
         10 . The metal-air battery of  claim 9 , wherein the electrolyte comprises lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) in tri(ethylene glycol) dimethyl ether (triglyme). 
     
     
         11 . The metal-air battery of  claim 9 , wherein the electrolyte comprises LiTFSI in di(ethylene glycol) dibutyl ether (or butyl diglyme). 
     
     
         12 . The metal-air battery of  claim 1 , further comprising discharge product stored in mesopores adjacent to the channels. 
     
     
         13 . A battery having a cathode comprising graphene, the cathode characterized by randomly arranged graphene nanosheets forming a network of channels defining continuous flow paths through the cathode and by liquid electrolyte diffusing through the channels. 
     
     
         14 . The battery of  claim 13 , wherein the graphene nanosheets are on average less than 1 μm in length, width, or both. 
     
     
         15 . The battery of  claim 13 , wherein the graphene nanosheets are on average less than 30 nm in length, width, or both. 
     
     
         16 . The battery of  claim 13 , wherein at least a portion of the cathode comprises fluorinated graphene nanosheets (CF x , where 0.5<x<1.5). 
     
     
         17 . The battery of  claim 13 , further comprising an anode comprising lithium. 
     
     
         18 . The battery of  claim 17 , further comprising a lithium intercalation anode selected from the group consisting of LiC 6 , Li x Si (x=0.5 to 4.4), Li x Sn (x=0.5 to 4.4), Li x SnO 2 , and Li x TiO y . 
     
     
         19 . The battery of  claim 17 , wherein the battery is a primary lithium battery. 
     
     
         20 . The battery of  claim 17 , wherein the battery is a rechargeable lithium battery. 
     
     
         21 . The battery of  claim 20 , wherein the liquid electrolyte comprises a compound selected from the group consisting of lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium bis(oxalate)borate (LiBOB), LiPF 6 , LiBF 4 , LiAsF 6 , and combinations thereof. 
     
     
         22 . The battery of  claim 21 , wherein the liquid electrolyte comprises a solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), dimethyl ether (DME) solvent, diethylene carbonate (DEC), ethyl methyl carbonate (EMC), triglyme, butyl diglyme, tetraglyme, diglyme, and combinations of thereof.