Nanostructured Metal Oxides Comprising Internal Voids and Methods of Use Thereof

Abstract

The present invention relates to nano structures of metal oxides having a nanostructured shell (or wall), and an internal space or void. Nanostructures may be nanoparticles, nanorod/belts/arrays, nanotubes, nanodisks, nanoboxes, hollow nanospheres, and mesoporous structures, among other nanostructures. The nanostructures are composed of polycrystalline metal oxides such as SnO2. The nanostructures may have concentric walls which surround the internal space of cavity. There may be two or more concentric shells or walls. The internal space may contain a core such ferric oxides or other materials which have functional properties. The invention also provides for a novel, inexpensive, high-yield method for mass production of hollow metal oxide nanostructures. The method may be template free or contain a template such as silica. The nanostructures prepared by the methods of the invention provide for improved cycling performance when tested using rechargeable lithium-ion batteries.

1 . A nanostructure comprising at least one metal oxide nanostructured shell defining an inner void. 
     
     
         2 . The nanostructure of  claim 1  comprising at least two metal oxide nanostructured concentric shells, wherein the shells are not covalently linked to each other. 
     
     
         3 . The nanostructure of  claim 2 , comprising two metal oxide nanostructured shell concentric shells, wherein the shells are not covalently linked to each other. 
     
     
         4 . The nanostructure of  claim 1  further comprising a solid core within the inner void. 
     
     
         5 . The nanostructure of  claim 4  wherein, the solid core comprises materials selected from the group consisting of Au, Ag, Pt and Pd. 
     
     
         6 . The nanostructure of  claim 5 , wherein the solid core comprises materials with magnetic properties. 
     
     
         7 . The nanostructures of  claim 6 , wherein the materials with magnetic properties comprise Fe, Co or Ni. 
     
     
         8 . The nanostructures of  claim 7 , wherein the materials with magnetic properties comprise ferric oxides. 
     
     
         9 . The nanostructures of  claim 6 , wherein the materials with magnetic properties are selected from the group consisting of ZnO, CuO, and Cu 2 O. 
     
     
         10 . The nanostructures of  claim 6 , wherein the materials with magnetic properties comprise metal sulfide semiconductors. 
     
     
         11 . The nanostructures of  claim 1 , wherein at least one metal oxide nanostructured shell has one or more pores. 
     
     
         12 . The nanostructures of  claim 8 , wherein the pore is an opening. 
     
     
         13 . The nanostructure of  claim 1 , wherein the nanostructure is spherical, cylindrical or polyhedral. 
     
     
         14 . The nanostructure of  claim 1 , wherein the nanostructure is bowl-shaped. 
     
     
         15 . The nanostructure of  claim 1 , wherein the nanostructure is selected from the group consisting of nanoparticles, nanorods, nanobelts, nano-arrays, nanotubes, nanodisks, nanoboxes, nanospheres, nanocylinders, nanococoons, and nanospindles. 
     
     
         16 . The nanostructure of  claim 1 , wherein the metal oxide comprises a metal selected from the group consisting of titanium, zirconium, aluminum, tin, germanium, indium, gallium, hafnium, vanadium, tantalum, zinc, copper, iron, cobalt, nickel, chromium, and manganese. 
     
     
         17 . The nanostructure of  claim 16 , wherein the metal oxide is tin oxide. 
     
     
         18 . The nanostructure of  claim 1 , wherein the nanostructure is polycrystalline. 
     
     
         19 . The polycrystalline nanostructure of  claim 18 , wherein the average size of each crystal is between 1.0 and 50.0 nm. 
     
     
         20 . The polycrystalline nanostructure of  claim 19 , wherein the average size of each crystal is between 10.0 and 20.0 nm. 
     
     
         21 . The nanostructure of  claim 1 , wherein the maximum average cross-sectional distance of the nanostructure is between 50.0 and 1,000.0 nm. 
     
     
         22 . The nanostructure of  claim 21 , wherein the maximum average cross-sectional distance of the nanostructure is between 100.0 and 500.0 nm. 
     
     
         23 . The nanostructure of  claim 22 , wherein the maximum average cross-sectional distance of the nanostructure is between 75.0 and 150.0 nm. 
     
     
         24 . The nanostructure of  claim 1 , wherein the thickness of the nanostructured shell defining the inner space is between 5.0 and 50.0 nm. 
     
     
         25 . The nanostructure of  claim 24 , wherein the thickness of the nanostructured shell defining the inner space is between 10.0 and 40.0 nm. 
     
     
         26 . The nanostructure of  claim 25 , wherein the thickness of the nanostructured shell defining the inner space is between 20.0 and 30.0 nm. 
     
     
         27 . The nanostructure of  claim 4 , wherein the average diameter of the solid core within the inner space is between 5.0 and 500.0 nm. 
     
     
         28 . The nanostructure of  claim 27 , wherein the average diameter of the solid core within the inner space is between 30.0 and 300.0 nm. 
     
     
         29 . The nanostructure of  claim 28 , wherein the average diameter of the solid core within the inner space is between 50.0 and 150.0 nm. 
     
     
         30 . The nanostructure of  claim 11 , wherein the average diameter of the pores in one or more of the nanostructured shells is between 1.0 and 100.0 nm. 
     
     
         31 . The nanostructure of  claim 30 , wherein the average diameter of the pores in one or more of the nanostructured shells is between 3.0 and 30.0 nm. 
     
     
         32 . The nanostructure of  claim 1 , wherein the nanostructure is rutile tetragonal SnO 2 . 
     
     
         33 . The nanostructure of  claim 29 , wherein the corresponding ring-like selected-area electron diffraction pattern of the nanostructure reveals diffraction rings from inside to outside which are indexed to (110, (101), (200), (211), and (112) planes of rutile SnO 2  respectively. 
     
     
         34 . A process to produce the nanostructures of  claim 1 , comprising: mixing a metal oxide precursor with a solvent, and optionally one or more yield enhancing additives to form a mixture; and heating said mixture for at least about 3 hours. 
     
     
         35 . The process of  claim 34 , wherein the nanostructure is selected from the group consisting of nanoparticles, nanorods, nanobelts, nano-arrays, nanotubes, nanodisks, nanoboxes, nanospheres, nanocylinders, nanococoons, and nano spindles. 
     
     
         36 . The process of  claim 34 , wherein the metal oxide precursor is a precursor of metal oxides selected from the group consisting of titanium, zirconium, aluminum, tin, germanium, indium, gallium, hafnium, vanadium, tantalum, zinc, copper, iron, cobalt, nickel, chromium, and manganese. 
     
     
         37 . The process of  claim 36 , wherein the metal oxide precursor is a precursor of tin oxide. 
     
     
         38 . The process of  claim 37 , wherein the precursor is an alkali metal precursor salt. 
     
     
         39 . The process of  claim 38 , wherein the alkali metal is potassium or sodium. 
     
     
         40 . The process of  claim 39 , wherein the alkali metal is potassium. 
     
     
         41 . The process of  claim 34 , wherein the solvent is a polar solvent. 
     
     
         42 . The process of  claim 41 , wherein the polar solvent is an alcohol and water mixture. 
     
     
         43 . The process of  claim 42 , wherein the alcohol is any C 2  to C 10  alcohol. 
     
     
         44 . The process of  claim 34 , wherein the solvent is a non-polar solvent seeded with a polar entity. 
     
     
         45 . The process of  claim 44 , wherein the polar entities are chosen from the group consisting of surfactants, polymers, charged oligomers and particulate materials. 
     
     
         46 . The process of  claim 34 , wherein the yield enhancing additives are selected from the group consisting of urea compounds and —NH2 compounds. 
     
     
         47 . The process of  claim 46 , wherein the urea compounds are chosen from the group consisting of biuret, thiourea, thiobiuret, alkyl substituted ureas, aryl substituted ureas, alkyl substituted thioureas, aryl substituted thioureas, alkylene ether ureas, arylene ether ureas, alkylene ether thioureas and arylene ether thioureas. 
     
     
         48 . The process of  claim 34 , wherein the mixture is heated at a temperature of between about 140° C. and about 200° C. for between about 3 to about 24 hours. 
     
     
         49 . The process of  claim 48 , further comprising the step of cooling the nanostructure formed after heating. 
     
     
         50 . The process of  claim 49 , further comprising the step of washing the cooled nanostructure. 
     
     
         51 . The process of  claim 34 , wherein the nanostructure is formed by inside-out Ostwald ripening. 
     
     
         52 . The process of  claim 34 , wherein the nanostructure formed has enhanced electrochemical properties when used as an anode material in lithium ion batteries. 
     
     
         53 . The process of  claim 34 , wherein the nanostructure formed has initial discharge capacities between about 1000.0 mAh/g and 1,300,0 mAh/g. 
     
     
         54 . The process of  claim 34 , wherein the nanostructure formed can undergo at least about 25 discharge cycles while still functioning effectively at a discharge capacity of at least 300.0 mAh/g. 
     
     
         55 . The process of  claim 34 , wherein the nanostructure formed can undergo between 25 and 50 cycles while still functioning effectively at a discharge capacity of at least 300.0 mAh/g. 
     
     
         56 . The nanostructure of  claim 1 , further comprising a magnetic core. 
     
     
         57 . The nanostructure of  claim 56 , wherein the magnetic core comprises a ferric-based material. 
     
     
         58 . The nanostructure of  claim 57 , wherein the ferric based material is a ferric oxide. 
     
     
         59 . The nanostructure of  claim 58 , wherein the ferric oxide is Fe 3 O 4 . 
     
     
         60 . The nanostructure of  claim 1 , further comprising a core having electrical properties. 
     
     
         61 . The nanostructure of  claim 1 , further comprising a core having semiconductor properties. 
     
     
         62 . The nanostructure of  claim 1 , further comprising a core bearing noble metals. 
     
     
         63 . The nanostructure of  claim 62 , wherein the noble metals are chosen from the group consisting of Au, Ag, Pt and Pd. 
     
     
         64 . A process to manufacture the nanostructure of  claim 60 , comprising: (a) coating a material capable of being magnetized with a silica-based material to form a particle in which said material is coated with the silica-based material; (b) coating the particle of step (a) with metal oxide such that the nanotemplate is surrounded by at least one metal oxide nanostructured shell; (c) heating the nanotemplate of step (b) at a temperature between 400 to 1000° C. to cause annealing; (d) suspending said annealed structure of step (c) in a solvent suitable to dissolve the silica-based material. 
     
     
         65 . The process of  claim 64 , wherein the silica based material is amorphous silicon dioxide. 
     
     
         66 . The process of  claim 64 , wherein the material capable of being magnetized is α-Fe 2 O 3 . 
     
     
         67 . The process of  claim 66 , wherein the process further comprises a step in which the α-Fe 2 O 3  is magnetized by H 2  reduction to Fe 3 O 4 . 
     
     
         68 . The nanostructure of  claim 60 , further comprising an outermost shell comprising a semiconductor material. 
     
     
         69 . The nanostructure of  claim 68 , wherein the semiconductor material comprises carbon black. 
     
     
         70 . The nanostructure of  claim 68 , wherein the semiconductor material comprises a propylenevinylidenefluoride compound. 
     
     
         71 . The nanostructure of  claim 11 , wherein the pores are formed by treatment with a poregen material followed by heating at a temperature between 100° C. to 1000° C. 
     
     
         72 . The nanostructure of  claim 11 , wherein the pores are formed by treatment with a poregen material followed by lyophilization at a temperature less than 0° C. 
     
     
         73 . A process to produce the nanostructure of  claim 1 , comprising: (a) hydrothermally depositing a metal oxide precursor on a template to form a nanostructure comprising a metal oxide nanostructured shell on said template; and (b) treating the nanostructure of step (a) with a solvent to dissolve the template material to create an internal void in said nanostructure. 
     
     
         74 . A process to produce the nanostructure of  claim 2 , comprising: (a) hydrothermally depositing a metal oxide precursor at least two times on a template to form a nanostructure comprising a plurality of metal oxide nanostructured shells on said template; and (b) treating the nanostructure of step (a) with a solvent to dissolve the template material to create an internal void in said nanostructure. 
     
     
         75 . The process of  claim 73 , wherein the metal oxide is SnO 2 . 
     
     
         76 . The process of  claim 73 , wherein the template is a silica-based compound.