Method of fabricating electrodes including high-capacity, binder-free anodes for lithium-ion batteries

Abstract

An electrode ( 110 ) is provided that may be used in an electrochemical device ( 100 ) such as an energy storage/discharge device, e.g., a lithium-ion battery, or an electrochromic device, e.g., a smart window. Hydrothermal techniques and vacuum filtration methods were applied to fabricate the electrode ( 110 ). The electrode ( 110 ) includes an active portion ( 140 ) that is made up of electrochemically active nanoparticles, with one embodiment utilizing 3d-transition metal oxides to provide the electrochemical capacity of the electrode ( 110 ). The active material ( 140 ) may include other electrochemical materials, such as silicon, tin, lithium manganese oxide, and lithium iron phosphate. The electrode ( 110 ) also includes a matrix or net ( 170 ) of electrically conductive nanomaterial that acts to connect and/or bind the active nanoparticles ( 140 ) such that no binder material is required in the electrode ( 110 ), which allows more active materials ( 140 ) to be included to improve energy density and other desirable characteristics of the electrode. The matrix material ( 170 ) may take the form of carbon nanotubes, such as single-wall, double-wall, and/or multi-wall nanotubes, and be provided as about 2 to 30 percent weight of the electrode ( 110 ) with the rest being the active material ( 140 ).

1 . An electrode for an electrochemical device, comprising:
 an active portion comprising an electrochemically active nanoparticles;   a matrix of electrically conductive nanomaterial connecting the electrochemically active particles, wherein the electrically conductive material of the matrix comprises less than about 30 percent by weight of the electrode.   
     
     
         2 . The electrode of  claim 1 , wherein the electrochemically active particles comprise active nanoparticles or active non-nanoparticles. 
     
     
         3 . The electrode of  claim 1 , wherein the active portion provides a remaining material make up of the electrode after consideration of the matrix, whereby the electrode is binder-free. 
     
     
         4 . The electrode of  claim 1 , wherein the electrically conductive nanomaterial of the matrix comprises at least one of carbon nanoparticles, graphene, a carbon-based nanostructured material, a doped carbon nanostructure, boron-doped nanotubes, nitrogen-doped nanotubes, and BCN nanostructures. 
     
     
         5 . The electrode of  claim 1 , wherein the electrically conductive nanomaterial of the matrix provides 2 to 10 percent by weight of the electrode. 
     
     
         6 . The electrode of  claim 5 , wherein the electrode is a cathode or an anode depending upon a material used for the electrochemically active nanoparticles. 
     
     
         7 . The electrode of  claim 5 , wherein the electrically conductive nanomaterial of the matrix comprises carbon single-wall nanotubes. 
     
     
         8 . The electrode of  claim 7 , wherein the carbon single-wall nanotubes are about 5 to about 10 percent by weight of the electrode. 
     
     
         9 . The electrode of  claim 1 , wherein the electrochemically active nanoparticles comprise metal oxide nanoparticles. 
     
     
         10 . The electrode of  claim 9 , wherein the metal oxide nanoparticles comprise iron oxide nanorods and provide at least about 70 percent by weight of the electrode and wherein the iron oxide nanorods are bound within the electrode by the matrix. 
     
     
         11 . An electrochemical device, comprising:
 a cathode layer; and   an anode or cathode layer proximate to the cathode layer comprising an electrochemically active material and a connective net binding the electrochemically active nanomaterial within the anode or cathode layer, wherein the connective net comprises at least semiconducting nanoparticles.   
     
     
         12 . The electrochemical device of  claim 11 , wherein the nanoparticles comprise at least one of semiconducting or metallic carbon nanotubes, fullerenes, graphene, a carbon-based nanostructured material, a doped carbon nanostructure, boron-doped nanotubes, nitrogen-doped nanotubes, and BCN nanostructures. 
     
     
         13 . The electrochemical device of  claim 12 , wherein the carbon nanotubes comprise single-wall nanotubes and the carbon nanotubes provide about 2 to about 10 percent by weight of the anode layer. 
     
     
         14 . The electrochemical device of  claim 13 , wherein the carbon nanotubes are substantially uniformly distributed within the anode layer. 
     
     
         15 . The electrochemical device of  claim 11 , wherein the electrochemically active material comprises metal oxide nanoparticles. 
     
     
         16 . The electrochemical device of  claim 15 , wherein the metal oxide nanoparticles comprise iron oxide nanorods that provide at least about 90 percent by weight of the anode layer. 
     
     
         17 . A battery, comprising:
 a lithium-ion cathode;   an electrolyte; and   an anode comprising a binder-free electrode layer comprising about 2 to 30 percent by weight carbon nanoparticles and at least about 70 percent by weight metal oxide nanoparticles.   
     
     
         18 . The battery of  claim 17 , wherein the carbon particles comprise carbon single-wall nanotubes, double-wall nanotubes, multi-wall nanotubes, carbon fiber, or fullerenes providing 5 to 10 percent by weight of the binder-free electrode layer with remaining material consisting of the metal oxide nanoparticles. 
     
     
         19 . The battery of  claim 17 , wherein the metal oxide nanoparticles comprise iron oxide nanorods. 
     
     
         20 . The battery of  claim 19 , wherein the iron oxide nanorods provide at least about 90 percent by weight of the binder-free electrode layer. 
     
     
         21 . The battery of  claim 17 , wherein the anode has a reversible capacity of at least about 1000 mAh/g at C rate over at least about 100 cycles. 
     
     
         22 . The battery of  claim 17 , wherein the carbon nanoparticles comprise carbon SWNTs providing less than about 10 percent weight of the binder-free electrode layer and wherein the metal oxide particles comprise nanorods of at least one 3d-transitional metal that are substantially uniformly mixed with the carbon SWNTs, whereby the metal oxide particles are bound by a connective matrix formed by the carbon SWNTs free of additional binder material.