Carbon-silicon composite structures and methods of fabricating thereof
Described herein are carbon-silicon composite structures and methods of producing such structures. A carbon-silicon composite structure comprises one or more carbon-containing structures that have pores at least partially filled with silicon-containing structures. Specifically, the silicon-containing structures are attached to the pore walls while maintaining void spaces within these pores. These void spaces can accommodate silicon expansion during lithiation. Carbon-silicon composite structures can be produced by submerging carbon-containing structures into a precursor liquid solution (comprising a precursor) and driving this solution into the pores. The silicon-containing structures are then formed (from the precursor) within the pores either electrochemically (e.g., by applying a voltage to the solution and structures) or chemically (e.g., by introducing the structures into a reducing liquid solution). In some examples, these void spaces are sealed from the environment by additional structures, e.g., separate silicon-containing structures and/or carbon structures.
1 . A method of producing carbon-silicon composite structures, the method comprising:
submerging carbon-containing structures into a liquid-phase precursor liquid solution comprising a liquid solvent and a molecular precursor dissolved in the liquid solvent, wherein the carbon-containing structures comprise pores defined by pore walls and an exterior surface extending among the pores;
reducing a gas pressure over a surface of the liquid-phase precursor liquid solution driving the liquid-phase precursor liquid solution into the pores of the carbon-containing structures; and
forming silicon-containing structures from the molecular precursor of the liquid-phase precursor liquid solution within the pores and on the exterior surface of the carbon-containing structures, thereby producing the carbon-silicon composite structures with the pores at least partially filled with the silicon-containing structures and with the silicon-containing structures attached to the pore walls,
wherein forming the silicon-containing structures comprises:
(a) removing the carbon-containing structures from a bulk of the liquid-phase precursor liquid solution such that a portion of the liquid-phase precursor liquid solution remains within the pores of the carbon-containing structures and on the exterior surface, and
(b) submerging the carbon-containing structures, with the portion of the liquid-phase precursor liquid solution remaining within the pores and on the exterior surface of the carbon-containing structures, into a reducing liquid solution comprising a reducing reagent that chemically reacts with the molecular precursor in the portion of the liquid-phase precursor liquid solution remaining within the pores and on the exterior surface forms the silicon-containing structures at least within the pores, and
wherein the reducing reagent is one or more of sodium borohydride (NaBH4), lithium aluminum hydride (LiAlH4), sodium hydride (NaH), silicon hydride (SiHx), sodium biphenyl, lithium biphenyl, potassium biphenyl, sodium naphthalene, lithium naphthalene, potassium naphthalene, and potassium crown ether.
2 . The method of claim 1 , wherein, prior to forming the silicon-containing structures, the carbon-containing structures have a porosity of at least 1 m2/g.
3 . The method of claim 1 , wherein the carbon-containing structures comprise at least one of graphite, hard carbon, glassy carbon, carbon foam, carbon paper, carbon molecular sieve, carbon black, activated carbon, carbon fibers, carbon nanotubes, graphene and graphene derivatives, and zero-dimensional fullerene and fullerene derivatives.
4 . The method of claim 1 , wherein the silicon-containing structures comprise a layer coating interior surfaces of the pores, coating the exterior surface of the carbon-containing structures, or coating both the interior surfaces of the pores and the exterior surface of the carbon-containing structures.
5 . The method of claim 4 , wherein an average thickness (T) of the layer formed by the silicon-containing structures is between 1 nanometer and 50 micrometers.
6 . The method of claim 1 , wherein the molecular precursor is one or more of silicon tetrafluoride (SiF4), silicon tetrachloride (SiCl4), silicon tetrabromide (SiBr4), silicon tetraiodide (SiI4), HSiF3, H2SiF2, H3SiF, HSiCl3, H2SiCl3, H3SiCl, HSiBr3, H2SiBr2, H3SiBr, HSiI3, H2SiI2, H3SiI, germanium tetrachloride (GeCl4), germanium tetrabromide (GeBr4), germanium tetraiodide (GeI4), tin tetrachloride (SnCl4), tin tetrabromide (SnBr4) tin nitrate (Sn(NO3)4), tin (II) chloride (SnCl2), aluminum chloride (AlCl3), phosphorous chloride (PCl3), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium Bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium nitrate (LiNO3), lithium chloride (LiCl), lithium bromide (LiBr), lithium iodode (LiI), cholorobenzene (C6H5Cl), dicholorbenze (C6H4Cl2), trichlorobenze (C6H3Cl3), hexacholorbenzene (C6Cl6), dibromobenzene (C6H4Br2), chloromethane (CH3Cl), dicholoromethane (CH2Cl2), trichloromethane (CHCl3), tetrachloro carbon (CCl4), and tetrabromo carbon (CBr4), pitch, acetylene (C2H2), methane (CH4), propylene (C3H6), methanol (CH3OH), ethanol (C2H5OH), isopropanol (C3H8O), acetonitrile (CH3CN), benzene (C6H6), toluene (C6H5CH3), propylene carbonate, glucose, dopamine, polyethylene glycol (PEG), melamine, phenol formaldehyde resin, polyimide resin, epoxy resin, cane sugar, and graphite powder.
7 . The method of claim 1 , wherein:
the carbon-containing structures are supported on a working electrode;
a reference electrode is further submerged into the liquid-phase precursor liquid solution; and
forming the silicon-containing structures comprises applying a potential between the working electrode and the reference electrode, thereby electrochemically forming the silicon-containing structures.
8 . The method of claim 1 , further comprising:
submerging the carbon-silicon composite structures, comprising the silicon-containing structures at least with the pores of the carbon-containing structures, into an additional precursor liquid solution such that the pores remain substantially free from the additional precursor liquid solution; and
forming additional structures at openings of the pores thereby sealing the pores from environment.
9 . The method of claim 8 , wherein a porosity of the carbon-silicon composite structures, after forming the additional structures at the openings of the pores, is at least 30%.
10 . The method of claim 1 , wherein the liquid-phase precursor liquid solution further comprises a supporting salt selected from the group consisting of tetrabutylammonium chloride (Bu 4 NCl), tetrapropylammonium chloride (Py 4 NCl), tetraethylammonium chloride (Et 4 NCl), lithium chloride (LiCl), 1-butyl-1-methylpyrrolidinium chloride (PYR 14 Cl), and 1-propyl-1-methylpyrrolidinium chloride (PYR 13 Cl).
11 . The method of claim 1 , wherein the liquid-phase precursor liquid solution further comprises one or more surfactant additives selected from the group consisting of polyvinylpyrrolidone (PVP), a polyoxyethylene glycol octylphenol, polyoxyethylene glycol alkylphenol, a block copolymer of polyethylene glycol (PEG), polypropylene glycol (PPG), and a siloxane.
12 . The method of claim 11 , wherein the one or more surfactant additives have a concentration of between 0.1% and 10% by weight in the liquid-phase precursor liquid solution.
13 . The method of claim 1 , wherein:
the liquid-phase precursor liquid solution further comprises solid particles forming a suspension, and
the solid particles are selected from the group consisting of carbon fillers, metal nanoparticles, and void-forming precursors.
14 . The method of claim 1 , further comprising, prior to submerging the carbon-containing structures into the liquid-phase precursor liquid solution, activating the carbon-containing structures using plasma.
15 . The method of claim 1 , wherein the gas pressure is reduced over the surface of the liquid-phase precursor liquid solution to below 0.1 Pa.
16 . The method of claim 1 , further comprising, after submerging the carbon-containing structures into the liquid-phase precursor liquid solution, agitating the liquid-phase precursor liquid solution while the liquid-phase precursor liquid solution enters the pores of the carbon-containing structures.
17 . The method of claim 1 , wherein:
the molecular precursor is silicon tetrachloride (SiCl4),
the reducing reagent is sodium borohydride (NaBH4), and
the reducing liquid solution further comprises sodium hydroxide (NaOH).
18 . The method of claim 1 , wherein the silicon-containing structures comprise one or more non-silicon materials selected from the group consisting of carbon, lithium, oxygen, titanium, nitrogen, magnesium, calcium, boron, phosphorous, fluorine, chlorine, bromine, iodine, hydrogen, iron, aluminum, copper, nickel, tin, and germanium.