Method for manufacturing a nanoparticle material and a fluoride ion battery

Abstract

A method is provided for manufacturing a nanoparticle material having an ionic conductivity as a battery material for Fluoride ion Batteries, thus, being capable for overcoming high resistances at the surfaces, grain-boundaries of nanoparticles or compartments of the nanoparticles by a material treatment selected from: (i) a ball-mill procedure under aerosol and/or vapour-pressure atmosphere, (ii) excess-synthesis, (iii) ball-milling with surface stabilizing and conductivity enhancing solid or/and gel/liquid additives or (iv) functionalizing the material to obtain functionalized nanoparticles (GSNP) comprising a dispersion of graphene, nanotubes and/or a further additive selected from carbon-black, graphite, Si and/or CF.sub.X, Herein, fluorides (Em.sub.mF.sub.h), fluorides composites (Em1.sub.m1Em2.sub.m2 . . . F.sub.h1) are synthesized, wherein a first metal, metalloid or non-metal Em or Em1 and a second metal, metalloid or non-metal Em2 are dissimilarly selected from various elements in a manner that a battery material having an increased ionic conductivity is obtained.

Claims

1. A method for manufacturing a nanoparticle material having an ionic conductivity as a battery material for a Fluoride Ion Battery, the method comprising the step of providing a fluoride compound, the fluoride compound comprising fluorine and at least one metal, metalloid or non-metal, wherein the fluoride compound is subjected to an aerosol or vapour-pressure atmosphere and subsequently treated in a ball-mill procedure, whereby the battery material having an increased ionic conductivity is obtained.

2. The method of claim 1, wherein a fluoride compound of formula Em.sub.mF.sub.h+x, wherein indices m, h and x are related to the number of atoms in the chemical formula for the fluoride compound, m times element Em and (h+x) times fluorine F, wherein Em is a metal, metalloid or non-metal selected from Cu, Pb, Fe, Sn, Zn, Bi, Cd, Co, Cr, Ni, Sb, C, Si, Ge, Ce, Se, Ca, Mg, Li, Na, K, Al, Sr, Ba, La or Sm and wherein x is equal to or greater than 0, is treated by an aerosol or vapour-pressure atmosphere and subsequently by the ball-mill procedure.

3. The method of claim 2, wherein the metal fluoride is CaF.sub.2 and source of vapour-pressure is H.sub.2O having an additive of KCl adapted for adjusting humidity and/or pH.

4. The method of claim 1, wherein a metal fluoride composite of formula Em1.sub.m1Em2.sub.m2 . . . F.sub.h1+x1, wherein the indices m1, m2, . . . , h1, and x1 are related to the number of atoms in the chemical formula for the fluoride compound, m1 times element Em1, m2 times element Em2, . . . and (h+x) times fluorine F, which comprises at least two fluorides, wherein at least two elements Em1 and Em2 are dissimilarly selected from Cu, Pb, Fe, Sn, Zn, Bi, Cd, Co, Cr, Ni, Sb, C, Si, Ge, Ce, Se, Ca, Mg, Li, Na, K, Al, Sr, Ba, La or Sm and wherein x1 is equal or greater than 0, is treated by an aerosol or vapour-pressure atmosphere and subsequently by the ball-mill procedure.

5. The method of claim 1, wherein the metal fluoride is, firstly, subjected to the aerosol or vapour-pressure atmosphere at a temperature of −10° C. to 300° C. for a first period of time of 1 hours to 48 hours and, subsequently, treated in the ball-mill procedure for a second period of time of 1 hours to 48 hours.

6. The method of claim 1, wherein the metal fluoride of the formula Em.sub.mF.sub.h+x, wherein Em is a metal selected from Ca, Li, Ba, Al, Pb, Fe, Sn, Co, Ce, La, Sm, Eu, Cs, Gd or V and wherein x is equal or greater than 0, is synthesized by an excess synthesis with stoichiometric excess of a fluoride precursor selected from NH.sub.4F, NH.sub.4HF.sub.2, HF, DMIF-2.3HF (1,3-dimethyl-imidazolium fluoride), EMIF-2.3HF (1-ethyl-3-methylimida-zolium fluoride), TMAF (Tetramethylammonium fluoride) or TBAF (Tetrabutylammonium fluoride).

7. The method of claim 1, wherein a metal fluoride composite of the formula Em1Em2.sub.m2 . . . F.sub.h1+x1 which comprises at least two metal fluorides, wherein at least two metals Em1 and Em2 are dissimilarly selected from Ca, Na, K, Li, Ba, Al, Pb, Fe, Sn, Co, Ce, La, Sm, Eu, Cs, Gd or Y and wherein x1 is equal or greater than 0, is synthesized by an excess synthesis with stoichiometric excess of a fluoride precursor selected from NH.sub.4F, NH.sub.4HF.sub.2, HF, DMIF-2.3HF (1,3-dimethyl-Imidazolium fluoride), EMIF-2.3HF (1-ethyl-3-methylimida-zolium fluoride), TMAF (Tetramethylammonium fluoride) or TBAF (Tetrabutylammonium fluoride).

8. The method of claim 1, wherein a solid synthesis of a fluoride (Em.sub.mF.sub.h) is performed by using a ball-mill procedure in the presence of at least one surface stabilizing and conductivity enhancing solid, or liquid additive being adapted for a transfer of ionic conductivity of nanoparticles or of composites comprising the nanoparticles to a macroscopic material, wherein Em is a metal, metalloid or non-metal selected from Cu, Pb, Fe, S, Zn, Bi, Cd, Co, Cr, Ni, Sb, C, Si, Ge, Ce, Se, Ca, Mg, Li, Na, K, Al, Sr, Ba, La, Sm, Eu, Cs, Gd or Y.

9. The method of claim 1, wherein a solid synthesis of a fluoride composite (Em1.sub.m1Em2.sub.m2 . . . F.sub.h1) is performed by using a ball-mill procedure in the presence of at least one surface stabilizing and conductivity enhancing solid, gel or liquid additive being adapted for a transfer of ionic conductivity of nanoparticles or of composites comprising the nanoparticles to a macroscopic material, wherein at least one metal, metalloid or non-metal Em1 and a second metal, metalloid or non-metal Em2 are dissimilarly selected from Cu, Pb, Fe, Sn, Zn, Bi, Cd, Co, Cr, Ni, Sb, C, Si, B, P, N, Ge, Ce, Se, Ca, Mg, Li, Na, K, Al, Sr, Ba, La, Sm, Eu, Cs, Gd or Y.

10. The method of claim 4, wherein the Em1 is selected from Ca, Ba or Pb and wherein Em2 is selected from Sn or Sm.

11. The method of claim 1, wherein the battery material having the increased ionic conductivity is further treated by a dispersion of graphene, nanotubes, further additive selected from carbon-black, graphite, Si, CF.sub.x, or a mixture thereof, whereby a battery material comprising nanoparticles having a functionalized graphene- or/and nanotube-surface is obtained.

12. A solid state Fluoride Ion Battery (FIB) comprising an anode material, a cathode material, and an electrolyte material, wherein a nanoparticle material having an ionic conductivity as a battery material for a Fluoride Ion Battery is manufactured by (A) providing a fluoride compound, the fluoride compound comprising fluorine and at least one metal, metalloid or non-metal, wherein the fluoride compound is subjected to an aerosol or a vapour-pressure atmosphere and subsequently treated in a ball-mill procedure; wherein the anode material comprises a battery material manufactured according to (A), wherein the cathode material comprises a battery material manufactured according to (A), and wherein the electrolyte material comprises a battery material manufactured according to (A) or wherein the electrolyte material comprises a battery material selected from nanotubes or additives selected from carbon-black, graphite, Si, CF.sub.x or a mixture thereof.

13. The solid state Fluoride Ion Battery (FIB) of claim 12, wherein the battery material further comprises nanoparticles having a surface comprising functionalised graphene or nanotubes, said nanoparticles being obtained by further treating the battery material manufactured according to (A) with a dispersion of graphene, nanotubes, a further additive selected from carbon black, graphite, Si, CF.sub.x, or a mixture thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is described below in more detail with references to the drawings, wherein

(2) FIG. 1 illustrates a process of surface stabilization due to vapour-pressure and/or ball-milling by examining humidity onto CaF.sub.2;

(3) FIG. 2 illustrates an SEM image and an illustrating sketch of a humidified CaF.sub.2 ball-milled surface stabilized nanoparticle;

(4) FIG. 3 illustrates an impedance spectroscopy measurement to prove low ionic resistance: 10.sup.−4 S/cm of humidified CaF.sub.2 nanomaterial (24 h humidity under KCl and 18 h ball-milling) at room temperature and .sup.19F-NMR spectrum indicating the surface contributions. No HF (hydrogen fluoride) could be found;

(5) FIG. 4 illustrates a TEM image of the excess-synthesized CaF.sub.2 nanoparticle and corresponding sketch of said CaF.sub.2 nanoparticle.

(6) FIG. 5 illustrates a .sup.1H-NMR spectrum of excess-synthesized CaF.sub.2 nanoparticle showing H.sub.3O.sup.+ as counter-ion for F.sup.− instead of OH.sup.− (surface stabilizing DEG and solvent is also present);

(7) FIG. 6 illustrates an impedance spectroscopy measurement as a proof of low ionic resistance (i.e. high conductivity) of excess-synthesized CaF.sub.2 nanoparticle: 10.sup.5S/cm at 40° C., 60° C. and .sup.19F spectrum indicating the increased surface contributions. No HF (hydrogen fluoride) visible;

(8) FIG. 7 illustrates an exemplary Electrode III with electric and ionic conductive surface (graphene layer as first layer), highly ionic conductive interphase (second layer) and core storage where the first layer and the second layer are forming a shell of the nanoparticle. Further FIG. 7 schematically illustrates the synthesis of MeF.sub.n+x˜-GSNPs;

(9) FIG. 8 illustrates an exemplary embodiment of an electrochemical cell according to present invention;

(10) FIG. 9 illustrates a photograph of a battery pellet comprising the different components according to present invention;

(11) FIG. 10 illustrates diagrams with known electrode materials (Mg/CoF.sub.2) but improved solid electrolyte material a solid state FIB performs and characteristics at room temperature;

(12) FIG. 11 illustrates an exemplary embodiment Iva of a battery device according to the present invention, wherein the battery device only comprises functionalized nanomaterials which are capable of mainly avoiding compositions such as intercalation materials or mixtures which may reduce graphite and binder, wherein the surface of the electrode nanoparticles are electrically conductive itself;

(13) FIG. 12 illustrates an exemplary embodiment of a further embodiment IVb of the battery device according to present invention, wherein the battery device only comprises functionalized nanomaterials which are capable of mainly avoiding compositions such as intercalation materials or mixtures which may reduce graphite and binder, wherein the surface of the electrode nanoparticles are electrically conductive itself:

(14) FIG. 13 illustrates an IS measurement of a PbF.sub.2/SnF.sub.2 composite as a proof of low ionic resistance (i.e. high conductivity) of 10.sup.−3S/cm at 25° C. and .sup.19F-NMR spectrum indicating the different phases and surface contributions herein.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(15) To facilitate cell preparation and material handling, cells were prepared in a discharged state with Cu, Pb, Fe, Sn, Zn, Bi, Cd, Co, Cr, Ni, Sb, C, Si, or composites or alloys thereof as cathode material and CeF.sub.3, CeF.sub.4, CaF.sub.2, MgF.sub.2, LiF, NaF, KF, AlF.sub.3, SrF.sub.2, BaF.sub.2, LaF.sub.3, SmF.sub.3, or composites and/or solid-solutions thereof, such as Na.sub.3AlF.sub.6 or Li.sub.3AlF.sub.6, as the anode material and, in addition, cells were prepared in a charged state comprising CuF.sub.2, PbF.sub.2, FeF.sub.2, FeF.sub.3, SnF.sub.2, ZnF.sub.2, BiF.sub.3, CdF.sub.2, CoF.sub.x, CrF.sub.x, NiF.sub.2, SbF.sub.3, CF.sub.x, SiF.sub.x, or composite and/or solid-solutions thereof, such as K.sub.2NiF.sub.4, Na.sub.2SiF.sub.6 or Na.sub.3FeF.sub.6, as the cathode material and Ce, Ca, Mg, Li, Na, K, Al, Sr, Ba, La, Sm, or composites or alloys thereof as the anode material.

(16) The possible charge and discharge mechanisms were examined by detailed ex situ X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) experiments, impedance spectroscopy (IS), battery testing equipment (e.g. battery cyclers and high precision power-meters) and Nuclear Magnetic Resonance Spectroscopy (NMR). Especially NMR is favoured analysing crystal but also non-crystalline contributions. Stabilized high mobile nanomaterial surfaces, grain-boundaries and/or inter-phases can be identified for instance with .sup.19F-NMR. Related spectral peaks are mostly smaller than the bulk and having isotropic chemical shift resonance frequencies around −115 to −140 ppm. If strong additional effects as for instance considerable material susceptibilities or paramagnetic shifts, these contributions have to be additionally taken into account.

(17) Excellent cycling performances were obtained for MgF.sub.2, PbF.sub.2, SnF.sub.2, BiF.sub.2, CoF.sub.2 also prepared in the half-discharged state (e.g. MgF.sub.2 mixed with Mg), together with high performance carbon materials and micro-grid electrode connectors, thus, forming a composite that could provide better interface contacts between the different reactive phases and surfaces within the electrodes. The results show that, apart from choosing carefully the electrode active materials, it is also advantageous to optimize the architecture of the electrodes.

Preferred Embodiments of the Electrolyte

Example I, Humidified and Ball-Milled CaF.SUB.2 .Nanoparticles, See FIGS. 1, 2 and 3

(18) Pure CaF.sub.2 powder is placed in a closed chamber, preferably, an enclosed desiccator comprising a solvent reservoir and a sample holder, on support under vapour pressure conditions (Pure water has, for instance, 3.2 kPa at 25° C.) between 49 and 51° C. for 24 hours in order to obtain humidified CaF.sub.2 material. Thereafter, said mixture is ball-milled for 18 hours. This two stage procedure can be repeated several times. As a result, humidified CaF.sub.2 ball-milled material with orders of magnitude improved ionic conductivity is obtained. The CaF.sub.2 ball-milled surface stabilized nanoparticle is schematically illustrated in FIG. 2, wherein the nanoparticle comprises a core surrounded by a highly ionic conductive surface. FIG. 3 shows an impedance spectroscopy (IS) measurement proving low ionic resistance of CaF.sub.2 nanomaterial at room temperature. No hydrogen fluoride can be found according to a correspondingly obtained NMR-spectrum.

Example II, Synthesis of MeF.SUB.(h+x) .Nanoparticles

(19) Surface-mediated synthesis with excess of fluoride precursor (NH.sub.4F) of nanoparticles having an assumed size of 10 nm and surface comprising stabilizing ligands:
Me(NO.sub.3).sub.h.Math.H.sub.2O+(h+x)(NH.sub.4)F.fwdarw.MeF.sub.(h+x)˜NPs+ . . . .

(20) Example IIa refers to a synthesis of CaF.sub.(2+x) nanoparticles using polyol ligand stabilization due to DEG (diethylene glycol), i.e.
Me=Ca
Ca(NO.sub.3).sub.2.Math.4H.sub.2O+(2+x)(NH.sub.4)F.fwdarw.CaF.sub.(2+x)-NPs+ . . . .

(21) In FIG. 4a TEM image and a schematic structure of the CaF.sub.2 nanoparticle comprising a solid core surrounded by an interphase of calcium fluoride with mobile F surplus which is stabilized by a surface layer of DEG/H.sub.3O.sup.+ is shown. FIGS. 5 and 6 further show results of NMR and impedance spectroscopy measurements, respectively.

Example III, Synthesis of MeF.SUB.(h+x).-GSNPs

(22) Surface-mediated excess-synthesis of metallic nanoparticles comprising a special graphene surface in order to obtain nanoparticles which can also be denoted as “graphene surface nanoparticles”, abbreviated to GSNPs:
Me(NO.sub.3).sub.h.Math.H.sub.2O+(h+x)(NH.sub.4)F.fwdarw.MeF.sub.(h+x)-NPs+ . . . .
MeF.sub.(h+x)-nanoparticles+dispersion of graphene and/or nanotubes
.fwdarw.MeF.sub.(h+x)-GSNPs

(23) The schematic structure of the GSNP is illustrated in FIG. 7.

Battery Devices

(24) In FIG. 8 an embodiment of battery according to the present invention is prepared from materials as mentioned above.

(25) FIG. 9 provides a photograph of this embodiment of the solid Fluoride Ion Battery (FIB) in shape of a pellet.

(26) In FIG. 10 a performance of the solid Fluoride Ion Battery comprising known electrodes but improved solid electrolyte material at room temperature is shown, in particular with respect to cycling, cell capacity and coulomb efficiency.

(27) FIG. 11 shows an embodiment Iva of the battery device, wherein the battery device only comprises the functionalized nanomaterials as described above, thus, being capable of mainly avoiding compositions such as intercalation materials or mixtures comprising graphite and binder. The surface of the electrode nanoparticles is electrically conductive itself.

(28) In this embodiment, each the anode material and the cathode material comprise the functionalized nanoparticles (GSNP) having a dispersion of graphene, wherein the electrolyte material is a material with increased ionic conductivity, in particular, comprising the metal fluoride nanoparticles as described above without functionalization.

(29) FIG. 12 illustrates a further exemplary embodiment IVb of the battery device according to present invention. Herein, the battery device only comprises the functionalized nanomaterials as described above. The anode material and cathode material of the battery device in this particular embodiment comprise the functionalized nanoparticles (GSNP) with a dispersion of graphene, wherein the electrolyte material comprises nanotubes and/or additives selected from carbon-black, graphite, Si and/or CF.sub.x.

(30) Applying these electrodes and the electrolyte materials according to the present invention, thus, allows providing FIBs having a higher applicability and safety. The corresponding battery devices con be considered as 3D-solid state devices intrinsically having 2D highly mobile nanosurfaces.

(31) In FIG. 13 impedance results and NMR-spectrum of PbF.sub.2/SnF.sub.2 composites are presented proving a conductivity of 10.sup.−3 S/cm at 25° C. originating from an interplay of different phases of the nanoparticles, such as nanocrystallites, and corresponding highly mobile F-surface contributions.