Electrodeposition of tin and antimony-based anode materials for sodium-ion batteries
Patent Information
- Application Number
- PCT/US2026/023921
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-04-15
- Filing Date
- 2026-04-15
- Publication Date
- 2026-10-22
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Figure US2026023921_22102026_PF_FP_ABST
Abstract
Description
ELECTRODEPOSITION OF TIN AND ANTIMONY-BASEDANODE MATERIALS FOR SODIUM-ION BATTERIESGOVERNMENT SUPPORT CLAUSE
[0001] This invention was made with government support under Grant Number 2211067 awarded by the National Science Foundation. The government has certain rights in the invention.CROSS-REFERENCE TO RELATED APPLICATIONS
[0002] The present application claims the benefit of United States Provisional Patent Application Number 63 / 789,276 for “Electrodeposition Of Tin and Antimony-Based Anode Materials for Sodium-Ion Batteries”, which was filed on 15 April 2025, the entire content of which Patent Application is hereby specifically incorporated by reference herein for all that it discloses and teaches.BACKGROUND
[0003] The economic and ecological push for renewable energy production presents a challenge in developing grid storage technology. Large-scale electrochemical storage is required for grid-level energy storage, and rechargeable batteries are an attractive avenue for short-term energy storage.1The dominant battery technology, the lithium-ion battery (LIB), is unable to fully address this issue due to the scarcity of lithium.2A sodium-ion battery (NIB) uses the same working principle as LIBs but utilizes earth-abundant, low-cost sodium compounds instead of lithium compounds. However, as they differ in their charge carrier, the components that operate in LIBs are not functional for NIBs. The most common LIB anode, graphite, presents challenges for NIBs as the relative atomic size of sodium inhibits complete intercalation.3Exploring compatible anode materials for NIBs is necessary for their viability in the current and future markets.SUMMARY
[0004] In accordance with the purposes of the present invention, as embodied and broadly described herein, an embodiment of the method for electrodeposition of SnSb on a substrate, hereof, includes: preparing a solution containing a chosen concentration of Sn(II) ions and between 1.5 and 9 times the chosen concentration of Sn(II) ions of Sb(III) ions in an anhydrous solvent; inserting a conducting metal substrate into said anhydrous solution; and applying a potential of -0.7 V to -0.9 V vs. [Fe(CN)₆]3- / 4-to the conducting metal substrate at between 50° C and 80° C for sufficient time to form a thin film of crystalline SnSb alloy thereon.
[0005] In another aspect of the purposes of the present invention as embodied and broadly described herein, an embodiment of the method for generating an anode for a sodium-ion battery having a stable specific capacity, includes: preparing a solution containing a chosen concentration of Sn(II) ions and between 1.5 and 9 times the chosen concentration of Sn(II) ions of Sb(III) ions in an anhydrous solvent; inserting a conducting metal substrate into said anhydrous solution; and applying an electrodeposition potential of -0.7 V to -0.9 V vs. [Fe(CN)6]3‘ / 4‘ to the conducting metal substrate at between 50° C and 80° C for sufficient time to form a thin film of crystalline SnSb thereon.
[0006] Benefits and advantages of the present invention include, but are not limited to, providing a method for electrodeposition of crystalline SnSb alloy on a conducting metal substrate from an anhydrous ethaline solution, for use as a sodium-ion battery anode, and having greater capacity retention.BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The accompanying drawings, which are incorporated in and form a part of the specification, illustrate the embodiments of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:
[0008] FIGURE 1 shows graphs of the cyclic voltammetry of ethaline Sn-Sb deposition solutions, with (a) Sn solution composed of 50 mM SnCl2*2H2O; (b) 3Sn: Sb solution composed of 25 mM SbCh + 75 mM SnCh*2H2O; (c) SnSb solution composed of 50 mM SnCl2*2H2O + 50 mM SbCh; (d) Sn:3Sb solution composed of 75 mM SbCh + 25 mM SnCh; and (e) Sb solution composed of 50 mM SbCh, where Voltammetry was performed at 50 mV / s and 50.0 °C.
[0009] FIGURE 2(a) is a graph of the integrated chronoamperometry of ethaline SnSb deposition solution with 0, 5, 10, 15, and 20 wt.% water spiking, where the ethaline contains 50 mM SnCl2*2H2O, and 50 mM SbCh, the single-pulse chronoamperogram is performed at -0.8V vs [Fe(CN)₆]3- / 4-at a temperature of 50.0 °C for 60 s, such that as water is added, the current passed during chronoamperometry increases, corresponding to an increase in ionic conductivity of the metals through the solution, and FIG.2(b) is a graph of the cyclic voltammetry of ethaline SnSb deposition solution with 0, and 20 wt.% water spiking in an ethaline solution having 50 mM SnCl2*2H2O and 50 mM SbCh, with a scan rate of 50 mV / s at 50.0 °C, such that as water is added, the redox peaks increase in magnitude and shift to less negative potentials, indicating an increased rate of electron transfer between the electrode and the solution.
[0010] FIGURE 3 shows the powder X-ray diffraction of SnSb electrodeposited at -0.8V vs [Fe(CN)6]3’ / 4’ from ethaline with 0, 5, 10, 15, and 20 wt. % water spikes, at 50 °C.
[0011] FIGURE 4 shows the cyclic voltammetry of ethaline SnSb deposition solution at 50.0, 60.070.0 and 80.0 °C with a blue hue gradient, where the ethaline contains 50 mM SnCl2*2H2O, 50 mM SbCh, the scan rate is 50 mV / s, and the peak heights are seen to increase with increasing temperatures, indicating increasing solution diffusivity as the temperature is increased.
[0012] FIGURE 5 shows the powder X-ray Diffraction of SnSb electrodeposited from ethaline at different temperatures, where the electrodeposition is undertaken at -0.8 V vs.[Fe(CN)6]3 / 4- for 60 s.
[0013] FIGURE 6 shows Scanning Electron Microscope (SEM) images of films electrodeposited from ethaline baths having Sn, 3:1 Sn: Sb, SnSb, 1:3 Sn: Sb, and Sb stoichiometry, where all images were taken at 9000 X magnification at 10.0 mm working distance with compositions being denoted as the composition of the deposition bath, as surface roughness, inhomogeneity, and the presence of solid solutions impeded characterization of film stoichiometry, where Sn and Sn-rich deposits exhibit large grains and uneven surface coverage, while Sb and Sb-rich films exhibit small grains.
[0014] FIGURE 7 shows glancing angle X-ray diffraction (GAXRD) for Sn electrodeposited on Ni substrate, where the phases identified in the refinement were Sn (5.1 wt%) and Ni (94.9 wt%), with RWp = 6.35, and crystal size (Lorentzian) = 60.5 nm for Sn, Strain (L) = 8.06E-3.
[0015] FIGURE 8 shows the GAXRD for 3:1 Sn: Sb electrodeposited on Ni substrate, where phases are identified in the refinement as Sn (5.4 wt%), Sn0.6Sb0.4(11.2 wt%), and Ni (83.4 wt%), with Rwp = 7.86, values for Sn0.6Sb0.4, crystal size (Lorentzian) = 73.4 nm for Sn0.6Sb0.4, strain (L) = 0.307 for SnoeSbo4, the preferred orientation in Sn0.6Sb0.4from spherical harmonics (4thorder): yoo =1, yso = 0.336, y4o = 0.790, y43m = 0, the crystal size (Lorentzian) = 138.0 nm for Sn, strain (L) = 0 for Sn, and the preferred orientation in Sn from spherical harmonics (4thorder): yoo =1, y2o = 0.173, y4o = 7.13E-2, and y43m = 0.373.
[0016] FIGURE 9 shows the GAXRD for SnSb electrodeposited on a Ni substrate, where the phases identified in the refinement are SnSb (14.5 wt%), and Ni (85.5 wt%), the Rwp = 8.77, crystal size (Lorentzian) = 73.4 nm, strain (L) = 2.57E-2, strain (G) = 1.00E-4m, and the preferred orientation from spherical harmonics (4thorder): yoo = 1, y2o = 0.832, y4o = 0.424, and y43m = 0.
[0017] FIGURE 10 shows the GAXRD for Sn:3Sb electrodeposited on Ni substrate, where the phases identified in the refinement are Sb (2.7 wt%), Sn0.25Sb0.75(13.2 wt%), and Ni (84.1 wt%), the Rwp= 9.62, values for Sn0.25Sb0.75crystal size (Lorentzian) = 107.0 nm, for Sn0.25Sb0.75, strain (L) = 3.761308E-10, the preferred orientation of Sn0.25Sb0.75from spherical harmonics (4th order): yoo = 1, y2o = 0.832, y40 = 0.424, and y43m = 0, values for Sb: Crystal size (Lorentzian): 32.8 nm for Sb, strain (L) = 8.68E-2, strain (G) = 1.48, and preferred orientation of Sn0.25Sb0.75from spherical harmonics (4th order): yoo = 1, y2o = 0.520, y4o = 0, and y43m = 5.49E-2.
[0018] FIGURE 11 shows the GAXRD for Sb electrodeposited on Ni substrate where the phases identified in the refinement are Sb (11.4 wt%) and Ni (88.6 wt%), the Rwp = 10.21, the crystal size (Lorentzian) = 59.3 nm for Sb, Strain (L) = 0.500, and the preferred orientation of Sb from spherical harmonics (8thorder): yoo = 1, y2o = 1.54, y4o = 0.303, y43m = 0.354, yeo = 0.743, y63m = 0.546, yeep = 0, yso = 3.29E-006, ys3m = 0.315, and ysep = 0.
[0019] FIGURE 12 shows the cycle life analysis for Sn-Sb anode materials at different stoichiometric compositions, where the following compositions, Sn, Sb, 3:1 SnSb, 1:3 SnSb, and 1:1 SnSb, were cycled in a sodium half-cell at a rate of C / 2, the shaded circles describe the charge capacity, the outlined circles depict the discharge capacity, and the x’s correspond to the coulombic efficiency plotted against the y-axis on the right.
[0020] FIG 13 shows the differential capacity (dQ / dV) vs. potential (V vs. Na / Na+) of Sn and Sb alloys in a sodium ion half-cell, where (a) is Sn, (b) is 3:1 Sn. Sb, (c) is SnSb, (d) is 1:3 Sn: Sb, and (e) is Sb, and cells were cycled at 0.5 C for 275 cycles.DETAILED DESCRIPTION
[0021] As an alternative to intercalation anodes, alloying anode materials are promising with competitive theoretical capacities for NIBs.45Sn and Sb are both individually attractive alloying anode materials due to their high theoretical capacities with sodium (847 mAh / g and 660 mAh / g from the formation of Na₃.₇₅Sn and Na₃Sb, respectively).6However, high-volume expansion during sodiation (420% for Sn and 380% for Sb, for example)6-8by alloying anodes must be accommodated. Tin antimonide (SnSb) is an anode of interest due to its high theoretical capacity (742 mAh / g) and stability. The theoretical overall reaction of SnSb with sodium is:and together, Sn and Sb have been shown to increase the overall cycle lifetimes of NIBs when compared to Sn or Sb alone.9Sputtering, bulk synthesis methods, and nanoparticle methods have been successfully employed in a number of studies9-23to synthesize tin and antimony-based anodes for battery applications. An example of a microscale synthesis was described by Yi et al., where hollow Sn-Sb spheres were generated using a displacement reaction between Sn powder and SbCh dissolved in ethanol.11Carbonaceous species have also been utilized in conjunction with tinantimonide through ball milling, electrospinning, template-assisted freeze drying, and carbothermal reduction.10-19,23The principal drawback to this type of synthesis is that it introduces binders and a degree of inhomogeneity.24DC and / or RF magnetron sputtering has been used to create films with control over stoichiometry.9'20-22
[0022] Electrodeposition-based synthesis, is scalable, reproducible, and does not depend on the introduction of carbonaceous binders.2425In Chem. Commun. 55, 6938- 6941 (2019)26(hereinafter, Ma et al.) an electrodeposition solution was developed for the electrochemical deposition of SnSb. Several variables were subsequently found by the present inventors to be sensitive. Specifically, films were forming sparse, uneven deposits in quantities much smaller than anticipated with these solutions, and it was found that the solution using a deep eutectic solvent was sensitive to deposition temperature, water incorporation, and the chosen reference electrode.
[0023] Deep eutectic solvents (DES) are regarded as an ionic liquid analog for their similar conductive properties and tunable chemistry.27The deep eutectic solvent used in embodiments of the present invention, ethaline, is a DES which is formed from the combination and complexation of quaternary ammonium salts (choline chloride as used herein) with hydrogen bond donors (ethylene glycol as used herein). The complexation creates an equilibrium where the chloride is dissociated from the ammonium, creating a highly conductive solvent with a large electrochemical window.28Because of the anhydrous nature of the solvent, electrodepositions can proceed at larger potentials than in aqueous systems without concern for H₂ gas evolution and subsequent passivation of the surface with oxides and hydroxides.29Despite these advantages, the viscosity of ethaline is an issue regarding room temperature electrodeposition30(40-80 cP)31, while aqueous electrodeposition baths, without bulky organic additives, tend to have viscosity values <1 cP32. An inverse correlation in ionic conductivity of several DES liquids, including ethaline has been identified, based on the viscosity of the solution.30Therefore, the viscosity was likely inhibiting electrodeposition, and methods for increasing the ionic conductivity of the dissolved metal ions are investigated.263334
[0024] Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. It will be understood that the FIGURES are presented for the purpose of describing particular embodiments of the invention and are not intended to limit the invention thereto.
[0025] Thin film materials of SnSb were selected using compositionally controlled electrodeposition, with results being applicable to a wide range of the SnSb phase space through stoichiometric control of the SnSb electrodeposition solution. The electrodeposition of crystalline SnSb was optimized by increasing the solution temperature, monitoring the stir rate, and minimizing water incorporation. Once synthesis parameters were established, we investigated the effects of solution stoichiometry on film composition and morphology, and electrochemical cycling studies were conducted to identify optimal stoichiometries for Sn and Sb in a NIB system.
[0026] Other suitable anhydrous solvents include a deep eutectic solvent with Urea instead of ethylene glycol (a 2:1 molar mixture of urea and choline chloride), a deep eutectic solvent with glycerol instead of ethylene glycol (a 2:1 molar mixture of glycerol and choline chloride), Other sources of tin ions include Tin (II) sulfate, Potassium stannate, Sodium Stannate, Tin (II) oxide, and Tin (II) pyrophosphate, and other sources of antimony ions include Antimony (III) Oxide, and Antimony (III) sulfate.
[0027] A. Preparation of Ethaline Deposition Solution
[0028] All glassware involved in synthesis was oven-dried overnight. Choline chloride (Acros Organics, 99%) was recrystallized in absolute ethanol, vacuum filtered, then left in a vacuum oven at 110°C overnight. Water was distilled off ethylene glycol (Fisher Scientific, 99.8%) in a simple distillation apparatus. Ethylene glycol and choline chloride were combined in a 2:1 molar ratio, respectively. The solution was mixed at 80 °C for 3-6 hours while vigorously stirring. Antimony (III) chloride (SbCh, Sigma Aldrich, >99.0%, 50 mM) and tin (II) chloride dihydrate (SnCl2*2H2O, Sigma Aldrich, 98%, 50 mM) were added to the ethaline solution and heated at 80 °C while vigorously stirring for roughly 20-30 min. (until mostly dissolved) then sonicated for 5 min. to ensure dissolution. Solutions were used within one week of preparation and stored in a sealed container.B. Electrodeposition Parameters
[0029] All electrochemical measurements of ethaline deposition solutions were performed using a Gamry Reference 3000 Potentiostat and analyzed using Gamry Analyst software. A water-circulating jacket beaker was used to bring the ethaline solution to 80 °C. Cyclic Voltammetry (CV) was performed using a three-electrode apparatus, having a platinum working electrode and platinum mesh counter electrode. Scans were conducted at 50 mV / s and started at 0 V vs. Fe(CN)₆3- / 4-, proceeding to-1.25 V for the initial sweep, followed by a positive sweep to 1 V, and a sweep to return to 0 V.
[0030] The reference electrode was a homemade reference electrode following a previous synthesis.35Briefly, the reference was made using a 2.5 mM potassium ferricyanide (K₃Fe(CN)₆, Fisher Scientific, 98%) combined with 2.5 mM potassium hexacyanoferrate (II) trihydrate (K₄Fe(CN)₆*3H₂O, Oakwood chemical, 98%) and dissolved in ethaline. Electrodepositions were performed using a single-step chronoamperogram for 60 s at -0.9V vs. [Fe(CN)₆]3- / 4-on a nickel substrate with an area of 3.00 cm2at 80 °C. A1 / 2” stir bar was placed at the bottom of the 50 mL heating jacket for stirred electrodepositions. After the films were deposited, they were immediately removed from the electrodeposition solution and thoroughly rinsed with ethanol, water, and then ethanol.C. Half-Cell Assembly and Galvanostatic Cycling
[0031] All electrolyte preparation and half-cells were assembled in an argon glovebox (<1 ppm O2) using a two-electrode Swagelok apparatus. Each electrodeposited film was cut into a ” diameter circle as the active material, and theoretical capacity was calculated using Faraday’s law of electrolysis to calculate deposition mass. The cut thin film was used as the working electrode, followed by a polypropylene separator (MTI Corp), then a Whatman glass filter paper, and another polypropylene separator. After this, ~20 pL of electrolyte was added, followed by a %” punch of sodium metal polished with dry hexanes before use. The electrolyte consisted of a 1M solution of sodium perchlorate (NaClO₄, Sigma-Aldrich, >98% ACS reagent) in propylene carbonate (PC, Sigma Aldrich, 99.7%) with a 5% by volume addition of fluoroethylene carbonate (FEC, Sigma-Aldrich, 99%). Cells were allowed to rest for 12 h before galvanostatically cycling with an Arbin battery tester between 0.005 V and 1.5 V vs. Na / Na+at a C / 2 rate in room temperature (25 °C). A C-rate was assigned based on the theoretical capacity of each anode.D. Characterization
[0032] The morphology of electrodeposited films was analyzed by Scanning Electron Microscopy (SEM) using a JEOL JSM-6500F Microscope at 15 kV, and Energy Dispersive X-ray Spectroscopy (EDS) with an Oxford instrument X-Max and Aztec Software. Crystalline phases were identified via Powder X-ray Diffraction (PXRD) using a Bruker D8 Discover DaVinci powder X-ray Diffractometer using Cu Ka radiation, and a 0.2 mm slit opening. X-ray Photoelectron Spectroscopy was performed with a Physical Electronics (PHI) 5800 series Multi-Technique ESCA system with a monochromatic Al Ka (hv = 1486.6 eV) X-ray source operating at 350.0 W.
[0033] For the compositional films (Sn, 1:3 Sn:Sb, SnSb, 3:1 Sn: Sb, and Sb), glancing angle X-ray diffraction was utilized on a Bruker D8 Discover Series II Thin Film Diffractometer using Cu Kα radiation and a 0.100 mm detector slit opening. Theta values used were between 1 and 3 °, which was decided by optimizing the signal from the
[0100] peak in Sn and the
[0101] plane in the remaining samples: Sn: 2.260 °q, 1:3 Sn: Sb: 2.114 °q, SnSb: 2.114 °q, 3:1 Sn: Sb: 1.538 °q, Sb: 1.987°q. Rietveld refinements were carried out using TOPAS v6 software. Quantification of Sb and Sn atomic percentages were evaluated with Rietveld refinements in conjunction with elemental mapping via EDS.
[0034] Rietveld refinements set forth in TABLE 1 were performed using an instrument function convoluted with a Voigt function. The fitting process started with a fit of the Ni substrate with spherical harmonics. This proceeded with a fit of one of the predicted active materials PDFs (Powder Diffraction Files used for assigning crystalline phases), which did not include corrections for strain or preferred orientation. The homogenous strain was then included in the next fit (both Lorentzian and Gaussian). Once the above parameters were included, preferential orientation was accounted for. It was predicted that these films would have some degree of both anisotropic strain and preferential orientation. Preferential orientation was accounted for using Spherical Harmonics2 and Anisotropic strain was accounted for using the Stephens Model.TABLE 1: Rietveld refinement values of Sn-Sb samples.E. Evaluating Electrodeposition parameters for SnSb
[0035] Before evaluating the importance of specific synthetic variables of the deposition solution, the redox phenomena of the electrodeposition bath were identified using cyclic voltammetry. Cyclic voltammetry was used throughout this study to evaluate solution conditions between depositions. A representative cyclic voltammogram of Sn, Sb, and SnSb electrodeposition solutions are shown in FIG. 1 to illustrate (i) how the electrodeposit potential was chosen, and (ii) the redox phenomena that were probed and how they correspond to tin and antimony salts in the solution. For the cyclic voltammogram of the SnSb electrodeposition solutions, the reduction of Sb appears to comprise two peaks, which implies that the reduction from Sb(III) to Sb(0) occurs over multiple steps. The oxidation peaks at ~-0.1 V vs [Fe(CN)6]3 / 4’ for Sb also exhibit this feature, indicating separate oxidation steps. The peaks seen at higher potentials, based on compositional scans, were assigned as the conversion between Sb(III) and Sb(V), as well as the conversion between Sn(II) and Sn(IV) (FIG. 1). These preliminary scans were used to assign deposition potentials sufficiently beyond the reduction potential of Sn. Based on the peak reduction potential of Sn maximizing at ~0.75 V vs. [Fe(CN)6]3- / 4-, a reduction potential of -0.8 V vs. [Fe(CN)6]3 / 4‘ was used for chronoamperometry. While this potential resulted in the deposited tin antimonide, surface coverage improved when the reduction potential was changed to -0.9 V vs. [Fe(CN)6]3' / 4‘. It was found that between -0.7 V and -0.9 V vs. [Fe(CN)6]3 / 4-gave desired electrodeposition results.
[0036] With the cyclic voltammetry of tin and antimony salts having been introduced, the synthetic variables for increasing ionic conductivity are studied. Ma et al.26first studied the electrodeposition of SnSb from ethaline, but in attempting to reproduce this electrodeposition, no Sn or Sb species could be identified. Because of the increased viscosity exhibited in ethaline relative to aqueous electrodeposition solvents, the low ionic conductivity of metal salts was suspected to be inhibiting the electrodeposition of SnSb. To optimize the ionic conductivity for electrodeposition, water spiking, temperature, and stirring as variables were investigated as each of these methods increase the mobility of ions in solution.(a) Water Spiking
[0037] The influence of water incorporation in ethaline has been investigated with mixed results.28’3637The hygroscopicity of ethaline at atmospheric conditions over time found that the electrochemical stability of ethaline decreased with water adsorption.37While water has been found to reduce the electrochemical stability window of ethaline, the influence of water spiking on the electrochemical stability window and the solvation dynamics of the solution does not change significantly with up to 10 wt.% added water.36In fact, it was found that solution viscosity decreased, and solvation dynamics were enhanced with increasing amounts of water (below 10 wt. % and above 1 wt.%). In order to investigate the influence of water on the electrodeposition of SnSb, water was added to the electrodeposition solution as a method for lowering solution viscosity. Water spiking tests were performed, where pristine ethaline solutions were spiked with 0, 5, 10, 15, and 20 wt.% water. Cyclic voltammetry was used to probe redox events in the solution as water was added (FIG. 2). The current of the reduction peaks produced at -0.3 and - 0.55 V vs. [Fe(CN)6]3- / 4-increased as the water was added due to the decrease in solution viscosity. Additionally, the reduction potential for Sn(II) and Sb(III) decreased in magnitude, indicating an increased electron transfer rate between the electrode and the solution. The integrated chronoamperometry of the SnSb samples electrodeposited from ethaline with water added show an increase in the charge passed water as water is increased, indicating that increased mass transfer could be occurring.
[0038] While the addition of water appears to have increased the ionic conductivity throughout the solution, all SnSb samples deposited from ethaline spiked with water immediately became dendritic, as seen by qualitative “scratch testing.” This resulted incrystalline SnSb (FIG. 3), but the dendritic morphology can be detrimental to film stability and robustness, and thus this method was not further employed to increase the overall ionic conductivity.(b) Temperature Elevation
[0039] Elevated temperatures (above room temperature) as a parameter were investigated for increasing metal ionic conductivity during electrodeposition. A study of the effect of elevated temperatures on ethaline for extended periods of time found that the optimal time to heat ethaline for full incorporation was between 3h - 9 h at 70.0 °C. After 9 hours, the choline chloride crashed out of the solution.37This was attributed to a deviation from the eutectic phase brought on by evaporation of the ethylene glycol. Because of this limitation, all solutions were heated for no longer than 6 h, whereby depositions could be carried out at elevated temperatures. Increasing the ethaline electrodeposition solution temperature appears to increase diffusion as displayed in the increased peak current in the cyclic voltammetry studies of FIG. 4. Homogeneous crystalline films of SnSb having even surface coverage were formed for each of the electrodepositions between 50 °C and 80 °C (FIG. 5), and increased electrodeposition temperature was identified as an important variable for increasing ionic conductivity of the electrodeposition solution.(c) Bath Stoichiometry
[0040] Changing the stoichiometry of the electrodeposition bath resulted in not only thin film compositions generally having the stoichiometry of the film matching the starting ratio, but also resulted in varied morphologies across samples (FIG. 6). When comparing the morphology among the Sn-Sb films, a general trend was noted where grain sizes were much larger for samples containing Sn and gradually got smaller with increasing amounts of Sb. This is supported by the reported brightening effect ethaline has on Sb.38The pure Sn sample exhibits large grains (ca. 0.5 pm diameter) with inhomogeneous surface coverage. This effect was first identified in a study on the electrodeposition of Sn from ethaline with and without carbon nanotubes.39It is expected by the present inventors that films having between 1.5 and 9 times the quantity of Sn of Sb would have greater capacity retention than 1:1 SnSb.
[0041] For the films with both Sn and Sb, stoichiometry was approximately quantified with elemental dispersive X-ray spectroscopy (EDS) and summarized in Table 2. In the case of the films deposited from 3:1 Sn. Sb electrodeposition bath, a thin film with large, island-like crystals was observed with a rough stoichiometry of ~2.6 Sn: Sb, as well as a thin surface coating with faint Sn and Sb signals. A more detailed description of the quantification results from EDS can be found in Table 2 and Table 3. The films electrodeposited from the 1:1 and the 1:3 Sn: Sb electrodeposition baths were more homogeneous, with EDS measuring relative stoichiometries as 1:1 and 1:2.3 Sn: Sb stoichiometry, respectively. With the crystal structures of both SnSb and Sb exhibiting rhombohedral symmetry, it is likely these form a solid solution of SnSb / Sb. To better understand the composition of these films, Rietveld refinements were pursued from X-ray diffraction (FIG. 7-FIG. 11).Table 2. Measured Atomic Concentrations of Sn and Sb from Compositional Samples.Table 3. Tabulated EDS Data of Sn, 3Sn: Sb, SnSb, Sn:3Sb and Sb depositions.Table 4. Tabulated EDS Data of 3Sn: Sb deposition. Spot-specific averages, fr=or spots denoted in FIG 7..
[0042] Rietveld refinements follow in line with the compositions identified in EDS mapping, and these compositions generally align with the bath stoichiometry (Table 2). XRD identified mixed phases in the 1:3 Sn: Sb 3:1 Sn: Sb samples. For 1:3 Sn: Sb, an Sb phase and a Sn0.25Sb0.75solid-solution phase was identified, whereas the 3:1 Sn: Sb film XRD identified a Sn and a Sn0.6Sb0.4solid-solution phase. The presence of solid solutions, as well as the mixed phases of these Sn-Sb films, could influence how these materials operate as anode materials.F. Evaluation of Sn-Sb thin-films in Na-ion Half-Cells.
[0043] Once deposition parameters were established, the as-deposited SnSb and Sn- Sb thin films could be studied as anode materials in Na-ion batteries. To study the performance and lifetime of the compositions and identify trends between samples, compositionally controlled films were cycled in sodium-ion half-cells (a 2-electrode cell having sodium metal as the counter electrode). This configuration was used to isolate electrochemical phenomena to the working electrode. Comparison between the differential capacity curves associated with each cell identified peaks correlating to cell death and solid electrolyte interphase (SEI) formation.
[0044] The Sn, 1:3 Sn: Sb, 1:1 Sn: Sb, 3:1 Sn: Sb, and Sb films were cycled at 0.5 C to study the lifetime of each film as an anode. The anode that was found to have the greatest capacity retention over 275 cycles (where one cycle is a galvanostatic charge and discharge between 0.01 and 1.5 V vs. Na / Na+) was the 1:3 Sn: Sb film. Each alloy cell had a steady decline in capacity over the total lifetime, while the Sb barely approached a precipitous death during the final ~75 cycles (FIG. 12). For the films containing both Sn and Sb, the capacity retention over 275 cycles increased as more Sb was added. The increased capacity retention exhibited in Sb-containing anodes could be due to properties of the anode itself, for example, how well the material adheres to the substrate, the grain size of the crystalline material, solid-state sodium diffusion mechanisms, perhaps from the presence of mixed phases between SnSb and Sb.
[0045] During battery cycling, electrolytes used in the battery tend to reduce at the surface of the anode, creating an interphase region between the anode and the electrolyte called the Solid Electrolyte Interphase (SEI). The SEI can provide a stable passivation layer between the electrode and electrolyte which inhibits further electrolyte reduction, but if the electrolyte is ill-suited for the anode material, the SEI that forms might not be passivating (leading to increased electrolyte reduction and often decreases in charge capacity), or it could inhibit the diffusion of sodium ions, which limits the power density of the battery. Sn alone was found to performed poorly, which might indicate that the chosen electrolyte was ill-suited for Sn. These cells were cycled using a carbonate-based electrolyte, which has been shown to be detrimental to SEI formation in Sn anodes.4041However, for the present system, the 1:3 SnSb exhibited the greatest capacity retention over 275 cycles.
[0046] Differential capacity curves were conducted to identify theoretical sodiation and desodiation mechanisms of SnSb and to find correlations between electrochemical events and capacity fade. Differential capacity plots of Sn, 1:3 Sn. Sb, SnSb, 3:1 Sn. Sb, and Sb thin films were conducted to look for common patterns in capacity fade as well (FIG. 13). In particular, the mechanisms involved in sodiation and desodiation for the samples containing both Sn and Sb are of interest, as these may provide context for the increased capacity retention exhibited in the 1:3 Sn: Sb material. The differential capacity of the samples with both Sn and Sb reveals similar peak locations to that of SnSb, indicating that the mixed-phase samples undergo similar electrochemical phenomena (FIG. 13). The sodiation and desodiation mechanisms of SnSb are not yet fully understood, but there have been many different approaches to characterizing the intermediate phases seen in SnSb during cycling, for example, X-ray diffraction, transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS), Mössbauer spectroscopy, Scanning Electron Microscopy (SEM), and in-situ Raman studies have each provided insight into this mechanism.20-224243A generalized trend taken from the observed sodiation and desodiation transformations of SnSb is as follows. First, sodium reacts with Sb, creating a broad peak at ~0.7 V, and leaving an amorphous (a-) Sn phase:SnSb + 3Na++ 3e−——→ a-Sn + Na3Sb . (i) At higher potentials, Sn is sodiated to create an amorphous Na-Sn phase, resulting in a broad peak ~0.5 V vs Na / Na+. During the first cycle, there is a large peak at ~0.5 V vs Na / Na+, which is attributed to irreversible reduction of the electrolyte on the surface of the anode which forms the Solid Electrolyte Interphase (SEI). This phase continues to sodiate until reaching a crystalline (c-) Na15Sn4phase, resulting in a peak ~0.3 V vs Na / Na+:Na3Sb + a-Sn + xNa++ xe−——→ a-NaxSn + Na3Sb . (ii) where x is less than 3.7, and represents the stoichiometric amount of Na incorporated before achieving the crystalline (c-) Na15Sn4phase:a-NaxSn + (15 − x)Na++ (15 − x)e−——→ c-Na15Sn4+ Na3Sb . (iii) There are reports indicating that Sn and Sb create a ternary phase during sodiation, however, the amorphous nature of the intermediate phases makes it difficult to identify.21 22
[0047] Desodiation begins with the desodiation of Sn, generating an amorphous Sn phase, which would correspond to the two peaks at -0.1 -0.3 V vs Na / Na+, followed by two additional peaks at -0.5 and -0.65 V vs Na / Na+.c-Na15Sn4+ Na3Sb ——→ a-Sn + a-NaxSn + yNa++ ye−(iv)Na3Sb + a-NaxSn ——→ a-Sn + Na3Sb + xNa++ xe−(v)The Sb phase is desodiated, generating a partially reformed SnSb anode.20This process begins at ~0.6 V vs Na / Na+in the Sb alone, creating a sharp peak followed by a shoulder. However, in the SnSb sample, this process is more convoluted with the Sn desodiation peaks, creating a broad set of overlapping peaks -0.5-1.2 V vs Na / Na+:a-Sn + Na3Sb ——→ SnSb + 3Na+. (vi)
[0048] In the cases of 1:3 Sn: Sb and 3:1 Sn: Sb, the differential capacity plots exhibit similar structural features, indicating they go through similar transformations. One pattern seen across the samples with both Sn and Sb is that the sodiation and desodiation peaks -0.15-0.3 V vs Na / Na+decrease in magnitude over time. These peaks correspond to the formation and deformation of Na15Sn4, and it has been observed in other Sn-based anodes44that this transformation is destabilizing. This might explain why the capacity retention is highest in the 1:3 Sn: Sb anode, as the smaller amount of Sn could be less destabilizing for the material upon full sodiation. However, when contrasting the 1:3 Sn: Sb with Sb alone, the Sn could be offering a stabilizing effect at lower potentials during Sb sodiation and desodiation.
[0049] In summary, SnSb and Sn-Sb alloys were electrodeposited from ethaline, and it was identified that the viscous nature of ethaline was inhibiting electrodeposition. Attention was then given to increasing ionic conductivity, where it was found that electrodepositing SnSb at elevated temperatures (between 50 and 80 °C) was effective in electrodepositing crystalline SnSb by increasing ionic conductivity. Water was found to be detrimental to SnSb electrodeposition from ethaline, as films electrodeposited from ethaline with water added were dendritic and poorly-adhered. After synthesis parameters were established for SnSb, Sn, Sb, Sn-rich and Sb-rich SnSb samples were deposited and cycled in sodium half-cells, which were compared to 1:1 SnSb, and Sn and Sb alone. The sample with 1:3 Sn: Sb retained the highest specific capacity after 275 cycles, followed by Sb. Many factors could be responsible for the increased capacity retention exhibited in the 1:3 Sn: Sb anode, including the smaller grain size and homogeneity of thefilm relative to the greater Sn-rich compositions, or mechanical factors of Sn and Sb sodiation mechanisms. Additionally, the role of the chosen electrolyte cannot be dismissed. It has been well established that for high energy anodes, where volume expansion remains a critical factor in storage capacity, the solid electrolyte interphase plays a significant role in secondary battery longevity.45-48For example, Sn has been shown to operate with greater capacity retention in glyme-based electrolytes compared to carbonate electrolytes.849’50However, this is not the situation for antimony, which exhibits poor capacity retention in glyme-based electrolytes.5051
[0050] The foregoing description of the invention has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.ReferencesJ. A. Jorgenson, W. Frazier, P. Denholm, and N. Blair, Grid Operational Impacts of Widespread Storage Deployment., National Renewable Energy Laboratory, Golden, CO, (2022), p. NREL / TP-6A40-80688.Y. Tian et al., Chem. Rev., 121, 1623-1669 (2021).H. Moriwake, A. Kuwabara, C. A. J. Fisher, and Y. Ikuhara, RSC Adv, 7, 36550-36554 (2017).J. Deng, W. B. Luo, S. L. Chou, H. K. Liu, and S. X. Dou, Adv. Energy Mater., 8 (2018). H. S. Hirsh et al., Adv. Energy Mater, 10, 2001274 (2020).W. T. Jing, C. C. Yang, and Q. Jiang, J. Mater. Chem. A, 8, 2913-2933 (2020).J. He, Y. Wei, T. Zhai, and H. Li, Mater Chem Front, 2, 437-455 (2018).B. Zhang et al., Adv. Mater, 28, 9824-9830 (2016).W. P. Kalisvaart, H. Xie, B. C. Olsen, E. J. Luber, and J. M. Buriak, ACS Appl. Energy Mater, 2, 5133-5139 (2019).W. Brehm, J. R. Buchheim, and P. Adelhelm, Energy Technology, 7, 1900389 (2019). Z. Yi et al., J. Power Sources, 342, 861-871 (2017).J. S. Gutierrez-Kolar et al., ACS Appl. Energy Mater, 2, 3578-3586 (2019).Z. Yuan et al., ACS Appl. Nano Mater, 4, 826-833 (2021).M. Walter, S. Doswald, and M. V. Kovalenko, J. Mater. Chem. A, 4, 7053-7059 (2016).. Song, G. Wang, Y. Chen, Y. Lu, and Z. Wen, Chem. Eng. J., 463, 142289 (2023). H. Jia et al., ACS Appl. Mater. Interfaces, 10, 9696-9703 (2018).. Jena et al., J. Alloys Compd., 854, 157238 (2021)..-H, Choi, C.-W. Ha, H.-Y. Choi, and S.-M. Lee, J. Ind. Eng. Chem., 60, 451-457 (2018).. Chen et al., RSC Adv., 5, 30793-30800 (2015).. Xie et al., ACS Energy Lett., 3, 1670-1676 (2018).. Ma et al., Nano Energy, 54, 349-359 (2018).. Baggetto et al., J. Power Sources, 267, 329-336 (2014).. Shiva, H. B. Rajendra, and A. J. Bhattacharyya, ChemPlusChem, 80, 516-521 (2015).. Nieto, N. J. Gimble, L. J. Rudolph, A. R. Kale, and A. L. Prieto, J. Electrochem. Soc., 69, 050537 (2022).K. Nieto et al., J. Phys. Chem. C, 127, 12415-12427 (2023).J. Ma and A. L. Prieto, Chem. Commun., 55, 6938-6941 (2019).E. L. Smith, A. P. Abbott, and K. S. Ryder, Chem. Rev., 114, 11060-11082 (2014). S. Kaur, A. Malik, and H. K. Kashyap, J. Phys. Chem. B, 123, 8291-8299 (2019).L. F. Audrieth and H. W. Nelson, Chem. Rev., 8, 335-352 (1931).A. P. Abbott, R. C. Harris, and K. S. Ryder, J. Phys. Chem. B, 111, 4910-4913 (2007). Y. Zhang et al., J. Phys. Chem. B, 124, 5251-5264 (2020).A. P. Abbott et al., Electrochimica Acta, 176, 718-726 (2015).L. Fathyunes and J. Khalil-Allafi, Ultrason. Sonochem., 42, 293-302 (2018).C. Sun, J. Zeng, H. Lei, W. Yang, and Q. Zhang, ACS Sustain. Chem. Eng., 7, 1529-1537 (2019).X. Shen, N. Sinclair, J. Wainright, R. Akolkar, and R. F. Savinell, J. Electrochem. Soc., 167, 086509 (2020).I. Alfurayj et al., J. Phys. Chem. B, 125, 8888-8901 (2021).J. R. Brusas and E. M. B. Dela Pena, J. Electrochem. Sci. Techno!., 12, 387-397 (2021). X.-Z. C. Hao Wang Xiang-Xin Xue, Journal of Electrochemistry, 28, 2103071 (2022). A. T. S. C. Brandao et al., Coatings, 9, 798 (2019).B. Zhang et al., Advanced Materials, 28, 9824-9830 (2016).B. Qin et al., ACS Appl. Mater. Interfaces, 12, 3697-3708 (2020).M. Fehse et al., J. Mater. Chem. A, 6, 8724-8734 (2018).A. Darwiche, M. T. Sougrati, B. Fraisse, L. Stievano, and L. Monconduit, Electrochem. Commun., 32, 18-21 (2013).T. Li et al., ACS Appl. Energy Mater., 2, 860-866 (2019).X. Du, Y. Gao, and B. Zhang, Adv. Fund. Mater., 31, 2102562 (2021).E. Olsson et al., Small Weinh. Bergstr. Ger., 18, e2200177 (2022).Y. Gao and B. Zhang, Adv. Mater., 35, 2205421 (2023).U. S. Meda, L. Lal, S. M, and P. Garg, Journal of Energy Storage, 47, 103564 (2022).. Huang et al., Energy Environ. Sci., 12, 1550-1557 (2019).50. B. Qin et al., ACS Appl Mater Interfaces, 12, 3708 (2020).51. K. Pfeifer et al., ChemElectroChem, 7, 348227–3495 (2020).
Claims
[0051] WHAT IS CLAIMED IS:
1. A method for electrodeposition of SnSb on a substrate, comprising:preparing a solution containing a chosen concentration of Sn(II) ions and between 1.5 and 9 times the chosen concentration of Sn(II) ions of Sb(III) ions in an anhydrous solvent;inserting a conducting metal substrate into said anhydrous solution; and applying a potential of -0.7 V to -0.9 V vs. [Fe(CN)6]3’ / 4' to the conducting metal substrate at between 50° C and 80° C for sufficient time to form a thin film of crystalline SnSb thereon.
2. The method of claim 1 wherein said anhydrous solvent comprises a mixture of choline chloride and ethylene glycol.
3. The method of claim 2, wherein said mixture of choline chloride and ethylene glycol is a deep eutectic mixture.
4. The method of claim 1, wherein the electrodeposition potential is -0.9 V vs.[Fe(CN)6]3- / 4-.
5. The method of claim 1, wherein said chosen concentration of Sn(II) ions and the Sb(III) ions are present in a ratio of 1:3.
6. The method of claim 1, wherein said Sn(II) ions and said Sb(III) ions are derived from Sn(II) chloride and Sb(III) chloride.
7. The method of claim 1, wherein the conducting metal substrate comprises a nickel substrate.
8. The method of claim 1, wherein the temperature of electrodeposition is 80° C.
9. The method of claim 1, wherein the electrodeposition is performed for 60s.
10. The method of claim 1, wherein said anhydrous solvent is chosen from a deep eutectic mixture of urea and choline chloride, and a deep eutectic mixture of glycerol and choline chloride.
11. The method of claim 1 wherein said Sn(II) ions and said Sb(III) ions are derived from compositions chosen from Sn(II) sulfate, Sn(II) pyrophosphate, potassium stannate, sodium stannate, and Sb(III) sulfate.
12. A method for generating an anode for a sodium-ion battery having a stable specific capacity, comprising:preparing a solution containing a chosen concentration of Sn(II) ions and between 1.5 and 9 times the chosen concentration of Sn(II) ions of Sb(III) ions in an anhydrous solvent;inserting a conducting metal substrate into said anhydrous solution; and applying an electrodeposition potential of -0.7 V to -0.9 V vs. [Fe(CN)6]3 / 4‘ to the conducting metal substrate at between 50° C and 80° C for sufficient time to form a thin film of crystalline SnSb thereon.
13. The method of claim 12 wherein said anhydrous solvent comprises a mixture of choline chloride and ethylene glycol.
14. The method of claim 13, wherein said mixture of choline chloride and ethylene glycol is a deep eutectic mixture.
15. The method of claim 12, wherein the electrodeposition potential is -0.9 V vs.[Fe(CN)6]3- / 4-.
16. The method of claim 12, wherein said chosen concentration of Sn(II) ions and said Sb(III) ions are present in a ratio of 1:3.
17. The method of claim 12, wherein said Sn(II) ions and said Sb(III) ions are derived from Sn(II) and Sb(III) chlorides.
18. The method of claim 12, wherein the conducting metal substrate comprises a nickel substrate.
19. The method of claim 12, wherein the temperature of electrodeposition is 80° C.
20. The method of claim 12, wherein the electrodeposition is performed for 60s.
21. The method of claim 12, wherein said anhydrous solvent is chosen from a deep eutectic mixture of urea and choline chloride, and a deep eutectic mixture of glycerol and choline chloride.
22. The method of claim 12 wherein said Sn(II) ions and said Sb(III) ions are derived from compositions chosen from Sn(II) sulfate, Sn(II) pyrophosphate, potassium stannate, sodium stannate, and Sb(III) sulfate.