Alloying of negative-electrode active material for sodium ion energy storage device, and method for the same

Abstract

To provide a negative-electrode active material for a sodium ion energy storage device, having improved volumetric capacitance, capacity retention rate and coulomb efficiency, and a method for forming a negative electrode film.SOLUTION: A sodium ion energy storage device comprises a positive electrode, an electrolyte containing a sodium salt, and a negative electrode including a composite negative-electrode active material. The composite negative-electrode active material contains a carbon active material and an alloying element selected from the group consisting of phosphorus (P), germanium (Ge), stannum (Sn), antimony (Sb), plumbum (Pb), bismuth (Bi), and a combination of them.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS All applications for which a foreign or domestic priority claim is identified in the Application Data Sheet or PCT patent application filed with this application are incorporated herein by reference under 37 CFR 1.57 and Rules 4.18 and 20.6. This application claims the benefit of U.S. Provisional Application No. 63 / 633,506, filed April 12, 2024, the entire contents of which are incorporated by reference for all purposes.

[0002] The present disclosure relates generally to energy storage devices, and more particularly to negative electrode active materials for sodium-ion energy storage devices and processes for forming the same. [Background technology]

[0003] Energy storage devices are widely used to power electronic, electromechanical, electrochemical, and other useful devices. Such cells include primary chemical cells, secondary (rechargeable) cells, fuel cells, and various types of capacitors, including ultracapacitors. Currently, lithium-ion batteries ("LIBs") are widely used as power sources for electronic devices. However, the availability of lithium is limited on Earth. The abundant abundance of sodium (Na) and its ability to be used as the basis for energy storage devices make it an attractive alternative to Li. However, one obstacle to more widespread use is the still-limited volumetric energy density of sodium-ion batteries compared to that of lithium-ion batteries. For example, the volumetric capacity of a typical Na-ion battery anode, such as hard carbon, is approximately 450 mAh / cm. 3 is limited to less than.

[0004] Therefore, a sodium ion energy storage device with improved volumetric energy density would be advantageous. Summary of the Invention

[0005] For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention are described herein. Not all such objects or advantages may be achieved in any particular embodiment of the invention. Thus, for example, those skilled in the art will understand that the invention may be embodied or implemented to achieve or optimize one or more advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

[0006] All of these embodiments are intended to be within the scope of the invention disclosed herein. These and other embodiments will become readily apparent to those skilled in the art from the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings, and it is to be understood that the invention is not limited to any particular preferred embodiment disclosed.

[0007] In one aspect, a composite anode active material for a sodium-ion energy storage device is disclosed, which comprises a carbon active material and an alloying element selected from the group consisting of phosphorus (P), germanium (Ge), tin (Sn), antimony (Sb), lead (Pb), bismuth (Bi), and combinations thereof.

[0008] In some embodiments, the composite negative electrode active material comprises about 5% to 95% by weight of carbon active material. In some embodiments, the composite negative electrode active material comprises about 5% to 95% by weight of an alloying element. In some embodiments, the alloying element is selected from the group consisting of P, Pb, Sn, and combinations thereof. In some embodiments, the alloying element comprises a plurality of particles having a particle size of up to about 150 μm. In some embodiments, the carbon active material comprises hard carbon.

[0009] In another aspect, a negative electrode coating is disclosed that includes a composite negative electrode active material. In some embodiments, the negative electrode coating has a thickness of about 2 to 100 μm. In some embodiments, the negative electrode coating further includes a binder. In some embodiments, the negative electrode coating includes the binder in an amount of up to about 5 wt %. In some embodiments, the negative electrode coating further includes a conductive additive. In some embodiments, the negative electrode coating includes the conductive additive in an amount of up to about 5 wt %.

[0010] In another aspect, a negative electrode is disclosed that includes a current collector and a negative electrode coating. In some embodiments, the negative electrode coating is disposed on the current collector. In some embodiments, the current collector has a thickness of up to about 30 μm.

[0011] In another aspect, a sodium-ion energy storage device is disclosed that includes a negative electrode. In some embodiments, the negative electrode of the sodium-ion energy storage device has a specific capacity after 100 cycles of at least about 370 mAh / g. In some embodiments, the negative electrode of the sodium-ion energy storage device has a first cycle efficiency of at least about 85%. In some embodiments, the sodium-ion energy storage device has a coulombic efficiency after 20 cycles of at least about 99%. In some embodiments, the sodium-ion energy storage device has a capacity retention after 200 cycles of at least about 90%.

[0012] In another aspect, an active negative electrode material for a sodium-ion energy storage device is disclosed, the active negative electrode material comprising an alloying element selected from the group consisting of phosphorus (P), germanium (Ge), tin (Sn), antimony (Sb), lead (Pb), bismuth (Bi), and combinations thereof.

[0013] In some embodiments, the alloying element is selected from the group consisting of Pb, Sn, P, and combinations thereof. In some embodiments, the alloying element comprises a plurality of particles having a particle size of up to about 150 μm. In some embodiments, the negative electrode active material comprises about 10% to 100% by weight of the alloying element.

[0014] In another aspect, a negative electrode coating is disclosed that includes a negative electrode active material. In some embodiments, the negative electrode coating has a thickness of about 2 to 100 μm. In some embodiments, the negative electrode coating further includes a binder. In some embodiments, the negative electrode coating includes the binder in an amount of up to about 5 wt %. In some embodiments, the negative electrode coating further includes a conductive additive. In some embodiments, the negative electrode coating includes the conductive additive in an amount less than about 5 wt %.

[0015] In another aspect, a negative electrode is disclosed that includes a current collector and a negative electrode coating. In some embodiments, the negative electrode coating is disposed on the current collector. In some embodiments, the current collector has a thickness of up to about 30 μm.

[0016] In another aspect, a sodium-ion energy storage device is disclosed that includes a negative electrode. In some embodiments, the negative electrode sodium-ion energy storage device has a specific capacity after 100 cycles of greater than about 370 mAh / g. In some embodiments, the sodium-ion energy storage device has a first cycle efficiency of greater than about 85%. In some embodiments, the sodium-ion energy storage device has a coulombic efficiency after 20 cycles of greater than about 99%. In some embodiments, the sodium-ion energy storage device has a capacity retention after 200 cycles of greater than about 90%.

[0017] In another aspect, a method for forming a negative electrode film for a sodium-ion energy storage device is disclosed. In some embodiments, the method includes combining an active material, a binder, and a conductive additive to form an electrode film mixture, and forming a negative electrode film from the electrode film mixture. In some embodiments, the method further includes reducing the size of the composite negative electrode active material to less than about 150 μm. In some embodiments, the combining includes mixing the negative electrode active material with the conductive additive to form a first mixture, and mixing the first mixture with the binder and the conductive additive to form the electrode film mixture. [Brief explanation of the drawings]

[0018] [Figure 1A] 1 is a bar graph showing exemplary London Metal Exchange (LME) and Shanghai Metal Market (SMM) prices in US dollars per kilogram or per mole for Ni (LME nickel), P (SMM yellow phosphorus), Sn (LME tin), Sb (SMM #1 antimony ingot), Pb (LME lead), and Bi (SMM refined bismuth), respectively. [Figure 1B] 1 is a bar graph showing exemplary London Metal Exchange (LME) and Shanghai Metal Market (SMM) prices in US dollars per kilogram or per mole for Ni (LME nickel), P (SMM yellow phosphorus), Sn (LME tin), Sb (SMM #1 antimony ingot), Pb (LME lead), and Bi (SMM refined bismuth), respectively.

[0019] [Figure 2] The atomic abundances in the Earth's crust of the same elements shown in Figures 1A and 1B are plotted relative to Si.

[0020] [Figure 3] 1 illustrates an exemplary process for fabricating an electrode, according to some embodiments.

[0021] [Figure 4A] 1 shows experimental data plots of voltage versus specific capacitance for Sn electrodes, according to some embodiments.

[0022] [Figure 4B] 1 shows experimental data plots of voltage vs. amount of Na for Sn electrodes according to some embodiments.

[0023] [Figure 5A] 1 shows experimental data plots of voltage versus specific capacitance for Pb electrodes, according to some embodiments.

[0024] [Figure 5B] 1 shows experimental data plots of voltage vs. amount of Na for a Pb electrode according to some embodiments.

[0025] [Figure 6] 1 shows experimental data plots of voltage versus specific capacitance curves at cycles 2, 20, and 40 for a P-HC electrode, according to some embodiments.

[0026] [Figure 7A] 1 shows experimental data plots of specific capacity versus cycle for P-HC, Sn, and Pb electrodes, according to some embodiments.

[0027] [Figure 7B] 1 shows experimental data plots of normalized capacity versus cycles for P-HC, Sn, and Pb electrodes, according to some embodiments.

[0028] [Figure 8A] 1 shows experimental data plots of specific capacity versus cycle for Sn and Pb electrodes, according to some embodiments.

[0029] [Figure 8B] 1 shows experimental data plots of normalized capacity versus cycles for Sn and Pb electrodes, according to some embodiments.

[0030] [Figure 9A] 1 shows experimental data plots of coulombic efficiency versus cycles for Sn, Pb, and hard carbon cells, according to some embodiments. [Figure 9B] 1 shows experimental data plots of coulombic efficiency versus cycles for Sn, Pb, and hard carbon cells, according to some embodiments.

[0031] [Figure 9C] 1 shows experimental data plots of specific capacity versus cycles during sodiation and desodiation of a Sn cell, according to some embodiments.

[0032] [Figure 9D]1 shows experimental data plots of specific capacity versus cycles during sodiation and desodiation of a Pb cell, according to some embodiments.

[0033] [Figure 9E] 10 shows an SEM image of a Sn electrode with Sn particles reconstructed into a uniformly distributed microstructure after 50 cycles, according to some embodiments.

[0034] [Figure 9F] 10 shows an SEM image of a Pb electrode with Pb particles reconstructed into a uniformly distributed microstructure after 100 cycles, according to some embodiments.

[0035] [Figure 10A] 1 shows SEM images of an initial Pb electrode and a Pb electrode after 1, 10, and 100 cycles, respectively, according to some embodiments. [Figure 10B] 1 shows SEM images of an initial Pb electrode and a Pb electrode after 1, 10, and 100 cycles, respectively, according to some embodiments. [Figure 10C] 1 shows SEM images of an initial Pb electrode and a Pb electrode after 1, 10, and 100 cycles, respectively, according to some embodiments. [Figure 10D] 1 shows SEM images of an initial Pb electrode and a Pb electrode after 1, 10, and 100 cycles, respectively, according to some embodiments.

[0036] [Figure 10E] 1 shows an SEM image of a Sn electrode after 50 cycles, according to some embodiments.

[0037] [Figure 11A] 1 shows experimental data plots of specific capacity versus cycles for Pb, hard carbon (HC), and Pb-HC electrodes, according to some embodiments.

[0038] [Figure 11B]1 shows experimental data plots of fully sodiated volumetric capacity versus cycles for Pb, hard carbon (HC), and Pb-HC electrodes, according to some embodiments.

[0039] [Figure 11C] 1 shows experimental data plots of normalized capacity-volume capacity versus cycles for Pb, hard carbon (HC), and Pb-HC electrodes, according to some embodiments.

[0040] [Figure 11D] 1 shows experimental data plots of specific capacity versus cycle for Pb—HC electrodes utilizing G1 or EC:DEC electrolytes, according to some embodiments.

[0041] [Figure 12A] 1 shows a calculated data plot of unsodiated volumetric capacity versus weight fraction of alloying element-hard carbon blend electrodes, according to some embodiments.

[0042] [Figure 12B] 1 shows a calculated data plot of fully sodiated volumetric capacity versus weight fraction of alloying element-hard carbon blend electrodes, according to some embodiments.

[0043] [Figure 12C] 1 shows a calculated data plot of volume expansion versus weight fraction of alloying element-hard carbon blend electrodes, according to some embodiments.

[0044] [Figure 12D] 1 shows a calculated data plot of unsodiated volumetric capacity versus volume expansion versus alloy weight fraction of alloying element-hard carbon blend electrodes, according to some embodiments.

[0045] [Figure 12E] 1 shows a calculated data plot of fully sodiated volumetric capacity versus volume expansion versus alloy weight fraction of alloying element-hard carbon blend electrodes, according to some embodiments.

[0046] [Figure 12F] 1 shows a calculated data plot of volume expansion during cycling when Na alloying elements including P, Sn, Pb and Si are blended with hard carbon. DETAILED DESCRIPTION OF THE INVENTION

[0047] The present disclosure may be understood by reference to the following detailed description: It should be noted that for clarity of illustration, certain elements in the various figures may not be drawn to scale, may be represented diagrammatically or conceptually, or may not precisely correspond to particular physical configurations of embodiments.

[0048] Various embodiments of electrode active materials and electrode films with improved energy density and capacity retention for Na-ion energy storage devices, as well as methods for preparing the same, are provided herein. The electrode active materials include alloying elements and may further include a carbon active material. In some embodiments, the alloying elements can be selected from phosphorus (P), germanium (Ge), tin (Sn), antimony (Sb), lead (Pb), bismuth (Bi), and combinations thereof. The electrode active materials and electrode films for Na-ion energy storage devices can enable improved energy storage device performance, such as electrode capacity and improved cell cycle usage, and can accommodate large volume expansion during charge and discharge.

[0049] 1A and 1B show the prices of P, Ge, Sn, Sb, Pb, and Bi in US dollars per kilogram or per mole, respectively. FIG. 2 shows the terrestrial abundances of P, Ge, Sn, Sb, Pb, and Bi. Therefore, based on the price and abundance of the elements, the selection of alloying elements Sn, Pb, P, or combinations thereof may allow for cost savings and / or be readily available. In some embodiments, amorphous red phosphorus, when fully sodiated, becomes crystalline NaP. 14 Sn and Pb are the same molar ratio of Na 15M4 (M = Sn or Pb). Therefore, the theoretical specific capacities of P, Sn, and Pb are 2596 mAh / g, 847 mAh / g, and 485 mAh / g, respectively. In addition, the theoretical volumetric capacities of P, Sn, and Pb using their fully sodiated densities are approximately 1523 mAh / cm, respectively. 3 , 1108mAh / cm 3 , and 1072mAh / cm 3 Therefore, the volumetric capacity when using alloying elements as the negative electrode is 1.45 g / cm3 when using a conventional hard carbon negative electrode in a Na-ion energy storage device. 3 Assuming no volume change, the volumetric capacity is approximately 435mAh / cm 3 can be significantly improved compared to

[0050] In some embodiments, energy storage devices including the electrode active materials disclosed herein may be characterized by improved performance, such as improved electrode capacity, improved cell cycling performance, reduced capacity loss over the device's lifetime, improved storage stability, improved power delivery, reduced electrode degradation, and / or reduced capacity fade. Volume expansion and contraction of electrode films containing alloying elements may occur during cycling of the energy storage device. For example, the volume expansion of amorphous red phosphorus relative to NaP may be approximately 292%. As another example, the volume expansion of Pb and Sn compared to the fully unsodiated phase is approximately 424% and 387%, respectively. Such volume expansion and contraction during cycling generally leads to the comminution and separation of active material particles from the bulk electrode, which can be expected to cause instability at the solid electrolyte interphase (SEI). Despite such volume expansion and contraction, Na-ion energy storage devices including the negative electrode active materials or composite negative electrode active materials disclosed herein have unexpectedly been found to exhibit acceptable capacity retention for over 200 cycles. Additionally, it was found that the agreement of the voltage curves between 100 and 200 cycles suggests that the negative electrodes disclosed herein did not experience an impedance increase or active mass loss despite the large volume change over 200 cycles. Furthermore, the negative electrodes disclosed herein were found to exhibit improved kinetic properties and rate capability.

[0051] A. Active material In some embodiments, the negative electrode active material or composite negative electrode active material includes an alloying element capable of alloying with sodium during charge and discharge processes in the energy storage device. In some embodiments, the alloying element includes a Group IV and / or Group V element. In some embodiments, the alloying element is selected from phosphorus (P), germanium (Ge), tin (Sn), antimony (Sb), lead (Pb), bismuth (Bi), or a combination thereof. In some embodiments, the alloying element is selected from tin (Sn), lead (Pb), phosphorus (P), or a combination thereof.

[0052] In some embodiments, the active negative electrode material or composite active negative electrode material includes an alloying element in an amount ranging from about, at least, or at least about 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 81 wt%, 82 wt%, 83 wt%, 84 wt%, 85 wt%, 86 wt%, 87 wt%, 88 wt%, 89 wt%, 90 wt%, 91 wt%, 92 wt%, 93 wt%, 94 wt%, 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt%, 100 wt%, or any value therebetween. In some embodiments, the negative electrode active material or composite negative electrode active material comprises, consists of, or consists essentially of an alloying element. In some embodiments, the negative electrode active material or composite negative electrode active material consists of, or consists essentially of, Sn. In some embodiments, the negative electrode active material or composite negative electrode active material consists of, or consists essentially of Pb. In some embodiments, the negative electrode active material or composite negative electrode active material consists of, or consists essentially of P.

[0053] In some embodiments, the alloying elements comprise particles having a D10, D50, or D90 size of about, at most, or up to about 300 μm, 200 μm, 150 μm, 125 μm, 100 μm, 90 μm, 80 μm, 70 μm, 60 μm, 50 μm, 45 μm, 40 μm, 35 μm, 30 μm, 25 μm, 20 μm, 15 μm, 10 μm, 5 μm, 2 μm, or any range of values ​​therebetween. In some embodiments, the alloying elements have a particle size of about, at most, or up to about 50 μm, 45 μm, 40 μm, 35 μm, 30 μm, 25 μm, 20 μm, 15 μm, 10 μm, or any range of values ​​therebetween. In some embodiments, the particle size of the alloying elements refers to the largest or average dimension of the particles. In some embodiments, the maximum dimension refers to the longest or greatest distance between any two points within an object, e.g., the greatest extent or measurement of the length, width, or height of the object, depending on the context. In some embodiments, the alloying element has a flat electrode film shape compared to the shape of the alloying element in powder form (e.g., prior to calendering the electrode film). In some embodiments, the alloying element has a particle size configured to pass through a US mesh size sieve of about, at most, or up to about 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 100, 120, 140, 170, 200, 230, 270, 325, 400, 450, 500, or 635, or any range of values ​​therebetween.

[0054] In some embodiments, the alloying elements are amorphous, crystalline, or a combination thereof. In some embodiments, the amorphous alloying elements may reduce or help reduce the volume expansion or contraction of the alloying elements during sodiation and desodiation.

[0055] In some embodiments, the negative electrode active material or composite negative electrode active material comprises a carbon active material. In some embodiments, the carbon active material is selected from graphitic carbon, graphite, hard carbon, soft carbon, and combinations thereof. In some embodiments, the carbon active material consists of or consists essentially of hard carbon. In some embodiments, the active anode material or composite active anode material comprises about, at most, or up to about 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1.5%, 1% by weight of carbon active material, or any value range therebetween.

[0056] In some embodiments, the negative electrode active material or composite negative electrode active material comprises, consists of, or consists essentially of a carbon active material and an alloying element. In some embodiments, the negative electrode active material or composite negative electrode active material comprises an alloying element and a carbon active material in a mass ratio of about, at least, or at least about 5:95, 5:10:90, 15:85, 18:82, 2:8, 3:7, 4:6, 4.5:5.5, 5:5, 5.5:4.5, 6:4, 6.5:3.5:7:3, 7.5:2.5, 8:2, 9:1, 9.5:0.5, or any value range therebetween. In some embodiments, the negative electrode active material comprises or consists of P and HC in a mass ratio of 18:82. In some embodiments, the negative electrode active material comprises or consists of P and HC in a 1:1 mass ratio. In some embodiments, the negative electrode active material comprises or consists of Sn and HC in a mass ratio of 31:69. In some embodiments, the negative electrode active material comprises or consists of Pb and HC in a mass ratio of 45:55. In some embodiments, the negative electrode active material comprises, consists of, or consists essentially of phosphorus and hard carbon. In some embodiments, the negative electrode active material comprises, consists of, or consists essentially of tin and hard carbon. In some embodiments, the negative electrode active material comprises, consists of, or consists essentially of lead and hard carbon.

[0057] B. Electrode membrane In some embodiments, the electrode film is a negative electrode coating. In some embodiments, the electrode film comprises a negative electrode active material or a composite negative electrode active material. In some embodiments, the electrode film comprises about, at least, or at least about 70 wt%, 75 wt%, 80 wt%, 81 wt%, 82 wt%, 83 wt%, 84 wt%, 85 wt%, 86 wt%, 87 wt%, 88 wt%, 89 wt%, 90 wt%, 91 wt%, 92 wt%, 93 wt%, 94 wt%, 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt%, 100 wt%, or any value range therebetween. In some embodiments, the alloying element is in elemental form (i.e., oxidation state 0) in the electrode film prior to formation and cycling of the energy storage device.

[0058] In some embodiments, the electrode film includes a binder. In some embodiments, the binder can include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyolefin, polyalkylene, polyether, styrene-butadiene, polysiloxane and polysiloxane copolymer, branched polyether, polyvinyl ether, carboxymethyl cellulose (CMC), polyacrylic acid (PAA), sodium polyacrylate (NaPAA), copolymers thereof, and / or combinations thereof. In some embodiments, the polyolefin can include polyethylene (PE), polypropylene (PP), copolymers thereof, and / or combinations thereof. The binder can include polyvinylene chloride, poly(phenylene oxide) (PPO), polyethylene-block-poly(ethylene glycol), poly(ethylene oxide) (PEO), poly(phenylene oxide) (PPO), polyethylene-block-poly(ethylene glycol), polydimethylsiloxane (PDMS), polydimethylsiloxane-coalkylmethylsiloxane, copolymers thereof, and / or combinations thereof. In some embodiments, the binder can include a thermoplastic. In some embodiments, the binder includes a fibrillizable polymer and / or a fibrillating polymer. In certain embodiments, the binder includes, consists essentially of, or consists of a single fibrillizable and / or fibrillating binder, such as PTFE. In some embodiments, the binder includes, consists essentially of, or consists of PTFE, PVDF, CMC, PAA, NaPAA, or combinations thereof. In some embodiments, the electrode film comprises a binder in an amount ranging from about, at most, or up to about 30 wt%, 25 wt%, 20 wt%, 19 wt%, 18 wt%, 17 wt%, 16 wt%, 15 wt%, 14 wt%, 13 wt%, 12 wt%, 11 wt%, 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, 3 wt%, 2 wt%, 1 wt%, 0.5 wt%, 0.25 wt%, 0.1 wt%, or any value therebetween.Without being limited by theory, the inventors have discovered that, compared to previous studies, fewer exotic binders may be required for alloy-based electrodes, which means that more negative electrode active material can be loaded into the negative electrode.

[0059] In some embodiments, the electrode film includes a conductive additive. In some embodiments, the conductive additive includes a conductive carbon additive. In some embodiments, the conductive carbon additive includes carbon black, carbon nanotubes, such as single-walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNT). In some embodiments, the electrode film includes a total of about, at most, or up to about 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, 3 wt%, 2 wt%, 1 wt%, 0.5 wt%, 0.25 wt%, 0.1 wt%, or any value range therebetween. In some embodiments, each of the conductive additives is present in an amount of about, at most, or up to about 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.25%, 0.1% by weight of the electrode film, or any value range therebetween. In some embodiments, the conductive additive is carbon black. In some embodiments, the conductive additive is carbon nanotubes. In some embodiments, the conductive additive includes both carbon black and carbon nanotubes.

[0060] In some embodiments, the electrode film has a thickness of about, at most, or up to about 500 μm, 400 μm, 300 μm, 250 μm, 200 μm, 150 μm, 100 μm, 90 μm, 80 μm, 70 μm, 60 μm, 50 μm, 40 μm, 30 μm, 20 μm, 15 μm, 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, or 1 μm, or any range of values ​​therebetween. The described relatively thin electrode film thicknesses can advantageously improve capacity retention while accommodating volume expansion of the electrode during the alloying process due at least in part to the relatively thin electrode film.

[0061] In some embodiments, the electrode film has a thickness of about, at least, at least about 1 mg / cm 2 , 2 mg / cm 2 , 3 mg / cm 2 , 4 mg / cm 2 , 5 mg / cm 2 , 6 mg / cm 2 , 7 mg / cm 2 , 8 mg / cm 2 , 9 mg / cm 2 , 10 mg / cm 2 , 11 mg / cm 2 , 12 mg / cm 2 , 15 mg / cm 2 , 20 mg / cm 2 , 25 mg / cm 2 , 30 mg / cm 2 , 35 mg / cm 2 , 40 mg / cm 2 , 45 mg / cm 2 , 50 mg / cm 2 or any range of values ​​therebetween, the active material loading (which may be expressed as a mass of electrode film per unit area of ​​electrode film or current collector) can be provided.

[0062] The electrode film thickness can be selected to correspond to a desired areal capacitance, specific capacitance, areal energy density, energy density, or specific energy density. In some embodiments, the electrode film has a capacitance of about, at least, or at least about 1 mAh / cm. 2 , 1.5mAh / cm 2 , 1.7mAh / cm2 , 1.9mAh / cm 2 , 2.0mAh / cm 2 , 2.5mAh / cm 2 , 3mAh / cm 2 , 3.5mAh / cm 2 , 4mAh / cm 2 , 4.5mAh / cm 2 , 5mAh / cm 2 , 5.5mAh / cm 2 , 6mAh / cm 2 , 6.5mAh / cm 2 , 7mAh / cm 2 , 7.5mAh / cm 2 , 8mAh / cm 2 , 9mAh / cm 2 , 10mAh / cm 2 , 11mAh / cm 2 , 12mAh / cm 2 , 13mAh / cm 2 , 14mAh / cm 2 , 15mAh / cm 2 , 20mAh / cm 2 , 25mAh / cm 2 , 30mAh / cm 2 , 35mAh / cm 2 , 40mAh / cm 2 , 50mAh / cm 2 , or any range of values ​​therebetween.

[0063] In some embodiments, the electrode film is disposed on a current collector. In some embodiments, the current collector can include a metallic material, such as a material including aluminum, nickel, copper, or a combination thereof. In some embodiments, the current collector includes a pure metal. In some embodiments, the current collector includes a metallized polymer film or a metal-coated polymer film. In some embodiments, the polymer includes polyethylene terephthalate (PET), biaxially oriented polypropylene (BOPP), or a combination thereof. In some embodiments, the metal coating includes aluminum. In some embodiments, coating the final electrode film mixture includes forming a uniform electrode film mixture coating. In some embodiments, the current collector has a thickness of about, at most, or up to about 30 μm, 20 μm, 15 μm, 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, 5 μm, or any range of values ​​therebetween.

[0064] C. Preparation of electrode films In some embodiments, the electrode film is fabricated by a wet process or a slurry process. In some embodiments, the electrode film is prepared by a wet or slurry-based electrode fabrication process.

[0065] 3 shows an exemplary process 300 for fabricating an electrode film. Process 300 includes an optional step 310 of reducing the size of the negative electrode active material or composite negative electrode active material to a desired size. In some embodiments, reducing the size of the negative electrode active material includes reducing the size of an alloying element. In some embodiments, reducing the size of the negative electrode active material includes breaking down the structure of the alloying element. In some embodiments, breaking down the structure includes a step selected from crushing, grinding, and combinations thereof. In some embodiments, reducing the size of the negative electrode active material includes sieving the negative electrode active material.

[0066] In some embodiments, particles of the negative electrode active material, such as alloying elements, have a D10, D50, or D90 size of about, at most, or up to about 300 μm, 200 μm, 150 μm, 125 μm, 100 μm, 90 μm, 80 μm, 70 μm, 60 μm, 50 μm, 45 μm, 40 μm, 35 μm, 30 μm, 25 μm, 20 μm, 15 μm, 10 μm, 5 μm, 2 μm, or any range of values ​​therebetween. In some embodiments, particles of the negative electrode active material, such as alloying elements, have a particle size of about, at most, or up to about 50 μm, 45 μm, 40 μm, 35 μm, 30 μm, 25 μm, 20 μm, 15 μm, 10 μm, or any range of values ​​therebetween. In some embodiments, particles of anode active material, such as an alloying element, have a particle size configured to pass through a U.S. mesh size sieve of about, at most, or up to about 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 100, 120, 140, 170, 200, 230, 270, 325, 400, 450, 500, or 635, or any range of values ​​therebetween.

[0067] Continuing with reference to FIG. 3 , fabrication process 300 includes an optional step 320 of mixing the negative electrode active material or composite negative electrode active material. In some embodiments, mixing is performed particularly when the negative electrode active material includes two or more components. In some embodiments, mixing the negative electrode active material includes a step selected from grinding, blending, and combinations thereof. In some embodiments, grinding includes ball milling. In some embodiments, the components of the negative electrode active material are mixed in the ratio intended for the electrode film. In some embodiments, mixing the negative electrode active material includes mixing an alloying element with a carbon active material. In some embodiments, mixing the negative electrode active material includes mixing an alloying element with a hard carbon. In some embodiments, mixing the negative electrode active material includes mixing phosphorus with a carbon active material. In some embodiments, mixing the negative electrode active material includes mixing tin with a carbon active material. In some embodiments, mixing the negative electrode active material includes mixing lead with a carbon active material. In some embodiments, mixing the negative electrode active material includes mixing the negative electrode active material with a conductive additive. In some embodiments, combining the negative electrode active material with the conductive additive includes combining phosphorus with the conductive additive, which, in some embodiments, can increase the conductivity of the negative electrode active material and reduce the amount of conductive additive material used.

[0068] In step 330, an electrode film mixture may be formed by combining the negative electrode active material, the conductive additive, and the binder. In some embodiments, the electrode film mixture comprises about, at least, or at least about 70 wt%, 75 wt%, 80 wt%, 81 wt%, 82 wt%, 83 wt%, 84 wt%, 85 wt%, 86 wt%, 87 wt%, 88 wt%, 89 wt%, 90 wt%, 91 wt%, 92 wt%, 93 wt%, 94 wt%, 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt%, 100 wt%, or any value range therebetween. In some embodiments, the negative electrode active material consists of, or consists essentially of, a carbon active material and an alloying element. In some embodiments, the negative electrode active material comprises an alloying element and a carbon active material in a mass ratio of about, at least about, or at least about 0.5:9.5, 1:9, 2:8, 3:7, 4:6, 5:5, 5.5:4.5, 6:4, 6.5:3.5:7:3, 7.5:2.5, 8:2, 9:1, 9.5:0.5, or any range of values ​​therebetween. In some embodiments, the negative electrode active material is hard carbon and phosphorus. In some embodiments, the negative electrode active material is hard carbon and lead. In some embodiments, the negative electrode active material is hard carbon and tin. In some embodiments, the negative electrode active material consists of, or consists essentially of, tin, lead, phosphorus, or combinations thereof.

[0069] In some embodiments, the electrode membrane mixture comprises a binder in an amount ranging from about, at most, or up to about 30%, 25%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.25%, 0.1% by weight, or any value therebetween. In some embodiments, the binder comprises PTFE, PVDF, CMC, PAA, NaPAA, PVDF, or a combination thereof.

[0070] In some embodiments, the electrode film mixture comprises a conductive material in an amount ranging from about, at most, or up to about 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.25%, 0.1%, or any value therebetween. In some embodiments, the conductive carbon additive comprises carbon black, carbon nanotubes, such as single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs), or a combination thereof.

[0071] In optional step 340, a slurry is formed by combining the electrode membrane mixture formed in step 330 with a solvent. In some embodiments, the solvent is selected from N-methylpyrrolidone (NMP), deionized water, or a combination thereof. In some embodiments, combining includes diluting the electrode membrane mixture to have a solids content of about, at most, or up to about 80%, 70%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 10% by weight of the final slurry mixture, or any value therebetween. In some embodiments, forming the slurry includes combining the electrode membrane mixture with a solvent.

[0072] In step 350, an electrode is formed from the electrode film mixture or slurry. In some embodiments, the electrode film mixture is formed into an electrode film and the electrode film is placed on a current collector to form an electrode. In some embodiments, the slurry is placed on the current collector to form a slurry coating. In some embodiments, the electrode film or slurry coating has a thickness of about, at most, or up to about 500 μm, 450 μm, 400 μm, 350 μm, 300 μm, 250 μm, 200 μm, 150 μm, 100 μm, 50 μm, 40 μm, 30 μm, 20 μm, 15 μm, 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, or any range of values ​​therebetween. In some embodiments, the thickness of the electrode film mixture or slurry coating is set to the intended areal capacity. In some embodiments, the electrode film or slurry coating is dried at a specific temperature. In some embodiments, the drying temperature is about, at least, or at least about 70° C., 75° C., 80° C., 85° C., 90° C., 95° C., 100° C., 110° C., 120° C., 130° C., 140° C., 150° C., 160° C., 170° C., 180° C., or any range of values ​​therebetween. In some embodiments, the electrode film or slurry coating is dried for about, at least, or at least about 1 minute, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, or any range of values ​​therebetween.

[0073] In some embodiments, forming the electrode includes calendering the electrode film. In some embodiments, the thickness of the electrode film is reduced by calendering. In some embodiments, after calendering, the electrode film has a thickness of about, at most, or up to about 200 μm, 150 μm, 100 μm, 90 μm, 80 μm, 70 μm, 60 μm, 50 μm, 40 μm, 30 μm, 20 μm, 15 μm, 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, or 1 μm, or any range of values ​​therebetween. In some embodiments, particles of the negative electrode active material, such as alloying elements, are flattened during calendering. In some embodiments, after calendering, the particles of the alloying elements have a D10, D50, or D90 size of about, at most, or up to about 300 μm, 200 μm, 150 μm, 125 μm, 100 μm, 90 μm, 80 μm, 70 μm, 60 μm, 50 μm, 45 μm, 40 μm, 35 μm, 30 μm, 25 μm, 20 μm, 15 μm, 10 μm, 5 μm, 2 μm, or any range of values ​​therebetween. In some embodiments, after calendering, the particles of the alloying elements have a particle size of about, at most, or up to about 50 μm, 45 μm, 40 μm, 35 μm, 30 μm, 25 μm, 20 μm, 15 μm, 10 μm, or any range of values ​​therebetween. In some embodiments, after calendering, the particles of the alloying elements have a particle size configured to pass through a US mesh size sieve of about, at most, or up to about 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 100, 120, 140, 170, 200, 230, 270, 325, 400, 450, 500, or 635, or any range of values ​​therebetween.

[0074] In some embodiments, the electrode is further dried at a temperature of about, at least, at least about 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, or any value range therebetween. In some embodiments, the electrode is dried for about, at least, at least about 30 minutes, 40 minutes, 60 minutes, 2 hours, 3 hours, 5 hours, 10 hours, 15 hours, 20 hours, or any value range therebetween. In some embodiments, the electrode is dried under vacuum. D. Energy Storage Device

[0075] The negative electrode active material or composite negative electrode active material may be used to fabricate an electrode film and / or electrode for an energy storage device. In some embodiments, the energy storage device includes a separator, a negative electrode, a positive electrode, an electrolyte, and a housing, wherein the electrolyte, separator, negative electrode, and positive electrode are disposed within the housing, and the separator is disposed between the negative electrode and the positive electrode. In some embodiments, the energy storage device is formed by disposing the electrolyte, separator, negative electrode, and positive electrode described herein within the housing, and the separator is disposed between the negative electrode and the positive electrode. In some embodiments, the energy storage device is a sodium (Na)-ion energy storage device. In some embodiments, the energy storage device includes a battery or a capacitor. In some embodiments, the energy storage device is a sodium (Na)-ion battery. In some embodiments, the electrode is a negative electrode for a Na-ion battery.

[0076] In some embodiments, the energy storage device is charged with a suitable sodium-containing electrolyte. For example, the energy storage device can include a sodium salt and a solvent, such as an aqueous and / or organic solvent. Generally, the sodium salt includes a redox-stable anion. In some embodiments, the anion can be monovalent. In some embodiments, the sodium salt can be selected from sodium hexafluorophosphate (NaPF), sodium bis(trifluoromethanesulfonyl)imide (NaFSI), sodium tetrafluoroborate (NaBF), sodium perchlorate (NaClO), sodium bis(trifluoromethanesulfonyl)imide (NaN(SOCF)), sodium trifluoromethanesulfonate (NaSOCF), sodium bis(oxalato)borate (NaB(CO)), sodium bis(fluorosulfonyl)imide (NaN(SOF)), sodium difluoro(oxalato)borate (NaCBFO), and combinations thereof. In some embodiments, the salt concentration can be about 0.1 mol / L (M) to about 5 M, about 0.2 M to about 3 M, or about 0.3 M to about 2 M. In further embodiments, the salt concentration of the electrolyte can be about 0.7 M to about 2 M. In certain embodiments, the salt concentration of the electrolyte can be about 0.2 M, about 0.3 M, about 0.4 M, about 0.5 M, about 0.6 M, about 0.7 M, about 0.8 M, about 0.9 M, about 1 M, about 1.1 M, about 1.2 M, 1.3 M, 1.4 M, 1.5 M, or any value therebetween.

[0077] In some embodiments, the energy storage device can include a solvent. The solvent need not dissolve all components of the electrolyte, nor need it completely dissolve any of the components. In further embodiments, the solvent can be an organic solvent. In some embodiments, the solvent can include one or more functional groups selected from carbonates, ethers, and / or esters. In some embodiments, the solvent can include a carbonate. In further embodiments, the carbonate can be selected from cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), vinyl ethylene carbonate (VEC), vinylene carbonate (VC), fluoroethylene carbonate (FEC), and combinations thereof, or acyclic carbonates such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), 1,2-dimethoxyethane (G1 or DME), and combinations thereof. In some embodiments, the electrolyte includes EC and DEC. In some embodiments, the ether can be selected from diethylene glycol dimethyl ether (diglyme or G2), triethylene glycol dimethyl ether (triglyme or G3), and tetraethylene glycol dimethyl ether (tetraglyme or G4). In some embodiments, one or more solvents can be used at a concentration of about, at least, or at least about 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, or 90 wt%, or any value in between. In some embodiments, the electrolyte does not include EC. In some embodiments, the electrolyte includes G1. In some embodiments, a solvent for an energy storage device having a negative electrode active material or a composite negative electrode active material containing Sn or Pb does not include EC.

[0078] In some embodiments, a solvent is utilized as an additive in an electrolyte system and may be used at a concentration ranging from about, at most, or up to about 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.7 wt%, 2.8 wt%, 2.9 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%, or any value therebetween. For example, in some embodiments, the amount of additive in the electrolyte is in or about any one of the following ranges: 0.1-10 wt%, 1-6 wt%, 2-5 wt%, 0.1-6 wt%, 2-8 wt%, 2-3 wt%, or 1-4 wt%. In some embodiments, the additive is selected from fluoroethylene carbonate (FEC), dioxathiolane (e.g., 1,3,2-dioxathiolane-2,2-dioxide (DTD)), 1,2,6-oxadithiane 2,2,6,6-tetraoxide ("ODTO"), and combinations thereof.

[0079] In some embodiments, the energy storage device has an initial specific capacity of about, at least, or at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, or 100% of the theoretical specific capacity, or any range of values ​​therebetween. In some embodiments, the negative electrode of the energy storage device has an initial specific capacity of about, at least, or at least about 300 mAh / g, 370 mAh / g, 400 mAh / g, 420 mAh / g, 450 mAh / g, 470 mAh / g, 500 mAh / g, 550 mAh / g, 600 mAh / g, 650 mAh / g, 700 mAh / g, 750 mAh / g, 800 mAh / g, 850 mAh / g, 900 mAh / g, 95 ... and an initial specific capacity ranging from 0 mAh / g, 900 mAh / g, 950 mAh / g, 1000 mAh / g, 1100 mAh / g, 1200 mAh / g, 1300 mAh / g, 1400 mAh / g, 1500 mAh / g, 1600 mAh / g, 1700 mAh / g, 1800 mAh / g, 1900 mAh / g, 2000 mAh / g, or any value therebetween. In some embodiments, the negative electrode of the energy storage device has a capacitance of about, at least, or at least about 300 mAh / g, 370 mAh / g, 400 mAh / g, 420 mAh / g, 450 mAh / g, 470 mAh / g, 500 mAh / g, 550 mAh / g, 600 mAh / g, 650 mAh / g, 700 mAh / g, 750 mAh / g, 800 mAh / g, 850 mAh / g, h / g, 900 mAh / g, 950 mAh / g, 1000 mAh / g, 1100 mAh / g, 1200 mAh / g, 1300 mAh / g, 1400 mAh / g, 1500 mAh / g, 1600 mAh / g, 1700 mAh / g, 1800 mAh / g, 1900 mAh / g, 2000 mAh / g, or any value therebetween.In some embodiments, the negative electrode of the energy storage device has a capacitance of about, at least, or at least about 300 mAh / g, 370 mAh / g, 400 mAh / g, 420 mAh / g, 450 mAh / g, 470 mAh / g, 500 mAh / g, 550 mAh / g, 600 mAh / g, 650 mAh / g, 700 mAh / g, 750 mAh / g, 800 mAh / g, 850 mAh / g, h / g, 900 mAh / g, 950 mAh / g, 1000 mAh / g, 1100 mAh / g, 1200 mAh / g, 1300 mAh / g, 1400 mAh / g, 1500 mAh / g, 1600 mAh / g, 1700 mAh / g, 1800 mAh / g, 1900 mAh / g, 2000 mAh / g, or any value therebetween.

[0080] In some embodiments, the negative electrode of the energy storage device has a first cycle coulombic efficiency of about, at least, or at least about 80%, 85%, 88%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or any value range therebetween. In some embodiments, the negative electrode of the energy storage device has a coulombic efficiency after 20 cycles of about, at least, or at least about 95%, 96%, 97%, 98%, 99%, 99.5%, 99.8%, 99.9%, or any value range therebetween. In some embodiments, the negative electrode of the energy storage device has a coulombic efficiency after 100 cycles of about, at least, or at least about 95%, 96%, 97%, 98%, 99%, 99.5%, 99.99%, or any value range therebetween.

[0081] In some embodiments, the capacity retention after 100 cycles is about, at least, or at least about 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, or 99.9% of the original capacity, or any range of values ​​therebetween. In some embodiments, the capacity retention after 200 cycles is about, at least, or at least about 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, or 99.9% of the original capacity, or any range of values ​​therebetween. In some embodiments, the irreversible capacity loss after 50 cycles is about, at most, or up to about 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0%, or any range of values ​​therebetween.

[0082] In some embodiments, after several cycles, the composite negative electrode active material, such as the negative electrode active material or alloying element, reconstitutes into particles of smaller, more uniform size compared to the size of the particles when used to form the electrode film. In some embodiments, the size of the negative electrode active material is reduced to about, at most, or up to about 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, 1 μm, 500 nm, 200 nm, or any value therebetween. In some embodiments, reconstitution occurs within the first 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 50, 100 cycles, or any value therebetween.

[0083] In some embodiments, the negative electrode of the energy storage device is configured to be discharged to a voltage of about, at least, or at least about 0.005 V vs. Na metal. In some embodiments, the negative electrode of the energy storage device is configured to be recharged to a voltage of about, up to, or at least about 1.4 V vs. Na metal. [Example]

[0084] Exemplary embodiments of the present disclosure, including processes, materials and / or resulting products, are described in the following examples.

[0085] Example 1 - Preparation of phosphorus-hard carbon electrodes Phosphorus-hard carbon (P-HC) electrodes were prepared by a slurry process. Red phosphorus was ball-milled with carbon black (Super S) at a mass ratio of 7:2 at 600 rpm for 12 hours. A slurry was then formed by mixing hard carbon powder (BSHC-320), single-walled carbon nanotubes (OCSiAl TUBALL 0611, 0.8% SWCNT, 1.2% CMC, 98% HO), polyacrylic acid sodium salt (PAANa, average Mw approximately 8,000, 45 wt% in HO), CMC, and a mixture of red phosphorus and carbon black in a weight ratio of 60%:2%:7%:3%:20%:8%. The slurry was diluted by adding deionized HO so that the final P-HC electrode film mixture had a solids content of approximately 26 wt%. The final P-HC electrode film mixture was formed by mixing three or four times with a planetary mixer at 100-second intervals. The final P-HC electrode film mixture was then added at approximately 3 mg / cm 2 and an active mass loading of approximately 2 mAh / cm 2 The P-HC electrode film coating on the aluminum foil was uniformly coated with a projected area capacity of 1000 kJ / cm2. The P-HC electrode film coating on the aluminum foil was dried at 90°C for approximately 2 hours and then calendered at 2000 atm. The dried and calendered P-HC electrode film coating on the aluminum foil was punched into circular electrodes with a diameter of 12.75 mm. The electrodes were then dried under vacuum at over 90°C for approximately 10 hours and transferred to an Ar-filled glove box where they were fabricated into coin cells.

[0086] Example 2 - Preparation of lead-hard carbon electrodes A lead-hard carbon (Pb-HC) electrode was prepared by a slurry process. The Pb-HC blend was made by blending hard carbon and Pb in a weight ratio of 1:1. Pb powder was sieved through a 625 mesh and then blended with hard carbon. A Pb-HC slurry was made by mixing the Pb-HC blend, PVDF, carbon black, and SWCNTs in a weight ratio of 96%:2%:1.5%:0.5%. The Pb-HC slurry was diluted with NMP to a solid content of 45% by weight. A Pb-HC electrode film mixture was formed using the same mixing procedure as in Example 1. The Pb-HC electrode film mixture was approximately 8 mg / cm. 2 coated on aluminum foil with an active mass loading of approximately 3 mAh / cm 2 The coated aluminum foil was dried, calendared, and punched in the same manner as the Pb-HC electrode in Example 1 to form a Pb-HC electrode.

[0087] Example 3 - Preparation of tin-hard carbon electrodes Tin-hard carbon (Sn-HC) electrodes were prepared by a slurry process. Hard carbon and Sn were blended in a weight ratio of 7:3 to produce an Sn-HC blend. The Sn-HC blend was abbreviated as Sn-HC blend. The Sn-HC blend, PAA, and SWCNTs were mixed in a weight ratio of 96%:3.5%:0.5% to produce an Sn-HC slurry. The Sn-HC slurry was diluted with deionized water to a solid content of 45 wt% to form an Sn-HC electrode film mixture. The Sn-HC electrode film mixture was mixed using the same mixing procedure as in Example 1. The Sn-HC electrode film mixture was approximately 8 mg / cm. 2 coated on aluminum foil with an active mass loading of approximately 3 mAh / cm 2 The coated aluminum foil was dried, calendared, and punched in the same manner as in the Sn-HC electrode of Example 1 to form an Sn-HC electrode.

[0088] Example 4 - Preparation of tin electrodes Tin (Sn) electrodes were prepared by a slurry process. Sn powder (-100 mesh, 99.85% metal basis), carbon black, SWCNTs, 9.9% NaPAA, and CMC were mixed in a weight ratio of 79.5%, 9.4%, 0.5%, 9.9%, and 0.7% to form a tin electrode slurry. The tin electrode slurry was then diluted by adding deionized water so that the final slurry had a solids content of approximately 40% by weight. A tin electrode film mixture was formed using the same mixing procedure, and the final slurry was coated onto aluminum foil using the same coating procedure as in the fabrication process for the P-HC electrode in Example 1. The active mass loading of the Sn electrode film coating on the aluminum foil was approximately 4.5 mg / cm. 2 is approximately 3.6mAh / cm 2 The projected area capacitance was obtained. The coated aluminum foil was dried, calendared, and punched in the same manner as the P-HC electrode to form the Sn electrode. The Sn electrode was then dried under vacuum at over 90 °C for approximately 10 hours and transferred to an Ar-filled glove box to be fabricated into a coin cell.

[0089] In another example, Sn powder, carbon black, SWCNTs, and polyacrylic acid were mixed in a weight ratio of approximately 90%:4.5%:0.5%:4.25% to form a second tin electrode slurry. The second final tin electrode film mixture was diluted by adding deionized water so that the final tin electrode slurry had a solids content of approximately 45%. The second final tin electrode film mixture was mixed, coated, dried, and calendered to fabricate a second tin electrode in the same manner as the first tin electrode described above. The second tin electrode had a coin cell mass loading similar to that of the first tin electrode described above.

[0090] Example 5 - Preparation of lead electrodes Lead (Pb) powder, PVDF, carbon black, and SWCNTs (OCSiAl TUBALL 0521, 1% SWCNTs, 2% Solvay Solef 5130 PVDF, 97% NMP) were mixed in a weight ratio of 90%:5%:4.5%:0.5% to prepare a Pb electrode slurry. Pb powder (-200 mesh, 99.9% metal basis) was used to form a slurry after sieving through a 625 mesh (20 μm). The lead electrode slurry was diluted by adding NMP (99.5%) so that the final slurry had a solids content of 40 wt % to form a lead electrode film mixture. The lead electrode film mixture was formed by mixing using the same mixing procedure as in the P-HC electrode fabrication process of Example 1. Approximately 4 mg / cm 2 or approximately 14 mg / cm 2 The lead electrode film mixture was coated onto aluminum foil with an active mass loading of approximately 2 mAh / cm, respectively. 2 or about 7mAh / cm 2 The coated aluminum foil was dried, calendared, and punched in the same manner as the P-HC electrode of Example 1 to form a lead electrode.

[0091] In another example, a second Pb slurry was prepared by mixing Pb powder, PVDF, carbon black, and SWCNTs in a weight ratio of 96%:2%:1.5%:0.5%. The second Pb slurry was diluted with NMP to a solids content of about 40% by weight to form a second lead electrode film mixture. The second lead electrode film mixture had a solids content of about 4 mg / cm. 2 coated on aluminum foil with an active mass loading of approximately 1.9 mAh / cm 2 The aluminum foil coated with the second lead electrode film mixture was dried, calendared, and punched in the same manner as the P-HC electrode of Example 1 to form a second lead electrode.

[0092] Table 1 summarizes the measured thicknesses and projected areal capacitances of several Pb electrodes. Samples 1 and 2 in Table 1 used Pb particles with a size of approximately 20 μm to form the electrode mixture. Sample 3 was formed with Pb particles that could pass through a 325 US mesh size. Sample 4 was formed from a Pb powder mixture consisting of 0.1% powder larger than 150 mesh, 10.6% powder larger than 200 mesh, 18.1% powder larger than 325 mesh, and 71.2% powder smaller than 325 mesh. Table 2 summarizes the areal capacitances for different thicknesses using the parameters summarized in Table 3. [Table 1] [Table 2] [Table 3]

[0093] Example 6 - Preparation of hard carbon electrodes For comparison, a hard carbon (HC) electrode was prepared as a control negative electrode. Hard carbon powder, PVDF, carbon black, and SWCNT were mixed in a weight ratio of 96%, 2%, 1.5%, and 0.5% to prepare a slurry. The slurry was diluted with NMP to a solid content of 40% by weight. The HC electrode membrane mixture was formed using the same mixing procedure as in Example 1. The HC electrode membrane mixture was approximately 7 mg / cm. 2 coated onto aluminum foil (approximately 15 microns thick) with an active mass loading of approximately 2 mAh / cm 2 The coated aluminum foil was dried, calendared, and punched in the same manner as in the P-HC electrode of Example 1 to form an HC electrode.

[0094] Example 7 - Preparation of electrolyte The electrolyte for the cell containing the P-HC electrode was formed by mixing 1.0 M NaPF6 salt with 5 wt% fluoroethylene carbonate (FEC; 4-fluoro-1,3-dioxolan-2-one) in 1:1 ethylene carbonate:diethyl carbonate (abbreviated EC:DEC, w / w) in a glove box.

[0095] The electrolyte of the cell containing the Sn, Pb and pure hard carbon electrodes is a mixture of 1,2-dimethoxyethane (G1; anhydrous, 99.5%) and 1.0 M NaPF6 salt.

[0096] Example 8 - Coin Cell Fabrication and Cycling CR2325 (23 mm diameter x 2.5 mm height) half-coin cells were assembled in an Ar-filled glove box with a negative electrode, two layers of polypropylene (PP) separator (25 μm thick, surfactant-coated), one layer of chemical-resistant PP mesh (98 × 98 mesh, 150 μm opening size, 34% opening area, 109 μm wire diameter, 200 μm thickness), two layers of PP separator, and finally, sodium metal foil. The PP mesh was sandwiched between the PP separators to increase the spacing between the positive and negative electrodes and prevent short circuits caused by sodium dendrites. The hardware used included a 400-series stainless steel base, a PP gasket, a 304-series stainless steel spacer, a stainless steel disc spring, and a 300-series stainless steel cap. Each cell contained a total of 100–125 μL of electrolyte. The crimped coin cells were then removed from the glove box for cycling.

[0097] Test half coin cells with Pb-HC electrodes (Pb-HC half cells) at 0.005 to 1 V vs. Na in a battery test system in a temperature-controlled chamber at 30.0 ± 0.1 °C. + Half coin cells with Sn electrodes (Sn half cells) were cycled at 0.005 to 0.8 V vs. Na in a battery test system. +The Pb-HC and Sn cells were cycled with 0.1% ethanol / Na. The first two cycles of the Pb-HC and Sn cells consisted of a C / 20 constant current (CC) charge and a C / 40 constant current constant voltage (CCCV) discharge with a C / 20 current interrupt. The following cycles consisted of a C / 5 CC charge and a C / 5 CCCV discharge with a C / 20 current interrupt. Two C / 20 "check-up" cycles were performed every 50 C / 5 cycles to examine low-rate capacity retention.

[0098] Half coin cells with Pb electrodes (Pb half cells) were cycled using a tester in a temperature-controlled chamber at 30.0 ± 0.1 °C. The formation protocol for half coin cells with Pb electrodes was 0.005 V to 0.8 V vs. Na. + The CC cycling of / Na involved initial 2C, C, and C / 2 discharges to 0.8 V, followed by a switch to C / 20 for two cycles. The initial 2C, C, and C / 2 discharges to 0.8 V allowed for the avoidance of anomalous high-voltage irreversible capacity.

[0099] Formation of half coin cells (HC half cells) with pure hard carbon electrodes: 0.005 to 1.5 V vs. Na + CC cycling at the / Na voltage limit and a C / 20 current for two cycles were used. After formation, the HC cells were cycled at a C / 5 current for subsequent extended cycling at the same voltage limit. Two C / 20 check-up cycles were performed every 50 C / 5 cycles.

[0100] Example 9 - Voltage profile of Sn half cell Figure 4A shows the voltage profiles for the formation cycle, cycle 100, and cycle 200 of a Sn half-cell containing NaPAA binder and 1 M NaPF6 in G1 electrolyte. As shown in Figure 4A, the first discharge (sodiated) and charge (desodiated) capacities are 877.8 mAh / g and 796.1 mAh / g, respectively, resulting in a first cycle coulombic efficiency (FCE) of 90.7%. Figure 4B shows that the first desodiated and second sodiated curves are consistent with the four Na xThe graph shows four stages between the plateaus corresponding to the Sn phase. As shown in Figure 4A, the second discharge and charge capacities were 802.4 mAh / g and 822.8 mAh / g, respectively, with a CE of 102.5%. After the first two formation cycles at C / 20, the Sn half-cell was cycled at C / 5 for long-term cycling. Notably, the voltage curves for cycles 100 and 200 substantially overlap with those for the formation cycle, achieving a reversible capacity of 820 mAh / g, similar to the theoretical capacity of 847 mAh / g. The consistency of the voltage curves suggests that the Sn electrode did not experience substantial impedance growth or active mass loss, despite repeatedly undergoing a 424% volume change over 200 cycles. Furthermore, the overlap of the voltage curves for C / 20 and C / 5 also indicates that the Sn electrode has excellent kinetic properties and rate capability.

[0101] Additionally, Figure 4A shows the Sn vs. Na concentration in the G1 electrolyte with 1 M NaPF6. + The results show that the Sn / Na cell had no anomalous high voltage irreversible capacity (AHVIC) during the first discharge at C / 20 from an open circuit voltage (OCV) of 1.8 V, suggesting good electrolyte stability on this Sn electrode.

[0102] Example 10 - Voltage profile of Pb half cell Figure 5A shows the sodiation and desodium voltage curves versus specific capacity for a Pb half-cell from formation to cycle 100. As shown in Figure 5A, the voltage curve from cycle 2 at C / 20 and the voltage curves for cycles 50 and 100 at C / 5 substantially overlap, indicating minimal capacity loss or average voltage increase. Additionally, Figure 5A shows that subsequent cycles after the formation cycle show substantially minimal fade, with the capacity remaining essentially at the theoretical capacity of 485 mAh / g. While the kinetics of Na in Pb can cause volume expansion of the Pb, the good capacity retention shown in Figure 5A indicates that volume expansion is not a significant issue for appropriately sized Pb particles. Figure 5A also shows that there is virtually no change in the voltage curve over 100 cycles, indicating little or no increase in voltage polarization or irreversible structural changes. Cycling the Pb half-cell demonstrates excellent results, despite the 387% volume change that occurred per cycle.

[0103] Figure 5B shows the Na-Pb phases with appropriate labeling. x The voltage versus x in Pb is shown. The experimental value of x matches the expected literature phase and indicates essentially 100% utilization of Pb in this cell. It is also noteworthy that the voltage polarization between the phase change plateaus is not identical. The Pb to NaPb3 plateau has a voltage polarization of 34 mV, the NaPb3 to NaPb plateau is maximum at 66 mV, the NaPb to Na9Pb4 plateau is 32 mV, and the Na9Pb4 to Na 15 The plateau to Pb4 is the smallest at 28 mV.

[0104] Example 11 - Voltage profile of P-HC half cell Figure 6 shows the charge and discharge curves of a P-HC electrode with a mass ratio of 1:3. Two charge plateaus exist at approximately 0.1 V and approximately 0.6 V, corresponding to the desodium processes of hard carbon and phosphorus, respectively. Unlike Sn and Pb, the conversion of P to NaP is characterized by a single voltage plateau. With 25 wt% P in the blend, the capacity of the P-HC electrode reaches approximately 560 mAh / g, which is much higher than the capacity of pure hard carbon, approximately 300 mAh / g. In addition, a carbonate electrolyte is used in the P-HC electrode, which has higher stability at higher voltages compared to G1.

[0105] Example 12 - Long-term cycling performance of P-HC half-cell, Sn half-cell, and Pb half-cell Figures 7A and 7B show the long-term cycling performance of the P-HC half-cell, Sn half-cell, and Pb half-cell. The Sn half-cell exhibits an initial capacity hump before stabilizing at 820 mAh / g for 200 cycles. This capacity hump may be caused by the fracture of large Sn particles, which coincides with SEI formation in the early cycles. After 15 cycles, the cell appears to reach a steady state, and the specific capacity remains stable over subsequent cycles.

[0106] The Pb half-cell in Figure 7A matches the theoretical specific capacity of 485 mAh / g even after 100 cycles at C / 5. Thus, there is no significant difference in capacity between the C / 5 and C / 20 check-up cycles, again confirming the superior kinetics of Na alloying in Pb shown in Figure 5B. The normalized capacity plot in Figure 7B shows no capacity loss over the entire life of the cell.

[0107] The P-HC half-cell also exhibits good cycling stability, initially increasing slightly in capacity to about 560 mAh / g, followed by stable cycling up to 30 cycles, as shown in Figure 7A.

[0108] Figure 8A shows the specific capacity versus cycling data for Sn with 80 wt % or 90 wt % active material and Pb with 90 wt % or 96 wt % active material in the electrode using 1 M NaPF in G1 electrolyte. Figure 8B shows the normalized capacity versus cycling data to the third cycle (first cycle at C / 5). Electrodes containing larger active material fractions of Pb and Sn were tested in half cells, as shown in Figures 8A and 8B.

[0109] In the case of Sn, increasing the amount of active material decreased the specific capacity from approximately 820 mAh / g to approximately 770 mAh / g after 80 cycles, as shown in Figure 8A, but the capacity retention remained similar, as shown in Figure 8B. In the case of Pb, the difference between using 90% and 96% active material was small, with the specific capacity only decreasing slightly from 485 mAh / g to 475 mAh / g after 80 cycles, as shown in Figure 8A. As shown in Figure 8B, increasing the amount of Pb active material showed almost no difference in capacity retention.

[0110] Example 13 - Ultra-Precision Coulometry Ultra-High Precision Coulometry (UHPC) cycling tests were performed on Sn cells (80% active material), Pb cells (96% active material), and HC cells. These cells were cycled at C / 20 in CC mode for 20 cycles in a temperature-controlled chamber at 40.0 ± 0.1°C on a UHPC system to collect accurate cycling statistics comparing various electrode pairs.

[0111] Figure 9A shows UHPC data for a Sn and hard carbon half-cell tested with 1 M NaPF6 in G1 electrolyte at C / 20 rate and 40 °C. Figure 9B shows UHPC data for a Pb half-cell and hard carbon half-cell tested with 1 M NaPF6 in G1 electrolyte at C / 20 rate and 40 °C, and a hard carbon cell tested with 1 M NaPF6 in G1 electrolyte at C / 20 rate and 40 °C. As shown in Figure 9A, the coulombic efficiency (CE) of the Sn cell decreased from an initial high value of 101.6% in cycle 2 (not shown), indicating that not all of the Na alloyed in the first sodiation was dealloyed in the first desodiation, but was dealloyed in the second desodiation. Over the next eight cycles, the CE returned to below 100%, decreasing to a minimum of 99.3%, and then leveling off at 99.8% after 30 cycles. In contrast, hard carbon and Pb in Figure 9B show a more traditional trend, with CE starting at a low value of about 98.9% and steadily increasing to 99.6% after 20 cycles.

[0112] Figure 9C shows the specific capacity of Sn sodiated and desodiated versus cycles, and Figure 9E shows an SEM image of a Sn electrode showing large Sn particles reorganized into a uniformly distributed microstructure after 50 cycles. Figure 9D shows the specific capacity of Pb sodiated and desodiated versus cycles, and Figure 9F shows an SEM image of a Pb electrode showing large Pb particles reorganized into a uniformly distributed microstructure after 100 cycles. The specific capacities of Sn and Pb, respectively, in Figures 9C and 9D are also significantly different at the initial cycles, consistent with the trend observed in the cycles shown in Figures 7A and 7B. The specific capacity of the Sn electrode in Figure 9C is slightly higher than that in Figure 7A, which may be due to the increased operating temperature. While the Pb specific capacity decreases slightly after formation and remains at approximately 460 mAh / g, Sn shows an initial increase in specific capacity over the first seven cycles. This is then followed by a decrease in the Sn specific capacity, plateauing at 840 mAh / g around cycle 20.

[0113] The specific capacities of the Sn and Pb half-cells level off during cycling, as shown in Figures 9C and 9D. This occurs almost immediately for the Pb cell and after approximately 20 cycles for the Sn cell. Once the capacities level off, it can be observed that the CE is less than 1 for both cells. The deviation from exactly 1 indicates that the sodiation capacity, which includes alloying and additional SEI formation, is greater than the desodiation capacity, which represents dealloying alone. As cycling progresses, the amount of Na lost per cycle due to SEI thickening decreases as the CE approaches exactly 1. Note that the experiments in Figures 9A–9F were performed at a very low current (C / 20) to allow more time for the SEI thickening reaction to occur, resulting in a larger deviation of the CE from 1.00000. Additionally, the high temperature of 40 °C is selected to also accelerate the SEI thickening reaction. The CE as high as 99.8% obtained under these conditions mirrors that observed for the Li / graphite half-cell. The data shown in Figures 9A-9F suggest that despite significant morphological restructuring of the Sn and Pb electrodes, the consumption of Na reserves by the SEI is moderate and limited in the early cycles, indicating good cycling performance of the Sn and Pb negative electrodes in full cells.

[0114] Example 14 - Sn and Pb electrode configurations Scanning electron microscope (SEM) images were taken of a desodium-cycled Sn electrode and a desodium-cycled Pb electrode (90% active material, following the cycling protocol for non-UHPC cells up to 10 cycles).

[0115] Figure 10A shows an SEM image of the pristine Pb electrode. Figures 10B-10D show SEM images of the Pb electrode after 1 cycle at C / 20, 10 cycles at C / 5, and 100 cycles. As shown in Figures 10A-10D, the initial large Pb particles were reconstructed into a uniformly distributed microstructure after 100 cycles. While the pristine Pb electrode contained particles up to 20 μm in size, the electrode after 100 cycles exhibits particles on the 1 μm scale.

[0116] Figure 10E shows an ex situ SEM image of a desodium-depleted Sn electrode after 50 cycles at C / 5 (the same cycling conditions as the cell in Figure 5A). Figure 10A shows that large Sn particles have reorganized into a uniformly distributed microstructure after 50 cycles. In contrast to the variable particle size of less than approximately 150 μm observed in the initial Sn powder, the cycled Sn electrode contains uniformly distributed Sn particles on the 1 μm scale.

[0117] Figure 10B shows an inset SEM image of a Pb electrode showing large Pb particles reorganized into a uniformly distributed microstructure after 100 cycles. Figure 10B shows a similar reorganization phenomenon for a desodium Pb electrode after 106 cycles. While the pristine Pb electrode contained particles up to 20 μm in size, the cycled electrode shows particles on the 1 μm scale.

[0118] Example 15 - Long-term cycling performance of Pb-HC half-cell, Pb half-cell and HC half-cell Figures 11A-11C show the cycling performance of a Pb half-cell with 1 M NaPF6 in G1 electrolyte, a hard carbon (HC) half-cell, and a half-cell with a 50:50 (w / w) blend of Pb and hard carbon (Pb-HC). Figure 11A shows the specific capacity vs. cycle for each electrode. Figure 11B shows the estimated fully sodiated volumetric capacity vs. cycle for each electrode based on the actual electrode dimensions and the assumption that volume expansion does not change electrode porosity. Figure 11C shows the normalized capacity vs. cycle to the third cycle (first cycle at C / 5).

[0119] As shown in Figures 11A and 11B, the Pb-HC blend exhibited a specific capacity of approximately 360 mAh / g and an estimated fully sodiated density of 1.01 g / cm 3 Therefore, it is approximately 360mAh / cm 3 This specific capacity is consistent with a pure Pb cell showing about 475 mAh / g, while pure hard carbon has about 285 mAh / g. Surprisingly, it is about 360 mAh / cm 3The volumetric capacity of the Pb-HC blend is only about 230 mAh / cm 3 The volumetric capacity of the pure hard carbon is 57% higher, at approximately 410mAh / cm 3 This is only 12% lower than pure Pb, showing 99% capacity retention after 60 cycles in Figure 11C. Overall, the Pb-HC blend reduces the maximum volume expansion to 44% compared to pure hard carbon, significantly increasing the volumetric capacity, while retaining the excellent cycling stability of pure Pb.

[0120] Figure 11D compares the cycling performance of Pb-HC electrodes in 1 M NaPF6 dissolved in G1 electrolyte or EC:DEC (1:1 w / w) electrolyte. As shown in Figure 11D, the Pb-HC cell exhibits a significant decrease in cycling performance in EC:DEC electrolyte compared to G1 electrolyte.

[0121] Example 16 - Volume expansion of alloy / hard carbon electrodes 12A and 12B show the calculated unsodiated and fully sodiated volumetric capacities of the alloy / hard carbon blends versus the weight fractions of P (red), Pb (black), and Sn (blue), respectively. The dashed lines in FIGS. 12A and 12B represent the 870 mAh / cm 3 Figure 12C shows the calculated volumetric expansion of the alloy / hard carbon blend versus the weight fraction of the alloy. The dashed line in Figure 12C shows the estimated volumetric expansion of 38% for a 10% Si / graphite blend operating in a Li-ion cell. Figures 12D and 12E show the unsodiated and fully sodiated volumetric capacity versus volume expansion, respectively, as the alloy weight fraction increases.

[0122] Figures 12A-12C show the calculated volumetric capacity and volume expansion of alloy-hard carbon (alloy-HC) blends with different alloy weight fractions. As shown in Figures 12A-12C, blending alloying elements with hard carbon provides an option for using Sn and Pb anodes in Na-ion cells with fixed-size casings (i.e., cylindrical cells). Pure P, Sn, and Pb have very similar volumetric capacities, but P-HC blends can achieve the same capacity with the lowest alloy weight fractions. For example, doubling the volumetric capacity of hard carbon requires approximately 12 wt% P in the P-HC blend, 29 wt% Sn in the Sn-HC blend, and 43 wt% Pb in the Pb-HC blend, resulting in volume expansions of approximately 24%, 32%, and 35%, respectively. In comparison, considering that 10% Si in Si-graphite blends results in approximately 38% volume expansion of Li-ion cells, the volume expansion of all these alloy-HC blends may be acceptable for today's battery cell and pack designs. This clearly demonstrates that alloy-HC blends have a high potential for increasing the volumetric energy density of sodium-ion energy storage devices while maintaining manageable volume expansion.

[0123] Figure 12F shows the calculated volume expansion during cycling when Na alloying elements such as P, Sn, and Pb are blended with hard carbon. The dashed line shows the volume expansion for a 10:90 Si:graphite (wt / wt) ratio that can be handled in a commercially available cell. As shown in Figure 12F, the volume expansions of P-HC, Sn-HC, and Pb-HC that can be handled in a commercially available cell are 18:82, 31:69, and 45:55, respectively.

[0124] While specific embodiments have been described, these embodiments are presented by way of example and are not intended to limit the scope of the present disclosure. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions, and modifications of the systems and methods may be made without departing from the spirit of the present disclosure. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the present disclosure.

[0125] It should be understood that any feature, material, characteristic, or grouping described in connection with a particular aspect, embodiment, or example is applicable to any other aspect, embodiment, or example described in this section or elsewhere in this specification, unless incompatible therewith. All features disclosed in this specification (including the accompanying claims, abstract, and drawings), and / or all steps of any method or process so disclosed, may be combined in any combination, except combinations in which at least some of such features and / or steps are mutually exclusive. Protection is not limited to the details of any foregoing embodiment. Protection extends to any novel, or any novel combination of, features disclosed in this specification (including the accompanying claims, abstract, and drawings), or any novel, or any novel combination of steps of any method or process so disclosed.

[0126] Furthermore, certain features that are described in this disclosure in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, while features may be described above as acting in a particular combination, one or more features from a claimed combination can, in some cases, be deleted from the combination, and the combination can be claimed as a subcombination or a variation of the subcombination.

[0127] Furthermore, while operations may be illustrated in the figures or described herein in a particular order, such operations need not be performed in the particular order illustrated, or in sequential order, or even all operations need to be performed to achieve desirable results. Other operations not illustrated or described may be incorporated into the example methods and processes. For example, one or more additional operations may be performed before, after, simultaneously with, or between any of the described operations. Furthermore, operations may be rearranged or reordered in other implementations. Those skilled in the art will appreciate that in some embodiments, the actual steps performed in the illustrated and / or disclosed processes may differ from those shown in the figures. Depending on the implementation, certain of the steps described above may be omitted, and other steps may be added. Furthermore, the features and attributes of the specific embodiments disclosed above may be combined in different ways to form additional embodiments, all of which are within the scope of the present disclosure. Also, the separation of various system components in the above implementations should not be understood as requiring such separation in all implementations, and it should be understood that the described components and systems may generally be integrated together in a single product or packaged in multiple products. For example, any of the components of the energy storage systems described herein may be provided separately or may be integrated (e.g., packaged together or attached together) to form an energy storage system.

[0128] For purposes of this disclosure, certain aspects, advantages, and novel features have been described herein. Not necessarily all such advantages may be achieved in accordance with any particular embodiment. Thus, for example, one skilled in the art will understand that the present disclosure may be embodied or implemented to achieve one or more advantages as taught herein, without necessarily achieving other advantages as may be taught or suggested herein.

[0129] Conditional language such as "can," "could," "might," or "may," unless otherwise specified or understood otherwise within the context in which it is used, is generally intended to convey that certain embodiments include certain features, elements, and / or steps, while other embodiments do not. Thus, such conditional language does not generally imply that the features, elements, and / or steps are somehow required in one or more embodiments, or that one or more embodiments necessarily include logic for determining whether those features, elements, and / or steps should be included in or performed in any particular embodiment, with or without user input or prompting.

[0130] Conjunctions such as the phrase "at least one of X, Y, and Z," unless otherwise specified, are understood in the context in which they are generally used to convey that an item, term, etc. can be either X, Y, or Z. Thus, such conjunctions are generally not intended to imply that a particular embodiment requires the presence of at least one of X, at least one of Y, and at least one of Z.

[0131] As used herein, language of degree, such as "approximately," "about," "generally," and "substantially," refers to a value, amount, or characteristic that is close to a stated value, amount, or characteristic that still performs a desired function or achieves a desired result. For example, the terms "approximately," "about," "generally," and "substantially" can refer to amounts that are less than 10%, less than 5%, less than 1%, less than 0.1%, and less than 0.01% of the stated amount, depending on the desired function or desired result.

[0132] The scope of the present disclosure is not intended to be limited by the specific disclosure of preferred embodiments in this section or elsewhere herein, but may be defined by the claims, as presented in this section or elsewhere herein, or as presented in the future. Claim language should be interpreted broadly based on the language used in the claims, and not limited to the examples described herein or during prosecution of the application, and examples should be construed as non-exclusive.

[0133] The headings provided herein, if any, are for convenience only and do not necessarily affect the scope or meaning of the devices and methods disclosed herein.

Claims

1. 1. A sodium ion energy storage device comprising: A positive electrode and an electrolyte comprising a sodium salt; A negative electrode comprising a composite negative electrode active material, the composite negative electrode active material comprising: a carbon active material; an anode comprising an alloying element selected from the group consisting of phosphorus (P), germanium (Ge), tin (Sn), antimony (Sb), lead (Pb), bismuth (Bi), and combinations thereof; A sodium ion energy storage device comprising:

2. 10. The sodium-ion energy storage device of claim 1, wherein the composite negative electrode active material comprises 5% to 95% by weight of the carbon active material.

3. 10. The sodium-ion energy storage device of claim 1, wherein the composite negative electrode active material comprises 5% to 95% by weight of the alloying element.

4. 4. The sodium-ion energy storage device of claim 1, wherein the alloying elements are selected from the group consisting of P, Pb, Sn, and combinations thereof.

5. 4. The sodium-ion energy storage device of claim 1, wherein the alloying element comprises a plurality of particles having a particle size of up to 150 μm.

6. 4. The sodium-ion energy storage device of claim 1, wherein the carbon active material comprises hard carbon.

7. 4. The sodium ion energy storage device of claim 1, wherein the negative electrode further comprises a negative electrode coating.

8. 8. The sodium ion energy storage device of claim 7, wherein the negative electrode coating has a thickness of 2 to 100 μm.

9. 8. The sodium-ion energy storage device of claim 7, wherein the negative electrode coating further comprises a binder.

10. 10. The sodium-ion energy storage device of claim 9, wherein the negative electrode coating comprises the binder in an amount of up to 5 wt.%.

11. 8. The sodium-ion energy storage device of claim 7, wherein the negative electrode coating further comprises a conductive additive.

12. 12. The sodium-ion energy storage device of claim 11, wherein the negative electrode coating comprises the conductive additive in an amount of up to 5% by weight.

13. 8. The sodium-ion energy storage device of claim 7, wherein the negative electrode comprises the negative electrode coating disposed on a current collector.

14. 14. The sodium-ion energy storage device of claim 13, wherein the current collector has a thickness of up to 30 μm.

15. 4. The sodium-ion energy storage device of claim 1, wherein the negative electrode of the sodium-ion energy storage device has a specific capacity after 100 cycles of at least 370 mAh / g.

16. 4. The sodium-ion energy storage device of claim 1, wherein the negative electrode of the sodium-ion energy storage device has a first cycle efficiency of at least 85%.

17. 4. The sodium-ion energy storage device of claim 1, wherein the sodium-ion energy storage device has a coulombic efficiency after 20 cycles of at least 99%.

18. 4. The sodium-ion energy storage device of claim 1, wherein the sodium-ion energy storage device has a capacity retention after 200 cycles of at least 90%.

19. 1. A method of forming a negative electrode film for a sodium-ion energy storage device, comprising: combining a composite negative electrode active material, a binder, and a conductive additive to form an electrode film mixture, the composite negative electrode active material comprising: a carbon active material; an alloying element selected from the group consisting of phosphorus (P), germanium (Ge), tin (Sn), antimony (Sb), lead (Pb), bismuth (Bi), and combinations thereof; forming a negative electrode film from the electrode film mixture; A method comprising:

20. 20. The method of claim 19, further comprising reducing the size of the composite negative electrode active material to less than 150 μm.

21. The combining step comprises: mixing the composite negative electrode active material with the conductive additive to form a first mixture; mixing the first mixture with the binder and the conductive additive to form the electrode film mixture; 21. The method of claim 19 or 20, comprising:

Images