Layered active materials for sodium-ion batteries

Abstract

This invention relates to a cathode compound for use in sodium-ion electrochemical batteries, the cathode compound comprising: - an active compound of formula I: Na x Ni 0.5‑y Zn y Mn 0.5‑z Ti z O2 (I), wherein x is a number in the range of 0.7 to 1.1, y is a number greater than 0 and at most 0.1, and z is a number between 0 and 0.5; and an electronically conductive additive, wherein the positive electrode compound is free of polymer binders.

Description

Technical Field

[0001] This invention relates generally to a novel sodium layered oxide compound, a device doped with said compound (such as an electrode containing said sodium layered oxide compound), or an electrochemical energy storage battery or device (e.g., a sodium-ion battery pack). The invention also relates to a method for manufacturing and / or using such compounds, and devices for incorporating them. Background Technology

[0002] Sodium-ion (Na-ion) battery packs are rapidly developing as a potential energy storage technology, where cost, rather than battery weight and / or energy density, is the decisive factor.

[0003] Several prototype sodium-ion battery packs have been proposed using polyanionic compounds (e.g., Na3V2(PO4)2F3, hereinafter referred to as NVPF) as cathode materials. The results are acceptable, but the use of rare and toxic elements (such as vanadium) will have adverse environmental consequences.

[0004] Alternative compounds, such as layered sodium transition metal oxides (e.g., Na), have been investigated. x MO2, where x can be up to 1, and M is at least one transition metal ion. Na x MO2 can be stabilized in different layered stacks depending on its sodium content x. For example, when x is about 1, Na x MO2 is an O3-type layered oxide, while when x is less than or equal to 0.8, it can be a P2 or P3-type layered oxide (see references 1 and 2). In the nomenclature used, such as O3, P2, and P3, the letters O or P represent sodium at octahedral (O) or prism (P) sites, respectively, and the numbers represent the number of MO2 layers in the unit cell, which is the smallest repeating unit with a completely symmetrical crystal structure (reference 3).

[0005] Na x The molecular weight of MO2 is smaller than that of NVPF. Therefore, compared with NVPF compounds, the theoretical values ​​of specific capacity and specific energy of sodium layered oxides are expected to be higher over a given voltage range (References 4, 5).

[0006] However, sodium layered oxides reported to date have shown worse capacity retention than NVPF after hundreds of cycles (References 6, 7). In fact, sodium layered oxides undergo volume shrinkage and / or expansion due to several phase transitions. Indeed, O3-Na... x MO2 can hardly reach 50% of its theoretical capacity because the material undergoes a continuous phase transition during cycling, especially over the extended voltage range, i.e., voltages greater than 4.0 V relative to Na. + / Na (References 6, 9). P2 and P3 sodium layered oxides Na x MO2 contains fewer than one sodium ion per transition metal ion, exhibiting a limited capacity. Therefore, when typical P2 / P3Na... x When MO2 is used as the positive electrode, the specific energy that can be obtained as the product of the average redox voltage and the specific capacity of the sodium-ion full cell is always less than the stoichiometric O3-type Na. x MO2.

[0007] Besides the phase transition during cycling, the low redox potential and humidity sensitivity of the material (requiring storage and handling of these layered oxides in an inert atmosphere) are factors associated with the use of O3 and Na. x Other major issues with MO2 materials.

[0008] Komaba et al. reported acceptable results for sodium layered oxides (NMO) in Inorg. Chem. 2012, 51, 6211−6220 (Reference 12), namely Na 1-x Ni 0.5 Mn 0.5 O2, with a voltage range of 2.2 to 3.8 V, exhibits poor cycling performance after charging to 4.5 V. Similarly, Kubota et al. reported in J. Phys. Chem. C 2015, 119, 166-175 that the discharge capacity of NMO materials significantly decreases when charging above the 3.8 V plateau. This shows consistency with many reports (see p169) demonstrating similar behavior in these types of NMO materials with an O3 structure. Therefore, the cutoff voltage for these materials is typically set to around 4 V.

[0009] Layered Na has been proposed x Various modifications to MO2 materials are proposed to improve their electrochemical properties. Specifically, the following document outlines modifications to O3-NaNi... 0.5 Mn 0.5 Ni cations are added to O2 (hereinafter referred to as NM) to partially replace Mn. 4+ Mariyappan et al., in Adv. Energy Mater., 8, 1702599 (2018) (Reference 8), proposed that in O3-NaNi 0.5 Mn 0.5 Sn in O2 4+ Perform another part Mn 4+ Replacement to obtain NaNi 0.5 Mn 0.5-x Sn x O2, where x is a number between 0 and 0.5.

[0010] Zheng et al., in Electrochimica Acta, 233, 284–291 (2017) (Reference 9), proposed using Ti 4+ Perform partial Mn 4+ Replacement, to obtain Na 0.9 Ni 0.45 Mn x Ti 0.55-x O2, where x is a number between 0 and 0.55.

[0011] WO 2014 009 710 A1 describes basic layered oxide compounds, such as Na 1.05 Ni 0.4 Mn 0.5 Mg 0.025 Ti 0.025 O2 and Na 1.05 Ni 0.4 Ti 0.025 Mg 0.025 Mn 0.5 O2.

[0012] WO 2014 132 174 A1 describes basic layered oxide compounds, such as Na 1.05 Ni 0.40 Mn 0.50 Mg 0.025 Ti 0.025 O2.

[0013] US 2015 020 713 8 A1 describes sodium layered oxide compounds, such as NaNi. 0.50 Mn 0.25 Ti 0.25 O2, NaNi 0.5 Mn 0.225 Ti 0.225 Zr 0.05 O2 and NaNi 0.5 Mn 0.2 Ti 0.2 Zr 0.1 O2.

[0014] US 2015 013 703 1 A1 describes the preparation of basic layered oxide compounds, such as NaNi. 0.4 Mn 0.4 Cu 0.1 Ti 0.1 O2, NaNi 0.45 Mn 0.45 Cu 0.05 Ti 0.05 O2, NaNi 0.45 Mn0.45 Mg 0.05 Ti 0.05 The O2 method is used to convert sodium ion materials into lithium ion materials using an ion exchange method.

[0015] US 2015 / 0194672 (Barker) discloses layered nickelate oxides doped with various other metals as dopants, including zinc, calcium, magnesium, copper, and cobalt. This patent does not disclose that compounds containing zinc exhibit good performance at voltages greater than 4.0 V, nor does it disclose how to prepare such compounds.

[0016] US 2018 / 0269522 (Treacher) discloses a layered nickelate oxide used as an active material for the positive electrode of a sodium-ion battery, which is doped with various other metal dopants, including zinc, calcium, magnesium, copper, and cobalt. For NaNi 0.33 Mn 0.33 Mg 0.167 Ti 0.167 For O2, it is recommended that the applied voltage not exceed or be less than 4.3 V.

[0017] None of the above documents publicly use Zn 2+ Ni 2+ Partial substitution is used to obtain a more stable composition and / or better or at least equal electrochemical performance than that obtained with NVPF, especially at voltages greater than 4.0 V, particularly greater than 4.3 V. Summary of the Invention

[0018] Therefore, one object of the present invention is to provide a novel layered sodium oxide-type electroactive compound, and an electrochemical energy storage device containing such a compound, said compound overcoming one or more of the disadvantages of prior art materials and devices and / or having one or more of the following properties:

[0019] - Compared to NVPF, it has a longer service life, especially with a higher energy retention rate after 100 cycles;

[0020] - By retaining at least 70% of the initial energy density, it is able to cycle at voltages greater than 4.0 V;

[0021] - It exhibits stability in humid environments; and

[0022] It is environmentally acceptable, or at least less toxic than vanadium or other available alternatives.

[0023] It has now been discovered that in O3-type NaNi 0.5 Mn 0.5 Introducing Zn into O2 (NM) layered oxides 2+It provides, especially in the presence of titanium, a compound that unexpectedly possesses at least one, preferably more, of the aforementioned properties.

[0024] Therefore, one object of the present invention is a method having the formula Na x Ni 0.5-y Zn y Mn 0.5-z Ti z A compound of O2 (hereinafter referred to as ZNMT), wherein x is a number in the range of 0.7 to 1.1, y is greater than 0 and less than or equal to 0.1, and z is a number between 0 and 0.5 (greater than 0 and less than 0.5). The range of x can be from 0.8 to 1.1. And, preferably, x is about 1 or equal to 1. This compound is electrochemically active. According to a specific embodiment of the invention, the compound is a homogeneous compound or material.

[0025] The active compound is preferably of the formula Na. x Ni 0.5-y Zn y Mn 0.5-z Ti z Compounds of O2, wherein x is about 1, y is a number in the range of 0.01 to 0.1, and z is a number in the range of 0.01 to 0.45. The active compound is also preferably of the formula Na. x Ni 0.5-y Zn y Mn 0.5-z Ti z Compounds of O2, wherein x is about 1, y is a number in the range of 0.03 to 0.1, and z is a number in the range of 0.05 to 0.25. Preferably, the active compound has the formula Na. x Ni 0.5-y Zn y Mn 0.5-z Ti z O2, where x is approximately 1, y is a number in the range of 0.04 to 0.1, and z is a number in the range of 0.08 to 0.22.

[0026] The following compounds are also preferred: NaNi 0.45 Zn 0.05 Mn 0.4 Ti 0.1 O2 (hereinafter referred to as ZNMT1), NaNi 0.4 Zn 0.1 Mn 0.4 Ti 0.1 O2 (hereinafter referred to as ZNMT2) and NaNi 0.45 Zn 0.05 Mn 0.3 Ti 0.2O2 (hereinafter referred to as ZNMT3) and its derivatives. Derivatives refer to elements whose atomic percentage can vary within a range of ±10%.

[0027] According to a variation of the invention, the active compound has the formula (V) Na x Ni y- z Zn z Mn (1-y-z) Ti n O2, where x is a number in the range of 0.7 to 1.1, y is greater than 0 and less than or equal to 0.5, z is a number between 0 and 0.1 (greater than 0 and less than 0.5), and n is a number between 0 and 0.6. The range of x can be from 0.8 to 1.1. Preferably, x is about 1 or equal to 1. This compound is electrochemically active.

[0028] Having the formula Na x Ni 0.45 Zn 0.05 Mn 0.35 Ti 0.15 Compounds of O2 (IV) are also compounds according to the invention, wherein x is in the range of 1.1 to less than 0.7, preferably 1 to 0.8.

[0029] According to a specific embodiment of the present invention, having the formula NaNi 0.4 Zn 0.1 Mn 0.4 Ti 0.1 Compounds containing O2 can be excluded from the scope of this invention.

[0030] According to a specific embodiment of the present invention, having the formula NaNi 0.4 Zn 0.0.5 Mn 0.45 Ti 0.05 Compounds containing O2 can be excluded from the scope of this invention.

[0031] According to a specific embodiment of the present invention, having the formula NaNi 0.5-x' Ti 0.5-x' Zn x' Mn x' Compounds of O2 can be excluded from the range where x' ranges from 0 to less than 0.5.

[0032] According to a specific embodiment of the present invention, having the formula NaNi 0.5-x' Ti y' Zn x' Mn 0.5-y'Compounds of O2 may be excluded from the scope of this invention, wherein x' ranges from 0 to less than 0.5 and y' ranges from 0 to less than 0.5.

[0033] According to a specific embodiment of the present invention, having the formula NaNi 0.5-x' Ti 0.25+x' / 2 Zn x' Mn 0.25-x' / 2 Compounds of O2 may be excluded from the scope of this invention, wherein x' ranges from 0 to less than 0.5.

[0034] The sodium layered oxide compound of the present invention can advantageously be in powder form. Preferably, the layered oxide powder can be prepared by ball milling, and preferably the weight ratio of powder to balls is 1:20.

[0035] Another object of the present invention is a conductive material comprising the aforementioned layered oxide compound (or active compound) and an electronically conductive additive. The electronically conductive additive may comprise, be substantially composed of, or consist of carbon black (i.e., completely disordered or substantially disordered carbon, CAS: 1333-86-4), such as Super-P TM C-45 TM C-65 TM Acetylene Black, Ketjen Black TM Volcanic carbon, etc., are typically in powder form. Essentially disordered carbon containing a small amount of graphitized carbon is preferred. This conductive material can be prepared by ball milling layered oxide powders, while another conductive material can be prepared by ball milling, preferably with a powder-to-ball weight ratio of 1:35. These materials are particularly suitable for manufacturing positive electrodes (i.e., as positive electrode materials).

[0036] The concentration of the electronically conductive additive is preferably in the range of 10-20 w / w% relative to the total weight of the layered oxide compound and the conductive additive. A preferred concentration is about 15 w / w%.

[0037] According to one particular embodiment, no polymer binder is used, and more preferably no adhesive material is used. The conductive material may be in powder form, and it may be compressed (e.g., disc-shaped) or not compressed.

[0038] Alternatively, the conductive material may additionally comprise an adhesive material that allows it to be cast. This adhesive may be a polymeric adhesive. The polymeric adhesive may advantageously comprise, consist of, or be substantially composed of polyvinylidene fluoride and / or its derivatives. Before casting the adhesive material onto the support, the adhesive material may be mixed with a suitable solvent, which is advantageously a non-aqueous (e.g., organic) solvent such as N-methylpyrrolidine (NMP).

[0039] In one embodiment, the compound of the present invention has, or is permitted to have, an initial discharge specific capacity of at least 120 mAh·g⁻¹, preferably at least about 150 mAh·g⁻¹. -1 220 mAh·g -1 The discharge rate can be measured in the range of C / 30 to 1C, particularly at a discharge rate of about C / 10. The C / 10 rate corresponds to the total amount of sodium ions removed or added to the compound of the present invention over 10 hours. For example, the initial discharge capacity of the battery can be 140 mAh·g. -1 Up to 250 mAh·g -1 Within the range.

[0040] In another embodiment, the compound of the present invention has or is permitted a specific energy (Wh·kg). -1 ) is based on Ah·kg -1 The specific energy is the product of the specific capacity and the average redox potential of the battery, expressed in volts. Specific energy can be normalized over the total mass of the electrode materials at the positive and negative electrodes of the battery.

[0041] In another embodiment of the compound of the present invention, the battery has a specific energy of at least about 200 Wh·kg⁻¹ when cycled at voltages below 4 V and / or at least about 250 Wh·kg⁻¹ when cycled at voltages above 4 V. For example, the specific energy can be 200 Wh·kg⁻¹. -1 Up to 300 Wh·kg -1 Within the range, preferably 240Wh·kg -1 Up to 270 Wh·kg -1 .

[0042] The capacity retention rate (or charge retention rate) can be defined as the fraction of the initial discharge specific capacity available under specific discharge conditions. The energy retention rate can be defined as the fraction of the initial specific energy available under specific discharge conditions. Initial capacity / initial energy refers to the specific capacity / energy obtained in the discharged state (i.e., the sodium state) at the end of the first complete cycle (i.e., the complete cycle of the battery).

[0043] In another preferred embodiment, when cycled at a voltage above 4 V, the compounds of the present invention have, or are permitted to have, an energy retention rate exceeding 70% over one hundred cycles. Specifically, the voltage can be selected between 4 and 5 V, preferably equal to or above 4.4 V. The percentage of energy retention of the compounds of the present invention can range from 73% to 99%; preferably 78% to 95%, for example 80% to 90%.

[0044] According to another embodiment, when cycled at voltages up to or above 4 V (e.g., 4.4 V), the energy retention of the material or the battery exceeds 80% over one hundred cycles, preferably exceeding or being about 90%.

[0045] According to another aspect, the present invention is characterized by an electrochemical cell comprising:

[0046] - A negative electrode, which is configured to reversibly accept sodium ions from the electrolyte and reversibly release sodium ions into the electrolyte, said negative electrode having at least one current collector;

[0047] - A positive electrode comprising a sodium layered oxide compound according to the invention, configured to reversibly accept sodium ions from the electrolyte and reversibly release sodium ions into the electrolyte, said positive electrode having at least one current collector; and

[0048] - A separator soaked in the electrolyte containing sodium ions, the separator being in contact with both the negative and positive electrodes.

[0049] In a preferred embodiment, the positive electrode comprises, is composed of, or is substantially composed of the conductive material of the present invention as described above, and is then used as the positive electrode material. The electronically conductive material additive is advantageously carbon black.

[0050] In one embodiment, the negative electrode has an active material comprising, consisting of, or substantially consisting of metallic sodium. This is especially true when the electrochemical cell is a half-cell configuration.

[0051] In another, practically preferred embodiment, the negative electrode has an active material that may comprise hard carbon, antimony, tin, phosphorus, and combinations thereof, substantially consisting of hard carbon, antimony, tin, phosphorus, and combinations thereof, or consisting of hard carbon, antimony, tin, phosphorus, and combinations thereof. This material is particularly suitable for full-cell configurations.

[0052] In a preferred embodiment, the negative electrode comprises a carbonaceous compound as the active material, preferably hard carbon powder. The Raman spectrum of hard carbon exhibits two characteristic bands at 1350 (D band) and 1580 (G band) cm⁻¹. -1 These correspond to the E2g graphite mode and the defect-induced mode, respectively. Hard carbon powders can have particle sizes of 1-20 μm and 1-10 μm. 2 ·g -1 The specific surface area. The active material can be mixed with an electronically conductive additive such as carbon black to obtain the material of the negative electrode. The concentration of the electronically conductive material relative to the total weight of the active material and the additive can be in the range of 1 to 8 w / w%, for example 4 w / w%.

[0053] This negative electrode material may additionally include a binder material that allows it to be cast and / or has cohesive, conductive, or dispersive properties. This binder may be a polymer binder. The polymer binder may advantageously comprise, consist substantially of, or consist of sodium carboxymethyl cellulose and / or its derivatives. It may also comprise, consist substantially of, or consist substantially of polyvinylidene fluoride and / or its derivatives. Before casting the binder material onto the support, the binder material may be mixed with a suitable solvent such as N-methylpyrrolidone (NMP) and / or water.

[0054] When using active materials, electronically conductive materials, and adhesives, their respective weight ratios can be, for example, 92:4:4.

[0055] The current collector of any one or both electrodes can be made of any suitable material, such as stainless steel, aluminum, copper or nickel.

[0056] The electrolyte comprises a suitable salt, which may advantageously be selected from the group consisting of sodium hexafluorophosphate (NaPF6), sodium perchlorate (NaClO4), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium bis(pentafluoroethanesulfonyl)imide (NaBETI), sodium tetrafluoroborate (NaBF4), and mixtures thereof. The electrolyte also comprises a non-aqueous solvent, for example, selected from the group consisting of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), propylene carbonate (PC), ethylene carbonate (EC), ethyl acetate (EA), ethyl propionate (EP), methyl propionate (MP), bis(2-methoxyethyl) ether (diethylene glycol dimethyl ether), and mixtures thereof. The proportion of the solvent in the total weight of the electrolyte may be in the range of 60 w / w% to 98 w / w%.

[0057] The concentration of the salt in the solvent can be 0.1 mol·L⁻¹ -1 Up to 3 mol·L -1 Within the range, advantageously at 0.5 mol·L⁻¹ -1 Up to 2 mol·L -1 Within the range.

[0058] According to a preferred aspect of the invention, an electrolyte additive may be added to the electrolyte. This electrolyte additive helps improve the high-temperature performance and low self-discharge performance of the sodium-ion battery or battery pack of the present invention. The additive may be selected from the group consisting of: vinylene carbonate (VC), 1,3-propanesulfonate lactone (PS), succinate (SN), sodium difluoro(oxalate)borate (NaODFB), and mixtures thereof. The concentration of vinylene carbonate (VC) relative to the total weight of the electrolyte may be in the range of 0.1 to 10 w / w%, advantageously in the range of 0.5 to 5.0 w / w%. The concentration of 1,3-propanesulfonate lactone (PS) relative to the total weight of the electrolyte may be in the range of 0.1 to 5 w / w%, preferably in the range of 0.5 to 3.0 w / w%. The concentration of succinate (SN) relative to the total weight of the electrolyte may be in the range of 0.1 to 5 w / w%, preferably in the range of 0.5 to 2.0 w / w%. The concentration of sodium difluoro(oxalate)borate (NaODFB) relative to the total weight of the electrolyte can be in the range of 0.05 to 10 w / w%, preferably in the range of 0.2 to 1.0 w / w%.

[0059] The separator is a permeable membrane or thin film, preferably having micropores. The separator can be made of a material selected from the group consisting of: glass fiber, polyolefin separators (including polypropylene (PP) and polyethylene (PE), cellulose, and combinations thereof). The separator can have a multilayer material arrangement, particularly PP and / or PE.

[0060] Another aspect of the invention is a battery pack comprising one or more electrochemical cells according to the invention, and may additionally include external connections. These connections can be advantageously adapted to connect to and power electrical devices. Such a battery pack can be configured as, for example, button cells, pouch cells, cylindrical cells (having various sizes, such as 18650, 21700, 36500, etc.) or prismatic cells.

[0061] The sodium layered oxide active compounds according to the present invention can be prepared by solid-state synthesis based on well-known principles. In short, precursors such as oxides like Na₂CO₃, NiO, ZnO, Mn₂O₃, and TiO₂ are ground or milled together in the desired proportions, for example using a ball mill. The mixture is then heated at a temperature above 800 °C, preferably above or equal to 900 °C, under an inert and / or air atmosphere. This is the first annealing or calcination step. Methods for preparing these compounds are within the scope of the present invention. Therefore, compounds obtained or available according to the method of the present invention are also an object of the present invention.

[0062] Advantageously, the method according to the invention includes a second calcination step at about 1000 °C, which is advantageously performed after a cooling step. It has been found that this method produces homogeneous materials having a single phase or near-single phase, with little or no multiphase material produced. The expression "about 1000 °C" encompasses temperatures in the range of 950 °C to 1100 °C, preferably 980 °C to 1020 °C. The second calcination step can be carried out for a duration of 1 hour to 24 hours, preferably 8 hours to 16 hours, more preferably 10 hours to 13 hours. A duration of about 12 hours has been found particularly advantageous. For the first calcination step, the second calcination step can be carried out in an inert and / or air atmosphere. An air atmosphere is preferred. The second calcination step, or both the first and second calcination steps, can be carried out at a heating rate of 1 to 10 °C per minute, preferably 3 °C per minute.

[0063] Another advantage is that, during the cooling step, the compound is cooled at a predetermined rate, which can be in the range of 1 to 5 °C per minute, preferably 1 °C per minute. This rate can be important for obtaining optimal results.

[0064] A particularly advantageous step is to grind, preferably cool, the obtained compound after the first calcination or annealing step. The grinding can be performed using known methods, such as a mortar and pestle or a ball mill. The powder-to-ball ratio can be from about 1:10 to about 1:20, but is preferably 1:10.

[0065] It has been found that the combination of a second calcination step at approximately 1000 °C, preferably for approximately 12 hours, with an intermediate grinding step provides a particularly homogeneous material (compound). Furthermore, it has been found that repeating the second calcination step a third time, along with another intermediate grinding step, is advantageous in terms of homogeneity.

[0066] According to a particular embodiment of the method of the present invention, no granulation step is performed before the second, preferably any one or more calcination steps.

[0067] Similarly, the use of the compounds, conductive materials, batteries or battery packs of the present invention in electrochemical devices, and electrodes containing the compounds and supports of the present invention, such as the electrodes described above, are also part of the present invention.

[0068] The use of battery packs according to the invention includes, for example, microgrids integrated into a stable power grid, electrochemical storage devices for intermittent renewable energy sources (e.g., solar, wind power), mobile storage devices for electric vehicles (end-of-life rechargeable buses, rental fleets), home power storage devices, and emergency power or energy storage devices for hospitals, schools, factories, computer clusters, servers, companies, and any other public and / or private buildings or infrastructure. The compounds according to the invention, or devices incorporating said compounds, can be used in industries such as automotive, computers, banking, video games, leisure, creative, cultural, cosmetics, life sciences, aerospace, pharmaceuticals, metals and steel, railways, military, nuclear energy, navy, space, food, agriculture, construction, glass, cement, textiles, packaging, electronics, petrochemicals, and chemicals.

[0069] Some of the technical effects associated with the compounds according to the present invention are summarized below.

[0070] The foregoing and other objects, aspects, features and advantages of the present invention will become apparent from the following embodiments and claims. Attached Figure Description

[0071] The invention will now be described with reference to the following figures, in which:

[0072] Figure 1 The Swagelok-type half-cell assembly used for electrochemical characterization is shown.

[0073] Figure 2 An overview of the half-cell assembly used for operational XRD analysis is shown.

[0074] Figure 3 An exploded view of the button-type full cell according to the present invention is shown.

[0075] Figure 4 The powder XRD patterns obtained for ZNMT1 and NM, NMT are shown in their original state compared with those obtained after exposure to 55% RH (relative humidity) for 24 hours.

[0076] Figure 4a The powder XRD patterns obtained for ZNMT2 and ZNMT3 are shown in their original state compared with those obtained after exposure to 55% RH (relative humidity) for 24 hours.

[0077] Figure 5 The left image shows differential capacity plots (dQ / dV, in mAh g / V relative to voltage) obtained from ZNMT1, NM, ZNM and NMT compounds incorporated into a half-cell. -1 ·V -1 (indicated on the right) and (on the left) are the voltage versus specific capacity (mAh·g) of the same compound for the first 5 cycles in a full-cell configuration. -1 The curve of ).

[0078] Figure 6 a shows the XRD pattern obtained for NZT, which is a structure without any Mn. 4+ Compounds. Figure 6 b shows the voltage versus specific capacity (mAh·g) for the same compound in the full-cell configuration for the first 5 cycles. -1 The curve of ).

[0079] Figure 7 a shows the specific discharge energy (Wh·kg⁻¹) of batteries containing ZNMT1 and ZNMT2 compared to NMT batteries. -1 () is a function of the number of iterations. Figure 7 b shows the discharge energy retention rate as a percentage, as a function of the number of cycles.

[0080] Figure 8 a shows the XRD pattern obtained for ZNMT3. Figure 8 b shows the constant current charge-discharge cycles obtained from the ZNMT3 battery for the first 5 cycles.

[0081] Figure 9 The comparison of full-cell cycling results (voltage (V) vs. specific capacity (mAh·g)) between Mg-doped NMT cells and NMT cells is shown. -1 )).

[0082] Figure 10Showing (left) the highest 4.0 V of ZNMT, NMT, and NM batteries relative to Na + The first charging curve of / Na and the charging curve in (right) operating XRD mode. The XRD values ​​at the beginning of the charging process are compared with those at the end of the charging process (4.0 V relative to Na). + The XRD patterns of the / Na period were compared.

[0083] Figure 11 Showing with Figure 10 The same measurement results were obtained, except that the charging potential was controlled to a maximum of 4.4 V relative to Na. + / Na outside.

[0084] Figure 12 The discharge energy (Wh·kg) of ZNMT1, ZNMT2, and ZNMT3 batteries is shown. -1 The evolution of ), and the percentage of energy retention over more than fifty cycles.

[0085] Figure 13 This shows (a) the evolution of discharge energy (Wh·kg) -1 (a) and (b) in the full-cell configuration, within a voltage window of 1.2–4.0 V, the percentage of energy retention for more than one hundred cycles of layered oxides according to the present invention ZNMT1 and comparative examples NMT, NM and polyanionic compound NVPF, except for NM (1.2–3.8 V) and NVPF (1–4.65 V for the first cycle and 2–4.3 V for subsequent cycles).

[0086] Figure 14 Showing with Figure 13 The same measurement results were obtained, but within a voltage window of 1.2–4.4 V, except for NM (1.2–4.2 V).

[0087] Figure 15 The powder XRD patterns of ZNMT1 (1Na), ZNMT1.1 (0.9Na), ZNMT1.2 (0.8Na) and ZNMT1.3 (0.7Na) in their original state are shown.

[0088] Figure 16 The reversible capacity and average cell voltage curves of full cells using ZNMT1 (1Na), ZNMT1.1 (0.9Na), ZNMT1.2 (0.8Na), and ZNMT1.3 (0.7Na) as active materials in their original state are shown.

[0089] Figure 17The constant current charge-discharge cycles of ZNMT1 (1Na), ZNMT1.1 (0.9Na), ZNMT1.2 (0.8Na) and ZNMT1.3 (0.7Na) are shown.

[0090] Figure 18 The following figures are shown: (Top) Powder XRD pattern of ZNMT4 (0.9Na) in its pristine state compared to the compound exposed to 55% RH (relative humidity) for 24 hours; (Middle) Reversible capacity and average cell voltage curves of the full cell with ZNMT4 (0.9Na) as the active material in its pristine state; (Bottom) 1) Specific discharge energy (Wh·kg) -1 ) and 2) Energy retention rate of batteries containing ZNMT4 (0.9Na) as a percentage of the number of cycles.

[0091] Figure 19 The figure above shows the specific discharge energy (Wh·kg) of the full cell containing ZNMT1-900 compared to full cells containing ZNMT1-1000 / 12h and ZNMT1-1000 / 24h. -1 The percentage of discharge energy retention for the same battery (see right figure) is a function of the number of cycles.

[0092] Figure 20 Powder XRD patterns of various ZNMT2 compounds prepared according to various methods are shown. Example

[0093] Example 1a: Method for synthesizing layered oxide compounds according to the present invention

[0094] The three compounds according to the invention were prepared by solid-state synthesis. All precursors used in the synthesis were purchased from Sigma Aldrich with a purity close to 99 w / w% or higher. The exact weights of each precursor oxide used to prepare approximately 1 g of the final sodium transition metal layered oxide compounds (named ZNMT1, 2, and 3) according to the invention are shown in Table 1 below.

[0095] Table 1

[0096]

[0097] The weight of each compound was calculated based on stoichiometry, and no additional sodium was used in the synthesis to compensate for the sodium loss that might occur during calcination at high temperatures, i.e., above 800 °C.

[0098] To synthesize all the above-described layered oxides, the same method was used: Powdered precursor oxides were weighed separately according to the required stoichiometry and then mixed together. The powders were ground in a mortar and pestle for 15 minutes, followed by a ball milling step for 1 hour. The ball milling step was performed using a SPEX 8000MTM mixing mill, with grinding balls and a container made of hardened steel. A ball-to-powder ratio of 1:20 was used to grind the precursors. The ground precursors were collected from the ball mill vials and transferred to an alumina crucible.

[0099] In the first annealing step, the precursor is annealed in air at 900 °C for 3 °C·min. -1 Calcination was carried out at a heating rate of 1 °C·min for 12 h, followed by calcination at a heating rate of 1 °C·min. -1 The temperature was slowly reduced to 300 °C. Therefore, the total reaction time of the first calcination step was approximately 27 hours (heating for about 5 hours, holding at a constant temperature of 900 °C for 12 hours, and cooling for about 10 hours).

[0100] Therefore, the sodium transition metal layered oxide product was removed from the furnace at 300 °C. After cooling to ambient temperature in air, the oxide product was ground (in air) with a mortar and pestle for 15 minutes to ensure the homogeneity of the material.

[0101] The product from the first annealing step was subjected to a second annealing (or calcination) step in air at 1000 °C for 12 hours. As described above, the heating and cooling rates were maintained at 3 °C·min. -1 and 1 ℃·min -1 When the temperature reaches 300 °C, the oxide material after the second calcination step is removed from the furnace and immediately (within 10 minutes) transferred to an argon-filled glove box while minimizing atmospheric exposure, especially moisture. The material obtained after the second calcination step shows some NiO impurities (close to 5 w / w%), such as... Figure 6 and 8 The XRD pattern is shown in the figure.

[0102] Example 1b: Method for synthesizing layered oxide compounds

[0103] To demonstrate the advantageous properties and characteristics of the compounds of the present invention, they are compared with other sodium transition metal O3 layered oxides not included in this invention. They were prepared according to the same method described in Example 1a. Similarly, the exact weights of each precursor used to prepare approximately 1 g of these comparative oxides are shown in Table 2 below.

[0104] Table 2

[0105]

[0106] Example 2: Structural characterization of the synthesized powdered compound by X-ray diffraction (XRD) analysis

[0107] The phase purity and structure of materials are analyzed using powder X-ray diffraction (XRD). X-ray diffraction measurements, such as XRD, are used to determine the crystal structure of synthesized compounds and / or materials. XRD operations can be performed using specific cells designed for this purpose to monitor the crystal structure of compounds and / or materials under actual cycling conditions. Therefore, the cell does not need to be disassembled, thus preserving the environment in which the active compound is located during non-destructive measurements, such as XRD. Furthermore, this type of analysis is particularly useful for alkaline ion techniques that require well-controlled humidity and a sealed environment.

[0108] XRD patterns were collected using a Bruker d8 advanced diffractometer. The following parameters were set to collect X-ray pattern data:

[0109] - Detector slit = 9.5 mm

[0110] - Beam slit = 0.6 mm

[0111] - Range: 2θ = 10°-70°

[0112] - X-ray wavelength = 1.5406 Å (CuKα)

[0113] - Speed: 0.36 seconds / step

[0114] - Increment: 0.018°

[0115] The data obtained in this way were analyzed using Fullprof software, a crystallographic tool developed by Institut Laue-Langevin for matching Rietveld spectra. The XRD patterns were compared with the software's integrated database and refined as needed.

[0116] The stability of the material exposed to humid air was analyzed by storing it at 55% RH (relative humidity) for 24 hours and analyzing the XRD evolution before and after storage. Controlled humidity of 55% RH was maintained using a saturated solution of Mg(NO3)2·6H2O (Sigma Aldrich) in water. The saturated magnesium nitrate solution and analytical samples were stored in a sealed desiccator to ensure the required relative humidity.

[0117] The XRD pattern of the obtained oxide powder was obtained using powder XRD analysis. The XRD pattern shows that it is a single-phase material.

[0118] The material obtained after the second calcination step showed some (close to 5 w / w%) NiO impurities, such as Figure 6 and 8 The XRD pattern is shown in the figure.

[0119] Example 3: Structural characterization of the synthesized powder by transmission electron microscopy (TEM) analysis

[0120] Transmission electron microscopy (TEM) enables high-resolution imaging (up to the subangstrom range). When coupled with energy-dispersive X-ray spectroscopy (EDS) mapping, TEM can determine the crystal structure of localized regions of a sample.

[0121] High-resolution transmission electron microscopy (HRTEM) with energy-dispersive X-ray spectroscopy (EDS) mapping was used to examine the homogeneity of the prepared (raw) material. A FEI Titan3 microscope (ThermoFisher Scientific) operating at 200–300 kV was used for these analyses.

[0122] Samples for TEM analysis were prepared in an argon-filled glove box. The dried raw material was pressed onto a copper grid covered with a porous carbon film. The grid was then gently tapped to remove loose powder. The copper grid, containing the sodium layered oxide particles for analysis, was then carefully transferred into the TEM chamber using a Gatan (Inc.) vacuum transfer holder, instead of being exposed to the atmosphere.

[0123] TEM-EDS mapping of particles at different locations after the first calcination step revealed sodium-rich and sodium-poor phases. However, the material obtained after the second calcination step at 1000 °C for 12 hours was homogeneous.

[0124] Example 4: Electrode according to the present invention

[0125] The prepared layered oxides were used to assess their electrochemical performance, and were tested in half-cell and full-cell configurations.

[0126] The electrode according to the invention is made by selecting one or more layered oxides obtained in Example 1a.

[0127] All layered oxide active materials (positive or working electrode) in all battery configurations were used in powder form. The layered oxide material used for electrochemical analysis was mixed with 15 w / w% carbon black (Super P-carbon, TIMCAL) and ball-milled for 30 minutes using a SPEX 8000M mixing mill. A hardened steel ball mill container (balls made of hardened steel) was used to grind 3 g of oxide at a compound-to-ball weight ratio of 1:35.

[0128] In this embodiment, the electrode is prepared without a binder; however, the use of binders is included in this invention, particularly for commercial products. It should be noted that the use of binder-free powder has shown results comparable to those obtained using binders (e.g., PVDF and NMP as solvents). Indeed, the ease of preparation without binders can be of interest in terms of proper loading of each component and implementation. The current collector used is an aluminum foil sheet.

[0129] When fabricating the electrodes according to the invention, special care is required when placing the electrodes together to enable XRD measurements. See also Figure 2 A beryllium (Be) window 16 (X-ray permeable material) was used as a current collector so that the beryllium window 16 could be studied by operational XRD analysis of the sodium layered oxide active material mixed with a 15 w / w% carbon underlayer. Furthermore, a thin aluminum foil (purchased from Goodfellow, France, 4-5 µm thick) was coated on the beryllium window 16 on the powder material deposition side to prevent the beryllium window 16 from interacting with the electrolyte at high potentials (above 4 V relative to Na). + The reaction occurs under the conditions of / Na. The aluminum foil is very thin (4-5 µm), sufficient to allow X-rays to pass through. Furthermore, due to the presence of the thin aluminum foil, baselines can be removed during the processing of the XRD pattern by measuring with the aluminum foil alone before placing the compound.

[0130] XRD measurements were performed using a self-made Swagelok-type cell, which consisted of a stainless steel body (hole) 12, a stainless steel plunger 2 on one side, and a beryllium window 16 current collector on the other side. The assembly of these cells is further described in Example 6.

[0131] Example 5: Preparation of negative electrode using hard carbon

[0132] Hard carbon thin films were used as the anode material in a full-cell configuration and were prepared in an ambient atmosphere outside a glove box. The hard carbon anode powder was supplied by Aekyung Petrochemical, South Korea. The average particle size and BET surface area of ​​this hard carbon were 9 µm and 3.29 m²·g, respectively. -1 The resulting hard carbon powder was mixed with 4 w / w% conductive carbon (Super P-carbon from TIMCAL) and a binder. The binder used here was PVDF in N-methylpyrrolidone (NMP) or sodium carboxymethyl cellulose and / or its derivatives in an aqueous solvent. The negative electrode slurry was prepared by mixing the active material, conductive carbon, and binder in NMP at a ratio of 92:4:4. The resulting slurry was then mixed at 5-6 mg·cm⁻¹. -2The mass load is coated onto aluminum foil. The coated hard carbon film is calendered to reduce the porosity of the electrode to close to 50%. The electrode is cut into discs with a diameter of 8-10 mm and dried at 80°C, then used in full-cell assemblies and stored in an argon-filled glove box.

[0133] Example 6: Electrochemical half-cell assembly and its characterization according to the present invention

[0134] Half-cell assembly - negative electrode is sodium

[0135] Two types of batteries are used in the half-cell configuration:

[0136] - Preliminary electrochemical analysis of the synthesized sodium layered oxide material was performed using a 1 / 2-inch diameter Swagelok-type battery.

[0137] - Operational XRD analysis was performed using a self-made operational XRD cell with an inner diameter of 2 cm.

[0138] All cells (i.e., half-cells and full cells (see below)) were assembled in an argon-filled glove box (MBRAUN, Germany) to ensure the cells were airtight. During cell assembly, the glove box atmosphere was maintained at <0.1 ppm O2 and <0.1 ppm H2O.

[0139] For both types of batteries, the positive electrode powder is completely covered with three layers of glass fiber separators made of fine glass fibers, purchased from Whatmann, model GF / D (pore size: 2.7 µm, diameter: 5.5 cm; thickness: 675 µm). Furthermore, a solution of 1M NaPF6 in propylene carbonate solvent is used as the electrolyte for all battery components.

[0140] The following explains the configurations of the two types of batteries.

[0141] (i) Swagelok-type battery for electrochemical analysis

[0142] See Figure 1 A stainless steel Swagelok fitting (1 / 2 inch, part number: SS-810-6) via a through-plate connector, purchased from Swagelok, was used as the body of battery 1. The inner diameter of the orifice was adjusted to 11 mm, and the orifice was constructed to connect to a rod with a diameter of 11 mm using an end fitting and a nylon ferrule. The rods used in this setup (diameter: 11 mm, height: 5-6 cm) are referred to as plungers 2 and 3, and are made of stainless steel 2 or aluminum 3 depending on the potential window used for electrochemical analysis. For this study of sodium layered oxides, when the oxidation potential used in the study is higher than 4 V relative to Na... +When the oxidation potential is below 4 V relative to Na, an aluminum 3 plunger is preferred as the current collector on the positive side, but this is not limited to situations where the oxidation potential is below 4 V relative to Na. + When the potential is / Na, an aluminum plunger is used. Similarly, a plunger made of stainless steel 2 is used on the negative electrode side. Of course, an aluminum plunger can also be used on the negative electrode side because sodium does not form an alloy with aluminum. Similarly, when the potential range is below 4 V relative to Na... + When / Na, a stainless steel plunger can be used on the positive side.

[0143] Weigh out 4-10 mg of sodium layered oxide active material 4 mixed with 15 w / w% carbon and place it in the middle of an aluminum plunger 2 (diameter = 10 mm) as the positive electrode. The negative electrode uses a stainless steel disc 5 with a thickness of 1 mm and a diameter of 9-10 mm as the current collector. A stainless steel spring 6 and the stainless steel plunger 2 cover the top of the stainless steel disc 5 to apply pressure. The battery 1 is sealed on both sides using nylon ferrules (not shown) through a through-plate connector (SS-810-6).

[0144] Separator 7 was cut into discs with a diameter of approximately 11 mm for use in electrochemical testing of cell 1. Approximately 0.8–1 mL of electrolyte was used to wet the three-layer separator 7.

[0145] Sodium metal 8, used for the negative electrode, was cut into small pieces and pressed onto a stainless steel disc 5 approximately 1 mm thick using plastic tweezers. For the Swagelok half-cell 1, the stainless steel disc 5 had a diameter of approximately 8 mm. The stainless steel disc 5 with the sodium metal 8 was placed on top of the separator 7 in such a way that the sodium metal 8 was in contact with the separator 7. The battery 1 was finally sealed with a screw cap by placing a stainless steel spring 6 and a stainless steel plunger 2 on the negative electrode side. The screw cap and the battery body were separated by a nylon ferrule purchased from Swagelok.

[0146] (ii) A half-cell used for operating XRD measurements:

[0147] See Figure 2 The operating battery 10 used for XRD measurements is similar to the reference battery. Figure 1A schematic diagram as described in Reference 10. It has a stainless steel body 12 with a hole of 2 cm in diameter. One end of the battery 10 is connected to a 5 cm large outer ring 14, which can be detached from the body 12 of the battery 10. The outer ring 14 also has a 2 cm diameter hole, which is generally aligned with the hole in the battery body 12 to ensure proper fit between the battery body 12 and the outer ring 14. The outer ring 14 is detachable and connected to the body 12 by a rubber O-ring (not shown). A beryllium window 16 with a thickness of 200 nm and a diameter of 4 cm is placed on the outer ring 14. This beryllium window 16, instead of the aluminum plunger 3 used in the Swagelok battery 1 which is only used for electrochemical analysis, is used as a current collector on the positive electrode side.

[0148] The beryllium window 16 is covered with an aluminum foil of 4-5 μm thickness (purchased from Goodfellow, France) to protect the beryllium window 16 from high potentials (above 4 V relative to Na). + The beryllium reacts with the electrolyte under the condition of / Na). Once the beryllium window 16 and the aluminum foil (not shown) are placed in the outer ring 14, the outer ring 14 is connected to the body 12 via an O-ring, and the components of the outer ring 14 and the body 12 are screwed together. A stainless steel disc 5 with a thickness of 1 mm and a diameter of 1.5 cm is used as a current collector on the negative electrode side. A stainless steel spring 6 and a stainless steel plunger 2' with a diameter of 2 cm are used on the negative side to apply pressure to the battery 10, and the negative part is closed with a stainless steel connector and a nylon ferrule (not shown).

[0149] The separator 7 is cut into discs with a diameter of approximately 20 mm for operating the XRD cell 10. Approximately 2 mL of electrolyte is used to wet the three layers of separator 7.

[0150] The sodium metal used as the counter electrode was cut into small pieces and pressed onto a stainless steel disk 5 (approximately 1 mm thick) using plastic tweezers. For operating the XRD cell, the stainless steel disk 5 had a diameter of approximately 15 mm.

[0151] The battery 10 is finally sealed with a screw cap by placing a stainless steel spring 6 and a stainless steel plunger 2' on the negative terminal side. The screw cap and the battery body 12 are separated by a nylon ferrule (not shown) purchased from Swagelok.

[0152] Electrochemical characterization of half-cell

[0153] All battery assembly was completed in an argon-filled glove box (O2 level < 0.1 ppm, H2O level < 0.1 ppm), however, battery testing was conducted in an air atmosphere because the assembled batteries were confirmed to be airtight.

[0154] Once assembled, the battery can be removed from the glove box and its electrochemical performance tested. Steel plungers on the positive and negative sides are used to connect the battery to a potentiostat for electrochemical performance analysis.

[0155] This assembly of a Swagelok half-cell results in a voltage of 1.5-4 V relative to Na. + / Na and 1.5 - 4.5 V relative to Na + Cycling at a constant current of C / 10 within the voltage window of / Na. The measured 1C rate (where 1C = 246.7 mAh·g) was... -1 Calculate using the following formula:

[0156] C-rate (mAh) = Weight (g) of active compound used for battery assembly × 26.8 (mAh·mol) -1 ) / Molecular weight of the active compound (g·mol) -1 ).

[0157] Constant current cycling is an electrochemical measurement that involves observing the voltage evolution of an electrochemical cell at a given current. Stagnation or change in potential can be associated with the onset of an electrochemical phenomenon. Constant current cycling is performed on each type of cell tested (i.e., half-cell or full-cell).

[0158] Since all the sodium layered oxides studied were prepared to have one sodium atom at the end of the synthesis, the capacity (mAh·g) -1 The values ​​were calculated assuming complete removal of sodium from the structure. Approximately 4–10 mg of active material was used in the Swagelok half-cell, and approximately 40 mg of active material was used in the XRD cell. Electrochemical analyses were performed using a bio-based (Seyssinet-Pariset, France) potentiostat / galvanostat model MPG-2 or VMP-3.

[0159] The battery 10 used for XRD measurements was placed on the XRD holder using a homemade Teflon holder 18 and connected to a VSP 50 (biological) potentiostat for electrochemical analysis. Figure 2 The cell portion with the beryllium window 16 faces the X-ray so that the X-rays can pass through the beryllium window 16 and be diffracted by the active material (a layered sodium oxide mixed with 15 w / w% carbon P). The XRD half-cell 10 is typically cycled at a C / 30 rate, and XRD patterns are recorded to show each 0.05Na insertion and / or re-insertion structure, respectively.

[0160] Example 7: Assembly and characterization of an electrochemical full cell according to the present invention

[0161] See Figure 3The full cell is a 2032 (diameter = 20 mm, height = 3.2 mm) button cell 20. Hard carbon coated on an aluminum foil electrode as described in Example 5 is used as the negative electrode, containing 0.8–1 mL of 1M NaPF6 electrolyte dissolved in PC and two layers of glass fiber separators 7' (Whatmann, model GF / D (pore size: 2.7 µm, diameter: 5.5 cm, thickness: 675 µm)). The separators 7' are cut into disks with a diameter of approximately 18 mm.

[0162] The weight ratio of positive to negative electrode materials is balanced by coordinating the actual capacity of each electrode active compound used (i.e., ZNMT / hard carbon). For example, the hard carbon electrode 22 used in all battery components exhibits 300 mAh·g. -1 The first cycle discharge capacity. In this case, the positive electrode shows approximately 180 mAh·g. -1 Therefore, a positive to negative electrode material weight ratio of approximately 1.7:1 (ZNMT) / (hard carbon) was used to balance the capacity of the positive electrode. However, the negative hard carbon electrode 22 was used in excess at approximately 4 w / w% to avoid any sodium plating. In other words, an additional amount of negative electrode active material (in mg) was used to obtain an additional capacity of 4% of the actual amount of negative hard carbon required to balance the positive electrode, corresponding to 12 mAh·g. -1 The active material's mg weight, because hard carbon shows 300 mAh·g -1 The actual specific charging capacity.

[0163] In other words, once the electrode capacity is known, the amount of active material on any electrode can be adjusted such that the capacity ratio of each electrode is expressed as follows:

[0164] Capacity ratio = Positive electrode capacity / Negative electrode capacity = pc / nc

[0165] Then, the total mass of the active compound in each electrode is adjusted so that the negative electrode mass of the active compound is as follows:

[0166] Negative electrode mass = Positive electrode mass × (pc / nc), where pc is less than nc.

[0167] The positive electrode in all full cells 20 is used in powder form 24 after being mixed with 15 w / w% carbon. The 2032 button cell assembly was purchased from Shenzhen Yongxingyue Precision Machinery Co., Ltd. (China) and is made of stainless steel. The positive electrode casing 26 of the 2032 battery is covered with aluminum foil 28 because the oxidation potential used for cycling is higher than 4 V relative to Na. + / Na, which causes oxidation of the stainless steel components. Weigh out sodium layered oxide active material 24 mixed with 15 w / w% carbon and place it in the middle of the positive electrode shell with aluminum (Al) foil. Two separators 7' with a diameter of 18-19 mm are held on top of the positive electrode powder 24, taking care not to spread the powder to other parts of the battery 20. Wet the separators 7' with 0.7 mL of electrolyte and place the hard carbon film 22, which serves as the negative electrode, on it. Then cover the carbon film 22 with a stainless steel disk 5', with a spring 6' placed on top of the stainless steel disk to provide pressure to the electrode. Finally, seal the button cell 20 with the negative electrode chamber 30 with an O-ring and crimp it using a button cell crimping machine purchased from MTI.

[0168] Full cell electrochemical characterization

[0169] The assembled button cell 30 was tested at C / 10 in a BCS-8 bio-battery cycler within a voltage window of 1.2–4 or 4.4 V. A relatively low discharge potential of 1 V was specifically chosen for NaNi due to the low redox process. 0.5 Mn 0.5 O2 (NM). All electrochemical analyses were performed at room temperature.

[0170] Unless otherwise specified, electrodes, half-cells and / or full cells for comparative purposes were prepared, assembled and characterized using the same methods as in Examples 1 to 7 above.

[0171] Example 8: Enhanced Humidity Stability of ZNMT1

[0172] Figure 4 XRD diffraction patterns of ZNMT1, NMT, and NM (raw) powders and materials exposed at 55% relative humidity (RH) for 24 hours (exposure) are shown. A closed desiccator was used to expose the materials to a controlled humid atmosphere of 55% RH. A beaker containing approximately 10 mL of saturated Mg(NO3)2·6H2O (humidity controlled at 55%) was held in the desiccator. The humidity within the desiccator was measured using a relative hygrometer, and approximately 50 mg of the sodium layered oxide material under study was stored in the desiccator. XRD patterns before and after 24 hours of exposure to 55% humid air were analyzed to understand the sensitivity of the sodium layered oxide material to humid air.

[0173] For some peaks in NMT and NM, a decrease in intensity was observed. Furthermore, these materials exhibit additional peaks. These phenomena can be explained by the emergence of a new phase triggered by the interlayer insertion of water molecules, resulting in two distinct phases in the crystal structure. Therefore, a decrease in the intensity of one peak leads to an increase in the intensity of another.

[0174] On the other hand, the XRD pattern of ZNMT1 remained stable, with no additional peaks observed despite 24 hours of exposure to humidity. Therefore, ZNMT1 exhibits higher stability when exposed to humid air.

[0175] Figure 4a ZNMT2 and ZNMT3 and Figure 18 ZNMT4 in the dataset exhibits the same stability.

[0176] Example 9: Phase transition behavior and capacity retention of ZNMT1 relative to single-doped materials, as confirmed by electrochemical characterization Holding rate

[0177] According to the Electrochemical Dictionary, Allen Bard, and Springer Verlag, the term "doping" is "...the process of adding a relatively small amount of a foreign component (dopant) to a solid material to alter its properties, or to add impurity atoms. Typically, dopant ions or atoms are incorporated into the crystal lattice of the host material. Depending on the type of host lattice and dopant, the incorporation of foreign matter can lead to the generation of electronic defects, other point defects, and defect clusters." However, the term "doping" is used more broadly below to refer to the presence of certain elements in a compound in relatively small amounts than other elements.

[0178] As described above, electrochemical characterization was performed on half-cells (Na metal anode) and full-cells (hard carbon anode). The cathode was made of ZNMT1, the material of this invention, and compared with similar cells made of other layered oxides: ZNM, NMT, and NM.

[0179] The results are as follows Figure 5 As shown. Figure 5 The left figure shows the differential capacity curve (charge versus voltage derivative plot, expressed in mAh·V) obtained from the active material assembled in a Swagelok-type half-cell. -1 (See Example 6).

[0180] Each peak of the differential capacitance curve corresponds to a plateau in the voltage-capacity curve. Specifically, at 3–4 V relative to Na… + These peaks, within the / Na voltage range, reveal the aforementioned O3-type layered oxide phase transition.

[0181] When comparing NM and ZNM or NM and NMT, Zn is doped alone. 2+ or Ti 4+ The associated O3 phase transition was reduced. Specifically, ZNMT1 showed the best reduction in phase transition compared to the comparative example.

[0182] Figure 5 The right figure compares the specific capacity (mAh·g).-1 The same materials shown in the left-hand figure exhibit capacity retention in the first 5 cycles in a full-cell configuration (see Example 7). While NM shows the best initial discharge capacity in its pristine state, it decays by approximately 20% over 5 cycles, a significantly higher rate than the other samples. ZNMT1, NMT, and ZNM materials show comparable initial discharge specific capacities (approximately 150 mAh·g⁻¹). -1 Compared to NM, Zn was observed to... 2+ The capacity decreases due to doping, because it reduces the redox activity of Ni in the active material. 2+ The amount.

[0183] Of all the materials studied, Zn 2+ Ti 4+ The co-doped material ZNMT1 exhibits the best initial discharge capacity stability during cycling. In other words, the best capacity retention is observed using ZNMT1.

[0184] Example 10: The role of manganese and the possibility of titanium replacing manganese

[0185] Mn 4+ Role in sodium layered oxides

[0186] In this embodiment, Mn is shown 4+ The role of Mn in the layered oxides of sodium O3. 4+ In doped NaNi 0.5 Mn 0.5 The role of O2 (NM) in materials, where there is no Mn in the structure. 4+ Materials NaNi 0.45 Zn 0.05 Ti 0.5 O 2 (NZT) powder XRD pattern obtained ( Figure 6 a), and the same material (NZT) was electrochemically characterized by constant current cycling. Figure 6 (b) The battery was first tested in a half-cell configuration with a metallic sodium counter electrode to calculate the actual capacity of the materials. This capacity calculated from the half-cell was then used to balance the ratio of positive to negative electrode materials in the full cell, as explained in Example 7. The sodium-ion full cell was assembled using a hard carbon negative electrode and 1M NaPF6 in PC as the electrolyte. The battery was cycled at a C / 10 rate within a voltage window of 1.2–4.4 V.

[0187] Figure 6 The XRD pattern in a shows that, as observed in other compositions, the material can be prepared as an O3 structure with a small amount of NiO impurities. Furthermore, Figure 6 Electrochemical characterization in b shows that NZT exhibits poor reversibility in continuous cycling. Due to the increased ionicity of the metal-oxygen bond, Ti...4+ The redox potential of the substituted material increases, therefore it is impossible to remove all Na from the structure within the studied voltage window of 1.2–4.4 V (full cell). + By oxidizing NZT to 4.4 V relative to Na... + / Na, almost no sodium is removed from NZT.

[0188] Using Ti 4+ Replacement of Mn 4+ Possibility

[0189] With Ti in NM 4+ Replacement of Mn 4+ With the increase of [amount], the synthesis of the O3 phase is possible. In fact, even in Ti [context missing]. 4+ Complete replacement of Mn 4+ In certain circumstances, pure-phase materials may be obtained to produce NZT. However, it has been found that Mn... 4+ The presence of this is essential for ions with balanced metal-oxygen bonds and covalent properties.

[0190] Example 11: Adding Zn to the ZNMT compound according to the present invention and comparative examples 2+ The role of doping

[0191] Figure 7 This demonstrates the addition of Zn to the material of the present invention. 2+ The effect of doping is illustrated, and comparative results obtained from NMT materials are also shown. Data are derived from sodium-ion full cells using ZNMT material electrodes with different Zn concentrations: 5 and 10 atomic%, named ZNMT1 and ZNMT2 (see Table 1), and using hard carbon anodes. Both full cells were cycled at a C / 10 rate within a potential window of 1.2–4.4 V.

[0192] Figure 7 a shows the specific energy (Wh·kg) of each research material. -1 () is a function of the number of iterations. Figure 7 b shows the energy retention rate expressed as a percentage. (This is achieved by using Zn...) 2+ An increase in energy retention was observed when doping increased from 5 atomic percent (ZNMT1) to 10 atomic percent (ZNMT2). ​​However, synthesis experiments introducing more than 10 atomic percent Zn into the material produced ZnO impurities, and no significant change in capacity retention was observed above 10 atomic percent Zn. However, doping levels exceeding 10 atomic percent (e.g., 20%) of Zn... 2+ Doping appears to lead to an increase in ZnO impurities. This result reveals a preferred threshold content to which Zn can be doped in layered oxides to optimize capacity retention while maintaining low ZnO impurities. On another front, Ti 4+ The doping amount can vary between 0 and 50 atomic percent, as shown in Example 10.

[0193] Example 12: Adding Ti to the ZNMT material according to the present invention 4+ The role of doping: ZNMT3

[0194] Figure 8 Demonstrates the addition of Ti in ZNMT 4+ The role of doping. Figure 8 a shows the powder XRD pattern obtained for ZNMT3. Figure 8 b shows the constant current charge-discharge cycles obtained from ZNMT3 for the first 5 cycles. The full cell assembled according to Example 7 used a mixture of ZNMT3 and 15 w / w% carbon black as the positive electrode (Example 4), a hard carbon film negative electrode (Example 5), and 1M NaPF6 in propylene carbonate as the electrolyte. The battery was cycled at a C / 10 rate within a voltage window of 1.2–4.4 V. Figure 8 The XRD pattern in a shows that, as observed in other compositions, the material can be prepared as an O3 structure with a small amount of NiO impurities. Compared to ZNMT1, it has more Ti. 4+ ZNMT3 material exhibits considerable capacity retention, such as Figure 8 As shown in b (see also) Figure 12 ).

[0195] Example 13: Using another cation Mg 2+ Alternative to Zn 2+ Function

[0196] In this embodiment, it has the same properties as Zn 2+ (Ionic radius = 0.74 Å) Mg with similar ionic radii 2+ (Ionic radius = 0.76 Å) was used to replace Zn 2+ .

[0197] Figure 9 Mg was shown 2+ Ti 4+ Co-doped NaNi 0.5 Mg 0.05 Mn 0.4 Ti 0.1 O2 (Mg-doped NMT or NMMT) and Mg 2+ Undoped NaNi 0.5 Mn 0.4 Ti 0.1 Comparative full-cell cycle performance of O2 (NMT) at C / 10 cycling over an extended voltage window of 1.2–4.4 V. Although the initial discharge capacity is lower compared to NMT, Mg… 2+ Co-doping slightly improved capacity retention. However, Mg 2+ Doping does not improve capacity retention as much as Zn. 2+ 。

[0198] Example 14: Compared to NM and NMT, the ZNMT1 material exhibits a reduced phase transition, as shown by XRD analysis performed up to a voltage of4.0 V relative to Na + / Na confirmed

[0199] Figure 10 Showing bare O3 NaNi 0.5 Mn 0.5 O2 (NM), Ti 4+ NaNi doping 0.5 Mn 0.4 Ti 0.1 O2 (NMT) and Zn 2+ Ti 4+ Co-doped NaNi 0.45 Zn 0.05 Mn 0.4 Ti 0.1 The first charge curve (left) is an operational XRD pattern of O2 (ZNMT1) at the beginning and end of charge. Electrochemical analysis was performed using an operational XRD cell with metallic sodium (half-cell) as the negative electrode, and the cell was charged at 1.5–4.0 V relative to Na. + / Na cycles at a rate of C / 30 within the voltage window (except for 1.5 - 3.8 V relative to Na). + (NM in / Na and outside of the first discharge). In other words, the charge potential is controlled to remove approximately 0.6Na from the structure. For clarity, the corresponding operational XRD measurements are followed throughout, and the XRD plots of the original period are shown in [data missing] compared to the individual corresponding charge end periods. Figure 10 (Right) Center. "Primitive" refers to the XRD pattern obtained in the assembled XRD cell before any electrochemical reaction (XRD at the end of synthesis), and "charged" refers to the XRD pattern obtained at the end of charging (voltage = 4.0 V relative to Na). + / Na).

[0200] Regardless of Ti 4+ and Zn 2+ Regardless of doping, a phase transition from O3 to P3 was observed in all compounds. This indicates that the stability resulting from the Na vacancy ordering in the P3 structure is greater than that resulting from the Zn ordering. 2+ Instabilities arising from steric effects and increased lattice ionicity. In contrast, the 4VO type phase exhibits significant differences, its evolution increasing with Ti. 4+ The substitution and delay occur within the voltage window studied, while Zn... 2+ Ti 4+ Co-doped ZNMT1 materials are completely eliminated.

[0201] Example 15: Compared to NM and NMT, the ZNMT1 material exhibits a reduced phase transition, as shown by XRD analysis performed up to a voltage of [voltage value missing]. 4.4 V relative to Na + / Na confirmed

[0202] Figure 11An experiment of the same type as in Example 14 was demonstrated; however, the potential was controlled at a maximum of 4.4 V relative to Na. + / Na, to remove 0.8 to 1 sodium ions from the structure. In this way, the phase transition behavior of ZNMT1 at full capacity can be compared with that of NM and NMT.

[0203] Electrochemical analysis was performed using an operational XRD half-cell with metallic sodium as the negative electrode, and the cell was cycled at a C / 10 rate.

[0204] In one respect, the potential shown by the sodium content curve on the left indicates that the NM and NMT materials exhibit a plateau at the end of charging, suggesting the presence of two separate phases (O1 and O3), in which the O1 phase has a very small unit cell compared to the original material—that is, the smallest repeating unit with a completely symmetrical crystal structure.

[0205] The degree of variation in the unit cell can be directly visualized from the d-value of the (003) peak, which is an indicator of the c-axis of the unit cell. If the peak occurs at a high angle, the corresponding d-interval is small, and therefore the unit cell is small. For NM materials, the d-interval varies from 5.21 Å in the original O3 to 4.36 Å in the fully charged phase. Similarly, in the NMT phase, a decrease in d-interval from 5.29 Å to 4.41 Å is observed as the NMT phase moves from the original O3 to the charged O-type phase. These reductions observed in NM and NMT indicate a corresponding decrease in unit cell volume.

[0206] In another aspect, ZNMT did not exhibit a plateau at the end of charging. Furthermore, the XRD characteristics of the charged state are characterized by a broad peak of (003) at 5.17 Å, indicating a very small reduction from the original d(003) = 5.25. The results show that the overall change in the ZNMT unit cell is very small compared to NMT and NM materials. The broad peak observed in the XRD indicates a mixed structure with different layer stacking and / or stacking faults. This behavior is expected to be related to the partial retention of P3 stacks and / or the migration of transition metal ions to van der Waals interstices at the end of charging, which reduces further layer slip to form an O-type phase with a reduced unit cell volume.

[0207] Due to this reduced phase transition and minute change in cell volume, ZNMT1 maintains its structural stability during long cycles, thus improving the material's cycle life even within an extended voltage window of 1.2–4.4 V (see [link to relevant documentation]). Figure 14 (and Example 17).

[0208] Example 16: Comparison of ZNMT1, ZNMT2, and ZNMT3 in terms of discharge energy density and energy retention rate

[0209] Figure 12 The discharge energies (Wh·kg) of ZNMT1, ZNMT2, and ZNMT3 according to the present invention are shown.-1 The evolution of the material and the percentage of energy retention over fifty cycles were also studied. According to Example 7, these materials were cycled in a full-cell configuration at a C / 10 rate of 1.2–4.4 V. At the end of fifty cycles, a reduction of approximately 10% was observed in three samples.

[0210] The energy evolution of these samples is similar, and the differences between each sample are within the error range.

[0211] Example 17: Energy retention of ZNMT1 full cell after 100 cycles and its comparison with other materials at different voltages. Comparison of materials (4 or 4.4 V relative to Na) + / Na)

[0212] Figure 13 The following data is displayed: (a) Discharge energy (Wh·kg) -1 (a) the evolution of (b) the energy retention percentage of the layered oxide ZNMT1 according to the invention after one hundred cycles, compared with materials NMT and NM. These materials cycle from 1.2 to 4 V at a C / 10 rate, except for NM, which cycles from 1.2 to 3.8 V.

[0213] In addition, for comparison, a full cell using the polyanionic material Na3V2(PO4)2F3 (named NVPF) from Energy Hub, Amiens was also tested. The data obtained for NVPF are comparable to... Figure 13 and 14 The NVPF was tested under the same conditions as the layered oxide, except for the voltage range. The voltage range of the NVPF was optimized to maximize its energy and cycling performance, according to Yan et al., Nature communications, 10, 585 (2019) (Reference 11). For the first cycle, the voltage window (1–4.65 V) was determined to be 2.35 Na removed from Na₃V₂(PO₄)₂F₃. The battery was then subsequently cycled between 2 V and 4.3 V.

[0214] The energies of all samples were normalized over the total mass of the positive and negative electrode active materials. The best energy retention was observed for ZNMT1 (approximately 10% reduction after 100 cycles), consistent with the reduced phase transition observed in Example 14, while NVPF showed an almost 25% reduction after 100 cycles, despite having excellent discharge energy in its pristine state (i.e., after the first cycle) (NVPF 300 Wh·kg⁻¹). -1 ZNMT1 has a capacity of 225 Wh·kg -1 )

[0215] Figure 14The same experiment was shown, where the layered oxide was cycled within a voltage window of 1.2–4.4 V, except for NM, which was cycled from 1.2–4.2 V. NVPF in comparison with Figure 13 Cycle under the same conditions.

[0216] For ZNMT1, the optimal energy retention rate was observed (a 20% reduction after 100 cycles), consistent with the reduced phase transition observed in Examples 9 and 15.

[0217] The results obtained at 4.4 V confirm that ZNMT1 has superior performance compared to NVPF, which was previously unfavorable for sodium O3 layered oxide materials, as the latter was characterized under optimized conditions to maximize its performance.

[0218] The ZNMT1 can cycle to voltages above 4.0 V without significant loss after 100 cycles. For example, considering that NVPFs exhibit a sharp capacity drop (retaining approximately 75% of the initial capacity at 4.4 V), retaining 90% of the initial capacity after 100 cycles at 4.0 V, and 80% of the initial capacity after 100 cycles at 4.4 V. 2+ Enhanced steric hindrance effect effectively reduces phase transition during cycling.

[0219] Example 18: The role of sodium content (x) in the original phase

[0220] In this embodiment, the amount of sodium (x) in the original phase varies from 0.7 to 1. The general formula Na is analyzed. x Ni 0.45 Zn 0.05 Mn 0.4 Ti 0.1 The compounds of O2 are ZNMT1 (1 Na), ZNMT1.1 (0.9 Na), ZNMT1.2 (0.8 Na) and ZNMT1.3 (0.7 Na). Figure 15 The results show that a pure O3 phase is obtained when the sodium content is equal to or greater than 8%. In contrast, at lower sodium percentages, such as 0.7%, Figure 15 The original compounds were shown to be an O3-P2 mixture / commensal. This is less advantageous considering the amount of sodium available in the original phase. This is demonstrated by measuring the reversible capacity and cell voltage of sodium-ion full cells prepared with these compounds. The full cells were prepared as described above and cycled at a C / 10 rate within a voltage window of 1.2–4.4 V. Figure 16 As shown, sodium content below 0.8 is related to the decreasing slope of the reversible capacity curve. Furthermore, when sodium content is below 0.8, the curve showing a slower average battery voltage decreases.

[0221] same, Figure 17 The galvanostatic charge-discharge cycles of ZNMT1 (1 Na), ZNMT1.1 (0.9 Na), ZNMT1.2 (0.8 Na) and ZNMT1.3 (0.7 Na) showed the total amount of sodium that could be removed from the active material, and thus the achievable capacity.

[0222] Example 19: Characterization of the ZNMT4 compound according to the present invention

[0223] Synthesize another compound according to the present invention. This compound has the formula NaNi. 0.45 Zn 0.05 Mn 0.35 Ti 0.15 O2(IV) was synthesized and tested according to the method described above. Its characteristics are as follows: Figure 18 As shown.

[0224] Example 20: Comparison Data

[0225] The compounds of the present invention prepared according to the method of the present invention show better homogeneity and therefore better capacity (energy retention) compared with the compounds of the present invention prepared according to the standard method.

[0226] To demonstrate the superiority of the compound obtained by the method according to the invention, comparative data were obtained. The ZNMT1-900 compound was synthesized using a temperature of 900°C / 12h instead of 1000°C / 12h in the second annealing step. Furthermore, no intermediate milling was performed between the two annealing steps. The resulting compound ZNMT1-900 was compared with compounds ZNMT1 (renamed ZNMT1-1000 / 12h to better distinguish the two ZNMT1 compounds) and ZNMT1–1000 / 24h (see [link to documentation]). Figure 19 ).

[0227] The compound ZNMT1–1000 / 24h was obtained by performing ZNMT1 (also known as ZNMT1–1000 / 12h) but followed by an additional (third) annealing step at 1000°C for 12 hours after an additional intermediate cooling / grinding step.

[0228] See Figure 19Although no differences were observed in XRD or initial cycling, better capacity (energy) retention was observed in ZNMT1-1000 materials at 12h and 24h. This is related to the homogeneity of the material, which can be achieved through a combination of intermediate milling and calcination at 1000 °C. This phenomenon is more pronounced for batch-synthesized materials (attempted at a maximum batch size of 200 g) used to assemble prototype sodium-ion batteries. It should also be noted that the material produced by a single second annealing step at 1000 °C for 24 hours is not as good as the material produced by two consecutive 1000 °C annealing steps for 12 hours followed by intermediate milling.

[0229] It was also noted that ZNMT2 (NaNi) could not be satisfactorily synthesized when subjected to two annealing processes at 900 °C for 12 or 24 hours. 0.4 Zn 0.1 Mn 0.4 Ti 0.1 O2). The resulting compound contained ZnO impurities, which prevented the material from being used in full cells due to insufficient phase purity. The ZnO impurities only disappeared when the temperature of the second annealing step was increased to 1000 °C. This is clearly shown in... Figure 20 Except for the temperature / duration of the final annealing step, the synthesis was carried out according to the method disclosed in Example 1 (i.e., with two annealing steps and intermediate grinding).

[0230] References cited

[0231] 1.S. Roberts and E. Kendrick, The Re-Emergence of Sodium IonBatteries: Testing, Processing, and Manufacturability.Nanotechnol. Sci.Appl., 11, 23–33 (2018).

[0232] 2. J. Deng, W.-B. Luo, S.-L. Chou, H.-K. Liu, and S.-X. Dou, Sodium-Ion Batteries: From Academic Research to Practical Commercialization. Adv.Energy Mater., 8, 1701428 (2018).

[0233] 3.C. Delmas, C. Fouassier, and P. Hagenmuller, StructuralClassification and Properties of the Layered Oxides. Phys. BC, 99, 81–85(1980).

[0234] 4.K. Smith, J. Treacher, D. Ledwoch, P. Adamson, and E. Kendrick,Novel High Energy Density Sodium Layered Oxide Cathode Materials: FromMaterial to Cells. ECS Trans., 75, 13–24 (2017).

[0235] 5.K. Kubota, S. Kumakura, Y. Yoda, K. Kuroki, and S. Komaba,Electrochemistry and Solid-State Chemistry of NaMeO2 (Me = 3d TransitionMetals). Adv. Energy Mater., 8, 1703415 (2018).

[0236] 6.S. Mariyappan, Q. Wang and J-M.Tarascon, “Will sodium layeredoxides- ever be successful candidate for sodium ion battery applications?”,Journal of the Electrochemical Society.165 (16) p. A3714- A3722 (2018).

[0237] 7.R. Dugas, B. Zhang, P. Rozier, and J. M. Tarascon, Optimization ofNa-Ion Battery Systems Based on Polyanionic or Layered Positive Electrodesand Carbon Anodes. J. Electrochem. Soc., 163, A867–A874 (2016).

[0238] 8.M. Sathiya, Q. Jacquet, M.-L. Doublet, O. M. Karakulina, J.Hadermann and J.-M. Tarascon, A Chemical Approach to Raise Cell Voltage andSuppress Phase Transition in O3 Sodium Layered Oxide Electrodes. Adv. EnergyMater., 8, 1702599 (2018).

[0239] 9.L. Zheng and M. N. Obrovac, Investigation of O3-TypeNa 0.9 Ni 0.45 Mn x Ti 0.55-x O2 (0 ≤ x ≤ 0.55) as Positive Electrode Materials forSodium-Ion Batteries. Electrochimica Acta, 233, 284–291 (2017).

[0240] 10. A. S. Prakash, D. Larcher, M. Morcrette, M. S. Hedge, J-B.Leriche, and C. Masquelier, Chem. Mater. 17, 4406-4415 (2005)

[0241] 11. G. Yan, S. Mariyappan, G. Rousse, Q. Jacquet, M. Deschamps, R. David, B. Mirvaux, J.W. Freeland, J.-M. Tarascon, Higher energy and safersodium ion batteries via an electrochemically made disordered Na3V2(PO4)2F3material, Nature communications, 10, 585 (2019).

[0242] 12. Shinichi Komaba, Naoaki Yabuuchi, Tetsuri Nakayama, AtsushiOgata, Toru Ishikawa, Izumi Nakai, Study on the Reversible Electrode Reactionof Na 1−x Ni 0.5 Mn 0.5 O2for a Rechargeable Sodium-Ion Battery, Inorg. Chem. 51, 6211–6220 (2012).

[0243] 13. Kei Kubota, Issei Ikeuchi, Tetsuri Nakayama, Chikara Takei, Naoaki Yabuuchi, Hiromasa Shiiba, Masanobu Nakayama, Shinichi Komaba, J. Phys.Chem.C, 119, 166−175 (2015).

Claims

1. A cathode compound for use in a sodium-ion electrochemical battery, the cathode compound comprising: - The active compound of formula I: Na x Ni 0.5-y Zn y Mn 0.5-z Ti z O2 (I), where x is a number in the range of 0.7 to 1.

1. y is a number greater than 0 and with a maximum value of 0.1, and z is a number between 0 and 0.5; - and an electronically conductive additive, The positive electrode compound therein does not contain a polymer binder.

2. The positive electrode compound according to claim 1, wherein, The concentration of the electronically conductive additive is in the range of 10-20 w / w relative to the total weight of the active compound and the electronically conductive additive.

3. The positive electrode compound according to claim 1 or 2, wherein, The electronically conductive additive contains or is composed of carbon black.

4. The cathode compound according to claim 1 or 2, wherein it meets at least one of the following conditions (i), (ii), (iii) and (iv): (i) x is approximately 1; (ii) y is a number in the range of 0.01 to 0.1, and z is a number in the range of 0.01 to 0.45; (iii) y is a number in the range of 0.03 to 0.1, and z is a number in the range of 0.05 to 0.25; (iv) y is a number in the range of 0.04 to 0.1, and z is a number in the range of 0.08 to 0.

22.

5. The cathode compound according to claim 1 or 2, wherein the cathode is selected from compounds having the following formulas II, III, and IV: Pretty 0.45 Zn 0.05 Mr 0.4 Tea 0.1 O2 (II); Pretty 0.45 Zn 0.05 Mr 0.3 Tea 0.2 O2 (III); Na1Ni 0.45 Zn 0.05 Mn 0.35 You 0.15 O2 (IV).

6. The positive electrode compound according to claim 1 or 2, having at least one of the following characteristics (a), (b), (c), and (d); (a) The initial discharge capacity is at least about 120 mAh·g -1 , as measured by discharge rates in the range of C / 30 to 1C; (b) When cycled at voltages below 4 V, the specific energy is at least about 200 Wh·kg. -1 And when cycled at voltages above 4 V, the specific energy is at least about 250 Wh·kg. -1 ; (c) When cycled at voltages above 4 V, the energy retention is in the range of 73% to 99% over 100 cycles.

7. A positive electrode for a sodium-ion electrochemical battery, said positive electrode having at least one current collector and a positive electrode compound according to any one of claims 1 to 6.

8. A method for preparing a positive electrode composition according to any one of claims 1 to 6, the method comprising: - The active compound is provided in the following sequence of steps: First calcination step: Calcining a powdered precursor oxide mixture containing Na2CO3, NiO, ZnO, Mn2O3 and TiO2 at a temperature above 800℃; Cooling steps: carried out at a rate of 1 to 5°C per minute; Grinding steps; The second calcination step is carried out at a temperature between 950°C and 1100°C. as well as - The obtained active compound is mixed with the electronically conductive additive without polymer binder to obtain the positive electrode composition.

9. The method of claim 8, wherein the mixing step is carried out in the absence of a solvent.

10. An electrochemical battery comprising: - A negative electrode, configured to reversibly accept sodium ions from an electrolyte and reversibly release sodium ions into the electrolyte, the negative electrode having at least one current collector; - A positive electrode, configured to reversibly accept sodium ions from the electrolyte and reversibly release sodium ions into the electrolyte, the positive electrode comprising a positive electrode compound and having at least one current collector; and - A separator soaked in the electrolyte containing sodium ions, the separator being in contact with both the negative electrode and the positive electrode. The positive electrode compound thereon is the positive electrode compound according to any one of claims 1 to 6.

11. The electrochemical cell according to claim 10, wherein the separator is selected from glass fiber, polyolefin separator and cellulose-based film.

12. The electrochemical cell of claim 10, wherein the negative electrode comprises metallic sodium, a carbonaceous compound, hard carbon, antimony, tin, phosphorus, or a mixture thereof.

13. The electrochemical battery according to claim 10, wherein the battery is a button cell, a pouch cell, a cylindrical cell, or a prismatic cell.

14. The electrochemical battery of claim 10, wherein when cycled at a voltage below 4 V, the specific energy of the battery is at least about 200 Wh·kg. -1 Furthermore, when cycled at voltages above 4 V, the specific energy is at least about 250 Wh·kg. -1 .

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