Sodium-Magnesium Hybrid Battery with P2-Phase Layered Oxide Cathode Material, Its Preparation Method and Application

Abstract

The present invention discloses a sodium-magnesium hybrid battery with a P2-phase layered oxide cathode material, which includes a positive electrode sheet, a negative electrode sheet and a Na / Mg double-salt electrolyte. The positive electrode sheet includes a P2-phase layered oxide cathode material, and the negative electrode sheet is pure magnesium or a magnesium alloy. The present invention also provides a preparation method and an application of the sodium-magnesium hybrid battery with the P2-phase layered oxide cathode material. The present invention fundamentally avoids the consumption of raw sodium, and the relatively high specific capacity of metallic magnesium can additionally compensate for Mg<supgt;2+< / supgt;, enabling the battery to have a relatively high energy density; dendrites will not be generated on the surface of the metallic magnesium negative electrode, improving the intrinsic safety of the battery; while giving play to the inherent advantages of magnesium batteries, it also takes into account the advantage of the high ion transfer rate of the P2-phase layered oxide cathode material, having a relatively high first-cycle charge-discharge specific capacity and cycle stability; it can be used for energy storage devices in hydropower generation, wind power generation, backup power supplies or communication base stations, as well as power batteries for electric bicycles and low-speed electric vehicles.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials, and particularly relates to a sodium-magnesium hybrid battery with a P2-phase layered oxide cathode material, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, lithium batteries have been widely used in the energy field due to their advantages of high voltage, large capacity, and long life. However, the lithium metal anode is extremely prone to grow dendrites during charge and discharge processes, piercing the separator, causing battery short circuit, and further leading to the risk of fire and explosion; and with the large consumption of limited lithium resources, the cost of lithium batteries is continuously increasing, unable to meet the low-cost requirements for large-scale preparation. Sodium and magnesium have much higher abundances in the earth's crust than lithium, so developing sodium batteries and magnesium batteries can significantly reduce the cost of batteries.

[0003] However, during the first charging process of sodium batteries, irreversible reduction occurs at the negative electrode, forming a solid electrolyte interphase, and continuous sodium loss will lead to rapid capacity decay, and sodium is unstable in air and not easy to transport. In addition, in currently studied magnesium batteries, divalent Mg 2+ has a strong interaction with the lattice of the cathode material, resulting in slow diffusion inside the solid phase and poor kinetic performance. Therefore, solving the problems of capacity loss in sodium batteries and poor Mg 2+ diffusion kinetics in magnesium batteries has become an important research direction for new rechargeable batteries.

[0004] As early as 2006, J. Baker et al. proposed the concept of hybrid ion batteries, and the sodium-magnesium hybrid battery system is one of them. However, there are few reports on the research and application of sodium-magnesium hybrid batteries so far, because there is a lack of cathode materials that can simultaneously achieve reversible insertion / extraction of magnesium ions and sodium ions, and a dual-salt electrolyte that can be stably compatible with the metal magnesium anode. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems in the related art to some extent. For this reason, the main object of the present invention is to provide a sodium-magnesium hybrid battery with a P2-phase layered oxide cathode material, aiming to solve the problems of capacity loss in existing sodium batteries and poor Mg 2+ diffusion kinetics in magnesium batteries.

[0006] The object of the present invention is achieved by the following technical solutions:

[0007] In a first aspect, a sodium-magnesium hybrid battery with a P2-phase layered oxide cathode material includes a positive electrode plate, a negative electrode plate, and a Na / Mg dual-salt electrolyte, wherein the positive electrode plate includes a P2-phase layered oxide cathode material, and the negative electrode plate is pure magnesium or a magnesium alloy.

[0008] In some specific embodiments, the positive electrode plate further includes a current collector, a positive electrode material layer coated on the current collector, and the positive electrode material layer includes a P2 phase layered oxide positive electrode material, a conductive additive and a binder.

[0009] In some specific embodiments, the Mg / Na atomic ratio of the Na / Mg double salt electrolyte is (0.5-1):1.

[0010] In some specific embodiments, the P2 phase layered oxide positive electrode material has a chemical formula of: Na x Mn y M z O 2-δ ;

[0011] Wherein M is an element doped to replace Mn, including any one or more of Li, Ni, Co, Al, Zn, Mg, Ti, B, V, Zr, Cu, Cr, Mo, Nb and Fe; x, y, z are the molar percentages of the corresponding elements respectively; x, y, z satisfy 0.6 <x<0.9;y> 0; z≥0; y+z≤1; 0≤δ≤0.05.

[0012] Furthermore, M is preferably one or more of Li, Ni and Mg; 0.67≤x<0.8; y>0; z≥0; y+z≤1; 0≤δ≤0.02.

[0013] In some specific embodiments, the P2 phase layered oxide positive electrode material is prepared by the following method: a sodium source, a manganese source and / or a metal source are evenly mixed to obtain a powder precursor, and the powder precursor is subjected to a solid phase sintering method to synthesize the P2 phase layered oxide positive electrode material.

[0014] Further, the P2 phase layered oxide positive electrode material is prepared by the following method, specifically:

[0015] Mixing sodium acetate, manganese acetate and / or acetate of M in proportion to form a precursor, grinding the precursor in a ball mill to obtain a powder precursor;

[0016] After the powder precursor is pressed into a block precursor, it is placed in an air atmosphere at 100-900° C. for heat treatment for 15-26 hours to obtain a P2 phase layered oxide positive electrode material.

[0017] In a second aspect, a method for preparing a sodium-magnesium hybrid battery of the above-mentioned P2 phase layered oxide positive electrode material comprises the following steps:

[0018] 1) Preparation of positive electrode

[0019] Mix the P2-phase layered oxide cathode material, conductive additive, and binder to form a slurry, uniformly coat it on the current collector, and dry to obtain the positive electrode sheet;

[0020] 2) Preparation of sodium-magnesium hybrid battery

[0021] Under an inert atmosphere, assemble the positive electrode sheet prepared in step 1), using pure magnesium or magnesium alloy as the negative electrode sheet, and a Na / Mg double-salt solution as the electrolyte, into a sodium-magnesium hybrid battery.

[0022] Thirdly, a use of a sodium-magnesium hybrid battery with the above-mentioned P2-phase layered oxide cathode material, wherein the sodium-magnesium hybrid battery is used for energy storage devices of hydroelectric power generation, wind power generation, backup power supply or communication base stations, and power batteries of bicycles and low-speed electric vehicles.

[0023] Compared with the prior art, the present invention has at least the following advantages:

[0024] 1) In the sodium-magnesium hybrid battery in the present application, the P2-phase layered structure of the cathode material in the positive electrode sheet has open prismatic channels, which can replace the O3-phase layered structure with an octahedral structure, overcoming the poor electrochemical kinetics and complex phase change process of the O3-phase layered structure, promoting charge transfer, and improving the cycle stability of the battery; and magnesium has a relatively high theoretical volumetric specific capacity (Mg: 3833 mA cm -3 vs. Li: 2061 mA cm -3 ), and the magnesium metal negative electrode can deposit without dendrites during charge and discharge, greatly ensuring the safety of the battery; therefore, a complementary design of the performance of the P2-phase layered oxide cathode material and the magnesium metal negative electrode to form a sodium-magnesium hybrid battery is an effective way for new rechargeable batteries to move towards practical application;

[0025] 2) The sodium-magnesium hybrid battery of the present invention fundamentally avoids the consumption of raw sodium, and the relatively high energy density of magnesium metal can additionally compensate for Mg 2+ , making the battery have a relatively high specific capacity; no dendrites will be generated on the surface of the magnesium metal negative electrode, improving the intrinsic safety of the battery; while giving full play to the inherent advantages of magnesium batteries, it also takes into account the advantage of the high ion transfer rate of the P2-phase layered oxide cathode material, having a relatively high first-cycle charge-discharge specific capacity and cycle stability; it can be used for energy storage devices of hydroelectric power generation, wind power generation, backup power supply or communication base stations, and power batteries of electric bicycles and low-speed electric vehicles;

[0026] 3) The preparation method of the sodium-magnesium hybrid battery provided by the present invention has simple and easy steps, rich raw material resources, low cost, is a pollution-free green material, and the equipment used in the process is all conventional equipment, which is easy to be applied on a large scale industrially. Description of the Drawings

[0027] To more clearly illustrate the specific embodiments of the present invention, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art.

[0028] Figure 1 Structural schematic diagram of the sodium-magnesium hybrid battery in the present invention;

[0029] Figure 2 XRD pattern of the Na 0.67 MnO2 cathode material provided in Example 1-1 of the present invention;

[0030] Figure 3 XRD pattern of the Na 0.67 MnO2 cathode material provided in Example 1-1 of the present invention;

[0031] Figure 4 XRD pattern of the Na 0.67 MnO2 cathode material provided in Example 1-1 of the present invention;

[0032] Figure 5 XRD pattern of the Na 0.67 Ni 0.17 Co 0.17 Mn 0.66 O2 cathode material provided in Example 1-2 of the present invention;

[0033] Figure 6 Charge-discharge curve of the magnesium-ion half-cell provided in Example 2-1 of the present invention;

[0034] Figure 7 Charge-discharge curve of the magnesium-ion half-cell provided in Example 2-2 of the present invention;

[0035] Figure 8 Charge-discharge curve of the magnesium-ion half-cell provided in Example 2-3 of the present invention;

[0036] Figure 9 Charge-discharge curve of the first cycle of the sodium-magnesium hybrid battery provided in Example 3-1 of the present invention;

[0037] Figure 10 Charge-discharge curve of the first cycle of the sodium-magnesium hybrid battery provided in Example 3-2 of the present invention. Specific embodiments

[0038] The present invention will be further described in detail below in conjunction with the drawings and embodiments. The following embodiments are only descriptive and not restrictive, and the protection scope of the present invention cannot be limited thereby.

[0039] When a quantity, concentration, or other value or parameter is expressed in the form of a range, a preferred range, or a preferred upper and lower limit of a numerical value, it should be understood that any range formed by combining any upper limit of the range or a preferred numerical value with any lower limit of the range or a preferred numerical value is specifically disclosed, regardless of whether the range is specifically disclosed. Unless otherwise indicated, the numerical range values listed herein include the endpoints of the range and all integers and fractions within the range.

[0040] Unless otherwise specified, all percentages, parts, ratios, etc. in this article are by weight.

[0041] The materials, methods, and examples in this article are exemplary and should not be construed as restrictive unless specifically stated. The raw materials used in this article, and the equipment or devices used in the production and detection processes that are not specifically described, can all be obtained through commercial channels or by conventional preparation methods in this field.

[0042] The chemical general formula of the P2-phase layered oxide cathode material in the sodium-magnesium hybrid battery in this application is: Na x Mn y M z O 2-δ ;

[0043] Where M is an element that dopes and replaces Mn, including any one or more of Li, Ni, Co, Al, Zn, Mg, Ti, B, V, Zr, Cu, Cr, Mo, Nb, and Fe; x, y, and z are the molar percentages of the corresponding elements respectively; x, y, and z satisfy 0.6 < x < 0.9; y > 0; z ≥ 0; y + z ≤ 1; 0 ≤ δ ≤ 0.05.

[0044] In some specific embodiments, M is preferably one or more of Li, Ni, and Mg; 0.67 ≤ x < 0.8; y > 0; z ≥ 0; y + z ≤ 1; 0 ≤ δ ≤ 0.02.

[0045] The P2-phase layered oxide cathode material in this application can be commercially purchased or prepared by the following method: Mix the sodium source, manganese source, and / or metal source evenly to obtain a powder precursor, and synthesize the P2-phase layered oxide cathode material from the powder precursor by solid-phase sintering.

[0046] Where the sodium source includes one or more of sodium acetate, sodium carbonate, and sodium hydroxide;

[0047] Where the manganese source includes one or more of manganese acetate, manganese sesquioxide, manganese oxide, manganese tetroxide, and manganese carbonate;

[0048] The metal source comprises one or more of nickel acetate, cobalt acetate, ferric oxide, ferrous oxide, zinc oxide, nickel oxide, magnesium oxide, copper oxide, boron oxide, zirconium oxide, lithium carbonate, cobalt oxide, molybdenum oxide, chromium oxide, vanadium pentoxide, niobium pentoxide, titanium dioxide and aluminum oxide;

[0049] A sodium-magnesium hybrid battery comprises a positive electrode sheet, a negative electrode sheet and a Na / Mg double salt electrolyte.

[0050] The positive electrode plate includes a current collector and a positive electrode material layer coated on the current collector, wherein the positive electrode material layer includes the aforementioned P2 phase layered oxide positive electrode material, a conductive additive and a binder.

[0051] Wherein, the negative electrode plate is pure magnesium or magnesium alloy.

[0052] Wherein, the Mg / Na atomic ratio of the Na / Mg double salt electrolyte is (0.5-1):1.

[0053] A use of the aforementioned sodium-magnesium hybrid battery, wherein the sodium-magnesium hybrid battery is used for energy storage equipment of hydropower generation, wind power generation, backup power supply or communication base station, as well as power batteries for electric bicycles and low-speed electric vehicles.

[0054] Example 1: Preparation of P2-phase layered oxide positive electrode material

[0055] Implementation Method 1-1

[0056] The preparation of the P2 phase layered oxide positive electrode material provided by the present invention comprises the following steps:

[0057] 1) weighing and mixing the required stoichiometric amounts of NaCH3COO (sodium acetate) and Mn(CH3COO)2 (manganese acetate) in proportion to form a precursor;

[0058] 2) adding the precursor into a ball mill and performing ball milling for three hours to obtain a uniformly mixed powder precursor;

[0059] 3) Press the powder precursor obtained by ball milling into a block precursor with a diameter of 9 mm and an unlimited thickness;

[0060] 4) placing the bulk precursor obtained in step 3) in a crucible and transferring it to a muffle furnace for heat treatment, heat-treating at 100° C. for 6 h, 400° C. for 5 h, and 900° C. for 15 h in an air atmosphere;

[0061] 5) Grind the heat-treated bulk precursor to obtain a black powder of P2-phase layered oxide positive electrode material Na 0.67 MnO2.

[0062] Implementation 1-2

[0063] The preparation of the P2-phase layered oxide cathode material provided by the present invention includes the following steps:

[0064] 1) Weigh and mix the required stoichiometric amounts of NaCH3COO, Mn(CH3COO)2, Ni(CH3COO)2, and Co(CH3COO)2 in proportion to form a precursor;

[0065] 2) Add the precursor into a ball-milling jar and perform ball-milling for three hours to obtain a uniformly mixed powder precursor;

[0066] 3) Press the powder precursor obtained by ball-milling into a block-shaped precursor with a diameter of 9 mm, and the thickness is not limited;

[0067] 4) Place the block-shaped precursor obtained in step 3) in a crucible, transfer it to a muffle furnace for heat treatment, and perform heat treatment at 100 °C for 6 h, 400 °C for 5 h, and 900 °C for 20 h respectively under an air atmosphere;

[0068] 5) Grind the heat-treated block-shaped precursor to obtain the P2-phase layered oxide cathode material Na 0.67 Ni 0.17 Co 0.17 Mn 0.66 O2;

[0069] This application conducts performance tests on the P2-phase layered oxide cathode materials prepared in the above embodiments 1-1 and 1-2. Among them, the XRD pattern of the P2-phase layered oxide cathode material (Na 0.67 MnO2) prepared in embodiment 1-1 is shown in Figure 2 . From the XRD pattern, it can be seen that the crystal structure of Na 0.67 MnO2 is an oxide with a P2-phase layered structure; Figure 3 is the scanning electron microscope (SEM) image of Na 0.67 MnO2. It can be seen from the figure that the particle size distribution of Na 0.67 MnO2 is mainly 1 μm to 5 μm, showing a lamellar shape. Figure 4 is the transmission electron microscope (TEM) image of Na 0.67 MnO2. It can be seen from the figure that the lattice spacing of Na 0.67 MnO2 is 0.25 nm, corresponding to the (100) plane.

[0070] Among them, the XRD pattern of the P2-phase layered oxide cathode prepared in embodiment 1-2 is shown in Figure 5 . From Figure 5 it can be known that Na 0.67 Ni 0.17 Co0.17 Mn 0.66 The crystal structure of the MnO2 cathode material is a P2-phase structure.

[0071] Example 2: A magnesium-ion half-cell containing a P2-phase layered oxide cathode material

[0072] Embodiment 2-1

[0073] In this example, the P2-phase layered oxide cathode material Na 0.67 MnO2 prepared in Embodiment 1-1 is taken as an example. This P2-phase layered oxide cathode material is used as the active material of the positive electrode sheet for the preparation of a magnesium-ion half-cell, and the specific steps are as follows:

[0074] 1) Preparation of the positive electrode sheet

[0075] The prepared Na 0.67 MnO2 powder is mixed with acetylene black and the binder polyvinylidene fluoride (PVDF) according to a mass ratio of 80:10:10, an appropriate amount of N-methylpyrrolidone (NMP) solution is added, and it is ground into a slurry in a dry environment at room temperature. Then the slurry is evenly coated on the current collector aluminum foil, dried under an infrared lamp, and cut into a (12×12) mm 2 electrode sheet. The electrode sheet is dried at 60 °C for 12 hours under vacuum conditions and then immediately transferred to a glove box for standby.

[0076] 2) Preparation of the magnesium-ion half-cell

[0077] The assembly of the magnesium-ion half-cell is carried out in a glove box under an Ar atmosphere. Using the positive electrode sheet prepared in step 1), a carbon paper as the negative electrode sheet, and a 0.3 M Mg(TFSI)2 / acetonitrile (AN) solution as the electrolyte, a CR2032 button cell is assembled. Using a constant current charge-discharge mode, charge-discharge tests are carried out at a current density of 100 mA g -1 . Under the conditions that the discharge cut-off voltage is -0.4 V and the charge cut-off voltage is 1.5 V, the test results are shown in Figure 6 . Figure 6 The charge-discharge curves of the first 3 cycles and the 50th cycle are shown. It can be seen that the initial discharge specific capacity of the battery is 80.7 mAh g -1 , and the discharge specific capacity after 50 cycles is 52.2 mAh g -1 , the Coulomb efficiency is close to 100%, and the cycle stability is good.

[0078] Embodiment 2-2

[0079] The preparation method of the electrode sheet in this embodiment is the same as that in Embodiment 2-1. The difference lies in the preparation process of the magnesium-ion half-cell as follows:

[0080] The assembly of the magnesium ion half-cell was carried out in a glove box under an Ar atmosphere. Using the positive electrode sheet prepared in the previous step 1), carbon paper as the negative electrode sheet, and a 0.3 M Mg(TFSI)2 / acetonitrile (AN) solution as the electrolyte, a CR2032 coin cell was assembled. Using the constant current charge-discharge mode, the charge-discharge test was carried out at a current density of 100 mA g -1 Under the condition that the discharge cut-off voltage is -1.0 V and the charge cut-off voltage is 1.8 V, the test results are shown in Figure 7 . Figure 7 The charge-discharge curves of the first cycle and the 15th cycle are shown in . It can be seen that the discharge specific capacity of the battery in the first cycle is 153.1 mAh g -1 , and the discharge specific capacity is 138.1 mAh g -1 after 15 cycles. The Coulombic efficiency is close to 100% after the first cycle, and the cycle stability is good.

[0081] Embodiment 2-3

[0082] In this embodiment, taking the P2-phase layered oxide cathode material Na 0.67 Ni 0.17 Co 0.17 Mn 0.66 O2 prepared in Embodiment 1-2 as an example, this P2-phase layered oxide cathode material was used as the active material of the positive electrode sheet for the preparation of the magnesium ion half-cell, which specifically included the following steps:

[0083] 1) Preparation of the positive electrode sheet

[0084] Mix the prepared Na 0.67 Ni 0.17 Co 0.17 Mn 0.66 O2 powder, acetylene black, and the binder polyvinylidene fluoride (PVDF) in a mass ratio of 80:10:10, add an appropriate amount of N-methylpyrrolidone (NMP) solution, grind to form a slurry in a normal temperature and dry environment, then evenly coat the slurry on the current collector aluminum foil, and after drying under an infrared lamp, cut it into a (12×12) mm 2 electrode sheet. The electrode sheet was dried at 60 °C for 12 hours under vacuum conditions, and then immediately transferred to the glove box for standby.

[0085] 2) Preparation of the magnesium ion half-cell

[0086] The assembly of the magnesium ion half-cell was carried out in a glove box under an Ar atmosphere. Using the positive electrode sheet prepared in the previous step 1), carbon paper as the negative electrode sheet, and a 0.3 M Mg(TFSI)2 / acetonitrile (AN) solution as the electrolyte, a CR2032 coin cell was assembled. Using the constant current charge-discharge mode, at a current density of 100 mA g -1Charge and discharge tests were carried out at a current density. Under the conditions that the discharge cut-off voltage is -1.0 V and the charge cut-off voltage is 1.8 V, the test results are shown in Figure 8 . Figure 8 The charge and discharge curves of the first 3 cycles are shown in Figure 8 . It can be seen that the initial charge specific capacity of the battery is 119.4 mAh g -1 , and the initial discharge specific capacity is 78.6 mAh g -1 . After the first cycle, the Coulombic efficiency is close to 100%.

[0087] Example 3: Sodium-magnesium hybrid battery containing P2-phase layered oxide cathode material

[0088] Embodiment 3-1

[0089] In this example, taking the P2-phase layered oxide cathode material Na 0.67 MnO2 prepared in Embodiment 1-1 as an example, this P2-phase layered oxide cathode material was used as the active material of the positive electrode sheet for the preparation of a sodium-magnesium hybrid battery, which specifically included the following steps:

[0090] 1) Preparation of the positive electrode sheet

[0091] The prepared Na 0.67 MnO2 powder was mixed with acetylene black and the binder polyvinylidene fluoride (PVDF) in a mass ratio of 80:10:10, and an appropriate amount of N-methylpyrrolidone (NMP) solution was added. The mixture was ground to form a slurry in a dry environment at room temperature. Then, the slurry was evenly coated on a current collector carbon paper, dried under an infrared lamp, and cut into a (12×12) mm 2 electrode sheet. The electrode sheet was dried in a vacuum at 60 °C for 12 hours and then immediately transferred to a glove box for standby.

[0092] 2) Preparation of the sodium-magnesium hybrid battery

[0093] The assembly of the sodium-magnesium hybrid battery was carried out in a glove box under an Ar atmosphere. The positive electrode sheet prepared in step 1) and a pure magnesium foil were used as the negative electrode sheet, and an [AlCl4] — / ethylene glycol dimethyl ether (DME) solution with a Mg / Na atomic ratio of 1:1 and a molar mass of 0.4 M was used as the electrolyte to assemble a CR2032 button cell. Using a constant current charge and discharge mode, charge and discharge tests were carried out at a current density of 100 mA g -1 . Under the conditions that the discharge cut-off voltage is 0.3 V and the charge cut-off voltage is 3.2 V, the test results are shown in Figure 9 (In the figure, change represents charging and dischange represents discharging). Figure 9 The charge and discharge curves of the first cycle are shown in Figure 9 . It can be seen that the initial charge specific capacity of the battery is 276.7 mAh g -1, the specific discharge capacity of the first cycle is 176.7 mAh g -1 , and the specific capacity of the first cycle is relatively high.

[0094] Embodiment 3-2

[0095] In this embodiment, the preparation method of the electrode is the same as that of Embodiment 3-1, except that the preparation process of the sodium-magnesium hybrid battery is as follows:

[0096] The assembly of the sodium-magnesium hybrid battery is carried out in a glove box under an Ar atmosphere. The positive electrode prepared in step 1) is used as the positive electrode, pure magnesium foil is used as the negative electrode, and [B(hfip)4] with a Mg / Na atomic ratio of 0.5:1 and a molar mass of 0.6 M - / ethylene glycol dimethyl ether (DME) solution is used as the electrolyte to assemble a CR2032 coin cell. The constant current charge-discharge mode is used, and the charge-discharge test is carried out at a current density of 100 mAg -1 . Under the conditions that the discharge cut-off voltage is 0.3 V and the charge cut-off voltage is 3.5 V, the test results are shown in Figure 10 . Figure 10 . The charge-discharge curves of the first cycle are shown in -1 , it can be seen that the specific charge capacity of the first cycle of the battery is 90.9 mAh g -1 , the specific discharge capacity of the first cycle is 114.0 mAh g

[0097] In summary, it can be seen that the P2-phase layered oxide cathode material provided by the embodiments of the present invention can be used as the positive electrode of the sodium-magnesium hybrid battery, and its battery structure is as Figure 1 shown. The sodium-magnesium hybrid battery uses the P2-phase layered oxide cathode material as the positive electrode, pure magnesium / magnesium alloy as the negative electrode and Na / Mg double salt electrolyte. Due to the large difference in redox potential, Na + cannot be dissolved / deposited on the negative electrode of pure magnesium / magnesium alloy, so the consumption of raw sodium is fundamentally avoided; at the same time, the relatively high specific capacity of metallic magnesium can additionally compensate for Mg 2+ , so that the battery has a relatively high energy density; and dendrites will not be generated on the surface of the negative electrode of pure magnesium / magnesium alloy, improving the intrinsic safety of the battery; while giving full play to the inherent advantages of magnesium batteries, it also takes into account the advantages of high ion transfer rate of the cathode material, and has a relatively high charge-discharge specific capacity in the first cycle.

[0098] The sodium-magnesium hybrid battery using the P2-phase layered oxide cathode material provided by the present invention has a simple preparation process for the P2-phase layered oxide cathode material, rich resources, and all use conventional equipment. Therefore, the preparation cost is low and it is convenient for industrial application. The sodium-magnesium hybrid battery using this cathode material has high safety, high ion migration rate, high specific capacity, and great practical value. It can be used for energy storage devices of hydropower generation, wind power generation, backup power supplies or communication base stations, as well as power batteries for electric bicycles and low-speed electric vehicles.

[0099] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered by the scope of the claims and the description of the present invention.

Claims

1. A sodium-magnesium hybrid battery with a P2-phase layered oxide cathode material, characterized in that, It includes a positive electrode plate, a negative electrode plate and a Na / Mg double salt electrolyte, wherein the positive electrode plate includes a P2-phase layered oxide positive electrode material, and its chemical general formula is: Na x Mn y M z O 2-δ ; where M is an element that dopes and replaces Mn, and it includes any one or more of Li, Ni, Co, Al, Zn, Mg, Ti, B, V, Zr, Cu, Cr, Mo, Nb and Fe; x, y, and z are the molar percentages of the corresponding elements respectively; x, y, and z satisfy 0.6 < x < 0.9; y > 0; z ≥ 0; y + z ≤ 1; 0 ≤ δ ≤ 0.05; The negative electrode plate is pure magnesium or magnesium alloy; The Mg / Na atomic ratio of the Na / Mg double salt electrolyte is (0.5 - 1):1, and the Na / Mg double salt electrolyte is a mixture of — [AlCl4] — / ethylene glycol dimethyl ether (DME) solution; or the Na / Mg double salt electrolyte is a mixture of [B(hfip)4] / ethylene glycol dimethyl ether (DME) solution.

2. The sodium-magnesium hybrid battery with the P2-phase layered oxide cathode material according to claim 1, characterized in that, The positive electrode plate also includes a current collector and a positive electrode material layer coated on the current collector, wherein the positive electrode material layer includes a P2 phase layered oxide positive electrode material, a conductive additive and a binder.

3. The sodium-magnesium hybrid battery with a P2-phase layered oxide cathode material according to claim 1, wherein, The M is one or more of Li, Ni and Mg; 0.67≤x<0.8; y>0; z≥0; y+z≤1; 0≤δ≤0.

02.

4. The sodium-magnesium hybrid battery using the P2-phase layered oxide cathode material according to claim 3, characterized in that, The P2 phase layered oxide positive electrode material is prepared by the following method: a sodium source and a manganese source are uniformly mixed or a sodium source, a manganese source and an M source are uniformly mixed to obtain a powder precursor, and the powder precursor is subjected to a solid phase sintering method to synthesize the P2 phase layered oxide positive electrode material.

5. The sodium-magnesium hybrid battery with the P2-phase layered oxide cathode material according to claim 4, characterized in that, The P2 phase layered oxide positive electrode material is prepared by the following method, specifically: Mixing sodium acetate and manganese acetate in proportion or mixing sodium acetate, manganese acetate and acetate of M in proportion to form a precursor, and grinding the precursor in a ball mill to obtain a powder precursor; After the powder precursor is pressed into a block precursor, it is placed in an air atmosphere at 100-900° C. for heat treatment for 15-26 hours to obtain a P2 phase layered oxide positive electrode material.

6. A method for preparing a sodium-magnesium hybrid battery with a P2-phase layered oxide cathode material as described in any one of claims 1-5, characterized in that, It includes the following steps: 1) Preparation of positive electrode The P2 phase layered oxide positive electrode material, conductive additive and binder are mixed into a slurry, uniformly coated on the current collector, and dried to obtain a positive electrode sheet; 2) Preparation of sodium-magnesium hybrid battery Under an inert atmosphere, the positive electrode plate prepared in step 1) is used, pure magnesium or magnesium alloy is used as the negative electrode plate, and Na / Mg double salt solution is used as the electrolyte to assemble a sodium-magnesium hybrid battery.

7. Use of a sodium-magnesium hybrid battery with a P2-phase layered oxide cathode material as described in any one of claims 1-5, characterized in that, The sodium-magnesium hybrid battery is used for hydroelectric power generation, wind power generation, backup power supply or energy storage equipment of communication base stations, as well as power batteries for electric bicycles and low-speed electric vehicles.

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