A high-performance sodium manganese titanium phosphate cathode material for sodium ion batteries doped with copper at the titanium site, and its preparation method and application

Abstract

The application discloses a titanium-site copper-doped high-performance sodium-ion battery positive electrode material of sodium titanium manganese phosphate and a preparation method and application thereof, and belongs to the technical field of sodium-ion batteries. The titanium-site copper-doped sodium-ion battery positive electrode material of sodium titanium manganese phosphate is obtained by doping copper at the titanium site of sodium titanium manganese phosphate; the general formula of the titanium-site copper-doped sodium-ion battery positive electrode material of sodium titanium manganese phosphate is Na 3+ 2x MnTi 1‑x Cu x (PO4)3, wherein 0 < x <= 0.2. The preparation method of the titanium-site copper-doped sodium-ion battery positive electrode material of sodium titanium manganese phosphate comprises the following steps: raw materials including a titanium source, a manganese source, a sodium source, a phosphorus source and a copper source are prepared into a precursor powder through a spray drying method or a ball milling method; and the precursor powder is calcined under an inert atmosphere to obtain the titanium-site copper-doped sodium-ion battery positive electrode material of sodium titanium manganese phosphate. The obtained positive electrode material has small polarization, reverse-site defects are effectively inhibited, reversible capacity is obviously improved, and rate performance is obviously improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion batteries, and more specifically relates to a high-performance sodium manganese titanium phosphate positive electrode material for sodium ion batteries doped with copper in the titanium position, and a preparation method and application thereof. Background Art

[0002] With the global shift towards reduced reliance on fossil fuels and green renewable energy, the application of secondary batteries in energy storage technology is gaining increasing attention. Lithium-ion batteries (LIBs), in particular, have become the mainstream of large-scale energy storage technology due to their high energy density and long cycle life. However, the scarcity and high cost of lithium, as well as its uneven global distribution, have prompted researchers to explore low-cost, sustainable alternatives. Sodium-ion batteries, due to their abundant sodium resources, low cost, and good safety, have become a promising alternative.

[0003] Research on cathode materials is particularly crucial in sodium-ion battery research. The larger radius of sodium ions compared to lithium ions makes the design of sodium-ion batteries challenging in terms of electrode material selection, particularly in terms of effectively accommodating sodium ions and facilitating their efficient transport. The energy density of sodium-ion batteries is relatively low, and one effective way to increase energy density is to increase the operating voltage. Therefore, it is necessary to identify sodium-ion cathode materials with excellent kinetics, stable structures, and high voltage characteristics.

[0004] At present, the positive electrode materials of sodium ion batteries are mainly concentrated in three categories of materials: layered oxides, Prussian blue analogues and polyanion compounds (such as NASICON structure). Among them, Na3V2(PO4)3(NVP) is a classic material in the NASICON system with a theoretical capacity of 117mAh / g, but its application is limited by the high cost and toxicity of vanadium. In order to solve this problem, researchers have developed a new manganese-based sodium ion battery Na3MnTi(PO4)3(NMTP) electrode material, which not only reduces cost and toxicity, but also increases the working voltage and has great potential in application. The study found that Na3MnTi(PO4)3 can undergo Mn during the charge and discharge process. 2+ / Mn 3+ 、Mn 3+ / Mn 4+ 、Ti 3+ / Ti 4+ However, the transport properties of Na3MnTi(PO4)3 are inferior to those of vanadium-based materials, resulting in poor rate and cycle performance. Therefore, further improving its electrochemical performance is key to its industrialization. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-performance sodium manganese titanium phosphate sodium ion battery positive electrode material doped with copper at the titanium position, and its preparation method and application, so as to solve the problems existing in the above-mentioned prior art and realize the preparation of Na3MnTi(PO4)3 positive electrode material doped with copper at the titanium position with better electrochemical performance.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is to provide a positive electrode material for a sodium manganese titanium phosphate battery doped with copper at a titanium site. The positive electrode material for a sodium manganese titanium phosphate battery doped with copper at the titanium site of sodium manganese titanium phosphate is obtained. The general formula of the positive electrode material for a sodium manganese titanium phosphate battery doped with copper at a titanium site is Na 3+2x MnTi 1-x Cu x (PO4)3, where 0<x≤0.2.

[0008] For Na3MnTi(PO4)3 material, from the molecular formula, doping can be based on sodium, manganese, titanium and phosphate positions. Current reports mainly focus on doping at the manganese position. The titanium doping described in the present invention is different from the existing manganese doping, which will reduce the content of active manganese elements (Mn 2+ / Mn 3+ and Mn 3+ / Mn 4+ Provide capacity), thereby reducing the theoretical gram capacity and energy density of the material. Compared with manganese doping, titanium doping has more advantages, because Ti 3+ / Ti 4+ Below 2V, the redox couple has no capacity within the electrochemical window of traditional cathode materials (2.5-4.3V); even when discharged to 1.5V, the full battery system still needs to be combined with a sodium supplement to fully utilize the capacity of the titanium couple. Therefore, from the perspective of traditional cathode materials (2.5-4.3V), the manganese site is an active site that provides capacity, while the titanium site is an inert site that does not provide capacity. Therefore, titanium doping can further activate the kinetics of the manganese redox couple by doping the inert site without reducing the manganese content, that is, without sacrificing the original capacity, thereby comprehensively improving the reversible capacity and rate performance.

[0009] In addition, there is also a preparation strategy of high entropy electrodes to improve the electrochemical performance of Na3MnTi(PO4)3 materials, but it is worth noting that the design of high entropy electrodes generally improves performance through entropy regulation, through the synergistic effect of multiple elements, similar to the cocktail effect, but the role of each element is not clear, and the high entropy electrode contains several elements that work together, and it cannot guarantee that each element will work when doped alone, and in most cases, the doping of a single element does not work. Therefore, clarifying the role of doping with a single element is of greater significance both for theoretical research and industrial application. The present invention can significantly improve the electrochemical performance of the resulting positive electrode material by doping a single copper element at the titanium position, effectively solving the problem that the existing high entropy electrode has multiple elements doping and synergistic effect, resulting in the inability to clarify the specific role of each element, and the doping elements involved in the high entropy electrode cannot work when doped alone.

[0010] Moreover, the titanium-copper doped sodium manganese titanium phosphate sodium ion battery positive electrode material of the present invention (general formula is Na 3+ 2x MnTi 1-x Cu x (PO4)3, where 0 < x ≤ 0.2) is different from the existing vanadium-containing (vanadium-based or vanadium-doped) positive electrode materials. If the polyanion positive electrode material contains vanadium, the electrochemical performance will be greatly improved because V 3+ / V 4+ / V 5+ It has the characteristics of multi-electron reaction, can provide capacity by itself, and V will have a synergistic effect with transition metal elements such as Mn, so the kinetic performance is very excellent, such as Na3V2(PO4)3 (the highest rate can reach 500C), Na4MnV(PO4)3 (the highest rate can reach 40C), etc. However, vanadium is expensive and toxic, and reducing the amount of vanadium will greatly affect the material properties. Similarly, the performance of vanadium-free material systems will be greatly reduced. The titanium-site copper doping proposed in the present invention can show obvious effects on vanadium-free positive electrode systems, significantly improving the electrochemical performance of vanadium-free positive electrode systems, which is of great significance.

[0011] The second technical solution of the present invention is to provide a method for preparing the above-mentioned titanium-copper-doped sodium manganese titanium phosphate positive electrode material for sodium ion batteries, comprising the following steps:

[0012] The raw materials including phosphorus source, titanium source, manganese source, sodium source and copper source are prepared by spray drying or ball milling to obtain precursor powder;

[0013] The precursor powder is calcined under an inert atmosphere to obtain the copper-doped sodium manganese titanium phosphate sodium ion battery positive electrode material.

[0014] Preferably, the spray drying method comprises mixing the carbon source, the phosphorus source, the sodium source, the manganese source, the titanium source, the copper source and water, and spray drying at an air outlet temperature of 160-220 DEG C to obtain the precursor powder.

[0015] The carbon source comprises citric acid; the phosphorus source comprises sodium dihydrogen phosphate; the sodium source comprises sodium nitrate and sodium dihydrogen phosphate; the manganese source comprises manganese acetate; the titanium source comprises titanium dihydroxy bis(ammonium lactate); and the copper source comprises copper sulfate.

[0016] Preferably, during the spray drying method for preparing the precursor powder, the molar ratio of the phosphorus source, the sodium source, the manganese source, the titanium source and the copper source is determined according to the general formula of the copper-doped sodium titanium manganese phosphate positive electrode material of sodium-ion batteries.

[0017] Further, the present application does not specially limit the amount of water involved in the spray drying method, as long as the spray drying process can be smoothly carried out.

[0018] Preferably, the ball milling method comprises mixing the carbon source, the phosphorus source, the sodium source, the manganese source, the titanium source and the copper source, and ball milling to obtain the precursor powder.

[0019] The carbon source comprises citric acid; the phosphorus source comprises sodium dihydrogen phosphate; the sodium source comprises sodium nitrate and sodium dihydrogen phosphate; the manganese source comprises manganese acetate; the titanium source comprises titanium acetylacetonate; and the copper source comprises copper sulfate.

[0020] Preferably, the ball milling method for preparing the precursor powder further comprises adding a filler, and the filler comprises one or more of conductive carbon black, Ketjen black, SP and carbon nanotubes.

[0021] The citric acid and the filler can provide a carbon source during the calcination process, thereby improving the electrical conductivity of the material.

[0022] Preferably, during the ball milling method for preparing the precursor powder, the molar ratio of the phosphorus source, the sodium source, the manganese source, the titanium source and the copper source is determined according to the chemical formula of the copper-doped sodium titanium manganese phosphate positive electrode material of sodium-ion batteries; and the amount of the filler is 30-60 g per mole of the copper-doped sodium titanium manganese phosphate positive electrode material of sodium-ion batteries.

[0023] Preferably, the rotation speed of the ball milling is 350-450 r / min, and the time is 6-9 h; the ball milling is intermittent, specifically, after ball milling for 20 min, the ball milling is paused for 10 min before the next ball milling, and the step is repeated until the ball milling is completed.

[0024] Further, the medium of the ball milling is zirconium oxide balls, and the size and proportion are as follows: the mass of the zirconium oxide balls with a particle size of 5mm is 10-15 times of the mass of the precursor powder, and the mass of the zirconium oxide balls with a particle size of 10mm is 1-3 times of the mass of the precursor powder, so that the material adhesion is reduced, and the ball milling efficiency is improved; and the ball-to-material ratio of the ball milling is 11-18:1.

[0025] Preferably, when the precursor powder is prepared by the spray drying method, the calcination temperature is 550-700℃, and the time is 3-12h.

[0026] Preferably, when the precursor powder is prepared by the ball milling method, the calcination is stepwise calcination, specifically: first, the temperature is raised to 350℃ and kept for 300min, and then the temperature is raised to 550-700℃ and kept for 720min.

[0027] When the precursor powder is prepared by different methods, the performance of the material is better by using different calcination processes and parameters. When the precursor powder is prepared by the spray drying method, the pure phase can be synthesized by the one-step calcination method, and the material is decomposed and the impurity phase appears when the temperature exceeds the upper limit (700℃) of the highest temperature range, which leads to the capacity reduction; and the crystallinity is reduced and the capacity is reduced when the temperature is lower than the lower limit (550℃) of the lowest temperature range; when the precursor powder is prepared by the ball milling method, the material is pre-decomposed in the calcination process by the stepwise calcination method, so that the performance of the material is improved.

[0028] The technical principle of the application is as follows:

[0029] The application dopes copper on the titanium site of the Na3MnTi(PO4)3 material. Different from the existing doping on the active manganese site, the titanium site doping can ensure that the active manganese content is not reduced, and the problem that the capacity of the electrode is reduced due to the reduction of the active manganese content is avoided. In addition, the doping on the electrochemically inert titanium site has better effects in the range of 2.5-4.3V, because the Cu redox couple itself has activity and contributes to the capacity improvement, and in addition, the Cu doping further activates the Mn 2+ / Mn 3+ / Mn 4+ conversion, which can further improve the capacity and promote the multi-electron reaction kinetics. Compared with other metal element doping, the electrochemical performance is best when the molar amount of the Cu doping is 0.05mol. In addition, compared with other Cu doping amounts of 0.1mol and 0.15mol, the Cu doping amount of 0.05mol has the highest capacity, and the impurity phase appears when the Cu doping amount is 0.25mol.

[0030] The third technical scheme of the present application provides application of the titanium site copper-doped sodium titanium manganese phosphate positive electrode material in a sodium ion battery.

[0031] The fourth technical scheme of the present application provides a sodium ion battery, wherein the positive electrode material of the sodium ion battery is the titanium site copper-doped sodium titanium manganese phosphate positive electrode material.

[0032] The present application discloses the following technical effects:

[0033] The present application obtains the copper-doped sodium titanium manganese phosphate positive electrode material of the sodium ion battery by copper doping Na3MnTi(PO4)3, and the positive electrode material can still maintain the structure of the pure-phase Na3MnTi(PO4)3 without appearing a heterogeneous phase, which indicates that the material will not appear other compounds to reduce the active material, and the rate performance and the charge-discharge reversible capacity of the positive electrode material can be improved. In addition, the polarization of the positive electrode material is small, the anti-site defects are effectively inhibited, the reversible capacity is obviously improved, and the rate performance is obviously improved. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The charge-discharge curves of the batteries obtained by assembling the positive electrode materials of Example 1 and Comparative Example 1 at a rate of 0.05C are shown in the following figure, wherein a is Example 1, and b is Comparative Example 1.

[0035] Figure 2 The XRD pattern of the positive electrode material of Comparative Example 1 is shown in the following figure.

[0036] Figure 3 The XRD pattern of the positive electrode material of Comparative Example 2 is shown in the following figure.

[0037] Figure 4 The XRD comparison figure of the positive electrode materials of Comparative Example 3 and Comparative Example 1 is shown in the following figure.

[0038] Figure 5 The XRD comparison figure of the positive electrode materials of Comparative Example 4 and Comparative Example 1 is shown in the following figure.

[0039] Figure 6 The XRD comparison figure of the positive electrode materials of Comparative Example 5 and Comparative Example 1 is shown in the following figure.

[0040] Figure 7 The XRD patterns of the positive electrode materials of Example 1, Example 3, Example 4, Example 5 and Comparative Example 6 are shown in the following figure. DETAILED DESCRIPTION

[0041] The detailed description of the various exemplary embodiments of the present application should not be considered to be limiting of the present application, but should be understood to be a more detailed description of certain aspects, features and embodiments of the present application.

[0042] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. Additionally, for a range of values of, for example, the upper limit of the range and the lower limit of the range are each implicitly disclosed. Each intermediate value of this range, as well as every range formed by each combination of intermediate values between any stated value or intervening value of the range is also specifically disclosed. The upper and lower limits of these smaller ranges can independently be included or excluded in the range, and are also encompassed by the application, subject to any specifically excluded limit in the stated

[0043] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe in detail the methods and / or materials which are related to the present application. In case of conflict, the content of the present specification will control.

[0044] Many modifications and variations of the present application described in the specification are possible without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples are illustrative only.

[0045] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", "contains", "containing", or variations thereof, are intended to be open-ended terms that mean including, but not limited to.

[0046] The raw materials used in the examples, comparative examples and performance tests are commercially available products, and the source of the commercially available products has no effect on the results.

[0047] Example 1

[0048] This example provides a copper-doped titanium manganese phosphate sodium sodium-ion battery cathode material prepared by a spray drying method, and the specific steps are as follows:

[0049] Weigh and measure 2 mmol of citric acid (C5H8O7), 3 mmol of sodium dihydrogen phosphate (NaH2PO4), 1 mmol of manganese acetate tetrahydrate (MnC4H5O4·4H2O), 0.95 mmol of titanium dihydroxide (ammonium lactate) (C5H 18N2O8Ti), 0.05mmol copper sulfate pentahydrate (CuSO4·5H2O) and 0.1mmol sodium nitrate (NaNO3) were added to 500mL of deionized water. Stirred on a magnetic stirring table until completely dissolved, and spray dried under the condition of an outlet air temperature of 220℃ to obtain a precursor powder. The precursor powder was placed in a tube furnace and calcined at 600℃ for 4h under argon atmosphere to obtain a black powder sample, which is the titanium-copper-doped sodium manganese titanium phosphate positive electrode material for sodium ion batteries with a chemical formula of Na 3.1 MnTi 0.95 Cu 0.05 (PO4)3, denoted as NMTP-Cu0.05.

[0050] Example 2

[0051] This embodiment provides a copper-doped sodium manganese titanium phosphate positive electrode material for sodium ion batteries prepared by ball milling, and the specific steps are as follows:

[0052] Weigh and measure 2mmol citric acid (C5H8O7), 3mmol sodium dihydrogen phosphate (NaH2PO4), 135mg Ketjen black, 1mmol manganese acetate tetrahydrate (MnC4H5O4·4H2O), 0.95mmol titanium dioxide acetylacetonate (C 10 H 14 O5Ti), 0.05mmol copper sulfate pentahydrate (CuSO4·5H2O) and 0.1mmol sodium nitrate (NaNO3), and the weighed medicines are mixed and added into a ball mill with zirconium oxide balls and stirred evenly. The size and proportion of the zirconium oxide balls are as follows: the mass of 5mm zirconium oxide balls is 12 times the total mass of the above raw materials, and the mass of 10mm zirconium oxide balls is 3 times the total mass of the above raw materials. The balls are ball milled at a speed of 450r / min for 9h (after each ball milling for 20min, pause for 10min and then proceed to the next ball milling); the black powder obtained by ball milling is placed in a tubular furnace and calcined in an argon atmosphere in a step-by-step manner (heating to 350℃ and holding for 300min, then heating to 650℃ and holding for 720min) to obtain titanium-site copper-doped sodium manganese titanium phosphate sodium ion battery positive electrode material, the chemical formula is Na 3.1 MnTi 0.95 Cu 0.05 (PO4)3, recorded as NMTP-ball-milled Cu0.05.

[0053] Example 3

[0054] Weigh and measure 2mmol citric acid (C5H8O7), 3mmol sodium dihydrogen phosphate (NaH2PO4), 1mmol manganese acetate tetrahydrate (MnC4H5O4·4H2O), 0.9mmol dihydroxy (ammonium lactate) titanium (C5H 18N2O8Ti), 0.2 mmol sodium nitrate (NaNO3), 0.1 mmol copper sulfate pentahydrate (CuSO4-5H2O), and the rest is the same as Example 1. The prepared titanium-site copper-doped titanium manganese sodium phosphate sodium-ion battery positive electrode material has a chemical formula of Na 3.2 MnTi 0.9 Cu 0.1 (PO4)3, denoted as NMTP-Cu0.1.

[0055] Example 4

[0056] weigh and measure 2 mmol of citric acid (C5H8O7), 3 mmol of sodium dihydrogen phosphate (NaH2PO4), 1 mmol of manganese acetate tetrahydrate (MnC4H5O4-4H2O), 0.85 mmol of titanium dihydroxide (ammonium lactate) (C5H 18 N2O8Ti), 0.3 mmol of sodium nitrate (NaNO3), and 0.15 mmol of copper sulfate pentahydrate (CuSO4-5H2O), and the rest is the same as Example 1. The prepared titanium-site copper-doped titanium manganese sodium phosphate sodium-ion battery positive electrode material has a chemical formula of Na 3.3 MnTi 0.85 Cu 0.15 (PO4)3, denoted as NMTP-Cu0.15.

[0057] Example 5

[0058] weigh and measure 2 mmol of citric acid (C5H8O7), 3 mmol of sodium dihydrogen phosphate (NaH2PO4), 1 mmol of manganese acetate tetrahydrate (MnC4H5O4-4H2O), 0.8 mmol of titanium dihydroxide (ammonium lactate) (C5H 18 N2O8Ti), 0.4 mmol of sodium nitrate (NaNO3), and 0.2 mmol of copper sulfate pentahydrate (CuSO4-5H2O), and the rest is the same as Example 1. The prepared titanium-site copper-doped titanium manganese sodium phosphate sodium-ion battery positive electrode material has a chemical formula of Na 3.4 MnTi 0.8 Cu 0.2 (PO4)3, denoted as NMTP-Cu0.2.

[0059] Comparative Example 1

[0060] weigh and measure 2 mmol of citric acid (C5H8O7), 3 mmol of sodium dihydrogen phosphate (NaH2PO4), 1 mmol of manganese acetate tetrahydrate (MnC4H5O4-4H2O), and 1 mmol of titanium dihydroxide (ammonium lactate) (C5H 18 N2O8Ti), and the rest is the same as Example 1. The prepared titanium manganese sodium phosphate sodium-ion battery positive electrode material has a chemical formula of Na3MnTi(PO4)3, denoted as NMTP.

[0061] Figure 2 This is the XRD pattern of the positive electrode material obtained in Comparative Example 1.

[0062] Comparison of the XRD patterns of the positive electrode materials obtained in Example 1 and Comparative Example 1 shows that (the XRD patterns of the positive electrode materials obtained in Example 1 are shown in FIG. Figure 7 ), after copper element doping, the positive electrode material can still maintain the structure of pure phase Na3MnTi(PO4)3 without the appearance of impurity phase, which can improve the electrochemical performance of the positive electrode material.

[0063] Comparative Example 2

[0064] Weigh and measure 2mmol citric acid (C5H8O7), 3mmol sodium dihydrogen phosphate (NaH2PO4), 45mg Ketjen black, 1mmol manganese acetate tetrahydrate (MnC4H5O4·4H2O) and 1mmol titanium acetylacetonate (C 10 H 14 O5Ti), and the rest is the same as in Example 2. The chemical formula of the prepared sodium manganese titanium phosphate sodium ion battery positive electrode material is Na3MnTi(PO4)3, denoted as NMTP-ball milling.

[0065] Figure 3 This is the XRD pattern of the positive electrode material obtained in Comparative Example 2.

[0066] Comparative Example 3

[0067] Weigh and measure 2mmol citric acid (C5H8O7), 3mmol sodium dihydrogen phosphate (NaH2PO4), 0.9mmol manganese acetate tetrahydrate (MnC4H5O4·4H2O), 1mmol dihydroxy (ammonium lactate) titanium (C5H 18 N2O8Ti) and 0.1mmol nickel nitrate hexahydrate (Ni(NO3)2·6H2O), and the rest is the same as in Example 1. The prepared manganese nickel doped sodium manganese titanium phosphate sodium ion battery positive electrode material has the chemical formula of Na3Mn 0.9 Ni 0.1 Ti(PO4)3, denoted as NMTP-Ni0.1.

[0068] Figure 4 This is a comparison chart of the XRD patterns of the positive electrode materials obtained in Comparative Example 3 and Comparative Example 1.

[0069] Comparative Example 4

[0070] Weigh and measure 2mmol citric acid (C5H8O7), 3mmol sodium dihydrogen phosphate (NaH2PO4), 1mmol manganese acetate tetrahydrate (MnC4H5O4·4H2O), 0.95mmol dihydroxy (ammonium lactate) titanium (C5H 18N2O8Ti), 0.1 mmol sodium nitrate (NaNO3) and 0.05 mmol magnesium acetate tetrahydrate (C4H 14 MgO8), the rest as in example 1. The obtained titanium site magnesium doped titanium manganese sodium phosphate sodium-ion battery cathode material has the chemical formula Na 3.1 MnTi 0.95 Mg 0.05 (PO4)3, denoted as NMTP-Mg0.05.

[0071] Figure 5 XRD comparison chart of the cathode material obtained in comparative example 4 and comparative example 1.

[0072] Comparative example 5

[0073] Weigh and measure 2 mmol citric acid (C5H8O7), 2.9 mmol sodium dihydrogen phosphate (NaH2PO4), 1 mmol manganese acetate tetrahydrate (MnC4H5O4·4H2O), 0.95 mmol titanium dihydroxide (ammonium lactate) (C5H 18 N2O8Ti), 0.1 mmol ammonium dihydrogen phosphate (NH4H2PO4) and 0.05 mmol ammonium heptamolybdate tetrahydrate ((NH4)6Mo7O 24 ·4H2O), the rest as in example 1. The obtained titanium site molybdenum doped titanium manganese sodium phosphate sodium-ion battery cathode material has the chemical formula Na 2.9 MnTi 0.95 Mo 0.05 (PO4)3, denoted as NMTP-Mo0.05.

[0074] Figure 6 XRD comparison chart of the cathode material obtained in comparative example 5 and comparative example 1.

[0075] Comparative example 6

[0076] Weigh and measure 2 mmol citric acid (C5H8O7), 3 mmol sodium dihydrogen phosphate (NaH2PO4), 1 mmol manganese acetate tetrahydrate (MnC4H5O4·4H2O), 0.75 mmol titanium dihydroxide (ammonium lactate) (C5H 18 N2O8Ti), 0.5 mmol sodium nitrate (NaNO3) and 0.25 mmol copper sulfate pentahydrate (CuSO4·5H2O), the rest as in example 1. The obtained titanium site copper doped titanium manganese sodium phosphate sodium-ion battery cathode material has the chemical formula Na 3.5 MnTi 0.75 Cu 0.25 (PO4)3, denoted as NMTP-Cu0.25.

[0077] Figure 7XRD patterns of the positive electrode materials obtained in Example 1, Example 3, Example 4, Example 5 and Comparative Example 6.

[0078] Performance test:

[0079] Firstly, the positive electrode materials prepared in Example 1, Example 3, Example 4, Comparative Example 1, Comparative Example 3, Comparative Example 4 and Comparative Example 5 were assembled into sodium ion batteries, and the specific assembly process was as follows:

[0080] The sodium ion batteries were assembled in a glove box with 1.0M NaClO4in EC:DEC = 1:1 Vol% with 5.0% FEC as electrolyte, glass fiber GF / D as separator, sodium sheet as negative electrode material, and the materials prepared in Example 1, Example 3, Example 4, Comparative Example 1, Comparative Example 3, Comparative Example 4 and Comparative Example 5 as positive electrode material.

[0081] Secondly, the electrochemical performance test was carried out on the above obtained sodium ion batteries, and the results were shown in Figure 1 and Table 1.

[0082] Table 1 Discharge capacity of the sodium ion batteries prepared by the materials of Example 1, Example 3, Example 4, Comparative Example 1, Comparative Example 3, Comparative Example 4 and Comparative Example 5 at different rates

[0083]

[0084] Figure 1 The charge-discharge curve of the battery assembled by the positive electrode material obtained in Example 1 and Comparative Example 1 at 0.05C rate, wherein a was Example 1 and b was Comparative Example 1.

[0085] From Table 1 and Figure 1 It can be seen that after the specific amount of copper doping, the reversible capacity of the positive electrode material was obviously improved, the polarization was reduced, and the rate performance was obviously improved.

[0086] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0087] The above description of the disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A titanium-copper doped sodium manganese titanium phosphate positive electrode material for sodium ion batteries, characterized in that: The titanium-site copper-doped sodium manganese titanium phosphate positive electrode material for sodium ion batteries is obtained by doping copper on the titanium site of sodium manganese titanium phosphate; the general formula of the titanium-site copper-doped sodium manganese titanium phosphate positive electrode material for sodium ion batteries is Na 3+2x MnTi 1-x Cu x (PO4)3, where 0<x≤0.

2.

2. The method for preparing the titanium-copper-doped sodium manganese titanium phosphate positive electrode material for sodium ion batteries according to claim 1, characterized in that: The steps include: The raw materials including phosphorus source, titanium source, manganese source, sodium source and copper source are prepared by spray drying or ball milling to obtain precursor powder; calcining the precursor powder under an inert atmosphere to obtain the copper-doped sodium manganese titanium phosphate sodium ion battery positive electrode material; During the preparation of the precursor powder by spray drying, the molar ratio of the phosphorus source, sodium source, manganese source, titanium source and copper source is determined according to the general formula of the copper-doped sodium manganese titanium phosphate sodium ion battery positive electrode material; During the ball milling process for preparing the precursor powder, the molar ratio of the phosphorus source, sodium source, manganese source, titanium source and copper source is determined according to the chemical formula of the copper-doped sodium manganese titanium phosphate sodium ion battery positive electrode material; The ball milling speed is 350-450 r / min, and the time is 6-9 hours. The ball milling is intermittent ball milling, specifically: after each ball milling for 20 minutes, pause for 10 minutes before the next ball milling, and repeat this step until the ball milling is completed; When the precursor powder is prepared by spray drying, the calcination temperature is 550-700°C and the time is 3-12 hours; When the precursor powder is prepared by ball milling, the calcination is a step-by-step calcination, specifically: first heating to 350° C. and keeping the temperature for 300 minutes, then heating to 550-700° C. and keeping the temperature for 720 minutes.

3. The preparation method according to claim 2, characterized in that The spray drying method comprises: mixing a carbon source, a phosphorus source, a sodium source, a manganese source, a titanium source, a copper source and water, and spray drying the mixture at an outlet air temperature of 160 to 220° C. to obtain a precursor powder; The carbon source includes citric acid; the phosphorus source includes sodium dihydrogen phosphate; the sodium source includes sodium nitrate and sodium dihydrogen phosphate; the manganese source includes manganese acetate; the titanium source includes dihydroxybis(ammonium lactate)titanium; and the copper source includes copper sulfate.

4. The preparation method according to claim 2, characterized in that The ball milling method comprises: mixing a carbon source, a phosphorus source, a sodium source, a manganese source, a titanium source and a copper source and then ball milling the mixture to obtain a precursor powder; The carbon source includes citric acid; the phosphorus source includes sodium dihydrogen phosphate; the sodium source includes sodium nitrate and sodium dihydrogen phosphate; the manganese source includes manganese acetate; the titanium source includes titanium acetylacetonate; and the copper source includes copper sulfate.

5. The preparation method according to claim 4, characterized in that The process of preparing the precursor powder by the ball milling method further includes adding fillers, and the fillers include one or more of conductive carbon black, Ketjen black, SP and carbon nanotubes.

6. Use of the titanium-copper-doped sodium manganese titanium phosphate sodium ion battery positive electrode material according to claim 1 in sodium ion batteries.

7. A sodium ion battery, characterized in that: The positive electrode material of the sodium ion battery is the titanium-copper-doped sodium manganese titanium phosphate sodium ion battery positive electrode material according to claim 1.

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