Titanium-site copper-doped high-performance titanium-manganese-sodium phosphate sodium-ion battery positive electrode material as well as preparation method and application thereof

Abstract

The invention discloses a titanium-copper-doped high-performance titanium manganese phosphate sodium-ion battery positive electrode material as well as a preparation method and application thereof, and belongs to the technical field of sodium-ion batteries. The titanium-site copper-doped titanium manganese sodium phosphate sodium ion battery positive electrode material is obtained by doping copper on a titanium site of titanium manganese sodium phosphate; the general formula of the titanium-site copper-doped sodium manganese titanium phosphate sodium ion battery positive electrode material is Na < 3 + 2x > MnTi < 1-x > Cux (PO4) 3, and x is more than 0 and less than or equal to 0.2. The preparation method of the titanium-site copper-doped sodium manganese titanium phosphate sodium ion battery positive electrode material comprises the following steps: preparing precursor powder from raw materials including a titanium source, a manganese source, a sodium source, a phosphorus source and a copper source through a spray drying method or a ball milling method; and calcining the precursor powder in an inert atmosphere to obtain the titanium-site copper-doped sodium manganese titanium phosphate positive electrode material for the sodium-ion battery. Polarization of the obtained positive electrode material is reduced, the anti-position defect is effectively inhibited, the reversible capacity is obviously improved, and the rate capability 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 sodium ion battery positive electrode material doped with copper in the titanium position, and a preparation method and application thereof. Background Art

[0002] With the reduction of global dependence on fossil fuels and the transition to green renewable energy, the application of secondary batteries in the field of energy storage technology has received increasing attention. In particular, lithium-ion batteries (LIBs) have become the mainstream in 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 and sustainable alternatives. Sodium-ion batteries have become a potential alternative due to their abundant sodium resources, low cost and good safety.

[0003] In the research of sodium-ion batteries, the research of positive electrode materials is particularly critical. The radius of sodium ions is larger than that of lithium ions, which leads to certain difficulties in the selection of electrode materials in the design of sodium-ion batteries, especially how to effectively accommodate sodium ions and promote their efficient transmission. The energy density of sodium-ion batteries is relatively low, and one of the effective ways to increase energy density is to increase the operating voltage. Therefore, it is necessary to find sodium-ion positive electrode materials with excellent kinetic properties, stable structure and high voltage characteristics.

[0004] At present, the cathode materials of sodium-ion batteries are mainly concentrated in three categories: layered oxides, Prussian blue analogs and polyanion compounds (such as NASICON structure). 3 V 2 (PO 4 ) 3 (NVP) is a classic material in the NASICON system with a theoretical capacity of 117 mAh / 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 Na 3 MnTi(PO 4 ) 3 (NMTP) electrode materials can not only reduce costs and toxicity, but also increase working voltage, and have great potential in application. 3 MnTi(PO 4 ) 3 During the charge and discharge process, Mn 2+ / Mn 3+ , Mn 3+ / Mn 4+ 、Ti 3+ / Ti 4+ etc. However, Na 3 MnTi(PO4 ) 3 The transport properties are inferior to those of vanadium-based materials, resulting in poor rate performance and cycle performance. Therefore, further improving its electrochemical performance is the 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 positive electrode material doped with copper at the titanium position, and a preparation method and application thereof, so as to solve the problems existing in the above-mentioned prior art and realize a sodium manganese titanium phosphate positive electrode material doped with copper at the titanium position with better electrochemical performance. 3 MnTi(PO 4 ) 3 Preparation of positive electrode materials.

[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 position, wherein the positive electrode material for a sodium manganese titanium phosphate battery doped with copper at a titanium position 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 position of sodium manganese titanium phosphate is Na 3+2x MnTi 1-x Cu x (PO 4 ) 3 , where 0<x≤0.2.

[0008] For Na 3 MnTi(PO 4 ) 3 From the molecular formula, the doping can be based on the sodium position, manganese position, titanium position and phosphate position. The 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. The manganese doping will reduce the content of active manganese elements (Mn 2+ / Mn 3+ and Mn 3+ / Mn 4+ Compared with manganese doping, titanium doping has more advantages because Ti 3+ / Ti 4+The redox couple has no capacity below 2V within the electrochemical window of traditional cathode materials (2.5-4.3V); even if discharged to 1.5V, it still needs to be combined with a sodium supplement in the full battery system 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 and replacing the inert site without reducing the manganese content, that is, without sacrificing its own capacity, thereby comprehensively improving the reversible capacity and rate performance.

[0009] In addition, there are also strategies to improve Na through the preparation of high entropy electrodes. 3 MnTi(PO 4 ) 3 The electrochemical properties of the material, 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 co-doping of several elements in the high entropy electrode does not guarantee that each element alone will work, 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 properties of the resulting positive electrode material by doping a single copper element at the titanium position, which effectively solves the problem that the existing technology of high entropy electrodes with multiple elements doping and synergistic effect leads to the unclear 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 (PO 4 ) 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 has a synergistic effect with transition metal elements such as Mn, so the kinetic performance is very good, such as Na 3 V 2 (PO 4 ) 3 (maximum rate up to 500C), Na 4 MnV(PO 4 )3 (The maximum 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 the vanadium-free material system will be greatly reduced. The titanium-site copper doping proposed in the present invention can show obvious effects on the vanadium-free positive electrode system, significantly improving the electrochemical performance of the vanadium-free positive electrode system, 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 sodium ion battery positive electrode material, comprising the following steps:

[0012] The raw materials including a phosphorus source, a titanium source, a manganese source, a sodium source and a copper source are prepared by spray drying or ball milling to obtain a 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 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 under the condition of an outlet air temperature of 160 to 220° C. to obtain a precursor powder;

[0015] 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.

[0016] Preferably, in the process of preparing 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 copper-doped sodium manganese titanium phosphate sodium ion battery positive electrode material.

[0017] Furthermore, the present invention does not impose any particular limitation on the amount of water used in the spray drying method, as long as the spray drying process can proceed smoothly.

[0018] Preferably, 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;

[0019] 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 oxide; and the copper source includes copper sulfate.

[0020] Preferably, the process of preparing the precursor powder by ball milling also includes adding fillers, and the fillers include one or more of conductive carbon black, Ketjen black, SP and carbon nanotubes.

[0021] The citric acid and filler can provide carbon sources during the firing process to improve the electrical conductivity of the material.

[0022] Preferably, in the process of preparing the precursor powder by ball milling, 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 amount of the filler is: 30 to 60 g of filler is added for each mole of copper-doped sodium manganese titanium phosphate sodium ion battery positive electrode material.

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

[0024] Furthermore, the medium of the ball mill is zirconia balls, and the size and proportion are as follows: the mass of the zirconia balls with a particle size of 5 mm is 10 to 15 times the mass of the precursor powder, and the mass of the zirconia balls with a particle size of 10 mm is 1 to 3 times the mass of the precursor powder. The zirconia balls with the above ratio can reduce the material adhesion to the wall and improve the ball milling efficiency; the ball-to-material ratio of the ball mill is 11 to 18:1.

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

[0026] Preferably, when the precursor powder is prepared by ball milling, the calcination is a step-by-step calcination, specifically: firstly heating to 350° C. and keeping the temperature for 300 min, then heating to 550-700° C. and keeping the temperature for 720 min.

[0027] When the precursor powder is prepared by different methods, different calcination processes and parameters can be used to prepare materials with better performance. When the precursor powder is prepared by spray drying, a pure phase can be synthesized by a single calcination method. Exceeding the upper limit of the maximum heating temperature range (700°C) will cause the material to decompose, resulting in the appearance of impurities, leading to a decrease in capacity; below the lower limit of the minimum heating range (550°C) will reduce the crystallinity and capacity; when the precursor powder is prepared by ball milling, the material can be pre-decomposed during the firing process by a step-by-step calcination method, thereby improving the performance of the resulting material.

[0028] The technical principles of the present invention are as follows:

[0029] The present invention is to Na 3 MnTi(PO 4 ) 3The material is doped with copper at the titanium position. Different from the existing doping at the active manganese position, the titanium doping of the present invention can ensure that the active manganese content does not decrease, avoiding the problem of the capacity of the electrode decreasing due to the decrease in the active manganese content. In addition, within the range of 2.5 to 4.3 V, doping at the electrochemically inert titanium position can achieve better results, because the Cu redox couple itself is active and will contribute to the capacity improvement. In addition, after Cu doping, Mn is further activated. 2+ / Mn 3+ / Mn 4+ The conversion of can further improve the capacity and promote the kinetics of multi-electron reactions. The electrochemical performance of Cu doping with a molar amount of 0.05 mol is the best compared with other metal element doping. In addition, compared with other Cu doping amounts of 0.1 mol and 0.15 mol, Cu doping 0.05 mol has the highest capacity, and an impurity phase appears when the Cu doping amount is 0.25 mol.

[0030] The third technical solution of the present invention is to provide the application of the above-mentioned titanium-copper-doped sodium manganese titanium phosphate sodium ion battery positive electrode material in sodium ion batteries.

[0031] The fourth technical solution of the present invention is to provide a sodium ion battery, wherein the positive electrode material of the sodium ion battery is the above-mentioned titanium-copper-doped sodium manganese titanium phosphate sodium ion battery positive electrode material.

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

[0033] The present invention adopts copper doping Na 3 MnTi(PO 4 ) 3 The copper-doped sodium manganese titanium phosphate positive electrode material for sodium-ion batteries was obtained, which can still maintain the pure phase Na 3 MnTi(PO 4 ) 3 The structure of the cathode material is free of impurities, indicating that the material will not contain other compounds that would reduce the active material, and can improve the rate performance and charge-discharge reversible capacity of the cathode material. In addition, the polarization of the cathode material is reduced, the anti-site defect is effectively suppressed, the reversible capacity is significantly increased, and the rate performance is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The charge and discharge curves of the battery assembled with the positive electrode materials obtained in Example 1 and Comparative Example 1 at a rate of 0.05C, wherein a is Example 1 and b is Comparative Example 1;

[0035] Figure 2 This is the XRD pattern of the positive electrode material obtained in Comparative Example 1;

[0036] Figure 3This is the XRD pattern of the positive electrode material obtained in Comparative Example 2;

[0037] Figure 4 XRD comparison diagram of the positive electrode materials obtained in Comparative Example 3 and Comparative Example 1;

[0038] Figure 5 XRD comparison diagram of the positive electrode materials obtained in Comparative Example 4 and Comparative Example 1;

[0039] Figure 6 XRD comparison diagram of the positive electrode materials obtained in Comparative Example 5 and Comparative Example 1;

[0040] Figure 7 1 and 2 are XRD diagrams of the positive electrode materials obtained in Example 1, Example 3, Example 4, Example 5 and Comparative Example 6. DETAILED DESCRIPTION

[0041] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0042] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0043] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0044] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0045] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0046] Unless otherwise specified, the raw materials used in the examples, comparative examples and performance tests of the present invention are all commercially available products, and the sources of the commercially available products have no effect on the effects.

[0047] Example 1

[0048] This embodiment provides a copper-doped sodium manganese titanium phosphate positive electrode material for sodium ion batteries prepared by a spray drying method, and the specific steps are as follows:

[0049] Weigh and measure 2mmol citric acid (C 5 H 8 O 7 )、3mmol sodium dihydrogen phosphate (NaH 2 PO 4 )、1mmol manganese acetate tetrahydrate (MnC 4 H 5 O 4 ·4H 2 O), 0.95mmol dihydroxy(ammonium lactate)titanium (C 5 H 18 N 2 O 8 Ti), 0.05mmol copper sulfate pentahydrate (CuSO 4 ·5H 2 O) and 0.1 mmol sodium nitrate (NaNO 3 ) was added to 500 mL 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°C to obtain a precursor powder. The precursor powder was placed in a tube furnace and calcined at 600°C for 4 hours under an argon atmosphere to obtain a black powder sample, which is a titanium-copper doped sodium manganese titanium phosphate sodium ion battery positive electrode material with a chemical formula of Na 3.1 MnTi 0.95 Cu 0.05 (PO 4 ) 3 , denoted as NMTP-Cu0.05.

[0050] Example 2

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

[0052] Weigh and measure 2mmol citric acid (C 5 H 8 O 7 )、3mmol sodium dihydrogen phosphate (NaH 2 PO 4 )、135mg Ketjen black, 1mmol manganese acetate tetrahydrate (MnC 4 H5 O 4 ·4H 2 O), 0.95mmol acetylacetonate titanium oxide (C 10 H 14 O 5 Ti), 0.05mmol copper sulfate pentahydrate (CuSO 4 ·5H 2 O) and 0.1 mmol sodium nitrate (NaNO 3 ), and mix the weighed drugs and add them into a ball mill with zirconium oxide balls and stir them 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. Ball milling is carried out at a speed of 450r / min for 9h (after each ball milling for 20min, pause for 10min and then carry out 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 keeping warm for 300min, then heating to 650℃ and keeping warm for 720min) to obtain titanium-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 (PO 4 ) 3 , recorded as NMTP-ball-milled Cu0.05.

[0053] Example 3

[0054] Weigh and measure 2mmol citric acid (C 5 H 8 O 7 )、3mmol sodium dihydrogen phosphate (NaH 2 PO 4 )、1mmol manganese acetate tetrahydrate (MnC 4 H 5 O 4 ·4H 2 O), 0.9mmol dihydroxy(ammonium lactate)titanium (C 5 H 18 N 2 O 8 Ti), 0.2mmol sodium nitrate (NaNO 3 )、0.1mmol copper sulfate pentahydrate (CuSO 4 ·5H 2 O), and the rest is the same as in Example 1. The chemical formula of the prepared titanium-copper doped sodium manganese titanium phosphate sodium ion battery positive electrode material is Na 3.2 MnTi 0.9 Cu 0.1 (PO 4 )3 , denoted as NMTP-Cu0.1.

[0055] Example 4

[0056] Weigh and measure 2mmol citric acid (C 5 H 8 O 7 )、3mmol sodium dihydrogen phosphate (NaH 2 PO 4 )、1mmol manganese acetate tetrahydrate (MnC 4 H 5 O 4 ·4H 2 O), 0.85mmol dihydroxy(ammonium lactate)titanium (C 5 H 18 N 2 O 8 Ti), 0.3mmol sodium nitrate (NaNO 3 ) and 0.15mmol copper sulfate pentahydrate (CuSO 4 ·5H 2 O), and the rest is the same as in Example 1. The prepared titanium-copper doped sodium manganese titanium phosphate sodium ion battery positive electrode material has the chemical formula of Na 3.3 MnTi 0.85 Cu 0.15 (PO 4 ) 3 , denoted as NMTP-Cu0.15.

[0057] Example 5

[0058] Weigh and measure 2mmol citric acid (C 5 H 8 O 7 )、3mmol sodium dihydrogen phosphate (NaH 2 PO 4 )、1mmol manganese acetate tetrahydrate (MnC 4 H 5 O 4 ·4H 2 O), 0.8 mmol dihydroxy(ammonium lactate)titanium (C 5 H 18 N 2 O 8 Ti), 0.4mmol sodium nitrate (NaNO 3 ) and 0.2 mmol copper sulfate pentahydrate (CuSO 4 ·5H 2 O), and the rest is the same as in Example 1. The chemical formula of the prepared titanium-copper doped sodium manganese titanium phosphate sodium ion battery positive electrode material is Na 3.4 MnTi 0.8Cu 0.2 (PO 4 ) 3 , denoted as NMTP-Cu0.2.

[0059] Comparative Example 1

[0060] Weigh and measure 2mmol citric acid (C 5 H 8 O 7 )、3mmol sodium dihydrogen phosphate (NaH 2 PO 4 )、1mmol manganese acetate tetrahydrate (MnC 4 H 5 O 4 ·4H 2 O) and 1 mmol dihydroxy(ammonium lactate)titanium (C 5 H 18 N 2 O 8 Ti), and the rest is the same as in Example 1. The chemical formula of the prepared sodium manganese titanium phosphate sodium ion battery positive electrode material is Na 3 MnTi(PO 4 ) 3 , denoted as NMTP.

[0061] Figure 2 This is the XRD diagram 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 pattern of the positive electrode material obtained in Example 1 is shown in Figure 7 ), after copper doping, the cathode material can still maintain pure phase Na 3 MnTi(PO 4 ) 3 The structure without impurities can improve the electrochemical performance of the positive electrode material.

[0063] Comparative Example 2

[0064] Weigh and measure 2mmol citric acid (C 5 H 8 O 7 )、3mmol sodium dihydrogen phosphate (NaH 2 PO 4 )、45mg Ketjen black, 1mmol manganese acetate tetrahydrate (MnC 4 H 5 O 4 ·4H 2 O) and 1 mmol acetylacetonate titanium oxide (C 10 H 14 O 5Ti), 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 Na 3 MnTi(PO 4 ) 3 , recorded as NMTP-ball milling.

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

[0066] Comparative Example 3

[0067] Weigh and measure 2mmol citric acid (C 5 H 8 O 7 )、3mmol sodium dihydrogen phosphate (NaH 2 PO 4 )、0.9mmol manganese acetate tetrahydrate (MnC 4 H 5 O 4 ·4H 2 O), 1mmol dihydroxy(ammonium lactate)titanium (C 5 H 18 N 2 O 8 Ti) and 0.1 mmol nickel nitrate hexahydrate (Ni(NO 3 ) 2 6H 2 O), and the rest is the same as in Example 1. The chemical formula of the prepared manganese-nickel doped sodium manganese titanium phosphate sodium ion battery positive electrode material is Na 3 Mn 0.9 Ni 0.1 Ti(PO 4 ) 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 (C 5 H 8 O 7 )、3mmol sodium dihydrogen phosphate (NaH 2 PO 4 )、1mmol manganese acetate tetrahydrate (MnC 4 H 5 O 4 ·4H 2 O), 0.95mmol dihydroxy(ammonium lactate)titanium (C 5 H 18 N2 O 8 Ti), 0.1mmol sodium nitrate (NaNO 3 ) and 0.05mmol magnesium acetate tetrahydrate (C 4 H 14 MgO 8 ), and the rest is the same as in Example 1. The prepared titanium-magnesium doped sodium manganese titanium phosphate sodium ion battery positive electrode material has the chemical formula Na 3.1 MnTi 0.95 Mg 0.05 (PO 4 ) 3 , denoted as NMTP-Mg0.05.

[0071] Figure 5 This is a comparison chart of the XRD patterns of the positive electrode materials obtained in Comparative Example 4 and Comparative Example 1.

[0072] Comparative Example 5

[0073] Weigh and measure 2mmol citric acid (C 5 H 8 O 7 )、2.9mmol sodium dihydrogen phosphate (NaH 2 PO 4 )、1mmol manganese acetate tetrahydrate (MnC 4 H 5 O 4 ·4H 2 O), 0.95mmol dihydroxy(ammonium lactate)titanium (C 5 H 18 N 2 O 8 Ti), 0.1mmol diammonium phosphate (NH 4 H 2 PO 4 ) and 0.05 mmol ammonium heptamolybdate tetrahydrate ((NH 4 ) 6 Mo 7 O 24 ·4H 2 O), and the rest is the same as in Example 1. The prepared titanium-molybdenum-doped sodium manganese titanium phosphate sodium ion battery positive electrode material has the chemical formula Na 2.9 MnTi 0.95 Mo 0.05 (PO 4 ) 3 , denoted as NMTP-Mo0.05.

[0074] Figure 6 This is a comparison chart of the XRD patterns of the positive electrode materials obtained in Comparative Example 5 and Comparative Example 1.

[0075] Comparative Example 6

[0076] Weigh and measure 2mmol citric acid (C 5 H 8 O 7 )、3mmol sodium dihydrogen phosphate (NaH 2 PO 4 )、1mmol manganese acetate tetrahydrate (MnC 4 H 5 O 4 ·4H 2 O), 0.75mmol dihydroxy(ammonium lactate)titanium (C 5 H 18 N 2 O 8 Ti), 0.5mmol sodium nitrate (NaNO 3 ) and 0.25mmol copper sulfate pentahydrate (CuSO 4 ·5H 2 O), and the rest is the same as in Example 1. The chemical formula of the prepared titanium-copper doped sodium manganese titanium phosphate sodium ion battery positive electrode material is Na 3.5 MnTi 0.75 Cu 0.25 (PO 4 ) 3 , denoted as NMTP-Cu0.25.

[0077] Figure 7 1 and 2 are XRD diagrams of the positive electrode materials obtained in Example 1, Example 3, Example 4, Example 5 and Comparative Example 6.

[0078] Performance Test:

[0079] First, 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 are assembled into a sodium ion battery, and the specific assembly process is as follows:

[0080] 1.0M NaClO 4 in EC:DEC=1:1Vol%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 materials were assembled in a glove box to obtain a sodium ion battery.

[0081] Secondly, the electrochemical performance of the sodium ion battery obtained above was tested, and the results were as follows Figure 1 And as shown in Table 1.

[0082] Table 1 Discharge capacity of sodium ion batteries prepared from 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 and discharge curves of the battery assembled with the positive electrode materials obtained in Example 1 and Comparative Example 1 at a rate of 0.05C, wherein a is Example 1 and b is Comparative Example 1.

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

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

[0087] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather 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 a phosphorus source, a titanium source, a manganese source, a sodium source and a copper source are prepared by spray drying or ball milling to obtain a precursor powder; The precursor powder is calcined under an inert atmosphere to obtain the copper-doped sodium manganese titanium phosphate sodium ion battery positive electrode material.

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 under the condition that the outlet air temperature is 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 3, characterized in that: In the process of preparing 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 copper-doped sodium manganese titanium phosphate sodium ion battery positive electrode material.

5. 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 oxide; and the copper source includes copper sulfate.

6. The preparation method according to claim 5, characterized in that: The process of preparing the precursor powder by the ball milling method also includes adding fillers, and the fillers include one or more of conductive carbon black, Ketjen black, SP and carbon nanotubes; and / or, in the process of preparing the precursor powder by the ball milling method, 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; and / or, the rotation speed of the ball milling is 350-450r / min, and the time is 6-9h; the ball milling is intermittent ball milling, specifically: after each ball milling for 20min, pause for 10min and then carry out the next ball milling, and repeat this step until the ball milling is completed.

7. The preparation method according to claim 2, characterized in that: When the precursor powder is prepared by spray drying, the calcination temperature is 550-700° C. and the calcination time is 3-12 hours.

8. The preparation method according to claim 2, characterized in that: When the precursor powder is prepared by ball milling, the calcination is a step-by-step calcination, specifically: firstly heating to 350° C. and keeping the temperature for 300 min, then heating to 550-700° C. and keeping the temperature for 720 min.

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

10. 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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