Metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material, preparation method thereof and battery

Abstract

The preparation method comprises the following steps: mixing a sodium source, a manganese source, a metal ion source and a carbon source according to a chemical molar ratio of Na < 0.44 > M < x > Mn < 1-x > O < 2 > / C (x is greater than or equal to 0.1 and greater than or equal to 0.3), then mixing the mixture with binder powder at a high speed, and granulating the mixed material to obtain the metal ion doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material. The preparation method comprises the following steps: preparing a small spherical sodium manganate positive electrode material precursor for a water-based sodium-ion battery, tabletting, calcining at high temperature, and crushing to prepare the metal ion doped sodium manganate and carbon composite water-based sodium-ion battery positive electrode material. The battery is a button battery assembled by a sodium sheet and a sodium manganate and carbon composite aqueous sodium ion battery positive electrode material doped with metal ions and an aqueous sodium ion total battery assembled by an active carbon pole piece, and has relatively good cycle stability.

Description

Technical Field

[0001] The invention relates to a metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material, a preparation method thereof, and a battery, belonging to the technical field of energy storage batteries. Background Art

[0002] Sodium-ion batteries have broad application prospects in large-scale energy storage, low-speed electric vehicles and other fields due to their advantages such as abundant sodium resource reserves, low prices, safety and stability. This has also driven the growth of market demand for their positive electrode materials.

[0003] Battery performance depends not only on the cathode material but also on other components such as the anode material and electrolyte. Further research is needed to determine the compatibility of cathode materials with other battery components, optimize overall battery performance, and address issues such as interface compatibility and electrolyte stability.

[0004] Although the material performance has been improved to a certain extent through doping and compounding, there is still a gap in energy density, cycle life, etc. compared with lithium-ion battery positive electrode materials. The structure and performance of the material need to be further optimized to meet the needs of different application scenarios.

[0005] After searching, I found that the invention patent with publication number: CN 108736005 A discloses a manganese-doped carbon-coated sodium ion battery positive electrode material and its preparation method, which introduces an iron source into the manganese-doped carbon-coated sodium ion battery positive electrode material. And the Fe-doped Na2Fe x Mn 2-x Compared with the undoped sample, the O7 material has more stable cycle performance and significantly improved initial charge capacity. At the same time, carbon composite can improve the electronic conductivity of the material, build a good conductive network, and enhance the overall performance of the material. However, in actual production, there are still great process challenges. There are still no reports of other metal ion doping in the existing technology, and how to overcome process difficulties, provide stable processes and stable product performance, and prepare high-performance metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode materials still has great professional challenges and is still in the research and development and exploration stage. Summary of the Invention

[0006] In order to solve the above problems, the present invention discloses a sodium manganate and carbon composite aqueous sodium ion battery positive electrode material doped with metal ions, a preparation method thereof, and a battery. The specific technical solution is as follows:

[0007] A metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery cathode material, the chemical formula is Na 0.44 M x Mn 1-xO2 / C, 0.3≥x≥0.1, M is a metal ion, one of Mg, Al, and Zn.

[0008] Furthermore, the chemical formula is Na 0.44 Mg 0.3 Mn 0.7 O2 / C, or Na 0.44 Al 0.2 Mn 0.7 O2 / C, or Na 0.44 Zn 0.1 Mn 0.9 O2 / C.

[0009] A method for preparing the above-mentioned sodium manganate and carbon composite aqueous sodium ion battery positive electrode material doped with metal ions comprises the following steps:

[0010] Step 1: The sodium manganate and carbon composite aqueous sodium ion battery cathode material having the chemical formula Na 0.44 M x Mn 1-x The chemical molar ratio of O2 / C is taken from a composite alkaline sodium source, a composite acidic manganese source, an organic metal ion source and a carbon source, which are fully mixed and then added together with the binder powder into a high-speed mixer for high-speed mixing to obtain a precursor material;

[0011] Step 2: Transferring the precursor material obtained in step 1 to a granulator for dry granulation to prepare a spherical aqueous sodium ion battery cathode material precursor;

[0012] Step 3: The spherical positive electrode material precursor granulated in step 2 is pressed into sheets by a tablet press to obtain a sheet, which is then calcined at high temperature in an air atmosphere. The calcined sheet is crushed in a grinder to prepare a sodium manganate and carbon composite aqueous sodium ion battery positive electrode material doped with metal ions.

[0013] Furthermore, the composite alkaline sodium source is a composite of two or more of sodium hydroxide, sodium acetate, sodium bicarbonate, sodium phenol, sodium hypochlorite, sodium phosphate, sodium benzoate, trisodium citrate, sodium citrate, and trisodium citrate;

[0014] The composite acidic manganese source is a composite of two or more of manganese oxalate, manganese acetate, manganese stearate, manganic anhydride, manganous anhydride, and permanganic anhydride;

[0015] The organic metal ion source is one of ethylmagnesium bromide, phenylmagnesium chloride, dialkylmagnesium, diethylmagnesium, dialkylzinc, methylzinc iodide, triethylaluminum, and triisobutylaluminum;

[0016] The carbon source is a composite of one or more of sucrose, asphalt, starch, carbon nanotubes, and carbon fibers, and the mass of the carbon source accounts for 10-20% of the mass of the precursor material obtained in step one. During the carbon coating process of the material, a reasonable amount of carbon source (10% to 20% of the mass of the solid powder) will form a continuous and uniform carbon layer. A carbon source ratio of 10% to 20% is sufficient to form a continuous and dense carbon coating layer on the surface of the material. Too little (<10%) can easily lead to incomplete coating and the appearance of exposed areas; too much (>20%) can easily lead to an excessively thick carbon layer or free carbon residue, affecting the performance of the material. At this ratio, the thickness of the carbon layer is at the nanometer level, which can provide conductivity / protection without significantly hindering ion / electron transport. Carbon coating can improve the conductivity of the material, but excess carbon will reduce the volume energy density. The cost of carbon sources (glucose, sucrose) is low, but excessive use will increase raw material and processing costs. 10% to 20% is the best price-performance range. The pyrolysis carbonization yield of the organic carbon source selected in this patent application is 20%. 10% glucose corresponds to a final carbon content of 2%. The actual carbon content matches the material requirements, and the battery electrode requires a carbon content of 2%-4%. Excessive carbon source will cause particles to stick together during high-temperature pyrolysis, destroying dispersibility. Under solid-state mixing, the mass of the carbon source accounts for 10-20% of the mass of the precursor material obtained in step one, which is easy to mix evenly with the raw material powder to ensure coating consistency. Excessive carbon source will consume too much inert atmosphere (N2 / Ar) or introduce impurities.

[0017] Furthermore, the binder powder in step one is one or more of polytetrafluoroethylene PTFE, polyvinyl alcohol PVA, polyvinylidene fluoride PVDF, polyvinyl pyrrolidone PVP and sodium carboxymethyl cellulose CMC, and the mass of the binder powder accounts for 5-10% of the mass of the precursor material obtained in step one.

[0018] Furthermore, the parameters of the high-speed mixer in step 1 are set as follows: speed 1000-5000 rpm, mixing time 2-6 h;

[0019] In the step 2, the heating temperature of the granulator is 200-400° C., the stirring speed is 1000-5000 rpm, and the granulator is heated for 4-10 hours to prepare a small spherical sodium manganate positive electrode material precursor for an aqueous sodium ion battery. The diameter of the small spherical particles is 5-15 mm.

[0020] Furthermore, the process of high-temperature calcination in air atmosphere in step three is: pre-calcination at 300-350° C. for 1-2 hours, and then calcination at 750-900° C. for 8-12 hours, with a heating rate of 2° C. / min.

[0021] Furthermore, when the metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material chemical formula is Na 0.44 Mg 0.3 Mn0.7 O2 / C, when the composite alkaline sodium source is a composite of sodium hydroxide and sodium bicarbonate in a mass ratio of 1:0.5, the composite acidic manganese source is a composite of manganese oxalate and permanganic anhydride in a mass ratio of 1:1, the organic metal magnesium ion source is dialkyl magnesium, and the carbon source is a composite of starch and carbon nanotubes in a mass ratio of 1:1; the strong base sodium hydroxide plays a role in regulating the oxidation state of manganese, and the oxidation state of manganese in the target product sodium manganate is +3.56, and the Mn in manganese oxalate is 2+ or Mn in manganic anhydride 7+ It is converted into manganese with an intermediate valence of +3.56. Manganese oxalate MnC2O4 is oxidized in a strong alkaline environment. The CO2 released by the decomposition of O2 or NaHCO3 in the air promotes oxidation. Manganese anhydride Mn2O7 itself is +7 valence manganese, which is reduced to +6 valence manganese under alkaline conditions. NaOH provides strong alkaline conditions. NaHCO3, as a mild alkaline source, decomposes under heat to produce Na2CO3 and CO2, which assist in adjusting pH or participating in the redox process, and synergizes with sodium hydroxide to control the reaction rate. Dialkyl magnesium R2Mg has strong reducing properties. It not only provides a magnesium source, but also reduces the valence of manganese. The hydroxyl -OH in starch can also form a soluble complex with the Mn source. The synergistic effect between the materials promotes the combination of sodium, manganese and oxygen elements, ensuring Na 0.44 Mg 0.3 Mn 0.7 The formation of O2 substances;

[0022] When sodium manganate doped with metal ions is combined with carbon to form the positive electrode material of aqueous sodium ion battery, the chemical formula is Na 0.44 Al 0.2 Mn 0.7 When the temperature is 02 / C, the composite alkaline sodium source is a composite of trisodium citrate and sodium acetate in a mass ratio of 1:0.5, the composite acidic manganese source is a composite of manganese acetate and permanganic anhydride in a mass ratio of 1:1, the organic metal aluminum ion source is triethylaluminum, and the carbon source is a composite of citric acid and carbon fiber in a mass ratio of 1:1;

[0023] When sodium manganate doped with metal ions is combined with carbon to form the positive electrode material of aqueous sodium ion battery, the chemical formula is Na 0.44 Zn 0.1 Mn 0.9 O2 / C, when the composite alkaline sodium source is a composite of trisodium citrate and sodium benzoate in a mass ratio of 1:0.5, the composite acidic manganese source is a composite of manganese acetate and manganous anhydride in a mass ratio of 1:1, the organic metal zinc ion source is dialkyl zinc, and the carbon source is a composite of sucrose and carbon fiber in a mass ratio of 1:1.

[0024] A metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material prepared by the above-mentioned method for preparing a metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material, and a button battery assembled from the metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material.

[0025] A battery, an aqueous sodium ion full battery composed of the above-mentioned sodium manganate-carbon composite aqueous sodium ion battery positive electrode material doped with metal ions and an activated carbon electrode sheet, and the use of the above-mentioned sodium manganate-carbon composite aqueous sodium ion battery positive electrode material doped with metal ions in an aqueous battery.

[0026] The working principle of the present invention is:

[0027] (1) A composite alkaline sodium source, a composite acidic manganese source, a reducing organic metal source and a carbon material are used in the material mixing process. The composite alkaline sodium source, the composite acidic manganese source and the reducing organic metal source undergo a chemical reaction of acid and base. At the same time, the reducing organic metal source prevents the formation of metal oxide elements and promotes the formation of new sodium, manganese and metal ion compounds in the mixed materials as precursors. At the same time, the addition of the carbon source forms a conductive network in the material, which not only ensures the stability of the sodium and manganese compound structure, but also provides a guarantee for the electrochemical performance of the metal magnesium-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material.

[0028] (2) The present invention prepares a small spherical precursor of a metal ion-doped sodium manganate positive electrode material for an aqueous sodium ion battery by using a high-speed mixing device and a granulator. The main purpose is to improve the uniformity of mixing between the raw materials and improve their reaction efficiency.

[0029] (3) The main purpose of tableting the material precursor by a tablet press is to improve the reaction degree and crystallinity of the preparation of metal ion-doped sodium manganate and avoid the formation of impurity phases.

[0030] (4) The technology of mixing with carbon source and calcining once is adopted, which not only reduces the process and reduces the cost, but also constructs a dense carbon conductive network, provides a conductive bridge between metal ion-doped sodium manganate particles and particles, and improves the electrochemical performance of metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode materials.

[0031] The beneficial effects of the present invention are:

[0032] The metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material prepared by the method of the present invention are assembled into a button cell. The battery is assembled into a button cell using the metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material. The cycle specific capacity reaches 118 mAh / g at a current density of 200 mA / g, and the capacity retention rate is 89.3% after 1000 cycles, showing good cycle stability. The prepared positive electrode material is then combined with activated carbon AC to form an aqueous sodium ion full battery. The prepared metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material is applied to aqueous batteries. The prepared positive electrode material is combined with lithium manganate to form a 15 mAh aqueous sodium ion full battery. After 1000 cycles at 1C, the capacity retention rate is nearly 88.4%. The prepared metal ion-doped sodium manganate carbon composite aqueous sodium ion battery positive electrode material has good cycle stability when applied to aqueous batteries, providing a reference for energy storage industry applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a SEM morphology photograph of the positive electrode material of an aqueous sodium ion battery made of magnesium-doped sodium manganate and carbon composite in Example 1 of the present invention.

[0034] Figure 2 This is the SEM morphology and EDS element distribution photo of the metal magnesium ion doped sodium manganate positive electrode material of Example 1 of the present invention.

[0035] Figure 3 This is the X-ray diffraction spectrum of the positive electrode material of aqueous sodium ion battery doped with sodium manganate and carbon composite in Example 1 of the present invention.

[0036] Figure 4 This is the cycle data of a half-cell of the positive electrode material of a sodium manganate-carbon composite aqueous sodium ion battery doped with metal magnesium ions in Example 1 of the present invention; Figure 5 This is the cycle data of an aqueous sodium ion full battery composed of activated carbon and metal magnesium ion-doped sodium manganate carbon composite aqueous sodium ion battery positive electrode material according to Example 1 of the present invention. DETAILED DESCRIPTION

[0037] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0038] Three specific embodiments of the present invention are given below

[0039] Example 1

[0040] This example produces Na 0.44 Mg 0.3 Mn 0.7O2 / C, using the chemical molar ratios in the formula, consists of a composite alkaline sodium source (sodium hydroxide and sodium bicarbonate, in a mass ratio of 1:0.5), a composite acidic manganese source (manganese oxalate and permanganic anhydride, in a mass ratio of 1:1), a dialkyl magnesium source (organic magnesium ion source), and a carbon source (starch and carbon nanotubes, in a mass ratio of 1:1, with the total mass fraction of the raw materials being 10%). During the carbon coating process, a reasonable amount of carbon source will form a continuous and uniform carbon layer. A carbon source ratio sufficient to form a continuous, dense carbon coating on the material surface. Too little carbon source results in incomplete coating, leaving exposed areas; too much carbon source can easily lead to an overly thick carbon layer or residual free carbon, affecting material performance. A carbon layer at the nanometer level provides conductivity and protection without significantly hindering ion and electron transport. Carbon coating can enhance the material's conductivity, but excessive carbon content can reduce volumetric energy density. The organic carbon source selected for this patent application has a pyrolysis carbonization yield of 20%. Battery electrodes require a carbon content of 2%-4%. Excessive carbon source causes particles to stick together during high-temperature pyrolysis, destroying dispersibility. Under solid-state mixing, the carbon source mass accounts for 10-20% of the mass of the precursor material and is easy to mix evenly with the raw material powder to ensure coating consistency. Excessive carbon source consumes too much inert atmosphere (such as N2 / Ar) or introduces impurities. Among them: strong base sodium hydroxide is mainly used to regulate the oxidation state of manganese. The oxidation state of manganese in the target product sodium manganate is +3.56. Manganese oxalate (Mn 2+ ) or manganic anhydride (Mn 7+ ) is converted into manganese with an intermediate valence of +3.56. Manganese oxalate (MnC2O4) is oxidized in a strong alkaline environment (such as O2 in the air or CO2 released by the decomposition of NaHCO3 to promote oxidation). Manganese anhydride (Mn2O7) itself is +7 valence manganese, which is reduced to low-valent manganese (+6) under alkaline conditions. NaOH provides strong alkaline conditions, and NaHCO3 acts as a mild alkali source. It decomposes under heat to produce Na2CO3 and CO2, which assist in adjusting pH or participating in the redox process, and synergizes with sodium hydroxide to control the reaction rate. Dialkyl magnesium (R2Mg) has strong reducing properties. It not only provides a magnesium source, but also reduces the valence of manganese. The hydroxyl group (-OH) in starch can also form a soluble complex with the Mn source. The synergistic effect between these raw materials promotes the combination of sodium, manganese and oxygen elements, ensuring Na 0.44 Mg 0.3 Mn 0.7 The generation of O2 substances.

[0041] Take 8% PTFE and 2% PVDF binder powders accounting for 8% of the mass fraction of the solid mixed powder and add them together with the mixed materials into a high-speed mixer for high-speed mixing, set the speed to 1000 rpm, and mix at high speed for 6 hours. Transfer the mixed materials to a granulator for dry granulation, set the heating temperature of the granulator to 200°C, the stirring speed to 5000 rpm, and heat for 10 hours to prepare a small spherical sodium manganate positive electrode material precursor for aqueous sodium ion battery. The small spherical particle size is 15 mm. Then, the granulated spherical powder is pressed into a sheet (length 60 mm * width 60 mm * height 5 mm) by a tablet press, and a high-temperature calcination is carried out in an air atmosphere. The calcination process is: pre-calcination at 350°C for 1 hour, then calcination at 900°C for 8 hours, and the heating rate is 2°C / min. The calcined sheet is crushed in a grinder to prepare a metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material.

[0042] Example 2

[0043] This example produces Na 0.44 Al 0.2 Mn 0.7 O2 / C, according to the chemical molar ratio in the chemical formula, a composite alkaline sodium source (trisodium citrate and sodium acetate, with a mass ratio of 1:0.5), a composite acidic manganese source (manganese acetate and permanganic anhydride, with a mass ratio of 1:1), an organic metal aluminum ion source of triethylaluminum, and a carbon source (citric acid and carbon fiber, with a mass ratio of 1:1, and a total mass fraction of 15% in the raw materials). Among them, trisodium citrate is a strongly basic ligand (oxidant) and functions similarly to the sodium hydroxide in Example 1. Sodium acetate provides a sodium source, adjusts the pH value, and synergizes with trisodium citrate to control the reaction rate, acting similarly to the sodium bicarbonate in Example 1. Manganese acetate is a low-valent manganese with a valence of +2, and permanganic anhydride is a high-valent manganese with a valence of +7, acting similarly to the manganese oxalate and permanganic anhydride in Example 1, respectively. Triethylaluminum (AlEt3) regulates the manganese valence state, acting similarly to the dialkylmagnesium in Example 1, and the reaction mechanism and process are similar to those of the dialkylmagnesium in Example 1. The synergistic effect between the substances promotes the combination of sodium, manganese, aluminum and oxygen, ensuring that Na 0.44 Al 0.2 Mn 0.7 Generation of O2 / C species.

[0044] Take 3% PVA and 7% PVDF binder powder, which account for 3% of the mass fraction of the solid mixed powder, and add them together with the mixed materials into a high-speed mixer for high-speed mixing. Set the speed to 5000 rpm and mix at high speed for 2 hours. Transfer the mixed materials to a granulator for dry granulation. Set the heating temperature of the granulator to 400°C, the stirring speed to 1000 rpm, and heat for 2 hours to prepare a small spherical sodium manganate positive electrode material precursor for aqueous sodium ion battery. The small spherical particle size is 5 mm. Then, the granulated spherical powder is pressed into a sheet (60 mm long * 60 mm wide * 5 mm high) by a tablet press, and a high-temperature calcination is carried out in an air atmosphere. The calcination process is: pre-calcination at 300°C for 2 hours, then calcination at 750°C for 12 hours, and the heating rate is 2°C / min. The calcined sheet is crushed in a grinder to prepare a metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material.

[0045] Example 3

[0046] This example produces Na 0.44 Zn 0.1 Mn 0.9 O2 / C, according to the chemical molar ratio in the chemical formula, a composite alkaline sodium source (trisodium citrate and sodium benzoate, with a mass ratio of 1:0.5), a composite acidic manganese source (manganese acetate and manganous anhydride, with a mass ratio of 1:1), an organic metal zinc ion source of dialkyl zinc, and a carbon source (sucrose and carbon fiber, with a mass ratio of 1:1, and a total mass fraction of 20% in the raw materials). Among them, trisodium citrate is a strongly basic ligand (oxidant) and functions similarly to the sodium hydroxide in Example 1. Sodium benzoate provides a sodium source, adjusts the pH value, and synergizes with trisodium citrate to control the reaction rate, acting similarly to the sodium bicarbonate in Example 1. Manganese acetate is a low-valent manganese with a valence of +2, and manganous anhydride is a high-valent manganese with a valence of +5, acting similarly to the manganese oxalate and permanganic anhydride in Example 1, respectively. The role of dialkyl zinc in regulating the manganese valence state is similar to that of dialkyl magnesium in Example 1, and the reaction mechanism and process are similar to those of dialkyl magnesium in Example 1. The synergistic effect between the substances promotes the combination of sodium, manganese, zinc and oxygen, ensuring that Na 0.44 Zn 0.1 Mn 0.9 O2 / C, formation of substances.

[0047] 6% PTFE and 4% PVDF binder powder accounting for the mass fraction of the solid mixed powder are added to the mixed material together with the high-speed mixer for high-speed mixing, the speed is set to 3000 rpm, and the high-speed mixing is carried out for 4 hours. The mixed material is transferred to a granulator for dry granulation, the heating temperature of the granulator is set to 300° C., the stirring speed is 3000 rpm, and the mixture is heated for 5 hours to prepare a small spherical sodium manganate positive electrode material precursor for aqueous sodium ion battery. The particle size of the small spherical particle is 10 mm. Then, the granulated spherical powder is pressed into a sheet (length 60 mm * width 60 mm * height 5 mm) by a tablet press, and a high-temperature calcination is carried out in an air atmosphere. The calcination process is: pre-calcination at 320° C. for 2 hours, then calcination at 850° C. for 9 hours, and the heating rate is 2° C. / min. The calcined sheet is crushed in a crusher to prepare a metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material.

[0048] The process of preparing button batteries is as follows:

[0049] The manganese-doped sodium manganate and carbon composite aqueous sodium ion battery cathode material, conductive carbon black Super-P, and binder PVDF from Example 1 were mixed in a mass ratio of 8:1:1. An appropriate amount of NMP was added as a solvent and uniformly mixed in an agate mortar to prepare a slurry. The slurry was evenly coated onto aluminum foil using a spatula. After vacuum drying at 120°C for 12 hours, the slurry was punched into circular electrode sheets with a diameter of 12 mm using a mold. This sample electrode served as the study electrode, and the sodium metal sheet served as the counter electrode. 2025 button cells were assembled in a glove box. The negative activated carbon electrode was prepared using the same method as the manganese-doped sodium manganate and carbon composite aqueous sodium ion battery cathode sheet. A 5M sodium hydroxide aqueous sodium ion battery electrolyte was prepared. Filter paper was used as the separator. The cells were assembled into a soft-pack battery using a positive electrode-diaphragm-positive electrode method.

[0050] The test environment is as follows:

[0051] The electrochemical cycle test was carried out using the Xinwei battery testing system. The charge and discharge current density of the button half-cell was 0.1C, and the charge and discharge cut-off voltage was 2-4.2V. The charge and discharge rate of the soft-pack battery was 1C, and the charge and discharge cut-off voltage was 0.1-1.4V. The test temperature was maintained at room temperature of 25°C.

[0052] The test results are as follows:

[0053] The metal magnesium doped sodium manganate carbon composite aqueous sodium ion battery positive electrode material prepared in Example 1 was used as the analysis object, and its microscopic SEM morphology is as follows Figure 1 As shown; the EDS element distribution results of SEM are as follows Figure 2 As shown; XRD phase analysis is as shown Figure 3 shown.

[0054] The battery is assembled into a button cell using metal ion doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode materials. The cycle specific capacity reaches 118mAh / g at a current density of 200mA / g, and the capacity retention rate is 89.3% after 1000 cycles, showing good cycle stability. Figure 4 As shown. Then the prepared positive electrode material is combined with activated carbon AC to form an aqueous sodium ion full battery. The prepared metal ion doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material is applied to aqueous batteries. The prepared positive electrode material is combined with lithium manganate to form a 15mAh aqueous sodium ion full battery. When it is cycled 1000 times at 1C, the capacity retention rate is nearly 88.4%. Figure 5 shown.

[0055] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material, characterized in that: The chemical formula is Na 0.44 M x Mn 1-x O2 / C, 0.3≥x≥0.1, M is a metal ion, one of Mg, Al, and Zn.

2. The metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material according to claim 1, characterized in that: The chemical formula is Na 0.44 Mg 0.3 Mn 0.7 O2 / C, or Na 0.44 Al 0.2 Mn 0.7 O2 / C, or Na 0.44 Zn 0.1 Mn 0.9 O2 / C.

3. A method for preparing the metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material according to claim 1 or 2, characterized in that: The steps include: Step 1: The sodium manganate and carbon composite aqueous sodium ion battery cathode material having the chemical formula Na 0.44 M x Mn 1-x The chemical molar ratio of O2 / C is taken from a composite alkaline sodium source, a composite acidic manganese source, an organic metal ion source and a carbon source, which are fully mixed and then added together with the binder powder into a high-speed mixer for high-speed mixing to obtain a precursor material; Step 2: Transferring the precursor material obtained in step 1 to a granulator for dry granulation to prepare a spherical aqueous sodium ion battery cathode material precursor; Step 3: The spherical positive electrode material precursor granulated in step 2 is pressed into sheets by a tablet press to obtain a sheet, which is then calcined at high temperature in an air atmosphere. The calcined sheet is crushed in a grinder to prepare a sodium manganate and carbon composite aqueous sodium ion battery positive electrode material doped with metal ions.

4. The method for preparing a metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material according to claim 3, characterized in that: The composite alkaline sodium source is a composite of two or more of sodium hydroxide, sodium acetate, sodium bicarbonate, sodium phenol, sodium hypochlorite, sodium phosphate, sodium benzoate, trisodium citrate, sodium citrate, and trisodium citrate; The composite acidic manganese source is a composite of two or more of manganese oxalate, manganese acetate, manganese stearate, manganic anhydride, manganous anhydride, and permanganic anhydride; The organic metal ion source is one of ethylmagnesium bromide, phenylmagnesium chloride, dialkylmagnesium, diethylmagnesium, dialkylzinc, methylzinc iodide, triethylaluminum, and triisobutylaluminum; The carbon source is one or a composite of two or more of sucrose, asphalt, starch, carbon nanotubes, and carbon fibers, and the mass of the carbon source accounts for 10-20% of the mass of the precursor material obtained in step one.

5. The method for preparing a metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material according to claim 3, characterized in that: The binder powder in step one is one or more of polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), polyvinyl pyrrolidone (PVP) and sodium carboxymethyl cellulose (CMC). The mass of the binder powder accounts for 5-10% of the mass of the precursor material obtained in step one.

6. The method for preparing a metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material according to claim 3, characterized in that: The parameters of the high-speed mixer in step 1 are set as follows: speed 1000-5000 rpm, mixing time 2-6 h; In the step 2, the heating temperature of the granulator is 200-400° C., the stirring speed is 1000-5000 rpm, and the granulator is heated for 4-10 hours to prepare a small spherical sodium manganate positive electrode material precursor for an aqueous sodium ion battery. The diameter of the small spherical particles is 5-15 mm.

7. The method for preparing a metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material according to claim 3, characterized in that: The process of high-temperature calcination in air atmosphere in step 3 is: pre-calcination at 300-350° C. for 1-2 hours, and then calcination at 750-900° C. for 8-12 hours, with a heating rate of 2° C. / min.

8. The method for preparing a metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material according to claim 3, characterized in that: When sodium manganate doped with metal ions is combined with carbon to form the positive electrode material of aqueous sodium ion battery, the chemical formula is Na 0.44 Mg 0.3 Mn 0.7 O2 / C, when the composite alkaline sodium source is a composite of sodium hydroxide and sodium bicarbonate in a mass ratio of 1:0.5, the composite acidic manganese source is a composite of manganese oxalate and permanganic anhydride in a mass ratio of 1:1, the organic metal magnesium ion source is dialkyl magnesium, and the carbon source is a composite of starch and carbon nanotubes in a mass ratio of 1:1; the strong base sodium hydroxide plays a role in regulating the oxidation state of manganese, and the oxidation state of manganese in the target product sodium manganate is +3.56, and the Mn in manganese oxalate is 2+ or Mn in manganic anhydride 7+ It is converted into manganese with an intermediate valence of +3.

56. Manganese oxalate MnC2O4 is oxidized in a strong alkaline environment. The CO2 released by the decomposition of O2 or NaHCO3 in the air promotes oxidation. Manganese anhydride Mn2O7 itself is +7 valence manganese, which is reduced to low-valent manganese with a valence of +6 under alkaline conditions. NaOH provides strong alkaline conditions. NaHCO3, as a mild alkaline source, decomposes under heat to produce Na2CO3 and CO2, which assist in adjusting pH or participating in the redox process, and synergizes with sodium hydroxide to control the reaction rate. Dialkyl magnesium R2Mg has strong reducing properties. It not only provides a magnesium source, but also reduces the valence of manganese. The hydroxyl -OH in starch can also form a soluble complex with the Mn source. The synergistic effect between the substances promotes the combination of sodium, manganese, magnesium and oxygen elements, ensuring Na 0.44 Mg 0.3 Mn 0.7 The formation of O2 substances; When sodium manganate doped with metal ions is combined with carbon to form the positive electrode material of aqueous sodium ion battery, the chemical formula is Na 0.44 Al 0.2 Mn 0.7 When the temperature is 02 / C, the composite alkaline sodium source is a composite of trisodium citrate and sodium acetate in a mass ratio of 1:0.5, the composite acidic manganese source is a composite of manganese acetate and permanganic anhydride in a mass ratio of 1:1, the organic metal aluminum ion source is triethylaluminum, and the carbon source is a composite of citric acid and carbon fiber in a mass ratio of 1:1; When sodium manganate doped with metal ions is combined with carbon to form the positive electrode material of aqueous sodium ion battery, the chemical formula is Na 0.44 Zn 0.1 Mn 0.9 O2 / C, when the composite alkaline sodium source is a composite of trisodium citrate and sodium benzoate in a mass ratio of 1:0.5, the composite acidic manganese source is a composite of manganese acetate and manganous anhydride in a mass ratio of 1:1, the organic metal zinc ion source is dialkyl zinc, and the carbon source is a composite of sucrose and carbon fiber in a mass ratio of 1:

1.

9. A metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material prepared by the method for preparing a metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material according to any one of claims 3 to 8, and a button battery assembled from the metal ion-doped sodium manganate and carbon composite aqueous sodium ion battery positive electrode material.

10. A battery, characterized in that: An aqueous sodium ion full battery composed of the metal ion-doped sodium manganate-carbon composite aqueous sodium ion battery positive electrode material and an activated carbon electrode sheet as claimed in claim 9, and the use of the metal ion-doped sodium manganate-carbon composite aqueous sodium ion battery positive electrode material in an aqueous battery.

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