CN113929069A

CN113929069A - Manganese-rich phosphate cathode material and preparation method and application thereof

Info

Publication number: CN113929069A
Application number: CN202111170822.0A
Authority: CN
Inventors: 赵君梅; 徐春柳; 刘会洲
Original assignee: Institute of Process Engineering of CAS
Current assignee: Institute of Process Engineering of CAS
Priority date: 2021-10-08
Filing date: 2021-10-08
Publication date: 2022-01-14
Anticipated expiration: 2041-10-08
Also published as: CN113929069B

Abstract

The invention provides a positive electrode material, which is a Mn-rich phosphate positive electrode material containing V and Ti, and the chemical formula of the positive electrode material is Na_{3+δ+(4‑n)x+2y}Ti_{1‑δ‑x‑y}Mⁿ⁺ _xV_δMn_1+y(PO₄)₃(ii) a Wherein, M isⁿ⁺Comprising Li⁺、K⁺、Mg²⁺、Ca²⁺、Sr²⁺、Zn²⁺、Co²⁺、Ni²⁺、Cu²⁺、Al³⁺、Cr³⁺、Fe³⁺、Y³⁺、La³⁺、Ga³⁺、Zr⁴⁺、Sn⁴⁺、Nb⁵⁺Or W⁶⁺Any one or a combination of at least two of; x is more than or equal to 0 and less than or equal to 0.5; 0 is described<Delta is less than or equal to 0.5; n is more than or equal to 1; y is more than or equal to 0 and less than or equal to 0.5. The positive electrode material prepared by the invention can obtain higher effective specific capacity, inhibit the voltage hysteresis phenomenon of the manganese-rich phosphate positive electrode, inhibit the manganese ion-containing Zingiber taylor structural distortion and the dissolution of the manganese ion, show good dynamic performance and rate capability, and further improve the electrochemical performance of the material.

Description

Manganese-rich phosphate cathode material and preparation method and application thereof

Technical Field

The invention relates to the field of sodium ion batteries, and relates to a novel manganese-rich phosphate positive electrode material, and a preparation method and application thereof.

Background

In recent years, with the increasing severity of two international problems of energy crisis and environmental pollution, China actively follows the global green low-carbon development trend, and therefore the carbon peak reaching and carbon neutralization targets are provided. Against this background, advanced technologies such as clean energy (solar, wind, tidal, etc.) and smart grid have been developed unprecedentedly. Therefore, higher demands are also placed on energy storage devices. Secondary rechargeable lithium ion batteries are widely studied as an energy storage device because of their high conversion efficiency and energy density. However, the problems of shortage and uneven distribution of lithium resources limit the future development of the lithium battery. With the rise of large-scale energy storage and the characteristics of high earth crust abundance and low price of sodium resources, the sodium ion battery becomes an important supplement of the lithium ion battery. The phosphate anode material of the sodium super-ion conductor has a three-dimensional ion channel, so that the research is widely carried out. The vanadium ions of the vanadium sodium phosphate anode can provide a stable and flat voltage platform, so that the vanadium sodium phosphate has excellent rate capability and cycle performance. But the industrial application of the sodium vanadium phosphate is greatly limited due to the relative expensive vanadium resource. Although the iron-based phosphate positive electrode with the sodium super-ion conductor structure has cost advantage, Fe²⁺/Fe³⁺The voltage platform is too low, is only about 2.5V, and has no practical application value. For the same green and cheap manganese-based phosphate anode material, such as vanadium manganese sodium phosphate, although two reaction couples exist, the dosage of vanadium is still higher, so that the cost of the material is still high, and the material is not easy to industrialize; for manganese phosphate titanium material without vanadium, the price is low, and positive quadrivalent titanium ion can activate Mn²⁺/Mn³⁺And Mn³⁺/Mn⁴⁺Two reaction pairs with voltage platforms of 3.6V and 4.1V, even higher than V³⁺/V⁴⁺Voltage level ofTable (3.4V), however, the mutual occupation of Na and Mn in the material is serious, which causes the material to be seriously attenuated in the sodium desorption process, and the material also has no practical application value.

In manganese-based phosphate, because the radiuses of manganese ions and sodium ions are similar, the manganese ions in the crystal structure easily occupy the active site (Na1 site) of sodium, and the phenomenon of sodium-manganese mixed exclusion is generated, so that the capacity of the material cannot be effectively exerted. During charging, divalent manganese ions migrate to a thermodynamically stable state upon oxidation to form smaller trivalent manganese ions (or tetravalent manganese ions). The migration process of the manganese ions causes a serious voltage hysteresis phenomenon to occur in a charge-discharge curve, which not only reduces the output voltage of the material, but also influences the capacity release of the material in an effective voltage window. And Mn³⁺Jahn-Teller effect and Mn of²⁺Dissolution in organic electrolytes can reduce the structural stability of the material and deteriorate the material dynamic properties. Therefore, a novel Mn-rich phosphate anode with low price is urgently developed, the defects of the structure of the Mn-rich phosphate are overcome, and better rate performance and cycle performance are obtained, which has important significance for future industrial application of the Mn-rich phosphate anode.

CN106981641A discloses a preparation method of a carbon-coated sodium titanium manganese phosphate anode material, wherein an organic compound is used as a reducing agent and a carbon source, a phosphorus source, a manganese source, a sodium source and a titanium source are mixed and ball-milled, and the carbon-coated sodium titanium manganese phosphate anode material can be obtained after high-temperature sintering. Although the overall conductivity of the cathode material can be improved by introducing carbon coating, the problems of sodium-manganese mixed discharge, the Zingiber Taylor effect of trivalent manganese ions, the dissolution of manganese ions and the like in the titanium manganese phosphate sodium structure are still not effectively solved, and the titanium manganese phosphate sodium cathode material has low specific discharge capacity and poor cyclicity, and is difficult to realize industrial-grade large-scale production.

CN111092220A discloses a modified tunnel type sodium ion battery manganese-based anode material doped with an M element body phase and a preparation method thereof, wherein a precursor is prepared by solid-phase ball milling, and the tunnel type sodium ion battery manganese-based material doped with the M element body phase with a rod-shaped structure is prepared by high-temperature solid-phase sintering reaction. The phase doping of the M element effectively improves the electricityThe electronic conductivity of the electrode material improves the structural stability of the material, and is beneficial to improving the rate capability and the cycling stability of the material. Wherein the M element includes Al³⁺、Co³⁺、Ni²⁺、Mg²⁺And Fe³⁺Any one or a combination of at least two of them. Although the conductivity of the material is improved by doping the M element phase, the improvement of the conductivity of the anode material is limited, and the improvement of the cycle performance and the rate performance of the material is also limited.

CN112563484A discloses a positive electrode material of a sodium-ion battery, a preparation method thereof and the sodium-ion battery, wherein the chemical formula of the positive electrode material of the sodium-ion battery is Na_xNi_yM_1-yO₂Wherein, 0.5<x<1，0.1<y<0.5, M is selected from at least one of Mn, Fe, Co, V, Cu, Cr and Ti; the positive electrode material of the sodium-ion battery is spherical-like particles, and the positive electrode material of the sodium-ion battery has a layered structure. Although the cycle performance of the battery positive electrode material is improved, the improvement of the electrical conductivity of the battery has no beneficial effect.

How to improve the electrochemical performance of the sodium-ion battery is an important research direction in the field.

Disclosure of Invention

The invention aims to provide a Mn-rich phosphate anode material containing V and Ti, which can obtain more effective specific capacity, inhibit the voltage hysteresis phenomenon of a Mn-rich phosphate anode, show good dynamic performance and rate capability, inhibit the distortion of a Mn-ion Zingiber Taylor structure and the dissolution of Mn ions, and further improve the electrochemical performance of the material.

In order to achieve the purpose, the invention adopts the following technical scheme:

one purpose of the invention is to provide a positive electrode material, wherein the positive electrode material is a Mn-rich phosphate positive electrode material containing V and Ti, and the chemical formula of the positive electrode material is Na_{3+δ+(4-n)x+2y}Ti_1-δ-x-yMⁿ⁺ _xV_δMn_1+y(PO₄)₃。

Wherein, M isⁿ⁺Comprising Li⁺、K⁺、Mg²⁺、Ca²⁺、Sr²⁺、Zn²⁺、Co²⁺、Ni²⁺、Cu²⁺、Al³⁺、Cr³⁺、Fe³⁺、Y³⁺、La³⁺、Ga³⁺、Zr⁴⁺、Sn⁴⁺、Nb⁵⁺Or W⁶⁺Any one or a combination of at least two of the following, typical but non-limiting examples being: li⁺And K⁺Combination of (1), K⁺And Mg²⁺Combination of (2), Mg²⁺And Ca²⁺Combination of (1) and Ca²⁺And Zn²⁺Combination of (A) and (B), Co²⁺And Ni²⁺Combination of (2) and Cu²⁺And Al³⁺Combination of (5) and Cr³⁺And Y³⁺And La³⁺Combination of (5) Sr²⁺And Fe³⁺And Sn⁴⁺Combination of (1) and Ga³⁺And Zr⁴⁺Combinations of (A) or (B)⁵⁺And W⁶⁺Combinations of (a), (b), and the like.

0. ltoreq. x.ltoreq.0.5, where the value of x may be 0, 0.1, 0.2, 0.3, 0.4 or 0.5, etc., but is not limited to the enumerated values, and other values not enumerated within the numerical range are also applicable.

The stated value 0< δ ≦ 0.5, where the stated value for δ may be 0.1, 0.2, 0.3, 0.4, or 0.5, etc., but is not limited to the recited values, and other values not recited in this range of values are equally applicable.

N is more than or equal to 1, wherein the value of n can be 1, 2, 3, 4, 5, 6 or 7, etc., but is not limited to the enumerated values, and other unrecited values in the numerical range are also applicable.

0. ltoreq. y.ltoreq.0.5, where the value of y may be 0, 0.1, 0.2, 0.3, 0.4 or 0.5, etc., but is not limited to the recited values, and other values not recited in the numerical range are also applicable.

Compared with many reported Mn and Ti-containing phosphate anode materials, the Mn-rich phosphate anode material can obtain more effective specific capacity due to doping of trivalent vanadium ions, and can reduce the mixed-discharging degree of sodium and manganese due to more sodium content, so that the Mn-rich phosphate anode material is inhibitedVoltage hysteresis of the poles; v³⁺And Ti⁴⁺And Mn²⁺The composite material has good solid solubility and synergistic effect, and shows good dynamic performance and rate capability; while the other Mn in the material⁺The ions can inhibit the distortion of the structure of the manganese ions Zingiber Taylor and the dissolution of the manganese ions, and further improve the electrochemical performance of the material.

In the present invention, V³⁺And Ti⁴⁺And Mn²⁺Has good solid solubility, and utilizes a small amount of active V to reduce the cost of raw materials³⁺With Ti⁴⁺And Mn²⁺A new Mn-rich phosphate is formed. By adjusting Mn⁺And the values of delta, x and y introduce more sodium ions to occupy lattice sites, so that the degree of sodium-manganese mixing is reduced, and the migration of trivalent or tetravalent manganese ions in the electrochemical reaction process is reduced, thereby inhibiting the voltage hysteresis phenomenon of the material. Due to V³⁺And Ti⁴⁺And Mn²⁺The composite material has good solid solubility, is beneficial to forming pure phase, has synergistic effect in the electrochemical reaction process, and shows good dynamic performance and rate capability. Mn incorporating typical stabilization⁺Ions can obtain a more stable frame structure, inhibit the distortion of a manganese ion ginger taylor structure and the dissolution of manganese ions, and improve the circulation stability of the material.

It is a second object of the present invention to provide a method for producing a positive electrode material according to the first aspect, the method comprising:

mixing the raw material of the anode material with a solvent to obtain a precursor, drying the precursor, and sintering to obtain the anode material.

The method for synthesizing the cathode material comprises any one of a solid phase method, a spray drying method and a sol-gel method.

As a preferable technical scheme of the invention, the raw materials comprise a sodium source, a manganese source, a titanium source, a vanadium source, a phosphorus source and a metal ion source.

As a preferred embodiment of the present invention, the sodium source comprises any one of sodium bicarbonate, sodium carbonate, sodium acetate, sodium nitrate, sodium hydroxide or sodium oxalate, or a combination of at least two of them, typical but non-limiting examples of which are: combinations of sodium bicarbonate and sodium carbonate, sodium carbonate and sodium acetate, sodium acetate and sodium nitrate, sodium nitrate and sodium hydroxide, or sodium hydroxide and sodium oxalate, and the like.

Preferably, the manganese source comprises any one of manganese acetate, manganese nitrate, manganese acetylacetonate, manganese oxalate, manganese carbonate, manganese monoxide, manganese dioxide, manganese sesquioxide, manganous oxide, manganous anhydride, manganic anhydride or manganous anhydride, or a combination of at least two of these, typical but non-limiting examples being: a combination of manganese acetate and manganese nitrate, a combination of manganese acetylacetonate and manganese oxalate, a combination of manganese oxalate and manganese carbonate, a combination of manganese monoxide and manganese dioxide, a combination of manganese sesquioxide and manganomanganic oxide, a combination of manganomanganic oxide and manganous anhydride, a combination of manganous anhydride and manganic anhydride, or a combination of manganic anhydride and manganic anhydride, and the like.

Preferably, the titanium source comprises any one of titanium dioxide, titanium trioxide, sodium titanate, titanium acetylacetonate, titanyl acetylacetonate or tetrabutyl titanate, or a combination of at least two of said combinations, typical but non-limiting examples being: combinations of titanium dioxide and titanium trioxide, combinations of titanium trioxide and sodium titanate, combinations of sodium titanate and titanium acetylacetonate, combinations of titanium acetylacetonate and titanyl acetylacetonate or combinations of titanium acetylacetonate and tetrabutyl titanate, and the like.

Preferably, the vanadium source comprises any one of the various types of vanadium pentoxide, vanadium tetraoxide, vanadium trioxide, vanadium oxide, sodium ammonium metavanadate, ammonium vanadate, vanadyl acetylacetonate or vanadium acetylacetonate in combination of at least two of the typical but non-limiting examples being: combinations of vanadium pentoxide and vanadium tetraoxide, vanadium tetraoxide and vanadium trioxide, vanadium trioxide and vanadium oxide, vanadium oxide and sodium ammonium metavanadate, sodium ammonium metavanadate and ammonium vanadate, ammonium vanadate and vanadyl acetylacetonate, or vanadyl acetylacetonate and vanadium acetylacetonate, and the like.

Preferably, the source of phosphorus comprises any one of phosphoric acid, sodium dihydrogen ammonium phosphate, ammonium dihydrogen phosphate, sodium diammonium hydrogen phosphate, ammonium phosphate, or sodium ammonium phosphate, or a combination of at least two of these, typical but non-limiting examples being: a combination of phosphoric acid and sodium monoammonium phosphate, a combination of sodium monoammonium phosphate and ammonium dihydrogen phosphate, a combination of ammonium dihydrogen phosphate and sodium diammonium hydrogen phosphate, a combination of sodium diammonium hydrogen phosphate and diammonium hydrogen phosphate, or a combination of ammonium phosphate and sodium ammonium phosphate, and the like.

Preferably, the metal ion source comprises Li⁺、K⁺、Mg²⁺、Ca²⁺、Sr²⁺、Zn²⁺、Co²⁺、Ni²⁺、Cu²⁺、Al³⁺、Cr³ ⁺、Fe³⁺、Y³⁺、La³⁺、Ga³⁺、Zr⁴⁺、Sn⁴⁺、Nb⁵⁺Or W⁶⁺Any one or a combination of at least two of the corresponding acid, base, sodium or ammonium salts, typical but non-limiting examples being: li⁺Corresponding bases and K⁺Combination of the corresponding acids, K⁺Corresponding acid and Mg²⁺Combination of corresponding bases, Mg²⁺Corresponding sodium salt and Ca²⁺Combination of corresponding ammonium salts, Ca²⁺Corresponding acid and Zn²⁺Corresponding combinations of bases, Co²⁺Corresponding sodium salt and Ni²⁺Corresponding base combination, Cu²⁺Corresponding ammonium salt and Al³⁺Combination of corresponding acids, Cr³⁺Corresponding bases and Y³⁺Corresponding base and La³⁺Combinations of corresponding bases, Ga³⁺Corresponding acid and Zr⁴⁺Combinations of corresponding bases or Nb⁵⁺Corresponding sodium salt and W⁶⁺Combinations of corresponding acids, and the like.

As a preferred technical scheme of the invention, the raw material also comprises a carbon source.

Preferably, the carbon source comprises any one or a combination of at least two of sodium citrate, citric acid, sodium oleate, oleic acid, polyvinylpyrrolidone, polyethylene glycol, glucose, ascorbic acid, sucrose, dopamine hydrochloride, starch, graphene oxide, reduced graphene, carbon nanotubes, or ketjen black, as typical but non-limiting examples: a combination of sodium citrate and citric acid, a combination of citric acid and sodium oleate, a combination of sodium oleate and oleic acid, a combination of oleic acid and polyvinylpyrrolidone, a combination of polyvinylpyrrolidone and polyethylene glycol, a combination of polyethylene glycol and glucose, a combination of ascorbic acid and sucrose, a combination of dopamine hydrochloride and starch, a combination of graphene oxide and reduced graphene, or a combination of carbon nanotubes and ketjen black, and the like.

Preferably, the molar ratio of the carbon source to the metal ion source is 0 to 10:1, wherein the molar ratio may be 0, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or 10:1, but is not limited to the recited values, and other values not recited within the range of values are also applicable, and more preferably 0 to 3: 1.

As a preferred embodiment of the present invention, the solvent includes any one or a combination of at least two of deionized water, ethanol, or acetone, and typical but non-limiting examples of the combination are: a combination of deionized water and ethanol, a combination of deionized water and acetone, a combination of ethanol and acetone, or the like.

In a preferred embodiment of the present invention, the drying is followed by a grinding treatment.

Preferably, the drying temperature is 60 to 150 ℃, the temperature can be 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃, 100 ℃, 105 ℃, 110 ℃, 115 ℃, 120 ℃, 125 ℃, 130 ℃, 135 ℃, 140 ℃, 145 ℃ or 150 ℃, but not limited to the cited values, and other non-cited values in the numerical range are also applicable, more preferably 90 to 120 ℃;

preferably, the time of the polishing treatment is 1min to 48 hours, wherein the time may be 1min, 5min, 10min, 20min, 30min, 40min, 50min, 1h, 5h, 10h, 15h, 20h, 25h, 30h, 35h, 40h, 45h, or 48h, etc., but is not limited to the recited values, and other values not recited in the range of the values are also applicable. More preferably 30min to 2 hours.

As a preferable technical scheme of the invention, the sintering atmosphere comprises an inert atmosphere and/or a reducing atmosphere.

Preferably, the reducing atmosphere comprises carbon monoxide and/or hydrogen.

Preferably, the inert atmosphere comprises argon and/or nitrogen.

In a preferred embodiment of the present invention, the sintering temperature is 500 to 900 ℃, wherein the temperature may be 500 ℃, 550 ℃, 600 ℃, 650 ℃, 700 ℃, 750 ℃, 800 ℃, 850 ℃, or 900 ℃, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, the sintering time is 2-20 h, wherein the sintering time can be 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h or 20h, but is not limited to the recited values, and other values not recited in the numerical range are also applicable.

It is a further object of the present invention to provide a use of the positive electrode material according to the first aspect, wherein the positive electrode material is used in a sodium ion battery.

The sodium ion battery is used for large-scale energy storage equipment of solar power generation, wind power generation, smart grid peak regulation, distributed power stations, backup power supplies or communication base stations.

Compared with the prior art, the invention has the following beneficial effects:

(1) the Mn-rich phosphate cathode material containing V and Ti prepared by the invention greatly reduces the cost due to less V consumption.

(2) The Mn-rich phosphate cathode material containing V and Ti prepared by the invention has good electrochemical performance, and the first discharge gram specific capacity of the Mn-rich phosphate cathode material reaches more than 110mAh/g and the discharge medium voltage is more than 3.5V when a charge-discharge test is carried out at 0.1C; more than 80mAh/g can be obtained at 10 ℃; the capacity retention rate is more than 90 percent after the circulation for 1000 weeks at 2C.

Drawings

Fig. 1 is an XRD pattern of Mn-rich based phosphate positive electrode material containing V and Ti prepared in example 1 of the present invention.

FIG. 2 is a scanning electron micrograph of a Mn-rich phosphate positive electrode material containing V and Ti prepared in example 1 of the present invention.

Fig. 3 is a graph of rate charge and discharge curves of Mn-rich phosphate positive electrode material containing V and Ti prepared in example 1 of the present invention.

Fig. 4 is a graph of cycle performance at 2C for Mn-rich based phosphate positive electrode material containing V and Ti prepared in example 1 of the present invention.

Fig. 5 is a charge and discharge curve of the phosphate positive electrodes prepared in examples 1-2 and comparative examples 1-2.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Example 1

This example provides a method for preparing a Mn-rich based phosphate positive electrode material containing V and Ti:

mixing the components in proportion of 1: 0.80: 0.15: 0.05: 3.25: 3 adding manganese acetate, titanium dioxide, ammonium metavanadate, magnesium acetate, sodium acetate and phosphoric acid into the ethanol solution containing the citric acid, wherein the mass ratio of carbon to transition metal is 1.5: 1. then the mixed solution is placed in a water bath kettle and is magnetically stirred at 70 ℃ until the ethanol is completely evaporated. Drying the obtained precursor at 100 ℃, grinding the precursor into powder, and sintering the powder in a tubular furnace in argon atmosphere at 700 ℃ for 10 hours to obtain Na_3.25Ti_0.8V_0.15Mg_0.05Mn(PO₄)₃@ C positive electrode material.

The structure of the cathode material in this example is analyzed, and XRD analysis is performed on the Mn-rich phosphate cathode material prepared in this example by using an X-ray instrument, and the test result is shown in fig. 1.

The surface morphology of the phosphate anode prepared in this example was analyzed by scanning electron microscopy, and the test results are shown in fig. 2, from which it can be seen that the prepared material was formed by stacking random primary particles. This agglomeration is caused by particles becoming embedded in the carbon layer and becoming cross-linked.

The phosphate positive electrode prepared in this example was assembled into a 2032 type testable button cell, and the rate charge-discharge curve is shown in fig. 3. The cycling performance at 2C is shown in figure 4.

Example 2

mixing the components in a ratio of 1.2: 0.65: 0.075: 0.025: 3.55: 3, adding manganese carbonate, titanium dioxide, vanadium trioxide, aluminum oxide, sodium hydroxide, ammonium dihydrogen phosphate and oleic acid into the aqueous solution, wherein the mass ratio of carbon to transition metal substances is 3: 1. then the mixture is put into a ball mill to be mixed uniformly. Drying the obtained precursor at 110 ℃, grinding the precursor into powder, and sintering the powder for 20 hours at 750 ℃ in a tubular furnace in an argon atmosphere to obtain Na_3.55Ti_0.65V_0.10Al_0.05Mn_1.2(PO₄)₃@ C positive electrode material.

Example 3

mixing the components in proportion of 1: 0.74: 0.25: 0.01: 3.19: 3 adding manganese acetate, tetrabutyl titanate, ammonium metavanadate, ammonium tungstate, sodium acetate and phosphoric acid into an acetone solution containing ascorbic acid, wherein the mass ratio of carbon to transition metal is 1: 1. the mixed solution was then placed in a water bath with magnetic stirring at 80 ℃ until the acetone evaporated completely. Drying the obtained precursor at 110 ℃, grinding the precursor into powder, and sintering the powder in a tubular furnace in argon atmosphere at 650 ℃ for 12 hours to obtain Na_3.19Ti_0.74V_0.25W_0.01Mn(PO₄)₃@ C positive electrode material.

Example 4

mixing the components in a ratio of 1.15: 0.7: 0.05: 0.05: 1.775: 3 manganese carbonate, titanium dioxide, vanadium trioxide, bisZirconium oxide, sodium carbonate, ammonium dihydrogen phosphate and glucose were added to the aqueous solution, wherein the mass ratio of carbon to transition metal was 1.25: 1. then the mixture is put into a ball mill to be mixed uniformly. Drying the obtained precursor at 120 ℃, grinding the precursor into powder, and sintering the powder in a tubular furnace in argon atmosphere at 800 ℃ for 10 hours to obtain Na_3.4Ti_0.7V_0.10Zr_0.05Mn_1.15(PO₄)₃@ C positive electrode material.

Example 5

mixing the components in proportion of 1: 0.75: 0.25: 3.25: adding manganese acetate, tetrabutyl titanate, vanadium acetylacetonate, sodium acetate and phosphoric acid into the ethanol solution, wherein the mass ratio of carbon to transition metal is 1.25: 1. then the mixture is put into a ball mill to be mixed uniformly. Drying the obtained precursor at 120 ℃, grinding the precursor into powder, and sintering the powder in a tubular furnace in argon atmosphere at 800 ℃ for 10 hours to obtain Na_3.4Ti_0.7V_0.10Zr_0.05Mn_1.15(PO₄)₃@ C positive electrode material.

Example 6

In this example, the composition ratio is 1: 0.80: 0.15: 0.05: 3.25: 3 adding manganese acetate, titanium dioxide, ammonium metavanadate, magnesium acetate, sodium acetate and phosphoric acid into the ethanol solution containing the citric acid, wherein the mass ratio of carbon to transition metal is 1.5: 1, replacing the components in the composition ratio of 1: 0.80: 0.15: 0.05: 3.25: 3 manganese acetate, titanium dioxide, ammonium metavanadate, magnesium acetate, sodium acetate and phosphoric acid are added to the ethanol solution containing more citric acid so that the mass ratio of carbon to transition metal therein is 10:1, the other conditions were the same as in example 1.

Example 7

In this example, the composition ratio is 1: 0.80: 0.15: 0.05: 3.25: 3 adding manganese acetate, titanium dioxide, ammonium metavanadate, magnesium acetate, sodium acetate and phosphoric acid into the ethanol solution containing the citric acid, wherein the mass ratio of carbon to transition metal is 1.5: 1 is replaced by 1: 0.80: 0.15: 0.05: 3.25: manganese acetate, titanium dioxide, ammonium metavanadate, magnesium acetate, sodium acetate and phosphoric acid of 3 were added to the ethanol solution, wherein the mass ratio of carbon to transition metal was 0, and the other conditions were the same as in example 1.

Comparative example 1

The present comparative example provides a method for preparing a phosphate positive electrode material containing only Ti and Mn:

the preparation steps are as follows:

mixing the components in proportion of 1: 1: 3: 3, adding manganese acetate, tetrabutyl titanate, sodium acetate and phosphoric acid into an ethanol solution containing citric acid, wherein the mass ratio of carbon to transition metal is 1.5: 1. then the mixed solution is placed in a water bath kettle and is magnetically stirred at the temperature of 80 ℃ until the ethanol is completely evaporated. Drying the obtained precursor at 100 ℃, grinding the precursor into powder, and sintering the powder in a tubular furnace in argon atmosphere at 700 ℃ for 10 hours to obtain Na₃TiMn(PO₄)₃@ C positive electrode material.

Comparative example 2

The comparative example provides a method of preparing a phosphate positive electrode material containing only Ti and Mn and a higher Mn content:

mixing the components in a ratio of 1.2: 0.8: 1.5: 3 adding manganese carbonate, titanium dioxide, sodium carbonate, ammonium dihydrogen phosphate and glucose into the aqueous solution, wherein the mass ratio of carbon to transition metal is 2: 1. then the mixture is put into a ball mill to be mixed uniformly. Drying the obtained precursor at 120 ℃, grinding the precursor into powder, and sintering the powder in a tubular furnace in argon atmosphere at 800 ℃ for 15 hours to obtain Na_3.4Ti_0.8Mn_1.2(PO₄)₃@ C positive electrode material.

Comparative example 3

The present comparative example provides a method for preparing a phosphate positive electrode material containing only V and Mn:

mixing the components in a ratio of 1.2: 0.8: 1.5: 3 manganese carbonate, vanadium trioxide, sodium carbonate, ammonium dihydrogen phosphate and glucose are added into the aqueous solution, wherein the carbon and transition metal areThe mass ratio of the substances is 2: 1. then the mixture is put into a ball mill to be mixed uniformly. Drying the obtained precursor at 120 ℃, grinding the precursor into powder, and sintering the powder in a tubular furnace in argon atmosphere at 800 ℃ for 15 hours to obtain Na_3.4Ti_0.8Mn_1.2(PO₄)₃@ C positive electrode material.

Electrochemical performance analysis was performed on the positive electrode materials prepared in examples 1 to 5 and comparative examples 1 to 3,

the electrochemical performance analysis is as follows:

1. battery preparation

(1) Preparing a battery positive plate: grinding and uniformly mixing the prepared phosphate anode material, Ketjen black and polytetrafluoroethylene binder according to the mass ratio of 7:2:1, and fully rolling by using a double-roller machine to form a film with uniform thickness. And (3) drying the obtained positive electrode film for 5 hours in a vacuum drying oven at the temperature of 120 ℃, cutting the obtained positive electrode film into square pole pieces with the side length of about 6mm, accurately weighing the mass of the square pole pieces, and calculating the mass of active substances in the positive pole pieces according to the formula composition.

(2) Assembling the battery:

the square positive pole piece, the diaphragm with the diameter of 16mm, the sodium piece with the diameter of 15mm, the elastic piece, the gasket and the like are assembled into a 2032 type testable button cell in a glove box (the oxygen content is less than 0.01ppm, and the water content is less than 0.01 ppm).

2. The electrochemical performance test method comprises the following steps:

the assembled battery was subjected to charge and discharge tests at various rates using the wuhan blue high performance battery test system, and the results are shown in table 1. Wherein the charge and discharge curves of the phosphate positive electrodes prepared in example 1, example 2, comparative example 1, and comparative example 2 are shown in fig. 5.

TABLE 1

As can be seen by comparing examples 1-5 and comparative examples 1-3 above, the Ti element activates two voltage plateaus associated with the manganese-rich based phosphate positive electrode and manganese; more effective specific capacity can be obtained by introducing V, the voltage hysteresis phenomenon of the manganese-rich phosphate positive electrode is inhibited, and V, Ti and Mn have good solid solution property and synergistic effect, so that good dynamic performance and rate capability are shown. And stable metal ions Mn + are introduced, so that the distortion of the Taylor structure of the manganese ions and the dissolution of the manganese ions can be effectively inhibited, and the electrochemical performance of the material is further improved. Comparing example 1 with example 7, it can be seen that without carbon coating, the electrochemical performance is correspondingly deteriorated due to poor electron conductivity; comparing example 1 with example 6, it can be seen that excessive carbon coating increases the interfacial resistance of the cathode material, and side reactions are more, which is not good for the electrochemical performance of the material.

The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.

Claims

1. The cathode material is characterized by being a Mn-rich phosphate cathode material containing V and Ti, and the chemical formula of the cathode material is Na_{3+δ+(4-n)x+2y}Ti_1-δ-x-yMⁿ⁺ _xV_δMn_1+y(PO₄)₃；

Wherein, M isⁿ⁺Comprising Li⁺、K⁺、Mg²⁺、Ca²⁺、Sr²⁺、Zn²⁺、Co²⁺、Ni²⁺、Cu²⁺、Al³⁺、Cr³⁺、Fe³⁺、Y³⁺、La³⁺、Ga³⁺、Zr⁴⁺、Sn⁴⁺、Nb⁵⁺Or W⁶⁺Any one or a group of at least two ofCombining;

x is more than or equal to 0 and less than or equal to 0.5;

delta is more than 0 and less than or equal to 0.5;

n is more than or equal to 1;

y is more than or equal to 0 and less than or equal to 0.5.

2. A method for producing a positive electrode material according to claim 1, comprising:

3. The method of claim 2, wherein the feedstock comprises a source of sodium, manganese, titanium, vanadium, phosphorus, and a source of metal ions.

4. The production method according to claim 3, wherein the sodium source comprises any one of sodium bicarbonate, sodium carbonate, sodium acetate, sodium nitrate, sodium hydroxide, or sodium oxalate, or a combination of at least two thereof;

preferably, the manganese source comprises any one of manganese acetate, manganese nitrate, manganese acetylacetonate, manganese oxalate, manganese carbonate, manganese monoxide, manganese dioxide, manganese sesquioxide, manganous oxide, manganous anhydride, or a combination of at least two thereof;

preferably, the titanium source comprises any one or a combination of at least two of titanium dioxide, titanium sesquioxide, sodium titanate, titanium acetylacetonate, titanyl acetylacetonate, or tetrabutyl titanate;

preferably, the vanadium source comprises any one or a combination of at least two of various vanadium pentoxide, vanadium tetraoxide, vanadium trioxide, vanadium oxide, sodium ammonium metavanadate, ammonium vanadate, vanadyl acetylacetonate or vanadium acetylacetonate;

preferably, the phosphorus source comprises any one of phosphoric acid, sodium dihydrogen ammonium phosphate, ammonium dihydrogen phosphate, sodium diammonium hydrogen phosphate, ammonium phosphate, or sodium ammonium phosphate, or a combination of at least two thereof;

preferably, the metal ion source comprises Li⁺、K⁺、Mg²⁺、Ca²⁺、Sr²⁺、Zn²⁺、Co²⁺、Ni²⁺、Cu²⁺、Al³⁺、Cr³⁺、Fe³ ⁺、Y³⁺、La³⁺、Ga³⁺、Zr⁴⁺、Sn⁴⁺、Nb⁵⁺Or W⁶⁺Any one or a combination of at least two of the corresponding acid, base, sodium salt or ammonium salt.

5. The production method according to claim 3 or 4, wherein the raw material further comprises a carbon source;

preferably, the carbon source comprises any one or a combination of at least two of sodium citrate, citric acid, sodium oleate, oleic acid, polyvinylpyrrolidone, polyethylene glycol, glucose, ascorbic acid, sucrose, dopamine hydrochloride, starch, graphene oxide, reduced graphene, carbon nanotubes or ketjen black;

preferably, the molar ratio of the carbon source to the metal ion source is 0 to 10:1, and more preferably 0 to 3: 1.

6. The method of any one of claims 2 to 5, wherein the solvent comprises any one of deionized water, ethanol, or acetone, or a combination of at least two thereof.

7. The production method according to any one of claims 2 to 6, wherein the drying is followed by a grinding treatment;

preferably, the drying temperature is 60-150 ℃, and further preferably 90-120 ℃;

the time for the polishing treatment is preferably 1min to 48 hours, and more preferably 30min to 2 hours.

8. The production method according to any one of claims 2 to 7, wherein the atmosphere for sintering comprises an inert atmosphere and/or a reducing atmosphere;

preferably, the reducing atmosphere comprises carbon monoxide and/or hydrogen;

preferably, the inert atmosphere comprises argon and/or nitrogen.

9. The method according to any one of claims 2 to 8, wherein the sintering temperature is 500 to 900 ℃;

preferably, the sintering time is 2-20 h.

10. Use of the positive electrode material according to claim 1, wherein the positive electrode material is used in a sodium ion battery.