High-capacity sodium-ion battery cathode material, preparation method thereof and sodium-ion battery

Abstract

The application discloses a high-specific-capacity sodium-ion battery positive electrode material, a preparation method thereof and a sodium-ion battery, and the positive electrode material is sodium manganate oxide which is modified by jointly doping elements N and M. x Mn 1‑y‑z N y M z O2, wherein 0.22<=x<=0.6, 0

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of sodium ion batteries, in particular to a high-specific-capacity sodium ion battery positive electrode material, a preparation method thereof and a sodium ion battery. BACKGROUND

[0002] Since the commercialization of lithium ion batteries, lithium ion batteries have occupied an absolute market share in portable mobile devices and the like due to many advantages such as high energy density, high energy conversion efficiency and no self-discharge. However, the reserves of lithium metal on the earth are limited and unevenly distributed, and with the large-scale application of lithium ion batteries in the field of electric vehicles, the shortage of lithium resources will inevitably become a major obstacle to the further development of electric vehicles. Sodium ion batteries are considered to be an important alternative to lithium ion batteries due to their abundant sodium resources, low cost and environmental friendliness.

[0003] Among sodium ion battery positive electrode materials, sodium-based layered transition metal oxides have attracted extensive attention. However, current transition metal oxide materials still have many problems, such as low capacity and poor cycle stability, which limit their commercial application. As early as 1981, Delmas et al. synthesized Na x CoO2, only P2-Na x CoO2 has good electrochemical performance. Na x MnO2 has a higher theoretical capacity (about 250 mAh / g) than Na x CoO2 and is low in price. In addition to O3, P2 phases, O2 phases and hydro-Na

[0004] However, due to the existence of continuous stress and distortion in the charging and discharging process, the cycle performance of layered Na x MnO2 is poor. In view of this, tunnel-type manganese oxide Na 0.44 MnO2 has attracted attention due to its good stability, but its specific capacity is about 120 mAh / g, which is at a low level. For example, the tunnel-type manganese oxide Na 0.44 MnO2 prepared by a sol-gel method has a capacity retention rate of 91.7% after 1000 cycles, but the specific capacity is only 122 mAh / g, which is a short board for its application. SUMMARY

[0005] The application aims to provide a high-specific-capacity sodium ion battery positive electrode material, a preparation method thereof and a sodium ion battery, which have the characteristics of high specific capacity, good cycle performance and low cost.

[0006] The application can be implemented by the following technical solutions:

[0007] The application discloses a high specific capacity sodium ion battery positive electrode material, and the positive electrode material is sodium manganate oxide which is doped with an induced phase change doping element N and a functional doping element M. x Mn 1-y-z N y M z O2, wherein 0.22<=x<=0.6, 0

[0008] Another aspect of the application is to protect the preparation method of the high specific capacity sodium ion battery positive electrode material, which comprises the following steps:

[0009] S1, raw material mixing: according to the stoichiometric ratio, the corresponding sodium source, manganese source, induced phase change doping source and functional doping source are weighed and mixed uniformly to obtain a premix;

[0010] S2, high-temperature sintering: the premix obtained in step S1 is subjected to high-temperature sintering, and then cooled to room temperature, so that the sodium ion battery positive electrode material of the sodium manganate oxide which is doped with the induced phase change doping element N and the functional doping element M is obtained.

[0011] Further, the high-temperature sintering in step S2 is performed at a sintering temperature of 500-1200℃, a sintering time of 5-20h, and a heating rate of 1-5℃ / min.

[0012] Further, the sodium source is one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium nitrate, sodium chloride, sodium acetate, and / or sodium fluoride.

[0013] Further, the manganese source is one or more of manganese carbonate, manganese chloride, manganese nitrate, manganese acetate, manganese sulfate, manganese dioxide, manganese sesquioxide, manganese monoxide, manganese trioxide, and / or manganese hydroxide.

[0014] Further, the functional doping source is one or more of a corresponding carbonate, oxide, acetate, and / or nitrate of the M element.

[0015] Further, the phase transition inducing doping source is one or more of a corresponding dihydrate, oxide, and / or carbide of the N element.

[0016] Preferably, the phase transition inducing doping source is one or more of sodium tungstate dihydrate, tungsten trioxide, tungsten dioxide, and / or tungsten carbide.

[0017] Preferably, the phase transition inducing doping source is one or more of sodium molybdate dihydrate, molybdenum trioxide, molybdenum dioxide, and / or molybdenum carbide.

[0018] Another aspect of the present application is to protect a sodium ion battery, in particular, the sodium ion battery employs the above-mentioned co-doping modified sodium manganate oxide as a positive electrode material.

[0019] The present application is a high specific capacity sodium ion battery positive electrode material, a preparation method thereof, and a sodium ion battery, which have the following beneficial effects:

[0020] By doping Na 0.44MnO2 co-doping, thereby inducing phase transition, the tunnel structure of the material body changes to layered structure, greatly improving the number of sodium storage sites of the material, greatly improving the sodium content that can be reversibly deintercalated, enhancing the electrochemical performance, and improving the specific capacity. At the same time, the introduction of the doping element with strong oxygen interaction can stabilize the structural change of the material in the charging and discharging process, and enhance the cycle stability; through functional doping, the structural stability of the material can be further enhanced and the specific capacity of the material can be further improved on the basis of the previous doping, so as to inhibit the phase transition of the material in the charging and discharging process, and be beneficial to the further improvement of the cycle stability. The co-doping of the two improves the electrochemical performance of the sodium ion battery oxide positive electrode material, so that it has higher specific capacity and better cycle performance. At the same time, the material using water-based binder can also exhibit excellent electrochemical performance, and the material is stable to water, which is beneficial to the preservation and transportation of the positive electrode material.

[0021] The present application uses resource-rich, low-cost and environmentally friendly raw materials, and adopts a simple high-temperature solid-phase synthesis method, so it has the characteristics of low production cost, simple synthesis process and environmental friendliness, is beneficial to industrialized production, and has good application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is the sodium manganese tungsten oxide Na 0.44 Mn 0.98 W 0.02 O2 synthesized material of application example 1.

[0023] Figure 2 is the sodium manganese tungsten oxide Na 0.44 Mn 0.98 W 0.02 O2 synthesized material of application example 1.

[0024] Figure 3 is the sodium manganese tungsten oxide Na 0.44 Mn 0.98 W 0.02 O2 synthesized material of application example 1. 0.44 MnO2 half-cell typical charge-discharge curve comparison chart.

[0025] Figure 4 is the sodium manganese tungsten oxide Na 0.44 Mn 0.98 W 0.02 O2 synthesized material of application example 1.

[0026] Figure 5 is the sodium manganese tungsten oxide Na 0.44 Mn 0.98W 0.02 Comparison chart of O2 half-cell charge-discharge curves.

[0027] Figure 6 Na0.7Mn0.7Mo0.3O2 is sodium manganese molybdenum oxide Na 0.44 Mn 0.98 Mo 0.02 SEM image of the synthesized material of O2.

[0028] Figure 7 Na0.7Mn0.7Mo0.3O2 is sodium manganese molybdenum oxide Na 0.44 Mn 0.98 Mo 0.02 XRD image of the synthesized material of O2

[0029] Figure 8 Na0.7Mn0.7Mo0.3O2 is sodium manganese molybdenum oxide Na 0.44 Mn 0.98 Mo 0.02 O2 and Na 0.44 Comparison chart of typical charge-discharge curves of O2 half-cell and Na

[0030] Figure 9 Na0.7Mn0.7Mo0.3O2 is sodium manganese molybdenum oxide Na 0.44 Mn 0.98 Mo 0.02 Cycle performance chart of O2 half-cell.

[0031] Figure 10 Na0.7Mn0.7W0.3O2 is sodium manganese tungsten aluminum oxide Na 0.44 Mn 0.93 W 0.02 Al 0.05 O2 and Na 0.44 Comparison chart of typical charge-discharge curves of O2 half-cell and Na

[0032] Figure 11 Na0.7Mn0.7W0.3O2 is sodium manganese tungsten aluminum oxide Na 0.44 Mn 0.93 W 0.02 Al 0.05 Cycle performance chart of O2 half-cell. DETAILED DESCRIPTION

[0033] In order to make the person skilled in the art better understand the technical solutions of the present application, the product of the present application is further described in detail below in combination with embodiments and drawings.

[0034] The present application discloses a high specific capacity sodium ion battery positive electrode material, which is sodium manganate oxide doped with induced phase change element N and functional doping element M for modification, and the chemical formula of the sodium manganate oxide after the modification is Na x Mn 1-y-z Ny M z O2, wherein 0.22≤x≤0.6, 0<y<0.4, 0≤z<0.2, N is selected from one or more of Sc, V, Y, Nb, Mo, W and / or B, and M is selected from one or more of Ti, Cr, Fe, Co, Ni, Cu, Zn, Zr, Al, Mg and / or K.

[0035] Another aspect of the present application is to protect the preparation method of the above-mentioned high specific capacity sodium ion battery cathode material, comprising the following steps:

[0036] S1, raw material mixing: according to the stoichiometric ratio, the corresponding sodium source, manganese source, phase transition inducing doping source and functional doping source are weighed and mixed uniformly to obtain a premix;

[0037] S2, high temperature sintering: the premix obtained in step S1 is subjected to high temperature sintering, and cooled to room temperature to obtain the sodium manganate oxide sodium ion battery cathode material modified by the above-mentioned methods.

[0038] Further, the high temperature sintering condition in step S2 is that the sintering temperature is 500-1200℃, the sintering time is 5-20h, and the heating rate is 1-5℃ / min.

[0039] Further, the sodium source is one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium nitrate, sodium chloride, sodium acetate and / or sodium fluoride.

[0040] Further, the manganese source is one or more of manganese carbonate, manganese chloride, manganese nitrate, manganese acetate, manganese sulfate, manganese dioxide, dimanganese trioxide, manganese monoxide and / or basic manganese hydroxide.

[0041] Further, the functional doping source is one or more of the corresponding carbonates, oxides, acetates and / or nitrates of M elements.

[0042] Further, the phase transition inducing doping source is one or more of the corresponding dihydrates, oxides and / or carbides of N elements.

[0043] Preferably, the phase transition inducing doping source is selected from one or more of sodium tungstate dihydrate, tungsten trioxide, tungsten dioxide and / or tungsten carbide.

[0044] Preferably, the phase transition inducing doping source is selected from one or more of sodium molybdate dihydrate, molybdenum trioxide, molybdenum dioxide and / or molybdenum carbide.

[0045] Another aspect of the present application is to protect the sodium ion battery, in particular, the sodium ion battery uses the above-mentioned sodium manganate oxide modified by common doping as the cathode material.

[0046] Example 1

[0047] The present invention discloses a cathode material for a high specific capacity sodium ion battery. The cathode material is a sodium manganate oxide co-doped and modified by an induced phase transition doping element N and a functional doping element M. The chemical formula of the co-modified sodium manganate oxide is Na x Mn 1-y-z N y M z O2, where 0.22 ≤ x ≤ 0.6, 0 < y < 0.4, 0 ≤ z < 0.2. The preparation method of the cathode material includes the following steps:

[0048] S1. Raw material mixing: Weigh the corresponding sodium source, manganese source, induced phase transition doping source, and functional doping source according to the stoichiometric ratio, and mix them evenly to obtain a premix;

[0049] S2. High-temperature sintering: Sinter the premix obtained in step S1 at high temperature, and cool it to room temperature to obtain the cathode material of the co-modified sodium manganate oxide sodium ion battery.

[0050] In this embodiment, the conditions for high-temperature sintering in step S2 are: the sintering temperature is 1200 °C, the sintering time is 12 h, and the heating rate is 1 °C / min.

[0051] In this embodiment, the sodium source is sodium carbonate. The manganese source is manganese carbonate, manganese tetraoxide, and / or basic manganese hydroxide.

[0052] In this embodiment, N is Sc, the functional doping source is the corresponding oxide of element M; M is Cr, Fe, Co; the induced phase transition doping source is the corresponding dihydrate of element N.

[0053] Example 2

[0054] The present invention discloses a cathode material for a high specific capacity sodium ion battery. The cathode material is a sodium manganate oxide co-doped and modified by an induced phase transition doping element N and a functional doping element M. The chemical formula of the co-modified sodium manganate oxide is Na x Mn 1-y-z N y M z O2, where 0.22 ≤ x ≤ 0.6, 0 < y < 0.4, 0 ≤ z < 0.2. The preparation method of the cathode material includes the following steps:

[0055] S1. Raw material mixing: Weigh the corresponding sodium source, manganese source, induced phase transition doping source, and functional doping source according to the stoichiometric ratio, and mix them evenly to obtain a premix;​​S2, high-temperature sintering: the premix obtained in step S1 is subjected to high-temperature sintering, and cooled to room temperature, to obtain the jointly modified sodium manganate oxide sodium-ion battery positive electrode material.

[0057] In this embodiment, the conditions for high-temperature sintering in step S2 are: a sintering temperature of 850 DEG C, a sintering time of 5 h, and a temperature increase rate of 5 DEG C / min.

[0058] In this embodiment, the sodium source is sodium bicarbonate and sodium hydroxide, and the manganese source is manganese carbonate.

[0059] In this embodiment, N is V and Y, the functional doping source is a corresponding carbonate and nitrate of element M, M is Ti, Cr, Fe, Co and Ni, and the phase transition inducing doping source is a corresponding dihydrate and oxide of element N.

[0060] Embodiment 3

[0061] The application discloses a high-specific-capacity sodium-ion battery positive electrode material, which is sodium manganate oxide jointly doped with phase transition inducing element N and functional doping element M. x Mn 1-y-z N y M z O2, wherein 0.22 <= x <= 0.6, 0 < y < 0.4 and 0 <= z < 0.2. The preparation method comprises the following steps:

[0062] S1, raw material mixing: according to the stoichiometric ratio, the corresponding sodium source, manganese source, phase transition inducing doping source and functional doping source are weighed and mixed uniformly to obtain a premix;

[0063] S2, high-temperature sintering: the premix obtained in step S1 is subjected to high-temperature sintering, and cooled to room temperature, to obtain the jointly modified sodium manganate oxide sodium-ion battery positive electrode material.

[0064] In this embodiment, the conditions for high-temperature sintering in step S2 are: a sintering temperature of 500 DEG C, a sintering time of 20 h, and a temperature increase rate of 3 DEG C / min.

[0065] In this embodiment, the sodium source is sodium nitrate, sodium chloride, sodium acetate and sodium fluoride, and the manganese source is manganese acetate, manganese sulfate, manganese dioxide and dimanganese trioxide.

[0066] In this embodiment, N is Mo, W and B, the functional doping source is a corresponding carbonate, oxide, acetate and nitrate of element M, M is Al, Mg and K, and the phase transition inducing doping source is a corresponding dihydrate, oxide and carbide of element N.

[0067] Embodiment 4

[0068] The application discloses a high specific capacity sodium ion battery positive electrode material, which is sodium manganate oxide doped with an induced phase change element N and a functional doping element M. x Mn 1-y-z N y M z O2, wherein 0.22<=x<=0.6, 0

[0069] S1, raw material mixing: according to the stoichiometric ratio, corresponding sodium sources, manganese sources, induced phase change doping sources and functional doping sources are weighed and fully mixed to obtain premix;

[0070] S2, high-temperature sintering: the premix obtained in step S1 is sintered at high temperature, and cooled to room temperature, so that the sodium ion battery positive electrode material of the sodium manganate oxide is obtained.

[0071] In the embodiment, the high-temperature sintering in step S2 is performed at a sintering temperature of 1000 DEG C, a sintering time of 14 h and a heating rate of 3 DEG C / min.

[0072] In the embodiment, the sodium sources are sodium hydroxide, sodium nitrate, sodium chloride, sodium acetate and sodium fluoride. The manganese sources are manganese sulfate, manganese dioxide, dimanganese trioxide, manganese monoxide, trimanganese tetraoxide and basic manganese hydroxide.

[0073] In the embodiment, N is Mo and W, the functional doping sources are corresponding carbonates, oxides, acetates and nitrates of M elements; M is Cu, Zn, Mg and K; and the induced phase change doping sources are corresponding dihydrates, oxides and carbides of N elements.

[0074] Embodiment 5

[0075] The application discloses a high specific capacity sodium ion battery positive electrode material, which is sodium manganate oxide doped with an induced phase change element N and a functional doping element M. x Mn 1-y-z N y M z O2, wherein 0.22<=x<=0.6, 0

[0076] S1, raw material mixing: according to the stoichiometric ratio, corresponding sodium sources, manganese sources, induced phase change doping sources and functional doping sources are weighed and fully mixed to obtain premix;

[0077] S2, high-temperature sintering: the premix obtained in step S1 is subjected to high-temperature sintering, and cooled to room temperature, to obtain the jointly modified sodium manganate oxide positive electrode material for sodium-ion batteries.

[0078] In this embodiment, the high-temperature sintering in step S2 is performed at a sintering temperature of 900℃, a sintering time of 10h, and a heating rate of 3℃ / min.

[0079] In this embodiment, the sodium source is sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium nitrate, sodium chloride, sodium acetate, and sodium fluoride. The manganese source is manganese carbonate, manganese chloride, manganese nitrate, manganese acetate, manganese sulfate, manganese dioxide, dimanganese trioxide, manganese monoxide, trimanganese tetraoxide, and basic manganese hydroxide.

[0080] In this embodiment, N is Sc, V, Y, Nb, Mo, W, and B, the functional doping source is a corresponding carbonate, oxide, acetate, and nitrate of element M; M is Ti, Cr, Fe, Co, Ni, Cu, Zn, Zr, Al, Mg, and / or K; and the phase transition inducing doping source is a corresponding dihydrate, oxide, and carbide of element N.

[0081] Application Example 1

[0082] Na2CO3, MnCO3, and WO3 are uniformly mixed by ball milling at a molar ratio of 0.22:0.98:0.02, and then uniformly ground in an agate mortar. The mixture is heated to 950℃ at a heating rate of 2℃ / min in a muffle furnace, and then held at 950℃ for 15h. The furnace is naturally cooled to room temperature, to obtain Na 0.44 Mn 0.98 W 0.02 O2. The particle size of the particles is 2-10μm, and the thickness is about 1μm. The particles are regular hexagonal blocks, and the surface is smooth, indicating good crystallinity of the material. The surface morphology is shown in FIG. 1. Figure 1 Figure 2 The XRD of Na

[0083] ​The material was mixed evenly with acetylene black and polyvinylidene fluoride (PVDF) in a ratio of 8:1:1. N-methylpyrrolidone (NMP) was added as a dispersant. The mixture was then evenly coated onto aluminum foil and baked in a 100℃ oven for 12 hours before being stamped into a 12mm diameter positive electrode sheet. A sodium metal sheet was used as the negative electrode, Whatman GF / D as the separator, and 1mol / L NaClO4EC:DEC:FEC = 49:49:2v% as the electrolyte. The battery was assembled in a glove box filled with high-purity argon gas, where both oxygen and water pressures were below 1ppm. Charge-discharge tests were then conducted on a battery testing system under the following conditions: current density of 12mA / g and voltage range of 2-4V. The test results are as follows: Figure 3 and Figure 4 The image shows an observation of tunnel-type Na+. 0.44 Compared to MnO2, Na 0.44 Mn 0.98 W 0.02 The specific capacity of the O2 material was significantly improved, increasing from 110 mAh / g to 210 mAh / g. The main increase in capacity comes from the plateau around 2.2V, attributed to the presence of Mn. 3+ / Mn 4+ The redox properties are good. The reversibility of the charge-discharge curve is good, indicating that the polarization during the charge-discharge process is small, which is beneficial to improving the structural stability of the material. After 30 cycles, the capacity retention rate is 96.7%, which shows excellent cycle stability and significantly enhanced electrochemical performance.

[0084] Application Example 2

[0085] The material Na synthesized in Example 1 0.44 Mn 0.98 W 0.02 O2, acetylene black, and CMC were mixed evenly in a ratio of 8:1:1. Deionized water was added as a dispersant, and the mixture was evenly coated onto aluminum foil. The foil was then baked in a 100℃ oven for 12 hours, and subsequently stamped into a positive electrode sheet with a diameter of 12 mm. A sodium metal sheet was used as the negative electrode, Whatman GF / D as the separator, and 1 mol / L NaClO4 EC:DEC:FEC = 49:49:2v% as the electrolyte. The battery was placed in a glove box filled with high-purity argon gas, where both oxygen and water pressures were below 1 ppm. Charge-discharge tests were then conducted on a battery testing system. The test conditions included a current density of 12 mA / g and a voltage range of 2-4 V. The test results are as follows: Figure 5 After using water-based adhesives, Na 0.44 Mn 0.98 W 0.02O2 still has similar performance as before, the platform of charge-discharge curve is basically consistent, indicating that even using water-based binder, the bulk structure of the material is not damaged by water, and the water stability is good, and the electrochemical performance does not change, indicating that compared with general manganese oxides, Na 0.44 Mn 0.98 W 0.02 O2 has good structural stability, is stable to water, and the storage conditions of the material are not harsh, meeting the requirements of practical application.

[0086] Application Example 3

[0087] Na2CO3, MnCO3, Na2MoO4 were uniformly mixed by ball milling in a molar ratio of 0.2:0.98:0.02, then uniformly ground in an agate mortar, then heated to 950℃ at a heating rate of 2℃ / min in a muffle furnace, and then naturally cooled to room temperature in the furnace, to obtain Na 0.44 Mn 0.98 Mo 0.02 O2. The particle size of the particles is 2-5μm, the thickness is about 1μm, the size is not uniform, but all presents regular hexagonal morphology, and the crystallinity is good, and the surface morphology is as shown in Figure 6 . Figure 7 The XRD of the material shows that the material has very obvious main peaks from the layered structure, the space group is P63 / mmc, the PDF card is 2751, and the P2 main peak belonging to the layered structure appears, the diffraction intensity of the main peak is strong, representing good crystallinity of the material, and part of the impurity peaks from the raw materials appear, indicating that the doping concentration at this time is possibly high.

[0088] After the material is uniformly mixed with acetylene black and polyvinylidene fluoride (PVDF) in a ratio of 8:1:1, N-methyl pyrrolidone (NMP) is added as a dispersant, the material is uniformly coated on an aluminum foil, and then placed in a 100℃ oven for 12h, and then punched into a positive electrode sheet with a diameter of 12mm. With a metal sodium sheet as a negative electrode, whatman GF / D as a separator, 1mol / L NaClO4EC:DE C:FEC=49:49:2v% as an electrolyte, the battery is assembled in a glove box filled with high-purity argon with oxygen and water pressures below 1ppm, and then the charge-discharge test is carried out on a battery test system, the current density in the test condition is 12mA / g, and the voltage range is 2-4V, and the test results are as shown in Figure 8 and Figure 9 Compared with the tunnel type Na 0.44 MnO2, Na 0.44 Mn 0.98 Mo 0.02The specific capacity of the Na Mn W Al O2 material is greatly improved, and the specific capacity is increased from the original 110 mAh / g to 140 mAh / g. The main capacity growth part is derived from the platform around 2.2 V, which is attributed to the redox of Mn 3+ / Mn 4+ . The degree of reversibility of the charge-discharge curve is good, representing that the polarization in the charge-discharge process is small, which is beneficial to improve the structural stability of the material. In addition, the platform of the doped material is not so obvious, indicating that part of the phase change is inhibited. After 30 cycles, the capacity retention rate is 91.3%, and the electrochemical performance is improved.

[0089] Application Example 4

[0090] Na2CO3, MnCO3, WO3, Al2O3 are uniformly mixed by ball milling in a molar ratio of 0.22:0.93:0.02:0.025, and then uniformly ground in an agate mortar. Then, the mixture is heated to 950°C at a heating rate of 2°C / min in a muffle furnace and kept for 15 h, and then naturally cooled to room temperature in the furnace. Thus, Na 0.44 Mn 0.93 W 0.02 Al 0.05 O2 is obtained. XRD shows that the material is a pure layered structure. The material is uniformly mixed with acetylene black and polyvinylidene fluoride (PVDF) in a ratio of 8:1:1, and then organic solvent N-methyl pyrrolidone (NMP) is added as a dispersant. The material is uniformly coated on an aluminum foil, and then placed in a 100°C oven for 12 h and punched into a positive electrode sheet with a diameter of 12 mm. With a metal sodium sheet as the negative electrode, whatman GF / D as the separator, and 1 mol / L NaClO4 EC:DEC:FEC=49:49:2 v% as the electrolyte, the battery is assembled in a glove box filled with high-purity argon with oxygen and water pressures below 1 ppm, and then the charge-discharge test is performed on a battery test system. The current density in the test condition is 12 mA / g, and the voltage range is 2-4 V. The test results are shown in Figure 10 and Figure 11 Compared with the tunnel-type Na 0.44 MnO2, the specific capacity of the Na 0.44 Mn 0.93 W 0.02 Al 0.05 O2 material is greatly improved, and the specific capacity is increased from the original 110 mAh / g to 225 mAh / g, which is more than the capacity of the doped material alone. This may be because the functional doping elements promote the complete phase transition, causing further improvement of the sodium storage site. In addition, the trend of multiple platforms is inhibited, indicating that the functional elements can inhibit part of the phase change and further stabilize the structure. After 30 cycles of the battery material, the capacity retention rate is 90%, and the cycle stability is improved.

[0091] In summary, the method for doping sodium ion battery oxide positive electrode by using tungsten / molybdenum ion pair has remarkable effect, is simple and easy to operate, and is high in safety, not only improves the capacity of the material, but also retains the cycle performance of the material itself, and has wide research prospect and application value.

[0092] The above examples are only specific embodiments of the present application, which are described in detail, but cannot be understood as limiting the scope of the patent of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, and these obvious replacement forms all belong to the protection scope of the present application.

Claims

1. A high-specific-capacity sodium-ion battery cathode material, characterized in that: The positive electrode material is a sodium manganate oxide modified by co-doping with an induced phase change doping element N and a functional doping element M. The chemical formula of the co-doped and modified sodium manganate oxide is Na x Mn 1-y-z N y M z O2. The co-doped and modified sodium manganate oxide has a layered structure, where 0.22 ≤ x ≤ 0.6, 0 < y < 0.4, 0 < z < 0.

2. N is selected from one or two of Mo and W, and M is selected from one or more of Ti, Cr, Fe, Co, Ni, Cu, Zn, Zr, Al, Mg, and / or K.

2. A method for preparing the high specific capacity sodium-ion battery cathode material according to claim 1, characterized in that... Includes the following steps: S1. Raw material mixing: Weigh the corresponding sodium source, manganese source, phase change induced doping source and functional doping source according to the stoichiometric ratio, mix them thoroughly and evenly to obtain the premix; S2. High-temperature sintering: The premix obtained in step S1 is sintered at high temperature and cooled to room temperature to obtain the co-modified sodium manganate oxide sodium-ion battery cathode material.

3. The method for preparing the high specific capacity sodium-ion battery cathode material according to claim 2, characterized in that: The conditions for high-temperature sintering in step S2 are: sintering temperature of 500-1200℃, sintering time of 5-20h, and heating rate of 1-5℃ / min.

4. The method for preparing the high specific capacity sodium-ion battery cathode material according to claim 2, characterized in that: The sodium source is one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium nitrate, sodium chloride, sodium acetate, and / or sodium fluoride.

5. The method for preparing the high specific capacity sodium-ion battery cathode material according to claim 2, characterized in that: The manganese source is one or more of the following: manganese carbonate, manganese chloride, manganese nitrate, manganese acetate, manganese sulfate, manganese dioxide, manganese trioxide, manganese monoxide, and manganese tetroxide.

6. The method for preparing the high specific capacity sodium-ion battery cathode material according to claim 2, characterized in that: The functional dopant source is one or more of the carbonates, oxides, acetates and / or nitrates corresponding to element M.

7. The method for preparing the high specific capacity sodium-ion battery cathode material according to claim 2, characterized in that: The induced phase transition doping source is one or more of the dihydrate, oxide and / or carbide of the N element; the dihydrate is sodium tungstate dihydrate or sodium molybdate dihydrate.

8. The method for preparing the high specific capacity sodium-ion battery cathode material according to claim 7, characterized in that: The induced phase transition doping source is selected from one or more of tungsten trioxide, tungsten dioxide and / or tungsten carbide.

9. The method for preparing the high specific capacity sodium-ion battery cathode material according to claim 7, characterized in that: The induced phase transition doping source is selected from one or more of molybdenum trioxide, molybdenum dioxide, and / or molybdenum carbide.

10. A sodium-ion battery, characterized in that: The high specific capacity sodium-ion battery cathode material described in claim 1 is used as the cathode material.

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