Mos 2 coated zr-doped sodium battery positive electrode material, and preparation method and use therefor

Abstract

A MoS 2 coated Zr-doped sodium battery positive electrode material, and a preparation method and use therefor. The sodium battery positive electrode material comprises a MoS 2 shell and a sodium battery core. The sodium battery core is a layered transition metal oxide, and the chemical formula is: NaNi aFe bMn 1-a-b-cZr cO 2; wherein 0.1≤a＜0.5, 0.2≤b＜0.4, 0＜c＜0.08. The sodium battery positive electrode material can reduce the difficulty in embedding and removing sodium ions, increase the transportation and diffusion rate of same, such that the specific capacity of the battery is improved, the stability of the material crystal structure is improved, the cycle performance of the battery is improved, the service life of the battery is prolonged, and large-scale promotion and application are facilitated.

Description

A MoS2-coated Zr-doped sodium cathode material and its preparation method and application Technical Field

[0001] The present application belongs to the field of battery manufacturing technology and relates to a sodium battery positive electrode material, and in particular to a MoS2-coated Zr-doped sodium battery positive electrode material and its preparation method and application. Background Art

[0002] 70% of the world's lithium resources are primarily located in South America, while my country holds only 6% of global reserves. Mining is difficult, costly, and driven by high downstream demand, making lithium resources highly dependent on imports. Currently, domestic companies face frequent restrictions on overseas lithium mining investments, and the growth rate of global lithium resource discovery has slowed in recent years. Therefore, replacing lithium batteries with sodium-ion batteries in relatively low-end applications holds significant strategic significance.

[0003] Currently, there are over 100 types of sodium battery cathode materials, but the three main ones are transition metal oxides, polyanionic compounds, and Prussian blue (white) compounds. Transition metal oxides are further divided into layered transition metal oxides and tunnel-type transition metal oxides. While transition metal oxides have relatively high specific capacities, they suffer from poor stability during electrochemical reactions. Therefore, improving their stability is a key research area in the field of transition metal oxide cathode materials.

[0004] In addition, the radius of sodium ions (0.102nm) is larger than that of lithium ions (0.076nm), so sodium ions are relatively stable in the rigid structure and difficult to reversibly intercalate and deintercalate. Even if intercalation and deintercalation occur, the kinetics of sodium ion insertion and extraction are very slow and can easily cause irreversible phase changes in the structure of the electrode material, thereby reducing the battery's cycle performance.

[0005] It can be seen from this that how to provide a sodium battery positive electrode material and its preparation method to reduce the difficulty of sodium ion insertion and extraction, thereby accelerating its transport and diffusion rate, increasing the specific capacity of the battery, while improving the stability of the material's crystal structure, improving the battery's cycle performance, and extending its service life has become an urgent problem that technical personnel in this field need to solve.

[0006] Summary of the Invention

[0007] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0008] In view of the shortcomings of the existing technology, the purpose of this application is to provide a MoS2-coated Zr-doped sodium cathode material and its preparation method and application. The sodium cathode material reduces the difficulty of sodium ion insertion and extraction, thereby accelerating its transport and diffusion rate, increasing the specific capacity of the battery, and at the same time enhancing the stability of the material's crystal structure, improving the battery's cycle performance, extending its service life, and facilitating large-scale promotion and application.

[0009] To achieve this goal, this application adopts the following technical solutions:

[0010] In a first aspect, the present application provides a MoS2-coated Zr-doped sodium battery positive electrode material, wherein the sodium battery positive electrode material comprises a MoS2 shell and a sodium battery core.

[0011] The sodium electrode core is a layered transition metal oxide with the chemical formula: NaNi a Fe b Mn 1-a-b-c Zr c O2.

[0012] Wherein: 0.1≤a<0.5, 0.2≤b<0.4, 0<c<0.08, for example, a=0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4 or 0.45, b=0.2, 0.22, 0.24, 0.26, 0.28, 0.3, 0.32, 0.34, 0.36 or 0.38, c=0.01, 0.02, 0.03, 0.04, 0.05, 0.06 or 0.07, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0013] The sodium battery positive electrode material provided by the present application dopes the metal element Zr into the sodium battery core of the layered transition metal oxide, thereby improving the stability of the atoms in the material lattice. At the same time, in order to avoid the possibility that Zr doping may slow down the deintercalation rate of sodium ions during charging and discharging, the present application coats a layer of MoS2 shell on the surface of the sodium battery core, which can increase the migration channel of sodium ions and accelerate their transport and diffusion rate during long cycles, and can also reinforce the coating layer to prevent it from falling off. Ultimately, with the synergistic effect between Zr doping and MoS2 coating, the specific capacity of the battery is significantly improved, while the stability of the material crystal structure is improved, the cycle performance of the battery is improved, and its service life is extended, which is conducive to large-scale promotion and application.

[0014] In one embodiment, the mass of the MoS2 shell is 2%-3% of the total mass of the sodium positive electrode material, for example, it can be 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9% or 3%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0015] In one embodiment, the average particle size of the sodium positive electrode material is 3-16 μm, for example, it can be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or 16 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0016] In a second aspect, the present application provides a method for preparing the sodium cathode material as described in the first aspect, the preparation method comprising the following steps:

[0017] (1) mixing nickel salt, iron salt, manganese salt and deionized water to obtain a ternary salt solution;

[0018] (2) mixing a zirconium salt and deionized water to obtain a zirconium salt solution;

[0019] (3) mixing a ternary salt solution, a zirconium salt solution, a precipitant solution, and a complexing agent solution to perform a coprecipitation reaction to obtain a mixed solution containing a sodium electrode precursor;

[0020] (4) removing the supernatant of the mixed solution in step (3), adding a mixed solution of MoS2 and nano-glue adhesive, stirring evenly and separating the solid and liquid, and then washing, drying and screening in sequence to obtain a MoS2-coated Zr-doped sodium electrode precursor;

[0021] (5) Mixing the sodium source and the sodium battery precursor described in step (4) and calcining them to obtain a MoS2-coated Zr-doped sodium battery positive electrode material.

[0022] Among them, step (1) and step (2) are performed in no particular order.

[0023] The preparation method provided in the present application directly adds a zirconium salt solution during the co-precipitation reaction by wet doping, so that the doping of zirconium ions is more uniform. At the same time, the precursor is coated with the MoS2 finished product, avoiding the problems of insufficient reaction and side reactions in the in-situ generation of the coating layer, thereby improving the uniformity of the coating.

[0024] In one embodiment, the nickel salt, iron salt and manganese salt in step (1) are independently any one of sulfate, nitrate, acetate or chloride salts of the corresponding metal ions, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of sulfate and nitrate, a combination of nitrate and acetate, a combination of acetate and chloride, a combination of sulfate, nitrate and acetate, or a combination of nitrate, acetate and chloride.

[0025] In one embodiment, the molar ratio of nickel ions, iron ions and manganese ions in the ternary salt solution of step (1) is (1-5):(2-4):(3-6), for example, it can be 1:2:3, 2:3:4, 3:4:5, 4:3:6 or 5:2:3, but is not limited to the listed values, and other values ​​not listed within this numerical range are also applicable.

[0026] In one embodiment, the total concentration of metal ions in the ternary salt solution in step (1) is 1-3 mol / L, for example, 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L, 2.4 mol / L, 2.6 mol / L, 2.8 mol / L or 3 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0027] In one embodiment, the zirconium salt in step (2) comprises any one or a combination of at least two of zirconium sulfate, zirconium nitrate, zirconium acetate or zirconium chloride. Typical but non-limiting combinations include a combination of zirconium sulfate and zirconium nitrate, a combination of zirconium nitrate and zirconium acetate, a combination of zirconium acetate and zirconium chloride, a combination of zirconium sulfate, zirconium nitrate and zirconium acetate, or a combination of zirconium nitrate, zirconium acetate and zirconium chloride.

[0028] In one embodiment, the zirconium ion concentration in the zirconium salt solution in step (2) is 0.01-0.5 mol / L, for example, it can be 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L or 0.5 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0029] In one embodiment, the mixing rate of the ternary salt solution in step (3) is 5-10 L / h, for example, 5 L / h, 5.5 L / h, 6 L / h, 6.5 L / h, 7 L / h, 7.5 L / h, 8 L / h, 8.5 L / h, 9 L / h, 9.5 L / h or 10 L / h, but is not limited to the listed values, and other values ​​not listed within this numerical range are also applicable.

[0030] In one embodiment, the mixing rate of the zirconium salt solution in step (3) is 1-3 L / h, for example, 1 L / h, 1.2 L / h, 1.4 L / h, 1.6 L / h, 1.8 L / h, 2 L / h, 2.2 L / h, 2.4 L / h, 2.6 L / h, 2.8 L / h or 3 L / h, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0031] In one embodiment, the precipitant solution in step (3) comprises any one or a combination of at least two of sodium hydroxide solution, potassium hydroxide solution or sodium carbonate solution. Typical but non-limiting combinations include a combination of sodium hydroxide solution and potassium hydroxide solution, a combination of potassium hydroxide solution and sodium carbonate solution, a combination of sodium hydroxide solution and sodium carbonate solution, or a combination of sodium hydroxide solution, potassium hydroxide solution and sodium carbonate solution. Sodium hydroxide solution may further be selected.

[0032] In one embodiment, the complexing agent solution in step (3) comprises any one of ammonia water, oxalic acid solution or EDTA solution, or a combination of at least two of them. Typical but non-limiting combinations include a combination of ammonia water and oxalic acid solution, a combination of oxalic acid solution and EDTA solution, a combination of ammonia water and EDTA solution, or a combination of ammonia water, oxalic acid solution and EDTA solution. Ammonia water can further be selected.

[0033] In one embodiment, the coprecipitation reaction in step (3) is carried out in an atmosphere of protective gas, and the protective gas includes any one or a combination of at least two of nitrogen, helium or argon. Typical but non-limiting combinations include a combination of nitrogen and helium, a combination of helium and argon, a combination of nitrogen and argon, or a combination of nitrogen, helium and argon, and nitrogen can further be selected.

[0034] In one embodiment, the pH value of the solution for the coprecipitation reaction in step (3) is 9-12, for example, 9, 9.5, 10, 10.5, 11, 11.5 or 12, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0035] In one embodiment, the temperature of the coprecipitation reaction in step (3) is 20-80°C, for example, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0036] In one embodiment, the coprecipitation reaction time in step (3) is 50-200h, for example, it can be 50h, 60h, 70h, 80h, 90h, 100h, 110h, 120h, 130h, 140h, 150h, 160h, 170h, 180h, 190h or 200h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] In one embodiment, the amount of the mixed solution of MoS2 and nano-glue adhesive added in step (4) is 100-500L, for example, it can be 100L, 150L, ​​200L, 250L, 300L, 350L, 400L, 450L or 500L, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0038] In one embodiment, the stirring time in step (4) is 20-60 min, for example, it can be 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] In one embodiment, the solid-liquid separation in step (4) comprises centrifugation and / or filtration.

[0040] In one embodiment, step (4) is performed by washing until the sodium precursor is neutral.

[0041] In one embodiment, the drying temperature in step (4) is 70-180°C, for example, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C or 180°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] In one embodiment, the drying time in step (4) is 10-25 hours, for example, it can be 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours, 24 hours or 25 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] In one embodiment, the sodium source in step (5) includes sodium carbonate and / or sodium bicarbonate, and can further be sodium carbonate.

[0044] In one embodiment, the temperature of the calcination treatment in step (5) is 400-700°C, for example, it can be 400°C, 450°C, 500°C, 550°C, 600°C, 650°C or 700°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] In one embodiment, the calcination time in step (5) is 5-20 hours, for example, 5 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours or 20 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] In one embodiment, after the calcination treatment in step (5), the sodium cathode material is crushed and sieved in sequence.

[0047] As an optional technical solution of the second aspect of the present application, the preparation method comprises the following steps:

[0048] (1) mixing nickel salt, iron salt, manganese salt and deionized water to obtain a ternary salt solution with a total metal ion concentration of 1-3 mol / L; the nickel salt, iron salt and manganese salt are independently any one of sulfate, nitrate, acetate or chloride salts of the corresponding metal ions, or a combination of at least two thereof; the molar ratio of nickel ion, iron ion and manganese ion in the ternary salt solution is (1-5):(2-4):(3-6);

[0049] (2) mixing a zirconium salt and deionized water to obtain a zirconium salt solution having a zirconium ion concentration of 0.01-0.5 mol / L; the zirconium salt comprises any one of zirconium sulfate, zirconium nitrate, zirconium acetate, or zirconium chloride, or a combination of at least two thereof;

[0050] (3) adding the ternary salt solution to the reactor at a rate of 5-10 L / h, and simultaneously adding the zirconium salt solution at a rate of 1-3 L / h, and adjusting the pH value of the solution in the reactor to 9-12 by adding sodium hydroxide solution and ammonia water in a nitrogen atmosphere, and coprecipitating the reaction at 20-80°C for 50-200 hours to obtain a mixed solution containing a sodium electrode precursor;

[0051] (4) stopping the feeding of the ternary salt solution, the zirconium salt solution, the sodium hydroxide solution and the ammonia solution, and stopping the stirring for 10-30 min, removing the supernatant of the mixed solution in step (3), adding 100-500 L of a mixed solution of MoS2 and a nano-glue adhesive, stirring for 20-60 min and centrifuging and / or filtering to wash to neutrality, drying at 70-180 ° C for 10-25 h, and sieving to obtain a MoS2-coated Zr-doped sodium electrode precursor;

[0052] (5) Mixing sodium carbonate and the sodium battery precursor described in step (4) and calcining them at 400-700° C. for 5-20 h, crushing and screening them after cooling to obtain MoS2-coated Zr-doped sodium battery positive electrode material.

[0053] Among them, step (1) and step (2) are performed in no particular order.

[0054] In a third aspect, the present application provides a sodium ion battery, which comprises the sodium cathode material as described in the first aspect.

[0055] The numerical range described in this application includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0056] Compared with the prior art, the present invention has the following advantages:

[0057] (1) The sodium cathode material provided by the present application is doped with the metal element Zr in the sodium core of the layered transition metal oxide, thereby improving the stability of the atoms in the material lattice. At the same time, in order to prevent Zr doping from slowing down the deintercalation rate of sodium ions during charging and discharging, the present application coats a layer of MoS2 shell on the surface of the sodium core. During the long cycle process, it can increase the migration channel of sodium ions, accelerate their transport and diffusion rate, and reinforce the coating layer to prevent them from falling off. Ultimately, the synergistic effect between Zr doping and MoS2 coating significantly improves the specific capacity of the battery, while improving the stability of the material crystal structure, improving the cycle performance of the battery, and extending its service life, which is conducive to large-scale promotion and application;

[0058] (2) The preparation method provided in the present application directly adds a zirconium salt solution during the co-precipitation reaction by wet doping, so that the doping of zirconium ions is more uniform. At the same time, the precursor is coated with the MoS2 finished product, avoiding the problems of insufficient reaction and side reactions in the in-situ generation of the coating layer, thereby improving the uniformity of the coating.

[0059] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0060] The technical solution of this application is further explained below through specific implementation methods.

[0061] Example 1

[0062] This embodiment provides a MoS2-coated Zr-doped sodium cathode material and a preparation method thereof, the preparation method comprising the following steps:

[0063] (1) mixing nickel sulfate, iron sulfate, manganese sulfate, and deionized water to obtain a ternary salt solution having a total metal ion concentration of 2 mol / L; wherein the molar ratio of nickel ions, iron ions, and manganese ions in the ternary salt solution is 2:2:6;

[0064] (2) mixing zirconium sulfate and deionized water to obtain a zirconium salt solution with a zirconium ion concentration of 0.05 mol / L;

[0065] (3) adding the ternary salt solution to the reactor at a rate of 5 L / h, and simultaneously adding the zirconium salt solution at a rate of 2 L / h. In a nitrogen atmosphere, sodium hydroxide solution and ammonia water were added to adjust the pH value of the solution in the reactor to 10.2±1. The coprecipitation reaction was carried out at 50°C for 72 hours to obtain a mixed solution containing a sodium electrode precursor.

[0066] (4) Stop feeding the ternary salt solution, zirconium salt solution, sodium hydroxide solution and ammonia solution, and stop stirring for 30 minutes, remove the supernatant of the mixed solution in step (3), add 500L of a mixed solution of MoS2 and nano-glue adhesive, stir for 60 minutes and centrifuge, wash to neutrality, dry at 100°C for 15 hours, and sieve to obtain MoS2-coated Zr-doped sodium electrode precursor;

[0067] (5) Mixing sodium carbonate and the sodium battery precursor described in step (4) and calcining them at 500° C. for 15 h, crushing and screening them after cooling to obtain MoS2-coated Zr-doped sodium battery positive electrode material.

[0068] The sodium cathode material obtained in this embodiment includes a MoS2 shell and a sodium core, wherein the sodium core is a layered transition metal oxide with the chemical formula: NaNi 0.2 Fe 0.2 Mn 0.59 Zr 0.01 O2; the mass of the MoS2 shell is 3% of the total mass of the sodium-based positive electrode material; the average particle size of the sodium-based positive electrode material is 16 μm.

[0069] Example 2

[0070] This embodiment provides a MoS2-coated Zr-doped sodium cathode material and a preparation method thereof, the preparation method comprising the following steps:

[0071] (1) mixing nickel nitrate, ferric nitrate, manganese nitrate and deionized water to obtain a ternary salt solution with a total metal ion concentration of 2 mol / L; the molar ratio of nickel ion, iron ion and manganese ion in the ternary salt solution is 1:4:5;

[0072] (2) mixing zirconium nitrate and deionized water to obtain a zirconium salt solution having a zirconium ion concentration of 0.5 mol / L;

[0073] (3) adding the ternary salt solution to the reactor at a rate of 10 L / h, and simultaneously adding the zirconium salt solution at a rate of 1 L / h. In a nitrogen atmosphere, sodium hydroxide solution and ammonia water were added to adjust the pH value of the solution in the reactor to 10.5±1. The coprecipitation reaction was carried out at 80°C for 50 hours to obtain a mixed solution containing a sodium electrode precursor.

[0074] (4) stopping the feeding of the ternary salt solution, the zirconium salt solution, the sodium hydroxide solution and the ammonia solution, and stopping the stirring for 10 minutes, removing the supernatant of the mixed solution in step (3), adding 100 L of a mixed solution of MoS2 and a nano-glue adhesive, stirring for 20 minutes and washing after centrifugation to neutrality, drying at 150 ° C for 10 hours, and sieving to obtain a MoS2-coated Zr-doped sodium electrode precursor;

[0075] (5) Mixing sodium carbonate and the sodium battery precursor described in step (4) and calcining them at 400° C. for 18 h, crushing and screening them after cooling to obtain MoS2-coated Zr-doped sodium battery positive electrode material.

[0076] The sodium cathode material obtained in this embodiment includes a MoS2 shell and a sodium core, wherein the sodium core is a layered transition metal oxide with the chemical formula: NaNi 0.1 Fe 0.39 Mn 0.49 Zr 0.02 O2; the mass of the MoS2 shell is 2% of the total mass of the sodium-based positive electrode material; the average particle size of the sodium-based positive electrode material is 3 μm.

[0077] Example 3

[0078] This embodiment provides a MoS2-coated Zr-doped sodium cathode material and a preparation method thereof. The preparation method is the same as that in Example 1 except that the ternary salts are respectively changed to nickel chloride, ferric chloride and manganese chloride, and the zirconium salt is changed to zirconium chloride. Therefore, the remaining steps and conditions are the same as those in Example 1, and therefore will not be repeated here.

[0079] The sodium cathode material obtained in this embodiment includes a MoS2 shell and a sodium core, wherein the sodium core is a layered transition metal oxide with the chemical formula: NaNi 0.2 Fe 0.2 Mn 0.59 Zr 0.01O2; the mass of the MoS2 shell is 3% of the total mass of the sodium-based positive electrode material; the average particle size of the sodium-based positive electrode material is 16 μm.

[0080] Example 4

[0081] This embodiment provides a MoS2-coated Zr-doped sodium cathode material and a preparation method thereof. Except for changing the molar ratio of nickel ions, iron ions and manganese ions in the ternary salt solution to 3:4:4, the remaining steps and conditions are the same as those in Example 1, so they are not repeated here.

[0082] The sodium cathode material obtained in this embodiment includes a MoS2 shell and a sodium core, wherein the sodium core is a layered transition metal oxide with the chemical formula: NaNi 0.25 Fe 0.35 Mn 0.35 Zr 0.05 O2; the mass of the MoS2 shell is 3% of the total mass of the sodium-based positive electrode material; the average particle size of the sodium-based positive electrode material is 16 μm.

[0083] Comparative Example 1

[0084] This comparative example provides a MoS2-coated sodium cathode material and a preparation method thereof, the preparation method comprising the following steps:

[0085] (1) mixing nickel sulfate, iron sulfate, manganese sulfate, and deionized water to obtain a ternary salt solution having a total metal ion concentration of 2 mol / L; wherein the molar ratio of nickel ions, iron ions, and manganese ions in the ternary salt solution is 2:2:6;

[0086] (2) adding a ternary salt solution to the reactor at a rate of 5 L / h, and simultaneously adding sodium hydroxide solution and ammonia water to adjust the pH value of the solution in the reactor to 10.2 ± 1 in a nitrogen atmosphere, and coprecipitating at 50 ° C for 72 h to obtain a mixed solution containing a sodium electrode precursor;

[0087] (3) Stop feeding the ternary salt solution, sodium hydroxide solution and ammonia solution, and stop stirring for 30 minutes, remove the supernatant of the mixed solution in step (2), add 500L of a mixed solution of MoS2 and nano-glue adhesive, stir for 60 minutes and centrifuge, wash to neutrality, dry at 100°C for 15 hours, and sieve to obtain a MoS2-coated sodium electrode precursor;

[0088] (4) Mixing sodium carbonate and the sodium battery precursor described in step (3) and calcining them at 500° C. for 15 h, and then crushing and screening them after cooling to obtain a MoS2-coated sodium battery positive electrode material.

[0089] The sodium positive electrode material obtained in this comparative example includes a MoS2 shell and a sodium core, wherein the sodium core is a layered transition metal oxide with the chemical formula: NaNi 0.2 Fe 0.2 Mn 0.6 O2; the mass of the MoS2 shell is 3% of the total mass of the sodium-based positive electrode material; the average particle size of the sodium-based positive electrode material is 16 μm.

[0090] Comparative Example 2

[0091] This comparative example provides a Zr-doped sodium cathode material and a preparation method thereof, the preparation method comprising the following steps:

[0092] (1) mixing nickel sulfate, iron sulfate, manganese sulfate, and deionized water to obtain a ternary salt solution having a total metal ion concentration of 2 mol / L; wherein the molar ratio of nickel ions, iron ions, and manganese ions in the ternary salt solution is 2:2:6;

[0093] (2) mixing zirconium sulfate and deionized water to obtain a zirconium salt solution with a zirconium ion concentration of 0.05 mol / L;

[0094] (3) adding the ternary salt solution to the reactor at a rate of 5 L / h, and simultaneously adding the zirconium salt solution at a rate of 2 L / h. In a nitrogen atmosphere, sodium hydroxide solution and ammonia water were added to adjust the pH value of the solution in the reactor to 10.2±1. The coprecipitation reaction was carried out at 50°C for 72 hours to obtain a mixed solution containing a sodium electrode precursor.

[0095] (4) centrifuging the mixed solution in step (3) and washing it to neutrality, drying it at 100° C. for 15 h, and sieving it to obtain a Zr-doped sodium electrolyte precursor;

[0096] (5) Mixing sodium carbonate and the sodium battery precursor described in step (4) and calcining them at 500° C. for 15 h, and then crushing and screening them after cooling to obtain a Zr-doped sodium battery positive electrode material.

[0097] The sodium cathode material obtained in this comparative example is a layered transition metal oxide with the chemical formula: NaNi 0.2 Fe 0.2 Mn 0.59 Zr 0.01 O2; the average particle size of the sodium positive electrode material is 12 μm.

[0098] Comparative Example 3

[0099] This comparative example provides a sodium cathode material and a preparation method thereof, the preparation method comprising the following steps:

[0100] (1) mixing nickel sulfate, iron sulfate, manganese sulfate, and deionized water to obtain a ternary salt solution having a total metal ion concentration of 2 mol / L; wherein the molar ratio of nickel ions, iron ions, and manganese ions in the ternary salt solution is 2:2:6;

[0101] (2) adding a ternary salt solution to the reactor at a rate of 5 L / h, and simultaneously adding sodium hydroxide solution and ammonia water to adjust the pH value of the solution in the reactor to 10.2 ± 1 in a nitrogen atmosphere, and coprecipitating at 50 ° C for 72 h to obtain a mixed solution containing a sodium electrode precursor;

[0102] (3) centrifuging the mixed solution in step (2) and washing it to neutrality, drying it at 100° C. for 15 h, and sieving it to obtain a sodium electrode precursor;

[0103] (4) Mixing sodium carbonate and the sodium battery precursor described in step (3) and calcining them at 500° C. for 15 h, crushing and screening them after cooling to obtain a sodium battery positive electrode material.

[0104] The sodium cathode material obtained in this comparative example is a layered transition metal oxide with the chemical formula: NaNi 0.2 Fe 0.2 Mn 0.56 O2; the average particle size of the sodium positive electrode material is 12 μm.

[0105] Performance Testing

[0106] At 25°C, the sodium cathode materials obtained in Examples 1-4 and Comparative Examples 1-3 were used as the main positive electrode materials, and hard carbon was used as the negative electrode. They were assembled into CR2032 button batteries, and then the electrochemical performance was tested at a voltage range of 2.0-4.0 V and a discharge current density of 20 mA / g. After 500 cycles, the battery discharge specific capacity test results are shown in Table 1 below.

[0107] Table 1

[0108] It can be seen from Table 1 that the button battery assembled using the sodium-based positive electrode material provided in Examples 1-4 as the positive electrode has a first discharge capacity of up to 159.0 mAh / g at a rate of 0.1C, a capacity retention rate of up to 98.9% after 500 charge-discharge cycles, and a first efficiency of up to 98.50%; while the first discharge capacity of the sodium-based positive electrode material without any treatment is only 145.3 mAh / g, the first efficiency is only 90.32%, and the capacity retention rate after 500 charge-discharge cycles is only 75.9%; in addition, the first discharge capacity, first efficiency, and 500 charge-discharge cycles of the sodium-based positive electrode material that is only doped or coated are all inferior to those of the doped and coated sodium-based positive electrode material obtained in Examples 1-4. It can be seen that the discharge capacity, first efficiency, and cycle performance of the battery made from the MoS2-coated Zr-doped sodium-based positive electrode material provided in this application are superior to those of conventional sodium-ion battery positive electrode materials.

[0109] It can be seen that the sodium positive electrode material provided by the present application does the metal element Zr in the sodium core of the layered transition metal oxide, which improves the stability of the atoms in the material lattice. At the same time, in order to avoid the possibility that Zr doping may slow down the deintercalation rate of sodium ions during charging and discharging, the present application coats a layer of MoS2 shell on the surface of the sodium core. During the long cycle process, it can not only increase the migration channel of sodium ions and accelerate their transport and diffusion rate, but also strengthen the coating layer to prevent it from falling off. Finally, with the synergistic effect between Zr doping and MoS2 coating, the specific capacity of the battery is significantly improved, while the stability of the material crystal structure is improved, the cycle performance of the battery is improved, and its service life is extended, which is conducive to large-scale promotion and application.

[0110] In addition, the preparation method provided in the present application directly adds a zirconium salt solution during the co-precipitation reaction by wet doping, so that the doping of zirconium ions is more uniform. At the same time, the precursor is coated with the MoS2 finished product, avoiding the problems of insufficient reaction and side reactions in the in-situ generation of the coating layer, thereby improving the uniformity of the coating.

[0111] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of this application. It should be understood that the above is only a specific embodiment of this application and is not intended to limit this application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application should be included in the scope of protection of this application.

Claims

1. A MoS 2 Zr-doped sodium cathode materials include MoS 2 outer shell and sodium core; The sodium electrode core is a layered transition metal oxide with the chemical formula: NaNi a Fe b Mn 1-a-b-c Zr c O 2 ; in: 0.1≤a<0.5, 0.2≤b<0.4, 0<c<0.

08.

2. The sodium positive electrode material according to claim 1, in, The MoS 2 The mass of the shell is 2%-3% of the total mass of the sodium positive electrode material; Optionally, the average particle size of the sodium positive electrode material is 3-16 μm.

3. A method for preparing the sodium positive electrode material as claimed in claim 1 or 2 The following steps are involved: (1) mixing nickel salt, iron salt, manganese salt and deionized water to obtain a ternary salt solution; (2) mixing a zirconium salt and deionized water to obtain a zirconium salt solution; (3) mixing a ternary salt solution, a zirconium salt solution, a precipitant solution and a complexing agent solution to perform a coprecipitation reaction to obtain a mixed solution containing a sodium electrode precursor; (4) Remove the supernatant of the mixed solution in step (3), add MoS 2 The mixed solution of the nano-adhesive binder is stirred evenly and separated into solid and liquid, and then washed, dried and sieved in sequence to obtain MoS 2 Coating Zr-doped sodium battery precursor; (5) Mixing the sodium source and the sodium precursor in step (4) and calcining to obtain MoS 2 Coating Zr-doped sodium positive electrode material; There is no particular order in which steps (1) and (2) are performed.

4. The preparation method according to claim 3, in, The nickel salt, iron salt and manganese salt in step (1) are independently any one of sulfate, nitrate, acetate or chloride of the corresponding metal ions or a combination of at least two thereof; Optionally, the molar ratio of nickel ions, iron ions and manganese ions in the ternary salt solution of step (1) is (1-5):(2-4):(3-6); Optionally, the total concentration of metal ions in the ternary salt solution in step (1) is 1-3 mol / L.

5. The preparation method according to claim 3 or 4, in, The zirconium salt in step (2) includes any one of zirconium sulfate, zirconium nitrate, zirconium acetate or zirconium chloride, or a combination of at least two thereof; Optionally, the zirconium ion concentration in the zirconium salt solution in step (2) is 0.01-0.5 mol / L.

6. The preparation method according to any one of claims 3 to 5, in, The mixing rate of the ternary salt solution in step (3) is 5-10 L / h; Optionally, the mixing rate of the zirconium salt solution in step (3) is 1-3 L / h; Optionally, the precipitant solution in step (3) comprises any one of sodium hydroxide solution, potassium hydroxide solution or sodium carbonate solution or a combination of at least two thereof, and further can be sodium hydroxide solution; Optionally, the complexing agent solution in step (3) comprises any one of ammonia water, oxalic acid solution or EDTA solution or a combination of at least two thereof, and may further be ammonia water; Optionally, the coprecipitation reaction in step (3) is carried out in an atmosphere of a protective gas, and the protective gas comprises any one or a combination of at least two of nitrogen, helium or argon, and may further be nitrogen; Optionally, the pH value of the solution in the coprecipitation reaction in step (3) is 9-12; Optionally, the temperature of the coprecipitation reaction in step (3) is 20-80°C; Optionally, the coprecipitation reaction time in step (3) is 50-200h.

7. The preparation method according to any one of claims 3 to 6, in, Step (4) MoS 2 The amount of the mixed solution added with the nano glue adhesive is 100-500L; Optionally, the stirring time in step (4) is 20-60 min; Optionally, the solid-liquid separation method in step (4) includes centrifugation and / or filtration; Optionally, the step (4) is washing until the sodium electrode precursor is neutral; Optionally, the drying temperature in step (4) is 70-180° C. and the drying time is 10-25 h.

8. The preparation method according to any one of claims 3 to 7, in, The sodium source in step (5) includes sodium carbonate and / or sodium bicarbonate, and may further be sodium carbonate; Optionally, the calcination treatment in step (5) is carried out at a temperature of 400-700° C. and for a time of 5-20 h; Optionally, after the calcination treatment in step (5), the sodium positive electrode material is crushed and sieved in sequence.

9. The preparation method according to any one of claims 3 to 8, in, The preparation method comprises the following steps: (1) mixing nickel salt, iron salt, manganese salt and deionized water to obtain a ternary salt solution with a total metal ion concentration of 1-3 mol / L; the nickel salt, iron salt and manganese salt are independently any one of sulfate, nitrate, acetate or chloride of the corresponding metal ion or a combination of at least two thereof; the molar ratio of nickel ion, iron ion and manganese ion in the ternary salt solution is (1-5):(2-4):(3-6); (2) mixing a zirconium salt and deionized water to obtain a zirconium salt solution having a zirconium ion concentration of 0.01-0.5 mol / L; the zirconium salt comprises any one of zirconium sulfate, zirconium nitrate, zirconium acetate or zirconium chloride, or a combination of at least two thereof; (3) adding a ternary salt solution to the reactor at a rate of 5-10 L / h, and adding a zirconium salt solution at a rate of 1-3 L / h, adding sodium hydroxide solution and ammonia water to adjust the pH value of the solution in the reactor to 9-12 in a nitrogen atmosphere, and coprecipitating at 20-80° C. for 50-200 hours to obtain a mixed solution containing a sodium electrode precursor; (4) Stop feeding the ternary salt solution, zirconium salt solution, sodium hydroxide solution and ammonia water, and stop stirring for 10-30 minutes, remove the supernatant of the mixed solution in step (3), add MoS 2 The mixed solution of 100-500 L of nano glue adhesive is stirred for 20-60 min and centrifuged and / or filtered to be neutral, dried at 70-180 ° C for 10-25 h, and sieved to obtain MoS 2 Coating Zr-doped sodium battery precursor; (5) Mixing sodium carbonate and the sodium precursor of step (4) and calcining them at 400-700° C. for 5-20 h, and then crushing and screening them after cooling to obtain MoS 2 Coating Zr-doped sodium positive electrode material; There is no particular order in which steps (1) and (2) are performed.

10. A sodium ion battery comprising the sodium positive electrode material according to claim 1 or 2.

Images