Potassium-nickel-iron-manganese composite hydroxide, sodium ion cathode material and its preparation method

Abstract

This disclosure belongs to the field of sodium-ion battery cathode material technology, and discloses potassium-nickel-iron-manganese composite hydroxide, sodium-ion cathode material and its preparation method. The preparation method of potassium-nickel-iron-manganese composite hydroxide involves adding additives during co-precipitation to dope metal / non-metal ions. Compared with dry mixing and sintering, the ion distribution in the precursor co-precipitation is more uniform. Furthermore, in this disclosure, potassium ions are doped after co-precipitation. At this time, the morphology of the original particles is not changed. Under the action of a strong oxidant, potassium ions can enter the hydroxide sites to form a solid solution structure prototype, thereby obtaining a composite hydroxide solid solution. Potassium ions replace nickel / iron / manganese sites to form a single phase.

Description

Technical Field

[0001] This disclosure relates to the field of sodium-ion battery cathode material technology, and more specifically, to potassium-nickel-iron-manganese intercalated composite hydroxides, sodium-ion cathode materials, and their preparation methods. Background Technology

[0002] Sodium-ion batteries have become a hot research topic in battery technology in recent years due to their high safety, abundant raw materials, and low cost. Potential applications for sodium-ion batteries include low-speed electric vehicles and energy storage devices. Cathode materials are one of the key materials in sodium-ion batteries. Layered transition metal oxides, in particular, possess high specific capacity and share many similarities with the synthesis and manufacturing processes of currently mature lithium-ion battery cathode materials, making them one of the materials with the potential for commercial production of sodium-ion battery cathode materials.

[0003] Manganese-based transition metal oxides have attracted widespread attention due to their high theoretical specific capacity and operating voltage. However, they are still difficult to put into practical use for the following reasons: (1) Mn 3+ (1) Jahn-Teller effect; (2) orderly arrangement of sodium ions and vacancies; (3) irreversible phase transition of P2-O2 when charged to above 4.2V.

[0004] Due to Ni 2+ / Ni 4+ and Fe 2+ / Fe 4+ With a high redox potential, it does not readily react with H2O and CO2 in air. Meanwhile, the doping of Ni and Fe can provide capacity, alleviate the Jahn-Teller effect of Mn, and inhibit its dissolution.

[0005] To improve battery capacity and charge / discharge efficiency, potassium ions are typically doped into sodium-ion cathode materials. The method for doping potassium ions usually involves uniformly mixing sodium source, precursor, and potassium source and then sintering. Conventional dry mechanical-physical mixing only achieves particle-level mixing, resulting in uneven element dispersion. Furthermore, the ionic radius of potassium ions is much larger than that of sodium ions, making it difficult for potassium ions to be embedded in the transition metal layer in large quantities. Therefore, the battery capacity and charge / discharge efficiency are relatively low.

[0006] In view of this, this disclosure is hereby made. Summary of the Invention

[0007] The purpose of this disclosure is to provide a potassium-nickel-iron-manganese composite hydroxide, a sodium ion cathode material, and a method for preparing the same.

[0008] This disclosure is implemented as follows:

[0009] In a first aspect, this disclosure provides a potassium-nickel-iron-manganese composite hydroxide with the chemical formula K. aNi b Fe c Mn 1-b-c-d Me d (OH)₂, where 0.01 < a ≤ 0.10, 0.1 ≤ b < 0.5, 0.4 ≤ c < 0.7, 0 < d ≤ 0.2; Me is at least one of magnesium, aluminum, boron, silicon, phosphorus, calcium, titanium, cobalt, copper, zinc, zirconium, tungsten, antimony, niobium, and molybdenum.

[0010] In a second aspect, the present disclosure provides a method for preparing a potassium - intercalated nickel - iron - manganese composite hydroxide, which includes:

[0011] Flowing a nickel - iron - manganese mixed salt solution, a precipitating agent, a complexing agent, and an additive solution into a reaction kettle respectively in parallel to obtain a coprecipitation mixture solution, wherein the additive solution is a solution containing at least one element of magnesium, aluminum, boron, silicon, phosphorus, calcium, titanium, cobalt, copper, zinc, zirconium, tungsten, antimony, niobium, and molybdenum;

[0012] Carrying out a coprecipitation reaction on the coprecipitation mixture solution to generate a coprecipitation product slurry, and performing solid - liquid separation to obtain a solid;

[0013] Mixing the solid, a potassium salt, an oxidant, and water, heating up to carry out a potassium - intercalation reaction, and performing solid - liquid separation and washing after the reaction to obtain a potassium - intercalated nickel - iron - manganese composite hydroxide.

[0014] In an optional embodiment, the pH value during the coprecipitation reaction is maintained at 10.0 - 11.5, and the concentration of the complexing agent in the system during the coprecipitation reaction is 0.15 - 0.35 mol / L.

[0015] In an optional embodiment, the temperature of the coprecipitation reaction is 50 - 75 °C.

[0016] In an optional embodiment, the stirring speed of the coprecipitation reaction is 400 - 800 r / min.

[0017] In an optional embodiment, the molar ratio of the solid, the potassium salt, and the oxidant is 10:2 - 5:1 - 10.

[0018] In an optional embodiment, the reaction temperature of the potassium - intercalation reaction is 50 - 80 °C, and the reaction time is 5 h - 24 h.

[0019] In an optional embodiment, the concentration of the solid during the potassium - intercalation reaction is 1 - 8 mol / L, and further optionally 3 - 6 mol / L.

[0020] In an optional embodiment, the potassium source includes one or a combination of more of potassium hydroxide, potassium acetate, potassium nitrate, potassium sulfate, potassium oxalate, and potassium carbonate;

[0021] Optionally, the potassium source includes one or a combination of potassium hydroxide, potassium sulfate, and potassium carbonate;

[0022] Alternatively, the potassium source may be potassium hydroxide.

[0023] In an optional embodiment, the oxidant includes one or more combinations of oxygen, hydrogen peroxide, ammonium persulfate, and sodium persulfate.

[0024] In an optional embodiment, the nickel-iron-manganese mixed salt solution is a mixture of nickel salt, iron salt and manganese salt, wherein the total molar concentration of Ni, Fe and Mn is 1.8 to 2.0 mol / L.

[0025] In an optional embodiment, the nickel salt includes one or more combinations of nickel sulfate, nickel chloride, and nickel nitrate.

[0026] In an optional embodiment, the iron salt includes one or more combinations of ferrous sulfate, ferrous chloride, and ferrous nitrate.

[0027] In an optional embodiment, the manganese salt includes one or more combinations of manganese sulfate, manganese chloride, and manganese nitrate.

[0028] In an optional embodiment, the precipitant comprises a sodium hydroxide or potassium hydroxide solution with a mass fraction of 20-40%.

[0029] In an optional embodiment, the complexing agent comprises an aqueous ammonia solution with a concentration of 1.5 to 3.5 mol / L.

[0030] In an optional embodiment, the additive solution is co-current doped at a total metal element molar content of 0.01 to 0.2%.

[0031] In an optional embodiment, the additive solution comprises one or more of the following: magnesium sulfate, aluminum sulfate, sodium borate, sodium silicate, sodium pyrophosphate, calcium sulfate, titanium trichloride, cobalt sulfate, copper sulfate, zinc sulfate, zirconium sulfate, niobium oxalate, sodium molybdate, antimony acetate, and sodium tungstate.

[0032] Thirdly, this disclosure provides a method for preparing a sodium-ion cathode material, which uses a potassium-nickel-iron-manganese composite hydroxide prepared as described in the foregoing embodiments or a potassium-nickel-iron-manganese composite hydroxide prepared by any of the foregoing embodiments as a precursor. After heat treatment of the precursor, a sodium source is added for mixing and calcination.

[0033] In an optional embodiment, the heat treatment temperature is 400–1000°C and the time is 10–24 hours;

[0034] Optionally, the heat treatment temperature is 500-900℃ and the time is 10-20h;

[0035] Optionally, the heat treatment temperature is 650-800℃ and the time is 10-15h.

[0036] In an optional embodiment, the molar amount of Na added to the sodium source is 1-1.05 times the total molar amount of metal elements in the precursor.

[0037] In an optional embodiment, the sodium source is one or more of sodium carbonate, sodium hydroxide, and sodium acetate.

[0038] In an optional embodiment, the calcination temperature is 400-1000℃ and the calcination time is 5-40h;

[0039] Optionally, the calcination temperature is 600-1000℃, and the calcination time is 5-25h;

[0040] Optionally, the calcination temperature is 700-1000℃; the calcination time is 10-20h.

[0041] In an optional embodiment, the calcination atmosphere is an air atmosphere or an oxygen atmosphere.

[0042] Fourthly, this disclosure provides a sodium-ion cathode material, which is prepared using the sodium-ion cathode material preparation method described in any of the foregoing embodiments.

[0043] Fifthly, this disclosure provides a sodium-ion battery comprising the sodium-ion cathode material as described in the foregoing embodiments.

[0044] This disclosure has the following beneficial effects:

[0045] This disclosure provides a potassium-nickel-iron-manganese composite hydroxide, which is doped with metal / non-metal ions by adding additives during co-precipitation. Compared with dry mixing and sintering, the ion distribution in the precursor co-precipitation is more uniform. Furthermore, this disclosure involves potassium ion doping after co-precipitation, without changing the original particle morphology. Under the action of a strong oxidant, potassium ions can enter the hydroxide sites, forming a preliminary solid solution structure, thus obtaining a composite hydroxide solid solution. Potassium ions replace nickel / iron / manganese sites, forming a single phase. Further, this application obtains a potassium-intercalated solid solution by first heat-treating the potassium-nickel-iron-manganese composite hydroxide, achieving atomic-level potassium dispersion. Subsequently, this solid solution is mixed with a sodium source and calcined to obtain a sodium-ion battery material. This battery material shows significant improvements in specific capacity and initial charge-discharge efficiency, which is beneficial for further preparation of high-performance energy storage batteries. Attached Figure Description

[0046] To more clearly illustrate the technical solutions of the embodiments of the present disclosure, the accompanying drawings required for the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present disclosure and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0047] Figure 1 SEM image of the precursor of the positive electrode material of the sodium-ion battery prepared in Example 1 of the present disclosure;

[0048] Figure 2 SEM image of the positive electrode material of the sodium-ion battery prepared in Example 1 of the present disclosure;

[0049] Figure 3 SEM image of the potassium-inserted nickel-iron-manganese composite hydroxide prepared in Comparative Example 3 of the present disclosure;

[0050] Figure 4 SEM image of the potassium-inserted nickel-iron-manganese composite hydroxide prepared in Comparative Example 4 of the present disclosure. Detailed implementation manners

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present disclosure clearer, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below. For those conditions not specified in the embodiments, they shall be carried out according to conventional conditions or conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0052] The present disclosure provides a potassium-inserted nickel-iron-manganese composite hydroxide with the chemical formula K[[ID=二十六]] a Ni b Fe c Mn 1-b-c-d Me d (OH)₂, where 0.01 < a ≤ 0.10, 0.1 ≤ b < 0.5, 0.4 ≤ c < 0.7, 0 < d ≤ 0.2; Me is at least one of magnesium, aluminum, boron, silicon, phosphorus, calcium, titanium, cobalt, copper, zinc, zirconium, tungsten, antimony, niobium, molybdenum.

[0053] The preparation method of the potassium-inserted nickel-iron-manganese composite hydroxide includes the following steps:

[0054] S1. Mixing materials.

[0055] The nickel-iron-manganese mixed salt solution, precipitant, complexing agent, and additive solution are respectively fed into the reaction kettle in parallel to obtain a coprecipitation mixture.

[0056] The total molar concentration of Ni, Fe, and Mn in the nickel-iron-manganese mixed salt solution is 1.8–2.0 mol / L. In some embodiments, the total molar concentration of Ni, Fe, and Mn in the nickel-iron-manganese mixed salt solution can be, for example, any one of 1.8 mol / L, 1.9 mol / L, 2.0 mol / L, or a range between any two. Nickel salts include, but are not limited to, combinations of one or more of nickel sulfate, nickel chloride, and nickel nitrate. Iron salts include, but are not limited to, combinations of one or more of ferrous sulfate, ferrous chloride, and ferrous nitrate. Manganese salts include, but are not limited to, combinations of one or more of manganese sulfate, manganese chloride, and manganese nitrate.

[0057] The precipitant comprises a sodium hydroxide or potassium hydroxide solution with a mass fraction of 20-40%. In some embodiments, the mass fraction of the precipitant may be, for example, any one or a range between any two of 20%, 22%, 25%, 28%, 30%, 32%, 34%, 35%, 37%, 39%, and 40%.

[0058] The complexing agent comprises an aqueous ammonia solution with a concentration of 1.5–3.5 mol / L. In some embodiments, the concentration of the aqueous ammonia solution can be any one or a range between any two of 1.5 mol / L, 1.8 mol / L, 2.0 mol / L, 2.2 mol / L, 2.4 mol / L, 2.5 mol / L, 2.6 mol / L, 2.9 mol / L, 3.0 mol / L, 3.2 mol / L, and 3.5 mol / L.

[0059] The additive solution is a solution containing at least one element selected from magnesium, aluminum, boron, silicon, phosphorus, calcium, titanium, cobalt, copper, zinc, zirconium, tungsten, antimony, niobium, and molybdenum. Specifically, the additive solution includes, but is not limited to, one or more of magnesium sulfate, aluminum sulfate, sodium borate, sodium silicate, sodium pyrophosphate, calcium sulfate, titanium trichloride, cobalt sulfate, copper sulfate, zinc sulfate, zirconium sulfate, niobium oxalate, sodium molybdate, antimony acetate, and sodium tungstate.

[0060] S2, coprecipitation reaction.

[0061] The coprecipitated mixture is subjected to a coprecipitation reaction to generate a coprecipitated product slurry. The solid and liquid are separated and washed to obtain the solid.

[0062] During the coprecipitation reaction, the pH value was maintained at 10.0-11.5, the concentration of the complexing agent in the system was 0.15-0.35 mol / L, the temperature of the coprecipitation reaction was 50-75℃, and the stirring speed of the coprecipitation reaction was 400-800 r / min.

[0063] In this disclosure, the pH value during the coprecipitation reaction is used to limit the amount of the nickel-iron-manganese mixed salt solution, the amount of the precipitant is limited by the pH value, and the concentration of the complexing agent in the system is used to limit the amount of the complexing agent. The additive solution is co-currently doped at a total metal element molar content of 0.01-0.2%. In some embodiments, the concentration of the complexing agent in the system during the coprecipitation reaction is any one or a range between any two of 0.15 mol / L, 0.18 mol / L, 0.2 mol / L, 0.22 mol / L, 0.24 mol / L, 0.25 mol / L, 0.26 mol / L, 0.29 mol / L, 0.30 mol / L, 0.32 mol / L, and 0.35 mol / L. The temperature of the coprecipitation reaction can be, for example, any one or a range between any two of 50°C, 55°C, 60°C, 65°C, 70°C, and 75°C. The stirring speed for the coprecipitation reaction can be, for example, any one or a range between 400 r / min, 500 r / min, 600 r / min, 700 r / min, and 800 r / min. This disclosure allows for the coprecipitation of metals or non-metals from an additive solution into the precursor lattice. The additives utilize high-valence or low-valence elements to generate electrons or holes, thereby improving conductivity, stabilizing the lattice structure, and enhancing the material's cycle stability. Simultaneously, washing removes residual precipitant from the solid surface, facilitating subsequent potassium intercalation.

[0064] S3, potassium intercalation reaction.

[0065] The solid, potassium salt, oxidant and water were mixed and heated to carry out the potassium intercalation reaction. After the reaction was completed, solid-liquid separation and washing were performed to obtain potassium-nickel-iron-manganese composite hydroxide.

[0066] The molar ratio of the solid, the potassium salt, and the oxidant is 10:2-5:1-10. The reaction temperature for the potassium intercalation reaction is 50-80℃, and the reaction time is 5-24 h. The concentration of potassium ions during the potassium intercalation reaction is 1-12 mol / L, optionally 3-10 mol / L, and further optionally 3-6 mol / L.

[0067] In some embodiments, the molar ratio of the solid, potassium salt, and oxidant can be, for example, any one or a range between 10:4:5, 10:3:6, and 10:4:10. The reaction temperature for the potassium intercalation reaction is any one or a range between 50°C, 60°C, 70°C, and 80°C. The reaction time is any one or a range between 5h, 8h, 10h, 12h, 18h, 20h, and 24h. The concentration of potassium ions during the potassium intercalation reaction can be, for example, any one or a range between 1mol / L, 2mol / L, 3mol / L, 4mol / L, 5mol / L, 6mol / L, 7mol / L, 8mol / L, 9mol / L, 10mol / L, 11mol / L, and 12mol / L. The potassium source includes, but is not limited to, one or a combination of potassium hydroxide, potassium acetate, potassium nitrate, potassium sulfate, potassium oxalate, and potassium carbonate; optionally, the potassium source includes one or a combination of potassium hydroxide, potassium sulfate, and potassium carbonate; further optionally, the potassium source is potassium hydroxide.

[0068] Oxidizing agents include, but are not limited to, one or more combinations of oxygen, hydrogen peroxide, ammonium persulfate, and sodium persulfate.

[0069] In this disclosure, a coprecipitation reaction is first carried out, and the product of the coprecipitation reaction is washed and taken as a solid. Then, potassium is intercalated into the solid. The intercalation of potassium does not change the morphological characteristics of the solid. This disclosure uses a strong oxidizing agent, which allows potassium ions to enter the hydroxide sites and form a prototype solid solution structure, thereby obtaining a composite hydroxide solid solution. The XRD pattern shows a single diffraction peak, and the intercalated potassium element is not reflected in the XRD pattern, indicating that potassium ions replace nickel / iron / manganese sites and form a single phase.

[0070] In addition, this disclosure provides a method for preparing sodium ion cathode material, which uses the above-mentioned potassium-nickel-iron-manganese composite hydroxide as a precursor. After heat treatment of the precursor, a sodium source is added for mixing and calcination.

[0071] Specifically, the heat treatment temperature is 400-1000℃, and the time is 10-24 hours. In some embodiments, the heat treatment temperature can be any one or a range between any two of 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, and 1000℃. The heat treatment time can be any one or a range between any two of 10 hours, 12 hours, 18 hours, 20 hours, and 24 hours. Optionally, the heat treatment temperature is 500-900℃, and the time is 10-20 hours; alternatively, the heat treatment temperature is 650-800℃, and the time is 10-15 hours.

[0072] The molar amount of Na added to the sodium source is 1 to 1.05 times the total molar amount of metal elements in the precursor.

[0073] The sodium source is one or more of sodium carbonate, sodium hydroxide, and sodium acetate.

[0074] The calcination temperature is 400-1000℃, and the calcination time is 5-40 hours. In some embodiments, the calcination temperature can be any one or a range between 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, and 1000℃. The heat treatment time can be any one or a range between 5 hours, 10 hours, 12 hours, 18 hours, 20 hours, 24 hours, 30 hours, 36 hours, and 40 hours. Optionally, the calcination temperature is 600-1000℃, and the calcination time is 5-25 hours; more preferably, the calcination temperature is 700-1000℃, and the calcination time is 10-20 hours. The calcination atmosphere is an air atmosphere or an oxygen atmosphere.

[0075] In this disclosure, heat treatment is performed before calcination to achieve atomic-level potassium dispersion and form a potassium-intercalated solid solution. This solution is then used as a precursor and mixed with a sodium source for calcination. The resulting sodium-ion battery material exhibits significant improvements in specific capacity and initial charge-discharge efficiency, which is beneficial for preparing high-performance energy storage batteries.

[0076] The features and performance of this disclosure will be further described in detail below with reference to embodiments.

[0077] Example 1

[0078] This embodiment prepares a sodium-potassium composite cathode material, and the preparation method includes the following steps:

[0079] S1. Prepare a mixed solution of NiSO4, FeSO4, and MnSO4, wherein the total molar concentration of Ni, Fe, and Mn in the mixed solution is 2.0 mol / L, and the ratio of Ni:Fe:Mn:W is 4:4:1.9:0.1. Add sodium tungstate solution as an additive, and prepare a 35% sodium hydroxide solution as a precipitant; prepare a 2.5 mol / L ammonia solution as a complexing agent.

[0080] S2. Keep the reactor stirring on. First, introduce protective gas into the reaction system. Add the mixed solution, precipitant, complexing agent, and additives from S1 into the reactor in parallel to carry out the co-precipitation reaction. Adjust the pH in the reactor and turn on the overflow. The pH value during the reaction process is maintained at 11.00-11.5, the concentration of complexing agent in the reactor is 0.2 mol / L, the synthesis temperature is maintained at 60℃, the reactor rotation speed is 650 r / min, and the overflow material is used as the co-precipitation product slurry.

[0081] S3. Take the co-precipitated product slurry, filter it under pressure, and wash it with water to obtain a solid. Add the solid to the reactor, and add the solid, potassium hydroxide, and ammonium persulfate in a molar ratio of 10:5:8 to carry out the potassium intercalation reaction. Control the potassium ion concentration at 3.0-3.5 mol / L, the reaction temperature at 65℃, and the reaction time at 20 h. After the reaction, perform solid-liquid separation, alkali washing, and water washing to obtain a potassium-intercalated nickel-iron-manganese composite hydroxide. The chemical formula of the potassium-intercalated nickel-iron-manganese composite hydroxide is Ni. 0.40 Fe 0.40 Mn 0.19 W 0.01 Scanning electron micrograph of (OH)₂, potassium-nickel-iron-manganese complex hydroxide, as shown in... Figure 1 As shown, from Figure 1 It can be seen that the particles are secondary spherical particles in the shape of inserts, while the primary particles are clear flakes.

[0082] S4. Heat-treat the potassium-nickel-iron-manganese composite hydroxide at 760℃ for 12 hours;

[0083] S5. Add sodium carbonate (the sodium source) according to the formula design. After mixing, calcine at 930℃ for 15 hours in air atmosphere to obtain Na. 0.7 5K 0.05 Ni 0.4 Fe 0.4 Mn 0.19 W 0.01 O2 cathode material, the scanning electron microscope image of the cathode material is as follows: Figure 2 As shown, from Figure 2 It can be seen that the sintered particles have smooth surfaces and good crystallinity.

[0084] Example 2

[0085] This embodiment prepares a sodium-potassium composite cathode material, and the preparation method includes the following steps:

[0086] S1. Prepare a mixed solution of NiCl2, FeCl2, and MnCl2, wherein the total molar concentration of Ni, Fe, and Mn in the mixed solution is 1.8 mol / L; prepare a sodium tungstate solution as an additive in the ratio of Ni:Fe:Mn:W of 4:4:1.8:0.2; prepare a 20% potassium hydroxide solution as a precipitant; and prepare a 3 mol / L ammonia solution as a complexing agent.

[0087] S2. Keep the reactor stirring on. First, introduce protective gas into the reaction system. Add the mixed solution, precipitant, complexing agent, and additives from S1 into the reactor in a co-precipitation reaction. Adjust the pH in the reactor and turn on the overflow. The pH value during the reaction process is maintained at 11.00-11.5, the concentration of complexing agent in the reactor is 0.3 mol / L, the synthesis temperature is maintained at 50℃, the reactor rotation speed is 800 r / min, and the overflow material is used as the co-precipitation product slurry.

[0088] S3. Take the co-precipitated product slurry, filter it, and wash it with water to obtain a solid. Add the solid to a reactor with pure water and stir. Add the solid, potassium hydroxide, and ammonium persulfate to the reactor in a molar ratio of 10:5:8 to carry out the potassium intercalation reaction. Control the potassium ion concentration at 7.0-7.5 mol / L, the reaction temperature at 55℃, and the reaction time at 24 h. After the reaction, perform solid-liquid separation, alkali washing, and water washing to obtain a potassium-intercalated nickel-iron-manganese composite hydroxide. The chemical formula of the potassium-intercalated nickel-iron-manganese composite hydroxide is Ni. 0.40 Fe 0.40 Mn 0.18 W 0.02 (OH)2.

[0089] S4. Heat-treat the potassium-nickel-iron-manganese composite hydroxide at 560℃ for 20 hours;

[0090] S5. Add sodium carbonate (the sodium source) according to the formula design. After mixing, calcine at 730℃ for 20 hours in air atmosphere to obtain Na. 0.7 5K 0.05 Ni 0.4 Fe 0.4 Mn 0.18 W 0.02 O2 cathode material.

[0091] Example 3

[0092] This embodiment prepares a sodium-potassium composite cathode material, and the preparation method includes the following steps:

[0093] S1. Prepare a mixed solution of Ni(NO3)2, Fe(NO3)2, and Mn(NO3)2, wherein the total molar concentration of Ni, Fe, and Mn in the mixed solution is 1.9 mol / L; prepare a sodium tungstate solution as an additive in the ratio of Ni:Fe:Mn:W of 4:4:1.6:0.4; prepare a 40% sodium hydroxide solution as a precipitant; and prepare a 1.5 mol / L ammonia solution as a complexing agent.

[0094] S2. Keep the reactor stirring on. First, introduce protective gas into the reaction system. Add the mixed solution, precipitant, complexing agent, and additives from S1 into the reactor in a co-precipitation reaction. Adjust the pH in the reactor and turn on the overflow. The pH value during the reaction process is maintained at 11.00-11.5, the concentration of complexing agent in the reactor is 0.15 mol / L, the synthesis temperature is maintained at 75℃, the reactor rotation speed is 400 r / min, and the overflow material is used as the co-precipitation product slurry.

[0095] S3. Take the co-precipitated product slurry, filter it, and wash it with water to obtain a solid. Add the solid to the reactor, and add the solid, potassium hydroxide, and ammonium persulfate in a molar ratio of 10:5:8 to carry out the potassium intercalation reaction. Control the potassium ion concentration at 11.0-11.5 mol / L, the reaction temperature at 80℃, and the reaction time at 8 hours. After the reaction, perform solid-liquid separation, alkali washing, and water washing to obtain a potassium-intercalated nickel-iron-manganese composite hydroxide. The chemical formula of the potassium-intercalated nickel-iron-manganese composite hydroxide is Ni. 0.40 Fe 0.40 Mn 0.16 W 0.04 (OH)2.

[0096] S4. Heat-treat the potassium-nickel-iron-manganese composite hydroxide at 950℃ for 12 hours;

[0097] S5. Add sodium carbonate (the sodium source) according to the formula design. After mixing, calcine at 1000℃ for 8 hours in air atmosphere to obtain Na. 0.7 5K 0.05 Ni 0.4 Fe 0.4 Mn 0.16 W 0.04 O2 cathode material.

[0098] Comparative Example 1

[0099] The only difference between this comparative example and Example 1 is that no additives were added in this comparative example; otherwise, they are exactly the same as Example 1.

[0100] Comparative Example 2

[0101] The only difference between this comparative example and Example 1 is that no oxidant was added in this comparative example; otherwise, they are exactly the same as Example 1.

[0102] Comparative Example 3

[0103] The only difference between this comparative example and Example 1 is that potassium hydroxide and ammonium persulfate are added during co-precipitation in this comparative example. The specific step S2 is as follows:

[0104] Keeping the reactor stirred, a protective gas was first introduced into the reaction system. The mixed solution, precipitant, complexing agent, additives, potassium hydroxide, and ammonium persulfate from S1 were then added concurrently to the reactor for co-precipitation and precipitation. The pH in the reactor was adjusted, and the overflow was turned on. The pH value during the reaction was maintained between 11.00 and 11.5, the complexing agent concentration in the reactor was 0.1 mol / L, the synthesis temperature was maintained at 60℃, and the reactor rotation speed was 650 r / min. The overflow material was used as the co-precipitated product slurry. The amounts of potassium hydroxide and ammonium persulfate were consistent with those in Example 1. After the reaction, solid-liquid separation, alkali washing, and water washing were performed to obtain a potassium-nickel-iron-manganese composite hydroxide. A scanning electron microscope image of the potassium-nickel-iron-manganese composite hydroxide is shown below. Figure 3 As shown, the particles have poor sphericity, the flaky texture basically disappears, and the surface morphology is blurred.

[0105] Comparative Example 4

[0106] The only difference between this comparative example and Example 1 is that the amount of ammonium persulfate oxidant is increased in this comparative example. Specifically, the molar ratio of the solid to potassium hydroxide and ammonium persulfate is 10:3:15. Scanning electron microscope images of the potassium-nickel-iron-manganese composite hydroxide are shown below. Figure 4 As shown, from Figure 4 It can be seen that the surface of the particles is pulverized, resulting in poor performance after sintering.

[0107] Comparative Example 5

[0108] The only difference between this comparative example and Example 1 is that no heat treatment was performed in S4 in this comparative example; otherwise, they are exactly the same as Example 1.

[0109] Comparative Example 6

[0110] The only difference between this comparative example and Example 1 is that the heat treatment temperature in this comparative example is 1200°C.

[0111] Comparative Example 7

[0112] The only difference between this comparative example and Example 1 is that no oxidant was added in this comparative example, and no heat treatment was performed in S4. Otherwise, it is exactly the same as Example 1.

[0113] Experimental Example 1

[0114] The sodium-ion battery cathode materials prepared in Examples 1-3 and Comparative Examples 1-7 were tested, and the statistical results of the test data are shown in Table 1.

[0115] Table 1: Statistical table of test data for sodium-ion battery cathode materials prepared from different examples

[0116]

[0117]

[0118] As shown in Table 1, Comparative Example 1, which did not add additives during the co-precipitation stage, exhibited poor electrical performance. This is because high-valence or low-valence elements generate electrons or holes, improving conductivity, stabilizing the crystal structure, and enhancing the material's cycle stability. Comparative Example 2, which did not add an oxidant during the potassium intercalation stage, also showed poor electrical performance. This is because the oxidant promotes the entry of potassium ions into the nickel-cobalt-manganese lattice. The intercalation of potassium ions facilitates the expansion of the interlayer spacing of the cathode material and the deintercalation of sodium ions, thereby improving the battery's specific capacity and rate performance. Comparative Example 3, which added potassium and an oxidant during the co-precipitation stage, showed poor electrical performance, mainly due to the poor morphology and low crystallinity of the precursor during the co-precipitation stage. The material's inherent properties led to unsatisfactory electrical performance in the later stages. In Comparative Example 4, the amount of oxidant added exceeded the scope of this disclosure. Excessive oxidant addition caused changes in the crystal structure and pulverization of the particle surface, resulting in poor performance after sintering. Comparative Example 5, which did not undergo heat treatment before sintering, exhibited poor electrical performance because the intercalated potassium elements were stably retained in the material's crystal lattice under heat treatment conditions. In Comparative Example 6, the excessively high heat treatment temperature caused different metal elements to form multiphase oxides individually, destroying the potassium hydroxide intercalation structure. In Comparative Example 7, no oxidant was added, and no heat treatment was performed, resulting in poor electrical properties.

[0119] Experimental Example 2

[0120] The XRD data of the sodium-ion battery cathode materials prepared in Example 1 and Comparative Examples 2-4 are refined.

[0121] Table 2. Statistical table of detailed XRD data results for the cathode materials provided in Example 1 and Comparative Examples 2-4

[0122]

[0123] Table 2 shows a comparison of the unit cell parameters of the cathode materials prepared in Example 1 and Comparative Examples 2-4. Combined with the electrical performance data of the cathode materials in Table 1, it can be found that the cathode material corresponding to the oxidized cathode material precursor has a larger unit cell parameter. A larger unit cell parameter is beneficial for the insertion and extraction of sodium ions, thereby improving its electrical performance, resulting in better capacity, cycle life, and rate performance. In Comparative Example 4, although the unit cell parameter is larger, the pulverization of its particle surface leads to poor performance after sintering, ultimately resulting in significantly lower capacity, cycle life, and rate performance than in Example 1. Therefore, the preparation method disclosed in this paper can obtain nano-sodium cathode materials with uniform particle size, good dispersibility, and no agglomeration.

[0124] In summary, this disclosure provides a potassium-nickel-iron-manganese composite hydroxide, which is doped with metal / non-metal ions by adding additives during co-precipitation. Compared with dry mixing and sintering, the ion distribution in the precursor co-precipitation is more uniform. Furthermore, this disclosure involves potassium ion doping after co-precipitation, which does not change the original particle morphology. Under the action of a strong oxidant, potassium ions can enter the hydroxide sites, forming a preliminary solid solution structure, thus obtaining a composite hydroxide solid solution. Potassium ions replace nickel / iron / manganese sites, forming a single phase. Further, this application achieves atomic-level potassium dispersion by heat-treating the potassium-nickel-iron-manganese composite hydroxide to obtain a potassium-intercalated solid solution. Subsequently, it is mixed with a sodium source and calcined, resulting in a sodium-ion battery material with significantly improved specific capacity and initial charge-discharge efficiency, which is beneficial for preparing high-performance energy storage batteries.

[0125] The optional embodiments of this disclosure have been described in detail above; however, this disclosure is not limited thereto. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in this disclosure and are all within the protection scope of this disclosure.

[0126] Industrial applicability

[0127] This disclosure provides a potassium-nickel-iron-manganese composite hydroxide, which is doped with metal / non-metal ions by adding additives during co-precipitation. Compared with dry mixing and sintering, the ion distribution in the precursor co-precipitation is more uniform. Furthermore, this disclosure involves potassium ion doping after co-precipitation, without changing the original particle morphology. Under the action of a strong oxidant, potassium ions can enter the hydroxide sites, forming a preliminary solid solution structure, thus obtaining a composite hydroxide solid solution. Potassium ions replace nickel / iron / manganese sites, forming a single phase. Further, this application achieves atomic-level potassium dispersion by heat-treating the potassium-nickel-iron-manganese composite hydroxide to obtain a potassium-intercalated solid solution. Subsequently, it is mixed with a sodium source and calcined. The resulting sodium-ion battery material shows significant improvements in specific capacity and initial charge-discharge efficiency, which is beneficial for preparing high-performance energy storage batteries.

Claims

1. A potassium-nickel-iron-manganese composite hydroxide, characterized in that, Its chemical formula is K a Ni b Fe c Mn 1-b-c-d Me d (OH)2, where 0.01 < a ≤ 0.10, 0.1 ≤ b < 0.5, 0.4 ≤ c < 0.7, 0 < d ≤ 0.2; Me is at least one of magnesium, aluminum, boron, silicon, phosphorus, calcium, titanium, cobalt, copper, zinc, zirconium, tungsten, antimony, niobium, molybdenum; The preparation method of the potassium-nickel-iron-manganese composite hydroxide includes: A nickel-iron-manganese mixed salt solution, a precipitant, a complexing agent, and an additive solution are fed into a reaction vessel in parallel to obtain a co-precipitated mixture. The additive solution is a solution containing at least one element selected from magnesium, aluminum, boron, silicon, phosphorus, calcium, titanium, cobalt, copper, zinc, zirconium, tungsten, antimony, niobium, and molybdenum. The coprecipitation mixture is subjected to a coprecipitation reaction to generate a coprecipitation product slurry, and solid-liquid separation is performed to obtain a solid. The solid, potassium salt, oxidant and water are mixed in a molar ratio of 10:2-5:1-10. The mixture is heated to carry out a potassium intercalation reaction. After the reaction is completed, solid-liquid separation and washing are performed to obtain potassium-nickel-iron-manganese composite hydroxide.

2. The potassium-nickel-iron-manganese composite hydroxide according to claim 1, characterized in that, The pH value is maintained at 10.0-11.5 during the coprecipitation reaction, and the concentration of the complexing agent in the system is 0.15-0.35 mol / L during the coprecipitation reaction.

3. The potassium-nickel-iron-manganese composite hydroxide according to claim 1, characterized in that, The temperature for the coprecipitation reaction is 50-75℃.

4. The potassium-nickel-iron-manganese composite hydroxide according to claim 1, characterized in that, The stirring speed for the coprecipitation reaction is 400~800 r / min.

5. The potassium-nickel-iron-manganese composite hydroxide according to claim 1, characterized in that, The potassium intercalation reaction is carried out at a temperature of 50-80℃ for 5-24 hours.

6. The method for preparing the potassium-nickel-iron-manganese composite hydroxide according to claim 1, characterized in that, The concentration of potassium ions during the potassium intercalation reaction is 1-12 mol / L.

7. The method for preparing potassium-nickel-iron-manganese composite hydroxide according to claim 1, characterized in that, The concentration of potassium ions during the potassium intercalation reaction is 3-10 mol / L.

8. The method for preparing the potassium-nickel-iron-manganese composite hydroxide according to claim 1, characterized in that, The concentration of potassium ions during the potassium intercalation reaction is 3-6 mol / L.

9. The method for preparing the potassium-nickel-iron-manganese composite hydroxide according to claim 1, characterized in that, The potassium salt includes one or a combination of potassium hydroxide, potassium acetate, potassium nitrate, potassium sulfate, potassium oxalate, and potassium carbonate.

10. The method for preparing the potassium-nickel-iron-manganese composite hydroxide according to claim 1, characterized in that, The oxidant includes one or more combinations of oxygen, hydrogen peroxide, ammonium persulfate, and sodium persulfate.

11. The method for preparing the potassium-nickel-iron-manganese composite hydroxide according to claim 1, characterized in that, The nickel-iron-manganese mixed salt solution is a mixture of nickel salt, iron salt and manganese salt, wherein the total molar concentration of Ni, Fe and Mn is 1.8~2.0 mol / L.

12. The method for preparing the potassium-nickel-iron-manganese composite hydroxide according to claim 11, characterized in that, The nickel salt includes one or more combinations of nickel sulfate, nickel chloride, and nickel nitrate.

13. The method for preparing the potassium-nickel-iron-manganese composite hydroxide according to claim 11, characterized in that, The iron salt includes one or more combinations of ferrous sulfate, ferrous chloride, and ferrous nitrate.

14. The method for preparing the potassium-nickel-iron-manganese composite hydroxide according to claim 11, characterized in that, The manganese salt includes one or more combinations of manganese sulfate, manganese chloride, and manganese nitrate.

15. The method for preparing the potassium-nickel-iron-manganese composite hydroxide according to claim 1, characterized in that, The precipitant comprises a sodium hydroxide or potassium hydroxide solution with a mass fraction of 20-40%.

16. The method for preparing the potassium-nickel-iron-manganese composite hydroxide according to claim 1, characterized in that, The complexing agent comprises an aqueous ammonia solution with a concentration of 1.5 to 3.5 mol / L.

17. The method for preparing the potassium-nickel-iron-manganese composite hydroxide according to claim 1, characterized in that, The additive solution is co-current doped at a total metal element molar content of 0.01~0.2%.

18. The method for preparing the potassium-nickel-iron-manganese composite hydroxide according to claim 1, characterized in that, The additive solution comprises one or more of the following: magnesium sulfate, aluminum sulfate, sodium borate, sodium silicate, sodium pyrophosphate, calcium sulfate, titanium trichloride, cobalt sulfate, copper sulfate, zinc sulfate, zirconium sulfate, niobium oxalate, sodium molybdate, antimony acetate, and sodium tungstate.

19. A method for preparing a sodium-ion cathode material, characterized in that, It uses the potassium-nickel-iron-manganese composite hydroxide as described in claim 1 as a precursor. After heat treatment of the precursor, a sodium source is added for mixing and calcination.

20. The method for preparing the sodium-ion cathode material according to claim 19, characterized in that, The heat treatment temperature is 400–1000℃, and the time is 10–24 hours.

21. The method for preparing the sodium-ion cathode material according to claim 19, characterized in that, The molar amount of Na added to the sodium source is 1 to 1.05 times the total molar amount of metal elements in the precursor.

22. The method for preparing the sodium-ion cathode material according to claim 19, characterized in that, The sodium source is one or more of sodium carbonate, sodium hydroxide, and sodium acetate.

23. The method for preparing the sodium-ion cathode material according to claim 19, characterized in that, The calcination temperature is 400-1000℃, and the calcination time is 5-40h.

24. The method for preparing the sodium-ion cathode material according to claim 19, characterized in that, The calcination atmosphere is an air atmosphere or an oxygen atmosphere.

25. A sodium-ion cathode material, characterized in that, It is prepared using the method for preparing sodium ion cathode material as described in claim 19.

26. A sodium-ion battery, characterized in that, It includes the sodium-ion cathode material as described in claim 25.

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