A quaternary precursor for sodium batteries and a preparation method thereof

Abstract

The application belongs to the technical field of sodium-ion battery cathode materials, and particularly relates to a quaternary precursor for sodium battery and a preparation method thereof; main elements of the quaternary precursor are Ni, Fe, Mn and Zn, and a doping or coating element is one of Y, Ti and Cr; the quaternary precursor is prepared by using a coprecipitation method in cooperation with an antioxidant, a complexing agent and a precipitant, and a molecular formula of the quaternary precursor is Ni 0.22 Fe 0.33 Mn 0.33 Zn m X n (OH)2, wherein m+n=0.12, m>0.06, n>0, and X is one of Y, Ti and Cr; the quaternary precursor for sodium battery is easy to be fired into a single crystal, the single crystal material is not prone to cracks in the expansion and shrinkage of the crystal grains, and can well avoid the reaction caused by the infiltration of electrolyte into the crystal grains; the fired single crystal material has a round shape, uniform particle size, less agglomeration and is easy to be broken by air; the precursor with the element ratio combination can effectively reduce the lattice distortion caused by Mn3+, and enhance the combination between M and O, so that the material has good high-rate cycle performance.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery cathode material technology, specifically relating to a quaternary precursor for sodium batteries and its preparation method. Background Technology

[0002] In recent years, layered oxide cathode materials for sodium-ion batteries (Na) x MO2 (where M represents a transition metal) has become a hot topic in sodium battery research, with preparation methods mainly including solid-state methods, sol-gel methods, and co-precipitation methods. Among these, the co-precipitation method, by controlling reaction conditions, can obtain precursors with specific physicochemical properties. The cathode materials prepared by this method have smooth surfaces, uniform particle size distribution, and high tap density, making it a suitable method for industrial production. The co-precipitation method is also the mainstream method for producing lithium battery precursors, and the advantage of inheriting existing equipment and process foundations from lithium batteries lies in the rapid industrialization of sodium batteries.

[0003] Currently, there is no unified consensus on the physicochemical characteristics, proportions, and elemental combinations of sodium-ion battery layered oxide precursors. Various manufacturers have prepared precursors with different physicochemical properties and elemental combinations to improve capacity, cycle life, rate performance, and reduce electrolyte side reactions. For example, patent CN114291852A prepared a nickel-aluminum coated nickel-iron-manganese precursor Ni to address the water sensitivity issue of sodium-ion batteries and reduce electrolyte side reactions. 0.35 Fe 0.32 Mn 0.32 Al 0.01 (OH)2, after mixing the precursor with Na2CO3 and sintering at 850℃ for 20 h, the resulting cathode material exhibits good constant current capacity retention, but its capacity is low and lacks characterization of high-rate cycling performance. Patent CN109817970A, to improve the side reaction problem between the electrode material and the electrolyte, first synthesized a battery-grade hydroxide precursor using a co-precipitation method, and then prepared Na(Fe)2 by sintering in an air atmosphere. 1-x-a Mn x M a Single-crystal materials such as O2 (where M represents Ni, Cu, Mg, Co, Cr, Ti, and Al) achieve a capacity of 121 mAh / g at low rates. For example, patent CN114644361A, to improve cycle performance, utilizes a co-precipitation method combined with an 850℃ sintering process to prepare NaMn. 0.50 Ni 0.28 Co 0.19 Ti 0.03 O2 has a capacity of 115.2 mAh / g at 1C and a capacity retention of 62.7% after 200 cycles at 1C.

[0004] The above patents do not explain the preparation method, but the precursor with this structure and element ratio can improve cycle life. Analysis shows that they all use essentially the same technical principle: coating the precursor to reduce the interfacial reaction between the positive electrode active material and the electrolyte after sintering. The coating should preferably use electrolyte-inert elements to minimize the impact on ion transport and electronic conductivity. Another approach is to dope the precursor to reduce lattice distortion and structural damage caused by frequent phase transitions during charge and discharge. Therefore, there is still considerable room for improvement in precursor optimization. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a quaternary precursor for sodium batteries and its preparation method, which reduces the interfacial reaction between the cathode material and the electrolyte while taking into account the sodium battery capacity, and reduces the sodium ion transport barrier, thereby improving the high-rate cycling performance of the material.

[0006] The objective of this invention is achieved as follows: a quaternary precursor for sodium batteries, wherein the main elements of the quaternary precursor are Ni, Fe, Mn, and Zn, and the doping or coating element is one of Y, Ti, and Cr; the quaternary precursor is prepared by co-precipitation in combination with an antioxidant, a complexing agent, and a precipitant, and its molecular formula is Ni. 0.22 Fe 0.33 Mn 0.33 Zn m X n (OH)2, where m+n=0.12, m≥0.06, n≥0, and X is one of Y, Ti, or Cr.

[0007] The method for preparing a sodium-ion battery quaternary precursor includes the following steps:

[0008] Step 1: Prepare a mixed salt solution of Ni, Fe, Mn, and Zn in a sealed stirring tank using pure water according to the designed ratio. Add L(+)-ascorbic acid to the solution at 0.01% to 0.1% of the total mass of the mixed salt to finally prepare salt ①. Then, prepare a 0.1-0.5 mol / L salt solution of one of Y, Ti, and Cr separately, and designate it as salt ②.

[0009] Step 2: Prepare an alkaline solution with a concentration of 4-8 mol / L as precipitant ①; dilute ammonia water to a solution of 4-8 mol / L, and then prepare trisodium citrate to a solution of 1-2 mol / L, which are respectively labeled as complexing agent ① and complexing agent ②;

[0010] Step 3: Inject a certain amount of pure water into the reactor, stir, heat up, and then blow N2 gas with a purity of ≥99.9% into the reactor. At the same time, nitrogen gas is also blown into the salt ① and precipitant ①.

[0011] Step 4: After nitrogen is introduced for 2 hours, add precipitant ① to the reactor, and add complexing agent ① and complexing agent ② to the reactor;

[0012] Step 5: Set the flow rates of salt ① and the precipitant and complexing agent in Step 4 according to the process requirements. Pump the above reagents evenly into the reactor through a metering pump to carry out the synthesis reaction. Maintain the temperature and stirring speed in the reactor as in Step 3.

[0013] Step 6: During the reaction, slowly lower the pH to 11.0-11.4 over 4-10 hours, then maintain the pH at 11.0-11.4 and continue the reaction for 48 hours. During the reaction, increase the solid content of the reactor using a concentrator. The concentrator discharge flow rate is 2-5 L / h, and nitrogen is introduced into the concentrator to maintain a slight positive pressure.

[0014] Step 7: After reacting for 48 hours, switch salt ① to salt ② with the set flow rate; at the same time, reduce the flow rate of precipitant ① to maintain the pH in the reactor as in step 6, and reduce the flow rates of complexing agents ① and ② to maintain the complexing agent concentration as in step 4; continue the reaction until the coating amount of salt ② reaches the design requirement; finally, reduce the stirring speed and maintain the constant temperature to obtain the required precursor slurry.

[0015] Step 8: Pump the slurry from Step 7 into a centrifuge for filtration, and wash the filter cake with 0.5-2 mol / L dilute alkali and hot pure water at 50-70℃; then perform dynamic drying, sieving, and demagnetization to finally obtain the precursor product Ni. 0.22 Fe 0.33 Mn 0.33 Zn m X n (OH)2(m+n=0.12, m≥0.06, n≥0);

[0016] Step 9: Place the precursor product from Step 8 and Na2CO3 into a mixer for uniform mixing; place the mixed material in an atmosphere furnace and keep it at a constant temperature; after cooling, perform grinding, air crushing, sieving, etc., to obtain the cathode material NaNi. 0.22 Fe 0.33 Mn 0.33 Zn m X n O2.

[0017] Preferably, the molar concentration of the mixed salt solution of Ni, Fe, Mn and Zn prepared in step 1 is 1.5-2.0 mol / L.

[0018] Preferably, in step 1, salt ① is a soluble salt with a total concentration of 1.5-2 mol / L, comprising raw materials NiSO4·6H2O, MnSO4·H2O, FeSO4·7H2O, and ZnSO4·7H2O; salt ② is a soluble salt with a concentration of 0.1-0.5 mol / L prepared from one of Y2(SO4)3·8H2O, TiCl4, and Cr2(SO4)3·6H2O.

[0019] Preferably, the precipitant ① in step 2 is prepared by diluting a 32% liquid alkali solution with pure water; the complexing agent ① is prepared by diluting a 20% concentration of ammonia water; and the complexing agent ② is prepared by dissolving Na3C6H5O7·2H2O in pure water.

[0020] Preferably, in step 3, the stirring speed is 600-900 rpm and the temperature is raised to 45-65°C.

[0021] Preferably, in step 4, after nitrogen is introduced for 2 hours, precipitant ① is added to the reactor until the bottom water pH is 11.7-12.1, and complexing agent ① and complexing agent ② are added to the reactor until the concentrations of the two complexing agents in the bottom water are 4-10 g / L and 0.01-0.1 mol / L, respectively; in step 5, the pH and complexing agent concentrations described in step 4 are maintained in the initial stage of the synthesis reaction.

[0022] Preferably, in step 6, nitrogen gas is introduced into the concentrator to maintain a slightly positive pressure of 0.02-0.04 MPa.

[0023] Preferably, in step 7, the stirring speed is reduced to 300-500 rpm and the temperature is kept constant for 2 hours to obtain the desired precursor slurry.

[0024] Preferably, in step 9, the precursor product and Na2CO3 are mixed uniformly in a mixer at a ratio of 1:1 to 1:1.07; the mixed material is placed in an atmosphere furnace and kept at 850 to 1000°C for 12-24 hours.

[0025] The sodium-ion battery quaternary precursor of the present invention has the following beneficial effects:

[0026] 1. It is easy to fire single crystals, and single crystal materials are less prone to cracking during the expansion and contraction of grains, which can effectively prevent electrolyte from penetrating into the grains and causing a reaction.

[0027] 2. The sintered single-crystal material has a rounded morphology, uniform particle size, minimal agglomeration, and is easily broken down by gas. These properties greatly improve the material's cycle performance and make it easier to process during production, thus reducing production and equipment costs.

[0028] 3. The precursor with this elemental ratio combination can effectively reduce the lattice distortion caused by Mn3+ and enhance the bonding between MO, thereby enabling the material to have better high-rate cycling performance. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a SEM image of the precursor in Embodiment 1 of the present invention.

[0031] Figure 2 This is the XRD pattern of the precursor in Embodiment 1 of the present invention.

[0032] Figure 3 This is a SEM morphology image of the positive electrode in Embodiment 1 of the present invention.

[0033] Figure 4 This is the XRD pattern of the positive electrode in Embodiment 1 of the present invention.

[0034] Figure 5 This is a cyclic test diagram from Embodiment 1 of the present invention.

[0035] Figure 6 This is a SEM image of the precursor in Embodiment 2 of the present invention.

[0036] Figure 7 This is a SEM morphology image of the positive electrode in Embodiment 2 of the present invention.

[0037] Figure 8 This is a cyclic test diagram from Embodiment 2 of the present invention.

[0038] Figure 9 This is a SEM image of the precursor in Embodiment 3 of the present invention.

[0039] Figure 10 This is a SEM morphology image of the positive electrode in Embodiment 3 of the present invention.

[0040] Figure 11 This is a cyclic test diagram from Embodiment 3 of the present invention.

[0041] Figure 12 This is a SEM image of the precursor Y ratio being 0 in Embodiment 4 of the present invention.

[0042] Figure 13 This is a SEM image of the precursor Y ratio of 0.02 in Embodiment 4 of the present invention.

[0043] Figure 14 This is a SEM image of the precursor Y ratio of 0.06 in Embodiment 4 of the present invention.

[0044] Figure 15 This is a SEM morphology image of the positive electrode with a Y ratio of 0 in Embodiment 4 of the present invention.

[0045] Figure 16 This is a SEM morphology image of the positive electrode with a Y ratio of 0.02 in Embodiment 4 of the present invention.

[0046] Figure 17 This is a SEM morphology image of the positive electrode with a Y ratio of 0.06 in Embodiment 4 of the present invention.

[0047] Figure 18 Ni in Embodiment 4 of the present invention 0.22 Fe 0.33 Mn 0.33 Zn 0.12 Cyclic test diagram of (OH)2.

[0048] Figure 19 Ni in Embodiment 4 of the present invention 0.22 Fe 0.33 Mn 0.33 Zn 0.1 Y 0.02 Cyclic test diagram of (OH)2.

[0049] Figure 20 Ni in Embodiment 4 of the present invention 0.22 Fe 0.33 Mn 0.33 Zn 0.06 Y 0.06 Cyclic test diagram of (OH)2.

[0050] Figure 21 This is a cyclic test diagram from Comparative Example 1 of the present invention.

[0051] Figure 22 NaNi in Comparative Example 2 of this invention 0.22 Fe 0.33 Mn 0.33 Zn 0.08 Y 0.04 Cyclic test diagram of O2.

[0052] Figure 23 NaNi in Comparative Example 2 of this invention 0.25 Fe 0.375 Mn 0.375 Cyclic test diagram of O2.

[0053] Figure 24 NaNi in Comparative Example 3 of this invention0.22 Fe 0.33 Mn 0.33 Zn 0.08 Y 0.04 Cyclic test diagram of O2.

[0054] Figure 25 NaNi in Comparative Example 3 of this invention 0.25 Fe 0.375 Mn 0.375 Cyclic test diagram of O2. Detailed Implementation

[0055] The present invention will now be further described with reference to the accompanying drawings.

[0056] It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0057] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] Example 1

[0059] 1) A quaternary mixed salt of nickel, iron, manganese, and zinc with a total metal concentration of 1.85M was prepared in a sealed stirring tank using pure water according to the designed ratio Ni:Fe:Mn:Zn:Y = 0.22:0.33:0.33:0.08:0.04. L(+)-ascorbic acid was added to the mixed salt solution at 0.025% of the total mass of the solution, resulting in "Salt ①". A 0.25M yttrium salt was prepared as "Salt ②".

[0060] 2) Dilute the NaOH solution with pure water to an 8M alkaline solution as "precipitant ①". Dilute ammonia water to an 8M solution, and then prepare trisodium citrate to a 2M solution, which are respectively labeled as "complexing agents ① and ②".

[0061] 3) Inject a certain amount of pure water into the reactor, turn on the stirrer at 800 rpm, heat to 65°C, and then blow N2 gas with a purity of ≥99.9% into the reactor. At the same time, nitrogen gas is also blown into "salt ①" and "precipitant ①".

[0062] 4) After nitrogen is introduced for 2 hours, add “precipitant ①” to the reactor until the bottom water pH = 12.0. Add “complexing agent ①” and “complexing agent ②” to the reactor until the concentrations of the two complexing agents in the bottom water are 8 g / L and 0.02 mol / L, respectively.

[0063] 5) Set the flow rate of "Salt ①" to 50 ml / min, "Precipitator ①" to 18.5 ml / min, "Complexing Agent ①" to 6.4 ml / min, and "Complexing Agent ②" to 1.5 ml / min. Pump these components evenly into the reactor using a metering pump for the synthesis reaction. Maintain the temperature and stirring as described in "3)" within the reactor. During the initial stage of the reaction, fine-tune the flow rates of "Precipitator ①" and "Complexing Agents ① and ②" to maintain the pH and complexing agent concentrations as described in "4)" within the reactor.

[0064] 6) During the reaction, slowly lower the pH to 11.2 over 4-10 hours, then maintain the pH at 11.2 and continue the reaction for 48 hours. During the reaction, increase the solid content of the reactor using a concentrator. The concentrator discharge flow rate is 4 L / h, and nitrogen is introduced into the concentrator to maintain a slight positive pressure (0.02-0.04 MPa).

[0065] 7) After reacting for 48 hours, switch "Salt ①" to "Salt ②" with a flow rate of 50 ml / min. Simultaneously, reduce the flow rate of "Precipitator ①" to 3 ± 1 ml / min to maintain the pH level as described in "6)", and reduce the flow rates of "Complexing Agent ①" and "Complexing Agent ②" to 5 ± 0.5 ml / min and 1.2 ± 0.2 ml / min respectively to maintain the complexing agent concentration as described in "4)". Continue the reaction until the coating amount of "Salt ②" reaches the designed ratio. Finally, reduce the stirring speed to 500 rpm and maintain the constant temperature for 2 hours to obtain the desired precursor slurry.

[0066] 8) Pump the slurry from step “7)” into a centrifuge for filtration, and wash the filter cake with 0.5-2 mol / L dilute alkali and hot pure water at 50-70℃. Then, perform dynamic drying, sieving, and demagnetization to finally obtain the precursor product Ni. 0.22 Fe 0.33 Mn 0.33 Zn 0.08 Y 0.04 (OH)2, its morphology and peak shape are shown in the attached figure. Figure 1-4

[0067] 9) The precursor product from step “8)” and Na2CO3 are mixed uniformly in a mixer at a ratio of 1:1.05. The mixed material is then placed in an atmosphere furnace and held at 930℃ for 12 hours. After cooling, it is ground, air-crushed, and sieved to obtain the cathode material NaNi. 0.22 Fe 0.33 Mn 0.33 Zn 0.08 Y 0.04 O2. Its morphology and peak shape are shown in the attached figure. Figure 1-4 .

[0068] Testing: The positive electrode product from step "9)" is mixed with PVDF adhesive, SP powder conductive agent, and NMP dispersant in a homogenizer to form an active material slurry. The slurry is coated onto aluminum foil, dried, and then cut into positive electrode sheets with a diameter of 12 mm. A 2032 coin cell is then fabricated using glass fiber as the separator, a mixture of DMC, EMC, EC, NaPF6, and FEC in a specific molar ratio as the electrolyte, and a sodium sheet with a diameter of 15.6 mm as the negative electrode. The fabricated coin cells are placed in a Blue Electric testing system for electrochemical testing. The charge / discharge voltage is selected as 2.0-4.0V, and the test temperature is 25℃. First, the cells are cycled at a rate of 0.1C for two weeks, then at 0.5C, 1C, 2C, and 3C for three weeks each. The cycle test results are attached. Figure 5 .

[0069] Example 2:

[0070] Prepared according to the method in Example 1, except that Y in step "1)" is replaced with Ti. Its precursor Ni 0.22 Fe 0.33 Mn 0.33 Zn 0.08 Ti 0.04 The morphology of (OH)2 is shown in the attached figure. Figure 6 The morphology of the cathode material is shown in the attached figure. Figure 7 The loop test is attached. Figure 8 .

[0071] Example 3:

[0072] Prepared according to the method in Example 1, except that Y in step "1)" is replaced with Cr. Its precursor Ni 0.22 Fe 0.33 Mn 0.33 Zn 0.08 Cr 0.04 The morphology of (OH)2 is shown in the attached figure. Figure 9 The morphology of the cathode material is shown in the attached figure. Figure 10 The loop test is attached. Figure 11 .

[0073] Example 4:

[0074] Prepared according to the method in Example 1, the Y ratio in step "1)" was configured to be 0, 0.02, and 0.06, respectively. The resulting precursors were Ni... 0.22 Fe 0.33 Mn 0.33 Zn 0.12 (OH)2, Ni 0.22 Fe 0.33 Mn 0.33 Zn 0.1 Y 0.02 (OH)2, Ni 0.22 Fe0.33 Mn 0.33 Zn 0.06 Y 0.06 (OH)2, the morphology of its precursor is shown in the attached figure. Figure 12-14 The morphology of the cathode material is shown in the attached figure. Figure 15-17 The loop test is attached. Figure 18-20 .

[0075] Comparative Example 1:

[0076] Prepared according to the method in Example 1, removing Zn and Y from step "1)". The resulting precursor is Ni. 0.25 Fe 0.375 Mn 0.375 The coin cell test results for the positive electrode material prepared from (OH)2 are shown in the attached figure. Figure 21 .

[0077] Comparative Example 2:

[0078] Following the method described in patent CN109817970A, NaNi with good electrochemical performance as shown in Example 1 was prepared. 0.22 Fe 0.33 Mn 0.33 Zn 0.08 Y 0.04 O2 and NaNi, which has poor electrochemical performance in Comparative Example 1 0.25 Fe 0.375 Mn 0.375 O2 materials. The cycling performance of the two materials is shown in the attached figure. Figure 22-23 .

[0079] Comparative Example 3:

[0080] Following the method described in patent CN114644361A, NaNi with good electrochemical performance as shown in Example 1 was prepared. 0.22 Fe 0.33 Mn 0.33 Zn 0.08 Y 0.04 O2 and NaNi, which has poor electrochemical performance in Comparative Example 1 0.25 Fe 0.375 Mn 0.375 O2 materials. The cycling performance of the two materials is shown in the attached figure. Figure 24-25 .

[0081] From the appendix Figure 1-25As can be seen from the results, the first-pass efficiency, 3C capacity, and cycle performance of Example 1 are all good. The performance of yttrium coating / doping is superior to that of coating / doping with other elements; the material performance when the zinc to yttrium ratio is 0.08:0.04 is superior to other ratios; the electrochemical performance of the precursor without zinc as the main element and without coating / doping with other elements is poor. The precursor prepared by the method described in the existing patent has weaker electrochemical properties after sintering, especially in terms of specific capacity, than the method in the examples. Statistical results are shown in Table 1.

[0082] Table 1: Key Data of Examples and Comparative Examples

[0083]

[0084]

[0085] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for preparing a quaternary precursor for sodium batteries, characterized in that, The main elements of the quaternary precursor are Ni, Fe, Mn, and Zn, and the doping or coating element is one of Y, Ti, and Cr. The quaternary precursor is prepared by co-precipitation with an antioxidant, a complexing agent, and a precipitant, and its molecular formula is Ni. 0.22 Fe 0.33 Mn 0.33 Zn m X n (OH)₂, where m+n=0.12, m≥0.06, n>0, and X is one of Y, Ti, and Cr; its preparation method includes the following steps: Step 1: Prepare a mixed salt solution of Ni, Fe, Mn, and Zn in a sealed stirring tank using pure water according to the designed ratio. Add L(+)-ascorbic acid to the solution at 0.01%~0.1% of the total mass of the mixed salt to finally prepare salt ①. Then, prepare a salt solution of one of Y, Ti, and Cr separately at 0.1-0.5 mol / L, and denote it as salt ②. Step 2: Prepare an alkaline solution with a concentration of 4-8 mol / L as precipitant ①; dilute ammonia water to a solution of 4-8 mol / L, and then prepare trisodium citrate to a solution of 1-2 mol / L, which are respectively labeled as complexing agent ① and complexing agent ②; Step 3: Inject a certain amount of pure water into the reactor, stir, heat up, and then blow N2 gas with a purity of ≥99.9% into the reactor. At the same time, nitrogen gas is also blown into the salt ① and precipitant ①. Step 4: After nitrogen is introduced for 2 hours, add precipitant ① to the reactor, and add complexing agent ① and complexing agent ② to the reactor; Step 5: Set the flow rates of salt ① and the precipitant and complexing agent in Step 4 according to the process requirements. Pump the above reagents evenly into the reactor through a metering pump to carry out the synthesis reaction. Maintain the temperature and stirring speed in the reactor as in Step 3. Step 6: During the reaction, slowly lower the pH to 11.0-11.4 over 4-10 hours, then maintain the pH at 11.0-11.4 and continue the reaction for 48 hours. During the reaction, increase the solid content of the reactor using a concentrator. The concentrator discharge flow rate is 2-5 L / h, and nitrogen is introduced into the concentrator to maintain a slight positive pressure. Step 7: After reacting for 48 hours, switch salt ① to salt ② with the set flow rate; at the same time, reduce the flow rate of precipitant ① to maintain the pH in the reactor as in step 6, and reduce the flow rates of complexing agents ① and ② to maintain the complexing agent concentration as in step 4; continue the reaction until the coating amount of salt ② reaches the design requirement; finally, reduce the stirring speed and maintain the constant temperature to obtain the required precursor slurry. Step 8: Pump the slurry from Step 7 into a centrifuge for filtration, and wash the filter cake with 0.5-2 mol / L dilute alkali and hot pure water at 50-70℃; then perform dynamic drying, sieving, and demagnetization to finally obtain the precursor product Ni. 0.22 Fe 0.33 Mn 0.33 Zn m X n (OH)2, where m+n=0.12, m≥0.06, n>0; Step 9: Place the precursor product from Step 8 and Na2CO3 into a mixer for uniform mixing; place the mixed material in an atmosphere furnace and keep it at a constant temperature; after cooling, grind, air-crush, and sieve to obtain the cathode material NaNi. 0.22 Fe 0.33 Mn 0.33 Zn m X n O2.

2. The method for preparing a sodium-ion battery quaternary precursor as described in claim 1, characterized in that, The molar concentration of the mixed salt solution of Ni, Fe, Mn and Zn prepared in step 1 is 1.5-2.0 mol / L.

3. The method for preparing a sodium-ion battery quaternary precursor as described in claim 2, characterized in that, In step 1, salt ① is a soluble salt with a total concentration of 1.5-2 mol / L, comprising raw materials NiSO4·6H2O, MnSO4·H2O, FeSO4·7H2O, and ZnSO4·7H2O; salt ② is a soluble salt with a concentration of 0.1-0.5 mol / L prepared from one of Y2(SO4)3·8H2O, TiCl4, and Cr2(SO4)3·6H2O.

4. The method for preparing a sodium-ion battery quaternary precursor as described in claim 1, characterized in that, In step 2, the precipitant ① is prepared by diluting a 32% liquid alkali solution with pure water; the complexing agent ① is prepared by diluting a 20% concentration of ammonia water; and the complexing agent ② is prepared by dissolving Na3C6H5O7·2H2O in pure water.

5. The method for preparing a sodium-ion battery quaternary precursor as described in claim 1, characterized in that, In step 3, the stirring speed is 600~900 rpm, and the temperature is raised to 45~65℃.

6. The method for preparing a sodium-ion battery quaternary precursor as described in claim 5, characterized in that, In step 4, after nitrogen is bubbled in for 2 hours, precipitant ① is added to the reactor until the bottom water pH is 11.7-12.

1. Complexing agent ① and complexing agent ② are added to the reactor until the concentrations of the two complexing agents in the bottom water are 4-10 g / L and 0.01-0.1 mol / L, respectively. In step 5, the pH and complexing agent concentrations described in step 4 are maintained in the initial stage of the synthesis reaction.

7. The method for preparing a sodium-ion battery quaternary precursor as described in claim 1, characterized in that, In step 6, nitrogen gas is introduced into the concentrator to maintain a slightly positive pressure of 0.02-0.04 MPa.

8. The method for preparing a sodium-ion battery quaternary precursor as described in claim 1, characterized in that, In step 7, the stirring speed is finally reduced to 300-500 rpm, and the temperature is kept constant for 2 hours to obtain the desired precursor slurry.

9. The method for preparing a sodium-ion battery quaternary precursor as described in claim 1, characterized in that, In step 9, the precursor product and Na2CO3 are mixed uniformly in a mixer at a ratio of 1:1 to 1:1.07; the mixed material is placed in an atmosphere furnace and kept at 850 to 1000°C for 12 to 24 hours.

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