High-performance sodium storage material based on Zn-doped modified P2 type sodium nickel manganese oxide, preparation method and battery

Abstract

The invention belongs to the technical field of preparation of sodium ion battery electrode materials, and provides a high-performance sodium storage material based on Zn-doped modified P2 type sodium nickel manganese oxide, a preparation method and a battery. The invention aims to solve the problems of rapid capacity attenuation under high voltage, obvious volume change in the phase change process, irreversible capacity loss and the like of the existing P2 type sodium nickel manganese oxide material. According to the main technical scheme, through low-concentration Zn doping, the structural stability of the material is optimized, and the electrochemical performance of the material is improved on the premise that voltage, capacity and energy density are not sacrificed. The preparation method comprises the following steps: dissolving a sodium source, a manganese source, a nickel source and a zinc source, adding a complexing agent for reaction, evaporating the solvent to dryness, and performing two-stage calcination to finally obtain the zinc-doped sodium-nickel-manganese oxide with the P2 type layered structure. The material can be used for high-safety sodium ion battery positive electrodes and is widely applied to the fields of energy storage power stations, low-speed electric vehicles and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sodium ion battery electrode material preparation, and particularly relates to a high-performance sodium storage material based on Zn-doped modified P2-type sodium nickel manganate, a preparation method and a battery. BACKGROUND

[0002] Sodium ion batteries have become an important choice in the field of energy storage power stations and low-speed electric vehicles due to cost advantages and excellent low-temperature performance, and are regarded as an ideal substitute for lithium ion batteries. As a core component of the battery, the positive electrode material directly determines the overall performance. Among them, the layered oxide positive electrode material has shown significant application potential in the development of sodium ion battery technology due to its simple process, high reversible capacity and excellent rate performance.

[0003] Na 0.67 Ni 0.33 Mn 0.67 O2 is a very typical P2-type layered oxide positive electrode material and has been widely studied by many researchers. However, this material still has many limitations: rapid capacity decay at high voltage, multiphase transition caused by Jahn-Teller distortion of Mn 3+ , significant volume change generated during the phase transition, and irreversible capacity loss caused by irreversible phase transition, which seriously affect the practical application of the material. Existing mitigation strategies (such as limiting the cutoff voltage) often come at the expense of voltage, capacity and energy density. SUMMARY

[0004] The purpose of the present application is to improve the stability of the material without sacrificing voltage, capacity and energy density by designing low-concentration transition metal doping, and to release the electrochemical performance of the material as much as possible.

[0005] In order to achieve the above purpose, the present application adopts the following technical means:

[0006] The present application provides a preparation method of a high-performance sodium storage material based on Zn-doped modified P2-type sodium nickel manganate, comprising the following steps:

[0007] Step 1: Dissolve a sodium source, a manganese source, a nickel source and a zinc source in deionized water, stir and mix to form a first solution;

[0008] Step 2: Dissolve a complexing agent in deionized water to form a second solution;

[0009] Step 3: Add the first solution dropwise to the second solution and stir to react;

[0010] Step 4: Evaporate the solvent of the solution obtained in step 3 at 80-100 DEG C to obtain a crystalline precursor;

[0011] Step 5: after the grinding of the crystalline precursor, two-stage calcination is carried out in an air atmosphere: first, calcination at 450-550 DEG C for 4-8 hours, and then calcination at 800-900 DEG C at a temperature increasing rate of 3-8 DEG C / min for 10-14 hours, to obtain a zinc-doped sodium nickel manganese oxide with a P2-type layered structure, whose general formula is Na 0.67 Ni x Mn 0.67 Zn y O2, wherein 0.26≤x≤0.33, 0.01≤y≤0.07, and x+y≈0.33.

[0012] In the above scheme, the sodium source, the manganese source, the nickel source and the zinc source are sodium acetate trihydrate, manganese acetate tetrahydrate, nickel acetate tetrahydrate and zinc acetate dihydrate, respectively.

[0013] In the above scheme, y is 0.01, 0.03, 0.05 or 0.07.

[0014] In the above scheme, 0.96 g of sodium acetate trihydrate, 1.633 g of manganese acetate tetrahydrate, 0.7750 g of nickel acetate tetrahydrate and 0.022 g of zinc acetate dihydrate are dissolved in 30 mL of a deionized water solution, and stirred for 30 min to obtain a first solution.

[0015] In the above scheme, 1.9213 g of anhydrous citric acid is dissolved in 30 mL of deionized water to obtain a second solution.

[0016] In the above scheme, the temperature increasing rate in step 5 is 5 DEG C / min.

[0017] In the above scheme, the calcination temperature after the temperature increasing in step 5 is 900 DEG C.

[0018] In the above scheme, the stirring reaction time in step 3 is 0.5-1.5 hours.

[0019] The application also provides a high-safety sodium ion battery positive electrode material obtained by the preparation method.

[0020] The application also provides a sodium ion battery comprising the high-safety sodium ion battery positive electrode material.

[0021] In summary, due to the adoption of the above technical solutions, the application has the following advantages:

[0022] 1. The application successfully synthesizes a zinc-doped P2-Na 0.67 Ni 0.32 Mn 0.67 Zn 0.01O2 (denoted as NMNZ) layered oxide cathode material. The introduction of zinc alleviates the volume expansion of the material during charge and discharge, thereby improving the cycle stability of the material during charge and discharge. Low doping also reduces capacity loss caused by doping.

[0023] 2. The Na prepared by this invention 0.67 Ni 0.32 Mn 0.67 Zn 0.01 When used as a sodium storage cathode, O2 exhibits excellent electrochemical performance. It demonstrates a high reversible capacity of 84.9 mAh / g at a 10C rate (1C = 170 mAh / g) over a wide voltage range of 1.5-4.3V. After 300 cycles, the capacity retention rate is 92.9% compared to the initial cycle.

[0024] 3. The role of Zn doping in P2-type layered structures: stabilizing lattice oxygen, suppressing phase transitions, and mitigating volume expansion. This invention introduces a low concentration of Zn (0.01≤y≤0.07) into P2-type sodium nickel manganate. Utilizing the full electron structure of Zn's d orbitals and the difference in ionic radius between Zn and Ni and Mn, the interlayer structural stability of the material is enhanced. Furthermore, it avoids the complex interaction mechanisms between multiple metals and the intrinsic defects caused by multiphase interfaces, better quantifies the effect of cation doping, and provides strong performance traceability. The study focuses on the mechanism by which Zn is introduced into the layers. The technical effects of Zn doping are achieved through the following mechanisms:

[0025] Lattice distortion suppression: The introduction of Zn fills the vacancies at Ni / Mn sites and suppresses Mn distortion. 3+ The Jahn-Teller distortion effect. In the P2 type structure, Mn 3+ The high reactivity of Mn can easily lead to interlayer slip and phase transition, while Zn doping reduces the reactivity of Mn by occupying some transition metal sites. 3+ The concentration of [something] was increased, thereby suppressing lattice distortion during the phase transition process.

[0026] Enhanced interlayer bonding: Zn doping strengthens the covalent bonds between TM and O, improving interlayer adhesion. This enhanced interlayer force effectively mitigates the volume expansion caused by sodium ion insertion / extraction during charging and discharging, preventing the material structure from collapsing.

[0027] Improved oxygen stability: Zn doping reduces the tendency for lattice oxygen to escape by modulating the electronic environment of oxygen in the crystal lattice. This is achieved through theoretical analysis combining DEMS and DFT. Figure 7 , Figure 8 Zn doping shifts the band center of the O 2p orbitals downward, suppressing oxygen activity under high pressure, thereby reducing capacity loss caused by irreversible phase transitions and lattice oxygen release.

[0028] The combination of Zn doping and the P2-type layered structure synergistically addresses the issues of phase transition runaway, volume expansion, and irreversible capacity loss under high voltage through a triple mechanism of lattice distortion suppression, interlayer bonding enhancement, and oxygen stability improvement. This structural optimization significantly improves cycle stability without sacrificing the material's voltage and capacity.

[0029] 4. Synergistic effect of two-stage calcination process and complexing agent: achieving uniform structure and high crystallinity.

[0030] This invention solves the problems of uneven precursor, insufficient crystallinity, and impurity formation in traditional preparation methods by using a two-stage calcination process (pre-calcination at 450-550℃ + main calcination at 800-900℃) and the synergistic effect of a complexing agent (such as citric acid). Specific technical effects are as follows:

[0031] Precursor homogenization: The complexing agent (citric acid) ensures the uniform distribution of sodium, nickel, manganese, and zinc in the solution by forming stable chelates with metal ions. This homogenized precursor avoids local enrichment or segregation during subsequent calcination, thereby reducing the formation of impurity phases.

[0032] Segmented calcination controls lattice growth: The first stage (450-550℃) of pre-calcination dehydrates and decomposes organic matter to form a uniform oxide precursor; the second stage (800-900℃) of high-temperature calcination promotes lattice ordering. By controlling the heating rate (3-8℃ / min) and temperature gradient, the two-stage calcination process avoids structural defects caused by rapid lattice growth at high temperatures, ultimately obtaining highly crystalline P2-type layered oxides.

[0033] Oxygen vacancy regulation: By combining a two-stage calcination process with the introduction of a complexing agent, the oxygen vacancy defects in the crystal lattice are reduced through control of the redox environment. This regulation further enhances the structural stability of the material and reduces irreversible capacity loss.

[0034] 5. Synergistic effect of Zn doping and two-stage calcination: improving electrochemical performance

[0035] This invention achieves a comprehensive improvement in the electrochemical performance of materials through the synergistic effect of Zn doping and a two-stage calcination process:

[0036] Optimization of ion diffusion kinetics: Zn doping lowers the diffusion barrier of sodium ions between layers by modulating the lattice structure. Combined with GITT test results ( Figure 2 In the Zn-doped material (g), the sodium ion diffusion coefficient is significantly higher than that of the undoped sample, indicating that it has a faster charge transport rate.

[0037] Enhanced interfacial stability: The dense structure formed by the two-stage calcination process, combined with the Zn-doped lattice optimization, reduces side reactions between the material surface and the electrolyte. This interfacial stability effectively suppresses capacity decay during high-voltage cycling.

[0038] Capacitive effect-dominated energy storage mechanism: through cyclic voltammetry testing ( Figure 4 Analysis showed that the capacitance contribution of the Zn-doped material was significantly higher than that of the undoped sample, indicating that it has superior pseudocapacitive characteristics. This improved energy storage mechanism further enhances the material's rate performance and cycle stability.

[0039] Zn doping enhances ion diffusion kinetics and interfacial stability through structural optimization, while the two-stage calcination process further strengthens these effects through lattice ordering and oxygen vacancy modulation. The synergistic effect of these two processes enables the material to maintain excellent capacity and cycling performance at high rates (10C), overcoming the performance bottleneck of existing materials at high voltages. Attached Figure Description

[0040] Figure 1 This is an electron microscope image of the sodium-ion battery electrode material of the present invention.

[0041] Figure 2 This is a graph showing the electrochemical performance test results of the sodium-ion battery electrode material of this invention.

[0042] Figure 3 These are the X-ray diffraction patterns of Examples 3-7 of the present invention.

[0043] Figure 4 This is a cyclic voltammetry test diagram and corresponding fitting analysis of the sodium-ion battery electrode material of the present invention.

[0044] Figure 5 This is an ex-situ X-ray photoelectron spectroscopy (XPS) analysis diagram of the sodium-ion battery electrode material of the present invention.

[0045] Figure 6 This is a graph showing the electrochemical performance of a full cell assembled with the sodium-ion battery electrode material of this invention and hard carbon.

[0046] Figure 7 This is a density functional theory (DFT) analysis diagram of the sodium-ion battery electrode material of the present invention;

[0047] Figure 8 This is a graph showing the in-situ electrochemical mass spectrometry (DEMS) test data of the sodium-ion battery electrode material of this invention. Detailed Implementation

[0048] The embodiments of the present invention will be described in detail below. Although the present invention will be described and illustrated in conjunction with some specific embodiments, it should be noted that the present invention is not limited to these embodiments. On the contrary, any modifications or equivalent substitutions made to the present invention should be covered within the scope of the claims of the present invention.

[0049] Furthermore, to better illustrate the present invention, numerous specific details are set forth in the following detailed embodiments. Those skilled in the art will understand that the present invention can be practiced without these specific details.

[0050] A method for preparing a high-safety sodium-ion battery material includes the following steps:

[0051] Example 1

[0052] Step 1: Dissolve 0.96g sodium acetate trihydrate, 1.633g manganese acetate tetrahydrate, 0.7750g nickel acetate tetrahydrate and 0.022g zinc acetate dihydrate in 30mL of deionized water and stir for 30min;

[0053] Step 2: Dissolve 1.9213g of anhydrous citric acid in 30ml of deionized water;

[0054] Step 3: Slowly add the solution obtained in Step 1 to the solution in Step 2, and stir for 1 hour;

[0055] Step 4: Place the solution obtained in Step 3 in a 90℃ oil bath, evaporate the solvent, and crystallize.

[0056] Step 5: Grind the crystalline sample obtained in Step 4 until homogeneous, calcine it in a muffle furnace at 500℃ for 6 hours, then raise the temperature to 900℃ and calcine for 12 hours at a heating rate of 5℃ / min, finally obtaining Zn-doped P2 type Na. 0.67 Ni 0.32 Mn 0.67 Zn 0.01 O2 (denoted as NMNZ).

[0057] Example 2

[0058] Step 1: Dissolve 0.96g sodium acetate trihydrate, 1.633g manganese acetate tetrahydrate and 0.8274g nickel acetate tetrahydrate in 30mL of deionized water and stir for 30min;

[0059] Step 2: Dissolve 1.9213g of anhydrous citric acid in 30ml of deionized water;

[0060] Step 3: Slowly add the solution obtained in Step 1 to the solution in Step 2, and stir for 1 hour;

[0061] Step 4: Place the solution obtained in Step 3 in a 90℃ oil bath, evaporate the solvent, and crystallize.

[0062] Step 5: Grind the crystalline sample obtained in Step 4 until homogeneous, calcine it in a muffle furnace at 500℃ for 6 hours, then raise the temperature to 900℃ and calcine for 12 hours at a heating rate of 5℃ / min, finally obtaining P2 type Na. 0.67 Ni 0.33 Mn 0.67 O2 (denoted as NMN).

[0063] Example 3

[0064] Step 1: Dissolve 0.96g sodium acetate trihydrate, 1.633g manganese acetate tetrahydrate, 0.8274g nickel acetate tetrahydrate and 0.066g zinc acetate dihydrate in 30mL of deionized water and stir for 30min;

[0065] Step 2: Dissolve 1.9213g of anhydrous citric acid in 30ml of deionized water;

[0066] Step 3: Slowly add the solution obtained in Step 1 to the solution in Step 2, and stir for 1 hour;

[0067] Step 4: Place the solution obtained in Step 3 in a 90℃ oil bath, evaporate the solvent, and crystallize.

[0068] Step 5: Grind the crystalline sample obtained in Step 4 until homogeneous, calcine it in a muffle furnace at 500℃ for 6 hours, then raise the temperature to 900℃ and calcine for 12 hours at a heating rate of 5℃ / min, finally obtaining Zn-doped P2 type Na. 0.67 Ni 0.30 Mn 0.67 Zn 0.03 O2.

[0069] Compared to Example 1, the zinc doping ratio is increased.

[0070] Example 4

[0071] Step 1: Dissolve 0.96g sodium acetate trihydrate, 1.633g manganese acetate tetrahydrate, 0.8274g nickel acetate tetrahydrate and 0.11g in 30mL of deionized water and stir for 30min;

[0072] Step 2: Dissolve 1.9213g of anhydrous citric acid in 30ml of deionized water;

[0073] Step 3: Slowly add the solution obtained in Step 1 to the solution in Step 2, and stir for 1 hour;

[0074] Step 4: Place the solution obtained in Step 3 in a 90℃ oil bath, evaporate the solvent, and crystallize.

[0075] Step 5: Grind the crystalline sample obtained in Step 4 until homogeneous, calcine it in a muffle furnace at 500℃ for 6 hours, then raise the temperature to 900℃ and calcine for 12 hours at a heating rate of 5℃ / min, finally obtaining Zn-doped P2 type Na. 0.67 Ni 0.28 Mn 0.67 Zn 0.05 O2.

[0076] Compared to Example 1, the zinc doping ratio is increased.

[0077] Example 5

[0078] Step 1: Dissolve 0.96g sodium acetate trihydrate, 1.633g acetic acid tetrahydrate, 0.8274g nickel acetate tetrahydrate and 0.132g in 30mL of deionized water and stir for 30min;

[0079] Step 2: Dissolve 1.9213g of anhydrous citric acid in 30ml of deionized water;

[0080] Step 3: Slowly add the solution obtained in Step 1 to the solution in Step 2, and stir for 1 hour;

[0081] Step 4: Place the solution obtained in Step 3 in a 90℃ oil bath, evaporate the solvent, and crystallize.

[0082] Step 5: Grind the crystalline sample obtained in Step 4 until homogeneous, calcine it in a muffle furnace at 500℃ for 6 hours, then raise the temperature to 900℃ and calcine for 12 hours at a heating rate of 5℃ / min, finally obtaining Zn-doped P2 type Na. 0.67 Ni 0.26 Mn 0.67 Zn 0.07 O2.

[0083] Compared to Example 1, the zinc doping ratio is increased.

[0084] Example 6

[0085] Step 1: Dissolve 0.96g sodium acetate trihydrate, 1.633g acetic acid tetrahydrate, 0.8274g nickel acetate tetrahydrate and 0.132g in 30mL of deionized water and stir for 30min;

[0086] Step 2: Dissolve 1.9213g of anhydrous citric acid in 30ml of deionized water;

[0087] Step 3: Slowly add the solution obtained in Step 1 to the solution in Step 2, and stir for 1 hour;

[0088] Step 4: Place the solution obtained in Step 3 in a 90℃ oil bath, evaporate the solvent, and crystallize.

[0089] Step 5: Grind the crystalline sample obtained in Step 4 until homogeneous, calcine it in a muffle furnace at 500℃ for 6 hours, then raise the temperature to 800℃ and calcine for 12 hours at a heating rate of 5℃ / min, finally obtaining P2 type Na. 0.67 Ni 0.33 Mn 0.67 O2 (denoted as NMN).

[0090] Compared to Example 2, the calcination temperature was reduced.

[0091] Example 7

[0092] Step 1: Dissolve 0.96g sodium acetate trihydrate, 1.633g acetic acid tetrahydrate, 0.8274g nickel acetate tetrahydrate and 0.132g in 30mL of deionized water and stir for 30min;

[0093] Step 2: Dissolve 1.9213g of anhydrous citric acid in 30ml of deionized water;

[0094] Step 3: Slowly add the solution obtained in Step 1 to the solution in Step 2, and stir for 1 hour;

[0095] Step 4: Place the solution obtained in Step 3 in a 90℃ oil bath, evaporate the solvent, and crystallize.

[0096] Step 5: Grind the crystalline sample obtained in Step 4 until homogeneous, calcine it in a muffle furnace at 500℃ for 6 hours, then raise the temperature to 850℃ and calcine for 12 hours at a heating rate of 5℃ / min, finally obtaining P2 type Na. 0.67 Ni 0.33 Mn 0.67 O2 (denoted as NMN).

[0097] Compared to Example 2, the calcination temperature was reduced.

[0098] Figure 1 For example, electron micrographs of NMN and NMNZ, and X-ray diffraction and electron diffraction (XRD) patterns, both show good crystallinity. Figure 1 a and Figure 1 (b) The (002) diffraction peak of NMNZ is shifted to the left compared to NMN, indicating that zinc doping leads to c-axis lattice expansion. Rietveld refinement confirmed that NMN has a hexagonal structure (space group P63 / mmc, Rwp = 4.46%), while NMNZ maintains the same space group P63 / mmc (Rwp = 3.26%). Scanning electron microscopy (SEM) shows that both have a hexagonal morphology. Figure 1(d). Transmission electron microscopy (TEM) analysis showed that NMNZ was plate-like, and high-resolution TEM images showed clear lattice fringes. Figure 1 Selected area electron diffraction (SAED) also confirmed that it is a P2 type structure, space group P63, exhibiting a clear honeycomb-like orderly arrangement along the 1001 band axis. Figure 1 (g). Elemental mapping clearly shows the uniform distribution of different elements in local regions within the NMNZ single crystal (g). Figure 1 (h).

[0099] To demonstrate the improved electrochemical performance of the NMNZ synthesized in Example 1 compared to the NMN in Example 2, a half-cell was assembled using metallic sodium as the counter electrode, and the electrochemical performance of both examples was tested. Figure 2 a and Figure 2 As shown in the charge-discharge curve (b), the capacity retention of NMNZ after 100 cycles is significantly higher than that of NMN. The plateau at 4.2V corresponds to the oxidation of the transition metal and the redox reaction of the anion, which leads to an irreversible phase transition in the crystal lattice and the release of lattice oxygen. It is evident that the introduction of Zn significantly suppresses the plateau of NMNZ at 4.2V. Cyclic voltammetry (CV) curves at a scan rate of 0.1 mV / s (…) Figure 2 d and Figure 2 As shown in (e), the redox peak pair at 4.2 V is correlated with the typical phase transition of the NMN cathode; the redox peaks in the 2.5–4.0 V voltage range can be attributed to Ni. 2+ / Ni 3+ / Ni 3+ Redox reaction; while the weak peak below 2.5V corresponds to Mn 3+ / Mn 3+ Electrochemical reaction, which is related to Figure 2 The long voltage plateau characteristics in a are consistent. Figure 2 The rate performance of the two electrodes was compared in sections c and d. NMNZ was significantly better than NMN. Furthermore, when the current dropped back to 0.1C, the capacity was fully recovered, indicating that the material has good structural stability. Figure 2 f and Figure 2 The comparison of performance of the two electrolytic methods at 5C and 10C rates is shown in Figure 1. After 300 cycles at a high current of 10C, NMNZ still exhibits a high reversible capacity of 84.9 mAh / g, representing a capacity retention of 92.9% compared to the initial cycle. In contrast, the initial capacity of the NMN sample is not only low (74.2 mAh / g), but also decays rapidly. This demonstrates the important role of zinc doping in enhancing structural stability. Measurements were performed using intermittent current titration (GITT). Figure 4As can be clearly seen from g), during the charge-discharge process, the diffusion coefficient of all electrodes changes with different states, while that of the NMNZ electrode remains constant at 10. -8 -10 -10 cm 2 It exhibits the highest diffusion coefficient in the range of / s, while NMN is 10. -9 -10 -11 cm 2 / s indicates that the introduction of Zn in Example 1 promoted Na + The spread of.

[0100] Subsequently, cyclic voltammetry curves and fitting analysis were performed on the two example samples (NMN, NMNZ). Figure 4 ), by performing CV analysis at different scan rates (from 0.1 to 0.6 mV s), -1 , Figure 4 The CV curves of NMNZ showed a consistent shape at different scan rates, with only a slight shift in peak position as the scan rate increased, reflecting the good dynamic performance of the electrode. In contrast, the CV curves of NMN showed significant changes in peak position and shape at high scan rates, indicating that both materials have higher polarizability. The relationship between current (i) and scan rate (v) can be described by the following equation:

[0101] i = av b (1)

[0102] log i = b logv + loga (2)

[0103] After fitting, we calculated the b-value to be 0.76 for the NMNZ electrode and 0.84 for NMN. This indicates that the sodium ion storage process in NMNZ is mainly controlled by the capacitance effect, while the sodium ion storage process in NMN is mainly controlled by the diffusion process. Furthermore, the capacitance contribution (k1v) and diffusion contribution (k2v) are calculated based on the following formulas. 1 / 2 Quantitative analysis of the proportion of )

[0104] i = k1v + k2v 1 / 2

[0105] Figure 5 The image shows two example samples from 0.1 mV s. -1 up to 0.6mV s -1 The contribution of capacitance ratio at different scan rates clearly shows that the capacitance effect control ratio in NMNZ is significantly higher than that in NMN.

[0106] Then via ex-location XPS ( Figure 6This study investigated the mechanistic contribution of Zn doping and demonstrated that zinc (Zn) doping enhances the overall electrode performance through a dual mechanism: on the one hand, it significantly reduces Mn... 3+ The ratio effectively suppresses Jahn-Teller lattice distortion and improves cycle stability; on the other hand, it promotes the discharge state of Ni. 4+ To Ni 2+ Reduction, reducing irreversible capacity loss, and Zn 2+ It acts as a structural stabilizer to enhance lattice integrity and synergistically optimizes the reversibility of the manganese / nickel redox reaction.

[0107] Subsequently, in order to verify the commercial potential of Example 1 (NMNZ), the applicant used commercially available hard carbon as the negative electrode to assemble a full cell (NMNZ / / HC) by pairing it with Example 1. Figure 6 Figure b shows a comparison of the charge-discharge curves of NMNZ and hard carbon for capacity matching. Figure 6 In the middle, c represents the charge-discharge curve of the assembled full battery. Figure 6 The middle d section describes a charge-discharge cycle test of the full battery at a current density of 1C. Figure 7 In section a), after 50 cycles, the battery exhibited a performance of 93.1 mAh g⁻¹. -1 The discharge capacity was 92.8%, with a capacity retention rate of 92.8%. This demonstrates the application potential of Example 1 in sodium-ion batteries.

[0108] Furthermore, by performing in-situ electrochemical mass spectrometry (DEMS) on two example samples at 0.2C (…), Figure 8 The test battery showed changes in gas production during cycling. As can be seen from the figure, in Example 1, compared to Example 2, no significant gas production was observed during charging and discharging. However, in Example 2, significant gas production was clearly observed when charging to a high voltage state. This indicates that the introduction of zinc improves the stability of lattice oxygen and inhibits the release of lattice oxygen under high voltage conditions.

[0109] To further explore the potential factors contributing to the excellent electrochemical performance of the NMNZ synthesized in Example 1, we conducted an in-depth analysis using density functional theory (DFT). Figure 8 As shown, compared to NMN, NMNZ exhibits smaller volume change during charge and discharge. ​ The results from the CE test show that the O2p in NMNZ has a lower band center, indicating that oxygen is more difficult to release and has higher stability. This further demonstrates that the introduction of Zn inhibits the release of lattice oxygen, which is consistent with the DEMS test results.

[0110] In summary, this invention successfully synthesized sodium nickel manganate, a P2-type sodium-ion layered oxide cathode material modified with Zn doping. This material maintains good specific capacity and cycle stability over a wide voltage range of 1.5V-4.3V. The introduction of Zn strengthens the interlayer structure of the material, alleviates volume expansion during charge and discharge, and inhibits the extraction of lattice oxygen, thereby leading to a series of improvements in electrochemical performance. When used as a sodium storage cathode, after 300 charge-discharge cycles at a current density of 10C, the material exhibits a specific capacity of 84.9 mAh g⁻¹. -1 The high reversible capacity, with a capacity retention of 92.9% compared to the initial cycle, confirms its excellent cycling stability. Calculations based on theoretical analysis indicate that the improved cycling stability can be attributed to the decrease in the O 2p center band, which suppresses oxygen activity and stabilizes lattice oxygen. This invention provides an innovative solution and method to address the challenges of irreversible phase transitions, poor stability, and lattice oxygen release faced by layered oxides in the electrochemical applications of P2-type sodium-ion batteries.

[0111] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A method for preparing a high-performance sodium storage material based on Zn-doped modified P2-type sodium nickel manganate, characterized in that, Includes the following steps: Step 1: Dissolve the sodium source, manganese source, nickel source and zinc source in deionized water, stir and mix to form the first solution; Step 2: Dissolve the complexing agent in deionized water to form a second solution; Step 3: Add the first solution dropwise to the second solution and stir to react; Step 4: Evaporate the solvent in the solution obtained in Step 3 at 80-100℃ to obtain the crystal precursor; Step 5: After grinding the crystal precursor, perform a two-stage calcination in air: first, calcinate at 450-550℃ for 4-8 hours, then raise the temperature to 800-900℃ at a rate of 3-8℃ / min and calcinate for 10-14 hours to obtain zinc-doped sodium-nickel-manganese oxide with a P2-type layered structure, whose general formula is Na. 0.67 Ni x Mn 0.67 Zn y O2, where 0.26≤x≤0.33, 0.01≤y≤0.07, and x+y≈0.

33.

2. The method according to claim 1, characterized in that, The sodium, manganese, nickel, and zinc sources are sodium acetate trihydrate, manganese acetate tetrahydrate, nickel acetate tetrahydrate, and zinc acetate dihydrate, respectively.

3. The method according to claim 2, characterized in that, y is 0.01, 0.03, 0.05 or 0.

07.

4. The method according to claim 2, characterized in that, Dissolve 0.96 g sodium acetate trihydrate, 1.633 g manganese acetate tetrahydrate, 0.7750 g nickel acetate tetrahydrate and 0.022 g zinc acetate dihydrate in 30 mL of deionized water and stir for 30 min to obtain the first solution.

5. The method according to claim 4, characterized in that, The complexing agent was anhydrous citric acid. 1.9213 g of anhydrous citric acid was dissolved in 30 ml of deionized water to obtain a second solution.

6. The method for preparing a high-performance sodium storage material based on Zn-doped modified P2-type sodium nickel manganate according to claim 1, characterized in that, The heating rate in step 5 is 5℃ / min.

7. The method for preparing a high-performance sodium storage material based on Zn-doped modified P2-type sodium nickel manganate according to claim 1, characterized in that, In step 5, the calcination temperature after heating is 900℃.

8. The method for preparing a high-performance sodium storage material based on Zn-doped modified P2-type sodium nickel manganate according to claim 1, characterized in that, The stirring reaction time in step 3 is 0.5-1.5 hours.

9. A high-safety sodium-ion battery cathode material obtained by the preparation method according to any one of claims 1-8, characterized in that, It is a zinc-doped sodium-nickel-manganese oxide with a P2-type structure.

10. A sodium-ion battery, characterized in that, It includes the high-safety sodium-ion battery cathode material as described in claim 9.

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