High-entropy doped manganese / iron-based layered material, preparation method thereof, pole piece and battery

Abstract

The application discloses a high-entropy doped manganese / iron-based layered material and a preparation method, an electrode sheet and a battery thereof, the material contains six different metal cations of manganese, iron, copper, titanium, lithium and magnesium in a transition metal layer, contains two different metal cations of sodium and calcium in a sodium layer, and the chemical formula of the layered material is Na 0.62 Ca 0.03 Mn 0.58 Fe 0.23 Cu 0.085 Mg 0.01 Ti 0.015 Li 0.08 O2, and problems of a reduced specific capacity and instability existing in the prior art are solved.

Description

Technical Field

[0001] This invention relates to the field of batteries, specifically to highly entropy-doped manganese / iron-based substrate materials, their preparation methods, electrodes, and batteries. Background Technology

[0002] In recent years, due to the widespread application of lithium-ion batteries and concerns about lithium resource shortages, sodium-ion batteries, with a similar mechanism to lithium-ion batteries, have attracted global attention and undergone extensive research. Valuable research has primarily focused on developing advanced cathode materials, anode materials, and separators, all of which have demonstrated good performance in sodium-ion battery applications. However, the development of sodium-ion batteries is currently hampered by the lack of low-cost, high-performance electrode materials. Among all common cathode materials, layered Na... x TMO2 has attracted great interest and high expectations from researchers due to its high theoretical capacity, high output voltage, and simple preparation process. Based on the coordination environment of its sodium sites, layered Na... x TMO2 is mainly divided into P2 type and O3 type. Due to the structural characteristics and wide sodium-ion diffusion channels of P2 type cathode materials, it exhibits excellent rate performance and long-term cycle stability at low voltages. However, at high voltages (>4.2V), the P2 type undergoes an irreversible P2-O2 phase transition, leading to a sharp decrease in capacity and severely limiting its application. O3 type cathode materials have a high theoretical specific capacity due to their high sodium content. However, the O3 type structure requires sodium ions to diffuse through tetrahedral sites surrounded by adjacent octahedral sites during cycling, which limits its electrochemical kinetics. P2 type manganese-based or manganese / iron-based oxides are considered the most promising cathode materials for sodium-ion batteries due to their high capacity and the abundance of iron and manganese resources. Layered manganese-based materials (Na... x Taking MnO2 as an example, manganese is mainly in the form of Mn 3+ and Mn 4+ Two valence states exist. Mn 3+ It has a high spin electron configuration, with a single electron occupying the eg* orbital, resulting in an octahedral distortion, the so-called Jahn-Teller distortion. This is a characteristic of Mn... 3+Ion-induced localized distortions lead to irreversible structural changes, resulting in rapid capacity decay. To date, researchers have made considerable efforts to address this issue, such as doping with elements like lithium, magnesium, aluminum, titanium, copper, zirconium, and tin to improve structural stability, surface modification to prevent metal dissolution, and developing P2-O3 composite structures to utilize the advantages of both phases. Despite encouraging progress, manganese / iron-based cathode materials still cannot meet industrial demands. Constructing a robust structure is fundamental for layered cathode materials to withstand repeated sodium ion insertion / extraction. Therefore, an effective method is urgently needed to significantly enhance the structure of layered cathode materials.

[0003] High-entropy materials are a novel type of material that, due to their high structural stability, mechanical properties, electrical performance, and catalytic properties, have been widely applied in electrochemical energy storage, catalysis, and environmental protection. High-entropy materials are typically mixtures of five or more metal cations, with an atomic percentage between 5% and 35%. When the concept of high entropy is introduced into the cathode material of sodium-ion batteries, the sodium ions and metal cations in the transition metal layer of the high-entropy material are disordered, making it difficult to form an ordered sodium ion / vacancy structure. This can delay or inhibit the formation of phase transitions in the cathode material. Simultaneously, the random distribution of various metal cations at the same sites increases the configurational entropy and stabilizes the crystal structure, resulting in high energy density and good cycle stability in the electrode material. The main redox metal centers in sodium-ion battery cathode materials are only iron, cobalt, nickel, and manganese. Traditional high-entropy materials typically introduce a large number of inert elements that do not undergo redox reactions to achieve solid solution of five or more metal elements. Furthermore, to achieve maximum configurational entropy, the proportions of all dopant elements are usually equimolar. Due to the stability brought by high entropy and the synergistic effect of multiple components, high-entropy layered oxide cathode materials typically exhibit high ionic conductivity and stable sodium ion desorption behavior. However, the influence of high-entropy structure and different doping elements on the phase transition of manganese / iron-based oxides during cycling has not yet been fully explored. The presence of a large number of inert elements and equimolar properties can lead to a loss of theoretical specific capacity in cathode materials, affecting the practical application of high-entropy materials. Summary of the Invention

[0004] This invention provides a high-entropy doped manganese / iron-based substrate material, its preparation method, electrode, and battery, which solves the problems of reduced specific capacity and instability in the prior art.

[0005] To solve this technical problem, this solution provides the following technical solution:

[0006] A high-entropy doped manganese / iron-based layered material, wherein the material contains six different metal cations (manganese, iron, copper, titanium, lithium, and magnesium) in the transition metal layer and two different metal cations (sodium and calcium) in the sodium layer, and the chemical formula of the layered material is Na.0.62 Ca 0.03 Mn 0.58 Fe 0.23 Cu 0.085 Mg 0.01 Ti 0.015 Li 0.08 O2.

[0007] Preferably, the high-entropy doped manganese / iron base layer material is of type P2.

[0008] High-entropy doped manganese / iron-based substrate materials, electrochemically active Fe 3+ and Mn 4+ Provides charge compensation, which is the main contributor to the contrast capacity; low valence state Mg 2+ and Cu 2+ This helps increase the valence of Mn and alleviate the Jahn-Teller distortion; meanwhile, Cu 2+ The presence of [Li] can effectively reduce local structural distortion of O₂ and enhance the redox reversibility of O₂ in the lattice. In the TM layer, Li doping acts as a structural stabilizer because monovalent Li […]. + It is beneficial to retain more Na in the deep desodium structure. + This maintains electrostatic balance, thereby suppressing the O2 phase transition. Because Ti 4+ and Mn 4+ The significant difference in Fermi levels between them, introducing Ti 4+ This will suppress the ordering of cations and charges in the TM layer, as well as the Na in the Na layer. + / Vacation ordering. Ca doping in the Na layer 2+ It can serve as a "pillar" because Ca 2+ and O 2- The strong interactions between them are beneficial to improving the structure and cycling stability of the material. Besides the various functionalities brought by different metal cations, the structural stability driven by high-entropy doping also suppresses the P2-P'2 phase transition and particle cracking, which is beneficial for reducing Na+ ionization. + The energy barrier for migration. Therefore, the functional integration of different metal cations, combined with the improved structural stability driven by high-entropy doping, synergistically brings about high reversible capacity, high-rate performance and long-cycle stability of NFM-HEO.

[0009] This solution also provides a method for preparing the aforementioned high-entropy doped manganese / iron-based morphological material, including the following steps:

[0010] S1. Dissolve Fe(NO3)3·9H2O, Mn(NO3)2·4H2O and Cu(NO3)2·3H2O in deionized water in stoichiometric ratios to form a mixed transition metal salt solution.

[0011] S2. Then, sodium hydroxide aqueous solution is added dropwise to the mixed transition metal salt solution; after 1 hour of addition, the pH value of the system is adjusted with ammonia water to obtain a precipitate; the precipitate is filtered, washed with deionized water and ethanol, and then dried to obtain the precursor;

[0012] S3. Subsequently, the dried precursor is mixed with stoichiometric amounts of TiO2, CaCO3, Li2CO3 and MgCO3, and an excess of 5% stoichiometric amount of Na2CO3 and ball-milled. The mixture is then calcined and ground.

[0013] S4. Finally, it is calcined at 900°C in an oxygen atmosphere at a heating rate of 5°C / min to form a high-entropy doped manganese / iron-based substrate material NFM-HEO.

[0014] Preferably, the total concentration of the transition metal salt solution in step S1 is 2.0 mol / L. -1 .

[0015] Preferably, the concentration of the sodium hydroxide aqueous solution in step S2 is 4.0 mol / L. -1 The concentration of ammonia water is 1.0 mol / L. -1 Adjust the pH of the system to 11.

[0016] Preferably, the drying temperature in step S2 is 100°C and the drying time is 6 hours.

[0017] Preferably, in step S3, the ball milling speed is 600 rpm and the ball milling time is 6 hours; the calcination temperature is 500℃ and the calcination time is 6 hours.

[0018] Preferably, the calcination time in step S4 is 12 hours.

[0019] This solution also provides an electrode, which comprises the above-mentioned high-entropy doped manganese / iron-based morphological material or the high-entropy doped manganese / iron-based morphological material prepared by the above-described preparation method.

[0020] This solution also provides a battery, which includes the aforementioned electrode, counter electrode, and separator, wherein the separator is disposed between the electrode and the counter electrode.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] The material contains six different metal cations (manganese, iron, copper, titanium, lithium, and magnesium) in the transition metal layer and two different metal cations (sodium and calcium) in the sodium layer. These different cations have different electrochemical activities, valence states, electronegativity, or bonding abilities with oxygen, and play different roles in high-entropy materials. Electrochemical activity Fe 3+ and Mn 4+It provides charge compensation, which is the main contributor to the relative capacity. Low valence state Mg 2+ and Cu 2+ This helps increase the valence of Mn and alleviate the Jahn-Teller distortion. Meanwhile, Cu... 2+ The presence of [Li] can effectively reduce local structural distortion of O₂ and enhance the redox reversibility of O₂ in the lattice. In the TM layer, Li doping acts as a structural stabilizer because monovalent Li […]. + It is beneficial to retain more Na in the deep desodium structure. + This maintains electrostatic balance, thereby suppressing the O2 phase transition. Because Ti 4+ and Mn 4+ The significant difference in Fermi levels between them, introducing Ti 4+ This will suppress the ordering of cations and charges in the TM layer, as well as the Na in the Na layer. + / Vacation ordering. Ca doping in the Na layer 2+ It can serve as a "pillar" because Ca 2+ and O 2- The strong interactions between these elements are beneficial for improving the material's structure and cycling stability. Therefore, the functional integration of different metal cations, combined with the improved structural stability driven by high-entropy doping, synergistically brings about high reversible capacity, high-rate performance, and long-cycle stability in NFM-HEO. Electrochemical measurements, as well as morphological and phase characterization, show that the high-entropy structure hinders the P2-P'2 phase transition, stabilizes the P2-OP4 phase transition and anion redox reaction, promotes sodium ion migration kinetics, and, due to the utilization of the reversible electrochemical redox reaction of oxygen at high voltage, suppresses voltage decay and improves high-rate reversible capacity. The prepared high-entropy layered oxide cathode material exhibits a smooth charge-discharge curve, with a reversible specific capacity of 134 mAh g⁻¹ at 0.1C rate. -1 After 500 cycles at 1C, the capacity retention reached 85.4%, and it exhibited good rate performance, with a reversible capacity of 70 mAh g at 5C. -1 Phase characterization showed that the phase transition at high voltage was well suppressed, and it also exhibited reversible redox reactions. The improved performance of high-entropy doped manganese / iron-based oxide cathode materials is largely due to the high-entropy-driven structural stability and the different functions of various elements. High-entropy P2-type cathode materials have great practical application potential in sodium-ion batteries. Attached Figure Description

[0023] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0024] Figure 1(a) X-ray diffraction patterns of high-entropy oxide (NFM-HEO) and NFM;

[0025] Figure 1 (b) is a scanning electron microscope image of high-entropy oxide (NFM-HEO);

[0026] Figure 1 (c) is a scanning electron microscope image of NFM;

[0027] Figure 1 (d) is a high-resolution transmission electron microscope image of high-entropy oxide (NFM-HEO), with the inset showing the corresponding fast Fourier transform (FFT) pattern and interlayer spacing;

[0028] Figure 1 (e) is the energy dispersive X-ray spectroscopy (EDS) surface scan of the selected particle surface of the high entropy oxide (NFM-HEO) material;

[0029] Figure 1 (f) is a selected area electron diffraction (SAED) image of high-entropy oxide (NFM-HEO);

[0030] Figure 1 (g) is a surface scan of the energy dispersive X-ray spectrum (EDS) of the selected particles of the NFM material;

[0031] Figure 2 (a) is the refined X-ray diffraction pattern of NFM;

[0032] Figure 2 (b) is the refined X-ray diffraction pattern of high-entropy oxide (NFM-HEO);

[0033] Figure 2 (c) is a schematic diagram of the crystal structure of NFM and high-entropy oxide (NFM-HEO);

[0034] Figure 3 (a) Comparison of the constant current charge-discharge curves of the novel high-entropy oxide (NFM-HEO) and NFM half-cell during the first cycle at 0.1C rate;

[0035] Figure 3 (b) shows the cyclic voltammetry curves of the high-entropy oxide (NFM-HEO) at a scan rate of 0.1 mV / sec;

[0036] Figure 3 (c) shows the differential capacity (dQ / dV) curve of the high-entropy oxide (NFM-HEO);

[0037] Figure 3 (d) Comparison of rate performance between high-entropy oxide (NFM-HEO) and NFM;

[0038] Figure 3 (e) shows the cyclic voltammetry curve of NFM at a scan rate of 0.1 mV / sec;

[0039] Figure 3 (f) is the differential capacity (dQ / dV) curve of NFM;

[0040] Figure 3 (g) shows the long-cycle performance of high-entropy oxide (NFM-HEO) and NFM at 1C rate;

[0041] Figure 4 (a) shows the impedance of high-entropy oxide (NFM-HEO) after different number of cycles;

[0042] Figure 4 (b) is the impedance of NFM after different number of cycles;

[0043] Figure 4 (c) Analysis of relaxation time distribution (DRT) of high-entropy oxide (NFM-HEO) after different number of cycles;

[0044] Figure 4 (d) is the relaxation time distribution (DRT) analysis of NFM after different number of cycles;

[0045] Figure 4 (e) Comparison of galvanostatic intermittent titration (GITT) curves of high entropy oxide (NFM-HEO) and NFM;

[0046] Figure 4 (f) Comparison of the calculated diffusion coefficients of high-entropy oxide (NFM-HEO) and NFM;

[0047] Figure 5 (a) X-ray photoelectron spectra of high-entropy oxides (NFM-HEO) in different charge states: 2p orbitals of iron (Fe);

[0048] Figure 5 (b) X-ray photoelectron spectra of high-entropy oxides (NFM-HEO) in different charge states: 2p orbitals of manganese (Mn);

[0049] Figure 5 (c) X-ray photoelectron spectra of high-entropy oxides (NFM-HEO) in different charge states: 1s orbital of oxygen (O);

[0050] Figure 5 (d) X-ray photoelectron spectra of high-entropy oxides (NFM-HEO) in different charge states: 2p orbitals of copper (Cu);

[0051] Figure 5 (e) X-ray photoelectron spectra of high-entropy oxides (NFM-HEO) in different charge states: 2p orbitals of titanium (Ti);

[0052] Figure 5 (f) X-ray photoelectron spectra of high-entropy oxides (NFM-HEO) in different charge states: 2p orbitals of calcium (Ca);

[0053] Figure 6 (a) is the in-situ X-ray diffraction (XRD) pattern of high-entropy oxide (NFM-HEO);

[0054] Figure 6 (b) is a magnified view of the evolution of X-ray diffraction peaks of high-entropy oxide (NFM-HEO) corresponding to the (002), (004) and (102) crystal planes;

[0055] Figure 6 (c) Comparison of X-ray diffraction patterns of high-entropy oxide (NFM-HEO) before and after 100 cycles at 1C magnification;

[0056] Figure 7 (a) shows the galvanostatic charge-discharge curves of high-entropy oxide (NFM-HEO) after different exposure times;

[0057] Figure 7 (b) is a magnified view of the X-ray diffraction pattern of high-entropy oxide (NFM-HEO) after being exposed to humid air for different durations at a small angle.

[0058] Figure 7 (c) is a magnified view of the X-ray diffraction pattern of high-entropy oxide (NFM-HEO) after being exposed to humid air for different durations;

[0059] Figure 7 (d) shows the constant current charge-discharge curves of NFM after different exposure times;

[0060] Figure 7 (e)NFM is a magnified view of the X-ray diffraction pattern after exposure to humid air for different durations at a small angle;

[0061] Figure 7 (f) NFM is a magnified view of the X-ray diffraction pattern after exposure to humid air for different durations;

[0062] Figure 7 (g) shows the changes in open-circuit voltage (OCV) and corresponding structural changes of high-entropy oxide (NFM-HEO) after exposure to humid air for different times;

[0063] Figure 7(h) shows the changes in the open-circuit voltage (OCV) and the corresponding structural changes of NFM after exposure to humid air for different times;

[0064] Figure 8 (a1) shows the evolution of particle cracks in high-entropy oxide (NFM-HEO) after 0 cycles;

[0065] Figure 8 (a2) shows the evolution of particle cracks in high-entropy oxide (NFM-HEO) after 50 cycles;

[0066] Figure 8 (a3) shows the evolution of particle cracks in high-entropy oxide (NFM-HEO) after 100 cycles;

[0067] Figure 8 (a4) shows the evolution of particle cracks in high-entropy oxide (NFM-HEO) after 200 cycles;

[0068] Figure 8 (b1) shows the particle crack evolution of NFM after 0 cycles;

[0069] Figure 8 (b2) shows the evolution of particle cracks in NFM after 50 cycles;

[0070] Figure 8 (b3) shows the evolution of particle cracks in NFM after 100 cycles;

[0071] Figure 8 (b4) shows the evolution of particle cracks in NFM after 200 cycles. Detailed Implementation

[0072] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. The illustrative embodiments and descriptions of this invention are only used to explain this invention and are not intended to limit this invention.

[0073] Sodium carbonate (Na2CO3), sodium hydroxide (NaOH), calcium carbonate (CaCO3), ethanol, and ammonia used in this specific implementation scheme were purchased from Chengdu Jinshan Chemical Reagent Co., Ltd.; ferric nitrate nonahydrate (Fe(NO3)3·9H2O) and titanium dioxide (TiO2) were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; manganese nitrate tetrahydrate (Mn(NO3)2·4H2O), copper nitrate trihydrate (Cu(NO3)2·3H2O), and magnesium carbonate (MgCO3) were purchased from Shanghai Titan Technology Co., Ltd.; lithium carbonate (Li2CO3) and N-methylpyrrolidone (NMP) were purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; metallic sodium was purchased from Shandong Xiya Chemical Co., Ltd.; conductive carbon black (Super P) was purchased from TIMCAL Graphite & Carbon Co., Ltd.; and polyvinylidene fluoride (PVDF) was purchased from Solvay Chemicals. Co., Ltd); Waterman GF / D glass fiber filter paper was purchased from Shanghai Jinpan Biotechnology Co., Ltd.; NC-008 electrolyte (1M sodium perchlorate (NaClO4) in ethylene carbonate (DEC) and ethylene carbonate (EC) (volume ratio 1:1) solution, containing 5% fluoroethylene carbonate (FEC)) was purchased from Suzhou Duoduo Chemical Technology Co., Ltd.

[0074] Example 1

[0075] P2-Na 0.62 Ca 0.03 Mn 0.58 Fe 0.23 Cu 0.085 Li 0.08 Ti 0.015 Mg 0.01 Preparation of O2 (NFM-HEO)

[0076] First, Fe(NO3)3·9H2O, Mn(NO3)2·4H2O, and Cu(NO3)2·3H2O in a stoichiometric ratio of 0.23:0.58:0.085 were fully dissolved in deionized water, resulting in a total concentration of 2.0 mol / L for the transition metal salt solution. -1 Then 4.0 mol L -1 A sodium hydroxide aqueous solution was added dropwise to the above mixed transition metal (TM) salt solution at a volume ratio of 2:1. After 1 hour of dropwise addition, 1.0 mol / L... -1The pH of the system was adjusted to 11 using ammonia water. The resulting precipitate was filtered, washed with deionized water and ethanol, and then dried at 100°C for 6 hours. Subsequently, the dried precipitate was mixed with stoichiometric amounts of TiO2, CaCO3, Li2CO3, and MgCO3, and an excess of 5% stoichiometric amount of Na2CO3 (TiO2:CaCO3:Li2CO3:MgCO3:Na2CO3 = 0.015:0.03:0.04:0.01:0.325), and ball-milled at 600 rpm for 6 hours. The mixture was then calcined at 500°C for 6 hours, ground, and finally calcined at 900°C for 12 hours in an oxygen atmosphere at a heating rate of 5°C / min to form the NFM-HEO sample.

[0077] Comparative Example 1

[0078] P2-Na 0.65 Mn 0.6 Fe 0.4 Preparation of O2 (NFM)

[0079] NFM cathode material was prepared using a co-precipitation method. First, stoichiometric amounts of Fe(NO3)3·9H2O and Mn(NO3)2·4H2O were fully dissolved in deionized water, followed by dropwise addition of sodium hydroxide aqueous solution. After 1 hour of addition, the pH of the system was adjusted to 11 with ammonia. The resulting precipitate was filtered, washed with deionized water and ethanol, and then dried at 100°C for 6 hours. Subsequently, the dried precipitate was mixed with an excess of 5% stoichiometric Na2CO3 and ball-milled at 600 rpm for 6 hours. The mixture was then calcined at 500°C for 6 hours, ground again, and finally calcined at 900°C for 12 hours in an oxygen atmosphere at a heating rate of 5°C / min to form the NFM sample.

[0080] Example 2

[0081] The NFM-HEO prepared in Example 1 and the NFM material prepared in Comparative Example 1 were mixed with polyvinylidene fluoride (PVdF) and conductive carbon black (SuperP) at a mass ratio of 85:8:7, respectively, and dispersed in N-methylpyrrolidone (NMP) to form a uniform slurry. This slurry was then uniformly coated onto aluminum foil using a doctor blade and dried at 120°C for 6 hours. The prepared electrode sheets were pressed using a double roller and then cut into 14 mm diameter discs with an active material loading of 2–3 mg, which were used as the working electrodes. Sodium metal was rolled and cut into 16 mm diameter discs, which were used as the counter electrode. In an argon-filled glove box, using GF / D glass fiber filter paper as the separator, and a 1M sodium perchlorate (NaClO4) solution of ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio 1:1) containing 5 wt% fluoroethylene carbonate (FEC) as the electrolyte, a CR2032 type button cell was assembled. Constant current charge-discharge (GCD) and constant current intermittent titration (GITT) tests were performed using a CT-4008T battery testing system (Shenzhen Xinwei Electronics Co., Ltd.), with a pulse current of 20 mAg. -1 The reaction was carried out for 0.5 hours, followed by 1 hour of rest for different batteries. Electrochemical impedance spectroscopy (EIS) was performed in the frequency range of 100 kHz to 10 mHz using a PARSTAT4000A electrochemical workstation (Princeton, USA), and cyclic voltammetry (CV) was performed in the voltage range of 2.0 to 4.3 V.

[0082] The crystal structures of NFM-HEO and NFM materials were confirmed using a D8 Advance X-ray diffractometer (Bruker, Germany) with 40 kV CuKα radiation. XRD data were processed and refined using GSAS-II software. In-situ XRD results were also obtained using a D8 Advance X-ray diffractometer (Bruker, Germany). The elemental molar ratios of NFM-HEO and NFM materials were determined using an Avio 200 inductively coupled plasma optical emission spectrometer (ICP-OES, PerkinElmer, USA). The morphology of NFM-HEO and NFM materials was observed using a JSM7800F field emission scanning electron microscope (FESEM, NEC Japan). The microstructure, lattice fringes, and elemental distribution of NFM-HEO and NFM materials were observed using a Tecnai F20 transmission electron microscope (TEM, NEC Japan). The surface elemental composition of NFM-HEO and NFM materials was determined using K-Alpha X-ray photoelectron spectroscopy (XPS, Thermo Fisher Scientific, USA) with MgKα radiation.

[0083] P2 type Na 0.65 Mn 0.6 Fe 0.4 O2 (NFM) and highly entropy-doped Na 0.62 Ca0.03 Mn 0.58 Fe 0.23 Cu 0.085 Li 0.08 Ti 0.01 5Mg 0.01 The XRD results of O2(NFM-HEO) are as follows Figure 1 As shown in (a), XRD results indicate that all diffraction peaks match well with the space group P63 / mmc (JCPDS#00-054-0894) of the P2 phase with a hexagonal crystal structure. Both oxides exhibit similar layered structures, where transition metal (TM) atoms coordinate with six surrounding oxygen atoms to form TMO6 octahedral units, and sodium atoms interact with oxygen atoms to form NaO6 octahedral units. No diffraction peaks corresponding to the superstructure derived from honeycomb order and sodium ion / vacancy order are observed in the 20°–29° range, indicating that the sodium ion / vacancy arrangement in the sodium layer and the metal cation arrangement in the transition metal layer are disordered in both materials. Furthermore, no impurities were observed in NFM-HEO, suggesting that all metal cations have entered the P2 structure.

[0084] Figure 2 (a) and Figure 2 (b) The XRD refinement results show that both NFM and NFM-HEO can be classified as P2 type structures.

[0085] NFM-HEO and NFM The differences in lattice parameters indicate that the substitution of dopants causes certain lattice changes. Although five metal cations were introduced into the NFM structure, the change in sodium interlayer spacing was only... This indicates that the P2 structure of the initial manganese / iron-based oxide is well preserved in NFM-HEO. Although it is difficult to characterize the local environment of all metal atoms in NFM-HEO, it can be predicted that elements such as copper, lithium, titanium, and magnesium are favorable for occupying the TMO6 layer because their ionic radii are much smaller than those of sodium ions, while calcium is favorable for occupying the NaO6 layer because of the six-coordinate sodium ion. The radius and six-coordinate calcium ions Their radii are similar, while iron ions (Fe) 3+ High spin is Low spin is ) and manganese ions (Mn 4+ , The radius of the copper ion (Cu) is much smaller than that of the calcium ion. Based on the refined crystallographic data obtained, the radius of the copper ion (Cu) is much smaller than that of the calcium ion. 2+ Lithium ion (Li) + ), titanium ions (Ti 4+ ) and magnesium ions (Mg 2+) is located at the transition metal site, while calcium ions (Ca) 2+ The presence of calcium at the sodium site confirms our hypothesis. We also refined the XRD results of NFM-HEO with calcium placed in the transition metal layer, where Rwp was 6.61%, higher than the results with calcium placed in the NaO6 layer. Figure 2 (c) shows a schematic diagram of the crystal structures of NFM and NFM-HEO. Furthermore, the metal elemental composition and proportions of NFM and NFM-HEO, determined by inductively coupled plasma optical emission spectrometry (ICP-OES), are shown in Tables 1 and 2, respectively.

[0086] Table 1

[0087] Na Fe Mn 0.648 0.400 0.599

[0088] Table 2

[0089] Na Ca Fe Mn Cu Mg Ti Li 0.621 0.03 0.23 0.58 0.085 0.011 0.015 0.078

[0090] High-entropy doping can alter the particle morphology of materials. (Comparison) Figure 1 (b) and Figure 1 (c) Scanning electron microscope (SEM) images of NFM-HEO and NFM show that NFM exhibits an irregular shape with many small particles adhering to its surface, while NFM-HEO has a more regular appearance with a significantly cleaner and smoother particle surface. This difference in morphology indicates that introducing multiple doped metal cations can optimize the surface properties and structure of manganese / iron-based oxides. Figure 1 (g) Energy dispersive spectroscopy (EDS) results show that the elemental distribution is uniform in NFM, while in NFM-HEO, such as Figure 1 As shown in (e), the various doped metal elements and matrix elements also exhibit a uniform distribution. The selected area electron diffraction (SAED) results are as follows: Figure 1 (f) shows that the exposed crystal planes of NFM-HEO are the same as those of NFM, indicating that high-entropy doping with copper (Cu), calcium (Ca), lithium (Li), titanium (Ti), and magnesium (Mg) does not destroy its original crystal structure. Figure 1 (d) The clear lattice fringes in the high-resolution transmission electron microscope (HRTEM) image show a d-spacing of 2.33 Å, corresponding to the (102) crystal plane. No phase separation or lattice distortion was found, indicating that a single phase with an ordered internal structure has been formed.

[0091] Different compositions and structures lead to variations in electrochemical performance. To evaluate the effect of high-entropy doping on electrochemical performance, various electrochemical tests were performed on NFM-HEO and NFM within a voltage range of 2.0–4.3 V. For example... Figure 3As shown in (a), the initial cyclic galvanostatic charge-discharge (GCD) curves indicate that the initial discharge specific capacity of NFM-HEO is 134 mAh / g, slightly lower than that of NFM (140 mAh / g). This is because the redox-active manganese (Mn) and iron (Fe) moieties are replaced by dopants without redox activity. Despite the slight decrease in capacity, the average discharge potential of NFM-HEO is significantly higher than that of NFM, resulting in higher output energy. The lower initial charge capacity of NFM materials is mainly due to the fact that during the initial charging process, the manganese in the original NFM material is in the +4 valence state, while only Fe is present. 3+ / Fe 4+ Redox couples participate in the reaction. In contrast, the initial charge capacity of NFM-HEO is higher than that of NFM, likely due to the presence of Mn in the original material. 3+ Furthermore, the contribution of high-pressure anionic redox reactions is even greater. Figure 3 The extension of the high-potential discharge plateau shown in (a) and Figure 3 (b) and Figure 3 (e) The cyclic voltammetry (CV) curve corresponding to Fe 3+ / Fe 4+ The increase in the high-potential oxidation peak indicates that high-entropy doping has an effect on Fe at high potentials. 4+ / Fe 3+ Redox reactions have a promoting effect. The CV curves of NFM-HEO at different cycle numbers (e.g.) Figure 3 (a)) and the dQ / dV curve ( Figure 3 (c) The overlap at low potentials is significantly better than that of the CV curve of NFM. Figure 3 (e) and the dQ / dV curve ( Figure 3 (f)) indicates that Mn in NFM-HEO 4+ / Mn 3+ The redox reaction exhibits higher reversibility. This characteristic may be due to the structural stability brought about by high-entropy doping, which helps suppress lattice distortion and mitigate phase transitions. Simultaneously, the dQ / dV curves also indicate that during cycling, NFM-HEO undergoes anionic redox reactions (O2- ... 2- / O2 n-The high cycling stability of NFM-HEO suggests that the anion redox reaction remains stable and reversible in highly entropy-doped cathode materials. GCD curves also show that the specific capacity provided by the oxygen redox reaction plateau in NFM-HEO is higher than that in NFM. It has been reported that substitution of inert elements, particularly lithium, can initiate and promote redox reactions of lattice oxygen, resulting in higher capacity. Therefore, highly entropy-doped NFM-HEO materials involving lithium substitution provide more capacity contributed by oxygen redox reactions than undoped NFM materials. Furthermore, as... Figure 3 As shown in (d), NFM-HEO exhibits improved sodium ion diffusion kinetics and better rate performance compared to NFM. Figure 3 As shown in (g), high entropy doping also greatly improves cycling stability. After 500 cycles at 1C rate, NFM-HEO achieved an encouraging capacity retention of 85.4%, while NFM's capacity retention was only 12.2%.

[0092] The electrochemical impedance spectroscopy results of NFM-HEO and NFM after different cycles were then tested, and the results were compiled and analyzed based on previous reports. Figure 4 (a) and Figure 4 (b) indicates that the interfacial film impedance (RCEI) / charge transfer impedance (R) of NFM-HEO ct The impedance remains stable during cycling, while the impedance of NFM deteriorates significantly after cycling. Figure 4 (c) and Figure 4 (d) shows the relaxation time distribution (DRT) results obtained from the analysis of EIS data. In 300 cycles, NFM-HEO corresponds to RCEI (s = 10). -4 ~10 -2 ) and Rct(s=10 -2 ~10 -0.5 The peak values ​​of ) changed relatively little, while those of NFM increased significantly. Furthermore, throughout the entire 300 cycles, the RCEI and R of NFM-HEO... ct The values ​​are typically lower than those of NFM, indicating that the interface film formed on NFM-HEO is thinner and charge transfer is faster, thus suggesting that the battery generates less heat during charging and discharging. All of the above results demonstrate that high-entropy doping can effectively reduce the RCEI and R of layered oxides. ct The sodium ion diffusion coefficient was maintained at a low level to improve electrochemical performance, especially long-cycle stability. Intermittent galvanostatic titration (GITT) was also performed, and the results, along with the calculated sodium ion diffusion coefficient, showed… Figure 4 (e) and Figure 4In (f), it is clear that the sodium ion diffusion coefficient of NFM-HEO is higher than that of NFM for almost the entire process from 2.0 to 4.3 V. This indicates that the sodium ion diffusion kinetics accompanying the redox reaction of active metal cations in NFM-HEO are significantly improved, and the redox reaction of oxygen ions under high pressure is also regulated.

[0093] At high voltages, the diffusion coefficient of NFM-HEO is lower than that of NFM. Studies have shown that the diffusion coefficient of high-entropy materials at high voltages is approximately 10. -10 cm 2 The diffusion coefficient of NFM-HEO is relatively low at high voltages, while that of the original material may be even higher. The high-entropy structure may increase the electrochemical polarization of the material, leading to increased resistance to sodium ion migration during charging and discharging. This polarization effect may be more pronounced in high-voltage regions, significantly reducing the sodium ion diffusion coefficient. The increased electron localization around oxygen in high-entropy materials reduces the electron density between sodium-oxygen (Na-O) bonds. While this reduces the electrostatic interaction between electrons and interlayer sodium ions, it may also make the sodium ion diffusion path more tortuous. All of these factors contribute to the lower diffusion coefficient of NFM-HEO at high voltages.

[0094] To investigate the possible reasons for the stability of high-entropy doped layered oxide materials, we performed X-ray photoelectron spectroscopy (XPS) tests on NFM-HEO at 0% state of charge (SOC, discharged to 2.0V) and 100% state of charge (charged to 4.3V). The results are as follows: Figure 5 As shown. All elements in the material can be divided into two groups: elements that are electrochemically active during charging and discharging, and electrochemically inert elements. Figure 5 (d) Figure 5 (e) Figure 5 (f) XPS spectra of Ca, Cu, Ti, Mg, and Li at 0% SOC and 100% SOC were compared. No significant changes in peak intensity and position were observed between fully charged and fully discharged states, indicating that they do not participate in redox reactions during battery charge and discharge. Although these components do not contribute to specific capacity, they act as "pillars" in the crystal lattice. Meanwhile, as... Figure 5 (a) Figure 5 (b) Figure 5 As shown in (c), for electrochemically active elements Mn, Fe, and O, the peak areas corresponding to different valence states changed significantly after sodium ion insertion / extraction, revealing their contribution to charge compensation. Specifically, the main peak corresponding to Fe2p3 / 2 in the Fe2p spectrum shifted significantly towards higher binding energies, such as... Figure 5 As shown in (a), it indicates that Fe 4+ The proportion is higher, which means that Fe after charging is higher. 3+ It is oxidized to a higher oxidation state (Fe).4+ At 100% SOC, the Mn2p spectrum corresponds to Mn 4+ The peak area ratio is significantly higher than that under 0% SOC conditions, such as... Figure 5 As shown in (b), this indicates that Mn 3+ →Mn 4+ The oxidation reaction participates in the charge-discharge process. At 100% SOC, the O1s spectrum shows corresponding peroxide species (O2). n- The peak of ) disappears at 0% SOC, indicating that the anion redox reaction (O) 2- / O2 n- It participated in the battery reaction process, such as Figure 5 As shown in (c). All of these are related to Figure 3 The dQ / dV results shown in (c) are consistent. In general, the NFM-HEO structure contains electrochemically active components such as Mn, Fe, and O, as well as electrochemically inert elements such as Ca, Cu, Ti, and Mg, with active / inert metal atoms randomly distributed in the bulk phase of the material. When sodium ions are inserted, the local variations in the randomly distributed redox active centers may combine with more diverse local features, thus helping to suppress potential phase transitions. From this perspective, the high-entropy doped material NFM-HEO may suppress structural evolution. Furthermore, it exhibits anionic redox reactions (O... 2- / O2 n- Layered oxide materials typically exhibit poor cycling stability. In contrast, NFM-HEO demonstrates good cycling stability, indicating the good reversibility of its anionic redox reactions. To demonstrate this, we performed XPS tests on NFM-HEO after cycling under different charge states and compared the results with those of NFM. After cycling at 100% SOC, the O1s spectrum corresponds to peroxide species (O2... n- The peak of ) still exists, indicating that the anionic redox reaction (O) involved in NFM-HEO is still present. 2- / O2 n- The redox reaction is reversible. In contrast, no obvious peaks corresponding to the anionic redox reaction were observed in NFM after cycling, indicating that the anionic redox reaction involved in NFM is less reversible. From this perspective, the high-entropy doped material NFM-HEO may play a role in stabilizing the anionic redox reaction.

[0095] To investigate the structural evolution of NFM-HEO during the initial charge-discharge process, we further performed in-situ X-ray diffraction (XRD) tests, the results of which are as follows: Figure 6As shown in (a), when charged from the open-circuit potential (OCV) to 4.3V, some diffraction peaks gradually shift, corresponding to the peaks of the (002), (004), and (102) crystal planes. Figure 6 As shown in (b), during the sodium ion insertion / extraction process, the peaks corresponding to the (002) and (004) crystal planes gradually shift to lower angles. This is because the electrostatic repulsion between oxide layers increases, while the peaks corresponding to the (100) and (102) crystal planes shift in the opposite direction. This is because the transition metal-oxygen (TM-O) bond length shortens with increasing oxidation state. After charging to over 4.2V, the main peaks corresponding to the (102) and (104) crystal planes become wider and shorter, while a new weak peak appears, corresponding to the OP4 phase (the incomplete transition from P2 to O2 phase). According to the XRD results, the electrode material is still dominated by the P2 phase at this time. During the subsequent discharge process, the peaks of the OP4 phase gradually disappear, while the (002) peak of the P2 phase gradually strengthens and shifts to a larger angle, indicating that the material has completely transformed back to the P2 phase. The presence of the OP4 phase alleviates the drastic change in interlayer spacing during the transition from the P phase to the O phase, thereby reducing the volume change during the sodium ion insertion / extraction process and thus helping to improve the cycle stability of the material. The transition from the P2 phase to the OP4 phase in the NFM-HEO material is consistent with previously reported results, indicating that high-entropy doping in P2-type manganese / iron-based substrate oxides leads to a P2-OP4 phase transition at high voltages, rather than a P2-O2 phase transition. Notably, no characteristic peaks of sodium or transition metal ordering were observed during charge-discharge cycling, and no distinct monoclinic P'2 phase was observed throughout the sodium ion insertion / extraction voltage range.

[0096] In addition, we collected X-ray diffraction (XRD) patterns of NFM-HEO and NFM after cycling and compared them with the results in their original state. Figure 6 As shown in (c), there is no significant difference in the XRD patterns of NFM-HEO before and after cycling, indicating that the original P2-type structure of NFM-HEO is well preserved after charge-discharge cycling. The refinement results show that after 100 cycles, the cell volume change of the high-entropy doped NFM-HEO material is only 0.72%. After 100 cycles, the (002) peak corresponding to the P2 phase shifts to a higher angle and becomes wider, indicating that the formation of Mn... 3+The induced Jamie-Taylor effect leads to the formation of the P'2 phase with strong local distortion. Calculated lattice parameters show that after 100 cycles, the a-axis increases from 2.9068 Å to 2.9228 Å, while the c-axis increases from 11.2619 Å to 11.2721 Å, with a cell volume change of 1.19%, significantly greater than the 0.72% for NFM-HEO. These results indicate that high-entropy doping can effectively mitigate the volume change during sodium ion insertion / extraction and stabilize the material's framework structure, making it more robust. Despite the P2-OP4 phase transition, after 100 cycles at 1C, the material remains predominantly P2 phase with a low capacity decay rate, indicating good long-range structural stability.

[0097] The improved stability of the high-entropy-doped NFM-HEO structure also enhances its tolerance to humid air. The ability of cathode materials to maintain high stability when exposed to humid air is a crucial indicator for practical applications. However, there are few reports on layered cathode materials with high humid air stability in sodium-ion batteries. Here, we investigated the stability of NFM-HEO materials exposed to humid air at 25°C and compared it with NFM. With increasing exposure time, the XRD peak intensities of both materials gradually decreased, but the peak positions did not shift significantly. The decrease in peak intensity may be due to the adsorption of air components and moisture on the material surface. For NFM, additional peaks appeared successively near 12.6° and 25.4° with increasing exposure time in humid air, such as... Figure 7 (e) and Figure 7 As shown in (f), these peaks correspond to hydration products. The appearance of these hydration phase peaks severely affects the electrochemical performance of NFM, manifested as a significant decrease in capacity, such as... Figure 7 As shown in (d). After exposure to humid air, as... Figure 7 (b) and Figure 7 As shown in (c), NFM-HEO did not exhibit such a peak, indicating that NFM-HEO does not readily react with water, thus allowing its electrochemical performance to remain stable. Figure 7 As shown in (a). From the constant current charge-discharge curves, it can also be observed that the open-circuit voltage (OCV) of both materials increases with the extension of exposure time in humid air, such as... Figure 7 (g) and Figure 7 As shown in (h), the OCV of NFM gradually increases with the appearance of the hydrated phase peak. The OCV of NFM increased by 10% (from 2.78V to 3.06V), which is greater than the increase in OCV of NFM-HEO (6%, from 2.69V to 2.86V). Both in-situ XRD results and humid air exposure experiments demonstrate that NFM-HEO has an advantage in structural stability.

[0098] To further explore the reasons for the superior performance of NFM-HEO from the perspective of the mechanical integrity of the material particles, we used focused ion beam (FIB) to slice the material particles and observed the cross-sectional microstructure of the cathode particles before and after cycling. For NFM, after 50 cycles, fine cracks appeared on the particle surface, while fewer cracks appeared inside the particles, indicating that the cracks initially originated on the surface. As cycling continued, the surface-initiated cracks propagated inward, eventually penetrating the entire particle. Figure 8 (b1) Figure 8 (b2) Figure 8 (b3) Figure 8 As shown in (b4), after 200 cycles, numerous obvious cracks were observed scattered across the particles. In stark contrast, NFM-HEO showed almost no significant change before and after cycling; no cracks appeared on the particle surface or inside. Figure 8 (a1) Figure 8 (a2) Figure 8 (a3) Figure 8 As shown in (a4), the rapid increase in cracks after cycling in NFM can disrupt its structural stability, leading to more side reactions during cycling and consequently degrading the material's properties.

[0099] Furthermore, we investigated the dissolution of transition metals (TMs) by performing energy-dispersive spectroscopy (EDS) on the glass fiber membranes disassembled after 200 cycles. NFM-HEO showed almost no significant dissolution of manganese (Mn) and iron (Fe), while NFM exhibited severe manganese and iron dissolution. The remaining peaks in the EDS spectrum likely correspond to elements in the glass fiber membrane (such as silicon (Si), oxygen (O), sodium (Na), calcium (Ca), magnesium (Mg), and titanium (Ti)) and solute components in the electrolyte (such as sodium (Na), carbon (C), nitrogen (N), oxygen (O), and fluorine (F)). The dissolution of transition metals into the electrolyte exacerbates the deterioration of the solid electrolyte interphase (SEI) film at the negative electrode, which explains the rapid increase in impedance of NFM after cycling.

[0100] In summary, high-entropy doping can effectively suppress the dissolution of transition metals during battery cycling, achieving high structural stability and mechanical integrity, thereby obtaining long-term cycling stability.

[0101] The high reversible capacity, high rate performance, and long cycling stability of NFM-HEO mainly stem from the specific functions of different metal cations and the structural stability brought about by high-entropy doping. Electrochemically active Fe... 3+ and Mn 3+ It provides charge compensation, which is the main source of contribution to specific capacity. Low valence state Mg 2+ and Cu 2+This helps to increase the valence state of Mn and alleviate the Ginger-Taylor distortion. Meanwhile, Cu... 2+ The presence of [Li] can effectively reduce the structural distortion of local OO bonds and enhance the redox reversibility of lattice oxygen. In transition metal (TM) layers, Li doping acts as a structural stabilizer because monovalent Li […]. + It is beneficial to retain more Na in structures with deep sodium removal + This maintains electrostatic balance, thereby suppressing the O2 phase transition. Because Ti 4+ and Mn 4+ There are significant differences in the Fermi levels of Ti. 4+ The introduction of [something] will suppress the ordered arrangement of cations and charges in the transition metal layer, as well as the Na in the sodium layer. + / Vacations are arranged in an ordered manner. Ca is doped into the sodium layer. 2+ It can serve as a "pillar" and because Ca 2+ With O 2- The strong interaction between them is beneficial to improving the structural stability and cycle stability of the material.

[0102] In addition to the various functionalities brought by different metal cations, the structural stability driven by high-entropy doping also suppresses the P2-P'2 phase transition and particle cracking, and is beneficial for reducing Na... + The energy barrier for migration. Therefore, the functional integration of different metal cations, combined with the improved structural stability brought about by high entropy doping, synergistically endows NFM-HEO with high reversible capacity, high rate performance and long cycling stability.

[0103] In summary, this study explored the high-entropy doping strategy for manganese / iron-based oxide cathode materials used in sodium-ion batteries. The electrochemical performance of the high-entropy-doped layered oxides was significantly improved, especially their excellent long-cycle stability. This performance enhancement depends on the significant improvement in structural stability after high-entropy doping. + During the insertion / deinsertion process, in-situ XRD test results showed that the interlayer spacing of the high-entropy doped NFM-HEO layered oxide cathode material changed smoothly, while the stable contribution of the high-voltage plateau and the enhanced cycling performance indicated that high-entropy doping stabilized the anion redox reaction under high voltage.

[0104] Meanwhile, the high-entropy doping method also improves the stability of layered oxide materials in humid air. Upon exposure to humid air, the lattice of NFM-HEO does not undergo significant changes, and its electrochemical performance remains relatively stable. Furthermore, high-entropy doping suppresses the formation of particle cracks in the layered oxide materials and significantly inhibits the dissolution of transition metals after cycling.

[0105] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-entropy doped manganese / iron-based substrate material, characterized in that, The material contains six different metal cations—manganese, iron, copper, titanium, lithium, and magnesium—in the transition metal layer, and two different metal cations—sodium and calcium—in the sodium layer. The chemical formula of the layered material is Na. 0.62 Ca 0.03 Mn 0.58 Fe 0.23 Cu 0.085 Mg 0.01 Ti 0.015 Li 0.08 O2; The highly entropy-doped manganese / iron-based substrate material is of type P2; The method for preparing the high-entropy doped manganese / iron-based substrate material includes the following steps: S1. Dissolve Fe(NO3)3·9H2O, Mn(NO3)2·4H2O and Cu(NO3)2·3H2O in deionized water in stoichiometric ratios to form a mixed transition metal salt solution. S2. Then, sodium hydroxide aqueous solution is added dropwise to the mixed transition metal salt solution; after 1 hour of addition, the pH value of the system is adjusted with ammonia water to obtain a precipitate; the precipitate is filtered, washed with deionized water and ethanol, and then dried to obtain the precursor; S3. Subsequently, the dried precursor is mixed with stoichiometric amounts of TiO2, CaCO3, Li2CO3 and MgCO3, and an excess of 5% stoichiometric amount of Na2CO3 and ball-milled. The mixture is then calcined and ground. S4. Finally, the material is calcined at 900°C in an oxygen atmosphere at a heating rate of 5°C / min to form a high-entropy doped manganese / iron-based substrate material NFM-HEO.

2. The method for preparing the high-entropy doped manganese / iron-based morphological material as described in claim 1, characterized in that, Includes the following steps: S1. Dissolve Fe(NO3)3·9H2O, Mn(NO3)2·4H2O and Cu(NO3)2·3H2O in deionized water in stoichiometric ratios to form a mixed transition metal salt solution. S2. Then, sodium hydroxide aqueous solution is added dropwise to the mixed transition metal salt solution; after 1 hour of addition, the pH value of the system is adjusted with ammonia water to obtain a precipitate; the precipitate is filtered, washed with deionized water and ethanol, and then dried to obtain the precursor; S3. Subsequently, the dried precursor is mixed with stoichiometric amounts of TiO2, CaCO3, Li2CO3 and MgCO3, and an excess of 5% stoichiometric amount of Na2CO3 and ball-milled. The mixture is then calcined and ground. S4. Finally, the material is calcined at 900°C in an oxygen atmosphere at a heating rate of 5°C / min to form a high-entropy doped manganese / iron-based substrate material NFM-HEO.

3. The method for preparing the high-entropy doped manganese / iron-based morphological material according to claim 2, characterized in that, The total concentration of the transition metal salt solution in step S1 is 2.0 mol L. -1 .

4. The method for preparing the high-entropy doped manganese / iron-based morphological material according to claim 2, characterized in that, The concentration of the sodium hydroxide aqueous solution in step S2 is 4.0 mol / L. -1 The concentration of ammonia water is 1.0 mol / L. -1 Adjust the pH of the system to 11.

5. The method for preparing the high-entropy doped manganese / iron-based morphological material according to claim 2, characterized in that, The drying temperature in step S2 is 100°C; the drying time is 6 hours.

6. The method for preparing the high-entropy doped manganese / iron-based morphological material according to claim 2, characterized in that, In step S3, the ball milling speed is 600 rpm and the ball milling time is 6 hours; the calcination temperature is 500°C and the calcination time is 6 hours.

7. The method for preparing the high-entropy doped manganese / iron-based morphological material according to claim 2, characterized in that, The calcination time for step S4 is 12 hours.

8. An electrode sheet, characterized in that, The electrode comprises the high-entropy doped manganese / iron-based morphological material as described in claim 1.

9. A battery, characterized in that, The battery includes an electrode, a counter electrode, and a separator as described in claim 8, wherein the separator is disposed between the electrode and the counter electrode.

Images