High-entropy doped NASICON-type sodium-ion battery cathode material, preparation method and application thereof

Abstract

The application provides a high-entropy doped NASICON type sodium ion battery positive electrode material, which has a chemical formula of Na3V 2‑y (M1,M2,M3…M n ) y (PO4)3, wherein 0 n y≤0.5, M1, M2, M3…M n is a transition metal element for activating high-valence oxidation-reduction of V elements, and the selection is at least five kinds of Al, Cr, Mn, Fe, Zn, Ga and In. The high-entropy doped NASICON type sodium ion battery positive electrode material provided by the application can realize the synergistic improvement of intrinsic conductivity and energy density, and can realize good cycle performance of the sodium ion battery. The application further provides a preparation method and application of the high-entropy doped NASICON type sodium ion battery positive electrode material.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of sodium ion battery positive electrode materials, in particular to a high-entropy doped NASICON type sodium ion battery positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development and popularization of renewable new energy, it is essential to develop low-cost, high-performance and sustainable electrochemical energy storage and conversion systems. Sodium ion batteries are considered to be a strong candidate for the next generation of large-scale electrical energy storage systems due to their wide resource distribution and low cost. However, in order to develop more competitive sodium ion batteries, it is necessary to have a more comprehensive understanding of the storage mechanism of sodium ions and to make great efforts to develop electrode materials with higher specific energy and longer service life, especially positive electrode materials.

[0003] At present, researchers have studied various types of sodium ion battery positive electrode materials, such as layered transition metal oxides, polyanion compounds and prussian blue analogues. Among them, polyanion materials have become a strong candidate due to their robust open structure. The most representative NASICON type compounds, such as Na3V2(PO4)3, Na3V2(PO4)2O2F and Na3V2(PO4)2F3, are connected through the corner sharing between PO4 tetrahedron and MO6 octahedron to form a very solid and stable open framework structure, and have good Na + mobility and thermal stability, so they are widely developed and researched for electrode materials. For example, Na3V2(PO4)3 has a working voltage of about 3.4V and can provide a theoretical capacity of about 118mA h g -1 . However, the only 3.4V (vs. Na + / Na) voltage platform limits the improvement of energy density, and in recent years, different transition metal ions (such as Cr, Mn, Fe, Zn, Al, Ga, In, etc.) have been doped to activate the V 4+ / V 5+ redox pair at a higher voltage to meet the demand for high energy density. At the same time, due to the inherent poor electronic conductivity, it affects its further widespread application. For this reason, various strategies have been developed to overcome this shortcoming, including composite carbon materials, structural nanocrystallization, cation doping, etc. Among them, carbon coating as the most common and effective means still faces the results of excessive carbon causing energy density reduction and complex preparation process.

[0004] Therefore, how to realize the intrinsic conductivity and energy density of the NASICON type sodium ion battery positive electrode material to be optimized and improved, and to maintain its own long cycle stability, is a technical problem to be solved. SUMMARY

[0005] The technical problem to be solved by the present invention is to provide a high-entropy doped NASICON-type sodium-ion battery cathode material that can achieve a synergistic improvement in intrinsic conductivity and energy density, and can achieve good cycle performance of sodium-ion batteries.

[0006] The technical solution of the present invention is as follows:

[0007] A high-entropy doped NASICON-type sodium-ion battery cathode material with the chemical formula Na3V 2-y (M1,M2,M3…M n ) y (PO4)3, where 0 < y ≤ 0.5, M1, M2, M3…M n The transition metal element selected to activate the redox reaction of V is at least five of the following: Al, Cr, Mn, Fe, Zn, Ga, and In.

[0008] This invention also provides a method for preparing a high-entropy doped NASICON-type sodium-ion battery cathode material, comprising the following steps:

[0009] Step S1: Sodium source, vanadium source, transition metal source and phosphorus source are mixed in a certain molar mass ratio, and an appropriate amount of dispersion medium is added for ball milling to obtain the precursor;

[0010] Step S2: Dry and dehydrate the precursor obtained in step S1;

[0011] Step S3: Under inert gas protection, the dried precursor obtained in step S2 is calcined and then cooled to room temperature to obtain a high-entropy doped NASICON-type sodium-ion battery cathode material; wherein the calcination process is as follows: the heating rate is 2-10℃ / min. -1 The calcination temperature is 650-850℃, and the holding time is 6-10h.

[0012] Specifically, in the roasting process, the heating rate can be 2℃ / min. -1 4℃min -1 5℃min -1 6℃min -1 8℃min -1 or 10℃min -1 It can also be any other value within that range;

[0013] The calcination temperature can be 650℃, 700℃, 750℃, 800℃ or 850℃, or other values ​​within this range;

[0014] The heat preservation time can be 6h, 7h, 8h, 9h or 10h, or other values ​​within this range.

[0015] Further, the dispersing medium is one of paraffin wax, palm wax, stearic acid or Span.

[0016] Further, in step S1, the amount of the dispersing medium added is 50-100% of the theoretically calculated mass of the harvested material, such as 50%, 60%, 70%, 80%, 90% or 100%, or other values within the range.

[0017] Further, in step S2, the drying temperature is 60-80℃, and the drying time is 8-12h. The drying temperature can be 60℃, 65℃, 70℃, 75℃ or 80℃, or other values within the range; the drying time can be 8h, 10h or 12h, or other values within the range.

[0018] Further, in step S3, the inert gas is one of argon, nitrogen, argon-hydrogen mixed gas or nitrogen-hydrogen mixed gas.

[0019] The application also provides a sodium ion battery positive electrode sheet, comprising a current collector, a positive electrode material layer coated on the current collector, the positive electrode material layer comprising the positive electrode material, a conductive additive and a binder.

[0020] The conductive additive is one or more of acetylene black, Super P and Ketjen black; and the binder is polyvinylidene fluoride.

[0021] The application also provides a sodium ion battery comprising the sodium ion battery positive electrode sheet.

[0022] Compared with the prior art, the high-entropy doped NASICON-type sodium ion battery positive electrode material provided by the application, the preparation method thereof and the application have the beneficial effects that:

[0023] Firstly, the high-entropy doped NASICON-type sodium ion battery positive electrode material provided by the application is doped with Al, Cr, Mn, Fe, Zn, Ga and In elements, which can affect the structural rearrangement of different sites of Na ions to activate V 4+ / V 5+ redox pairs (3.9V) to meet the demand for high energy density. The high-entropy doping strategy is applied to the Na3V2(PO4)3 electrode material to change the fine structure inside the crystal and improve its intrinsic conductivity; at the same time, the high-entropy effect is used to adjust the voltage platform and reaction phase change during the charging and discharging process, and the adjustment of the voltage platform can improve the energy density, and the adjustment of the reaction phase change makes the reaction process more stable, so that the structure is more stable during the sodium ion deintercalation process.

[0024] II. The high-entropy doped NASICON-type sodium-ion battery cathode material provided by this invention is prepared by one-step solid-state and high-temperature calcination, which is simple, low-cost, and has high material stability.

[0025] Third, the high-entropy doped NASICON-type sodium-ion battery cathode material provided by this invention does not introduce a carbon source for coating, which further improves the overall working voltage and energy density of the material compared with the prior art.

[0026] IV. The high-entropy doped NASICON-type sodium-ion battery cathode material provided by this invention has excellent electrochemical performance. After 450 cycles at a current density of 1C, the capacity retention rate can reach 95%, indicating that it has excellent cycle stability and rate performance. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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.

[0028] Figure 1 The Na3V2(PO4)3 and Na3V prepared for this invention 1.8 (CrMnFeZnAl) 0.2 (PO4)3, Na3V 1.5 (CrMnFeZnAl) 0.5 (PO4)3, Na3V 1.8 (CrFeZnAlGa) 0.2 (PO4)3, Na3V 1.8 (CrFeAlGaIn) 0.2 (PO4)3 and Na3V 1.8 (FeCoNiCuZn) 0.2 XRD pattern of (PO4)3NASICON type sodium-ion battery cathode material;

[0029] Figure 2 The Na3V2(PO4)3 and Na3V prepared for this invention 1.8 (CrMnFeZnAl) 0.2 (PO4)3 and Na3V 1.5 (CrMnFeZnAl) 0.5 Thermogravimetric diagram of (PO4)3NASICON type sodium-ion battery cathode material;

[0030] Figure 3SEM image of Na3V2(PO4)3 NASICON type sodium ion battery positive electrode material prepared in the application;

[0031] Figure 4 Na3V2(PO4)3, Na3V 1.8 (CrMnFeZnAl) 0.2 (PO4)3 NASICON type sodium ion battery positive electrode material prepared in the application;

[0032] Figure 5 Na3V2(PO4)3, Na3V 1.5 (CrMnFeZnAl) 0.5 (PO4)3 NASICON type sodium ion battery positive electrode material prepared in the application;

[0033] Figure 6 Na3V2(PO4)3, Na3V 1.8 (CrMnFeZnAl) 0.2 (PO4)3 and Na3V 1.5 (CrMnFeZnAl) 0.5 (PO4)3 NASICON type sodium ion battery positive electrode material prepared in the application;

[0034] Figure 7 Na3V2(PO4)3, Na3V 1.8 (CrMnFeZnAl) 0.2 (PO4)3 and Na3V 1.5 (CrMnFeZnAl) 0.5 (PO4)3 NASICON type sodium ion battery positive electrode material prepared in the application;

[0035] Figure 8 Na3V2(PO4)3, Na3V 1.8 (CrMnFeZnAl) 0.2 (PO4)3 and Na3V 1.5 (CrMnFeZnAl) 0.5 (PO4)3 NASICON type sodium ion battery positive electrode material prepared in the application;

[0036] Figure 9 Na3V2(PO4)3, Na3V 1.8 (CrMnFeZnAl) 0.2 (PO4)3 and Na3V 1.5 (CrMnFeZnAl) 0.5In-situ XRD pattern of (PO4)3 NASICON-type sodium-ion battery cathode material in one charge-discharge cycle. DETAILED DESCRIPTION

[0037] In order to better understand the technical solutions in the embodiments of the present application by those skilled in the art, and to make the above-mentioned purposes, features and advantages of the present application more apparent and easy to understand, the specific embodiments of the present application are further described below.

[0038] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The ranges or values should be construed to be approximations that allow for significant variation. Various ranges of values that are explicitly delineated are not to be construed as having only the precise values given. The endpoints of the ranges of values, the individual values, and the individual points are not to be construed as being mutually exclusive. The individual values and individual points are to be considered to be included in the ranges or values that they are a part of.

[0039] The high-entropy doped NASICON-type sodium-ion battery cathode material of the present application has a chemical formula of Na3V 2-y (M1,M2,M3…M n ) y (PO4)3, wherein 0 n V element high-valence redox transition metal element is selected from at least five of Al, Cr, Mn, Fe, Zn, Ga, and In, i.e., n≥5.

[0040] The cathode material and the preparation method thereof of the present application are described in detail below through specific embodiments.

[0041] Comparative Example 1: Preparation of Na3V2(PO4)3 NASICON-type sodium-ion battery cathode material

[0042] The preparation method of the Na3V2(PO4)3 cathode material comprises the following steps:

[0043] (1) 9 mmol of CH3COONa, 6 mmol of VOC2O4·nH2O, 9 mmol of NH4H2PO4, and 0.68 g of paraffin are sealed in a stainless steel tank and ground by a QM-3B high-speed vibration ball mill using a one-step solid-phase method. The mixture is uniformly obtained to obtain a precursor, which is dehydrated and dried in an 80℃ oven for 12 h;

[0044] (2) The precursor obtained in step (1) is heated to 750℃ at a rate of 2℃ / min under an argon atmosphere, heat-treated for 8 h, and naturally cooled to room temperature to obtain the Na3V2(PO4)3 cathode material.

[0045] Example 1: Preparation of Na3V 1.8(CrMnFeZnAl) 0.2 (PO4)3NASICON-type sodium-ion battery cathode material

[0046] Na3V 1.8 (CrMnFeZnAl) 0.2 A preparation method of (PO4)3cathode material, comprising the following steps:

[0047] (1) A one-step solid-phase method is used to seal 9 mmol CH3COONa, 5.4 mmol VOC2O4·nH2O, 0.12 mmol Al(NO3)3·9H2O, 0.12 mmol Fe(NO3)3·9H2O, 0.12 mmol Cr(NO3)3·9H2O, 0.12 mmol Zn(NO3)2·6H2O, 0.12 mmol MnC4H6O4, 9 mmol NH4H2PO4 and 0.68 g of paraffin in a stainless steel tank, and grinding is performed by using a QM-3B high-speed vibration ball mill. The mixture is uniformly obtained to obtain a precursor, and the precursor is dehydrated and dried in an 80°C oven for 12 h;

[0048] (2) The precursor obtained in step (1) is heated to 750°C at a rate of 2°C / min under the protection of an argon atmosphere, heat-treated for 8 h, and naturally cooled to room temperature to obtain Na3V 1.8 (CrMnFeZnAl) 0.2 (PO4)3cathode material.

[0049] Example 2: Preparation of Na3V 1.5 (CrMnFeZnAl) 0.5 (PO4)3NASICON-type sodium-ion battery cathode material

[0050] Na3V 1.5 (CrMnFeZnAl) 0.5 A preparation method of (PO4)3cathode material, comprising the following steps:

[0051] (1) A one-step solid-phase method is used to seal 9 mmol CH3COONa, 5.4 mmol VOC2O4·nH2O, 0.12 mmol Al(NO3)3·9H2O, 0.12 mmol Fe(NO3)3·9H2O, 0.12 mmol Cr(NO3)3·9H2O, 0.12 mmol Zn(NO3)2·6H2O, 0.12 mmol MnC4H6O4, 9 mmol NH4H2PO4 and 0.68 g of paraffin in a stainless steel tank, and grinding is performed by using a QM-3B high-speed vibration ball mill. The mixture is uniformly obtained to obtain a precursor, and the precursor is dehydrated and dried in an 80°C oven for 12 h;

[0052] (2) The precursor obtained in step (1) is heated to 750°C at a rate of 2°C / min under an argon atmosphere, and heat-treated for 8 hours, and then naturally cooled to room temperature to obtain Na3V 1.5 (CrMnFeZnAl) 0.5 (PO4)3 cathode material.

[0053] Example 3: Preparation of Na3V 1.8 (CrFeZnAlGa) 0.2 (PO4)3 NASICON-type sodium ion battery cathode material

[0054] Na3V 1.8 (CrFeZnAlGa) 0.2 A method for preparing the (PO4)3 cathode material, comprising the following steps:

[0055] (1) A one-step solid-phase method is used to grind 9 mmol CH3COONa, 5.4 mmol VOC2O4·nH2O, 0.12 mmol Al(NO3)3·9H2O, 0.12 mmol Fe(NO3)3·9H2O, 0.12 mmol Cr(NO3)3·9H2O, 0.12 mmol Zn(NO3)2·6H2O, 0.12 mmol Ga(NO3)3·xH2O, 9 mmol NH4H2PO4, and 0.68 g of paraffin in a stainless steel can, and a QM-3B high-speed vibration ball mill is used for grinding. The mixture is uniformly obtained, and is dehydrated and dried in an 80°C oven for 12 h;

[0056] (2) The precursor obtained in step (1) is heated to 750°C at a rate of 2°C / min under an argon atmosphere, and heat-treated for 8 hours, and then naturally cooled to room temperature to obtain Na3V 1.8 (CrFeZnAlGa) 0.2 (PO4)3 cathode material.

[0057] Example 4: Preparation of Na3V 1.8 (CrFeAlGaIn) 0.2 (PO4)3 NASICON-type sodium ion battery cathode material

[0058] Na3V 1.8 (CrFeAlGaIn) 0.2 A method for preparing the (PO4)3 cathode material, comprising the following steps:

[0059] (1) One-step solid phase method, 9mmol CH3COONa, 5.4mmol VOC2O4·nH2O, 0.12mmol Fe(NO3)3·9H2O, 0.12mmol Cr(NO3)3·9H2O, 0.12mmol Al(NO3)3·9H2O, 0.12mmol Ga(NO3)3·xH2O, 0.12mmol In(NO3)3, 9mmol NH4H2PO4 and 0.68g paraffin were sealed in a stainless steel tank and ground by QM-3B high-speed vibration ball mill. The mixture was uniformly obtained, and the precursor was dehydrated and dried in an oven at 80℃ for 12h;

[0060] (2) The precursor obtained in step (1) was heated to 750℃ at a rate of 2℃ / min under an argon atmosphere, heat treated for 8 hours, and naturally cooled to room temperature to obtain Na3V 1.8 (CrFeAlGaIn) 0.2 (PO4)3 positive electrode material.

[0061] Example 5: Preparation of Na3V 1.8 (FeCoNiCuZn) 0.2 (PO4)3 NASICON type sodium ion battery positive electrode material

[0062] Na3V 1.8 (FeCoNiCuZn) 0.2 The preparation method of the Na3V

[0063] (1) One-step solid phase method, 9mmol CH3COONa, 5.4mmol VOC2O4·nH2O, 0.12mmol Zn(NO3)2·6H2O, 0.12mmol Fe(NO3)3·9H2O, 0.12mmol Co(NO3)2·6H2O, 0.12mmol NiC4H6O4·4H2O, 0.12mmol Cu(NO3)2, 9mmol NH4H2PO4 and 0.68g paraffin were sealed in a stainless steel tank and ground by QM-3B high-speed vibration ball mill. The mixture was uniformly obtained, and the precursor was dehydrated and dried in an oven at 80℃ for 12h;

[0064] (2) The precursor obtained in step (1) was heated to 750℃ at a rate of 2℃ / min under an argon atmosphere, heat treated for 8 hours, and naturally cooled to room temperature to obtain Na3V 1.8 (FeCoNiCuZn) 0.2 (PO4)3 positive electrode material.

[0065] Please refer to Figure 1Na3V2(PO4)3, Na3V 1.8 (CrMnFeZnAl) 0.2 Na3V2(PO4)3, Na3V 1.5 (CrMnFeZnAl) 0.5 Na3V2(PO4)3, Na3V 1.8 (CrFeZnAlGa) 0.2 Na3V2(PO4)3, Na3V 1.8 (CrFeAlGaIn) 0.2 Na3V2(PO4)3, Na3V 1.8 (FeCoNiCuZn) 0.2 XRD pattern of Na3V2(PO4)3NASICON-type sodium-ion battery cathode material prepared by the present application. From Figure 1 It can be seen that the samples all have high crystallinity and similar diffraction peaks, and can be well indexed to pure phase Na3V2(PO4)3of NASICON structure, indicating that the high-entropy elements successfully replace part of the central active element (V) sites.

[0066] Please refer to Figure 2 Na3V2(PO4)3, Na3V 1.8 (CrMnFeZnAl) 0.2 Na3V2(PO4)3, Na3V 1.5 (CrMnFeZnAl) 0.5 TG pattern of Na3V2(PO4)3NASICON-type sodium-ion battery cathode material prepared by the present application. From Figure 2 It can be seen that the Na3V2(PO4)3, Na3V 1.8 (CrMnFeZnAl) 0.2 Na3V2(PO4)3, Na3V 1.5 (CrMnFeZnAl) 0.5 The carbon content of Na3V2(PO4)3does not exceed 5% of the overall weight.

[0067] Please refer to Figures 3 to 5 Wherein Figure 3 SEM image of Na3V2(PO4)3NASICON-type sodium-ion battery cathode material prepared by the present application; Figure 4 Na3V2(PO4)3, Na3V 1.8 (CrMnFeZnAl) 0.2 SEM image of Na3V2(PO4)3NASICON-type sodium-ion battery cathode material prepared by the present application; Figure 5 Na3V2(PO4)3, Na3V 1.5 (CrMnFeZnAl) 0.5 SEM image of Na3V2(PO4)3NASICON-type sodium-ion battery cathode material prepared by the present application;Figure 3 It can be seen that the prepared Na3V2(PO4)3 consists of bulk particles of approximately 3-4 μm; Figure 4 It can be seen that the prepared Na3V 1.8 (CrMnFeZnAl) 0.2 (PO4)3 consists of particles of 300 nm; Figure 5 It can be seen that the prepared Na3V 1.5 (CrMnFeZnAl) 0.5 (PO4)3 is composed of even smaller particles, approximately 200 nm in size. This indicates that high-entropy doping has an inhibitory effect on crystal growth.

[0068] Example 5: Preparation of a coin cell sodium-ion battery

[0069] The active material, acetylene black (AB), and polyvinylidene fluoride (PVDF) were added to an N-methyl-2-pyrrolidone (NMP) solution in a molar ratio of 7:2:1. After grinding and dispersing, the slurry was uniformly coated onto aluminum foil and dried overnight in a vacuum oven at 80°C to prepare the positive electrode sheet. The active materials were Na3V2(PO4)3 prepared in Comparative Example 1 and Na3V2(PO4)3 prepared in Example 1, respectively. 1.8 (CrMnFeZnAl) 0.2 (PO4)3, Na3V prepared in Example 2 1.5 (CrMnFeZnAl) 0.5 (PO4)3; Acetylene black is a conductive additive, polyvinylidene fluoride (PVDF) is a binder, and aluminum foil is a current collector.

[0070] In an argon-filled glove box with H2O and O2 concentrations below 0.1 ppm, 2025 coin cells were assembled. The electrolyte was a solution of 1 M NaPF6 dissolved in propylene carbonate (PC) and 5% fluoroethylene carbonate (FEC). Sodium foil was used as the counter electrode, and a glass fiber membrane was used as the separator for the half-cell, assembling a CR2025 coin cell. Testing was conducted using a constant current charge-discharge mode, with a charge cutoff voltage of 4.3 V and a discharge cutoff voltage of 2.5 V, at 100 mA g. -1 The experiment was conducted at a current density of [specific value].

[0071] Please see Figure 6 The Na3V2(PO4)3 and Na3V prepared in this invention 1.8 (CrMnFeZnAl) 0.2 (PO4)3 and Na3V 1.5 (CrMnFeZnAl) 0.5 CV curve of (PO4)3NASICON type sodium-ion battery cathode material at a scan rate of 1 mV / s. Figure 6It can be seen that Na3V 1.8 (CrMnFeZnAl) 0.2 (PO4)3and Na3V 1.5 (CrMnFeZnAl) 0.5 (PO4)3has a new redox peak at about 3.9V compared with Na3V2(PO4)3, which can be identified as the redox reaction of V 4+ / 5+ .

[0072] Please refer to Figure 7 , Na3V2(PO4)3, Na3V 1.8 (CrMnFeZnAl) 0.2 (PO4)3and Na3V 1.5 (CrMnFeZnAl) 0.5 (PO4)3NASICON-type sodium-ion battery cathode material at 1C (100mA / g) rate. From Figure 7 It can be seen that Na3V 1.8 (CrMnFeZnAl) 0.2 (PO4)3and Na3V 1.5 (CrMnFeZnAl) 0.5 (PO4)3has a new redox pair corresponding to the CV curve, which improves the overall voltage of Na3V2(PO4)3, and the increase of the content of the doping element also improves the capacity of the high redox platform, but Na3V 1.5 (CrMnFeZnAl) 0.5 (PO4)3has a low overall capacity.

[0073] Please refer to Figure 8 , Na3V2(PO4)3, Na3V 1.8 (CrMnFeZnAl) 0.2 (PO4)3and Na3V 1.5 (CrMnFeZnAl) 0.5 (PO4)3NASICON-type sodium-ion battery cathode material at 1C current density. From Figure 8 It can be seen that the appropriate amount of high-entropy element reduces the content of active element vanadium without reducing the capacity, but rather makes Na3V 1.8 (CrMnFeZnAl) 0.2 (PO4)3has more stable cycle performance than Na3V2(PO4)3, but excessive doping may cause structural instability and thus lead to capacity reduction. The capacity retention rate can reach 95% after 450 cycles at 1C current density, indicating that the cathode material of the application has excellent cycle stability and rate performance.

[0074] Reference is made to Figure 9 Na3V2(PO4)3, Na3V 1.8 (CrMnFeZnAl) 0.2 (PO4)3and Na3V 1.5 (CrMnFeZnAl) 0.5 (PO4)3NASICON-type sodium-ion battery cathode material in one charge-discharge cycle. From Figure 9 It can be seen that all of them undergo solid solution reaction mechanism and two-phase reaction mechanism. The difference is that Na3V 1.8 (CrMnFeZnAl) 0.2 (PO4)3and Na3V 1.5 (CrMnFeZnAl) 0.5 (PO4)3in the marked area, which means the appearance of the transition state, and with the increase of high-entropy content, the intensity of the peak is more obvious, indicating that the stability of the crystal structure in this area is higher. It can be seen that the increase of entropy caused by multi-element doping leads to the interaction of each element, thus realizing the evolution adjustment of the structure transition state in the charge-discharge process, further stabilizing the crystal structure and enhancing the performance.

[0075] It should be noted that in addition to the above embodiments, the high-entropy doped NASICON-type sodium-ion battery cathode material of the present application has the chemical formula Na3V 2-y (M1,M2,M3…M n ) y (PO4)3, y can also be 0.1, 0.3 or 0.4, or other values in the range of 0

[0076] The above detailed description of the embodiments of the present application, but the present application is not limited to the described embodiments. For those skilled in the art, various changes, modifications, replacements and variations of these embodiments without departing from the principles and spirit of the present application, still fall within the scope of the present application.

Claims

1. A high-entropy doped NASICON-type sodium-ion battery cathode material, characterized in that, Its chemical formula is Na3V 2-y (M1,M2,M3…M n ) y (PO4)3, where 0 < y ≤ 0.5, M1, M2, M3…M n To activate the high-valence redox transition metal element of element V, at least five of the following elements are selected: Al, Cr, Mn, Fe, Zn, Ga, and In, for high-entropy doping. The high-entropy doped NASICON type sodium ion battery cathode material is prepared by the following method: In step S1, a sodium source, a vanadium source, a transition metal source and a phosphorus source are mixed in a certain molar mass ratio, and a proper amount of a dispersing medium is added for ball milling to obtain a precursor; the dispersing medium is one of paraffin, palm wax, stearic acid or Span; In step S2, the precursor obtained in step S1 is dried and dehydrated; Step S3, under inert gas protection, the dry precursor obtained in step S2 is calcined, and then cooled to room temperature to obtain a high-entropy doped NASICON type sodium ion battery cathode material; wherein the calcination process is: the heating rate is 2-10 ℃min -1 , the calcination temperature is 650-850℃, and the holding time is 6-10h.

2. A method of preparing a high entropy doped NASICON-type sodium-ion battery cathode material as claimed in claim 1, characterized in that, The method comprises the following steps: In step S1, a sodium source, a vanadium source, a transition metal source and a phosphorus source are mixed in a certain molar mass ratio, and a proper amount of a dispersing medium is added for ball milling to obtain a precursor; the dispersing medium is one of paraffin, palm wax, stearic acid or Span; In step S2, the precursor obtained in step S1 is dried and dehydrated; Step S3, under inert gas protection, the dry precursor obtained in step S2 is calcined, and then cooled to room temperature to obtain a high-entropy doped NASICON type sodium ion battery cathode material; wherein the calcination process is: the heating rate is 2-10 ℃min -1 , the calcination temperature is 650-850℃, and the holding time is 6-10h.

3. The method for preparing the high-entropy doped NASICON-type sodium-ion battery cathode material according to claim 2, characterized in that, In step S1, the amount of the dispersing medium added is 50-100% of the theoretically calculated material mass.

4. The method for preparing the high-entropy doped NASICON-type sodium-ion battery cathode material according to claim 2, characterized in that, In step S2, the drying temperature is 60-80 DEG C, and the drying time is 8-12 h.

5. The process for the preparation of high entropy doped NASICON type sodium-ion battery cathode material as claimed in claim 2, wherein, In step S3, the inert gas is one of argon, nitrogen, argon-hydrogen mixed gas or nitrogen-hydrogen mixed gas.

6. A sodium-ion battery positive electrode sheet, characterized by, The sodium ion battery cathode sheet comprises a current collector, a cathode material layer coated on the current collector, and the cathode material layer comprises the cathode material of claim 1, a conductive additive and a binder.

7. A sodium-ion battery, characterized in that, The sodium ion battery cathode sheet comprises the cathode material of claim 6.

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