High-entropy sodium ion battery positive electrode material and preparation method thereof

Abstract

The invention discloses a high-entropy sodium-ion battery positive electrode material and a preparation method thereof, belongs to the technical field of secondary batteries, and discloses a preparation method of a high-entropy O3 type sodium-ion battery positive electrode material NaxNiaFebMncCudAleTifMggZnhO2. The preparation method comprises the following steps: regulating and controlling component materials of Na2CO3, NiO, Fe2O3, Mn2O3, CuO, Al2O3, TiO2, MgO and ZnO, and sintering in an oxidizing gas condition, so that raw material powder is subjected to a high-temperature solid-phase reaction, and the high-entropy O3 type sodium-ion battery positive electrode material NaxNiaFebMncCudAleTifMggZnhO2 is obtained. And the material Na < x > Ni Fe Mn < c > Cu < d > Al < e > Ti < f > Mg < g > Zn < h > O < 2 > with high capacity and high performance is successfully prepared. The positive electrode material prepared by the invention has good rate capability and cycling stability and excellent total battery performance under the action of high-entropy components of the material.

Description

Technical Field

[0001] The present invention belongs to the technical field of secondary batteries, and relates to a high-entropy sodium-ion battery cathode material and a preparation method thereof. Background Art

[0002] With the continuous growth of energy demand, renewable energy and energy storage technologies have received extensive attention. As an important part of the energy storage field, the market demand for batteries is expanding day by day. Lithium-ion batteries have been widely used in fields such as mobile communication and electric vehicles due to their advantages such as high energy density and long cycle life. However, problems such as limited reserves, uneven distribution, and price fluctuations of lithium resources have restricted their large-scale application. Therefore, seeking a new energy storage system to replace lithium-ion batteries has become a research hotspot.

[0003] Sodium is abundant in the earth's crust, widely distributed, and has similar chemical properties to lithium. This makes sodium-ion batteries an ideal choice to replace lithium-ion batteries. Sodium-ion batteries have the following advantages: 1) Abundant resources: The reserves of sodium in the earth's crust are more than 1000 times that of lithium, which is conducive to reducing the cost of batteries; 2) Low cost: The raw materials such as cathode materials, anode materials, and electrolytes of sodium-ion batteries are relatively low in price, which is conducive to large-scale application; 3) Environmentally friendly: Sodium-ion batteries have less impact on the environment during the preparation and recycling processes.

[0004] At present, the research on sodium-ion battery cathode materials mainly focuses on layered oxides, polyanion-type compounds, Prussian blue compounds, etc. Among them, layered oxide sodium-ion batteries have attracted wide attention from scholars due to their high theoretical specific capacity and good cycle performance. Especially in sodium-ion full batteries, they are considered to be sodium-ion battery cathode materials with application prospects. However, due to the fact that layered metal oxide cathode materials will undergo multiple phase transitions during the cycling process, resulting in structural collapse and affecting their cycling capacity, the large-scale commercial application process has been restricted.

[0005] The high-entropy effect refers to a phenomenon in high-entropy alloys (HEAs), where the alloy is composed of five or more elements in near-equiatomic ratios, forming a high-entropy solid solution at the microscale. In recent years, the high-entropy concept has also been introduced into the design of battery materials, especially cathode materials for sodium-ion batteries. The following are the advantages of applying the high-entropy effect in sodium-ion battery cathode materials: 1) Element synergy: In high-entropy sodium-ion battery cathode materials, the presence of multiple metal elements can optimize the electronic structure and electrochemical activity of the material through synergy, thereby improving its energy density and power density; 2) Stability and durability: The multi-element characteristics in high-entropy materials can increase the structural stability, reduce phase transitions and volume expansion that may occur during charge and discharge, thus improving the cycle stability and service life of the material. 3) Environmental friendliness: By using high-entropy materials, the demand for rare and toxic elements can be reduced, thereby reducing the impact on the environment.

[0006] However, the synthesis of high-entropy materials requires the elements to be mixed in near-equiatomic ratios, which is difficult to precisely control in the actual synthesis process. Moreover, not all element combinations can form a single solid solution phase, and sometimes complex phase structures may be formed, which may affect the performance of the material. Therefore, selecting appropriate high-entropy components and adopting reasonable element ratios are particularly crucial in the preparation of sodium-ion battery cathode materials and also play a significant role in the entire sodium-ion battery system. Summary of the Invention

[0007] Aiming at the problems existing in the synthesis of high-entropy materials in the prior art, the present invention provides a high-entropy sodium-ion battery cathode material and its preparation method. The present invention aims to overcome the problems in the synthesis of high-entropy sodium-ion cathode materials. After the raw material powders are fully mixed by mechanical mixing, the mixed powders are calcined in an oxidizing gas atmosphere to obtain the sodium-ion battery cathode material. This material has a uniform structure and is closely connected; the doping of trace elements strengthens the bond energy between the structures, thereby improving the structural stability of the material. The sodium-ion battery containing this material has good rate performance and cycle stability.

[0008] To achieve the above invention purpose, the technical solution adopted by the present invention is:

[0009] A high-entropy sodium-ion battery cathode material and its preparation method, which is a high-entropy O3-type sodium-ion battery cathode material Na x Ni a Fe b Mn c Cu d Al e Ti f Mg g Zn hThe preparation method of O2 includes the following steps: Weigh the raw materials Na2CO3, NiO, Fe2O3, Mn2O3, CuO, Al2O3, TiO2, MgO, ZnO according to the corresponding molar ratio, fully ball-mill and mix them, and then place them in a quartz crucible; Put the quartz crucible into a muffle furnace, keep it at 750°C - 1000°C for a period of time for high-temperature melting, and then Na x Ni a Fe b Mn c Cu d Al e Ti f Mg g Zn h O2 sodium-ion battery cathode material can be obtained. Through the regulation of the component materials of Na2CO3, NiO, Fe2O3, Mn2O3, CuO, Al2O3, TiO2, MgO, ZnO in the present invention, sintering is carried out under oxidizing gas conditions, and high-temperature solid-phase reaction occurs in the raw material powder, and a material Na x Ni a Fe b Mn c Cu d Al e Ti f Mg g Zn h O2 is successfully prepared. The cathode material prepared in the present invention has good rate performance, cycle stability, and excellent full-cell performance under the action of the high-entropy composition of the material.

[0010] The present invention is realized through the following method:

[0011] A preparation method of a high-entropy sodium-ion battery cathode material includes the following steps:

[0012] S1. Weigh the raw material sodium source and metal oxide powder according to the molar ratio to obtain a mixed precursor powder;

[0013] The sodium source is one of Na2CO3 and NaHCO3; the metal oxide powder is selected from NiO, Fe2O3, Mn2O3, CuO, Al2O3, TiO2, MgO, ZnO;

[0014] The molar ratio is Na x Ni a Fe b Mn c Cu d Al e Ti f Mg g Zn hO₂, where 0.9 ≤ x ≤ 1.05, a + b + c + d + e + f + g + h = 1, and 0 ≤ a, b, c, d, e, f, g, h ≤ 1;

[0015] S2. Thoroughly mix the mixed precursor powders, and place the obtained mixed powder in a crucible;

[0016] S3. Calcinate the crucible containing the mixed powder under an oxidizing gas atmosphere at a temperature of 750 °C to 1000 °C for a time of 1 h to 24 h to obtain a high-entropy sodium-ion battery cathode material. The high-entropy sodium-ion cathode material is of the layered oxide type. The microstructure of the high-entropy sodium-ion cathode material is an O3-type (Octahedral) stacking configuration, with an average particle size of 5 μm to 10 μm. The chemical formula of the O3-type high-entropy layered oxide cathode material is Na x Ni a Fe b Mn c Cu d Al e Ti f Mg g Zn h O₂, where 0.9 ≤ x ≤ 1.05, a + b + c + d + e + f + g + h = 1; For the high-entropy sodium-ion battery cathode material, the initial efficiency is 95.10% - 96.80%, the 0.2C gram capacity is 149.0 mAh / g - 155.5 mAh / g, the capacity retention rate is 88.30% - 90.30%, the rate performance is 86.01% - 89.10%, and there are no cracks between crystals after 100 cycles.

[0017] Further, in S2, the mixing method is ball milling, with a rotation speed of 300 rpm to 500 rpm and a time of 1 h to 24 h; In S2, the crucible is one of a quartz crucible and a corundum crucible.

[0018] Further, in S3, the gas in the oxidizing gas atmosphere is at least one of air and oxygen.

[0019] The present invention also relates to a preparation method of a high-entropy sodium-ion battery cathode material, obtained according to the above preparation method of a high-entropy sodium-ion battery cathode material. The high-entropy sodium-ion battery cathode material is obtained by calcining a mixture of a raw material sodium source and a metal oxide material under an oxidizing gas atmosphere, and has an O3-type stacking structure; The average particle size of the sodium-ion battery cathode material is 5 μm to 10 μm. The chemical formula of the O3-type high-entropy layered oxide cathode material is Na x Ni a Fe b Mn c Cu d Ale Ti f Mg g Zn h O₂, where 0.9 ≤ x ≤ 1.05, a + b + c + d + e + f + g + h = 1; for the cathode material of the high-entropy sodium-ion battery, the initial efficiency is 95.10% - 96.80%, the 0.2C specific capacity is 149.0 mAh / g - 155.5 mAh / g, the capacity retention rate is 88.30% - 90.30%, the rate performance is 86.01% - 89.10%, and there are no cracks between crystals after 100 cycles.

[0020] The present invention also relates to a positive electrode sheet, which includes the above-mentioned cathode material of the high-entropy sodium-ion battery.

[0021] The present invention also relates to a sodium-ion battery, which includes the above-mentioned positive electrode sheet.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The cathode material of the high-entropy sodium-ion battery described in the present invention is a high-entropy O3-phase layered oxide Na x Ni a Fe b Mn c Cu d Al e Ti f Mg g Zn h O₂. With a layered microstructure as the main body and the addition of multiple elements to achieve fine-tuning of composition and performance, the density of the battery cell is effectively increased, and the intrinsic characteristics of the material, such as long cycle life, high safety, and high capacity, can be taken into account.

[0024] 2. In the high-entropy sodium-ion battery cathode material of the present invention, doping a small amount of Zn, Al, and Ti in the high-entropy O3-phase layered oxide sodium-ion battery cathode material can effectively inhibit the lattice distortion problem caused by the Jahn-Teller effect. The more stable TM-O bonds can reduce the volume change of the material, thereby improving the cycle stability performance of the material; doping a small amount of Cu can increase the capacity of the material and is also beneficial to improving the stability of the battery at low rates; although doping a small amount of Mg will have a certain adverse effect on the rate performance, the doping of Mg will further activate Cu, thereby increasing the capacity of the material, and the mixing ratio of Mg is small, so the selection of Mg doping has no obvious impact on the performance of the battery cell; the high-entropy O3-phase layered oxide is formed by the aggregation of nanoscale primary particles into secondary spherical particles with a size of 5 μm - 10 μm. The migration path of sodium ions between the metal layers is short, and the rate performance is good. Although the components of the material are complex, the synthesized crystal phase is relatively uniform, which makes the volume expansion effect caused by the high pressure not obvious; after 100 cycles, there are no cracks between the crystals of the sodium-ion battery cathode material. The high-entropy composition design makes the material system have good cycle performance and thermal stability performance. In addition, the specific capacity of the high-entropy material is slightly higher than that of the original material system, and the synthesis process is relatively simple, which can be applied to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 It is the electron microscope image of the high-entropy sodium-ion battery cathode material prepared in Example 5 of the present invention;

[0027] Figure 2 It is the electron microscope image of the high-entropy sodium-ion battery cathode material prepared in Example 5 of the present invention after 500 cycles;

[0028] Figure 3 It is the XRD powder diffraction pattern of the high-entropy sodium-ion battery cathode material prepared in Example 5 of the present invention;

[0029] Figure 4 It is the 0.2C cycle performance curve of the high-entropy sodium-ion battery cathode material prepared in Example 5 of the present invention;

[0030] Figure 5 It is the 8C cycle performance curve of the high-entropy sodium-ion battery cathode material prepared in Example 5 of the present invention;

[0031] Figure 6 Diagram of the cylindrical battery and soft-pack battery assembled with the high-entropy sodium-ion battery cathode material prepared in Example 5 of the present invention. Specific Embodiments

[0032] The following will describe in detail the implementation schemes of the present invention in combination with the implementation manners and examples. However, those skilled in the art will understand that the following implementation manners and examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Based on the examples in the present invention, all other examples obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention. Those not specifying specific conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not indicating the manufacturer can be obtained as conventional products through commercial purchase.

[0033] In a first aspect, the present invention provides a cathode material for a sodium-ion battery. The cathode material for the sodium-ion battery has an O3-type layered oxide structure. The cathode material for the sodium-ion battery is obtained by calcining a raw material sodium source and a metal oxide in an oxidizing gas atmosphere.

[0034] In a specific embodiment of the present invention, the chemical formula of the O3-type layered oxide cathode material is Na x Ni a Fe b Mn c Cu d Al e Ti f Mg g Zn h O2, where 0.9 ≤ x ≤ 1.05, a + b + c + d + e + f + g + h = 1, and 0 ≤ a, b, c, d, e, f, g, h ≤ 1. As an example, x can be but is not limited to 0.9, 0.95, 1.0, 1.05; a, b, c, d, e, f, g, h can independently be but are not limited to 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, as long as a + b + c + d + e + f + g + h = 1 is satisfied.

[0035] In a specific embodiment of the present invention, the average particle size of the cathode material for the sodium-ion battery is 5 - 10 μm. Specifically, the average particle size of the cathode material for the sodium-ion battery is 7.5 μm.

[0036] The present invention also provides a method for preparing a cathode for a sodium-ion battery, including the steps:

[0037] S1. Weigh the raw material sodium source and the metal oxide powder according to the molar ratio.

[0038] S2. Thoroughly mix the mixed precursor powders and place the obtained mixed powder in a crucible.

[0039] S3. Calcinate the crucible containing the mixed powder under the condition of an oxidizing gas atmosphere to obtain the positive electrode material of the sodium-ion battery.

[0040] In a specific embodiment of the present invention, in step S1, trace elements such as Cu, Al, Ti, Mn, Mg, Zn, etc. can not only optimize the cycling performance of the sodium-ion battery material but also have a certain effect on improving the capacity.

[0041] In a specific embodiment of the present invention, in step S2, the precursor powders are mixed by ball milling, which can not only refine the particles of the raw materials but also increase the solid-phase reaction area of the powder mixture. The rotation speed of the ball milling is preferably 300 - 600 r / min, such as 300, 350, 400, 450, 500, 550, 600 r / min; the preferred ball milling time is 3 - 8 h, such as 3, 4, 5, 6, 7, 8 h, etc.

[0042] In a specific embodiment of the present invention, in step S3, the gas in the oxidizing atmosphere includes at least one of air and oxygen. As an example, the gas in the oxidizing gas atmosphere can be air introduced.

[0043] In a specific embodiment of the present invention, in step S3, calcining the mixed material under the oxidizing gas atmosphere can cause solid-phase reactions between the powders, thereby obtaining a compositionally uniform O3-type sodium-ion battery positive electrode material. The calcination temperature is preferably 800 - 950 °C, such as 800, 830, 850, 870, 890, 910, 930, 950 °C; the calcination time is preferably 10 - 30 h, such as 10, 15, 20, 25, 30 h; during the calcination process, the temperature is raised to 800 - 950 °C at a heating rate of 5 °C / min.

[0044] The present invention also provides a positive electrode sheet including the above-mentioned positive electrode material of the sodium-ion battery.

[0045] The sodium-ion battery prepared with this positive electrode sheet can effectively improve the energy density of the battery and also take into account the intrinsic characteristics of the material with long cycling and high safety.

[0046] The above positive electrode sheet can be prepared by using the general electrode sheet preparation process in the art. For example: mix the above positive electrode material, conductive agent, and binder to prepare a slurry, coat it on at least one side of the positive electrode current collector, and obtain the positive electrode sheet after drying and pressing.

[0047] In the above method for preparing the positive electrode sheet, the type and content of the conductive agent are not specifically limited and can be selected according to actual needs. In some embodiments, the above conductive agent includes at least one of conductive carbon black, carbon nanotubes, acetylene black, graphene, carbon nanofibers, etc. It should be understood that without departing from the spirit of the present application, other conductive agents that can achieve the functions of the present application can be selected according to needs, without being limited thereto.

[0048] In the above method for preparing the electrode sheet, in the method for preparing the positive electrode sheet, the type and content of the binder are not specifically limited and can be selected according to actual requirements. In some embodiments, the above binder includes at least one of polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, sodium carboxymethyl cellulose, polymethacrylamide, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyamide, etc.

[0049] The type of the above positive current collector is not specifically limited and can be selected according to actual requirements. For example, the positive current collector can be aluminum foil, nickel foil or a polymer conductive film. Preferably, the positive current collector is aluminum foil.

[0050] The present invention also provides a sodium ion battery, including the above positive electrode sheet, negative electrode sheet, separator and electrolyte, and the separator is arranged to isolate the positive electrode sheet from the negative electrode sheet.

[0051] In the above sodium ion battery, the type of the separator is not limited and can be any separator material used in existing batteries, such as polyethylene, polypropylene, polyvinylidene fluoride, non-woven fabric, their multi-layer composite films, and modified separators such as ceramic modification and PVDF modification of the above separators, but not limited to these.

[0052] In the above sodium-ion battery, the electrolyte can be one or more of an organic liquid electrolyte, an organic solid electrolyte, a solid ceramic electrolyte, and a gel electrolyte. Preferably, the electrolyte is an organic liquid electrolyte, which is obtained by dissolving a sodium salt in a non-aqueous organic solvent; wherein, the above sodium salt may include one or more of sodium difluorophosphate (NaPO2F2), sodium hexafluorophosphate (NaPF6), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSi), and sodium difluorooxalate borate (NaDFOB). The above non-aqueous organic solvent may include one or several of cyclic carbonates, chain carbonates, and carboxylic acid esters. Among them, the cyclic carbonate can be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, and γ-butyrolactone; the chain carbonate can be selected from one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), methyl acetate (MA), ethyl acetate (EA), and ethyl propionate (EP). In some embodiments, a certain amount of additive can also be added to the organic liquid electrolyte. The additive may include one or more of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), ethylene sulfate (DTD), ethylene sulfite (ES), methylene methane disulfonate (MMDS), 1,3-propane sultone (PS), propylene sultone (PES), propylene sulfate (TMS), trimethylsilyl phosphate (TMSP), trimethylsilyl borate (TMSB), and fluoroethylene carbonate (FEC).

[0053] The present invention further provides an electrical device, including the above sodium-ion battery.

[0054] In some embodiments, the electrical device of the present invention includes, but is not limited to, a backup power supply, a motor, an electric vehicle, an electric motorcycle, an assisted bicycle, a bicycle, an electric tool, a large household battery, etc.

[0055] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the embodiments cited do not limit the present invention.

[0056] Example 1:

[0057] A cathode material for a high-entropy sodium-ion battery, whose structure is a high-entropy O3-type layered oxide, specifically Na 0.9 Ni 0.2 Fe 0.2 Mn 0.4 Cu 0.1 Al 0.03 Ti 0.03 Mg0.02 Zn 0.02 O2;

[0058] The above-mentioned method for preparing a high entropy sodium ion battery positive electrode material comprises the following steps:

[0059] S1. Raw material preparation: according to the molar ratio of each element in the high entropy O3-type layered oxide, sodium carbonate, nickel oxide, iron oxide, manganese oxide, copper oxide, aluminum oxide, titanium oxide, magnesium oxide and zinc oxide were weighed and mixed thoroughly, and mixed at 300 r / min for 4 h to obtain a mixture powder;

[0060] S2, calcination treatment: the mixed powder is further calcined in an air atmosphere at a heating rate of 5°C / min to 800°C, calcined for 10 hours and then cooled to room temperature to obtain a high entropy O3 phase layered oxide;

[0061] S3. Product crushing: The high entropy O3 phase layered oxide obtained by high temperature calcination is crushed into powder by a planetary ball mill. The grinding time of the planetary ball mill is 6 hours.

[0062] Embodiment 2:

[0063] The only difference between this embodiment and embodiment 1 is that step S2 is to heat the mixture powder to 850°C at a heating rate of 5°C / min, calcine for 12 hours and then cool to room temperature. The other steps and specific parameter conditions are the same as those in embodiment 1.

[0064] Embodiment 3:

[0065] The only difference between this embodiment and embodiment 1 is that the temperature program used in step S2 high temperature smelting is changed to: heating to 900°C at a heating rate of 5°C / min, calcining for 14 hours and then cooling to room temperature. The other steps and specific parameter conditions are the same as those in embodiment 1.

[0066] Embodiment 4:

[0067] A positive electrode material for a high entropy sodium ion battery, the structure of which is a high entropy O3 type layered oxide, specifically NaNi 0.1 5Fe 0.15 Mn 0.5 Cu 0.1 Al 0.03 Ti 0.03 Mg 0.02 Zn 0.02 O2;

[0068] The above-mentioned method for preparing a high entropy sodium ion battery positive electrode material comprises the following steps:

[0069] S1. Raw material preparation: according to the molar ratio of each element in the high entropy O3-type layered oxide, sodium carbonate, nickel oxide, iron oxide, manganese oxide, copper oxide, aluminum oxide, titanium oxide, magnesium oxide and zinc oxide were weighed and mixed thoroughly, and mixed at 300 r / min for 4 h to obtain a mixture powder;

[0070] S2, calcination treatment: the mixed powder is further calcined in an air atmosphere at a heating rate of 5°C / min to 800°C, calcined for 10 hours and then cooled to room temperature to obtain a high entropy O3 phase layered oxide;

[0071] S3. Product crushing: The high entropy O3 phase layered oxide obtained by high temperature calcination is crushed into powder by a planetary ball mill. The grinding time of the planetary ball mill is 6 hours.

[0072] Embodiment 5:

[0073] The only difference between this embodiment and embodiment 4 is that the temperature program used for high temperature smelting in step S2 is changed to: heating the mixture powder to 850°C at a heating rate of 5°C / min, calcining for 12 hours and then cooling to room temperature. The other steps and specific parameter conditions are the same as those in embodiment 4.

[0074] The result is shown in the figure: Figure 1 This is an electron microscope image of the high entropy sodium ion battery positive electrode material prepared in Example 5; Figure 2 This is an electron microscope image of the high entropy sodium ion battery positive electrode material prepared in Example 5 after 500 cycles; Figure 3 The XRD powder diffraction pattern of the high entropy sodium ion battery positive electrode material prepared in Example 5; Figure 4 0.2C cycle performance curve of the high entropy sodium ion battery positive electrode material prepared in Example 5; Figure 5 8C cycle performance curve of the high entropy sodium ion battery positive electrode material prepared in Example 5; Figure 6 A diagram of a cylindrical battery and a soft-pack battery assembled using the high-entropy sodium-ion battery positive electrode material prepared in Example 5.

[0075] Embodiment 6:

[0076] The only difference between this embodiment and embodiment 4 is that the temperature program used in step S2 high temperature smelting is changed to: heating the mixture powder to 900°C at a heating rate of 5°C / min, calcining for 14 hours and then cooling to room temperature. The other steps and specific parameter conditions are the same as those in embodiment 4.

[0077] Embodiment 7:

[0078] A positive electrode material for a high entropy sodium ion battery, the structure of which is a high entropy O3 type layered oxide, specifically NaNi 0.1 3Fe 0.12 Mn0.55 Cu 0.1 Al 0.03 Ti 0.03 Mg 0.02 Zn 0.02 O2;

[0079] The above-mentioned method for preparing a high entropy sodium ion battery positive electrode material comprises the following steps:

[0080] S1. Raw material preparation: according to the molar ratio of each element in the high entropy O3-type layered oxide, sodium carbonate, nickel oxide, iron oxide, manganese oxide, copper oxide, aluminum oxide, titanium oxide, magnesium oxide and zinc oxide were weighed and mixed thoroughly, and mixed at 300 r / min for 4 h to obtain a mixture powder;

[0081] S2, calcination treatment: the mixed powder is further calcined in an air atmosphere at a heating rate of 5°C / min to 800°C, calcined for 10 hours and then cooled to room temperature to obtain a high entropy O3 phase layered oxide;

[0082] S3. Product crushing: The high entropy O3 phase layered oxide obtained by high temperature calcination is crushed into powder by a planetary ball mill. The grinding time of the planetary ball mill is 6 hours.

[0083] Embodiment 8:

[0084] The only difference between this embodiment and embodiment 7 is that the temperature program used for high temperature smelting in step S2 is changed to: heating the mixture powder to 850°C at a heating rate of 5°C / min, calcining for 12 hours and then cooling to room temperature. The other steps and specific parameter conditions are the same as those in embodiment 7.

[0085] Embodiment 9:

[0086] The only difference between this embodiment and embodiment 7 is that the temperature program used in step S2 high temperature smelting is changed to: heating the mixture powder to 900°C at a heating rate of 5°C / min, calcining for 14 hours and then cooling to room temperature. The other steps and specific parameter conditions are the same as those in embodiment 7.

[0087] Comparative Example 1:

[0088] A positive electrode powder for a ternary sodium ion battery, the structure of which is an O3-type layered oxide, specifically NaNi 1 / 3 Fe 1 / 3Mn 1 / 3 O2.

[0089] (1) Raw material preparation: Sodium carbonate, nickel oxide, iron oxide, and manganese oxide were weighed according to the molar ratio of each element in the O3-type layered oxide and mixed thoroughly. The mixture was mixed at 300 r / min for 4 h to obtain a mixture powder.

[0090] (2) Calcination treatment: The mixture powder is further calcined. Under an air atmosphere, it is heated to 850 °C at a heating rate of 5 °C / min, calcined for 12 h, and then cooled to room temperature to obtain a high-entropy O3-phase layered oxide.

[0091] (3) Product pulverization: The high-entropy O3-phase layered oxide obtained by high-temperature calcination is pulverized into powder under the action of a planetary ball mill, and the grinding time using the planetary ball mill is 6 hours.

[0092] Comparative Example 2:

[0093] A cathode powder for a ternary sodium-ion battery, its structure is an O3-type layered oxide, specifically NaNi 1 / 4 Fe 1 / 4Mn 1 / 2 O2.

[0094] (1) Raw material preparation: According to the molar ratio of each element in the O3-type layered oxide, sodium carbonate, nickel oxide, iron oxide, and manganese oxide are measured and fully mixed, and mixed at 300 r / min for 4 h to obtain a mixture powder.

[0095] (2) Calcination treatment: The mixture powder is further calcined. Under an air atmosphere, it is heated to 850 °C at a heating rate of 5 °C / min, calcined for 12 h, and then cooled to room temperature to obtain a high-entropy O3-phase layered oxide.

[0096] (3) Product pulverization: The O3-phase layered oxide obtained by high-temperature calcination is pulverized into powder under the action of a planetary ball mill, and the grinding time using the planetary ball mill is 6 hours.

[0097] Button cell assembly:

[0098] The cathode materials prepared in the above examples and comparative examples are mixed according to the mass ratio of cathode material: conductive carbon black: binder PVDF of 90:5:5, and a cathode slurry is prepared using NMP as a solvent. Then the cathode slurry is coated on aluminum foil, vacuum dried at 100 °C, and roll-pressed to obtain a cathode electrode sheet; then the cathode electrode sheet, counter electrode sheet (sodium metal), electrolyte (1 mol / L NaClO4 dissolved in a mixed solvent of EC:DEC with a volume ratio of 1:1), and glass fiber separator are assembled into a button cell (button cell).

[0099] Performance testing:

[0100] (1) Initial Coulombic efficiency: First, place the coin cell in an environment of 25 ± 2 °C and let it stand for 8 h. Charge it at a constant current of 0.05C to 4.0V, and the obtained capacity is recorded as the 0.1C charge capacity. Then let it stand for 5 min, and then discharge it at a constant current of 0.1C to a voltage of 2.0V. The obtained capacity is recorded as the 0.1C discharge capacity. Finally, stop the operation. The initial Coulombic efficiency (first efficiency) = 0.1C discharge capacity / 0.1C charge capacity;

[0101] (2) Discharge capacity corresponding to a current density of 0.2C: First, place the coin cell in an environment of 25 ± 2 °C and let it stand for 8 h. Charge it at a constant current of 0.2C to 4.0V, then immediately let it stand for 5 min, and then discharge it at a constant current of 0.2C to a voltage of 2.0V. Then let it stand for 5 min, then charge it at a constant current of 0.2C to 4.0V, let it stand for 5 min, and then discharge it at a constant current of 0.2C to a voltage of 2.0V. The obtained capacity is the discharge capacity corresponding to 0.2C. Finally, stop the operation and record the second discharge capacity as the discharge capacity corresponding to 0.2C;

[0102] (3) Capacity retention rate after 500 cycles at 1C: First, place the coin cell in an environment of 25 ± 2 °C and let it stand for 8 h. Charge it at a constant current of 0.2C to 4.0V, then immediately let it stand for 5 min, and then charge it at a constant voltage of 4.0V until the current is 0.05C. Let it stand for 5 min, and then discharge it at a constant current of 1C to a voltage of 2.0V. Repeat the above cycle 500 times. Finally, stop the operation and record the discharge capacities of the first and 500th times. The capacity retention rate = discharge capacity of the 500th time / discharge capacity of the first time.

[0103] (4) Rate performance: Record the constant current and constant voltage charging at 0.1C to 4.0V; discharge at 0.1C to 2.0V, and the obtained capacity is C1; record the constant current and constant voltage charging at 0.1C to 4.0V; discharge at 5C to 2.0V, and the obtained capacity is C2; the rate performance of the battery is measured by the calculated value of C2 / C1 × 100%. The larger this value is, the better the rate performance.

[0104] Table 1 Performance test results of Examples 1 - 9 and Comparative Examples 1 - 3

[0105]

[0106] The above test results show that for the cathode material of the high-entropy sodium-ion battery provided by the embodiments of the present invention, the initial efficiency is 95.10%-96.80%, the specific capacity at 0.2C is 149.0 mAh / g-155.5 mAh / g, the capacity retention rate is 88.30%-90.30%, and the rate performance is 86.01%-89.10%. It not only improves the specific capacity of the cathode material of the sodium-ion battery, but also improves the rate performance and cycle stability of the material. Compared with the comparative example, the specific capacity, initial cycle efficiency, and rate performance of the ternary layered oxide sodium-ion material are improved to varying degrees. This shows the excellent performance of the high-entropy sodium-ion battery cathode material provided by the present invention.

[0107] Those skilled in the art can easily understand that the above is only an example for clear illustration and not a limitation on the implementation manner. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a high entropy sodium ion battery positive electrode material, characterized in that: The steps include: S1. Weighing the raw material sodium source and the metal oxide powder according to the molar ratio to obtain a mixed precursor powder; The sodium source is one of Na2CO3 and NaHCO3; the metal oxide powder is NiO, Fe2O3, Mn2O3, CuO, Al2O3, TiO2, MgO, and ZnO; The molar ratio is Na x Ni a Fe b Mn c Cu d Al e Ti f Mg g Zn h O2, where 0.9≤x≤1.05, a+b+c+d+e+f+g+h=1, 0≤a, b, c, d, e, f, g, h≤1; S2, fully mixing the mixed precursor powders, and placing the obtained mixed powders in a crucible; S3. The crucible containing the mixed powder is calcined in an oxidizing gas atmosphere at a temperature of 750°C to 1000°C for 1 hour to 24 hours to obtain a high entropy sodium ion battery positive electrode material. The high entropy sodium ion positive electrode material is a layered oxide positive electrode material. The high entropy sodium ion positive electrode material has an O3 type (Octahedral) stacking configuration at a microscopic level and an average particle size of 5 μm to 10 μm. The chemical formula of the O3 type high entropy layered oxide positive electrode material is Na x Ni a Fe b Mn c Cu d Al e Ti f Mg g Zn h O2, wherein 0.9≤x≤1.05, a+b+c+d+e+f+g+h=1; the high entropy sodium ion battery positive electrode material has an initial efficiency of 95.10%-96.80%, a 0.2C gram capacity of 149.0mAh / g-155.5mAh / g, a capacity retention rate of 88.30%-90.30%, a rate performance of 86.01%-89.10%, and no cracks between crystals after 100 cycles.

2. The method for preparing a high entropy sodium ion battery positive electrode material according to claim 1, characterized in that: In S2, the mixing method is ball milling, the rotation speed is 300 rpm to 500 rpm, and the time is 1 hour to 24 hours; in S2, the crucible is one of a quartz crucible and a corundum crucible.

3. The method for preparing a high entropy sodium ion battery positive electrode material according to claim 1, characterized in that: In S3, the gas in the oxidizing gas atmosphere is at least one of air and oxygen.

4. A high entropy sodium ion battery positive electrode material, characterized in that: According to any one of claims 1 to 3, the high entropy sodium ion battery positive electrode material is obtained by calcining a mixture of a raw sodium source and a metal oxide material in an oxidizing gas atmosphere, and has an O3 type stacking structure in microscopic terms; the average particle size of the sodium ion battery positive electrode material is 5 μm to 10 μm, and the chemical formula of the high entropy sodium ion positive electrode material is Na x Ni a Fe b Mn c Cu d Al e Ti f Mg g Zn h O2, wherein 0.9≤x≤1.05, a+b+c+d+e+f+g+h=1; the high entropy sodium ion battery positive electrode material has an initial efficiency of 95.10%-96.80%, a 0.2C gram capacity of 149.0mAh / g-155.5mAh / g, a capacity retention rate of 88.30%-90.30%, a rate performance of 86.01%-89.10%, and no cracks between crystals after 100 cycles.

5. A positive electrode sheet, characterized in that: Including a high entropy sodium ion battery positive electrode material as described in claim 4.

6. A sodium ion battery, characterized in that: Including a positive electrode plate as described in claim 5.

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