Multicomponent composite cathode material and preparation method thereof, battery

Abstract

The application relates to the technical field of sodium ion batteries, in particular to a multi-element composite positive electrode material and a preparation method and a battery thereof. The application aims at solving the problems of poor storage stability and cycle performance of the positive electrode material of the sodium ion battery in the related art. A multi-element composite positive electrode material, the chemical formula of the multi-element composite positive electrode material is Na x Ni y Fe z Mn u Bi v Cs w O2; wherein, 0.6 <= x <= 1.0, 0

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sodium ion batteries, in particular to a multi-element composite cathode material and a preparation method thereof and a battery. BACKGROUND

[0002] At present, lithium ion batteries have been widely used in small 3C fields, and are gradually developing towards large-scale energy storage fields such as electric vehicles, artificial intelligence and aerospace. However, the reserves of lithium resources in the earth's crust are relatively scarce, and the regional distribution is extremely uneven. The rapidly growing market of lithium ion batteries will inevitably exacerbate the consumption of lithium resources, thus prompting a substantial rise in the price of lithium, which makes it difficult to meet the low-cost requirements of large-scale applications. Sodium resources are very abundant and widely distributed, and the physical and chemical properties of sodium and lithium are similar. It is completely feasible to use sodium ions to replace lithium ions for energy storage in technology. In addition to the gradual development of some high-performance electrode materials, sodium ion batteries are expected to gradually replace lithium ion batteries to achieve low-cost large-scale energy storage.

[0003] The cathode material, as an important component of sodium ion batteries, is the key to affecting the reversible capacity and working voltage of the battery. Therefore, the development of cathode materials with excellent performance is crucial for the industrial application of sodium ion batteries. Among various cathode materials, layered oxides have the advantages of high energy density, simple preparation process, low price and good industrial compatibility, which provides an effective solution for the industrialization of sodium ion batteries and is widely concerned and highly valued.

[0004] However, the layered structure of transition metal oxides has the disadvantages of poor storage stability in air and easy occurrence of serious interface side reactions in electrolyte, which makes the capacity decay seriously during long cycle and large current charge and discharge, i.e. the cycle performance and rate performance are difficult to meet the requirements of commercial applications.

[0005] Therefore, it is of great significance to develop sodium ion battery cathode materials with good storage stability and cycle performance for the development of sodium ion batteries. SUMMARY

[0006] Therefore, the present application provides a multi-element composite cathode material and a preparation method thereof and a battery to solve the problem of poor storage stability and cycle performance of sodium ion battery cathode materials in the related art.

[0007] In a first aspect, the present application provides a multi-element composite cathode material, and the chemical formula of the cathode material is Na x Ni y Fe z Mn u Bi v Cs wO2; wherein, 0.6≤x≤1.0, 0<y≤0.8, 0<z≤0.8, 0<u≤0.8, 0≤v≤0.2, 0≤w≤0.2, and v and w are not 0 at the same time.

[0008] In a possible implementation of the first aspect, 0.1≤y≤0.8, 0.1≤z≤0.8, 0.1≤u≤0.8, 0.1≤v≤0.2, 0.1≤w≤0.2.

[0009] In a possible implementation of the first aspect, the chemical formula of the multi-element composite cathode material is Na 0.2 Fe 0.2 Mn 0.2 Cs 0.1 Bi 0.2 O2.

[0010] In a second aspect, a preparation method of a multi-element composite cathode material is provided, comprising:

[0011] According to the chemical formula Na x Ni y Fe z Mn u Bi v Cs w O2, preparation raw materials of corresponding elements are prepared, each preparation raw material is added into a first solvent according to a preset ratio, a mixed solution is prepared, the chemical formula Na x Ni y Fe z Mn u Bi v Cs w O2, wherein, 0.6≤x≤1.0, 0<y≤0.8, 0<z≤0.8, 0<u≤0.8, 0≤v≤0.2, 0≤w≤0.2, and v and w are not 0 at the same time.

[0012] A chelating agent is added into the mixed solution to prepare a sol;

[0013] The sol is subjected to drying treatment to prepare a dry gel;

[0014] The dry gel is ground, sieved, and tabletted, and then subjected to calcination treatment.

[0015] In a possible implementation of the second aspect, the chemical formula Na x Ni y Fe z Mn u Bi v Cs w O2, preparation raw materials of each metal element are as follows:

[0016] The preparation raw material containing Na element includes at least one of sodium nitrate, sodium nitrite, sodium acetate, sodium citrate and sodium alginate;

[0017] The preparation raw material containing Ni element includes at least one of nickel nitrate hydrate, nickel acetate hydrate and nickel oxide;

[0018] The preparation raw material containing Fe element includes at least one of ferric nitrate hydrate, iron oxide and ferric acetate hydrate;

[0019] The preparation raw material containing Mn element is at least one of manganese nitrate hydrate, manganese acetate hydrate and manganese oxide;

[0020] The preparation raw material containing Bi element includes at least one of bismuth nitrate hydrate and bismuth oxide;

[0021] The preparation raw material containing Cs element includes at least one of cesium nitrate hydrate, cesium oxide, cesium carbonate and cesium bicarbonate.

[0022] In a possible implementation of the second aspect, the first solvent is a dilute nitric acid solution;

[0023] The concentration of nitric acid in the dilute nitric acid solution is 0.5-2M.

[0024] In a possible implementation of the second aspect, the solid-liquid ratio in the mixed solution is 1:(20-100).

[0025] In a possible implementation of the second aspect, the stirring rate during preparation of the mixed solution is 30-300r / min, and the stirring time is 0.5-3h.

[0026] In a possible implementation of the second aspect, the chelating agent is at least one of citric acid and oxalic acid.

[0027] In a possible implementation of the second aspect, the molar ratio of the chelating agent to the total amount of metal ions in the mixed solution is 1:1-1.2:1.

[0028] In a possible implementation of the second aspect, the heating temperature during preparation of the sol is 70-85℃, the stirring rate is 30-300r / min, and the stirring time is 7-12h.

[0029] In a possible implementation of the second aspect, the drying temperature is 80-120℃, and the time is 12-24h.

[0030] In a possible implementation of the second aspect, the calcination temperature is 800-1000℃, the time is 10-20h, and the heating rate during calcination is 2-10℃ / min.

[0031] Thirdly, a sodium-ion battery is provided, comprising:

[0032] Positive electrode sheet, including multi-component composite positive electrode materials as described in the first aspect.

[0033] Fourthly, an electrical device is provided, comprising: a sodium-ion battery as described in the third aspect.

[0034] In the multi-component composite cathode material provided in this application, Bi and Cs ions have larger ionic radii than transition metal ions, thus better stabilizing the crystal structure of the cathode material and reducing phase transitions. Furthermore, the unstable interaction between the 5d orbitals of Bi ions and oxygen reduces orbital overlap, allowing electrons to exist stably and locally within the transition metal layer. This enables other transition metal ions to form stronger ionic bonds with oxygen, not only enhancing bond energy but also significantly increasing the redox potential of the cathode material, thereby improving capacity.

[0035] Experiments have shown that, compared with traditional sodium-ion battery cathode materials in related technologies, the sodium-ion battery cathode material provided in this application has higher capacity and better cycle stability. For example, at a current density of 1C, the sodium-ion battery prepared from this multi-element composite cathode material can achieve an initial discharge capacity of 152.3 mAh / g, and the capacity retention rate of this sodium-ion battery is as high as 89.4% after 200 cycles. Attached Figure Description

[0036] Figure 1 Scanning electron microscope image of the multi-component composite cathode material provided in Example 1;

[0037] Figure 2 The XRD pattern of the multi-component composite cathode material provided in Example 1;

[0038] Figure 3 The image shows the cycle performance of the battery prepared using the multi-component composite cathode material provided in Example 1.

[0039] Figure 4 The image shows the cycle performance of the battery prepared using the multi-component composite cathode material provided in Example 2.

[0040] Figure 5 The image shows the cycle performance of the battery prepared using the multi-component composite cathode material provided in Example 3.

[0041] Figure 6 Scanning electron microscope image of the multi-component composite cathode material provided in Example 4;

[0042] Figure 7 The XRD pattern of the multi-component composite cathode material provided in Example 4;

[0043] Figure 8A cycle performance graph of a battery prepared using the multi-element composite cathode material provided in Example 4. DETAILED DESCRIPTION

[0044] For the purposes of this application, reference will be made to the accompanying drawings in which the preferred embodiments of the application are illustrated. The application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the application to those skilled in the art.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0046] The application is further described in connection with the following embodiments. The application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the application to those skilled in the art.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0048] In the present application, "one or more" means any one, any two or more than two of the listed items. In this case, "more than two" means any two or more than two.

[0049] In the present application, "combination thereof", "any combination thereof", "any combination manner thereof" and the like include all suitable combination manners of any two or more of the listed items.

[0050] In the present application, "preferably" is only used to describe the embodiments or examples with better effects, and it should be understood that it does not constitute a limitation on the protection scope of the present application.

[0051] In the present application, the technical features described in an open manner include both the closed technical solution consisting of the listed features and the open technical solution containing the listed features.

[0052] In the present application, if no special instructions are given, the numerical interval includes both ends of the numerical interval.

[0053] In the present application, percentage content is involved. Unless otherwise specified, mass percentage is referred to for solid-liquid mixing and solid-solid mixing, and volume percentage is referred to for liquid-liquid mixing.

[0054] In the present application, percentage concentration is involved. Unless otherwise specified, final concentration is referred to. The final concentration refers to the proportion of the added component in the system after the component is added.

[0055] In the present application, temperature parameters are involved. Unless otherwise specified, both constant temperature treatment and treatment within a certain temperature range are allowed. The constant temperature treatment allows fluctuations within the accuracy range controlled by the instrument.

[0056] Some embodiments of the present application provide a multi-element composite cathode material, which has a chemical formula of Na x Ni y Fe z Mn u Bi v Cs w O2; wherein, 0.6≤x≤1.0, 0<y≤0.8, 0<z≤0.8, 0<u≤0.8, 0≤v≤0.2, 0≤w≤0.2, and v and w are not 0 at the same time.

[0057] The multi-element composite cathode material refers to a cathode material composed of multiple chemical components (or elements). The multi-element composite cathode material is a sodium ion battery cathode material.

[0058] In the related art, sodium ion battery cathode materials generally include sodium elements, transition metal elements, and oxygen elements. These sodium ion battery cathode materials are layered transition metal oxides, which are composed of MO6 octahedral sheets that share edges. Sodium ions are located between the octahedral sheets to form a layered structure. Typical layered transition metal oxides can be divided into two types: O3 type and P2 type. The classification depends on the number of oxygen layer stacking types and the environment around the sodium ions. “O” or “P” represents the octahedral or triangular prismatic coordination environment of the sodium ions, and the number represents the number of different oxygen layer repeating stacking units.

[0059] Due to the sliding of the sheets, both O3 and P2 phases will undergo a series of phase transitions during electrochemical cycling. The O3 phase usually undergoes the following phase transitions: O3 to P3 to O3 to P3. Unlike the O3 phase, the P2 phase is converted to the O2 phase by MO2 sheet sliding to form octahedral sites after sodium ions are removed. The structure of the P2 phase is more stable than that of the O3 phase because the phase transition of the P2 phase is accompanied by π / 3 rotation of the MO6 octahedron and breaking of the M-O bond. Although the O3 phase usually exhibits higher capacity due to the increase in sodium content, the P2 phase often exhibits better cycle stability and rate performance due to its good structural stability and low diffusion barrier.

[0060] In the multi-element composite cathode material provided in the embodiments of the present application, because the Bi ion and the Cs ion have a larger ionic radius than the transition metal ion, the crystal structure of the cathode material can be better stabilized, and phase transition can be reduced. The unstable interaction between the 5d orbital of the Bi ion and oxygen reduces orbital overlap, so that the electrons exist stably in the transition metal layer, and the other transition metal ions form stronger ionic bonds with oxygen, which not only enhances the bond energy, but also significantly improves the redox potential of the cathode material, so that the capacity can be improved.

[0061] It is found through experiments that, compared with the traditional sodium ion battery cathode material in the related art, the sodium ion battery cathode material provided in the present application has high capacity and good cycle stability. For example, the sodium ion battery prepared from the cathode material has a first discharge capacity of 152.3 mAh / g at a current density of 1C, and the capacity retention rate of the sodium ion battery is as high as 89.4% after 200 cycles.

[0062] In addition, it is found through experiments that, by adjusting the amount of the preparation raw material containing sodium elements, a pure O3 and P2 phase cathode material can also be prepared, which can reduce the influence of impurities on the electrochemical performance of the battery.

[0063] For example, in some embodiments, the chemical formula of the multi-element composite cathode material is NaNi 0.2 Fe 0.2 Mn 0.2 Cs 0.1 Bi 0.2 O2.

[0064] The multi-element composite cathode material is a sodium-rich phase, that is, a relatively pure O3 phase.

[0065] In other embodiments, the chemical formula of the multi-element composite cathode material is Na 0.6 Ni 0.2 Fe 0.2 Mn 0.2 Cs 0.1 Bi 0.2 O2.

[0066] The multi-element composite cathode material is a sodium-deficient phase, that is, a relatively pure P2 phase.

[0067] In addition, the multi-element composite positive electrode material provided by the application can effectively inhibit the problems of structural distortion and irreversible phase change under high voltage, thereby improving the structural stability of the material in the charging and discharging process. In addition, due to the existence of the heterovalent element in the multi-element composite positive electrode material, the ordered arrangement of ions in the transition metal layer of the layered material can be destroyed, thereby inhibiting the ordered transformation of Na vacancies in the battery during the charging and discharging process, reducing the diffusion energy barrier of sodium ions, and further improving the diffusion rate of sodium ions and the performance of the battery.

[0068] In the formula, the heterovalent element refers to a doping element whose valence state is different from that of the transition metal element. For example, in the application, the valence state of nickel is +2 to +3, the valence state of iron is +2 to +3, the valence state of manganese is +3 to +4, the average valence state of nickel, iron and manganese is +3, the valence state of the doping element cesium is +1, and the valence state of bismuth is +3. Therefore, the doping element can be regarded as a heterovalent element.

[0069] In some embodiments, 0.1≤y≤0.8, 0.1≤z≤0.8, 0.1≤u≤0.8, 0.1≤v≤0.2, and 0.1≤w≤0.2.

[0070] Embodiments of the application also provide a preparation method of the multi-element composite positive electrode material, which comprises:

[0071] According to the chemical formula Na x Ni y Fe z Mn u Bi v Cs w O2, preparation raw materials containing corresponding elements are prepared, and each preparation raw material is added to a first solvent in a predetermined proportion to prepare a mixed solution, the chemical formula Na x Ni y Fe z Mn u Bi v Cs w O2, 0.6≤x≤1.0, 0<y≤0.8, 0<z≤0.8, 0<u≤0.8, 0≤v≤0.2, 0≤w≤0.2, and v and w are not zero at the same time;

[0072] A chelating agent is added to the mixed solution to prepare a sol;

[0073] The sol is subjected to drying treatment to prepare a dry gel;

[0074] The dry gel is ground, sieved, and tabletted, and then subjected to calcination treatment.

[0075] In the formula, the heterovalent element refers to a doping element whose valence state is different from that of the transition metal element. For example, in the application, the valence state of nickel is +2 to +3, the valence state of iron is +2 to +3, the valence state of manganese is +3 to +4, the average valence state of nickel, iron and manganese is +3, the valence state of the doping element cesium is +1, and the valence state of bismuth is +3. Therefore, the doping element can be regarded as a heterovalent element. x Ni y Fe z Mnu Bi v Cs w The raw materials for preparing each metal element in O2may be any salt or oxide containing Na element, Ni element, Fe element, Mn element, Bi element, Cs element and O element, which can obtain the above-mentioned multi-element composite positive electrode material by heating.

[0076] In some embodiments, the chemical formula of Na x Ni y Fe z Mn u Bi v Cs w The raw materials for preparing each metal element in O2are as follows:

[0077] The raw materials containing Na element include at least one of sodium nitrate, sodium nitrite, sodium acetate, sodium citrate and sodium alginate; the raw materials containing Ni element include at least one of nickel nitrate hydrate, nickel acetate hydrate and nickel oxide; the raw materials containing Fe element include at least one of iron nitrate hydrate, iron oxide and iron acetate hydrate; the raw materials containing Mn element include at least one of manganese nitrate hydrate, manganese acetate hydrate and manganese oxide; the raw materials containing Bi element include at least one of bismuth nitrate hydrate and bismuth oxide; and the raw materials containing Cs element include at least one of cesium nitrate hydrate, cesium oxide, cesium carbonate and cesium bicarbonate.

[0078] In some embodiments, the first solvent is a dilute nitric acid solution, and the concentration of nitric acid in the dilute nitric acid solution is 0.5-2M. This can facilitate the dissolution of the oxides into nitrate, and is conducive to the uniform dispersion of the elements in the liquid phase.

[0079] In some embodiments, the solid-liquid ratio in the above-mentioned mixed solution is 1:(20-100).

[0080] In some embodiments, the stirring rate when preparing the mixed solution is 30-300r / min, and the stirring time is 0.5-3h.

[0081] In some embodiments, the above-mentioned chelating agent is at least one of citric acid and oxalic acid.

[0082] In other embodiments, the molar ratio of the chelating agent to the total amount of metal ions in the mixed solution is 1:1-1.2:1.

[0083] In some embodiments, the heating temperature when preparing the sol is 70-85℃, the stirring rate is 30-300r / min, and the stirring time is 7-12h.

[0084] In some embodiments, the drying temperature is 80-120℃, and the time is 12-24h.

[0085] In some embodiments, the temperature for calcination is 800-1000℃, and the time is 10-20h.

[0086] In some embodiments, the heating rate during calcination is 2-10℃ / min.

[0087] In some embodiments, the mesh size for sieving can be 50-80 mesh, and the size of the tablet is a cylinder with R*D. Wherein, R represents the diameter of the tablet, and is 2-8cm, and D represents the thickness of the tablet, and the size is 1-2cm.

[0088] Embodiments of the present application also provide a sodium ion battery, comprising:

[0089] The positive electrode sheet, the negative electrode sheet, the electrolyte and the separator, wherein the positive electrode sheet comprises the multi-element composite positive electrode material as described above. The negative electrode sheet can be a metal sodium sheet.

[0090] The technical effects of the sodium ion battery provided by the embodiments of the present application are basically the same as those of the multi-element composite positive electrode material provided by the embodiments of the present application, and will not be described here.

[0091] Wherein, the positive electrode material is used as an active material in a sodium ion battery, a binder and a conductive agent are prepared into a slurry, and the slurry is coated on an aluminum foil to prepare a positive electrode sheet.

[0092] The mass ratio of the active material, the binder and the conductive agent can be 5:5:5.

[0093] The binder example can be PVDF (polyvinylidene fluoride), and the conductive agent can be SP and KS-6.

[0094] The solvent for preparing the slurry is NMP, and the mass ratio of the total mass of the active material, the binder and the conductive agent to the mass of the solvent can be 15:85.

[0095] Embodiments of the present application also provide an electric device, which comprises the above-mentioned sodium ion battery.

[0096] Wherein, the electric device can be an electric vehicle, a handheld mobile terminal or a tablet computer, etc.

[0097] The specific embodiments of the present application are introduced above, in order to objectively describe the technical effects of the present application, next, the following examples and comparative examples will be described.

[0098] In the following examples and comparative examples, all raw materials can be obtained by commercial form, and in order to keep the reliability of the experiment, the raw materials used in the following examples and comparative examples all have the same physical and chemical parameters or are treated in the same way.

[0099] Example 1

[0100] Positive electrode material NaMn 0.4 Ni 0.3 Fe 0.2 Bi 0.1 Method for preparing O2:

[0101] Step S1: 21.0 g of sodium nitrate, 24.1 g of manganese nitrate hydrate, 19.4 g of iron nitrate hydrate, 20.9 g of nickel nitrate hydrate, and 11.6 g of bismuth nitrate hydrate were accurately weighed using an analytical balance and added to a stirring device. Then, 3000 ml of 0.5M dilute nitric acid was added to the stirring device, the stirring time was set to 1 h, and the stirring rate was set to 100 r / min to completely dissolve them.

[0102] Step S2: 55.3 g of citric acid was accurately weighed using an analytical balance and dissolved in 200 ml of industrial pure water. The dissolved citric acid aqueous solution was added to the above stirring device, the stirring temperature was set to 70℃, the stirring time was set to 10 h, and the stirring rate was set to 100 r / min to form a sol.

[0103] Step S3: The above sol was transferred to multiple glassware, and then the glassware was transferred to a vacuum drying oven. The drying temperature was set to 100℃, the drying time was set to 12 h, and finally a xerogel was obtained.

[0104] Step S4: After the above xerogel was simply ground, it was transferred to a 50 mesh vibrating screen. The obtained xerogel powder was pressed into a 5 cm*2 cm cylinder. The above cylinder was placed in a corundum box, and the corundum box was transferred to a kiln. The temperature was set to 900℃, the calcination time was set to 15 h, the calcination atmosphere was air, the heating rate was 4℃ / min, and after natural cooling, the sodium ion battery layered positive electrode material NaMn 0.4 Ni 0.3 Fe 0.2 Bi 0.1 O2.

[0105] Example 2

[0106] NaNi 0.4 Fe 0.2 Mn 0.3 Cs 0.1 Method for preparing O2:

[0107] Step S1 : accurately weigh 21.9 g of sodium nitrate, 18.8 g of manganese nitrate hydrate, 20.2 g of iron nitrate hydrate, 29.1 g of nickel nitrate hydrate, and 4.8 g of cesium bicarbonate using an analytical balance, and add them to a stirring device, then add 3800 ml of 0.5M dilute nitric acid to the stirring device, set the stirring time to 1 h, and the stirring rate to 150 r / min, and allow it to completely dissolve.

[0108] Step S2: accurately weigh 57.6 g of citric acid using an analytical balance, dissolve it in 200 ml of industrial pure water, and add the dissolved citric acid aqueous solution to the above stirring device, set the stirring temperature to 70°C, the stirring time to 10 h, and the stirring rate to 100 r / min, and allow it to form a sol.

[0109] Step S3: transfer the above sol to multiple glassware, then transfer the glassware to a vacuum drying oven, set the drying temperature to 100°C, and the drying time to 12 h, and finally obtain a xerogel.

[0110] Step S4: after the above xerogel is simply ground, it is transferred to a 50 mesh vibrating screen, the obtained xerogel powder is pressed into a 5 cm*2 cm cylinder, the above cylinder is placed in a corundum crucible, the corundum crucible is transferred to a kiln, the temperature is set to 900°C, the calcination time is 15 h, the calcination atmosphere is air, the heating rate is 4°C / min, after natural cooling, it is taken out to obtain a sodium-ion battery layered positive electrode material NaNi 0.4 Fe 0.2 Mn 0.3 Cs 0.1 O2.

[0111] Example 3

[0112] NaNi 0.2 Fe 0.2 Mn 0.2 Cs 0.1 Bi 0.2 O2.

[0113] Step S1 : accurately weigh 21.9 g of sodium nitrate, 18.8 g of manganese nitrate hydrate, 20.2 g of iron nitrate hydrate, 29.1 g of nickel nitrate hydrate, and 4.8 g of cesium bicarbonate using an analytical balance, and add them to a stirring device, then add 3800 ml of 0.5M dilute nitric acid to the stirring device, set the stirring time to 1 h, and the stirring rate to 150 r / min, and allow it to completely dissolve.

[0114] Step S2: 73.8 g of citric acid was accurately weighed using an analytical balance and dissolved in 300 ml of industrial pure water. The dissolved citric acid aqueous solution was added to the above stirring device, the stirring temperature was set to 70°C, the stirring time was set to 10 h, and the stirring rate was set to 100 r / min, so as to form a sol.

[0115] Step S3: The above sol was transferred to multiple glassware, and then the glassware was transferred to a vacuum drying oven, the drying temperature was set to 100°C, the drying time was set to 12 h, and finally a xerogel was obtained.

[0116] Step S4: After the above xerogel was simply ground, it was transferred to a 50 mesh vibrating screen. The obtained xerogel powder was pressed into a 5 cm*2 cm cylinder. The above cylinder was placed in a corundum crucible, and the corundum crucible was transferred to a kiln. The temperature was set to 900°C, the calcination time was set to 15 h, the calcination atmosphere was air, the heating rate was 4°C / min, and after natural cooling, the sodium ion battery layered positive material NaNi 0.2 Fe 0.2 Mn 0.2 Cs 0.1 Bi 0.2 O2.

[0117] Example 4

[0118] Na 0.6 Ni 0.2 Fe 0.2 Mn 0.2 Cs 0.1 Bi 0.2 O2.

[0119] Step S1: 16.8 g of sodium nitrate, 16.1 g of manganese nitrate hydrate, 25.9 g of iron nitrate hydrate, 12.2 g of nickel nitrate hydrate, 12.4 g of cesium bicarbonate, and 29.8 g of bismuth oxide were accurately weighed using an analytical balance and added to a stirring device. Then 5000 ml of 0.5M dilute nitric acid was added to the stirring device, the stirring time was set to 1 h, and the stirring rate was set to 150 r / min, so as to completely dissolve it.

[0120] Step S2: 65.8 g of citric acid was accurately weighed using an analytical balance and dissolved in 300 ml of industrial pure water. The dissolved citric acid aqueous solution was added to the above stirring device, the stirring temperature was set to 70°C, the stirring time was set to 10 h, and the stirring rate was set to 100 r / min, so as to form a sol.

[0121] Step S3: The sol prepared above was transferred into multiple glass containers, and then the glass containers were transferred into a vacuum drying oven, and the drying temperature was set to 100℃, and the drying time was 12h, and finally a dry gel was obtained.

[0122] Step S4: After the dry gel prepared above was simply ground, it was transferred into a 50-mesh vibrating sieve, and the dry gel powder obtained was pressed into a 5cm*2cm cylinder, and the cylinder was placed in a corundum crucible, and the corundum crucible was transferred into a kiln, and the temperature was set to 900℃, and the calcination time was 15h, and the calcination atmosphere was air, and the heating rate was 4℃ / min, and after natural cooling, it was taken out to obtain a sodium-ion battery layered positive electrode material Na 0.6 Ni 0.2 Fe 0.2 Mn 0.2 Cs 0.1 Bi 0.2 O2. Performance test

[0123] In the above examples and comparative examples, the performance of the 2032 type button cell was tested by using a battery test system.

[0124] The preparation process of the 2032 type button cell is as follows:

[0125] The multi-element composite positive electrode material prepared above was used as a positive electrode active material, PVDF with a model number of 5130 was used as a binder, SP and KS-6 were used as conductive agents, and NMP was used as a solvent, and the mass ratio of the solvent, the active material, the binder and the conductive agent was 85:5:5:5, and the mixture was stirred to a uniform slurry state. The prepared positive electrode slurry was uniformly coated on an aluminum foil, and then it was transferred into a vacuum drying oven at 120℃ for vacuum drying for 12h. According to the calculation of the compaction density, the thickness of the electrode sheet to be rolled was calculated and rolled, and the rolled electrode sheet was cut into a 14mm diameter electrode sheet with uniform thickness by a sheet cutting machine, and assembled into a button cell in a vacuum glove box. Among them, the button cell used a metal sodium sheet as a counter electrode, used glass fiber as a separator, and used NaClO4-based electrolyte to prepare.

[0126] 1. Morphology test: The layered positive electrode materials obtained in Examples 1 and 4 were microscopically characterized by scanning electron microscopy, and the micro-morphology graphs are shown in Figure 1 , 6 .

[0127] 2. XRD analysis: The layered positive electrode materials obtained in Examples 1 and 4 were analyzed by X-ray diffraction, and the diffraction patterns of the layered positive electrode materials are shown in Figure 2 , 7 .

[0128] 3. Electrochemical performance testing: The charge and discharge voltage range was controlled at 2.0-4.3V (cutoff voltage at 4.3V). At room temperature, the coin cell was charged and discharged 200 times at a current density of 1C to evaluate the capacity retention and cycle performance of the cathode material.

[0129] Test Results

[0130] 1. For example Figure 1 The image shown is a scanning electron microscope image of the multi-component composite cathode material provided in Example 1. Figure 1 It can be seen that the multi-component composite cathode material has relatively uniform particles and a high tap density.

[0131] 2. For example Figure 2 The image shown is the XRD pattern of the multi-component composite cathode material provided in Example 1. Figure 2 It can be seen that this multi-component composite cathode material has a good crystal structure.

[0132] 3. For example Figure 3 The figure shows the cycle performance of the battery prepared from the multi-component composite cathode material provided in Example 1. Figure 3 It can be seen that the battery retains a capacity of up to 89.4% after 200 cycles, demonstrating excellent cycle stability.

[0133] 4. For example Figure 4 The figure shows the cycle performance of the battery prepared from the multi-component composite cathode material provided in Example 2. Figure 4 It can be seen that the battery retains a capacity of up to 92.6% after 200 cycles, demonstrating excellent cycle stability.

[0134] 5. For example Figure 5 The figure shows the cycle performance of the battery prepared from the multi-component composite cathode material provided in Example 3. Figure 5 It can be seen that the battery retains a capacity of up to 99.6% after 200 cycles, demonstrating excellent cycle stability.

[0135] 6. For example Figure 6 The image shown is a scanning electron microscope image of the multi-component composite cathode material provided in Example 4. Figure 6 It can be seen that the multi-component composite cathode material has relatively uniform particles and a high tap density.

[0136] 7. For example Figure 7 The image shown is the XRD pattern of the multi-component composite cathode material provided in Example 4. Figure 7 It can be seen that this multi-component composite cathode material has a good crystal structure.

[0137] 8. For example Figure 8The cycle performance chart of the battery prepared by the multi-element composite cathode material provided in Example 4 is shown in FIG. 4, wherein Figure 8 It can be seen that the capacity retention rate of the battery is as high as 99.0% after 200 cycles, showing excellent cycle stability.

[0138] The technical features of the above-described embodiments can be combined in any manner. In order to make the description simple, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combinations of the technical features do not contradict, they should be considered as falling within the scope of the present disclosure.

[0139] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the patent scope of the present application. It should be pointed out that, for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all fall within the protection scope of the present application. Therefore, the patent protection scope of the present application should be subject to the appended claims.

Claims

1. A multi-element composite cathode material, characterized in that, The chemical formula of the multi-element composite cathode material is Na x Ni y Fe z Mn u Bi v Cs w O2; wherein, 0.6≤x≤1.0, 0.1≤y≤0.8, 0.1≤z≤0.8, 0.1≤u≤0.8, 0.1≤v≤0.2, 0.1≤w≤0.

2.

2. The multi-element composite cathode material of claim 1, wherein, The chemical formula of the multi-element composite cathode material is NaNi 0.2 Fe 0.2 Mn 0.2 Cs 0.1 Bi 0.2 O2.

3. A method for preparing a multi-element composite cathode material, characterized in that, The method comprises the following steps: According to the chemical formula Na x Ni y Fe z Mn u Bi v Cs w O2, prepare the preparation raw materials containing the corresponding elements, add each preparation raw material to the first solvent according to a predetermined ratio, prepare a mixed solution, and the chemical formula Na x Ni y Fe z Mn u Bi v Cs w O2, 0.6≤x≤1.0, 0.1≤y≤0.8, 0.1≤z≤0.8, 0.1≤u≤0.8, 0.1≤v≤0.2, 0.1≤w≤0.

2. adding a chelating agent to the mixed solution to prepare a sol; drying the sol to prepare a xerogel; grinding, sieving and tabletting the xerogel and then calcining the tablet.

4. The method of claim 3, wherein, Chemical formula Na x Ni y Fe z Mn u Bi v Cs w The raw materials for preparing each metal element in O2are as follows: The raw material containing Na element includes at least one of sodium nitrate, sodium nitrite, sodium acetate, sodium citrate and sodium alginate; The raw material containing Ni element includes at least one of nickel nitrate hydrate, nickel acetate hydrate and nickel oxide; The raw material containing Fe element includes at least one of iron nitrate hydrate, iron oxide and iron acetate hydrate; The raw material containing Mn element includes at least one of manganese nitrate hydrate, manganese acetate hydrate and manganese oxide; The raw material containing Bi element includes at least one of bismuth nitrate hydrate and bismuth oxide; The raw material containing Cs element includes at least one of cesium nitrate hydrate, cesium oxide, cesium carbonate and cesium bicarbonate.

5. The method according to claim 3, wherein: the first solvent is a dilute nitric acid solution; the concentration of nitric acid in the dilute nitric acid solution is 0.5-2 M.

6. The method according to claim 3, wherein: the solid-liquid ratio in the mixed solution is 1:(20-100).

7. The method according to claim 3, wherein: the stirring rate during preparation of the mixed solution is 30-300 r / min, and the stirring time is 0.5-3 h.

8. The method according to claim 3, wherein: the chelating agent is at least one of citric acid and oxalic acid.

9. The method according to claim 3, wherein: the molar ratio of the chelating agent to the total amount of metal ions in the mixed solution is 1:1-1.2:

1.

10. The method according to claim 3, wherein: the heating temperature during preparation of the sol is 70-85℃, the stirring rate is 30-300 r / min, and the stirring time is 7-12 h.

11. The method according to claim 3, wherein: the drying temperature is 80-120℃, and the time is 12-24 h.

12. The method according to claim 3, wherein: the calcination temperature is 800-1000℃, the time is 10-20 h, and the heating rate during calcination is 2-10℃ / min.

13. A sodium-ion battery, characterized in that, The method comprises the following steps: a positive electrode tab, wherein the positive electrode tab comprises the multi-element composite positive electrode material according to any one of claims 1-2.

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