Copper-manganese-based layered oxide material and preparation method, positive electrode and sodium-ion battery

Abstract

The application provides a copper-manganese-based layered oxide material and a preparation method, a positive electrode and a sodium ion battery. A molecular general formula of the copper-manganese-based layered oxide material is Na x M y Cu a Mn 0.7 O 2+α , wherein M is one or more of alkali metal and alkaline earth metal elements, the 0.75<=x<=1, 0

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sodium ion batteries, in particular to a copper-manganese-based layered oxide material, a preparation method thereof, a positive electrode and a sodium ion battery. BACKGROUND

[0002] Due to the substantial rise in the price of lithium carbonate, sodium ion batteries have become a hot research topic for various enterprises. At present, a large number of literatures have reported electrode materials for sodium ion batteries, among which positive electrode materials mainly include layered oxides, tunnel-type oxides, polyanion compounds and Prussian blue / white; and a plurality of enterprises have developed materials for the above four types of positive electrode materials.

[0003] Among them, the layered oxide positive electrode material has obtained more attention due to its simple synthesis process and high energy density, and NaTMO2 in P2 phase (Na coordination environment is triangular prism, oxygen layer stacking order is 2, and space group is p63 / mmc or p63 / mcm) and NaTMO2 in O3 phase (Na coordination environment is octahedron, oxygen layer stacking order is 3, and space group is ) are the most studied materials at present. Among them, the sodium content of the O3 phase is high, and the initial charge capacity is high, but its electrochemical cycle performance is poor, and it is sensitive to air and water, which has certain difficulty in application; the P2 phase has a larger space for sodium ions, and has good stability in the electrochemical cycle process, and the sodium ions are faster to be deintercalated, but most of the P2 phase materials are unstable in air, and the initial charge capacity is generally low due to the low sodium content. SUMMARY

[0004] In view of the above problems, the present application provides a copper-manganese-based layered oxide material in P3 phase (Na coordination environment is triangular prism, oxygen layer stacking order is 3, and space group is R3m), a preparation method thereof, a positive electrode and a sodium ion battery, aiming to improve the air stability, initial charge capacity, cycle performance and rate performance of the material.

[0005] The first aspect of the present application provides a copper-manganese-based layered oxide material.

[0006] The second aspect of the present application provides a preparation method of the copper-manganese-based layered oxide material.

[0007] The third aspect of the present application provides a positive electrode for a sodium ion battery.

[0008] The fourth aspect of the present application provides a sodium ion battery.

[0009] To solve the above technical problems, the present application adopts the following technical solutions:

[0010] The copper-manganese-based layered oxide material according to the first aspect of the present application is used for a sodium-ion battery, and is characterized in that the copper-manganese-based layered oxide material has a general formula of Na x M y Cu a Mn 0.7 O 2+α wherein M is one or more of alkali metal and alkaline earth metal elements, 0.75≤x≤1, 0

[0011] Further, M is any one or more selected from sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium.

[0012] Further, y+a=0.3.

[0013] The preparation method of the copper-manganese-based layered oxide material according to the second aspect of the present application comprises the following steps:

[0014] S1, proportionally weighing a sodium source, a copper source, a manganese source, and a M metal source, wherein M in the M metal source is one or more of alkali metal and alkaline earth metal elements;

[0015] S2, sufficiently mixing the sodium source, the copper source, the manganese source, and the M metal source to obtain a precursor powder;

[0016] S3, sintering the precursor powder, wherein the sintering temperature is 550-850℃, and the sintering time is 10-15h, to obtain the copper-manganese-based layered oxide material.

[0017] Further, in the step S1,

[0018] the sodium source is selected from one or more of sodium carbonate, sodium bicarbonate, sodium nitrate, sodium acetate, sodium oxalate, and sodium citrate;

[0019] the copper source, the manganese source, and the M metal source are respectively selected from one or more of oxides, chlorides, nitrates, sulfates, carbonates, acetates, oxalates, and citrates of the respective metals.

[0020] Further, in the step S1, the amount of the sodium source, calculated based on sodium therein, is 100-108wt% of stoichiometry.

[0021] Further, in the step S2, each raw material is processed by any one of a dry mixing method, a spray drying method, a sol-gel method, or a co-precipitation method to obtain the precursor powder.

[0022] Further, in the step S3, the heating rate during sintering is 3-5℃ / min, and the sintering temperature is 700-800℃.

[0023] Further, the preparation method further comprises the following steps:

[0024] S4, grinding and sieving the sintered powder to obtain the copper-manganese-based layered oxide material powder.

[0025] According to the third aspect of the present application, the positive electrode comprises:

[0026] a positive electrode current collector;

[0027] a positive electrode active material layer, which is arranged on the surface of the positive electrode current collector, and contains the copper-manganese-based layered oxide material according to any one of the embodiments of the first aspect.

[0028] Further, the positive electrode active material layer further contains a conductive agent and a binder.

[0029] Further, the conductive agent is selected from any one or more of conductive carbon black, conductive graphite, carbon nanotubes, carbon fibers, and graphene.

[0030] Further, the binder is any one or more of polyvinylidene fluoride, polytetrafluoroethylene, sodium alginate, sodium carboxymethyl cellulose, and butadiene styrene rubber.

[0031] According to the fourth aspect of the present application, the sodium ion battery comprises the positive electrode according to any one of the embodiments of the third aspect.

[0032] The above technical solution of the present application has at least one of the following beneficial effects:

[0033] According to the copper-manganese-based layered oxide material of the present application, the space group is R3m, i.e. P3 phase, the Na coordination environment is a triangular prism, and the oxygen layer stacking sequence is 3. Therefore, compared with the P2 phase (the Na coordination environment is a triangular prism, the oxygen layer stacking sequence is 2, and the space group is p63 / mmc or p63 / mcm), the repulsion between adjacent transition metal layers is weaker, more Na ions can be introduced, the stability during electrochemical cycling is good, and the sodium ion deintercalation is faster. In addition, compared with the O3 phase, the material is stable in air, has excellent rate performance, and is beneficial to improve the charging capacity.

[0034] The sodium ion secondary battery using the copper-manganese-based layered oxide material of the present application has high activity of alkali metal or alkaline earth metal, divalent to trivalent copper conversion, and three-point five valence to four valence manganese transformation, which can realize relatively high initial charging capacity, excellent cycle performance and rate performance. The copper element realizes good air stability and safety, and has great practical value.

[0035] In addition, according to the preparation method of the embodiment of the present application, the preparation process is simple, the raw material is safe and non-toxic, and the manufacturing cost is low. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 XRD patterns of copper-manganese-based layered oxide materials obtained at different sintering temperatures for Examples 1-2 and Comparative Examples;

[0037] Figure 2 SEM image of the copper-manganese-based layered oxide material obtained in Example 2;

[0038] Figure 3 Charge-discharge curves of sodium ion batteries obtained in Examples 1-2 and Comparative Examples;

[0039] Figure 4 Cycle performance curves of sodium ion batteries obtained in Examples 1-2 and Comparative Examples. DETAILED DESCRIPTION

[0040] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be described in detail below with reference to the drawings of the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the described embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present application.

[0041] Next, the copper-manganese-based layered oxide material and the preparation method thereof according to the embodiment of the present application will be specifically described.

[0042] For the sodium ion battery, which is one of the current research hotspots, the P2 phase NaTMO2 and the O3 phase NaTMO2, which are currently studied more, have the problem that the electrochemical cycle performance and the first-week charge capacity cannot be considered simultaneously. In view of this, the present inventors have found through a large amount of research that the P3 phase copper-manganese-based layered oxide can simultaneously consider both.

[0043] According to the copper-manganese-based layered oxide material provided in the first aspect of the present application, for use in a sodium ion battery, the molecular general formula of the copper-manganese-based layered oxide material is Na x M y Cu a Mn 0.7 O 2+α , wherein M is one or more of alkali metal and alkaline earth metal elements, the 0.75≤x≤1, 0<y≤0.3, 0<a≤0.3, and -0.02≤α≤0.02, and the space group of the copper-manganese-based layered oxide material is R3m.

[0044] The copper-manganese-based layered oxide material according to the embodiments of the present application not only realizes good air stability and safety by using the copper element, but also realizes relatively high initial charge capacity, excellent cycle performance and rate performance by virtue of the high activity of the M metal (i.e., an alkali metal or an alkaline earth metal), the divalent-to-trivalent copper transition and the trivalent-to-tetravalent manganese transition. Moreover, the cycle stability at high voltage can be realized without introducing a metal (such as Fe) that causes the material to be unstable. In addition, in combination with the preparation process, the space group of the copper-manganese-based layered oxide material is R3m, that is, P3 phase, and more Na ions can be accommodated by introducing more Na (the repulsion between adjacent transition metal layers in the P3 phase is weaker than that in the P2 phase) relative to the P2 phase, so that the stability is better during the electrochemical cycle, and the charge capacity can be further improved while maintaining high electrochemical cycle performance.

[0045] According to some embodiments of the present application, M is any one or more selected from sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium. As the M metal, potassium, magnesium, calcium and barium are further preferred in combination with the activity, economy, resource abundance and the like.

[0046] Further, y+a=0.3. That is, 30 at% of Mn is substituted by M and Cu together. By this composition ratio, the stability in air can be further improved, while the initial charge capacity and the electrochemical cycle performance can be taken into account.

[0047] For example, the copper-manganese-based layered oxide material according to the present application may, for example, include Na 0.75 K 0.2 Mn 0.7 Cu 0.1 O2、Na 0.8 K 0.1 Mn 0.7 Cu 0.2 O2、Na 0.8 Mg 0.05 Mn 0.7 Cu 0.2 O2、Na 0.8 Mg 0.1 Mn 0.7 Cu 0.1 O2、Na 0.8 Mg 0.1 Mn 0.7 Cu 0.1 O2、Na 0.8 K 0.1 Mn 0.7 Cu 0.2 O2、Na 0.8 K 0.1 Mn 0.7 Cu 0.2O2, etc. Of course, the above are merely examples, and the present application is not limited thereto.

[0048] The preparation method of the above-mentioned copper-manganese-based layered oxide material, i.e. the preparation method of the copper-manganese-based layered oxide material according to the embodiment of the present application, is described below.

[0049] The preparation method of the copper-manganese-based layered oxide material according to the embodiment of the present application comprises the following steps:

[0050] S1, proportionally weigh a sodium source, a copper source, a manganese source, and a M metal source, wherein M in the M metal source is one or more of alkali metal and alkaline earth metal elements.

[0051] That is, first, weigh various starting materials.

[0052] The sodium source is selected from one or more of sodium carbonate, sodium bicarbonate, sodium nitrate, sodium acetate, sodium oxalate, and sodium citrate;

[0053] The copper source, the manganese source, and the M metal source are respectively selected from one or more of oxides, chlorides, nitrates, sulfates, carbonates, acetates, oxalates, and citrates of the respective metals.

[0054] More specifically, as the copper source, for example, one or more of copper oxide (in the present application, refers to the total of copper oxide and cuprous oxide), copper chloride, copper nitrate, copper sulfate, copper carbonate, copper acetate, copper oxalate, and copper citrate can be selected.

[0055] Similarly, as the manganese source, for example, one or more of manganese oxide (in the present application, refers to the total of manganese monoxide and manganese dioxide), manganese chloride, manganese nitrate, manganese sulfate, manganese carbonate, manganese acetate, manganese oxalate, and manganese citrate can be selected.

[0056] The M metal source, for example, one or more of oxides, chlorides, nitrates, sulfates, carbonates, acetates, oxalates, and citrates of alkali metals, and oxides, chlorides, nitrates, sulfates, carbonates, acetates, oxalates, and citrates of alkaline earth metals can be selected.

[0057] The above-mentioned various raw materials can be appropriately selected according to the specific processing method (specifically, step S2 below). The specific details will be further described below in combination with step S2.

[0058] In some embodiments of the present application, the amount of the sodium source used is 100-108 wt% of the stoichiometric amount of sodium. That is, a slight excess of Na is used. This is to take into account the fact that there will be some loss of the Na source during alloying, and a slight excess of the Na source can be added to achieve the desired chemical composition. In addition, the slight excess of the sodium source helps to promote the formation of the stable P3 phase.

[0059] S2, the sodium source, the copper source, the manganese source, and the M metal source are thoroughly mixed to obtain a precursor powder.

[0060] That is, after the above-mentioned starting materials are weighed, they are thoroughly mixed to serve as a precursor powder for the production of the copper-manganese-based layered oxide material.

[0061] In some embodiments of the present application, the starting materials can be processed by a dry mixing method, a spray drying method, a sol-gel method, or a co-precipitation method to obtain the precursor powder.

[0062] The processing methods will be described one by one below.

[0063] (1) Dry mixing method

[0064] In the dry mixing method, the starting materials are directly mixed by dry mixing, for example, by ball milling, planetary milling, or the like, without adding a solvent or a dispersion liquid, and the resulting mixture is dispersed to obtain the precursor powder.

[0065] In the dry mixing method, the sodium source can be one or more of sodium carbonate, sodium acetate, sodium bicarbonate, sodium oxalate, or sodium citrate; the copper source can be one or more of an oxide, copper chloride, copper nitrate, copper sulfate, or copper carbonate; the manganese source can be one or more of manganese oxide (which refers to manganese monoxide and manganese dioxide in the present application), manganese chloride, manganese nitrate, manganese sulfate, or manganese carbonate; and the M metal source can be one or more of an oxide, a chloride, a nitrate, a sulfate, or a carbonate of an alkali metal or an oxide, a chloride, a nitrate, a sulfate, or a carbonate of an alkaline earth metal.

[0066] Specifically, the weighed powders and grinding balls are placed in a ball mill tank for ball milling.

[0067] The mass ratio of the ball-mixed powder to the grinding balls is (1-50): 1. Preferably, the powder-to-ball ratio is 3:1. By selecting an appropriate powder-to-ball ratio, not only can the mixing effect be improved, but also the powder can be given sufficient surface energy in the ball milling, which is conducive to promoting the subsequent solid-phase sintering reaction.

[0068] Further, the rotation speed is, for example, 200-1000 rpm, preferably 400 rpm. The appropriate rotation speed can improve the mixing efficiency.

[0069] Further, the ball milling time is, for example, 1-24 h, preferably 6 h. The appropriate ball milling time can ensure sufficient mixing while improving the production efficiency.

[0070] The particle size of the precursor powder is 1-15 μm, preferably 1-10 μm. Too coarse powder is not conducive to subsequent solid phase sintering to form the positive active material powder, and too fine powder is prone to agglomeration, affecting uniformity.

[0071] (2) Spray drying method

[0072] That is, the raw material powders are dispersed in the dispersion liquid to form a uniform slurry, and then the slurry is formed into a precursor powder by a spray drying method.

[0073] In the process of forming the slurry, for example, wet ball milling can also be combined so that the slurry is more stable and the dispersion is more uniform.

[0074] Further, in the wet ball milling, a certain dispersant can also be introduced, such as PAA (polyacrylic acid), PMAA (polymethyl acrylic acid), etc.

[0075] As the dispersion liquid, for example, water, ethanol, etc. can be used. Using ethanol for dispersion, it is not easy to agglomerate again in the spray drying process, and therefore it is preferred.

[0076] Further, for the spray drying method, there is no special requirement for each powder, and all the above-mentioned raw material powders can be arbitrarily selected.

[0077] (3) Sol-gel method

[0078] The so-called sol-gel method is to first form a sol of each raw material powder in a solvent, then form a precursor gel by evaporating the solvent, and finally make the precursor gel lose fat by heating to obtain the precursor powder.

[0079] Specifically, for example, each raw material powder can be dispersed in water or ethanol to form a precursor solution; then an appropriate amount of chelating agent, such as citric acid, is added, and stirring is carried out at 50-100°C to evaporate the dispersion liquid (i.e. water or ethanol) to obtain a precursor gel; finally, pre-burning at 200-500°C for 1-4 hours to obtain the precursor powder.

[0080] For the sol-gel method, a relatively larger molecular weight organic salt is preferred to be more stable during the formation of the gel, so as to obtain better dispersion uniformity. Specifically, for example, the sodium source can be selected from one or more of sodium carbonate, sodium bicarbonate, sodium oxalate, or sodium citrate; the copper source can be selected from one or more of copper acetate, copper oxalate, copper citrate, etc.; as the manganese source, similarly, for example, one or more of manganese acetate, manganese oxalate, manganese citrate, etc. can be selected; and the M metal source can be selected from one or more of acetate, oxalate, citrate of alkali metal, and acetate, oxalate, citrate of alkaline earth metal.

[0081] (4) Coprecipitation method

[0082] The so-called coprecipitation method is to dissolve each of the raw powders except the sodium source in a solvent, and then acetone is used to adjust the pH value of the solution to cause coprecipitation, after which the sodium source is mixed (such as dry ball milling, etc.) to obtain the precursor powder.

[0083] Specifically, for example, each of the raw material powders is dissolved in water to form a solution of a certain concentration; then the solution is slowly added to an alkaline aqueous solution of a certain concentration and pH value, such as ammonia, by a peristaltic pump to generate a coprecipitate; the coprecipitate is then washed with water, dried, and thoroughly mixed with the sodium source powder to obtain the precursor powder.

[0084] For the sol-gel method, the sodium source is not limited and any of the above-mentioned sodium sources can be appropriately selected. For other raw materials, good solubility is preferred. Specifically, the copper source can be selected from one or more of copper chloride, copper nitrate, copper sulfate, etc.; the manganese source can be selected from one or more of manganese chloride, manganese nitrate, manganese sulfate; and the M metal source can be selected from one or more of chloride, nitrate, sulfate, carbonate of alkali metal, and chloride, nitrate, sulfate of alkaline earth metal, etc.

[0085] S3, sintering the precursor powder, the sintering temperature is 550-850℃, and the sintering time is 10-15h, to obtain a copper-manganese-based layered oxide material.

[0086] That is, after the precursor powder is obtained by mixing, it needs to be sintered in solid phase to cause solid phase reaction to generate a positive active material for sodium ion battery.

[0087] To obtain stable P3 phase, preferably, the heating rate during sintering is 3-5℃ / min, and the sintering temperature is 700-800℃.

[0088] The appropriate heating rate helps the by-products generated by the thermal decomposition reaction of the precursor powder to be released sufficiently, the appropriate sintering temperature and holding time help to control the crystal phase and to facilitate the grain growth without abnormal growth.

[0089] In addition, in order to facilitate the formation of a slurry with good dispersibility for coating on the positive current collector, the preparation method preferably further comprises the following steps:

[0090] S4, grinding and sieving the sintered powder to obtain the copper-manganese-based layered oxide material powder.

[0091] Thus, the copper-manganese-based layered oxide material powder according to the present application can be prepared.

[0092] Next, a positive electrode using the above-mentioned copper-manganese-based layered oxide material is described.

[0093] The positive electrode according to the embodiment of the present application comprises:

[0094] a positive current collector;

[0095] a positive active material layer disposed on the surface of the positive current collector, and the positive active material layer contains the copper-manganese-based layered oxide material according to any one of the above-mentioned embodiments.

[0096] Further, the positive active material layer further contains a conductive agent and a binder. The conductive agent can improve the conductivity thereof, and the binder helps to improve the bonding strength between the positive active material layer and the positive current collector.

[0097] Specifically, the conductive agent is selected from any one or more of conductive carbon black, conductive graphite, carbon nanotubes, carbon fibers, and graphene.

[0098] In addition, the binder is any one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), sodium alginate (SA), sodium carboxymethyl cellulose (CMC), and styrene butadiene rubber (SBR).

[0099] The use of one or more of PVDF, PTFE, sodium alginate, CMC, and SBR as the binder can further improve the interfacial contact performance of the positive active material layer and the positive current collector and the battery performance.

[0100] Specifically, PVDF has high dielectric constant, good chemical stability and temperature characteristics, and has a positive effect on improving the adhesion of the positive active material layer and the positive current collector.

[0101] PTFE is a kind of polytetrafluoroethylene-containing high molecular chemical material. Polytetrafluoroethylene is generated by free radical polymerization of tetrafluoroethylene. Polytetrafluoroethylene PTFE has the advantages of high temperature resistance (use working temperature up to 250 DEG C), low temperature resistance (even if the temperature drops to -196 DEG C, it can maintain 5% elongation), corrosion resistance (inert to most chemicals and solvents, resistant to strong acid and strong base, water and various organic solvents), etc.

[0102] Using sodium alginate (SA) as a binder, the formation of metal ion-coordinated sodium alginate on the surface of metal fluoride particles during the electrode manufacturing process successfully inhibits the dissolution into the layered oxide material. That is, the copper-manganese-based layered oxide can be cross-linked in situ with the SA binder to form a conformal complex layer on the surface of the copper-manganese-based layered oxide particles, which can effectively inhibit the dissolution of metal ions in the copper-manganese-based layered oxide in the electrolyte and enhance the reversibility of the positive electrode.

[0103] CMC is widely used as a binder for negative materials in aqueous systems, and CMC can achieve larger battery capacity, improve the cycle life of the battery, and reduce the internal resistance of the battery.

[0104] SBR binder has high bonding strength and good mechanical stability and operability, and is used as a binder in the battery industry, with good binder effect and stable quality.

[0105] There is no particular limitation on the method of arranging the positive active material layer on the surface of the positive current collector, for example, which can include:

[0106] The above-mentioned copper-manganese-based layered oxide material 60-100 parts by mass, 0-10 parts by mass of a conductive agent, and 0-10 parts by mass of a binder are dispersed in a solvent (such as water, methanol, ethanol, etc.) to form a positive electrode slurry, and then the positive electrode slurry is coated on the surface of the positive current collector.

[0107] The above-mentioned positive electrode can be used to form a sodium ion battery.

[0108] In the following, the preparation of the copper-manganese-based layered oxide material, the positive electrode, and the sodium ion battery according to the present application are further illustrated by examples.

[0109] Example 1

[0110] (1) Preparation of copper-manganese-based layered oxide material Na0.75K0.2Mn0.7Cu0.1O2

[0111] The copper-manganese-based layered oxide material is prepared by a dry mixing method. Specifically, it includes:

[0112] Na2CO3(analytical pure), K2CO3(analytical pure), CuO, Mn2O3 were mixed in a molar ratio of 0.375:0.1:0.35:0.1; after ball milling mixing with ethanol solvent for 5h, drying, the precursor mixed powder was placed in a muffle furnace, treated at 700℃ for 12h, to obtain a black powder of layered oxide material Na0.75K0.2Mn0.7Cu0.1O2, whose XRD pattern is shown in (a) of Figure 1 From the XRD pattern, it can be determined that the crystal structure of Na0.75K0.2Mn0.7Cu0.1O2 is a P3 phase layered structure oxide.

[0113] (2) Preparation of sodium-ion battery

[0114] The copper-manganese-based layered oxide material prepared above was used as an active material of a battery positive electrode material for the preparation of a sodium-ion battery, and the specific steps were as follows:

[0115] The prepared Na0.75K0.2Mn0.7Cu0.1O2 powder was mixed with acetylene black and a binder polyvinylidene fluoride (PVDF) in a mass ratio of 80:10:10, and an appropriate amount of N-methyl pyrrolidone (NMP) solution was added. The mixture was ground to form a slurry in a dry environment at room temperature, and then the slurry was uniformly coated on a current collector aluminum foil. After drying under an infrared lamp, the electrode was cut into a (8x8) mm2polar piece. The polar piece was dried at 110℃ for 10h under vacuum conditions, and then transferred to a glove box for standby.

[0116] The assembly of the simulated battery was carried out in an Ar atmosphere glove box, with metallic sodium as the counter electrode and NaClO4 / carbonic acid diethyl ester (EC:DEC) solution as the electrolyte, to assemble a CR2032 button cell.

[0117] The constant current charge and discharge mode was used, and the charge and discharge test was carried out at a current density of C / 10. Under the conditions of a discharge cutoff voltage of 1.5V and a charge cutoff voltage of 4.5V, the test results are shown in Figure 3 and 4 It can be seen from the figure that the first week discharge specific capacity can reach 187.2mAh / g, the first week coulombic efficiency is about 95%, and the capacity retention rate after 100 cycles is 74.9%.

[0118] Example 2

[0119] (1) Preparation of copper-manganese-based layered oxide material Na0.8K0.1Mn0.7Cu0.2O2

[0120] The specific preparation steps are the same as those of Example 1, but the starting materials used are NaHCO3 (analytical pure), KHCO3 (analytical pure), manganese acetate, and copper acetate, and the component ratio is different from that of Example 1. In this example, the molar ratio of each component is 0.8:0.1:0.7:0.2.

[0121] In addition, the heat treatment condition is 800°C for 10h, and the layered oxide material in the form of black powder obtained is Na0.8K0.1Mn0.7Cu0.2O2. Its XRD pattern is shown in (b) of FIG. 6. Figure 1 From the XRD pattern, it can be determined that the crystal structure of Na0.8K0.1Mn0.7Cu0.2O2 is still a P3-phase layered oxide.

[0122] Figure 2 The scanning electron microscope (SEM) image thereof is shown in FIG. 7. Figure 2 As can be seen from FIG. 7, the material is in the form of a sheet, and the particle size distribution is mainly from 1 micrometer to 10 micrometers.

[0123] (2) Preparation of a sodium-ion battery

[0124] The copper-manganese-based layered oxide material prepared above is used as an active material of a battery positive electrode material for the preparation of a sodium-ion battery, and electrochemical charge and discharge tests are performed. The preparation process and test method are the same as those of Example 1.

[0125] The test voltage range is 1.5-4.5V, and the test results are shown in FIG. 8 and FIG. 9. Figure 3 4 As can be seen from the figures, the first-week specific discharge capacity is 213.8mAh / g, the first-week coulombic efficiency is about 95%, and the capacity retention rate after 100 cycles is 80.68%.

[0126] Example 3

[0127] (1) Preparation of a copper-manganese-based layered oxide material Na0.8Mg0.05Mn0.7Cu0.2O2

[0128] The specific preparation steps are the same as those of Example 1, but the starting materials used are NaHCO3 (analytical pure), KHCO3 (analytical pure), manganese acetate, and copper acetate, and the component ratio is different from that of Example 1. In this example, the molar ratio of each component is 0.8:0.1:0.7:0.2.

[0129] The layered oxide material in the form of black powder obtained is Na0.8Mg0.05Mn0.7Cu0.2O2. Its XRD pattern is similar to that of Example 1, and therefore the detailed pattern and description thereof are omitted.

[0130] (2) Preparation of a sodium-ion battery

[0131] ​The copper-manganese-based layered oxide material prepared above is used as an active substance of a battery positive electrode material for the preparation of a sodium ion battery, and electrochemical charge-discharge tests are performed. The preparation process and test method are the same as in Example 1. The test voltage range is 1.5-4.5 V, the first cycle discharge specific capacity can reach 193.2 mAh / g, the first cycle coulombic efficiency is about 95%, and the capacity retention rate after 100 cycles is 79.54%.

[0132] Example 4

[0133] (1) Preparation of copper-manganese-based layered oxide material Na0.8Mg0.1Mn0.7Cu0.1O2

[0134] The specific preparation steps are the same as in Example 2 above, but the starting materials used are NaHCO3 (analytical pure), magnesium acetate (analytical pure), copper acetate, and manganese acetate, and the component ratio is different from that in Example 2. In this example, the molar ratio of each component is 0.8:0.1:0.7:0.1, and the layered oxide material obtained as a black powder is Na0.8Mg0.1Mn0.7Cu0.1O2.

[0135] (2) Preparation of a sodium ion battery

[0136] The copper-manganese-based layered oxide material prepared above is used as an active substance of a battery positive electrode material for the preparation of a sodium ion battery, and electrochemical charge-discharge tests are performed. The preparation process and test method are the same as in Example 1. The test voltage range is 1.5-4.5 V, the first cycle discharge specific capacity can reach 193.2 mAh / g, the first cycle coulombic efficiency is about 95%, and the capacity retention rate after 100 cycles is 79.54%.

[0137] Example 5

[0138] (1) Preparation of copper-manganese-based layered oxide material Na0.8Mg0.1Mn0.7Cu0.1O2

[0139] In this example, a spray drying method is used to prepare the precursor powder.

[0140] Specifically, sodium nitrate, potassium nitrate, copper nitrate, and manganese acetate precursors with a molar ratio of 0.8:0.1:0.7:0.1 are weighed, the precursors are dissolved in water to obtain a transparent solution; the solution is placed in a spray dryer and spray dried at 130°C; the dried precursors sprayed are collected and transferred to an alumina crucible, and treated at 700°C in a muffle furnace under air atmosphere for 6h to obtain a dark brown powder of copper-manganese-based layered oxide material Na0.8Mg0.1Mn0.7Cu0.1O2, which has an XRD pattern similar to Figure 1 .

[0141] (2) Preparation of a sodium ion battery

[0142] The copper-manganese-based layered oxide material prepared above was used as an active material of a battery positive electrode material for the preparation of a sodium ion battery, and electrochemical charge-discharge tests were performed. The preparation process and test method were the same as in Example 1. The test voltage range was 1.5-4.5 V, the first cycle discharge specific capacity was 185.6 mAh / g, the first cycle coulombic efficiency was about 95%, and the capacity retention rate after 100 cycles was 72.4%.

[0143] Example 6

[0144] (1) Preparation of copper-manganese-based layered oxide material Na0.8K0.1Mn0.7Cu0.2O2

[0145] In this example, a sol-gel method was used to prepare the precursor powder.

[0146] Specifically, first, the precursor compounds sodium sulfate, potassium sulfate, copper sulfate, and manganese sulfate were weighed according to the molar ratio of 0.4:0.05:0.7:0.2, and were dissolved in deionized water in turn, and an appropriate amount of citric acid was added as a chelating agent, and was placed in an 80°C oil bath for stirring; the dry gel obtained by evaporation was transferred to an alumina crucible, and was pre-fired at 200°C for 2 h; and then was heat-treated at 800°C in a muffle furnace under air atmosphere for 10 h, to obtain a red-brown black powder of copper-manganese-based layered oxide material, which was Na0.8K0.1Mn0.7Cu0.2O2, and its XRD pattern was similar to Figure 1 .

[0147] (2) Preparation of a sodium ion battery

[0148] The copper-manganese-based layered oxide material prepared above was used as an active material of a battery positive electrode material for the preparation of a sodium ion battery, and electrochemical charge-discharge tests were performed. The preparation process and test method were the same as in Example 1. The test voltage range was 1.5-4.5 V, the first cycle discharge specific capacity was 185.6 mAh / g, the first cycle coulombic efficiency was about 95%, and the capacity retention rate after 100 cycles was 72.4%.

[0149] Example 7

[0150] (1) Preparation of copper-manganese-based layered oxide material

[0151] In this example, a sol-gel method was used to prepare the precursor powder.

[0152] Specifically, the precursors potassium acetate, copper acetate and manganese acetate were weighed according to the molar ratio of 0.05:0.7:0.2, respectively dissolved in deionized water; the prepared potassium acetate, copper acetate and manganese acetate aqueous solution was slowly added into the ammonia solution with a certain concentration and pH value by using a peristaltic pump tube; after the reaction was completed, the generated precipitate was taken out, washed with deionized water, and then placed in a 80℃ vacuum oven for drying; the dried powder was uniformly mixed with sodium hydroxide according to the stoichiometric ratio to obtain the precursor; then the precursor was transferred to a muffle furnace for heat treatment at 800℃ for 12h. The powder after heat treatment was ground to obtain a black copper-manganese-based layered oxide material Na0.8K0.1Mn0.7Cu0.2O2, and the XRD pattern thereof was similar to Figure 1 .

[0153] (2) Preparation of sodium ion battery

[0154] The copper-manganese-based layered oxide material prepared above was used as the active material of the battery positive electrode material for the preparation of a sodium ion battery, and electrochemical charge-discharge test was performed. The preparation process and test method were the same as in Example 1. The test voltage range was 1.5-4.5V, the first cycle discharge specific capacity was 215.3mAh / g, the first cycle coulombic efficiency was about 95%, and the capacity retention rate after 100 cycles was 82.3%.

[0155] Comparative example

[0156] Except that the final sintering temperature of the powder was different from that of Example 1, the rest was the same as Example 1.

[0157] In the comparative example, the sintering temperature was 900℃.

[0158] It can be seen from (c) in Figure 1 that under this high-temperature sintering, the P2 phase has been converted.

[0159] In addition, Figure 3 and Figure 4 show the test results of the electrical performance of the comparative example. From Figure 3 and Figure 4 , it can be seen that the first cycle discharge specific capacity and the electrical cycle performance of the sodium ion battery of the comparative example are significantly lower than those of the sodium ion battery of the present application.

[0160] The above is a preferred embodiment of the present application, and it should be pointed out that for ordinary skilled persons in the technical field, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A copper-manganese-based layered oxide material for a sodium-ion battery, characterized by, The copper-manganese-based layered oxide material has a general formula of Na x M y Cu a Mn 0.7 O 2+α , the M is any one or more selected from sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, the 0.75≤x≤1, 0<y≤0.3, 0<a≤0.3, and -0.02≤α≤0.02, The space group of the copper-manganese-based layered oxide material is R3m, the Na coordination environment in the copper-manganese-based layered oxide material is a prism, and the oxygen layer stacking sequence is 3.

2. The copper-manganese-based layered oxide material according to claim 1, characterized by, wherein, y+a=0.

3.

3. A process for the preparation of a copper-manganese-based layered oxide material as claimed in any one of claims 1 or 2, characterized in that, The method comprises the following steps: S1, proportionally weighing a sodium source, a copper source, a manganese source, and an M metal source, wherein M in the M metal source is one or more of alkali metal and alkaline earth metal elements; S2, sufficiently mixing the sodium source, the copper source, the manganese source, and the M metal source to obtain a precursor powder; S3, sintering the precursor powder, wherein the sintering temperature is 550-850℃, and the sintering time is 10-15h, to obtain a copper-manganese-based layered oxide material.

4. The production method according to claim 3, characterized by, In the step S1, the sodium source is selected from one or more of sodium carbonate, sodium bicarbonate, sodium nitrate, sodium acetate, sodium oxalate, and sodium citrate; the copper source, the manganese source, and the M metal source are respectively selected from one or more of oxides, chlorides, nitrates, sulfates, carbonates, acetates, oxalates, and citrates of the respective metals.

5. The preparation method according to claim 3, characterized in that, In the step S1, the amount of the sodium source, calculated based on sodium therein, is 100-108wt% of the stoichiometric amount.

6. The preparation method according to claim 3, characterized in that, In the step S2, each raw material is processed by any one of a dry mixing method, a spray drying method, a sol-gel method, or a co-precipitation method to obtain the precursor powder.

7. The preparation method according to claim 3, characterized in that, In the step S3, the heating rate during sintering is 3-5℃ / min, and the sintering temperature is 700-800℃.

8. The preparation method according to claim 3, characterized in that, The method further comprises the following step: S4, grinding and sieving the sintered powder to obtain a copper-manganese-based layered oxide material powder.

9. A positive electrode, characterized by comprising: The method comprises: a positive electrode current collector; a positive electrode active material layer disposed on the surface of the positive electrode current collector, wherein the positive electrode active material layer contains the copper-manganese-based layered oxide material of claim 1 or 2, or the copper-manganese-based layered oxide material prepared by the method of any one of claims 3 to 8.

10. A sodium-ion battery, characterized in that, An electrode comprising the positive electrode of claim 9.

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