Sodium ion battery composite negative electrode material, preparation method thereof and sodium ion battery

Abstract

The embodiment of the present application provides a sodium ion battery composite negative material, a preparation method thereof and a sodium ion battery, which comprise hard carbon and Co3Se4 particles combined on the hard carbon. The sodium ion battery composite negative material has good cycle stability and high sodium storage theoretical capacity, and when the sodium ion battery composite negative material is applied to a sodium ion battery, the demand of the market for high energy and power density, high cycle stability and energy storage devices can be met.

Description

TECHNICAL FIELD

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

[0002] With the rapid development of the new energy automobile industry, the market demand for batteries increases, and lithium ion batteries will not be able to meet the demand in the future due to the global lack of lithium resources. Sodium and lithium are two elements in the same first main group, and their chemical properties are similar, and sodium has obvious advantages over lithium in cost and reserves, making sodium ion batteries a very promising alternative to lithium ion batteries.

[0003] Sodium ion battery negative electrode energy storage materials have an important influence on the electrochemical performance of sodium ion batteries. Currently, sodium ion energy storage negative electrodes mainly use carbon materials or transition metal chalcogen compounds. Among them, the sodium ion battery negative electrode carbon material represented by hard carbon (HC) has the advantage of good cycle stability, but is limited by the low theoretical capacity of carbon, and the sodium storage capacity is low. Although transition metal chalcogen compounds have high sodium storage theoretical capacity, the conversion type energy storage mechanism leads to severe volume expansion during sodium storage, and the cycle stability is poor. Therefore, at present, it has become an urgent need of the new energy automobile industry to develop a sodium ion battery negative electrode material that has good cycle stability and high sodium storage theoretical capacity. SUMMARY

[0004] In view of this, the first aspect of the embodiments of the present application provides a sodium ion battery composite negative electrode material which has good cycle stability and high sodium storage theoretical capacity. When applied to a sodium ion battery, it can effectively improve the electrochemical performance of the battery, to a certain extent, solve the problems of low sodium storage capacity of carbon material sodium ion energy storage negative electrode and poor cycle stability of transition metal chalcogen compound sodium ion energy storage negative electrode.

[0005] Specifically, the first aspect of the embodiments of the present application provides a sodium ion battery composite negative electrode material, which comprises hard carbon and Co3Se4 particles combined on the hard carbon.

[0006] The sodium ion battery composite negative electrode material provided by the embodiment of the present application has high sodium storage capacity and good cycle stability, is applied to a secondary battery, and can effectively improve the electrochemical performance of the battery, because the sodium ion battery composite negative electrode material comprises hard carbon and Co3Se4 particles combined on the hard carbon, the hard carbon can be used as a loading substrate of the Co3Se4 particles, and due to its good physical properties and sodium storage mode, the composite negative electrode material can provide good electrical conductivity and strong mechanical strength, and the Co3Se4 can react with sodium to provide high sodium storage capacity. Compared with single hard carbon material, the composite negative electrode material can exhibit higher reversible capacity than hard carbon because it contains a large amount of Co3Se4 with high sodium storage capacity. Compared with single Co3Se4 material, the composite negative electrode material uses hard carbon as a high-mechanical-strength conductive substrate, and can exhibit better cycle stability than Co3Se4.

[0007] In the first aspect of the present application, the Co3Se4 particles are distributed on the surface of the hard carbon and in the open pores of the hard carbon.

[0008] In the first aspect of the present application, the total mass of the Co3Se4 particles is 21% to 70% of the total mass of the sodium ion battery composite negative electrode material.

[0009] In the first aspect of the present application, the total mass of the Co3Se4 particles is 50% to 60% of the total mass of the sodium ion battery composite negative electrode material.

[0010] In the first aspect of the present application, the particle size of the hard carbon is 1 μm to 70 μm.

[0011] In the first aspect of the present application, the particle size of the hard carbon is 5 μm to 10 μm.

[0012] In the first aspect of the present application, the particle size of the Co3Se4 particles is 50 nm to 1 μm.

[0013] In the first aspect of the present application, the particle size of the Co3Se4 particles is 100 to 200 nm.

[0014] In the first aspect of the present application, the hard carbon comprises one or both of resin hard carbon and biomass hard carbon.

[0015] In the first aspect of the present application, the Co3Se4 particles are combined with the hard carbon through chemical bonding.

[0016] The sodium ion battery composite negative electrode material provided by the first aspect of the embodiment of the present application has Co3Se4 particles uniformly combined on the surface and open pores of the hard carbon. The hard carbon can be used as a loading substrate for the Co3Se4 particles, and provides good electrical conductivity for the composite negative electrode material. The Co3Se4 particles are used as active substances, and provide high reversible sodium storage capacity for the composite negative electrode material. When the composite negative electrode material is applied to a sodium ion battery, the sodium ion battery can exhibit high capacity and good cycle stability.

[0017] Correspondingly, the second aspect of the embodiment of the present application provides a preparation method of a sodium ion battery composite negative electrode material, including the following steps:

[0018] The hard carbon and the soluble cobalt salt are added to water, stirred, and then filtered after standing to obtain hard carbon with cobalt ions attached thereto;

[0019] The hard carbon with cobalt ions attached thereto is mixed with selenium powder, and a selenization reaction is performed under an inert atmosphere to obtain Co3Se4, thereby preparing a sodium ion battery composite negative electrode material. The sodium ion battery composite negative electrode material includes hard carbon and Co3Se4 particles combined on the hard carbon.

[0020] In the preparation method of the present application, the soluble cobalt salt includes one or more of Co(NO3)2, CoCl2, CoSO4, CoS2 and CoF2.

[0021] In the preparation method of the present application, the temperature of the selenization reaction process is 700-800℃, and the time is 1-4h.

[0022] The preparation method provided by the second aspect of the embodiment of the present application is simple, and the sodium ion battery composite negative electrode material prepared by the method has good cycle stability and high sodium storage theoretical capacity.

[0023] The third aspect of the embodiment of the present application provides a battery negative electrode sheet, which includes the sodium ion battery composite negative electrode material described in the first aspect of the embodiment of the present application.

[0024] The fourth aspect of the embodiment of the present application provides a sodium ion battery, which includes a positive electrode, a negative electrode, and a separator and an electrolyte between the positive electrode and the negative electrode. The negative electrode includes the sodium ion battery composite negative electrode material described in the first aspect of the embodiment of the present application.

[0025] The fifth aspect of the embodiment of the present application provides an electrical equipment, which includes a shell, and a power supply assembly and a functional assembly in the shell. The power supply assembly includes the sodium ion battery provided by the fourth aspect of the embodiment of the present application.

[0026] By implementing the embodiments of the present application, the electrochemical performance of the sodium ion battery is greatly improved, and the problem that the existing sodium ion battery cannot have high sodium storage capacity and good cycle stability is solved. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the background art, the drawings needed to be used in the embodiments of the present application or the background art will be described below.

[0028] Figure 1 is a structural schematic diagram of a sodium ion battery composite negative electrode material 100 in an embodiment of the present application;

[0029] Figure 2 is a flow chart of a preparation method of a sodium ion battery composite negative electrode material provided by the embodiments of the present application;

[0030] Figure 3 is a structural schematic diagram of a battery negative electrode sheet 200 in an embodiment of the present application;

[0031] Figure 4 is a structural schematic diagram of a sodium ion battery 300 in an embodiment of the present application.

[0032] BRIEF DESCRIPTION OF DRAWINGS

[0033] 100-sodium ion battery composite negative electrode material; 10-Co3Se4 particles; 20-hard carbon; 200-battery negative electrode sheet; 110-current collector; 120-negative electrode active material layer; 40-conductive agent; 50-binder; 300-sodium ion battery; 1-negative electrode; 2-electrolyte; 3-separator; 4-positive electrode; 5-battery shell. DETAILED DESCRIPTION

[0034] The embodiments of the present application will be described below in combination with some specific embodiments of the present application.

[0035] With the rapid development of electric vehicles and smart grids in recent years, and the increasing preference of humans for intermittent renewable energy (such as solar, wind, tidal, and geothermal energy), it is imperative to develop large-scale energy storage devices. In order to meet the demand for large-scale energy storage, an ideal secondary battery must not only have excellent electrochemical performance, but also take into account social and economic indicators such as abundant resources and low prices. Sodium ions are abundant, widely distributed, and low in price, so sodium-ion batteries are considered to be one of the ideal choices for the next generation of large-scale energy storage technologies. Carbon-based materials, due to their widespread existence and renewability in nature, are the most studied negative electrode materials for sodium-ion batteries, but their sodium storage capacity is poor because the large radius of sodium ions makes it difficult for sodium ions to be intercalated and deintercalated between carbon-based negative electrode materials. In addition, the sodium storage process of sodium-ion batteries can easily cause large volume changes in the electrode material, and even induce irreversible structural phase changes, affecting the cycle stability of the battery. Therefore, it is necessary to provide a sodium-ion battery negative electrode material that can improve the sodium storage capacity of the battery while maintaining good cycle stability of the battery.

[0036] Based on this, the embodiment of the present application provides a kind of sodium-ion battery composite negative material, including hard carbon and Co3Se4 Particle combined on the hard carbon. Figure 1 It is the structural schematic diagram of sodium-ion battery composite negative material 100 in an embodiment of the present application. As shown in some embodiments, Figure 1 Co3Se4 Particle 10 is distributed on the surface of hard carbon 20 and the open hole hole of hard carbon 20. Hard carbon 20 is an amorphous carbon material with high specific surface area and porosity, has a large number of microporous structures inside, including closed hole hole and open hole hole, can adsorb sodium ions on its surface and open hole hole, and form sodium ion storage layer. Among them, open hole hole refers to the cavity and channel in hard carbon connected with the outside world;Closed hole hole refers to the cavity and channel in hard carbon not connected with the outside world.

[0037] The sodium ion battery composite negative electrode material provided by the embodiment of the present application has high sodium storage capacity and good cycle stability, is applied to a secondary battery, and can effectively improve the electrochemical performance of the battery. This is because the sodium ion battery composite negative electrode material comprises hard carbon and Co3Se4 particles combined on the hard carbon. The hard carbon can be used as a loading substrate for the Co3Se4 particles. Due to the good physical properties and sodium storage mode of the hard carbon, the overall material can have good electrical conductivity and strong mechanical strength. The Co3Se4 can react with sodium to provide high sodium storage capacity. The valence state of cobalt in Co3Se4 is low, and the same amount of sodium can generate more cobalt metal nanoclusters, which can help to enhance the electrical conductivity of the overall electrode in the reaction process and reduce the energy barrier of the sodium storage reaction. Compared with layered selenium compounds, the application selects Co3Se4 with a monoclinic crystal structure, so more crystal faces can be exposed to provide more surface active sites. Compared with single hard carbon material, the composite negative electrode material contains a large amount of Co3Se4 with high sodium storage capacity, and can exhibit higher reversible capacity than hard carbon. Compared with single Co3Se4 material, the composite negative electrode material uses hard carbon as a high-mechanical-strength conductive substrate, and can exhibit better cycle stability and rate performance than Co3Se4.

[0038] In the embodiment of the present application, the total mass of the Co3Se4 particles is 20% to 70% of the total mass of the sodium ion battery composite negative electrode material. When the content of Co3Se4 particles in the composite negative electrode material is low and the content of hard carbon is high, it is beneficial to the full sodium storage of Co3Se4 particles and the improvement of cycle stability, but the reduction of the content of Co3Se4 particles will reduce the specific capacity of the composite negative electrode material and affect its sodium storage effect as a negative electrode material. When the content of Co3Se4 particles in the composite negative electrode material is high and the content of hard carbon is low, it is beneficial to the improvement of the specific capacity of the composite negative electrode material, but it will reduce the electrical conductivity of the composite negative electrode material and is not conducive to the uniform distribution of Co3Se4 particles. Considering the sodium storage capacity, cycle stability and rate, the mass percentage of Co3Se4 particles is controlled to be 21% to 70% in some embodiments of the present application. Within this range, the composite negative electrode material can better have good electrical conductivity, high mechanical strength and high specific capacity, and the Co3Se4 particles can better realize uniform distribution and stable combination on the hard carbon, thereby improving the cycle stability of the overall material. In some embodiments of the present application, the total mass of the Co3Se4 particles is 50% to 60% of the total mass of the sodium ion battery composite negative electrode material. In some embodiments of the present application, the total mass of the Co3Se4 particles can be 21%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% of the total mass of the sodium ion battery composite negative electrode material.

[0039] In the embodiments of the present application, the particle size of the hard carbon is 1-70 μm. In the composite anode material, the hard carbon serves as a loading substrate for the Co3Se4 particles, and the Co3Se4 particles are combined on the surface and open pores of the hard carbon to perform the sodium storage reaction. For the same mass of hard carbon, the larger the particle size, the smaller the specific surface area and the number of particles, and the less the Co3Se4 particles loaded, which reduces the sodium storage capacity of the Co3Se4 particles. The smaller the particle size of the hard carbon, the larger the specific surface area and the number of particles, and the more the Co3Se4 particles loaded, which is beneficial to the sodium storage of the Co3Se4 particles, but increases the contact resistance between the hard carbon particles, and an excessively large specific surface area generates a large amount of solid electrolyte interface (SEI) film, reducing the first cycle coulombic efficiency. Considering the sodium storage capacity and the coulombic efficiency, in some embodiments of the present application, the particle size of the hard carbon is controlled to be 1-70 μm. Controlling the particle size of the hard carbon in this range is beneficial to obtaining a higher sodium storage capacity while reducing the contact resistance and improving the first cycle coulombic efficiency. In some embodiments of the present application, the particle size of the hard carbon is 5-10 μm. In some embodiments of the present application, the particle size of the hard carbon can be 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 20 μm, 25 μm, 30 μm, 40 μm, 50 μm, 60 μm, or 70 μm.

[0040] In the embodiments of the present application, the particle size of the Co3Se4 particles is 50 nm to 1 μm. As an active material for sodium storage, the Co3Se4 particles need to undergo a conversion reaction with sodium. For the same mass of Co3Se4 particles, the larger the particle size of the Co3Se4 particles, the smaller the specific surface area of the Co3Se4 particles, on the one hand, the proportion of the Co3Se4 molecules in contact with sodium in the total molecular weight of the Co3Se4 is lower, which will slow down the conversion reaction rate and affect the completion degree of the polarization reaction, on the other hand, the larger the particle size of the Co3Se4 particles, the more obvious the volume expansion during the conversion reaction, and the risk of material pulverization will increase; the smaller the particle size of the Co3Se4 particles, the larger the specific surface area of the Co3Se4 particles, and the higher the proportion of the Co3Se4 molecules in contact with sodium in the total molecular weight of the Co3Se4, which is beneficial to the sodium storage reaction, but the total amount of Co3Se4 particles combined with the same mass of hard carbon will be less, thereby resulting in smaller specific capacity of the composite negative electrode material. Considering the conversion reaction rate of the Co3Se4 particles, the volume expansion rate and the specific capacity of the composite negative electrode material, in some embodiments of the present application, the particle size of the Co3Se4 particles is controlled to be 50 nm to 1 μm. Controlling the particle size of the Co3Se4 particles in this range can better obtain a composite negative electrode material with higher specific capacity, higher conversion reaction rate of the Co3Se4 particles and higher structural stability. In some embodiments of the present application, the particle size of the Co3Se4 particles is 100 nm to 200 nm. In some embodiments of the present application, the particle size of the Co3Se4 particles can be 50 nm, 60 nm, 80 nm, 100 nm, 130 nm, 140 nm, 180 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 μm. Controlling the particle size of the Co3Se4 particles within the above range can better load the Co3Se4 particles into the open pores of the hard carbon.

[0041] In the embodiments of the present application, the hard carbon includes one or both of resin hard carbon and biomass hard carbon. The resin hard carbon is a resin-based hard carbon material obtained by pyrolysis and carbonization of a resin-based precursor such as phenolic resin or epoxy resin. The molecular structure of the resin-based precursor is relatively simple and controllable, and related molecular structures can be designed as needed to accurately construct adjustable pore structures and active sites at the molecular level, so that the hard carbon material has better rate and cycle stability. The hard carbon material prepared using the resin-based precursor has high gravimetric capacity, good electrochemical performance and good consistency, and has obvious performance advantages. The biomass hard carbon is a hard carbon material prepared by taking coconut shell, starch, bamboo, straw and the like as a precursor. The richness of carbon elements and the directional channels in the metabolic process of the biomass hard carbon enable it to realize the rapid migration of sodium ions when used as an electrode material, and it is very suitable for energy storage materials. At the same time, due to its wide availability, renewability and low cost, when used as an energy storage material, it can greatly reduce the industrialization cost.

[0042] In the embodiments of the present application, the Co3Se4 particles are combined with the hard carbon through chemical bonding. Compared with a weakly bonded mode such as physical adsorption, the chemical bonding mode between the Co3Se4 particles and the hard carbon has strong bonding force, can effectively prevent the Co3Se4 particles from falling off during sodium storage, and enhances the stability of the composite negative electrode material.

[0043] The sodium ion battery composite negative electrode material provided by the embodiments of the present application has high sodium storage capacity and good cycle stability, and when applied to a secondary battery, can effectively improve the electrochemical performance of the battery, can meet the market demand for high energy / power density and good cycle stability of energy storage devices, and can be specifically applied to the fields of two-wheeled electric vehicles, micro or medium-low endurance new energy vehicles, industrial vehicles, commercial backup power supplies, mobile signal base station power supplies, electric power storage, engineering machinery, and the like.

[0044] Correspondingly, the embodiments of the present application also provide a preparation method of a sodium ion battery composite negative electrode material, as shown in Figure 2 The preparation method comprises the following steps:

[0045] A1, adding hard carbon and a soluble cobalt salt into water, stirring, and then filtering to obtain hard carbon with cobalt ions attached thereto;

[0046] A2, mixing the hard carbon with cobalt ions attached thereto and selenium powder, and performing a selenization reaction under an inert atmosphere to obtain Co3Se4, thereby preparing a sodium ion battery composite negative electrode material, wherein the sodium ion battery composite negative electrode material comprises hard carbon and Co3Se4 particles combined on the hard carbon.

[0047] In the present application, in step A1, the feeding ratio of the hard carbon and the soluble cobalt salt can be 1:(2-15). The soluble cobalt salt comprises a mixture of one or more of Co(NO3)2, CoCl2, CoSO4, CoS2 and CoF2, the hard carbon comprises one or both of resin hard carbon and biomass hard carbon, and the particle size of the hard carbon is 1-70 μm, and further can be 5-10 μm. The hard carbon and the soluble cobalt salt are dissolved in water to form a mixed solution, the cobalt ions are fully adsorbed onto the hard carbon material through sufficient stirring, and finally the hard carbon with cobalt ions attached thereto is obtained through filtration and drying. The cobalt ions are attached to the hard carbon through metal ion adsorption, on one hand, the cobalt ions are ion-exchange adsorbed on the surface and open pores of the hard carbon, and on the other hand, the cobalt ions also exist in chemical adsorption with oxygen-containing functional groups on the surface and open pores of the hard carbon. In the embodiments of the present application, the filtration mode can be, for example, suction filtration.

[0048] In Step A2, the seleniumization reaction can be carried out by mixing the cobalt ion-attached hard carbon prepared in Step A1 and selenium powder in a certain mass ratio, placing them in a tube furnace, and introducing an inert gas into the tube furnace to carry out the seleniumization reaction in an inert atmosphere. The mixing ratio of the cobalt ion-attached hard carbon and the selenium powder is 1:(0.8-1.2), the inert gas can be argon, and the heating rate of the tube furnace can be set to 0.5-5°C / min. In the embodiments of the present application, the seleniumization reaction is carried out at a temperature of 700-800°C for 1-4h. In some specific embodiments, the temperature of the seleniumization reaction can be, for example, 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, or 800°C, and the time of the seleniumization reaction can be, for example, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, or 4h. Through the above in-situ seleniumization reaction, the cobalt ions attached to the hard carbon are converted into Co3Se4 particles and chemically bonded to the hard carbon, thereby obtaining a sodium ion battery composite negative electrode material. The Co3Se4 particles have a particle size of 50-1μm, and further, 100-200nm. The total mass of the Co3Se4 particles is 21-70% of the total mass of the sodium ion battery composite negative electrode material, and further, 50-60%.

[0049] Compared with the method of simply physically mixing Co3Se4 particles and hard carbon to obtain a composite negative electrode material, the method of combining metal ion adsorption and in-situ seleniumization in the present application can make the cobalt source more uniformly distributed on the surface of the hard carbon through the adsorption of the hard carbon to the cobalt ions in the solution, thereby reducing the uneven stacking of the Co3Se4 particles and improving the utilization rate of the active material. On the other hand, the adsorption of the hard carbon to the cobalt ions can also make the cobalt ions enter the open pores of the hard carbon, effectively improve the Co3Se4 particle loading, and the open pores of the hard carbon can physically bind the Co3Se4 particles, thereby inhibiting the volume expansion and shedding of the active material Co3Se4 particles caused by sodium storage. Furthermore, the in-situ seleniumization method can improve the contact effect between the hard carbon and the Co3Se4 particles, improve the mechanical strength of the overall material, and reduce the contact resistance in the composite material.

[0050] The method for preparing the sodium ion battery composite negative electrode material provided in the embodiments of the present application is simple, and the prepared sodium ion battery composite negative electrode material has high sodium storage capacity and good cycle stability.

[0051] As Figure 3As shown, the embodiment of the present application also provides a battery negative plate 200, which comprises a current collector 110 and a negative active material layer 120 arranged on the current collector 110, the negative active material layer 120 comprises the sodium ion battery composite negative material 100, the conductive agent 40 and the binder 50, and the sodium ion battery composite negative material 100 is uniformly dispersed in the negative active material layer 120. It should be noted that the negative active material layer 120 can use only the sodium ion battery composite negative material 100 described in the embodiment of the present application as the active material, or use the combination of the sodium ion battery composite negative material 100 and one or more other sodium ion battery negative materials as the active material. Among them, the other sodium ion battery negative material can be a carbon-based material, a titanium-based material, an alloy material, an organic compound material, etc.

[0052] As shown in the formula (I), the embodiment of the present application also provides a sodium ion battery composite negative material 100, which comprises a hard carbon material 10, a Co3Se4 particle 20 and a conductive agent 40, wherein the hard carbon material 10 is uniformly dispersed in the sodium ion battery composite negative material 100. Figure 4 As shown, the embodiment of the present application also provides a sodium ion battery 300, which comprises a negative electrode 1, an electrolyte 2, a separator 3, a positive electrode 4 and a battery shell 5, the electrolyte 2 and the separator 3 are located between the negative electrode 1 and the positive electrode 4, and the battery shell 5 is used to encapsulate the negative electrode 1, the electrolyte 2, the separator 3 and the positive electrode 4, wherein the negative electrode 1 comprises the negative plate 200 described above in the embodiment of the present application. The principle of sodium ion deintercalation of the sodium ion battery 300 of the embodiment of the present application is that on the one hand, sodium ions realize reversible charge and discharge by deintercalation in the hard carbon layer and the nanopore, and on the other hand, sodium ions realize reversible charge and discharge by conversion reaction (replacement reaction) with Co3Se4. The first charge causes oxidation reaction, sodium ions are deintercalated and accompanied by the generation of metallic cobalt element, the evolution of structure and the conversion of phase; the first discharge causes reduction reaction, generating a composite phase material of sodium-rich selenide and metallic cobalt element. The sodium ion battery prepared by using the sodium ion battery composite negative material described above in the embodiment of the present application cooperatively plays the advantages of hard carbon material and Co3Se4 particles, and has high specific capacity and good cycle stability.

[0053] The embodiment of the present application also provides a power-consuming device, which comprises a shell, a power supply component and a functional component located in the shell, and the power supply component comprises the above-mentioned sodium ion battery. The power-consuming device can be a 3C product such as a mobile phone, a notebook computer, a tablet computer, a pen input type computer, an electronic book player, a wearable device, etc., or an electric vehicle such as an electric car, an electric motorcycle, an electric bicycle, etc.

[0054] The embodiment of the present application is further described in the following multiple embodiments.

[0055] Embodiment 1

[0056] The sodium ion battery composite negative material is prepared and applied to a sodium ion battery, and the method is as follows:

[0057] (1) Preparation of sodium-ion battery composite negative electrode material:

[0058] 20 parts by weight of hard carbon powder (particle size 5 μm) and 100 parts by weight of CoCl2 were dissolved in 1000 parts by weight of water, and after standing at room temperature for 2 min, the mixture was filtered and dried to obtain hard carbon with CoCl2 attached thereto; the hard carbon with CoCl2 attached thereto was mixed with 100 parts by weight of selenium powder and placed in a tube furnace, and the temperature was raised to 800°C at a rate of 2°C / min under an argon atmosphere, and the selenium was allowed to react for 2 hours, to obtain a sodium-ion battery composite negative electrode material (Co3Se4@HC) with a mass ratio of Co3Se4: HC = 1:1 (the total mass of Co3Se4 particles is 50% of the total mass of the sodium-ion battery composite negative electrode material), labeled S1, which comprises hard carbon and Co3Se4 particles uniformly combined on the hard carbon, wherein the particle size of the Co3Se4 particles is about 100 nm.

[0059] (2) Preparation of battery negative electrode sheet:

[0060] A test battery negative electrode sheet was prepared by mixing S1 as the negative electrode material, acetylene black as the conductive agent, and polyvinylidene fluoride (PVDF) as the binder in a mass ratio of negative electrode material: acetylene black: PVDF = 80:10:10, and then pressing the mixture into a sheet, and the negative electrode sheet was vacuum dried at 120°C for more than 12 hours to obtain a battery negative electrode sheet.

[0061] (3) Preparation of sodium-ion battery:

[0062] A battery sample S10 was obtained by assembling a test battery in an argon-filled glove box, using a piece of metallic sodium as the positive electrode, a glass fiber membrane as the separator, the battery negative electrode sheet obtained in step (2) of Example 1 as the negative electrode, and 1 mol / L NaPF6 (volume ratio of ethylene carbonate (EC) and dimethyl carbonate (DMC) = 1:1) as the electrolyte.

[0063] Example 2

[0064] (1) Preparation of sodium-ion battery composite negative electrode material:

[0065] 20 parts by weight of hard carbon powder (particle size 8 μm) and 120 parts by weight of CoCl2 were dissolved in 1000 parts by weight of water, and a sodium-ion battery composite negative electrode material was prepared according to the method of step (1) of Example 1, to finally obtain a Co3Se4@HC material with a mass ratio of Co3Se4: HC = 1.1:1 (the total mass of Co3Se4 particles is 52% of the total mass of the sodium-ion battery composite negative electrode material), labeled S2, wherein the particle size of the Co3Se4 particles is about 130 nm.

[0066] (2) Preparation of battery negative electrode sheet:

[0067] A battery negative electrode sheet was prepared according to the method of step (2) of Example 1, with S2 as the negative electrode material.

[0068] (3) Preparation of a sodium-ion battery:

[0069] A sodium-ion battery was prepared according to the method of step (3) of Example 1, with the battery negative electrode sheet obtained in step (2) of Example 2 as the negative electrode, to obtain a battery sample S20.

[0070] Example 3

[0071] (1) Preparation of a sodium-ion battery composite negative electrode material:

[0072] Co3Se4@HC material with a mass ratio of Co3Se4: HC = 1.2: 1 (the total mass of Co3Se4particles is 55% of the total mass of the sodium-ion battery composite negative electrode material) was prepared according to the method of step (1) of Example 1, with 20 parts by weight of hard carbon powder (particle size 8 μm) and 150 parts by weight of CoCl2dissolved in 1000 parts by weight of water, and was labeled as S3, wherein the particle size of the Co3Se4particles was about 160 nm.

[0073] (2) Preparation of a battery negative electrode sheet:

[0074] A battery negative electrode sheet was prepared according to the method of step (2) of Example 1, with S3 as the negative electrode material.

[0075] (3) Preparation of a sodium-ion battery:

[0076] A sodium-ion battery was prepared according to the method of step (3) of Example 1, with the battery negative electrode sheet obtained in step (2) of Example 3 as the negative electrode, to obtain a battery sample S30.

[0077] Example 4

[0078] (1) Preparation of a sodium-ion battery composite negative electrode material:

[0079] Co3Se4@HC material with a mass ratio of Co3Se4: HC = 2.0: 1 (the total mass of Co3Se4particles is 67% of the total mass of the sodium-ion battery composite negative electrode material) was prepared according to the method of step (1) of Example 1, with 20 parts by weight of hard carbon powder (particle size 8 μm) and 240 parts by weight of CoCl2dissolved in 1000 parts by weight of water, and was labeled as S4, wherein the particle size of the Co3Se4particles was about 200 nm.

[0080] (2) Preparation of a battery negative electrode sheet:

[0081] A battery negative electrode sheet was prepared according to the method of step (2) of Example 1, with S4 as the negative electrode material.

[0082] (3) Preparation of a sodium-ion battery:

[0083] A sodium-ion battery was prepared according to the method of step (3) of Example 1, with the battery negative electrode sheet obtained in step (2) of Example 4 as the negative electrode, to obtain a battery sample S40.

[0084] Example 5

[0085] (1) Preparation of a sodium-ion battery composite negative electrode material:

[0086] Co3Se4@HC material with a mass ratio of Co3Se4: HC = 0.3: 1 (the total mass of Co3Se4particles is 23% of the total mass of the sodium-ion battery composite negative electrode material) was prepared according to the method of step (1) of Example 1, with 20 parts by weight of hard carbon powder (particle size 8 μm) and 50 parts by weight of CoCl2dissolved in 1000 parts by weight of water, and was labeled as S5, wherein the particle size of the Co3Se4particles was about 80 nm.

[0087] (2) Preparation of a battery negative electrode sheet:

[0088] A battery negative electrode sheet was prepared according to the method of step (2) of Example 1, with S5 as the negative electrode material.

[0089] (3) Preparation of a sodium-ion battery:

[0090] A sodium-ion battery was prepared according to the method of step (3) of Example 1, with the battery negative electrode sheet obtained in step (2) of Example 5 as the negative electrode, to obtain a battery sample S50.

[0091] Example 6

[0092] (1) Preparation of a sodium-ion battery composite negative electrode material:

[0093] Co3Se4@HC material with a mass ratio of Co3Se4: HC = 0.2: 1 (the total mass of Co3Se4particles is 17% of the total mass of the sodium-ion battery composite negative electrode material) was prepared according to the method of step (1) of Example 1, with 20 parts by weight of hard carbon powder (particle size 8 μm) and 30 parts by weight of CoCl2dissolved in 1000 parts by weight of water, and was labeled as S6, wherein the particle size of the Co3Se4particles was about 60 nm.

[0094] (2) Preparation of a battery negative electrode sheet:

[0095] A battery negative electrode sheet was prepared according to the method of step (2) of Example 1, with S6 as the negative electrode material.

[0096] (3) Preparation of sodium-ion battery:

[0097] The sodium-ion battery was prepared according to the method of step (3) of Example 1, taking the battery negative plate obtained in step (2) of Example 6 as the negative electrode, to obtain a battery sample S60.

[0098] Example 7

[0099] (1) Preparation of sodium-ion battery composite negative electrode material:

[0100] Co3Se4@HC material with mass ratio Co3Se4: HC = 2.5: 1 (the total mass of Co3Se4particles is 72% of the total mass of the sodium-ion battery composite negative electrode material) was finally prepared, labeled as S7, wherein the particle size of Co3Se4particles is about 300 nm, by dissolving 20 parts by weight of hard carbon powder (particle size 8 μm) and 230 parts by weight of CoCl2in 1000 parts by weight of water, and preparing the sodium-ion battery composite negative electrode material according to the method of step (1) of Example 1.

[0101] (2) Preparation of battery negative plate:

[0102] The battery negative plate was prepared according to the method of step (2) of Example 1, taking S7 as the negative electrode material.

[0103] (3) Preparation of sodium-ion battery:

[0104] The sodium-ion battery was prepared according to the method of step (3) of Example 1, taking the battery negative plate obtained in step (2) of Example 7 as the negative electrode, to obtain a battery sample S70.

[0105] Comparative Example 1

[0106] (1) Preparation of battery negative plate:

[0107] The battery negative plate was prepared according to the method of step (2) of Example 1, taking HC powder (particle size 8 μm) as the negative electrode material of the sodium-ion battery, labeled as DS1.

[0108] (2) Preparation of sodium-ion battery:

[0109] The sodium-ion battery was prepared according to the method of step (3) of Example 1, taking the battery negative plate obtained in step (1) of Comparative Example 1 as the negative electrode, to obtain a battery sample DS10.

[0110] Comparative Example 2

[0111] (1) Preparation of battery negative plate:

[0112] The battery negative plate was prepared according to the method of step (2) of Example 1, taking Co3Se4particles (particle size 150 nm) as the negative electrode material of the sodium-ion battery, labeled as DS2.

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

[0114] The sodium-ion battery was prepared according to the method of step (3) of Example 1, taking the battery anode sheet obtained in step (1) of Comparative Example 2 as the anode, to obtain battery sample DS20.

[0115] Comparative Example 3

[0116] (1) Preparation of the sodium-ion battery composite anode material:

[0117] CoCl2-attached hard carbon was obtained by dissolving 20 parts by weight of hard carbon powder (particle size 5 μm) and 120 parts by weight of CoCl2 in 1000 parts by weight of water, filtering and drying; the CoCl2-attached hard carbon was mixed with 180 parts by weight of selenium powder and placed in a tube furnace, and the sodium-ion battery composite anode material was prepared according to the method of step (1) of Example 1, to finally obtain CoSe2@HC material with mass ratio CoSe2: HC = 1.1: 1 (the total mass of CoSe2 particles is 52% of the total mass of the sodium-ion battery composite anode material), which is marked as DS3, wherein the particle size of the CoSe2 particles is about 130 nm.

[0118] (2) Preparation of the battery anode sheet:

[0119] The battery anode sheet was prepared according to the method of step (2) of Example 1, taking DS3 as the anode material.

[0120] (3) Preparation of the sodium-ion battery:

[0121] The sodium-ion battery was prepared according to the method of step (3) of Example 1, taking the battery anode sheet obtained in step (2) of Comparative Example 3 as the anode, to obtain battery sample DS30.

[0122] Effect Example

[0123] To provide strong support for the beneficial effects brought by the technical solutions of the embodiments of the present application, the following product performance tests are provided:

[0124] The charge-discharge specific capacity and cycle performance of the sodium-ion battery samples of Examples 1-7 and Comparative Examples 1-3 of the present application were compared and tested, and the results are as follows:

[0125] 1. Charge-discharge specific capacity

[0126] The battery was set to a charge-discharge state, i.e., the sodium was deintercalated from the working electrode, the charge and discharge current density was 0.1 A / g, the charging was stopped at the cut-off voltage of 3.0 V, and the discharging was stopped at the cut-off voltage of 0.01 V, and the first charge-discharge specific capacity was calculated.

[0127] First charge specific capacity (mAh / g) = first charge capacity / mass of active material

[0128] First discharge specific capacity (mAh / g) = first discharge capacity / mass of active material

[0129] 2. Cycle performance

[0130] The battery sample was cycled 100 times at a current of 0.1 A / g in a charge-discharge state, and the cycle capacity retention rate was tested to evaluate the cycle performance.

[0131] 3. Rate performance

[0132] The battery sample was tested for charge-discharge at a large current density (1.0 A / g), and the rate capacity retention rate was tested to evaluate the rate performance.

[0133] The first charge-discharge specific capacity results are shown in Table 1.

[0134] Table 1. First charge-discharge specific capacity test results of batteries corresponding to different sodium-ion battery negative electrode materials

[0135]

[0136] From the first charge-discharge specific capacity test results in Table 1, it can be known that the S1-S7 samples in the embodiments 1-7 have higher cycle, rate reversible capacity and capacity retention rate than the DS1 sample in the comparative example 1, indicating that the Co3Se4@HC sample provided by the embodiments can exhibit higher sodium storage capacity than the HC sample during battery use. When used as a negative electrode of a sodium-ion battery with the same mass of positive electrode material, the Co3Se4@HC sample can be added in a smaller amount.

[0137] In addition, from the test results in Table 1, it can be seen that the Co3Se4@HC sample in the embodiments 1-7 has higher cycle, rate reversible capacity and capacity retention rate than the DS20 sample in the comparative example 2, indicating that the Co3Se4@HC sample provided by the embodiments can effectively avoid sodium loss and improve the use efficiency of the positive electrode material.

[0138] From the test results in Table 1, it can be seen that the S2 sample in the embodiment 2 with the same mass ratio of loaded selenium compound has higher cycle, rate reversible capacity and capacity retention rate than the DS3 sample in the comparative example 3, indicating that the Co3Se4@HC sample provided by the embodiments can exhibit more excellent sodium storage performance than the CoSe2@HC sample during battery use.

[0139] The above merely describes preferred embodiments of the present application, and is not used to limit the present application, any modification, equivalent replacement and improvement within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A sodium-ion battery composite anode material, characterized in that, The sodium ion battery composite negative electrode material comprises hard carbon and Co3Se4 particles combined on the hard carbon.

2. The sodium-ion battery composite anode material of claim 1, wherein, The Co3Se4 particles are distributed on the surface of the hard carbon and in the open pores of the hard carbon.

3. The sodium-ion battery composite anode material of claim 1 or 2, wherein, The total mass of the Co3Se4 particles is 21% to 70% of the total mass of the sodium ion battery composite negative electrode material.

4. The sodium-ion battery composite anode material of any one of claims 1-3, wherein, The particle size of the hard carbon is 1 μm to 70 μm.

5. The sodium-ion battery composite anode material of any one of claims 1-4, wherein, The particle size of the Co3Se4 particles is 50 nm to 1 μm.

6. The sodium-ion battery composite anode material of any one of claims 1-5, wherein, The hard carbon comprises one or both of resin hard carbon and biomass hard carbon.

7. The sodium-ion battery composite anode material of any one of claims 1-6, wherein, The Co3Se4 particles are combined with the hard carbon by chemical bonding.

8. A method for preparing a sodium-ion battery composite anode material, characterized in that, The method comprises the following steps: adding hard carbon and a soluble cobalt salt to water, stirring, and then standing and filtering to obtain hard carbon with cobalt ions attached thereto; mixing the hard carbon with cobalt ions attached thereto and selenium powder, and performing a selenization reaction under an inert atmosphere to obtain Co3Se4, thereby preparing a sodium ion battery composite negative electrode material comprising hard carbon and Co3Se4 particles combined on the hard carbon.

9. The method for preparing the sodium-ion battery composite negative electrode material as described in claim 8, characterized in that, The soluble cobalt salt comprises one or more of Co(NO3)2, CoCl2, CoSO4, CoS2 and CoF2.

10. The method of producing a sodium-ion battery composite anode material according to claim 8 or 9, characterized in that, The selenization reaction process is performed at a temperature of 700°C to 800°C for 1 h to 4 h.

11. A battery negative electrode sheet, characterized by, The sodium ion battery composite negative electrode material as claimed in any one of claims 1 to 7.

12. A sodium-ion battery, characterized in that, The sodium ion battery composite negative electrode material as claimed in any one of claims 1 to 7.

13. An electrical device, characterized by The sodium ion battery composite negative electrode material as claimed in any one of claims 1 to 7.

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