Negative active material and preparation method thereof, negative pole piece, battery and electric equipment

Abstract

The invention provides a negative active material and a preparation method thereof, a negative pole piece, a battery and electric equipment. And the negative electrode active material comprises a FeIn2S4 / FeS heterostructure. The FeIn2S4 / FeS heterostructure in the negative electrode active material can improve the conductivity of the negative electrode active material and the capability of storing active ions, so that the negative electrode active material with excellent cycle performance and rate capability is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a negative electrode active material, a preparation method thereof, a negative electrode sheet, a battery and an electric device. BACKGROUND

[0002] Metal sulfides are a kind of battery negative electrode materials that are currently popular in research. Compared with oxides of the same metal, sulfides of the same metal generally have higher electrical conductivity. However, the electrical conductivity of metal sulfides, although stronger than that of oxides, is still relatively low, and the ability of metal sulfides to store active ions is generally poor, for example, the performance of storing sodium or lithium is poor, which affects the use performance of the battery. SUMMARY

[0003] In view of this, the present application provides a negative electrode active material, a preparation method thereof, a negative electrode sheet, a battery and an electric device.

[0004] In a first aspect, the present application provides a negative electrode active material, which comprises a FeIn2S4 / FeS heterostructure.

[0005] Optionally, the FeIn2S4 / FeS heterostructure comprises FeIn2S4 and FeS, and the molar ratio of the FeIn2S4 to the FeS is 0.5-2.

[0006] Optionally, the negative electrode active material further comprises a carbon material, and the carbon material is dispersed on the surface and inside of the FeIn2S4 / FeS heterostructure.

[0007] Optionally, the mass content of the carbon material in the negative electrode active material is 10%-20%.

[0008] Optionally, the negative electrode active material has a cauliflower structure, and the cauliflower structure comprises a plurality of rod-like structures, and each rod-like structure comprises a rod structure and a plurality of rod structures on the surface of the rod structure.

[0009] Further, the length of the rod-like structure is 2 μm-4 μm.

[0010] Further, the length of the rod structure is 50 nm-200 nm.

[0011] Optionally, the particle size D50 of the negative electrode active material is 2 μm-3 μm.

[0012] Optionally, the specific surface area of the negative electrode active material is 10 m 2 / g-25 m 2 / g.

[0013] In a second aspect, the present application provides a preparation method of a negative electrode active material, which comprises:

[0014] the iron source and the indium source are mixed to form a mixed powder, a molar ratio of iron element in the iron source to indium element in the indium source being greater than or equal to 0.6;

[0015] the mixed powder and a sulfur source are mixed to form the negative electrode active material of the first aspect through a second heating.

[0016] Optionally, the iron source includes at least one of ferric nitrate, ferric oxalate and ferrous citrate.

[0017] Optionally, the indium source includes at least one of indium chloride and indium oxide.

[0018] Optionally, the sulfur source includes at least one of sublimed sulfur, sulfur powder and thiourea.

[0019] Optionally, the first heating includes processing at 160-220℃ for 8-24h.

[0020] Optionally, the second heating includes processing at 250-400℃ for 2-5h under an inert atmosphere, and then processing at 600-800℃ for 2-5h.

[0021] Optionally, the mixing of the iron source and the indium source further includes mixing the iron source, the indium source and a carbon source.

[0022] Further, the carbon source includes at least one of polyvinylpyrrolidone, polyethylene, polypyrrole, polydopamine and glucose.

[0023] In a third aspect, the present application provides a negative electrode tab, including a negative electrode current collector and a negative electrode active material layer arranged on a surface of the negative electrode current collector, the negative electrode active material layer including the negative electrode active material of the first aspect or the negative electrode active material prepared by the preparation method of the second aspect.

[0024] In a fourth aspect, the present application provides a battery, including a positive electrode tab and the negative electrode tab of the third aspect.

[0025] In a fifth aspect, the present application provides a power consumption device, including the battery of the fourth aspect.

[0026] The FeIn2S4 / FeS heterostructure in the negative electrode active material of the present application can improve the electrical conductivity and the ability to store active ions of the negative electrode active material, thereby obtaining a negative electrode active material with excellent cycle performance and rate performance, and the preparation method of the negative electrode active material is simple and convenient to operate, which is conducive to the use of the negative electrode active material; the negative electrode tab and the battery with the negative electrode active material have excellent electrochemical performance, which is conducive to the use of the battery in the power consumption device. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced. The specific embodiments described herein are only used to explain the present application and not used to limit the present application.

[0028] Figure 1 A preparation method of the negative active material is provided for an embodiment of the present application.

[0029] Figure 2 A preparation method of the negative active material is provided for another embodiment of the present application.

[0030] Figure 3 A cross-sectional schematic diagram of the negative electrode sheet is provided for an embodiment of the present application.

[0031] Figure 4 A scanning electron microscope (SEM) image of the negative active material prepared in Example 1 is shown in FIG. 1. Figure 4 The scale in FIG. 1 (a) is 1 μm, Figure 4 The scale in FIG. 1 (b) is 200 nm.

[0032] Figure 5 A transmission electron microscope (TEM) image of the negative active material prepared in Example 1 is shown in FIG. 2.

[0033] Figure 6 A scanning electron microscope (SEM) image of the negative active material prepared in Example 2 is shown in FIG. 3.

[0034] Figure 7 A scanning electron microscope (SEM) image of the negative active material prepared in Comparative Example 1 is shown in FIG. 4.

[0035] Figure 8 A scanning electron microscope (SEM) image of the negative active material prepared in Comparative Example 2 is shown in FIG. 5.

[0036] Figure 9 A scanning electron microscope (SEM) image of the negative active material prepared in Comparative Example 3 is shown in FIG. 6.

[0037] Figure 10 An X-ray powder diffraction pattern is shown in FIG. 7.

[0038] Figure 11 Cycle capacity detection results of the batteries prepared in Example 1, Comparative Example 1 and Comparative Example 3 are shown in Table 1.

[0039] Figure 12 Charge-discharge cycle performance results of the battery prepared in Example 1 are shown in Table 2.

[0040] Figure 13 Rate performance results of the batteries prepared in Example 1, Comparative Example 1 and Comparative Example 3 are shown in Table 3. DETAILED DESCRIPTION

[0041] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0042] The present application provides a negative electrode active material, comprising a FeIn2S4 / FeS heterostructure. The FeIn2S4 / FeS heterostructure has two different crystal structures of FeIn2S4 and FeS, the built-in electric field of the heterostructure can accelerate the movement of active ions and electrons, improve the electrical conductivity, and the electrons can be redistributed around the heterojunction, can adsorb more positively charged active ions, the heterojunction provides additional movement sites and storage sites for active ions (such as lithium ions, sodium ions, etc.), thereby facilitating to improve the cycle performance and rate performance of the negative electrode active material. Compared with the physical coating method to improve the performance of the negative electrode active material, the present application regulates the negative electrode active material through the heterostructure composed of double-metal sulfide, which can essentially improve and enhance the performance of the negative electrode active material, avoids the influence of coating on the active ion storage capacity of the negative electrode active material, and is beneficial to the use of the negative electrode active material.

[0043] The interface of a heterostructure constructed by combining different components with different crystal structures can produce electronic interactions and induce synergistic effects between different parts. The FeIn2S4 / FeS heterostructure has two different lattices of FeIn2S4 and FeS, both of which have different work functions. By forming a heterostructure through suitable electron flow, the different electron binding energies enable electron flow between the two, inducing a built-in electric field, accelerating the diffusion kinetics of active ions and electrons, reducing the active ion diffusion barrier, and the charge redistribution in the heterostructure can induce more active sites for energy storage, improving the reversible capacity of the negative electrode sheet. FeIn2S4 and FeS are transition metal sulfides, and their open framework structure, stable thermodynamic properties, high specific capacity, and high theoretical active ion storage capacity are conducive to the preparation of high-capacity negative electrode active materials. At the same time, the synergistic effect of FeIn2S4 and FeS can improve the structural stability and electrochemical performance of the negative electrode active material. The inventors analyzed the FeIn2S4 / FeS heterostructure by first principles, and found that the FeIn2S4 / FeS heterostructure formed by FeIn2S4 and FeS can improve the electrical conductivity through the establishment of a built-in electric field, and the ability to store active ions at the interface is better than that of FeIn2S4 and FeS. It can be understood that the FeIn2S4 / FeS heterostructure or the negative electrode active material can be detected by transmission electron microscopy (TEM), and by observing the interface of the two composite materials, which is a heterojunction, it is proved that the FeIn2S4 / FeS heterostructure is formed. FeIn2S4 and FeS can also be analyzed by theoretical analysis (such as density functional theory, etc.), which can prove that the FeIn2S4 and FeS composite material can form a heterojunction, and then form a FeIn2S4 / FeS heterostructure.

[0044] In an embodiment of the present application, the FeIn2S4 / FeS heterostructure includes FeIn2S4 and FeS, and the molar ratio of FeIn2S4 to FeS is 0.5-2, which is conducive to the synergistic effect of FeIn2S4 and FeS in the FeIn2S4 / FeS heterostructure, and improves the electrical conductivity and active ion storage capacity of the negative electrode active material. Specifically, the molar ratio of FeIn2S4 to FeS in the FeIn2S4 / FeS heterostructure can be, but is not limited to, 0.5, 0.6, 0.8, 0.9, 1, 1.2, 1.3, 1.5, 1.7, 1.8, 1.9 or 2, etc.

[0045] In an embodiment of the present application, the negative active material further comprises a carbon material, and the carbon material is dispersed on the surface and inside of the FeIn2S4 / FeS heterostructure. The carbon material in the negative active material is randomly distributed on the surface and inside of the heterostructure, and the carbon material in the negative active material can not only relieve the volume expansion of the negative active material during the charging and discharging process and improve the structural stability of the negative active material during the cycle process, but also further improve the electrical conductivity of the negative active material, which is beneficial to the use of the negative active material. In an embodiment of the present application, the carbon material is amorphous carbon. In an embodiment of the present application, the mass content of the carbon material in the negative active material is 10% to 20%, which is beneficial to improving the use performance of the negative active material. Specifically, the mass content of the carbon material in the negative active material can be, but is not limited to, 10%, 12%, 13%, 15%, 17%, 18% or 20%, etc.

[0046] In an embodiment of the present application, the particle size D50 of the negative active material is 2 μm to 3 μm. Specifically, the particle size D50 of the negative active material can be, but is not limited to, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm or 3 μm, etc.

[0047] In an embodiment of the present application, the specific surface area of the negative active material is 10 m 2 / g to 25 m 2 / g. The negative active material has a high specific surface area, which is beneficial to reducing the volume expansion and improving the use performance of the negative active material. Specifically, the specific surface area of the negative active material can be, but is not limited to, 10 m 2 / g, 11 m 2 / g, 12 m 2 / g, 15 m 2 / g, 17 m 2 / g, 18 m 2 / g, 20 m 2 / g, 21 m 2 / g, 22 m 2 / g, 23 m 2 / g, 24 m 2 / g or 25 m 2 / g, etc.

[0048] In an embodiment of the present application, the negative electrode active material has a cauliflower structure, and the cauliflower structure includes a plurality of rod-like structures, and each rod-like structure includes a rod structure and a plurality of rod structures on the surface of the rod structure. The negative electrode active material has a cauliflower structure, which can provide an effective diffusion channel for the transmission of electrons and active ions, and can also reduce the volume expansion and improve the use performance of the negative electrode active material. It can be understood that when the negative electrode active material is a FeIn2S4 / FeS heterostructure, the FeIn2S4 / FeS heterostructure has a cauliflower structure; when the negative electrode active material includes a FeIn2S4 / FeS heterostructure and a carbon material, the FeIn2S4 / FeS heterostructure and the negative electrode active material both have a cauliflower structure, and the carbon material has little effect on the morphology of the negative electrode active material. In an embodiment of the present application, the rod structures can be located at the end of the rod structure.

[0049] In an embodiment of the present application, the length of the rod-like structure is 2-4 μm. Specifically, the length of the rod-like structure can be, but is not limited to, 2 μm, 2.5 μm, 3 μm, 3.5 μm or 4 μm, etc. In an embodiment of the present application, the length of the rod structure is 50-200 nm. The nanoscale rod structure is beneficial to increase the direct contact area with the electrolyte, beneficial to the infiltration of the electrolyte, shorten the diffusion path of the active ions, and beneficial to the transportation of the active ions. Specifically, the length of the rod structure can be, but is not limited to, 50 nm, 75 nm, 90 nm, 100 nm, 120 nm, 130 nm, 150 nm, 160 nm, 175 nm, 180 nm or 200 nm, etc.

[0050] Please refer to Figure 1 The preparation method of the negative electrode active material provided in an embodiment of the present application includes:

[0051] S101: After mixing the iron source and the indium source, a mixed powder is formed by first heating, and the molar ratio of iron elements in the iron source to indium elements in the indium source is greater than or equal to 0.6.

[0052] S102: The mixed powder and the sulfur source are mixed, and the negative electrode active material is formed by second heating, and the negative electrode active material includes a FeIn2S4 / FeS heterostructure.

[0053] The preparation method of the negative electrode active material provided in the present application is simple to operate, and the negative electrode active material in any of the above embodiments can be prepared by the preparation method, which is beneficial to the use of the negative electrode active material.

[0054] In S101, the iron source and the indium source are mixed and heated to form a mixed powder, and the molar ratio of iron elements in the iron source to indium elements in the indium source is greater than or equal to 0.6, so as to ensure the formation of the FeIn2S4 / FeS heterostructure. Specifically, the molar ratio of iron elements in the iron source to indium elements in the indium source can be, but is not limited to, 0.6 or more, 0.65 or more, 0.66 or more, 0.7 or more, 0.8 or more, etc.

[0055] In the present application, the iron source can be at least one of a divalent iron source and a trivalent iron source. In an embodiment of the present application, the iron source includes at least one of ferric nitrate, ferric oxalate, and ferrous citrate. The above-mentioned iron source is easy to obtain and has excellent mixing performance, which is conducive to uniform mixing with the indium source.

[0056] In an embodiment of the present application, the indium source includes at least one of indium chloride and indium oxide. The above-mentioned indium source is easy to obtain and has excellent mixing performance, which is conducive to uniform mixing with the iron source.

[0057] In an embodiment of the present application, the first heating includes processing at 160-220°C for 8-24h. Specifically, the temperature of the first heating can be, but is not limited to, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, or 220°C, etc., and the time of the first heating can be, but is not limited to, 8h, 12h, 15h, 18h, 20h, 23h, or 24h, etc. The mixed powder formed by the first heating has iron element-containing hydroxides, oxides, hydrates, etc., and indium elements, which can react with the sulfur source in the second heating to form the negative electrode active material.

[0058] In S102, the mixed powder and the sulfur source are reacted under the second heating to form the negative electrode active material.

[0059] In an embodiment of the present application, the sulfur source includes at least one of sublimed sulfur, sulfur powder, and thiourea. The above-mentioned iron source is easy to obtain and reacts with the mixed powder, which is conducive to the formation of the FeIn2S4 / FeS heterostructure.

[0060] In an embodiment of the present application, the second heating includes processing at 250-400°C for 2-5h, and then processing at 600-800°C for 2-5h in an inert atmosphere (such as argon, etc.). Specifically, the second heating includes processing at 250°C, 280°C, 300°C, 330°C, 350°C, 375°C, 390°C, or 400°C, etc. for 2h, 3h, 4h, or 5h, etc., and then processing at 600°C, 630°C, 650°C, 680°C, 700°C, 725°C, 750°C, 780°C, or 800°C for 2h, 3h, 4h, or 5h, etc. In an embodiment of the present application, the mixed powder and the sulfur source can be uniformly mixed in a crucible and then placed in a tube furnace or other heating device for the second heating.

[0061] Please refer toFigure 2 The preparation method of the negative electrode active material provided in another embodiment of the present application comprises:

[0062] S201: After mixing the iron source, the indium source and the carbon source, a mixed powder is formed through first heating, and the molar ratio of iron elements in the iron source to indium elements in the indium source is greater than or equal to 0.6.

[0063] S202: The mixed powder and a sulfur source are mixed, and a negative electrode active material is formed through second heating, wherein the negative electrode active material comprises a FeIn2S4 / FeS heterostructure and a carbon material.

[0064] In S202, the related description can be referred to in S102 described above, and will not be repeated here.

[0065] In S201, the iron source and the indium source are mixed with the carbon source, so that the negative electrode active material containing the carbon material can be prepared.

[0066] In an embodiment of the present application, the carbon source comprises at least one of polyvinylpyrrolidone, polyethylene, polypyrrole, polydopamine and glucose. The above-mentioned carbon source has good mixing performance with the iron source and the indium source, which is beneficial to the preparation of the negative electrode active material. The carbon source does not change in the mixed powder, and is cracked to form a carbon material under the action of high temperature in the second heating process, and is distributed on the surface and inside of the FeIn2S4 / FeS heterostructure. In an embodiment of the present application, the carbon source comprises polyvinylpyrrolidone, which can not only play the role of the carbon source, but also play the role of a surfactant, thereby improving the uniformity of the morphology of the negative electrode active material.

[0067] In an embodiment of the present application, the carbon source is mixed with a solvent (such as ethylene glycol) to form a solution, the iron source is added into the solution and stirred uniformly, and then the indium source is added to form a mixed solution. It can be understood that the indium source can also be added into the solution and stirred uniformly, and then the iron source is added. The mixed solution can be subjected to the first heating process in a heating device such as a reaction kettle.

[0068] Please refer to Figure 3 A cross-sectional schematic view of the negative electrode tab provided in an embodiment of the present application is shown, wherein the negative electrode tab 100 comprises a negative electrode current collector 110 and a negative electrode active material layer 120 arranged on the surface of the negative electrode current collector 110, and the negative electrode active material layer 120 comprises the negative electrode active material in any of the above-mentioned embodiments. The negative electrode tab has excellent cycle performance and rate performance, which is beneficial to its use in a battery.

[0069] In an embodiment of the present application, the mass content of the negative active material in the negative active material layer is greater than or equal to 80%, which is beneficial to improve the electrochemical performance of the negative electrode. Specifically, the mass content of the negative active material in the negative active material layer is greater than or equal to 80%, 83%, 85%, 87%, 90%, 92%, 95%, 97% or 98%, etc.

[0070] In an embodiment of the present application, the negative active material layer can further include at least one of a negative conductive agent and a negative binder. Specifically, the negative conductive agent can include, but is not limited to, at least one of conductive carbon black, carbon nanotubes, carbon fibers, carbon black and graphite; and the negative binder can include, but is not limited to, at least one of polytetrafluoroethylene, polyvinylidene fluoride, sodium carboxymethyl cellulose, butyl rubber latex, butyronitrile rubber. In an embodiment of the present application, the mass content of the negative conductive agent in the negative active material layer is less than or equal to 5%. Specifically, the mass content of the negative conductive agent in the negative active material layer can be, but is not limited to, 0.1%, 0.5%, 1%, 2%, 3%, 4% or 5%, etc. In an embodiment, the mass content of the negative conductive agent in the negative active material layer can be 0.1%-5%. In an embodiment of the present application, the mass content of the negative binder in the negative active material layer is less than or equal to 10%. Specifically, the mass content of the negative binder in the negative active material layer can be, but is not limited to, 0.1%, 0.5%, 2%, 4%, 5%, 7%, 8% or 9%, etc. In an embodiment, the mass content of the negative binder in the negative active material layer is 0.1%-10%.

[0071] In an embodiment of the present application, the thickness of the negative active material layer is 10-100 μm, which can ensure the electrochemical performance of the negative electrode, and at the same time, will not increase the weight of the negative electrode too much. Specifically, the thickness of the negative active material layer can be, but is not limited to, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm, etc.

[0072] In an embodiment of the present application, the negative current collector is selected from a metal foil or an alloy foil. The metal foil includes copper, aluminum, nickel, iron, or cobalt foil, and the alloy foil includes an alloy of at least one of copper, aluminum, nickel, iron, and cobalt or stainless steel. In an embodiment of the present application, the negative current collector is made of at least one of copper, aluminum, nickel, iron, and cobalt or stainless steel. Specifically, the negative current collector can be a copper foil. In an embodiment of the present application, at least one of the negative binder and the negative conductive agent is mixed with the negative active material in a solvent to form a negative slurry, the negative slurry is coated on the surface of the negative current collector, and the negative electrode sheet is obtained after drying. The solvent can include, but is not limited to, at least one of ethanol, toluene, xylene, anisole, acetonitrile, heptane, decane, ethyl acetate, ethyl propionate, butyl butyrate, N-methyl pyrrolidone, acetone, water, and the like.

[0073] The present application provides a battery including the negative electrode sheet of any one of the above embodiments. The battery with the negative electrode has excellent rate capability and cycle performance, which is beneficial to the use of the battery. Specifically, the battery can be, but is not limited to, a lithium ion battery, a sodium ion battery, and the like.

[0074] In an embodiment of the present application, the positive electrode sheet includes a positive current collector and a positive active material layer disposed on the surface of the positive current collector. In an embodiment of the present application, the positive current collector is selected from a metal foil or an alloy foil. The metal foil includes copper, titanium, aluminum, platinum, iridium, ruthenium, nickel, tungsten, tantalum, gold, or silver foil, and the alloy foil includes stainless steel or an alloy containing at least one of copper, titanium, aluminum, platinum, iridium, ruthenium, nickel, tungsten, tantalum, gold, and silver. Specifically, the positive current collector can be an aluminum foil.

[0075] In an embodiment of the present application, the positive electrode active material layer comprises at least one of a positive electrode binder and a positive electrode conductive agent, and a positive electrode active material. Specifically, the positive electrode active material can be a lithium battery positive electrode active material, a sodium battery positive electrode active material, the lithium battery positive electrode active material comprising at least one of lithium iron phosphate, lithium iron manganese phosphate, lithium cobaltate, lithium manganate, lithium nickel cobalt manganate, and lithium nickel cobalt aluminate, and the sodium battery positive electrode active material comprising at least one of a layered structure oxide, a Prussian blue compound, and a polyanion compound; the positive electrode conductive agent can comprise, but is not limited to, at least one of conductive carbon black, carbon nanotubes, carbon fibers, carbon black, and graphite; and the positive electrode binder can comprise, but is not limited to, at least one of polytetrafluoroethylene, polyvinylidene fluoride, sodium carboxymethyl cellulose, butyl rubber latex, and butyronitrile rubber. In an embodiment of the present application, the mass content of the positive electrode active material in the positive electrode active material layer is greater than or equal to 80%, which is beneficial to improving the electrochemical performance of the positive electrode. Specifically, the mass content of the positive electrode active material in the positive electrode active material layer can be greater than or equal to 82%, 85%, 88%, 90%, 93%, 95%, 97%, or 98%, etc. In an embodiment of the present application, the mass content of the positive electrode conductive agent in the positive electrode active material layer is less than or equal to 5%. Specifically, the mass content of the positive electrode conductive agent in the positive electrode active material layer can be, but is not limited to, 0.1%, 0.5%, 1%, 2%, 3%, 4%, or 5%, etc. In an embodiment of the present application, the mass content of the positive electrode binder in the positive electrode active material layer is less than or equal to 10%. Specifically, the mass content of the positive electrode binder in the positive electrode active material layer can be, but is not limited to, 0.1%, 0.5%, 2%, 4%, 5%, 7%, 8%, or 9%, etc. In the present application, at least one of the positive electrode binder and the positive electrode conductive agent can be mixed with the positive electrode active material in a solvent to form a positive electrode slurry, the positive electrode slurry is coated on the surface of the positive electrode current collector, and the positive electrode slurry is dried to obtain a positive electrode sheet. The solvent can comprise, but is not limited to, at least one of ethanol, toluene, xylene, anisole, acetonitrile, heptane, decane, ethyl acetate, ethyl propionate, butyl butyrate, N-methyl pyrrolidone, and acetone.

[0076] In an embodiment of the present application, the battery further comprises a separator arranged between the positive electrode and the negative electrode. The present application does not have special restrictions on the separator, and any material that can be used as a battery separator in the art can be used, but is not limited to. In an embodiment of the present application, the battery further comprises an electrolyte, at least part of the positive electrode sheet is immersed in the electrolyte, and at least part of the negative electrode sheet is immersed in the electrolyte, so as to ensure the normal operation of the battery. In an embodiment of the present application, the electrolyte comprises an electrolyte and an organic solvent. The electrolyte can be selected according to the type of the battery, for example, the electrolyte in a lithium ion battery is a lithium salt, and the electrolyte in a sodium ion battery is a sodium salt; and the organic solvent can comprise, but is not limited to, at least one of ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, vinylene carbonate, and fluoroethylene carbonate.

[0077] The application also provides a power-using device comprising the battery in any of the above embodiments. Specifically, the power-using device can be a vehicle, an electronic device, an energy storage system, etc., and the battery can be arranged in the power-using device in the form of a single battery, a battery module, a battery pack, etc.

[0078] The effects of the technical solutions of the application are further described below through specific examples.

[0079] Embodiment 1

[0080] A preparation method of a negative electrode active material comprises the following steps:

[0081] 500 mg of polyvinylpyrrolidone is added to 60 mL of ethylene glycol solvent, and stirred vigorously for 2 h until the polyvinylpyrrolidone is dissolved; 4 mmol of ferrous sulfate particles are ground in a mortar and then added to the above solvent and stirred slowly for 1 h, and then 4 mmol of indium chloride is added and stirred slowly for another 1 h. The uniformly mixed solution is placed in a reaction kettle and heated at 180℃ for 10 h, and then cooled and centrifuged to collect the powder. 200 mg of the powder is mixed with 400 mg of sublimed sulfur and placed in a crucible, and the crucible is placed in a tube furnace under the protection of an inert atmosphere, and then heated at 400℃ for 3 h and then at 600℃ for 2 h to obtain the negative electrode active material.

[0082] The negative electrode active material comprises a FeIn2S4 / FeS heterostructure and carbon material dispersed on the surface and inside the FeIn2S4 / FeS heterostructure, wherein the molar ratio of FeIn2S4 and FeS is 1:1, and the scanning electron microscope image thereof is as shown in Figure 4 , wherein Figure 4 The scale in (a) of Figure 4 is 1 μm, The scale in (b) of 2 is 200 nm, and it can be seen that the negative electrode active material has a cauliflower structure, the particle size D50 is 2.5 μm, and the specific surface area of the negative electrode active material is 18 m Figure 5 / g, and the transmission electron microscope image thereof is as shown in Figure 5 , and the two-phase interface (indicated by the line in the figure) can be clearly observed, indicating that a heterostructure is formed.

[0083] Embodiment 2

[0084] The difference from Embodiment 1 is that the amount of indium chloride added is 2 mmol, and the molar ratio of FeIn2S4 and FeS in the prepared negative electrode active material is 1:3, and the scanning electron microscope image thereof is as shown in Figure 6 , the particle size D50 is 3 μm, and the specific surface area of the negative electrode active material is 15 m 2 / g.

[0085] Embodiment 3

[0086] The difference from Example 1 is that the amount of indium chloride added is 6 mmol, the molar ratio of FeIn2S4 and FeS in the prepared negative electrode active material is 3:1, the particle size D50 is 2.1 μm, and the specific surface area of the negative electrode active material is 22 m 2 / g.

[0087] Example 4

[0088] The difference from Example 1 is that polyvinylpyrrolidone is not added, and the prepared negative electrode active material is a FeIn2S4 / FeS heterostructure.

[0089] Comparative Example 1

[0090] The difference from Example 1 is that indium chloride is not added, and the prepared negative electrode active material includes FeS and carbon material dispersed on the surface and inside of the FeS, and the scanning electron microscope image thereof is as shown in Figure 7 It can be seen that the morphology of the negative electrode active material is a micron sphere with a smooth surface.

[0091] Comparative Example 2

[0092] The difference from Example 1 is that ferrous sulfate is not added, and the amount of indium chloride added is 8 mmol, and the prepared negative electrode active material includes In2S3 and carbon material dispersed on the surface and inside of the In2S3, and the scanning electron microscope image thereof is as shown in Figure 8 It can be seen that the negative electrode active material is a micron sphere formed by multiple sheets.

[0093] Comparative Example 3

[0094] The difference from Example 1 is that the amount of indium chloride added is 8 mmol, and the prepared negative electrode active material includes FeIn2S4 and carbon material dispersed on the surface and inside of the FeIn2S4, and the scanning electron microscope image thereof is as shown in Figure 9 It can be seen that the negative electrode active material is a nanoflower formed by multiple sheets.

[0095] Performance detection

[0096] The negative electrode active materials prepared in Example 1 and Comparative Examples 1-3 are detected by an X-ray powder diffractometer, and the results are as shown in Figure 10 The "PDF#75-0602", "PDF#51-0934", and "PDF#51-1160" in the figure are the XRD detection peak positions of the FeS, FeIn2S4, and In2S3 standards, respectively, and it can be seen that the negative electrode active material prepared in Comparative Example 1 only contains FeS, the negative electrode active material prepared in Comparative Example 2 only contains In2S3, the negative electrode active material prepared in Comparative Example 3 only contains FeIn2S4, and the negative electrode active material prepared in Example 1 contains FeIn2S4 and FeS.

[0097] The negative electrode active material prepared in the above examples and comparative examples was mixed with conductive carbon black and a binder carboxymethyl cellulose at a mass ratio of 0.9:0.05:0.05 to prepare a negative electrode slurry, which was uniformly coated on an aluminum foil using a coating machine, and then rolled to prepare a negative electrode sheet. A metal sodium was made into a sheet with a certain thickness. A separator was made of polypropylene, and an electrolyte was 1 mmol of sodium hexafluorophosphate dissolved in ethylene carbonate and diethyl carbonate. A battery was assembled. The cycle capacity of the batteries prepared in Example 1, Comparative Example 1 and Comparative Example 3 was detected by a blue battery test system, wherein the detection was carried out at room temperature, 0.2V-2.4V voltage and 1A / g current density, and the results are shown in Table 1. Figure 11 As can be seen, compared with Comparative Examples 1 and 3 using monomer materials as negative electrode active materials, the battery prepared in Example 1 using FeIn2S4 / FeS heterostructure as negative electrode active material has better cycle stability and capacity. The charge-discharge cycle performance of the battery prepared in Example 1 was detected by a blue battery test system, wherein the detection was carried out at room temperature, 0.2V-2.4V voltage and 4A / g current density, and the results are shown in Table 2. Figure 12 As can be seen, the battery prepared in Example 1 still has excellent cycle stability under the condition of large current density. The rate performance of the batteries prepared in Example 1, Comparative Example 1 and Comparative Example 3 was detected by a blue battery test system, wherein the detection was carried out at room temperature, 0.2V-2.4V voltage and different current densities, and the results are shown in Table 3. Figure 13 As can be seen, compared with Comparative Examples 1 and 3, the battery prepared in Example 1 has better rate performance. Therefore, the negative electrode active material with FeIn2S4 / FeS heterostructure of the present application can improve the cycle performance and rate performance of the battery, and obtain a battery with excellent electrochemical performance, which is beneficial to the use of the battery.

[0098] The above is the preferred embodiment of the present application, but it cannot be understood as limiting the scope of the present application. It should be noted that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which are also considered as the protection scope of the present application.

Claims

1. A negative electrode active material, characterized in that, The negative electrode active material includes a FeIn2S4 / FeS heterostructure.

2. The negative electrode active material as described in claim 1, characterized in that, The FeIn2S4 / FeS heterostructure comprises FeIn2S4 and FeS, wherein the molar ratio of FeIn2S4 to FeS is 0.5-2.

3. The negative electrode active material as described in claim 1, characterized in that, The negative electrode active material also includes carbon material, which is dispersed on the surface and inside the FeIn2S4 / FeS heterostructure.

4. The negative electrode active material as described in claim 3, characterized in that, The carbon material in the negative electrode active material has a mass content of 10%-20%.

5. The negative electrode active material as described in claim 1, characterized in that, The negative electrode active material has a cauliflower structure, which includes multiple rod-like structures, including rod-like structures and multiple rod-like structures located on the surface of the rod-like structures. The length of the rod-like structure is 2μm-4μm; The length of the rod-shaped structure is 50nm-200nm.

6. The negative electrode active material as described in claim 1, characterized in that, The particle size D50 of the negative electrode active material is 2μm-3μm; The specific surface area of ​​the negative electrode active material is 10m². 2 / g-25m 2 / g.

7. A method for preparing a negative electrode active material, characterized in that, include: After mixing iron source and indium source, a mixed powder is formed by first heating, wherein the molar ratio of iron element in iron source to indium element in indium source is greater than or equal to 0.6; The mixed powder and sulfur source are mixed and then heated in a second manner to form the negative electrode active material according to any one of claims 1-6.

8. The preparation method according to claim 7, characterized in that, The iron source includes at least one of ferric nitrate, ferric oxalate, and ferrous citrate. The indium source includes at least one of indium chloride and indium oxide; The sulfur source includes at least one of sublimed sulfur, sulfur powder, and thiourea.

9. The preparation method according to claim 7, characterized in that, The first heating includes treatment at 160℃-220℃ for 8h-24h; The second heating process includes treatment at 250℃-400℃ for 2h-5h under an inert atmosphere, followed by treatment at 600℃-800℃ for 2h-5h.

10. The preparation method according to claim 7, characterized in that, The mixture of the iron source and the indium source further includes: a mixture of the iron source, the indium source, and a carbon source; the carbon source includes at least one of polyvinylpyrrolidone, polyethylene, polypyrrole, polydopamine, and glucose.

11. A negative electrode sheet, characterized in that, It includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector, wherein the negative electrode active material layer includes the negative electrode active material according to any one of claims 1-6 or the negative electrode active material prepared by the preparation method according to any one of claims 7-10.

12. A battery, characterized in that, It includes the positive electrode sheet and the negative electrode sheet as described in claim 11.

13. An electrical appliance, characterized in that, Includes the battery as described in claim 12.

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