Zinc diphosphide / zinc phosphate composite material, and preparation method therefor and use thereof

Abstract

The present application belongs to the technical field of battery materials, and in particular relates to a zinc diphosphide / zinc phosphate composite material, and a preparation method therefor and the use thereof. The zinc diphosphide / zinc phosphate composite material of the present application comprises zinc diphosphide, zinc phosphate, and a carbon-based material or a hybrid material thereof, wherein the zinc diphosphide is coated with the zinc phosphate and the carbon-based material or the hybrid material thereof. In the present application, amorphous zinc phosphate is utilized, and therefore the volume expansion of a battery during the processes of charging and discharging can be effectively relieved, and the cycling performance of the material can be improved; in addition, the carbon-based material or the hybrid material thereof coats the zinc diphosphide, and therefore the conductivity of the material can be improved, the rate capability can be enhanced, the problem of a reduction in conductivity due to the presence of zinc phosphate can be solved, and the battery has good rate capability and cycling stability. Moreover, by performing coating with the carbon-based material or the hybrid material thereof, the generation of white phosphorus during ball milling can be reduced, and the thermal stability of the material can be improved; and ball milling further promotes the connection of phosphorus-carbon covalent bonds, thereby improving the electrochemical performance while stabilizing the structure.

Description

A zinc diphosphide / zinc phosphate composite material and its preparation method and application Technical Field

[0001] The present application belongs to the technical field of battery materials, and in particular relates to a zinc diphosphide / zinc phosphate composite material and a preparation method and application thereof. Background Art

[0002] With the growing demand for high energy density energy storage devices, lithium-ion batteries have become the most widely used portable storage devices due to their advantages such as long cycle life, high energy density, and good rate performance. One of the key challenges in designing fast-charging lithium-ion batteries is to construct negative electrode materials with high rate and excellent safety. There are three main types of negative electrode materials for lithium-ion batteries. The first is graphite (theoretical specific capacity 372mAh / g), but since the specific capacity of natural graphite and artificial graphite has been applied to the theoretical limit of the raw materials, it is difficult to improve it. Secondly, the conductivity and capacity of nanostructured carbon-based materials and metal oxides are very low, and the performance is poor. For silicon-carbon negative electrode materials, various lithium-silicon compounds are formed during the silicon-lithium alloying process, the phase change is complex, the volume changes greatly during charging and discharging, and the stability is poor. Finally, for phosphorus-based negative electrode materials, because phosphorus has abundant natural reserves and is cheap, the theoretical specific capacity is as high as 2596mAh / g (Li3P), and the voltage platform is low (Li / Li + , 0.8V). Phosphorus and silicon are both alloyed negative electrodes, but their lithium insertion potential is high. Even when polarized at high rates, it is difficult to reach the lithium deposition potential. However, phosphorus-based negative electrode materials also have obvious disadvantages, such as poor conductivity and high expansion rate. These lead to poor cycle stability during charge and discharge, which greatly limits the application of phosphorus-based negative electrode materials in metal ion batteries.

[0003] Therefore, there is an urgent need to provide a composite material that can effectively alleviate the volume expansion of the battery during the charge and discharge process, improve the cycle performance, conductivity and rate performance of the material, so that the prepared battery has good rate performance and cycle stability. Summary of the Invention

[0004] This application aims to solve one or more technical problems existing in the prior art and at least provide a beneficial alternative or create conditions. This application provides a zinc diphosphide / zinc phosphate composite material that can effectively alleviate the volume expansion of batteries during charge and discharge, improve the material's cycle performance, conductivity, and rate performance, and enable the prepared battery to have good rate performance and cycle stability.

[0005] The inventive concept of the present application is as follows: The composite material of the present application includes zinc diphosphide, zinc phosphate, a carbon-based material, or a hybrid of a carbon-based material; and the zinc diphosphide is coated with the zinc phosphate, the carbon-based material, or a hybrid of a carbon-based material. The presence of zinc phosphate can effectively alleviate the volume expansion of the zinc diphosphide composite material during the charge and discharge process, prevent the composite material from shedding due to volume expansion, improve the material's cycle performance, and to a certain extent, act as an SEI film; in addition, the carbon-based material or its hybrid coating zinc diphosphide can improve the material's conductivity, improve the material's rate performance, and compensate for the problem of decreased conductivity caused by the presence of zinc phosphate, thereby enabling the prepared battery to have good rate performance and cycle stability. At the same time, the coating with the carbon-based material or the carbon-based hybrid can also reduce the generation of white phosphorus during ball milling, improve the material's thermal stability, and thus improve the battery's electrochemical performance.

[0006] Therefore, a first aspect of the present application provides a zinc diphosphide / zinc phosphate composite material.

[0007] Specifically, the zinc diphosphide / zinc phosphate composite material includes zinc diphosphide, zinc phosphate, a carbon-based material, or a hybrid material of a carbon-based material; and the zinc diphosphide is coated by the zinc phosphate, the carbon-based material, or the hybrid material of a carbon-based material.

[0008] Preferably, in the composite material, the mass ratio of the zinc diphosphide, zinc phosphate, carbon-based material or hybrid material of carbon-based material is 1:(0.01-1.1):(0.01-2.2).

[0009] Further preferably, in the composite material, the mass ratio of the zinc diphosphide, zinc phosphate, carbon-based material or carbon-based material hybrid material is 1:(0.01-1):(0.01-2).

[0010] Preferably, the carbon-based material is selected from at least one of graphite, graphene, carbon nanotubes, carbon nanofibers, carbon nanodots, carbon nanocones, coke, activated carbon, conductive carbon black, and acetylene black.

[0011] Preferably, the hybrid material of the carbon-based material is obtained by introducing hybrid elements into the carbon-based material; the hybrid elements include at least one of Li, P, and N.

[0012] Preferably, the specific surface area of ​​the composite material is 1m 2 / g-10m 2 / g; Further preferably, the specific surface area of ​​the composite material is 2m 2 / g-5m 2 / g.

[0013] Preferably, the pore size of the composite material is 18 nm-130 nm; further preferably, the pore size of the composite material is 20 nm-120 nm.

[0014] Preferably, the particle size of the composite material is 10 nm-100 μm; further preferably, the particle size of the composite material is 100 nm-10 μm.

[0015] The second aspect of the present application provides a method for preparing the zinc diphosphide / zinc phosphate composite material described in the first aspect of the present application.

[0016] Specifically, the preparation method of the zinc diphosphide / zinc phosphate composite material comprises the following steps:

[0017] Zinc oxide, phosphorus, carbon-based material or a hybrid material of carbon-based material are mixed to obtain a mixture, and then the mixture is ball-milled to obtain the composite material; or zinc oxide and phosphorus are mixed to obtain a mixture, and then the mixture is ball-milled to obtain the composite material, and then the carbon-based material or a hybrid material of carbon-based material is added to obtain the composite material; or zinc diphosphide, zinc phosphate, carbon-based material or a hybrid material of carbon-based material are mixed to obtain a mixture, and then the mixture is ball-milled to obtain the composite material.

[0018] Specifically, since particle collision and friction during the ball milling process are conducive to particle refinement and surface modification, zinc diphosphide, zinc phosphate, carbon-based materials or carbon-based hybrid materials are mixed and then ball milled, so that the zinc diphosphide is coated with the zinc phosphate, the carbon-based material or the carbon-based hybrid material.

[0019] Preferably, the phosphorus element includes at least one of red phosphorus (RP), white phosphorus (WP), purple phosphorus (PP), black phosphorus (BP) and yellow phosphorus (YP).

[0020] Preferably, the size of the zinc oxide is 0.9 nm-11 mm; further preferably, the size of the zinc oxide is 1 nm-10 mm.

[0021] Preferably, the size of the elemental phosphorus is 0.9 nm-110 mm, and more preferably, the size of the elemental phosphorus is 1 nm-100 mm.

[0022] Preferably, the scale of the elemental phosphorus is 0-dimensional to 3-dimensional.

[0023] Preferably, the carbon-based material or the hybrid material of the carbon-based material accounts for 3% to 99% of the total mass of the zinc oxide, phosphorus element, carbon-based material or the hybrid material of the carbon-based material.

[0024] Further preferably, the carbon-based material or the hybrid material of the carbon-based material accounts for 20%-60% of the total mass of the zinc oxide, phosphorus element, carbon-based material or the hybrid material of the carbon-based material.

[0025] Preferably, the molar ratio of the zinc oxide to the phosphorus element is 0.1-20:1.

[0026] More preferably, the molar ratio of the zinc oxide to the phosphorus element is 0.3-3:1.

[0027] Preferably, the mass ratio of the ball milling balls to the mixed material used in the ball milling is 18-110:1.

[0028] Further preferably, the mass ratio of the ball milling balls to the mixed material used in the ball milling is 20-100:1.

[0029] More preferably, the mass ratio of the ball milling balls to the mixed material used in the ball milling is 40:1.

[0030] Preferably, the ball milling speed is 200 rpm-1500 rpm; and the ball milling time is 9.5 h-100 h.

[0031] Further preferably, the ball milling speed is 800 rpm-1000 rpm; and the ball milling time is 10 h-96 h.

[0032] Preferably, the ball milling is performed in an inert atmosphere, which is an argon atmosphere.

[0033] Specifically, the ball milling can promote the covalent bonding of phosphorus and carbon, thereby stabilizing the structure while improving the conductivity of lithium ions within the material, enhancing the conductivity of the composite material, and helping to obtain stable and excellent electrochemical properties.

[0034] The third aspect of the present application provides a negative electrode material.

[0035] Specifically, the negative electrode material includes the zinc diphosphide / zinc phosphate composite material described in the first aspect of the present application.

[0036] Preferably, the negative electrode material further includes a conductive agent and a binder.

[0037] Preferably, the mass ratio of the zinc diphosphide / zinc phosphate composite material, the conductive agent and the binder is 7:(0.04-110):(0.04-33).

[0038] Further preferably, the mass ratio of the zinc diphosphide / zinc phosphate composite material, the conductive agent and the binder is 7:(0.05-100):(0.05-30).

[0039] Preferably, the conductive agent includes at least one of conductive carbon black (Super P), acetylene black (AB), Ketjen black (KB), vapor grown carbon fiber (VGCF), carbon nanotube (CNT), conductive graphite, and graphene.

[0040] More preferably, the conductive agent is acetylene black.

[0041] Preferably, the binder includes at least one of polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR).

[0042] More preferably, the adhesive includes at least one of CMC and SBR.

[0043] The fourth aspect of the present application also provides a negative electrode plate.

[0044] Specifically, the negative electrode plate includes a coating formed by the negative electrode material described in the third aspect of the present application.

[0045] Preferably, the method for preparing the negative electrode sheet comprises the following steps:

[0046] (1) mixing a zinc diphosphide / zinc phosphate composite material, a conductive agent, and a binder to obtain a slurry;

[0047] (2) The slurry is coated on the surface of the metal foil and dried to obtain a negative electrode sheet.

[0048] Preferably, in step (2), the metal foil is copper foil.

[0049] Preferably, in step (2), the drying is vacuum drying; the temperature of the vacuum drying is 45° C.-130° C.; and the time of the vacuum drying is 1.5 h-40 h.

[0050] More preferably, the vacuum drying temperature is 50° C.-120° C.; and the vacuum drying time is 2 h-36 h.

[0051] The fifth aspect of the present application also provides a battery.

[0052] Specifically, the battery includes the negative electrode plate described in the fourth aspect of the present application.

[0053] Preferably, the battery is a lithium-ion battery.

[0054] Preferably, the lithium-ion battery is a lithium-ion battery half-cell.

[0055] Preferably, the method for preparing the lithium-ion battery half-cell comprises the following steps:

[0056] The negative electrode sheet, diaphragm, metal lithium sheet, gasket and spring are stacked from top to bottom and placed in the battery shell, and then the electrolyte is dripped into the battery shell. The battery shell is covered, sealed and left to stand to obtain a lithium-ion battery half-cell.

[0057] Preferably, the sealing pressure is 18 MPa-110 MPa; further preferably, the sealing pressure is 20 MPa-100 MPa.

[0058] Preferably, the standing time is 9 hours to 80 hours; further preferably, the standing time is 10 hours to 72 hours.

[0059] Compared with the prior art, the technical solution provided by this application has the following beneficial effects:

[0060] (1) The composite material of the present application includes zinc diphosphide, zinc phosphate, a carbon-based material, or a hybrid material of a carbon-based material; and the zinc diphosphide is coated by the zinc phosphate, carbon-based material, or a hybrid material of a carbon-based material. The presence of zinc phosphate can effectively alleviate the volume expansion of the zinc diphosphide composite material during the charge and discharge process, avoid the composite material from falling off due to volume expansion, improve the cycle performance of the material, and at the same time play the role of an SEI film to a certain extent; in addition, the carbon-based material or its hybrid material coating zinc diphosphide can improve the conductivity of the material, improve the rate performance of the material, and can compensate for the problem of decreased conductivity caused by the presence of zinc phosphate, thereby making the prepared battery have good rate performance and cycle stability. At the same time, the coating of the carbon-based material or the carbon-based hybrid material can also reduce the generation of white phosphorus during the ball milling process, improve the thermal stability of the material, and thus improve the electrochemical performance of the battery.

[0061] (2) The increase in the content of carbon-based materials or hybrid materials of carbon-based materials in the present application is beneficial to improving the conductivity of the material system, enhancing the fineness of the powder after ball milling, improving the dense agglomeration of zinc diphosphide particles, and at the same time helping zinc diphosphide to transform from a crystalline state to an amorphous structure, adding richer porous structures and holes, improving lithium storage capacity, and thus improving the electrochemical performance of the battery.

[0062] (3) The composite material of the present invention has nanopores on its surface, which are beneficial to improving the diffusion and penetration of electrolytes and can also be used for Li + Provide more entrances to reduce Li + The diffusion resistance of the lithium ion battery is improved, and the rate performance and cycle stability of the fast-charge lithium ion battery are improved. In addition, the composite material system of the present application has a reversible Li + The storage mechanism helps to reduce the structural stress during the cycle and alleviates the volume expansion of the electrode during charge and discharge, giving the battery good cycle stability.

[0063] (4) The preparation process of the present application is simple, and a simple and efficient high-energy ball milling method can be used to achieve large-scale production of the composite material, which has high production efficiency, low cost, and is convenient for industrial production. In addition, the present application uses ball milling to generate amorphous zinc phosphate in situ while generating zinc diphosphide. The presence of zinc phosphate can effectively alleviate the volume expansion of the zinc diphosphide composite material during the charging and discharging process, avoid the composite material from falling off due to volume expansion, and improve the cycle performance of the material. At the same time, high-energy ball milling also promotes the covalent bonding of phosphorus and carbon, which not only stabilizes the structure but also improves the internal conductivity of the material for lithium ions, enhances the conductivity of the composite material, and helps to obtain stable and excellent electrochemical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] FIG1 is an SEM image of the zinc diphosphide / zinc phosphate composite material prepared in Examples 1-3 of the present application and the material of Comparative Example 1;

[0065] FIG2 is a nitrogen adsorption / desorption curve of the zinc diphosphide / zinc phosphate composite materials prepared in Examples 1-3 of the present application and the material of Comparative Example 1;

[0066] FIG3 is a pore size distribution curve of the zinc diphosphide / zinc phosphate composite materials prepared in Examples 1-3 of the present application and the material of Comparative Example 1;

[0067] FIG4 is an EDS spectrum of the zinc diphosphide / zinc phosphate composite material prepared in Examples 1-3 of the present application;

[0068] FIG5 is an XRD diffraction pattern of the zinc diphosphide / zinc phosphate composite material prepared in Examples 1-3 of the present application;

[0069] FIG6 is an FTIR graph of the zinc diphosphide / zinc phosphate composite material prepared in Examples 1-3 of the present application;

[0070] FIG7 is a TEM image of the zinc diphosphide / zinc phosphate composite material prepared in Example 1 of the present application;

[0071] FIG8 is a graph showing the rate performance of lithium-ion battery half-cells prepared in Application Examples 1-3 and Comparative Application Example 1 of the present application at 0.1 A / g-5 A / g;

[0072] FIG9 is a graph showing the rate performance of the lithium-ion battery half-cell prepared in Application Examples 1-3 of the present application at 0.1 A / g-10 A / g;

[0073] FIG10 is a rate performance diagram of a lithium-ion battery half-cell prepared in Application Example 3 of the present application at 0.05 A / g-25 A / g;

[0074] FIG11 is a graph showing the long cycle performance of the lithium-ion battery half-cell prepared in Application Examples 1-3 of the present application at 5 A / g;

[0075] FIG12 is a graph showing the long cycle performance of the lithium-ion battery half-cell prepared in Application Example 3 of the present application at 15 A / g. DETAILED DESCRIPTION

[0076] In order to make the technical solution of this application more clearly understood by those skilled in the art, the following examples are given for illustration. It should be noted that the following examples do not limit the scope of protection claimed in this application.

[0077] Unless otherwise specified, the raw materials, reagents, or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0078] The examples of the present application use nanometer-sized ZnO particles and millimeter-sized red phosphorus as raw materials. In Example 1, the average particle size D50 of ZnO is 100 nm, and the average particle size D50 of red phosphorus is 2 mm. In Example 2, the average particle size D50 of ZnO is 200 nm, and the average particle size D50 of red phosphorus is 5 mm. In Example 3, the average particle size D50 of ZnO is 100 nm, and the average particle size D50 of red phosphorus is 5 mm.

[0079] In the performance tests of the embodiments of the present application, the negative electrode specific capacity is calculated based on the weight of zinc diphosphide and zinc phosphate active materials, and the mass of conductive carbon black is not included.

[0080] Example 1

[0081] A zinc diphosphide / zinc phosphate composite material comprises zinc diphosphide, zinc phosphate and conductive carbon black; wherein the zinc diphosphide is coated by the zinc phosphate and the conductive carbon black.

[0082] A method for preparing a zinc diphosphide / zinc phosphate composite material comprises the following steps:

[0083] Weigh 0.53g ZnO, 0.40g red phosphorus and 0.28g conductive carbon black (Super P), where Super P accounts for 23% of the total weight of ZnO, red phosphorus and Super P, and place them in a ball mill with a ball-to-material ratio of 40:1. Under argon atmosphere, the ball mill speed is 800rpm and the ball milling time is 4.5h to obtain a zinc diphosphide / zinc phosphate composite material c-ZnP2 / Zn3(PO4)2 / C23.

[0084] Example 2

[0085] A zinc diphosphide / zinc phosphate composite material comprises zinc diphosphide, zinc phosphate and conductive carbon black; wherein the zinc diphosphide is coated by the zinc phosphate and the conductive carbon black.

[0086] A method for preparing a zinc diphosphide / zinc phosphate composite material comprises the following steps:

[0087] Weigh 1.10g ZnO, 0.84g red phosphorus and 0.83g Super P, where Super P accounts for 30% of the total weight of ZnO, red phosphorus and Super P, and place them in a ball mill with a ball-to-material ratio of 40:1. Under argon atmosphere, the ball mill speed is 850rpm and the ball milling time is 4h to obtain a zinc diphosphide / zinc phosphate composite material c-ZnP2 / Zn3(PO4)2 / C30.

[0088] Example 3

[0089] A zinc diphosphide / zinc phosphate composite material comprises zinc diphosphide, zinc phosphate and conductive carbon black; wherein the zinc diphosphide is coated by the zinc phosphate and the conductive carbon black.

[0090] A method for preparing a zinc diphosphide / zinc phosphate composite material comprises the following steps:

[0091] Weigh 0.98g ZnO, 0.75g red phosphorus and 0.97g Super P, where Super P accounts for 36% of the total weight of ZnO, red phosphorus and Super P, and place them in a ball mill with a ball-to-material ratio of 40:1. Under argon atmosphere, the ball mill speed is 850rpm and the ball milling time is 4.5h to obtain a zinc diphosphide / zinc phosphate composite material a-ZnP2 / Zn3(PO4)2 / C36.

[0092] Comparative Example 1

[0093] Commercially purchased artificial graphite was used as the material for Comparative Example 1.

[0094] Application Example 1

[0095] The zinc diphosphide / zinc phosphate composite material prepared in Example 1 was used as the active material.

[0096] A method for preparing a lithium ion battery half-cell comprises the following steps:

[0097] (1) mixing a zinc diphosphide / zinc phosphate composite material, a binder (CMC to SBR mass ratio = 1:1), and a conductive agent, acetylene black, in a mass ratio of 7:1.5:1.5 to obtain a slurry;

[0098] (2) The slurry obtained in step (1) is evenly coated on a Cu foil current collector, and vacuum dried at 60° C. for 16 h to obtain a negative electrode sheet;

[0099] (3) In an argon atmosphere glove box, the negative electrode sheet, diaphragm, metal lithium sheet, gasket, and spring obtained in step (2) are stacked and placed in a battery casing in order from top to bottom, and then an electrolyte 1.0M LiPF6 (the solvent is ethylene carbonate / diethyl carbonate (EC / DEC), volume ratio = 1:1; the additives are 10wt% fluoroethylene carbonate (FEC), 1wt% vinylene carbonate (VC)) is added dropwise to the battery casing, the battery casing is covered, and the casing is sealed under a pressure of 50MPa, and finally allowed to stand at room temperature for 24h to obtain a lithium-ion battery half-cell.

[0100] Application Example 2

[0101] The only difference between Application Example 2 and Application Example 1 is that Application Example 2 uses the zinc diphosphide / zinc phosphate composite material prepared in Example 2 as the active material, and the rest is the same as Application Example 1.

[0102] Application Example 3

[0103] The only difference between Application Example 3 and Application Example 1 is that Application Example 3 uses the zinc diphosphide / zinc phosphate composite material prepared in Example 3 as the active material, and the rest is the same as Application Example 1.

[0104] Comparative Application Example 1

[0105] The only difference between Comparative Application Example 1 and Application Example 1 is that Comparative Application Example 1 uses the material of Comparative Example 1 as the active material, and the rest is the same as Application Example 1.

[0106] Performance Testing

[0107] 1.SEM testing

[0108] SEM morphology observations were performed on the zinc phosphide / zinc phosphate composite materials prepared in Examples 1-3 and the material in Comparative Example 1, and the results are shown in Figure 1. Figure 1(A) is an SEM image of the material in Comparative Example 1, where "artificial graphite" represents artificial graphite; Figures 1(B), 1(C), and 1(D) are SEM images of the zinc phosphide / zinc phosphate composite materials prepared in Examples 1-3, respectively. As can be seen in Figure 1, the composite materials in Examples 1-3 have relatively small and uniform particle sizes, ranging from tens of nanometers to several microns, while the graphite material in Comparative Example 1 has larger and more variable particle sizes.

[0109] 2. Nitrogen adsorption and desorption test

[0110] The zinc diphosphide / zinc phosphate composite materials prepared in Examples 1-3 and the material of Comparative Example 1 were subjected to nitrogen adsorption and desorption tests using the nitrogen adsorption and desorption (BET) method. The nitrogen adsorption and desorption curves are shown in FIG2 , wherein Artificial graphite represents the artificial graphite of Comparative Example 1; the abscissa Relative Pressure (P / P0) represents the relative pressure of nitrogen, P0 represents the saturated vapor pressure of the gas at the adsorption temperature, and P represents the pressure of the gas phase at adsorption equilibrium; the ordinate Quantity adsorbed (cm 3 / g STP) represents the adsorption amount (STP is the standard state). The pore size distribution curve is shown in Figure 3, wherein Figure 3 (a), Figure 3 (b), Figure 3 (c), and Figure 3 (d) in Figure 3 are the pore size distribution curves of the artificial graphite material of Comparative Example 1, Example 1, Example 2, and Example 3, respectively, and the horizontal coordinate Pore Width / nm represents the pore size distribution (nanometer), the vertical coordinate dV / dlog (W) Pore Volume (cm 3 / g) represents the pore area.

[0111] As shown in Figure 2, the specific surface areas of the zinc diphosphide / zinc phosphate composite materials prepared in Examples 1-3 of the present application are 2.89 m 2 / g, 3.78m 2 / g, 5.11m 2 / g, the specific surface area of ​​the artificial graphite material of Comparative Example 1 is 2.43m 2 / g. This indicates that the specific surface area of ​​the zinc diphosphide / zinc phosphate composite material prepared in the present application is greater than the specific surface area of ​​the artificial graphite in Comparative Example 1, and as the amount of conductive carbon black added to the carbon-based material gradually increases, the specific surface area of ​​the zinc diphosphide / zinc phosphate composite material prepared in Examples 1-3 of the present application also gradually increases.

[0112] As shown in Figure 3, the pore size distribution of the composite materials prepared in Examples 1-3 of the present application is mainly 20nm-100nm, and the pore size distribution of the artificial graphite material of Comparative Example 1 is mainly 10nm-120nm. The nanopores in the present application are beneficial to improving the diffusion and penetration of the electrolyte, and can also be Li + Provide more entrances to reduce Li + The diffusion resistance is reduced, and the rate performance and cycle stability of fast-charging lithium-ion batteries are improved.

[0113] 3. EDS spectrum analysis

[0114] EDS energy dispersive spectrometer analysis of the zinc diphosphide / zinc phosphate composites prepared in Examples 1-3 was performed using an energy dispersive spectrometer equipped with a scanning electron microscope. The results are shown in Figure 4 . Figures A, B, and C in Figure 4 are EDS spectra of the zinc diphosphide / zinc phosphate composites prepared in Examples 1-3, respectively. As can be seen in Figure 4 , the elements Zn, P, O, and C are uniformly dispersed throughout the granular material.

[0115] 4.XRD diffraction analysis

[0116] The zinc diphosphide / zinc phosphate composite materials prepared in Examples 1-3 were subjected to XRD diffraction analysis, and the XRD diffraction patterns are shown in Figure 5. The abscissa 2Theta (deg.) represents the diffraction angle 2θ (°), and the ordinate Intesity represents the diffraction intensity.

[0117] As can be seen from Figure 5, the zinc phosphide obtained by ball milling ZnO and red phosphorus with a molar ratio of 1:2 and 23 wt% conductive carbon black in Example 1 is crystalline and shows obvious diffraction peaks of tetragonal ZnP2 (PDF#72-1626), such as (104), (112) and (114), with a space group of P41212 and a lattice parameter of In Example 2, the zinc diphosphide obtained by high-energy ball milling of ZnO and red phosphorus at a molar ratio of 1:2 with 30wt% conductive carbon black was amorphous and lacked distinct characteristic diffraction peaks. In Example 3, the zinc diphosphide obtained by high-energy ball milling of ZnO and red phosphorus at a molar ratio of 1:2 with 36wt% conductive carbon black was amorphous and lacked distinct characteristic diffraction peaks. This indicates that increasing the conductive carbon content during ball milling not only improves the conductivity of the material system, enhances the fineness of the milled powder, and improves the dense agglomeration of zinc phosphide particles, but also facilitates the transformation of zinc diphosphide from a crystalline to an amorphous structure, increasing the porous structure and vacancies, improving lithium storage capacity, and thus enhancing the electrochemical performance of the battery.

[0118] 5. FTIR infrared analysis

[0119] The zinc phosphide / zinc phosphate composite materials prepared in Examples 1-3 were subjected to FTIR infrared analysis, and the FTIR curve is shown in FIG6 . -1 ) represents the wavelength, and the vertical axis Transmittance (au) represents the absorbance.

[0120] As can be seen from FIG6 , phosphate is generated, indicating that in Example 1-3, amorphous zinc phosphate is also generated in situ while zinc diphosphide is produced by ball milling, which synergistically suppresses volume expansion and improves the electrochemical stability of the zinc diphosphide / zinc phosphate composite material system.

[0121] 6.TEM test

[0122] The zinc phosphide / zinc phosphate composite material prepared in Example 1 was observed under transmission electron microscopy, and the TEM microstructure is shown in Figure 7, where "ZnP2 was surrounded by amorphous super P and zinc phosphate" indicates that zinc phosphide is coated with conductive carbon black and zinc phosphate, and the dotted box represents ZnP2. As can be seen from Figure 7, in the zinc phosphide / zinc phosphate composite material of Example 1, crystalline ZnP2 is distributed within the coating layer of the amorphous carbon-based material Super P and the in-situ generated amorphous zinc phosphate material, providing a good buffer zone for phase change and material deformation during the battery's charge and discharge cycles, thereby improving the battery's cycle stability and rate performance.

[0123] 7. Rate performance test

[0124] The lithium-ion battery half-cells prepared in Example 1-3 and Comparative Example 1 were subjected to rate performance testing. The rate performance curves for the range of 0.1 A / g to 5 A / g are shown in FIG8 , where Current Density represents current density; Artificial graphite represents the artificial graphite of Comparative Example 1; the horizontal axis "Cycle number" represents the number of cycles; and the vertical axis "Discharge Capacity (mAh / g)" represents the specific discharge capacity (milliampere-hours per gram). The rate performance curves for the lithium-ion battery half-cells prepared in Example 1-3 in the range of 0.1 A / g to 10 A / g are shown in FIG9 , where Current Density represents current density; the horizontal axis "Cycle number" represents the number of cycles; the left vertical axis "Discharge Capacity (mAh / g)" represents the specific capacity (milliampere-hours per gram); and the right vertical axis "Coulombic Efficiency (%)" represents the coulombic efficiency (%).

[0125] As can be seen from Figure 9, the battery of Application Example 1 has a specific capacity of 1243mAh / g, 1150mAh / g, 1061mAh / g, 980mAh / g, 899mAh / g and 774mAh / g when the current density is 0.1A / g, 0.2A / g, 0.5A / g, 1.0A / g, 2.0A / g and 5.0A / g, respectively, showing good rate performance. The battery of Application Example 2 has a specific capacity of 1577mAh / g, 1462mAh / g, 1331mAh / g, 1238mAh / g, 1145mAh / g and 1006mAh / g when the current density is 0.1A / g, 0.2A / g, 0.5A / g, 1.0A / g, 2.0A / g and 5.0A / g, respectively, showing good rate performance. The battery of Application Example 3 has a specific capacity of 1669mAh / g, 1546mAh / g, 1407mAh / g, 1299mAh / g, 1193mAh / g, 1121mAh / g, 1069mAh / g and 800mAh / g at current densities of 0.1A / g, 0.2A / g, 0.5A / g, 1.0A / g, 2.0A / g, 3.0A / g, 5.0A / g and 10A / g, respectively. And as can be seen from Figure 9, Application Example 1 has a specific capacity of 619mAh / g at a high current density of 10.0A / g. Application Example 2 has a specific capacity of more than 800mAh / g at a high current density of 10.0A / g. Application Example 3 has a specific capacity of 800mAh / g at a high current density of 10.0A / g.

[0126] As can be seen from Figure 8, for the battery using Comparative Example 1, under the charge and discharge conditions of 0.01V-3.0V, when the current density is 0.1A / g, 0.2A / g, 0.5A / g, 1.0A / g, 2.0A / g and 5.0A / g, the specific capacity is 346mAh / g, 286mAh / g, 175mAh / g, 85mAh / g, 44mAh / g and 21mAh / g, respectively. At a high current density of 5.0A / g, the capacity decay is obvious.

[0127] The rate performance curve of the lithium-ion battery half-cell prepared in Application Example 3 at 0.05A / g-25A / g is shown in Figure 10, where "activation" represents the activation of the battery at a low current, "charge" represents charging, "discharge" represents discharging, and "current density" represents the current density. The horizontal axis "Cycle number" represents the number of cycles, the left vertical axis "Capacity (mAh / g)" represents the specific capacity (milliampere-hours per gram), and the right vertical axis "Coulombic Efficiency (%)" represents the coulombic efficiency (%). As shown in Figure 10, the battery of Application Example 3 has a specific capacity exceeding 580mAh / g at a high current density of 25.0A / g.

[0128] It can be seen from the rate performance test results that the in-situ generation of zinc diphosphide and zinc phosphate in this application can significantly improve the rate performance of the battery, and the amorphous structure reduces the structural stress during the cycle and improves the electrochemical performance of the battery.

[0129] 8. Long cycle performance test

[0130] The lithium-ion battery half-cells prepared for Examples 1-3 were subjected to long-cycle performance testing at a current density of 5A / g. The long-cycle performance curve is shown in Figure 11, where 5A / g represents the current density and "Equal to 3C" represents equivalent to 3C. The horizontal axis "Cycle number" represents the number of cycles, the left vertical axis "Discharge Capacity (mAh / g)" represents the discharge capacity (milliampere-hours per gram), and the right vertical axis "Coulombic Efficiency (%)" represents the coulombic efficiency (%). As can be seen from Figure 11, the battery of Example 1 still has a capacity of 762mAh / g after 1500 cycles under the conditions of 5.0A / g and 0.01V-3.0V charge and discharge range. The battery of Example 2 still has a capacity of 914mAh / g after 1500 cycles under the conditions of 5.0A / g and 0.01V-3.0V charge and discharge range. The battery of Application Example 3 maintained a capacity of 1037 mAh / g after 1500 cycles at 5.0 A / g (3C) and a charge-discharge range of 0.01 V to 3.0 V, with a capacity retention rate of 97%, indicating that the battery of Application Example 3 has good cycle stability.

[0131] The battery prepared in Example 3 was subjected to a long-cycle performance test at a current density of 15A / g. The results are shown in Figure 12, where "Gradient activation from 0.05A / g to 12A / g" indicates gradient activation of the test current from 0.05A / g to 12A / g; 15A / g indicates current density, and "Equal to 9C" indicates equivalent to 9C; the horizontal axis "Cycle number" indicates the number of cycles, the left vertical axis "Discharge Capacity (mAh / g)" indicates the discharge capacity (milliampere-hours per gram), and the right vertical axis "Coulombic Efficiency (%)" indicates the coulombic efficiency (%). As can be seen from Figure 12, after 2500 stable cycles at a higher current density such as 15.0A / g (9C), the capacity is still 616mAh / g, indicating excellent long-cycle performance.

[0132] In summary, the battery prepared by the composite material of the present application has good rate performance and long cycle performance. It also shows that the ZnP2 / Zn3(PO4)2 / C system of the present application has reversible Li + The storage mechanism can alleviate the volume expansion of the electrode during charging and discharging, and has great application value in the field of fast-charging lithium-ion negative electrodes.

[0133] The above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit the scope of protection of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A composite material, characterized in that: It comprises zinc diphosphide, zinc phosphate, carbon-based material or a hybrid material of carbon-based material; and the zinc diphosphide is coated by the zinc phosphate, the carbon-based material or the hybrid material of carbon-based material.

2. The composite material according to claim 1, characterized in that In the composite material, the mass ratio of the zinc diphosphide, zinc phosphate, carbon-based material or a hybrid material of the carbon-based material is 1:(0.01-1.1):(0.01-2.2).

3. The composite material according to claim 2, characterized in that The carbon-based material is selected from at least one of graphite, graphene, carbon nanotubes, carbon nanofibers, carbon nanodots, carbon nanocones, coke, activated carbon, conductive carbon black, and acetylene black; the hybrid material of the carbon-based material is obtained by introducing hybrid elements into the carbon-based material; the hybrid elements include at least one of Li, P, and N.

4. The composite material according to claim 1, characterized in that The specific surface area of ​​the composite material is 1m 2 / g-10m 2 / g; and / or, the pore size of the composite material is 18nm-130nm; and / or, the particle size of the composite material is 10nm-100μm.

5. A method for preparing a composite material according to any one of claims 1 to 4, characterized in that: The following steps are involved: Zinc oxide, phosphorus, carbon-based materials or hybrid materials of carbon-based materials are mixed to obtain a mixture, and then the mixture is ball-milled to obtain the composite material; or zinc oxide and phosphorus are mixed to obtain a mixture, and then the mixture is ball-milled to obtain the composite material, and then the carbon-based material or the hybrid material of carbon-based materials is added to obtain the composite material; or zinc diphosphide, zinc phosphate, carbon-based materials or hybrid materials of carbon-based materials are mixed to obtain a mixture, and then the mixture is ball-milled to obtain the composite material.

6. The preparation method according to claim 5, characterized in that: The carbon-based material or the hybrid material of the carbon-based material accounts for 3%-99% of the total mass of the zinc oxide, phosphorus, carbon-based material or the hybrid material of the carbon-based material; and / or the molar ratio of the zinc oxide to the phosphorus is 0.1-20:

1.

7. The preparation method according to claim 5, characterized in that: The ball milling is performed using grinding balls; the mass ratio of the grinding balls to the mixed material is 18-110:1; and / or the rotation speed of the ball milling is 200rpm-1500rpm; the ball milling time is 9.5h-100h.

8. A negative electrode material, characterized in that The composite material comprises the composite material according to any one of claims 1 to 4.

9. A negative electrode plate, characterized in that: A coating layer formed by the negative electrode material according to claim 8.

10. A battery, characterized in that: Including the negative electrode sheet as described in claim 9.

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