Lithium composite negative electrode material, preparation method thereof, negative electrode and solid-state lithium battery

Abstract

According to the lithium composite negative electrode material, Li2Se with high ionic conductivity is introduced, and a stable lithium ion transmission path is constructed in a negative electrode, so that lithium ions can be stably transmitted in the negative electrode in the cycle process, the cycle stability of the negative electrode is improved, and the cycle performance of a battery is further improved. The invention further relates to a preparation method of the lithium composite negative electrode material, a negative electrode, a solid-state lithium battery, a preparation method of the solid-state lithium battery and a power utilization device.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a lithium composite negative electrode material and a preparation method thereof, a negative electrode, a solid-state lithium battery and a preparation method thereof, and an electrical device. Background Art

[0002] Solid-state lithium batteries are batteries that use solid electrolytes instead of liquid electrolytes and separators. They have the advantages of high safety, large capacity, and high temperature resistance, and are expected to become an important trend to replace traditional liquid lithium batteries. Most solid-state lithium batteries use metallic lithium as the negative electrode to increase the energy density of the battery. However, the existing negative electrode materials have poor cycle stability, which deteriorates the cycle performance of the battery.

[0003] Therefore, it is necessary to develop a negative electrode material that can improve the cycle stability of the negative electrode and thus improve the cycle performance of the battery. Summary of the invention

[0004] In view of the problems existing in the background technology, the present application provides a lithium composite negative electrode material, which can improve the cycle stability of the negative electrode and thus improve the cycle performance of the battery.

[0005] The lithium composite negative electrode material provided in the first aspect of the present application comprises at least Li-M and Li 2 Se. Among them, M includes one or more of the second main group metal elements, the third main group metal elements and the transition metal elements.

[0006] This application utilizes Li with high ionic conductivity 2 Se builds a stable lithium ion transmission pathway inside the negative electrode, allowing lithium ions to be stably transmitted inside the negative electrode during the cycle, thereby improving the cycle stability of the negative electrode and further improving the cycle performance of the battery.

[0007] In some embodiments, according to the first aspect, a first example of the first aspect is provided, wherein the lithium composite negative electrode material further includes a metallic lithium component to construct a Li-M / Li 2 Se / Li lithium composite anode material.

[0008] The lithium composite negative electrode material of the present application is obtained by the reaction of metal selenide and molten metal lithium. In the case where the lithium composite negative electrode material contains a metal lithium component, the molten metal lithium in the reaction raw material is in excess relative to the metal selenide, so that the metal selenide can fully participate in the reaction and avoid the presence of metal selenide in the lithium composite negative electrode material. The metal selenide ions have poor electrical conductivity and will undergo a conversion reaction with lithium, thereby resulting in poor interface contact between the lithium composite negative electrode material and the solid electrolyte, and worsening the interface impedance. Therefore, the metal lithium, Li-M alloy and Li in the lithium composite negative electrode material of the present application are controlled. 2The Se component can indirectly improve the poor interface contact problem between the lithium composite negative electrode material and the solid electrolyte, thereby reducing the interface impedance.

[0009] In some embodiments, according to the first aspect, a second example of the first aspect is provided, wherein the ratio of the amount of Se element in the lithium composite negative electrode material to the total amount of Se element and Li element is (2.5-25):100.

[0010] By controlling the ratio of the amount of Se element in the lithium composite negative electrode material to the total amount of Se element and Li element, the Li 2 The mass proportion of Se in the lithium composite negative electrode material is conducive to further improving the cycle stability of the negative electrode and improving the cycle performance of the battery.

[0011] In some embodiments, according to the first aspect, a third example of the first aspect is provided, wherein the ratio of the amount of Se element in the lithium composite negative electrode material to the total amount of Se element and Li element is (10-20):100.

[0012] By optimizing the ratio of the amount of Se element in the lithium composite negative electrode material to the total amount of Se element and Li element within the above range, it is beneficial to further improve the cycle stability of the negative electrode and improve the cycle performance of the battery.

[0013] In some embodiments, according to the first aspect, a fourth example of the first aspect is provided, and M includes one or more of magnesium, calcium, aluminum, titanium, zirconium, manganese, cobalt, nickel, copper, zinc, and niobium.

[0014] Based on the different reduction potentials of different Li-M alloys, the stability inside the negative electrode is different. Therefore, optimizing the type of element M is beneficial to further improve the cycle stability of the negative electrode and improve the cycle performance of the battery.

[0015] The second aspect of the present application provides a method for preparing a lithium composite negative electrode material, comprising the following steps:

[0016] Under an inert atmosphere, a metal selenide is reacted with molten metal lithium to obtain a lithium composite negative electrode material, wherein the metal element in the metal selenide includes one or more of a second main group metal element, a third main group metal element and a transition metal element.

[0017] The present invention introduces Li into the negative electrode material system by reacting metal selenide with molten metal lithium. 2 Se. Li introduced in this way 2 Se can be evenly dispersed in the entire negative electrode material system, improving the uniformity and consistency of the negative electrode material, thereby building a stable lithium ion transmission pathway in the entire system and improving the cycle stability of the negative electrode.

[0018] The third aspect of the present application provides a negative electrode for a solid-state lithium battery, wherein the negative electrode comprises the lithium composite negative electrode material of the first aspect of the present application or the lithium composite negative electrode material obtained by the preparation method of the second aspect of the present application.

[0019] A fourth aspect of the present application provides a solid-state lithium battery, which includes a positive electrode, a solid electrolyte sheet and a negative electrode according to the third aspect of the present application.

[0020] A fifth aspect of the present application provides a method for preparing a solid-state lithium battery, comprising the following steps:

[0021] Prepare a lithium composite negative electrode material by the preparation method of the second aspect of the present application;

[0022] Injecting molten lithium composite negative electrode material into a mold so that the lithium composite negative electrode material contacts one side of the solid electrolyte sheet, and obtaining a negative electrode after cooling;

[0023] The positive electrode slurry is coated on the positive electrode current collector, and the positive electrode is obtained after drying;

[0024] After the positive electrode is soaked with electrolyte, it is contacted with the other side of the solid electrolyte sheet to obtain a solid-state lithium battery.

[0025] The preparation method of the present application is simple in process and highly repeatable, and is suitable for mass production. The solid-state lithium battery obtained by the preparation method of the present application has improved cycle performance.

[0026] In addition, when the prepared lithium composite negative electrode material contains a metallic lithium component, in the process of preparing a solid-state lithium battery, reacting molten metallic lithium with a metal selenide can reduce the surface tension of the molten metallic lithium and increase the affinity of the molten metallic lithium to the solid electrolyte, thereby reducing the interface impedance between the lithium composite negative electrode material and the solid electrolyte, and solving the problem of poor original interface contact between the metallic lithium and the solid electrolyte.

[0027] The sixth aspect of the present application provides an electrical device, characterized in that it includes the solid-state lithium battery of the fourth aspect of the present application or the solid-state lithium battery obtained by the preparation method of the fifth aspect of the present application.

[0028] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. DETAILED DESCRIPTION

[0029] The exemplary embodiments of the present disclosure will be described in more detail below. However, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to enable the scope of the present disclosure to be fully communicated to those skilled in the art.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application. The terms "including" and "having" and any variations thereof in the specification and claims of this application are intended to cover non-exclusive inclusions.

[0031] For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form an unambiguous range; and any lower limit can be combined with other lower limits to form an unambiguous range, and any upper limit can be combined with any other upper limit to form an unambiguous range. In addition, although not explicitly stated, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unambiguous range.

[0032] In the description of this article, it should be noted that, unless otherwise specified, "above" and "below" are inclusive of the number itself, and the "multiple" in "one or more" means more than two (including two).

[0033] The above-mentioned summary of the invention of the present application is not intended to describe each disclosed embodiment or each implementation in the present application. The following description more specifically illustrates exemplary embodiments. In many places throughout the application, guidance is provided by a series of examples, which can be used in various combinations. In each example, enumeration is only used as a representative group and should not be interpreted as exhaustive.

[0034] Solid-state lithium batteries are batteries that use solid electrolytes instead of liquid electrolytes and separators. They have the advantages of high safety, large capacity, and high temperature resistance, and are expected to become an important trend to replace traditional liquid lithium batteries. Most solid-state lithium batteries use metallic lithium as the negative electrode to increase the energy density of the battery. However, the existing negative electrode materials have poor cycle stability, which deteriorates the cycle performance of the battery.

[0035] Therefore, it is necessary to develop a negative electrode material that can improve the cycle stability of the negative electrode and thus improve the cycle performance of the battery.

[0036] Research has found that the cycle stability of the negative electrode is related to whether there is a stable lithium ion transmission path inside the negative electrode. A stable lithium ion transmission path inside the negative electrode is conducive to improving the cycle stability of the negative electrode, and thus to improving the cycle performance of the battery. In order to form a stable lithium ion transmission path inside the negative electrode, this application introduces Li 2 Se components form a lithium composite negative electrode material. 2 Se has high intrinsic ionic conductivity (~10 -5 S / cm), using Li 2 Se can build a stable lithium ion transmission pathway inside the negative electrode, allowing lithium ions to be stably transmitted inside the negative electrode during the cycle, thereby improving the cycle stability of the negative electrode and further improving the cycle performance of the battery.

[0037] Specifically, the first aspect of the present application provides a lithium composite negative electrode material. It at least includes Li-M and Li 2 Se. Among them, M includes one or more of the second main group metal elements, the third main group metal elements and the transition metal elements.

[0038] By constructing a lithium composite negative electrode material with a stable lithium ion transmission pathway, the problem of poor lithium ion transmission capacity inside the negative electrode is solved.

[0039] In addition, using the lithium composite negative electrode material of the present application for the negative electrode of a solid-state lithium battery can also increase the maximum charge and discharge current density of the battery, that is, the limiting current density, thereby improving the rate performance of the solid-state lithium battery.

[0040] In some embodiments, the lithium composite negative electrode material further includes a metallic lithium component to construct a Li-M / Li 2 Se / Li lithium composite anode material.

[0041] Lithium composite negative electrode materials contain metallic lithium components, which are beneficial to improving the capacity of solid-state lithium batteries.

[0042] Metallic lithium has the advantages of high theoretical capacity and high energy density as negative electrode material, but at the same time, the metal lithium negative electrode also has the problem of poor cycle stability. 2 Se component, constructing Li-M / Li 2 Se / Li lithium composite negative electrode material enables the negative electrode material to have a higher capacity while also enabling lithium ions to be stably transmitted inside the negative electrode, so that the negative electrode has both higher capacity and cycle stability, thereby improving the overall performance of the battery.

[0043] In some embodiments, the ratio of the amount of Se element to the total amount of Se element and Li element in the lithium composite negative electrode material may be (2.5-25):100.

[0044] By controlling the ratio of the amount of Se element in the lithium composite negative electrode material to the total amount of Se element and Li element, the Li 2 The mass proportion of Se in the lithium composite negative electrode material is conducive to further improving the cycle stability of the negative electrode and improving the cycle performance of the battery.

[0045] In some embodiments, the ratio of the amount of Se element in the lithium composite negative electrode material to the total amount of Se element and Li element can be (10-20):100.

[0046] By optimizing the ratio of the amount of Se element in the lithium composite negative electrode material to the total amount of Se element and Li element within the above range, it is beneficial to further improve the cycle stability of the negative electrode and improve the cycle performance of the battery.

[0047] In some specific embodiments, the ratio of the amount of Se element in the lithium composite negative electrode material to the total amount of Se element and Li element may be 2.5:100, 5:100, 7.5:100, 10:100, 11:100, 12:100, 13:100, 14:100, 15:100, 16:100, 17:100, 18:100, 19:100, 20:100, 22.5:100 or 25:100.

[0048] In some embodiments, M includes one or more of magnesium, calcium, aluminum, titanium, zirconium, manganese, cobalt, nickel, copper, zinc, and niobium.

[0049] Based on the different reduction potentials of different Li-M alloys, the stability inside the negative electrode is different. Therefore, by optimizing the type of element M, it is beneficial to further improve the cycle stability of the negative electrode and improve the cycle performance of the battery.

[0050] The second aspect of the present application provides a method for preparing a lithium composite negative electrode material, comprising the following steps:

[0051] Under an inert atmosphere, a metal selenide is reacted with molten metal lithium to obtain a lithium composite negative electrode material, wherein the metal element in the metal selenide includes one or more of a second main group metal element, a third main group metal element and a transition metal element.

[0052] The present invention introduces Li into the negative electrode material system by reacting metal selenide with molten metal lithium. 2 Se. Li introduced in this way 2 Se can be evenly dispersed in the entire negative electrode material system, improving the uniformity and consistency of the negative electrode material, thereby building a stable lithium ion transmission pathway in the entire system and improving the cycle stability of the negative electrode.

[0053] In some embodiments, the inert atmosphere may include one or more of argon, helium, and the like.

[0054] In some embodiments, the metal element in the metal selenide may include one or more of magnesium, calcium, aluminum, titanium, zirconium, manganese, cobalt, nickel, copper, zinc, and niobium. The metal selenide may include magnesium selenide MgSe, calcium selenide CaSe, aluminum selenide AlSe, 2 Se 3 , Titanium Selenide TiSe 2 、Zirconium selenide ZrSe 2 , manganese selenide MnSe, cobalt selenide CoSe, nickel selenide NiSe, copper selenide CuSe, zinc selenide ZnSe, niobium selenide Nb 2 Se 5 One or more of .

[0055] In some embodiments, before reacting the metal selenide with the molten lithium metal, the lithium metal is heated to above 200° C. in an inert atmosphere, and after the lithium metal is melted, surface impurities are removed to obtain bright molten lithium metal. The present application has no particular limitation on the heating temperature, as long as the lithium metal can be melted.

[0056] The present invention can control the ratio of the amount of Se element in the obtained lithium composite negative electrode material to the total amount of Se element and Li element by controlling the molar amount of metal selenide and molten metal lithium. In the case where metal lithium fully participates in the reaction, the lithium composite negative electrode material may include Li-M, Li 2 Se. In the case of excess metallic lithium, the lithium composite negative electrode material may include Li-M, Li 2 Se, Li three components, construct Li-M / Li 2 Se / Li lithium composite negative electrode material. Li-M / Li 2 Se / Li lithium composite anode material can achieve both high capacity and cycle stability.

[0057] The third aspect of the present application provides a negative electrode for a solid-state lithium battery, wherein the negative electrode comprises the lithium composite negative electrode material of the first aspect of the present application or the lithium composite negative electrode material obtained by the preparation method of the second aspect of the present application.

[0058] Since the lithium composite negative electrode material of the first aspect of the present application or the lithium composite negative electrode material obtained by the preparation method of the second aspect of the present application is used, the negative electrode of the present application has improved cycle stability.

[0059] A fourth aspect of the present application provides a solid-state lithium battery, which includes a positive electrode, a solid electrolyte sheet and a negative electrode according to the third aspect of the present application.

[0060] Since the negative electrode of the third aspect of the present application is adopted, the solid-state lithium battery of the present application has improved cycle performance.

[0061] A fifth aspect of the present application provides a method for preparing a solid-state lithium battery, comprising the following steps:

[0062] Prepare a lithium composite negative electrode material by the preparation method of the second aspect of the present application;

[0063] Injecting molten lithium composite negative electrode material into a mold so that the lithium composite negative electrode material contacts one side of the solid electrolyte sheet, and obtaining a negative electrode after cooling;

[0064] The positive electrode slurry is coated on the positive electrode current collector, and the positive electrode is obtained after drying;

[0065] After the positive electrode is soaked with electrolyte, it is contacted with the other side of the solid electrolyte sheet to obtain a solid-state lithium battery.

[0066] The preparation method of the present application is simple in process and highly repeatable, and is suitable for industrial large-scale production. The solid-state lithium battery obtained by the preparation method of the present application has improved cycle performance.

[0067] In addition, when the prepared lithium composite negative electrode material contains a metallic lithium component, in the process of preparing a solid-state lithium battery, reacting molten metallic lithium with a metal selenide can reduce the surface tension of the molten metallic lithium and increase the affinity of the molten metallic lithium to the solid electrolyte, thereby reducing the interface impedance between the lithium composite negative electrode material and the solid electrolyte, and solving the problem of poor original interface contact between the metallic lithium and the solid electrolyte.

[0068] In some embodiments, the molten lithium composite negative electrode material may be poured into the mold.

[0069] In some embodiments, the solid electrolyte may be one of the oxide solid electrolyte systems, such as lithium lanthanum zirconium oxide Li 7 La 3 Zr 2 O 12 、Lithium Lanthanum Zirconium Tantalum Oxide Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 .

[0070] In some embodiments, the electrolyte may include an electrolyte salt and a solvent.

[0071] As an example, the electrolyte salt may be selected from lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ) lithium hexafluoroarsenate (LiAsF6 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), one or more of lithium difluorooxalate phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP).

[0072] As an example, the solvent can be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), cyclopentane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl sulfone (ESE).

[0073] Before assembling the positive electrode, negative electrode and solid electrolyte sheet into a solid-state lithium battery, the positive electrode is infiltrated with electrolyte, which is beneficial to the diffusion of lithium ions in the positive electrode and ensures the lithium ion transmission performance of the positive electrode.

[0074] In some embodiments, after cooling, the edges of the solid electrolyte are polished to prevent short circuits.

[0075] In some embodiments, the preparation of the positive electrode slurry includes: mixing a positive electrode active material, a conductive agent, a binder, a solvent, and the like.

[0076] There is no limitation on the specific type of the positive electrode active material. Any active material known in the art that can be used for the positive electrode of a secondary battery can be used. Those skilled in the art can select the material according to actual needs.

[0077] As an example, the positive electrode active material may include, but is not limited to, one or more of lithium transition metal oxides, lithium-containing phosphates of olivine structure and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and their modified compounds. Examples of lithium-containing phosphates of olivine structure may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon and their modified compounds. These materials can all be obtained commercially.

[0078] In some embodiments, the modified compounds of the above materials may be doping-modified and / or surface-coated modified materials.

[0079] As an example, the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, Super P (SP), graphene and carbon nanofibers.

[0080] As an example, the binder can be one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA) and polyvinyl butyral (PVB).

[0081] In some embodiments, the positive electrode current collector may be a conventional metal foil or a composite current collector (a metal material may be disposed on a polymer substrate to form a composite current collector). As an example, the positive electrode current collector may be an aluminum foil.

[0082] The sixth aspect of the present application provides an electrical device, characterized in that it includes the solid-state lithium battery of the fourth aspect of the present application or the solid-state lithium battery obtained by the preparation method of the fifth aspect of the present application.

[0083] The present application is further described below in conjunction with the examples. The following examples describe the disclosure of the present application in more detail, and these examples are merely illustrative, because it is obvious to those skilled in the art that various modifications and variations are made within the scope of the disclosure of the present application. Unless otherwise stated, all reagents used in the examples are commercially available or synthesized according to conventional methods, and the instruments used in the examples are commercially available.

[0084] Preparation of lithium composite negative electrode materials

[0085] Example 1

[0086] Under an argon atmosphere, metallic lithium is placed in a stainless steel container and heated to 250°C. After the metallic lithium is melted, surface impurities are removed to obtain bright molten metallic lithium.

[0087] Under argon atmosphere, a certain amount of CuSe is added to molten lithium, where the molar ratio of CuSe to lithium is 15:85. Stirring continuously, the reaction process continues until CuSe and molten lithium react completely, and finally Li-Cu / Li 2 Se / Li lithium composite negative electrode material. By testing the X-ray diffraction pattern (XRD) of the reaction system, if there is no CuSe peak in the spectrum, it can be determined that the reaction is complete. In the obtained lithium composite negative electrode material, the ratio of the amount of Se element to the total amount of Se element and Li element is 15:100.

[0088] Embodiment 2-8

[0089] The lithium composite negative electrode material was prepared according to the method of Example 1, except that the molar ratio of CuSe to metallic lithium was different, the ratio of the amount of Se element in the obtained lithium composite negative electrode material to the total amount of Se element and Li element was different, and the components in the lithium composite negative electrode material were different, as shown in Table 1 below.

[0090] Table 1

[0091]

[0092] Embodiment 9-19

[0093] The lithium composite negative electrode material was prepared according to the method of Example 1, except that the metal selenide reacting with the molten metal lithium was different, as shown in Table 2 below.

[0094] Table 2

[0095]

[0096] Comparative Example 1

[0097] A metallic lithium negative electrode material was prepared according to the method of Example 1, except that CuSe was not used.

[0098] Comparative Example 2

[0099] A lithium composite negative electrode material was prepared according to the method of Example 1, except that GeSe was used instead of CuSe to react with molten metal lithium.

[0100] Preparation of symmetrical battery

[0101] Using the lithium composite negative electrode materials or metal lithium negative electrode materials prepared in Examples 1-19 and Comparative Examples 1-2, symmetric batteries were prepared according to the following general preparation method.

[0102] The prepared molten lithium composite negative electrode material or metallic lithium negative electrode material is quantitatively poured into the mold to form a solid electrolyte sheet (lithium lanthanum zirconium oxide Li) with a thickness of 0.5 mm. 7 La 3 Zr 2 O 12 ) are combined with the negative electrode material on both sides. After the whole body is cooled, the edges of the solid electrolyte are polished to prevent short circuits, and then assembled into a symmetrical battery.

[0103] Preparation of solid-state lithium batteries

[0104] Using the lithium composite negative electrode material or the metallic lithium negative electrode material prepared in Examples 1-19 and Comparative Examples 1-2, a solid-state lithium battery was prepared according to the following general preparation method.

[0105] (1) The prepared molten lithium composite negative electrode material or metallic lithium negative electrode material is quantitatively poured into a mold so that the negative electrode material and a solid electrolyte sheet (lithium lanthanum zirconium oxide Li) with a thickness of 0.5 mm are 7 La 3 Zr 2 O 12 ) and bonded. After the whole body cools down, the edge of the solid electrolyte is polished to prevent short circuit.

[0106] (2) The positive electrode active material lithium iron phosphate, the conductive agent Super P, and the binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 96.5:1.5:2, added to the solvent N-methylpyrrolidone (NMP), and stirred evenly under the action of a vacuum mixer to obtain a positive electrode slurry, wherein the solid content in the positive electrode slurry is 65% by weight; the positive electrode slurry is evenly coated on the positive electrode collector aluminum foil and dried at 85°C, and then cold pressed, trimmed, cut into pieces, and slit, and finally continued to be dried under vacuum conditions at 85°C to obtain a positive electrode sheet.

[0107] (3) The organic solvent is a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), wherein the volume ratio of EC, EMC and DEC is 20:20:60. In an argon atmosphere glove box with a water content of <10 ppm, a fully dried lithium salt LiPF 6 Dissolve in the above organic solvent, then add additives, mix evenly, and obtain an electrolyte, wherein the concentration of the lithium salt is 1 mol / L.

[0108] (4) After the positive electrode sheet is soaked with a trace amount of electrolyte, it is contacted with the other side of the solid electrolyte sheet to assemble a solid-state lithium battery.

[0109] Battery performance test

[0110] 1. Interface impedance test between negative electrode and solid electrolyte

[0111] The interfacial impedance of the symmetrical battery was tested using an electrochemical workstation. The test conditions were: voltage amplitude 10 mV, frequency range 0.1-10 6 Hz. The results are shown in Table 3 below.

[0112] 2. Limiting current density test

[0113] The charge and discharge tester is used for constant current charge and discharge, and the current density is 0.1 / 0.2 / 0.3 / 0.4 / 0.5 / 0.6 / 0.7 / 0.8 / 0.9 / 1.0 / 1.1 / 1.2 / 1.3 / 1.4 / 1.5 / 1.6 / 1.7.1.8 / 1.9 / 2.0mA / cm 2 The charge and discharge time is 30 min. The results are shown in Table 3. The greater the limiting current density, the better the rate performance of the battery.

[0114] 3. Capacity retention test

[0115] The constant current charge and discharge were performed using a charge and discharge tester, and the charge and discharge cycles were performed 500 times at a rate of 0.5C, and the capacity retention rate was calculated based on the capacity before and after the cycle. The results are shown in Table 3 below.

[0116] Table 3

[0117]

[0118]

[0119] It can be seen from the examples and comparative examples that the present invention utilizes Li with high ionic conductivity. 2 Se builds a stable lithium ion transmission path inside the negative electrode, so that lithium ions can be stably transmitted inside the negative electrode during the cycle, thereby improving the cycle stability of the negative electrode and further improving the cycle performance of the battery. 2 Se reduces the interfacial impedance between the negative electrode and the solid electrolyte, while also improving the rate performance of the battery.

[0120] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A lithium composite negative electrode material, characterized in that: It comprises at least two components, Li-M and Li2Se, wherein M comprises one or more of the second main group metal elements, the third main group metal elements and the transition metal elements.

2. The lithium composite negative electrode material according to claim 1, characterized in that: A metallic lithium component is also included to construct a Li-M / Li2Se / Li lithium composite negative electrode material.

3. The lithium composite negative electrode material according to claim 1 or 2, characterized in that: The ratio of the amount of Se element in the lithium composite negative electrode material to the total amount of Se element and Li element is (2.5-25):

100.

4. The lithium composite negative electrode material according to claim 3, characterized in that: The ratio of the amount of Se element in the lithium composite negative electrode material to the total amount of Se element and Li element is (10-20):

100.

5. The lithium composite negative electrode material according to any one of claims 1 to 4, characterized in that M includes one or more of magnesium, calcium, aluminum, titanium, zirconium, manganese, cobalt, nickel, copper, zinc, and niobium.

6. A method for preparing a lithium composite negative electrode material, characterized in that: The following steps are involved: Under an inert atmosphere, a metal selenide is reacted with molten metal lithium to obtain a lithium composite negative electrode material, wherein the metal element in the metal selenide includes one or more of a second main group metal element, a third main group metal element and a transition metal element.

7. A negative electrode for a solid-state lithium battery, characterized in that: The negative electrode comprises the lithium composite negative electrode material according to any one of claims 1 to 5 or the lithium composite negative electrode material obtained by the preparation method according to claim 6.

8. A solid-state lithium battery, characterized in that: The invention comprises a positive electrode, a solid electrolyte sheet and the negative electrode according to claim 7.

9. A method for preparing a solid-state lithium battery, characterized in that: The following steps are involved: Prepare the lithium composite negative electrode material by the preparation method according to claim 6; Injecting the molten lithium composite negative electrode material into a mold so that the lithium composite negative electrode material contacts one side of a solid electrolyte sheet, and obtaining a negative electrode after cooling; The positive electrode slurry is coated on the positive electrode current collector, and the positive electrode is obtained after drying; After the positive electrode is soaked with electrolyte, it is contacted with the other side of the solid electrolyte sheet to obtain a solid-state lithium battery.

10. An electrical device, characterized in that: Including the solid-state lithium battery according to claim 8 or the solid-state lithium battery obtained by the preparation method according to claim 9.

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