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

Abstract

The application relates to a lithium composite negative electrode material, a stable lithium ion transmission path is constructed in the negative electrode by introducing Li2Se with high ion conductivity, lithium ions can be stably transmitted in the negative electrode during the cycle process, the cycle stability of the negative electrode is improved, and the cycle performance of the battery is further improved. The application also relates to a preparation method of the lithium composite negative electrode material, a negative electrode, a solid-state lithium battery and a preparation method thereof, and an electric device.

Description

TECHNICAL FIELD

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

[0002] A solid-state lithium battery is a battery using a solid electrolyte instead of a liquid electrolyte and a separator, and has the advantages of high safety, large capacity and high temperature resistance, and is expected to become an important trend to replace traditional liquid lithium batteries. Most solid-state lithium batteries use metal lithium as the negative electrode to improve the energy density of the battery. However, the existing negative electrode material has poor cycle stability, which deteriorates the cycle performance of the battery.

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

[0004] In view of the problems in the background art, 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 at least includes two components of Li-M and Li2Se. Wherein M includes one or more of a second main group metal element, a third main group metal element and a transition metal element.

[0006] The present application uses Li2Se with high ionic conductivity to construct a stable lithium ion transmission path inside the negative electrode, so that the lithium ion can be stably transmitted inside the negative electrode during the cycle process, thereby improving the cycle stability of the negative electrode and thus 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, the lithium composite negative electrode material further includes a metal lithium component to construct a Li-M / Li2Se / Li lithium composite negative electrode material.

[0008] The lithium composite negative electrode material of the present application is obtained by reacting a metal selenide with molten lithium. In the case where the lithium composite negative electrode material contains a metal lithium component, the molten lithium in the reaction raw material is excessive 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 has poor ionic conductivity and will undergo a conversion reaction with lithium, thereby causing poor interface contact between the lithium composite negative electrode material and the solid electrolyte and deteriorating the interface impedance. Therefore, controlling the metal lithium, Li-M alloy and Li2Se components in the lithium composite negative electrode material of the present application can indirectly improve the problem of poor interface contact 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 substance of Se element to the total amount of substance of Se element and Li element in the lithium composite negative electrode material is (2.5-25):100.

[0010] By controlling the ratio of the amount of substance of Se element to the total amount of substance of Se element and Li element in the lithium composite negative electrode material, the mass proportion of Li2Se in the lithium composite negative electrode material can be controlled, which 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 substance of Se element to the total amount of substance of Se element and Li element in the lithium composite negative electrode material is (10-20):100.

[0012] By optimizing the ratio of the amount of substance of Se element to the total amount of substance of Se element and Li element in the lithium composite negative electrode material within the above range, the cycle stability of the negative electrode can be further improved, and the cycle performance of the battery can be improved.

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

[0014] Based on the difference in the reduction potential of different Li-M alloys, the stability inside the negative electrode has differences, and therefore, by optimizing the type of element M, the cycle stability of the negative electrode can be further improved, and the cycle performance of the battery can be improved.

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

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

[0017] The present application introduces Li2Se in the negative electrode material system by reacting the metal selenide with molten lithium metal. The Li2Se introduced in this way can be uniformly dispersed in the entire negative electrode material system, improving the uniformity and consistency of the negative electrode material, thereby constructing a stable lithium ion transmission path within 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. 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] The fourth aspect of the present application provides a solid-state lithium battery, which comprises a positive electrode, a solid electrolyte sheet and the negative electrode of the third aspect of the present application.

[0020] The fifth aspect of the present application provides a preparation method of a solid-state lithium battery, which comprises the following steps:

[0021] The lithium composite negative electrode material is prepared by the preparation method of the second aspect of the present application;

[0022] The molten lithium composite negative electrode material is injected into a mold, so that the lithium composite negative electrode material contacts one side of the solid electrolyte sheet, and the negative electrode is obtained 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 infiltrated with an electrolyte, the other side of the solid electrolyte sheet is contacted, and the solid-state lithium battery is obtained.

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

[0026] In addition, in the case that the prepared lithium composite negative electrode material contains a metal lithium component, during the preparation of the solid-state lithium battery, the molten metal lithium reacts with the metal selenide, which can reduce the surface tension of the molten metal lithium and improve the affinity of the molten metal 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 metal lithium and the solid electrolyte.

[0027] The sixth aspect of the present application provides a power utilization device, which is characterized by comprising 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 a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application, the specific embodiments of the present application can be implemented in accordance with the content of the description, and in order to make the above and other purposes, characteristics and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. 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 described herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be fully conveyed to those skilled in the art.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. Unless otherwise required by context, singular terms shall include pluralities and vice versa. The nomenclature used herein and the laboratory procedures are well known and commonly employed by those skilled in the art.

[0031] For convenience, only some numerical ranges are explicitly recited herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with any other lower limit to form a range not explicitly recited, and likewise any upper limit can be combined with any other upper limit to form a range not explicitly recited. Furthermore, although a range includes endpoints, each point or individual number within that range is also included. Thus, each point or individual number can be combined as the lower limit or the upper limit with any other point or individual number or with other lower or upper limits to form a range not explicitly recited.

[0032] In the description herein, it is to be understood that the terms "above" and "below" are used in their broadest context to include the number itself, unless otherwise indicated. The term "one or more" is used in its broadest context to mean two or more (including two).

[0033] The above summary of the application does not necessarily describe all embodiments or all implementations of the application. The following description more particularly describes example embodiments. In the description, numerous specific details are discussed, which can be embodied in various combinations to form different aspects of the application. In various examples, specific details are not described in order to avoid obscuring the application.

[0034] A solid-state lithium battery is a battery using a solid electrolyte instead of a liquid electrolyte and a separator, has advantages of high safety, large capacity, high temperature resistance, etc., and is expected to become an important trend to replace a conventional liquid lithium battery. Most solid-state lithium batteries use metal lithium as a negative electrode to improve the energy density of the battery. However, the cycle stability of the existing negative electrode material is poor, 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] It is found that the cycle stability of the negative electrode is related to whether the negative electrode has a stable lithium ion transport path inside. The stable lithium ion transport path inside the negative electrode is beneficial to improving the cycle stability of the negative electrode and thus improving the cycle performance of the battery. In order to form a stable lithium ion transport path inside the negative electrode, the application introduces a Li2Se component into the negative electrode material to form a lithium composite negative electrode material. Li2Se has a high intrinsic ionic conductivity (~ 10 -5The Li2Se can be used to build a stable lithium ion transmission path inside the negative electrode, so that the lithium ion is stably transmitted inside the negative electrode during the cycle process, thereby improving the cycle stability of the negative electrode and the cycle performance of the battery.

[0037] Specifically, the first aspect of the application provides a lithium composite negative electrode material. It at least includes two components of Li-M and Li2Se. Wherein, 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 building a lithium composite negative electrode material with a stable lithium ion transmission path, the problem of poor lithium ion transmission capacity inside the negative electrode is solved.

[0039] In addition, the lithium composite negative electrode material of the application used for the negative electrode of the solid-state lithium battery can also improve the maximum charge and discharge current density of the battery, i.e. the limit 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 metal lithium component to build a Li-M / Li2Se / Li lithium composite negative electrode material.

[0041] The lithium composite negative electrode material contains a metal lithium component, which is beneficial to improve the capacity of the solid-state lithium battery.

[0042] Metal lithium as a negative electrode material has the advantages of high theoretical capacity and large energy density, but at the same time, the metal lithium negative electrode also has the problem of poor cycle stability. The application introduces the Li2Se component into the metal lithium to build a Li-M / Li2Se / Li lithium composite negative electrode material, so that the negative electrode material has high capacity while the lithium ion is stably transmitted inside the negative electrode, so that the negative electrode has high capacity and cycle stability, and the comprehensive performance of the battery is improved.

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

[0044] By controlling the ratio of the amount of substance of Se element to the total amount of substance of Se element and Li element in the lithium composite negative electrode material, the mass proportion of Li2Se in the lithium composite negative electrode material can be controlled, which is beneficial to further improve the cycle stability of the negative electrode and the cycle performance of the battery.

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

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

[0047] In some specific embodiments, the ratio of the amount of substance of Se element to the total amount of substance of Se element and Li element in the lithium composite negative electrode material can 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 difference in the reduction potential of different Li-M alloys, the stability inside the negative electrode has differences, and therefore, by optimizing the type of element M, the cycle stability of the negative electrode is further improved, and the cycle performance of the battery is improved.

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

[0051] Under an inert atmosphere, the metal selenide is reacted with molten 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 application introduces Li2Se in the negative electrode material system by reacting the metal selenide with molten lithium. The Li2Se introduced in this way can be uniformly dispersed in the entire negative electrode material system, improving the uniformity and consistency of the negative electrode material, thereby constructing a stable lithium ion transmission path in the entire system and improving the cycle stability of the negative electrode.

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

[0054] In some embodiments, the metal element in the metal selenide can include one or more of magnesium, calcium, aluminum, titanium, zirconium, manganese, cobalt, nickel, copper, zinc, and niobium. The metal selenide can include one or more of magnesium selenide MgSe, calcium selenide CaSe, aluminum selenide Al2Se3, titanium selenide TiSe2, zirconium selenide ZrSe2, manganese selenide MnSe, cobalt selenide CoSe, nickel selenide NiSe, copper selenide CuSe, zinc selenide ZnSe, and niobium selenide Nb2Se5.

[0055] In some embodiments, before the metal selenide is reacted with the molten lithium metal, the lithium metal is heated to above 200°C under an inert atmosphere, and after the lithium metal is molten, surface impurities are removed to obtain bright molten lithium metal. The application does not have a particular limitation on the heating temperature, as long as the lithium metal can be molten.

[0056] By controlling the molar amount of the metal selenide and the molten lithium metal, the application can control the ratio of the amount of substance of Se element to the total amount of substance of Se element and Li element in the obtained lithium composite negative material. In the case that the lithium metal fully participates in the reaction, the lithium composite negative material can include two components of Li-M and Li2Se. In the case that the lithium metal is excessive, the lithium composite negative material can include three components of Li-M, Li2Se and Li, and a Li-M / Li2Se / Li lithium composite negative material is constructed. The Li-M / Li2Se / Li lithium composite negative material can take into account both high capacity and cycle stability.

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

[0058] Due to the use of the lithium composite negative material of the first aspect of the application or the lithium composite negative material obtained by the preparation method of the second aspect of the application, the negative electrode of the application has improved cycle stability.

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

[0060] Due to the use of the negative electrode of the third aspect of the application, the solid-state lithium battery of the application has improved cycle performance.

[0061] The fifth aspect of the application provides a preparation method of a solid-state lithium battery, which includes the following steps:

[0062] The lithium composite negative material is prepared by the preparation method of the second aspect of the application;

[0063] The molten lithium composite negative material is injected into a mold to make the lithium composite negative material contact one side of the solid electrolyte sheet, and the negative electrode is obtained 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 impregnated with the electrolyte, the other side of the solid electrolyte sheet is contacted to obtain the solid-state lithium battery.

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

[0067] In addition, in the case that the prepared lithium composite negative electrode material contains a metal lithium component, in the process of preparing the solid-state lithium battery, the molten metal lithium is reacted with the metal selenide, which can reduce the surface tension of the molten metal lithium and improve the affinity of the molten metal 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 metal lithium and the solid electrolyte.

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

[0069] In some embodiments, the solid electrolyte can be one of the oxide solid electrolyte systems, such as lithium lanthanum zirconium oxide Li7La3Zr2O12. 12 , lithium lanthanum zirconium tantalum oxide Li 6.5 La3Zr 1.5 Ta 0.5 O 12 .

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

[0071] As an example, the electrolyte salt can be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium bisoxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate 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), methyl ethyl 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), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

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

[0074] In some embodiments, after cooling, the solid electrolyte edge is polished to prevent short circuiting.

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

[0076] The specific type of positive electrode active material is not limited, and active materials known in the art that can be used in the positive electrode of a secondary battery can be used, and a person skilled in the art can select according to actual needs.

[0077] By way of example, the positive electrode active material can include, but is not limited to, one or more of lithium transition metal oxides, olivine-structured lithium-containing phosphates, and their respective modified compounds. Examples of lithium transition metal oxides can 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 olivine-structured lithium-containing phosphates can include, but are not limited to, one or more of lithium iron phosphate, a composite of lithium iron phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon, and their modified compounds. These materials can all be obtained through commercial channels.

[0078] In some embodiments, the modified compounds of the above-mentioned materials can be doping modification and / or surface coating modification of the materials.

[0079] By way of example, the conductive agent can be one or more of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, Super P (SP), graphene, and carbon nanofibers.

[0080] By way of 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 can use a conventional metal foil or a composite current collector (a metal material can be arranged on a polymer substrate to form a composite current collector). By way of example, the positive electrode current collector can use an aluminum foil.

[0082] The sixth aspect of the present application provides a power utilization device, characterized in that the power utilization device comprises 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 examples. The following examples more specifically describe the content disclosed in the present application, and the examples are only used for illustrative description, since various modifications and changes within the scope of the content disclosed in the present application are obvious to those skilled in the art. 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 materials

[0085] Example 1

[0086] Under an argon atmosphere, the metallic lithium was placed in a stainless steel container and heated to 250℃, and after the metallic lithium was molten, the surface impurities were removed to obtain bright molten metallic lithium.

[0087] Under an argon atmosphere, a certain amount of CuSe was added to the molten metallic lithium, wherein the molar ratio of CuSe to metallic lithium was 15:85. The reaction was continuously stirred until the CuSe was completely reacted with the molten lithium, and finally the Li-Cu / Li2Se / Li lithium composite negative electrode material was prepared. The reaction was completely determined by testing the X-ray diffraction pattern (XRD) of the reaction system, and there was no peak of CuSe in the pattern. The ratio of the amount of substance of Se element to the total amount of substance of Se element and Li element in the obtained lithium composite negative electrode material was 15:100.

[0088] Examples 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 substance of Se element to the total amount of substance of Se element and Li element in the obtained lithium composite negative electrode material 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] Examples 9-19

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

[0094] Table 2

[0095]

[0096] Comparative Example 1

[0097] A metal 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 the molten metal lithium.

[0100] Preparation of symmetric batteries

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

[0102] The molten lithium composite negative electrode material or metal lithium negative electrode material prepared was quantitatively poured into a mold so that the negative electrode material contacted and bonded to one side of a solid electrolyte sheet (lithium lanthanum zirconium oxide Li7La3Zr2O 12 ) having a thickness of 0.5 mm. After the entire body cooled, the edges of the solid electrolyte were polished to prevent short circuiting, and then assembled into a symmetric battery.

[0103] Preparation of solid-state lithium batteries

[0104] Solid-state lithium batteries were prepared according to the following general preparation method using the lithium composite negative electrode materials or metal lithium negative electrode materials prepared in Examples 1-19 and Comparative Examples 1-2.

[0105] (1) The molten lithium composite negative electrode material or metal lithium negative electrode material prepared was quantitatively poured into a mold so that the negative electrode material contacted and bonded to one side of a solid electrolyte sheet (lithium lanthanum zirconium oxide Li7La3Zr2O 12 ) having a thickness of 0.5 mm. After the entire body cooled, the edges of the solid electrolyte were polished to prevent short circuiting.

[0106] (2) A positive electrode active material lithium iron phosphate, a conductive agent Super P, and a binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 96.5:1.5:2, added to a solvent N-methyl pyrrolidone (NMP), and stirred uniformly under the action of a vacuum stirrer to obtain a positive electrode slurry, wherein the solid content in the positive electrode slurry was 65% by weight; the positive electrode slurry was uniformly coated on a positive electrode current collector aluminum foil and dried at 85°C, then subjected to cold pressing, edge cutting, sheet cutting, and slitting, and finally dried again under vacuum at 85°C to obtain a positive electrode sheet.

[0107] (3) The organic solvent is a mixture of ethylene carbonate (EC), methyl ethyl carbonate (EMC) and diethyl carbonate (DEC), wherein the volume ratio of EC, EMC and DEC is 20:20:60. In an argon glove box with a water content <10 ppm, a fully dried lithium salt LiPF6 is dissolved in the above organic solvent, then an additive is added, mixed uniformly to obtain an electrolyte. The concentration of the lithium salt is 1 mol / L.

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

[0109] Battery performance testing

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

[0111] The interface impedance of the symmetric battery was tested by an electrochemical workstation, and 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 constant current charge-discharge test was carried out by a charge-discharge tester, and the current density was 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 / 2.0 mA / cm 2 , and the charge-discharge time was 30 min. The results are shown in Table 3 below. The greater the limiting current density, the better the rate performance of the battery.

[0114] 3. Capacity retention rate test

[0115] The constant current charge-discharge test was carried out by a charge-discharge tester, and the charge-discharge cycle was carried out at 0.5C rate for 500 times, and the capacity retention rate was calculated by the capacity before and after the cycle. The results are shown in Table 3 below.

[0116] Table 3

[0117]

[0118]

[0119] As can be seen from the examples and comparative examples, the application utilizes Li2Se with high ionic conductivity to construct a stable lithium ion transmission path inside the negative electrode, so that the lithium ion can be stably transmitted inside the negative electrode during the cycle process, thereby improving the cycle stability of the negative electrode, and further improving the cycle performance of the battery. In addition, by introducing Li2Se, the interface impedance between the negative electrode and the solid electrolyte is reduced, and the rate performance of the battery is also improved.

[0120] The above description is only the preferred embodiment of the application, but the protection scope of the application is not limited to this. Any changes or replacements within the technical range disclosed by the application can be easily thought by those skilled in the art, and should be covered in the protection scope of the application. Therefore, the protection scope of the application should be subject to the protection scope of the claims.

Claims

1. A lithium composite negative electrode material, characterized by, The lithium composite negative electrode material comprises at least two components of Li-M and Li2Se, wherein M comprises one or more of a second main group metal element, a third main group metal element and a transition metal element.

2. The lithium composite anode material of claim 1, wherein, The lithium composite negative electrode material further comprises a metallic lithium component to form a Li-M / Li2Se / Li lithium composite negative electrode material. 3.The lithium composite negative material according to claim 1 or 2, characterized in that, The ratio of the amount of substance of Se to the total amount of substance of Se and Li in the lithium composite negative electrode material is (2.5-25):

100.

4. The lithium composite anode material of claim 3, wherein the carbon-based material is selected from the group consisting of graphite, carbon black, carbon nanotubes, carbon nanofibers, and combinations thereof. The ratio of the amount of substance of Se to the total amount of substance of Se and Li in the lithium composite negative electrode material is (10-20):

100.

5. The lithium composite anode material of any one of claims 1-4, wherein, M comprises 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 material, characterized in that, The method comprises the following steps: reacting a metal selenide with molten lithium under an inert atmosphere to obtain a lithium composite negative electrode material, wherein the metal element in the metal selenide comprises one or more of a second main group metal element, a third main group metal element and a transition metal element, and the molten lithium is in excess relative to the metal selenide.

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

8. A solid-state lithium battery, characterized by, The solid-state lithium battery comprises a positive electrode, a solid electrolyte sheet and the negative electrode of claim 7.

9. A method of producing a solid-state lithium battery, characterized by, The method comprises the following steps: The lithium composite negative electrode material is prepared by the preparation method of claim 6; The molten lithium composite negative electrode material is injected into a mold to make the lithium composite negative electrode material contact one side of a solid electrolyte sheet, and the negative electrode is obtained after cooling; A positive electrode slurry is coated on a positive electrode current collector, and the positive electrode is obtained after drying; After the positive electrode is impregnated with an electrolyte, the other side of the solid electrolyte sheet is contacted to obtain a solid-state lithium battery.

10. An electrical device, characterized by The solid-state lithium battery comprises the solid-state lithium battery of claim 8 or the solid-state lithium battery obtained by the preparation method of claim 9.

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