Negative electrode composition, negative electrode sheet and preparation method therefor, battery and electric device

Abstract

The present application belongs to the technical field of batteries. Provided are a negative electrode composition, a negative electrode sheet and a preparation method therefor, a battery and an electric device. The negative electrode sheet comprises a negative electrode current collector and a negative electrode modification layer located on a surface of the negative electrode current collector, wherein the negative electrode modification layer comprises lithium sulfide, a lithium alloy formed by lithium and a lithiophilic metal, and a lithiophobic metal, the atomic molar ratio of the lithiophilic metal in the lithium alloy to the lithiophobic metal being (1-30):1. The negative electrode sheet can improve the safety and cycling stability of a battery.

Description

Negative electrode composition, negative electrode sheet and preparation method thereof, battery and electrical device

[0001] Priority information

[0002] This application claims priority to and the benefits of patent application 202410002342.0 filed with the State Intellectual Property Office of China on January 2, 2024, and the entire text of which is incorporated herein by reference. Technical Field

[0003] The present application belongs to the field of battery technology, and specifically relates to a negative electrode composition, a negative electrode plate and a preparation method thereof, a battery and an electrical device. Background Art

[0004] Lithium-ion batteries have been widely used in electronic devices such as electric vehicles, mobile phones, and laptop computers due to their high energy density, long discharge life, and low self-discharge. With the development of technology and market demand, higher requirements are placed on the capacity, cycle performance, and safety performance of batteries. As the main material in lithium-ion batteries, the negative electrode material is the carrier of lithium ions and electrons during the charging process of the battery, and plays the role of energy storage and release. Currently, the commercial lithium-ion battery negative electrode materials mainly include carbon negative electrodes (such as natural graphite, disordered carbon), silicon negative electrodes, etc., but these negative electrode materials have problems such as low capacity and short cycle life. Lithium metal can be used as a new battery negative electrode due to its high theoretical capacity and lowest reduction potential. However, it can easily lead to safety hazards, excessive impedance, poor stability, and other problems in the battery.

[0005] Therefore, it is necessary to further improve the negative electrode sheet.

[0006] Summary of the Invention

[0007] In response to the above-mentioned problems, the present application aims to provide a negative electrode composition, a negative electrode sheet, a method for preparing the same, a battery, and an electrical device. The negative electrode sheet is introduced with a negative electrode modification layer formed from the negative electrode composition to inhibit metal dendrite growth and improve battery safety and cycle stability.

[0008] In a first aspect, the present application provides a negative electrode plate, comprising a negative electrode current collector and a negative electrode modification layer located on the surface of the negative electrode current collector, wherein the negative electrode modification layer comprises lithium sulfide, a lithium alloy formed by lithium and a lithium-philic metal, and a lithium-phobic metal, and the atomic molar ratio of the lithium-philic metal in the lithium alloy to the lithium-phobic metal is (1 to 30):1.

[0009] In the negative electrode sheet of the present application, the negative electrode modification layer is introduced on the surface of the current collector, which can make the negative electrode have high electrical conductivity / lithium conduction / lithium affinity properties, and form a barrier protection effect on the lithium metal in the negative electrode sheet to a certain extent, thereby improving the cycle performance, rate performance and safety performance of the battery. Specifically, lithium sulfide (Li2S) has the ability to conduct lithium ions and stabilize the interface, and the lithium alloy has a lithium affinity property, which can effectively reduce the initial nucleation overpotential of the negative electrode lithium metal, promote the subsequent uniform nucleation of lithium metal on the negative electrode surface, and inhibit dendrite formation. The lithium-phobic metal has high stability and conductivity, which helps to uniform the electrode surface electric field, and creates a dendrite-free growth behavior. It can also avoid the lithium metal in the negative electrode from directly contacting the electrolyte to a certain extent to produce side reactions, thereby improving the cycle life of the battery. Moreover, controlling the relative content of the lithium-philic metal and the lithium-phobic metal can avoid excessive resistance while inhibiting dendrite formation. In this way, the battery has high rate performance while ensuring safety.

[0010] In some embodiments of the present application, the atomic molar ratio of the lithiophilic metal to the lithiophobic metal in the lithium alloy is (2-10) : 1. This can improve the battery's safety and cycle stability while also enhancing its rate performance.

[0011] In some embodiments of the present application, the ratio of the total mass of the lithiophilic metal and the lithiophobic metal in the lithium alloy to the mass of lithium sulfide is (4-60):1.

[0012] Optionally, the ratio of the total mass of the lithiophilic metal and the lithiophobic metal in the lithium alloy to the mass of lithium sulfide is (10-50):1.

[0013] In some embodiments of the present application, the lithium-affinity metal includes at least one of zinc, indium, aluminum, magnesium, silver, tin, gallium, antimony, bismuth, or germanium. Alternatively, the lithium-affinity metal includes indium. Thus, the lithium-indium alloy formed by indium and lithium has a higher affinity for lithium, thereby enhancing ion migration.

[0014] In some embodiments of the present application, the resistivity of the lithium-phobic metal is lower than 15 μΩ·cm at 20° C. Optionally, the lithium-phobic metal includes at least one of copper, iron, nickel, cobalt or tungsten.

[0015] In some embodiments of the present application, the negative electrode modification layer further includes a binder, which can provide adhesion between the components in the modification layer and between the negative electrode modification layer and the current collector, thereby improving the stability of the modification layer in the negative electrode sheet.

[0016] In some embodiments of the present application, the binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinylidene fluoride-hexafluoropropylene, or tetrafluoroethylene-hexafluoroethylene copolymer, thereby further improving the structural stability of the negative electrode modification layer.

[0017] In some embodiments of the present application, based on the total weight of lithium sulfide, binder, lithium-phobic metal and lithium-philic metal in lithium alloy, the mass content of lithium sulfide is 1% to 16%, the total mass content of lithium-phobic metal and lithium-philic metal in lithium alloy is 75% to 98%, and the mass content of binder is 1% to 10%.

[0018] Optionally, based on the total weight of lithium sulfide, binder, lithium-repelling metal, and the lithium-philic metal in the lithium alloy, the mass content of lithium sulfide is 2% to 8%, the total mass content of the lithium-repelling metal and the lithium-philic metal in the lithium alloy is 85% to 95%, and the mass content of the binder is 3% to 7%. Controlling the lithium sulfide within this range not only ensures good lithium conductivity and stabilizes the SEI film, but also further prevents excessive impedance on the negative electrode side, thereby improving the rate performance of the battery.

[0019] In some embodiments of the present application, the total weight of lithium sulfide, binder, lithium-phobic metal and lithium-philic metal in lithium alloy per unit area of ​​the negative electrode sheet is 0.3 mg / cm 2 ~1.0mg / cm 2 As a result, the growth of dendrites is effectively suppressed while the impact on the quality and volume energy density of the battery cell is reduced.

[0020] In some embodiments of the present application, the negative electrode plate further includes a lithium metal negative electrode layer, and the lithium metal negative electrode layer is located on a side of the negative electrode modification layer away from the negative electrode current collector.

[0021] In some embodiments of the present application, the negative electrode current collector includes at least one of copper foil, titanium foil, or stainless steel.

[0022] In a second aspect, the present application provides a negative electrode composition comprising lithium sulfide, a lithiophilic metal and a lithiophobic metal; wherein the molar ratio of the lithiophilic metal to the lithiophobic metal is (1-30):1.

[0023] In the negative electrode composition provided by the present application, during the first lithium deposition process, the lithium-philic metal can form a lithium alloy with lithium. The lithium alloy has a high lithium conductivity, which is conducive to the rapid lateral and longitudinal migration of lithium metal at high current density, promoting the uniform deposition of lithium on the one hand, and reducing the polarization potential of the negative electrode on the other hand; lithium sulfide has the ability to conduct lithium ions and stabilize the negative electrode interface, and the lithium-phobic metal can exist stably and has high conductivity, which helps to uniform the electrode surface electric field and can avoid the side reaction of lithium metal in direct contact with the electrolyte to a certain extent. In this way, the negative electrode composition and the negative electrode modification layer formed after lithium deposition can effectively protect the negative electrode sheet and improve the cycle performance, rate performance and safety performance of the battery.

[0024] In some embodiments of the present application, the molar ratio of the lithiophilic metal to the lithiophobic metal is (2-10) : 1. This can improve the battery's safety and cycle stability while also enhancing its rate performance.

[0025] In some embodiments of the present application, the ratio of the total mass of the lithiophilic metal and the lithiophobic metal to the mass of lithium sulfide is (4-60):1.

[0026] Optionally, the ratio of the total mass of the lithiophilic metal and the lithiophobic metal to the mass of lithium sulfide is (10-50):1.

[0027] In some embodiments of the present application, the lithium-philic metal includes at least one of zinc, indium, aluminum, magnesium, silver, tin, gallium, antimony, bismuth, or germanium. Optionally, the lithium-philic metal includes indium. Thus, the lithium-indium alloy formed with the subsequently deposited lithium has a higher affinity for lithium, thereby enhancing ion migration.

[0028] In some embodiments of the present application, the resistivity of the lithium-phobic metal is lower than 15 μΩ·cm at 20° C. Optionally, the lithium-phobic metal includes at least one of copper, iron, nickel, cobalt or tungsten.

[0029] In some embodiments of the present application, the negative electrode composition further includes a binder.

[0030] In some embodiments of the present application, the binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinylidene fluoride-hexafluoropropylene, or tetrafluoroethylene-hexafluoropropylene copolymer, thereby facilitating the maintenance of structural stability of the modified layer.

[0031] In some embodiments of the present application, based on the total weight of the negative electrode composition, the mass content of lithium sulfide is 1% to 16%, the total mass content of the lithium-phobic metal and the lithium-philic metal is 75% to 98%, and the mass content of the binder is 1% to 10%.

[0032] Optionally, based on the total weight of the negative electrode composition, the mass content of lithium sulfide is 2% to 8%, the total mass content of the lithiophobic metal and the lithiophilic metal is 85% to 95%, and the mass content of the binder is 3% to 7%. Controlling the lithium sulfide content within this range not only provides good lithium conductivity and stabilizes the SEI film, but also further prevents excessive impedance on the negative electrode side, thereby improving the rate performance of the battery.

[0033] In some embodiments of the present application, the median particle size Dv of the lithium-philic metal 50 The median particle size Dv of the lithium-phobic metal is 20nm to 500nm. 50 Thus, the lithium-philic metal and the lithium-phobic metal cooperate with each other, so that the negative electrode modification layer formed can further uniformize the electric field and promote ion conduction.

[0034] In a third aspect, the present application provides a method for preparing a negative electrode sheet, comprising:

[0035] Preparation of composite layer:

[0036] applying the negative electrode composition described in the second aspect of the present application on the negative electrode current collector to form a composite layer;

[0037] Pre-deposition of lithium metal:

[0038] The lithium-philic metal in the composite layer forms a lithium alloy with the deposited lithium ions, thereby forming a negative electrode modification layer on the surface of the negative electrode current collector.

[0039] In the preparation method of the present application, the negative electrode composition, combined with the deposited lithium ions, can in situ form a negative electrode modification layer on the current collector surface, giving the negative electrode plate both high electrical conductivity, lithium conductivity, and lithium affinity, while also forming a barrier protection for lithium metal, thereby improving the cycle performance, rate capability, and safety performance of the lithium-ion battery. Furthermore, the method of the present application can directly control the composition of the negative electrode composition, easily obtaining a negative electrode modification layer with better performance, and improving the applicability of the negative electrode plate.

[0040] In some embodiments of the present application, the weight of the negative electrode composition per unit area of ​​the negative electrode sheet is 0.3 mg / cm 2 ~1.0mg / cm 2 As a result, the growth of dendrites is effectively suppressed while the impact on the quality and volume energy density of the battery cell is reduced.

[0041] In some embodiments of the present application, the process of pre-depositing metallic lithium further comprises: continuing to form a lithium metal negative electrode layer on the negative electrode modification layer by depositing lithium ions.

[0042] In some embodiments of the present application, the conditions for pre-depositing lithium metal include: a current density of 0.5 mA / cm2 ~2mA / cm 2 Thus, while ensuring the preparation efficiency, lithium alloying and the formation of the lithium metal negative electrode layer can be further promoted.

[0043] In some embodiments of the present application, the pre-deposition makes the pre-deposition capacity of lithium on the negative electrode sheet 1 mAh / cm 2 ~20mAh / cm 2 As a result, while lithium and the lithium-philic metal form a lithium alloy, the thickness of the lithium metal layer can be further controlled, minimizing the impact of an excessively high lithium metal layer on the cell volume and mass energy density, and avoiding the problem of excessive lithium depletion leading to premature battery capacity drop caused by a low lithium metal layer. This improves the overall performance of the battery.

[0044] In a fourth aspect, the present application provides a battery, comprising the negative electrode sheet described in the first aspect of the present application or the negative electrode sheet prepared by the preparation method described in the third aspect of the present application.

[0045] In a fifth aspect, the present application provides an electrical device comprising the battery described in the fourth aspect of the present application.

[0046] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Various other advantages and benefits will become apparent to those skilled in the art by reading the detailed description of the preferred embodiment below. The accompanying drawings are only for the purpose of illustrating the preferred embodiment and are not to be considered as limiting the present application. In the accompanying drawings:

[0048] FIG1 is a schematic diagram of a negative electrode sheet according to an embodiment of the present application;

[0049] FIG2 is an exploded view of a battery cell according to an embodiment of the present application;

[0050] FIG3 is an exploded view of a battery cell according to an embodiment of the present application;

[0051] FIG4 is a schematic diagram of a battery module according to an embodiment of the present application;

[0052] FIG5 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0053] FIG6 is an exploded view of the battery pack shown in FIG5 according to an embodiment of the present application;

[0054] FIG7 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0055] Description of reference numerals:

[0056] 1: Battery pack; 2: Upper case; 3: Lower case; 4: Battery module; 5: Battery cell; 51: Shell; 52: Electrode assembly; 53: Top cover assembly; 6: Negative electrode sheet; 61: Negative current collector; 62: Negative electrode modification layer; 621: Lithium sulfide particles; 622: Lithium alloy particles; 623: Lithium-phobic metal particles. DETAILED DESCRIPTION

[0057] The present application will be further described below in conjunction with specific embodiments. It should be understood that these specific embodiments are only used to illustrate the present application and are not used to limit the scope of the present application.

[0058] In this application, references to "embodiments" mean that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of such phrases in various locations in the specification does not necessarily refer to the same embodiment, nor do they represent independent or alternative embodiments that are mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0059] " Scope " disclosed in the present application is limited in the form of lower limit and / or upper limit, and given range is limited by selecting a lower limit and / or an upper limit, and the selected lower limit and / or the rear upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form the scope of not clearly recording, and any lower limit can be combined with other lower limits to form the scope of not clearly recording, and any upper limit can be combined with any other upper limit to form the scope of not clearly recording. In addition, each separately disclosed point or single numerical value itself can be used as lower limit or upper limit and any other point or single numerical value combination or with other lower limit or upper limit combination to form the scope of not clearly recording.

[0060] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0061] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of this application.

[0062] Unless otherwise specified, the terms "include," "comprising," "containing," "having," and "having" used in this application may be open-ended or closed-ended. For example, "include," "comprising," "containing," "having," and "having" may indicate that other components not listed may also be included or contained, or may indicate that only the listed components are included or contained. In addition, in this application, the terms "plurality," "multiple," and "at least one" refer to more than two. "Above" and "below" are inclusive of the number itself. For example, "two or more" includes two itself, such as two, three, four, or more.

[0063] Unless otherwise specified, the term "and / or" in this application simply describes an association between related objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Furthermore, the character " / " in this document generally indicates that the related objects are in an "or" relationship.

[0064] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and any variations thereof are intended to cover non-exclusive inclusions. Unless otherwise specified, the terms used in this application have the well-known meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

[0065] Lithium-ion batteries using lithium metal as the negative electrode have an extremely high theoretical energy density and have therefore attracted extensive research attention. However, compared to the carbon material negative electrodes such as graphite in commercial lithium-ion batteries, which use an embedding / extraction mechanism, the lithium metal negative electrode in lithium-ion batteries belongs to a metal deposition / stripping mechanism, which has problems such as metal dendrite growth. Specifically, the inherent roughness, defects and uneven composition of the lithium metal negative electrode interface lead to uneven negative electrode interface properties. During the cycle process, it is very easy to form "hot spot" areas with high electric field / ionic field intensity, which in turn causes non-uniform deposition and stripping of lithium metal, forming dendrites and dead lithium. On the one hand, this will cause a large amount of electrolyte to react with lithium to form a solid electrolyte interface (SEI film), consuming limited active lithium and electrolyte; on the other hand, the growing dendrites will puncture the diaphragm, causing a short circuit between the positive and negative electrodes, posing a safety hazard.

[0066] To this end, a first aspect of the present application provides a negative electrode plate, comprising a negative electrode current collector and a negative electrode modification layer located on a surface of the negative electrode current collector. The negative electrode modification layer comprises lithium sulfide, a lithium alloy, and a lithium-phobic metal, wherein the lithium alloy is formed from lithium and a lithium-philic metal, and the atomic molar ratio of the lithium-philic metal to the lithium-phobic metal in the lithium alloy is (1-30):1.

[0067] In the negative electrode sheet of the present application, the negative electrode modification layer is introduced on the surface of the current collector, which can make the negative electrode have the properties of high conductivity / lithium conduction / lithium affinity, and form a barrier protection effect on the lithium metal in the negative electrode sheet to a certain extent, thereby improving the cycle performance, rate performance and safety performance of the battery. Specifically, lithium sulfide (Li2S) has the ability to conduct lithium ions and stabilize the negative electrode interface, and the lithium alloy has a lithium affinity property, which can effectively reduce the initial nucleation overpotential of the negative electrode lithium metal, promote the subsequent uniform nucleation of lithium metal on the negative electrode surface, and inhibit dendrite formation. The lithium-phobic metal has high stability and conductivity, which helps to uniform the electrode surface electric field. By introducing the modification layer to create a dendrite-free growth behavior itself, it can also avoid the lithium metal in the negative electrode from directly contacting the electrolyte to a certain extent to produce side reactions, thereby improving the cycle life of the battery; controlling the relative content of the lithium-philic metal and the lithium-phobic metal can avoid excessive resistance while inhibiting dendrite formation. In this way, the battery has high rate performance while ensuring safety.

[0068] In the present application, a lithiophilic metal refers to a metal that can form a lithium alloy with lithium. Lithiophilic metals have high wettability to lithium, and these metals usually have a Gibbs free energy (ΔG) of reaction with molten lithium in the temperature range of 180°C to 300°C that is less than 0. Specific examples of lithiophilic metals include, but are not limited to, Mg, Ca, Sc, Al, Se, Sr, Sn, In, Ba, Ag, Zn, Sb, Rh, Ir, Pb, Au, Ge, Ga, etc. Lithiophobic metals refer to metals with poor wettability to lithium, and usually have a Gibbs free energy (ΔG) of reaction with molten lithium that is greater than 0. Specific examples of lithiophilic metals include, but are not limited to, Cu, Ti, V, Ni, Co, Mn, Fe, Cr, W, Re, Cs, etc.

[0069] In some embodiments, the lithiophilic metal includes at least one of zinc (Zn), indium (In), aluminum (Pb), magnesium (Mg), silver (Ag), tin (Sn), gallium (Ga), antimony (Sb), bismuth (Bi), or germanium (Ge). Alternatively, the lithiophilic metal includes indium. Thus, the lithium-indium alloy formed by indium and lithium has a higher affinity for lithium, thereby improving ion migration.

[0070] In some embodiments, the resistivity of the lithium-phobic metal is lower than 15 μΩ·cm at 20° C. From the perspective of reducing costs, the lithium-phobic metal optionally includes at least one of copper, iron, nickel, cobalt, or tungsten.

[0071] According to the present application, in the negative electrode modification layer, the lithium alloy (lithium-lithium-philic metal) helps to suppress dendrite formation, and the lithium-phobic metal has lithium-phobic properties, has high conductivity, and can stably exist in the electrolyte and charge and discharge environment. To this end, the atomic molar ratio of the lithium-philic metal in the lithium alloy and the lithium-phobic metal is controlled to be (1 to 30): 1, which can enable the battery to have higher comprehensive performance. As some examples, in the negative electrode modification layer, the atomic molar ratio of the lithium-philic metal and the lithium-phobic metal can be 1: 1, 2: 1, 3: 1, 4: 1, 5: 1, 6: 1, 7: 1, 8: 1, 9: 1, 10: 1, 11: 1, 12: 1, 15: 1, 17: 1, 20: 1, 25: 1, 30: 1, etc.

[0072] Optionally, the atomic molar ratio of the lithiophilic metal to the lithiophobic metal in the lithium alloy is (2-10) : 1. Thus, the battery can have higher safety and cycle stability while improving the rate performance of the battery.

[0073] In some embodiments, the ratio of the total mass of the lithiophilic metal and the lithiophobic metal in the lithium alloy to the mass of lithium sulfide is (4-60):1, for example, 4:1, 5:1, 8:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 18:1, 20:1, 25:1, 30:1, 40:1, 45:1, 47:1, 50:1, 60:1, etc.

[0074] Optionally, the ratio of the total mass of the lithiophilic metal and the lithiophobic metal in the lithium alloy to the mass of lithium sulfide is (10-50):1.

[0075] In some embodiments, the negative electrode modification layer further includes a binder. The binder can provide adhesion between the components of the modification layer and between the negative electrode modification layer and the current collector, thereby improving the stability of the modification layer within the negative electrode sheet. For example, the binder can be an oil-soluble binder. This binder is miscible with the organic solvent during slurry preparation, allowing the organic solvent to evaporate more easily during coating formation, thereby reducing the impact of residual solvent on the battery.

[0076] Optionally, the binder includes at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP, CAS No.: 9011-17-0), or tetrafluoroethylene-hexafluoropropylene copolymer (FEP), thereby facilitating the maintenance of structural stability of the modified layer.

[0077] In some embodiments, the negative electrode modification layer is based on the total weight of lithium sulfide, binder, lithium-phobic metal and lithium-philic metal in lithium alloy.

[0078] The mass content of lithium sulfide is 1% to 16%, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 15%, 16%, etc.;

[0079] The total mass content of the lithiophilic metal in the lithiophobic metal and the lithium alloy is 75% to 98%, for example, 75%, 78%, 79%, 80%, 85%, 86%, 87%, 89%, 90%, 91%, 92%, 93%, 95%, 98%, etc.;

[0080] The mass content of the binder is 1% to 10%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.

[0081] It can be understood that the mass of the lithium-philic metal in the lithium alloy refers to the mass contributed by the lithium-philic metal atoms. For example, if the lithium-philic metal is indium, the mass of the lithium-philic metal in the lithium alloy refers to the mass of indium atoms in the lithium-indium alloy.

[0082] Furthermore, in the negative electrode modification layer, based on the total weight of lithium sulfide, binder, lithium-phobic metal, and lithium-philic metal in the lithium alloy, the mass content of lithium sulfide is 2% to 8%, the total mass content of the lithium-phobic metal and the lithium-philic metal in the lithium alloy is 85% to 95%, and the mass content of the binder is 3% to 7%. Therefore, controlling the lithium sulfide within this range can not only play a role in good lithium conduction and stabilizing the SEI film, but also further avoid excessive impedance on the negative electrode side, thereby improving the rate performance of the battery.

[0083] In the present application, the total weight of lithium sulfide, binder, lithium-phobic metal and lithium-philic metal in lithium alloy per unit area of ​​the negative electrode plate can be, for example, 0.1 mg / cm 2 ~2mg / cm 2 In some embodiments, the total weight of lithium sulfide, binder, lithium-phobic metal, and lithium-philic metal in the lithium alloy per unit area of ​​the negative electrode sheet is 0.3 mg / cm 2 ~1.0mg / cm 2 , for example 0.3 mg / cm 2 , 0.4mg / cm 2 , 0.5mg / cm 2 , 0.6mg / cm 2 , 0.7mg / cm 2 , 0.8mg / cm 2 , 0.9mg / cm 2 , 1.0mg / cm 2Thus, while effectively suppressing the growth of dendrites, the impact on the quality and volume energy density of the battery cell is reduced. Optionally, the total weight of lithium sulfide, binder, lithium-phobic metal and lithium-philic metal in the lithium alloy per unit area of ​​the negative electrode sheet is 0.4 mg / cm 2 ~0.6mg / cm 2 .

[0084] According to the present application, generally, the thickness of the negative electrode modification layer can be, for example, 2 μm to 8 μm, such as 2 μm, 2.5 μm, 3 μm, 4 μm, 5 μm, 6 μm, etc.

[0085] In some embodiments, the negative electrode plate further includes a lithium metal negative electrode layer, and the lithium metal negative electrode layer is located on a side of the negative electrode modification layer away from the negative electrode current collector.

[0086] In the present application, the negative electrode current collector may be, for example, a metal foil. In some embodiments, the negative electrode current collector includes at least one of copper foil, titanium foil, or stainless steel.

[0087] In the present application, the thickness of the negative electrode current collector can be selected according to the specific application of the battery. Generally, the thickness of the negative electrode current collector can be 4 μm to 20 μm, for example, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, etc.

[0088] A second aspect of the present application provides a negative electrode composition comprising lithium sulfide, a lithiophilic metal and a lithiophobic metal, wherein the atomic molar ratio of the lithiophilic metal to the lithiophobic metal is (1-30):1.

[0089] In the negative electrode composition provided by the present application, during the first lithium deposition process, the lithium-philic metal can form a lithium alloy with lithium, which, on the one hand, promotes the uniform deposition of lithium, and on the other hand, can reduce the polarization potential of the negative electrode; lithium sulfide has the ability to conduct lithium ions and stabilize the negative electrode interface, and the lithium-phobic metal can exist stably and has high conductivity, which helps to uniform the electrode surface electric field and can, to a certain extent, avoid the side reactions caused by direct contact between lithium metal and electrolyte. In this way, the negative electrode composition and the negative electrode modification layer formed after lithium deposition can effectively protect the negative electrode sheet and improve the cycle performance, rate performance and safety performance of the battery.

[0090] In some embodiments, the negative electrode composition further includes a binder.

[0091] Unless otherwise specified, the descriptions of the lithiophilic metal, the lithiophobic metal and the binder are as described in the first aspect of the present application and will not be repeated here.

[0092] As some examples, in the negative electrode composition, the ratio of the lithiophilic metal to the lithiophobic metal can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 15:1, 17:1, 20:1, 25:1, 30:1, etc.

[0093] Optionally, in the negative electrode composition, the molar ratio of the lithiophilic metal to the lithiophobic metal is (2-10) : 1. This can improve the battery's safety and cycle stability while also increasing its rate performance.

[0094] In some embodiments, in the negative electrode composition, the ratio of the total mass of the lithiophilic metal and the lithiophobic metal to the mass of lithium sulfide is (4-60):1, for example, 4:1, 5:1, 8:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 18:1, 20:1, 25:1, 30:1, 40:1, 45:1, 47:1, 50:1, 60:1, etc.

[0095] Optionally, in the negative electrode composition, the ratio of the total mass of the lithiophilic metal and the lithiophobic metal to the mass of lithium sulfide is (10-50):1.

[0096] In some embodiments, based on the total weight of the negative electrode composition,

[0097] The mass content of lithium sulfide is 1% to 16%, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 15%, 16%, etc.;

[0098] The total mass content of the lithiophobic metal and the lithiophilic metal is 75% to 98%, for example, 75%, 78%, 79%, 80%, 85%, 86%, 87%, 89%, 90%, 91%, 92%, 93%, 95%, 98%, etc.;

[0099] The mass content of the binder is 1% to 10%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.

[0100] Optionally, based on the total weight of the negative electrode composition, the mass content of lithium sulfide is 2% to 8%, the total mass content of the lithiophobic metal and the lithiophilic metal is 85% to 95%, and the mass content of the binder is 3% to 7%. Thus, controlling the lithium sulfide within this range not only provides good lithium conductivity and stabilizes the SEI film, but also further prevents excessive impedance on the negative electrode side, thereby improving the rate performance of the battery.

[0101] In some embodiments, the median particle size (D V50) is 20nm to 500nm, and the median particle size (Dv 50 ) is 50nm to 200nm. As a result, the lithiophilic metal and the lithiophobic metal cooperate with each other, so that the formed negative electrode modification layer can further uniformize the electric field and promote ion conduction. In this application, the median particle size Dv50 can be obtained by particle size distribution-laser diffraction method with reference to GB / T19077-2016 standard.

[0102] As some examples, the Dv of the lithiophilic metal 50 For example, it is 20nm, 50nm, 80nm, 100nm, 150nm, 200nm, 300nm, etc.

[0103] As some examples, the Dv of the lithium-phobic metal 50 For example, it is 50nm, 80nm, 100nm, 150nm, 200nm, etc.

[0104] A third aspect of the present application provides a method for preparing a negative electrode sheet, comprising:

[0105] Preparation of composite layer:

[0106] applying the negative electrode composition described in the second aspect of the present application on the negative electrode current collector to form a composite layer;

[0107] Pre-deposition of lithium metal:

[0108] The lithium-philic metal in the composite layer forms a lithium alloy with lithium ions, thereby forming a negative electrode modification layer on the surface of the negative electrode current collector.

[0109] In the preparation method of the present application, the negative electrode composition can be combined with the deposited lithium ions to generate an in-situ negative electrode modification layer on the surface of the current collector, so that the negative electrode plate has the properties of high conductivity / lithium conductivity / lithium affinity, while forming a barrier protection effect on lithium metal, thereby improving the cycle performance, rate performance and safety performance of the lithium-ion battery.

[0110] In some embodiments, the negative electrode composition and a solvent (such as NMP) may be mixed to form a slurry, and the slurry may be coated on a negative electrode current collector and dried to form the composite layer.

[0111] In some embodiments, the weight of the negative electrode composition per unit area of ​​the negative electrode sheet is 0.3 mg / cm 2 ~1mg / cm 2 , thereby effectively inhibiting the growth of dendrites while reducing the impact on the quality and volume energy density of the battery cell. Optionally, the weight of the negative electrode composition per unit area of ​​the negative electrode sheet is 0.4 mg / cm 2 ~0.6mg / cm 2 .

[0112] As some examples, methods of forming a composite layer include:

[0113] Mixing the lithiophilic metal and the lithiophobic metal and grinding them uniformly to obtain a metal mixed dry material;

[0114] Mixing the metal dry material, lithium sulfide and a binder and grinding them uniformly to obtain a negative electrode composition;

[0115] Stirring the negative electrode composition and the solvent to obtain a modified layer slurry;

[0116] The modified layer slurry is coated on the negative electrode current collector and dried in a vacuum to form the composite layer.

[0117] In some embodiments, the thickness of the composite layer formed on the current collector can be 0.5 μm to 2 μm, for example, 0.5 μm, 1 μm, 1.2 μm, 1.5 μm, 2 μm, etc. Thus, the formed negative electrode modification layer can fully exert its electrical conductivity, lithium conductivity, and lithium affinity effects, have good interface stability, and at the same time enable the battery to have a higher energy density.

[0118] In the present application, in the step of pre-depositing lithium metal, lithium can penetrate into the composite layer to form a lithium alloy with the lithium-philic metal, and the composite layer swells to form the negative electrode modification layer.

[0119] In some embodiments, the pre-deposition of metallic lithium further includes: continuing to form a lithium metal negative electrode layer on the negative electrode modification layer by depositing lithium ions. In this case, the pre-deposition of metallic lithium can be divided into a first stage and a second stage, which are performed consecutively. In the first stage, lithium ions penetrate into the composite layer to form a lithium alloy with the lithium-philic metal. In the second stage, lithium ions continue to deposit on the negative electrode modification layer to form a lithium metal negative electrode layer.

[0120] In some embodiments, the conditions for pre-depositing lithium metal include: a current density of 0.5 mA / cm 2 ~2mA / cm 2 Thus, while ensuring the efficiency of electrode preparation, the alloying of lithium and the formation of the lithium metal negative electrode layer can be further promoted.

[0121] In some embodiments, lithium metal pre-deposition can be performed by assembling a half-cell.

[0122] As some examples, methods of pre-depositing lithium metal include:

[0123] The negative electrode current collector with a composite layer was used as the working electrode, the lithium copper composite tape was used as the counter electrode, 1 mol / L LiPF6 was used as the electrolyte (solvent: EC and EMC, volume ratio of 3:7), PE was used as the separator, and the electrolyte was 1 mA / cm2 The working electrode is discharged to 0V at a low current density. During this process, the lithium forms an indium-lithium alloy with the lithium-philic metal in the composite layer. As the voltage continues to drop below 0V, lithium ions are deposited to form lithium metal until the lithium deposition capacity reaches a certain level, resulting in a negative electrode. In this method, X-ray photoelectron spectroscopy (XPS) can be used to detect that the indium element is primarily present in the form of a lithium-indium alloy.

[0124] In some embodiments, the pre-deposition allows the pre-deposition capacity of lithium metal on the negative electrode to be 1 mAh / cm 2 ~20mAh / cm 2 , for example 1mAh / cm 2 、3mAh / cm 2 , 5mAh / cm 2 、10mAh / cm 2 、15mAh / cm 2 wait.

[0125] As some examples, FIG1 is a schematic diagram of a negative electrode sheet with a negative electrode modification layer. In FIG1 , the negative electrode sheet 6 includes a negative electrode current collector 61 and a negative electrode modification layer 62 located on its surface. The negative electrode modification layer 62 includes lithium sulfide particles 621, lithium alloy particles 622 (composed of a lithium-philic metal and a deposited Li + Formation) and lithium-phobic metal particles 623.

[0126] The fourth aspect of the present application provides a battery, comprising the negative electrode sheet described in the first aspect of the present application or the negative electrode sheet prepared by the preparation method described in the third aspect of the present application.

[0127] In the present application, the battery may be a secondary battery. It is understood that the secondary battery may be a lithium-ion battery. In some embodiments, the secondary battery further comprises a positive electrode sheet, a separator, and an electrolyte. During the battery charge and discharge process, active ions are intercalated and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte acts as an ion conductor between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet to prevent a short circuit between the positive and negative electrodes while allowing ions to pass through.

[0128] [Positive electrode]

[0129] In some embodiments, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector.

[0130] In the present application, the positive electrode current collector may be, for example, a metal foil or a composite current collector. The metal foil may be, for example, aluminum foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one side of the polymer base layer. The metal layer may be made of, but is not limited to, aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The polymer material of the polymer base layer may be, for example, polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), and the like.

[0131] In the present application, the positive electrode film layer may include a positive electrode active material. The positive electrode active material may be a type commonly used in lithium-ion batteries. In some embodiments, the positive electrode active material may include one or more of a lithium transition metal oxide, an olivine-structured lithium-containing phosphate, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, also referred to as NCM333); LiNi 0.5 Co 0.2 Mn 0.3 O2, also known as NCM523; LiNi 0.5 Co 0.25 Mn 0.25 O2, also referred to as NCM211; LiNi 0.6 Co 0.2 Mn 0.2 O2, also known as NCM622; LiNi 0.8 Co 0.1 Mn 0.1 O2, also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 015 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4, also referred to as LFP), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0132] In the present application, the positive electrode film layer may optionally include a conductive agent. However, the type of conductive agent is not specifically limited and may be selected based on actual needs. As some examples, the conductive agent used in the positive electrode material may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0133] In the present application, the positive electrode film layer may optionally include a binder. As some examples, the binder for the positive electrode material may 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).

[0134] This application does not particularly limit the preparation method of the positive electrode sheet, and the preparation method can refer to existing methods. For example, the positive electrode slurry is coated on the positive electrode current collector, dried, and cold pressed to form the positive electrode sheet. The positive electrode slurry can be formed by dispersing the positive electrode active material, optional conductive agent, optional binder, and other components in a solvent (e.g., N-methylpyrrolidone) and stirring them uniformly.

[0135] As some examples, the ratio of the surface loading of the positive electrode active material in the positive electrode sheet to the surface loading of the negative electrode modification layer in the negative electrode sheet is 30 to 60:1, such as 50:1. The surface loading of the negative electrode modification layer is based on the weight of the negative electrode composition. Optionally, the surface loading of the positive electrode active material in the positive electrode sheet is 20 mg / cm 2 ~40mg / cm 2 .

[0136] In addition, the positive electrode sheet of the present application does not exclude other additional functional layers in addition to the positive electrode film layer. For example, the positive electrode sheet may also include a conductive primer layer (e.g., composed of a conductive agent and a binder) disposed between the positive electrode current collector and the positive electrode film layer. For another example, the positive electrode sheet may also include a protective layer covering the surface of the positive electrode film layer.

[0137] [Electrolytes]

[0138] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0139] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0140] In some embodiments, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0141] In some embodiments, the solvent may include at least one 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), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0142] In some embodiments, the electrolyte may optionally include additives. Such additives may include, for example, negative electrode film-forming additives, positive electrode film-forming additives, and additives capable of improving certain battery properties, such as additives that improve battery overcharge performance, or additives that improve battery high or low temperature performance.

[0143] [Isolation film]

[0144] The separator is placed between the positive and negative electrodes to prevent short circuits between the positive and negative electrodes while allowing active ions to pass through. This application does not impose any particular restrictions on the type of separator, and any porous separator known in the art may be used.

[0145] In some embodiments, the material of the separator can include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. Furthermore, the separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer can be the same or different.

[0146] In some embodiments, a ceramic coating and / or a metal oxide coating is further provided on the isolation membrane.

[0147] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0148] In some embodiments, the battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0149] In some embodiments, the outer packaging may include a housing and a cover plate. The housing may include a bottom plate and side plates connected to the bottom plate, with the bottom plate and side plates enclosing a receiving cavity. The housing may have an opening communicating with the receiving cavity, and the cover plate may be positioned over the opening to seal the receiving cavity. The electrode assembly may be enclosed within the receiving cavity.

[0150] In some embodiments, the outer packaging of the battery is a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.

[0151] In other embodiments, the outer packaging of the battery is a soft package, such as a bag-type soft package. The material of the soft package can be plastic, such as polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0152] The battery of the present application may include a battery cell form, a battery module form, and a battery pack form. The battery cell, battery module, and battery pack of the present application will be described below with reference to the accompanying drawings as appropriate.

[0153] The present application has no particular limitation on the shape of the battery, which can be cylindrical, square, or any other shape. For example, FIG2 shows a square-structured battery cell 5 as an example.

[0154] In some embodiments, referring to Figure 3, the outer packaging may include a shell 51 and a top cover assembly 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the top cover assembly 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell can be one or more, and those skilled in the art can select according to specific actual needs.

[0155] In some embodiments, batteries may be assembled into a battery module. The number of batteries contained in the battery module may be one or more. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0156] Figure 4 shows an example battery module 4. Referring to Figure 4 , within the battery module 4, multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 5 may be secured together using fasteners.

[0157] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0158] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0159] Figures 5 and 6 illustrate an example battery pack 1. Referring to Figures 5 and 6 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be positioned over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0160] The fifth aspect of the present application provides an electrical device comprising the battery described in the fourth aspect of the present application.

[0161] Batteries, battery modules, and battery packs can be used as power sources or energy storage units for electrical devices. Electrical devices may include, but are not limited to, mobile devices (e.g., mobile phones, laptops), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks), electric trains, ships, satellites, and energy storage systems.

[0162] As an electrical device, a battery, battery module or battery pack can be selected according to its usage requirements.

[0163] Figure 7 shows an example of an electric device. This device can be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the battery, a battery pack or battery module can be used.

[0164] As another example, the electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be light and thin, and may use a battery as a power source.

[0165] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0166] Example 1

[0167] (1) Preparation of finishing layer slurry

[0168] Indium powder (Dv 50 =50nm) and copper powder (Dv 50=100 nm) were mixed at a molar ratio of 6:1 and ground uniformly to obtain a metal mixed dry material;

[0169] The metal mixed dry material, lithium sulfide and PVDF-HFP were mixed in a mass ratio of 89:6:5 to obtain a negative electrode composition, and NMP solvent was added and stirred at 500 rpm to obtain a modified layer slurry.

[0170] (2) Preparation of negative electrode sheet

[0171] The modified layer slurry was coated on one side of a copper foil (thickness of 12 μm) and vacuum dried to form a uniform composite layer on the surface of the copper foil. The surface loading of the negative electrode composition was 0.5 mg / cm 2 The negative electrode sheet was cut into a rectangle of 41 mm x 51 mm and the tabs were welded.

[0172] The lithium metal was pre-deposited by assembling a half-cell: the copper foil forming the composite layer was used as the working electrode, the lithium-copper composite tape was used as the counter electrode (lithium-copper composite tape: a lithium foil with a thickness of 50 μm was composited with a copper foil with a thickness of 12 μm by rolling, and then cut into a rectangle of 41 mm × 51 mm and welded to the tabs), 1 mol / L LiPF6 was used as the electrolyte (solvent: EC and EMC, volume ratio of 3:7) as the electrolyte, PE as the separator, and the reaction temperature was 0.15 V at 1 mA / cm 2 At the same current density, the working electrode is discharged to 0V. During this process, lithium ions form an indium-lithium alloy with the indium in the composite layer. The voltage is continuously discharged below 0V, and lithium ions are deposited to form a lithium metal negative electrode layer until the lithium deposition capacity reaches 5mAh cm -2 Until now, the negative electrode sheet is obtained.

[0173] Examples 2-7

[0174] A negative electrode sheet was prepared according to the method of Example 1, except that the molar ratio of indium powder to copper powder was adjusted when preparing the modification layer slurry.

[0175] Examples 8-12

[0176] The negative electrode sheet was prepared according to the method of Example 1, except that when preparing the modification layer slurry, the mass of lithium sulfide was adjusted and the amount of the metal mixed dry material was adjusted accordingly, so that the mass ratio of the total amount of the two to the binder was maintained at 95:5.

[0177] Example 13

[0178] A negative electrode sheet was prepared according to the method of Example 1, except that, when preparing the modification layer slurry, indium powder and copper powder were used in a molar ratio of 5:1 to form a metal dry mixture, and the metal dry mixture, lithium sulfide, and PVDF-HFP were added in a mass ratio of 86:7:7 to form a negative electrode composition.

[0179] Examples 14-15

[0180] The negative electrode sheets were prepared according to the method of Example 1, except that indium powder was replaced by zinc powder (Dv 50 =50nm), silver powder (Dv 50 =50nm).

[0181] Comparative Example 1

[0182] A negative electrode sheet was prepared according to the method of Example 1, except that a copper foil without any modification (same as Example 1) was used as the negative electrode current collector:

[0183] The lithium metal was pre-deposited by assembling a half-cell: copper foil was used as the working electrode, lithium copper composite tape (same as in Example 1) was used as the counter electrode, 1 mol / L LiPF6 was used as the electrolyte (solvent: EC and EMC, volume ratio of 3:7), PE was used as the separator, and the electrolyte was 1 mA / cm 2 At a current density of 500 volts, the working electrode is discharged to below 0 V, and lithium ions are deposited to form a lithium metal negative electrode layer until the lithium deposition capacity reaches 5 mAh cm. -2 Until now, the negative electrode sheet is obtained.

[0184] Comparative Example 2

[0185] A negative electrode sheet was prepared according to the method of Example 1, except that lithium sulfide and copper powder were not added when preparing the modification layer slurry. That is, only PVDF-HFP and indium powder were mixed and ground at a mass ratio of 5:95 to prepare the slurry.

[0186] Comparative Example 3

[0187] A negative electrode sheet was prepared according to the method of Example 1, except that lithium sulfide and indium powder were not added when preparing the modification layer slurry. That is, only PVDF-HFP and copper powder were mixed and ground at a mass ratio of 5:95 to prepare the slurry.

[0188] Comparative Example 4

[0189] A negative electrode sheet was prepared according to the method of Example 1, except that no copper powder was added when preparing the modification layer slurry. That is, only indium powder, lithium sulfide, and PVDF-HFP were mixed and ground in a mass ratio of 89:6:5 to prepare the slurry.

[0190] Comparative Example 5

[0191] A negative electrode sheet was prepared according to the method of Example 1, except that no indium powder was added when preparing the modification layer slurry. That is, only copper powder, lithium sulfide, and PVDF-HFP were mixed and ground in a mass ratio of 89:6:5 to prepare the slurry.

[0192] In the above examples and comparative examples, the amounts of the raw materials used in the modification layer are shown in Table 1.

[0193] Table 1 Note: “Pro-lithium / repellent (n / n)” refers to the molar ratio of the pro-lithium metal to the repellent metal; “area loading” refers to the weight of the negative electrode composition per unit area in the negative electrode sheet; “In / 50” refers to Dv 50 =50nm indium powder, "Cu / 100" represents Dv 50 =100nm copper powder, "Zn / 50" means Dv 50 =50nm zinc powder, "Ag / 50" means Dv 50 =50nm silver powder.

[0194] Test section

[0195] 1. Preparation of batteries

[0196] [Positive electrode]

[0197] The positive electrode active material is lithium nickel cobalt manganese oxide LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive agent acetylene black and binder polytetrafluoroethylene (PVDF) were mixed in a mass ratio of 98:1:1, and N-methylpyrrolidone (NMP) solvent was added and stirred until completely uniform to obtain a positive electrode slurry.

[0198] The positive electrode slurry was evenly coated on both sides of the aluminum foil current collector, with an active material loading of 25 mg / cm 2 After drying and cold pressing steps, it is then cut into 40mm×50mm rectangles as positive electrode sheets.

[0199] [Isolation film]

[0200] Polypropylene film as the separator

[0201] [Electrolyte]

[0202] LiPF6 with a concentration of 1 mol / L is used as the electrolyte, wherein the solvents are EC and EMC, and the volume ratio of the two is 3:7.

[0203] One positive electrode sheet and two negative electrode sheets are stacked in sequence, with a separator film between the positive and negative electrodes to completely isolate them and prevent short circuits. The positive electrode tabs are then welded to the positive electrode. The bare cell is placed in an aluminum-plastic film, electrolyte is injected, and vacuum hot-pressed to seal the package. The sealed cell is left to rest for 8 hours before performance testing. The stacked battery produced in this way has a rated capacity of 140 mAh.

[0204] 2. Performance Testing

[0205] 2-1) First Week Capacity Test

[0206] The test process of the first-week capacity is as follows: at 25°C, the above-prepared battery is charged at a constant current of 0.2C to 4.3V, and then charged at a constant voltage until the current decays to 0.13C; during the discharge process, it is discharged at a rate of 1C until the battery voltage drops to 2.8V, and then the first-week discharge capacity is obtained.

[0207] 2-2) Cyclic performance test

[0208] The cycle performance test process is as follows: at 25°C, the battery is charged at a constant current of 0.2C to 4.3V, and then charged at a constant voltage until the current decays to 0.13C; during the discharge process, it is discharged at a rate of 1C until the battery voltage drops to 2.8V, at which time the initial cycle capacity is obtained. The above charge and discharge system is repeated 150 times, and the discharge capacity of 50 cycles and 150 cycles is recorded. The discharge capacity is divided by the discharge capacity of the first week to obtain the capacity retention rate of 50 cycles and 150 cycles.

[0209] The test results are shown in Table 2.

[0210] Table 2

[0211] Comparing Examples 1-15 with Comparative Examples 1-5, it can be seen that the present application introduces a modified layer formed by the negative electrode composition on the negative electrode plate, which can inhibit the growth of metal dendrites and improve the rate performance, safety and cycle stability of the battery.

[0212] According to the analysis of Examples 1-7, controlling the molar ratio of the lithiophilic metal to the lithiophobic metal in the negative electrode composition to (2-10):1 can further improve the overall performance of the battery.

[0213] By comparing Example 1 with Examples 8-12, it can be seen that controlling the lithium sulfide content in the negative electrode composition to 2wt%-8wt% can further promote lithium conduction and stabilize the SEI film, and the negative electrode side impedance is also small.

[0214] By comparing Example 1 with Examples 14-15, it can be seen that by using indium powder as the lithium-affinity metal, the lithium-indium alloy formed has a higher affinity for lithium and is conducive to the migration of lithium ions.

[0215] By comparing and analyzing Example 1 and Comparative Examples 1-5, it can be seen that the negative electrode sheet prepared by the copper foil current collector without a modified layer does not have the ability to uniformly deposit / strip lithium metal, and cannot achieve the effect of suppressing dendrites and achieving a long cycle life; in addition, the single addition of lithium-philic metal or lithium-phobic metal cannot achieve the effect of both lithium conduction / lithium-philicity and electrical conductivity, and the battery's cycle stability is poor and the safety is not high.

[0216] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A negative electrode plate, wherein, It includes a negative electrode current collector and a negative electrode modification layer located on the surface of the negative electrode current collector. Among them, the negative electrode modification layer contains lithium sulfide, a lithium alloy formed by lithium and a lithiumophilic metal, and a lithium-phobic metal. The atomic molar ratio of the lithiumophilic metal to the lithium-phobic metal in the lithium alloy is (1 to 30):

1.

2. The negative electrode sheet according to claim 1, wherein, The atomic molar ratio of the lithiumophilic metal to the lithium-phobic metal in the lithium alloy is (2 to 10):

1.

3. The negative electrode plate according to claim 1 or 2, wherein The total mass ratio of the lithiumophilic metal and the lithium-phobic metal in the lithium alloy to the mass of lithium sulfide is (4 to 60):1, and can be optionally (10 to 50):

1.

4. The negative electrode sheet according to any one of claims 1-3, wherein, The lithiumophilic metal includes at least one of zinc, indium, aluminum, magnesium, silver, tin, gallium, antimony, bismuth, or germanium; Optionally, the lithiumophilic metal includes indium.

5. The negative electrode sheet according to any one of claims 1-4, wherein, The resistivity of the lithium-phobic metal at 20 °C is lower than 15 μΩ·cm; Optionally, the lithium-phobic metal includes at least one of copper, iron, nickel, cobalt, or tungsten.

6. The negative electrode sheet according to any one of claims 1-5, wherein, The negative electrode modification layer further includes a binder; Optionally, the binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinylidene fluoride-hexafluoropropylene, or tetrafluoroethylene-hexafluoropropylene copolymer.

7. The negative electrode sheet according to claim 6, wherein, Based on the total weight of lithium sulfide, the binder, the lithium-phobic metal, and the lithiumophilic metal in the lithium alloy, the mass content of lithium sulfide is 1% to 16%, the total mass content of the lithium-phobic metal and the lithiumophilic metal in the lithium alloy is 75% to 98%, and the mass content of the binder is 1% to 10%; Optionally, based on the total weight of lithium sulfide, the binder, the lithium-phobic metal, and the lithiumophilic metal in the lithium alloy, the mass content of lithium sulfide is 2% to 8%, the total mass content of the lithium-phobic metal and the lithiumophilic metal in the lithium alloy is 85% to 95%, and the mass content of the binder is 3% to 7%.

8. The negative electrode sheet according to claim 6 or 7, wherein, In the negative electrode sheet per unit area, the total weight of lithium sulfide, binder, lithium-phobic metal and lithium-philic metal in the lithium alloy is 0.3 mg / cm 2 ~1.0 mg / cm 2 .

9. The negative electrode sheet according to any one of claims 1-8, wherein The negative electrode plate further includes a lithium metal negative electrode layer, and the lithium metal negative electrode layer is located on the side of the negative electrode modification layer away from the negative electrode current collector.

10. The negative electrode sheet according to any one of claims 1-9, wherein, The negative electrode current collector includes at least one of copper foil, titanium foil, or stainless steel.

11. A negative electrode composition, wherein, It contains lithium sulfide, a lithiumophilic metal, and a lithium-phobic metal; among them, the molar ratio of the lithiumophilic metal to the lithium-phobic metal is (1 to 30):

1.

12. The negative electrode composition according to claim 11, wherein, The molar ratio of the lithiumophilic metal to the lithium-phobic metal is (2 to 10):

1.

13. The negative electrode composition according to claim 11 or 12, wherein, The total mass ratio of the lithiumophilic metal and the lithium-phobic metal to the mass of lithium sulfide is (4 to 60):1, and can be optionally (10 to 50):

1.

14. The negative electrode composition according to any one of claims 11-13, wherein, The lithiumophilic metal includes at least one of zinc, indium, aluminum, magnesium, silver, tin, gallium, antimony, bismuth, or germanium; Optionally, the lithiumophilic metal includes indium.

15. The negative electrode composition according to any one of claims 11-14, wherein, The resistivity of the lithium-phobic metal at 20 °C is lower than 15 μΩ·cm; Optionally, the lithium-phobic metal includes at least one of copper, iron, nickel, cobalt, or tungsten.

16. The negative electrode composition according to any one of claims 11-15, wherein, The negative electrode composition further includes a binder; Optionally, the binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinylidene fluoride-hexafluoropropylene, or tetrafluoroethylene-hexafluoropropylene copolymer.

17. The negative electrode composition according to claim 16, wherein, Based on the total weight of the negative electrode composition, the mass content of lithium sulfide is 1% to 16%, the total mass content of the lithium-phobic metal and the lithiumophilic metal is 75% to 98%, and the mass content of the binder is 1% to 10%; Optionally, based on the total weight of the negative electrode composition, the mass content of lithium sulfide is 2% to 8%, the total mass content of lithium-phobic metal and lithium-philic metal is 85% to 95%, and the mass content of the binder is 3% to 7%.

18. The negative electrode composition according to any one of claims 11-17, wherein The median particle size Dv of the lithiumophilic metal 50 is 20 nm to 500 nm, and the median particle size Dv of the lithium-phobic metal 50 is 50 nm to 200 nm.

19. A method for preparing a negative electrode plate, wherein, Comprising: Preparing a composite layer: Applying the negative electrode composition according to any one of claims 11-18 on a negative electrode current collector to form a composite layer; Pre-depositing lithium metal: Forming a lithium alloy by reacting the lithium-philic metal in the composite layer with the deposited lithium ions, and forming a negative electrode modification layer on the surface of the negative electrode current collector.

20. The preparation method according to claim 19, wherein In the negative electrode sheet per unit area, the weight of the negative electrode composition is 0.3 mg / cm 2 ~1.0 mg / cm 2 .

21. The preparation method according to claim 19 or 20, wherein, The process of pre-depositing metallic lithium further includes: continuously forming a lithium metal negative electrode layer on the negative electrode modification layer by depositing lithium ions.

22. The preparation method according to any one of claims 19-21, wherein, The conditions for pre-depositing lithium metal include: a current density of 0.5 mA / cm 2 ~2 mA / cm 2 ; Optionally, the pre-deposition results in a pre-deposited lithium capacity of 1 mAh / cm 2 to 20 mAh / cm 2 on the prepared negative electrode sheet.

23. A battery, wherein, Comprising the negative electrode sheet according to any one of claims 1-10 or the negative electrode sheet prepared by the preparation method according to any one of claims 19-22.

24. An electrical device, wherein, Comprising the battery according to claim 23.

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