Lithium metal battery and preparation method thereof, negative electrode sheet and electric device

Abstract

The application provides a lithium metal battery, a preparation method thereof, a negative electrode sheet and an electric device. The lithium metal battery comprises a negative electrode sheet, the negative electrode sheet comprises a negative electrode current collector, an ion-conducting layer and an interface modification layer, the ion-conducting layer is arranged on at least one side of the negative electrode current collector, the interface modification layer is arranged on the surface of the ion-conducting layer away from the negative electrode current collector, the thickness of the ion-conducting layer is 5 microns to 30 microns, and the interface modification layer comprises a polymer and a lithium salt. The lithium metal battery provided by the application has good cycle performance.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a lithium metal battery and its preparation method, negative electrode sheet, and electrical device. Background Technology

[0002] In recent years, with the increasingly wide range of applications of secondary batteries, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace.

[0003] Lithium metal batteries are favored for their high energy density and safer manufacturing process; however, traditional lithium metal batteries currently suffer from poor cycle life. Summary of the Invention

[0004] This application provides a lithium metal battery and its preparation method, negative electrode sheet, and power device, which enables the lithium metal battery to have good cycle performance.

[0005] To achieve the above objectives, a first aspect of this application provides a lithium metal battery, including a negative electrode sheet, the negative electrode sheet including a negative current collector, an ion-conducting layer and an interface modification layer, the ion-conducting layer being disposed on at least one side of the negative current collector, the interface modification layer being disposed on the surface of the ion-conducting layer away from the negative current collector, the thickness of the ion-conducting layer being 5 μm to 30 μm, and the interface modification layer including a polymer and a lithium salt.

[0006] The lithium metal battery provided in this application has a thick ion-conducting layer on its negative electrode. This ion-conducting layer can facilitate the rapid conduction of active lithium ions to the surface of the negative electrode current collector during charging and discharging, and deposit lithium metal on the surface of the negative electrode current collector (i.e., between the negative electrode current collector and the ion-conducting layer). Moreover, this thick ion-conducting layer has high mechanical strength, which can withstand lithium deposition cycles with a high areal capacity, and it is not easily penetrated by lithium metal during cycling, thus improving the structural stability of the interface modification layer and thus extending the cycle life of the battery. In addition, the interface modification layer, which includes polymer and lithium salt, is provided on the surface of the ion-conducting layer. On the one hand, the interface modification layer can isolate the direct contact between the electrolyte and the deposited lithium metal, thereby reducing the occurrence of side reactions between the electrolyte and lithium metal and reducing the loss of active lithium. On the other hand, the flexibility of the interface modification layer can improve the interfacial adhesion between the negative electrode and other layers, which helps to reduce the obstruction of electron and ion transport between layers, thus enabling the battery to have good cycle performance.

[0007] In some embodiments of this application, one or more of the following conditions are met:

[0008] (1) The polymer includes one or more of polyethylene oxide, polyvinyl alcohol, polyimide, styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene and tetrafluoroethylene-hexafluoropropylene copolymer;

[0009] (2) The lithium salt includes one or more of lithium fluoride, lithium chloride, lithium perchlorate, lithium nitride, lithium difluorooxalate borate, lithium bis(trifluoromethanesulfonyl)imide, lithium oxide, lithium tetrafluoroborate and lithium hexafluorophosphate;

[0010] (3) The polymer accounts for 75% to 99% of the mass percentage of the interface modification layer;

[0011] (4) The lithium salt accounts for 1% to 20% of the total mass of the interface modification layer.

[0012] (5) The thickness of the interface modification layer is 500nm~5μm.

[0013] Polymers possess good flexibility, which can improve interfacial adhesion. For example, they can improve the interfacial adhesion between the negative electrode and the separator, especially with gel electrolytes or solid electrolytes.

[0014] The addition of lithium salt can improve the ionic conductivity of the interface modification layer, so lithium ions can pass through the interface modification layer quickly, while the solvent is blocked by the interface modification layer. Therefore, when the electrolyte in the lithium metal battery contains liquid electrolyte, the interface modification layer can block the solvent and lithium salt in the liquid electrolyte from directly contacting the deposited lithium to a certain extent, reducing the continuous occurrence of side reactions.

[0015] In some embodiments of this application, the interface modification layer further includes an ionic conductor; optionally, the ionic conductor includes a solid electrolyte.

[0016] In some embodiments of this application, one or more of the following conditions are met:

[0017] (1) The ionic conductor includes one or more of LATP, LLZNO and silicon nitride;

[0018] (2) The mass percentage of the ionic conductor is 1% to 5% based on the mass percentage of the interface modification layer.

[0019] The interface modification layer also includes an ion conductor, so that the interface modification layer can conduct ions. It not only has flexibility to improve interface adhesion, but also prevents the solvent in the electrolyte in the semi-solid electrolyte system and liquid electrolyte system from passing through, blocking the solvent and lithium salt in the electrolyte from directly contacting the deposited lithium, and reducing the continuous occurrence of side reactions.

[0020] In some embodiments of this application, the lithium metal battery further includes an electrolyte, which includes one of a semi-solid electrolyte and an all-solid electrolyte.

[0021] In some embodiments of this application, one or more of the following conditions are met:

[0022] (1) The solid content of the semi-solid electrolyte is 5wt%~20wt%, and can be selected as 10wt%~15wt%;

[0023] (2) The thickness of the interface modification layer is 500nm~3μm.

[0024] By controlling the thickness of semi-solid electrolytes within this low range, a good barrier effect can be achieved, reducing the continuous occurrence of side reactions.

[0025] In some embodiments of this application, the lithium metal battery further includes an electrolyte, which is a liquid electrolyte;

[0026] Optionally, the thickness of the interface modification layer is 3μm to 5μm.

[0027] For electrolyte systems, controlling the thickness within this larger range can provide a good barrier effect and reduce the continuous occurrence of side reactions.

[0028] In some embodiments of this application, one or more of the following conditions are met:

[0029] (1) The thickness of the ion-conducting layer is 5μm~20μm, and can be selected as 5μm~10μm;

[0030] (2) The porosity of the ion-conducting layer is less than or equal to 40%, and can be selected as less than or equal to 20%;

[0031] (3) The compaction density of the ion-conducting layer is 0.8 g / cm³. 3 ~1.4g / cm 3 ; 1g / cm can be selected 3 ~1.4g / cm 3 .

[0032] This configuration not only allows lithium ions to be rapidly conducted to the surface of the negative electrode current collector and deposited as lithium metal, but also isolates the electrolyte from direct contact with lithium metal, which is beneficial for improving coulombic efficiency and cycle life.

[0033] In some embodiments of this application, the ion-conducting layer comprises a carbon material.

[0034] In some embodiments of this application, the median particle size D50 of the carbon material is 30nm~700nm, optionally 30nm~500nm, and more preferably 30nm~200nm.

[0035] The median particle size D50 of the carbon material is within the above range, which not only enables the ion-conducting layer to have a suitable specific surface area, thus facilitating the rapid conduction of lithium ions and reducing the side reactions between active lithium and the electrolyte; but also makes the carbon material easier to compact during the cold pressing process of the electrode, so that the ion-conducting layer has a relatively low porosity and a relatively high compaction density, thus facilitating the transport of lithium ions.

[0036] In some embodiments of this application, one or more of the following conditions are met:

[0037] (1) The carbon material accounts for 80% to 95% of the mass of the ion-conducting layer;

[0038] (2) The carbon material includes one or more of hard carbon, carbon black, natural graphite, artificial graphite and resin carbon, and optionally includes one or more of hard carbon and carbon black.

[0039] In some embodiments of this application, the ion-conducting layer further comprises a binder;

[0040] Optionally, the binder accounts for 5% to 20% of the mass of the ion-conducting layer, and is optionally 10% to 15%.

[0041] Optionally, the adhesive includes one or more of polyvinyl alcohol, polyimide, styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, and carboxymethyl cellulose.

[0042] In some embodiments of this application, the ion-conducting layer further comprises a dispersant;

[0043] Optionally, the dispersant in the ion-conducting layer accounts for 0-5% by mass;

[0044] Optionally, the dispersant includes one or more of polyvinyl alcohol, polyacrylamide, and polyvinylpyrrolidone.

[0045] In some embodiments of this application, the negative electrode further includes a lithium metal layer disposed between the ion-conducting layer and the negative electrode current collector.

[0046] A second aspect of this application provides a method for preparing a lithium metal battery, including the step of preparing a negative electrode sheet, comprising the following steps:

[0047] An ion-conducting layer is formed on at least one side of the negative electrode current collector;

[0048] An interface modification layer is formed on the surface of the ion-conducting layer away from the negative electrode current collector;

[0049] The thickness of the ion-conducting layer is 5 μm to 30 μm, and the interface modification layer includes a polymer and a lithium salt.

[0050] In a third aspect, this application provides a negative electrode sheet, the negative electrode sheet comprising a negative current collector, an ion-conducting layer and an interface modification layer, the ion-conducting layer being disposed on at least one side of the negative current collector, the interface modification layer being disposed on the surface of the ion-conducting layer away from the negative current collector, the thickness of the ion-conducting layer being 5 μm to 30 μm, and the interface modification layer comprising a polymer and a lithium salt.

[0051] In a fourth aspect, this application provides an electrical device comprising one or more of the following: the lithium metal battery described in the first aspect of this application, the lithium metal battery prepared by the preparation method provided in the second aspect of this application, and the negative electrode sheet provided in the third aspect of this application.

[0052] The electrical device of this application includes the lithium metal battery provided in this application, and therefore has at least the same advantages as the lithium metal battery.

[0053] Details of one or more embodiments of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0054] To better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, or the best mode of conduct of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0055] Figure 1 This is a schematic diagram of the negative electrode sheet according to one embodiment of this application.

[0056] Figure 2 This is a schematic diagram of the negative electrode sheet according to another embodiment of this application.

[0057] Figure 3 This is a schematic diagram of a battery cell according to one embodiment of this application.

[0058] Figure 4 for Figure 3 An exploded view of a battery cell according to one embodiment of this application is shown.

[0059] Figure 5This is a schematic diagram of a battery device according to one embodiment of this application.

[0060] Figure 6 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0061] Figure 7 for Figure 6 An exploded view of a battery pack according to one embodiment of this application is shown.

[0062] Figure 8 This is a schematic diagram of an electrical device using a lithium metal battery as a power source according to an embodiment of this application.

[0063] Explanation of reference numerals in the attached figures:

[0064] 1. Battery pack; 2. Upper casing; 3. Lower casing; 4. Battery assembly; 5. Battery cell; 51. Housing; 52. Electrode assembly; 53. Cover plate; 6. Electrical device; 7. Negative electrode current collector; 71. Ion-conducting layer; 72. Ion-conducting layer; 73. Interface modification layer; 74. Lithium metal layer. Detailed Implementation

[0065] Hereinafter, some embodiments of this application are described in detail with appropriate reference to the accompanying drawings. However, some unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0066] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be combined arbitrarily, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0" and "5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when describing a parameter as an integer ≥ 2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 for that parameter. For instance, when describing a parameter as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0067] In this application, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0068] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0069] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The term "implementation" as used herein has a similar understanding.

[0070] Those skilled in the art will understand that the order in which the steps are written in the methods of various embodiments or examples does not imply a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0071] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0072] While lithium metal batteries offer higher energy density and a safer manufacturing process, a side reaction occurs where the electrolyte directly contacts the lithium deposited at the negative electrode. The electrolyte salt and solvent are reduced to form an SEI (solide-electrolyte interphase), consuming active lithium. During battery cycling, as lithium is continuously deposited and stripped from the negative electrode, the SEI formed during stripping breaks down, exposing fresh lithium metal. This fresh lithium metal then comes into contact with the electrolyte again, leading to further side reactions and continuous loss of active lithium and accumulation of byproducts. Some lithium becomes trapped by these non-conductive byproducts, losing electrical contact with the electrode and becoming "dead lithium." This process results in continuous capacity loss and a short cycle life.

[0073] Based on this, one embodiment of this application provides a lithium metal battery, including a negative electrode sheet, the negative electrode sheet including a negative current collector, an ion-conducting layer and an interface modification layer, the ion-conducting layer being disposed on at least one side of the negative current collector, the interface modification layer being disposed on the surface of the ion-conducting layer away from the negative current collector, the thickness of the ion-conducting layer being 5μm~30μm, and the interface modification layer including a polymer and a lithium salt.

[0074] The lithium metal battery provided in this application has a thick ion-conducting layer on its negative electrode. This ion-conducting layer facilitates the rapid conduction of active ions such as lithium ions to the surface of the negative electrode current collector during charging and discharging, where lithium metal is deposited (between the negative electrode current collector and the ion-conducting layer). Furthermore, this thick ion-conducting layer possesses high mechanical strength, enabling it to withstand lithium deposition cycles with high areal capacity. During cycling, it is not easily penetrated by lithium metal, thus preventing damage to the surface interface modification layer. This improves the structural stability of the interface modification layer, thereby extending the battery's cycle life. In addition, the interface modification layer, comprising polymer and lithium salt, on the surface of the ion-conducting layer serves two purposes. First, it isolates the electrolyte from direct contact with the deposited lithium metal, reducing side reactions between the electrolyte and lithium metal and minimizing the loss of active lithium. Second, the flexibility of the interface modification layer improves the interfacial adhesion between the negative electrode and other layers, reducing obstacles to electron and ion transport between layers, thus giving the battery excellent cycle performance. Ultimately, this allows the battery to achieve both good coulombic efficiency and good cycle performance.

[0075] See Figure 1 In one embodiment, the negative electrode of the lithium metal battery includes a negative current collector 71, an ion-conducting layer 72, and an interface modification layer 73. The ion-conducting layer 72 is disposed on one side of the negative current collector 71, and the interface modification layer 73 is disposed on the surface of the ion-conducting layer 72 away from the negative current collector 71. The thickness of the ion-conducting layer 72 is 5 μm to 30 μm, and the interface modification layer 73 includes a polymer and a lithium salt.

[0076] As an example, the thickness of the ion-conducting layer can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, or within any two of the above values.

[0077] In some embodiments, the thickness of the ion-conducting layer is 5 μm to 20 μm, and can be selected as 5 μm to 10 μm.

[0078] This design has two advantages. First, it gives the ion-conducting layer high mechanical strength, making it less susceptible to penetration and breakage by lithium metal deposited on the surface of the negative electrode current collector during cycling. This promotes lithium metal deposition between the negative electrode current collector and the ion-conducting layer, and also prevents the surface interface modification layer from being damaged. The interface modification layer plays a good role in isolating the electrolyte and the deposited lithium metal from direct contact and improving interface adhesion, which helps to extend cycle life. Second, it helps to control the lithium ion transport distance, allowing lithium ions to be quickly transported through the ion-conducting layer to the surface of the negative electrode current collector and deposited as lithium metal, reducing battery polarization and improving cycle life.

[0079] The interface modification layer comprises a polymer and a lithium salt. Further, the lithium salt is distributed within the polymer.

[0080] As examples, the polymer includes one or more of polyethylene oxide, polyvinyl alcohol, polyimide, styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, and tetrafluoroethylene-hexafluoropropylene copolymer. The polymer exhibits good flexibility, which can improve interfacial adhesion. For example, it can improve the interfacial adhesion between the negative electrode and the separator, particularly with gel electrolytes or solid electrolytes.

[0081] In some embodiments of this application, the polymer accounts for 75% to 99% of the mass percentage of the interface modification layer. For example, the polymer accounts for 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% of the mass percentage of the interface modification layer, or a range formed by any two of the above values ​​as endpoints.

[0082] As an example, the lithium salt includes one or more of lithium fluoride, lithium chloride, lithium perchlorate, lithium nitride, lithium difluorooxalate borate, lithium bis(trifluoromethanesulfonyl)imide, lithium oxide, lithium tetrafluoroborate, and lithium hexafluorophosphate. The addition of lithium salt can improve the ionic conductivity of the interface modification layer, allowing lithium ions to pass through quickly. The solvent is blocked by the interface modification layer. Therefore, when the electrolyte in a lithium metal battery contains a liquid electrolyte, the interface modification layer can, to a certain extent, prevent the solvent and lithium salt in the liquid electrolyte from directly contacting the deposited lithium, reducing the continuous occurrence of side reactions.

[0083] In some embodiments of this application, the mass percentage of the lithium salt in the interface modification layer is 1% to 20%. As an example, the mass percentage of the lithium salt in the interface modification layer can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%, or within the range formed by any two of the above values ​​as endpoints.

[0084] In some embodiments of this application, the thickness of the interface modification layer is 500 nm to 5 μm. As an example, the thickness of the interface modification layer is 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or within any range of the above values.

[0085] In some embodiments of this application, the interface modification layer is a dense layer.

[0086] In some embodiments of this application, the interface modification layer further includes an ionic conductor; optionally, the ionic conductor comprises a solid electrolyte. This can further improve the ionic conductivity of the interface modification layer.

[0087] As an example, the ionic conductor includes one or more of LATP (lithium aluminum titanium phosphate), LLZNO (lithium lanthanum zirconium niobium oxide), and silicon nitride.

[0088] In some embodiments of this application, the mass percentage of the ionic conductor is 1% to 5% based on the mass percentage of the interface modification layer. As an example, the mass percentage of the ionic conductor based on the mass percentage of the interface modification layer can be 1%, 2%, 3%, 4%, 5%, or within a range formed by any two of the above values ​​as endpoints.

[0089] The interface modification layer also includes an ion conductor, so that the interface modification layer can conduct ions. It not only has flexibility to improve interface adhesion, but also prevents the solvent in the electrolyte in the semi-solid electrolyte system and liquid electrolyte system from passing through, blocking the solvent and lithium salt in the electrolyte from directly contacting the deposited lithium, and reducing the continuous occurrence of side reactions.

[0090] In some embodiments of this application, the lithium metal battery further includes an electrolyte, which includes one of a semi-solid electrolyte and an all-solid electrolyte.

[0091] In this application, unless otherwise specified, "all-solid-state electrolyte" refers to an electrolyte material or substance that exists in a solid form throughout the storage and fabrication of the battery and its components, as well as during the operation of the battery. This includes, but is not limited to, all-solid-state electrolytes existing in a solid form at room temperature. "Semi-solid-state electrolyte" refers to an electrolyte material or substance that exists in a transitional state between liquid and solid states during the storage and fabrication of the battery and its components, as well as during the operation of the battery, possessing some characteristics of both liquid and all-solid-state electrolytes. This includes, but is not limited to, semi-solid-state electrolytes existing in a transitional state between liquid and solid states at room temperature, such as gel electrolytes.

[0092] Electrolytes include all-solid electrolytes, and lithium metal batteries are solid-state batteries. The interfacial adhesion between the layers of a solid-state battery is quite important. The interface modification layer is flexible and can improve the interfacial adhesion between the negative electrode and the solid electrolyte layer. This can help reduce the obstacles to the transport of electrons and ions between layers, thereby improving coulombic efficiency and cycle life.

[0093] Furthermore, the semi-solid electrolyte includes a gel electrolyte and an electrolyte solution. The interface modification layer not only has flexibility to improve interface adhesion, but also prevents the solvent in the semi-solid electrolyte system from passing through, blocking the solvent and lithium salt in the electrolyte from directly contacting the deposited lithium, thus reducing the continuous occurrence of side reactions.

[0094] Furthermore, the solid content of the semi-solid electrolyte is 5wt% to 20wt%, and can be selected as 10wt% to 15wt%. As an example, the solid content of the semi-solid electrolyte can be 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, 20wt%, or within any two of the above values.

[0095] Furthermore, semi-solid electrolytes include gel electrolytes and electrolyte solutions, where the solid content refers to the mass content of the gel electrolyte. Semi-solid electrolytes can be obtained by adding polymeric monomers and optionally an initiator to the electrolyte solution, and then initiating the polymerization of the monomers by heating or other methods; alternatively, the solid content of the semi-solid electrolyte can be controlled by controlling the amount of polymeric monomers added and the degree of polymerization. As an example, the type of polymeric monomer includes polyurea, which does not require an initiator.

[0096] Furthermore, in systems where the electrolyte includes either a semi-solid electrolyte or an all-solid electrolyte, the thickness of the interface modification layer is 500 nm to 3 μm. Controlling the thickness within this relatively low range for semi-solid electrolytes provides a good barrier effect, reducing the continuous occurrence of side reactions.

[0097] In some embodiments, the semi-solid electrolyte includes one or more of gel polymer electrolytes, ionic liquid-based semi-solid electrolytes, inorganic filler-reinforced semi-solid electrolytes, and composite semi-solid electrolytes. In some embodiments, the gel polymer electrolyte may include one or more of PEO-based gel electrolytes (such as PEO-LiClO4-ether solvents), PVDF-based gel electrolytes (such as PVDF-HFP-LiPF6-ether solvents, HFP: hexafluoropropylene), and PAN-based gel electrolytes (such as PAN-LiTFSI-ether solvents, TFSI: bis(trifluoromethanesulfonyl)imide); the ionic liquid-based semi-solid electrolyte may include EMIM-TFSI-based electrolytes (such as EMIM-TFSI-LiTFSI, ... EMIM (1-ethyl-3-methylimidazolium) and BMIM-PF6-based electrolytes (such as BMIM-PF6-LiPF6, BMIM: 1-butyl-3-methylimidazolium) are among the following: Inorganic filler-reinforced semi-solid electrolytes may include one or more of SiO2-reinforced electrolytes (such as PEO-LiClO4-SiO2), Al2O3-reinforced electrolytes (such as PVDF-HFP-LiPF6-Al2O3), and TiO2-reinforced electrolytes (such as PAN-LiTFSI-TiO2); Composite semi-solid electrolytes may include one or more of polymer-ionic liquid composite electrolytes (such as PEO-EMIM-TFSI-LiTFSI) and inorganic-polymer composite electrolytes (such as LLZO-PEO-LiClO4, LLZO: lithium lanthanum zirconium oxide). In some embodiments, the ether solvent includes one or more of ethylene glycol dimethyl ether (DME), hydrofluoroether tetrafluoroethyl tetrafluoropropyl ether (HFE), and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE).

[0098] In some embodiments, the all-solid-state electrolyte includes one or more of polymer-based all-solid-state electrolytes, sulfide-based all-solid-state electrolytes, halide-based all-solid-state electrolytes, and oxide-based all-solid-state electrolytes. In some embodiments, the all-solid-state electrolyte may independently include, but is not limited to, one or more of Argyrodite-type sulfide electrolytes and halide electrolytes. Non-limiting examples of oxide-based solid electrolytes may include LISICON-type oxide electrolytes (such as γ-Li3PO4), NASICON-type oxide electrolytes (such as Li... 1+x Alx Ge 2-x (PO4)3, Li 1+ x Al x Ti 2-x (PO4)3, etc., 0≤x≤1), Garnet type (such as Li7La3Zr2O12, etc.), perovskite type oxide electrolytes (such as Li 3x La 2 / 3-x One or more of the following: TiO3, etc. (0≤x≤0.5). Non-limiting examples of sulfide solid electrolytes may include Li. 10 GeP2S 12 Li₂S-P₂S₅, Argyrodite type (such as Li₆PS₅Cl, Li 5.5 PS 5.5 Cl 1.5 One or more of the following (etc.). Non-limiting examples of halide solid electrolytes may include one or more of the following: Li3InCl6, Li3YCl6, Li3ScCl6, Li3ErCl6, Li2ZrCl6, etc.

[0099] In some embodiments of this application, the lithium metal battery further includes an electrolyte, which is a liquid electrolyte (i.e., an electrolyte solution). The interface modification layer can also prevent the solvent in the electrolyte system from passing through, blocking the solvent and lithium salt in the electrolyte from directly contacting the deposited lithium, thereby reducing the continuous occurrence of side reactions. Further, the thickness of the interface modification layer is 3 μm to 5 μm. For the electrolyte system, controlling the thickness within this larger range can provide a good barrier effect and reduce the continuous occurrence of side reactions.

[0100] Furthermore, the electrolyte includes an electrolyte salt and a solvent.

[0101] As an example, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0102] In some embodiments, the solvent includes at least one of ether solvents, ester solvents, and sulfone solvents. As an example, the ether solvent may include at least one of ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (DEGDME), triethylene glycol dimethyl ether (TRGDME), tetraethylene glycol dimethyl ether (TEGDME), and 1,3-dioxolane (DOL); as an example, the ester solvent may include at least one of ethylene carbonate (EC), propylene carbonate (PC), butenyl carbonate (BC), vinylene carbonate (VC), fluoroethylene carbonate (FEC), methyl ethyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), γ-butyrolactone (BL), 1,3-propanesulfonate lactone (1,3-PS), methyl propionate (MP), methyl butyrate (MB), ethyl acetate (EA), ethyl propionate (EP), propyl propionate (PP), and ethyl butyrate (EB). Furthermore, the ester solvent may include ethyl propionate (EP), the addition of which can improve low-temperature performance. As an example, the sulfone solvent includes dimethyl sulfoxide (DMSO). Further, the solvent includes ester solvents and ether solvents.

[0103] In some embodiments of this application, the porosity of the ion-conducting layer is less than or equal to 40%, and may be less than or equal to 20%. As an example, the porosity of the ion-conducting layer may be 0, 1wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, or within any two of the above values.

[0104] This configuration not only allows lithium ions to be rapidly conducted to the surface of the negative electrode current collector and deposited as lithium metal, but also isolates the electrolyte from direct contact with lithium metal, which is beneficial for improving coulombic efficiency and cycle life.

[0105] The porosity of the ion-conducting layer is a well-known concept in the art and can be tested using methods known in the art. An exemplary test method is as follows: Take a cold-pressed negative electrode sheet, punch it into small circular samples of a certain area, and calculate the apparent volume V1 of the negative electrode sheet; referring to GB / T24586-2009, use an inert gas (such as helium or nitrogen) as the medium, employ the gas displacement method, and measure the true volume V2 of the negative electrode sheet using a true density meter. The porosity of the ion-conducting layer = (V1-V2) / V1×100%. Multiple negative electrode sheet samples (e.g., 30 sheets) with good appearance and no powder shedding at the edges can be tested, and the average value of the results is taken, thereby improving the accuracy of the test results. The testing instrument can be a Micromeritics AccuPyc II 1340 true density meter.

[0106] In some embodiments of this application, the compaction density of the ion-conducting layer is 0.8 g / cm³. 3 ~1.4g / cm 3 ; 1g / cm can be selected 3 ~1.4g / cm 3 As an example, the compaction density of the ion-conducting layer can be 0.8 g / cm³. 3 0.9g / cm 3 1g / cm 3 1.1g / cm 3 1.2g / cm 3 1.3g / cm 3 1.4g / cm 3 Or it may fall within any of the above value ranges. This configuration facilitates the conduction of lithium ions by the ion-conducting layer.

[0107] The areal density of the ion-conducting layer is a well-known concept in the art and can be tested using methods known in the art. For example, a cold-pressed negative electrode sheet can be punched into small circular pieces with an area of ​​S1, and its weight can be weighed and recorded as M1. Then, the ion-conducting layer of the weighed negative electrode sheet can be wiped off, and the weight of the remaining part can be weighed and recorded as M0. The areal density of the ion-conducting layer is then calculated as (M1-M0) / S1. The above test can be repeated on three small circular pieces to obtain the areal density of the ion-conducting layer for each piece. The average value of these values ​​is then taken to obtain the final areal density of the ion-conducting layer.

[0108] The compaction density of the ion-conducting layer has a well-known meaning in the art and can be tested using methods known in the art. The compaction density of the ion-conducting layer = areal density of the ion-conducting layer / thickness of the ion-conducting layer. The thickness of the ion-conducting layer has a well-known meaning in the art and can be tested using methods known in the art, such as using a micrometer (e.g., Mitutoyo 293-100, with an accuracy of 0.1 μm).

[0109] In some embodiments of this application, the ion-conducting layer comprises a carbon material. The ion-conducting layer can be formed by coating or other methods, which is simple to prepare and facilitates achieving a relatively high thickness. This ion-conducting layer simultaneously possesses good electronic and ionic conductivity, ensuring a relatively high lithium-ion transport rate even at a relatively high thickness, i.e., with a relatively long lithium-ion conduction path, thus reducing battery polarization. Furthermore, the relatively high thickness provides sufficient mechanical strength, making it less susceptible to penetration and breakage by lithium metal deposited on the surface of the negative electrode current collector during cycling, thus maintaining the integrity and stability of the ion-conducting layer structure.

[0110] In some embodiments of this application, the median particle size D50 of the carbon material is 30nm~700nm, optionally 30nm~500nm, and more preferably 30nm~200nm.

[0111] As an example, the median particle size D50 of carbon materials can be 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 120nm, 150nm, 180nm, 200nm, 250nm, 280nm, 300nm, 350nm, 380nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, or within any range of the above values.

[0112] The median particle size D50 of the carbon material is within the above range, which not only enables the ion-conducting layer to have a suitable specific surface area, thus facilitating the rapid conduction of lithium ions and reducing the side reactions between active lithium and the electrolyte; but also makes the carbon material easier to compact during the cold pressing process of the electrode, so that the ion-conducting layer has a relatively low porosity and a relatively high compaction density, thus facilitating the transport of lithium ions.

[0113] The median particle size D50 of carbon materials refers to the count median particle size of carbon materials. When carbon materials are tested for particle size, the particles are sorted by size. Based on the particle size distribution, the particle size corresponds to the particle size at which the percentage of particles in the volume distribution accumulates to 50%.

[0114] As an example, methods known in the art can be used for testing. An exemplary testing method is as follows: Observe or test the porosity of the negative electrode sheet using ion polishing cross-sectional morphology methods. When significant fluctuations in porosity are observed, it indicates the boundary between the ion-conducting layer and the lithium metal layer, thus identifying the ion-conducting layer and the lithium metal layer. Within the ion-conducting layer, take a sample with a thickness of 2 / 3 from the side relatively far from the lithium metal layer. Immerse this sample in a dimethyl carbonate (DMC) solution for cleaning, then filter to separate and remove the binder and dispersant, obtaining the sample to be tested. The D50 of this sample can be determined using a laser particle size analyzer according to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method. The testing instrument can be a Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK.

[0115] In some embodiments of this application, the carbon material accounts for 80% to 95% of the mass of the ion-conducting layer. As an example, the mass percentage of carbon material in the ion-conducting layer can be 80%, 82%, 84%, 85%, 86%, 88%, 90%, 91%, 93%, 95%, or any of the above values.

[0116] In some embodiments of this application, the carbon material includes one or more of hard carbon, carbon black, natural graphite, artificial graphite, and resin carbon, optionally including one or more of hard carbon and carbon black. Hard carbon and carbon black typically have spherical or near-spherical particle morphology, which can provide better ion transport channels for lithium ion conduction.

[0117] The resins from which the carbon is derived include one or more of phenolic resins, epoxy resins, and polyfurfuryl alcohol.

[0118] Hard carbon includes organic polymer pyrolytic carbon, from which the organic polymers from which the pyrolytic carbon is derived include one or more of polyvinyl alcohol, polyvinyl chloride, polyvinylidene fluoride, and polyacrylonitrile.

[0119] In some embodiments of this application, the ion-conducting layer further comprises a binder. Optionally, the binder accounts for 5% to 20% of the mass of the ion-conducting layer, and optionally 10% to 15%. For example, the mass percentage of the binder in the ion-conducting layer can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any range thereof. This configuration not only provides better adhesion to the ion-conducting layer but also enables it to possess high ion conductivity, facilitating rapid lithium-ion conduction.

[0120] Optionally, the adhesive includes one or more of polyvinyl alcohol, polyimide, styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, and carboxymethyl cellulose.

[0121] In some embodiments of this application, the ion-conducting layer further comprises a dispersant. The dispersant can play a role in uniformly dispersing the carbon material and binder during the preparation process.

[0122] Furthermore, the mass percentage of the dispersant in the ion-conducting layer is 0 to 5%; as an example, the mass percentage of the dispersant in the ion-conducting layer can be 0, 0.5%, 1%, 2%, 3%, 4%, 5%, or within any of the above values.

[0123] As an example, dispersants include, but are not limited to, one or more of polyvinyl alcohol, polyacrylamide, and polyvinylpyrrolidone.

[0124] In some embodiments of this application, the negative electrode further includes a lithium metal layer disposed between the ion-conducting layer and the negative electrode current collector. The lithium metal layer is the active layer of the negative electrode.

[0125] Furthermore, the thickness of the lithium metal layer can be 5μm to 20μm, and can be selected as 5μm to 10μm. As an example, the thickness of the lithium metal layer can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, or within any two of the above values.

[0126] Please see Figure 2 In one embodiment, the negative electrode of a lithium metal battery includes a negative current collector 71, a lithium metal layer 74, an ion-conducting layer 72, and an interface modification layer 73. The ion-conducting layer 72 is disposed on one side of the negative current collector 71, and the interface modification layer 73 is disposed on the surface of the ion-conducting layer 72 away from the negative current collector 71. The thickness of the ion-conducting layer 72 is 5 μm to 30 μm, and the interface modification layer 73 includes a polymer and a lithium salt. The lithium metal layer 74 is formed between the ion-conducting layer 72 and the negative current collector 71. The lithium metal layer 74 is formed during the first charge cycle.

[0127] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector can be obtained by forming a metal material on the polymeric material substrate. Non-limiting examples of the metal material in the negative electrode current collector may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymeric material substrate in the negative electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0128] Typically, a lithium-ion secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The positive and negative electrodes are positioned opposite each other, and the separator is placed between them, primarily to prevent short circuits while allowing ions to pass through.

[0129] Positive electrode sheet

[0130] The positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive active material layer including a positive active material.

[0131] As a non-limiting example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0132] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector can be obtained by forming a metal material on a polymeric material substrate. Non-limiting examples of the metal material in the positive electrode current collector may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymeric material substrate in the positive electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0133] In some embodiments, the positive electrode active material may be a known positive electrode active material for batteries. As a non-limiting example, the positive electrode active material may include one or more of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, one or more of lithium cobalt oxides (such as LiCoO2), lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and their modified compounds. Non-limiting examples of lithium-containing phosphates with an olivine structure include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium manganese iron phosphate and carbon composites. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 Examples of lithium nickel cobalt aluminum oxides include LiNi, etc. 0.8 Co 0.15 Al 0.05 O2.

[0134] Understandably, lithium (Li) is intercalated and deintercalated during the charging and discharging process of a battery, and the Li content in the positive electrode varies depending on the state of discharge. Unless otherwise specified, the Li content in the examples of positive electrode materials listed in this application refers to the initial state of the material. When a positive electrode material is applied to a positive electrode in a battery system, the Li content in the positive electrode material typically changes after charge-discharge cycles. The Li content can be measured using molar content, but is not limited to this. Regarding "Li content refers to the initial state of the material," the initial state of the material refers to its state before being added to the positive electrode slurry. It is understood that new materials obtained by appropriately modifying the listed positive electrode materials are also within the scope of positive electrode materials. The aforementioned appropriate modification refers to acceptable modification methods for the positive electrode material; non-limiting examples include coating modification.

[0135] In the examples of cathode materials in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause changes in the molar content of oxygen, and the actual O content will fluctuate. The O content can be measured in molar content, but is not limited to this.

[0136] In some embodiments, the positive electrode active material layer may optionally include a positive electrode binder. As a non-limiting example, the positive electrode binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0137] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0138] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive active material, conductive agent, positive binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry onto at least one surface of the positive electrode current collector, and obtaining the positive electrode sheet after drying, cold pressing, and other processes. The solvent can be selected from, but is not limited to, any of the solvents described in the foregoing embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector or both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40wt%~80wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000~25000 mPa·s. When coating the positive electrode slurry, the coating areal density (dry weight, minus solvent) can be 15~35 mg / cm³. 2 The compaction density of the positive electrode sheet can be 3.0~3.6 g / cm³. 3 The concentration can be selected as 3.3~3.5 g / cm³. 3 .

[0139] Separating membrane

[0140] In some embodiments, the lithium metal battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0141] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0142] In some embodiments, the thickness of the isolation membrane is 6μm to 40μm, and optionally 12μm to 20μm.

[0143] In some embodiments, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding process or a stacking process.

[0144] In some embodiments, the lithium metal battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0145] In some embodiments, the outer packaging of the lithium metal battery can be a rigid shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the lithium metal battery can also be a soft pack, such as a pouch. The soft pack can be made of plastic; further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0146] Another embodiment of this application provides a method for preparing a lithium metal battery, including the step of preparing a negative electrode sheet, comprising the following steps:

[0147] The aforementioned ion-conducting layer is formed on at least one side of the negative electrode current collector;

[0148] The aforementioned interface modification layer is formed on the surface of the ion-conducting layer away from the negative electrode current collector.

[0149] The surface of the negative electrode current collector coated with the ion-conducting layer slurry can be a single surface of the negative electrode current collector or two surfaces of the negative electrode current collector.

[0150] In some embodiments, forming the aforementioned ion-conducting layer on at least one side of the negative electrode current collector includes the following steps: dispersing the aforementioned carbon material, binder, and any other components (e.g., dispersant) in a solvent to form an ion-conducting layer slurry; coating the ion-conducting layer slurry onto at least one surface of the negative electrode current collector and drying to obtain the ion-conducting layer. Further, the solvent includes, but is not limited to, NMP (N-methylpyrrolidone).

[0151] In some embodiments, forming the interface modification layer on the surface of the ion-conducting layer away from the negative electrode current collector includes the following steps: dispersing the polymer, lithium salt, and optionally an ion conductor in a solvent to form an interface modification layer slurry; coating the interface modification layer slurry onto at least one side surface of the ion-conducting layer and drying to obtain the interface modification layer. Further, the solvent includes, but is not limited to, acetonitrile. As an example, the preparation steps of the interface modification layer slurry are as follows: first, stirring the polymer in acetonitrile at 50°C for 6 hours until clear and transparent; then adding the lithium salt and stirring for 2 hours; finally, adding the ion conductor to form a white / gray emulsion.

[0152] Then, after the electrode with the interface modification layer is dried and cold-pressed, the negative electrode can be obtained.

[0153] In a third aspect, this application provides a negative electrode sheet as described above.

[0154] In a fourth aspect, this application provides an electrical device comprising one or more of the lithium metal battery described above, the lithium metal battery prepared by the above preparation method, and the negative electrode sheet described above.

[0155] The electrical device of this application includes the lithium metal battery provided in this application, and therefore has at least the same advantages as the lithium metal battery.

[0156] The lithium metal battery and power device of this application will be described below with appropriate reference to the accompanying drawings.

[0157] A lithium metal battery includes at least one battery cell. A lithium metal battery may include one or more battery cells.

[0158] In this application, unless otherwise specified, "cell battery" refers to the basic unit capable of converting chemical energy into electrical energy, and generally includes at least a positive electrode, a negative electrode, and an electrolyte. During the charging and discharging process of the battery, active ions move back and forth between the positive and negative electrode plates, inserting and extracting. The electrolyte acts as a conductor for the active ions between the positive and negative electrode plates.

[0159] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 3 The lithium metal battery shown is a single cell, which serves as an example of a square-structured battery cell.

[0160] In some embodiments, the lithium metal battery may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above. In some embodiments, the outer packaging of the lithium metal battery can be a rigid shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the lithium metal battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0161] In some of these embodiments, reference is made to Figure 4 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be selected by those skilled in the art according to actual needs.

[0162] In some embodiments, the lithium metal battery can be a battery module or a battery pack. A battery module includes at least one battery cell. The number of battery cells in a battery module can be one or more, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0163] Figure 5 This is battery module 4, used as an example. (See reference...) Figure 5 In battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0164] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0165] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select an appropriate number according to the application and capacity of the battery pack.

[0166] Figure 6 and Figure 7 This is battery pack 1 as an example. (See reference...) Figure 6 and Figure 7 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0167] In addition, one embodiment of this application also provides an electrical device, which includes the lithium metal battery provided in this application. The lithium metal battery can be used as a power source for the electrical device or as an energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Among them, mobile devices may be, for example, mobile phones, laptops, etc.; electric vehicles may be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to.

[0168] As an electrical device, lithium metal batteries can be selected based on its usage requirements.

[0169] Figure 8 Here is an example of an electrical device 6. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of lithium metal batteries for this electrical device, a battery pack or battery module can be used.

[0170] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use lithium metal batteries as their power source.

[0171] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0172] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0173] Example 1

[0174] (1) Preparation of the positive electrode sheet:

[0175] Positive electrode active material: lithium nickel cobalt manganese oxide (LiNi) 0.8 Co 0.1 Mn 0.1 O2 (NCM811) (NMC), conductive agent acetylene black, and binder PVDF were mixed at a mass ratio of 98:1:1. N-methylpyrrolidone (NMP) solvent was added and stirred until the system was homogeneous, yielding a positive electrode slurry (70% solid content). The positive electrode slurry was then subjected to a reaction at approximately 12.5 mg / cm³. 2 The load is evenly coated on both sides of the positive current collector aluminum foil, dried at room temperature, transferred to an oven for further drying, and then cut into 40 mm × 50 mm rectangles as positive electrode sheets.

[0176] (2) Preparation of negative electrode sheet:

[0177] Hard carbon, PVDF binder, and polyvinylpyrrolidone (PVP) dispersant are mixed, with the total mass of the three substances as the basis, where hard carbon accounts for 86% of the mass, PVDF accounts for 12% of the mass, and PVP accounts for 2% of the mass. The solvent NMP (N-methylpyrrolidone) is added and mixed to form a slurry with a solid content of 20%. The slurry is then coated onto one side of a copper foil using a doctor blade, and after drying and cold pressing, an ion-conducting layer is formed.

[0178] A polymer (specifically, polyethylene oxide (PEO), 1 g) for forming the interface modification layer, a lithium salt (specifically, LiFSI, 0.2165 g), and an ion conductor (specifically, LLZNO, 0.05 g) were mixed. The resulting mixture was dispersed in a solvent (specifically, acetonitrile, 20 g) to form an interface modification layer slurry. The interface modification layer slurry was coated onto the surface of the ion-conducting layer and dried to obtain the interface modification layer. It was then cut into rectangles of 41 mm × 51 mm for later use, thus obtaining the negative electrode sheet.

[0179] The ion-conducting layer has a thickness of 10 μm and a compaction density of 1.3 g / cm³. 3 The porosity is 43%; the median particle size D50 (count average particle size) of hard carbon is 100 nm.

[0180] The thickness of the interface modification layer is 1 micrometer.

[0181] (3) Preparation of the diaphragm:

[0182] A polyethylene porous membrane (12 μm thick) was selected and cut into 45 mm × 55 mm cuboids for later use.

[0183] (4) Preparation of electrolytes:

[0184] 4.1 Take solvent EC (ethylene carbonate), solvent EMC (ethyl methyl carbonate) and solvent DEC (diethyl carbonate) in a volume ratio of 1:1:1 to form a solvent stock solution. Then take 2.244g of LiFSI (lithium bisfluorosulfonyl imide) and add it to 5mL of the solvent stock solution. Then add VC (ethylene carbonate) equivalent to 0.5% of the total mass of the solution at this time as an additive. Stir thoroughly to form a colorless and transparent non-aqueous electrolyte.

[0185] 4.2 Add the polyurea monomer to the above-prepared non-aqueous electrolyte and stir until homogeneous to form a gel electrolyte, such that the mass fraction of the monomer is 15% (i.e., the mass content of the gel electrolyte that can be polymerized by the monomer is about 15%, i.e., the solid content is 15%).

[0186] (5) Battery assembly:

[0187] One pre-cut positive electrode sheet and one pre-cut negative electrode sheet are matched together, with the aforementioned separator used to isolate the positive and negative electrodes, and then wrapped in an aluminum-plastic film bag to form a stacked dry cell. 0.6g of the aforementioned prepared gel electrolyte is injected, and the aluminum-plastic film bag is vacuum heat-sealed. After standing at 60°C for at least 12 hours, formation and degassing processes are performed to obtain the battery.

[0188] The following are performance tests.

[0189] (1) Morphological test

[0190] The ion-conducting layer and its thickness can be observed by ion polishing cross-sectional morphology analysis (CP) combined with scanning electron microscopy (SEM).

[0191] (2) Coulomb efficiency (CE) and cycle life

[0192] Under normal temperature and pressure conditions, the battery was charged and discharged within a voltage range of 3.2~4.3V. The battery was discharged at a constant current rate of 0.2C to a voltage of 3.2V, and the discharge specific capacity at this point was recorded, which is the initial lithium insertion capacity. Then, the battery was charged at a constant current rate of 0.1C to a voltage of 4.3V, and the charging specific capacity at this point was recorded, which is the initial lithium de-lithiation capacity. The battery was cycled and discharged using the above method, and the lithium de-lithiation capacity was recorded each time. When the discharge capacity decayed to 80% of the discharge capacity of the second cycle, the battery life was considered to have ended, and the number of cycles at this point was recorded as n.

[0193] Initial coulombic efficiency (%) = Initial delithiation capacity / Initial lithiation capacity × 100%;

[0194] Examples 2-6

[0195] Similar to the preparation process of Example 1, the main difference is that in step (2), hard carbon with median particle sizes of 30nm, 50nm, 200nm, 500nm and 700nm is used for replacement, as detailed in Table 1 below.

[0196] Table 1

[0197]

[0198] Examples 7-9

[0199] The preparation process is similar to that in Example 1, the main difference is that in step (2), the thickness of the ion-conducting layer is 5 μm, 20 μm and 30 μm respectively, as detailed in Table 2 below.

[0200] Table 2

[0201]

[0202] Examples 10-12

[0203] Similar to the preparation process of Example 1, the main difference is that in step (2), the coating thickness of the interface modification layer is different, which in turn makes the thickness of the interface modification layer different, as detailed in Table 3 below.

[0204] Table 3

[0205]

[0206] Examples 14-15

[0207] The preparation process of Example 14 is similar to that of Example 12, the main difference being that in step (4), step 4.2 is omitted and an electrolyte is used directly.

[0208] The preparation process of Example 15 is similar to that of Example 14, the main difference being that the coating thickness of the interface modification layer is different, resulting in different thicknesses of the interface modification layer. See Table 4 below for details.

[0209] Table 4

[0210]

[0211] Example 16

[0212] The preparation process is similar to that of Example 1, with the main difference being the composition of the interface modification layer. The addition of an ionic conductor is omitted, and the polymer content in the interface modification layer is correspondingly increased. See Table 5 below for details.

[0213] Table 5

[0214]

[0215] Comparative Example 1

[0216] Similar to the preparation process of Example 1, the main difference is that the preparation process of the ion-conducting layer is omitted in step (2), that is, the negative electrode in step (2) does not contain the ion-conducting layer, as detailed in Table 6 below.

[0217] Comparative Examples 2-3

[0218] The preparation process is similar to that in Example 1, the main difference is that in step (2), the thickness of the ion-conducting layer is 2 μm and 35 μm, respectively, as detailed in Table 6 below.

[0219] Table 6

[0220]

[0221] Table 1 shows that by comparing Examples 1 to 6, controlling the median particle size of carbon materials within a suitable range can enable the battery to achieve both good first-cycle coulombic efficiency and cycle life.

[0222] Table 2 shows that by comparing Examples 1 and 7-9, controlling the thickness of the ion-conducting layer within a suitable range can enable the battery to achieve both good first-cycle coulombic efficiency and cycle life.

[0223] Table 3 shows that by comparing Examples 1, 10-12, controlling the coating thickness of the interface modification layer within a suitable range can enable the battery to achieve both good first-cycle coulombic efficiency and cycle life. Furthermore, by controlling the coating thickness of the interface modification layer within 500 nm to 3 μm in the gel electrolyte system, the battery can achieve even higher first-cycle coulombic efficiency and cycle life.

[0224] Table 4 shows that by comparing Examples 1, 14 and 15, it can be seen that controlling the coating thickness of the interface modification layer in the liquid system to be within 3 μm to 5 μm can enable the battery to achieve higher first-cycle coulombic efficiency and cycle life.

[0225] Table 5 shows that by comparing Examples 1 and 16, adding ion conductors to the interface modification layer can enable the battery to achieve higher first-cycle coulombic efficiency and cycle life.

[0226] As shown in Table 6, Comparative Example 1, which lacks an ion-conducting layer, has a poor cycle life. Comparative Example 2, although equipped with an ion-conducting layer, has a low thickness, resulting in minimal improvement in cycle performance. Comparative Example 3, while equipped with an ion-conducting layer, has a high thickness, which actually worsens the first-cycle coulombic efficiency and cycle performance. A comparison of Example 1 with Comparative Examples 1-2 shows that the inclusion of an ion-conducting layer and an interface modification layer can improve cycle life without significantly affecting the first-cycle coulombic efficiency. Furthermore, a comparison of Example 1 with Comparative Example 3 shows that controlling the thickness of the ion-conducting layer within a suitable range can lead to higher first-cycle coulombic efficiency and cycle life.

[0227] The description of the various embodiments above tends to emphasize the differences between the various embodiments. The similarities or similarities between them can be referred to, and for the sake of brevity, they will not be repeated here.

[0228] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A lithium metal battery, characterized in that, The device includes a negative electrode sheet, which comprises a negative current collector, an ion-conducting layer, and an interface modification layer. The ion-conducting layer is disposed on at least one side of the negative current collector, and the interface modification layer is disposed on the surface of the ion-conducting layer away from the negative current collector. The thickness of the ion-conducting layer is 5 μm to 30 μm. The ion-conducting layer contains carbon material with a median particle size D50 of 30 nm to 700 nm. The interface modification layer comprises a polymer and a lithium salt, and the carbon material accounts for 80% to 95% of the mass of the ion-conducting layer. The negative electrode sheet further includes a lithium metal layer, which is located between the ion-conducting layer and the negative electrode current collector.

2. The lithium metal battery as described in claim 1, characterized in that, One or more of the following conditions must be met: (1) The polymer includes one or more of polyethylene oxide, polyvinyl alcohol, polyimide, styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene and tetrafluoroethylene-hexafluoropropylene copolymer; (2) The lithium salt includes one or more of lithium fluoride, lithium chloride, lithium perchlorate, lithium nitride, lithium difluorooxalate borate, lithium bis(trifluoromethanesulfonyl)imide, lithium oxide, lithium tetrafluoroborate and lithium hexafluorophosphate; (3) The polymer accounts for 75% to 99% of the mass percentage of the interface modification layer; (4) The lithium salt accounts for 1% to 20% of the total mass of the interface modification layer. (5) The thickness of the interface modification layer is 500nm~5μm.

3. The lithium metal battery as described in claim 1, characterized in that, The interface modification layer also includes ionic conductors.

4. The lithium metal battery as described in claim 3, characterized in that, The ionic conductor includes a solid electrolyte.

5. The lithium metal battery as described in claim 3, characterized in that, One or more of the following conditions must be met: (1) The ionic conductor includes one or more of LATP, LLZNO and silicon nitride; (2) The mass percentage of the ionic conductor is 1% to 5% based on the mass percentage of the interface modification layer.

6. The lithium metal battery according to any one of claims 1 to 5, characterized in that, The lithium metal battery also includes an electrolyte, which includes one of a semi-solid electrolyte and an all-solid electrolyte.

7. The lithium metal battery as described in claim 6, characterized in that, One or more of the following conditions must be met: (1) The solid content of the semi-solid electrolyte is 5wt%~20wt%; (2) The thickness of the interface modification layer is 500nm~3μm.

8. The lithium metal battery as described in claim 7, characterized in that, The solid content of the semi-solid electrolyte is 10wt%~15wt%.

9. The lithium metal battery according to any one of claims 1 to 5, characterized in that, The lithium metal battery also includes an electrolyte, which is a liquid electrolyte.

10. The lithium metal battery as described in claim 9, characterized in that, The thickness of the interface modification layer is 3μm~5μm.

11. The lithium metal battery according to any one of claims 1 to 5, 7 to 8, and 10, characterized in that, One or more of the following conditions must be met: (1) The thickness of the ion-conducting layer is 5 μm to 20 μm; (2) The porosity of the ion-conducting layer is less than or equal to 40%; (3) The compaction density of the ion-conducting layer is 0.8 g / cm³. 3 ~1.4g / cm 3 .

12. The lithium metal battery as described in claim 11, characterized in that, One or more of the following conditions must be met: (1) The thickness of the ion-conducting layer is 5 μm to 10 μm; (2) The porosity of the ion-conducting layer is less than or equal to 20%; (3) The compaction density of the ion-conducting layer is 1 g / cm³. 3 ~1.4g / cm 3 .

13. The lithium metal battery according to any one of claims 1 to 5, 7 to 8, 10, and 12, characterized in that, The median particle size D50 of the carbon material is 30 nm to 500 nm.

14. The lithium metal battery as described in claim 13, characterized in that, The median particle size D50 of the carbon material is 30 nm to 200 nm.

15. The lithium metal battery as described in claim 13, characterized in that, The carbon material includes one or more of hard carbon, carbon black, natural graphite, artificial graphite, and resin carbon.

16. The lithium metal battery as described in claim 15, characterized in that, The carbon material includes one or more of hard carbon and carbon black.

17. The lithium metal battery according to any one of claims 1 to 5, 7 to 8, 10, 12, 14 to 16, characterized in that, The ion-conducting layer also includes a binder.

18. The lithium metal battery as claimed in claim 17, characterized in that, The binder accounts for 5% to 20% of the mass of the ion-conducting layer.

19. The lithium metal battery as described in claim 18, characterized in that, The binder accounts for 10% to 15% of the mass of the ion-conducting layer.

20. The lithium metal battery as claimed in claim 17, characterized in that, The adhesive includes one or more of polyvinyl alcohol, polyimide, styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, and carboxymethyl cellulose.

21. The lithium metal battery according to any one of claims 1 to 5, 7 to 8, 10, 12, 14 to 16, 18 to 20, characterized in that, The ion-conducting layer also contains a dispersant.

22. The lithium metal battery as described in claim 21, characterized in that, The dispersant has a mass percentage of 0-5% in the ion-conducting layer.

23. The lithium metal battery as described in claim 21, characterized in that, The dispersant includes one or more of polyvinyl alcohol, polyacrylamide, and polyvinylpyrrolidone.

24. A method for preparing a lithium metal battery, characterized in that, The steps involved in preparing the negative electrode sheet include the following: An ion-conducting layer is formed on at least one side of the negative electrode current collector; An interface modification layer is formed on the surface of the ion-conducting layer away from the negative electrode current collector; A lithium metal layer is formed during the first charge cycle, and the lithium metal layer is located between the ion-conducting layer and the negative electrode current collector; The thickness of the ion-conducting layer is 5 μm to 30 μm, the ion-conducting layer contains carbon material, the median particle size D50 of the carbon material is 30 nm to 700 nm, the interface modification layer includes polymer and lithium salt, and the mass percentage of the carbon material in the ion-conducting layer is 80% to 95%.

25. A negative electrode sheet, characterized in that, The negative electrode includes a negative current collector, an ion-conducting layer, and an interface modification layer. The ion-conducting layer is disposed on at least one side of the negative current collector, and the interface modification layer is disposed on the surface of the ion-conducting layer away from the negative current collector. The thickness of the ion-conducting layer is 5 μm to 30 μm. The ion-conducting layer contains carbon material with a median particle size D50 of 30 nm to 700 nm. The interface modification layer includes a polymer and a lithium salt. The carbon material accounts for 80% to 95% of the mass of the ion-conducting layer. The negative electrode sheet further includes a lithium metal layer, which is located between the ion-conducting layer and the negative electrode current collector.

26. An electrical appliance, characterized in that, It includes one or more of the following: the lithium metal battery according to any one of claims 1 to 23, the lithium metal battery prepared by the preparation method according to claim 24, and the negative electrode sheet according to claim 25.

Images