Lithium metal battery cell, battery apparatus and electric apparatus

Abstract

Provided in the present disclosure are a lithium metal battery cell, a battery apparatus and an electric apparatus. The lithium metal battery cell comprises a negative electrode sheet, a positive electrode sheet and a separator, wherein the separator is located between the negative electrode sheet and the positive electrode sheet. The negative electrode sheet comprises: a negative electrode current collector; a lithiophilic layer, which is located on at least one surface of the negative electrode current collector; and an interface modification layer, which is located on the surface of the lithiophilic layer that is away from the negative electrode current collector, wherein the interface modification layer comprises an interface modification material, the ionic conductivity of which at 25°C is greater than or equal to 1×10-8S / cm, and the electronic conductivity of which at 25°C is less than or equal to 0.1S / cm. An NP ratio of the lithium metal battery cell is greater than 0 and less than 1, wherein the NP ratio is the ratio of the capacity per unit area of the interface modification layer of a negative electrode to the capacity per unit area of a positive electrode. The lithium metal battery cell can achieve a high energy density, a high coulombic efficiency, and a long cycle life.

Description

Lithium metal battery cells, battery devices, electrical appliances

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese patent application 202510111759.5, filed on January 23, 2025, entitled “Lithium Metal Battery Cell, Battery Device, Electrical Device”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to a lithium metal battery cell, a battery device, and an electrical device. Background Technology

[0004] High energy density and long cycle life are the common goals of current battery cells. Lithium metal battery cells, which use lithium metal as the negative electrode, usually have higher energy density. However, these lithium metal battery cells have low coulombic efficiency and suffer from serious dendrite growth and volume expansion problems, which limit their practical application. Summary of the Invention

[0005] This disclosure provides a lithium metal battery cell, a battery device, and an electrical device. The lithium metal battery cell can combine high energy density, high coulombic efficiency, and long cycle life.

[0006] In a first aspect, this disclosure provides a lithium metal battery cell, comprising a negative electrode, a positive electrode, and a separator, wherein the separator is located between the negative electrode and the positive electrode, the negative electrode comprising a negative current collector, a lithiophilic layer on at least one surface of the negative current collector, and an interface modification layer on the surface of the lithiophilic layer away from the negative current collector; the interface modification layer comprises an interface modification material, wherein the ionic conductivity of the interface modification material at 25°C is greater than or equal to 1×10⁻⁶. -8 The electronic conductivity of the interface modification material at 25°C is less than or equal to 0.1 S / cm; the NP ratio of the lithium metal battery cell is greater than 0 and less than 1, where the NP ratio is the ratio of the unit area capacity of the negative electrode interface modification layer to the unit area capacity of the positive electrode.

[0007] The lithium metal battery cell disclosed herein has an NP ratio greater than 0 and less than 1. By making the unit area capacity of the negative electrode interface modification layer smaller than that of the positive electrode, during charging, some lithium metal can be deposited between the negative electrode current collector and the interface modification layer. The interface modification layer can act as an insulating layer for lithium dendrites, preventing them from directly piercing the separator. In addition, the interface modification layer can also reduce the volume expansion of the negative electrode. A lithiophilic layer is provided on the surface of the negative electrode current collector. This lithiophilic layer can induce lithium metal deposition between the negative electrode current collector and the interface modification layer, reducing lithium metal deposition on the surface of the interface modification layer, thereby further preventing lithium dendrites from directly piercing the separator.

[0008] The interface modification layer includes an interface modification material, the ionic conductivity of which at 25°C is greater than or equal to 1×10⁻⁶. -8 The electronic conductivity of the interface modification material at 25°C is less than or equal to 0.1 S / cm. The high ionic conductivity of the interface modification material enables the interface modification layer to have sufficient lithium-ion transport capacity, allowing lithium ions to embed into the interface modification layer during charging and continue to be transported in bulk to deposit between the negative electrode current collector and the interface modification layer. The low electronic conductivity of the interface modification material results in poor electronic conductivity for the interface modification layer, thereby reducing the risk of lithium ions being reduced to lithium metal on the surface of the interface modification layer. Therefore, the interface modification layer of this disclosure can serve as a medium to isolate the electrolyte from direct contact with lithium metal, reducing lithium metal side reactions and the continuous consumption of active lithium caused by contact between the electrolyte and lithium metal. Simultaneously, the high ionic conductivity of the interface modification layer ensures that the negative electrode interface impedance does not increase significantly from the initial stage to the cycling process, thereby improving the coulombic efficiency and cycle life of the lithium metal battery cell.

[0009] Therefore, the lithium metal battery cell disclosed herein can simultaneously possess high energy density, high coulombic efficiency, and long cycle life.

[0010] In some embodiments, the NP ratio of the lithium metal battery cell is 0.05 to 0.4. This can further improve the energy density, coulombic efficiency, and cycle life of the lithium metal battery cell.

[0011] In some embodiments, the lower limit operating voltage of the lithium metal battery cell is greater than the delithiation potential of the interface modification material. This can improve the coulombic efficiency and cycle life of the lithium metal battery cell.

[0012] In some embodiments, the thickness of the interface modification layer is 5μm-50μm, optionally 10μm-20μm. This allows lithium metal battery cells to have both high energy density and better cycle performance.

[0013] In some embodiments, the porosity of the interface modification layer is 5%-50%, optionally 15%-40%.

[0014] In some embodiments, the volumetric particle size Dv50 of the interface modification material is 5nm-20μm, and can be optionally 10nm-5μm.

[0015] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the interface modification material is greater than 0 and less than or equal to 5.

[0016] In some embodiments, the interface modification material includes expanded graphite and / or silicon oxide materials.

[0017] In some embodiments, the interlayer spacing d of the expanded graphite C(002) crystal plane 002 Greater than 3.4 angstroms.

[0018] In some embodiments, the expanded graphite I D / I G >0.5, I D The Raman spectrum of the expanded graphite is at 1350±50 cm⁻¹. -1 D peak intensity at I G The Raman spectrum of the expanded graphite is at 1580±50 cm⁻¹. -1 The intensity of the G peak at that location. This is beneficial for improving the coulombic efficiency and cycle life of lithium metal battery cells.

[0019] In some embodiments, the specific surface area of ​​the expanded graphite is less than or equal to 500 m². 2 / g.

[0020] In some embodiments, the initial coulombic efficiency of the expanded graphite is ≥50%. The high initial coulombic efficiency of expanded graphite means it does not consume a large amount of active lithium, thereby improving the coulombic efficiency and cycle life of lithium metal battery cells.

[0021] In some embodiments, the porosity of the expanded graphite is ≤30%.

[0022] In some embodiments, the specific surface area of ​​the silicon-oxygen material is less than or equal to 5 m². 2 / g.

[0023] In some embodiments, the silicon-oxygen material includes lithium. This can reduce irreversible loss of active lithium and improve the coulombic efficiency and cycle life of lithium metal battery cells.

[0024] In some embodiments, the surface of the silicon-oxygen material has a carbon coating layer.

[0025] In some embodiments, the initial coulombic efficiency of the silicon-oxygen material is ≥80%. The high initial coulombic efficiency of the silicon-oxygen material means it does not consume a large amount of active lithium, thereby improving the coulombic efficiency and cycle life of lithium metal battery cells.

[0026] In some embodiments, the nucleation overpotential of lithium in the lithiophilic layer is lower than that in the interface modification layer. This promotes lithium ion deposition between the negative electrode current collector and the interface modification layer.

[0027] In some embodiments, the lithiophilic layer comprises one or more of a lithiophilic metal element, a lithiophilic metal alloy, and a lithiophilic oxide.

[0028] Optionally, the lithiophilic layer includes one or more of Bi, Au, Ag, Mg, Zn, Sn, Sb, silver alloy, magnesium alloy, tin alloy, antimony alloy, MgO, and SnO2.

[0029] In some embodiments, the thickness of the lithiophilic layer is 10 nm-1000 nm, optionally 200 nm-500 nm. A thickness within this range allows for better induction of lithium metal deposition between the negative electrode current collector and the interface modification layer, reducing lithium metal deposition on the surface of the interface modification layer, thereby further improving the cycle performance of the lithium metal battery cell. Furthermore, a thickness within this range also enables the lithium metal battery cell to have a higher energy density.

[0030] In some embodiments, the interface modification material accounts for 30%-95% of the mass of the interface modification layer.

[0031] In some embodiments, the separator is an inorganic solid electrolyte layer or a gel electrolyte separator membrane.

[0032] In some embodiments, the positive electrode sheet includes a positive current collector and a positive active material layer located on at least one side of the positive current collector. The positive active material layer includes a positive active material, which includes one or more of lithium transition metal oxides and their modified materials, lithium phosphates and their modified materials, lithium titanate, lithium niobate, sulfur, selenium, and tellurium.

[0033] In a second aspect, this disclosure provides a battery device comprising a plurality of lithium metal battery cells as described in the first aspect.

[0034] Thirdly, this disclosure provides an electrical device that includes a lithium metal battery cell (as described in the first aspect) or a battery device (as described in the second aspect). Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments of this disclosure will be briefly described below. Obviously, the drawings described below are merely some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on the drawings without any creative effort.

[0036] Figure 1 shows a schematic diagram of a lithium metal battery cell provided in some embodiments of this disclosure.

[0037] Figure 2 shows a schematic diagram of an electrical device provided in some embodiments of this disclosure.

[0038] Figure 3 shows the lithium metal deposition morphology on the negative electrode side of Example 1.

[0039] Figure 4 shows the lithium metal deposition morphology on the negative electrode side of Comparative Example 1.

[0040] Figure 5 shows the lithium metal deposition morphology on the negative electrode side of Comparative Example 2.

[0041] The accompanying drawings are not necessarily drawn to scale. Detailed Implementation

[0042] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the lithium metal battery cell, battery device, and power-consuming device of this disclosure. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions 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 disclosure and are not intended to limit the subject matter of the claims.

[0043] The "range" disclosed in this disclosure is defined by a lower limit and an upper limit, whereby a given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, 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 expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this disclosure, 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 "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0044] Unless otherwise specified, all embodiments and optional embodiments of this disclosure may be combined with each other to form new technical solutions, and such technical solutions should be considered as included in the disclosure of this disclosure.

[0045] Unless otherwise specified, all technical features and optional technical features of this disclosure can be combined to form new technical solutions, and such technical solutions should be considered as included in the disclosure of this disclosure.

[0046] Unless otherwise specified, all steps in this disclosure may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may 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.

[0047] Unless otherwise specified, in this disclosure, the terms "first," "second," etc., are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0048] In this disclosure, the terms "multiple" or "a variety" refer to two or more kinds.

[0049] In the description of the embodiments of this disclosure, unless otherwise specified, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0050] Unless otherwise stated, the test temperature for all parameters mentioned in this disclosure is 25°C.

[0051] The lithium metal battery cells mentioned in the embodiments of this disclosure can independently perform charging and discharging functions. The lithium metal battery cells may be cylindrical, cuboid, or other shapes, and the embodiments of this disclosure are not limited to these shapes. Figure 1 shows an example of a cuboid lithium metal battery cell 5.

[0052] The battery apparatus mentioned in the embodiments of this disclosure may include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly may include multiple lithium metal battery cells, which are connected in series, parallel, or mixed connections via a busbar.

[0053] In some embodiments, the battery cell assembly is typically formed by arranging multiple lithium metal battery cells.

[0054] As an example, a battery cell assembly can be a battery module, which consists of multiple lithium metal battery cells arranged and fixed together to form an independent module. As another example, a battery module can be formed by bundling multiple lithium metal battery cells together with cable ties.

[0055] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0056] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0057] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple lithium metal battery cells to the housing.

[0058] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0059] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0060] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0061] The technical solutions described in this disclosure are applicable to various electrical devices that use lithium metal battery cells or battery devices, such as, but not limited to, mobile devices (e.g., mobile phones, tablets, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc. Lithium metal battery cells and battery devices are used to store or provide electrical energy.

[0062] Figure 2 is a schematic diagram of an example electrical device. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0063] A lithium-ion battery cell is a typical rechargeable battery cell that relies on the chemical reaction of lithium ions intercalating and deintercalating between the positive and negative electrodes for charging and discharging. During charging, lithium ions are released from the positive electrode active material, transported to the negative electrode via the electrolyte, and intercalated into its active material. During discharging, lithium ions are released from the negative electrode active material, transported to the positive electrode via the electrolyte, and intercalated into its active material. Lithium-ion battery cells typically use artificial graphite as the negative electrode active material, and its relatively limited theoretical capacity restricts the development of high-energy-density battery cells.

[0064] Lithium metal battery cells directly use lithium metal as the negative electrode active material. Lithium metal has a high theoretical specific capacity (3860 mAh / g) and a low reduction potential (-3.04 V vs. SHE), making it a highly promising negative electrode active material. In the preparation of lithium metal battery cells, either lithium sheets or negative electrode current collectors can be used directly as the negative electrode; these types of lithium metal battery cells are often referred to as negative electrode-free lithium metal battery cells. During the first charge of a negative electrode-free lithium metal battery cell, lithium ions gain electrons on the negative electrode side and deposit on the surface of the negative electrode current collector to form lithium metal. During discharge, the lithium metal can be converted back into lithium ions and return to the positive electrode, achieving cyclic charging and discharging. Compared with other lithium metal battery cells, negative electrode-free lithium metal battery cells have higher volumetric energy density and gravimetric energy density, better reliability, and do not require free lithium metal during assembly, thus simplifying the manufacturing process.

[0065] The main challenge facing lithium metal battery cells lies in the high reducing properties of lithium metal. During cycling, it continuously undergoes side reactions with the electrolyte, leading to the growth of an unstable solid electrolyte interphase (SEI) film. This SEI film continuously consumes the electrolyte and the active lithium in the positive electrode, resulting in low coulombic efficiency and cycle capacity retention of lithium metal battery cells. Furthermore, lithium dendrites are prone to form during cycling. These dendrites can pierce the separator, causing internal short circuits and posing safety hazards. In addition, lithium metal deposition during cycling causes significant volume expansion of the negative electrode, further reducing the cycle life of lithium metal battery cells and limiting their commercial application.

[0066] The commonly used strategies are to adjust the composition of the electrolyte in order to form a dense SEI film on the lithium metal surface, or to use a gel electrolyte separator to reduce the direct contact between the lithium metal and the electrolyte by binding the free electrolyte with gel. However, none of the above methods can significantly improve the cycle life of lithium metal battery cells.

[0067] Based on this, the present disclosure provides a lithium metal battery cell with a long cycle life.

[0068] The lithium metal battery cell provided in this disclosure includes a negative electrode, a positive electrode, and a separator, with the separator located between the negative and positive electrode. The negative electrode, positive electrode, and separator form an electrode assembly. The electrode assembly can be a wound structure or a stacked structure, and this disclosure does not limit this. The lithium metal battery cell also includes an outer packaging, which can be used to encapsulate the electrode assembly. The outer packaging can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging can also be a soft package, such as a pouch. The material of the soft package can be plastic, such as aluminum-plastic film, polypropylene, polybutylene terephthalate (PBT), and polybutylene succinate (PBS) or one or more of these materials.

[0069] The negative electrode sheet provided in this embodiment includes a negative current collector, a lithiophilic layer on at least one surface of the negative current collector, and an interface modification layer on the surface of the lithiophilic layer away from the negative current collector; the interface modification layer includes an interface modification material, and the ionic conductivity of the interface modification material at 25°C is greater than or equal to 1×10⁻⁶. -8 The electronic conductivity of the interface modification material at 25℃ is less than or equal to 0.1 S / cm.

[0070] The lithium metal battery cell provided in this embodiment has an NP ratio greater than 0 and less than 1. The NP ratio is the ratio of the unit area capacity of the negative electrode interface modification layer to the unit area capacity of the positive electrode.

[0071] The lithium metal battery cell disclosed herein has an NP ratio greater than 0 and less than 1. By making the unit area capacity of the negative electrode interface modification layer smaller than that of the positive electrode, during charging, some lithium metal can be deposited between the negative electrode current collector and the interface modification layer. The interface modification layer can act as an insulating layer for lithium dendrites, preventing them from directly piercing the separator. In addition, the interface modification layer can also reduce the volume expansion of the negative electrode. A lithiophilic layer is provided on the surface of the negative electrode current collector. This lithiophilic layer can induce lithium metal deposition between the negative electrode current collector and the interface modification layer, reducing lithium metal deposition on the surface of the interface modification layer, thereby further preventing lithium dendrites from directly piercing the separator.

[0072] The interface modification layer includes an interface modification material, the ionic conductivity of which at 25°C is greater than or equal to 1×10⁻⁶. -8 The electronic conductivity of the interface modification material at 25°C is less than or equal to 0.1 S / cm. The high ionic conductivity of the interface modification material enables the interface modification layer to have sufficient lithium-ion transport capacity, allowing lithium ions to embed into the interface modification layer during charging and continue to be transported in bulk to deposit between the negative electrode current collector and the interface modification layer. The low electronic conductivity of the interface modification material results in poor electronic conductivity for the interface modification layer, thereby reducing the risk of lithium ions being reduced to lithium metal on the surface of the interface modification layer. Therefore, the interface modification layer of this disclosure can serve as a medium to isolate the electrolyte from direct contact with lithium metal, reducing lithium metal side reactions and the continuous consumption of active lithium caused by contact between the electrolyte and lithium metal. Simultaneously, the high ionic conductivity of the interface modification layer ensures that the negative electrode interface impedance does not increase significantly from the initial stage to the cycling process, thereby improving the coulombic efficiency and cycle life of the lithium metal battery cell.

[0073] Therefore, the lithium metal battery cell disclosed herein can simultaneously possess high energy density, high coulombic efficiency, and long cycle life.

[0074] Optionally, the NP ratio of the lithium metal battery cell can be greater than 0 and less than or equal to 0.9, greater than 0 and less than or equal to 0.85, greater than 0 and less than or equal to 0.8, greater than 0 and less than or equal to 0.75, greater than 0 and less than or equal to 0.7, greater than 0 and less than or equal to 0.65, greater than 0 and less than or equal to 0.6, greater than 0 and less than or equal to 0.55, greater than 0 and less than or equal to 0.5, greater than 0 and less than or equal to 0.45, greater than 0 and less than or equal to 0.4, greater than 0 and less than or equal to 0.35, greater than 0 and less than or equal to 0.3, greater than 0 and less than or equal to 0.25, or greater than 0 and less than or equal to 0.2.

[0075] More optionally, the NP ratio of the lithium metal battery cell can be 0.05 to 0.9, 0.05 to 0.85, 0.05 to 0.8, 0.05 to 0.7, 0.05 to 0.75, 0.05 to 0.7, 0.05 to 0.65, 0.05 to 0.6, 0.05 to 0.55, 0.05 to 0.5, 0.05 to 0.45, 0.05 to 0.4, 0.08 to 0.9, 0.08 to 0.85, 0.08 to 0.8, 0.08 to 0.7, 0.08 To 0.75, 0.08 to 0.7, 0.08 to 0.65, 0.08 to 0.6, 0.08 to 0.55, 0.08 to 0.5, 0.08 to 0.45, 0.08 to 0.4, 0.1 to 0.9, 0.1 to 0.85, 0.1 to 0.8, 0.1 to 0.7, 0.1 to 0.75, 0.1 to 0.7, 0.1 to 0.65, 0.1 to 0.6, 0.1 to 0.55, 0.1 to 0.5, 0.1 to 0.45, 0.1 to 0.4.

[0076] When the NP ratio of a lithium metal battery cell is within the above range, more lithium metal can be deposited between the negative electrode current collector and the interface modification layer, reducing the consumption of active lithium by the interface modification layer. This can further improve the energy density, coulombic efficiency and cycle life of the lithium metal battery cell.

[0077] The NP ratio of a lithium metal battery cell can be tested using the following method.

[0078] The negative electrode was removed from a lithium metal battery cell and tested using a coin cell (or mold cell). A lithium sheet was used as the counter electrode, separated by an separator. The battery was discharged to 0.005V (vs. Li) at a current density of 0.1C. + / Li), and then charged to 2V at a current density of 0.1C (vs. Li). + The resulting charging capacity ( / Li) is the negative electrode capacity. Negative electrode capacity per unit area = negative electrode capacity / negative electrode area.

[0079] The positive electrode is extracted from a lithium metal battery cell and tested using a coin cell (or mold cell). A lithium sheet is used as the counter electrode, separated by an insulator. The battery is charged at a current density of 0.1C to the upper cutoff voltage, and then discharged at a current density of 0.1C to the lower cutoff voltage. The resulting discharge capacity is the positive electrode capacity. Positive electrode capacity per unit area = Positive electrode capacity / Positive electrode area.

[0080] NP ratio = negative electrode unit area capacity / positive electrode unit area capacity.

[0081] Both the upper and lower cutoff voltages are known in the art, and the voltages recommended in the product specifications can be used. For example, the positive electrode active material is a lithium transition metal oxide or its modified form, such as LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (abbreviated as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (abbreviated as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (abbreviated as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (abbreviated as NCM811), LiNi 0.96 Co 0.02 Mn 0.02 O2 (abbreviated as Ni96), LiNi 0.80 Co 0.15 Al 0.05 O2, the upper limit cutoff voltage can be 4.3V (vs. Li). + / Li), the lower cutoff voltage can be 2.8V (vs. Li). + / Li).

[0082] The ionic conductivity of interface-modified materials can be tested using the blocked electrode method. First, a certain mass of the test material powder is added to a mold sleeve and pressed into a test piece using electrode posts. A certain mass of solid electrolyte material powder (e.g., Li6PS5Cl) is added to both sides of the test piece, and then pressed into solid electrolyte sheets using electrode posts. Li-indium alloy sheets are then placed outside the solid electrolyte sheets on both sides of the mold sleeve, and the electrode posts are inserted into both sides of the mold sleeve. A certain pressure is then applied to the electrode posts on both sides of the mold sleeve using a press, and the ionic conductivity of the test material powder is measured by electrochemical impedance spectroscopy (EIS). The test temperature is 25℃. The total impedance of the test piece and the two solid electrolyte sheets is R1, and the total impedance of the two solid electrolyte sheets is R2; R1-R2 is the impedance of the test piece. The total thickness of the test piece and the two solid electrolyte sheets is D1, and the total thickness of the two solid electrolyte sheets is D2; D1-D2 is the thickness of the test piece. The ionic conductivity σ of the powder material to be tested can be calculated using the formula σ=(D1-D2) / [(R1-R2)×S]. S is the cross-sectional area of ​​the test piece.

[0083] The electronic conductivity of interface-modified materials can be tested using the blocked electrode method. First, a certain mass of the test material powder is added to a mold sleeve and pressed into a test piece using electrode posts. A certain mass of solid electrolyte material powder (e.g., Li6PS5Cl) is added to both sides of the test piece, and then pressed into solid electrolyte sheets using electrode posts. Li-indium alloy sheets are then placed outside the solid electrolyte sheets on both sides of the mold sleeve, and the electrode posts are inserted into both sides of the mold sleeve. A certain pressure is then applied to the electrode posts on both sides of the mold sleeve using a press, followed by a constant-voltage polarization test. The electronic conductivity λ of the test material powder is calculated based on the measured steady-state current I, applied voltage V, test piece thickness D1-D2, and cross-sectional area S under constant-voltage conditions. λ = (D1-D2) / (S×V / I). The test temperature is 25℃. The total thickness of the test piece and the two solid electrolyte sheets is D1, and the total thickness of the two solid electrolyte sheets is D2. D1-D2 is the thickness of the test piece. S is the cross-sectional area of ​​the test piece.

[0084] In some embodiments, the lower limit operating voltage of the lithium metal battery cell can be greater than the delithiation potential of the interface modification material. That is, during the discharge process of the lithium metal battery cell, the interface modification material does not undergo a delithiation reaction. This allows the lithium metal battery cell to completely switch to a lithium metal deposition / stripping mechanism during subsequent charge and discharge processes, thereby reducing irreversible loss of active lithium and improving the coulombic efficiency and cycle life of the lithium metal battery cell.

[0085] In some embodiments, the thickness of the interface modification layer can be 5μm-50μm, for example, it can be 5μm, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, 22μm, 24μm, 26μm, 28μm, 30μm, 32μm, 34μm, 36μm, 38μm, 40μm, 42μm, 44μm, 46μm, 48μm, 50μm, or any range of the above values.

[0086] Within the aforementioned range, the thickness of the interface modification layer can effectively prevent the electrolyte from penetrating to the lithium metal side, block lithium dendrites from piercing the interface modification layer, reduce the risk of internal short circuits in lithium metal battery cells, and also enable the interface modification layer to have good lithium-ion transport capabilities. This allows lithium ions to be embedded in the interface modification layer during charging and continue to be transported in bulk to deposit below the interface modification layer between the negative electrode current collector and the interface modification layer. This also reduces the risk of lithium ions being reduced to lithium metal on the surface of the interface modification layer, thereby enabling lithium metal battery cells to have better cycle performance.

[0087] Optionally, the thickness of the interface modification layer can be 5μm-40μm, 5μm-36μm, 5μm-32μm, 5μm-28μm, 5μm-24μm, 5μm-20μm, 8μm-40μm, 8μm-36μm, 8μm-32μm, 8μm-28μm, 8μm-24μm, 8μm-20μm, 10μm-40μm, 10μm-36μm, 10μm-32μm, 10μm-28μm, 10μm-24μm, or 10μm-20μm.

[0088] This allows lithium metal battery cells to have both high energy density and better cycle performance.

[0089] In some embodiments, the porosity of the interface modification layer can be 5%-50%, for example, it can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 42%, 44%, 46%, 48%, 50%, or any range of the above values.

[0090] The porosity of the interface modification layer can be adjusted by modifying its composition, such as the particle size, particle size distribution, and content of the interface modification material, as well as the preparation process parameters of the interface modification layer, such as the cold pressing process parameters.

[0091] The low porosity of the interface modification layer can better prevent the electrolyte from penetrating into the lithium metal side, and at the same time, it can better prevent lithium dendrites from piercing the interface modification layer. This can further reduce the risk of internal short circuits in lithium metal battery cells and further improve the cycle performance of lithium metal battery cells.

[0092] Optionally, the porosity of the interface modification layer can be 15%-40%, 15%-38%, or 15%-36%.

[0093] This reduces the difficulty of manufacturing the negative electrode and improves the cycle performance of lithium metal battery cells.

[0094] In some embodiments, the volumetric particle size Dv50 of the interface modification material can be 5nm-20μm, for example, it can be 5nm, 10nm, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, or any range of the above values.

[0095] Optionally, the volumetric particle size Dv50 of the interface modification material can be 10nm-15μm, 10nm-12μm, 10nm-10μm, 10nm-8μm, 10nm-5μm, 100nm-15μm, 100nm-12μm, 100nm-10μm, 100nm-8μm, 100nm-5μm, 200nm-15μm, 200nm-12μm, 200nm-10μm, 200nm-8μm, 200nm-5μm, 500nm-15μm, 500nm-12μm, 500nm-10μm, 500nm-8μm, 500nm-5μm, 1μm-15μm, 1μm-12μm, 1μm-10μm, 1μm-8μm, 1μm-5μm.

[0096] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the interface modification material can be greater than 0 and less than or equal to 5.

[0097] Optionally, the particle size distribution (Dv90-Dv10) / Dv50 of the interface modification material can be greater than 0 and less than or equal to 4.5, greater than 0 and less than or equal to 4, greater than 0 and less than or equal to 3.5, greater than 0 and less than or equal to 3, greater than 0 and less than or equal to 2.5, or greater than 0 and less than or equal to 2.

[0098] In some embodiments, the mass percentage of the interface modification material in the interface modification layer can be 30%-95%, for example, it can be 30%, 35%, 40%, 45%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, 91%, 92%, 93%, 94%, 95%, or any range of the above values.

[0099] Optionally, the mass percentage of the interface modification material in the interface modification layer can be 50%-95%, 60%-95%, 70%-95%, 80%-95%, 84%-95%, 88%-95%, 90%-95%, 50%-93%, 60%-93%, 70%-93%, 80%-93%, 84%-93%, 88%-93%, or 90%-93%.

[0100] In some embodiments, the interface modification layer may further include an adhesive for bonding the interface modification material and reducing powdering issues. As an example, the adhesive may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0101] The interface modification layer can be formed by coating a slurry including an interface modification material onto a lithiophilic layer, followed by drying and cold pressing. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0102] In some embodiments, the interface modification material may include expanded graphite and / or silicon oxide materials.

[0103] In some embodiments, the interlayer spacing d of the expanded graphite C(002) crystal planes 002 It can be greater than 3.4 angstroms (i.e., greater than 0.34 nm).

[0104] In some embodiments, the I of expanded graphite D / I G >0.5, I D The Raman spectrum of expanded graphite is at 1350±50 cm⁻¹ -1 D peak intensity at I G The Raman spectrum of expanded graphite is at 1580±50 cm⁻¹ -1 The intensity of the G peak at that location.

[0105] In Raman spectroscopy, ID / I G It reflects the degree of defects and disorder in expanded graphite, as well as the degree of graphitization. The D peak represents the degree of defects and disorder in expanded graphite, while the I peak... D The smaller the value, the more complete and ordered the structure of expanded graphite is. The G peak represents lattice vibrations and the degree of order, while the I peak represents... G The larger the value, the more compact and stable the structure of expanded graphite. D / I G The smaller the IL, the higher the graphitization degree and the lower the disorder degree of expanded graphite. A higher degree of graphitization increases its own lithium intercalation capacity, thereby reducing the amount of lithium metal deposited between the negative electrode current collector and the interface modification layer, thus lowering the coulombic efficiency and cycle capacity retention of the lithium metal battery cell. Therefore, by increasing the IL of expanded graphite... D / I G A value greater than 0.5 is beneficial for improving the coulombic efficiency and cycle life of lithium metal battery cells.

[0106] In some embodiments, the specific surface area of ​​expanded graphite may be less than or equal to 500 m². 2 / g. Optionally, the specific surface area of ​​expanded graphite can be less than or equal to 400m². 2 / g, less than or equal to 350m 2 / g.

[0107] In some embodiments, the initial coulombic efficiency of expanded graphite can be ≥50%, optionally ≥60%, ≥70%, or ≥80%.

[0108] Expanded graphite has high initial coulombic efficiency and does not consume a large amount of active lithium, thereby improving the coulombic efficiency and cycle life of lithium metal battery cells.

[0109] In some embodiments, the porosity of expanded graphite may be ≤30%, optionally ≤25%, or ≤20%.

[0110] Expanded graphite can be obtained by expanding graphite materials or by sintering single or multiple layers of graphene.

[0111] In some embodiments, the specific surface area of ​​the silicon-oxygen material may be less than or equal to 5 m². 2 / g.

[0112] In some embodiments, the silicon-oxygen material includes lithium. That is, the silicon-oxygen material can be a pre-lithium-intercalated silicon-oxygen material, which can reduce the irreversible loss of active lithium and improve the coulombic efficiency and cycle life of lithium metal battery cells.

[0113] In some embodiments, the surface of the silicon-oxygen material may have a carbon coating layer.

[0114] In some embodiments, the initial coulombic efficiency of the silicon-oxygen material can be ≥80%, and optionally ≥90%.

[0115] Silicon-oxygen materials have high initial coulombic efficiency and do not consume a large amount of active lithium, thereby improving the coulombic efficiency and cycle life of lithium metal battery cells.

[0116] The specific surface area of ​​expanded graphite and silica materials can be measured using the nitrogen adsorption specific surface area analysis method according to GB / T 19587-2017, and calculated using the BET (Brunauer Emmett Teller) method. The testing instrument can be the Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, USA.

[0117] Interlayer spacing d of expanded graphite C(002) crystal plane 002 X-ray diffractometers (such as Bruker D8 Discover) can be used for testing. The testing methods can be referenced in JIS K 0131-1996 and JB / T 4220-2011.

[0118] The porosity of expanded graphite can be tested using the gas displacement method, referring to GB / T 24586-2009. Porosity = (V1-V2) / V1×100%, where V1 is the apparent volume of the sample and V2 is the true volume. Nitrogen gas is used for the test. A Micromeritics AccuPyc II 1340 true density meter can be used as the testing instrument.

[0119] I of expanded graphite D / I G The test can be performed using a Raman spectrometer. D The Raman spectrum of expanded graphite is at 1350±50 cm⁻¹ -1 D peak intensity at I G The Raman spectrum of expanded graphite is at 1580±50 cm⁻¹ -1 The intensity of the G peak at the location was measured. The test conditions were: excitation wavelength 532 nm, grating 600 lines, objective lens 50x, integration time 10 s, cumulative scan 3 times, area scan, obtaining the D and G peak intensities at 100 points, and calculating the I at 100 points. D / I G Remove the largest and smallest 30 I's. D / I G The average value of the remaining 40 points is the I of expanded graphite. D / I G The testing instrument can be a Horiba LabRAM HR800 Raman spectrometer.

[0120] The initial coulombic efficiency of expanded graphite and silicon oxide materials was tested as follows: The negative electrode was removed from a fully discharged lithium metal battery cell and tested using a coin cell (or mold cell). A lithium sheet was used as the counter electrode, separated by an separator. The cells were first discharged to 0.005V (vs. Li) at a current density of 0.1C. + The initial lithium intercalation capacity was obtained by ( / Li); then it was charged to 2V (vs. Li) at a current density of 0.1C. + The initial delithiation capacity was obtained by calculating the initial coulombic efficiency (COP) = initial delithiation capacity / initial lithiation capacity × 100%.

[0121] The negative electrode current collector has two surfaces opposite each other in its thickness direction, and the lithiophilic layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0122] In some embodiments, the nucleation overpotential of lithium in the lithiophilic layer is lower than that in the interface modification layer, thereby promoting lithium ion deposition between the negative electrode current collector and the interface modification layer.

[0123] In some embodiments, the lithiophilic layer comprises one or more of a lithiophilic metal element, a lithiophilic metal alloy, and a lithiophilic oxide.

[0124] As an example, the lithiophilic layer may include one or more of Bi, Au, Ag, Mg, Zn, Sn, Sb, silver alloy, magnesium alloy, tin alloy, antimony alloy, MgO, and SnO2.

[0125] In some embodiments, the thickness of the lithiophilic layer can be 10nm-1000nm, for example, it can be 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 120nm, 140nm, 160nm, 180nm, 200nm, 220nm, 240nm, 260nm, 280nm, 300nm, 320nm, 340nm, 360nm, 380nm, 400nm, 420nm, 440nm, 460nm, 480nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, or any combination of the above values.

[0126] Within the aforementioned thickness range, lithium metal deposition can be better induced between the negative electrode current collector and the interface modification layer, reducing lithium metal deposition on the surface of the interface modification layer, thereby further improving the cycle performance of lithium metal battery cells. Within the aforementioned thickness range, lithium metal battery cells can also have higher energy density.

[0127] Optionally, the thickness of the lithiophilic layer can be 50nm-1000nm, 80nm-1000nm, 100nm-1000nm, 120nm-1000nm, 140nm-1000nm, 160nm-1000nm, 180nm-1000nm, 200nm-1000nm, 220nm-1000nm, 240nm-1000nm, 50nm-800nm, 80nm-800nm, 100nm-800nm, 120nm-800nm, 140nm-800nm, 160nm-800nm, 180nm-800nm, 200nm-800nm, or 220nm-800nm. 240nm-800nm, 50nm-600nm, 80nm-600nm, 100nm-600nm, 120nm-600nm, 140n m-600nm, 160nm-600nm, 180nm-600nm, 200nm-600nm, 220nm-600nm, 240nm- 600nm, 50nm-500nm, 80nm-500nm, 100nm-500nm, 120nm-500nm, 140nm-500n m, 160nm-500nm, 180nm-500nm, 200nm-500nm, 220nm-500nm, 240nm-500nm.

[0128] When the thickness of the lithiophilic layer is within the above range, lithium metal battery cells can better combine high energy density and good cycle performance.

[0129] In some embodiments, the lithiophilic layer can be deposited on at least one surface of the negative electrode current collector by a sputtering process.

[0130] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. The metal foil may be a pure metal, an alloy, or a surface-treated metal, such as, but not limited to, stainless steel foil, copper foil, and nickel foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. As an example, the metal layer may include, but is not limited to, one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer substrate may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0131] [Positive electrode plate]

[0132] In some embodiments, the positive electrode includes a positive current collector and a positive active material layer located on at least one side of the positive current collector. The positive active material layer includes a positive active material, which may include one or more of lithium transition metal oxides and their modified forms, lithium phosphates and their modified forms, lithium titanate, lithium niobate, sulfur, selenium, and tellurium. The positive current collector has two surfaces opposite each other in its thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0133] Optionally, examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxides, 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 lithium-rich manganese-based materials.

[0134] Optionally, examples of lithium phosphates may 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 manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0135] In some embodiments, to further improve the energy density of lithium metal battery cells, the positive electrode active material may include materials with the general formula Li. a Ni b Co c M d O e A f One or more of lithium transition metal oxides and their modified materials. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M may include one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A may include one or more of N, F, S and Cl.

[0136] As an example, the positive electrode active material may include, but is not limited to, LiCoO2, LiNiO2, LiMnO2, LiMn2O4, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (abbreviated as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (abbreviated as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (abbreviated as NCM622), LiNi0.8 Co 0.1 Mn 0.1 O2 (abbreviated as NCM811), LiNi 0.83 Mn 0.08 Co 0.07 O2 (abbreviated as Ni83), LiNi 0.90 Mn 0.05 Co 0.05 O2 (abbreviated as Ni90), LiNi 0.94 Mn 0.03 Co 0.03 O2 (abbreviated as Ni94), LiNi 0.96 Co 0.02 Mn 0.02 O2 (abbreviated as Ni96), LiNi 0.80 Co 0.15 Al 0.05 One or more of O2, LiFePO4, LiMnPO4 and their respective modified materials.

[0137] During the charging and discharging process, lithium metal battery cells undergo lithium (Li) insertion / extraction and consumption, resulting in varying Li molar content at different discharge states. In this disclosure, the molar content of Li in the positive electrode active materials refers to the initial state of the material, i.e., the state before feeding. When the positive electrode active material is applied to a lithium metal battery cell, the Li molar content changes after charge-discharge cycles. Similarly, the molar content of O in the positive electrode active materials listed in this disclosure is only a theoretical value. Lattice oxygen release causes changes in the O molar content, leading to fluctuations in the actual O molar content.

[0138] The modified materials for the above-mentioned positive electrode active materials can be doped and / or surface coated.

[0139] In some embodiments, the positive electrode active material layer may include a positive electrode binder, which may include, but is not limited to, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0140] In some embodiments, the positive electrode active material layer may include a positive electrode conductive agent, which may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0141] In some embodiments, the positive current collector can be a metal foil or a composite current collector. The metal foil can be a pure metal, an alloy, or a surface-treated metal. For example, the metal foil can be carbon-coated aluminum foil, aluminum foil, nickel foil, or titanium foil. The composite current collector can include a polymer substrate and a metal material layer formed on at least one surface of the polymer substrate. For example, the metal material can be one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer substrate can be one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0142] In some embodiments, the positive electrode active material layer can be formed by coating a slurry comprising the positive electrode active material onto the positive electrode current collector, followed by drying and cold pressing. The solvent for the slurry can be N-methylpyrrolidone (NMP), but is not limited thereto.

[0143] [Isolation Component]

[0144] In some embodiments, the separator may be an inorganic solid electrolyte layer. As an example, the inorganic solid electrolyte layer may include one or more of oxide solid electrolytes, sulfide solid electrolytes, halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0145] Optionally, the oxide solid electrolyte may include one or more of the following: NASICON type solid electrolyte, LISICON type solid electrolyte, perovskite type solid electrolyte, and garnet type solid electrolyte.

[0146] As an example, oxide solid electrolytes may include, but are not limited to, Li5La3Ti2O 12 Li7La3Zr2O 12 Li4Ti5O 12 Li 14 Zn(GeO4)4, LiTi2(PO4)3, Li 1+x Al x Ti 2-x (PO4)3, Li 1+y Al y Ge 2-y One or more of (PO4)3, 0 < x < 2, 0 < y < 2.

[0147] Optionally, the sulfide solid electrolyte may include, but is not limited to, one or more of the following sulfide solid electrolyte materials: silver-germanium sulfide type, LGPS type, and lithium pentaphosphide-sulfide complex type. Optionally, the silver-germanium sulfide type sulfide solid electrolyte material may include materials with the chemical formula Li 6±s P1-j A j S 5±s-t B t X 1±s material, where 0 ≤ j < 1, 0 ≤ t < 1, 0 ≤ s < 1, A includes one or more elements selected from Ge, Si, Sn, and Sb, B includes one or more elements selected from O, Se, and Te, and X includes one or more elements selected from Cl, Br, I, and F. Optionally, the LGPS-based sulfide solid electrolyte material may include a material having the chemical formula Li 10±δ5 Ge 1-g G g P 2-q Q q S 12-w W w where 0 ≤ δ5 < 1, 0 ≤ g ≤ 1, 0 ≤ q ≤ 2, 0 ≤ w < 1, G includes one or two elements selected from Si and Sn, Q includes Sb, and W includes one or more elements selected from O, Se, Te, Cl, Br, I, and F. Optionally, the lithium sulfide - diphosphorus pentasulfide composite - based sulfide solid electrolyte material may include a material having the chemical formula (100 - u - v)Li2S·uP2S5·vM m N n where 0 < u < 100, 0 ≤ v < 100, 0 ≤ u + v < 100, 0 ≤ m < 4, 0 ≤ n < 6, M includes one or more elements selected from Li, B, Ge, Si, Sn, and Sb, and N includes one or more elements selected from S, Se, Te, O, Cl, Br, I, and F.

[0148] As an example, the sulfide solid electrolyte may include, but is not limited to, one or more of Li6PS5Cl, Li6PS5Br, Li 10 GeP2S 12 , Li3PS4, Li7P3S 11 among others.

[0149] Optionally, the halide solid electrolyte may include, but is not limited to, one or more of Li '3YCl6, Li3YBr6, Li3ErCl6, Li3InCl6, Li3InBr6.

[0150] In some embodiments, the separator may be a gel electrolyte separator membrane. The gel electrolyte separator membrane includes a separator membrane matrix and a gel layer.

[0151] This disclosure does not impose any particular limitation on the type of separator membrane substrate; any known porous membrane with good chemical and mechanical stability can be selected. In some embodiments, the material of the separator membrane substrate may include, but is not limited to, one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and polyimide. The separator membrane substrate can be a single-layer film or a multilayer composite film. When the separator membrane substrate is a multilayer composite film, the materials of each layer may be the same or different.

[0152] The gel layer comprises a polymer matrix, electrolyte salts, and plasticizers.

[0153] The polymer matrix acts as a skeletal support in the gel electrolyte layer. For example, the polymer matrix may include polyacrylonitrile, polyoxyethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethyl methacrylate, etc.

[0154] Electrolyte salts are used to provide ionic conductivity. As an example, electrolyte salts may include one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium dioxalateborate, lithium difluorooxalateborate, lithium difluorophosphate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0155] Plasticizers are used to improve the plasticity of the polymer matrix and enhance the ionic conductivity of the gel electrolyte layer. Plasticizers may include one or more of carbonate compounds, nitrile compounds, and ether compounds. For example, plasticizers may include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, vinylene carbonate, dipropyl carbonate, methyl ethyl carbonate, succinic acid, 1,3-dioxolane, ethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0156] The preparation method of lithium metal battery cells is well known. In some embodiments, positive electrode sheets, separators, and negative electrode sheets can be formed into electrode assemblies through winding or stacking processes, and the electrode assemblies can be placed in outer packaging and then encapsulated to obtain lithium metal battery cells.

[0157] Example

[0158] The following embodiments describe the disclosure of this disclosure in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of this disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0159] Example 1

[0160] Preparation of positive electrode sheet

[0161] LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2, conductive carbon black (positive electrode conductive agent), and polyvinylidene fluoride (PVDF) (positive electrode binder) are mixed in a mass ratio of 95:3:2 and then dispersed in N-methylpyrrolidone (NMP) solvent to form a slurry. This slurry is then coated onto one surface of the positive electrode current collector aluminum foil. After drying, cold pressing, and cutting, the positive electrode sheet is obtained.

[0162] Preparation of negative electrode sheet

[0163] Expanded graphite, polyvinylidene fluoride (PVDF) binder, and N-methylpyrrolidone (NMP) solvent are uniformly mixed in a mass ratio of 90:10:200 to prepare an interface modification layer slurry. This slurry is then coated onto one surface of a copper foil sputtered with a Bi metal lithiophilic layer. After drying, cold pressing, and cutting, the negative electrode sheet is obtained.

[0164] The expanded graphite has a volumetric particle size Dv50 of 1 μm and a specific surface area of ​​55 m². 2 / g、I D / I G The thickness of the interface modification layer is 15 μm. The porosity of the interface modification layer is 35%. The thickness of the lithiophilic layer is 500 nm, and the lithiophilic layer is located between the interface modification layer and the copper foil.

[0165] The ratio of the unit area capacity of the negative electrode interface modification layer to the unit area capacity of the positive electrode, i.e., the NP ratio, is 0.15.

[0166] Separating membrane substrate

[0167] A polyethylene film with a thickness of 13 μm was used as the substrate for the isolation membrane.

[0168] Preparation of gel electrolyte precursor fluid

[0169] Acrylonitrile monomer, initiator azobisisobutyronitrile (AIBN), and electrolyte are mixed to obtain a precursor solution. The electrolyte preparation method includes the following steps: ethylene carbonate and ethyl methyl carbonate are mixed at a mass ratio of 30:70 to obtain an organic solvent; fully dried electrolyte salt LiPF6 is dissolved in the above organic solvent at a concentration of 1.0 mol / L; and the mixture is thoroughly mixed to obtain the electrolyte.

[0170] Preparation of lithium metal battery cells

[0171] The positive electrode and separator substrate are stacked and placed in an aluminum-plastic bag. The gel electrolyte precursor liquid is injected, the aluminum-plastic bag is sealed and left to stand for 12 hours, and then cured at 60°C for 2 hours. After curing, the gel electrolyte separator and positive electrode are removed, and then stacked with the negative electrode and placed in an aluminum-plastic bag for sealing and standing to obtain a lithium metal battery cell.

[0172] The prepared lithium metal battery cell was charged to 4.3V at a constant current of 0.1C. The negative electrode was then disassembled and the lithium metal deposition state and morphology on the negative electrode side were observed.

[0173] Take the prepared lithium metal battery cell, set the ambient temperature to 25℃, and charge it at a constant current of 0.2C until the cutoff voltage of 4.3V is reached. Then, continue charging at a constant voltage of 4.3V until the current decays to 0.1C. Next, discharge it at a constant current of 0.5C to 3.2V to obtain the first discharge capacity. Repeat the above charge-discharge cycle and record the discharge capacity after each cycle. When the discharge capacity decays to 80% of the first cycle's discharge capacity, the lithium metal battery cell is considered to have reached the end of its lifespan, and the number of cycles experienced by the lithium metal battery cell at this point is recorded. The average coulombic efficiency of the lithium metal battery cell = (sum of discharge capacity per cycle / sum of charge capacity per cycle) × 100%.

[0174] Weigh the lithium metal battery cell W using an electronic scale. At 25°C, charge at a constant current of 0.33C until the cutoff voltage of 4.3V is reached. Continue charging at a constant voltage of 4.3V until the current decreases to 0.1C. Then discharge at a constant current of 0.33C to 3.2V to obtain the discharge energy of the lithium metal battery cell. Repeat the test three times and take the average value to obtain the average discharge energy E of the lithium metal battery cell. The gravimetric energy density of a lithium metal battery cell = E / W.

[0175] Example 2

[0176] Except for the following differences, the preparation method and performance testing method of the lithium metal battery cell are the same as those in Example 1.

[0177] Preparation of negative electrode sheet

[0178] A pre-lithiated silicon oxide material with a carbon coating layer, a binder polyvinylidene fluoride (PVDF), and a solvent N-methylpyrrolidone (NMP) are uniformly mixed in a mass ratio of 90:10:200 to prepare an interface modification layer slurry. This slurry is then coated onto one surface of a copper foil sputtered with a Bi metal lithiophilic layer. After drying, cold pressing, and cutting, a negative electrode sheet is obtained.

[0179] The pre-lithiated silicon oxide material with a carbon coating on its surface has a volume distribution particle size Dv50 of 3 μm and a specific surface area of ​​2 m². 2 / g. The thickness of the interface modification layer is 15μm. The porosity of the interface modification layer is 20%. The thickness of the lithiophilic layer is 500nm, and the lithiophilic layer is located between the interface modification layer and the copper foil.

[0180] The ratio of the unit area capacity of the negative electrode interface modification layer to the unit area capacity of the positive electrode, i.e., the NP ratio, is 0.3.

[0181] Comparative Example 1

[0182] Except for the following differences, the preparation method and performance testing method of the lithium metal battery cell are the same as those in Example 1.

[0183] Preparation of positive electrode sheet

[0184] LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2, conductive carbon black (positive electrode conductive agent), and polyvinylidene fluoride (PVDF) (positive electrode binder) are mixed in a mass ratio of 95:3:2 and then dispersed in N-methylpyrrolidone (NMP) solvent to form a slurry. This slurry is then coated onto one surface of the positive electrode current collector aluminum foil. After drying, cold pressing, and cutting, the positive electrode sheet is obtained.

[0185] Preparation of negative electrode sheet

[0186] The negative electrode is a copper foil with a Bi metal lithiophilic layer sputtered on one side. The thickness of the lithiophilic layer is 500 nm.

[0187] Separating membrane

[0188] A polyethylene film with a thickness of 13 μm was used as the separator.

[0189] Preparation of gel electrolyte precursor fluid

[0190] Acrylonitrile monomer, initiator azobisisobutyronitrile (AIBN), and electrolyte are mixed to obtain a precursor solution. The electrolyte preparation method includes the following steps: ethylene carbonate and ethyl methyl carbonate are mixed at a mass ratio of 30:70 to obtain an organic solvent; fully dried electrolyte salt LiPF6 is dissolved in the above organic solvent at a concentration of 1.0 mol / L; and the mixture is thoroughly mixed to obtain the electrolyte.

[0191] Preparation of lithium metal battery cells

[0192] The positive electrode, separator, and negative electrode are stacked and placed in an aluminum-plastic bag. The gel electrolyte precursor liquid is injected, the aluminum-plastic bag is sealed, and the mixture is left to stand for 12 hours. Then, it is cured at 60°C for 2 hours to obtain a lithium metal battery cell.

[0193] Comparative Example 2

[0194] Except for the following differences, the preparation method and performance testing method of the lithium metal battery cell are the same as those in Example 1.

[0195] Preparation of positive electrode sheet

[0196] LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2, conductive carbon black (positive electrode conductive agent), and polyvinylidene fluoride (PVDF) (positive electrode binder) are mixed in a mass ratio of 95:3:2 and then dispersed in N-methylpyrrolidone (NMP) solvent to form a slurry. This slurry is then coated onto one surface of the positive electrode current collector aluminum foil. After drying, cold pressing, and cutting, the positive electrode sheet is obtained.

[0197] Preparation of negative electrode sheet

[0198] Artificial graphite, polyvinylidene fluoride (PVDF) binder, and N-methylpyrrolidone (NMP) solvent are uniformly mixed in a mass ratio of 90:10:200 to prepare an interface modification layer slurry. This slurry is then coated onto one surface of a copper foil sputtered with a Bi metal lithiophilic layer. After drying, cold pressing, and cutting, a negative electrode sheet is obtained.

[0199] The artificial graphite has a volumetric particle size Dv50 of 5 μm and a specific surface area of ​​1 m². 2 / g、I D / I G The thickness of the interface modification layer is 15 μm. The porosity of the interface modification layer is 20%. The thickness of the lithiophilic layer is 500 nm, and the lithiophilic layer is located between the interface modification layer and the copper foil.

[0200] The ratio of the unit area capacity of the negative electrode interface modification layer to the unit area capacity of the positive electrode, i.e., the NP ratio, is 0.15.

[0201] Separating membrane

[0202] A polyethylene film with a thickness of 13 μm was used as the separator.

[0203] Preparation of gel electrolyte precursor fluid

[0204] Acrylonitrile monomer, initiator azobisisobutyronitrile (AIBN), and electrolyte are mixed to obtain a precursor solution. The electrolyte preparation method includes the following steps: ethylene carbonate and ethyl methyl carbonate are mixed at a mass ratio of 30:70 to obtain an organic solvent; fully dried electrolyte salt LiPF6 is dissolved in the above organic solvent at a concentration of 1.0 mol / L; and the mixture is thoroughly mixed to obtain the electrolyte.

[0205] Preparation of lithium metal battery cells

[0206] After stacking the positive electrode and separator, they are placed in an aluminum-plastic bag, and the gel electrolyte precursor liquid is injected. The aluminum-plastic bag is sealed and left to stand for 12 hours. Then, it is cured at 60°C for 2 hours. After curing, the gel electrolyte layer separator and positive electrode are removed, and then stacked with the negative electrode and placed in an aluminum-plastic bag for sealing and standing to obtain a lithium metal battery cell.

[0207] Table 1

[0208] Figure 3 shows the lithium metal deposition morphology on the negative electrode side of Example 1. Figure 4 shows the lithium metal deposition morphology on the negative electrode side of Comparative Example 1. Figure 5 shows the lithium metal deposition morphology on the negative electrode side of Comparative Example 2.

[0209] As shown in Figure 3, the lithium metal in the lithium metal battery cell of this disclosure is deposited between the interface modification layer and the copper current collector. The deposited lithium metal is dense and free of black byproducts. In the charge-discharge cycle test, the average coulombic efficiency is close to 100%.

[0210] As shown in Figure 4, the lithium metal deposited on the negative electrode side of Comparative Example 1 has a loose and porous morphology, and obvious black substances can be observed. During the charge-discharge cycle test, the lithium metal battery cell fails rapidly.

[0211] As shown in Figure 5, in Comparative Example 2, lithium metal was deposited on the negative electrode side above the interface modification layer and exhibited obvious lithium dendrite morphology. During charge-discharge cycle testing, the lithium metal battery cell failed rapidly.

[0212] Example 1-1

[0213] Except for the following differences, the preparation method and performance testing method of the lithium metal battery cell are the same as those in Example 1.

[0214] The thickness of the interface modification layer of the negative electrode sheet is 5 μm.

[0215] The ratio of the unit area capacity of the negative electrode interface modification layer to the unit area capacity of the positive electrode, i.e., the NP ratio, is 0.05.

[0216] Examples 1-2

[0217] Except for the following differences, the preparation method and performance testing method of the lithium metal battery cell are the same as those in Example 1.

[0218] The thickness of the interface modification layer of the negative electrode sheet is 10 μm.

[0219] The ratio of the unit area capacity of the negative electrode interface modification layer to the unit area capacity of the positive electrode, i.e., the NP ratio, is 0.1.

[0220] Examples 1-3

[0221] Except for the following differences, the preparation method and performance testing method of the lithium metal battery cell are the same as those in Example 1.

[0222] The thickness of the interface modification layer of the negative electrode sheet is 20 μm.

[0223] The ratio of the unit area capacity of the negative electrode interface modification layer to the unit area capacity of the positive electrode, i.e., the NP ratio, is 0.2.

[0224] Examples 1-4

[0225] Except for the following differences, the preparation method and performance testing method of the lithium metal battery cell are the same as those in Example 1.

[0226] The thickness of the interface modification layer of the negative electrode sheet is 50 μm.

[0227] The ratio of the unit area capacity of the negative electrode interface modification layer to the unit area capacity of the positive electrode, i.e., the NP ratio, is 0.5.

[0228] Table 2

[0229] The test results above show that the smaller the thickness of the interface modification layer, the higher the gravimetric energy density of the lithium metal battery cell. By further adjusting the thickness of the interface modification layer, the lithium metal battery cell can have both high energy density and good cycle performance.

[0230] Example 2-1

[0231] Except for the following differences, the preparation method and performance testing method of the lithium metal battery cell are the same as those in Example 2.

[0232] The thickness of the interface modification layer of the negative electrode sheet is 5 μm.

[0233] The ratio of the unit area capacity of the negative electrode interface modification layer to the unit area capacity of the positive electrode, i.e., the NP ratio, is 0.1.

[0234] Example 2-2

[0235] Except for the following differences, the preparation method and performance testing method of the lithium metal battery cell are the same as those in Example 2.

[0236] The thickness of the interface modification layer of the negative electrode sheet is 10 μm.

[0237] The ratio of the unit area capacity of the negative electrode interface modification layer to the unit area capacity of the positive electrode, i.e., the NP ratio, is 0.2.

[0238] Example 2-3

[0239] Except for the following differences, the preparation method and performance testing method of the lithium metal battery cell are the same as those in Example 2.

[0240] The thickness of the interface modification layer of the negative electrode sheet is 20 μm.

[0241] The ratio of the unit area capacity of the negative electrode interface modification layer to the unit area capacity of the positive electrode, i.e., the NP ratio, is 0.4.

[0242] Examples 2-4

[0243] Except for the following differences, the preparation method and performance testing method of the lithium metal battery cell are the same as those in Example 2.

[0244] The thickness of the interface modification layer of the negative electrode sheet is 40 μm.

[0245] The ratio of the unit area capacity of the negative electrode interface modification layer to the unit area capacity of the positive electrode, i.e., the NP ratio, is 0.8.

[0246] Table 3

[0247] The test results above show that the smaller the thickness of the interface modification layer, the higher the gravimetric energy density of the lithium metal battery cell. By further adjusting the thickness of the interface modification layer, the lithium metal battery cell can have both high energy density and good cycle performance.

[0248] Example 3-1

[0249] Except for the following differences, the preparation method and performance testing method of the lithium metal battery cell are the same as those in Example 1.

[0250] Preparation of negative electrode sheet

[0251] Expanded graphite, polyvinylidene fluoride (PVDF) binder, and N-methylpyrrolidone (NMP) solvent are uniformly mixed in a mass ratio of 90:10:200 to prepare an interface modification layer slurry. This slurry is then coated onto one surface of a copper foil sputtered with a Bi metal lithiophilic layer. After drying, cold pressing, and cutting, the negative electrode sheet is obtained.

[0252] The expanded graphite has a volumetric particle size Dv50 of 0.5 μm and a specific surface area of ​​350 m². 2 / g、I D / I G The thickness of the interface modification layer is 15 μm. The porosity of the interface modification layer is 40%. The thickness of the lithiophilic layer is 500 nm, and the lithiophilic layer is located between the interface modification layer and the copper foil.

[0253] The ratio of the unit area capacity of the negative electrode interface modification layer to the unit area capacity of the positive electrode, i.e., the NP ratio, is 0.15.

[0254] Example 3-2

[0255] Except for the following differences, the preparation method and performance testing method of the lithium metal battery cell are the same as those in Example 1.

[0256] Preparation of negative electrode sheet

[0257] Expanded graphite, polyvinylidene fluoride (PVDF) binder, and N-methylpyrrolidone (NMP) solvent are uniformly mixed in a mass ratio of 90:10:200 to prepare an interface modification layer slurry. This slurry is then coated onto one surface of a copper foil sputtered with a Bi metal lithiophilic layer. After drying, cold pressing, and cutting, the negative electrode sheet is obtained.

[0258] The expanded graphite has a volumetric particle size Dv50 of 5 μm and a specific surface area of ​​50 m². 2 / g、I D / I G The thickness of the interface modification layer is 15 μm. The porosity of the interface modification layer is 27%. The thickness of the lithiophilic layer is 500 nm, and the lithiophilic layer is located between the interface modification layer and the copper foil.

[0259] The ratio of the unit area capacity of the negative electrode interface modification layer to the unit area capacity of the positive electrode, i.e., the NP ratio, is 0.15.

[0260] Table 4

[0261] The test results above show that the interface modification layer has low porosity, which can better prevent the electrolyte in the gel electrolyte separator from penetrating to the lithium metal side. This can further reduce lithium metal side reactions, reduce the continuous consumption of active lithium caused by the contact between the electrolyte and lithium metal, and improve the coulombic efficiency and cycle life of the lithium metal battery cell.

[0262] Example 4-1

[0263] Except for the following differences, the preparation method and performance testing method of the lithium metal battery cell are the same as those in Example 1.

[0264] The thickness of the lithiophilic layer is 100 nm.

[0265] Example 4-2

[0266] Except for the following differences, the preparation method and performance testing method of the lithium metal battery cell are the same as those in Example 1.

[0267] The thickness of the lithiophilic layer is 200 nm.

[0268] Example 4-3

[0269] Except for the following differences, the preparation method and performance testing method of the lithium metal battery cell are the same as those in Example 1.

[0270] The thickness of the lithiophilic layer is 800 nm.

[0271] Example 4-4

[0272] Except for the following differences, the preparation method and performance testing method of the lithium metal battery cell are the same as those in Example 1.

[0273] The thickness of the lithiophilic layer is 1000 nm.

[0274] Examples 4-5

[0275] Except for the following differences, the preparation method and performance testing method of the lithium metal battery cell are the same as those in Example 1.

[0276] Preparation of negative electrode sheet

[0277] Expanded graphite, polyvinylidene fluoride (PVDF) binder, and N-methylpyrrolidone (NMP) solvent are uniformly mixed in a mass ratio of 90:10:200 to prepare an interface modification layer slurry. This slurry is then coated onto one surface of a copper foil sputtered with an Ag metal lithiophilic layer. After drying, cold pressing, and cutting, the negative electrode sheet is obtained.

[0278] The expanded graphite has a volumetric particle size Dv50 of 1 μm and a specific surface area of ​​55 m². 2 / g、I D / I G The thickness of the interface modification layer is 15 μm. The porosity of the interface modification layer is 35%. The thickness of the lithiophilic layer is 500 nm, and the lithiophilic layer is located between the interface modification layer and the copper foil.

[0279] The ratio of the unit area capacity of the negative electrode interface modification layer to the unit area capacity of the positive electrode, i.e., the NP ratio, is 0.15.

[0280] Table 5

[0281] The test results above show that increasing the thickness of the lithiophilic layer can better induce lithium metal deposition between the negative electrode current collector and the interface modification layer, reducing lithium metal deposition on the surface of the interface modification layer, thereby further improving the coulombic efficiency and cycle performance of lithium metal battery cells. However, after the lithiophilic layer thickness reaches 500 nm, further increasing the thickness of the lithiophilic layer has little effect on improving the cycle performance of lithium metal battery cells, and may even reduce the energy density of the lithium metal battery cells.

[0282] Example 5-1

[0283] Take the lithium metal battery cell prepared in Example 1, set the ambient temperature to 25°C, and charge it using a 0.2C constant current until the cutoff voltage of 4.3V is reached. Then, continue charging with a 4.3V constant voltage until the current decays to 0.1C. Then, discharge it using a 0.5C constant current until 2.8V, obtaining the first discharge capacity. Repeat the above charge-discharge cycle and record the discharge capacity after each cycle. When the discharge capacity decays to 80% of the first discharge capacity, the lithium metal battery cell is considered to have reached the end of its lifespan, and the number of cycles experienced by the lithium metal battery cell at this time is recorded.

[0284] Table 6

[0285] The test results above show that by making the lower limit operating voltage of the lithium metal battery cell greater than the delithiation potential of the expanded graphite, the lithium metal battery cell can be completely transformed into a lithium metal deposition / stripping mechanism during subsequent charge-discharge cycles, thereby reducing the irreversible loss of active lithium and improving the cycle life of the lithium metal battery cell.

[0286] It should be noted that this disclosure 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 disclosure are included within the technical scope of this disclosure. 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, are also included within the scope of this disclosure without departing from the spirit of this disclosure.

Claims

1. A lithium metal battery cell, comprising a negative electrode, a positive electrode, and a separator, wherein the separator is located between the negative electrode and the positive electrode, wherein, The negative electrode sheet includes a negative current collector, a lithiophilic layer on at least one surface of the negative current collector, and an interface modification layer on the surface of the lithiophilic layer away from the negative current collector. The interface modification layer comprises an interface modification material, the ion conductivity of the interface modification material at 25°C is greater than or equal to 1x10 -8 S / cm, and the electronic conductivity of the interface modification material at 25°C is less than or equal to 0.1 S / cm. The NP ratio of the lithium metal battery cell is greater than 0 and less than 1. The NP ratio is the ratio of the unit area capacity of the negative electrode interface modification layer to the unit area capacity of the positive electrode.

2. The lithium metal battery cell of claim 1, wherein, The NP ratio of the lithium metal battery cell is from 0.05 to 0.

4.

3. The lithium metal battery cell of any of claims 1-2, wherein, The lower limit operating voltage of the lithium metal battery cell is greater than the delithiation potential of the interface modification material.

4. The lithium metal battery cell according to any one of claims 1-3, wherein, The thickness of the interface modification layer is 5μm-50μm; and / or, The porosity of the interface modification layer is 5%-50%.

5. The lithium metal battery cell according to claim 4, wherein, The thickness of the interface modification layer is 10μm-20μm; and / or, The porosity of the interface modification layer is 15%-40%.

6. The lithium metal battery cell according to any one of claims 1-5, wherein, The volumetric particle size Dv50 of the interface modification material is 5nm-20μm; and / or, The particle size distribution (Dv90-Dv10) / Dv50 of the interface modification material is greater than 0 and less than or equal to 5.

7. The lithium metal battery cell of claim 6, wherein, The volumetric particle size Dv50 of the interface modification material is 10 nm-5 μm.

8. The lithium metal battery cell of any one of claims 1-7, wherein, The interface modification material includes expanded graphite and / or silicon-oxygen materials.

9. The lithium metal battery cell of claim 8, wherein, The expanded graphite satisfies at least one of the following conditions (1) to (5): (1) the interlayer distance d of the (002) plane of the expanded graphite C 002 greater than 3.4 angstroms; (2) the I D / I G of the expanded graphite is 0.5 or more D D peak intensity at 1350 ± 50 cm -1 -1 of the Raman spectrum of the expanded graphite; and G G peak intensity at 1580 ± 50 cm -1 -1 of the Raman spectrum of the expanded graphite. (3) the specific surface area of the expanded graphite is less than or equal to 500 m 2 / g; (4) The initial coulombic efficiency of the expanded graphite is ≥50%; (5) The porosity of the expanded graphite is ≤30%.

10. The lithium metal battery cell of claim 8, wherein, The silicon-oxygen material satisfies at least one of the following conditions (1) to (4): (1) the silicon-oxygen material has a specific surface area less than or equal to 5 m 2 / g; (2) The silicon-oxygen material includes lithium; (3) The surface of the silicon-oxygen material has a carbon coating layer; (4) The initial coulombic efficiency of the silicon-oxygen material is ≥80%.

11. The lithium metal battery cell of any one of claims 1-10, wherein, The nucleation overpotential of lithium in the lithiophilic layer is lower than that in the interface modification layer.

12. The lithium metal battery cell according to any one of claims 1-11, wherein, The lithiophilic layer comprises one or more of a lithiophilic elemental metal, a lithiophilic metal alloy, and a lithiophilic oxide; and / or, The thickness of the lithiophilic layer is 10nm-1000nm.

13. The lithium metal battery cell of claim 12, wherein, The thickness of the lithiophilic layer is 200nm-500nm.

14. The lithium metal battery cell of any one of claims 11-13, wherein, The lithiophilic layer includes one or more of Bi, Au, Ag, Mg, Zn, Sn, Sb, silver alloy, magnesium alloy, tin alloy, antimony alloy, MgO, and SnO2.

15. The lithium metal battery cell of any one of claims 1-14, wherein, The interface modification material accounts for 30%-95% of the mass of the interface modification layer.

16. The lithium metal battery cell according to any one of claims 1-15, wherein, The separator is an inorganic solid electrolyte layer or a gel electrolyte separator membrane; and / or, The positive electrode tab includes a positive electrode current collector and a positive electrode active material layer on at least one side of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material, the positive electrode active material including one or more of lithium transition metal oxides and modified materials thereof, lithium-containing phosphates and modified materials thereof, lithium titanate, lithium niobate, sulfur, selenium, tellurium.

17. A battery device comprising a plurality of lithium metal battery cells according to any one of claims 1-16.

18. An electrically powered device comprising a lithium metal battery cell according to any one of claims 1-16 or a battery device according to claim 17.

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