Negative pole piece, battery monomer, battery and electric device

Abstract

The invention discloses a negative pole piece, a battery monomer, a battery and a power utilization device, the negative pole piece comprises a negative current collector and a modification layer located on at least one surface of the negative current collector, and the modification layer comprises an alkali metal affinity layer and a non-metal conductive layer located on the surface, away from the negative current collector, of the alkali metal affinity layer; the nucleation overpotential of the alkali metal affinity layer is recorded as V1, the nucleation overpotential of the non-metal conductive layer is recorded as V2, the unit is mV, and V2-V1 is greater than or equal to 40mV. The negative pole piece provided by the invention can enable the battery to have good cycle performance and also enable the battery to have high reliability.

Description

Technical Field

[0001] The present application relates to a negative electrode plate, a battery cell, a battery and an electrical device. Background Art

[0002] Compared with ion-type batteries, metal batteries can have higher energy density. However, unlike the negative electrode of ion-type batteries, the negative electrode of metal batteries has a more serious dendrite problem, which affects its commercialization. The growth of dendrites will cause internal short circuits in the battery, affecting the reliability of the battery; at the same time, during the metal deposition and stripping process, the unstable solid electrolyte interface (SEI) film is repeatedly torn and rebuilt, which will continuously consume active ions and electrolytes, thereby affecting the battery's cycle performance. The above statements are only used to provide background technical information related to this application and do not necessarily constitute prior art. Summary of the invention

[0003] The present application provides a negative electrode plate, a battery cell, a battery and an electrical device, which can enable the battery to have good cycle performance and high reliability.

[0004] In a first aspect, the present application provides a negative electrode pole piece, which includes a negative electrode current collector and a modified layer located on at least one surface of the negative electrode current collector, the modified layer includes an alkali metal affinity layer and a non-metallic conductive layer located on the surface of the negative electrode current collector away from the alkali metal affinity layer; the nucleation overpotential of the alkali metal affinity layer is recorded as V1, and the nucleation overpotential of the non-metallic conductive layer is recorded as V2, both in mV, and V2-V1 is greater than or equal to 40mV.

[0005] The present application starts from the structure of the negative electrode plate, by first forming an alkali metal affinity layer on the negative electrode current collector, and then forming a non-metallic conductive layer. Since the non-metallic conductive layer itself is conductive, it will not affect the passage of metal ions such as lithium ions and sodium ions.

[0006] The alkali metal affinity layer includes those that have affinity with metals such as lithium and sodium, thereby reducing the volume change of the negative electrode plate caused by metal deposition and stripping during the battery cycle, thereby stabilizing the skeleton structure of the negative electrode plate and improving the cycle stability of the battery.

[0007] By further adjusting the difference V2-V1 between the nucleation overpotential V2 of the non-metallic conductive layer and the nucleation overpotential V1 of the alkali metal affinity layer to be greater than or equal to 40mV, metal ions such as lithium ions and sodium ions can pass through the non-metallic conductive layer and fall on the surface of the alkali metal affinity layer under the induction of this difference in nucleation overpotential, forming a large number of active points in the alkali metal affinity layer. These active points can act as "seeds" to induce the uniform deposition of metals such as lithium and sodium, thereby reducing the dominant growth points, reducing the formation of dendrites, and reducing the localized deposition of metals; moreover, the formed active points can also increase the negative electrode potential, thereby also helping to improve the film formation quality of the SEI film on the negative electrode surface.

[0008] In addition, under the pressure of the non-metallic conductive layer, the deposited metals such as lithium and sodium can also grow evenly between the non-metallic conductive layer and the negative electrode current collector, which can further reduce the formation of dendrites and further reduce the electrolyte side reactions and active ion consumption caused by repeated tearing and reconstruction of the SEI film.

[0009] Therefore, the negative electrode plate provided in the embodiment of the present application can make the battery have good cycle performance and high reliability.

[0010] In some embodiments, V2-V1 is 48mV-121mV, and can be 57mV-94mV. By further adjusting V2-V1 within the above range, the battery can better have both high reliability and good cycle performance.

[0011] In some embodiments, V1 is 0mV-40mV, optionally 8mV-22mV.

[0012] In some embodiments, V2 is 60mV-120mV, optionally 78mV-110mV.

[0013] By further adjusting the nucleation overpotential V1 of the alkali metal affinity layer and / or the nucleation overpotential V2 of the non-metallic conductive layer within the above range, the battery can better have both high reliability and good cycle performance.

[0014] In some embodiments, the non-metallic conductive layer includes a non-metallic conductive material.

[0015] Optionally, the non-metallic conductive material includes one or more of a carbon-based conductive material and a phosphorus-based conductive material.

[0016] More optionally, the non-metallic conductive material includes one or more of porous carbon, hard carbon, carbon tubes, red phosphorus, black phosphorus, and phosphorus-carbon composites.

[0017] In some embodiments, the alkali metal affinity layer includes a lithium affinity material.

[0018] In some embodiments, the lithium-philic material includes a lithium-philic metal element. Optionally, the lithium-philic metal element includes one or more of Ag, Mg, Sn, Al, Bi, Au, In, Cu, and Zn.

[0019] In some embodiments, the lithium-philic material includes one or more of the elemental substance, oxide, nitride, and phosphide of the lithium-philic metal element, and can be optionally one or more of elemental Ag, elemental Mg, elemental Sn, elemental Al, elemental Bi, elemental Au, elemental In, silver oxide, magnesium oxide, aluminum oxide, bismuth oxide, cuprous oxide, zinc oxide, magnesium nitride, aluminum nitride, copper nitride, zinc nitride, copper phosphide, and zinc phosphide.

[0020] In some embodiments, the alkali metal affinity layer comprises a sodium affinity material.

[0021] In some embodiments, the sodium-philic material includes a sodium-philic metal element. Optionally, the sodium-philic metal element includes one or more of Ag, Mg, Sn, Cu, and Zn.

[0022] In some embodiments, the sodium-philic material includes one or more of the elemental substance, oxide, nitride, and phosphide of the sodium-philic metal element, and can be optionally one or more of elemental Ag, elemental Mg, elemental Sn, silver oxide, magnesium oxide, cuprous oxide, zinc oxide, magnesium nitride, copper nitride, zinc nitride, copper phosphide, and zinc phosphide.

[0023] In some embodiments, the total thickness of the modification layer is 11 μm-55 μm, and optionally 18 μm-53 μm.

[0024] In some embodiments, the thickness of the alkali metal affinity layer is 1 μm-6 μm, and can be 1 μm-5 μm. The thickness of the alkali metal affinity layer is within the above range. On the one hand, it can provide a large number of active points, induce uniform metal deposition, and make the battery have high reliability. On the other hand, it can also reduce active ion consumption and make the battery have good cycle performance.

[0025] In some embodiments, the thickness of the non-metallic conductive layer is 10 μm-50 μm, and can be 15 μm-50 μm. The thickness of the non-metallic conductive layer is within the above range, which can increase the driving force of metal ions such as lithium ions and sodium ions to pass through the non-metallic conductive layer to reach the alkali metal affinity layer, induce uniform metal deposition, and can also make the deposited lithium, sodium and other metals grow uniformly between the non-metallic conductive layer and the negative electrode current collector under pressure, further reducing dendrite formation, reducing electrolyte side reactions and consumption of active ions; in addition, it can also reduce the resistance of metal ions such as lithium ions and sodium ions when passing through the non-metallic conductive layer, reduce battery polarization, reduce battery kinetic losses, and make the battery have good cycle performance.

[0026] In some embodiments, the surface density of the alkali metal affinity layer is 1 g / m 2 -8g / m 2 The surface density of the alkali metal affinity layer is within the above range. On the one hand, it can provide a large number of active sites to induce uniform metal deposition, so that the battery has high reliability. On the other hand, it can also reduce the consumption of active ions and make the battery have good cycle performance.

[0027] In some embodiments, the surface density of the non-metallic conductive layer is 18 g / m 2 -92g / m 2 The surface density of the metal conductive layer is within the above range, which can increase the driving force of metal ions such as lithium ions and sodium ions to pass through the non-metallic conductive layer to reach the alkali metal affinity layer, induce uniform deposition of metals, and under the action of pressure, make the deposited lithium, sodium and other metals grow uniformly between the non-metallic conductive layer and the negative electrode current collector, further reduce dendrite formation, reduce electrolyte side reactions and consumption of active ions; in addition, it can also reduce the resistance of metal ions such as lithium ions and sodium ions when passing through the non-metallic conductive layer, so that the battery has good cycle performance.

[0028] In some embodiments, the negative electrode current collector includes a metal material, and the metal material includes one or more of copper, nickel, titanium, magnesium, aluminum, copper alloys, nickel alloys, titanium alloys, magnesium alloys, and aluminum alloys.

[0029] In a second aspect, the present application provides a battery cell, which includes the negative electrode plate of the first aspect of the present application, and the battery cell includes at least one of a negative electrode-free lithium metal battery cell and a negative electrode-free sodium metal battery cell.

[0030] In a third aspect, the present application provides a battery, which includes the battery cell of the second aspect of the present application.

[0031] In a fourth aspect, the present application provides an electrical device, comprising the battery of the third aspect of the present application, wherein the battery is used to provide electrical energy.

[0032] The electric device of the present application includes the battery provided by the present application, and thus has at least the same advantages as the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some implementation methods of the present application, and for ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0034] Figure 1A schematic diagram showing a battery cell provided by some embodiments of the present application.

[0035] Figure 2 A schematic diagram of an exploded view of a battery cell provided by some embodiments of the present application is shown.

[0036] Figure 3 A schematic diagram of a battery module provided in some embodiments of the present application is shown.

[0037] Figure 4 A schematic diagram of a battery pack provided in some embodiments of the present application is shown.

[0038] Figure 5 yes Figure 4 An exploded diagram of the battery pack is shown.

[0039] Figure 6 Schematic diagram showing metal deposition of conventional metal current collectors during battery charging and discharging.

[0040] Figure 7 A schematic diagram showing metal deposition of the negative electrode plate provided in the present application during the battery charging and discharging process is shown.

[0041] Figure 8 A schematic diagram of an electrical device provided in some embodiments of the present application is shown.

[0042] In the accompanying drawings, the drawings may not be drawn according to the actual scale. The reference numerals are as follows: 1, battery pack; 2, upper box; 3, lower box; 4, battery module; 5, battery; 51, housing; 52, electrode assembly; 53, cover plate; 101, negative electrode current collector; 102, alkali metal affinity layer; 102a, alkali metal affinity layer with active points; 103, non-metallic conductive layer; 104, deposited metal layer. DETAILED DESCRIPTION

[0043] Below, the embodiments of the negative electrode plate, battery cell, battery and electrical device of the present application are specifically disclosed in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0044] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0045] If not otherwise specified, all embodiments and optional embodiments of the present application may be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of the present application.

[0046] Unless otherwise specified, all technical features and optional technical features of the present application may be combined with each other to form a new technical solution, and such a technical solution should be deemed to be included in the disclosure of the present application.

[0047] If there is no special explanation, all steps of the present application can 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 may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0048] In the present application, the terms "plurality" and "multiple" refer to two or more.

[0049] In the description of the embodiments of the present application, unless otherwise specified, a first feature being “above” or “below” a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, a first feature being “above”, “above”, or “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, or “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0050] Unless otherwise specified, the terms used in this application have the commonly understood meanings that are commonly understood by those skilled in the art.

[0051] Unless otherwise specified, the values ​​of the parameters mentioned in this application can be measured by various test methods commonly used in the art, for example, they can be measured according to the test methods given in the examples of this application. Unless otherwise specified, the test temperature of each parameter is 25°C.

[0052] The battery mentioned in the embodiments of the present application may be a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application may include a battery cell, a battery module or a battery pack.

[0053] A battery cell is the smallest unit of a battery, which can independently realize the functions of charging and discharging. The battery cell can be cylindrical, rectangular or in other shapes, etc., which is not limited in the embodiments of the present application. Figure 1 The battery cell 5 is a rectangular parallelepiped structure as an example.

[0054] When there are multiple battery cells, the multiple battery cells are connected in series, in parallel, or in mixed connection through a busbar. In some embodiments, the battery may be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery may be a battery pack, which includes a case and battery cells, and the battery cells or battery modules are accommodated in the case. In some embodiments, the case may serve as part of the chassis structure of the vehicle. For example, part of the case may become at least a part of the floor of the vehicle, or part of the case may become at least a part of the crossbeam and longitudinal beam of the vehicle.

[0055] In some embodiments, the battery may be an energy storage device, which includes an energy storage container, an energy storage cabinet, and the like.

[0056] The battery cell includes an electrode assembly. The electrode assembly may be a winding structure or a laminated structure, which is not limited in the present application.

[0057] The battery cell may also include an outer package, which may be used to encapsulate the electrode assembly. The outer package may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).

[0058] In some embodiments, Figure 2 As shown, the outer package may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The electrode assembly 52 is encapsulated in the receiving cavity. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be adjusted according to demand.

[0059] In some embodiments, battery cells may be assembled into a battery module. The battery module may contain multiple battery cells, and the specific number may be adjusted according to the application and capacity of the battery module. Figure 3 FIG. 4 is a schematic diagram of a battery module 4 as an example. Figure 3 As shown, in the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0060] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0061] In some embodiments, the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0062] Figure 4 and Figure 5 FIG. 1 is a schematic diagram of a battery pack 1 as an example. Figure 4 and Figure 5 As shown, the battery pack 1 may include a box body and a plurality of battery modules 4 disposed in the box body. The box body includes an upper box body 2 and a lower box body 3, and the upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the box body in any manner.

[0063] The battery cells provided in the embodiments of the present application may include negative electrode-free lithium metal battery cells, negative electrode-free sodium metal battery cells, and the like.

[0064] A battery cell without a negative electrode generally refers to a battery cell that is formed by not actively setting a negative electrode active material layer on the negative electrode side during the manufacturing process of the battery cell, for example, in the manufacturing process of the battery cell, a layer is not set at the negative electrode through processes such as coating or deposition, or a negative electrode active material layer is formed by a carbonaceous active material layer. During the first charge, the ions obtain electrons on the negative electrode side and deposit on the surface of the negative electrode current collector to form a metal. During discharge, the metal can be converted into ions and return to the positive electrode to achieve cyclic charge and discharge. Compared with other battery cells, a battery cell without a negative electrode can obtain a higher energy density because it does not have a negative electrode active material layer. The CB (Cell Balance) value of a battery cell without a negative electrode is usually very small. For example, in some embodiments, the CB value of a battery cell without a negative electrode can be less than or equal to 0.1. The CB value is the unit area capacity of the negative electrode in the battery cell divided by the unit area capacity of the positive electrode. Since the battery cell without a negative electrode does not contain or only contains a small amount of negative electrode active material, the unit area capacity of the negative electrode is small, and thus the CB value is very small, for example, usually less than or equal to 0.1.

[0065] Different from the negative electrode of ion-type batteries, the negative electrode of metal batteries has a more serious dendrite problem, so the negative electrode of metal batteries has a crucial impact on its performance.

[0066] The embodiment of the present application provides a negative electrode plate, which can be used in a negative electrode-free lithium metal battery or a negative electrode-free sodium metal battery to enable the battery to have good cycle performance and high reliability.

[0067] The negative electrode sheet provided in the embodiment of the present application includes a negative electrode current collector and a modified layer located on at least one surface of the negative electrode current collector. The modified layer includes an alkali metal affinity layer and a non-metallic conductive layer located on the surface of the alkali metal affinity layer away from the negative electrode current collector. The nucleation overpotential of the alkali metal affinity layer is recorded as V1, and the nucleation overpotential of the non-metallic conductive layer is recorded as V2, both in mV, and V2-V1 is greater than or equal to 40mV.

[0068] Since lithium, sodium and other metals have a large nucleation overpotential on conventional metal current collectors (such as copper foil), they tend to preferentially nucleate at certain surface defect locations of conventional metal current collectors. The preferential nucleation locations will form advantageous growth points, which can easily lead to dendrite formation and internal short circuits in the battery, affecting the reliability of the battery. On the other hand, during the metal deposition and stripping process, the unstable SEI film is repeatedly torn and rebuilt, which will continuously expose fresh surfaces and continuously consume active ions and electrolytes, affecting the battery's cycle performance.

[0069] Figure 6 Figure 2 shows a schematic diagram of metal deposition in conventional metal current collectors during battery charging and discharging. Figure 6As shown, the surface of conventional metal current collectors easily forms advantageous growth points, which in turn easily form sharp dendrites during the battery charging and discharging process.

[0070] The present application starts from the structure of the negative electrode plate, by first forming an alkali metal affinity layer on the negative electrode current collector, and then forming a non-metallic conductive layer. Since the non-metallic conductive layer itself is conductive, it will not affect the passage of metal ions such as lithium ions and sodium ions.

[0071] The alkali metal affinity layer includes those that have affinity with metals such as lithium and sodium, thereby reducing the volume change of the negative electrode plate caused by metal deposition and stripping during the battery cycle, thereby stabilizing the skeleton structure of the negative electrode plate and improving the cycle stability of the battery.

[0072] By further adjusting the difference V2-V1 between the nucleation overpotential V2 of the non-metallic conductive layer and the nucleation overpotential V1 of the alkali metal affinity layer to be greater than or equal to 40mV, metal ions such as lithium ions and sodium ions can pass through the non-metallic conductive layer and fall on the surface of the alkali metal affinity layer under the induction of this difference in nucleation overpotential, forming a large number of active points in the alkali metal affinity layer. These active points can act as "seeds" to induce the uniform deposition of metals such as lithium and sodium, thereby reducing the dominant growth points, reducing the formation of dendrites, and reducing the localized deposition of metals; moreover, the formed active points can also increase the negative electrode potential, thereby also helping to improve the film formation quality of the SEI film on the negative electrode surface.

[0073] In addition, under the pressure of the non-metallic conductive layer, the deposited metals such as lithium and sodium can also grow evenly between the non-metallic conductive layer and the negative electrode current collector, which can further reduce the formation of dendrites and further reduce the electrolyte side reactions and active ion consumption caused by repeated tearing and reconstruction of the SEI film.

[0074] When the difference V2-V1 between the nucleation overpotential V2 of the non-metallic conductive layer and the nucleation overpotential V1 of the alkali metal affinity layer is less than 40mV, the driving force for metal ions such as lithium ions and sodium ions to pass through the non-metallic conductive layer to reach the alkali metal affinity layer is small. At this time, metal ions such as lithium ions and sodium ions tend to nucleate directly in the non-metallic conductive layer, thereby failing to play the role of the alkali metal affinity layer, and failing to reduce localized metal deposition and dendrite formation, which in turn reduces the reliability and cycle performance of the battery.

[0075] Therefore, the negative electrode plate provided in the embodiment of the present application can make the battery have good cycle performance and high reliability.

[0076] Figure 7 A schematic diagram showing metal deposition of the negative electrode plate provided in the present application during the battery charging and discharging process is shown.

[0077] like Figure 7As shown in A, the negative electrode plate includes a negative electrode current collector 101, an alkali metal affinity layer 102 located on one surface of the negative electrode current collector 101, and a non-metallic conductive layer 103 located on the surface of the alkali metal affinity layer 102 away from the negative electrode current collector 101.

[0078] like Figure 7 As shown in B, when the battery is initially charged, metal ions such as lithium ions and sodium ions can pass through the non-metallic conductive layer 103 and fall on the surface of the alkali metal affinity layer 102, forming a large number of active points on the alkali metal affinity layer 102, thereby forming an alkali metal affinity layer 102a having a large number of active points.

[0079] like Figure 7 C and Figure 7 As shown in FIG. 1D , the active points in the alkali metal affinity layer 102a can act as "seeds" to induce uniform deposition of metals such as lithium and sodium, and form a deposited metal layer 104. Moreover, under the pressure of the non-metallic conductive layer 103, the deposited metals such as lithium and sodium can grow uniformly between the non-metallic conductive layer 103 and the negative electrode current collector 101, thereby further reducing the formation of dendrites.

[0080] The difference V2-V1 between the nucleation overpotential V2 of the non-metallic conductive layer and the nucleation overpotential V1 of the alkali metal affinity layer is greater than or equal to 40mV, for example, it can be 40mV, 48mV, 54mV, 57mV, 60mV, 64mV, 70mV, 75mV, 80mV, 85mV, 89mV, 94mV, 100mV, 108mV, 121mV, or a range composed of any of the above values. In some embodiments, V2-V1 can be 48mV-121mV, optionally 48mV-108mV, 57mV-94mV.

[0081] By further adjusting V2-V1 within the above range, the battery can better combine high reliability and good cycle performance.

[0082] In some embodiments, the nucleation overpotential V1 of the alkali metal affinity layer can be 0mV-40mV, for example, 0mV, 4mV, 8mV, 10mV, 11mV, 12mV, 13mV, 14mV, 15mV, 16mV, 17mV, 18mV, 19mV, 20mV, 21mV, 22mV, 24mV, 26mV, 28mV, 30mV, 32mV, 34mV, 36mV, 38mV, 40mV, or a range consisting of any of the above values. In some embodiments, the nucleation overpotential V1 of the alkali metal affinity layer can be 0mV-35mV, 0mV-30mV, 8mV-30mV, 8mV-22mV.

[0083] In some embodiments, the nucleation overpotential V2 of the non-metallic conductive layer can be 60mV-120mV, for example, 60mV, 65mV, 69mV, 74mV, 78mV, 82mV, 88mV, 96mV, 102mV, 110mV, 120mV or any range thereof. In some embodiments, the nucleation overpotential V2 of the non-metallic conductive layer can be 69mV-120mV, 78mV-110mV, 78mV-102mV.

[0084] By further adjusting the nucleation overpotential V1 of the alkali metal affinity layer and / or the nucleation overpotential V2 of the non-metallic conductive layer within the above range, the battery can better have both high reliability and good cycle performance.

[0085] The nucleation overpotential V1 of the alkali metal affinity layer and the nucleation overpotential V2 of the non-metallic conductive layer can be tested using button cells.

[0086] During the test, a lithium metal sheet was used as the counter electrode in an argon-protected glove box to assemble a button cell with the negative electrode. The assembled button cell was then left to stand for 12 hours at 25°C and then charged at 1 mA / cm 2 The current density is constant current discharge to 1 mAh / cm 2 . At the beginning of the lithium metal deposition process, there will be an obvious voltage drop, followed by a flat voltage platform. The difference between the voltage at the lowest point and the flat part of the voltage platform is used as the nucleation overpotential. The electrolyte salt of the button battery electrolyte can be LiFSI with a concentration of 1 mol / L, and the solvent of the electrolyte can be ethylene glycol dimethyl ether (DME). The isolation membrane of the button battery can be a PE film with a thickness of 12μm.

[0087] In the above-mentioned nucleation overpotential test, the negative electrode plate includes both the alkali metal affinity layer and the non-metallic conductive layer. When testing the nucleation overpotential of the alkali metal affinity layer, a negative electrode plate including the alkali metal affinity layer but not including the non-metallic conductive layer can be prepared under the same process conditions for testing. When testing the nucleation overpotential of the non-metallic conductive layer, a negative electrode plate including the non-metallic conductive layer but not including the alkali metal affinity layer can be prepared under the same process conditions for testing.

[0088] The nucleation overpotential V1 of the alkali metal affinity layer is related to the material of the alkali metal affinity layer and the thickness, surface density, preparation process and other parameters of the alkali metal affinity layer. By adjusting one or more of the above parameters, the desired nucleation overpotential V1 can be obtained.

[0089] The nucleation overpotential V2 of the non-metallic conductive layer is related to the material of the non-metallic conductive layer and the thickness, surface density, preparation process and other parameters of the non-metallic conductive layer. By adjusting one or more of the above parameters, the desired nucleation overpotential V2 can be obtained.

[0090] In some embodiments, the alkali metal affinity layer may include an alkali metal affinity material. When the battery is initially charged, metal ions such as lithium ions and sodium ions can pass through the non-metallic conductive layer and fall on the surface of the alkali metal affinity layer, forming a large number of active points in the alkali metal affinity layer by forming an alloy or solid solution with the alkali metal affinity material, or by a conversion reaction with the alkali metal affinity material.

[0091] Taking lithium as the metal and cuprous oxide Cu2O as the alkali metal affinity material as an example, the conversion reaction is as follows: Cu2O+Li→Cu+Li2O. The product of the conversion reaction can also be used as an inorganic salt in the SEI film, thereby helping to improve the film quality of the SEI film on the negative electrode surface.

[0092] In some embodiments, the alkali metal affinity layer may include a lithium affinity material.

[0093] Alternatively, the lithiophilic material may include a lithiophilic metal element.

[0094] Optionally, the lithium-philic metal element may include one or more of Ag, Mg, Sn, Al, Bi, Au, In, Cu, and Zn.

[0095] In some embodiments, the lithium-philic material may include one or more of a simple substance, oxide, nitride, and phosphide of a lithium-philic metal element. As an example, the lithium-philic material may include one or more of simple substance Ag, simple substance Mg, simple substance Sn, simple substance Al, simple substance Bi, simple substance Au, simple substance In, silver oxide, magnesium oxide, aluminum oxide, bismuth oxide, cuprous oxide, zinc oxide, magnesium nitride, aluminum nitride, copper nitride, zinc nitride, copper phosphide, and zinc phosphide. Optionally, the lithium-philic material may include simple substance Ag and simple substance Bi.

[0096] In some embodiments, the alkali metal affinity layer may include a sodium affinity material.

[0097] Alternatively, the sonaphilic material may include a sonaphilic metal element.

[0098] Optionally, the sodium-philic metal element may include one or more of Ag, Mg, Sn, Cu, and Zn.

[0099] In some embodiments, the sodium-philic material may include one or more of the simple substance, oxide, nitride, and phosphide of the sodium-philic metal element. As an example, the sodium-philic material may include one or more of simple substance Ag, simple substance Mg, simple substance Sn, silver oxide, magnesium oxide, cuprous oxide, zinc oxide, magnesium nitride, copper nitride, zinc nitride, copper phosphide, and zinc phosphide. Optionally, the sodium-philic material may include simple substance Ag.

[0100] In some embodiments, the non-metallic conductive layer may include a non-metallic conductive material.

[0101] Optionally, the non-metallic conductive material may include one or more of a carbon-based conductive material and a phosphorus-based conductive material.

[0102] Optionally, the non-metallic conductive material may include one or more of porous carbon, hard carbon, carbon tube, red phosphorus, black phosphorus, and phosphorus-carbon composite.

[0103] In some embodiments, the total thickness of the modification layer may be 11 μm-55 μm, optionally 13 μm-53 μm, or 18 μm-53 μm.

[0104] In some embodiments, the thickness of the alkali metal affinity layer may be 1 μm-6 μm, optionally 1 μm-5 μm, 1.5 μm-5 μm, 1.5 μm-4 μm, 1.5 μm-3 μm.

[0105] As the thickness of the alkali metal affinity layer increases, the number of active points it can provide increases, thereby better inducing uniform metal deposition; however, the active ions consumed during metal deposition also increase, thereby reducing the battery capacity and affecting the battery's cycle performance. Therefore, when the thickness of the alkali metal affinity layer is within the above range, on the one hand, a large number of active points can be provided to induce uniform metal deposition, making the battery highly reliable; on the other hand, active ion consumption can be reduced, making the battery have good cycle performance.

[0106] In some embodiments, the thickness of the non-metallic conductive layer may be 10 μm-50 μm, optionally 15 μm-50 μm, 15 μm-40 μm, or 20 μm-40 μm.

[0107] As the thickness of the non-metallic conductive layer increases, the difference between the nucleation overpotential of the non-metallic conductive layer and the nucleation overpotential of the alkali metal affinity layer increases, and the driving force of metal ions such as lithium ions and sodium ions passing through the non-metallic conductive layer to reach the alkali metal affinity layer increases. However, the resistance of metal ions such as lithium ions and sodium ions passing through the non-metallic conductive layer also increases, resulting in increased battery polarization and increased kinetic loss, which will affect the battery cycle performance. Therefore, when the thickness of the non-metallic conductive layer is within the above range, the driving force of metal ions such as lithium ions and sodium ions passing through the non-metallic conductive layer to reach the alkali metal affinity layer can be increased, inducing uniform metal deposition, and under the action of pressure, the deposited lithium, sodium and other metals can grow uniformly between the non-metallic conductive layer and the negative electrode current collector, further reducing dendrite formation, reducing electrolyte side reactions and consumption of active ions; in addition, the resistance of metal ions such as lithium ions and sodium ions passing through the non-metallic conductive layer can be reduced, battery polarization can be reduced, and battery kinetic loss can be reduced, so that the battery has good cycle performance.

[0108] In some embodiments, the surface density of the alkali metal affinity layer may be 1 g / m 2 -8g / m 2 .

[0109] The surface density of the alkali metal affinity layer is within the above range. On the one hand, it can provide a large number of active sites to induce uniform metal deposition, so that the battery has high reliability. On the other hand, it can also reduce the active ion consumption and make the battery have good cycle performance.

[0110] In some embodiments, the surface density of the non-metallic conductive layer can be 18 g / m 2 -92g / m 2 .

[0111] The surface density of the non-metallic conductive layer is within the above range, which can increase the driving force for metal ions such as lithium ions and sodium ions to pass through the non-metallic conductive layer to reach the alkali metal affinity layer, induce uniform deposition of the metal, and under the action of pressure, make the deposited lithium, sodium and other metals grow uniformly between the non-metallic conductive layer and the negative electrode current collector, further reduce dendrite formation, reduce electrolyte side reactions and consumption of active ions; in addition, it can also reduce the resistance of metal ions such as lithium ions and sodium ions when passing through the non-metallic conductive layer, so that the battery has good cycle performance.

[0112] In some embodiments, the alkali metal affinity layer can be formed by processes such as electrodeposition, evaporation, magnetron sputtering, ion beam sputtering, atomic layer deposition, etc.

[0113] In some embodiments, the non-metallic conductive layer can be formed by processes such as electrodeposition, evaporation, magnetron sputtering, ion beam sputtering, and atomic layer deposition.

[0114] The parameters (such as thickness, surface density, etc.) of the above-mentioned modified layer, alkali metal affinity layer, and non-metallic conductive layer are all parameters of a single side of the negative electrode current collector. When the modified layer is provided on both sides of the negative electrode current collector, the parameters of any one side satisfy the present application and are considered to fall within the protection scope of the present application.

[0115] In some embodiments, the negative electrode current collector includes a metal material, and the metal material may include one or more of copper, nickel, titanium, magnesium, aluminum, copper alloys, nickel alloys, titanium alloys, magnesium alloys, and aluminum alloys.

[0116] In some embodiments, the negative electrode current collector may include a metal foil or a three-dimensional porous current collector. As an example of a three-dimensional porous current collector, a mesh metal structure or a foam metal structure may be used.

[0117] [Positive electrode]

[0118] The battery cell includes a positive electrode plate.

[0119] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material. For example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0120] In some embodiments, the positive electrode active material includes a material capable of extracting and inserting lithium.

[0121] As an example, the positive electrode active material may include, but is not limited to, one or more of lithium transition metal oxides, metal chalcogenides, lithium-containing phosphates, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium titanium oxide, and their respective modified compounds. Lithium transition metal oxides may include, but are not limited to, layered structures and spinel structures. Examples of lithium-containing phosphates may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon, and their respective modified compounds.

[0122] In some embodiments, in order to further improve the energy density of the battery, the positive electrode active material may include a general formula of Li a Ni b Co c M d O e D fOne or more of lithium transition metal oxides and modified compounds thereof. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M may include but is not limited to one or more of Ge, Mo, Sn, Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and D may include but is not limited to one or more of N, F, S and Cl.

[0123] In some embodiments, the positive electrode active material may include both lithium transition metal oxide and lithium-containing phosphate, thereby facilitating obtaining a battery having both large capacity and high reliability.

[0124] As an example, the positive electrode active material may include but is not limited to LiCoO2, LiNiO2, LiMnO2, LiNi 1 / 2 Mn 1 / 2O2, LiMn2O4, Li 4 / 3 Ti 5 / 3 O4、LiNi 1 / 2 Mn 1 / 2 O2、LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.80 Co 0.15 Al 0.05 O2, LiFePO4, LiMnPO4, Li 1.13 Ti 0.57 Fe 0.3 One or more of S2.

[0125] In some embodiments, the positive electrode active material includes a material capable of extracting and embedding sodium. For example, the positive electrode active material may include, but is not limited to, one or more of layered transition metal oxides (including but not limited to P2 type, O3 type, etc.), polyanionic materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian materials.

[0126] In some embodiments, as examples, the positive electrode active material may include but is not limited to NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, Na 0.67MO2 (M includes at least two of Fe, Co, Cr, Mn, Ni, V, Ti, and Mo), NaMO2 (M includes at least two of Fe, Co, Ni, V, Ti, and Mo), NaFePO4, NaMnPO4, NaCoPO4, Na4Fe3(PO4)2O7, Na3V2(PO4)2F3, Na3V2(PO4)3, Prussian blue, Prussian white, and one or more of their respective modified compounds.

[0127] The modified compounds of the above-mentioned positive electrode active materials may be the ones that undergo doping modification and / or surface coating modification on the positive electrode active materials.

[0128] In some embodiments, the positive electrode film layer may also optionally include a positive electrode conductive agent. As an example, the positive electrode conductive agent 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.

[0129] In some embodiments, the positive electrode film layer may also optionally include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene oxide, fluorinated acrylic resin, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS) One or more.

[0130] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include, but is not limited to, one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0131] The positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, the optional positive electrode conductive agent, the optional positive electrode binder and any other components in a solvent and stirring them uniformly. The solvent can be N-methylpyrrolidone (NMP), but is not limited thereto.

[0132] [Electrolytes]

[0133] The battery cells include an electrolyte.

[0134] In some embodiments, the electrolyte is an electrolyte solution including an electrolyte salt and an organic solvent.

[0135] In some embodiments, the electrolyte includes anions, which may include bis(fluorosulfonyl)imide anions (FSI - ), bis(trifluoromethanesulfonyl)imide anion (TFSI - ), borate oxalate anion (BOB - ), difluorooxalatoborate anion (DFOB - ), difluorobis(oxalate)phosphate anion (DFOP - ), tetrafluorooxalophosphate anion (TFOP - ), difluorophosphate anion (PO2F2 - ), hexafluorophosphate anion (PF6 - ), tetrafluoroborate anion (BF4 - ), hexafluoroarsenate anion (AsF6 - ), trifluoromethanesulfonate anion (CF3SO3 - )

[0136] In some embodiments, the electrolyte includes cations, and the cations may include one or more of lithium ions and sodium ions.

[0137] In some embodiments, the concentration of the electrolyte salt may be 0.3 mol / L or more, and may be 0.7 mol / L or more, and the concentration of the electrolyte salt may be 4 mol / L or less, and may be 2.5 mol / L or less, or 1.7 mol / L or less. When the concentration of the electrolyte salt is within the above range, the electrolyte solution may have a suitable ionic conductivity.

[0138] Organic solvents may include, but are not limited to, one or more of esters, ethers, sulfones, nitriles, etc. Esters may include, but are not limited to, one or more of carbonates, phosphates, carboxylates, sulfates, sulfonates, etc. Carbonates may include cyclic carbonates and / or linear carbonates, and optionally, carbonates may include cyclic carbonates and linear carbonates simultaneously. Linear carbonates may include low-viscosity polar linear carbonates, aliphatic branched-chain carbonates, etc.

[0139] As an example, the organic solvent may include, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), diethyl sulfone (ESE), tetraethylene glycol dimethyl ether (TEGDME), ethylene glycol dimethyl ether (DME), 1,3-dioxolane (DOL), trimethyl phosphate, 3-methoxypropionitrile, H(CF2)2OCH3, C4F9O CH3, H(CF2)2OCH2CH3, H(CF2)2OCH2CF3, H(CF2)2CH2O(CF2)2H, CF3CHFCF2OCH3, CF3CHFCF2OCH2CH3, 2-trifluoromethylhexafluoropropylmethyl ether, 2-trifluoromethylhexafluoropropylethyl ether, 2-trifluoromethylhexafluoropropylpropyl ether, 3-trifluoromethyloctafluorobutylmethyl ether, 3-trifluoromethyloctafluorobutylethyl ether, 4-trifluoromethyl The invention further comprises one or more of trifluoromethyl decafluoropentyl methyl ether, 4-trifluoromethyl decafluoropentyl ethyl ether, 4-trifluoromethyl decafluoropentyl propyl ether, 5-trifluoromethyl dodecafluorohexyl methyl ether, 5-trifluoromethyl dodecafluorohexyl ethyl ether, 5-trifluoromethyl dodecafluorohexyl propyl ether, 6-trifluoromethyl tetradecafluoroheptyl methyl ether, 6-trifluoromethyl tetradecafluoroheptyl ethyl ether, 6-trifluoromethyl tetradecafluoroheptyl propyl ether, 7-trifluoromethyl hexadecafluorooctyl methyl ether, 7-trifluoromethyl hexadecafluorooctyl ethyl ether, and 7-trifluoromethyl hexadecafluorooctyl propyl ether.

[0140] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, and additives that improve battery low temperature power performance.

[0141] [Isolation film]

[0142] The battery cell may also include a separator, which is located between the positive electrode sheet and the negative electrode sheet and mainly plays a role in preventing internal short circuit.

[0143] The present application has no particular limitation on the type of isolation membrane, and any known porous isolation membrane with good chemical stability and mechanical stability can be selected.

[0144] In some embodiments, the material of the isolation membrane may include, but is not limited to, one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The isolation membrane may be a single-layer film or a multi-layer composite film. When the isolation membrane is a multi-layer composite film, the materials of each layer are the same or different.

[0145] The preparation method of battery cells is well known. In some embodiments, the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, the separator, and the negative electrode sheet can be formed into an electrode assembly through a winding process and / or a lamination process, and the electrode assembly is placed in an outer package, and the above-mentioned electrolyte is injected after drying. After vacuum packaging, standing, formation and other processes, a battery cell is obtained. Multiple battery cells can also be further connected in series, in parallel or in mixed connection to form a battery module. Multiple battery modules can also be connected in series, in parallel or in mixed connection to form a battery pack. In some embodiments, multiple battery cells can also directly form a battery pack.

[0146] The present application also provides an electrical device, which includes a battery provided in the present application. The battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0147] The electric device can select the type of battery according to its usage requirements, such as a battery cell, a battery module or a battery pack.

[0148] Figure 8 Schematic diagram of an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the requirements of the electric device for high power and high energy density, a battery pack or a battery module may be used.

[0149] As another example, the electric device may be a mobile phone, a tablet computer, a notebook computer, etc. The electric device is usually required to be light and thin, and a battery cell may be used as a power source.

[0150] Example

[0151] The following examples describe the disclosure of the present application in more detail, and these examples are intended for illustrative purposes only, as various modifications and variations within the scope of the disclosure of the present application are apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0152] Example 1

[0153] Commercially available double-sided polished copper foil with a thickness of 8 μm was first wiped with a 1 mol / L acetic acid solution, then ultrasonically cleaned with ethanol and deionized water, and then vacuum dried at 80°C.

[0154] Cut the dried copper foil into 4cm×4cm samples and place them on the sample stage of the ion sputtering instrument. First, use the Ag target for sputtering. The parameters of the ion sputtering instrument are: vacuum degree 3.0Pa, current 30mA, sputtering time 2min. After the end, let air into the working chamber and open the door. Replace the Ag target with a carbon target. The parameters of the ion sputtering instrument are adjusted to: vacuum degree 3.0Pa, current 60mA, sputtering time 4min. After the end, let air into the working chamber and take out the sample to obtain the negative electrode sheet.

[0155] Example 2

[0156] The preparation method of the negative electrode plate is similar to that of Example 1, except that the sputtering time of the carbon target is 6 minutes.

[0157] Example 3

[0158] The preparation method of the negative electrode plate is similar to that of Example 1, except that the sputtering time of the carbon target is 16 minutes.

[0159] Example 4

[0160] The preparation method of the negative electrode plate is similar to that of Example 1, except that the sputtering time of the carbon target is 20 minutes.

[0161] Example 5

[0162] The preparation method of the negative electrode plate is similar to that of Example 1, except that the sputtering time of the carbon target is 28 minutes.

[0163] Example 6

[0164] The preparation method of the negative electrode plate is similar to that of Example 1, except that the sputtering time of the Ag target is 40 s, and the sputtering time of the carbon target is 16 min.

[0165] Example 7

[0166] The preparation method of the negative electrode plate is similar to that of Example 1, except that the sputtering time of the Ag target is 3.3 min, and the sputtering time of the carbon target is 16 min.

[0167] Example 8

[0168] The preparation method of the negative electrode plate is similar to that of Example 1, except that the sputtering time of the Ag target is 4.7 min, and the sputtering time of the carbon target is 16 min.

[0169] Example 9

[0170] Commercially available double-sided polished copper foil with a thickness of 8 μm was first wiped with a 1 mol / L acetic acid solution, then ultrasonically cleaned with ethanol and deionized water, and then vacuum dried at 80°C.

[0171] Cut the dried copper foil into 4cm×4cm samples and place them on the sample stage of the ion sputtering instrument. First, use the Bi target for sputtering. The parameters of the ion sputtering instrument are: vacuum degree 3.0Pa, current 30mA, sputtering time 4min. After the end, let air into the working chamber and open the door. Replace the Bi target with a carbon target. The parameters of the ion sputtering instrument are adjusted to: vacuum degree 3.0Pa, current 60mA, sputtering time 28min. After the end, let air into the working chamber and take out the sample to obtain the negative electrode sheet.

[0172] Example 10

[0173] Commercially available double-sided polished copper foil with a thickness of 8 μm was first wiped with a 1 mol / L acetic acid solution, then ultrasonically cleaned with ethanol and deionized water, and then vacuum dried at 80°C.

[0174] Cut the dried copper foil into 4cm×4cm samples and place them on the sample stage of the ion sputtering instrument. First, use the Bi target for sputtering. The parameters of the ion sputtering instrument are: vacuum degree 3.0Pa, current 30mA, sputtering time 4min. After the end, let air into the working chamber and open the door. Replace the Bi target with a carbon target. The parameters of the ion sputtering instrument are adjusted to: vacuum degree 3.0Pa, current 60mA, sputtering time 16min. After the end, let air into the working chamber and take out the sample to obtain the negative electrode sheet.

[0175] Embodiment 11

[0176] Commercially available double-sided polished copper foil with a thickness of 8 μm was first wiped with a 1 mol / L acetic acid solution, then ultrasonically cleaned with ethanol and deionized water, and then vacuum dried at 80°C.

[0177] Cut the dried copper foil into 4cm×4cm samples and place them on the sample stage of the ion sputtering instrument. First, use the Ag target for sputtering. The parameters of the ion sputtering instrument are: vacuum degree 3.0Pa, current 30mA, sputtering time 2min. After the end, let air into the working chamber and open the door. Replace the Ag target with a phosphorus target. The parameters of the ion sputtering instrument are adjusted to: vacuum degree 3.0Pa, current 60mA, sputtering time 22min. After the end, let air into the working chamber and take out the sample to obtain the negative electrode sheet.

[0178] Example 12

[0179] Commercially available double-sided polished copper foil with a thickness of 8 μm was first wiped with a 1 mol / L acetic acid solution, then ultrasonically cleaned with ethanol and deionized water, and then vacuum dried at 80°C.

[0180] Cut the dried copper foil into 4cm×4cm samples and place them on the sample stage of the ion sputtering instrument. First, use the silver oxide target for sputtering. The parameters of the ion sputtering instrument are: vacuum degree 3.0Pa, current 30mA, sputtering time 1.5min. After the end, let air into the working chamber and open the door. Replace the silver oxide target with a carbon target. The parameters of the ion sputtering instrument are adjusted to: vacuum degree 3.0Pa, current 60mA, sputtering time 16min. After the end, let air into the working chamber and take out the sample to obtain the negative electrode sheet.

[0181] Example 13

[0182] Commercially available double-sided polished copper foil with a thickness of 8 μm was first wiped with a 1 mol / L acetic acid solution, then ultrasonically cleaned with ethanol and deionized water, and then vacuum dried at 80°C.

[0183] Cut the dried copper foil into 4cm×4cm samples and place them on the sample stage of the ion sputtering instrument. First, use the copper nitride target for sputtering. The parameters of the ion sputtering instrument are: vacuum degree 3.0Pa, current 30mA, sputtering time 1.5min. After the end, let air into the working chamber, open the door, replace the copper nitride target with a carbon target, and adjust the parameters of the ion sputtering instrument to: vacuum degree 3.0Pa, current 60mA, sputtering time 16min. After the end, let air into the working chamber to take out the sample and obtain the negative electrode sheet.

[0184] Embodiment 14

[0185] Commercially available double-sided polished copper foil with a thickness of 8 μm was first wiped with a 1 mol / L acetic acid solution, then ultrasonically cleaned with ethanol and deionized water, and then vacuum dried at 80°C.

[0186] Cut the dried copper foil into 4cm×4cm samples and place them on the sample stage of the ion sputtering instrument. First, use the copper-phosphorus alloy target for sputtering. The parameters of the ion sputtering instrument are: vacuum degree 3.0Pa, current 30mA, sputtering time 1.5min. After the end, let air into the working chamber and open the door. Replace the copper-phosphorus alloy target with a carbon target. The parameters of the ion sputtering instrument are adjusted to: vacuum degree 3.0Pa, current 60mA, sputtering time 16min. After the end, let air into the working chamber and take out the sample to obtain the negative electrode sheet.

[0187] Comparative Example 1

[0188] The method for preparing the negative electrode plate is similar to that of Example 1, except that the carbon target is not sputtered.

[0189] Comparative Example 2

[0190] The preparation method of the negative electrode plate is similar to that of Example 1, except that the Ag target is not sputtered.

[0191] Comparative Example 3

[0192] Commercially available double-sided polished copper foil with a thickness of 8 μm was first wiped with a 1 mol / L acetic acid solution, then ultrasonically cleaned with ethanol and deionized water, and then vacuum dried at 80°C.

[0193] Cut the dried copper foil into 4cm×4cm samples and place them on the sample stage of the ion sputtering instrument. First, use the Fe target for sputtering. The parameters of the ion sputtering instrument are: vacuum degree 3.0Pa, current 30mA, sputtering time 1.6min. After the end, let air into the working chamber, open the door, replace the Fe target with a carbon target, and adjust the parameters of the ion sputtering instrument to: vacuum degree 3.0Pa, current 60mA, sputtering time 16min. After the end, let air into the working chamber to take out the sample and obtain the negative electrode.

[0194] Comparative Example 4

[0195] Commercially available double-sided polished copper foil with a thickness of 8 μm was first wiped with a 1 mol / L acetic acid solution, then ultrasonically cleaned with ethanol and deionized water, and then vacuum dried at 80°C.

[0196] Cut the dried copper foil into 4cm×4cm samples and place them on the sample stage of the ion sputtering instrument. First, use Ag target for sputtering. The parameters of the ion sputtering instrument are: vacuum degree 3.0Pa, current 30mA, sputtering time 2min. After the end, let air into the working chamber, open the door, and take out the sample; then put the sample into the deposition furnace, pass hydrogen and argon mixed gas as protective gas, and heat to about 1000℃. After the temperature stabilizes, keep it for about 20min, then stop passing hydrogen and argon mixed gas, and change to pass methane gas. After 30min, the reaction is over, cut off the power supply, stop passing methane gas, and change to pass hydrogen and argon mixed gas to exhaust the methane gas in the furnace tube. Then cool down to about 25℃ in the hydrogen and argon mixed gas protective gas atmosphere, take out the sample, and obtain the negative electrode sheet. The volume ratio of hydrogen and argon in the hydrogen and argon mixed gas is 5:95.

[0197] Comparative Example 5

[0198] Cut the dried copper foil into 4cm×4cm samples and place them on the sample stage of the ion sputtering instrument. First, use the copper-phosphorus alloy target for sputtering. The parameters of the ion sputtering instrument are: vacuum degree 3.0Pa, current 30mA, sputtering time 1.5min. After the end, let air into the working chamber and open the door. Replace the copper-phosphorus alloy target with a carbon target. The parameters of the ion sputtering instrument are adjusted to: vacuum degree 3.0Pa, current 60mA, sputtering time 4min. After the end, let air into the working chamber and take out the sample to obtain the negative electrode sheet.

[0199] Performance Testing

[0200] (1) Short circuit time test

[0201] In an argon-protected glove box, a metal lithium sheet was used as the counter electrode and assembled into a button cell with the negative electrode sheet prepared above. The electrolyte salt of the electrolyte was LiFSI with a concentration of 1 mol / L, and the solvent of the electrolyte was ethylene glycol dimethyl ether (DME). The isolation membrane was a PE film with a thickness of 12 μm.

[0202] At 25°C, the assembled button cell was left to stand for 12 hours and then charged at 1 mA / cm 2 The battery is discharged at a constant current density of 10000V until a short circuit signal appears, that is, the button battery voltage jumps to 0V, and the time T from the start of discharge to short circuit is recorded.

[0203] During the test, the number of button cell samples may be more than 6, and the test results shall be averaged.

[0204] (2) Nucleation overpotential test

[0205] In an argon-protected glove box, a metal lithium sheet is used as the counter electrode and assembled with the negative electrode sheet into a button cell. The electrolyte salt of the electrolyte is LiFSI with a concentration of 1 mol / L, and the solvent of the electrolyte is ethylene glycol dimethyl ether (DME). The isolation membrane is a PE film with a thickness of 12 μm.

[0206] At 25°C, the assembled button cell was left to stand for 12 hours and then charged at 1 mA / cm 2 The current density is constant current discharge to 1 mAh / cm 2 At the beginning of the lithium metal deposition process, there will be an obvious voltage drop, followed by a flat voltage platform. The difference between the voltage at the lowest point and the flat part of the voltage platform is used as the nucleation overpotential of the negative electrode current collector.

[0207] The negative electrode sheets of Examples 1 to 14 and Comparative Examples 3 to 5 include both an alkali metal affinity layer and a non-metallic conductive layer. When testing the nucleation overpotential of the alkali metal affinity layer, the negative electrode sheet is prepared according to the same process conditions as above, but the carbon target or phosphorus target is not sputtered, that is, the negative electrode sheet is not provided with a non-metallic conductive layer. When testing the nucleation overpotential of the non-metallic conductive layer, the negative electrode sheet is prepared according to the same process conditions as above, but the Fe target, Ag target, Bi target, silver oxide target, copper nitride target or copper-phosphorus alloy target is not sputtered, that is, the negative electrode sheet is not provided with an alkali metal affinity layer.

[0208] (3) Cyclic performance test

[0209] Lithium iron phosphate, conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) are mixed evenly in a proper amount of solvent N-methylpyrrolidone (NMP) at a weight ratio of 8:1:1 to obtain a positive electrode slurry; the positive electrode slurry is coated on a positive electrode current collector aluminum foil, and after drying, a positive electrode sheet is obtained.

[0210] In an argon-protected glove box, the positive electrode sheet and the negative electrode sheet prepared above were assembled into a button cell. The electrolyte salt of the electrolyte was LiFSI with a concentration of 1 mol / L, and the solvent of the electrolyte was ethylene glycol dimethyl ether (DME). The isolation membrane was a PE film with a thickness of 12 μm.

[0211] At 25°C, after the assembled button cell was left to stand for 12 hours, it was charged to 3.65V at a constant current of 0.2C, and then charged to 0.05C at a constant voltage of 3.65V; after the button cell was left to stand for 10 minutes, it was discharged to 2V at a constant current of 0.5C. The button cell was cycled 200 times according to the above method, and the number of cycles corresponding to the discharge capacity being 50% of the first cycle discharge capacity was recorded.

[0212] During the test, the number of button cell samples may be more than 6, and the test results shall be averaged.

[0213] Table 1 shows the test results of Examples 1 to 14 and Comparative Examples 1 to 5.

[0214] Table 1

[0215]

[0216] It can be seen from the test results in Table 1 that by setting an alkali metal affinity layer and a non-metallic conductive layer on the surface of the negative electrode current collector, and controlling the difference V2-V1 between the nucleation overpotential V2 of the non-metallic conductive layer and the nucleation overpotential V1 of the alkali metal affinity layer to be greater than or equal to 40mV, it is possible to induce uniform deposition of Li, extend the short-circuit time of the battery, reduce electrolyte side reactions, and improve the cycle performance of the battery.

[0217] It can also be seen from the test results in Table 1 that by further adjusting the nucleation overpotential V2 of the non-metallic conductive layer, the nucleation overpotential V1 of the alkali metal affinity layer, and the range of the difference between the two V2-V1, the battery short-circuit time can be further extended and the battery cycle performance can be further improved.

[0218] It can also be seen from the test results in Table 1 that by further adjusting the thickness of the alkali metal affinity layer and / or the thickness of the non-metallic conductive layer, the short circuit time of the battery can be further extended and the cycle performance of the battery can be further improved.

[0219] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A negative electrode sheet, comprising a negative electrode current collector and a modified layer located on at least one surface of the negative electrode current collector, characterized in that: The modified layer includes an alkali metal affinity layer and a non-metallic conductive layer located on the surface of the alkali metal affinity layer away from the negative electrode current collector; The nucleation overpotential of the alkali metal affinity layer is recorded as V1, and the nucleation overpotential of the non-metallic conductive layer is recorded as V2, both in mV, and V2-V1 is greater than or equal to 40mV.

2. The negative electrode sheet according to claim 1, characterized in that: V2-V1 is 48mV-121mV, and can be selected as 57mV-94mV.

3. The negative electrode sheet according to any one of claims 1 to 2, characterized in that: V1 is 0mV-40mV, optionally 8mV-22mV; and / or, V2 is 60mV-120mV, and can be selected as 78mV-110mV.

4. The negative electrode sheet according to any one of claims 1 to 3, characterized in that: The non-metallic conductive layer comprises a non-metallic conductive material, Optionally, the non-metallic conductive material includes one or more of a carbon-based conductive material and a phosphorus-based conductive material; More optionally, the non-metallic conductive material includes one or more of porous carbon, hard carbon, carbon tubes, red phosphorus, black phosphorus, and phosphorus-carbon composites.

5. The negative electrode sheet according to any one of claims 1 to 4, characterized in that: The alkali metal affinity layer comprises a lithium affinity material, Optionally, the lithium-philic material comprises a lithium-philic metal element, More optionally, the lithium-philic metal element includes one or more of Ag, Mg, Sn, Al, Bi, Au, In, Cu, and Zn.

6. The negative electrode sheet according to claim 5, characterized in that: The lithium-philic material includes one or more of the elemental substance, oxide, nitride, and phosphide of the lithium-philic metal element, and can be optionally one or more of elemental Ag, elemental Mg, elemental Sn, elemental Al, elemental Bi, elemental Au, elemental In, silver oxide, magnesium oxide, aluminum oxide, bismuth oxide, cuprous oxide, zinc oxide, magnesium nitride, aluminum nitride, copper nitride, zinc nitride, copper phosphide, and zinc phosphide.

7. The negative electrode sheet according to any one of claims 1 to 4, characterized in that: The alkali metal affinity layer comprises a sodium affinity material, Optionally, the sodium-philic material comprises a sodium-philic metal element; More optionally, the sodium-philic metal element includes one or more of Ag, Mg, Sn, Cu, and Zn.

8. The negative electrode sheet according to claim 7, characterized in that: The sodium-philic material includes one or more of the simple substance, oxide, nitride, and phosphide of the sodium-philic metal element, and can be optionally one or more of simple substance Ag, simple substance Mg, simple substance Sn, silver oxide, magnesium oxide, cuprous oxide, zinc oxide, magnesium nitride, copper nitride, zinc nitride, copper phosphide, and zinc phosphide.

9. The negative electrode sheet according to any one of claims 1 to 8, characterized in that: The total thickness of the modified layer is 11 μm-55 μm, and can be optionally 18 μm-53 μm.

10. The negative electrode sheet according to any one of claims 1 to 9, characterized in that: The thickness of the alkali metal affinity layer is 1 μm-6 μm, and can be 1 μm-5 μm; and / or, The thickness of the non-metallic conductive layer is 10 μm-50 μm, and can be optionally 15 μm-50 μm.

11. The negative electrode sheet according to any one of claims 1 to 10, characterized in that: The surface density of the alkali metal affinity layer is 1 g / m 2 -8g / m 2 and / or, The surface density of the non-metallic conductive layer is 18 g / m 2 -92g / m 2 .

12. The negative electrode sheet according to any one of claims 1 to 11, characterized in that: The negative electrode current collector includes a metal material, and the metal material includes one or more of copper, nickel, titanium, magnesium, aluminum, copper alloy, nickel alloy, titanium alloy, magnesium alloy, and aluminum alloy.

13. A battery cell, characterized in that: It comprises the negative electrode plate according to any one of claims 1 to 12, and the battery cell comprises at least one of a negative electrode-free lithium metal battery cell and a negative electrode-free sodium metal battery cell.

14. A battery, characterized in that: Comprising the battery cell according to claim 13.

15. An electrical device, characterized in that: The battery according to claim 14 is used to provide electrical energy.

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