Magnesium metal batteries and electrical devices based on conductive composite current collectors

Abstract

The present application relates to the field of secondary battery technology, and in particular to a magnesium metal battery and electrical device based on a conductive composite current collector. The magnesium metal battery comprises a negative electrode plate, the negative electrode plate comprising a negative current collector and a negative active layer disposed on at least one surface of the negative current collector; the negative current collector comprises a negative conductive support layer, a negative undercoat layer disposed on at least one surface of the negative conductive support layer, and a negative conductive layer disposed on a surface of the negative undercoat layer facing away from the negative conductive support layer; the lattice mismatch between the negative conductive layer and the negative active layer is less than 10%. The magnesium metal battery provided in the present application exhibits excellent cycle performance. In some embodiments, the battery can maintain over 80% of its capacity after 180 charge and discharge cycles.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to a magnesium metal battery and an electrical device based on a conductive composite current collector. Background Art

[0002] The rapid development of emerging industries such as energy storage systems, power batteries, and smart wearable devices has placed higher demands on the energy density, cost, and safety of secondary batteries. Multivalent metal batteries, using elements such as calcium, magnesium, zinc, and aluminum as active ions, have garnered widespread attention due to their low cost, high storage capacity, and high safety.

[0003] Currently, magnesium metal batteries dominate multivalent metal batteries for several reasons: Magnesium is one of the world's most abundant elements and is inexpensive, which facilitates cost reduction. Magnesium occupies a diagonal position with lithium in the periodic table, and the two share similar physical and chemical properties. Magnesium metal is non-toxic and safer than more reactive alkali metals. Furthermore, the magnesium anode has a low reduction potential of -2.37 V (vs. SHE) and a high theoretical specific capacity of 2205 mAh / g. Therefore, magnesium metal batteries hold great promise for development in large-scale power grids, energy storage systems, and power batteries. However, conventional magnesium metal batteries suffer from a low cycle life. Summary of the Invention

[0004] Based on this, it is necessary to provide a magnesium metal battery and an electrical device based on a conductive composite current collector to solve the problem of low cycle life of magnesium metal batteries.

[0005] The above-mentioned purpose of this application is achieved through the following technical solutions:

[0006] In a first aspect of the present application, a magnesium metal battery based on a conductive composite current collector is provided, comprising a negative electrode plate, wherein the negative electrode plate comprises a negative electrode current collector and a negative electrode active layer disposed on at least one surface of the negative electrode current collector;

[0007] The negative electrode current collector includes a negative electrode conductive support layer, a negative electrode primer layer disposed on at least one surface of the negative electrode conductive support layer, and a negative electrode conductive layer disposed on a surface of the negative electrode primer layer away from the negative electrode conductive support layer;

[0008] The lattice mismatch rate between the negative electrode conductive layer and the negative electrode active layer is less than 10%.

[0009] In some embodiments, the material of the negative electrode conductive layer includes one or more of titanium, zirconium, and scandium, and the material of the negative electrode active layer includes magnesium or a magnesium alloy.

[0010] In some embodiments, the thickness of the negative electrode conductive layer is 0.5 μm to 5 μm.

[0011] In some embodiments, the thickness of the negative electrode active layer is 0.5 μm to 10 μm.

[0012] In some embodiments, the negative electrode conductive support layer includes a conductive polymer fiber membrane having a three-dimensional network structure formed by interweaving conductive polymer fibers.

[0013] In some embodiments, the material of the conductive polymer fiber includes a conductive polymer A, and the conductive polymer A includes one or more of polypyrrole, polyaniline, poly(3,4-ethylenedioxythiophene), poly-3-hexylthiophene, poly(3-dodecylthiophene), poly(3-dodecylthiophene-3-hexyl-3-triethylene glycol) and poly(3-octylpyrrole):poly(styrenesulfonic acid).

[0014] In some embodiments, the conductive polymer fiber has a length of 0.1 mm to 10 mm and a diameter of 200 nm to 1000 nm.

[0015] In some embodiments, the conductive polymer fiber membrane has a pore size of 200 nm to 1000 nm and a porosity of 20% to 60%.

[0016] In some embodiments, the conductive polymer fiber film has a thickness of 2 μm to 6 μm.

[0017] In some embodiments, the method for preparing the conductive polymer fiber membrane comprises electrospinning.

[0018] In some embodiments, the negative electrode undercoat layer includes a conductive polymer B and a conductive agent B dispersed in the conductive polymer B.

[0019] In some embodiments, the conductive polymer B includes one or more of polypyrrole, polyaniline, poly(3,4-ethylenedioxythiophene), poly(3-hexylthiophene), poly(3-dodecylthiophene), poly(3-dodecylthiophene-3-hexyl-3-triethylene glycol) and poly(3-octylpyrrole):poly(styrenesulfonic acid).

[0020] In some embodiments, the conductive agent B includes one or more of an inorganic carbon material and a material containing a metal element; the inorganic carbon material includes one or more of conductive carbon black, conductive graphite, acetylene black, Ketjen black, carbon quantum dots, carbon nanotubes, carbon nanofibers, graphene and fullerene; the material containing a metal element includes one or more of copper, aluminum, nickel, gold, silver and MXene materials.

[0021] In some embodiments, the mass ratio of the conductive polymer B to the conductive agent B is 100:(1-50).

[0022] In some embodiments, the thickness of the negative electrode undercoat layer is 0.5 μm to 3 μm.

[0023] In some embodiments, the negative electrode plate further includes a negative ion transport layer with a negative charge, and the negative ion transport layer is disposed on a surface of the negative active layer facing away from the negative current collector;

[0024] The negative charges in the negative electrode ion transport layer are evenly distributed, or the negative charges in the negative electrode ion transport layer decrease gradually in a direction away from the negative electrode active layer.

[0025] In some embodiments, the negative electrode ion transport layer includes a negatively charged material, and the negatively charged material includes one or more of an organic carboxylic acid, an organic carboxylate, a carboxylated carbon nanotube, a polyhydroxyfullerene, and a MXene material.

[0026] In some embodiments, the negative electrode ion transport layer further comprises a positively charged material, and the negative charge of the negatively charged material is greater than the positive charge of the positively charged material;

[0027] The positively charged material includes one or more of chitosan and organic amine materials.

[0028] In a second aspect of the present application, an electrical device is provided, comprising the magnesium metal battery as described above.

[0029] This application has at least the following beneficial effects:

[0030] In the magnesium metal battery provided by the present application, the negative electrode current collector in the negative electrode sheet includes a negative electrode conductive support layer, a negative electrode bottom coating and a negative electrode conductive layer, which is a composite current collector. Compared with metal foils of the same thickness, it is lighter in weight, which is beneficial to improving the energy density of the battery. Among them, the lattice mismatch rate of the negative electrode conductive layer and the negative electrode active layer is less than 10%, so that the negative electrode conductive layer has a lattice locking effect on the negative electrode active layer, which can promote the formation of a highly ordered crystal structure of the negative electrode active layer, thereby reducing interface defects and structural stress. During the charge and discharge cycle, the negative electrode conductive layer can also promote the uniform deposition and peeling of the magnesium metal in the surface through the lattice locking effect, thereby effectively improving the cycle stability of the battery.

[0031] At the same time, the negative electrode conductive layer is disposed on the negative electrode base coating, which can not only increase the bonding force between the negative electrode conductive support layer and the negative electrode conductive layer, improve the peel strength of the negative electrode current collector, but also improve the flatness of the negative electrode conductive layer, making the interface conductive current collection effect better, and is conducive to reducing the interface defects and structural stress of the negative electrode active layer, thereby improving the cycle stability of the battery. As a result, the magnesium metal battery provided by this application has excellent cycle performance. In some embodiments, the capacity can still be maintained at more than 80% after 180 charge and discharge cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application and to more fully understand the present application and its beneficial effects, the following is a brief introduction to the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present application. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0033] Figure 1 Schematic diagram of the structure of the negative electrode sheet in some embodiments of the present application;

[0034] Figure 2 Schematic diagram of the structure of the negative electrode current collector in some embodiments of the present application;

[0035] Figure 3 Schematic diagram of the structure of the negative electrode sheet in some other embodiments of the present application.

[0036] Reference numerals: 10, negative electrode current collector; 11, negative electrode conductive support layer; 12, negative electrode undercoat layer; 13, negative electrode conductive layer; 20, negative electrode active layer; 30, negative electrode ion transport layer. DETAILED DESCRIPTION

[0037] To facilitate understanding of the present application, the present application will be further described in detail below with reference to specific embodiments. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of the present application.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0039] In this application, the meaning of "and / or" includes any and all combinations of one or more related listed items. "At least one" means more than one, such as one, two and more than two. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layer" means at least two layers, such as two layers, three layers, etc., unless otherwise clearly and specifically defined. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise clearly and specifically defined.

[0040] When a numerical range is disclosed in this application, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed in this application should be understood to include any and all subranges subsumed therein.

[0041] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly. For example, the method includes steps (a) and (b), which means 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 further include step (c), which means 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.

[0042] In this application, “above” or “below” includes the number itself. For example, “1 below” includes 1.

[0043] Unless otherwise specified, the temperature parameters in this application allow for both constant temperature treatment and temperature fluctuations within a certain temperature range. It should be understood that the constant temperature treatment allows for temperature fluctuations within the accuracy range of instrument control. Fluctuations within ranges such as ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are permitted.

[0044] In this application, room temperature refers to indoor temperature, normal temperature or general temperature. Generally speaking, the range of room temperature can be any one of the following temperature intervals: 23℃±2℃, 25℃±5℃ or 20℃±5℃.

[0045] The pole piece is a crucial component of a secondary battery. It includes a current collector and an active layer disposed on at least one surface of the current collector. The current collector can be made of metal foil or a composite current collector. A composite current collector comprises a polymer layer and metal layers disposed on both surfaces of the polymer layer, forming a typical sandwich structure. Compared to metal foil, composite current collectors are lighter at the same thickness, resulting in a higher energy density in the resulting secondary battery.

[0046] For magnesium metal batteries, the active ions are magnesium ions (Mg 2+ ), typically using magnesium or its alloys as the negative electrode active material. During the charge and discharge process, the deposition and stripping of magnesium metal causes the accumulation of interface defects and structural stress, thus affecting the cycle stability of the battery.

[0047] The present application provides a magnesium metal battery based on a conductive composite current collector, aiming to improve the cycle stability of the magnesium metal battery.

[0048] In some embodiments, a magnesium metal battery includes a negative electrode plate, wherein the negative electrode plate includes a negative electrode current collector and a negative electrode active layer disposed on at least one surface of the negative electrode current collector;

[0049] The negative electrode current collector includes a negative electrode conductive support layer, a negative electrode primer layer disposed on at least one surface of the negative electrode conductive support layer, and a negative electrode conductive layer disposed on a surface of the negative electrode primer layer facing away from the negative electrode conductive support layer;

[0050] The lattice mismatch rate between the negative electrode conductive layer and the negative electrode active layer is less than 10%.

[0051] In the magnesium metal battery provided by the present application, the negative electrode current collector in the negative electrode sheet includes a negative electrode conductive support layer, a negative electrode bottom coating and a negative electrode conductive layer, which is a composite current collector. Compared with metal foils of the same thickness, it is lighter in weight, which is beneficial to improving the energy density of the battery. Among them, the lattice mismatch rate of the negative electrode conductive layer and the negative electrode active layer is less than 10%, so that the negative electrode conductive layer has a lattice locking effect on the negative electrode active layer, which can promote the formation of a highly ordered crystal structure of the negative electrode active layer, thereby reducing interface defects and structural stress. During the charge and discharge cycle, the negative electrode conductive layer can also promote the uniform deposition and peeling of the magnesium metal in the surface through the lattice locking effect, thereby effectively improving the cycle stability of the battery.

[0052] At the same time, the negative electrode conductive layer is disposed on the negative electrode base coating, which can not only increase the bonding force between the negative electrode conductive support layer and the negative electrode conductive layer, improve the peel strength of the negative electrode current collector, but also improve the flatness of the negative electrode conductive layer, making the interface conductive current collection effect better, and is conducive to reducing the interface defects and structural stress of the negative electrode active layer, thereby improving the cycle stability of the battery. As a result, the magnesium metal battery provided by this application has excellent cycle performance. In some embodiments, the capacity can still be maintained at more than 80% after 180 charge and discharge cycles.

[0053] In this application, magnesium metal battery is a kind of multivalent metal battery in secondary battery, which includes positive electrode, negative electrode, electrolyte and separator. 2+ Deposition and stripping are carried out between the positive electrode and the negative electrode. The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The isolation membrane is set between the positive electrode and the negative electrode, mainly to prevent the positive and negative electrodes from short-circuiting, and at the same time to allow Mg 2+ pass.

[0054] The following is some description of the negative electrode sheet of the magnesium metal battery.

[0055] In some embodiments, as Figure 1 As shown, the negative electrode sheet includes a negative electrode current collector 10 and a negative electrode active layer 20 disposed on both surfaces of the negative electrode current collector 10 .

[0056] It can be understood that the negative electrode current collector 10 has two surfaces facing each other in its thickness direction. Figure 1 The negative electrode active layer 20 is disposed on two opposite surfaces of the negative electrode current collector 10 . However, the present application is not limited thereto. In other examples, the negative electrode active layer 20 may also be disposed on any one surface of the negative electrode current collector 10 .

[0057] In some embodiments, as Figure 2 As shown, the negative electrode current collector 10 includes a negative electrode conductive support layer 11 , a negative electrode undercoat layer 12 disposed on both surfaces of the negative electrode conductive support layer 11 , and a negative electrode conductive layer 13 disposed on the surface of the negative electrode undercoat layer 12 facing away from the negative electrode conductive support layer 11 .

[0058] It can be understood that the negative electrode conductive support layer 11 has two surfaces opposite to each other in its thickness direction. Figure 2 The negative electrode undercoat layer 12 is disposed on two opposing surfaces of the negative electrode conductive support layer 11. However, the present application is not limited thereto. In other examples, the negative electrode undercoat layer 12 may also be disposed on any surface of the negative electrode conductive support layer 11. On any surface of the negative electrode conductive support layer 11, the negative electrode undercoat layer 12, the negative electrode conductive layer 13, and the negative electrode active layer 20 are sequentially stacked from bottom to top.

[0059] In some embodiments, the negative electrode conductive support layer 11 includes a conductive polymer fiber membrane having a three-dimensional network structure formed by interweaving conductive polymer fibers.

[0060] In traditional technology, the polymer layer in the composite current collector usually adopts a polymer film with poor conductivity, which is easy to cause heat accumulation under high-rate and high-current working conditions, causing electrochemical performance degradation and even thermal runaway problems. There are reports on the use of conductive polymer films to optimize the conductivity of the composite current collector, but its poor mechanical properties and low ductility will also affect the cycle stability of the battery. Therefore, the present application adopts a conductive polymer fiber membrane as the negative electrode conductive support layer 11, which has a three-dimensional network structure composed of conductive polymer fibers arranged and interwoven, with excellent mechanical strength, high ductility and high conductivity, while also achieving a weight reduction effect, which is beneficial to the lightweighting of the battery.

[0061] In some embodiments, the material of the conductive polymer fiber includes a conductive polymer A, and the conductive polymer A includes one or more of polypyrrole (PPy), polyaniline (PANI), poly(3,4-ethylenedioxythiophene) (PEDOT), poly-3-hexylthiophene (P3HT), poly(3-dodecylthiophene) (P3DDT), poly(3-dodecylthiophene-3-hexyl-3-triethylene glycol) (PDDHEO) and poly(3-octylpyrrole):poly(styrenesulfonic acid) (P3OPy:PSS).

[0062] In some embodiments, the material of the conductive polymer fiber further includes a dispersant A. Thus, the dispersant A can promote uniform dispersion of the conductive polymer A, thereby enhancing the mechanical strength of the conductive polymer fiber film.

[0063] In some embodiments, dispersant A includes one or more of polyvinylpyrrolidone (PVP), sodium polyacrylate (PAAS), sodium lignin sulfonate, and sodium polystyrene sulfonate (PSS).

[0064] In some embodiments, the mass ratio of the conductive polymer A to the dispersant A is (20-30):1, for example, 20:1, 21:1, 22:1, 23:1, 24:1, 25:1, 26:1, 27:1, 28:1, 29:1 or 30:1.

[0065] In some embodiments, the conductive polymer fiber material further includes a conductive agent A, which comprises one or more of an inorganic carbon material and a material containing a metal element. Thus, the conductive agent A can further enhance the conductivity of the conductive polymer fiber membrane, suppress heat generation under high-rate and high-current conditions, and thus improve the battery's cycling stability.

[0066] In some embodiments, the inorganic carbon material includes one or more of conductive carbon black, conductive graphite, acetylene black, Ketjen black, carbon quantum dots, carbon nanotubes (CNTs), carbon nanofibers (CNFs), graphene, and fullerenes. For example, the conductive carbon black may be selected from Super-P (SP), Super-C (SC), and the like.

[0067] In some embodiments, the material containing the metal element includes one or more of copper (Cu), aluminum (Al), nickel (Ni), gold (Au), silver (Ag), and MXene materials.

[0068] In some embodiments, the molecular formula of the MXene material is M n+1 X n T xWhere n = 1, 2, 3; M represents a transition metal element, including one or more of Ti, Ta, Mo, V, Sr, and Zr; X represents one or more of carbon and nitrogen; T represents a surface active functional group, including one or more of -OH, -F, and -O, and x represents the number of T, where x>0. As an example, MXene materials can be selected from Ti3C2T x 、Ti2CT x 、Ti3CNT x 、Ta4C3T x 、V2CT x 、V3C2T x 、Mo2CT x or Mo2TiC2T x wait.

[0069] In some embodiments, the particle size of the conductive agent A is 20 nm to 400 nm, for example, 20 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, or 400 nm.

[0070] In some embodiments, the mass ratio of the conductive polymer A to the conductive agent A is 100:(1-30), for example, 100:1, 100:2, 100:5, 100:10, 100:12, 100:15, 100:20, 100:25 or 100:30.

[0071] In some embodiments, the conductive polymer fibers have a length of 0.1 mm to 10 mm and a diameter of 200 nm to 1000 nm. For example, the conductive polymer fibers may have a length of 0.1 mm, 0.5 mm, 1 mm, 2 mm, 5 mm, 8 mm, or 10 mm and a diameter of 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, or 1000 nm.

[0072] In some embodiments, the conductive polymer fiber membrane has a pore size of 200 nm to 1000 nm and a porosity of 20% to 60%. As an example, the conductive polymer fiber membrane can have a pore size of 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, or 1000 nm, and a porosity of 20%, 30%, 40%, 50%, or 60%.

[0073] In some embodiments, the conductivity of the conductive polymer fiber membrane is 50 S / cm to 500 S / cm, for example, 50 S / cm, 100 S / cm, 200 S / cm, 300 S / cm, 400 S / cm, or 500 S / cm.

[0074] In some embodiments, the thickness of the conductive polymer fiber film is 2 μm to 6 μm, for example, 2 μm, 3 μm, 4 μm, 5 μm or 6 μm.

[0075] In some embodiments, the preparation method of the conductive polymer fiber membrane includes an electrospinning method. Specifically, the conductive polymer fiber can be prepared by the following method: dispersing the conductive polymer A, dispersant A, and conductive agent A in a solvent, stirring at 40°C to 80°C for 6 hours to 24 hours to form a uniform spinning solution; controlling the feed rate to 0.1mL / h to 5mL / h and the operating voltage to 10kV to 20kV, and performing electrospinning to form the conductive polymer fiber membrane. The solvent of the spinning solution can be toluene, chloroform, etc.

[0076] In the present application, a negative electrode bottom coating layer 12 is arranged between the negative electrode conductive support layer 11 and the negative electrode conductive layer 13, which can prevent the negative electrode conductive layer 13 from being deposited into the pores of the fiber membrane, reduce the amount of metal material used, and is beneficial to the weight reduction and lightweighting of the current collector; the negative electrode bottom coating layer 12 provides a continuous membrane layer structure and has a certain surface roughness, which can enhance the bonding effect between the negative electrode conductive support layer 11 and the negative electrode conductive layer 13, and enhance the peel strength of the negative electrode current collector 10; further, the negative electrode conductive layer 13 is deposited on the negative electrode bottom coating layer 12, and its flatness is good, and the conductive current collection effect of the interface is good. At the same time, it is also beneficial to the epitaxial growth of the negative electrode active layer 20, effectively reducing the interface defects and structural stress of the negative electrode active layer 20, thereby improving the cycle stability of the battery.

[0077] In some embodiments, the negative electrode undercoat layer 12 includes a conductive polymer B and a conductive agent B dispersed in the conductive polymer B. In some examples, the negative electrode undercoat layer 12 may further include a binder B.

[0078] In the negative electrode bottom coating 12 of the present application, the conductive polymer B is doped with anions, which makes the negative electrode bottom coating 12 have good electrical conductivity and a more significant positive temperature coefficient (PTC) effect. The conductive polymer B realizes the PTC effect based on the doping and dedoping mechanism of anions. The conductive polymer B will undergo anion dedoping at a high critical temperature, thereby causing disorder of the polymer main chain and a sharp increase in the resistance value. This process does not involve changes in the main chain of the conductive polymer B and has a certain degree of reversibility. The introduction of the conductive agent B also promotes the doping and dedoping reaction of anions to a certain extent. Therefore, the negative electrode bottom coating 12 responds more quickly to temperature changes and has a stronger reaction reversibility, so that the negative electrode current collector 10 has both excellent conductivity and safety.

[0079] In some embodiments, the conductive polymer B includes one or more of polypyrrole (PPy), polyaniline (PANI), poly(3,4-ethylenedioxythiophene) (PEDOT), poly-3-hexylthiophene (P3HT), poly(3-dodecylthiophene) (P3DDT), poly(3-dodecylthiophene-3-hexyl-3-triethylene glycol) (PDDHEO), and poly(3-octylpyrrole):poly(styrenesulfonic acid) (P3OPy:PSS).

[0080] In some embodiments, conductive agent B comprises one or more of an inorganic carbon material and a metal-containing material. The types of inorganic carbon material and metal-containing material in conductive agent B are substantially the same as those in conductive agent A and are not further described here. Furthermore, conductive agent B comprises one or more of conductive carbon black (such as Super-P, Super-C, etc.), acetylene black, carbon nanotubes, and graphene.

[0081] In some embodiments, the particle size of the conductive agent B is 20 nm to 400 nm, for example, 20 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, or 400 nm.

[0082] In some embodiments, binder B includes one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), hydrogenated nitrile rubber (HNBR), polyvinyl alcohol (PVA), polymethacrylic acid (PMAA), polymethyl methacrylate (PMMA), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), sodium alginate (SA), sodium carboxymethyl cellulose (CMC) and carboxymethyl chitosan (CMCS), and may further be PVDF.

[0083] In some embodiments, the mass ratio of the conductive polymer B to the conductive agent B is 100:(1-50); the mass ratio of the conductive polymer B to the binder B is 100:(1-15). As an example, the mass ratio of the conductive polymer B to the conductive agent B can be 100:1, 100:5, 100:10, 100:15, 100:20, 100:25, 100:30, 100:35, 100:40, 100:45, or 100:50, and the mass ratio of the conductive polymer B to the binder B can be 100:1, 100:2, 100:5, 100:8, 100:10, 100:12, 100:14, or 100:15.

[0084] In some embodiments, the thickness of the negative electrode undercoat layer 12 is 0.5 μm to 3 μm, for example, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, or 3 μm.

[0085] In some embodiments, the negative electrode undercoat layer 12 is prepared by dissolving the conductive polymer B in a solvent, adding the conductive agent B and the binder B, and ultrasonically dispersing the solution for 0.5 to 3 hours to obtain a dispersion. The dispersion is then applied to the surface of the negative electrode conductive support layer 11 using a doctor blade coating method, and then vacuum-dried at 60°C to 100°C for 24 to 48 hours. The solvent for the dispersion can be toluene, chloroform, or the like, and the mass fraction of the conductive polymer B in the solution B can be 1% to 5%.

[0086] In some embodiments, the material of the negative electrode conductive layer 13 includes one or more of titanium (Ti), zirconium (Zr), and scandium (Sc). Ti, Zr, and Sc not only have good electrical conductivity but also have a hexagonal close-packed (HCP) structure, similar to that of Mg. Their lattice constants are closest to those of Mg, facilitating the epitaxial growth of the negative electrode active layer 20.

[0087] In some embodiments, the thickness of the negative electrode conductive layer 13 is 0.5 μm to 5 μm, for example, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm or 5 μm.

[0088] In some embodiments, the preparation method of the negative electrode conductive layer 13 includes magnetron sputtering. Specifically, the negative electrode conductive layer 13 can be prepared by the following method: vacuuming to ≤ (2~8)×10 -5 Pa, an inert gas is introduced at a flow rate of 50 sccm to 100 sccm, and DC magnetron sputtering is performed under the conditions of a sputtering pressure of 0.5 Pa to 5 Pa and a sputtering power of 100 W to 300 W to form a negative electrode conductive layer 13 on the surface of the negative electrode undercoat layer 12. The inert gas includes one or more of helium, neon, argon, krypton, and xenon.

[0089] In some embodiments, the negative electrode active layer 20 includes magnesium or a magnesium alloy, wherein the magnesium alloy includes magnesium silicon alloy (MgSi), magnesium germanium alloy (MgGe), or magnesium tin alloy (MgSn). Further, the negative electrode active layer 20 is Mg.

[0090] In some embodiments, the lattice mismatch between the negative electrode conductive layer 13 and the negative electrode active layer 20 is less than 10%. Further, the lattice mismatch between the negative electrode conductive layer 13 and the negative electrode active layer 20 is less than 8%.

[0091] For example, the in-plane lattice constant (a=b) of Ti is 2.95Å, the lattice constant of Zr is 3.23Å, and the in-plane lattice constant of Sc is 3.30Å. The lattice mismatch rates with the in-plane lattice constant of Mg (3.20Å) are 7.8%, 0.9%, and 3.1%, respectively. As a result, the negative electrode conductive layer 13 has a lattice locking effect (also known as an anchoring effect, pinning effect, etc.), which can promote the formation of a highly ordered crystal structure in the negative electrode active layer 20 through epitaxial growth, thereby reducing interfacial defects and structural stress. Furthermore, during charge and discharge cycles, the negative electrode conductive layer 13 can also promote the uniform in-plane deposition and stripping of magnesium metal through the lattice locking effect, thereby effectively improving the battery's capacity, rate capability, and cycle performance.

[0092] In some embodiments, the thickness of the negative electrode active layer 20 is 0.5 μm to 10 μm, for example, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm.

[0093] In some embodiments, the preparation method of the negative electrode active layer 20 includes magnetron sputtering. Specifically, the negative electrode active layer 20 can be prepared by the following method: vacuuming to ≤ (2~8)×10 -5 Pa, an inert gas is introduced at a flow rate of 50 sccm to 100 sccm, and DC magnetron sputtering is performed under the conditions of a sputtering pressure of 0.5 Pa to 5 Pa and a sputtering power of 100 W to 300 W to epitaxially grow a negative active layer 20 on the surface of the negative conductive layer 13. The inert gas includes one or more of helium, neon, argon, krypton, and xenon.

[0094] In some embodiments, as Figure 3 As shown, the negative electrode plate further includes a negative ion transport layer 30 with negative charge. The negative ion transport layer 30 is disposed on the surface of the negative active layer 20 facing away from the negative current collector 10 .

[0095] The electrolyte of magnesium metal batteries is mostly added with halogen-containing magnesium salts, which are abundant, cheap and easy to obtain, but Cl - Corrosive anions such as magnesium metal will cause harmful side reactions when they approach the negative electrode, which will deteriorate the electrochemical performance of the battery. However, the present invention provides a negative electrode ion transport layer 30 with negative charge on the surface of the negative electrode active layer 20, which can promote the Mg metal to be transported by electrostatic attraction. 2+ The migration and diffusion of magnesium metal can be promoted to promote uniform and dense magnesium metal deposition and reduce the formation of interface defects such as pores and cracks. On the other hand, the electrostatic repulsion can prevent corrosive anions from approaching the negative electrode active layer 20, thereby inhibiting the occurrence of harmful side reactions.

[0096] In some embodiments, the negative charge in the negative electrode ion transport layer 30 is uniformly distributed. It is understood that the uniform distribution of negative charge means that the amount of negative charge in the negative electrode ion transport layer 30 is substantially uniform in the thickness direction, and no difference in concentration or potential is formed between the two opposing surfaces of the negative electrode ion transport layer 30.

[0097] In the negative electrode ion transport layer 30, if the negative charge increases gradually in the direction away from the negative electrode active layer 20, the Mg 2+ Far away from the negative electrode active layer 20, it is impossible to provide fast and sufficient Mg 2+ supply, it is easy to form pores during the deposition process, which is not conducive to uniform deposition. 2+ It is also evenly distributed in the negative electrode ion transport layer 30 , and the deposition uniformity of the magnesium metal is improved compared to the example of the gradual increase.

[0098] In some embodiments, the negative charge in the negative electrode ion transport layer 30 decreases gradually along the direction away from the negative electrode active layer 20. 2+ The migration of Mg 2+ Gathered on the surface of the negative electrode active layer 20, providing rapid and sufficient Mg 2+ Supply, improve the uniformity and density of magnesium metal deposition.

[0099] In some embodiments, the cathode ion transport layer 30 includes a negatively charged material.

[0100] In some embodiments, the negative electrode ion transport layer 30 further includes a positively charged material, and the negative charge of the negatively charged material is greater than the positive charge of the positively charged material.

[0101] In this application, a negatively charged material is a material that has a negative charge in a solution environment, and a positively charged material is a material that has a positive charge in a solution environment. The solution environment can be water, an organic solvent, or a solution containing a dispersed electrolyte salt. In magnesium metal batteries, the solution environment refers to the electrolyte.

[0102] The Zeta potential test method can usually be used to characterize the surface charge of a material. For example, the following method can be used for characterization: the sample to be tested is dispersed in deionized water at a mass fraction of 0.01% to 0.1% to obtain a suspension, and then a Zeta potential meter is used for testing.

[0103] Negatively charged materials usually carry functional groups such as hydroxyl, carboxyl, halogen, and oxygen-metal bonds. Specifically, hydroxyl (-OH) and carboxyl (-COOH) groups can carry negative charges (-O - and -COO -Halogens (-F, -Cl, -Br, or -I) inherently have high electronegativity, which can impart a negative charge to the surface of a material. Oxygen-metal bonds (-O, or MO bonds) form stable chemical bonds between oxygen atoms and surface metal atoms through substitution or adsorption. The high electronegativity of oxygen atoms imparts a certain degree of negative charge to the surface of the material, especially in a solution environment.

[0104] In some embodiments, the negatively charged material comprises one or more of organic carboxylic acid, organic carboxylate salt, carboxylated carbon nanotube, polyhydroxy fullerene and MXene material. In particular, organic carboxylic acid and its salt can form negatively charged -COO in solution. - Suitable examples include formic acid, acetic acid, propionic acid, butyric acid, oxalic acid, succinic acid, malic acid, tartaric acid, citric acid, ascorbic acid, benzoic acid, salicylic acid, phthalic acid, stearic acid, glutamic acid, lactic acid, alginic acid, and their salts (e.g., sodium and potassium salts). Furthermore, carboxylated carbon nanotubes contain numerous carboxyl groups, polyhydroxyfullerenes contain numerous hydroxyl groups, and MXene materials contain numerous reactive functional groups, such as -OH, -F, or -O, which can acquire a negative charge through deprotonation or adsorption, and thus can also be used as negatively charged materials.

[0105] In some embodiments, the positively charged material includes one or more of chitosan and organic amine materials. Chitosan (CS) is obtained by deacetylation of chitin, and its molecular chain contains amino groups (-NH2), which can be protonated in a solution environment to have a positive charge (-NH3 + The organic amine material generally has an amino group or an imino group, which can be protonated in a solution environment to carry a positive charge. Suitable examples include ethylamine, diethylamine, ethylenediamine, triethylamine, polyethyleneimine, and the like.

[0106] In some embodiments, the ratio of the negative charge of the negatively charged material to the positive charge of the positively charged material is 1:(0-0.96), for example, it can be 1:0 (i.e., no positively charged material is added), 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9 or 1:0.96.

[0107] In some embodiments, the conductivity of the negative ion transport layer is 50 S / cm to 500 S / cm, for example, 50 S / cm, 100 S / cm, 150 S / cm, 200 S / cm, 250 S / cm, 300 S / cm, 350 S / cm, 400 S / cm, 450 S / cm or 500 S / cm.

[0108] In some embodiments, the thickness of the negative ion transport layer is 0.5 μm to 5 μm, for example, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm or 5 μm.

[0109] In some embodiments, the negative electrode ion transport layer 30 can be prepared by the following method: a negative precursor solution containing a negatively charged material is coated on the surface of the negatively charged active layer, and dried at 40°C to 80°C for 6h to 24h to form the negative electrode ion transport layer 30. The solvent of the negative precursor solution includes deionized water, ethanol, etc., and the concentration of the negatively charged material is 1mmol / L to 10mmol / L. In some examples, a binder C can also be added to the negative precursor solution to enhance the bonding effect of the negative electrode ion transport layer 30. The type of binder C is basically the same as that of the binder B and will not be repeated.

[0110] Therefore, no positively charged material is added to the negative electrode ion transport layer 30 , and the negatively charged material is evenly distributed, so the negative charges are also evenly distributed in the negative electrode ion transport layer 30 .

[0111] In some embodiments, the negative electrode ion transport layer 30 can be prepared by the following method: a negative precursor liquid containing a negatively charged material is coated on the surface of the negatively charged active layer to form a liquid film; a positive precursor liquid droplet containing a positively charged material is coated on the surface of the liquid film to allow the positive and negative materials to undergo an electrostatic complexation reaction, and then dried at 40°C~80°C for 6h~24h to form the negative electrode ion transport layer 30.

[0112] The solvents of the positive and negative precursor solutions independently include deionized water, ethanol, etc. The concentration of the negative material is 1 mmol / L to 10 mmol / L, and the concentration of the positive material is 0.1 mmol / L to 9.6 mmol / L. The negative charge of the negative material is greater than the positive charge of the positive material to ensure that the negative electrode ion transport layer 30 is negatively charged. In some examples, the negative and / or positive precursor solutions may be added with a binder C to enhance the bonding effect of the negative electrode ion transport layer 30. Furthermore, the negative material is selected from sodium alginate (SA) containing two carboxyl groups, and the positive material is selected from chitosan (CS) containing two amino groups. Both can be obtained from marine organisms and are environmentally friendly and inexpensive.

[0113] Therefore, after the positive precursor droplets are coated on the surface of the liquid film, the protonated functional groups of the positive material (such as -NH3 + ) and the deprotonated functional groups of negatively charged materials (such as -O - 、-COO -) Electrostatic complexation begins to occur at the interface to form a complex intermediate layer. As the positive material diffuses toward the negative active layer 20, the thickness of the complex intermediate layer gradually increases. In this process, the concentration of the positive material decreases gradually along the diffusion direction, and the concentration of the negative material remains unchanged, so that the reaction intensity of the electrostatic complexation reaction also decreases gradually along the diffusion direction. The reaction intensity is high away from the negative active layer 20, and the amount of negative charge after the reaction is small; the reaction intensity is low close to the negative active layer 20, and the amount of negative charge after the reaction is large. Therefore, in the negative electrode ion transport layer 30 formed by drying, the negative charge decreases gradually along the direction away from the negative active layer 20, thereby being Mg 2+ Provides acceleration for migration.

[0114] The following is some description of the positive electrode sheet of the magnesium metal battery.

[0115] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active layer disposed on at least one surface of the positive electrode current collector.

[0116] It can be understood that the positive electrode current collector has two surfaces opposite to each other in its thickness direction. The positive electrode active layer can be arranged on the two opposite surfaces of the positive electrode current collector or on any one surface of the positive electrode current collector.

[0117] In some embodiments, the positive current collector includes a positive conductive support layer, a positive undercoat layer disposed on at least one surface of the positive conductive support layer, and a positive metal layer disposed on a surface of the positive undercoat layer facing away from the positive conductive support layer.

[0118] It can be understood that the positive electrode conductive support layer has two surfaces opposite to each other in its own thickness direction. The positive electrode primer layer can be provided on the two opposite surfaces of the positive electrode conductive support layer, or on any surface of the positive electrode conductive support layer. On any surface of the positive electrode conductive support layer, a positive electrode primer layer, a positive electrode metal layer, and a positive electrode active layer are stacked in sequence from bottom to top. Among them, the structure, materials, and preparation method of the positive electrode conductive support layer are basically the same as those of the negative electrode conductive support layer 11, and the structure, materials, and preparation method of the positive electrode primer layer are basically the same as those of the negative electrode primer layer 12, and will not be repeated in this application.

[0119] In some embodiments, the material of the positive electrode metal layer includes aluminum (Al) or stainless steel. In addition, the thickness and preparation method of the positive electrode metal layer are substantially the same as those of the negative electrode conductive layer 13 and will not be described in detail in this application.

[0120] In some embodiments, the positive electrode active layer includes a positive electrode material, and the positive electrode material includes one or more of a transition metal oxide, a transition metal sulfide, a transition metal phosphate, and a transition metal silicate.

[0121] As an example, the transition metal oxide includes one or more of vanadium oxides and manganese dioxide (MnO2). Among them, the vanadium oxide includes vanadium pentoxide (V2O5) with a layered structure and a layered vanadium oxide with ion pre-intercalation, such as Mg with magnesium ion pre-intercalation. 0.3 V2O5·1.1H2O, Mn with manganese ion pre-intercalation 0.04 V2O5·1.17H2O, etc.

[0122] As an example, the transition metal sulfide includes one or more of vanadium sulfide, cobalt sulfide, and molybdenum sulfide. Among them, the vanadium sulfide can be selected from VS2, VS4, etc., the cobalt sulfide can be selected from Co3S4, and the molybdenum sulfide can be selected from MoS2, Mo6S8, etc.

[0123] As examples, transition metal phosphates include vanadium oxyphosphate (VOPO4) with a layered structure and sodium fast ion conductor (NASICON) type Mg 0.5 Ti2(PO4)3, etc.

[0124] As an example, transition metal silicates include polyanionic Mg x M y SiO4, wherein M is selected from transition metals such as Fe, Mn, Co, Ni, and x+y=2, such as MgCoSiO4.

[0125] In some embodiments, the positive electrode active layer may include a modified positive electrode material, which includes the above-mentioned positive electrode material and a coating layer coated on the surface of the positive electrode material. The coating layer may be made of a carbon material to enhance the conductivity; the coating layer may also be made of the conductive polymer mentioned above to promote the Mg 2+ The migration and diffusion of the modified positive electrode material are improved, and the transmission kinetics of the modified positive electrode material are protected to prevent the dissolution of the transition metal elements, ensure its structural stability, and thus improve the cycle stability of the battery.

[0126] In some embodiments, the positive electrode active layer further comprises a positive electrode conductor and a positive electrode binder, with the mass ratio of the positive electrode material (or modified positive electrode material), positive electrode conductor, and positive electrode binder being (6-9):(0.5-2.5):(0.5-1.5), and further optionally 7:2:1. The positive electrode binder comprises one or more of polyvinylidene fluoride (PVDF), sodium alginate (SA), polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), hydrogenated nitrile rubber (HNBR), polytetrafluoroethylene (PTFE), and polyacrylic acid (PAA), and further optionally PVDF. The positive electrode conductor comprises one or more of conductive carbon black, conductive graphite, acetylene black, Ketjen black, carbon quantum dots, carbon nanotubes, graphene, and carbon nanofibers, and further optionally acetylene black.

[0127] In some embodiments, the preparation method of the positive electrode sheet includes the following steps: dispersing the positive electrode material (or modified positive electrode material), the positive electrode conductive agent and the positive electrode binder in a solvent (such as NMP), and obtaining a positive electrode slurry after homogenization; covering the positive electrode slurry on at least one surface of the positive electrode current collector, and obtaining a positive electrode sheet after drying, rolling and cutting.

[0128] The following are some other descriptions of magnesium metal batteries.

[0129] In the present application, the electrolyte in the magnesium metal battery can be liquid, gel or all-solid.

[0130] In some embodiments, the electrolyte of the magnesium metal battery is an electrolyte solution comprising a magnesium salt and a solvent.

[0131] In some embodiments, the magnesium salt includes one or more of magnesium chloride (MgCl2), magnesium sulfate (MgSO4), magnesium nitrate (Mg(NO3)2), magnesium perchlorate (Mg(ClO4)2), calcium bis(trifluoromethanesulfonyl imide) (Mg(TFSI)2), organic aluminum magnesium salts, and organic boron magnesium salts. The organic aluminum magnesium salts may be selected from (PhMgCl)2-AlCl3, Mg(AlCl2EtBu)2, and the like, and the organic boron magnesium salts may be selected from (PhMgCl)2-BR3, and the like, where Ph represents a phenyl group and R represents a 3,5-xylyl group.

[0132] In some embodiments, the concentration of the magnesium salt in the electrolyte is 0.1 mol / L to 10 mol / L, for example, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L or 10 mol / L.

[0133] In some embodiments, the solvent of the electrolyte includes one or more of tetrahydrofuran (THF), acetonitrile (AN), diethyl ether, 1,3-dioxane, 1,2-dimethoxyethane, dimethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and propylene carbonate (PC).

[0134] In some embodiments, the separator is made of one or more materials selected from the group consisting of fiberglass (GF), non-woven fabric, polyethylene (PE), polypropylene (PP), and polyimide (PI). It is understood that the separator can be a single-layer film or a multi-layer composite film. If the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0135] In some embodiments, the thickness of the isolation film is 10 μm to 20 μm, for example, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, or 20 μm.

[0136] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator are formed into an electrode assembly through a winding process or a lamination process.

[0137] In some embodiments, the magnesium metal battery further includes an outer packaging for encapsulating the electrode assembly and electrolyte. The outer packaging of the magnesium metal battery includes one or more of a hard shell and a soft shell. The hard shell may be a hard plastic shell, an aluminum shell, a steel shell, etc., and the soft shell may be a pouch-type soft shell or a plastic soft shell.

[0138] The present application also provides a battery module comprising a housing and a plurality of magnesium metal batteries disposed within the housing. In the battery module, the plurality of magnesium metal batteries may be arranged sequentially along the length of the battery module, and the number of magnesium metal batteries may be determined based on the application and capacity of the battery module.

[0139] The present application also provides a battery pack, which includes a battery box and a plurality of battery modules disposed inside the battery box. In the battery pack, the plurality of battery modules can be arranged in the battery box in any manner, and the number of battery modules can be determined according to the application and capacity of the battery pack.

[0140] The present application also provides an electrical device comprising the magnesium metal battery described above. The magnesium metal battery can serve as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, and the like. Examples of mobile devices include, but are not limited to, mobile phones and laptop computers; and examples of electric vehicles include, but are not limited to, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, and electric trucks.

[0141] The following is further described in conjunction with specific examples and comparative examples. Unless otherwise specified, the raw materials involved in the following specific examples and comparative examples can be sourced from commercial sources. The instruments used can be sourced from commercial sources unless otherwise specified. The processes involved can be selected conventionally by those skilled in the art unless otherwise specified.

[0142] Example 1

[0143] The magnesium metal battery of this embodiment is prepared by the following method:

[0144] (1) Preparation of positive electrode:

[0145] Polypyrrole (PPy) and dispersant PVP were dispersed in chloroform in a mass ratio of 25:1 and stirred at 60°C for 12 hours to obtain a uniform spinning solution. The feed rate was controlled at 1 mL / h and the operating voltage was 16 kV for electrospinning to form a 5 µm thick conductive polymer fiber membrane as the positive electrode conductive support layer.

[0146] Poly(3-dodecylthiophene) (P3DDT) was dissolved in toluene with a mass fraction of 2%, and a conductive agent SP was added with a mass ratio of P3DDT and SP of 10:3. Ultrasonic dispersion was performed for 2 hours to obtain a dispersion. The dispersion was coated on both surfaces of the positive electrode conductive support layer by a doctor blade method, and then vacuum dried at 65°C for 48 hours to obtain a 1µm thick positive electrode base coating.

[0147] The chamber of the magnetron sputtering equipment was evacuated to 5×10 -5 Pa, argon gas is introduced at a flow rate of 80 sccm, and DC magnetron sputtering is carried out under the conditions of a working gas pressure of 2 Pa and a working power of 150 W to form a 1 μm thick Al layer on the surface of the positive electrode base coating as a positive electrode metal layer to obtain a positive electrode current collector.

[0148] The positive electrode material Mg 0.3 V2O5·1.1H2O (MVO), conductive carbon black SP and binder PVDF are mixed in a mass ratio of 7:2:1, and NMP is added to obtain a positive electrode slurry; the positive electrode slurry is coated on both surfaces of the positive electrode current collector, and after drying, roll pressing and cutting, a positive electrode sheet is obtained.

[0149] (2) Preparation of negative electrode sheet:

[0150] According to step (1), the negative electrode conductive support layer and the negative electrode bottom coating layer are prepared respectively.

[0151] The chamber of the magnetron sputtering equipment was evacuated to 5×10 -5 Pa, argon gas is introduced at a flow rate of 60 sccm, and DC magnetron sputtering is carried out under the conditions of a working gas pressure of 1.2 Pa and a working power of 200 W to form a 2 μm thick Zr layer on the surface of the negative electrode base coating as a negative electrode conductive layer to obtain a negative electrode current collector.

[0152] Subsequently, DC magnetron sputtering coating was performed under the conditions of a working gas pressure of 1 Pa and a working power of 220 W, and a 4 μm thick Mg layer was epitaxially grown on the surface of the Zr layer to obtain a negative electrode active layer.

[0153] Sodium alginate (SA) was dispersed in deionized water to prepare a 5 mmol / L negative precursor solution; chitosan (CS) was dispersed in deionized water to prepare a 4.8 mmol / L positive precursor solution; the negative precursor solution was coated on the surface of the negative electrode active layer to form a 1 μm thick liquid film; an equal volume of positive precursor droplets was applied to the liquid film surface, CS diffused into the negative electrode active layer and underwent an electrostatic complexation reaction with SA, and then vacuum dried at 65 ° C for 48 hours to obtain a 2 μm thick negative electrode ion transport layer, thereby preparing a negative electrode sheet.

[0154] (3) Preparation of isolation membrane: A 12 μm thick glass fiber film was used as the isolation membrane.

[0155] (4) Preparation of electrolyte: Dissolve organic aluminum magnesium salt (PhMgCl)2-AlCl3 in tetrahydrofuran (THF) to obtain an electrolyte with a concentration of 0.4 mol / L.

[0156] (5) Assembly of magnesium metal batteries: In a glove box (Ar atmosphere, water and O2 content <0.1ppm), the positive electrode, isolation membrane and negative electrode are encapsulated with aluminum plastic film, dried and dehydrated, and then injected with electrolyte. The magnesium metal battery is obtained after standing, hot and cold pressing, formation, clamping, and capacity separation.

[0157] Examples 2 to 12 and Comparative Example 1

[0158] Examples 2 to 12 and Comparative Example 1 are substantially the same as Example 1, except that:

[0159] Example 2: The material of the negative electrode conductive layer is Sc.

[0160] Example 3: The material of the negative electrode conductive layer is Ti.

[0161] Example 4: The material of the negative electrode active layer is magnesium-germanium alloy (MgGe).

[0162] Example 5: The positive electrode material is MnO2.

[0163] Example 6: Both the positive electrode conductive support layer and the negative electrode conductive support layer are made of P3DDT to prepare conductive polymer fiber membranes.

[0164] Example 7: Both the positive electrode conductive support layer and the negative electrode conductive support layer are PPy thin films and do not have a three-dimensional porous structure.

[0165] Example 8: The positive electrode conductive support layer adopts PET fiber membrane, and the negative electrode conductive support layer adopts PP fiber membrane.

[0166] Example 9: SA concentration is 5 mmol / L, and CS concentration is 2.5 mmol / L.

[0167] Example 10: SA concentration is 5 mmol / L, CS concentration is 1 mmol / L,

[0168] Example 11: The SA concentration is 5 mmol / L, and the CS concentration is 0 mmol / L, that is, no positively charged material is added.

[0169] Example 12: No negative electrode ion transport layer is provided.

[0170] Comparative Example 1: The negative electrode conductive layer is made of Cu, and no negative electrode ion transport layer is provided.

[0171] The differences between Examples 1 to 12 and Comparative Example 1 are shown in Table 1 below:

[0172] Table 1. Relevant parameters of magnesium metal batteries

[0173]

[0174] Test Case

[0175] The following tests were carried out on each embodiment and each comparative example:

[0176] (1) Tensile strength: Cut three sample strips with a length and width of 150 mm × 15 mm, ensure that the samples are placed vertically on the test clamp of the tensile testing machine, set the parameters, and then test and record the tensile strength.

[0177] (2) Peel strength: Attach the tape evenly to the steel plate, fix the sample on the tape, attach the auxiliary tape to the surface of the sample, fix the steel plate and the auxiliary tape on the constant speed tensile testing machine to start the test, and record the peel strength of each sample.

[0178] (3) Room temperature cycle test: The battery is subjected to a room temperature cycle test at 2C / 2C, and the first discharge specific capacity of the battery at 2C and the number of cycles at which the capacity decays to 80% are recorded.

[0179] (4) Lithium-to-drag ratio: After the battery is fully charged, its internal resistance values ​​R1 and R2 at 25°C and 120°C are tested respectively, and the battery's lift-to-drag ratio is calculated based on R2 / R1.

[0180] The above test results are shown in Table 2.

[0181] Table 2. Performance test results of magnesium metal batteries

[0182]

[0183] As shown in Table 2, in Examples 1-12, the tensile strength of the positive current collector ranged from 167 MPa to 186 MPa, and the peel strength of the positive electrode tab ranged from 7.1 N / 25 mm to 7.4 N / 25 mm. The tensile strength of the negative current collector ranged from 168 MPa to 185 MPa, and the peel strength of the negative electrode tab ranged from 7.6 N / 25 mm to 8.3 N / 25 mm. This indicates that the positive / negative current collectors of Examples 1-12 are composite current collectors, with a conductive support layer made of a conductive polymer fiber film, a primer layer made of conductive polymer B, and a conductive layer made of a metal material with good current collection performance. These composite current collectors exhibit high tensile strength, and the positive / negative tabs employing these positive / negative current collectors exhibit high peel strength, thereby improving the battery's cycling stability. After assembling the positive / negative electrode sheets into a magnesium metal battery, the initial discharge specific capacity is 148.3mAh / g~153.5mAh / g, the number of cycles when the capacity is reduced to 80% is more than 182 times, and the lift-to-drag ratio is 9.25~9.72. Overall, it has the characteristics of high capacity, good cycle stability and excellent safety performance.

[0184] (1) Negative electrode conductive layer: The negative electrode conductive layer of comparative example 1 adopts the traditional Cu layer, while the negative electrode conductive layers of Examples 1 to 3 respectively use Zr, Sc and Ti, which effectively improves the peel strength of the negative electrode sheet. This is because the lattice adaptation rate of the above metals with Mg is all below 10%, and they have a lattice locking effect on Mg, thereby improving the interaction between the negative electrode conductive layer and the negative electrode active layer, improving the peel strength of the negative electrode sheet, and thus effectively improving the capacity and cycle performance of the battery, especially the cycle stability.

[0185] (2) Negative electrode active layer: The negative electrode active layer of Example 4 uses a magnesium-germanium alloy. Compared with Example 1, the lattice locking effect of the negative electrode active layer is weakened, which reduces the peel strength of the negative electrode sheet and significantly reduces the capacity and cycle stability of the battery.

[0186] (3) Positive electrode active layer: Example 5 uses MnO2 as the positive electrode active material, which has a weak interaction with the positive electrode conductive layer, resulting in poor peel strength of the positive electrode sheet. In addition, MnO2 2+ The volume change during the insertion and extraction process is greater than that of MVO, and the positive electrode stability deteriorates, thereby reducing the capacity and cycle stability of the battery.

[0187] (4) Positive / negative electrode conductive support layer: From the comparison between Examples 1 and 6, it can be seen that the P3DDT fiber membrane has better strength, toughness and conductivity, which significantly improves the tensile strength and electronic conductivity of the current collector, and the battery cycle performance is better. Example 7 uses a conductive polymer film, and the tensile strength of the current collector is greatly reduced, and the battery cycle performance deteriorates. Example 8 uses a traditional polymer fiber membrane, and the tensile strength of the current collector is better than that of Example 7. Due to the poor conductivity of the polymer fiber membrane, it is easy to accumulate heat under high-rate and high-current working conditions, affecting the cycle stability of the battery, but it is beneficial to improve the safety performance of the battery.

[0188] (5) Negative electrode ion transport layer: Example 12 does not have a negative electrode ion transport layer, and the peel strength of the current collector, as well as the capacity, cycle performance and safety performance of the battery are all higher than those of Comparative Example 1. From Example 1 to Examples 9 to 11, the conductivity of the negative electrode ion transport layer gradually increases, the tensile strength of the negative electrode current collector and the peel strength of the negative electrode sheet do not change, the capacity and cycle performance of the battery first increase and then decrease, and the safety performance gradually weakens. Among them, the negative charge of the negative electrode ion transport layer of Example 11 is uniformly distributed. Compared with Examples 1 to 10, it lacks the Mg 2+ The acceleration of migration and transmission will not cause most of the Mg 2+ They accumulate on the surface of the negative electrode active layer, thereby reducing capacity and cycle performance.

[0189] In summary, the magnesium metal battery based on the composite current collector provided in this application has excellent cycle stability, can still maintain more than 80% of its capacity after 182 cycles, and has a high discharge specific capacity and excellent safety performance.

[0190] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0191] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of protection of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and such modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A magnesium metal battery based on a conductive composite current collector, characterized in that: The negative electrode comprises a negative electrode plate, wherein the negative electrode plate comprises a negative electrode current collector and a negative electrode active layer provided on at least one surface of the negative electrode current collector; The negative electrode current collector includes a negative electrode conductive support layer, a negative electrode primer layer disposed on at least one surface of the negative electrode conductive support layer, and a negative electrode conductive layer disposed on a surface of the negative electrode primer layer away from the negative electrode conductive support layer; The lattice mismatch rate between the negative electrode conductive layer and the negative electrode active layer is less than 10%; The negative electrode plate also includes a negative electrode ion transport layer with a negative charge, and the negative electrode ion transport layer is arranged on the surface of the negative electrode active layer away from the negative electrode current collector; the negative electrode ion transport layer includes a negative electrode material and a positive electrode material, the negative charge of the negative electrode material is greater than the positive charge of the positive electrode material, and the negative electrode ion transport layer includes a complex intermediate layer formed by electrostatic complexation between the negative electrode material and the positive electrode material. The concentration gradient of the positive electrode material in the complex intermediate layer decreases toward the negative electrode active layer, and the concentration of the negative electrode material remains unchanged, so that the negative charge in the negative electrode ion transport layer decreases gradually along the direction away from the negative electrode active layer.

2. The magnesium metal battery according to claim 1, wherein The material of the negative electrode conductive layer includes one or more of titanium, zirconium and scandium, and the material of the negative electrode active layer includes magnesium or a magnesium alloy.

3. The magnesium metal battery according to claim 2, wherein One or more of the following conditions are met: (1) The thickness of the negative electrode conductive layer is 0.5 μm to 5 μm; (2) The thickness of the negative electrode active layer is 0.5 μm to 10 μm.

4. The magnesium metal battery according to any one of claims 1 to 3, wherein The negative electrode conductive support layer includes a conductive polymer fiber membrane having a three-dimensional network structure formed by interweaving conductive polymer fibers. The negative electrode conductive support layer satisfies one or more of the following conditions: (1) The material of the conductive polymer fiber includes a conductive polymer A, and the conductive polymer A includes one or more of polypyrrole, polyaniline, poly(3,4-ethylenedioxythiophene), poly(3-hexylthiophene), poly(3-dodecylthiophene), poly(3-dodecylthiophene-3-hexyl-3-triethylene glycol) and poly(3-octylpyrrole):poly(styrene sulfonic acid); (2) The conductive polymer fiber has a length of 0.1 mm to 10 mm and a diameter of 200 nm to 1000 nm; (3) The conductive polymer fiber membrane has a pore size of 200 nm to 1000 nm and a porosity of 20% to 60%; (4) The thickness of the conductive polymer fiber film is 2 μm to 6 μm; (5) The preparation method of the conductive polymer fiber membrane includes an electrospinning method.

5. The magnesium metal battery according to any one of claims 1 to 3, wherein The negative electrode undercoat layer includes a conductive polymer B and a conductive agent B dispersed in the conductive polymer B.

6. The magnesium metal battery according to claim 5, wherein The negative electrode undercoat layer satisfies one or more of the following conditions: (1) The conductive polymer B includes one or more of polypyrrole, polyaniline, poly(3,4-ethylenedioxythiophene), poly(3-hexylthiophene), poly(3-dodecylthiophene), poly(3-dodecylthiophene-3-hexyl-3-triethylene glycol) and poly(3-octylpyrrole):poly(styrene sulfonic acid); (2) The conductive agent B includes one or more of an inorganic carbon material and a material containing a metal element; the inorganic carbon material includes one or more of conductive carbon black, conductive graphite, carbon quantum dots, carbon nanotubes, carbon nanofibers, graphene, and fullerene; the material containing a metal element includes one or more of copper, aluminum, nickel, gold, silver, and MXene materials; (3) The mass ratio of the conductive polymer B to the conductive agent B is 100:(1-50); (4) The thickness of the negative electrode bottom coating is 0.5 μm to 3 μm.

7. The magnesium metal battery according to any one of claims 1 to 3, wherein The conductivity of the negative electrode ion transport layer is 50S / cm~500S / cm.

8. The magnesium metal battery according to claim 1, wherein The negatively charged material includes one or more of organic carboxylic acid, organic carboxylate, carboxylated carbon nanotube, polyhydroxyfullerene and MXene material.

9. The magnesium metal battery according to claim 8, wherein The positively charged material includes one or more of chitosan and organic amine materials.

10. An electrical device, characterized in that: A magnesium metal battery comprising the magnesium metal battery according to any one of claims 1 to 9.

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