Magnesium metal battery based on conductive composite current collector and electric device

Abstract

The invention relates to the technical field of secondary batteries, in particular to a magnesium metal battery based on a conductive composite current collector and an electric device. The magnesium metal battery comprises a negative pole piece, wherein the negative pole piece comprises a negative current collector and a negative active layer arranged on at least one surface of the negative current collector; the negative electrode current collector comprises a negative electrode conductive supporting layer, a negative electrode bottom coating arranged on at least one surface of the negative electrode conductive supporting layer, and a negative electrode conductive layer arranged on the surface, deviating from the negative electrode conductive supporting layer, of the negative electrode bottom coating; the lattice mismatch rate of the negative electrode conductive layer and the negative electrode active layer is lower than 10%. The magnesium metal battery provided by the invention is excellent in cycle performance, and in some embodiments, the magnesium metal battery can still keep over 80% of capacity after 180 times of charge-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 put forward higher requirements on the energy density, cost and safety performance of secondary batteries. Multivalent metal batteries with elements such as calcium, magnesium, zinc and aluminum as active ions have attracted widespread attention due to their low cost, high storage capacity and high safety.

[0003] At present, magnesium metal batteries dominate multivalent metal batteries for the following reasons: magnesium is one of the most abundant elements in the world, and its price is low, which is conducive to reducing costs; magnesium is in a diagonal position with lithium in the periodic table, and the two have similar physical and chemical properties. Magnesium metal is non-toxic and safer than active alkali metals; the magnesium negative electrode has a low reduction potential, with a relative standard electrode potential of -2.37V (vs. SHE), and a high theoretical specific capacity (2205mAh / g). Therefore, magnesium metal batteries have broad development prospects in the fields of large-scale power grids, energy storage systems, and power batteries. However, traditional magnesium metal batteries have the problem of 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 the present 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 comprises a negative electrode conductive support layer, a negative electrode bottom coating 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 bottom coating 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(styrene sulfonic 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 thickness of the conductive polymer fiber film is 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 bottom coating 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(styrene sulfonic 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 bottom coating layer is 0.5 μm to 3 μm.

[0023] In some embodiments, the negative electrode plate further includes a negative electrode ion transport layer with a negative charge, and the negative electrode ion transport layer is disposed on a surface of the negative electrode active layer away from the negative electrode 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 in the present application, the negative electrode current collector in the negative electrode plate includes a negative electrode conductive support layer, a negative electrode bottom coating layer 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 negative electrode active layer to form a highly ordered crystal structure, thereby reducing interface defects and structural stress. In the charge and discharge cycle, the negative electrode conductive layer can also promote the uniform deposition and peeling of magnesium metal in the plane 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 arranged on the negative electrode bottom coating, which can increase the bonding force between the negative electrode conductive support layer and the negative electrode conductive layer, improve the peeling strength of the negative electrode current collector, and improve the flatness of the negative electrode conductive layer, so that the conductive current collection effect of the interface is better, and it is conducive to reducing the interface defects and structural stress of the negative electrode active layer, thereby improving the cycle stability of the battery. Therefore, the magnesium metal battery provided by the present 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 completely understand the present application and its beneficial effects, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative work.

[0033] Figure 1 It is a 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 plate 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] In order to facilitate the understanding of the present application, the present application is further described in detail below in conjunction with 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 make the understanding of the disclosure of the present application more thorough and comprehensive.

[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 belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0039] In the present 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 the present 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 above range is considered to be 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 features or characteristics, 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 included 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 also 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] The temperature parameters in this application, unless otherwise specified, are allowed to be either constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0044] In the present 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°C ± 2°C, 25°C ± 5°C or 20°C ± 5°C.

[0045] The pole piece is an important component of the secondary battery. The pole piece includes a current collector and an active layer arranged on at least one surface of the current collector. Among them, the current collector can be a metal foil or a composite current collector. The composite current collector includes a polymer layer and a metal layer arranged on both surfaces of the polymer layer, thereby forming a typical sandwich structure. Compared with metal foil, at the same thickness, the composite current collector is lighter in weight, and the energy density of the assembled secondary battery is higher.

[0046] For magnesium metal batteries, the active ions are magnesium ions (Mg 2+ ), usually magnesium or its alloy is used as the negative electrode active material. During the charge and discharge process, the deposition and stripping of magnesium metal causes the continuous 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, the magnesium metal battery includes a negative electrode sheet, the negative electrode sheet 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 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 in the present application, the negative electrode current collector in the negative electrode plate includes a negative electrode conductive support layer, a negative electrode bottom coating layer 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 negative electrode active layer to form a highly ordered crystal structure, thereby reducing interface defects and structural stress. In the charge and discharge cycle, the negative electrode conductive layer can also promote the uniform deposition and peeling of magnesium metal in the plane 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 arranged on the negative electrode bottom coating, which can increase the bonding force between the negative electrode conductive support layer and the negative electrode conductive layer, improve the peeling strength of the negative electrode current collector, and improve the flatness of the negative electrode conductive layer, so that the conductive current collection effect of the interface is better, and it is conducive to reducing the interface defects and structural stress of the negative electrode active layer, thereby improving the cycle stability of the battery. Therefore, the magnesium metal battery provided by the present 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, a magnesium metal battery is a type of multivalent metal battery in a secondary battery, which includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the battery charge and discharge process, the active ion Mg 2+ Deposition and stripping are repeated 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 separator 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 make the Mg 2+ pass.

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

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

[0056] It can be understood that the negative electrode current collector 10 has two surfaces opposite to 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 some 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, 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 a 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 bottom coating 12 is arranged on two opposite surfaces of the negative electrode conductive support layer 11. However, the present application is not limited thereto. In some other examples, the negative electrode bottom coating 12 can also be arranged 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 bottom coating 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. It has been reported that conductive polymer films are used to optimize the conductivity of composite current collectors, but their poor mechanical properties and low ductility will also affect the cycle stability of the battery. Therefore, the present application adopts a conductive polymer fiber film as the negative electrode conductive support layer 11, which is a three-dimensional network structure formed by the arrangement and interweaving of conductive polymer fibers, has excellent mechanical strength, high ductility and high conductivity, and can also achieve a weight reduction effect, which is conducive to the lightweight 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(styrene sulfonic 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 polyvinyl pyrrolidone (PVP), sodium polyacrylate (PAAS), sodium lignin sulfonate, and sodium polystyrene sulfonate (PSS).

[0064] In some embodiments, the mass ratio of conductive polymer A to 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 material of the conductive polymer fiber further includes a conductive agent A, and the conductive agent A includes one or more of an inorganic carbon material and a material containing a metal element. Thus, the conductive agent A can further enhance the conductive properties of the conductive polymer fiber membrane, inhibit the heat generation effect under high rate and high current conditions, and thus improve the cycle stability of the battery.

[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 fullerene. As an example, the conductive carbon black can 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, M includes 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, T includes one or more of -OH, -F and -O, x represents the number of T, x>0. As an example, MXene materials can be selected from Ti 3 C 2 T x 、Ti 2 CT x 、Ti 3 CNT x 、 4 C 3 T x 、V 2 CT x 、V 3 C 2 T x 、Mo 2 CT x Or Mo 2 TiC 2 T 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, it can be 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 fiber has a length of 0.1 mm to 10 mm and a diameter of 200 nm to 1000 nm. As an example, the conductive polymer fiber can 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 pore size of the conductive polymer fiber membrane is 200nm~1000nm, and the porosity is 20%~60%. As an example, the pore size of the conductive polymer fiber membrane can be 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm or 1000nm, and the porosity can be 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 electrostatic spinning method. Specifically, the conductive polymer fiber can be prepared by the following method: disperse the conductive polymer A, dispersant A and conductive agent A in a solvent, stir at 40°C to 80°C for 6h to 24h to form a uniform spinning solution; control the feed rate to 0.1mL / h to 5mL / h and the working voltage to 10kV to 20kV, and perform electrostatic spinning to form a 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 lightweight of the current collector; the negative electrode bottom coating layer 12 provides a continuous film 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 peeling 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, and 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, so that the negative electrode bottom coating 12 has good conductivity and a more significant positive temperature coefficient (PTC) effect. Conductive polymer B realizes the PTC effect based on the doping and dedoping mechanism of anions. Conductive polymer B will undergo anion dedoping at the high temperature critical temperature, thereby causing disorder of the polymer main chain and a sharp increase in resistance. This process does not involve changes in the main chain of conductive polymer B and has a certain degree of reversibility. The introduction of conductive agent B also promotes the doping and dedoping reactions 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(styrene sulfonic acid) (P3OPy:PSS).

[0080] In some embodiments, the conductive agent B includes one or more of an inorganic carbon material and a material containing a metal element. The types of the inorganic carbon material and the material containing a metal element in the conductive agent B are substantially the same as those of the conductive agent A, and are not described in detail herein. Further, the conductive agent B includes 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 PVDF may be further selected.

[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 may 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 may 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 bottom coating 12 is prepared by the following method: dissolving the conductive polymer B in a solvent, adding the conductive agent B and the binder B, and ultrasonically dispersing for 0.5h to 3h to obtain a dispersion; applying the dispersion on the surface of the negative electrode conductive support layer 11 by a doctor blade method, and vacuum drying at 60°C to 100°C for 24h to 48h. The solvent of the dispersion can be toluene, chloroform, etc., 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). The three metal elements Ti, Zr and Sc not only have good conductivity, but also have a unit cell structure that is the same as that of Mg, and both belong to a hexagonal close packed (HCP) structure, and the lattice constant is closest to that of Mg, which is conducive to 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: vacuumizing to ≤ (2~8)×10 -5 Pa, an inert gas is introduced at a flow rate of 50 sccm to 100 sccm, and a DC magnetron sputtering coating 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 base coating 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 a magnesium silicon alloy (MgSi), a magnesium germanium alloy (MgGe) or a magnesium tin alloy (MgSn). Further, the negative electrode active layer 20 is Mg.

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

[0091] As an example, the in-plane lattice constant of Ti (a=b) is 2.95Å, the lattice constant of Zr is 3.23Å, and the in-plane lattice constant of Sc is 3.30Å, and 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 called anchoring effect, pinning effect, etc.), which can promote the negative electrode active layer 20 to form a highly ordered crystal structure through epitaxial growth, thereby reducing interface defects and structural stress. In addition, during the charge and discharge cycle, the negative electrode conductive layer 13 can also promote the uniform deposition and stripping of magnesium metal in the plane through the lattice locking effect, thereby effectively improving the capacity, rate and cycle performance of the battery.

[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: vacuumizing to ≤ (2~8)×10 -5 Pa, an inert gas is introduced at a flow rate of 50 sccm to 100 sccm, and a DC magnetron sputtering coating 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, and a negative active layer 20 is epitaxially grown 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, Figure 3 As shown, the negative electrode plate further includes a negative electrode ion transport layer 30 with negative charge, and the negative electrode ion transport layer 30 is arranged on the surface of the negative electrode active layer 20 away from the negative electrode 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 MgO will cause harmful side reactions when approaching the magnesium metal negative electrode, which will deteriorate the electrochemical performance of the battery. However, the present application 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 MgO to 2+ On the other hand, it can also prevent corrosive anions from approaching the negative electrode active layer 20 through electrostatic repulsion, thereby inhibiting the occurrence of harmful side reactions.

[0096] In some embodiments, the negative charges in the negative electrode ion transport layer 30 are uniformly distributed. It can be understood that the negative charges are uniformly distributed, which means that the amount of negative charges in the negative electrode ion transport layer 30 is substantially consistent in the thickness direction, and there is no difference in concentration and potential between the two opposite 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 from the negative electrode active layer 20, it is impossible to provide fast and sufficient Mg 2+ supply, which easily forms pores during the deposition process and is not conducive to uniform deposition. 2+ It will also be evenly distributed in the negative electrode ion transport layer 30, and the deposition uniformity of the magnesium metal is improved compared with the example of gradient 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+ Aggregated 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, negatively charged materials refer to materials that carry a negative charge in a solution environment, and positively charged materials refer to materials that carry a positive charge in a solution environment. The solution environment may be water, an organic solvent, or a solution dispersed with an electrolyte salt. In magnesium metal batteries, the solution environment refers to an electrolyte.

[0102] The Zeta potential test method can usually be used to characterize the surface charge of the 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) can carry negative charges (-O - and -COO - ). Halogens (-F, -Cl, -Br or -I) have high electronegativity and can make the surface of materials negatively charged. Oxygen-metal bonds (-O, or MO bonds) are stable chemical bonds formed by oxygen atoms combining with surface metal atoms through substitution or adsorption. Oxygen atoms have high electronegativity, which makes the surface of materials have a certain degree of negative charge, especially in solution environments.

[0104] In some embodiments, the negatively charged material includes one or more of organic carboxylic acid, organic carboxylate salt, carboxylated carbon nanotube, polyhydroxy fullerene and MXene material. Among them, organic carboxylic acid and its salt can form negatively charged -COO in solution environment. - 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 salts thereof (such as sodium salt, potassium salt, etc.). In addition, carboxylated carbon nanotubes contain a large number of carboxyl groups, polyhydroxyfullerenes contain a large number of hydroxyl groups, and MXene materials contain a large number of active functional groups, such as -OH, -F or -O, which can carry negative charges through deprotonation or adsorption, and 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 (-NH 2 ), can undergo protonation reaction in solution environment and still have positive charge (-NH 3 + ). The organic amine material usually 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, it can be 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 a negative electrode ion transport layer 30. Among them, 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, the negative electrode ion transport layer 30 does not contain any positively charged material, 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 positively charged material and the negatively charged material 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] Among them, the solvents of the positive precursor solution and the negative precursor solution independently include deionized water, ethanol, etc., the concentration of the negative material is 1mmol / L~10mmol / L, and the concentration of the positive material is 0.1mmol / L~9.6mmol / 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 precursor solution and / or the positive precursor solution can 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, which are environmentally friendly and inexpensive.

[0113] Therefore, after the positively charged precursor droplets are coated on the surface of the liquid film, the protonated functional groups of the positively charged material (such as -NH 3 + ) and the deprotonated functional groups of negatively charged materials (such as -O - 、-COO - ) Electrostatic complexation begins 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 intensity of the electrostatic complex 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, so that 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, and 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, and the positive electrode primer layer can be arranged on 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 sequentially stacked from bottom to top. Among them, the structure, material 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, material and preparation method of the positive electrode primer layer are basically the same as those of the negative electrode primer layer 12, and this application will not repeat them.

[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 examples, transition metal oxides include vanadium oxides and manganese dioxide (MnO 2 ) or more thereof. Among them, the vanadium oxide compound includes vanadium pentoxide (V 2 O 5 ) and layered vanadium oxides with ion pre-intercalation, such as Mg with magnesium ion pre-intercalation 0.3 V 2 O 5 1.1H 2 O, Mn with Mn ion pre-intercalation 0.04 V 2 O 5 1.17H 2 O 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 VS 2 VS 4 etc., the cobalt sulfide may be selected from Co 3 S 4 , the molybdenum sulfide can be selected from MoS 2 、Mo 6 S 8 wait.

[0123] As an example, transition metal phosphates include vanadyl phosphate (VOPO) having a layered structure. 4 ) and sodium fast ion conductor (NASICON) type Mg 0.5 Ti 2 (PO 4) 3 wait.

[0124] As an example, transition metal silicates include polyanionic Mg x M y SiO 4 , where M is selected from transition metals such as Fe, Mn, Co, Ni, and x+y=2, for example, MgCoSiO 4 .

[0125] In some embodiments, the positive electrode active layer may include a modified positive electrode material, and the modified positive electrode material 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 described above to promote the Mg 2+ The migration and diffusion of the modified positive electrode material can be improved, and the transmission kinetics of the modified positive electrode material can be improved. The positive electrode material in the inner core can be protected to prevent the dissolution of transition metal elements and ensure its structural stability, thereby improving the cycle stability of the battery.

[0126] In some embodiments, the positive electrode active layer further includes a positive electrode conductor and a positive electrode binder, and the mass ratio of the positive electrode material (or modified positive electrode material), the positive electrode conductor and the positive electrode binder is (6-9): (0.5-2.5): (0.5-1.5), and can further be 7:2:1. Among them, the positive electrode binder includes 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 can further be PVDF. The positive electrode conductor includes one or more of conductive carbon black, conductive graphite, acetylene black, Ketjen black, carbon quantum dots, carbon nanotubes, graphene and carbon nanofibers, and can further be 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 collector, and obtaining a positive electrode sheet after drying, rolling and cutting.

[0128] Below 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 uses an electrolyte solution including a magnesium salt and a solvent.

[0131] In some embodiments, the magnesium salt comprises magnesium chloride (MgCl 2 )、Magnesium sulfate(MgSO 4 )、Mg(NO 3 ) 2 )、Magnesium perchlorate(Mg(ClO 4 ) 2 ), calcium bis(trifluoromethanesulfonyl)imide (Mg(TFSI) 2 ), one or more of organic aluminum magnesium salts and organic boron magnesium salts. Among them, the organic aluminum magnesium salt can be selected from (PhMgCl) 2 -AlCl 3 Mg(AlCl 2 EtBu) 2 etc., the organic boron magnesium salt can be selected from (PhMgCl) 2 -BR 3 etc., Ph represents phenyl, and R represents 3,5-xylyl.

[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 material of the isolation membrane includes one or more of glass fiber (GF), non-woven fabric, polyethylene (PE), polypropylene (PP) and polyimide (PI). It can be understood that the isolation membrane can be a single-layer film or a multi-layer composite film. If the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different without special restrictions.

[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 comprises an outer package for encapsulating the electrode assembly and the electrolyte. The outer package of the magnesium metal battery comprises one or more of a hard shell and a soft package. The hard shell may be a hard plastic shell, an aluminum shell, a steel shell, etc., and the soft package may be a bag-type soft package or a plastic soft package.

[0138] The present application also provides a battery module, which includes a housing and a plurality of magnesium metal batteries disposed inside the housing. In the battery module, the plurality of magnesium metal batteries may be arranged in sequence along the length direction of the battery module, and the number of magnesium metal batteries may be determined according to 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 arranged 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, which includes the magnesium metal battery as described above. The magnesium metal battery can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto. Among them, the mobile device may be, for example, a mobile phone, a laptop computer, etc.; the electric vehicle may be, for example, 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., but are not limited thereto.

[0141] The following is further described in conjunction with specific embodiments and comparative examples. The raw materials involved in the following specific embodiments and comparative examples, unless otherwise specified, can all be commercially available, the instruments used, unless otherwise specified, can all be commercially available, and the processes involved, unless otherwise specified, are all routinely selected by those skilled in the art.

[0142] Example 1

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

[0144] (1) Preparation of positive electrode sheet:

[0145] Polypyrrole (PPy) and dispersant PVP were dispersed in chloroform at 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 to 1 mL / h and the working voltage was controlled to 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 working gas pressure of 2 Pa and working power of 150 W to form a 1 μm thick Al layer as a positive electrode metal layer on the surface of the positive electrode base coating to obtain a positive electrode current collector.

[0148] The positive electrode material Mg 0.3 V 2 O 5 1.1H 2 O (MVO), conductive carbon black SP and binder PVDF are evenly 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 collector, and the positive electrode sheet is obtained after drying, rolling and cutting.

[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 working gas pressure of 1.2 Pa and 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, a DC magnetron sputtering coating was carried out 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 coated on the surface of the liquid film, CS diffused into the negative electrode active layer and reacted with SA by electrostatic complexation, 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: Organic aluminum magnesium salt (PhMgCl) 2 -AlCl 3 Dissolved 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, O 2 The positive electrode sheet, the separator and the negative electrode sheet are packaged with an aluminum-plastic film, dried and dehydrated, and then the electrolyte is injected and then sealed. After standing, hot and cold pressing, formation, clamping, capacity division and other processes, a magnesium metal battery is obtained.

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

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

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

[0162] Example 5: The positive electrode material is MnO 2 .

[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] Embodiment 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: The SA concentration is 5 mmol / L, and the 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] Embodiment 12: No negative electrode ion transport layer is provided.

[0170] Comparative Example 1: The material of the negative electrode conductive layer is 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 performed 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 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 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 battery's first discharge specific capacity 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 are tested at 25°C and 120°C 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 to 12, the tensile strength of the positive current collector is 167 MPa to 186 MPa, the peel strength of the positive electrode sheet is 7.1 N / 25 mm to 7.4 N / 25 mm, the tensile strength of the negative current collector is 168 MPa to 185 MPa, and the peel strength of the negative electrode sheet is 7.6 N / 25 mm to 8.3 N / 25 mm. It can be seen that the positive / negative current collectors of Examples 1 to 12 are composite current collectors, the conductive support layer uses a conductive polymer fiber film, the bottom coating layer uses a conductive polymer B, and the conductive layer uses a metal material with a good current collection effect, showing the advantage of high tensile strength. The positive / negative electrode sheet using the above-mentioned positive / negative current collector has a high peel strength, which is beneficial to improving the cycle stability of the battery. 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 embodiments 1 to 3 respectively select Zr, Sc and Ti, so that the peel strength of the negative electrode plate is effectively improved. This is because the lattice matching rate of the above metals with Mg is less than 10%, which has 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 plate, and 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, so that the peel strength of the negative electrode sheet is reduced, and the capacity and cycle stability of the battery are also significantly reduced.

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

[0187] (4) Positive / negative 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, 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, which affects the battery cycle stability, but is beneficial to improving the battery safety performance.

[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 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, and compared with Examples 1 to 10, it lacks the Mg 2+ The acceleration of migration and transport will not cause most of the Mg 2+ They accumulate on the surface of the negative electrode active layer, thus reducing capacity and cycle performance.

[0189] In summary, the magnesium metal battery based on the composite current collector provided in the present 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-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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 only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of protection of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the scope of protection of the present application. Therefore, the scope of protection of the present application shall be subject to the attached claims.

Claims

1. A magnesium metal battery based on a conductive composite current collector, characterized in that: A negative electrode sheet is included, wherein the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer disposed on at least one surface of the negative electrode current collector; The negative electrode current collector comprises a negative electrode conductive support layer, a negative electrode bottom coating 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 bottom coating 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%.

2. The magnesium metal battery according to claim 1, characterized in that 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, characterized in that: 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, characterized in that The negative electrode conductive support layer comprises a conductive polymer fiber membrane, wherein the conductive polymer fiber membrane has a three-dimensional network structure formed by interweaving conductive polymer fibers, and 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 pore size of the conductive polymer fiber membrane is 200nm~1000nm, and the porosity is 20%~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, characterized in that 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, characterized in that The negative electrode bottom coating 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, 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; (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, characterized in that The negative electrode plate further comprises a negative electrode ion transport layer with negative charge, wherein the negative electrode ion transport layer is arranged on a surface of the negative electrode active layer away from the negative electrode current collector; 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.

8. The magnesium metal battery according to claim 7, characterized in that 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.

9. The magnesium metal battery according to claim 8, characterized in that The negative electrode ion transport layer further comprises a positive material, wherein the negative charge of the negative material is greater than the positive charge of the positive material; 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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