Coating for magnesium batteries

Abstract

The invention provides a magnesium anode and an electrochemical cell comprising the anode.

Description

[0001] This invention relates to an anode comprising a body containing or substantially composed of a conductive material and a protective layer disposed on at least one surface of the body, wherein the protective layer comprises silylated cellulose (optionally containing at least one ionicly conductive additive) and a solvent or thereof, the solvent causing at least one ionicly conductive additive present in the protective layer to form a solvate. The invention also relates to an electrochemical cell comprising the anode of this invention, and to a method for coating a surface with a conductive material. Background Technology

[0002] Further development of vehicle exhaust management is needed to reduce adverse impacts on the global environment. Therefore, specifically, electric power is playing an increasingly important role in avoiding vehicle exhaust emissions.

[0003] For years, lithium-ion batteries have become the most commonly used rechargeable batteries in many modern applications such as laptops, mobile phones, and other portable devices. Moreover, for electric and hybrid vehicles, lithium-ion batteries have been provided at what is considered an acceptable cruising range, thus preparing the market for mass adoption of electric power.

[0004] WO 2020 / 007980 discloses the preparation of a trimethylsilyl cellulose coating containing ion-conducting additives on the surface of a lithium metal anode.

[0005] Due to the high cost and low availability of lithium, there is an urgent need for lithium alternatives, and researchers are attempting to replace expensive lithium with less expensive, highly abundant materials that allow for the fabrication of rechargeable batteries with even higher capacities. In the last decade, materials such as aluminum, zinc, and magnesium have shown promise, offering better storage capacities than lithium in terms of specific energy. All such materials are readily available in large quantities and will be needed as electrodynamics further develops.

[0006] DE 10 2019 219 007 describes a method for producing a magnesium-based powdered material for use in electrochemical cells, as well as a negative electrode and a composite electrode comprising such a magnesium-based powdered material, and an electrochemical cell comprising such a negative electrode or a composite electrode. Summary of the Invention

[0007] According to a first aspect, the present invention provides an anode comprising a body containing or substantially composed of a conductive material and a protective layer disposed on at least one surface of the body, wherein the protective layer comprises silylated cellulose (optionally containing at least one ionicly conductive additive) and a solvent or thereof, the solvent causing at least one ionicly conductive additive present in the protective layer to form a solvate.

[0008] A second aspect of the invention relates to an electrochemical battery comprising an anode, a cathode, a separator inserted between the anode and the cathode as described herein, and an electrolyte, wherein the protective layer is positioned on the electrolyte-facing side of the anode.

[0009] A third aspect of the invention relates to a method for coating the surface of a conductive material, specifically the surface of an electrode, with silyl cellulose or silyl cellulose containing at least one ionic conductive additive, the method comprising (i) cleaning the surface of the conductive material to prevent any natural passivation layer and impurities, (ii) optionally smoothing the clean surface, (iii) depositing a solution of silyl cellulose or a solution of silyl cellulose containing at least one ionic conductive additive on the surface, and (iv) evaporating the solvent, wherein the conductive material comprises at least one of Mg, Zn, Ca, Al, K, and Na.

[0010] In a fourth aspect, the present invention relates to the use of silylated cellulose, optionally containing at least one ionic conductive additive, as a protective layer on the surface of a conductive material, particularly on the anode surface, wherein the at least one ionic conductive additive present in the protective layer forms a solvate with a solvent. Detailed Implementation

[0011] Prior art discloses the preparation of a trimethylsilyl cellulose coating comprising an ion-conducting additive on the surface of a lithium metal anode. Lithium metal anodes comprising such a coating can function in electrochemical cells without a liquid electrolyte.

[0012] In this invention, the inventors observed that anodes containing other metals, such as magnesium, can be produced as trimethylsilyl cellulose containing ion-conducting additives. Considering applications with other metals, the inventors have found that a solvent is needed to form solvates of the ion-conducting additives in the silyl cellulose. Specifically, the solvent causes crystals in the layer to form solvates and imparts ion conductivity to those solvated crystals.

[0013] The anode surface, specifically the Mg anode surface, can be protected by silylated cellulose. The pores of the silylated cellulose can be filled with a conductive salt, which is solid and seals the pores. The surface is conductive and ensures ion transport without introducing any other substances. This invention...

[0014] - To prevent passivation of the anode surface, specifically the Mg surface, thus achieving stable performance.

[0015] - Improve the deposition of metals, specifically Mg, making it more uniform, and / or

[0016] - Allows the use of Cl-free electrolytes, thus eliminating the corrosion problem in electrochemical cells, specifically Mg electrochemical cells.

[0017] In a first aspect, the present invention provides an anode comprising a body comprising or substantially composed of a conductive material and a protective layer disposed on at least one surface of the body, wherein the protective layer comprises silylated cellulose (optionally comprising at least one ionicly conductive additive) and a solvent or thereof, the solvent causing at least one ionicly conductive additive present in the protective layer to form a solvate.

[0018] According to a preferred embodiment, the conductive material of the anode comprises at least one selected from Mg, Zn, Ca, Al, K, and Na. In a preferred embodiment, lithium is not included. Magnesium is particularly preferred.

[0019] “Magnesium” and “Mg” are used interchangeably in this article.

[0020] This invention provides protection for metal anode surfaces, specifically Mg anode surfaces, using silylated cellulose or cellulose derivatives. The pores in the silylated cellulose, i.e., the protective layer, can be filled with ion-conductive additives, such as salts, to seal the pores. Embodiments comprising conductive salts are preferred herein.

[0021] The solvent causes the ion-conducting additives added to the silylated cellulose to form a solvate. In this way, the surface is conductive and ensures ion transport without introducing any other substances.

[0022] This invention provides a coated anode as described herein and an electrochemical cell comprising such an anode. The coating as described herein prevents passivation of the anode surface, specifically the Mg surface, thereby achieving stable performance. Specifically, the coated Mg anode as described herein allows the use of a Cl-free electrolyte, thus eliminating corrosion problems in electrochemical cells, and specifically in Mg electrochemical cells.

[0023] The conductive material of the anode body may be composed of materials selected from magnesium metal, magnesium metal alloys, and any magnesium powder-based material, including magnesium alloy powder. Other metals that may be contained in the magnesium alloy used in this invention include Zn, Al, Si, and / or Mn, or any combination thereof such as Al-Zn or Al-Si. Preferably, the Mg metal alloy or alloy powder according to the invention does not contain Li. Those skilled in the art will understand that "does not contain" in the context does not exclude unavoidable Li impurities.

[0024] For example, the anode body can be a magnesium foil with a thickness of no more than 1,000 μm, preferably no more than 500 μm.

[0025] In a particularly preferred embodiment of the anode according to the invention, the body is composed of conductive material Mg, wherein the protective layer is composed of silylated cellulose.

[0026] At least one conductive additive may specifically be a salt of a conductive material.

[0027] At least one ionic conductive additive may be present in the protective layer, wherein the mass ratio of the ionic conductive additive to silyl cellulose is 1 to 10, preferably 3 to 8, and most preferably 5.

[0028] At least one conductive additive, including one or more salts of the conductive materials described herein, may contain anions selected from the group consisting of: borohydrides, bis(trifluoromethane)sulfonylimide, bis(fluorosulfonyl)imide, chlorides, (BH4)(NH2), hexafluoroisopropylborate, 2-trifluoromethyl-4,5-dicyanoimidazole, closed-type dodecoborate family anions, pentacyanoborate, bis(hexamethyldisilazane), perchlorate, bromides, iodides, B(OR) x )4 and hexafluorophosphate.

[0029] At least one conductive additive may specifically be a magnesium salt, preferably a magnesium salt selected from the group consisting of: Mg(BH4)2 (magnesium hydrogen borate), Mg(TFSI)2 (magnesium bis(trifluoromethane)sulfonylimide), Mg(FSI)2 (magnesium bis(fluorosulfonyl)imide), MgCl2 (magnesium chloride), Mg(BH4)(NH2), Mg[B(hfip)4]2 (magnesium hexafluoroisopropylborate), Mg(TDI)2 (2-trifluoromethyl-4,5-dicyanimidazolium magnesium), Mg[RB 12 H 11 (Closed-type magnesium dodecoborate family), MgB(CN)5 (magnesium pentacyanoborate), Mg(HMDS)2 (bis(hexamethyldisilazane)magnesium), Mg(ClO4)2 (magnesium perchlorate), MgBr2 (magnesium bromide), MgI2 (magnesium iodide), Mg(B(OR) x )4)2, Mg(PF6)2 (magnesium hexafluorophosphate), or any combination thereof, most preferably Mg(BH4)2, or the corresponding salt of calcium or zinc.

[0030] Particularly preferred is that at least one conductive salt is a Na or K salt, preferably one or more of the following: nitrate, tetrafluoroborate, perchlorate, hexafluoroborate, thiocyanate hydrate, trifluoromethane sulfonate, bis(trifluoromethane)sulfonylimide, bis(fluorosulfonyl)imide, tetracyanoborate, bis(oxalate)borate, 4,5-dicyano-1,2,3,triazolate, or 2-trifluoromethyl-4,5-dicyanoimidazolium.

[0031] According to another preferred embodiment, at least one ionic conductive additive is an aluminum salt, which may preferably be one or more of AlCl3, Al(TFSI)3, Al(PF6)3, Al(FSI)3, Al(ClO4)3, AlBr3, and any combination thereof.

[0032] According to another preferred embodiment, the Mg anode described herein is used in combination with at least one Li conductive salt. Preferred Li conductive salts are selected from the group consisting of: Li(BH4), LiNO3, LiBF4, LiClO4, LiPF6, LiTf, LiSCN, LiTFSI, LiFSI, LiB(CN)4, LiBOB, LiDCTA, LiTDI, and any combination thereof.

[0033] Any conductive salts described herein can be combined, provided that the resulting mixture is chemically stable and / or inert.

[0034] The thickness of the protective layer can preferably be in the range of 100 nm to 500 μm, more preferably in the range of 10 μm to 50 μm, and even more preferably in the range of 1 μm to 10 μm.

[0035] To achieve good functionality, the protective layer preferably has high ionic conductivity, but at the same time, it must be impermeable to other battery components.

[0036] The silylated cellulose (also called silyl cellulose) used in the protective layer of the present invention can, in principle, be any reaction product of cellulose and a silylating agent. In the silylated cellulose, one or more hydroxyl groups of the glucose units forming cellulose are replaced with silyl groups. In principle, up to three hydroxyl groups can be replaced. According to the present invention, the silylated cellulose preferably contains 0.5 to 3 silyl groups per glucose unit in each cellulose. More preferably, it contains 2 to 3 silyl groups per glucose unit. The silyl groups can be the same or different -SIR3 groups, wherein each R can be the same or different. Preferred residues R are independently selected from the group consisting of: alkyl, cycloalkyl, alkenyl, alkoxy, aryl, and alkylaryl. The alkyl group can have 1 to 12 carbon atoms (C1 to C2). 1-12 Alkyl groups, specifically 1 to 4 carbon atoms (C 1-4 Alkyl groups. Cycloalkyl groups can have 3 to 12 carbon atoms (C60-122 carbon atoms). 3-12 Cycloalkyl). Alkenyl groups can have 2 to 12 carbon atoms (C60-124 carbon atoms). 2-12 Alkyl groups can have 1 to 12 carbon atoms (C1 to C2). 1-12 Alkoxy groups, specifically 1 to 4 carbon atoms (C 1-4 Alkyl groups can have 6 to 12 carbon atoms (C66-124 ... 6-12 Aryl groups can have 7 to 13 carbon atoms (C66).7-13 Alkyl aryl). Particularly preferred are alkyl residues, specifically C10. 1-4 Alkyl group. According to a particularly preferred embodiment, the alkyl group is methyl.

[0037] Silylated cellulose can be derived from microfibrillated cellulose or nanofibrillated cellulose, microcrystalline cellulose or nanocrystalline cellulose or bacterial cellulose. Nanofibrillated cellulose is preferred.

[0038] According to a particularly preferred embodiment, silyl cellulose, specifically a silyl cellulose-based membrane, is prepared using silyl cellulose nanofibers (“TMSC” - trimethylsilyl cellulose) and magnesium borohydride in organic solvents such as tetrahydrofuran, dimethyl sulfoxide, propylene carbonate, chloroform, polyvinyl ether, or other solvents compatible with Mg. Tetrahydrofuran is particularly preferred. For such TMSC-salt membranes serving as a protective layer on a conductive material (specifically Mg), a dried thickness of 20 μm to 40 μm is preferred, specifically about 30 μm.

[0039] In a preferred embodiment, the solvent in which at least one ionicly conductive additive present in the protective layer forms a solvate is selected from polar aprotic solvents. Such preferred solvents may be tetraethylene glycol dimethyl ether (2,5,8,11,14-pentapentadecane), ethylene glycol dimethyl ether (1,2-dimethoxyethane), diethylene glycol dimethyl ether (1-methoxy-2-(2-methoxyethoxy)ethane), triethylene glycol dimethyl ether (1,2-bis(2-methoxyethoxy)ethane), THF (tetrahydrofuran), PC (propylene carbonate), EC (ethylene carbonate), ACN (acetonitrile), DMSO (dimethyl sulfoxide), sulfolane (tetrahydrothiophene-1,1-dioxide), DMF (dimethylformamide), NMP (N-methylpyrrolidone), and most preferably include tetraethylene glycol dimethyl ether. Of course, any suitable mixture of such solvents is also within the scope of this invention.

[0040] The polar aprotic solvent may also be included in the electrolyte in an amount of 10 vol% to 100 vol%, more preferably 30 vol% to 70 vol%, and in a most preferred embodiment in an amount of about 50 vol%.

[0041] A second aspect of the invention relates to an electrochemical battery comprising an anode, a cathode, a separator inserted between the anode and the cathode as described herein, and an electrolyte, wherein the protective layer is positioned on the electrolyte-facing side of the anode.

[0042] The electrochemical cell according to the invention may include a negative current collector on the opposite side of the anode from the electrolyte and / or a positive current collector on the opposite side of the cathode from the electrolyte. Such current collectors are preferably made of conductive materials that are inert to the materials of the anode and cathode, respectively. According to a preferred aspect of the invention, the electrochemical cell is a magnesium battery, specifically a magnesium secondary battery.

[0043] Negative current collectors may include, for example, metal foil, metal mesh, or metal strips, wherein the metal may be nickel, copper, or stainless steel. Positive current collectors may include, for example, carbon-coded aluminum foil or mesh.

[0044] In principle, any common material can be used as the cathode. For example, the cathode can contain magnesium or any other metal intercalation compound, sulfur, and / or redox-active organic compounds, either as a single-phase material or as a mixed material, such as mixed with carbon or other conductive compounds and binders. According to a preferred embodiment, the cathode can also be protected with a protective layer as described herein.

[0045] The electrochemical cell of the present invention may have a cathode, a membrane impregnated with electrolyte, and a magnesium metal anode with a protective layer, the protective layer being disposed between the magnesium metal anode and the membrane impregnated with electrolyte.

[0046] In principle, the diaphragm can be made of any common material suitable for separating the anode and cathode compartments. For example, the diaphragm may include a porous membrane impregnated with electrolyte.

[0047] Any suitable electrolyte can be used. For example, a polar solvent containing a dissolved salt, such as a magnesium salt, can be used as the electrolyte. However, any other electrolyte material is also suitable. Preferably, the electrolyte is Cl-free, thus eliminating the corrosion problem in electrochemical cells, specifically Mg cells. Moreover, in such electrochemical cells that do not contain Cl-containing electrolytes, the performance of the Mg anode, as protected herein, is stable.

[0048] Ideally, magnesium should not react with the electrolyte medium used.

[0049] A third aspect of the invention is a method for coating a surface of a conductive material. Methods for coating a surface of a conductive material using silylated cellulose or silylated cellulose containing at least one ionic conductive additive are described, for example, in WO 2020 / 007980, which is incorporated herein by reference.

[0050] Specifically, the method of the present invention for coating a surface of a conductive material (e.g., Mg) with silyl cellulose or silyl cellulose containing at least one ionic conductive additive may include...

[0051] (i) Clean the surface of the conductive material to prevent any adverse passivation layer and impurities.

[0052] (ii) Optionally, the cleaned surface may be smoothed.

[0053] (iii) A solution of silylated cellulose deposited on the surface, or a solution of silylated cellulose further comprising at least one ion-conducting additive, and

[0054] (iv) Evaporate the solvent.

[0055] This method provides a simple and direct preparation and coating technique. The method can provide protection for electrodes based on metallic Mg, Mg alloys, and / or Mg powder.

[0056] The coated silyl cellulose-based film exhibits excellent adhesion to conductive materials, such as TMSC-films on Mg-surfaces. The film thickness is adjustable. Preferably, the surface of the conductive material is substantially completely covered.

[0057] Before forming the protective layer, the surface to be coated, specifically the magnesium surface, is desiredly activated. For this purpose, the surface is cleaned in step (i) to remove any passivation layer and impurities. Activation increases the reactivity of the surface and in this way enhances the adhesion between the magnesium material and the protective layer of silyl cellulose or silyl cellulose containing at least one ionicly conductive additive. Activation can be performed by extrusion from an ingot or by mechanically scraping the surface.

[0058] Following the cleaning step, in step (ii), the surface is optionally smoothed, for example by rolling it with a roller to align the surface. The surface should be activated and cleaned of the natural passivation layer and impurities, and ultimately smoothed so that the protective layer adheres well.

[0059] In subsequent step (iii), a solution of silyl cellulose, or a solution of silyl cellulose containing at least one ionicly conductive additive, is deposited onto a clean and optionally smoothed surface. Thus, silyl cellulose or another silyl cellulose and at least one ionicly conductive additive are dissolved in a suitable solvent, and the surface is brought into contact with the solution. The deposition of the silyl cellulose or the solution of silyl cellulose containing at least one ionicly conductive additive can be achieved using various techniques, including solution casting, spray coating, spin coating, dip coating, or by using the Langmuir-Blodgett coating technique. The choice of deposition technique is largely controlled by the desired thickness of the protective layer and the desired surface area size to be coated. Regarding thickness, the protective layer should be as thin as possible while still effectively protecting the metal electrode, specifically the magnesium electrode. The thickness of the layer will affect the flexibility and ionic conductivity of the interfacial protective layer. A high-quality protective layer should be smooth and continuous and free of pores or defects that could provide pathways for harmful substances to drain from the electrolyte.

[0060] Finally, in step (iv), the solvent is evaporated. The corresponding techniques are known to those skilled in the art.

[0061] In the method of this invention, the conductive material may be as described above and / or may contain at least one of Mg, Zn, Ca, Al, K, and Na. Mg is preferred.

[0062] In the method of the present invention, the conductive material may be selected from magnesium metal, magnesium metal alloy and magnesium powder-based materials as described above.

[0063] At least one ion-conducting additive is preferably a magnesium salt, specifically a magnesium salt selected from the group consisting of: Mg(BH4)2 (magnesium hydrogen borate), Mg(TFSI)2 (magnesium bis(trifluoromethane)sulfonylimide), Mg(FSI)2 (magnesium bis(fluorosulfonyl)imide), MgCl2 (magnesium chloride), Mg(BH4)(NH2), Mg[B(hfip)4]2 (magnesium hexafluoroisopropylborate), Mg(TDI)2 (2-trifluoromethyl-4,5-dicyanimidazolium magnesium), Mg[RB 12 H 11 (Closed-type magnesium dodecoborate family), MgB(CN)5 (magnesium pentacyanoborate), Mg(HMDS)2 (bis(hexamethyldisilazane)magnesium), Mg(ClO4)2 (magnesium perchlorate), MgBr2 (magnesium bromide), MgI2 (magnesium iodide), Mg(B(OR) x )4)2, Mg(PF6)2 (magnesium hexafluorophosphate), or any combination thereof, most preferably Mg(BH4)2.

[0064] A fourth aspect of the invention is the use of silylated cellulose, optionally containing at least one ionic conductive additive, as a protective layer on the surface of a conductive material, specifically on the anode surface, wherein the at least one ionic conductive additive present in the protective layer forms a solvate with a solvent.

[0065] Specifically, this aspect of the invention can be used to coat any commercially available conductive material and specifically to coat anode surfaces commonly used in the art. In a particularly preferred embodiment, the anode material of the battery is coated. Examples and Figure 8 and 9 It is clearly shown that the protective coating of magnesium electrodes with silyl cellulose can provide beneficial effects, specifically providing extended cycle life.

[0066] In the applications described herein, the conductive material may be selected from magnesium metal, magnesium alloys, and magnesium powder-based materials as described above, and / or wherein the at least one ionic conductive additive is a magnesium salt, preferably a magnesium salt selected from the group consisting of: Mg(BH4)2 (magnesium hydrogen borate), Mg(TFSI)2 (magnesium bis(trifluoromethane)sulfonylimide), Mg(FSI)2 (magnesium bis(fluorosulfonyl)imide), MgCl2 (magnesium chloride), Mg(BH4)(NH2), Mg[B(hfip)4]2 (magnesium hexafluoroisopropylborate), Mg(TDI)2 (2-trifluoromethyl-4,5-dicyanimidazolium magnesium), Mg[RB 12 H 11 (Closed-type magnesium dodecoborate family), MgB(CN)5 (magnesium pentacyanoborate), Mg(HMDS)2 (bis(hexamethyldisilazane)magnesium), Mg(ClO4)2 (magnesium perchlorate), MgBr2 (magnesium bromide), MgI2 (magnesium iodide), Mg(B(OR) x )4)2, Mg(PF6)2 (magnesium hexafluorophosphate), or any combination thereof, most preferably Mg(BH4)2.

[0067] According to the present invention, it is particularly preferred that the conductive material is selected from magnesium metal, magnesium metal alloys and especially magnesium powder-based materials, and that at least one ionic conductive additive is Mg(BH4)2.

[0068] This invention is by Figures 1 to 7 Further explanation is provided in the examples.

[0069] Figure 1 The cross-section of the magnesium metal battery of the present invention, specifically the magnesium secondary battery 1, is shown. The battery includes a negative current collector 2, a magnesium metal anode 3, an interface protective layer 4 (also referred to herein as the "protective layer"), a separator 5, a positive electrode 6 (cathode), and a positive current collector 7. Figure 1A preferred embodiment of the present invention is shown.

[0070] The negative current collector 2 can be made of any conductive material, such as metal foil, like nickel foil, copper foil, stainless steel foil, preferably copper foil. Importantly, the negative current collector is inert towards the negative electrode 3.

[0071] The magnesium metal anode 3 attached to the negative current collector 2 may be made of magnesium foil as described herein and includes an interface protection layer 4 on the electrolyte-facing side of the magnesium metal anode 3 opposite to the negative current collector 2. The magnesium metal anode 3 should be no more than 1,000 μm thick, more preferably no more than 500 μm thick.

[0072] Element 5 represents a battery separator impregnated with a liquid electrolyte medium. In the context of this invention, such a separator 5 is a highly porous membrane that prevents electrical contact between the positive and negative electrodes and can be made, for example, of polyolefins or glass fibers. This separator 5 should be no more than 300 μm thick, preferably no more than 100 μm thick. The protective layer 4 comprises a solvent that forms a solvate from at least one conductive additive present therein. Such solvents have been described above. Preferably, magnesium does not react with the electrolyte medium used.

[0073] The positive electrode 6 is in contact with the diaphragm 5 opposite the negative magnesium anode 3. The positive electrode can be directly attached to the positive current collector 7 by using a slurry casting method or by compressing a separate positive electrode onto the current collector. The positive current collector 7 can be made of a conductive material, preferably carbon-coated aluminum foil. The positive electrode 6 can include any magnesium intercalation compound, sulfur, or any polymeric organic compound, either as a single-phase material or mixed with carbon or any other conductive compound.

[0074] Figure 2 This is a schematic diagram illustrating repeating silylated dehydrated glucose units in a cellulose molecule according to the present invention. Cellulose is an organic compound composed of D-glucose units linked by β(1→4). Cellulose matrix materials are well known to those skilled in the art.

[0075] Figure 3 The stripping and deposition of symmetric Mg-Mg cells are shown. Using a TMSC-salt film, the overpotential is lower and the cycling time is longer.

[0076] Figure 4 In unprotected batteries, polarization increases and short circuits occur, while batteries with a TMSC-salt film exhibit stable performance and much lower polarization. Using a TMSC-salt film results in lower overpotentials and longer cycle times. These effects are more pronounced at higher numbers of cycles (longer durations).

[0077] Figure 5The image shows a cross-sectional SEM image of drawn Mg compared to Mg with a TMSC protective layer. The TMSC provides a dense protective film on the Mg surface.

[0078] Figure 6 SEM images of the deposited TMSC protective layer are shown. The TMSC-salt film exhibits excellent adhesion to the Mg surface. The Mg surface is completely covered by the TMSC-salt film. The layer thickness is adjustable.

[0079] Figure 7 The properties of protected Mg are also stable in electrolytes that do not contain Cl-.

[0080] Figure 8 This demonstrates the reversible stripping and deposition process of Mg deposition.

[0081] Figure 9 Electrodes with protected Mg powder surfaces and protected Pt foil surfaces exhibit much longer cycle life.

[0082] Example

[0083] Exfoliation / deposition demonstrating reversible Mg deposition

[0084] The experiment was designed using the following UFO-type electrode: an excess of Mg was deposited on a Pt foil (5000 mAh) and half of this amount (2500 mAh) was stripped off. Subsequently, 2500 mAh of magnesium was deposited and stripped off consecutively.

[0085] The stripping and deposition of Mg on the Pt foil is not entirely reversible, despite the addition of excess Mg during the first cycle. This is due to Mg passivation that occurs when the fresh magnesium surface is exposed to the electrolyte.

[0086] Two experiments were conducted:

[0087] 1) Exposed surfaces of Mg powder and Pt foil

[0088] 2) Protected surfaces of Mg powder and Pt foil

[0089] Silicylated cellulose is used for protection, and Mg(BH4)2 is incorporated as a salt between the cellulose fibers.

[0090] The experiment demonstrated the quality of the protective layer, specifically the number of cycles required to lose one-time excess magnesium. If the degradation was severe, the experiment failed after several cycles (insufficient magnesium and inability to achieve 2500 mAh).

[0091] This was observed on bare surfaces (see...). Figure 8After approximately 25 cycles, the pre-deposited magnesium is exhausted, and more magnesium is lost per cycle than is deposited. For this reason, the capacity is zero after 100 cycles.

[0092] Figure 9 The same experiment using the protective layer is shown. Longer cycle life. Degradation is due to the so-called edge effect*—edges are unprotected, but the total protective layer achieves approximately 10 times longer battery life. This undoubtedly demonstrates the technical impact of the invention.

[0093] *Edge effect refers to the inadequate coverage of electrode edges by the protective layer. This is common in unoptimized lab cells. This effect can be eliminated when the cell is engineered for optimization.

Claims

1. An anode comprising: The invention comprises a body and a protective layer, the body comprising or being composed of a conductive material, the protective layer being disposed on at least one surface of the body, wherein the protective layer comprises silylated cellulose and a solvent, and the silylated cellulose comprises at least one ion-conducting additive. The conductive material of the anode comprises at least one selected from Mg, Zn, Ca, Al, K, and Na. The solvent causes the at least one ionic conductive additive present in the protective layer to form a solvate.

2. The anode as described in claim 1, The conductive material is composed of magnesium metal, and the main body is a magnesium foil with a thickness of no more than 1000 μm.

3. The anode as described in claim 1, The at least one ionic conductive additive is a salt of the conductive material.

4. The anode as described in claim 1, The at least one ion-conducting additive is present in the protective layer, and the mass ratio of the ion-conducting additive to silyl cellulose is 1 to 10.

5. The anode as described in claim 1, The at least one ionic conductive additive comprises one or more salts of the conductive material containing anions selected from the group consisting of: Borohydride, bis(trifluoromethane)sulfonylimide, bis(fluorosulfonyl)imide, chloride, (BH4)(NH2), hexafluoroisopropylborate, 2-trifluoromethyl-4,5-dicyanoimidazolium, closed-type dodecoborate family anions, pentacyanoborate, bis(hexamethyldisilazane), perchlorate, bromide, iodide, B(OR) x )4 and hexafluorophosphate.

6. The anode as described in claim 1, The at least one of the ionic conductive additives is a magnesium salt.

7. The anode as described in claim 1, The at least one ionic conductive additive is a Na salt or a K salt.

8. The anode as described in claim 1, The at least one of the ionic conductive additives is an aluminum salt.

9. The anode as described in claim 1, The thickness of the protective layer ranges from 100 nm to 500 μm.

10. The anode as claimed in claim 1, Each glucose unit of the silylated cellulose contains 0.5 to 3 silyl groups.

11. The anode as claimed in claim 10, The silyl group therein is the same or different group -SiR3, wherein each R is independently selected from the group consisting of: alkyl, cycloalkyl, alkenyl, alkoxy, aryl and alkylaryl.

12. The anode as claimed in claim 1, The silylated cellulose described therein is derived from microfibrillated cellulose or nanofibrillated cellulose, microcrystalline cellulose or nanocrystalline cellulose or bacterial cellulose.

13. An electrochemical battery, It includes an anode, a cathode, a diaphragm inserted between the anode and the cathode, and an electrolyte, wherein the anode is as defined in claim 1, and wherein the protective layer is located on the electrolyte-facing side of the anode.

14. The electrochemical battery as described in claim 13, The solvent is selected from polar aprotic solvents.

15. The electrochemical battery as described in claim 14, The polar aprotic solvent is contained in the electrolyte in an amount of 10% to 100% by volume.

16. The electrochemical battery as described in claim 13, It also includes a negative current collector on the opposite side of the anode from the electrolyte and / or a positive current collector on the opposite side of the cathode from the electrolyte, wherein the negative current collector and / or the positive current collector are made of a conductive material that is inert to the materials of the anode and the cathode, respectively.

17. The electrochemical battery as described in claim 13, It is a magnesium secondary battery.

18. Use of silyl cellulose as a protective layer on the surface of a conductive material in an anode, wherein at least one ionic conductive additive present in the protective layer forms a solvate with a solvent, the anode comprising a body and the protective layer, the body comprising or being composed of the conductive material, the protective layer being disposed on at least one surface of the body, wherein the conductive material of the anode comprises at least one of Mg, Zn, Ca, Al, K and Na.

19. The use as claimed in claim 18, wherein the conductive material is selected from magnesium metal, magnesium metal alloys and magnesium powder-based materials, and / or wherein the at least one ionic conductive additive is a magnesium salt.

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