A composite separator and its preparation method, and a metal carbon dioxide battery

Abstract

This invention provides a composite separator and its preparation method, as well as a metal-carbon dioxide battery. The composite separator includes a separator and an amorphous carbon coating located on the side of the separator. The amorphous carbon coating on the negative electrode side has a higher Young's modulus than that of metal dendrites. The amorphous carbon coating has high bonding strength with the separator and is not easily detached. The high Young's modulus can suppress lithium dendrite formation. In the metal-carbon dioxide battery, the amorphous carbon can undergo an in-situ lithium / sodium / potassium / zinc oxidation reaction to become an ion conductor, promoting metal ion transport. The amorphous carbon coating has good gas shielding properties, preventing the transmission of one or more mixed gases such as carbon dioxide, oxygen, and nitrogen through the amorphous carbon coating composite separator, thus preventing gas corrosion of the metal negative electrode. The positive electrode side is a heteroelement-doped amorphous carbon coating, which can suppress the transmembrane migration of anions in the battery, thus inhibiting corrosion of the metal negative electrode. The amorphous carbon coating can solve the problem of poor cycle stability in metal negative electrodes and metal-carbon dioxide batteries.

Description

Technical Field

[0001] This invention relates to the field of energy storage device technology, and in particular to a composite separator and its preparation method, and a metal carbon dioxide battery. Background Technology

[0002] Metals such as lithium, sodium, potassium, and zinc possess extremely high theoretical specific capacity and low electrode potential. Batteries using these metals as negative electrodes hold great promise for solving the capacity bottleneck currently faced by lithium-ion batteries, attracting significant attention. However, due to the non-uniformity of mass transfer in the liquid phase of the battery, the continuous deposition / stripping of metal ions on the negative electrode surface can easily lead to the formation of uncontrollable metal dendrites. Excessive growth of these dendrites can pierce the separator, reaching the positive electrode and causing short circuits or even thermal runaway. Furthermore, to fully utilize the capacity advantages of metal negative electrodes, finding high-capacity positive electrodes is equally crucial. In the exploration of novel positive electrodes, novel metal secondary batteries using sulfur, oxygen, and carbon dioxide as positive electrodes have received widespread attention. Taking lithium metal as an example, its theoretical energy densities can reach 2600, 3500, and 1876 Wh·kg, respectively. -1 While some progress has been made in related research, it remains far from practical application. The problem of poor lithium anode stability is a common issue: for example, in lithium-sulfur batteries, the shuttle effect of polysulfide ions corrodes the lithium anode and causes severe self-discharge. In lithium-air / carbon dioxide batteries, due to the complexity of the discharge product decomposition mechanism, superoxide radicals and gases that corrode the lithium anode and electrolyte are generated during battery cycling, severely impairing coulombic efficiency and cycle stability. Therefore, solving the problem of poor lithium anode stability in these novel lithium metal batteries is extremely important. However, in addition to lithium dendrites, these batteries also generate polysulfide anions, superoxide radicals, and corrosive gases that corrode the lithium anode during cycling, seriously hindering their application.

[0003] To address the issue of poor stability of the metal anode in current metal carbon dioxide batteries, it is necessary to make improvements. Summary of the Invention

[0004] In view of this, the present invention proposes a composite separator and its preparation method, as well as a metal carbon dioxide battery, to solve the technical problems existing in the prior art.

[0005] In a first aspect, the present invention provides a composite membrane, comprising a membrane and an amorphous carbon coating located on the side of the membrane.

[0006] Preferably, the composite diaphragm is a modified diaphragm that has undergone surface modification treatment by physical or chemical means, and the surface modification treatment includes any one of plasma surface modification treatment, laser surface modification treatment, polishing surface modification treatment, and sandblasting surface modification treatment.

[0007] And / or, the amorphous carbon coating includes one or more of the following: hydrogen-containing amorphous carbon coating, non-hydrogen-containing amorphous carbon coating, heteroelement-doped amorphous carbon coating, nanoporous amorphous carbon coating, and soft carbon amorphous carbon coating.

[0008] And / or, the heteroelement includes at least one of nitrogen, oxygen, and sulfur.

[0009] Preferably, the composite membrane comprises one or more of the following: polyolefin membrane, glass fiber membrane, nylon membrane, and polyethylene membrane.

[0010] Preferably, the plasma surface modification treatment of the composite diaphragm specifically involves placing the diaphragm in a plasma surface treatment device and evacuating the vacuum chamber to a pressure of 6 × 10⁻⁶. -3 ~8×10 -3 ×Pa, then introduce nitrogen or oxygen at a flow rate of 25-35 sccm into the vacuum chamber, apply a bias voltage of -45 to -55V and control the power of 15-25W, and perform plasma treatment on the diaphragm for 10-20 minutes.

[0011] Preferably, in the composite membrane, if the heteroelement is nitrogen, the method for preparing the heteroelement-doped amorphous carbon coating is as follows:

[0012] After mixing a nitrogen source with an organic acid, the mixture is calcined at 700–800℃ for 6–10 h to obtain amorphous carbon material doped with heterogeneous elements.

[0013] Then, amorphous carbon material is coated onto the side of the membrane to form a heteroelement-doped amorphous carbon coating.

[0014] Preferably, the thickness of the amorphous carbon coating in the composite diaphragm is 1–7 μm.

[0015] Secondly, the present invention also provides a method for preparing a composite diaphragm, comprising the following steps:

[0016] Provide a diaphragm;

[0017] An amorphous carbon coating is prepared on the side surface of the diaphragm;

[0018] The preparation methods for amorphous carbon coatings include one of the following: plasma chemical vapor deposition, electron cyclotron resonance chemical vapor deposition, magnetron sputtering deposition, filtered cathode vacuum arc deposition, and coating method.

[0019] Preferably, the preparation method of the composite membrane, the magnetron sputtering deposition method, specifically involves: placing the membrane in a magnetron sputtering device, installing a carbon target, introducing argon gas, controlling the pulse bias voltage to -45 to -50V and the carbon target deposition power to 15 to 25W to perform deposition, thereby preparing an amorphous carbon coating.

[0020] And / or, the diaphragm is a modified diaphragm that has undergone surface modification treatment by physical or chemical means, the surface modification treatment including any one of plasma surface modification treatment, laser surface modification treatment, polishing surface modification treatment, and sandblasting surface modification treatment.

[0021] Thirdly, the present invention also provides a metal carbon dioxide battery, comprising: a positive electrode, a separator, an electrode solution, and a negative electrode, wherein the separator comprises the composite separator described above or a composite separator prepared by the preparation method described above.

[0022] Preferably, in the metal carbon dioxide battery, the composite separator has an amorphous carbon coating on the side near the negative electrode and an amorphous carbon coating doped with heterogeneous elements on the side near the positive electrode.

[0023] The composite separator and its preparation method of the present invention, and the metal carbon dioxide battery thereof, have the following advantages over the prior art:

[0024] The present invention relates to a composite separator and a metal-carbon dioxide battery. The composite separator comprises a separator and an amorphous carbon coating. The amorphous carbon coating has the following advantages: the amorphous carbon coating on the negative electrode side has a high Young's modulus, which is greater than or much greater than the Young's modulus of metal dendrites; the amorphous carbon coating has high bonding strength with the separator and is not easily detached; the high Young's modulus can suppress lithium dendrite formation; in the metal-carbon dioxide battery, amorphous carbon can undergo an in-situ lithium / sodium / potassium / zinc oxidation reaction to become an ion conductor, promoting metal ion transport; the amorphous carbon coating has good gas shielding properties, which can prevent the transmission of one or more mixed gases such as carbon dioxide, oxygen, and nitrogen through the amorphous carbon coating composite separator, thus preventing gas corrosion of the metal negative electrode; the positive electrode side is a heteroelement-doped amorphous carbon coating, which can suppress the transmembrane migration of anions in the battery and its corrosion of the metal negative electrode. Overall, the amorphous carbon coating can solve the problem of poor cycle stability in metal negative electrodes and metal-carbon dioxide batteries. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the structure of the metal carbon dioxide battery of the present invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] This application provides a composite membrane, including a membrane and an amorphous carbon coating located on the side of the membrane.

[0029] It should be noted that the composite separator of this application includes a separator and an amorphous carbon coating. Obviously, the amorphous carbon coating can be located on one side of the separator or on both sides of the separator. The amorphous carbon coating has the following advantages: the amorphous carbon coating itself has a high Young's modulus, which is greater than or much greater than the Young's modulus of metal dendrites; the amorphous carbon coating has high bonding strength with the separator and is not easy to fall off; the high Young's modulus can suppress lithium dendrites; in metal carbon dioxide batteries, amorphous carbon can undergo in-situ lithium / sodium / potassium / zinc metallization reaction to become an ion conductor, promoting metal ion transport; the amorphous carbon coating has good gas shielding properties, which can prevent one or more mixed gases such as carbon dioxide, oxygen, and nitrogen from passing through the amorphous carbon coating composite separator, thus preventing corrosion of the metal anode; in-situ metallization can transform the amorphous carbon coating into an ion conductor, promoting metal ion transport; the amorphous carbon coating can solve the problem of poor cycle stability of metal anodes and metal carbon dioxide batteries.

[0030] In some embodiments, the diaphragm is a modified diaphragm that has undergone surface modification treatment by physical or chemical means, and the surface modification treatment includes any one of plasma surface modification treatment, laser surface modification treatment, polishing surface modification treatment, and sandblasting surface modification treatment.

[0031] And / or, the amorphous carbon coating includes one or more of the following: hydrogen-containing amorphous carbon coating, non-hydrogen-containing amorphous carbon coating, heteroelement-doped amorphous carbon coating, nanoporous amorphous carbon coating, and soft carbon amorphous carbon coating.

[0032] And / or, the heteroelement includes at least one of nitrogen, oxygen, and sulfur.

[0033] In the above embodiments, the separator is a modified separator that has undergone surface modification treatment through physical or chemical means. Surface modification of the separator can effectively inhibit the transmembrane migration of one or more anions. Through the synergistic effect of the surface modification of the separator and the amorphous carbon coating, the composite separator formed by surface modification and the amorphous carbon coating can inhibit metal dendrite growth, block anion transmembrane migration, and shield the metal anode from gas corrosion in metal carbon dioxide batteries, effectively improving the stability of the metal anode and the cycle life of the modified metal carbon dioxide battery. Specifically, the amorphous carbon coating includes composite coating structures composed of the above-mentioned different types of amorphous carbon coatings, or composite or gradient coatings of any two or more of the above-mentioned types of coatings including heteroelement-doped amorphous carbon coatings.

[0034] Preferably, the amorphous carbon coating includes a low-hydrogen amorphous carbon coating and a heteroelement-doped amorphous carbon coating.

[0035] The heteroelement-doped amorphous carbon coating has good anion adsorption and barrier properties, which can inhibit the migration of superoxide radicals, soluble polysulfides and other anions across the membrane.

[0036] Specifically, the composite membrane includes a membrane and an amorphous carbon coating on both sides of the membrane. The amorphous carbon coating near the negative electrode side can be one or more of hydrogen-containing amorphous carbon coating, non-hydrogen-containing amorphous carbon coating, amorphous carbon coating, nanoporous amorphous carbon coating, and soft carbon amorphous carbon coating. The amorphous carbon coating near the positive electrode side can be a heteroelement-doped amorphous carbon coating.

[0037] In some embodiments, the diaphragm includes one or more composites of polyolefin diaphragms, glass fiber diaphragms, nylon diaphragms, and polyethylene diaphragms.

[0038] The diaphragm may include one type of diaphragm or a combination of several different types of diaphragms, and obviously may also include one type of modified / unmodified diaphragm or a combination of several different types of modified / unmodified diaphragms.

[0039] Preferably, the diaphragm is a diaphragm formed of polypropylene / glass fiber composite.

[0040] In some embodiments, the plasma surface modification treatment specifically involves: placing the diaphragm in a plasma surface treatment device and evacuating the vacuum chamber to a pressure of 6 × 10⁻⁶. -3 ~8×10 -3 ×Pa, then nitrogen or oxygen gas with a flow rate of 25-35 sccm is introduced into the vacuum chamber, a bias voltage of -45 to -55V is applied and the control power is 15-25W to generate nitrogen or oxygen plasma, and the diaphragm is subjected to plasma treatment for 10-20 minutes.

[0041] In some embodiments, if the heteroelement is nitrogen, the method for preparing the heteroelement-doped amorphous carbon coating is as follows:

[0042] After mixing a nitrogen source with an organic acid, the mixture is calcined at 700–800℃ for 6–10 h to obtain amorphous carbon material doped with heterogeneous elements.

[0043] Then, amorphous carbon material is coated onto the side of the membrane to form a heteroelement-doped amorphous carbon coating.

[0044] In the above embodiments, the nitrogen source can be any form of nitride or one or more mixtures of nitrogen-containing organic compounds, and the doping temperature can be any temperature at which effective nitrogen doping can be achieved. Specifically, the nitrogen source can be urea, and the organic acid can be citric acid.

[0045] Specifically, in some embodiments, the method for preparing the heteroelement-doped amorphous carbon coating is as follows:

[0046] Weigh out 200 ml of a mixed solution of water and ethanol in a volume ratio of 1:3;

[0047] Weigh 1g of citric acid and 10g of urea and add them to the above mixed solution. Stir until clear, then heat in a water bath at 75°C for 5 hours, and then dry in an oven at 100°C for 12 hours to obtain the precursor.

[0048] The aforementioned precursor was placed in a corundum ceramic boat and then placed in a sealed tube furnace. Argon gas was introduced for 30 minutes. After the air in the tube furnace was removed, the temperature was increased to 350°C at a rate of 2°C / min and held for 2 hours. Then, the temperature was increased to 750°C at a rate of 5°C / min and held for 4 hours. Argon gas was used for protection throughout the heating process, with an argon gas flow rate of 100ccm. After heating, nitrogen-doped amorphous carbon material was obtained. The amorphous carbon material was then coated onto the side of the diaphragm to form a heteroelement-doped amorphous carbon coating.

[0049] In some embodiments, the thickness of the amorphous carbon coating is 1–7 μm.

[0050] Based on the same inventive concept, this application also provides a method for preparing a composite separator, comprising the following steps:

[0051] Provide a diaphragm;

[0052] An amorphous carbon coating is prepared on the side of the diaphragm;

[0053] The preparation methods for amorphous carbon coatings include one of the following: plasma chemical vapor deposition, electron cyclotron resonance chemical vapor deposition, magnetron sputtering deposition, filtered cathode vacuum arc deposition, and coating method.

[0054] Specifically, if an amorphous carbon coating is prepared on both sides of the separator, the preparation method of the amorphous carbon coating on the negative electrode side includes one of plasma chemical vapor deposition, electron cyclotron resonance chemical vapor deposition, magnetron sputtering deposition, filtered cathode vacuum arc deposition, and coating method; if the amorphous carbon coating on the positive electrode side is a heteroelement-doped amorphous carbon coating, the coating method is used to prepare the amorphous carbon coating on the positive electrode side.

[0055] In some embodiments, the magnetron sputtering deposition method specifically involves: placing the diaphragm in a magnetron sputtering device, installing a carbon target, introducing argon gas, controlling the pulse bias voltage to -45 to -50V and the carbon target deposition power to 15 to 25W to perform deposition, thereby preparing an amorphous carbon coating.

[0056] In some embodiments, the diaphragm is a modified diaphragm that has undergone surface modification treatment by physical or chemical means, wherein the surface modification treatment includes any one of plasma surface modification treatment, laser surface modification treatment, polishing surface modification treatment, and sandblasting surface modification treatment.

[0057] Based on the same inventive concept, this application also provides a metal carbon dioxide battery, including: a positive electrode, a separator, an electrode liquid, and a negative electrode, wherein the separator includes the composite separator described above or a composite separator prepared by the above preparation method.

[0058] In some embodiments, the composite separator has an amorphous carbon coating on the side near the negative electrode and an amorphous carbon coating doped with heterogeneous elements on the side near the positive electrode.

[0059] Specifically, the positive electrode includes a positive electrode current collector / support and a catalyst composite positive electrode material coated or deposited on the current collector.

[0060] The positive electrode current collector / load refers to: aluminum, tin, nickel, titanium metal, or graphene, carbon nanotubes, nanoporous amorphous carbon, carbon paper, or any composite of these materials, or any one or more composite current collectors of the above-mentioned metallic or non-metallic porous or foam structure materials. Preferably, the positive electrode load is nanoporous amorphous carbon / carbon cloth or foam nickel current collector.

[0061] The cathode material includes cathode materials with or without catalysts that meet the requirements of metal-air / carbon dioxide battery cathodes; specifically, it can be: one or a mixture of several metal oxides such as nano-ruthenium oxide, manganese oxide, copper oxide, nickel oxide, and cobalt oxide; alloys of one or several metals such as ruthenium, rhodium, palladium, gold, platinum, copper, and cobalt; and novel perovskite, metal-organic framework compounds, and other catalyst materials; or one or a mixture of the above catalyst materials, etc.

[0062] Preferably, the cathode is a composite cathode consisting of heteroatom-doped porous amorphous carbon or a cathode supported by a nickel foam current collector and a transition metal or its oxide-based catalyst. For example, the cathode could be carbon nanotubes supported on MnO2, nickel foam supported on nano-RuO2, or nanoporous amorphous carbon supported on CoNiO. x .

[0063] The electrolyte is prepared by adding a certain amount of lithium / sodium / potassium / zinc salt electrolyte to a water / non-aqueous solvent, stirring thoroughly to dissolve the resulting product, and the concentration is 0.1-30 mol / L; or a solid / quasi-solid electrolyte that can meet the requirements for normal metal ion transport.

[0064] The salt added to the electrolyte can be one or a mixture of several of the following: lithium hexafluorophosphate / sodium / potassium / zinc, lithium tetrafluoroborate / sodium / potassium / zinc, lithium perchlorate / sodium / potassium / zinc, lithium trifluoromethanesulfonate / sodium / potassium / zinc, lithium bis(fluorosulfonyl)imide / sodium / potassium / zinc, lithium bis(trifluorosulfonyl)imide / sodium / potassium / zinc, lithium chloride / sodium / potassium / zinc, lithium fluoride / sodium / potassium / zinc, lithium sulfate / sodium / potassium / zinc, lithium carbonate / sodium / potassium / zinc, lithium phosphate / sodium / potassium / zinc, lithium nitrate / sodium / potassium / zinc, lithium difluorooxalate borate / sodium / potassium / zinc, lithium hexafluoroarsenate / sodium / potassium / zinc, lithium bis(oxalate borate) borate / sodium / potassium / zinc, lithium acetate / sodium / potassium / zinc, etc.; preferably: lithium bis(trifluoromethanesulfonyl)imide / sodium / potassium / zinc.

[0065] The aqueous / non-aqueous solvents include one or more of esters, ethers, sulfones, acids, and bases, such as diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, dimethyl sulfoxide, dimethyl ether, dimethylformamide, dimethylacetamide, tetrahydrofuran, 1,3-dioxolane, ethylene carbonate, ethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, sulfuric acid, hydrochloric acid, acetic acid, etc.; preferably, tetraethylene glycol dimethyl ether or dimethyl sulfoxide.

[0066] The negative electrode includes any one or a composite negative electrode sheet in which metal dendrites are generated during the battery reaction, such as lithium / sodium / potassium / zinc / tin / aluminum foil, lithium / sodium / potassium / zinc / tin / aluminum deposited copper foil, metal or graphite negative electrode with pre-intercalated lithium / sodium / potassium / zinc / tin / aluminum, and novel silicon-carbon negative electrode; preferably, the negative electrode is metallic lithium / sodium / potassium / zinc foil.

[0067] For details, please refer to Figure 1 As shown, the structure of a metal carbon dioxide battery is as follows: Figure 1 As shown, it includes a positive current collector 1, a positive electrode material 2, electrolytes 3 and 7, an amorphous carbon coating 4, a separator 5, a heteroelement-doped amorphous carbon coating 6, and a negative electrode 8. The amorphous carbon coating 4, separator 5, and heteroelement-doped amorphous carbon coating 6 constitute the separator of the metal carbon dioxide battery of this application.

[0068] The preparation method of the above-mentioned metal carbon dioxide battery includes the following steps:

[0069] S1: Preparation of the negative electrode: A conventional commercially available electrode with a diameter of [missing information] was selected. A 0.4 mm thick metal foil is used as the negative electrode;

[0070] S2. Preparation of electrode solution (taking non-aqueous system as an example): A certain amount of metal salt electrolyte is added to an organic solvent, and the product is dissolved after thorough stirring, with a concentration of 0.1-30 mol / L.

[0071] S3: Separator: The composite separator prepared above is selected;

[0072] S4: Provides the positive electrode;

[0073] S5: Assemble the materials prepared in steps S1-S4 into a battery in a certain order in an anhydrous and oxygen-free environment and seal it.

[0074] The following specific embodiments further illustrate the preparation method of the composite separator and the preparation method of the metal carbon dioxide battery of this application.

[0075] Example 1

[0076] This embodiment provides a method for preparing a composite membrane, including the following steps:

[0077] S1. A polypropylene / glass fiber composite diaphragm is fixed in the plasma surface treatment equipment. The vacuum chamber is closed, and a vacuum is evacuated to a pressure of 6 × 10⁻⁶. -3 Pa, oxygen is introduced into the vacuum chamber at a flow rate of 30 sccm, a bias voltage of -50V is applied, the power supply is turned on at 20W, oxygen plasma is generated, and the diaphragm surface is plasma-treated for 15 minutes.

[0078] S2. Cut the plasma-treated polypropylene / glass fiber composite diaphragm to a certain length (lower than the substrate diameter of the coating system and plasma treatment system), place it in the desktop vacuum coating and plasma treatment system, and then evacuate the system to 5×10⁻⁶. -3 Pa, argon gas flow rate of 30 sccm, under pulse bias voltage of -50V, carbon target deposition power of 20W, and deposition time controlled to prepare a high modulus amorphous carbon thin film coating with a thickness of 2.5 μm (as the negative electrode side);

[0079] S3. Weigh 200 ml of a mixed solution of water and ethanol in a volume ratio of 1:3;

[0080] S4. Weigh 1g of citric acid and 10g of urea and add them to the mixed solution in step S3 above. Stir until clear, then heat in a water bath at 75°C for 5 hours, and then dry in an oven at 100°C for 12 hours to obtain the precursor.

[0081] S5. Place the above precursor in a corundum ceramic boat and put it into a tube furnace and seal it. Purge with argon gas for 30 minutes. After removing the air from the tube furnace, heat it to 350°C at a rate of 2°C / min and hold it for 2 hours. Then heat it to 750°C at a rate of 5°C / min and hold it for 4 hours. Argon gas is used for protection throughout the heating process. The argon gas flow rate is 100ccm. After heating, nitrogen-doped amorphous carbon material is obtained, which can be used as raw material for heterocyclic element-doped amorphous carbon coating.

[0082] S6. Nitrogen-doped amorphous carbon material is added to a binder and then uniformly coated onto the positive electrode side of a polypropylene / glass fiber composite separator. After drying, an amorphous carbon-modified composite separator is obtained. The composite separator is then removed and cut into... Dry in an oven and store in a glove box for later use.

[0083] This application also provides a metal carbon dioxide battery, comprising: a positive electrode, a separator, an electrode electrolyte, and a negative electrode, wherein the negative electrode is lithium foil; the separator is a composite separator prepared in Example 1 above; the electrolyte is 1 mol / L LiTFSI / EC:DEC (1:1 vol%), or 1 mol / L LiClO4 / DMSO or 1 mol / L LiTSFI / TEGDME, wherein LiTFSI is lithium bis(trifluoromethanesulfonyl)imide, EC is ethylene carbonate, DEC is diethyl carbonate, and tetraethylene glycol dimethyl ether (TEGDME); the positive electrode is carbon nanotube-supported MnO2 or nickel foam-supported nano RuO2 or nanoporous amorphous carbon-supported CoNiOx. Specifically, in this embodiment, the positive electrode uses nickel foam-supported nano RuO2, and the electrolyte uses 1 mol / L LiTSFI / TEGDME.

[0084] Examples 2-5

[0085] Examples 2-5 are identical to the metal carbon dioxide batteries based on amorphous carbon coating modified composite membranes in Example 1, except for the thickness of the amorphous carbon thin film coating in the composite membrane.

[0086] The electrochemical performance of different metal carbon dioxide batteries in Examples 1-5 (all under 0.5C cycling) is shown in Table 1 below.

[0087] Table 1 - Electrochemical performance of different metal carbon dioxide batteries in Examples 1-5

[0088]

[0089]

[0090] Examples 6-15

[0091] Examples 6-15 are the same as those in Example 1, which are lithium metal secondary batteries based on amorphous carbon coating modified composite separators, except that the type of separator and the modification method are different.

[0092] The electrochemical performance of different metal carbon dioxide batteries in Examples 6-15 (all under 0.5C cycling) is shown in Table 2 below.

[0093] Table 2 - Electrochemical performance of different metal carbon dioxide batteries in Examples 6-15

[0094]

[0095]

[0096]

[0097] In Table 2, the process parameters for plasma modification in different embodiments are the same as those in Example 1; the process conditions for laser-induced functional group grafting modification in Table 2 are: under an ammonia atmosphere, the laser power is controlled at 10W and the laser irradiation time is 60s.

[0098] Examples 16-21

[0099] The lithium metal secondary batteries in Examples 16-21 are the same as those in Example 1, which are based on amorphous carbon coating modified composite separators, except that the cathode material is different.

[0100] The electrochemical performance of different metal carbon dioxide batteries in Examples 16-21 (all under 0.5C cycling) is shown in Table 3 below.

[0101] Table 3 - Electrochemical performance of different metal carbon dioxide batteries in Examples 16-21

[0102]

[0103]

[0104] Examples 22-29

[0105] Examples 22-29 are the same as those in Example 1, which are lithium metal secondary batteries based on amorphous carbon coating modified composite separators, except that the positive electrode, negative electrode and electrolyte are different (the salt concentration in the electrolyte is 1 mol / L).

[0106] The electrochemical performance of different metal carbon dioxide batteries in Examples 22-29 (all under 0.5C cycling) is shown in Table 4 below.

[0107] Table 4 - Electrochemical performance of different metal carbon dioxide batteries in Examples 22-29

[0108]

[0109]

[0110]

[0111] As can be seen from Tables 1 to 4 above, the lithium metal secondary batteries assembled using the amorphous carbon coating modified composite separator of this application all have good capacity retention. This indicates that the amorphous carbon coating modified composite separator of this application can effectively improve the stability of the metal anode and improve the cycle life of the metal carbon dioxide battery.

[0112] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite diaphragm, characterized in that, The membrane includes a separator and an amorphous carbon coating located on the side of the separator; wherein, the amorphous carbon coating near the negative electrode side is a hydrogen-containing amorphous carbon coating or a non-hydrogen-containing amorphous carbon coating; the amorphous carbon coating near the positive electrode side is a heteroelement-doped amorphous carbon coating; the separator is a modified separator that has undergone surface modification treatment by physical or chemical means, and the surface modification treatment includes plasma surface modification treatment. The hetero-elements include nitrogen; The plasma surface modification treatment specifically involves placing the diaphragm in a plasma surface treatment device and evacuating the vacuum chamber to a pressure of 6 × 10⁻⁶. -3 ~8×10 -3 Pa, then nitrogen or oxygen gas with a flow rate of 25~35 sccm is introduced into the vacuum chamber, a bias voltage of -45~-55V is applied and the power is controlled at 15~25W, and the diaphragm is subjected to plasma treatment for 10~20 min; The method for preparing the heteroelement-doped amorphous carbon coating is as follows: After mixing a nitrogen source with an organic acid, the mixture is calcined at 700-800℃ for 6-10 hours to obtain amorphous carbon materials doped with heterogeneous elements. The amorphous carbon material doped with heterogeneous elements is then coated onto the side of the diaphragm to form a heterogeneous element doped amorphous carbon coating.

2. The composite diaphragm as described in claim 1, characterized in that, The diaphragm includes one or more of the following: polyolefin diaphragm, glass fiber diaphragm, and nylon diaphragm.

3. The composite diaphragm as described in claim 2, characterized in that, The thickness of the amorphous carbon coating is 1~7μm.

4. A method for preparing the composite diaphragm as described in claim 1, characterized in that, Includes the following steps: Provide a diaphragm; An amorphous carbon coating is prepared on the side surface of the diaphragm; The preparation methods for amorphous carbon coatings include one of the following: plasma chemical vapor deposition, electron cyclotron resonance chemical vapor deposition, magnetron sputtering deposition, filtered cathode vacuum arc deposition, and coating method.

5. The method for preparing the composite diaphragm as described in claim 4, characterized in that, The magnetron sputtering deposition method is as follows: the diaphragm is placed in a magnetron sputtering device, a carbon target is installed, argon gas is introduced, and the pulse bias voltage is controlled at -45~-50 V and the carbon target deposition power is 15~25 W to deposit an amorphous carbon coating.

6. A metal carbon dioxide battery, characterized in that, include: A positive electrode, a separator, an electrode solution, and a negative electrode, wherein the separator comprises a composite separator as described in any one of claims 1 to 3 or a composite separator prepared by any one of claims 4 to 5.

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