Alkali metal ion secondary battery, preparation method thereof and electric device

Abstract

The invention provides an alkali metal ion secondary battery, a preparation method thereof and an electric device, a negative electrode material in the alkali metal ion secondary battery comprises an elemental sulfur-carbon composite material and / or an alkali metal sulfide-carbon composite material, and an electrolyte comprises an ether electrolyte or a carbonate electrolyte. And the electrolyte contains fluoroethylene carbonate and / or ionic liquid. The active material in the negative electrode material of the alkali metal ion secondary battery adopts the elemental sulfur-carbon composite material and / or the alkali metal sulfide-carbon composite material, so that the safety risk caused by generation of alkali metal dendritic crystals is reduced; besides, after the negative pole piece prepared from the negative pole material is subjected to one alkali metal ion intercalation / deintercalation cycle in the electrolyte in an electrochemical mode, fluoroethylene carbonate contained in the electrolyte and / or anions of the ionic liquid can be degraded on the surface of the negative pole piece to form a stable SEI film; and the battery is ensured to have relatively high coulombic efficiency, specific capacity and relatively good cycling stability.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and relates to an alkali metal ion secondary battery, and more particularly to an alkali metal ion secondary battery, its preparation method and electric device. Background Technology

[0002] Given the increasing demand for energy storage in large-scale power grids, power transmission, and mobile devices, lithium / sodium secondary batteries have attracted widespread attention and achieved great success due to their high energy density, high power density, and stable and efficient voltage output. In existing lithium / sodium secondary battery systems, graphite, hard carbon, and soft carbon are commonly used as anode materials to achieve stable long-cycle operation. However, using these carbon materials as anodes results in a low voltage plateau, easy deposition of lithium / sodium on the surface, large volume, and low specific capacity (<400 mAh·g). -1 This method cannot meet the requirements for safety and high specific energy of secondary batteries in practical applications.

[0003] In the prior art, although metal sulfide (cuprous sulfide or ferrous sulfide) anode materials based on conversion reaction have been widely studied due to their high theoretical specific capacity, these metal sulfides have serious impacts on their cycle performance due to large volume deformation and low electronic conductivity. In particular, the presence of transition metals makes the materials unable to meet the requirements of high specific energy secondary batteries and leads to high material costs.

[0004] Existing technologies also disclose the use of sulfur-carbon composite materials and alkali metal sulfide-carbon composite materials as positive electrode materials, combined with alkali metal negative electrodes, to prepare high-energy-density alkali metal secondary batteries. However, during the charging and discharging process of such secondary batteries, polysulfide intermediates that can dissolve in strongly polar ether electrolytes are generated. These polysulfides shuttle to the negative electrode and undergo severe chemical reactions with the alkali metal negative electrode, leading to the loss of active sulfur and the formation of dendrites or pulverization of the negative electrode. Such batteries often have poor cycle performance. More importantly, these batteries are prone to safety problems such as short circuits, combustion, and explosions in the later stages of cycling.

[0005] CN116190601A discloses a method for preparing a single-atom sulfur-carbon composite, comprising: mixing hollow spheres of phenolic resin polymer with sulfur powder uniformly, and performing heat treatment under an inert atmosphere to obtain a single-atom sulfur-carbon composite with high sulfur content; as a negative electrode material for potassium-ion batteries, the composite has high specific capacity, high rate capability and high stability battery performance.

[0006] CN103346327A discloses a lithium-ion battery anode material and a lithium-ion power battery. The lithium-ion battery anode material includes an anode active material, a conductive agent, a binder, and a solvent. The anode active material includes graphitized carbon material and non-graphitized carbon material; wherein the non-graphitized carbon material accounts for 10% to 88% of the total mass of the anode active material.

[0007] Existing alkali metal ion secondary batteries often use carbon materials, transition metal sulfides, and alkali metals as anode materials. These materials all have certain drawbacks, resulting in alkali metal ion secondary batteries with low specific capacity, low coulombic efficiency, poor stability, high production costs, and poor safety performance. Therefore, developing a novel alkali metal ion secondary battery, its preparation method, and its associated electric device is crucial. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide an alkali metal ion secondary battery, its preparation method, and an electric device. Firstly, the active material in the negative electrode material of the alkali metal ion secondary battery provided by the present invention is a single-element sulfur-carbon composite material and / or an alkali metal sulfide-carbon composite material, reducing the safety risks such as battery short circuits caused by alkali metal dendrite formation. Secondly, the negative electrode sheet prepared with the aforementioned negative electrode material undergoes one alkali metal ion insertion / extraction cycle in an electrolyte containing fluoroethylene carbonate and / or ionic liquid via electrochemical means. This allows the anions of fluoroethylene carbonate and / or ionic liquid contained in the electrolyte of the alkali metal ion secondary battery to be degraded on the surface of the negative electrode sheet, forming a stable SEI film, suppressing the shuttle effect of the sulfur-containing negative electrode material, and ensuring that the battery has high initial coulombic efficiency, specific capacity, and good cycle stability. Thirdly, the active lithium / sodium content in the negative electrode material of the alkali metal ion secondary battery can be freely adjusted, effectively alleviating the problem of low initial coulombic efficiency. Finally, the production cost of the alkali metal ion secondary battery is low.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides an alkali metal ion secondary battery, wherein the negative electrode material of the alkali metal ion secondary battery includes elemental sulfur-carbon composite material and / or alkali metal sulfide-carbon composite material, the electrolyte includes ether electrolyte or carbonate electrolyte, and the electrolyte contains fluoroethylene carbonate and / or ionic liquid, and the positive electrode material and / or negative electrode material of the alkali metal ion secondary battery contains alkali metal ions.

[0011] The alkali metal ion secondary battery provided by this invention uses elemental sulfur-carbon composite materials and / or alkali metal sulfide-carbon composite materials as the active materials in the negative electrode material. This material has advantages such as low cost, high specific capacity, and a discharge voltage plateau much higher than the alkali metal deposition potential, reducing safety risks such as battery short circuits caused by alkali metal dendrite formation. Secondly, the electrolyte of the alkali metal ion secondary battery is an ether electrolyte or carbonate electrolyte containing fluoroethylene carbonate and / or ionic liquids. The negative electrode sheet prepared with the aforementioned negative electrode material undergoes one electrochemical alkali metal ion insertion / extraction cycle in the electrolyte, thereby improving the electrolyte properties of the alkali metal ion secondary battery. The fluoroethylene carbonate and / or ionic liquid anions contained in the battery are degraded on the negative electrode surface to form a stable SEI film, achieving uniform deposition and reversibility between sulfur and sulfides, suppressing the shuttle effect of sulfur-containing negative electrode materials, and ensuring that the battery has high initial coulombic efficiency, specific capacity, and good cycle stability. Most importantly, the content of active lithium / sodium in the negative electrode material of the alkali metal ion secondary battery can be freely adjusted, thereby adapting to positive electrode materials with different initial states and effectively alleviating the problem of low initial coulombic efficiency. Furthermore, the alkali metal ion secondary battery has a simple composition and low raw material cost, making it suitable for large-scale promotion and use.

[0012] Preferably, when the alkali metal ion secondary battery is a sodium ion battery, the positive electrode material includes sodium iron sulfate, sodium nickel iron manganese cuprate, manganese dioxide, or Na+. 0.72 The sodium-ion battery comprises any one or at least two of MnO2, wherein the positive and / or negative electrode materials include a sodium source.

[0013] When the alkali metal ion secondary battery described in this invention is a sodium ion battery, the positive electrode material includes sodium iron sulfate, sodium nickel iron manganese cuprate, manganese dioxide, or Na. 0.72 Any combination of one or at least two of MnO2, typical but non-limiting combinations include the combination of sodium ferric sulfate and sodium nickel manganese cuprate, the combination of sodium nickel manganese cuprate and manganese dioxide, and the combination of manganese dioxide and Na. 0.72 Combinations of MnO2, or combinations of sodium ferric sulfate, sodium nickel iron manganese copper sulfate, and manganese dioxide.

[0014] Preferably, when the alkali metal ion secondary battery is a lithium-ion battery, the positive electrode material includes any one or a combination of at least two of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium manganese iron phosphate, or manganese dioxide, and the positive electrode material and / or negative electrode material of the lithium-ion battery includes a lithium source.

[0015] The cathode material described in this invention includes any one or a combination of at least two of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium manganese iron phosphate, or manganese dioxide. Typical but non-limiting combinations include combinations of lithium cobalt oxide and lithium nickel cobalt manganese oxide, combinations of lithium nickel cobalt manganese oxide and lithium manganese iron phosphate, combinations of lithium manganese iron phosphate and manganese dioxide, or combinations of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium manganese iron phosphate.

[0016] Preferably, the electrolyte further includes a main salt;

[0017] When the alkali metal ion secondary battery is a sodium ion battery, the main salt is a sodium salt with a concentration of 1 to 5 mol / L, for example, it can be 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L or 5 mol / L, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0018] When the alkali metal ion secondary battery is a lithium-ion battery, the main salt is a lithium salt with a concentration of 1 to 5 mol / L, for example, it can be 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L or 5 mol / L, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] Preferably, the electrolyte further includes additives; when the alkali metal ion secondary battery is a sodium ion battery, the additive includes sodium nitrate; when the alkali metal ion secondary battery is a lithium ion battery, the additive includes lithium nitrate.

[0020] Preferably, the negative electrode material further includes a conductive agent and a binder.

[0021] Preferably, the conductive agent includes any one or a combination of at least two of acetylene black, Ketjen black, conductive carbon black, carbon nanotubes, or graphene. Typical but non-limiting combinations include a combination of acetylene black and Ketjen black, a combination of conductive carbon black and carbon nanotubes, a combination of carbon nanotubes and graphene, or a combination of Ketjen black, conductive carbon black, and carbon nanotubes.

[0022] Preferably, the adhesive comprises any one or a combination of at least two of carboxymethyl cellulose, polyvinylpyrrolidone, polyvinylidene fluoride, or polyacrylonitrile. Typical but non-limiting combinations include combinations of carboxymethyl cellulose and polyvinylpyrrolidone, combinations of polyvinylpyrrolidone and polyvinylidene fluoride, and combinations of polyvinylidene fluoride and polyacrylonitrile.

[0023] Preferably, based on the mass of the negative electrode material, the mass fraction of the elemental sulfur-carbon composite material and / or alkali metal sulfide-carbon composite material in the negative electrode material is 60-99 wt%, the mass fraction of the conductive agent is 0.5-30 wt%, and the mass fraction of the binder is 0.5-20 wt%.

[0024] In this invention, the mass of the negative electrode material is taken as 100%. The mass fraction of the elemental sulfur-carbon composite material and / or alkali metal sulfide-carbon composite material in the negative electrode material is 60 to 99 wt%, for example, it can be 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%, or 99 wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] In this invention, the mass of the negative electrode material is taken as 100%. The mass fraction of the conductive agent in the negative electrode material is 0.5 to 30 wt%, for example, it can be 0.5 wt%, 1 wt%, 2 wt%, 5 wt%, 7 wt%, 10 wt%, 12 wt%, 15 wt%, 17 wt%, 20 wt%, 22 wt%, 25 wt%, 27 wt%, or 30 wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0026] In this invention, the mass of the negative electrode material is taken as 100%. The mass fraction of the binder in the negative electrode material is 0.5 to 20 wt%, for example, it can be 0.5 wt%, 1 wt%, 2 wt%, 5 wt%, 7 wt%, 10 wt%, 12 wt%, 15 wt%, 17 wt%, or 20 wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] Preferably, based on the mass of the negative electrode material, the mass fraction of the elemental sulfur-carbon composite material and / or alkali metal sulfide-carbon composite material in the negative electrode material is 80-97 wt%, the mass fraction of the conductive agent is 1-20 wt%, and the mass fraction of the binder is 1-10 wt%.

[0028] Preferably, the mass fraction of elemental sulfur and / or alkali metal sulfide-carbon composite material is 30-99 wt%, for example, 30 wt%, 35 wt%, 40 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, or 90 wt%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, with the balance being carbon material.

[0029] Preferably, the alkali metal sulfide in the alkali metal sulfide-carbon composite material includes sodium sulfide and / or lithium sulfide.

[0030] Preferably, the carbon material in the elemental sulfur-carbon composite material and / or alkali metal sulfide-carbon composite material includes any one or a combination of at least two of microporous carbon, porous carbon, Ketjen black, carbon nanotubes, graphene, conductive carbon black, or high-temperature carbonized organic materials. Typical but non-limiting combinations include combinations of microporous carbon and porous carbon, combinations of porous carbon and Ketjen black, combinations of carbon nanotubes and graphene, combinations of conductive carbon black and high-temperature carbonized organic materials, or combinations of porous carbon, Ketjen black, and carbon nanotubes.

[0031] The microporous carbon described in this invention is a carbon material with a pore size of 1 to 2 nm, and the micropores are distributed inside the carbon material.

[0032] Preferably, the high-temperature carbonized organic compound is obtained by carbonizing polyacrylonitrile and / or polyvinylpyrrolidone at high temperature.

[0033] Preferably, the negative electrode material further includes a catalyst.

[0034] Preferably, the catalyst comprises any one or a combination of at least two of cuprous sulfide, ferrous sulfide, nickel sulfide, metal nitride, or metal oxide. Typical but non-limiting combinations include a combination of cuprous sulfide and ferrous sulfide, a combination of ferrous sulfide and nickel sulfide, a combination of metal nitride and metal oxide, or a combination of cuprous sulfide, ferrous sulfide, and nickel sulfide.

[0035] Preferably, the mass of the catalyst is 0.01% to 30% of the mass of the elemental sulfur-carbon composite material and / or the alkali metal sulfide-carbon composite material, for example, it can be 0.01, 0.05, 0.1, 0.5, 1%, 3%, 5%, 7%, 10%, 12%, 15%, 17%, 20wt%, 22%, 25%, 27% or 30%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 1% to 10%.

[0036] In a second aspect, the present invention provides a method for preparing the alkali metal ion secondary battery described in the first aspect, the method comprising:

[0037] (1) A positive electrode sheet is prepared by using a positive electrode material, and a negative electrode sheet is prepared by using a negative electrode material including elemental sulfur-carbon composite material and / or alkali metal sulfide-carbon composite material; wherein the positive electrode material and / or negative electrode material contains alkali metal;

[0038] (2) The negative electrode obtained in step (1) is subjected to an electrochemical insertion / extraction of alkali metal ions once in an ether electrolyte or carbonate electrolyte containing fluoroethylene carbonate and / or ionic liquid to obtain a negative electrode containing a stable surface SEI film.

[0039] (3) The battery is assembled using the positive electrode obtained in step (1) and the negative electrode with a surface SEI film obtained in step (2) to obtain the alkali metal ion secondary battery.

[0040] Thirdly, the present invention provides an electric device comprising the alkali metal ion secondary battery described in the first aspect.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) The active material in the negative electrode material of the alkali metal ion secondary battery provided by the present invention is a single sulfur-carbon composite material and / or an alkali metal sulfide-carbon composite material, which has the advantages of low cost, high specific capacity and discharge voltage plateau that is much higher than the alkali metal deposition potential, thereby reducing the safety risks such as battery short circuit caused by alkali metal dendrite formation.

[0043] (2) The electrolyte of the alkali metal ion secondary battery provided by the present invention is an ether electrolyte or a carbonate electrolyte containing fluoroethylene carbonate and / or ionic liquid. Before the negative electrode sheet prepared by the material is equipped with the alkali metal ion secondary battery, it is pre-treated by electrochemical means in the electrolyte to undergo one alkali metal ion insertion / extraction cycle. This allows the anions of fluoroethylene carbonate and / or ionic liquid contained in the electrolyte of the alkali metal ion secondary battery to be degraded on the surface of the negative electrode to form a stable SEI film. This achieves uniform deposition and reversibility between sulfur and sulfides, suppresses the shuttle effect of sulfur-containing negative electrode materials, and ensures that the battery has high initial coulombic efficiency, specific capacity and good cycle stability.

[0044] (3) The content of active lithium / sodium in the negative electrode material of the alkali metal ion secondary battery provided by the present invention can be freely adjusted, so as to adapt to the positive electrode material with different initial states and effectively alleviate the problem of low initial coulombic efficiency.

[0045] (4) The alkali metal ion secondary battery provided by the present invention has a simple composition and low raw material cost, so it is suitable for large-scale promotion and use. Detailed Implementation

[0046] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0047] Example 1

[0048] This embodiment provides an alkali metal ion secondary battery;

[0049] The active material in the positive electrode material of the alkali metal ion secondary battery is sodium iron sulfate.

[0050] The active material in the negative electrode material of the alkali metal ion secondary battery is a sulfur-carbon composite material, wherein the sulfur in the sulfur-carbon composite material is sublimated sulfur and the carbon material is microporous carbon; based on the mass of the sulfur-carbon composite material, the mass fraction of sublimated sulfur is 60 wt%, and the remainder is microporous carbon.

[0051] The negative electrode material further includes a conductive agent and a binder, wherein the conductive agent is Ketjen Black and the binder is polyvinylidene fluoride; based on the mass of the negative electrode material, the mass fraction of the elemental sulfur-carbon composite material in the negative electrode material is 80 wt%, the mass fraction of the conductive agent is 10 wt%, and the mass fraction of the binder is 10 wt%.

[0052] The electrolyte in the alkali metal ion secondary battery is a 1 mol / L sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) solution. The solvent of the NaTFSI solution is a mixed solvent of PC (propylene carbonate) and FEC (fluoroethylene carbonate) (PC:FEC = 1:1, the ratio is by volume).

[0053] The preparation method of the alkali metal ion secondary battery is as follows:

[0054] (1) Preparation of elemental sulfur-carbon composite material: Sublimed sulfur and microporous carbon with a mass ratio of 6:4 were mixed evenly by grinding and placed in a tube furnace and kept at 155°C for 12 hours. Then, under the condition of Ar gas, the temperature was heated to 200°C at a heating rate of 5°C / min and kept for 2 hours. After cooling, the elemental sulfur-carbon composite material was obtained.

[0055] (2) Preparation of elemental sulfur-carbon negative electrode sheet: Take the elemental sulfur-carbon composite material obtained in step (1) with a mass ratio of 8:1:1, Ketjen black and polyvinylidene fluoride (PVDF), first completely dissolve PVDF in N-methylpyrrolidone (NMP), then mix it with the mixture of elemental sulfur-carbon composite material and Ketjen black, stir, coat and dry in sequence, and finally obtain sulfur-carbon negative electrode sheet;

[0056] (3) Pre-film treatment of elemental sulfur-carbon negative electrode sheet: The elemental sulfur-carbon negative electrode sheet obtained in step (2) is used to pre-treat a sodium metal battery (in this battery, the elemental sulfur-carbon negative electrode sheet is the positive electrode and the sodium metal is the negative electrode) by charging / discharging cycle once in the electrolyte of the above-mentioned alkali metal ion secondary battery. After disassembling the battery, an elemental sulfur-carbon negative electrode sheet containing a surface SEI film is obtained.

[0057] (4) Preparation of sodium-ion battery: The elemental sulfur-carbon negative electrode with surface SEI film obtained in step (3) is matched with sodium iron sulfate positive electrode to obtain a full cell. The electrolyte is the electrolyte in the above-mentioned alkali metal ion secondary battery.

[0058] Example 2

[0059] This embodiment provides an alkali metal ion secondary battery;

[0060] The active material in the positive electrode material of the alkali metal ion secondary battery is lithium cobalt oxide.

[0061] The active material in the negative electrode material of the alkali metal ion secondary battery is a sulfur-carbon composite material; the sulfur in the sulfur-carbon composite material is sublimated sulfur, and the carbon material is microporous carbon; based on the mass of the sulfur-carbon composite material, the mass fraction of sublimated sulfur is 60 wt%, and the remainder is microporous carbon.

[0062] The negative electrode material further includes a conductive agent and a binder, wherein the conductive agent is Ketjen Black and the binder is polyvinylidene fluoride (PVDF); based on the mass of the negative electrode material, the mass fraction of the elemental sulfur-carbon composite material in the negative electrode material is 80 wt%, the mass fraction of the conductive agent is 10 wt%, and the mass fraction of the binder is 10 wt%.

[0063] The electrolyte in the alkali metal ion secondary battery is a 1 mol / L lithium bis(fluorosulfonyl)imide (LiTFSI) solution. The solvent of the LiTFSI solution is a mixed solvent of PY13FSI (1-methyl-1-propylpyrrolidone bis(fluorosulfonyl)imide) and FEC (fluoroethylene carbonate) (PY13FSI:FEC = 9:1, the ratio is by volume).

[0064] The preparation method of the alkali metal ion secondary battery is as follows:

[0065] (1) Preparation of elemental sulfur-carbon composite material: Sublimed sulfur and microporous carbon with a mass ratio of 6:4 were mixed evenly by grinding and placed in a tube furnace and kept at 155°C for 12 hours. Then, under the condition of Ar gas, the temperature was heated to 200°C at a heating rate of 5°C / min and kept for 2 hours. After cooling, the elemental sulfur-carbon composite material was obtained.

[0066] (2) Preparation of elemental sulfur-carbon negative electrode sheet: Take the elemental sulfur-carbon composite material obtained in step (1) with a mass ratio of 8:1:1, Ketjen black and polyvinylidene fluoride (PVDF), first completely dissolve PVDF in N-methylpyrrolidone (NMP), then mix it with the mixture of elemental sulfur-carbon composite material and Ketjen black, stir, coat and dry in sequence, and finally obtain sulfur-carbon negative electrode sheet;

[0067] (3) Pre-film treatment of elemental sulfur-carbon negative electrode sheet: The elemental sulfur-carbon negative electrode sheet obtained in step (2) is used to pre-treat a lithium metal battery (in this battery, the elemental sulfur-carbon negative electrode sheet is the positive electrode and the lithium metal is the negative electrode) by charging / discharging cycle once in the electrolyte of the above-mentioned alkali metal ion secondary battery. After disassembling the battery, an elemental sulfur-carbon negative electrode sheet containing a surface SEI film is obtained.

[0068] (4) Preparation of lithium-ion battery: The elemental sulfur-carbon negative electrode sheet containing the surface SEI film obtained in step (3) is combined with the lithium cobalt oxide positive electrode sheet to obtain a full cell. The electrolyte is the electrolyte in the above-mentioned alkali metal ion secondary battery.

[0069] Example 3

[0070] This embodiment provides an alkali metal ion secondary battery.

[0071] The active material in the positive electrode material of the alkali metal ion secondary battery is sodium iron sulfate.

[0072] The active material in the negative electrode material of the alkali metal ion secondary battery is a mixture of elemental sulfur-carbon composite material and sodium sulfide-carbon composite material; the elemental sulfur in the elemental sulfur and sodium sulfide-carbon composite material is sublimed sulfur, and the carbon material is microporous carbon; based on the mass of the elemental sulfur and sodium sulfide-carbon composite material, the mass fraction of sublimed sulfur is 54.5 wt%, the mass fraction of sodium sulfide is 36.4 wt%, and the balance is carbon material.

[0073] The negative electrode material also includes a conductive agent and a binder. The conductive agent is Ketjen Black, and the binder is polyvinylidene fluoride (PVDF). Based on the mass of the negative electrode material, the mass fraction of elemental sulfur and sodium sulfide-carbon composite material in the negative electrode material is 80 wt%, the mass fraction of the conductive agent is 10 wt%, and the mass fraction of the binder is 10 wt%.

[0074] The electrolyte in the alkali metal ion secondary battery is a 1 mol / L sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) solution. The solvent of the NaTFSI solution is a mixed solvent of PC (propylene carbonate) and FEC (fluoroethylene carbonate) (PC:FEC = 1:1, the ratio is by volume).

[0075] The preparation method of the alkali metal ion secondary battery is as follows:

[0076] (1) Preparation of elemental sulfur and sodium sulfide-carbon composite material: Sublimed sulfur and microporous carbon with a mass ratio of 6:4 were mixed evenly by grinding and placed in a tube furnace and kept at 155℃ for 12 hours. Then, under the condition of Ar gas, the temperature was heated to 200℃ at a heating rate of 5℃ / min and kept for 2 hours. After cooling, the initial mixture was obtained. Then, sodium sulfide with a mass of 66.7% of the initial mixture was added and ball-milled for 20 minutes to obtain elemental sulfur and sodium sulfide-carbon composite material.

[0077] (2) Preparation of elemental sulfur and sodium sulfide-carbon negative electrode: Take the elemental sulfur and sodium sulfide-carbon composite material obtained in step (1) with a mass ratio of 8:1:1, Ketjen black and polyvinylidene fluoride (PVDF), first completely dissolve PVDF in N-methylpyrrolidone (NMP), then mix it with the mixture of elemental sulfur and sodium sulfide-carbon composite material and Ketjen black, stir, coat and dry in sequence, and finally obtain elemental sulfur and sodium sulfide-carbon negative electrode;

[0078] (3) Pre-film treatment of elemental sulfur and sodium sulfide-carbon negative electrode sheet: The elemental sulfur and sodium sulfide-carbon negative electrode sheet obtained in step (2) is used to prepare a sodium metal battery (in this battery, the elemental sulfur and sodium sulfide-carbon negative electrode sheet is the positive electrode and the sodium metal is the negative electrode). The battery is pre-treated once by charging / discharging cycle in the electrolyte of the above-mentioned alkali metal ion secondary battery. After the battery is disassembled, the elemental sulfur and sodium sulfide-carbon negative electrode sheet containing the surface SEI film is obtained.

[0079] (4) Preparation of sodium-ion battery: The elemental sulfur and sodium sulfide-carbon negative electrode with surface SEI film obtained in step (3) are matched with sodium iron sulfate positive electrode to obtain a full battery. The electrolyte is the electrolyte in the above-mentioned alkali metal ion secondary battery.

[0080] Example 4

[0081] This embodiment provides an alkali metal ion secondary battery;

[0082] The active material in the positive electrode material of the alkali metal ion secondary battery is lithium cobalt oxide.

[0083] The active material in the negative electrode material of the alkali metal ion secondary battery is a mixture of elemental sulfur-carbon composite material and lithium sulfide-carbon composite material (elemental sulfur and sodium sulfide-carbon composite material); the elemental sulfur in the elemental sulfur and lithium sulfide-carbon composite material is sublimated sulfur, and the carbon material is microporous carbon; based on the mass of the elemental sulfur and lithium sulfide-carbon composite material, the mass fraction of sublimated sulfur is 50 wt%, the mass fraction of lithium sulfide is 20 wt%, and the balance is microporous carbon.

[0084] The negative electrode material also includes a conductive agent and a binder. The conductive agent is Ketjen Black, and the binder is polyvinylidene fluoride (PVDF). Based on the mass of the negative electrode material, the mass fraction of elemental sulfur and lithium sulfide-carbon composite material in the negative electrode material is 80 wt%, the mass fraction of the conductive agent is 10 wt%, and the mass fraction of the binder is 10 wt%.

[0085] The electrolyte in the alkali metal ion secondary battery is a 5 mol / L lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) solution. The solvent of the LiTFSI solution is a mixed solvent of PC (propylene carbonate) and FEC (fluoroethylene carbonate) (PC:FEC = 7:3, in volume ratio). The LiTFSI solution also contains 3 wt% LiNO3 by mass.

[0086] The preparation method of the alkali metal ion secondary battery is as follows:

[0087] (1) Preparation of elemental sulfur and lithium sulfide-carbon composite material: Sublimed sulfur and microporous carbon with a mass ratio of 5:3 were mixed evenly by grinding and placed in a tube furnace and kept at 155℃ for 12 hours. Then, under the condition of Ar gas, the temperature was heated to 200℃ at a heating rate of 5℃ / min and kept for 2 hours. After cooling, the initial mixture was obtained. Then, lithium sulfide with a mass of 10% of the initial mixture was added and ball-milled for 20 minutes to obtain elemental sulfur and lithium sulfide-carbon composite material.

[0088] (2) Preparation of elemental sulfur and lithium sulfide-carbon negative electrode: Take the sulfur and lithium sulfide-carbon composite material obtained in step (1) with a mass ratio of 8:1:1, Ketjen black and polyvinylidene fluoride (PVDF), first completely dissolve PVDF in N-methylpyrrolidone (NMP), then mix it with the mixture of elemental sulfur and lithium sulfide-carbon composite material and Ketjen black, stir, coat and dry in sequence, and finally obtain elemental sulfur and lithium sulfide-carbon negative electrode;

[0089] (3) Pre-film treatment of elemental sulfur and lithium sulfide-carbon negative electrode: The elemental sulfur and lithium sulfide-carbon negative electrode obtained in step (2) are used to prepare a lithium metal battery (in this battery, the elemental sulfur and lithium sulfide-carbon negative electrode is the positive electrode and the lithium metal is the negative electrode). The battery is pre-treated once by charging / discharging cycle in the electrolyte of the above-mentioned alkali metal ion secondary battery. After the battery is disassembled, elemental sulfur and lithium sulfide-carbon negative electrode containing surface SEI film is obtained.

[0090] (4) Preparation of lithium-ion battery: The elemental sulfur and lithium sulfide-carbon negative electrode with surface SEI film obtained in step (3) are combined with lithium cobalt oxide positive electrode to obtain a full battery. The electrolyte is the electrolyte in the above-mentioned alkali metal ion secondary battery.

[0091] Example 5

[0092] This embodiment provides an alkali metal ion secondary battery;

[0093] The active material in the positive electrode material of the alkali metal ion secondary battery is sodium nickel iron manganese copper oxide.

[0094] The active material in the negative electrode material of the alkali metal ion secondary battery is a mixture of elemental sulfur-carbon composite material and sodium sulfide-carbon composite material (elemental sulfur and sodium sulfide-carbon composite material); the elemental sulfur in the elemental sulfur and sodium sulfide-carbon composite material is sublimated sulfur, and the carbon material is microporous carbon and Ketjen black; based on the mass of the elemental sulfur and sodium sulfide-carbon composite material, the mass fraction of sublimated sulfur is 63.6 wt%, the mass fraction of sodium sulfide is 9.1 wt%, and the balance is microporous carbon and Ketjen black in a mass ratio of 25:5.

[0095] The negative electrode material also includes a conductive agent and a binder. The conductive agent is Ketjen Black, and the binder is polyvinylidene fluoride (PVDF). Based on the mass of the negative electrode material, the mass fraction of elemental sulfur and sodium sulfide-carbon composite material in the negative electrode material is 80 wt%, the mass fraction of the conductive agent is 10 wt%, and the mass fraction of the binder is 10 wt%.

[0096] The electrolyte in the alkali metal ion secondary battery is a 1 mol / L sodium hexafluorophosphate (NaPF6) solution. The solvent of the NaPF6 solution is a mixed solvent of DME (ethylene glycol dimethyl ether) and FEC (fluoroethylene carbonate) (DME:FEC = 3:7, the ratio is by volume).

[0097] The preparation method of the alkali metal ion secondary battery is as follows:

[0098] (1) Preparation of elemental sulfur and sodium sulfide-carbon composite material: Sublimed sulfur, microporous carbon and Ketjen black with a mass ratio of 70:25:5 were mixed evenly by grinding and placed in a tube furnace and kept at 155℃ for 12 hours. Then, under the condition of Ar gas, the temperature was heated to 200℃ at a heating rate of 5℃ / min and kept for 2 hours. After cooling, the initial mixture was obtained. Then, sodium sulfide with a mass of 10% of the initial mixture was added and ball-milled for 20 minutes to obtain sulfur and sodium sulfide-carbon composite material.

[0099] (2) Preparation of elemental sulfur and sodium sulfide-carbon negative electrode: Take the elemental sulfur and sodium sulfide-carbon composite material obtained in step (1) with a mass ratio of 8:1:1, Ketjen black and polyvinylidene fluoride (PVDF), first completely dissolve PVDF in N-methylpyrrolidone (NMP), then mix it with the mixture of elemental sulfur and sodium sulfide-carbon composite material and Ketjen black, stir, coat and dry in sequence, and finally obtain elemental sulfur and sodium sulfide-carbon negative electrode;

[0100] (3) Pre-film treatment of elemental sulfur and sodium sulfide-carbon negative electrode sheet: The elemental sulfur and sodium sulfide-carbon negative electrode sheet obtained in step (2) is used to prepare a sodium metal battery (in this battery, the elemental sulfur and sodium sulfide-carbon negative electrode sheet is the positive electrode and the sodium metal is the negative electrode). The battery is pre-treated once by charging / discharging cycle in the electrolyte of the above-mentioned alkali metal ion secondary battery. After the battery is disassembled, the elemental sulfur and sodium sulfide-carbon negative electrode sheet containing a stable surface SEI film is obtained.

[0101] (4) Preparation of sodium-ion battery: The elemental sulfur and lithium sulfide-carbon negative electrode with surface SEI film obtained in step (3) are matched with sodium nickel iron manganese copper oxide positive electrode to obtain a full battery. The electrolyte is the electrolyte in the above-mentioned alkali metal ion secondary battery.

[0102] Example 6

[0103] This embodiment provides an alkali metal ion secondary battery.

[0104] The active material in the positive electrode material of the alkali metal ion secondary battery is lithium nickel cobalt manganese oxide.

[0105] The active material in the negative electrode material of the alkali metal ion secondary battery is a mixture of elemental sulfur-carbon composite material and lithium sulfide-carbon composite material (elemental sulfur and sodium sulfide-carbon composite material); the elemental sulfur in the elemental sulfur and lithium sulfide-carbon composite material is sublimed sulfur, and the carbon material is microporous carbon and Ketjen black; based on the mass of the elemental sulfur and lithium sulfide-carbon composite material, the mass fraction of sublimed sulfur is 63.6 wt%, the mass fraction of lithium sulfide is 9.1 wt%, and the balance is microporous carbon and Ketjen black in a mass ratio of 25:5.

[0106] The negative electrode material also includes a conductive agent and a binder. The conductive agent is Ketjen Black, and the binder is polyvinylidene fluoride (PVDF). Based on the mass of the negative electrode material, the mass fraction of elemental sulfur and lithium sulfide-carbon composite material in the negative electrode material is 80 wt%, the mass fraction of the conductive agent is 10 wt%, and the mass fraction of the binder is 10 wt%.

[0107] The electrolyte in the alkali metal ion secondary battery is a 3 mol / L lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) solution. The solvent of the LiTFSI solution is a mixed solvent of PC (propylene carbonate) and FEC (fluoroethylene carbonate) (PC:FEC = 1:1, the ratio is by volume).

[0108] The preparation method of the alkali metal ion secondary battery is as follows:

[0109] (1) Preparation of elemental sulfur and lithium sulfide-carbon composite material: Sublimed sulfur, microporous carbon and Ketjen black with a mass ratio of 70:25:5 were mixed evenly by grinding and placed in a tube furnace and kept at 155°C for 12 hours. Then, under the condition of Ar gas, the temperature was heated to 200°C at a heating rate of 5°C / min and kept for 2 hours. After cooling, the initial mixture was obtained. Then, lithium sulfide with a mass of 10% of the initial mixture was added and ball-milled for 20 minutes to obtain elemental sulfur and lithium sulfide-carbon composite material.

[0110] (2) Preparation of elemental sulfur and lithium sulfide-carbon negative electrode: Take the sulfur and lithium sulfide-carbon composite material obtained in step (1) with a mass ratio of 8:1:1, Ketjen black and polyvinylidene fluoride (PVDF), first completely dissolve PVDF in N-methylpyrrolidone (NMP), then mix it with the mixture of elemental sulfur and lithium sulfide-carbon composite material and Ketjen black, stir, coat and dry in sequence, and finally obtain elemental sulfur and lithium sulfide-carbon negative electrode;

[0111] (3) Pre-film treatment of elemental sulfur and lithium sulfide-carbon negative electrode: The elemental sulfur and lithium sulfide-carbon negative electrode obtained in step (2) are used to prepare a lithium metal battery (in this battery, the elemental sulfur and lithium sulfide-carbon negative electrode is the positive electrode and the lithium metal is the negative electrode). The battery is pre-treated once by charging / discharging cycle in the electrolyte of the above-mentioned alkali metal ion secondary battery. After the battery is disassembled, elemental sulfur and lithium sulfide-carbon negative electrode containing surface SEI film is obtained.

[0112] (4) Preparation of lithium-ion battery: The elemental sulfur and lithium sulfide-carbon negative electrode with surface SEI film obtained in step (3) are matched with lithium nickel cobalt manganese oxide positive electrode to obtain a full cell. The electrolyte is the electrolyte in the above-mentioned alkali metal ion secondary battery.

[0113] Example 7

[0114] This embodiment provides an alkali metal ion secondary battery.

[0115] The active material in the positive electrode material of the alkali metal ion secondary battery is lithium nickel cobalt manganese oxide.

[0116] The active material in the negative electrode material of the alkali metal ion secondary battery is a mixture of elemental sulfur-carbon composite material and lithium sulfide-carbon composite material (elemental sulfur and sodium sulfide-carbon composite material); the elemental sulfur in the elemental sulfur and lithium sulfide-carbon composite material is sublimated sulfur, and the carbon material is Ketjen black and carbon nanotubes; based on the mass of the elemental sulfur and lithium sulfide-carbon composite material, the mass fraction of sublimated sulfur is 60wt%, the mass fraction of lithium sulfide is 10wt%, and the balance is Ketjen black and carbon nanotubes in a mass ratio of 25:5.

[0117] The negative electrode material also includes a conductive agent and a binder. The conductive agent is Ketjen Black, and the binder is polyvinylidene fluoride (PVDF). Based on the mass of the negative electrode material, the mass fraction of elemental sulfur and lithium sulfide-carbon composite material in the negative electrode material is 80 wt%, the mass fraction of the conductive agent is 10 wt%, and the mass fraction of the binder is 10 wt%.

[0118] The electrolyte in the alkali metal ion secondary battery is a 5 mol / L lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) solution. The solvent of the LiTFSI solution is a mixed solvent of PC (propylene carbonate) and FEC (fluoroethylene carbonate) (PC:FEC = 1:1, the ratio is by volume).

[0119] The preparation method of the alkali metal ion secondary battery is as follows:

[0120] (1) Preparation of elemental sulfur and lithium sulfide-carbon composite material: Sublimed sulfur, lithium sulfide, Ketjen black and carbon nanotubes with a mass ratio of 60:10:25:5 were mixed evenly by grinding and placed in a tube furnace and kept at 155°C for 12 hours. Then, under the condition of Ar gas, the temperature was heated to 200°C at a heating rate of 5°C / min and kept for 2 hours. After cooling, the initial mixture was obtained, and elemental sulfur and lithium sulfide-carbon composite material was obtained.

[0121] (2) Preparation of elemental sulfur and lithium sulfide-carbon negative electrode: Take the sulfur and lithium sulfide-carbon composite material obtained in step (1) with a mass ratio of 8:1:1, Ketjen black and polyvinylidene fluoride (PVDF), first completely dissolve PVDF in N-methylpyrrolidone (NMP), then mix it with the mixture of elemental sulfur and lithium sulfide-carbon composite material and Ketjen black, stir, coat and dry in sequence, and finally obtain elemental sulfur and lithium sulfide-carbon negative electrode;

[0122] (3) Pre-film treatment of elemental sulfur and lithium sulfide-carbon negative electrode: The elemental sulfur and lithium sulfide-carbon negative electrode obtained in step (2) are used to prepare a lithium metal battery (in this battery, the elemental sulfur and lithium sulfide-carbon negative electrode is the positive electrode and the lithium metal is the negative electrode). The battery is pre-treated once by charging / discharging cycle in the electrolyte of the above-mentioned alkali metal ion secondary battery. After the battery is disassembled, elemental sulfur and lithium sulfide-carbon negative electrode containing surface SEI film is obtained.

[0123] (4) Preparation of lithium-ion battery: The elemental sulfur and lithium sulfide-carbon negative electrode with surface SEI film obtained in step (3) are matched with lithium nickel cobalt manganese oxide positive electrode to obtain a full cell. The electrolyte is the electrolyte in the above-mentioned alkali metal ion secondary battery.

[0124] Example 8

[0125] This embodiment provides an alkali metal ion secondary battery.

[0126] The active material in the positive electrode material of the alkali metal ion secondary battery is manganese dioxide;

[0127] The active material in the negative electrode material of the alkali metal ion secondary battery is a sodium sulfide-carbon composite material; the carbon material in the sodium sulfide-carbon composite material is Ketjen black and carbon nanotubes; based on the mass of the sodium sulfide-carbon composite material, the mass fraction of sodium sulfide is 73.7 wt%, and the balance is Ketjen black and carbon nanotubes in a mass ratio of 20:5.

[0128] The negative electrode material also includes a conductive agent and a binder. The conductive agent is Ketjen Black, and the binder is polyvinylidene fluoride (PVDF). Based on the mass of the negative electrode material, the mass fraction of the sodium sulfide-carbon composite material in the negative electrode material is 80 wt%, the mass fraction of the conductive agent is 10 wt%, and the mass fraction of the binder is 10 wt%.

[0129] The electrolyte in the alkali metal ion secondary battery is a 2 mol / L NaFSI (sodium bis(fluorosulfonyl)imide) solution. The solvent for the NaFSI solution is a mixed solvent of DME (ethylene glycol dimethyl ether) and Py13FSI (1-methyl-1-propylpyrrolidone bis(fluorosulfonyl)imide) (DME:Py13FSI = 1:1, the ratio is by volume).

[0130] The preparation method of the alkali metal ion secondary battery is as follows:

[0131] (1) Preparation of sodium sulfide-carbon composite material: Sodium sulfide, Ketjen black and carbon nanotubes with a mass ratio of 70:20:5 were mixed uniformly by ball milling to obtain sodium sulfide-carbon composite material.

[0132] (2) Preparation of sodium sulfide-carbon negative electrode sheet: Take sodium sulfide-carbon composite material, Ketjen black and polyvinylidene fluoride (PVDF) obtained in step (1) with a mass ratio of 8:1:1. First, completely dissolve PVDF in N-methylpyrrolidone (NMP), then mix it with the mixture of sodium sulfide-carbon composite material and Ketjen black, and stir, coat and dry in sequence to finally obtain sodium sulfide-carbon negative electrode sheet;

[0133] (3) Pre-film treatment of sodium sulfide-carbon negative electrode sheet: The sodium sulfide-carbon negative electrode sheet obtained in step (2) is used to prepare a sodium metal battery (the sodium sulfide-carbon negative electrode sheet is the positive electrode and the sodium metal is the negative electrode). The battery is pre-treated by charging / discharging cycle once in the electrolyte of the above-mentioned alkali metal ion secondary battery. After the battery is disassembled, elemental sulfur and sodium sulfide-carbon negative electrode sheet containing surface SEI film are obtained.

[0134] (4) Preparation of sodium-ion battery: The elemental sulfur and sodium sulfide-carbon negative electrode with surface SEI film obtained in step (3) are matched with manganese dioxide positive electrode to obtain a full battery. The electrolyte is the electrolyte in the above-mentioned alkali metal ion secondary battery.

[0135] Example 9

[0136] This embodiment provides an alkali metal ion secondary battery;

[0137] The active material in the positive electrode material of the alkali metal ion secondary battery is Na. 0.72 MnO2;

[0138] The active material in the negative electrode material of the alkali metal ion secondary battery is a mixture of elemental sulfur-carbon composite material and sodium sulfide-carbon composite material (elemental sulfur and sodium sulfide-carbon composite material); the sulfur in the elemental sulfur and sodium sulfide-carbon composite material is sublimated sulfur, and the carbon material is microporous carbon; based on the mass of the sulfur and sodium sulfide-carbon composite material, the mass fraction of sublimated sulfur is 47.6 wt%, the mass fraction of sodium sulfide is 28.6 wt%, and the balance is microporous carbon;

[0139] The negative electrode material also includes a conductive agent and a binder. The conductive agent is Ketjen Black, and the binder is polyvinylidene fluoride (PVDF). Based on the mass of the negative electrode material, the mass fraction of elemental sulfur and sodium sulfide-carbon composite material in the negative electrode material is 80 wt%, the mass fraction of the conductive agent is 10 wt%, and the mass fraction of the binder is 10 wt%.

[0140] The electrolyte in the alkali metal ion secondary battery is a 1 mol / L sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) solution. The solvent of the NaTFSI solution is a mixed solvent of PC (propylene carbonate) and FEC (fluoroethylene carbonate) (PC:FEC = 1:1, the ratio is by volume).

[0141] The preparation method of the alkali metal ion secondary battery is as follows:

[0142] (1) Preparation of elemental sulfur and sodium sulfide-carbon composite material: Sublimed sulfur and microporous carbon with a mass ratio of 8:4 were mixed evenly by grinding and placed in a tube furnace and kept at 155℃ for 12 hours. Then, under the condition of Ar gas, the temperature was heated to 200℃ at a heating rate of 5℃ / min and kept for 2 hours. After cooling, the initial mixture was obtained. Then, sodium sulfide with a mass of 40% of the initial mixture was added and ball-milled for 30 minutes to obtain elemental sulfur and sodium sulfide-carbon composite material.

[0143] (2) Preparation of elemental sulfur and sodium sulfide-carbon negative electrode: Take the elemental sulfur and sodium sulfide-carbon composite material obtained in step (1) with a mass ratio of 8:1:1, Ketjen black and polyvinylidene fluoride (PVDF), first completely dissolve PVDF in N-methylpyrrolidone (NMP), then mix it with the mixture of elemental sulfur and sodium sulfide-carbon composite material and Ketjen black, stir, coat and dry in sequence, and finally obtain elemental sulfur and sodium sulfide-carbon negative electrode;

[0144] (3) Pre-film treatment of elemental sulfur and sodium sulfide-carbon negative electrode sheet: The elemental sulfur and sodium sulfide-carbon negative electrode sheet obtained in step (2) is used to prepare a sodium metal battery (the elemental sulfur and sodium sulfide-carbon negative electrode sheet is the positive electrode and the sodium metal is the negative electrode). The battery is pre-treated by charging / discharging cycle once in the electrolyte of the above-mentioned alkali metal ion secondary battery. After the battery is disassembled, elemental sulfur and sodium sulfide-carbon negative electrode sheet containing surface SEI film is obtained.

[0145] (4) Preparation of sodium-ion battery: The elemental sulfur and sodium sulfide-carbon negative electrode sheet containing the surface SEI film obtained in step (3) are mixed with Na 0.72 The MnO2 positive electrode is matched and assembled to obtain a full cell, and the electrolyte is the same as that used in the alkali metal ion secondary cell.

[0146] Example 10

[0147] This embodiment provides an alkali metal ion secondary battery;

[0148] The active material in the positive electrode material of the alkali metal ion secondary battery is sodium iron sulfate.

[0149] The active material in the negative electrode material of the alkali metal ion secondary battery is a mixture of elemental sulfur-carbon composite material and sodium sulfide-carbon composite material (elemental sulfur and sodium sulfide-carbon composite material); the sulfur in the elemental sulfur and sodium sulfide-carbon composite material is sublimed sulfur, and the carbon material is microporous carbon; based on the mass of the elemental sulfur and sodium sulfide-carbon composite material, the mass fraction of sublimed sulfur is 54.5 wt%, the mass fraction of sodium sulfide is 9.1 wt%, and the balance is microporous carbon;

[0150] The negative electrode material also includes a conductive agent, a binder, and a catalyst. The conductive agent is Ketjen Black, the binder is N-methylpyrrolidone (NMP), and the catalyst is cuprous sulfide.

[0151] Based on the mass of the negative electrode material, the mass fraction of elemental sulfur and sodium sulfide-carbon composite material in the negative electrode material is 76.5 wt%, the mass fraction of the conductive agent is 10 wt%, the mass fraction of the binder is 10 wt%, and the mass fraction of the catalyst is 3.5 wt%.

[0152] The electrolyte in the alkali metal ion secondary battery is a 1 mol / L sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) solution. The solvent of the NaTFSI solution is a mixed solvent of PC (propylene carbonate) and FEC (fluoroethylene carbonate) (PC:FEC = 1:1, the ratio is by volume).

[0153] The preparation method of the alkali metal ion secondary battery is as follows:

[0154] (1) Preparation of elemental sulfur and sodium sulfide-carbon composite material: Sublimed sulfur and microporous carbon with a mass ratio of 6:4 were mixed evenly by grinding and placed in a tube furnace and kept at 155°C for 12 hours. Then, under the condition of Ar gas, the temperature was heated to 200°C at a heating rate of 5°C / min and kept for 2 hours. After cooling, the initial mixture was obtained. Then, sodium sulfide with a mass of 10% of the initial mixture and cuprous sulfide with a mass of 5% of the initial mixture were added and ball-milled for 20 minutes to obtain a mixture of elemental sulfur and sodium sulfide-carbon composite material and cuprous sulfide.

[0155] (2) Preparation of elemental sulfur and sodium sulfide-carbon negative electrode: Take the mixture of elemental sulfur and sodium sulfide-carbon composite material obtained in step (1) with a mass ratio of 8:1:1 and cuprous sulfide, Ketjen black and polyvinylidene fluoride (PVDF), first completely dissolve PVDF in N-methylpyrrolidone (NMP), then mix it with the mixture of elemental sulfur and sodium sulfide-carbon composite material and cuprous sulfide, and Ketjen black, stir, coat and dry in sequence, and finally obtain elemental sulfur and sodium sulfide-carbon negative electrode;

[0156] (3) Pre-film treatment of elemental sulfur and sodium sulfide-carbon negative electrode sheet: The elemental sulfur and sodium sulfide-carbon negative electrode sheet obtained in step (2) is used to prepare a sodium metal battery (in this battery, the elemental sulfur and sodium sulfide-carbon negative electrode sheet is the positive electrode and the sodium metal is the negative electrode). The battery is pre-treated once by charging / discharging cycle in the electrolyte of the above-mentioned alkali metal ion secondary battery. After the battery is disassembled, the elemental sulfur and sodium sulfide-carbon negative electrode sheet containing the surface SEI film is obtained.

[0157] (4) Preparation of sodium-ion battery: The elemental sulfur and sodium sulfide-carbon negative electrode with surface SEI film obtained in step (3) are matched with sodium iron sulfate positive electrode to obtain a full battery. The electrolyte is the electrolyte in the above-mentioned alkali metal ion secondary battery.

[0158] Example 11

[0159] This embodiment provides an alkali metal ion secondary battery;

[0160] The active material in the positive electrode material of the alkali metal ion secondary battery is manganese dioxide;

[0161] The active material in the negative electrode material of the alkali metal ion secondary battery is a sodium sulfide-carbon composite material; the carbon material in the sodium sulfide-carbon composite material is Ketjen Black; based on the mass of the sodium sulfide-carbon composite material, the mass fraction of sodium sulfide is 75 wt% and the mass fraction of Ketjen Black is 75 wt%.

[0162] The negative electrode material also includes a conductive agent, a binder, and a catalyst. The conductive agent is Ketjen Black, the binder is polyvinylidene fluoride (PVDF), and the catalyst is cuprous oxide.

[0163] Based on the mass of the negative electrode material, the mass fraction of the lithium sulfide-carbon composite material in the negative electrode material is 75 wt%, the mass fraction of the conductive agent is 10 wt%, the mass fraction of the binder is 10 wt%, and the mass fraction of the catalyst is 5 wt%.

[0164] The electrolyte in the secondary battery is a 1 mol / L lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) solution, which is a mixed solution of the solvents DOL (1,3-dioxolane), DME (dimethoxyethane), and FEC (fluoroethylene carbonate) (DOL:DME:FEC = 1:1:1, in volume ratio); the LiTFSI solution also contains 3 wt% LiNO3 by mass.

[0165] The preparation method of the alkali metal ion secondary battery is as follows:

[0166] (1) Preparation of sodium sulfide-carbon composite material: Sodium sulfide, cuprous oxide, Ketjen black and polyvinylpyrrolidone (PVP) in a mass ratio of 7:1:0.9:2 were taken. PVP was completely dissolved in NMP. Then, sodium sulfide, cuprous oxide and Ketjen black were ground evenly and added to obtain a mixed slurry. The mixed slurry was stirred for 2 hours and then taken out and dried. Then it was placed in a tube furnace and heated to 500°C at a heating rate of 5°C / min under Ar gas conditions and held for 1 hour. After cooling, it was taken out to obtain a mixture of sodium sulfide-carbon composite material and cuprous oxide.

[0167] (2) Preparation of sodium sulfide-carbon negative electrode sheet: Take the mixture of sodium sulfide-carbon composite material and cuprous oxide obtained in step (1) with a mass ratio of 8:1:1, Ketjen black and polyvinylidene fluoride (PVDF), first completely dissolve PVDF in N-methylpyrrolidone (NMP), then mix it with the mixture of sodium sulfide-carbon composite material and cuprous oxide and Ketjen black, stir, coat and dry in sequence, and finally obtain sodium sulfide-carbon negative electrode sheet;

[0168] (3) Pre-film treatment of sodium sulfide-carbon negative electrode sheet: The sodium sulfide-carbon negative electrode sheet obtained in step (2) is used to prepare a sodium metal battery (the sodium sulfide-carbon negative electrode sheet is the positive electrode and the sodium metal is the negative electrode). The battery is pre-treated by charging / discharging cycle once in the electrolyte of the above-mentioned alkali metal ion secondary battery. After the battery is disassembled, elemental sulfur and sodium sulfide-carbon negative electrode sheet containing surface SEI film are obtained.

[0169] (4) Preparation of sodium-ion battery: The elemental sulfur and sodium sulfide-carbon negative electrode with surface SEI film obtained in step (3) are matched with manganese dioxide positive electrode to obtain a full battery. The electrolyte is the electrolyte in the above-mentioned alkali metal ion secondary battery.

[0170] Example 12

[0171] This embodiment provides an alkali metal ion secondary battery; except that the mass fraction of sublimed sulfur is 25 wt% based on the mass of the sulfur-carbon composite material, and the remainder is microporous carbon, everything else is the same as in Example 1.

[0172] Example 13

[0173] This embodiment provides an alkali metal ion secondary battery; except that the mass fraction of sublimed sulfur is 99.5 wt% based on the mass of the sulfur-carbon composite material, and the remainder is microporous carbon, everything else is the same as in Example 1.

[0174] Example 14

[0175] This embodiment provides an alkali metal ion secondary battery; except that, based on the mass of the negative electrode material as 100%, the mass fraction of sulfur and sodium sulfide-carbon composite material in the negative electrode material is 79.5 wt%, the mass fraction of the conductive agent is 10 wt%, the mass fraction of the binder is 10 wt%, and the mass fraction of the catalyst is 0.5 wt%, the rest are the same as in Example 10.

[0176] Example 15

[0177] This embodiment provides an alkali metal ion secondary battery. Except that the mass fraction of sulfur and sodium sulfide-carbon composite material in the negative electrode material is 45 wt%, the mass fraction of the conductive agent is 10 wt%, the mass fraction of the binder is 10 wt%, and the mass fraction of the catalyst is 35 wt%, the rest are the same as in Example 10.

[0178] Comparative Example 1

[0179] This comparative example provides an alkali metal ion secondary battery, which is the same as in Example 1 except that the electrolyte in the alkali metal ion secondary battery is a 1 mol / L sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) solution and the solvent of the NaTFSI solution is PC (propylene carbonate).

[0180] The alkali metal ion secondary batteries provided in the above embodiments and comparative examples were subjected to specific capacity testing, initial coulombic efficiency testing, capacity retention testing after 100 cycles at 0.5C, and average coulombic efficiency testing.

[0181] The specific capacity test method is as follows: constant current charge and discharge is performed at 0.1C within the rated voltage range, and the specific capacity of the fifth discharge cycle is taken. The mass of the active material is calculated according to the mass of the positive electrode active material. The test results are shown in Table 1.

[0182] The method for the first coulomb efficiency test is as follows: constant current charging and discharging at 0.1C within the rated voltage range, charging first and then discharging, to obtain the charging specific capacity / discharging specific capacity. The test results are shown in Table 1.

[0183] The method for testing the capacity retention rate after 100 cycles at 0.5C is as follows: constant current charge and discharge for 5 cycles at 0.1C within the rated voltage range, then the current is adjusted to 0.5C for cycling, and the discharge specific capacity of the 100th cycle is divided by the discharge specific capacity of the first cycle. The test results are shown in Table 1.

[0184] The method for testing the average coulombic efficiency is as follows: after 100 cycles of constant current charging and discharging at 0.5C within the rated voltage range, the average coulombic efficiency is obtained, and the test results are shown in Table 1.

[0185] Table 1

[0186]

[0187] From Table 1, we can obtain:

[0188] (1) The lithium-ion secondary battery and sodium-ion secondary battery provided in Examples 1 to 11 of the present invention have high specific capacity, high initial coulombic efficiency, high capacity retention rate and high average coulombic efficiency.

[0189] (2) By comparing Example 1 with Examples 12 and 13, it can be seen that the mass fraction of elemental sulfur-carbon composite material and / or alkali metal sulfide-carbon composite material in this invention will affect the performance of alkali metal ion secondary battery. When the mass fraction of elemental sulfur-carbon composite material and / or alkali metal sulfide-carbon composite material is too low, the energy density of alkali metal ion secondary battery will be too low, which is due to the low proportion of active material. When the mass fraction of elemental sulfur-carbon composite material and / or alkali metal sulfide-carbon composite material is too high, the specific capacity, initial coulombic efficiency, capacity retention rate and average coulombic efficiency of alkali metal ion secondary battery will be too low, which is due to the high S content leading to reduced electronic conductivity, greater volume expansion and hindered conversion kinetics.

[0190] (3) By comparing Example 1 with Examples 14 and 15, it can be seen that the mass fraction of the catalyst in this invention affects the performance of the alkali metal ion secondary battery. When the mass fraction of the catalyst is too low, the specific capacity, initial coulombic efficiency, capacity retention rate and average coulombic efficiency of the alkali metal ion secondary battery will be low. This is because the conversion kinetics of active sulfur is limited due to insufficient catalyst. When the mass fraction of the catalyst is too high, the energy density of the alkali metal ion secondary battery will be reduced. This is because the mass fraction of the catalyst is too high and does not contribute to the capacity.

[0191] (4) By comparing Example 1 and Comparative Example 1, it can be seen that the electrolyte in the alkali metal ion secondary battery of the present invention is an ether electrolyte or carbonate electrolyte containing fluoroethylene carbonate and / or ionic liquid. The anions of fluoroethylene carbonate and / or ionic liquid contained in the electrolyte can be degraded during the first discharge process, thereby degrading and forming a stable SEI film on the negative electrode surface. This can suppress the shuttle effect of sulfur-containing negative electrode materials, realize uniform deposition and reversibility between sulfur and sulfides, and thus ensure that the battery has a high specific capacity and good cycle stability.

[0192] In summary, the negative electrode material of the alkali metal ion secondary battery provided by this invention adopts elemental sulfur-carbon composite material and / or alkali metal sulfide-carbon composite material, which reduces the safety risks such as battery short circuits caused by alkali metal dendrite formation. In addition, the anions of fluoroethylene carbonate and / or ionic liquid contained in the electrolyte of the alkali metal ion secondary battery can be degraded during the first discharge, thereby degrading and forming a stable SEI film on the negative electrode surface, which can suppress the shuttle effect of sulfur-containing negative electrode materials and ensure that the battery has a high specific capacity and good cycle stability. Furthermore, the active lithium / sodium content in the negative electrode material of the alkali metal ion secondary battery can be freely adjusted, which can effectively alleviate the problem of low initial coulombic efficiency. Finally, the production cost of the alkali metal ion secondary battery is low.

[0193] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. An alkali metal ion secondary battery, characterized in that, The negative electrode material of the alkali metal ion secondary battery includes elemental sulfur-carbon composite material and / or alkali metal sulfide-carbon composite material, the electrolyte includes ether electrolyte or carbonate electrolyte, and the electrolyte contains fluoroethylene carbonate and / or ionic liquid, and the positive electrode material and / or negative electrode material of the alkali metal ion secondary battery contains alkali metal ions.

2. The alkali metal ion secondary battery according to claim 1, characterized in that, When the alkali metal ion secondary battery is a sodium ion battery, the positive electrode material includes sodium iron sulfate, sodium nickel iron manganese cuprate, manganese dioxide, or Na. 0.72 The sodium-ion battery contains any one or at least two of MnO2, and the positive and / or negative electrode materials include a sodium source. Preferably, when the alkali metal ion secondary battery is a lithium-ion battery, the positive electrode material includes any one or a combination of at least two of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium manganese iron phosphate, or manganese dioxide, and the positive electrode material and / or negative electrode material of the lithium-ion battery includes a lithium source.

3. The alkali metal ion secondary battery according to claim 1 or 2, characterized in that, The electrolyte also includes a main salt; when the alkali metal ion secondary battery is a sodium ion battery, the main salt is a sodium salt with a concentration of 1 to 5 mol / L; when the alkali metal ion secondary battery is a lithium ion battery, the main salt is a lithium salt with a concentration of 1 to 5 mol / L. Preferably, the electrolyte further includes additives; when the alkali metal ion secondary battery is a sodium ion battery, the additive includes sodium nitrate; when the alkali metal ion secondary battery is a lithium ion battery, the additive includes lithium nitrate.

4. The alkali metal ion secondary battery according to any one of claims 1 to 3, characterized in that, The negative electrode material also includes a conductive agent and a binder; Preferably, the conductive agent includes any one or a combination of at least two of acetylene black, Ketjen black, conductive carbon black, carbon nanotubes, or graphene. Preferably, the adhesive comprises any one or a combination of at least two of carboxymethyl cellulose, polyvinylpyrrolidone, polyvinylidene fluoride, or polyacrylonitrile.

5. The alkali metal ion secondary battery according to claim 4, characterized in that, Based on the mass of the negative electrode material, the mass fraction of the elemental sulfur-carbon composite material and / or alkali metal sulfide-carbon composite material in the negative electrode material is 60-99 wt%, the mass fraction of the conductive agent is 0.5-30 wt%, and the mass fraction of the binder is 0.5-20 wt%. Preferably, based on the mass of the negative electrode material, the mass fraction of the elemental sulfur-carbon composite material and / or alkali metal sulfide-carbon composite material in the negative electrode material is 80-97 wt%, the mass fraction of the conductive agent is 1-20%, and the mass fraction of the binder is 1-10 wt%. Preferably, based on the mass of the elemental sulfur-carbon composite material and / or alkali metal sulfide-carbon composite material, the mass fraction of elemental sulfur and / or alkali metal sulfides is 30-99 wt%, preferably 50-80 wt%, with the remainder being carbon material.

6. The alkali metal ion secondary battery according to any one of claims 1 to 5, characterized in that, The alkali metal sulfide-carbon composite material includes sodium sulfide and / or lithium sulfide; Preferably, the carbon material in the elemental sulfur-carbon composite material and / or alkali metal sulfide-carbon composite material includes any one or a combination of at least two of microporous carbon, porous carbon, Ketjen black, carbon nanotubes, graphene, conductive carbon black, or high-temperature carbonized organic materials.

7. The alkali metal ion secondary battery according to any one of claims 1 to 6, characterized in that, The negative electrode material also includes a catalyst; Preferably, the catalyst comprises any one or a combination of at least two of cuprous sulfide, ferrous sulfide, nickel sulfide, metal nitride, or metal oxide.

8. The alkali metal ion secondary battery according to claim 7, characterized in that, The mass of the catalyst is 0.01-30% of the mass of the elemental sulfur-carbon composite material and / or the alkali metal sulfide-carbon composite material, preferably 0.01-10%.

9. A method for preparing an alkali metal ion secondary battery according to any one of claims 1 to 8, characterized in that, The preparation method includes: (1) A positive electrode sheet is prepared by using a positive electrode material, and a negative electrode sheet is prepared by using a negative electrode material including elemental sulfur-carbon composite material and / or alkali metal sulfide-carbon composite material; wherein the positive electrode material and / or negative electrode material contains alkali metal ions; (2) The negative electrode obtained in step (1) is subjected to an electrochemical insertion / extraction of alkali metal ions once in an ether electrolyte or carbonate electrolyte containing fluoroethylene carbonate and / or ionic liquid to obtain a negative electrode containing a surface SEI film. (3) The battery is assembled using the positive electrode obtained in step (1) and the negative electrode with a surface SEI film obtained in step (2) to obtain the alkali metal ion secondary battery.

10. An electric device, characterized in that, The electric device includes the alkali metal ion secondary battery as described in any one of claims 1 to 8.

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