Pre-sodium-modified negative electrode dry-method electrode and preparation method thereof

Abstract

The preparation method comprises the following steps: S1, mixing a hydrochloric acid solution with organic sodium sulfonate, then adding aniline and water, stirring and dissolving, then adding an oxidizing agent to carry out doping reaction, and carrying out suction filtration, washing, drying and grinding on a reaction product to obtain sodium-modified polyaniline; s2, uniformly mixing a negative electrode active material, a conductive agent and polytetrafluoroethylene, and then adding sodium polyaniline and an organic sodium supplement agent in a nitrogen or inert atmosphere for fibration treatment to obtain fibration powder; and S3, performing hot pressing on the fiberized powder onto the current collector to obtain the lithium ion battery. The prepared pre-sodium-modified negative electrode dry-method electrode has relatively good peeling strength and pole piece flexibility, and the condition that a traditional wet-method thick electrode is easy to crack is relieved; meanwhile, the dry-method electrode subjected to sodium modification treatment can induce uniform deposition of sodium ions, so that the dynamic performance of the whole sodium battery is improved, the problem of cyclic sodium precipitation is avoided, and the service life of the battery is further prolonged.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sodium ion batteries, and in particular, the application relates to a pre-sodiumized negative electrode dry electrode and a preparation method thereof. BACKGROUND

[0002] Lithium ion batteries are widely used in portable electronic products, communication equipment and electric vehicles due to their high energy density, low self-discharge, long service life, green environmental protection, reasonable cost and other advantages. However, the limited lithium resources and uneven distribution in the world limit the development of lithium ion batteries, so the market urgently needs the emergence of lithium ion battery substitutes. Sodium ion batteries become excellent substitutes for lithium ion batteries due to their similar physical and chemical properties, lower cost and higher safety.

[0003] At present, the preparation of sodium ion battery pole pieces mostly adopts the traditional wet manufacturing process. However, in the solvent evaporation process of the wet electrode, the binder and the conductive agent will float up with the solvent and gather near the surface, while the active material will precipitate, resulting in electrode delamination, which will damage the construction of the electrode conductive network and reduce the bonding strength between the active material and the current collector. Moreover, the existing sodium ion negative electrode material has a low compaction density, resulting in a relatively large thickness of the negative electrode pole piece, which not only reduces the flexibility of the pole piece and causes the pole piece to crack, but also affects the ion transmission kinetics, leading to sodium precipitation during the battery cycle.

[0004] Therefore, the dry electrode is becoming a "new engine" of battery technology revolution due to its low cost, excellent performance and strong adaptability. The dry preparation process usually involves dry mixing of active material, binder and conductive agent powder, and then directly spraying it onto the current collector or pressing it into a self-supporting pole piece. Since it does not require a solvent drying process, the preparation process is simple, which not only reduces production costs, but also helps to control the microstructure of the pole piece, establish a good electrode conductive network, and improve the flexibility and electrical conductivity of high-thickness pole pieces. However, the existing dry preparation process has difficulty in controlling the uniformity of the material, which can lead to uneven material dispersion, resulting in coating defects and affecting the stability of the electrode and the cycle life of the battery. Moreover, since the dry process requires precise control of parameters such as pressure, temperature and mixing time, the precision of the special equipment is extremely high. If the parameters are not controlled properly, it will directly affect the uniformity of the coating layer and the consistency of the product.

[0005] In summary, it is crucial to find a new dry preparation process that can further improve the electrochemical performance of sodium ion batteries while being simple and easy to operate. SUMMARY

[0006] The present application aims to at least partially solve one of the technical problems in the related art. To this end, the present application embodiment provides a pre-sodium negative dry electrode and a preparation method thereof.

[0007] In a first aspect, the present application embodiment provides a preparation method of a pre-sodium negative dry electrode, comprising the following steps:

[0008] S1: mixing hydrochloric acid solution and organic sulfonic acid sodium, then adding aniline and water to stir and dissolve, and then adding an oxidizing agent to perform a doping reaction, and the reaction product is subjected to suction filtration, washing, drying, and grinding to obtain sodiumized polyaniline;

[0009] S2: mixing negative active material, conductive agent, and polytetrafluoroethylene, then adding the sodiumized polyaniline and organic sodium supplementing agent under nitrogen or inert atmosphere, and performing fiberization treatment to obtain fiberized powder;

[0010] S3: hot pressing the fiberized powder onto a current collector to obtain a pre-sodium negative dry electrode.

[0011] In some embodiments, in the step S1, the organic sulfonic acid sodium includes at least one of sodium methyl sulfonate, sodium benzene sulfonate, and sodium naphthalene sulfonate;

[0012] And / or, the oxidizing agent includes at least one of ammonium persulfate and hydrogen peroxide;

[0013] And / or, the sum of the concentrations of the hydrochloric acid solution and the organic sulfonic acid sodium is 2-3 mol / L;

[0014] And / or, the molar ratio of the organic sulfonic acid sodium, the aniline, and the oxidizing agent is (0.3-0.8):(5-7):(0.02-0.04).

[0015] In some embodiments, in the step S1, the reaction temperature of the doping reaction is 10-20℃, and the reaction time is 4-6h;

[0016] And / or, the washing liquid used in the washing is a hydrochloric acid solution, and the concentration of the hydrochloric acid solution is 0.3-0.5 mol / L;

[0017] And / or, the drying method is vacuum drying, the temperature of the vacuum drying is 60-80℃, and the drying time is 16-20h.

[0018] In some embodiments, in the step S2, the negative active material includes at least one of graphene, graphene oxide, soft carbon, hard carbon, expanded graphite, silicon, and mesocarbon microbeads, and is preferably hard carbon;

[0019] And / or, the conductive agent comprises at least one of a metal-based conductive agent, a metal oxide-based conductive agent, a non-metallic particulate conductive agent, a non-metallic fibrous conductive agent, a non-metallic flaky conductive agent, and a composite conductive agent.

[0020] And / or, the organic sodium supplement agent comprises at least one of sodium naphthalene, sodium biphenyl, sodium anthraquinone, and preferably sodium biphenyl.

[0021] And / or, the mass ratio of the negative electrode active material, the conductive agent, the polytetrafluoroethylene, the sodium-doped polyaniline, and the organic sodium supplement agent is (93-97):(0.5-1.5):(1-2):(1-2):(0.5-1.5).

[0022] In some embodiments, in the step S2, the inert atmosphere comprises at least one of argon and helium.

[0023] And / or, the stirring speed of the mixing is 100-200 r / min, and the stirring time is 0.5-1 h.

[0024] And / or, the fiberization treatment is performed by ball milling, the ball-to-material ratio in the ball milling is (6-10):1, the rotation speed is 1500-400 r / min, and the ball milling time is 2-6 h.

[0025] In some embodiments, in the step S3, the current collector is a copper foil or an aluminum foil.

[0026] And / or, the temperature of the hot pressing is 150-200 DEG C, and the pressure is 5-10 MPa.

[0027] In a second aspect, the embodiments of the present application further provide a pre-sodiumized negative electrode dry electrode prepared by the preparation method of the first aspect.

[0028] In some embodiments, the thickness of the pre-sodiumized negative electrode dry electrode is 100-250 mu m.

[0029] In a third aspect, the embodiments of the present application further provide a sodium ion battery comprising the pre-sodiumized negative electrode dry electrode of the second aspect and a positive electrode sheet, a separator, and an electrolyte.

[0030] In some embodiments, the active material of the positive electrode sheet comprises at least one of sodium iron phosphate, sodium vanadium phosphate, sodium iron sulfate, sodium iron pyrophosphate, sodium nickel manganese acid, and sodium copper manganese acid.

[0031] The embodiments of the present application have the following advantages and beneficial effects:

[0032] The sodium treatment of the binder and the pre-sodium treatment of the negative electrode material make the prepared dry electrode have better peeling strength and electrode flexibility, and alleviate the cracking of the traditional wet thick electrode; meanwhile, the sodium treatment of the dry electrode can induce the uniform deposition of sodium ions, improve the kinetic performance of the overall sodium ion battery, avoid the problem of sodium precipitation during cycling, and further improve the service life of the sodium ion battery. DETAILED DESCRIPTION

[0033] The embodiments of the present application are described in detail below, which are exemplary and intended to explain the present application, and cannot be understood as a limitation of the present application.

[0034] In this document, where a range of values is provided, it is understood that each intervening value, to the exclusion of which the disclosure does not explicitly state, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the scope of the disclosure. The upper and lower limits of these too broad ranges will also be encompassed, subject to any limit of the range or the individual numerical limits in the range.

[0035] In this document, the words "comprise" and "include", and variations such as "comprises", "comprising", "includes" and "including", are not intended to exclude any element or step, whether specifically mentioned or not.

[0036] In this document, the term "and / or" is merely a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which means that there are three cases of A alone, A and B together, and B alone.

[0037] In a first aspect, the embodiments of the present application provide a preparation method of a pre-sodium negative dry electrode, comprising the following steps:

[0038] S1: mixing hydrochloric acid solution and sodium organic sulfonate, then adding aniline and water to stir and dissolve, and then adding an oxidizing agent to carry out doping reaction, and the reaction product is filtered, washed, dried and ground to obtain sodiumized polyaniline;

[0039] S2: mixing negative active material, conductive agent and polytetrafluoroethylene, then adding the sodiumized polyaniline and organic sodium supplementing agent under nitrogen or inert atmosphere, and carrying out fiberization treatment to obtain fiberized powder;

[0040] S3: hot pressing the fiberized powder onto the current collector to obtain a pre-sodium negative dry electrode.

[0041] The preparation process of the negative electrode dry electrode of the embodiment of the present application is on one hand to perform sodium doping treatment on polyaniline (PANI) to obtain polyaniline dry binder with high conductivity and high dispersibility; on the other hand, the organic sodium supplementing agent is used to modify polytetrafluoroethylene (PTFE) dry binder, and the negative electrode material is pre-sodium treated, so that a high-strength SEI film rich in NaF phase can be pre-formed on the surface of the negative electrode, the volume expansion of the material particles can be effectively relieved, and the interface stability can be improved.

[0042] In some embodiments, in the step S1, the sodium organic sulfonate includes at least one of sodium methyl sulfonate, sodium benzene sulfonate and sodium naphthalene sulfonate; by selecting the sodium organic sulfonate as the sodium source, the polyaniline can be effectively doped and sodiumized, and polyaniline with high conductivity, high dispersibility and high adhesion can be obtained, so that the peeling strength of the dry electrode and the flexibility of the electrode sheet can be improved.

[0043] And / or, the oxidizing agent includes at least one of ammonium persulfate and hydrogen peroxide.

[0044] And / or, the sum of the concentrations of the hydrochloric acid solution and the sodium organic sulfonate is 2-3 mol / L.

[0045] And / or, the molar ratio of the sodium organic sulfonate, the aniline and the oxidizing agent is (0.3-0.8):(5-7):(0.02-0.04). The inventors have found that if the addition amount of the sodium organic sulfonate is too high, the conjugated structure of the polyaniline will be damaged, and the conductivity will not increase but decrease; but if the addition amount is too low, the improvement of the conductivity, dispersibility and adhesion of the polyaniline will be limited, so the addition amount of the sodium organic sulfonate is controlled within the above range.

[0046] In some embodiments, in the step S1, the reaction temperature of the doping reaction is 10-20℃, and the reaction time is 4-6h.

[0047] And / or, the washing liquid used for washing is a hydrochloric acid solution, and the concentration of the hydrochloric acid solution is 0.3-0.5 mol / L.

[0048] And / or, the drying method is vacuum drying, the temperature of the vacuum drying is 60-80℃, and the drying time is 16-20h.

[0049] In some embodiments, in the step S2, the negative electrode active material includes at least one of graphene, graphene oxide, soft carbon, hard carbon, expanded graphite, silicon and mesocarbon microbeads, and is preferably hard carbon.

[0050] And / or, the conductive agent includes at least one of metal conductive agent (such as silver powder, copper powder, nickel powder, etc.), metal oxide conductive agent (such as tin oxide, iron oxide, zinc oxide, etc.), non-metallic particulate conductive agent (such as conductive graphite, conductive carbon black), non-metallic fibrous conductive agent (such as carbon nanotubes, nanofiber VGCF carbon fiber, etc.), non-metallic flaky conductive agent (such as graphene, etc.), composite conductive agent (such as composite powder, composite fiber, etc.);

[0051] And / or, the organic sodium supplement agent includes at least one of naphthalene sodium, biphenyl sodium, anthraquinone sodium (i.e. anthraquinone disulfonic acid disodium salt, for example: anthraquinone-2, 6-disulfonic acid disodium, anthraquinone-1, 5-disulfonic acid disodium, anthraquinone-1, 8-disulfonic acid disodium salt, etc.), preferably biphenyl sodium; by selecting the above-mentioned substances as the organic sodium supplement agent, it can realize uniform sodium supplement through liquid phase penetration, and the sodium supplement process is simple, effective and safe and controllable;

[0052] And / or, the mass ratio of the negative electrode active material, the conductive agent, the polytetrafluoroethylene, the sodium polyaniline and the organic sodium supplement agent is (93-97):(0.5-1.5):(1-2):(1-2):(0.5-1.5); and the inventors have found that if the addition amount of the organic sodium supplement agent is too much, it will cause the SEI film to be too thick and the interface polarization to increase; but if the addition amount is too low, it will cause incomplete sodium, limited cycle and energy density improvement, therefore the addition amount of the organic sodium supplement agent is controlled in the above-mentioned range in the embodiment.

[0053] In some embodiments, in the step S2, the inert atmosphere includes at least one of argon and helium;

[0054] And / or, the stirring speed of the mixing is 100-200 r / min, and the stirring time is 0.5-1 h;

[0055] And / or, the fiberization treatment is ball milling, the ball-to-material ratio in the ball milling is (6-10):1, the rotation speed is 1500-400 r / min, and the ball milling time is 2-6 h.

[0056] In some embodiments, in the step S3, the current collector is a copper foil or an aluminum foil.

[0057] And / or, the temperature of the hot pressing is 150-200 DEG C, and the pressure is 5-10 Mpa.

[0058] In the second aspect, the embodiment also provides a pre-sodium negative electrode dry electrode prepared by the preparation method in the first aspect.

[0059] In some embodiments, the thickness of the pre-sodium negative electrode dry electrode is 100-250 μm. In the second aspect, the embodiment also provides a pre-sodium negative electrode dry electrode prepared by the preparation method in the first aspect.

[0060] In a third aspect, the embodiments of the present application also provide a sodium-ion battery, which comprises the pre-sodiated negative electrode dry electrode of the second aspect and a positive electrode sheet, a separator and an electrolyte.

[0061] In some embodiments, the active material of the positive electrode sheet comprises at least one of sodium iron phosphate, sodium vanadium phosphate, sodium iron sulfate, sodium iron pyrophosphate, sodium nickel manganese acid, and sodium copper manganese acid.

[0062] It should be noted that the separator in the above sodium-ion battery is a PE+OBS separator (polyethylene+solvent type coating separator).

[0063] The electrolyte in the above sodium-ion battery is not particularly limited and can be selected by those skilled in the art according to actual needs. For example, a conventional electrolyte in the art can be used, and more specifically, the electrolyte comprises a solvent, a sodium salt and an additive; the solvent is a mixture of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC) and dimethyl carbonate (DMC); the sodium salt is a mixture of sodium hexafluorophosphate (NaPF6) and sodium bisfluorosulfonylimide (NaFSI); and the additive is a mixture of vinylene carbonate (VC), fluoroethylene carbonate (FEC), vinyl sulfate (DTD) and 1,3-propane sulfonate lactone (1-3PS).

[0064] The following are non-limiting examples and comparative examples of the present application. It should be noted that the schemes of the comparative examples are not prior art and are only set up for comparison with the schemes of the examples, and do not limit the present application. Unless otherwise specified, the various raw materials used in the examples and comparative examples are conventional commercially available products or can be prepared by known methods.

[0065] Example 1

[0066] The present embodiment provides a preparation method of a pre-sodiated negative electrode dry electrode, which comprises the following steps:

[0067] S1: hydrochloric acid solution and sodium benzenesulfonate are prepared into a 2 mol / L solution, then aniline and water are added and stirred until completely dissolved, followed by adding ammonium persulfate and reacting at 20℃ for 6h. The reaction product is suction filtered, washed with 0.4 mol / L hydrochloric acid solution, and then ground after vacuum drying at 70℃ for 18h to obtain sodiated polyaniline; wherein the molar ratio of sodium benzenesulfonate, aniline and ammonium persulfate is 0.5:6:0.03;

[0068] S2: the hard carbon, conductive carbon black, polytetrafluoroethylene are preferentially mixed uniformly at a rotating speed of 150 r / min for 0.5 h, sodium polyaniline and sodium diphenyl are then added under a nitrogen atmosphere, and the mixture is transferred to a ball mill, the ball-to-material ratio is controlled to be 8:1, and the mixture is ball milled at a rotating speed of 240 r / min for 3 h to obtain a fiberized powder; wherein the mass ratio of the hard carbon, the conductive carbon black, the polytetrafluoroethylene, the sodium polyaniline, and the sodium diphenyl is 95:1:1.8:1.2:1;

[0069] S3: the fiberized powder is uniformly hot-pressed onto an aluminum foil, the hot-pressing temperature is controlled to be 180℃, the pressure is controlled to be 7 Mpa, and a 200 μm-thick pre-sodium negative electrode dry electrode is obtained.

[0070] Example 2

[0071] The embodiment provides a preparation method of a pre-sodium negative electrode dry electrode, which comprises the following steps:

[0072] S1: hydrochloric acid solution and sodium benzenesulfonate are prepared into a 2 mol / L solution, aniline is then added and stirred until completely dissolved, ammonium persulfate is then added, and the mixture is reacted at 20℃ for 6 h; the reaction product is extracted and filtered, and then washed with 0.4 mol / L hydrochloric acid solution; the mixture is then vacuum dried at 70℃ for 18 h, and then ground to obtain sodium polyaniline; wherein the molar ratio of the sodium benzenesulfonate, the aniline, and the ammonium persulfate is 0.7:6:0.03;

[0073] S2: the hard carbon, conductive carbon black, polytetrafluoroethylene are preferentially mixed uniformly at a rotating speed of 150 r / min for 0.5 h, sodium polyaniline and sodium diphenyl are then added under a nitrogen atmosphere, and the mixture is transferred to a ball mill, the ball-to-material ratio is controlled to be 8:1, and the mixture is ball milled at a rotating speed of 240 r / min for 3 h to obtain a fiberized powder; wherein the mass ratio of the hard carbon, the conductive carbon black, the polytetrafluoroethylene, the sodium polyaniline, and the sodium diphenyl is 95:1:1.8:1.2:1;

[0074] S3: the fiberized powder is uniformly hot-pressed onto an aluminum foil, the hot-pressing temperature is controlled to be 180℃, the pressure is controlled to be 7 Mpa, and a 200 μm-thick pre-sodium negative electrode dry electrode is obtained.

[0075] Example 3

[0076] The embodiment provides a preparation method of a pre-sodium negative electrode dry electrode, which comprises the following steps:

[0077] S1: hydrochloric acid solution is prepared into a 2 mol / L solution with sodium benzenesulfonate, then aniline is added and stirred until completely dissolved, followed by adding ammonium persulfate and reacting at 20℃ for 6h, the reaction product is filtered and washed with 0.4 mol / L hydrochloric acid solution, and then vacuum dried at 70℃ for 18h to obtain sodiumized polyaniline after grinding; wherein the molar ratio of sodium benzenesulfonate, aniline and ammonium persulfate is 0.3:6:0.03;

[0078] S2: hard carbon, conductive carbon black and polytetrafluoroethylene are preferentially mixed at a rotation speed of 150r / min for 0.5h, then sodiumized polyaniline and sodium biphenyl are added under a nitrogen atmosphere, and transferred to a ball mill, the ball-to-material ratio is controlled to be 8:1, and ball milling is performed at a rotation speed of 240r / min for 3h to obtain fibrous powder; wherein the mass ratio of hard carbon, conductive carbon black, polytetrafluoroethylene, sodiumized polyaniline and sodium biphenyl is 95.2:1:1.8:1:1;

[0079] S3: the fibrous powder is uniformly hot-pressed onto an aluminum foil, the hot-pressing temperature is controlled to be 180℃, and the pressure is 7Mpa to obtain a 200μm-thick pre-sodiumized negative dry electrode.

[0080] Example 4

[0081] The embodiment provides a preparation method of a pre-sodiumized negative dry electrode, comprising the following steps:

[0082] S1: hydrochloric acid solution is prepared into a 2 mol / L solution with sodium benzenesulfonate, then aniline is added and stirred until completely dissolved, followed by adding ammonium persulfate and reacting at 20℃ for 6h, the reaction product is filtered and washed with 0.4 mol / L hydrochloric acid solution, and then vacuum dried at 70℃ for 18h to obtain sodiumized polyaniline after grinding; wherein the molar ratio of sodium benzenesulfonate, aniline and ammonium persulfate is 0.5:6:0.03;

[0083] S2: hard carbon, conductive carbon black and polytetrafluoroethylene are preferentially mixed at a rotation speed of 150r / min for 0.5h, then sodiumized polyaniline and sodium biphenyl are added under a nitrogen atmosphere, and transferred to a ball mill, the ball-to-material ratio is controlled to be 8:1, and ball milling is performed at a rotation speed of 240r / min for 3h to obtain fibrous powder; wherein the mass ratio of hard carbon, conductive carbon black, polytetrafluoroethylene, sodiumized polyaniline and sodium biphenyl is 97:0.5:1:1:0.5;

[0084] S3: the fibrous powder is uniformly hot-pressed onto an aluminum foil, the hot-pressing temperature is controlled to be 180℃, and the pressure is 7Mpa to obtain a 200μm-thick pre-sodiumized negative dry electrode.

[0085] Example 5

[0086] The embodiment provides a preparation method of a pre-sodiated negative dry electrode, and comprises the following steps:

[0087] S1: hydrochloric acid solution is prepared into a 2mol / L solution with sodium benzenesulfonate, then aniline is added and stirred with water until completely dissolved, then ammonium persulfate is added, and the reaction is carried out at 20℃ for 6h; the reaction product is extracted and washed with 0.4mol / L hydrochloric acid solution, and then is ground after being dried at 70℃ under vacuum for 18h to obtain sodiated polyaniline; wherein the molar ratio of sodium benzenesulfonate, aniline and ammonium persulfate is 0.5:6:0.03;

[0088] S2: hard carbon, conductive carbon black and polytetrafluoroethylene are uniformly mixed at a rotation speed of 150r / min for 0.5h, then sodiated polyaniline and sodium biphenyl are added under a nitrogen atmosphere, and are transferred into a ball mill, the ball-to-material ratio is controlled to be 8:1, and ball milling is carried out at a rotation speed of 240r / min for 3h to obtain fibrous powder; wherein the mass ratio of hard carbon, conductive carbon black, polytetrafluoroethylene, sodiated polyaniline and sodium biphenyl is 93:1.5:2:2:1.5;

[0089] S3: the fibrous powder is uniformly hot-pressed onto an aluminum foil, the hot-pressing temperature is controlled to be 180℃, and the pressure is controlled to be 7Mpa, so that a pre-sodiated negative dry electrode with a thickness of 200μm is obtained.

[0090] Embodiment 6

[0091] The embodiment provides a preparation method of a pre-sodiated negative dry electrode, and comprises the following steps:

[0092] S1: hydrochloric acid solution is prepared into a 2mol / L solution with sodium benzenesulfate, then aniline is added and stirred with water until completely dissolved, then ammonium persulfate is added, and the reaction is carried out at 20℃ for 6h; the reaction product is extracted and washed with 0.4mol / L hydrochloric acid solution, and then is ground after being dried at 70℃ under vacuum for 18h to obtain sodiated polyaniline; wherein the molar ratio of sodium benzenesulfate, aniline and ammonium persulfate is 0.5:6:0.03;

[0093] S2: hard carbon, conductive carbon black and polytetrafluoroethylene are uniformly mixed at a rotation speed of 150r / min for 0.5h, then sodiated polyaniline and sodium biphenyl are added under a nitrogen atmosphere, and are transferred into a ball mill, the ball-to-material ratio is controlled to be 8:1, and ball milling is carried out at a rotation speed of 240r / min for 3h to obtain fibrous powder; wherein the mass ratio of hard carbon, conductive carbon black, polytetrafluoroethylene, sodiated polyaniline and sodium biphenyl is 95:1:1.8:1.2:1;

[0094] S3: the fibrous powder is uniformly hot-pressed onto an aluminum foil, the hot-pressing temperature is controlled to be 180℃, and the pressure is controlled to be 7Mpa, so that a pre-sodiated negative dry electrode with a thickness of 200μm is obtained.

[0095] Example 7

[0096] The embodiment provides a preparation method of a pre-sodium negative electrode dry electrode, and the method comprises the following steps:

[0097] S1: hydrochloric acid solution is prepared into a 2mol / L solution with sodium benzenesulfonate, then aniline is added and stirred with water until completely dissolved, then ammonium persulfate is added, and the reaction is carried out at 20℃ for 6h; the reaction product is extracted and filtered, then washed with 0.4mol / L hydrochloric acid solution, and then ground after vacuum drying at 70℃ for 18h to obtain sodiumized polyaniline; wherein the molar ratio of sodium benzenesulfonate, aniline and ammonium persulfate is 0.5:6:0.03;

[0098] S2: hard carbon, conductive carbon black and polytetrafluoroethylene are uniformly mixed at a rotation speed of 150r / min for 0.5h, then sodiumized polyaniline and naphthalene sodium are added under a nitrogen atmosphere, and then transferred to a ball mill, the ball-to-material ratio is controlled to be 8:1, and the rotation speed is controlled to be 240r / min for ball milling for 3h to obtain fibrous powder; wherein the mass ratio of hard carbon, conductive carbon black, polytetrafluoroethylene, sodiumized polyaniline and naphthalene sodium is 95:1:1.8:1.2:1;

[0099] S3: the fibrous powder is uniformly hot-pressed onto an aluminum foil, the hot-pressing temperature is controlled to be 180℃, and the pressure is controlled to be 7Mpa to obtain a 200μm-thick pre-sodium negative electrode dry electrode.

[0100] Example 8

[0101] The embodiment provides a preparation method of a pre-sodium negative electrode dry electrode, and the method comprises the following steps:

[0102] S1: hydrochloric acid solution is prepared into a 2mol / L solution with sodium benzenesulfonate, then aniline is added and stirred with water until completely dissolved, then ammonium persulfate is added, and the reaction is carried out at 20℃ for 6h; the reaction product is extracted and filtered, then washed with 0.4mol / L hydrochloric acid solution, and then ground after vacuum drying at 70℃ for 18h to obtain sodiumized polyaniline; wherein the molar ratio of sodium benzenesulfonate, aniline and ammonium persulfate is 0.5:6:0.03;

[0103] S2: hard carbon, conductive carbon black and polytetrafluoroethylene are uniformly mixed at a rotation speed of 150r / min for 0.5h, then sodiumized polyaniline and naphthalene sodium are added under a nitrogen atmosphere, and then transferred to a ball mill, the ball-to-material ratio is controlled to be 8:1, and the rotation speed is controlled to be 240r / min for ball milling for 3h to obtain fibrous powder; wherein the mass ratio of hard carbon, conductive carbon black, polytetrafluoroethylene, sodiumized polyaniline and naphthalene sodium is 95:1:1.8:1.2:1;

[0104] S3: uniformly hot-press the fibrous powder to the aluminum foil, control the hot-pressing temperature to be 180℃, the pressure to be 7Mpa, and obtain the 200pm-thick pre-sodiumized negative electrode dry electrode.

[0105] Comparative Example 1

[0106] The comparative example provides a preparation method of a negative electrode dry electrode, including the following steps:

[0107] S1: uniformly mix hard carbon, conductive carbon black and polytetrafluoroethylene at a rotation speed of 150r / min for 0.5h, then add polyaniline under a nitrogen atmosphere, and transfer to a ball mill, control the ball-to-material ratio to be 8:1, and ball mill at a rotation speed of 240r / min for 3h to obtain fibrous powder; wherein the mass ratio of hard carbon, conductive carbon black, polytetrafluoroethylene and polyaniline is 96:1:1.8:1.2;

[0108] S2: uniformly hot-press the fibrous powder to the aluminum foil, control the hot-pressing temperature to be 180℃, the pressure to be 7Mpa, and obtain the 200pm-thick negative electrode dry electrode.

[0109] Comparative Example 2

[0110] The comparative example provides a preparation method of a negative electrode dry electrode, including the following steps:

[0111] S1: uniformly mix hard carbon, conductive carbon black and polytetrafluoroethylene at a rotation speed of 150r / min for 0.5h, then add polyaniline and sodium biphenyl under a nitrogen atmosphere, and transfer to a ball mill, control the ball-to-material ratio to be 8:1, and ball mill at a rotation speed of 240r / min for 3h to obtain fibrous powder; wherein the mass ratio of hard carbon, conductive carbon black, polytetrafluoroethylene, polyaniline and sodium biphenyl is 95:1:1.8:1.2:1;

[0112] S2: uniformly hot-press the fibrous powder to the aluminum foil, control the hot-pressing temperature to be 180℃, the pressure to be 7Mpa, and obtain the 200pm-thick negative electrode dry electrode.

[0113] Comparative Example 3

[0114] The comparative example provides a preparation method of a negative electrode dry electrode, including the following steps:

[0115] S1: prepare a 2mol / L solution of hydrochloric acid and sodium benzenesulfonate, then add aniline and stir until completely dissolved, then add ammonium persulfate, and react at 20℃ for 6h, then filter the reaction product, wash with 0.4mol / L hydrochloric acid solution, and then vacuum dry at 70℃ for 18h, and then grind to obtain sodiumized polyaniline; wherein the molar ratio of sodium benzenesulfonate, aniline and ammonium persulfate is 0.5:6:0.03;

[0116] S2: The hard carbon, conductive carbon black, and polytetrafluoroethylene are uniformly mixed at a rotation speed of 150 r / min for 0.5 h, and then sodiumized polyaniline is added under a nitrogen atmosphere, and transferred to a ball mill, the ball-to-material ratio is controlled to be 8:1, and the rotation speed is 240 r / min for 3 h to obtain a fibrous powder; wherein the mass ratio of the hard carbon, conductive carbon black, polytetrafluoroethylene, and sodiumized polyaniline is 96:1:1.8:1.2;

[0117] S3: The fibrous powder is uniformly hot-pressed onto an aluminum foil, the hot-pressing temperature is controlled to be 180℃, and the pressure is 7Mpa to obtain a 200μm-thick dry electrode of the negative electrode.

[0118] The pre-sodiumized dry electrode of the negative electrode prepared in the above examples 1-8 and the dry electrode of the negative electrode prepared in the above comparative examples 1-3 are assembled into sodium ion batteries, and the specific process is as follows:

[0119] The negative electrode tab: the pre-sodiumized dry electrode of the negative electrode prepared in the above examples 1-8 and the dry electrode of the negative electrode prepared in the above comparative examples 1-3 are used as the negative electrode tab, the thickness of the negative electrode tab is 200μm, and the single-sided area density is 200g / m 2 , and the compacted density is 1.00g / cm 3 ;

[0120] The positive electrode tab: the positive electrode tab using a nickel-iron-manganese sodium material as the active material is used;

[0121] The electrolyte: includes a solvent, a sodium salt, and an additive; wherein the solvent is a mixture of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), and dimethyl carbonate (DMC), and the mass ratio is EC:PC:EMC:DMC=20:10:50:20; the sodium salt is a mixture of sodium hexafluorophosphate (NaPF6, concentration of 14wt%) and sodium bisfluorosulfonylimide (NaFSI, concentration of 3wt%); and the additive is a mixture of vinylene carbonate (VC, concentration of 0.8wt%), fluoroethylene carbonate (FEC, concentration of 3wt%), vinyl sulfate (DTD, concentration of 0.3wt%), and 1,3-propane sulfonate lactone (1-3PS, concentration of 0.3wt%);

[0122] Preparation of the sodium ion battery: the above negative electrode tab is assembled with the positive electrode tab into an electric core, and a soft package lamination process is used to produce a soft package sodium ion battery, that is, the nickel-iron-manganese sodium positive electrode tab, the hard carbon negative electrode tab, and the polyethylene separator (for example, PE+OBS separator) are laminated and assembled, baked to qualified moisture, then injected with electrolyte, and packaged after heat pressing, high-temperature standing, and capacity distribution, to obtain a soft package finished battery, and the theoretical capacity is 4Ah.

[0123] Performance test:

[0124] (1) Negative electrode peeling force test: For the pre-sodiumized negative electrode dry electrodes prepared in Examples 1-8 above and the negative electrode dry electrodes prepared in Comparative Examples 1-3, the electrode sheet was peeled at a rate of 10 mm / min and an angle of 180° according to the ASTM-D903 test method, and the peeling strength was tested, and the test results are shown in Table 1.

[0125] (2) Negative electrode flexibility test: The pre-sodiumized negative electrode dry electrodes prepared in Examples 1-8 above and the negative electrode dry electrodes prepared in Comparative Examples 1-3 were all cut into negative electrode sheets of 100 mm*10 mm, and one end of the sample was fixed on a bending tester, the bending angle was set to 180°, the bending speed was 10 times / min, the clamping force was 2N, and the number of bends before the sample broke was recorded, and the test results are shown in Table 1.

[0126] (3) Soft package direct current resistance DCR test: The sodium ion battery prepared above was tested on an electrochemical workstation battery test system at 25°C, the sodium ion battery capacity was adjusted to 50% SOC and left for 2h, the end voltage U1 was recorded, the current I (2C) was discharged for 10s, the end voltage U2 was recorded, and DCR = (U1-U2) / I, and the test results are shown in Table 1.

[0127] (4) Soft package cycle test: The sodium ion battery prepared above was tested on an electrochemical workstation battery test system at 45°C, 1C / 1C charge-discharge cycle test, the charge-discharge voltage range was 2.0V-4.0V, and the cycle number at 80% SOH was obtained by testing, as shown in Table 1.

[0128] Table 1

[0129]

[0130] As can be seen from Table 1, compared with Comparative Examples 1-3, the sodiumized polyaniline obtained by doping sodium treatment of polyaniline in the present application can effectively promote the formation of a homogeneous conductive bonding network in the dry electrode, enhance the peeling strength of the dry electrode, improve the flexibility of the electrode sheet, reduce the electrode resistance, and improve the cycle stability. At the same time, the present application also modifies the polytetrafluoroethylene dry binder by using an organic sodium supplement and pre-sodiumizes the negative electrode material, thereby pre-forming a high-strength SEI film rich in NaF phase on the surface of the negative electrode, which can induce uniform deposition of sodium ions, improve the kinetic performance of the overall sodium ion battery, and further enhance the cycle performance.

[0131] In this disclosure, the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" mean that a particular feature, structure, material, or characteristic is included in at least one embodiment or example of the present disclosure. The illustrative appearances of the above-mentioned terms in various places in the specification are not necessarily referred to the same embodiment or example. Moreover, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples. Furthermore, the terminology "comprising" is used in the disclosure as comprising but not limited to, that is, it is open-ended and does not exclude the presence of additional features, structures, materials, or characteristics.

[0132] Although the embodiments of the present disclosure have been shown and described above, it is understood that the above-described embodiments are exemplary, and are not to be interpreted as limiting the present disclosure, and the ordinary skilled in the art can make changes, modifications, replacements, and variations to the above-described embodiments within the scope of the present disclosure.

Claims

1. A method for preparing a pre-sodiumized negative electrode dry process, characterized in that: The steps include: S1: After mixing hydrochloric acid solution and organic sodium sulfonate, aniline is added and dissolved with water by stirring, and then an oxidant is added to carry out a doping reaction. The reaction product is filtered, washed, dried, and ground to obtain sodium polyaniline; S2: After mixing the negative electrode active material, the conductive agent, and polytetrafluoroethylene, the sodium-containing polyaniline and the organic sodium supplement are added under nitrogen or an inert atmosphere to perform a fiberization treatment to obtain a fiberized powder; S3: hot pressing the fiberized powder onto a current collector to obtain a pre-sodiumized negative electrode dry process electrode.

2. The method for preparing a pre-sodiumized negative electrode dry process according to claim 1, wherein In step S1, the organic sodium sulfonate includes at least one of sodium methanesulfonate, sodium benzenesulfonate, and sodium naphthalenesulfonate; and / or, the oxidant comprises at least one of ammonium persulfate and hydrogen peroxide; and / or, the sum of the concentrations of the hydrochloric acid solution and the organic sodium sulfonate is 2 to 3 mol / L; And / or, the molar ratio of the organic sodium sulfonate, the aniline and the oxidant is (0.3-0.8):(5-7):(0.02-0.04).

3. The method for preparing a pre-sodiumized negative electrode dry process according to claim 1, wherein In step S1, the reaction temperature of the doping reaction is 10-20° C., and the reaction time is 4-6 hours; And / or, the washing liquid used in the washing is a hydrochloric acid solution, and the concentration of the hydrochloric acid solution is 0.3-0.5 mol / L; And / or, the drying method is vacuum drying, the vacuum drying temperature is 60-80° C., and the drying time is 16-20 hours.

4. The method for preparing a pre-sodiumized negative electrode dry process according to claim 1, wherein In step S2, the negative electrode active material includes at least one of graphene, graphene oxide, soft carbon, hard carbon, expanded graphite, silicon, and mesocarbon microbeads; And / or, the conductive agent includes at least one of a metal conductive agent, a metal oxide conductive agent, a non-metallic granular conductive agent, a non-metallic fibrous conductive agent, a non-metallic flaky conductive agent, and a composite conductive agent; And / or, the organic sodium supplement includes at least one of sodium naphthalene, sodium biphenyl, and sodium anthraquinone; And / or, the mass ratio of the negative electrode active material, the conductive agent, the polytetrafluoroethylene, the sodium-containing polyaniline and the organic sodium supplement is (93-97):(0.5-1.5):(1-2):(1-2):(0.5-1.5).

5. The method for preparing a pre-sodiumized negative electrode dry process according to claim 1, wherein In step S2, the inert atmosphere includes at least one of argon and helium; And / or, the mixing stirring speed is 100-200 r / min, and the stirring time is 0.5-1 h; And / or, the fiberization treatment is performed by ball milling, wherein the ball-to-material ratio during the ball milling is (6-10):1, the rotation speed is 1500-400 r / min, and the ball milling time is 2-6 h.

6. The method for preparing a pre-sodiumized negative electrode dry process according to claim 1, wherein: In step S3, the current collector is copper foil or aluminum foil; And / or, the hot pressing temperature is 150-200° C. and the pressure is 5-10 MPa.

7. A pre-sodiumized negative electrode dry process electrode, characterized in that: The pre-sodiumized negative electrode dry process electrode is prepared by the preparation method according to any one of claims 1 to 6.

8. The pre-sodiumized negative electrode dry process electrode according to claim 7, characterized in that The thickness of the pre-sodiumized negative dry electrode is 100 to 250 μm.

9. A sodium ion battery, characterized in that: The invention comprises the pre-sodiumized negative electrode dry process electrode according to claim 7 or 8, as well as a positive electrode sheet, a diaphragm and an electrolyte.

10. The sodium ion battery according to claim 9, characterized in that The active material of the positive electrode plate includes at least one of sodium iron phosphate, sodium vanadium phosphate, sodium iron sulfate, sodium iron pyrophosphate, sodium nickel iron manganate, and sodium copper iron manganate.

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