WO2024001591A1 - 一种基于干法制备电极膜的钠离子电池负极预钠化方法 - Google Patents

一种基于干法制备电极膜的钠离子电池负极预钠化方法 Download PDF

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WO2024001591A1
WO2024001591A1 PCT/CN2023/094744 CN2023094744W WO2024001591A1 WO 2024001591 A1 WO2024001591 A1 WO 2024001591A1 CN 2023094744 W CN2023094744 W CN 2023094744W WO 2024001591 A1 WO2024001591 A1 WO 2024001591A1
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sodium
electrode
film
rolling
sodiumization
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PCT/CN2023/094744
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French (fr)
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郜明文
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宝晟(苏州)能源科技有限公司
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/04—Hybrid capacitors
    • H01G11/06—Hybrid capacitors with one of the electrodes allowing ions to be reversibly doped thereinto, e.g. lithium ion capacitors [LIC]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
    • H01G11/86—Processes for the manufacture of hybrid or EDL capacitors, or components thereof specially adapted for electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/043—Processes of manufacture in general involving compressing or compaction
    • H01M4/0435—Rolling or calendering
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes

Definitions

  • the invention relates to the field of sodium-ion batteries, and specifically relates to a method for pre-sodiumization of the negative electrode of a sodium-ion battery based on dry preparation of electrode membranes.
  • the hard carbon material will still form the SEI film during the first cycle of charging in the sodium-ion battery and store sodium ions in the structural defects of the hard carbon, causing the capacity of the sodium-ion full battery to have a large irreversible loss after the first cycle. Capacity loss.
  • the hard carbon anode due to the disordered structural defects of hard carbon itself, the hard carbon anode exhibits the characteristics of adsorbing and storing sodium in the first half of the sodium-ion full battery charging. Therefore, there is no fixed potential platform, and the half-cell discharge curve after this stage shows It is a sodium ion embedding platform between graphene layers. Supplementing the hard carbon negative electrode with sodium ions in advance can effectively reduce the consumption of sodium ions in the positive electrode material and solvent, significantly extend the cycle life of sodium-ion batteries, and is of great significance to solving the industrial application of sodium-ion batteries.
  • the graphite negative electrode sheet is pretreated using a film-forming agent, in which sodium polycyclic aromatic hydrocarbons are used to generate an SEI layer on the surface of the graphene negative electrode.
  • This method has limited effect on pre-sodiumization of hard carbon because the structural defects within the hard carbon will continue to consume sodium ions in the solution.
  • the mechanical pre-sodiumization method mentioned in the patent CN111952532A or CN107240715A uses a rolling method to composite the metal sodium sheet and the metal negative electrode material into an alloy, or uses a traditional wet coating process to make the negative electrode sheet and then paste it with the metal sodium. Combined isostatic pressure.
  • This method does not have large-scale operability for battery structures that mainly use hard carbon negative electrodes, but it proves that metallic sodium and hard carbon can react in contact and undergo alloying and pre-sodiumization.
  • sodium salt is added to the solution before use. Pre-sodiumization. The added sodium salt decomposes into CO gas and metallic sodium during the first charge.
  • the positive electrode material is capacitor material such as activated carbon or graphene. For crystalline materials, corresponding side reactions will occur at the positive electrode.
  • the present invention provides a method for pre-sodiumization of the negative electrode of a sodium ion battery based on dry preparation of electrode membranes.
  • This method uses a dry electrode film-forming method to pre-mix the active material with the powder binder. Fiberized and then rolled to form a self-supporting film. Then it is rolled and compounded with metallic sodium. During this process, due to the potential difference between metallic sodium and the hard carbon negative electrode, a sodium embedding reaction will spontaneously occur. Alternatively, spraying a small amount of sodium ion solvent before rolling can accelerate the natural reaction between metallic sodium and the active material. Support membrane response.
  • the electrode film that has been composited with the sodium sheet for the first time is rolled and composited with the other two self-supporting films for the second time to provide secondary protection for the electrode sheet that has been pre-sodiumized.
  • This method is convenient for large-scale production and manufacturing.
  • the invention provides a pre-sodiumization method, which includes the following steps:
  • the electrode material is made into a self-supporting electrode film using a dry method and rolled into rolls to obtain multi-roll electrode film rolls;
  • step (3) Roll the composite film obtained in step (2) for the first time, compound it with the electrode film of step 1 again, and roll it for the second time;
  • the mass ratio of the electrode material to metallic sodium can be adjusted according to the film thickness of the low-temperature dry electrode and the thickness of the metallic sodium sheet, sodium belt or sodium mesh belt, or can also be adjusted according to the number of rolling presses.
  • the preferred composite The number of rolling operations is two.
  • the metallic sodium in step (2) includes sodium flakes, sodium belts and/or sodium mesh belts.
  • the electrode material in step (1) includes a positive electrode material or a negative electrode material
  • the positive electrode material includes a metal oxide material, specifically including one or more of a polyanionic positive electrode, Prussian blue and Prussian white
  • the negative electrode material includes one or more of hard carbon, soft carbon activated carbon, and mesocarbon microspheres MCMB.
  • the electrode material includes one or more of activated carbon, hard carbon, soft carbon and mesocarbon microspheres MCMB.
  • a protective gas is used for blowing protection.
  • the thickness of the film in step (1) is 10 micrometers-2 millimeters. Preferably 100 microns.
  • the composite environmental humidity is less than 50RH.
  • the thickness of the metallic sodium in step (2) is 5 microns-2 centimeters. Preferably, as described in step (2) The thickness of metallic sodium is 200 microns.
  • the solvent described in step (2) includes organic non-aqueous solvents.
  • the solvent includes cyclic carbonate solvents, such as ethylene carbonate (EC), propylene carbonate (PC); or chain carbonate solvents, such as diethyl carbonate (DEC), dimethyl carbonate (DMC). ) and ethyl methyl carbonate (EMC).
  • cyclic carbonate solvents such as ethylene carbonate (EC), propylene carbonate (PC); or chain carbonate solvents, such as diethyl carbonate (DEC), dimethyl carbonate (DMC). ) and ethyl methyl carbonate (EMC).
  • EC ethylene carbonate
  • PC propylene carbonate
  • chain carbonate solvents such as diethyl carbonate (DEC), dimethyl carbonate (DMC).
  • EMC ethyl methyl carbonate
  • the solvent is EC, DEC and DMC in a volume ratio of 1:1:1.
  • the time interval between the first rolling and the second rolling in step (3) is 1 second to 1 week.
  • the time interval between the first rolling and the second rolling is 3 minutes.
  • the temperature of rolling described in step (3) is -40 ⁇ 120°C; the number of rolling is 1-10 times.
  • the rolling temperature is 60°C.
  • the thickness of the first rolling in step (3) is adjusted to 200 microns-2 centimeters, and the thickness of the second rolling is 20 microns-200 microns.
  • the thickness of the first rolling in step (3) is adjusted to 200 microns, and the thickness of the second rolling is 150 microns.
  • the pre-sodiumization method includes the following steps:
  • the sodium-ion battery negative active electrode material is prepared into a self-supporting film with a certain mechanical strength using a dry process, it is not combined with the current collector and is rolled independently.
  • the film thickness is 10 microns-2 mm.
  • a preferred film thickness is 100 microns.
  • the composite film is rolled by a roller press with a temperature ranging from -40 to 120 degrees Celsius for 1 to 10 times.
  • the preferred temperature is 80 degrees Celsius, and the thickness of the first roll is preferably adjusted to 200 microns.
  • the composite film after rolling is compounded again with a dry self-supporting film of active material with a thickness of 100 microns.
  • the material of the self-supporting film can be the same material as the active material of the first self-supporting film, or it can be the same material as the active material of the first self-supporting film.
  • a self-supporting membrane made of active substances of different materials.
  • the self-supporting film for the second time of compound rolling can be made of hard carbon material or other sodium battery negative electrode materials such as activated carbon and soft carbon.
  • the second roll thickness is 150 microns.
  • First rolling The time interval between the second rolling process and the second rolling process ranges from 1 second to 1 week, and the preferred time interval is 3 minutes.
  • the roller shaft of the roller press can be made of metal or plastic, with metal steel being preferred.
  • the composite electrode is rolled up and stored in a sealed temperature of -40 degrees Celsius to 100 degrees Celsius in a dry environment.
  • the pre-sodiumization method in the present invention is simple, efficient and low-cost. There have been no similar technologies and methods before.
  • This pre-sodiumization method is safe and efficient, and has average environmental requirements, because the metal sodium strip is covered and protected by active materials after being released from the reel.
  • This method can roll the metal sodium belt to any thickness, so it can accurately adjust the mass ratio of metal sodium and active materials. Currently, there is no similar or similar method.
  • This method can be used for almost all powder electrode materials. As long as the material can be film-formed by low-temperature dry method, the material can be used for pre-sodiumization, and the practical scope is extremely wide.
  • This method can structurally compound different types of electrode membranes and pre-sodiumize them as needed, ensuring the special needs of energy storage devices such as sodium-ion batteries and sodium-ion capacitors.
  • This method can use different types of active materials to be pre-sodiumized and then composited into a film, thereby achieving the effect of different types of active materials cooperatively storing sodium ions.
  • the material of the second roll-compounded self-supporting film may be the same material as the active material of the first self-supporting film, or may be a different material from the active material of the first self-supporting film.
  • the self-supporting membrane before being rolled and compounded with the sodium belt for the first time is a hard carbon material
  • the self-supporting film for the second time of compound rolling can be made of hard carbon material or other sodium battery negative electrode materials such as activated carbon and soft carbon.
  • Figure 1 is a schematic diagram of the dry electrode film being composited with metallic sodium and then composited with the dry electrode film again.
  • Figure 2 is a schematic diagram of the dry electrode film being composited with metallic sodium and then rolled and thinned separately again.
  • Figure 3 is a schematic diagram of the dry process electrode film being composited with metallic sodium and then being rolled and composited with the dry process self-supporting electrode film multiple times.
  • 1-sodium ion battery negative electrode material dry self-supporting film 2-sodium belt, sodium sheet or sodium mesh belt, 3-composite electrode winding, 4-protective gas, 5-first Second rolling, 6-second rolling, 7-solvent.
  • Figure 4 is a half-cell performance curve of a hard carbon negative electrode charging and discharging metallic sodium; (a) is a half-cell performance curve of a hard carbon negative electrode that is not pre-sodiumized and is charging and discharging metallic sodium; (b) is a half-cell performance curve of a hard carbon negative electrode that has been pre-sodiumized. Half-cell performance curve of charging and discharging sodium metal with hardened carbon anode.
  • Figure 5 shows the sodium ion full battery performance curve of the ternary cathode material charging and discharging without pre-sodiumized hard carbon negative electrode and pre-sodiumized hard carbon negative electrode.
  • This example is a simple pre-sodiumization process of a single active electrode material, which specifically includes the following steps:
  • the hard carbon electrode material is made into a film with a certain mechanical strength through a low-temperature dry preparation process and then rolled into a roll.
  • the film thickness is 200 microns.
  • the hard carbon sodium tape composite film is rolled for the first time by a roller press with a temperature of 80 degrees Celsius.
  • the rolling thickness is adjusted to 300 microns.
  • the composite film after the first rolling is automatically pressed with the hard carbon with a thickness of 100 microns.
  • the support film is laminated and rolled for the second time to a thickness of 200 microns.
  • the time interval between the first rolling and the second rolling is 3 minutes.
  • the roller shaft of the roller press is made of chrome-plated stainless steel.
  • the positive electrode is a ternary sodium salt oxide
  • the negative electrode is a full battery of pre-sodiumized hard carbon (Example 1). The specific effects of the full battery are shown in Figure 5.
  • This example is a single active electrode material that is pre-sodiumized for the first time and then rolled again to ensure a higher mass ratio of metallic sodium in the active material. It specifically includes the following steps:
  • the activated carbon is made into a self-supporting film with a certain mechanical strength through a low-temperature dry preparation process and rolled into a roll.
  • the film thickness is 200 microns.
  • the composite film is rolled through a roller press at a temperature of 40 degrees Celsius for the first time, and the rolling thickness is adjusted to 300 microns, and the second rolling thickness is 150 microns.
  • the time interval between the first rolling and the second rolling is 3 minutes.
  • the roller shaft of the roller press is made of chrome-plated stainless steel.
  • the composite electrode is rolled up and stored in a sealed temperature of 25 degrees Celsius in a dry environment.
  • the soft carbon and hard carbon electrode materials are made into films with a certain mechanical strength by a low-temperature dry preparation process and then rolled into rolls.
  • the film thickness is 100 microns.
  • the hard carbon and sodium ribbon composite film is rolled for the first time by a roller press with a temperature of 80 degrees Celsius.
  • the rolling thickness is adjusted to 450 microns.
  • the composite film is again rolled with soft carbon with a thickness of 100 microns.
  • the dry self-supporting membrane electrode membrane is composited, and the second rolling thickness is 300 microns.
  • the time interval between the first rolling and the second rolling is 3 minutes.
  • the roller shaft of the roller press is made of chrome-plated stainless steel.
  • the composite electrode is rolled up and stored in a sealed temperature of 25 degrees Celsius in a dry environment.
  • This example involves multiple rolling processes to form a multi-layered composite of active material and metallic sodium to form a pre-sodiumized electrode with an extremely uniform and detailed structure. Specifically, it includes the following steps:
  • the hard carbon electrode material is made into a film with a certain mechanical strength through a low-temperature dry preparation process and then rolled into a roll.
  • the film thickness is 200 microns.
  • the hard carbon sodium tape composite film is rolled for the first time by a roller press with a temperature of 80 degrees Celsius. The rolling thickness is adjusted to 300 microns. The composite film is divided into one roll, two rolls, three rolls or multiple rolls as needed. As shown in the dotted line part of Figure 3.
  • One roll, two rolls, three rolls or multiple rolls of the composite film are rolled together again at the same time.
  • three rolls are rolled together at the same time.
  • the rolling thickness is adjusted to 500 microns, and then it is rolled again through the multi-stage roller press to Thickness is 150 microns.
  • Thickness is 150 microns.
  • the composite electrode is rolled up and stored in a sealed temperature of 25 degrees Celsius in a dry environment.
  • This example is a multi-level composite of the positive active material and metallic sodium formed by multiple rolling processes to form a pre-sodiumized electrode with an extremely uniform and detailed structure. It specifically includes the following steps:
  • the positive ternary sodium salt oxide electrode material is made into a film with a certain mechanical strength by a low-temperature dry preparation process and then rolled into a roll.
  • the film thickness is 100 microns.
  • the positive ternary sodium salt oxide electrode film and the sodium ribbon composite film are rolled for the first time by a roller press at a temperature of 70 degrees Celsius.
  • the rolling thickness is adjusted to 450 microns.
  • the sodium ribbon composite film after the first rolling Composite again with a ternary cathode sodium ribbon composite film with a thickness of 450 microns.
  • This composite can be two layers of ternary cathode sodium ribbon composite films, or it can be two or more layers of multi-layer ternary cathode sodium ribbon composite films. , adjust according to needs and actual conditions, as shown in the dotted line part of Figure 3.
  • the second roll thickness is 750 microns, or adjust again as needed.
  • the time interval between the first rolling and the second rolling is 3 minutes.
  • the roller shaft of the roller press is made of chrome-plated stainless steel.
  • the composite electrode is rolled up and stored in a sealed temperature of 25 degrees Celsius in a dry environment.
  • Example 1 The only difference from Example 1 is that the electrode material hard carbon is not pre-sodiumized. The specific effects of the half-cell are shown in Figure 4.
  • Example 1A The only difference from Example 1A is that the electrode material hard carbon is not pre-sodiumized. The specific effect of the full battery is shown in Figure 5.
  • the electrode charging and discharging voltage window is 0V-2.0V.
  • the charge and discharge rate is 0.1C.
  • Example 1 The electrochemical tests of Example 1, Example 2, Example 3, Example 4, Example 5, and Comparative Example 1 were all half-cells in which the counter electrode was metallic sodium.
  • the electrode charging and discharging voltage window is 2.0V-3.8V.
  • the charge and discharge rate is 0.1C.
  • Example 1A is a positive electrode of a ternary sodium salt oxide, and the negative electrode is a full battery of pre-sodiumized hard carbon.
  • the electrochemical test of Comparative Example 1A shows that the positive electrode is a ternary sodium salt oxide, and the negative electrode is a non-pre-sodiumized hard carbon. Carbon full battery.
  • Example 2 In the activated carbon peeling experiment, use tape to evenly paste the tape on both sides of the electrode, and then tear it apart at a constant speed. Observe the state of metallic sodium in the activated carbon interlayer. In Example 2, no metallic sodium was found in the activated carbon pre-sodiumized using a solvent after being torn open for 5 hours, while in Comparative Example 2, residual metallic sodium was still visible after being torn open for 5 hours.

Abstract

本发明提供了一种基于干法制备电极膜的钠离子电池负极预钠化方法，涉及钠离子电池领域，该预钠化方法具体包括：(1)将电极材料制成薄膜后成卷，得到电极薄膜；(2)将步骤(1)得到的电极薄膜与金属钠的表面涂抹溶剂后，复合，得到复合膜；(3)将步骤(2)得到的复合膜进行第一次辊压，再次与电极薄膜进行复合，进行第二次辊压；(4)将辊压后的复合膜收卷，即得。该制备方法简单、高效、成本低廉，便于进行大规模生产制造。

Description

一种基于干法制备电极膜的钠离子电池负极预钠化方法 技术领域
本发明涉及钠离子电池领域，具体涉及一种基于干法制备电极膜的钠离子电池负极预钠化方法。
背景技术
钠离子电池的产业化应用却仍然面临着诸多问题，目前钠离子电池正极材料的研究有着多种选择。如金属氧化物类，聚阴离子类正极，普鲁士蓝，普鲁士白等多种正极材料。但是使用硬碳作为钠离子电池负极材料目前已经成为科研及产业界的共同选择。其区别主要在于合成硬碳方法的不同。目前来看，硬碳材料造价低廉，嵌钠电位更低，理论容量更高，是钠离子电池产业化中较为理想的负极材料，然而同硬碳材料作为负极在钠离子电池中出现的问题一样，硬碳材料在钠离子电池中的首圈充电的过程中依然会形成SEI膜以及在硬碳的结构缺陷中存钠离子，使得钠离子全电池的容量在首圈之后会有较大的不可逆容量损耗。此外，由于硬碳本身的无序结构缺陷，导致硬碳负极在钠离子全电池充电的前半部分表现为吸附存钠的特性，因此没有固定电位平台，而该阶段之后的半电池放电曲线才表现为石墨烯层之间的钠离子嵌入平台。预先对硬碳负极补充钠离子可以有效减少正极材料和溶剂中钠离子的消耗，显著延长钠离子电池的循环寿命，对解决钠离子电池的产业化应用具有重要意义。
类比于锂离子电池的预锂化工艺，其预钠化工艺的诸多产业化问题尚未完全解决，金属钠相比与金属锂缺少表面钝化层的保护，其性质更为活泼，空气稳定性更差，实际应用生产中更加危险，相比于预锂化使用金属钠进行预钠化难度更大，因此国内对于预钠化的工作开展较少，且大部分集中在正极预钠化，负极硬碳预钠化的工艺研究屈指可数。
如专利CN113178548A中所述使用成膜剂的方式石墨负极片进行预处理，其中使用多环芳烃钠在石墨烯负极表面生成SEI层。该方式对硬碳的预钠化作用有限，因为硬碳内部的结构缺陷会继续消耗溶液中的钠离子。如专利CN111952532A或CN107240715A中提到的机械预钠化方法使用辊压方式将金属钠片与金属负极材料复合制成合金，或者使用传统湿法涂布工作做成负极极片后再与金属钠贴合等静压。该方法对于使用硬碳负极为主的电池结构来说并不具备大规模可操作性，但是证明了金属钠与硬碳可以发生接触反应并且进行合金化和预钠化。再如专利CN113113235A所述为钠离子电容器中，在使用之前进行溶液中添加钠盐的方式进行 预钠化。添加的钠盐在首次充电过程中分解为CO2气体和金属钠。该方法适用于正极材料为活性炭或石墨烯等电容器材料。对于晶体材料其正极会发生相应副反应。
针对现有技术存在的问题，亟需寻找一种便于进行大规模生产制造的简单、高效、成本低廉的钠离子电池负极预钠化方法。
发明内容
本发明针对现有技术存在的问题，提供了一种基于干法制备电极膜的钠离子电池负极预钠化方法，该方法使用干电极成膜方式，将活性物质预先与粉料混合粘结剂纤维化，而后辊压形成自支撑膜。再与金属钠辊压复合，这个过程中由于金属钠与硬碳负极之间的电位差，会自发进行嵌钠反应，或者再辊压之前喷洒少量钠离子溶剂，可以加速金属钠与活性材料自支撑膜的反应。同时将已经第一次与钠片复合的电极膜再与另外两层自支撑膜进行第二次辊压复合，对已经预钠的极片进行二次保护，该方法便于进行大规模生产制造。
为实现上述目的，本发明采用的技术方案如下：
本发明提供了一种预钠化方法，包括以下步骤：
(1)将电极材料使用干法制成自支撑电极膜后成卷，得到多卷电极膜卷；
(2)将步骤(1)得到的自支撑电极膜与金属钠直接复合，或者表面喷洒少量溶剂后与金属钠复合，得到复合膜；
(3)将步骤(2)得到的复合膜进行第一次辊压，再次与步骤1的电极薄膜进行复合，进行第二次辊压；
(4)将辊压后的复合膜收卷，即得。
进一步地，所述电极材料与金属钠的质量比例可以根据低温干法电极的膜厚与金属钠片，钠带或钠网带的厚度来调节，也可以根据辊压次数来调节，优选的复合辊压次数为两次。
进一步地，步骤(2)中所述金属钠包括钠片、钠带和/或钠网带。
进一步地，步骤(1)中所述电极材料包括正极材料或负极材料，所述正极材料包括金属氧化物类材料，具体包括聚阴离子类正极、普鲁士蓝和普鲁士白中的一种或多种；所述负极材料包括硬碳、软碳活性碳和中间相碳微球MCMB中的一种或多种。
进一步地，所述电极材料包括活性炭、硬碳、软碳和中间相碳微球MCMB中的一种或多种。
进一步地，步骤(2)中所述电极薄膜与金属钠复合前使用保护气体进行吹气保护。
进一步地，步骤(1)中所述薄膜的厚度为10微米-2毫米。优选为100微米。
进一步地，所述复合的环境湿度小于50RH。
进一步地，步骤(2)中所述金属钠的厚度为5微米-2厘米。优选地，步骤(2)中所述 金属钠的厚度为200微米。
进一步地，步骤(2)中所述溶剂包括有机非水系类溶剂。
优选地，所述溶剂包括环状碳酸酯溶剂，如碳酸乙烯酯(EC)、碳酸丙烯酯(PC)；或是链状碳酸酯溶剂如碳酸二乙酯(DEC)、碳酸二甲酯(DMC)和碳酸甲乙酯(EMC)中的一种或多种组合。优选地，所述溶剂为体积比为1:1:1的EC、DEC和DMC。
进一步地，步骤(3)中所述第一次辊压和第二次辊压的时间间距为1秒至1周。优选地，所述第一次辊压和第二次辊压的时间间距为3分钟。
进一步地，步骤(3)中所述辊压的温度为-40～120℃；辊压次数为1-10次。优选地，所述辊压的温度为60℃。
进一步地，步骤(3)中所述第一次辊压厚度调节为200微米-2厘米，所述第二次辊压的厚度为20微米-200微米。
优选地，步骤(3)中所述第一次辊压厚度调节为200微米，所述第二次辊压的厚度为150微米。
在一些具体的实施方式中，所述预钠化方法包括以下步骤：
(1)将钠离子电池负极活性电极材料，使用干法工艺制备成具有一定机械强度的自支撑薄膜后，先不与集流体复合，自己独立成卷，薄膜厚度为10微米-2毫米。优选薄膜厚度为100微米。
(2)将干法制备的自支撑硬碳或软碳等钠离子负极电极薄膜与钠片，钠带或钠网带复合。优选的钠片，钠带或钠网带复合厚度为200微米，其复合结构如图1所示。复合环境湿度小于50RH。
(3)或将干法制备的自支撑钠离子负极电极薄膜与钠片，钠带或钠网带复合前，在其与钠片，钠带或钠网带的接触面喷洒适量钠离子电池用溶剂，该溶剂为有机非水系类溶剂。而后再与钠片，钠带或钠网带复合。优选的钠片，钠带或钠网带复合厚度为200微米，该复合结构如图2所示。复合环境湿度小于50RH。钠电及钠片辊压前用保护性气体如氮气，氩气等气体吹气保护，优选的气体为氮气。复合膜经过温度从-40～120摄氏度辊压机进行1到10次辊压，优选的温度为80摄氏度，优选第一次辊压厚度调节为200微米。辊压过后的复合膜再次与厚度为100微米的活性材料干法自支撑膜进行复合，该自支撑膜的材料可以是与第一次自支撑膜的活性物质相同的材料，也可以是与第一次自支撑膜的活性物质不同的材料。如第一次与钠带辊压复合前的自支撑膜是硬碳材料，那么第二次复合辊压的自支撑膜可以使用硬碳材料或者活性炭，软碳等其他钠电池负极材料。第二次辊压厚度为150微米。第一次辊压 与第二次辊压时间间距为1秒至1周时间不等，优选的时间间隔为3分钟。辊压机辊轴可选择金属及塑料材质，优选金属钢材。
(4)辊压后复合电极收卷，密封储存密封温度为-40摄氏度至100摄氏度，干燥环境。
本发明所取得的技术效果是：
1.本发明中的预钠化方法简单，高效，成本低廉。此前无类似技术及方法。
2.自支撑干电极膜表面喷洒溶剂后与金属钠辊压复合属于专利首创应用，大幅提升预钠化效率，充分发挥了自支撑干电极的优势和特点。
3.该预钠化方法安全高效，对环境要求一般，因为金属钠带从卷轴放出后即被活性材料覆盖保护。
4.该方法可以将金属钠带辊压至任意厚度，因此能够准确调节金属钠与活性材料的质量比例，目前尚无同类及相似方法。
5.该方法可以使用对几乎所有粉体电极材料，只要该种材料可以低温干法成膜就可以利用该材料进行预钠化，实用范围极广。
6.该方法可以根据需要对不同种类电极膜进行结构复合的同时预钠化，保证钠离子电池及钠离子电容器等储能器件的特种需求。
7.该方法可以使用不同种类活性材料预钠化后复合成膜，从而达到不同种类活性材料协同存储钠离子的效果。如第二次辊压复合的自支撑膜的材料可以是与第一次自支撑膜的活性物质相同的材料，也可以是与第一次自支撑膜的活性物质不同的材料。如第一次与钠带辊压复合前的自支撑膜是硬碳材料，那么第二次复合辊压的自支撑膜可以使用硬碳材料或者活性炭，软碳等其他钠电池负极材料。
附图说明
图1为干法电极膜与金属钠复合后再次与干法电极膜复合示意图。
图2为干法电极膜与金属钠复合后自己单独再次辊压减薄示意图。
图3为干法电极膜与金属钠复合后多次与干法自支撑电极膜辊压复合示意图。
其中，图1-3中，1-钠离子电池负极材料干法自支撑膜，2-钠带、钠片或钠网带，3-复合电极收卷，4-保护性气体，5-第一次辊压，6-第二次辊压，7-溶剂。
图4为硬碳负极对金属钠充放电的半电池性能曲线图；其中，(a)为未预钠化硬碳负极对金属钠充放电的半电池性能曲线图，(b)为已经预钠化硬碳负极对金属钠充放电的半电池性能曲线图。
图5为未预钠化硬碳负极和已经预钠化硬碳负极对三元正极材料充放电的钠离子全电池性能曲线。
具体实施方式
以下通过特定的具体实例说明本发明的实施方式，本领域技术人员可由本说明书所揭露的内容轻易地了解本发明的其他优点与功效。本发明还可以通过另外不同的具体实施方式加以实施或应用，本说明书中的各项细节也可以基于不同观点与应用，在没有背离本发明的精神下进行各种修饰或改变。
在进一步描述本发明具体实施方式之前，应理解，本发明的保护范围不局限于下述特定的具体实施方案；还应当理解，本发明实施例中使用的术语是为了描述特定的具体实施方案，而不是为了限制本发明的保护范围。
当实施例给出数值范围时，应理解，除非本发明另有说明，每个数值范围的两个端点以及两个端点之间任何一个数值均可选用。除非另外定义，本文中使用的所有技术和科学术语具有与本发明所属技术领域的普通技术人员通常理解的相同意义。
值得说明的是，本发明中使用的原料均为普通市售产品，因此对其来源不做具体限定。
实施例1
该实例为单一活性电极材料简单预钠化过程，具体包括以下步骤：
(1)将硬碳电极材料由低温干法制备工艺制作成具有一定机械强度的薄膜后成卷，薄膜厚度为200微米。
(2)将硬碳电极薄膜与钠网带复合，钠网带厚度为200微米，其复合结构如图1所示。复合环境湿度小于50RH。且硬碳电极复合之前与钠带接触表面喷洒钠离子电池用溶剂，该溶剂为有机非水系类溶剂组合EC:DEC:DMC＝1:1:1(体积比)，钠网带与硬碳电极复合辊压前用氮气保护性气体吹气保护。
(3)硬碳钠带复合膜经过温度80摄氏度辊压机进行第一次辊压，辊压厚度调节为300微米，第一次辊压过后的复合膜再次与厚度为100微米的硬碳自支撑膜进行复合，第二次辊压厚度为200微米。第一次辊压与第二次辊压时间间距为3分钟。辊压机辊轴为表面镀铬不锈钢。
(4)辊压后复合电极收卷，密封储存密封温度为25摄氏度，干燥环境。半电池具体效果详见图4。
实施例1A
正电极三元钠盐氧化物，负极为预钠化硬碳(实施例1)的全电池，全电池具体效果详见图5。
实施例2
该实例为单一活性电极材料首次预钠化后再次辊压以便保证活性材料中较高的金属钠的质量比例，具体包括以下步骤：
(1)将活性炭由低温干法制备工艺制作成具有一定机械强度的自支撑薄膜后成卷，薄膜厚度为200微米。
(2)将活性炭电极薄膜与钠带复合，钠带厚度为200微米，其复合结构如图2所示。且活性炭电极复合之前与钠带接触表面喷洒钠离子电池用溶剂，该溶剂为有机非水系类溶剂组合EC:DEC:DMC＝1:1:1(体积比)。钠带与活性炭电极复合辊压前用氮保护性气体吹气保护。
(3)复合膜经过温度40摄氏度辊压机进行第一次辊压，辊压厚度调节为300微米，第二次辊压厚度为150微米。第一次辊压与第二次辊压时间间距为3分钟。辊压机辊轴为表面镀铬不锈钢。
(4)辊压后复合电极收卷，密封储存密封温度为25摄氏度，干燥环境。
实施例3
该实例为多种电极混合材料均匀复合后预钠化，具体包括以下步骤：
(1)将软碳和硬碳电极材料分别由低温干法制备工艺制作成具有一定机械强度的薄膜后成卷，薄膜厚度为100微米。
(2)将硬碳电极薄膜与钠带复合，钠带厚度为500微米，其复合结构如图2所示。复合环境湿度小于50RH。钠带与硬碳电极膜复合辊压前用氮气吹气保护。硬碳电极复合之前与钠带接触表面喷洒钠离子电池用溶剂，该溶剂为有机非水系类溶剂组合EC:DEC:DMC＝1:1:1(体积比)。
(3)硬碳和钠带复合膜经过温度80摄氏度辊压机进行第一次辊压，辊压厚度调节为450微米，第一次辊压过后的复合膜再次与厚度为100微米的软碳干法自支撑膜电极膜进行复合，第二次辊压厚度为300微米。第一次辊压与第二次辊压时间间距为3分钟。辊压机辊轴为表面镀铬不锈钢。
(4)辊压后复合电极收卷，密封储存密封温度为25摄氏度，干燥环境。
实施例4
该实例为多次辊压形成活性材料与金属钠的多层次复合，形成结构极为均匀细致的预钠化电极，具体包括以下步骤：
(1)将硬碳电极材料由低温干法制备工艺制作成成具有一定机械强度的薄膜后成卷，薄膜厚度为200微米。
(2)将硬碳电极薄膜与钠网带复合，钠网带厚度为200微米，其复合结构如如图3所示。复合环境湿度小于50RH。钠网带与硬碳电极复合辊压前用氮气保护性气体吹气保护。且硬碳电极复合之前与钠带接触表面喷洒钠离子电池用溶剂，该溶剂为有机非水系类溶剂组合EC:DEC:DMC＝1:1:1(体积比)。
(3)硬碳钠带复合膜经过温度80摄氏度辊压机进行第一次辊压，辊压厚度调节为300微米，将该复合膜根据需要分为一卷，二卷，三卷或多卷如图3虚线部分所示所示。
(4)一卷，二卷，三卷或多卷该复合膜再次同时复合辊压，优选三卷同时复合辊压，辊压厚度调节为500微米，之后再次经过辊压机多级辊压至厚度为150微米。此时该电极的硬碳活性材料与金属钠的层状结构均匀细致。
(5)辊压后复合电极收卷，密封储存密封温度为25摄氏度，干燥环境。
实施例5
该实例为多次辊压形成的正极活性材料与金属钠的多层次复合，形成结构极为均匀细致的预钠化电极，具体包括以下步骤：
(1)将正极三元钠盐氧化物电极材料由低温干法制备工艺制作成成具有一定机械强度的薄膜后成卷，薄膜厚度为100微米。
(2)将正极三元钠盐氧化物电极材料薄膜与钠带复合，钠带厚度为500微米，其复合结构如图2所示。且正极三元钠盐氧化物电极材料复合之前与钠带接触表面喷洒钠离子电池用溶剂，该溶剂为有机非水系类溶剂组合EC:DEC:DMC＝1:1:1(体积比)。钠片与正极三元钠盐氧化物电极薄膜辊压前用氮气吹气保护。
(3)正极三元钠盐氧化物电极薄膜与钠带复合膜经过温度70摄氏度辊压机进行第一次辊压，辊压厚度调节为450微米，第一次辊压过后的钠带复合膜再次与厚度为450微米的三元正极钠带复合膜进行复合，该次复合可以是两层三元正极钠带复合膜复合，也可以是两层以上的多层三元正极钠带复合膜复合，根据需要及实际情况进行调整，如图3虚线部分所示。第二次辊压厚度为750微米，或根据需要进行再次调整。第一次辊压与第二次辊压时间间距为3分钟。辊压机辊轴为表面镀铬不锈钢。
(4)辊压后复合电极收卷，密封储存密封温度为25摄氏度，干燥环境。
对比例1
与实施例1的区别仅在于，电极材料硬碳不进行预钠化，半电池具体效果详见图4。
对比例1A
与实施例1A的区别仅在于，电极材料硬碳不进行预钠化，全电池具体效果详见图5。
对比例2
与实施例2的区别仅在于，活性炭预钠化不喷洒溶剂EC:DEC:DMC＝1:1:1。
试验方法：
实验使用的半电池正极为预钠化的复合电极，负极为金属钠片，电解液为1mol·L-1的NaPF6在溶剂EC:DEC:DMC＝1:1:1(体积比)中。电极充放电压窗口为0V-2.0V。充放电速率为0.1C。
其中实施例1，实施例2，实施例3，实施例4，实施例5，对比例1的电化学测试均为对电极为金属钠的半电池。
实验使用的全电池正极为三元钠盐氧化物，负极为预钠化的硬碳电极，电解液为1mol·L-1的NaPF6在溶剂EC:DEC:DMC＝1:1:1(体积比)中。电极充放电压窗口为2.0V-3.8V。充放电速率为0.1C。
其中实施例1A为正电极三元钠盐氧化物，负极为预钠化硬碳的全电池，对比例1A的电化学测试为正电极为三元钠盐氧化物，负极为未预钠化硬碳的全电池。
活性炭剥离实验使用胶带将电极两侧均匀贴上胶带后，匀速撕开。观察活性炭夹层中金属钠的状态。其中实施例2中使用溶剂进行预钠化的活性炭5小时撕开后中间未见金属钠存在，而对比例2中的活性炭5小时撕开后仍可见金属钠残余。
表1
最后应当说明的是，以上内容仅用以说明本发明的技术方案，而非对本发明保护范围的限制，本领域的普通技术人员对本发明的技术方案进行的简单修改或者等同替换，均不脱离本发明技术方案的实质和范围。

Claims (10)

  1. 一种预钠化方法，其特征在于：包括以下步骤：
    (1)将电极材料制成薄膜后成卷，得到电极薄膜；
    (2)将步骤(1)得到的电极薄膜与金属钠的表面涂抹溶剂后，复合，得到复合膜；
    (3)将步骤(2)得到的复合膜进行第一次辊压，再次与电极薄膜进行复合，进行第二次辊压；
    (4)将辊压后的复合膜收卷，即得。
  2. 根据权利要求1所述的预钠化方法，其特征在于：步骤(2)中所述金属钠包括钠片、钠带和/或钠网带。
  3. 根据权利要求1所述的预钠化方法，其特征在于：步骤(1)中所述电极材料包括正极材料或负极材料，所述正极材料包括金属氧化物类材料，具体包括聚阴离子类正极、普鲁士蓝和普鲁士白中的一种或多种；所述负极材料包括硬碳、软碳活性碳和中间相碳微球MCMB中的一种或多种。
  4. 根据权利要求1所述的预钠化方法，其特征在于：步骤(2)中所述电极薄膜与金属钠复合前使用保护气体进行吹气保护。
  5. 根据权利要求1所述的预钠化方法，其特征在于：步骤(1)中所述薄膜的厚度为10微米-2毫米。
  6. 根据权利要求1所述的预钠化方法，其特征在于：步骤(2)中所述金属钠的厚度为5微米-2厘米。
  7. 根据权利要求1所述的预钠化方法，其特征在于：步骤(2)中所述溶剂包括有机非水系类溶剂。
  8. 根据权利要求1所述的预钠化方法，其特征在于：步骤(3)中所述第一次辊压和第二次辊压的时间间距为1秒至1周。
  9. 根据权利要求1所述的预钠化方法，其特征在于：步骤(3)中所述辊压的温度为-40～120℃；辊压次数为1-10次。
  10. 根据权利要求1所述的预钠化方法，其特征在于：步骤(3)中所述第一次辊压厚度调节为200微米-2厘米，所述第二次辊压的厚度为20微米-200微米。
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