WO2022151944A1 - 一种极片及其制备方法和电池 - Google Patents

一种极片及其制备方法和电池 Download PDF

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WO2022151944A1
WO2022151944A1 PCT/CN2021/140823 CN2021140823W WO2022151944A1 WO 2022151944 A1 WO2022151944 A1 WO 2022151944A1 CN 2021140823 W CN2021140823 W CN 2021140823W WO 2022151944 A1 WO2022151944 A1 WO 2022151944A1
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Prior art keywords
pole piece
preparation
laminating machine
optionally
lithium
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PCT/CN2021/140823
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English (en)
French (fr)
Inventor
朱亮
赵瑞瑞
邱欣斌
祝媛
刘建华
刘金成
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惠州亿纬锂能股份有限公司
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Priority to EP21919131.9A priority Critical patent/EP4167308A1/en
Priority to US18/018,983 priority patent/US20240014370A1/en
Publication of WO2022151944A1 publication Critical patent/WO2022151944A1/zh

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Definitions

  • the application belongs to the technical field of batteries, and relates to a pole piece, a preparation method thereof, and a battery.
  • lithium batteries are more and more widely used in life; they can be found in various fields from small household appliances to new energy vehicles to large-scale energy storage.
  • the mainstream positive electrode systems include LCO, NCM, NCA, LFP, LMO, etc.
  • the negative electrode systems include artificial graphite, natural graphite, LTO, Si-C composite, artificial and natural composite systems, etc., and their structures are diverse, including square, cylindrical And button-type lithium battery; according to the outsourcing material, it is divided into aluminum shell, steel shell and soft-pack lithium battery.
  • Square aluminum shell batteries are widely used in lithium power and energy storage due to their simple structure, high energy density, flexible size, simple pack grouping, and high packaging reliability.
  • LiFePO 4 with olivine structure has the advantages of good structural stability, stable discharge platform, good cycle performance, wide source of raw materials, low price and no environmental pollution. It has been widely used in the two fields of power and energy storage. applications, and square aluminum case LFP batteries are the most common.
  • the positive electrode material is an important factor that determines the performance and cost of lithium batteries, and is a key technological breakthrough direction for improving battery energy density; negative electrodes with excellent performance have high specific energy, low electrode potential, and good lithium-deintercalation stability. , is the key to affecting the performance of the battery; the main function of the diaphragm is to separate the positive and negative electrodes of the lithium battery, prevent the two electrodes from contacting and short-circuit, and allow the ions of the electrolyte to pass through; the electrolyte is the "blood" of the lithium battery, and Li + The liquid is deintercalated back and forth between the positive and negative electrodes, and at the same time affects the key performance of the battery, such as safety, high and low temperature performance, and power performance.
  • the electrolyte is generally composed of solvents, lithium salts and additives in a certain proportion, and the composition is different according to different electrical performance requirements. During the use of the battery, the electrolyte will be consumed, especially for batteries with long cycle life. The amount of liquid retention is as large as possible to meet the consumption of electrolyte during the cycle.
  • the main problems are: 1.
  • the distribution of pores in the pole piece is not uniform, resulting in different current densities in different regions of the pole piece during the battery discharge process, which cannot maximize the discharge capacity of the battery.
  • the depth of discharge in different regions of the pole piece is different, and the swelling situation is also different.
  • the resistance of the battery is likely to increase due to the separation (powder) of the active material and the current collector, and the pulse capacity in the final stage decreases rapidly; serious; There may be an internal short circuit in the battery caused by partial powder drop.
  • CN107919459A discloses a preparation method of a lithium ion battery negative electrode sheet, a lithium ion battery negative electrode sheet and a lithium ion battery, which belong to the technical field of lithium ion batteries.
  • the preparation method of the negative electrode sheet of the lithium ion battery comprises the following steps: mixing the negative electrode material with water uniformly to prepare the negative electrode slurry; the negative electrode material comprises negative electrode active material, conductive agent, binder, additive, negative electrode active material, conductive material
  • the mass ratio of agent, binder and additive is 85.5-95.5:1-3:1.5-3.5:2-8; the additive is at least one of ethylene carbonate and propylene carbonate; the prepared negative slurry
  • the material is coated on the negative electrode current collector and dried.
  • CN103531811A discloses a method for preparing a positive electrode sheet for a lithium ion battery, comprising the following steps: according to a solid-liquid ratio of (0.1g-2g):100mL, refluxing a carbon material in a mixed acid composed of concentrated nitric acid and concentrated sulfuric acid, The carboxylated carbon material is obtained; according to the solid-liquid ratio of (0.1g ⁇ 2g):100mL, the carboxylated carbon material is refluxed in dichlorohydrin to obtain the acid-chlorinated carbon material; according to the solid-liquid ratio of (0.1 g-1 g): 100 mL: 200 mL, the acyl-chlorinated carbon material and ethylenediamine are refluxed in anhydrous toluene to obtain an amidated carbon material; the amidated carbon material is dissolved in water to form a dispersion; The fluid is soaked in the dispersion liquid, and then the current collector is alternately soaked in the dispersion liquid and Li 2 C
  • the purpose of this application is to provide a pole piece, a preparation method thereof, and a battery.
  • the preparation method of the pole piece provided by the present application can improve the consistency of the thickness of the membrane piece in the process of film bonding, and can make the distribution of the inner hole of the pole piece more uniform, the porosity is better, and the discharge capacity of the battery can be improved.
  • the application provides a method for preparing a pole piece, the method comprising the following steps:
  • step (2) Coupling the mixed particles and the current collector in step (1) in a film laminating machine to obtain the pole piece, wherein the number of rolls of the film laminating machine is 3 or more.
  • step (1) the purpose of making uniform particles is achieved by mixing and granulating
  • step (2) a film laminating machine with multiple rollers is used to first form the mixed particles into sheets, and then press them on a set. Fluidly, improve uniformity.
  • the mutual cooperation of the above two steps enables the pole piece obtained by the method of the present application to have better porosity under the condition of maintaining a higher compaction density, so that the battery prepared by it has better discharge capacity, especially in larger current and discharge capability at lower temperatures.
  • the number of rolls of the laminating machine is 3, 4, or 5, etc.
  • the number of rolls of the film laminating machine is 3 or more, because the film is formed in advance, the bonding force and thickness uniformity between the active substances can be improved, so the effect is much better than that of the double-roll laminating machine (2). rolls).
  • the pole piece is a positive pole piece or a negative pole piece.
  • the active material in step (1) includes any one of manganese dioxide, lithium manganate, lithium cobaltate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium iron phosphate, graphite or silicon carbon material.
  • One or a combination of at least two, typical but non-limiting combinations are: a combination of manganese dioxide and lithium manganate, a combination of lithium manganate and lithium cobaltate, a combination of lithium cobaltate and lithium nickel cobalt manganate, graphite and the combination of silicon carbon materials, etc.
  • the conductive agent in step (1) includes any one or a combination of at least two of carbon black, graphite, graphene or carbon nanotubes. Typical but non-limiting combinations are: a combination of carbon black and graphene, a combination of graphite and graphene, a combination of graphene and carbon nanotubes, and the like.
  • the binder described in step (1) includes any one or at least one of styrene-butadiene rubber, polytetrafluoroethylene, polyvinyl fluoride, sodium hydroxymethyl cellulose, polyvinylidene fluoride or lithium polyacrylate. combination of the two. Typical but non-limiting combinations are: SBR and PTFE, PTFE and PTFE, PTFE and sodium carboxymethylcellulose, PVDF and the combination of lithium polyacrylate, etc.
  • the solvent described in step (1) is water, ethanol, ethylene glycol, glycerol, isopropanol, n-butanol, 1-methylpyrrolidone (NMP) or N,N-dimethylformamide (DMF) any one or a combination of at least two.
  • NMP 1-methylpyrrolidone
  • DMF N,N-dimethylformamide
  • the mass ratio of the active material, conductive agent, solvent and binder described in step (1) is (58-88):(1-6):(10-30):(1 -6), such as 58:6:30:6; 61:6:27; 6; 66:6:22:6; 70:6:18:6; 8975:2:18:5; 80:3:12 :5 or 88:1:10:1 etc.
  • step (1) the mixing and granulation in step (1) is carried out with a granulator.
  • the rotational speed of the granulator is 50-1200rpm, such as 50rpm, 100rpm, 200rpm, 300rpm, 400rpm, 500rpm, 600rpm, 700rpm, 800rpm, 900rpm, 1000rpm, 1100rpm or 1200rpm, and the like.
  • the mixing and granulating time of step (1) is 1-10min, such as 1min, 1.5min, 2min, 2.5min, 3min, 3.5min, 4min, 4.5min, 5min, 5.5min, 6min, 6.5min , 7min, 7.5min, 8min, 8.5min, 9min, 9.5min or 10min, etc., but not limited to the listed values, and other unlisted values within the numerical range are also applicable.
  • the uniformity of the particles can be controlled, and the consistency of the thickness of the composite film and the pore distribution of the pole pieces can be controlled.
  • the current collector in step (2) includes any one or a combination of at least two of steel mesh, aluminum mesh, copper mesh, nickel mesh, aluminum foil or copper foil.
  • the temperature of the film bonding in step (2) is 15-35° C., that is, the film bonding at room temperature.
  • the laminating machine in step (2) is a three-roll laminating machine or a four-roll laminating machine.
  • the distance between the rolls of the laminating machine in step (2) is 0.05-0.5 mm, such as 0.05 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm or 0.5 mm, etc., in the present application , if the roller spacing is too large, it will lead to weak adhesion between the film and the current collector; if the roller spacing is too small, it will cause jamming.
  • the rotation speed of the rollers of the laminating machine in step (2) is 1-10r/min, such as 1r/min, 2r/min, 3r/min, 4r/min, 5r/min, 6r/min, 7r /min, 8r/min, 9r/min or 10r/min etc.
  • the rotational speed of the rollers of the laminating machine is too high, the uniformity of the pole piece will be deteriorated; if the rotational speed of the rollers of the laminating machine is too low, it will cause material jams.
  • step (2) further includes: baking the product obtained after the film is combined.
  • the temperature of the baking is 100-300°C, such as 100°C, 120°C, 140°C, 160°C, 200°C, 250°C or 300°C, etc., but not limited to the listed values. The same applies to other non-recited values in the range.
  • the baking time is 5-28h, such as 5h, 8h, 12h, 16h, 20h, 24h, 26h, 27h or 28h, etc., but is not limited to the listed values, and other values within the range are not limited to. The values listed also apply.
  • the method comprises the following steps:
  • the active material, conductive agent and binder are mixed and granulated in a granulator for 1-10min to obtain mixed granules;
  • step (2) The mixed particles described in step (1) are combined with the current collector in a film-combining machine, and after the film is combined, the obtained product is baked at 100-300° C. for 5-28 hours to obtain the pole piece, wherein,
  • the laminating machine is a three-roll laminating machine or a four-roll laminating machine;
  • the pole piece is a positive pole piece or a negative pole piece
  • the active material of step (1) includes any one or at least two of manganese dioxide, lithium manganate, lithium cobaltate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium iron phosphate, graphite or silicon carbon material. a combination of species;
  • the conductive agent of step (1) includes any one or a combination of at least two in carbon black, graphite, graphene or carbon nanotubes;
  • the binder in step (1) includes any one or a combination of at least two of styrene-butadiene rubber, polytetrafluoroethylene, polyvinyl fluoride, sodium hydroxymethyl cellulose, polyvinylidene fluoride or lithium polyacrylate ;
  • the solvent described in step (1) is any one in water, ethanol, ethylene glycol, glycerol, isopropanol, n-butanol, 1-methylpyrrolidone NMP or N,N-dimethylformamide DMF or a combination of at least two;
  • the mass ratio of the active material, conductive agent, solvent and binder described in step (1) is (58-88):(1-6):(10-30):(1-6);
  • the current collector includes any one or a combination of at least two of steel mesh, aluminum mesh, copper mesh, nickel mesh, aluminum foil or copper foil;
  • the distance between the rolls of the film laminating machine in step (2) is 0.05-0.25 mm; the rotational speed of the rollers of the laminating machine in step (2) is 1-10 r/min.
  • the present application provides a pole piece prepared by the preparation method described in the first aspect.
  • the thickness of the diaphragm is 0.2-1.0mm;
  • the compacted density of the pole piece is 1.5-3.0 g/cm 3
  • the present application provides a battery comprising the pole piece according to the second aspect.
  • the preparation method provided in this application can enable the pole piece to obtain a better porosity while maintaining a higher compaction density, so that the battery has a better discharge capacity, especially under the conditions of larger current and lower temperature At the same time, the thickness consistency of the pole piece is good, and the overall standard deviation of the pole piece thickness is within 0.005mm.
  • the pole piece preparation method provided by the present application has a simple manufacturing process and a high level of automation, and can realize one process output from feeding material to pole piece forming.
  • Fig. 1 is the schematic flow sheet of the preparation method of embodiment 1;
  • Example 2 is a schematic diagram of the laminating machine in the preparation method of Example 1, and 1, 2 and 3 marked in the figure represent the numbers of the rollers;
  • Figure 3 is a schematic diagram of the laminating machine in the preparation method of Example 2, and the numbers 1, 2, 3 and 4 marked in the figure represent the numbers of the rollers;
  • FIG. 4 is a schematic diagram of a laminating machine in the preparation method of Comparative Example 1.
  • FIG. 4 is a schematic diagram of a laminating machine in the preparation method of Comparative Example 1.
  • step (1) Using a three-roll film laminating machine (the distance between roll 1 and roll 2 is 0.1mm, and the distance between roll 2 and roll 3 is 0.08mm) in step (1) at a temperature of 25°C with a roll speed of 3r/min and The current collector aluminum foil is formed into a membrane, which is then baked in an oven at 120° C. for 8 hours, and then baked and cut to obtain a positive electrode sheet.
  • FIG. 1 The schematic flow chart of the preparation method of this embodiment is shown in FIG. 1 .
  • FIG. 2 The schematic diagram of the film laminating machine in this embodiment is shown in FIG. 2 .
  • Rolls 1 and 2 of the laminating machine preform the mixed particles, and rolls 2 and 3 combine the precompressed mixed particles with the current collector.
  • the schematic diagram of the film laminating machine in this embodiment is shown in Figure 3.
  • the roll 1 and roll 2 of the laminating machine preform the mixed particles, and the rolls 3 and 4 also preform the mixed particles.
  • 3 Combine the pre-pressed mixed particles with the current collector.
  • step (1) The mixed particles described in step (1) were used with the same four-roll film laminating machine as in Example 2 to form a positive electrode sheet with the current collector aluminum foil at a temperature of 15°C at a roller speed of 1 r/min, and then placed in a 200°C Bake in an oven for 28 hours to obtain a positive electrode sheet.
  • step (1) The mixed particles described in step (1) were used with the same four-roll film laminating machine as in Example 2 to form a negative electrode sheet with the current collector aluminum foil at a temperature of 35° C. at a roller speed of 10 r/min, and then placed in a 240° C. Bake in an oven for 20h to obtain a negative electrode sheet.
  • the pole piece preparation method of this comparative example is the same as Example 1 in other aspects, except that in step (2), a three-roll film laminating machine is used instead of a two-roll laminating machine (2 rolls).
  • the preparation method of the pole piece of this comparative example is the same as that of Example 4 in other aspects, except that the three-roll film laminating machine is not used in step (2), but a pair of roll laminating machine (2 rolls) is used.
  • the thickness uniformity of the pole pieces was tested with a micrometer (characterized by the overall standard deviation of the thickness of the three pole pieces prepared in a certain example or comparative example).
  • Standard cycle standard charge ⁇ standby for 0.5h ⁇ standard discharge ⁇ standby for 0.5h;
  • the electrolyte of comparative example 1 is solvent (EC, PC, EMC, FB), additive (VC, MMDS), lithium salt (LiPF6) composition
  • the electrolyte of embodiment 4 is: lithium perchlorate ethylene glycol dimethyl ether and propylene carbonate solution
  • the negative electrode of embodiment 1-3 is graphite
  • the negative electrode of embodiment 4 is metal lithium
  • the preparation method of the example can make the pole piece keep a relatively high compaction density (1.5-3.0g/cm 3 ) by using a suitable film machine to cooperate with the granulation process. Obtaining better porosity enables the battery to have better discharge capacity, especially discharge capacity under larger current and lower temperature conditions, and at the same time, the thickness of the pole piece is consistent.
  • Comparative Example 1 because the film lamination equipment used was not suitable, particles were generated on both sides of the current collector, the uniformity was poor, and the pores formed after rolling were not uniform. Moreover, the requirements for the strength of the current collector are relatively high.

Abstract

本申请提供了一种极片及其制备方法和电池。所述制备方法包括以下步骤：（1）将活性物质、导电剂、溶剂和粘结剂混合造粒，得到混合颗粒；（2）将步骤（1）所述混合颗粒与集流体在合膜机中进行合膜，得到所述极片，其中，所述合膜机的辊数在3个或3个以上。

Description

一种极片及其制备方法和电池 技术领域
本申请属于电池技术领域，涉及一种极片及其制备方法和电池。
背景技术
随着科学技术的进步，锂电池在生活中的应用越来越广泛；从小型家用电器到新能源汽车到大型储能，各个领域均可发现它的存在。目前主流的正极体系有LCO、NCM、NCA、LFP、LMO等，负极体系有人造石墨、天然石墨、LTO、Si-C复合、人造和天然复合体系等，且其结构多样化，包括方形、圆柱和扣式锂电池；按外包材料分为铝壳、钢壳和软包锂电池。方形铝壳电池因其结构简单，能量密度高、尺寸灵活、pack成组简单、且其封装可靠性高等优点在锂动力和储能方向应用较为广泛。其中橄榄石结构的LiFePO 4具备了良好的结构稳定性和放电平台平稳、循环性能好、原物料来源广泛、价格低廉且无环境污染等优点，目前已在动力和储能两大领域得到了广泛的应用，且以方形铝壳LFP电池最为常见。
正极材料是决定锂电池性能和成本的重要因素，是电池能量密度提高的关键技术突破方向；性能优异的负极具备较高的比能量、较低的电极电势，且具有良好的脱嵌锂稳定性，是影响电池性能的关键；隔膜的主要作用是将锂电池的正、负极隔开，防止两极接触而短路，并且允许电解质的离子通过；电解液是锂电池的“血液”，Li +通过电解液在正负极之间往返脱嵌，同时影响电池的关键性能，例如安全性、高低温性能和功率性能等。电解液一般由溶剂、锂盐和添加剂按一定的比例组成，且按照不同的电性能需求组成有差异，电池在使用过程，电解液会有消耗，尤其是长循环寿命的电池，通常让电池的保液量尽 可能多，以满足循环过程电解液的消耗。
目前的极片制备工艺中，主要存在的问题有：1、极片内部孔隙分布不均匀，导致电池放电过程极片不同区域的电流密度不同，不能最大程度发挥电池的放电能力。2、极片不同区域的放电深度不同，膨胀情况亦不相同，电池在放电过程中易发生因活性物质与集流体脱离(掉粉)导致的电池阻值变大，末期脉冲能力下降迅速；严重时可能会发生因局部掉粉导致的电池内部短路。
CN107919459A公开了一种锂离子电池负极片的制备方法、锂离子电池负极片及锂离子电池，属于锂离子电池技术领域。该锂离子电池负极片的制备方法，包括如下步骤：将负极材料与水混合均匀制得负极浆料；所述负极材料包括负极活性物质、导电剂、粘结剂、添加剂，负极活性物质、导电剂、粘结剂、添加剂的质量比为85.5-95.5:1-3:1.5-3.5:2-8；所述添加剂为碳酸乙烯酯、碳酸丙烯酯中的至少一种；将制得的负极浆料涂布在负极集流体上，烘干即得。
CN103531811A公开了一种锂离子电池正极片的制备方法，包括如下步骤：按照固液比为(0.1g～2g):100mL，将碳材料在由浓硝酸和浓硫酸组成的混合酸中回流反应，得到羧基化的碳材料；按照固液比为(0.1g～2g):100mL，将羧基化的碳材料在二氯亚酚中回流反应，得到酰氯化的碳材料；按照固液比为(0.1g-1g):100mL:200mL，将酰氯化的碳材料与乙二胺在无水甲苯中回流反应，得到酰胺化的碳材料；将酰胺化的碳材料溶解于水中形成分散液；先将集流体在分散液中浸泡，然后将集流体于分散液和Li 2C 6O 6溶液中交替浸泡，干燥，得到锂离子电池正极片。
但上述方法均存在着极片厚度不均匀以及大电流放电能力差的问题。
发明内容
本申请的目的在于提供一种极片及其制备方法和电池。本申请提供的极片制备方法能够提高合膜过程中膜片厚度的一致性，并且可使极片内部孔分布更加均匀，孔隙率更优，可提高电池的放电能力。
为达此目的，本申请采用如下技术方案
第一方面，本申请提供一种极片的制备方法，所述方法包括以下步骤：
(1)将活性物质、导电剂、溶剂和粘结剂混合造粒，得到混合颗粒；
(2)将步骤(1)所述混合颗粒与集流体在合膜机中进行合膜，得到所述极片，其中，所述合膜机的辊数在3个或3个以上。
本申请提供的制备方法中，步骤(1)通过混合造粒实现制作均匀颗粒的目的，步骤(2)通过带有多个辊的合膜机，能够先使混合颗粒形成片，再压在集流体上，提高均匀性。上述两个步骤的相互配合使得本申请的方法得到的极片在保持较高的压实密度情况下具有较好的孔隙率，使得其制备的电池具有更好的放电能力，尤其是在较大电流和较低温度条件下的放电能力。
本申请中，所述合膜机的辊数为3个、4个或5个等。合膜机的辊数在3个或3个以上时，因为预先对膜片成型，可提升活性物质之间的粘结力及厚度均匀性，所以效果远好于使用对辊合膜机(2个辊)。
以下作为本申请可选的技术方案，但不作为本申请提供的技术方案的限制，通过以下技术方案，可以更好的达到和实现本申请的技术目的和有益效果。
作为本申请可选的技术方案，所述极片为正极片或负极片。
可选地，步骤(1)所述活性物质包括二氧化锰、锰酸锂、钴酸锂、镍钴锰酸锂、镍钴铝酸锂、磷酸铁锂、石墨或硅碳材料中的任意一种或至少两种的组合，典型但是非限制性的组合有：二氧化锰和锰酸锂的组合，锰酸锂和钴酸锂 的组合，钴酸锂和镍钴锰酸锂的组合，石墨和硅碳材料的组合等。
可选地，步骤(1)所述导电剂包括炭黑、石墨、石墨烯或碳纳米管中的任意一种或至少两种的组合。典型但是非限制性的组合有：炭黑和石墨烯的组合，石墨和石墨烯的组合，石墨烯和碳纳米管的组合等。
可选地，步骤(1)所述粘结剂包括丁苯橡胶、聚四氟乙烯、聚氟代乙烯、羟甲基纤维素钠、聚偏氟乙烯或聚丙烯酸锂中的任意一种或至少两种的组合。典型但是非限制性的组合有：丁苯橡胶和聚四氟乙烯的组合，聚四氟乙烯和聚氟代乙烯的组合，聚氟代乙烯和羟甲基纤维素钠的组合，聚偏氟乙烯和聚丙烯酸锂的组合等。
可选地，步骤(1)所述溶剂为水、乙醇、乙二醇、丙三醇、异丙醇、正丁醇、1-甲基吡咯烷酮(NMP)或N,N-二甲基甲酰胺(DMF)中的任意一种或至少两种的组合。典型但是非限制性的组合有：水和乙醇的组合，水和异丙醇的组合，水和乙二醇的组合等。
作为本申请可选的技术方案，步骤(1)所述活性物质、导电剂、溶剂和粘结剂的质量比为(58-88):(1-6):(10-30):(1-6)，例如58:6:30:6；61:6:27；6；66:6:22:6；70:6:18:6；8975:2:18:5；80:3:12:5或88:1:10:1等。
作为本申请可选的技术方案，步骤(1)所述混合造粒用造粒机进行。
可选地，所述造粒机转速为50-1200rpm，例如50rpm、100rpm、200rpm、300rpm、400rpm、500rpm、600rpm、700rpm、800rpm、900rpm、1000rpm、1100rpm或1200rpm等。
可选地，步骤(1)所述混合造粒的时间为1-10min，例如1min、1.5min、2min、2.5min、3min、3.5min、4min、4.5min、5min、5.5min、6min、6.5min、 7min、7.5min、8min、8.5min、9min、9.5min或10min等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
采用上述造粒机转速和混合造粒时间，可以控制颗粒的均匀性，进而控制合膜膜片厚度的一致性和极片孔隙分布。
作为本申请可选的技术方案，步骤(2)所述集流体包括钢网、铝网、铜网、镍网、铝箔或铜箔中的任意一种或至少两种的组合。
作为本申请可选的技术方案，步骤(2)所述合膜的温度为15-35℃，即常温合膜。
可选地，步骤(2)所述合膜机为三辊合膜机或四辊合膜机。
作为本申请可选的技术方案，步骤(2)所述合膜机的辊间距为0.05～0.5mm，例如0.05mm、0.1mm、0.2mm、0.3mm、0.4mm或0.5mm等，本申请中，如果辊间距过大，会导致膜片同集流体附着力弱；如果辊间距过小，会导致卡机。
可选地，步骤(2)所述合膜机的辊轮转速为1～10r/min，例如1r/min、2r/min、3r/min、4r/min、5r/min、6r/min、7r/min、8r/min、9r/min或10r/min等。本申请中，如果合膜机的辊轮转速过高，会导致极片均匀度变差；如果合膜机的辊轮转速过低，会导致卡料。
可选地，步骤(2)还包括：对合膜后得到的产品进行烘烤。
可选地，所述烘烤的温度为100-300℃，例如100℃、120℃、140℃、160℃、200℃、250℃或300℃等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
可选地，所述烘烤的时间为5-28h，例如5h、8h、12h、16h、20h、24h、 26h、27h或28h等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
作为本申请所述方法的进一步可选的技术方案，所述方法包括以下步骤：
(1)将活性物质、导电剂和粘结剂在造粒机中进行混合造粒1-10min，得到混合颗粒；
(2)将步骤(1)所述混合颗粒与集流体在和合膜机中进行合膜，合膜后对得到的产品进行100-300℃烘烤5-28h，得到所述极片，其中，所述合膜机三辊合膜机或四辊合膜机；
其中，所述极片为正极片或负极片；
步骤(1)所述活性物质包括二氧化锰、锰酸锂、钴酸锂、镍钴锰酸锂、镍钴铝酸锂、磷酸铁锂、石墨或硅碳材料中的任意一种或至少两种的组合；
步骤(1)所述导电剂包括炭黑、石墨、石墨烯或碳纳米管中的任意一种或至少两种的组合；
步骤(1)所述粘结剂包括丁苯橡胶、聚四氟乙烯、聚氟代乙烯、羟甲基纤维素钠、聚偏氟乙烯或聚丙烯酸锂中的任意一种或至少两种的组合；
步骤(1)所述溶剂为水、乙醇、乙二醇、丙三醇、异丙醇、正丁醇、1-甲基吡咯烷酮NMP或N,N-二甲基甲酰胺DMF中的任意一种或至少两种的组合；
步骤(1)所述活性物质、导电剂、溶剂和粘结剂的质量比为(58-88):(1-6):(10-30):(1-6)；
步骤(2)所述集流体包括钢网、铝网、铜网、镍网、铝箔或铜箔中的任意一种或至少两种的组合；
步骤(2)所述合膜机的辊间距为0.05～0.25mm；步骤(2)所述合膜机的 辊轮转速为1～10r/min。
第二方面，本申请提供一种如第一方面所述的制备方法制备得到的极片。
可选地，所述极片上，膜片的厚度为0.2-1.0mm；
可选地，所述极片的压实密度为1.5-3.0g/cm 3
第三方面，本申请提供一种电池，所述电池包含如第二方面所述的极片。
与现有技术相比，本申请具有以下有益效果：
(1)本申请提供的制备方法可以使极片在保持较高压实密度的情况下获得较好的孔隙率，使得电池具有更好的放电能力，尤其是在较大电流和较低温度条件下的放电能力，同时极片的厚度一致性好，极片厚度总体标准差在0.005mm以内。
(2)本申请提供的极片制备方法制造工艺简单，自动化水平高，可实现从投料到极片成型一个流程产出。
附图说明
图1为实施例1的制备方法的流程示意图；
图2为实施例1的制备方法中的合膜机示意图，图中标记的1、2和3代表辊的编号；
图3为实施例2的制备方法中的合膜机示意图，图中标记的1、2、3和4代表辊的编号；
图4为对比例1的制备方法中的合膜机示意图。
具体实施方式
为更好地说明本申请，便于理解本申请的技术方案，下面对本申请进一步详细说明。但下述的实施例仅仅是本申请的简易例子，并不代表或限制本申请 的权利保护范围，本申请保护范围以权利要求书为准。
以下为本申请典型但非限制性实施例：
实施例1
本实施例按照如下方法制备：
(1)将78wt％LiFePO 4与2wt％导电碳充分混合，再与3％聚四氟乙烯粘结剂、17wt％乙醇/水(1/2)混合溶剂充分混合后，采用高速造粒机以1000rpm的转速混合造粒5min，制备得到混合颗粒；
(2)将步骤(1)所述混合颗粒用三辊合膜机(辊1和辊2间距0.1mm，辊2和辊3间距0.08mm)在25℃温度下以3r/min辊轮转速与集流体铝箔形成膜片，之后置于120℃的烘箱中烘烤8h，烘烤分切得到正极片。
本实施例的制备方法流程示意图如图1所示。
本实施例的合膜机示意图如图2所示，该合膜机的辊1和辊2对混合颗粒进行预压成型，辊2和辊3将预压成型的混合颗粒与集流体合膜。
本实施例制备的正极片的测试结果见表1
实施例2
本实施例按照如下方法制备：
(1)同实施例1的步骤1
(2)将步骤(1)所述混合颗粒用四辊合膜机(辊1和辊2及辊3和辊4间距0.1mm，辊2和辊3之间的间距为0.1mm),在25℃温度下以3r/min辊轮转速与集流体铝箔形成膜片，之后置于120℃的烘箱中烘烤8h，烘烤分切得到正极片。
本实施例的合膜机示意图如图3所示，该合膜机的辊1和辊2对混合颗粒 进行预压成型，辊3和辊4也对混合颗粒进行预压成型，辊2和辊3将预压成型的混合颗粒与集流体合膜。
本实施例制备的正极片的测试结果见表1。
实施例3
本实施例按照如下方法制备：
(1)将95wt％磷酸铁锂与2.5wt％导电碳充分混合，再与2.5％聚四氟乙烯粘结剂充分混合后，采用高速造粒机以200rpm的转速混合造粒1min，制备得到混合颗粒；
(2)将步骤(1)所述混合颗粒用与实施例2相同的四辊合膜机在15℃温度下以1r/min辊轮转速与集流体铝箔形成正极片，之后置于200℃的烘箱中烘烤28h，得到正极片。
本实施例制备的正极片的测试结果见表1。
实施例4
本实施例按照如下方法制备：
(1)将85wt％MnO 2与7.5wt％导电碳充分混合，再与7.5％聚四氟乙烯粘结剂充分混合后，采用高速造粒机以1200rpm的转速混合造粒10min，制备得到混合颗粒；
(2)将步骤(1)所述混合颗粒用与实施例2相同的四辊合膜机在35℃温度下以10r/min辊轮转速与集流体铝箔形成负极片，之后置于240℃的烘箱中烘烤20h，得到负极片。
本实施例制备的负极片的测试结果见表1。
对比例1
本对比例的极片制备方法除了步骤(2)中不使用三辊合膜机，而是使用对辊合膜机(2辊)之外，其他方面与实施例1均相同。
本对比例的合膜机示意图如图4所示。
本对比例制备的正极片的测试结果见表1。
对比例2
本对比例的极片的制备方法除了步骤(2)中不使用三辊合膜机，而是使用对辊合膜机(2辊)之外，其他方面与实施例4均相同。
本对比例制备的正极片的测试结果见表1。
测试方法
对各实施例和对比例提供的极片进行测试。
用千分尺测试极片厚度一致性(以某个实施例或对比例制备的3个极片的厚度总体标准差来表征)。
用电解液在干燥条件下(露点≤-45℃)测试吸液量。用新威测试柜采用标准工步测试电池在-10℃和常温(25℃)时1C容量保持率。
测试标准工步：
标准充电：电池以1C(A)电流恒流充电至3.65V时，转恒压充电，截止电流0.05C；
标准放电：电池以1C(A)电流恒流放电至2.50V；
标准循环：标准充电→搁置0.5h→标准放电→搁置0.5h；
实施例1-3，对比例1的电解液为溶剂(EC、PC、EMC、FB)，添加剂(VC、MMDS)，锂盐(LiPF6)组成，实施例4的电解液为：高氯酸锂的乙二醇二甲醚与碳酸丙烯酯溶液；实施例1-3的负极为石墨，实施例4的负极为金属锂
测试结果如下表所示：
表1
Figure PCTCN2021140823-appb-000001
综合上述实施例和对比例可知，实施例的制备方法通过采用合适合膜机与造粒工艺相配合，可以使极片在保持较高压实密度(1.5-3.0g/cm 3)的情况下获得较好的孔隙率，使得电池具有更好的放电能力，尤其是在较大电流和较低温度条件下的放电能力，同时极片的厚度一致性好。
对比例1因为采用的合膜设备不合适，集流体两边产生颗粒，均匀性较差，辊压之后形成的孔不均匀。而且对集流体强度要求较高。
申请人声明，以上所述仅为本申请的具体实施方式，但本申请的保护范围并不局限于此。

Claims (12)

  1. 一种极片的制备方法，其包括以下步骤：
    (1)将活性物质、导电剂、溶剂和粘结剂混合造粒，得到混合颗粒；
    (2)将步骤(1)所述混合颗粒与集流体在合膜机中进行合膜，得到所述极片，其中，所述合膜机的辊数在3个或3个以上。
  2. 根据权利要求1所述的制备方法，其中，步骤(2)所述合膜机的辊间距为0.05-0.5mm。
  3. 根据权利要求1或2所述的制备方法，其中，步骤(2)所述合膜机的辊轮转速为1-10r/min。
  4. 根据权利要求1-3任一项所述的制备方法，其中，所述极片为正极片或负极片；
    可选地，步骤(1)所述活性物质包括二氧化锰、锰酸锂、钴酸锂、镍钴锰酸锂、镍钴铝酸锂、磷酸铁锂、石墨或硅碳材料中的任意一种或至少两种的组合；
    可选地，步骤(1)所述导电剂包括炭黑、石墨、石墨烯或碳纳米管中的任意一种或至少两种的组合；
    可选地，步骤(1)所述粘结剂包括丁苯橡胶、聚四氟乙烯、聚氟代乙烯、羟甲基纤维素钠、聚偏氟乙烯或聚丙烯酸锂中的任意一种或至少两种的组合；
    可选地，所述溶剂为水、乙醇、乙二醇、丙三醇、异丙醇、正丁醇、1-甲基吡咯烷酮或N,N-二甲基甲酰胺中的任意一种或至少两种的组合。
  5. 根据权利要求1-4任一项所述的制备方法，其中，步骤(1)所述活性物质、导电剂、溶剂和粘结剂的质量比为(58-88):(1-6):(10-30):(1-6)。
  6. 根据权利要求1-5任一项所述的制备方法，其中，步骤(1)所述混合 造粒用造粒机进行；
    可选地，所述造粒机转速为50-1200rpm；
    可选地，步骤(1)所述混合造粒的时间为1-10min。
  7. 根据权利要求1-6任一项所述的制备方法，其中，步骤(2)所述集流体包括钢网、铝网、铜网、镍网、铝箔或铜箔中的任意一种或至少两种的组合。
  8. 根据权利要求1-7任一项所述的制备方法，其中，步骤(2)所述合膜的温度为15-35℃；
    可选地，步骤(2)所述合膜机为三辊合膜机或四辊合膜机。
  9. 根据权利要求1-8任一项所述的制备方法，其中，步骤(2)还包括：对合膜后得到的产品进行烘烤；
    可选地，所述烘烤的温度为100-300℃；
    可选地，所述烘烤的时间为5-28h。
  10. 根据权利要求1-9任一项所述的制备方法，其中，所述方法包括以下步骤：
    (1)将活性物质、导电剂和粘结剂在造粒机中进行混合造粒1-10min，得到混合颗粒；
    (2)将步骤(1)所述混合颗粒与集流体在和合膜机中进行合膜，合膜后对得到的产品进行100-300℃烘烤5-28h，得到所述极片，其中，所述合膜机三辊合膜机或四辊合膜机；
    其中，所述极片为正极片或负极片；
    步骤(1)所述活性物质包括二氧化锰、锰酸锂、钴酸锂、镍钴锰酸锂、镍钴铝酸锂、磷酸铁锂、石墨或硅碳材料中的任意一种或至少两种的组合；
    步骤(1)所述导电剂包括炭黑、石墨、石墨烯或碳纳米管中的任意一种或至少两种的组合；
    步骤(1)所述粘结剂包括丁苯橡胶、聚四氟乙烯、聚氟代乙烯、羟甲基纤维素钠、聚偏氟乙烯或聚丙烯酸锂中的任意一种或至少两种的组合；
    步骤(1)所述溶剂为水、乙醇、乙二醇、丙三醇、异丙醇、正丁醇、1-甲基吡咯烷酮或N,N-二甲基甲酰胺中的任意一种或至少两种的组合；
    步骤(1)所述活性物质、导电剂、溶剂和粘结剂的质量比为(58-88):(1-6):(10-30):(1-6)；
    步骤(2)所述集流体包括钢网、铝网、铜网、镍网、铝箔或铜箔中的任意一种或至少两种的组合；
    步骤(2)所述合膜机的辊间距为0.05-0.25mm；步骤(2)所述合膜机的辊轮转速为1-10r/min。
  11. 一种如权利要求1-10任一项所述的制备方法制备得到的极片；
    可选地，所述极片上，膜片的厚度为0.2-1.0mm；
    可选地，所述极片的压实密度为1.5-3.0g/cm 3。
  12. 一种电池，其包含如权利要求9所述的极片。
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