Secondary battery and electric device

Abstract

The application discloses a secondary battery and an electric device. The secondary battery comprises a pole piece, the pole piece comprises a current collecting layer, an active material layer arranged on at least one side of the current collecting layer, and a modification layer arranged on the active material layer, the modification layer comprises a skeleton material and a gelled polymer, and the gelled polymer is dispersed in the pores of the skeleton material. The skeleton material is not only firm and stable, but also has high porosity and complete pore structure, so that the electrolyte can be quickly absorbed. The gelled polymer uniformly dispersed in the skeleton material has strong transport capacity for lithium ions, so that the influence of the modification layer on the internal resistance of the battery is effectively reduced.

Description

Technical Field

[0001] The present application relates to the technical field of lithium-ion batteries, and in particular to a secondary battery and electrical equipment. Background Art

[0002] Secondary batteries, such as lithium-ion batteries, are one of the most important components of clean energy. Their high energy density, long cycle life, and excellent environmental friendliness have led to a huge market demand. However, there are many links that restrict the actual production efficiency of lithium-ion batteries, among which liquid injection is a key link. Because the pores of the electrode sheet are greatly compressed after rolling, the porosity decreases sharply. In addition, the poor affinity between the electrode material and the electrolyte prevents the electrode sheet from quickly absorbing the electrolyte. At the same time, the poor affinity between the electrode material and the electrolyte is also a major reason why the electrode sheet is difficult to wet after rolling. Therefore, aluminum shell batteries are currently filled with liquid using a cycle of negative pressure exhaust and high-pressure liquid injection. Multiple cycles of liquid injection result in a long time consumption. Because the electrode sheet is difficult to wet, a long period of high-temperature soaking must be carried out after liquid injection, which greatly affects production efficiency. If the liquid injection efficiency can be significantly improved and the electrode sheet soaking time can be reduced, the efficiency of battery production can be greatly improved. Therefore, it is necessary to find a strategy that can improve the efficiency of the electrode in absorbing and storing electrolyte without changing the electrode compression design, and reduce the time required for high-temperature immersion, so as to significantly improve the production efficiency of the battery without increasing the internal resistance of the electrode. Summary of the Invention

[0003] The present application provides a secondary battery and electrical equipment, which solves the problem of long injection time in the current battery production process.

[0004] According to the secondary battery in the first embodiment of the present application, the secondary battery includes a pole piece, which includes a current collecting layer, an active material layer arranged on at least one side of the current collecting layer, and a modifying layer arranged on the active material layer, wherein the modifying layer includes a skeleton material and a gelled polymer, and the gelled polymer is dispersed in the pores of the skeleton material.

[0005] Optionally, in other embodiments of the present application, the skeleton material includes at least one of polyvinylidene fluoride-hexafluoropropylene or polyethylene glycol dimethacrylate.

[0006] Optionally, in other embodiments of the present application, the gelling polymer includes one or more of polyethylene oxide (PEO), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA) or polyvinyl alcohol (PVA).

[0007] Optionally, in other embodiments of the present application, the porosity of the modified layer may be 50% to 85%, or 60% to 80%, or 70% to 75%.

[0008] Optionally, in other embodiments of the present application, the liquid absorption rate of the modification layer may be 150% to 350 wt %, or 180% to 300 wt %, or 200% to 250 wt %.

[0009] Optionally, in other embodiments of the present application, the molecular weight of polyvinylidene fluoride-hexafluoropropylene may be 10,000 to 1,000,000, 100,000 to 800,000, or 300,000 to 500,000.

[0010] Optionally, in other embodiments of the present application, the thickness of the modification layer may be 1 to 10 μm, 2 to 9 μm, or 5 to 8 μm.

[0011] Optionally, in other embodiments of the present application, the liquid retention rate of the electrode is 70% to 80%.

[0012] Optionally, in other embodiments of the present application, the electrode is prepared by: dissolving the skeleton material in a first solvent to obtain a skeleton material solution; dissolving the gelled polymer in a second solvent to obtain a gelled polymer solution; coating the active material slurry on the surface of the current collecting layer, and obtaining a current collecting layer having an active material layer on the surface after drying; coating the skeleton material solution on the active material layer, and the skeleton material is attached to the active material layer after drying; coating the gelled polymer solution on the skeleton material to obtain a electrode with a modified layer.

[0013] Optionally, in other embodiments of the present application, after coating the skeleton material solution on the active material layer, the method includes soaking the coated material in a third solvent.

[0014] According to the electric device in the second embodiment of the present application, the electric device includes the above-mentioned secondary battery, and the secondary battery serves as a power supply for the electric device.

[0015] The secondary battery according to the embodiment of the present application has at least the following technical effects:

[0016] (1) The secondary battery of the present application includes a pole piece, the pole piece includes a modified layer, and the modified layer includes a skeleton material. The skeleton material is not only strong and stable, but also helps the pole piece to quickly absorb and store a large amount of electrolyte, effectively improving the injection efficiency, reducing the overflow, and shortening the injection time;

[0017] (2) The modified layer of the present application also includes a gelled polymer, which is uniformly dispersed in the pores of the skeleton material. The gelled polymer has a strong lithium ion transmission ability and can effectively reduce the impact of the polymer coating on the internal resistance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 is a cross-sectional view of the skeleton material provided in the examples of the present application;

[0020] Figure 2 1 is a cross-sectional view of the modified layer provided in an embodiment of the present application.

[0021] The marks in the figure are: 1-skeleton material, 2-pores, 3-gelled polymer. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0023] The embodiments of the present application provide a secondary battery and an electrical device. These are described in detail below. It should be noted that the order in which the following embodiments are described does not limit the preferred order of the embodiments.

[0024] In this specification, a numerical range expressed using “to” means a range including the numerical values ​​described before and after “to” as the minimum value and the maximum value, respectively.

[0025] An embodiment of the present application provides a secondary battery comprising a pole piece, the pole piece comprising a current collecting layer, an active material layer disposed on at least one side of the current collecting layer, and a modifying layer disposed on the active material layer, the modifying layer comprising a skeleton material and a gelling polymer, the gelling polymer being dispersed within the pores of the skeleton material. The present application utilizes the skeleton material's high affinity for electrolyte and high porosity to rapidly absorb and store large amounts of electrolyte, significantly improving injection efficiency. The modifying layer of the present application also comprises a gelling polymer, which is uniformly dispersed within the pores of the skeleton material. The gelling polymer has strong lithium ion transport capabilities, effectively reducing the impact of the polymer coating on the battery's internal resistance.

[0026] See also Figure 1 and Figure 2 The skeleton material 1 has a plurality of pores 2 , and the gelling polymer 3 is uniformly dispersed in the pores 2 of the skeleton material 1 . Specifically, the gelling polymer 3 is uniformly dispersed on the pore walls of the pores 2 of the skeleton material 1 .

[0027] Specifically, the electrode sheets include positive electrode sheets and negative electrode sheets, the positive electrode active material layer is located on at least one surface of the positive electrode current collecting layer, and the modified layer is located on the positive electrode active material layer; or, the negative electrode active material layer is located on at least one surface of the negative electrode current collecting layer, and the modified layer is located on the negative electrode active material layer.

[0028] Specifically, the positive electrode active material layer may be one or more layers. The positive electrode active material layer includes a positive electrode active material, a positive electrode conductive agent, a positive electrode binder, and a solvent. Each layer of the multilayer positive electrode active material may contain the same or different positive electrode active materials. The positive electrode active material is any substance that can reversibly intercalate and deintercalate metal ions such as lithium ions. Examples of positive electrode active materials may include, but are not limited to, lithium transition metal composite oxides and lithium-containing transition metal phosphate compounds.

[0029] There is no particular restriction on the type of the positive electrode current collecting layer, and it may be any material known to be suitable for use as a positive electrode current collecting layer. Examples of the positive electrode current collecting layer may include, but are not limited to, metal materials such as aluminum, stainless steel, nickel plating, titanium, tantalum, and carbon materials such as carbon cloth and carbon paper. In some embodiments, the positive electrode current collecting layer is a metal material. In some embodiments, the positive electrode current collecting layer is aluminum. There is no particular restriction on the form of the positive electrode current collecting layer. In some embodiments, the positive electrode current collecting layer is a metal foil. In some embodiments, the metal foil is mesh-shaped. There is no particular restriction on the thickness of the metal foil. In some embodiments, the thickness of the metal foil is greater than 1 μm, greater than 3 μm, or greater than 5 μm. In some embodiments, the thickness of the metal foil is less than 1 mm, less than 100 μm, or less than 50 μm. In some embodiments, the thickness of the metal foil is within the range formed by any two of the above values.

[0030] Specifically, the negative electrode active material layer can be one or more layers. The negative electrode active material layer includes a negative electrode active material, a conductive agent, a binder, an additive, and a solvent. Each layer of the multi-layer negative electrode active material can contain the same or different negative electrode active materials. The negative electrode active material is any material that can reversibly embed and deintercalate metal ions such as lithium ions. In some embodiments, the negative electrode active material includes, but is not limited to, carbon materials such as graphite, hard carbon, soft carbon, mesophase carbon microbeads (MCMB), silicon, SiO x Silicon compounds such as silicon oxide represented by (0<x<2), metallic lithium, metals forming alloys with lithium and their alloys, amorphous compounds mainly composed of oxides such as tin dioxide, and lithium titanate (Li4Ti5O 12 ).

[0031] Furthermore, the negative electrode current collecting layer includes, but is not limited to, metal foil, metal cylinder, metal strip, metal plate, metal film, metal mesh, stamped metal, foamed metal, etc. In some embodiments, the negative electrode current collecting layer is metal foil. In some embodiments, the negative electrode current collecting layer is copper foil.

[0032] In some embodiments of the present application, the skeleton material includes at least one of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) or polyethylene glycol dimethacrylate (PEGDMA). The skeleton material has good mechanical properties, film forming properties and electrochemical properties. Preferably, the skeleton material is PVDF-HFP, and PVDF-HFP is a skeleton material with strong mechanical properties and stable structure after film formation. The structural stability of PVDF-HFP in the electrolyte is the best in currently common synthetic base polymer matrix and its derivatives. PVDF-HFP is not only strong and stable as a skeleton, but also has high porosity and a complete pore structure that can quickly absorb electrolyte.

[0033] In some embodiments of the present application, the gelling polymer includes one or more of polyethylene oxide (PEO), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA) or polyvinyl alcohol (PVA); preferably, the gelling polymer is polyethylene oxide. The gelling polymer has a strong transport capacity for lithium ions and can effectively reduce the influence of the modified layer on the internal resistance of the battery. During high-temperature infiltration, the low glass transition temperature of the gelling polymer makes its polymer chain segments have excellent mobility at high temperatures, which can quickly transport the solvent molecules in the electrolyte to the uninfiltrated areas of the electrode. When the gel state formed by the gelling polymer and the electrolyte contacts the electrode, there is no surface tension, which is conducive to the diffusion of the electrolyte from the gelling polymer phase to the electrode, thereby improving the efficiency of the electrode infiltration.

[0034] In some embodiments of the present application, the porosity of the modified layer may be 50% to 85%, or 60% to 80%, or 70% to 75%.

[0035] In some embodiments of the present application, the electrolyte absorption rate of the modified layer can be 150% to 350 wt%, 180% to 300 wt%, or 200% to 250 wt%. Since the skeleton material has a high porosity, the skeleton material can store more electrolyte.

[0036] In some embodiments of the present application, the molecular weight of polyvinylidene fluoride-hexafluoropropylene may be 10,000 to 1,000,000, 100,000 to 800,000, or 300,000 to 500,000.

[0037] In some embodiments of the present application, the thickness of the modification layer may be 1 to 10 μm, 2 to 9 μm, or 5 to 8 μm.

[0038] In some embodiments of the present application, the liquid retention rate of the electrode may be 70% to 80%, or 73% to 78%, or 75% to 77%.

[0039] In some embodiments of the present application, the electrode is prepared by the following method: dissolving the skeleton material in a first solvent to obtain a skeleton material solution; dissolving the gelled polymer in a second solvent to obtain a gelled polymer solution; coating the active material slurry on the surface of the current collecting layer, and obtaining the current collecting layer having an active material layer on the surface after drying; coating the skeleton material solution on the active material layer, and the skeleton material is attached to the active material layer after drying; coating the gelled polymer solution on the skeleton material to obtain a electrode with a modified layer.

[0040] In some embodiments of the present application, the concentration of the skeleton material solution can be 1% to 25% by weight, 5% to 15% by weight, or 8% to 10% by weight. A too low concentration will reduce the coating effect of the skeleton material, and a further increase in concentration will increase the solution viscosity and reduce the electrode wetting effect.

[0041] In some embodiments of the present application, the concentration of the gelled polymer solution may be 5% to 15% by weight, 8% to 13% by weight, or 10% to 12% by weight. A too low concentration will reduce the adhesion effect, while a too high concentration will affect the penetration effect into the pores.

[0042] In some embodiments of the present application, coating the skeleton material solution on the active material layer includes soaking the coated material in a third solvent. Soaking the coated material in the third solvent performs a phase transfer process, thereby increasing the porosity.

[0043] Specifically, the first solvent includes N-methylpyrrolidone (NMP), and the second and third solvents include at least one of deionized water, methanol, ethanol, acetone, or acetonitrile. The third solvent is a non-solvent for the framework material, can be volatilized by heating, and is compatible with the first solvent.

[0044] The phase transfer method is that the skeleton material solution is transferred from the solvent phase to the non-solvent phase under the action of the solubility gradient in the non-solvent system, so as to separate the first solvent from the polymer. The skeleton material prepared by the phase transfer method can store a large amount of electrolyte, which not only reduces the existence of free electrolyte, but also improves the liquid retention capacity of the pole piece; then the gel polymer is absorbed into the pores of the skeleton material, and after the solvent volatilizes, the gel polymer layer is formed in the pores of the skeleton material, the gel polymer layer has strong transport capacity for lithium ions, which can effectively reduce the influence of the polymer coating on the internal resistance of the battery.

[0045] The application also provides a kind of power utilization equipment, including the above-mentioned secondary battery, the secondary battery is used as the power supply of power utilization equipment.

[0046] The power utilization equipment of the application is, but not limited to, backup power supply, motor, electric vehicle, electric motorcycle, power-assisted bicycle, bicycle, electric tool, household large storage battery, etc.

[0047] The following will be described in conjunction with specific embodiments, the following only lists the preparation examples of the positive pole piece with the modification layer, the negative pole piece with the modification layer can be prepared according to the steps and parameter control of the following examples, which will not be repeated here.

[0048] Example 1

[0049] The preparation method of the pole piece of the present embodiment includes the following steps:

[0050] 1) PVDF-HFP solution preparation: dissolve PVDF-HFP (number average molecular weight 500000) in 60℃ N-methyl pyrrolidone (NMP) to prepare a 20wt% PVDF-HFP solution.

[0051] 2) Preparation of pole piece base layer: mix LiNi0.8Co0.1Mn0.1O2, conductive carbon black and binder PVDF in a ratio of 94:2:2 in solvent NMP to obtain a positive electrode slurry, coat the obtained slurry on the foil (aluminum foil) by extrusion coating equipment and dry thoroughly to obtain a dry positive electrode pole piece base layer.

[0052] 3) Preparation of modification layer

[0053] The prepared PVDF-HFP solution is evenly coated on the dried positive electrode base through an extrusion coating device with a coating thickness of 6 μm. The electrode coated with the PVDF-HFP solution is then immersed in deionized water for 30 minutes to perform a phase transfer process, and then placed in an oven for drying to obtain an electrode containing PVDF-HFP prepared by the phase transfer method. A layer of 5% PEO dilute solution is applied on the electrode containing PVDF-HFP so that it is completely absorbed by the PVDF-HFP layer, and then placed in an oven for drying so that the PEO layer is evenly attached to the PVDF-HFP skeleton. After rolling, die-cutting and slitting processes, a positive electrode electrode containing a modified layer is obtained.

[0054] Example 2

[0055] The method for preparing the electrode in this embodiment includes the following steps:

[0056] 1) Preparation of PVDF-HFP solution: PVDF-HFP was dissolved in 60° C. N-methylpyrrolidone (NMP) to prepare a 20 wt % PVDF-HFP solution.

[0057] 2) Preparation of electrode substrate: The positive electrode raw materials are mixed in a certain proportion, and after sufficient stirring, the obtained slurry is coated on the foil through an extrusion coating device and fully dried to obtain a dry positive electrode substrate.

[0058] 3) Modification layer preparation

[0059] The prepared PVDF-HFP solution is evenly coated on the dried positive electrode substrate through an extrusion coating device, and the electrode coated with the PVDF-HFP solution is immersed in deionized water for 30 minutes to perform a phase transfer process, and then placed in an oven for drying to obtain an electrode containing PVDF-HFP prepared by the phase transfer method. A layer of 5% PAN dilute solution is coated on the electrode containing PVDF-HFP so that it is completely absorbed by the PVDF-HFP layer, and then placed in an oven for drying so that the PAN layer is evenly attached to the PVDF-HFP skeleton. Rolling, die-cutting and slitting processes are performed to obtain a positive electrode electrode containing a modified layer.

[0060] Example 3

[0061] The method for preparing the electrode in this embodiment includes the following steps:

[0062] 1) Preparation of PVDF-HFP solution: PVDF-HFP was dissolved in 60° C. N-methylpyrrolidone (NMP) to prepare a 20 wt % PVDF-HFP solution.

[0063] 2) Preparation of electrode substrate: The positive electrode raw materials are mixed in a certain proportion, and after sufficient stirring, the obtained slurry is coated on the foil through an extrusion coating device and fully dried to obtain a dry positive electrode substrate.

[0064] 3) Modification layer preparation

[0065] The prepared PVDF-HFP solution is evenly coated on the dried positive electrode base through an extrusion coating device, and the electrode coated with the PVDF-HFP solution is immersed in deionized water for 30 minutes to perform a phase transfer process, and then placed in an oven for drying to obtain an electrode containing PVDF-HFP prepared by the phase transfer method. A layer of 5% PMMA dilute solution is coated on the electrode containing PVDF-HFP so that it is completely absorbed by the PVDF-HFP layer, and then placed in an oven for drying so that the PMMA layer is evenly attached to the PVDF-HFP skeleton. Rolling, die-cutting and slitting processes are performed to obtain an electrode containing a modified layer.

[0066] Example 4

[0067] The method for preparing the electrode in this embodiment includes the following steps:

[0068] 1) Preparation of PVDF-HFP solution: PVDF-HFP was dissolved in 60° C. N-methylpyrrolidone (NMP) to prepare a 20 wt % PVDF-HFP solution.

[0069] 2) Preparation of electrode substrate: The positive electrode raw materials are mixed in a certain proportion, and after sufficient stirring, the obtained slurry is coated on the foil through an extrusion coating device and fully dried to obtain a dry positive electrode substrate.

[0070] 3) Modification layer preparation

[0071] The prepared PVDF-HFP solution is evenly coated on the dried positive electrode base through an extrusion coating device, and the electrode coated with the PVDF-HFP solution is immersed in deionized water for 30 minutes to perform a phase transfer process, and then placed in an oven for drying to obtain an electrode containing PVDF-HFP prepared by the phase transfer method. A layer of 5% PVA dilute solution is coated on the electrode containing PVDF-HFP so that it is completely absorbed by the PVDF-HFP layer, and then placed in an oven for drying so that the PVA layer is evenly attached to the PVDF-HFP skeleton, and rolling, die-cutting and slitting processes are performed to obtain an electrode containing a modified layer.

[0072] Example 5

[0073] The method for preparing the electrode in this embodiment includes the following steps:

[0074] 1) PEGDMA (polyethylene glycol dimethacrylate) solution preparation: PEGDMA was dissolved in N-methyl pyrrolidone (NMP) at 60 °C to prepare a 20 wt% PEGDMA solution.

[0075] 2) Preparation of electrode sheet base layer: Positive electrode raw materials were mixed in a certain proportion, and after being stirred thoroughly, the obtained slurry was coated on a foil by an extrusion coating device and dried thoroughly to obtain a dried positive electrode sheet base layer.

[0076] 3) Preparation of modification layer

[0077] The prepared PEGDMA solution was uniformly coated on the dried positive electrode sheet base layer by an extrusion coating device, and then the electrode sheet coated with the PEGDMA solution was immersed in deionized water for 30 minutes to perform a phase transfer process, and then dried in an oven to obtain an electrode sheet containing PEGDMA prepared by a phase transfer method. A PEO dilute solution with a concentration of 5% was coated on the electrode sheet containing PEGDMA, so that it was completely absorbed by the PEGDMA layer, and then dried in an oven to make the PEO layer uniformly adhere to the PEGDMA skeleton. The electrode sheet containing the modification layer was obtained by rolling, die cutting and slitting processes.

[0078] Example 6

[0079] The same as Example 1, except that the number average molecular weight of PVDF-HFP was 10000.

[0080] Example 7

[0081] The same as Example 1, except that the number average molecular weight of PVDF-HFP was 300000.

[0082] Example 8

[0083] The same as Example 1, except that the number average molecular weight of PVDF-HFP was 800000.

[0084] Example 9

[0085] The same as Example 1, except that the number average molecular weight of PVDF-HFP was 1000000.

[0086] Example 10

[0087] The same as Example 1, except that a 8 wt% PVDF-HFP solution was prepared. The porosity of the modification layer was adjusted by adjusting the concentration of the PVDF-HFP solution.

[0088] Example 11

[0089] The same as Example 1, except that a 15 wt% PVDF-HFP solution was prepared.

[0090] Example 12

[0091] The same as Example 1, except that a 25 wt% PVDF-HFP solution was prepared.

[0092] Example 13

[0093] The same as Example 1, except that the coating thickness of the PVDF-HFP solution is 2 μm, and the thickness of the prepared modified layer is 1 μm.

[0094] Example 14

[0095] The same as Example 1, except that the coating thickness of the PVDF-HFP solution is 4 μm, and the thickness of the prepared modified layer is 3 μm.

[0096] Example 15

[0097] The same as Example 1, except that the coating thickness of the PVDF-HFP solution is 9 μm, and the thickness of the prepared modified layer is 8 μm.

[0098] Example 16

[0099] The same as Example 1, except that the coating thickness of the PVDF-HFP solution is 11 μm, and the thickness of the prepared modified layer is 10 μm.

[0100] Comparative Example 1

[0101] The preparation method of the electrode of this embodiment is the same as that of embodiment 1, except that the electrode of this embodiment does not include a modification layer.

[0102] Comparative Example 2

[0103] The preparation method of the electrode piece of this embodiment is the same as that of embodiment 1, except that the electrode piece of this embodiment only contains PVDF-HFP.

[0104] The characteristic parameters related to the positive electrode plates prepared in the examples and comparative examples are recorded, and the liquid absorption rate and liquid retention rate of the positive electrode plates prepared above are tested. In addition, the positive electrode plates prepared in the above examples and comparative examples are assembled with the prepared diaphragm (PP / PE diaphragm) and negative electrode plates (the components of the negative electrode plates are: graphite, conductive carbon black, thickener CMC and binder SBR, with a weight ratio of 96:1:1:2), and the injection and packaging processes are carried out to form a battery, and the corresponding injection time is recorded. The characteristic parameters and test data of the positive electrode plates and the injection time are recorded in Table 1. The electrolyte components include ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) organic solvents with a mass ratio of 30:40:30, and 1 mol / L LiPF6 solution.

[0105] The test method for liquid absorption and liquid retention is as follows: Weigh the mass m1 of the positive electrode sheet, completely immerse it in the electrolyte, let it sit for 30 minutes, remove it, remove the electrolyte adsorbed on the surface, and weigh the mass m2 of the positive electrode sheet at this time. Then, expose the positive electrode sheet to air for 60 minutes to allow the electrolyte to evaporate, and weigh the mass m3 of the positive electrode sheet at this time. The liquid absorption rate v (%) = [(m2 - m1) / m1] × 100%; the liquid retention rate n (%) = m3 / m2 × 100%.

[0106] Filling time test method: evacuate the battery cell to a vacuum degree of ≤-95kPa, then inject electrolyte into the battery cell and charge the battery cell with positive pressure in the range of 200-300kPa and for 30-60s; then charge the battery cell with negative pressure in the range of -50--90kPa and for 3-10s; repeat this cycle until the battery cell reaches the set filling volume, and record the time it takes to reach the set filling volume, which is recorded as the filling time in seconds (s).

[0107] Table 1

[0108]

[0109]

[0110] From the comparison of Examples 1 to 16 and Comparative Example 1, it can be seen that the injection time of Examples 1 to 16 is significantly shortened, and the electrode liquid retention rate is significantly improved. Examples 1 to 16 use electrodes with added modified layers, which shows that the excellent affinity of the modified layer with the electrolyte and the high porosity of the modified layer promote the rapid absorption of the electrolyte by the electrode. In addition, the pore structure of the electrode base layer after rolling is severely compressed and destroyed, making it difficult to infiltrate, and the electrolyte stored in the surface pores evaporates quickly and is difficult to preserve. The electrode containing the modified layer benefits from the good gelation ability of the gelled polymer, and has a good binding effect on the absorbed electrolyte, thus showing excellent liquid retention ability.

[0111] A comparison of Examples 1-16 and Comparative Example 2 shows that the injection times of Examples 1-16 and Comparative Example 2 are similar, while the electrode liquid retention rates of Examples 1-16 are all higher than those of Comparative Example 2. Since Examples 1-16 and Comparative Example 2 all contain a skeleton material, the high porosity of the skeleton material promotes the rapid absorption of the electrolyte by the electrode. However, since Comparative Example 2 does not contain a gelling polymer, the electrode's liquid retention capacity is poor. This indicates that the electrode containing both a skeleton material and a gelling polymer modification layer has a shorter injection time and a higher liquid retention rate.

[0112] From the comparison between Example 1 and Examples 2 to 4, it can be seen that the injection time of Example 1 is shorter and the electrode liquid retention rate is higher. The gelling polymer in Example 1 is PEO, which indicates that PEO is preferably used as the gelling polymer in this application.

[0113] From the comparison between Example 1 and Example 5, it can be seen that the injection time of Example 1 is shorter and the electrode liquid retention rate is higher. The skeleton material in Example 1 is PVDF-HFP, which indicates that PVDF-HFP is preferably used as the skeleton material in this application.

[0114] The present application provides a secondary battery, wherein the electrode of the secondary battery includes a current collecting layer, an active material layer, and a modifying layer, wherein the modifying layer includes a skeleton material and a gelled polymer, wherein the gelled polymer is uniformly dispersed in the pores of the skeleton material. The skeleton material of the present application is not only strong and stable, but also has a high porosity and a complete pore structure capable of rapidly absorbing electrolyte. The gelled polymer uniformly dispersed in the skeleton material forms a gel state with the electrolyte, and when in contact with the electrode, there is no surface tension, which facilitates the diffusion of electrolyte from the gelled polymer phase into the electrode, thereby improving the efficiency of electrode infiltration.

[0115] The above is a detailed introduction to a secondary battery and electrical equipment provided by the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method and core idea of ​​the present application. At the same time, for those skilled in the art, based on the ideas of the present application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present application.

Claims

1. A secondary battery, characterized in that: The invention comprises a pole piece, which comprises a current collecting layer, an active material layer arranged on at least one side of the current collecting layer, and a modification layer arranged on the active material layer, wherein the liquid absorption rate of the modification layer is 150% to 350wt%, and the modification layer comprises a skeleton material and a gelled polymer, wherein the gelled polymer is dispersed in the pores of the skeleton material; the skeleton material comprises at least one of polyvinylidene fluoride-hexafluoropropylene or polyethylene glycol dimethacrylate; and the gelled polymer comprises one or more of polyethylene oxide, polyacrylonitrile, polymethyl methacrylate or polyvinyl alcohol.

2. The secondary battery according to claim 1, wherein The porosity of the modified layer is 50% to 85%.

3. The secondary battery according to claim 2, wherein The number average molecular weight of the polyvinylidene fluoride-hexafluoropropylene is 10,000 to 1,000,000.

4. The secondary battery according to claim 1, wherein The thickness of the modified layer is 1 to 10 μm.

5. The secondary battery according to claim 1, wherein The liquid retention rate of the electrode is 70% to 80%.

6. The secondary battery according to any one of claims 1 to 5, characterized in that The pole piece is prepared by: dissolving the skeleton material in a first solvent to obtain a skeleton material solution; dissolving the gelled polymer in a second solvent to obtain a gelled polymer solution; Applying the active material slurry on the surface of the current collecting layer, and drying to obtain the current collecting layer having the active material layer on the surface; coating the skeleton material solution on the active material layer, so that the skeleton material adheres to the active material layer after drying; The gelled polymer solution is coated on the skeleton material to prepare the pole piece with the modified layer.

7. The secondary battery according to claim 6, characterized in that After coating the skeleton material solution on the active material layer, the method further includes soaking the coated material in a third solvent.

8. An electrical device, characterized in that: The secondary battery according to any one of claims 1 to 7 is used as a power supply for the electrical device.

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