A separator and a battery containing the same

Abstract

The present application provides a kind of diaphragm and the battery containing the diaphragm.The present application sets the functional layer containing the polymer of chelate-like structure on the surface of substrate, and part of the side chain of the polymer has chelate-like structure, which can be chelated with transition metal ions, and then adsorbed on the diaphragm, so as to block the migration of transition metal ions to the negative electrode.As the migration of transition metal ions to the negative electrode is blocked, the SEI film on the surface of the negative electrode will not be destroyed by transition metal ions, and the cycle life of the battery can be prolonged.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of batteries, and particularly relates to a separator and a battery containing the same. BACKGROUND

[0002] Lithium ion batteries are widely used in electric vehicles, mobile phones, energy storage power stations and other fields due to their high energy density and wide temperature range. Currently, the positive electrode of mainstream lithium ion batteries mainly uses lithium-containing transition metal oxides, such as lithium cobaltate, lithium manganate and nickel-cobalt-manganese ternary positive electrode materials.

[0003] During the charging and discharging cycle of the battery, part of the transition metal in the positive electrode will be separated from the positive electrode due to corrosion of the electrolyte or lattice change of the positive electrode material or other reasons, and will be dissolved in the electrolyte in the form of ions. The transition metal ions dissolved in the electrolyte will migrate to the negative electrode and be adsorbed by the solid electrolyte layer (i.e. SEI film) on the surface of the negative electrode. Due to the low potential of the negative electrode, the transition metal ions adsorbed on the surface of the negative electrode will be reduced to metal elements, and the metal elements will catalyze the decomposition of alkyl lithium in the SEI film into lithium carbonate and ethylene, continuously exposing the fresh negative electrode surface and forming the SEI film again, while the metal elements are oxidized to metal ions, and the metal ions are reduced to metal elements again. The above process is repeated, resulting in repeated destruction and repair of the SEI film, which seriously consumes the electrolyte and active lithium in the battery, and leads to short cycle life of the battery. SUMMARY

[0004] In order to improve the problem of the migration of the transition metal ions dissolved from the positive electrode material to the negative electrode, the destruction of the SEI film on the surface of the negative electrode, the consumption of the electrolyte and active lithium in the battery, and the short cycle life of the battery in the prior art, the present application provides a separator and a battery containing the same which can improve the above problems. The present application sets a functional layer containing a polymer with a chelate-like structure on the separator, which can capture the transition metal ions dissolved and firmly fix the transition metal ions dissolved in the separator, thereby hindering the migration of the transition metal ions to the negative electrode, reducing the deposition of the transition metal ions on the surface of the negative electrode, preventing the destruction of the SEI film on the surface of the negative electrode by the transition metal ions, and thus significantly improving the cycle life of the battery.

[0005] The purpose of the present application is achieved by the following technical solutions:

[0006] A separator, comprising a functional layer and a substrate, the functional layer is arranged on at least one side surface of the substrate, and the functional layer comprises a polymer, the polymer comprises a repeating unit represented by formula (1) and / or formula (2):

[0007]

[0008] In formula (1), R is selected from Dotted lines represent the chemical bond between the structural unit of the main chain of the polymer and the R group;

[0009] In formula (2), R1, R2 are the same or different, and are independently selected from OH, R, and at least one is selected from R, and the definition of R is as described above.

[0010] * represents the connecting end of the repeating unit.

[0011] According to an embodiment of the present application, in formula (2), R1 is selected from OH, and R2 is selected from R; or, R1 is selected from R, and R2 is selected from OH; or, R1 is selected from R, and R2 is selected from R, and the definition of R is as described above.

[0012] According to an embodiment of the present application, the side chain of the polymer has a chelate-like structure, i.e. includes at least one ligand (R group), which can capture metal ions (for example, two or more ligands can form a chelate ring with the same metal ion), thereby locking the metal ion, hindering its migration to the negative electrode, and further preventing the metal ion from destroying the SEI film on the surface of the negative electrode, thereby prolonging the cycle life of the battery.

[0013] According to an embodiment of the present application, the polymer can further include repeating units represented by formula (3) and / or formula (4):

[0014]

[0015] * represents the connecting end of the repeating unit.

[0016] According to an embodiment of the present application, the introduction of the repeating units represented by formula (3) and / or formula (4) is conducive to the transmission of ions (such as lithium ions), and does not increase the internal resistance of the battery.

[0017] According to an embodiment of the present application, the polymer can further include repeating units represented by formula (5):

[0018]

[0019] * represents the connecting end of the repeating unit.

[0020] According to an embodiment of the present application, the introduction of the repeating units represented by formula (5) is conducive to the transmission of ions (such as lithium ions), and does not increase the internal resistance of the battery.

[0021] According to an embodiment of the present application, the polymer comprises repeating units represented by formula (1) and repeating units represented by formula (3) and / or formula (4), wherein the molar percentage of the repeating units represented by formula (1) is greater than 0 to less than or equal to 50 mol%, for example, 0.1 mol%, 0.2 mol%, 0.5 mol%, 0.8 mol%, 1 mol%, 1.5 mol%, 2 mol%, 2.5 mol%, 3 mol%, 4 mol%, 5 mol%, 6 mol%, 8 mol%, 10 mol%, 12 mol%, 15 mol%, 18 mol%, 20 mol%, 25 mol%, 30 mol%, 35 mol%, 40 mol%, 45 mol%, 50 mol%, or any point value in the range consisting of any two of the above endpoint values. The higher the molar percentage of the repeating units represented by formula (1) in the polymer, the stronger the chelating ability of the polymer to transition metal particles in the electrolyte; the higher the molar percentage of the repeating units represented by formula (3) and / or formula (4) in the polymer, the higher the ionic conductivity of the polymer.

[0022] According to an embodiment of the present application, the polymer comprises repeating units represented by formula (2) and repeating units represented by formula (5), wherein the molar percentage of the repeating units represented by formula (2) is greater than 0 to less than or equal to 50 mol%, for example, 0.1 mol%, 0.2 mol%, 0.5 mol%, 0.8 mol%, 1 mol%, 1.5 mol%, 2 mol%, 2.5 mol%, 3 mol%, 4 mol%, 5 mol%, 6 mol%, 8 mol%, 10 mol%, 12 mol%, 15 mol%, 18 mol%, 20 mol%, 25 mol%, 30 mol%, 35 mol%, 40 mol%, 45 mol%, 50 mol%, or any point value in the range consisting of any two of the above endpoint values. The higher the molar percentage of the repeating units represented by formula (2) in the polymer, the stronger the chelating ability of the polymer to transition metal particles in the electrolyte; the higher the molar percentage of the repeating units represented by formula (5) in the polymer, the higher the ionic conductivity of the polymer.

[0023] According to an embodiment of the present application, the polymer has a structure represented by formula (a) as follows:

[0024]

[0025] In formula (a), x, y represent the molar percentage of the corresponding repeating units in the molecular chain, and y is greater than 0 and less than or equal to 0.5, with x+y=1.

[0026] The main chain of the polymer represented by the above formula (a) has a structure similar to polyvinyl alcohol (PVA), and the side group has a structure similar to ethylenediaminetetraacetic acid (EDTA), so the side chain of the polymer can chelate with transition metal ions (e.g., manganese ions) dissolved from the positive electrode to form a chelate. By disposing the polymer on the surface of the separator, the side group of the polymer chelates with the transition metal ions, which can prevent the transition metal ions from migrating to the negative electrode, thereby preventing the destruction of the SEI film on the surface of the negative electrode and prolonging the cycle life of the battery. At the same time, the main chain has a structure similar to PVA, which can transport ions (e.g., lithium ions) without increasing the internal resistance of the battery. The structure similar to PVA is connected to the structure similar to EDTA by a chemical bond, which prevents the structure similar to EDTA from detaching from the separator and dissolving in the electrolyte. The structure similar to EDTA, which is rich in active hydrogen, dissolves in the electrolyte, which can cause redox reactions at the electrode and generate gas, and at the same time, lose the function of chelating transition metal ions.

[0027] According to an embodiment of the present application, the polymer has a structure as shown below:

[0028]

[0029]

[0030] wherein x and y are defined as above.

[0031] These polymers, like the polymer represented by the above formula (a), have a main chain with ion (e.g., lithium ion) transport function, and a side chain that can chelate with transition metal ions.

[0032] According to an embodiment of the present application, the functional layer further comprises a crosslinked product of the above polymer.

[0033] According to an embodiment of the present application, the functional layer is disposed on one side surface of the substrate, or the functional layer is disposed on both side surfaces of the substrate.

[0034] According to an embodiment of the present application, the functional layer further comprises ceramic particles.

[0035] The ceramic particles are selected from at least one of alumina particles, boehmite particles, silica, titanium dioxide, and zirconium oxide, and the introduction of the ceramic particles can enhance the thermal stability of the separator.

[0036] According to an embodiment of the present application, the mass ratio of the polymer to the ceramic particles in the functional layer is 1:(0-100) and the mass of the ceramic particles is not 0, for example, 1:(1-50), preferably 1:(10-30).

[0037] According to embodiments of the present application, the functional layer further comprises an ion-conductor polymer.

[0038] According to embodiments of the present application, the mass ratio of the polymer to the ion-conductor polymer in the functional layer is 1:(0-100) and the mass of the ion-conductor polymer is not 0, for example 1:(0.1-50), and further for example 1:(1-10).

[0039] According to embodiments of the present application, the ion-conductor polymer is selected from at least one of polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polyimide (PI), polyethylene oxide (PEO), polyacrylonitrile (PAN), polyacrylic acid, polymethacrylic acid. The introduction of the ion-conductor polymer can enhance the ionic conductivity of the separator.

[0040] According to embodiments of the present application, the separator is disposed between a positive electrode and a negative electrode.

[0041] According to embodiments of the present application, the thickness of the functional layer is 0.1 μm-10 μm, for example 0.5 μm-2 μm, for example 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.5 μm, 2.8 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm.

[0042] According to embodiments of the present application, the thickness of the substrate is 3 μm-50 μm, for example 3 μm, 10 μm, 15 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm or 50 μm.

[0043] According to embodiments of the present application, the substrate is a porous substrate, and the porosity of the substrate is ≥ 35%, for example ≥ 40%, and further for example ≥ 50%, for example the porosity of the substrate is 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49% or 50%.

[0044] According to embodiments of the present application, the substrate is selected from a polymer substrate, and the polymer is selected from at least one of polyethylene, polypropylene, polyethylene and polypropylene composite, polyimide, polyamide, polyethylene terephthalate, polybutylene terephthalate, polystyrene, poly-p-phenylene.

[0045] The application also provides a preparation method of the above-mentioned separator, which comprises the following steps:

[0046] (1) dissolving the chelating polymer in a solvent to prepare a functional layer slurry;

[0047] (2) using a coating machine to coat the functional layer slurry on the surface of the substrate, and drying to prepare the separator.

[0048] According to an embodiment of the application, the method further comprises: adding ceramic particles and / or ion conductor polymers into the functional layer slurry and mixing uniformly.

[0049] According to an embodiment of the application, the solvent can be at least one of water, N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide and N,N-dimethylacetamide.

[0050] According to an embodiment of the application, the drying is performed at 30-90°C in a vacuum drying oven for 12-24h.

[0051] According to an embodiment of the application, the solid content in the slurry is 1-80wt%, preferably 10-20wt%.

[0052] The application also provides a battery comprising the above-mentioned separator.

[0053] According to an embodiment of the application, the battery is at least one of a lithium ion battery, a sodium ion battery, a magnesium ion battery and an aluminum ion battery.

[0054] According to an embodiment of the application, the battery further comprises a positive electrode sheet.

[0055] According to an embodiment of the application, the positive electrode active material in the positive electrode sheet is selected from lithium cobaltate and / or a ternary material.

[0056] The ternary material is selected from LiNi a Co b Mn c O2 or LiNi d Co e Al f O2, wherein a+b+c≤1, 0 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.8 Co0.1 Mn 0.1 O2, LiNi 0.6 Co 0. 2Mn 0.2 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiNi 0.88 Co 0.11 Mn 0.11 O2.

[0057] The present application also provides an electronic device comprising the above-mentioned separator, or comprising the above-mentioned battery.

[0058] Advantages of the present application:

[0059] The present application provides a separator and a battery comprising the same. The present application provides a functional layer comprising a polymer with a chelate-like structure on the surface of a substrate, and the polymer has a chelate-like structure in part of the side chains, which can chelate transition metal ions and then adsorb them on the separator, so as to block the migration of transition metal ions to the negative electrode. Since the migration of transition metal ions to the negative electrode is blocked, the SEI film on the surface of the negative electrode will not be destroyed by transition metal ions, thereby prolonging the cycle life of the battery. Compared with directly using a chelating agent, grafting a chelate-like structure on the polymer chain can avoid the dissolution of the chelating agent in the electrolyte and the decomposition of the chelating agent containing active hydrogen on the electrode to produce gas, thereby losing the function of chelating transition metal ions. At the same time, the main chain of the polymer of the present application also has the function of transporting ions, and the coating layer of the separator will not increase the internal resistance of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 Schematic diagram for blocking transition metal ions by the functional layer on the surface of the separator.

[0061] Figure 2 Infrared spectrum of EDTA-g-PVA and PVA of Example 1.

[0062] Figure 3 is Figure 2 the partial enlarged view of the infrared spectrum.

[0063] Figure 4 is Figure 2 the partial enlarged view of the infrared spectrum.

[0064] Figure 5 Scanning electron microscope image of the uncoated separator of Example 1.

[0065] Figure 6 Scanning electron microscope image of the PVA-coated separator of Example 1.

[0066] Figure 7 Scanning electron micrograph of the EDTA-g-PVA coated separator of Example 1. DETAILED DESCRIPTION

[0067] <Chelation>

[0068] A metal atom or ion reacts with a ligand containing two or more coordinating atoms to form a complex with a ring structure, which is called a chelate. The ligand substance that can form a chelate is called a chelating agent. There are two or more coordinating atoms in the ligand, and they simultaneously form a chelate ring with a central atom (or ion). The chelate is more stable than a non-chelate coordination compound with similar composition and structure due to the ring formation of the chelating agent. The "chelate" describes such compounds because the molecular structure is very similar to the "two large pincers" of a "crab" clamping a metal atom or ion. For example, ethylenediaminetetraacetic acid (EDTA) is a commonly used chelating agent, which can form a ring-shaped chelate with transition metal ions. The chelating agent EDTA and Co 2+ The formation of the chelate structure is shown in the following structure:

[0069]

[0070] The application will be described in further detail below with reference to the embodiments. It should be understood that the following embodiments are only illustrative and explanatory of the application, and should not be interpreted as limiting the scope of protection of the application. Any technology achieved based on the above description of the application is included in the scope of protection intended by the application.

[0071] The experimental methods used in the following examples are conventional methods unless otherwise specified. The reagents, materials, etc. used in the following examples can be obtained from commercial sources unless otherwise specified.

[0072] In the description of the application, it should be noted that the terms "first", "second", etc. are only for the purpose of description, and do not indicate or imply relative importance.

[0073] Example 1

[0074] Synthesis of polyvinyl alcohol side chain grafted ethylenediaminetetraacetic acid

[0075] 1. Take 1 gram of polyvinyl alcohol (PVA for short, molecular weight 145,000, Shanghai Aladdin Bio-Chem Technology Co., Ltd. (hereinafter referred to as Aladdin Company)) and 20 milliliters of dimethyl sulfoxide (analytical pure, Aladdin Company) and mix and stir until complete dissolution.

[0076] 2. Take 6.5 grams of triphenylphosphine (Aladdin Company), 7.3 grams of ethylenediaminetetraacetic acid (EDTA for short, Aladdin Company) and add to 100 milliliters of dimethyl sulfoxide, stir at 80°C until complete dissolution, then cool to room temperature.

[0077] 3. Mix the solution of step 1 and step 2, stir until completely mixed.

[0078] 4. Take 4.3 grams of diethyl azodicarboxylate (Aldrich) and add to the mixed solution of step 3, stir at room temperature for 12 hours.

[0079] 5. Add the mixed solution of step 4 to a dialysis membrane (Shanghai Yuan Ye Biotechnology Co., Ltd., molecular weight cut-off 3000), dialyze for 48 hours using fresh dimethyl sulfoxide.

[0080] 6. After dialysis, the solution is heated at 60°C to remove the solvent, obtaining PVA grafted with EDTA on the side chain (referred to as EDTA-g-PVA).

[0081] The structure of the prepared polyvinyl alcohol grafted with ethylenediaminetetraacetic acid (EDTA-g-PVA) is shown in the following schematic diagram:

[0082]

[0083] wherein x, y represent the molar proportion of the corresponding repeating units in the molecular chain, x+y=1, x is 0.87, and y is 0.13.

[0084] Figure 2 The infrared spectra of the synthesized EDTA-g-PVA and PVA are as follows: Figure 3 and Figure 4 is Figure 2 The partial enlarged view of the infrared spectrum. It can be seen from Figures 2 to 4 that EDTA-g-PVA has characteristic peaks at 1720 cm -1 (ester C=O stretching vibration), 1625 cm -1 (carboxylic acid C=O stretching vibration), and 1207 cm -1 (ester C-C(=O)-O stretching vibration), while PVA does not have the above peaks, indicating that EDTA is successfully grafted onto the side chain of PVA.

[0085] To verify the adsorption (chelation) effect of EDTA-g-PVA on transition metal ions, 1 gram of EDTA-g-PVA and PVA were respectively dissolved in 10 milliliters of deionized water, and the solution was poured onto a polytetrafluoroethylene plate and dried at 60°C to obtain an EDTA-g-PVA film and a PVA film.

[0086] EDTA-g-PVA film and PVA film were taken out, and the concentration of cobalt ions in the EDTA-g-PVA film and PVA film was determined by inductively coupled plasma atomic emission spectrometer (ICP).

[0087] Table 1 Change in concentration of cobalt ions in EDTA-g-PVA film and PVA film before and after soaking

[0088] Cobalt ion content in the membrane before soaking (ppm) Cobalt ion content in the membrane after soaking (ppm) EDTA-g-PVA membrane 0 1246.2 PVA membrane 0 154.8

[0089] As can be seen from Table 1, the EDTA-g-PVA film contains a higher concentration of cobalt ions, indicating that the EDTA-g-PVA film has a better adsorption (chelation) effect on cobalt ions.

[0090] Two 10 cm long, 7 cm wide, and 12 μm thick PP substrates were respectively soaked in 10 mL of 0.01 g / L (~10% by weight fraction) EDTA-g-PVA aqueous solution and PVA aqueous solution for 5 minutes, taken out, air-dried, and vacuum dried at 40°C for 24 hours to obtain EDTA-g-PVA coated separators and PVA coated separators.

[0091] Figure 5 、 Figure 6 and Figure 7 are scanning electron microscope images of the uncoated separator, EDTA-g-PVA coated separator, and PVA coated separator, respectively. Figure 5 、 Figure 6 and Figure 7 As can be seen from

[0092] The uncoated separator, EDTA-g-PVA coated separator, and PVA coated separator (diameter 19 mm) were respectively combined with lithium manganate positive electrode sheets (diameter 15 mm, surface capacity 1.2 mAh / cm 2 , Zhuhai Guanyu Battery Co., Ltd. (hereinafter referred to as Zhuhai Guanyu)), and graphite negative electrode sheets (diameter 16 mm, surface capacity 1.26 mAh / cm 2The battery was assembled with CR2025 button cell, the electrolyte was 1M LiPF6EC / DMC / EMC (V / V / V=1 / 1 / 1) (Guangyu, Zhuhai). The battery cycle performance test was completed on the Blue Electric test system, the test current was 0.5C, the voltage range was 4.2~2.75V, and the test was carried out at room temperature.

[0093] Table 2 is the capacity retention rate of the battery assembled with different separators of Example 1 after 200 cycles. As can be seen from Table 2, the battery using EDTA-g-PVA coated separator has higher capacity retention rate, because the EDTA-g-PVA coated separator prevents the migration of transition metal ions to the negative electrode, thereby preventing the destruction of the negative electrode SEI layer, so the capacity retention rate is higher.

[0094] Table 2 is the capacity retention rate of the battery assembled with different separators of Example 1 after 200 cycles

[0095]

[0096] Example 2

[0097] Chitosan grafted ethylenediaminetetraacetic acid.

[0098] Chitosan was purchased from Aladdin Reagent Company, and EDTA was reacted with the hydroxyl group of chitosan to graft it on the side chain of chitosan using the same method as in Example 1, and the structure is shown below, wherein x is 0.75 and y is 0.25.

[0099]

[0100] The same battery system as in Example 1 was used to test the cycle performance of the battery assembled with uncoated separator, chitosan coated separator and EDTA grafted chitosan coated separator.

[0101] Table 3 is the capacity retention rate of the battery assembled with different separators of Example 2 after 200 cycles. As can be seen from Table 3, the battery using EDTA grafted chitosan coated separator has higher capacity retention rate, because the EDTA grafted chitosan coated separator prevents the migration of transition metal ions to the negative electrode, thereby preventing the destruction of the negative electrode SEI layer, so the capacity retention rate is higher.

[0102] Table 3 is the capacity retention rate of the battery assembled with different separators of Example 2 after 200 cycles

[0103]

[0104] Example 3

[0105] Nitrilotriacetic acid grafted polyvinyl alcohol.

[0106] Nitrilotriacetic acid was purchased from Aldrich and was grafted to the side chain of polyvinyl alcohol by reacting with the hydroxyl group of polyvinyl alcohol using the same method as in Example 1. The structure is shown below, where x is 0.9 and y is 0.1.

[0107]

[0108] The same battery system as in Example 1 was used to test the cycle performance of batteries assembled using uncoated separators, polyvinyl alcohol coated separators, and nitrilotriacetic acid grafted polyvinyl alcohol coated separators.

[0109] Table 4 is the capacity retention rate of batteries assembled using different separators of Example 3 after 200 cycles. As can be seen from Table 4, the battery using the nitrilotriacetic acid grafted polyvinyl alcohol coated separator has a higher capacity retention rate. This is because the grafted nitrilotriacetic acid adsorbs transition metal ions, preventing the destruction of the negative electrode by transition metal ions and improving the cycle performance of the battery.

[0110] Table 4 is the capacity retention rate of batteries assembled using different separators of Example 3 after 200 cycles.

[0111]

[0112] Example 4

[0113] Nitrilotriacetic acid grafted chitosan.

[0114] Nitrilotriacetic acid was grafted to the side chain of chitosan using the same method as in Example 1. The structure is shown below, where x is 0.91 and y is 0.09.

[0115]

[0116] The same battery system as in Example 1 was used to test the cycle performance of batteries assembled using uncoated separators, chitosan coated separators, and nitrilotriacetic acid grafted chitosan coated separators.

[0117] Table 5 is the capacity retention rate of batteries assembled using different separators of Example 4 after 200 cycles. As can be seen from Table 5, the battery using the nitrilotriacetic acid grafted chitosan coated separator has a better capacity retention rate. This shows that the adsorption of transition metal ions by the separator is beneficial to improving the cycle performance of the battery.

[0118] Table 5 is the capacity retention rate of batteries assembled using different separators of Example 4 after 200 cycles.

[0119]

[0120] Example 5

[0121] Diethylenetriamine pentaacetic acid grafted polyvinyl alcohol.

[0122] Diethylenetriamine pentaacetic acid was purchased from Aladdin Reagent and grafted on the side chain of polyvinyl alcohol using the same method as in Example 1, and the structure is shown below, where x is 0.87 and y is 0.13.

[0123]

[0124] The same battery system as in Example 1 was used to test the cycle performance of the batteries assembled using the uncoated separator, the polyvinyl alcohol coated separator, and the diethylenetriamine pentaacetic acid grafted polyvinyl alcohol coated separator.

[0125] Table 6 is the capacity retention rate of the batteries assembled using the different separators of Example 5 after 200 cycles. As can be seen from Table 6, the battery using the diethylenetriamine pentaacetic acid grafted polyvinyl alcohol coated separator has a higher capacity retention rate, because the grafted diethylenetriamine pentaacetic acid adsorbs transition metal ions, preventing the destruction of the negative electrode by transition metal ions and improving the cycle performance of the battery.

[0126] Table 6 is the capacity retention rate of the batteries assembled using the different separators of Example 5 after 200 cycles.

[0127]

[0128] Example 6

[0129] Diethylenetriamine pentaacetic acid grafted chitosan.

[0130] Diethylenetriamine pentaacetic acid was grafted on the side chain of chitosan using the same method as in Example 1, and the structure is shown below, where x is 0.86 and y is 0.14.

[0131]

[0132] The same battery system as in Example 1 was used to test the cycle performance of the batteries assembled using the uncoated separator, the chitosan coated separator, and the diethylenetriamine pentaacetic acid grafted chitosan coated separator.

[0133] Table 7 is the capacity retention rate of the batteries assembled using the different separators of Example 6 after 200 cycles. As can be seen from Table 7, the battery using the diethylenetriamine pentaacetic acid grafted chitosan coated separator has a better capacity retention rate. This shows that the adsorption of transition metal ions by the separator is beneficial to improving the cycle performance of the battery.

[0134] Table 7 is the capacity retention rate of the batteries assembled using the different separators of Example 6 after 200 cycles.

[0135]

[0136]

[0137] The above describes the embodiments of the present application. However, the present application is not limited to the above-described embodiments. It can also be used for sodium ion batteries, magnesium ion batteries, aluminum ion batteries, and the like. Any modification, equivalent replacement, improvement, and the like made within the spirit and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A separator comprising a functional layer and a substrate, the functional layer being provided on at least one side surface of the substrate, characterized in that, The functional layer comprises a polymer comprising repeating units represented by formula (1) and / or formula (2): In formula (1), R is selected from The dotted lines represent the chemical bonds by which the structural units of the polymer's main chain are attached to the R groups; In formula (2), R1, R2 are the same or different, and are independently selected from OH, R, and at least one is selected from R, and the definition of R is as described above; * represents the connecting end of the repeating unit.

2. The separator according to claim 1, characterized in that The polymer can further comprise repeating units represented by formula (3) and / or formula (4): * represents the connecting end of the repeating unit.

3. The separator according to claim 1 or 2, characterized in that The polymer can further comprise repeating units represented by formula (5): * represents the connecting end of the repeating unit.

4. The diaphragm of claim 2, wherein The polymer comprises repeating units represented by formula (1) and repeating units represented by formula (3) and / or formula (4), wherein the mole percentage of the repeating units represented by formula (1) is greater than 0 to less than or equal to 50 mol%.

5. The diaphragm of claim 3, wherein The polymer comprises repeating units represented by formula (2) and repeating units represented by formula (5), wherein the mole percentage of the repeating units represented by formula (2) is greater than 0 to less than or equal to 50 mol%.

6. The separator of claim 1, wherein The polymer has a structure represented by formula (a) as follows: In formula (a), x, y represent the mole percentage of the corresponding repeating units in the molecular chain, and y is greater than 0 and less than or equal to 0.5, with x+y=1.

7. The separator according to any one of claims 1 to 6, characterized in that The functional layer further comprises ceramic particles; the mass ratio of the polymer to the ceramic particles in the functional layer is 1:(0-100), and the mass of the ceramic particles is not 0.

8. The separator according to any one of claims 1 to 6, characterized in that The functional layer further comprises an ion conductor polymer; the mass ratio of the polymer to the ion conductor polymer in the functional layer is 1:(0-100), and the mass of the ion conductor polymer is not 0.

9. A battery, characterized by The battery comprises the separator according to any one of claims 1-8.

10. An electronic device, comprising: The electronic device comprises the separator according to any one of claims 1-8, or the battery according to claim 9.

Images