Battery separator and method for manufacturing the same, and battery

Abstract

This application provides a battery separator, its preparation method, and a battery, belonging to the field of battery manufacturing technology. The battery separator comprises porphyrin-based compound-grafted silicon particles, inorganic oxides, and polymers, and has multiple pores with pore sizes ranging from 0.1 nm to 100 nm. By introducing porphyrin-based compound-grafted silicon particles into the battery separator, the separator exhibits high porosity, ensuring battery safety and lithium-ion permeability while efficiently adsorbing transition metal ions, thus improving battery cycle performance.

Description

Technical Field

[0001] This application relates to the field of battery manufacturing technology, and in particular to a battery separator, a method for preparing the same, and a battery. Background Technology

[0002] In lithium-ion batteries, the separator is typically located between the positive and negative electrodes. It prevents direct contact between the positive and negative electrodes while simultaneously conducting lithium ions to ensure normal battery operation. During cycling, transition metal ions from the positive electrode material (such as ions corresponding to Fe, Co, Ni, and Mn) slowly dissolve into the electrolyte, migrate through the separator to the negative electrode, and damage the solid electrolyte interface (SEI) film on the negative electrode surface. This increases the negative electrode interface resistance and reduces the battery's cycle performance.

[0003] Patent application CN201911144312.9, entitled "A membrane slurry for efficiently capturing metal ions, a membrane and its application", discloses a membrane slurry for efficiently capturing metal ions. It adsorbs transition metal ions by adding multidentate complexing agents, macrocyclic complexing agents or polymeric complexing agents to the membrane. However, these complexing agents cannot effectively improve the cycle performance of the battery during long-term use, and may even reduce the cycle stability of the battery. Summary of the Invention

[0004] To address the aforementioned issues, the present application aims to provide a separator slurry and its preparation method, a battery separator, and a battery, which can efficiently adsorb transition metal ions while ensuring safety and lithium-ion permeability, thereby improving the battery's cycle performance.

[0005] In a first aspect, this application provides a battery separator comprising porphyrin-based compound-grafted silicon particles, inorganic oxides, and polymers. The battery separator has multiple pores with pore sizes ranging from 0.1 nm to 100 nm.

[0006] In the above technical solution, porphyrin-based compounds grafted onto silicon particles are introduced into the battery separator. These materials exhibit good durability, excellent wettability with the electrolyte, and high material utilization. They can efficiently adsorb transition metal ions dissolved from the positive electrode, thereby effectively improving the battery's cycle performance. Furthermore, the battery separator formed by porphyrin-based compounds grafted onto silicon particles, inorganic oxides, and polymers possesses good safety and structural stability, along with sufficient pore structure and ideal pore size, minimizing its impact on lithium-ion permeability and further ensuring the battery's cycle stability during long-term cycling.

[0007] In some embodiments of this application, the thickness of the battery separator is 1 nm to 100 μm.

[0008] In the above technical solutions, the thickness range of the battery separator is large and can be adjusted according to actual conditions to ensure the safety and ion permeability of the battery separator, making it suitable for a wider range of battery systems.

[0009] In some embodiments of this application, the inorganic oxide includes at least one of boehmite, alumina, silicon dioxide, titanium dioxide, ferric oxide, or magnetite.

[0010] Polymers include polyvinylidene fluoride (PVDF) and poly(vinylidene fluoride) At least one of the following: hexafluoropropylene, polytetrafluoroethylene, polyhexafluoropropylene, polyacrylate, polymethacrylate, polyacrylamide, polymethacrylamide, epoxy resin, polyvinylpyrrolidone, carboxymethyl cellulose, sodium carboxymethyl cellulose, cellulose, or chitosan.

[0011] In the above technical solutions, inorganic oxides can enhance the mechanical properties and thermal stability of the battery separator, and polymers can improve the processability of the separator slurry. The selection range of inorganic oxides and polymers is wide, which can provide a variety of feasible solutions.

[0012] In some embodiments of this application, the mass ratio of porphyrin-based compounds grafted onto silicon particles, inorganic oxides, and polymers is (1-99):(0-99):(0-99).

[0013] In the above technical solutions, the mass ratio of porphyrin-based compounds grafted onto silicon particles, inorganic oxides, and polymers has a wide range and can be adjusted according to actual application needs.

[0014] In some embodiments of this application, the battery separator includes a functional layer and a polymer base film. The functional layer includes porphyrin-based compounds grafted with silicon particles, inorganic oxides, and polymers. The functional layer is located on at least one side surface of the polymer base film.

[0015] In the above technical solution, adding a polymer base film to the battery separator can improve structural stability and mechanical strength, and reduce production costs.

[0016] In some embodiments of this application, the thickness of the polymer base film is 1 nm to 100 μm.

[0017] Optionally, the polymer base film may be made of at least one of polyethylene terephthalate, polyvinyl chloride, polyethylene, polyacrylonitrile, polypropylene, polyamide, polyetherimide, and polyvinylidene fluoride.

[0018] In the above technical solution, the thickness of the functional layer and the polymer base film, as well as the material of the polymer base film, can be adjusted according to the actual application needs.

[0019] Secondly, embodiments of this application provide a method for preparing the above-mentioned battery separator, comprising the following steps:

[0020] Porphyrin compounds with alkenyl groups were dissolved in a first solvent and mixed with mercapto-functionalized silicon particles. The mixture was then subjected to a grafting reaction under ultraviolet light to prepare porphyrin-grafted silicon particles.

[0021] A slurry is formed by dispersing porphyrin-based compounds grafted onto silicon particles, inorganic oxides, and polymers in a second solvent, and then curing the slurry to obtain a battery separator.

[0022] In the above technical solution, porphyrin compounds with alkenyl groups and thiol-functionalized silicon particles are selected as raw materials. The alkenyl and thiol groups can react directly under ultraviolet light to complete the grafting. The preparation method is simple, with a high grafting rate and few by-products. The porphyrin-grafted silicon particles prepared are not easily chemically reacted in the battery system, and the chemical bonds are not easily broken, exhibiting excellent stability. The battery separator can be prepared by mixing and dispersing porphyrin-grafted silicon particles, inorganic oxides, and polymers, and then using conventional spinning or coating curing methods. The preparation method is simple.

[0023] In some embodiments of this application, the thiol-functionalized silicon particles are 3-mercaptopropyl-grafted silicon particles, and the alkenyl porphyrin compounds include at least one of protoporphyrin, protoporphyrin monomethyl ester, protoporphyrin dimethyl ester, protoporphyrin monosodium salt, protoporphyrin disodium salt, protoporphyrin monolithium salt, or protoporphyrin dilithium salt.

[0024] In the above technical solutions, specific thiol-functionalized silicon particles and porphyrin compounds are selected, and the raw materials are simple and readily available, which can improve reaction efficiency and reduce production costs.

[0025] In some embodiments of this application, the grafting reaction temperature is 40–80°C and the time is 6–24 hours.

[0026] In the above technical solution, by controlling the conditions of the grafting reaction, the grafting stability and grafting rate can be enhanced, and the purity of the product can be guaranteed.

[0027] In some embodiments of this application, the method for forming a battery separator after curing the slurry includes:

[0028] The separator slurry is spun to form a battery separator; or the separator slurry is spun or coated on at least one side of a polymer base membrane to form a battery separator.

[0029] In the above technical solutions, the separator slurry can be directly spun into a nonwoven membrane, or it can be formed on a polymer base membrane by spinning or coating. The preparation method is simple and the thickness and pore size are controllable, which makes the battery separator widely used in various battery systems.

[0030] Thirdly, embodiments of this application provide a battery including a positive electrode, a negative electrode, an electrolyte, and the aforementioned battery separator, wherein the battery separator is located between the positive electrode and the negative electrode, and the electrolyte wets the positive electrode, the negative electrode, and the battery separator. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a cross-sectional schematic diagram of the battery separator provided in an embodiment of this application;

[0033] Figure 2 A cross-sectional schematic diagram of another battery separator provided in an embodiment of this application;

[0034] Figure 3 This is a cross-sectional schematic diagram of another battery separator provided in an embodiment of this application.

[0035] Explanation of reference numerals in the attached figures:

[0036] 100 - Battery separator; 10 - Functional layer; 20 - Polymer base film. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0038] During the charging and discharging process of lithium-ion batteries, the continuous intercalation and deintercalation of lithium ions leads to structural distortion. Transition metal ions in the positive electrode active material slowly dissolve into the electrolyte and deposit on the negative electrode surface, causing damage to the SEI film and a decline in battery cycle performance. While research has explored adding metal complexing agents such as porphyrin, porphyrin, and their derivatives to the separator to address this issue, the applicant's research has found that these complexing agents do not effectively improve battery cycle performance in long-cycle systems and may even reduce cycle stability.

[0039] Based on this, the researchers of this application have creatively discovered that porphyrin-based compound-grafted silicon particles obtained by grafting functionalized silicon particles with porphyrin-based compounds, when added to the battery separator, not only have good safety and structural stability in long-cycle systems, but can also efficiently adsorb transition metal ions (such as Fe, Co, Ni and Mn ions) released by the cathode material during charge and discharge cycles, thereby effectively improving the cycle performance of the battery.

[0040] The following is a detailed description of a battery separator, its preparation method, and the battery according to an embodiment of this application.

[0041] First, this application provides a battery separator and its preparation method. The battery separator comprises porphyrin-based compound-grafted silicon particles, inorganic oxides, and polymers. The preparation method may include the following steps:

[0042] S1: Porphyrin compounds with alkenyl groups are dissolved in a first solvent and mixed with mercapto-functionalized silicon particles. Grafting reaction is carried out under ultraviolet light to prepare porphyrin-grafted silicon particles.

[0043] It should be noted that porphyrin-based compounds grafted onto silicon particles can be easily understood as substances obtained by grafting porphyrin compounds onto silicon particles. These porphyrin-based compounds can be porphyrins, protoporphyrins, or porphyrin derivatives.

[0044] The general structural formula of porphyrin-based compounds grafted onto silicon particles is shown in formula (Ⅰ):

[0045]

[0046] Among them, R3, R5, R7, R8, R 10 R 12 R 13 R 15 R 17 R 18 R 20 Each is independently phenyl, vinyl, allyl, C n H 2n+1 C n H 2n OH, C n H 2n CHO, C n H 2n COOH, C n H 2n COONa, C n H 2n COOLi、C n H 2n COOC n H 2nC n H 2n SH, where n is an integer between 0 and 20; i and j are each an integer between 0 and 10 independently.

[0047] As an example, the thiol-functionalized silicon particles may be 3-mercaptopropyl-grafted silicon particles, and the alkenyl porphyrin compounds may include at least one of protoporphyrin, protoporphyrin monomethyl ester, protoporphyrin dimethyl ester, protoporphyrin monosodium salt, protoporphyrin disodium salt, protoporphyrin monolithium salt, or protoporphyrin dilithium salt.

[0048] The grafting reaction is carried out at a temperature of 40–80°C for 6–24 hours, and the first solvent can be methanol.

[0049] The grafting reaction may also include: filtration and washing with methanol, followed by vacuum drying at 60–100°C.

[0050] As an example, when the porphyrin compound is protoporphyrin IX and the mercaptofunctionalized silicon particles are 3-mercaptopropylfunctionalized silica, the preparation method of the porphyrin compound grafted silicon particles can be represented by the following structural formula:

[0051]

[0052] S2: Porphyrin-based compounds grafted with silicon particles, inorganic oxides and polymers are dispersed in a second solvent and mixed to form a separator slurry. The separator slurry is then solidified to form a battery separator.

[0053] The mass ratio of porphyrin-grafted silicon particles, inorganic oxides, and polymers can be (1–99):(0–99):(0–99). As an example, the mass ratio of porphyrin-grafted silicon particles, inorganic oxides, and polymers is 10:10:80.

[0054] Inorganic oxides include at least one of boehmite, alumina, silicon dioxide, titanium dioxide, ferric oxide, or iron oxide.

[0055] Polymers include polyvinylidene fluoride (PVDF) and poly(vinylidene fluoride) The polymer contains at least one of the following: hexafluoropropylene, polytetrafluoroethylene, polyhexafluoropropylene, polyacrylate, polymethacrylate, polyacrylamide, polymethacrylamide, epoxy resin, polyvinylpyrrolidone, carboxymethyl cellulose, sodium carboxymethyl cellulose, cellulose, or chitosan. The weight-average molecular weight of the polymer is from 0.1 to 3 million, for example, but not limited to, any one of 0.1 million, 0.5 million, 1 million, 10 million, 1 million, 1 million, and 3 million, or a range between any two.

[0056] The second solvent may be at least one of water, acetone, N-methylpyrrolidone (NMP) or N,N-dimethylformamide (DMF).

[0057] As an example, a method for curing a separator slurry to form a battery separator may include the steps of: directly spinning the separator slurry into a film and drying it to obtain the battery separator. The structure of the corresponding battery separator 100 can be found in [reference needed]. Figure 1 .

[0058] Specifically, the spinning process can be electrospinning, and the drying temperature can be 100°C for 2 hours. In some embodiments, after drying, the process may further include hot pressing to a predetermined thickness.

[0059] As an example, a method for curing a separator slurry to form a battery separator may include the steps of:

[0060] The separator slurry is spun or coated onto at least one surface of a polymer-based membrane to form a functional layer, thereby obtaining a battery separator. The corresponding battery separator structure can be found in [reference needed]. Figure 2 and Figure 3 The battery separator 100 includes a polymer base film 20 and a functional layer 10 disposed on at least one side surface of the polymer base film 20.

[0061] The thickness of the polymer base film is 1 nm to 100 μm. The material of the polymer base film may include at least one of polyethylene terephthalate, polyvinyl chloride, polyethylene, polyacrylonitrile, polypropylene, polyamide, polyetherimide, and polyvinylidene fluoride.

[0062] The specific coating methods can include roller coating, spray coating, electro-spraying, ultrasonic spraying, etc. The specific spinning methods can include melt spinning or electrospinning, etc.

[0063] It should be noted that since spinning and coating are common and well-known preparation methods in the field, they can be set according to the conventional methods in the field during specific implementation, and will not be elaborated here.

[0064] In addition, this application also provides a battery separator prepared by the above preparation method. The thickness of the battery separator can be 1 nm to 100 μm, and the battery separator has multiple pores with a porosity of 30% to 80% and a pore size of 0.1 nm to 100 nm.

[0065] In addition, this application embodiment also provides a battery, including a positive electrode, a negative electrode, an electrolyte and the battery separator, wherein the battery separator is located between the positive electrode and the negative electrode, and the electrolyte wets the positive electrode, the negative electrode and the battery separator.

[0066] It should be noted that the battery in this application can be a lithium-ion battery, a lithium-sulfur battery, a sodium-ion battery, etc., and is not limited thereto.

[0067] The features and performance of this application will be further described in detail below with reference to specific embodiments.

[0068] Example 1

[0069] This application provides a battery C1, the preparation method of which includes the following steps:

[0070] (1) Preparation of porphyrin-based compounds grafted onto silicon particles

[0071] 100 g of silicon particles (100 nm in diameter) were slowly added to 1 L of Piranha solution under magnetic stirring. The mixture was then stirred at 90 °C for 1 h. After stirring, the mixture was filtered, washed with plenty of pure water, and dried under vacuum at 60 °C. The activated silicon particles were then taken and 600 mL of a 60 mmol / L toluene solution of 3-mercaptopropyltrimethoxysilane was added. The mixture was stirred for 12 h. Finally, the silicon particles were filtered, washed with acetone and pure water, and dried under vacuum at 120 °C to obtain 3-mercaptopropyl-grafted silicon particles. The mercapto loading was 0.3 mmol / g.

[0072] 134.9 g of protoporphyrin IX (Aladdin, CAS: 553-12-8) was dissolved in 1214.1 g of anhydrous methanol, and then 100 g of 3-mercaptopropyl-grafted silicon particles were added. The mixture was stirred and dispersed at 60 °C and irradiated with ultraviolet light for 12 h. After filtration and washing with 12000 g of anhydrous methanol, the mixture was dried under vacuum at 80 °C to obtain protoporphyrin IX-grafted silicon particles (Pr-Si).

[0073] (2) Preparation of battery separator

[0074] 80g of polyacrylonitrile (PAN, weight average molecular weight 100,000) was dissolved in 900g of NMP, then 10g of alumina and 10g of protoporphyrin IX-grafted silica particles were added and dispersed at high speed for 5h to obtain a separator slurry. The obtained separator slurry was electrospun into a membrane, then dried at 100℃ for 2h, and then hot-pressed at 150℃ for 12h to obtain battery separator S1 with a thickness of 14μm. The porosity of battery separator S1 is 50% and the average pore size is 80nm.

[0075] (3) Preparation of positive electrode

[0076] Take 96g of lithium nickel manganese oxide (LNMO, chemical formula LiNi). 0.5 Mn 1.5 O4), 1.8g polyvinylidene fluoride, and 2.2g conductive carbon were dispersed at high speed for 8 hours and then coated on both sides of an aluminum foil with a thickness of 12μm. The mixture was then dried at 100℃ and cut into positive electrode sheets for later use.

[0077] (4) Preparation of negative electrode

[0078] Take 95.6g of artificial graphite, 1.5g of carboxymethyl cellulose, 1.1g of conductive carbon, and 4.5g of styrene-butadiene rubber latex (solid content 40wt%), disperse them at high speed for 8h, and then coat them on both sides of a copper foil with a thickness of 8μm. Then dry them at 100℃ and cut them into negative electrode sheets for later use.

[0079] (5) Battery manufacturing

[0080] The above-mentioned positive electrode sheet, negative electrode sheet and battery separator are used to make a small soft-pack battery through a stacking process. Then, the battery is obtained by normal liquid injection, formation and capacity testing.

[0081] Example 2

[0082] This application provides a battery C2, which differs from embodiment 1 only in that:

[0083] Step (2) of the battery separator also includes a polymer base membrane. The specific steps include: taking 80g of polyacrylonitrile (PAN, weight-average molecular weight 100,000), dissolving it in 900g of NMP, then adding 10g of alumina and 10g of protoporphyrin IX-grafted silicon particles, and dispersing at high speed for 5h to obtain a separator slurry. The obtained separator slurry is then electrospinned and deposited onto one side of a 12μm thick polyethylene separator, dried at 100℃ for 0.5h, and then hot-pressed at 110℃ for 12h to finally obtain a 13μm thick battery separator S2. The porosity of battery separator S2 is 40%, and the average pore size is 50nm.

[0084] Example 3

[0085] This application provides a battery C3, which differs from embodiment 2 only in that:

[0086] In step (2), the separator slurry is deposited on the two opposite surfaces of the polyethylene separator. The porosity of the battery separator S3 is 41%, and the average pore size is 52 nm.

[0087] Example 4

[0088] This application provides a battery C4, which differs from embodiment 2 only in that:

[0089] In step (2), the separator slurry is coated onto one side of the polyethylene separator using a coating process. The battery separator S4 has a porosity of 40% and an average pore size of 40 nm.

[0090] Example 5

[0091] This application provides a battery C5, which differs from embodiment 4 only in that:

[0092] In step (2), the separator slurry is coated onto the two opposite surfaces of the polyethylene separator using a coating process. The battery separator S5 has a porosity of 41% and an average pore size of 42 nm.

[0093] Example 6

[0094] This application provides a battery C6, which differs from Embodiment 1 only in that:

[0095] In step (3), the positive electrode active material is lithium nickel cobalt manganese oxide (NCM811, chemical formula LiNi). 0.8 Co 0.1 Mn 0.1 O2).

[0096] Example 7

[0097] This application provides a battery C7, which differs from embodiment 2 only in that:

[0098] In step (3), the positive electrode active material is lithium nickel cobalt manganese oxide (NCM811, chemical formula LiNi). 0.8 Co 0.1 Mn 0.1 O2).

[0099] Example 8

[0100] This application provides a battery C8, which differs from embodiment 3 only in that:

[0101] In step (3), the positive electrode active material is lithium nickel cobalt manganese oxide (NCM811, chemical formula LiNi). 0.8 Co 0.1 Mn 0.1 O2).

[0102] Example 9

[0103] This application provides a battery C9, which differs from embodiment 4 only in that:

[0104] In step (3), the positive electrode active material is lithium nickel cobalt manganese oxide (NCM811, chemical formula LiNi). 0.8 Co 0.1 Mn 0.1 O2).

[0105] Example 10

[0106] This application provides a battery C10, which differs from embodiment 5 only in that:

[0107] In step (3), the positive electrode active material is lithium nickel cobalt manganese oxide (NCM811, chemical formula LiNi). 0.8 Co 0.1Mn 0.1 O2).

[0108] Example 11

[0109] This application provides a battery C11, which differs from Embodiment 1 only in that:

[0110] In step (3), the positive electrode active material is lithium iron phosphate (LFP, chemical formula LiFePO4).

[0111] Example 12

[0112] This application provides a battery C12, which differs from Embodiment 2 only in that:

[0113] In step (3), the positive electrode active material is lithium iron phosphate (LFP, chemical formula LiFePO4).

[0114] Example 13

[0115] This application provides a battery C13, which differs from embodiment 3 only in that:

[0116] In step (3), the positive electrode active material is lithium iron phosphate (LFP, chemical formula LiFePO4).

[0117] Example 14

[0118] This application provides a battery C14, which differs from embodiment 4 only in that:

[0119] In step (3), the positive electrode active material is lithium iron phosphate (LFP, chemical formula LiFePO4).

[0120] Example 15

[0121] This application provides a battery C15, which differs from embodiment 5 only in that:

[0122] In step (3), the positive electrode active material is lithium iron phosphate (LFP, chemical formula LiFePO4).

[0123] Comparative Example 1

[0124] This application provides a battery R1 as a comparative example, which differs from that of Example 1 in that:

[0125] Excluding steps (1) and (2), the battery separator in step (5) is a conventional polyethylene separator with a thickness of 12 μm.

[0126] Comparative Example 2

[0127] This application provides a battery R2 as a comparative example, which differs from that of Example 6 in that:

[0128] Excluding steps (1) and (2), the battery separator in step (5) is a conventional polyethylene separator with a thickness of 12 μm.

[0129] Comparative Example 3

[0130] This application provides a battery R3 as a comparative example, which differs from that of Example 11 in that:

[0131] Excluding steps (1) and (2), the battery separator in step (5) is a conventional polyethylene separator with a thickness of 12 μm.

[0132] Comparative Example 4

[0133] This application provides a battery R4 as a comparative example, which differs from that of Example 1 in that:

[0134] In step (2), protoporphyrin IX grafted silicon particles were replaced with protoporphyrin IX to prepare battery separator RS-1 with a porosity of 50% and an average pore size of 70 nm.

[0135] For ease of viewing, some important preparation conditions of the batteries in Examples 1-15 and Comparative Examples 1-4 are listed in Table 1 below.

[0136] Table 1. Partial preparation conditions of the batteries in Examples 1-15 and Comparative Examples 1-4.

[0137]

[0138]

[0139] Test case

[0140] The membranes prepared in the above examples and comparative examples were subjected to performance testing. Simultaneously, the prepared batteries were cycled 1000 times at room temperature and 1C to test their cycle performance, and the content of transition metal ions in the electrolyte after 1000 cycles was measured. The specific testing methods are as follows:

[0141] 1. Battery separator performance test

[0142] The porosity and puncture strength of the battery separator were tested according to GB / T 36363-2018, and the thermal shrinkage of the battery separator was tested according to GB / T12027-2004. The results were compared with those of conventional polyethylene separators. The test results are shown in Table 2.

[0143] 2. Battery cycle performance test

[0144] The batteries from Examples 1-15 and the batteries prepared in Comparative Examples 1-4 were tested according to the following steps:

[0145] (1) Let it sit for 1 minute;

[0146] (2) Discharge from the open circuit voltage with a constant current of 1C to the lower limit voltage;

[0147] (3) Let it rest for 1 minute;

[0148] (4) Charge at a constant current of 1C to the upper limit voltage, and then maintain the voltage at 0.05C;

[0149] (5) Let it sit for 1 minute;

[0150] (6) Discharge at a constant current of 1C to the lower limit voltage;

[0151] (7) Let it rest for 1 minute;

[0152] (8) Repeat steps (4) to (7) for 1000 cycles.

[0153] The upper voltage limit for Examples 1-5 and Comparative Examples 1 and 4 was 4.8V, and the lower voltage limit was 3.5V; the upper voltage limit for Examples 6-10 and Comparative Example 2 was 4.3V, and the lower voltage limit was 2.8V; the upper voltage limit for Examples 11-15 and Comparative Example 3 was 3.85V, and the lower voltage limit was 2.5V. The test results are shown in Table 3.

[0154] 3. Test for the content of transition metal ions

[0155] The aluminum-cased battery that had undergone 1000 cycles at room temperature (1C) was disassembled, and 0.5g of free electrolyte was extracted and diluted to 10g with dimethyl carbonate. The diluted sample was then analyzed using the ICP external standard method to determine the contents of Fe, Co, Ni, and Mn. The measurement results are shown in Table 4.

[0156] Table 2 shows the battery separator performance test results of Examples 1-5 and Comparative Example 4.

[0157]

[0158] As can be seen from Table 2, the battery separator prepared in the embodiments of this application has comparable porosity and puncture strength to conventional polyethylene separators, but significantly reduced thermal shrinkage, indicating better safety and reliability.

[0159] Table 3 shows the cycle performance test results of Examples 1-15 and Comparative Examples 1-4.

[0160]

[0161]

[0162] Table 4. Transition metal ion content in Examples 1-15 and Comparative Examples 1-4

[0163]

[0164]

[0165] As shown in Tables 3 and 4, the batteries prepared in Examples 1 to 15 exhibited low levels of transition metal ions in the electrolyte after 1000 cycles at 1C at room temperature. Correspondingly, the batteries prepared in Examples 1 to 15 maintained a capacity retention of no less than 85% after 1000 cycles at 1C at room temperature, with the capacity retention in Example 11 reaching as high as 97%.

[0166] Comparing the performance test results of Example 1 and Comparative Example 1, it can be seen that the capacity retention rate of battery C1 is 92%, while in battery R1 of Comparative Example 1, the content of nickel and manganese ions in the electrolyte is significantly increased, and the capacity retention rate is significantly reduced to 65%. Comparing the performance test results of Example 6 and Comparative Example 2, it can be seen that the capacity retention rate of battery C6 is 95%, while in battery R2 of Comparative Example 2, the content of nickel, cobalt, and manganese ions is significantly increased, and the corresponding capacity retention rate is reduced to 88%. Comparing the performance test results of Example 11 and Comparative Example 3, it can be seen that the capacity retention rate of battery C11 is 97%, while in battery R3 of Comparative Example 3, the content of iron ions is increased, and the corresponding capacity retention rate is reduced to 93%. This indicates that the porphyrin-based compound-grafted silicon particles in the battery separator can effectively adsorb transition metal ions dissolved from the cathode material during cycling, enhance the cycle stability of the battery, and especially effectively improve the cycle performance of lithium nickel manganese oxide batteries.

[0167] Comparing the performance test results of Example 1 and Comparative Example 4, it can be seen that although pure porphyrin can also adsorb a certain amount of transition metal ions, its cycling performance is significantly worse than that of Example 1 during long-term cycling. This may be due to the poor stability of pure porphyrin and its slow electrochemical oxidation, which reduces the lithium ion permeability of the battery separator and increases the internal resistance of the battery.

[0168] Examples 1-5 and Comparative Examples 1 and 4 above are batteries based on the lithium nickel manganese oxide system; Examples 6-10 and Comparative Example 2 above are batteries based on the lithium nickel cobalt manganese oxide system; Examples 11-15 and Comparative Example 3 above are batteries based on the lithium iron phosphate system. As can be seen from Tables 2 and 3, for batteries with different positive electrode active material systems, the technical solution provided in this application can efficiently adsorb transition metal ions dissolved from the positive electrode active material during cycling by setting a battery separator including porphyrin-based compounds grafted with silicon particles, and effectively improve cycle performance during long cycles, especially effectively improving the cycle stability of the lithium nickel manganese oxide battery system.

[0169] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A battery separator, characterized by, The battery separator comprises inorganic oxides, polymers, and porphyrin compounds grafted onto silicon particles, and has multiple pores with a pore size of 0.1 nm to 100 nm.

2. The battery separator of claim 1, wherein, The thickness of the battery separator is 1 nm to 100 μm.

3. The battery separator of claim 1, wherein The inorganic oxide includes at least one of boehmite, alumina, silicon dioxide, titanium dioxide, ferric oxide, or iron oxide. The polymer includes at least one of polyvinylidene fluoride, poly(vinylidene fluoride hexafluoropropylene), polytetrafluoroethylene, polyhexafluoropropylene, polyacrylate, polymethacrylate, polyacrylamide, polymethacrylamide, epoxy resin, polyvinylpyrrolidone, carboxymethyl cellulose, sodium carboxymethyl cellulose, cellulose, or chitosan.

4. The battery separator according to claim 1, characterized in that, The mass ratio of the porphyrin-based compound-grafted silicon particles, the inorganic oxide, and the polymer is (1~99):(0~99):(0~99).

5. The battery separator according to claim 1, characterized in that, The battery separator includes a functional layer and a polymer base film. The functional layer includes the porphyrin-based compound-grafted silicon particles, the inorganic oxide, and the polymer. The functional layer is located on at least one side surface of the polymer base film.

6. The battery separator according to claim 5, characterized in that, The thickness of the polymer base film is 1 nm to 100 μm.

7. The battery separator according to claim 6, characterized in that, The polymer base film is made of at least one of polyethylene terephthalate, polyvinyl chloride, polyethylene, polyacrylonitrile, polypropylene, polyamide, polyetherimide, and polyvinylidene fluoride.

8. A method for preparing a battery separator as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Porphyrin compounds with alkenyl groups were dissolved in a first solvent and mixed with mercapto-functionalized silicon particles. The mixture was then subjected to a grafting reaction under ultraviolet light to prepare porphyrin-grafted silicon particles. The porphyrin-based compound grafted with silicon particles, inorganic oxides, and polymers are dispersed in a second solvent and mixed to form a separator slurry. The separator slurry is then cured to form a battery separator.

9. The preparation method according to claim 8, characterized in that, The mercaptofunctionalized silicon particles are 3-mercaptopropyl grafted silicon particles. The alkenyl porphyrin compounds include at least one of protoporphyrin, protoporphyrin monomethyl ester, protoporphyrin dimethyl ester, protoporphyrin monosodium salt, protoporphyrin disodium salt, protoporphyrin monolithium salt, or protoporphyrin dilithium salt.

10. The preparation method according to claim 9, characterized in that, The grafting reaction is carried out at a temperature of 40-80°C for 6-24 hours.

11. The preparation method according to claim 8, characterized in that, The method for forming a battery separator by curing the slurry includes: The diaphragm slurry is spun to form the battery diaphragm; Alternatively, the separator slurry can be spun or coated onto at least one side of the polymer base membrane to form a functional layer, thereby obtaining the battery separator.

12. A battery, characterized in that, The battery includes a positive electrode, a negative electrode, an electrolyte, and a battery separator as described in any one of claims 1 to 7, wherein the battery separator is located between the positive electrode and the negative electrode, and the electrolyte wets the positive electrode, the negative electrode, and the battery separator.

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