High-safety rechargeable magnesium battery diaphragm capable of inhibiting magnesium dendrites as well as preparation method and application of high-safety rechargeable magnesium battery diaphragm

Abstract

The invention relates to the technical field of rechargeable magnesium batteries, and particularly provides a high-safety rechargeable magnesium battery diaphragm for inhibiting magnesium dendrites as well as a preparation method and application of the high-safety rechargeable magnesium battery diaphragm. A high-safety rechargeable magnesium battery diaphragm capable of inhibiting magnesium dendrites is prepared from a first component and a second component through electrostatic spinning, the first component is one or more of nylon-based derivatives, and the second component is one or more of nylon-based derivatives. And the second component is one or more of polysaccharide or polyester derivatives containing polar group carboxyl, sulfonic group, hydroxyl, ether oxygen group or ester group. Through an electrostatic spinning technology, the nanofiber composite battery diaphragm with a spider network structure is obtained, and the nanofiber composite battery diaphragm has excellent electrolyte wettability, tensile strength and thermal stability. According to the invention, cellulose or polyester derivatives rich in polar functional groups are introduced on the basis of nylon derivatives with good chemical stability, and the solvation structure of the electrolyte is regulated and controlled through the dipole-dipole interaction of diaphragm polymer molecules and the electrolyte solvent, so that the desolvation of magnesium ions is accelerated; and thus, the magnesium ion deposition behavior is improved to inhibit the growth of magnesium dendrites, and the cycling stability and safety of the battery are greatly improved.

Description

Technical Field

[0001] This invention relates to the field of rechargeable magnesium battery technology, and in particular to a high-safety rechargeable magnesium battery separator that suppresses magnesium dendrites, its preparation method, and its application. Background Technology

[0002] Magnesium metal anodes are advantageous due to their low reduction potential (-2.37 V vs. SHE) and high theoretical volumetric capacity (3833 mAh / cm³). -3 Magnesium oxide (MgO) is considered an ideal negative electrode for developing next-generation rechargeable batteries due to its abundant resources. Unfortunately, the spontaneous and irreversible reaction between the liquid electrolyte and the metal forms an unstable solid electrolyte interfacial film, which is destroyed during repeated magnesium ion deposition / stripping processes, continuously consuming the electrolyte. Simultaneously, the damaged solid electrolyte interfacial film leads to differences in interfacial charge distribution, inducing uneven metal ion deposition. Even at current densities far below the critical current density, anomalous deposition behavior gradually forms dendrites in the uneven regions. Affected by the "point effect," magnesium dendrites grow uncontrollably, eventually penetrating the polymer separator and short-circuiting the battery.

[0003] As a crucial component of batteries, the separator serves as a physical barrier preventing direct contact between the positive and negative electrodes, while also significantly influencing the chemical behavior of magnesium ions at the negative electrode interface. Currently, commercially available polypropylene and polyethylene separators are easy to manufacture and possess strong mechanical properties; however, their poor thermal stability makes them prone to dimensional shrinkage, potentially causing short circuits. Glass fiber separators exhibit excellent thermal stability, but their large pore size and brittleness make them susceptible to dendrite penetration, and their thickness of several hundred micrometers cannot meet the requirements of flexible devices and microelectronic devices, hindering their use as commercially viable separators.

[0004] Therefore, it is extremely important to develop a rechargeable magnesium battery separator that has high safety, appropriate thickness, and can prevent dendrite growth.

[0005] Patent CN117096547A discloses a composite modified cellulose nylon membrane. The preparation method is as follows: cellulose, nylon, polyvinylpyrrolidone-K30, and polyacrylonitrile are dissolved and blended using an ionic liquid to obtain a blend casting solution; the blend casting solution is used to prepare a film through an extruder; after washing off excess solvent from the film with deionized water, it is dried to obtain a cellulose nylon membrane; the cellulose nylon membrane is immersed in lithium bis(trifluoromethanesulfonyl)imide at a certain mass concentration to obtain a modified cellulose nylon membrane; a pre-prepared polyamide slurry is coated onto the modified cellulose nylon membrane, and after drying, a composite modified cellulose nylon membrane is obtained. The cellulose comprises one or more of the following: polymeric cellulose, lignin fiber, cellulose ether, methylcellulose, hydroxypropyl methylcellulose, hydroxyethyl cellulose, and carboxymethyl cellulose. Cellulose and nylon are cross-linked to form a three-dimensional network film. The addition of nylon compensates for the low mechanical strength of cellulose, thereby improving the tensile strength of the membrane. The polyimide coating has microporous characteristics, which not only enhances the mechanical strength and high-temperature resistance of the membrane but also, to some extent, avoids the reduction in ionic conductivity due to the polyimide coating. However, the extrusion process and the presence of the coating in this patent result in relatively few pores on the membrane surface and internally, leading to lower liquid absorption and ionic conductivity (liquid absorption 166.3-201%, ionic conductivity 1.40-1.75 mS / cm). -1 ).

[0006] Patent CN113506951A discloses a composite separator, which is prepared by compounding a polymer matrix material or a homopolymer, copolymer, or blend of the polymer material and an inorganic filler through various preparation methods to obtain a polymer electrolyte separator. After the separator absorbs a certain amount of electrolyte, a gel polymer electrolyte or a solid polymer electrolyte is obtained and applied to metal secondary batteries. Another method involves blending or copolymerizing one or more polymer materials, including natural cellulose, cellulose-modified materials, or cellulose derivatives, as well as one or more polyacrylonitrile, polyester, polyether, fluorinated polyolefin, polycarbonate, polyamine, natural polysaccharides, and their derivatives, with natural cellulose, cellulose-modified materials, or cellulose derivatives. The polymer materials are dissolved in a solvent and then prepared by electrospinning or other methods to obtain a separator. After drying, the separator is further soaked in electrolyte to obtain the modified composite membrane, which can be used in secondary batteries such as magnesium batteries. However, the separator prepared by this method has low liquid absorption performance (liquid absorption rate of only 97.1%) and low room temperature ionic conductivity (1.80 mS / cm). -1 It exhibits weak tensile strength (1.6 MPa), low thermal stability (180℃), and poor suppression of lithium dendrites (current density 1 mA cm⁻¹). -2 It can only be cycled for 350 hours. Summary of the Invention

[0007] To address the technical problems of existing separators, this invention proposes a high-safety rechargeable magnesium battery separator that suppresses magnesium dendrite growth, along with its preparation method and applications. When applied to rechargeable magnesium batteries, this separator effectively solves the problem of magnesium dendrite growth on the magnesium electrode during charging and discharging, preventing separator puncture and reducing internal short circuits and failures. It also improves the battery's coulombic efficiency, cycle stability, and rate performance. Furthermore, the battery separator prepared by this invention exhibits excellent electrolyte wettability (0° contact angle with various electrolytes), mechanical strength (16 MPa), and thermal stability (maintaining dimensional stability even after 30 minutes at 210 °C).

[0008] To achieve the above objectives, the technical solution of the present invention is implemented as follows: A high-safety rechargeable magnesium battery separator that suppresses magnesium dendrites, the separator being made of a first component and a second component, wherein the first component is one or more nylon-based derivatives, and the second component is one or more polysaccharide or polyester derivatives, wherein the polysaccharide or polyester derivative is a polysaccharide or polyester derivative containing polar groups such as carboxyl (-COOH), sulfonic acid (-SO3H), hydroxyl (-OH), etheroxy (COC), or ester (-COOR).

[0009] The nylon-based derivative polymer is any one of nylon 6, nylon 6 / 6, nylon 6 / 10, nylon 6 / 12, nylon 11, nylon 12, nylon 10 / 10, nylon 12 / 12, nylon 4 / 6, nylon 5 / 6, nylon 6T, nylon 9T, nylon 10T, and nylon MXD6.

[0010] The polysaccharide containing carboxyl, sulfonic acid, hydroxyl, etheroxy, and ester groups is one or more of cellulose acetate, chitosan, hyaluronic acid, cellulose acetate butyrate, and cyanoethyl cellulose; the polyester derivative containing carboxyl, sulfonic acid, hydroxyl, etheroxy, and ester groups is one or more of polyglycolic acid, polylactic acid, and sodium chondroitin sulfate.

[0011] The first component accounts for 50-90% of the mass, and the second component accounts for 10-50% of the mass.

[0012] The average molecular weight of the first component is 10,000 to 500,000, and the average molecular weight of the second component is 5,000 to 1,000,000; the thickness of the diaphragm is 1 to 100 μm.

[0013] The method for preparing the high-safety rechargeable magnesium battery separator that suppresses magnesium dendrites includes the following steps: (1) Dissolve the first component and the second component in a solvent to obtain a spinning solution; the solvent is formic acid / hexafluoroisopropanol or a mixture of formic acid / hexafluoroisopropanol with dichloromethane, acetic acid, N,N-dimethylformamide; when the solvent is a mixture, formic acid / hexafluoroisopropanol accounts for at least 80 wt% of the mixture.

[0014] (2) Prepare a diaphragm from the spinning solution in step (1) by electrospinning, and obtain the diaphragm after separation.

[0015] In step (1), the concentration of the spinning solution is 10-30 wt%; in step (2), the electrospinning parameters are: inner diameter of the flat-head needle is 0.72-0.84 mm, voltage is 10-30 kV, and spinning speed is 0.5-2 mL / h. -1 The distance from the needle tip to the roller is 15-30 cm, and the roller speed is 100-500 r / min. -1 Aluminum foil or high-definition photographic paper can be used as the receiver.

[0016] In step (2), a deionized water separator and a diaphragm are used. After separation, the diaphragm is dried at a temperature of 40-80℃ for 12-24 hours.

[0017] A high-safety rechargeable magnesium battery, comprising a high-safety rechargeable magnesium battery separator for inhibiting magnesium dendrites, a positive electrode material, a negative electrode material, and an electrolyte.

[0018] The electrolyte includes any one of the following: bis(trifluoromethanesulfonyl)imide magnesium-based electrolyte, trifluoromethanesulfonate magnesium-based electrolyte, magnesium borate-based electrolyte, magnesium-aluminum chloride complex-based electrolyte, non-nucleophilic electrolyte, and organic Grignard reagent electrolyte; the positive electrode material includes any one of the following: sulfide, selenide, vanadium oxide, manganese oxide, iron silicate-based, iron phosphate-based, and organic positive electrode; the negative electrode material includes metallic magnesium and its alloys.

[0019] The present invention has the following beneficial effects: 1. The battery separator prepared by this invention utilizes the advantages of two or more complementary polymers. Specifically, the first component, a nylon-based polymer, exhibits good chemical stability, while the second component, a polysaccharide or polyester derivative, contains abundant polar functional groups. The strong electronegative polar functional groups in the second component form stronger hydrogen bonds with the amide groups of the first component, thus broadening the amorphous region of the first component and enhancing ion transport. Through electrospinning, with formic acid and hexafluoroisopropanol as good solvents for the first component, and dichloromethane, acetic acid, and N,N-dimethylformamide as good solvents for the second component, a nanofiber composite battery separator is obtained. By controlling the choice of spinning solution solvent and combining formic acid and other solvents with high dielectric constants, the obtained nanofiber separator possesses a spiderweb structure, further significantly improving the tensile strength (16 MPa) and thermal stability of the separator, maintaining dimensional stability even after being held at 210 °C for 30 minutes.

[0020] 2. In the high-safety rechargeable magnesium battery separator prepared by this invention, which suppresses magnesium dendrite growth, the highly electronegative polar functional groups on the polymer molecular chain interact with the polar solvent in the electrolyte via dipole-dipole interactions. This reduces the surface potential of the solvent molecules, weakens the coordination between the solvent and magnesium ions, accelerates the dissociation of magnesium ions, promotes the uniform deposition of magnesium ions, and further inhibits the growth of magnesium dendrites. The increased amorphous region, abundant nanofiber structure, and oxygen-containing polar functional groups endow the separator with rapid ionic conductivity and excellent ion selectivity, significantly improving electrolyte affinity. The contact angle with different ester and ether electrolyte solvents is close to 0°. Electrochemical performance shows that using this separator in rechargeable magnesium batteries can effectively solve the problem of magnesium dendrite growth, improving battery life and safety. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 Scanning electron microscope images of the diaphragm planes prepared in Examples 3 and 7.

[0023] Figure 2 Digital images of the diaphragms prepared in Examples 1, 3, 4, 5, and 7, and the Celgard 2500 diaphragm of Comparative Example 1, after being kept at 210 °C for 30 minutes.

[0024] Figure 3 Contact angles of the diaphragm prepared in Example 3 with four different electrolytes and a mixed solvent.

[0025] Figure 4 Tensile properties of the diaphragm prepared in Example 3 and the Celgard 2500 diaphragm in Comparative Example 1.

[0026] Figure 5 The membranes prepared in Examples 1, 3, and 4, and the Celgard 2500 membrane of Comparative Example 1, were subjected to a 0.5 mol / L solution. -1 Ionic conductivity performance of bis(trifluoromethanesulfonyl)imide magnesium / ethylene glycol dimethyl ether + 2-methoxyethylamine electrolyte.

[0027] Figure 6 The magnesium metal symmetric cell assembled with a separator prepared in Example 3 was used in a 0.4 mol L⁻¹ solar cell. -1 Electrochemical performance diagram of phenyl magnesium chloride + aluminum chloride / tetrahydrofuran electrolyte. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1 This embodiment provides a high-safety rechargeable magnesium battery separator that suppresses magnesium dendrites, and the preparation method is shown below: 1.6 g of nylon MXD6 solid particles (molecular weight 20,000), 0.2 g of cellulose acetate solid particles (molecular weight 120,000), and 0.2 g of polylactic acid (molecular weight 110,000) were dissolved in a mixed solvent of 6.86 g formic acid and 1.14 g dichloromethane (mass ratio 6:1). After magnetic stirring for 6 h, a nylon MXD6-cellulose acetate-polylactic acid spinning solution with a mass concentration of 20% was obtained. The spinning solution was transferred to a 10 mL syringe, and electrospinning parameters were set as follows: flat-tipped needle inner diameter of 0.84 mm, voltage of 22.5 kV, and spinning speed of 0.8 mL / h. -1 The drum speed is 100-500 r / min -1 The distance from the needle to the roller was 25 cm, and aluminum foil was used as the receiver. Deionized water was used to separate the aluminum foil and nonwoven fabric. The obtained nylon MXD6-cellulose acetate-polylactic acid diaphragm was dried in a 60 ℃ oven for 12 h. The volume of the solution used for spinning was 16 mL, and the initial diaphragm thickness was 70 μm.

[0030] Example 2 This embodiment provides a high-safety rechargeable magnesium battery separator that suppresses magnesium dendrites, and the preparation method is shown below: 1.8 g of nylon 10T solid particles (molecular weight 20,000), 0.1 g of cellulose acetate solid particles (molecular weight 120,000), and 0.1 g of chondroitin sulfate sodium salt (5,000) were dissolved in a mixed solvent of 6.68 g formic acid and 1.11 g acetic acid (mass ratio 6:1). After magnetic stirring for 6 h, a nylon 10T-cellulose acetate-chondroitin sulfate sodium salt spinning solution with a mass concentration of 20% was obtained. The spinning solution was transferred to a 10 mL syringe, and electrospinning parameters were set as follows: flat-tipped needle inner diameter 0.72 mm, voltage 10 kV, and spinning speed 0.5 mL / h. -1 The drum speed is 100 r / min -1 The distance from the needle to the roller was 15 cm, and aluminum foil was used as the receiver. Deionized water was used to separate the aluminum foil and nonwoven fabric. The obtained nylon 10T-cellulose acetate-chondroitin sulfate sodium salt diaphragm was dried in a 60 ℃ oven for 12 h. The volume of the solution used for spinning was 16 mL, and the initial diaphragm thickness was 60 μm.

[0031] Example 3 This embodiment provides a high-safety rechargeable magnesium battery separator that suppresses magnesium dendrites, and the preparation method is shown below: 1.8 g of nylon 6 solid particles (molecular weight 20,000) and 0.2 g of cellulose acetate solid particles (molecular weight 120,000) were dissolved in a mixed solvent of 6.86 g formic acid and 1.14 g dichloromethane (mass ratio 6:1). After magnetic stirring for 6 h, a nylon 6-cellulose acetate spinning solution with a mass concentration of 20% was obtained. The spinning solution was transferred to a 10 mL syringe, and electrospinning parameters were set as follows: flat-tipped needle inner diameter of 0.84 mm, voltage of 30 kV, and spinning speed of 0.8 mL / h. -1 The distance from the needle tip to the roller is 25 cm, and the roller speed is 300 r / min. -1 Aluminum foil was used as the receiver. The aluminum foil and nonwoven fabric were separated using deionized water, and the resulting nylon 6-acetic acid cellulose membrane was dried in a 60 ℃ oven for 12 h. The volume of the solution used for spinning was 16 mL, and the initial membrane thickness was 70 μm.

[0032] Example 4 This embodiment provides a high-safety rechargeable magnesium battery separator that suppresses magnesium dendrites, and the preparation method is shown below: 1.6 g of nylon 10 / 10 solid particles (molecular weight 20,000) and 0.4 g of cellulose acetate solid particles (molecular weight 120,000) were dissolved in a mixed solvent of 6.4 g formic acid and 1.6 g N,N-dimethylformamide (mass ratio 4:1). After magnetic stirring for 6 h, a nylon 10 / 10-cellulose acetate spinning solution with a mass concentration of 20% was obtained. The spinning solution was transferred to a 10 mL syringe, and electrospinning parameters were set as follows: flat-tipped needle inner diameter 0.84 mm, voltage 30 kV, and spinning speed 0.8 mL / h. -1 The distance from the needle tip to the roller is 25 cm, and the roller speed is 300 r / min. -1 Aluminum foil was used as the receiver. The aluminum foil and nonwoven fabric were separated using deionized water, and the resulting nylon 10 / 10-cellulose acetate membrane was dried in a 60 ℃ oven for 12 h. The volume of the solution used for spinning was 16 mL, and the initial membrane thickness was 70 μm.

[0033] Example 5 This embodiment provides a high-safety rechargeable magnesium battery separator that suppresses magnesium dendrites, and the preparation method is shown below: 1.8 g of nylon 9T solid particles (molecular weight 20,000) and 0.2 g of chitosan solid particles (molecular weight 120,000) were dissolved in 4.7 g of formic acid solvent. After magnetic stirring for 6 h, a nylon 9T-chitosan spinning solution with a mass concentration of 30% was obtained. The spinning solution was transferred to a 10 mL syringe, and electrospinning parameters were set as follows: flat-tipped needle inner diameter of 0.84 mm, voltage of 30 kV, and spinning speed of 0.8 mL / h. -1 The distance from the needle to the roller was 30 cm, and aluminum foil was used as the receiver. Deionized water was used to separate the aluminum foil and nonwoven fabric, and the obtained nylon 9T-chitosan membrane was dried in a 60 ℃ oven for 12 h. The volume of the solution used for spinning was 16 mL, and the initial membrane thickness was 100 μm.

[0034] Example 6 This embodiment provides a high-safety rechargeable magnesium battery separator that suppresses magnesium dendrites, and the preparation method is shown below: 1.0 g of nylon 6 / 6 solid particles (molecular weight 20,000) and 1.0 g of cellulose acetate solid particles (molecular weight 120,000) were dissolved in a mixed solvent of 15 g formic acid and 3 g dichloromethane (mass ratio 5:1). After magnetic stirring for 6 h, a nylon 6 / 6-cellulose acetate spinning solution with a mass concentration of 10% was obtained. The spinning solution was transferred to a 10 ml syringe, and electrospinning parameters were set as follows: flat-tipped needle inner diameter 0.84 mm, voltage 20 kV, and spinning speed 2 mL / h. -1The distance from the needle tip to the roller is 15 cm, and the roller speed is 500 r / min. -1 High-resolution photographic paper was used as the receiver. Deionized water was used to separate the high-resolution photographic paper and nonwoven fabric. The obtained nylon 6 / 6-cellulose acetate membrane was dried in a 60 ℃ oven for 12 h. The volume of the solution used for spinning was 16 mL, and the initial membrane thickness was 50 μm.

[0035] Example 7 This embodiment provides a high-safety rechargeable magnesium battery separator that suppresses magnesium dendrites, and the preparation method is shown below: 1.8 g of nylon 6 solid particles (molecular weight 20,000) and 0.2 g of cellulose acetate solid particles (molecular weight 120,000) were dissolved in 8 g of hexafluoroisopropanol solvent. After magnetic stirring for 6 h, a nylon 6-cellulose acetate spinning solution with a mass concentration of 20% was obtained. The spinning solution was transferred to a 10 ml syringe, and electrospinning parameters were set as follows: flat-tipped needle inner diameter 0.84 mm, voltage 30 kV, and spinning speed 0.8 mL / h. -1 The distance from the needle tip to the roller is 25 cm, and the roller speed is 300 rpm. -1 Aluminum foil was used as the receiver. The aluminum foil and nonwoven fabric were separated using deionized water, and the resulting nylon 6-acetic acid cellulose membrane was dried in a 60℃ oven for 12 h. The volume of the solution used for spinning was 16 mL, and the initial membrane thickness was 70 μm.

[0036] Comparative Example 1 In this comparative example, commercial diaphragm (Celgard 2500, PP) was cut to an appropriate size and dried in an oven at 60 ℃ for 12 hours.

[0037] Effect Experiment: The high-safety rechargeable magnesium battery separator for suppressing magnesium dendrites obtained in Examples 3 and 7 was tested by scanning electron microscopy (SEM). Figure 1 and Figure 2 A comparison of the test data shows that the formic acid-containing spinning solution solvent mixture helps form spider web-like nanofibers. This is because some amide groups on the nylon backbone react with formic acid solvent molecules to generate short-chain oligomers and protonated amide monomers -CONH2-. + It forms stronger hydrogen bonds with the oxygen element on the main chain and the strongly electronegative polar functional groups of the second component, thereby improving thermal stability.

[0038] Thermal stability tests were conducted on the high-safety rechargeable magnesium battery separators for suppressing magnesium dendrites obtained in Examples 1, 3, 4, 5, and 7. After being kept at 210 °C for 30 minutes, the high-safety rechargeable magnesium battery separators for suppressing magnesium dendrites obtained in Examples 1, 3, 4, and 5 did not exhibit dimensional shrinkage. The high-safety rechargeable magnesium battery separator for suppressing magnesium dendrites obtained in Example 7 exhibited relatively small dimensional shrinkage. The Celgard 2500 separator in Comparative Example 1 exhibited significant dimensional shrinkage (e.g., ...). Figure 2 As shown in the figure, the diaphragm prepared by the present invention has high thermal stability.

[0039] An electrolyte wettability test was conducted on a high-safety rechargeable magnesium battery separator that suppresses magnesium dendrites obtained in Example 3. The magnesium electrolyte used was a 0.4 mol / L solution. -1 Phenylated magnesium chloride + aluminum chloride / tetrahydrofuran, 0.5 mol / L -1 Magnesium bis(trifluoromethanesulfonyl)imide / ethylene glycol dimethyl ether + 2-methoxyethylamine and mixed solvents such as ethylene carbonate + diethyl carbonate + fluoroethylene carbonate, and diethylene glycol dimethyl ether. The magnesium electrolyte was placed in a microsyringe. After adjusting the droplet volume, the stage was moved to bring the diaphragm into contact with the droplet. The contact angle was measured using the three-point method. The first optical photograph of the droplet landing on the diaphragm was taken. Tests showed that the contact angle between the diaphragm and the electrolyte and mixed solvent in Example 3 was 0°, while the contact angle between the commercial diaphragm and the electrolyte in Comparative Example 1 was 80° (e.g., ...). Figure 3 (As shown).

[0040] A tensile strength test was conducted on the high-safety rechargeable magnesium battery separator obtained in Example 3, which suppresses magnesium dendrites. The tensile strength of the separator obtained in Example 3 was 16 MPa (e.g., Figure 4 (As shown).

[0041] Liquid absorption rate refers to the ratio of the mass of the membrane after absorbing electrolyte to the mass of the dried electrospun membrane or commercial membrane. The liquid absorption rate (η) is calculated using equation (1): (1) Among them, W0 and W t These represent the mass of the dry film and the mass after it has absorbed the electrolyte, respectively.

[0042] The liquid absorption rate of the high-safety rechargeable magnesium battery separator with magnesium dendrite suppression obtained in Example 1 was 528%, the liquid absorption rate of the high-safety rechargeable magnesium battery separator with magnesium dendrite suppression obtained in Example 3 was 515%, the liquid absorption rate of the high-safety rechargeable magnesium battery separator with magnesium dendrite suppression obtained in Example 4 was 481%, the liquid absorption rate of the high-safety rechargeable magnesium battery separator with magnesium dendrite suppression obtained in Example 5 was 448%, and the liquid absorption rate of the Celgard 2500 separator in Comparative Example 1 was 124%.

[0043] The ionic conductivity is calculated using formula (2): (2) Where σ is the ionic conductivity, with units of S cm. -1 ;R b Ω is the bulk resistance; l is the film thickness; A is the contact area between the stainless steel electrode and the film; and A is the contact area between the stainless steel electrode and the film. -2 .

[0044] The high-safety rechargeable magnesium battery separator obtained in Example 1, which suppresses magnesium dendrites, has an ionic conductivity of 3.48 mS / cm. -1 The high-safety rechargeable magnesium battery separator obtained in Example 3, which suppresses magnesium dendrites, has an ionic conductivity of 3.21 mS / cm. -1 The high-safety rechargeable magnesium battery separator obtained in Example 4, which suppresses magnesium dendrites, has an ionic conductivity of 3.10 mS / cm. -1 The Celgard 2500 membrane in Comparative Example 1 has an ionic conductivity of 0.62 mS / cm. -1 (like Figure 5 The diaphragm obtained by this invention has higher ionic conductivity.

[0045] The electrochemical performance of the high-safety rechargeable magnesium battery separator that suppresses magnesium dendrites obtained in Example 3 was tested. The separator was then used to assemble a 2025 type button cell in an argon-filled glove box. Both the positive and negative electrode materials were magnesium metal, 0.4 mol / L. -1 The electrolyte is phenylmagnesium chloride + aluminum chloride / tetrahydrofuran. The current density is 3 mA cm⁻¹. -2 Specific capacity is 3 mAhcm -2 Under test conditions (such as) Figure 6 As shown in the figure, the voltage curve dropped in the first 100 h due to the incomplete removal of the passivation layer on the magnesium metal surface. After 100 h of activation, it can be stably cycled for 1200 h, showing excellent magnesium dendrite suppression ability. In contrast, Celgard 2500 in Comparative Example 1 showed a significant short circuit (sudden voltage drop) after 260 h due to dendrites piercing the diaphragm.

[0046] In summary, the high-safety rechargeable magnesium battery separator for inhibiting magnesium dendrites provided in this embodiment of the invention not only has good electrolyte affinity, thermal stability, tensile strength, and liquid absorption, but also has rapid ionic conductivity in the magnesium electrolyte system. Therefore, when the high-safety rechargeable magnesium battery separator for inhibiting magnesium dendrites is applied to rechargeable magnesium batteries, it can significantly inhibit the growth of magnesium dendrites and improve the cycle stability and safety of the battery.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-safety rechargeable magnesium battery separator that suppresses magnesium dendrites, characterized in that: The diaphragm is made by electrospinning a first component and a second component. The first component is one or more nylon-based derivatives, and the second component is one or more polysaccharide or polyester derivatives containing polar groups such as carboxyl, sulfonic acid, hydroxyl, etheroxy, or ester groups.

2. The high-safety rechargeable magnesium battery separator for suppressing magnesium dendrites according to claim 1, characterized in that: The nylon-based derivative is any one of nylon 6, nylon 6 / 6, nylon 6 / 10, nylon 6 / 12, nylon 11, nylon 12, nylon 10 / 10, nylon 12 / 12, nylon 4 / 6, nylon 5 / 6, nylon 6T, nylon 9T, nylon 10T and nylon MXD6.

3. The high-safety rechargeable magnesium battery separator for suppressing magnesium dendrites according to claim 1, characterized in that: The polysaccharide or polyester derivative containing polar groups such as carboxyl, sulfonic acid, hydroxyl, etheroxy, or ester groups is one or more of cellulose acetate, chitosan, hyaluronic acid, cellulose acetate butyrate, cyanoethyl cellulose, polyglycolic acid, polylactic acid, and sodium chondroitin sulfate.

4. The high-safety rechargeable magnesium battery separator for suppressing magnesium dendrites according to claims 1-4, characterized in that, The first component accounts for 50-90% of the mass, and the second component accounts for 10-50% of the mass.

5. The high-safety rechargeable magnesium battery separator for suppressing magnesium dendrites according to claims 1-5, characterized in that: The first component has an average molecular weight of 10,000 to 500,000, and the second component has an average molecular weight of 5,000 to 100,000; the membrane thickness is 1 to 100 μm.

6. The method for preparing a high-safety rechargeable magnesium battery separator that suppresses magnesium dendrites according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Dissolve the first component and the second component in a solvent to obtain a spinning solution; the solvent is formic acid / hexafluoroisopropanol or formic acid / hexafluoroisopropanol and one or more mixed solvents selected from dichloromethane, acetic acid, and N,N-dimethylformamide; (2) Prepare a diaphragm by electrospinning the spinning solution in step (1), and obtain the diaphragm after separation.

7. The method for preparing a high-safety rechargeable magnesium battery separator that suppresses magnesium dendrites according to claim 6, characterized in that, In step (1), the concentration of the spinning solution is 10-30 wt%; in step (2), the electrospinning parameters are: inner diameter of the flat-head needle is 0.72-0.84 mm, voltage is 10-30 kV, and spinning speed is 0.5-2 mL / h. -1 The distance from the needle tip to the roller is 15-30 cm, and the roller speed is 100-500 r / min. -1 Aluminum foil or high-definition photographic paper can be used as the receiver.

8. The method for preparing a high-safety rechargeable magnesium battery separator that suppresses magnesium dendrites according to claim 7, characterized in that, In step (2), a deionized water separator and a diaphragm are used. After separation, the diaphragm is dried at a temperature of 40-80℃ for 12-24 hours.

9. A high-safety rechargeable magnesium battery, characterized in that, The high-safety rechargeable magnesium battery includes the high-safety rechargeable magnesium battery separator for inhibiting magnesium dendrites as described in any one of claims 1-5, the positive electrode material, the negative electrode material, and the electrolyte.

10. The high-safety rechargeable magnesium battery according to claim 9, characterized in that: The electrolyte includes any one of the following: bis(trifluoromethanesulfonyl)imide magnesium-based electrolyte, trifluoromethanesulfonate magnesium-based electrolyte, magnesium borate-based electrolyte, magnesium-aluminum chloride complex-based electrolyte, non-nucleophilic electrolyte, and organic Grignard reagent electrolyte; the positive electrode material includes any one of the following: sulfide, selenide, vanadium oxide, manganese oxide, iron silicate-based, iron phosphate-based, and organic positive electrode; the negative electrode material includes metallic magnesium and its alloys.

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