Design method of high-entropy MXene-high-viscosity colloid composite coating battery diaphragm

Abstract

The invention discloses a high-entropy MXene-high-viscosity colloid composite coating battery diaphragm design method, and belongs to the technical field of lithium battery diaphragms.The method comprises the steps that after a multi-layer high-entropy MAX phase raw material is subjected to etching treatment, high-entropy MXene nanosheets are obtained through a high-pressure homogenizer; dissolving the high-viscosity polyacrylamide colloid in deionized water to form a homogeneous adhesive solution; high-entropy MXene nanosheets are dispersed in the solution, and mixed slurry is formed; coating the slurry on the surface of a polypropylene diaphragm, and drying to form a compact coating; and bonding the coated diaphragm and a copper current collector through a hot pressing process to form an integrated interface structure. Through the lithium migration energy barrier regulation and control characteristic of high-entropy MXene and the in-situ film forming effect of fluorinated functional groups, and in combination with the strong adhesion of PAM colloid, the synergistic effect of lithium ion desolvation process acceleration, SEI component optimization and lithium deposition homogenization is realized, the growth of lithium dendrites is inhibited, and the cycling stability of the non-cathode battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery separators, and particularly to a design method for a high-entropy MXene-high-viscosity colloid composite coating battery separator. Background Art

[0002] With the explosive growth of the demand for high-energy-density energy storage, the lithium metal battery without a negative electrode has become the focus of a new generation of battery technologies due to its advantages such as high theoretical capacity (3860 mAh / g), simplified structure, and controllable cost. In this system, the copper foil current collector is directly used as the lithium deposition substrate, and the traditional negative electrode active material is abandoned, which can significantly improve the energy density and safety. However, its core challenge lies in the dendrite growth problem caused by the slow desolvation kinetics and uneven interfacial ion flux during the lithium metal deposition / stripping process, which is extremely likely to lead to separator perforation, interfacial failure, and battery thermal runaway.

[0003] Currently, the modification strategies for separators mainly focus on improving the mechanical strength and regulating the ion transport path. For example, by introducing ceramic particles (such as Al2O3, SiO2) or polymer coatings (such as PVDF, aramid) on the surface of polyolefin separators, the puncture resistance of the separator can be enhanced and the electrolyte wettability can be improved. However, these methods have significant limitations: on the one hand, it is difficult to balance the high mechanical strength and flexible adaptation requirements due to the brittleness of the ceramic coating and the low modulus of the polymer coating; on the other hand, the single-functional design of traditional coatings cannot simultaneously optimize the ion transport kinetics and interfacial stability, resulting in problems such as high desolvation energy barriers and uneven lithium deposition. More severely, the physical contact gap between the coating and the current collector will exacerbate the interfacial impedance and further deteriorate the lithium deposition behavior.

[0004] In recent years, two-dimensional MXene materials have been regarded as ideal candidate materials for separator modification due to their high conductivity, interlayer ion channels, and tunable surface functional groups. However, the severe interlayer self-stacking tendency of conventional MXene (such as Ti3C2T x ) seriously weakens its ion sieving ability, and the chemical stability of a single metal component is insufficient to maintain the structural integrity during long-term cycling. In addition, existing MXene-based composite separators mostly rely on physical coating processes, and their weak interfacial bonding with the current collector is prone to cause coating peeling, and it is impossible to achieve the synergistic improvement of ion transport - mechanical support - interfacial stability. Therefore, there is an urgent need to develop a separator modification strategy that takes into account high mechanical strength, fast desolvation kinetics, and an integrated interfacial structure. Through material design and process innovation, break through the performance bottleneck of traditional coatings and provide reliable guarantee for the efficient and long-cycle operation of lithium metal batteries without a negative electrode. Summary of the Invention

[0005] The purpose of the present invention is to provide a design method for a high-entropy MXene-high-viscosity colloid composite coating battery separator.

[0006] To achieve the above object, the present invention provides a design method for a high-entropy MXene-high-viscosity colloid composite coating battery separator, comprising the following steps: S1. Place the multi-layer high-entropy MAX phase raw material, i.e., TiVNbMoAlC3, in a mixed solution of lithium fluoride and hydrochloric acid for etching treatment. After washing with deionized water until neutral, perform cyclic peeling through a high-pressure homogenizer and centrifugally separate to obtain high-entropy MXene nanosheets rich in fluorinated functional groups on the surface, i.e., TiVNbMoC3 nanosheets; S2. Dissolve polyacrylamide (PAM) colloid in deionized water and stir evenly at a constant speed to form a homogeneous adhesive solution; S3. Disperse the high-entropy MXene nanosheets in step S1 in the PAM colloid in step S2 and mix through a high-speed homogenizer to form a high-entropy MXene / PAM mixed slurry; S4. Uniformly coat the mixed slurry in step S3 on the surface of a polypropylene (PP) separator using a wire bar coating process, and then dry it at a gradient temperature to form a dense composite coating; S5. Bond the coated separator in step S4 with a copper current collector through a soft-packaging process of first hot pressing and then injecting electrolyte to form an integrated interface structure.

[0007] Preferably, in the above design method for a high-entropy MXene-high-viscosity colloid composite coating battery separator, in step S1, the composition of the mixed solution of lithium fluoride and hydrochloric acid is: 1 g of lithium fluoride, the concentration of hydrochloric acid is 12 mol / L, and the usage amount of hydrochloric acid is 40 mL; the high-entropy MAX raw material is 1 g; the etching temperature for the etching treatment is 45 °C, and the treatment time is 72 h; the working pressure of the high-pressure homogenizer is 1100 - 1200 MPa, and the number of cyclic treatments is 10 - 15 times.

[0008] Preferably, in the above design method for a high-entropy MXene-high-viscosity colloid composite coating battery separator, in step S1, the single-layer thickness of the high-entropy MXene nanosheets is 1 - 2 nm, and the number of layers is 3 - 5 layers.

[0009] Preferably, in the above design method for a high-entropy MXene-high-viscosity colloid composite coating battery separator, in step S2, the stirring time for generating the homogeneous adhesive solution is 4 - 6 h, and the mass concentration of the adhesive solution is 8% - 12%.

[0010] Preferably, in the above design method for a high-entropy MXene-high-viscosity colloid composite coating battery separator, in step S3, the rotation speed of the high-speed homogenizer is 2000 r / min, the mixing time is 30 - 60 min, and the viscosity of the slurry is controlled at 500 - 800 mPa·s.

[0011] Preferably, in the above-mentioned design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator, in S3, the mass ratio of high-entropy MXene to polyacrylamide in the high-entropy MXene / PAM mixed slurry is 8:1, and the solid content of the slurry is 25%.

[0012] Preferably, in the above-mentioned design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator, in S4, the wire bar coating process uses an OSP-1.5 type wire bar, the coating speed is 0.5 - 1.5 m / min, and the thickness of the dried coating is 4 - 5 μm.

[0013] Preferably, in the above-mentioned design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator, in S4, the thickness of the PP separator substrate is 12 - 16 μm, and the drying conditions are pre-baking at 40°C for 1 h and final baking at 60°C for 6 h.

[0014] Preferably, in the above-mentioned design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator, in S5, the hot pressing process has a hot pressing temperature of 80°C, a pressure of 0.5 MPa, and a pressure holding time of 30 - 60 s.

[0015] Preferably, for the composite coating separator prepared by the above-mentioned design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator, the lithium ion transference number is 0.76, the fracture energy is 50.15 J / m 3 , and the capacity retention rate after 100 cycles in a non-negative electrode soft-pack battery is 82.6%.

[0016] Therefore, the present invention adopts the above-mentioned design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator, and its beneficial effects are as follows: (1) The lattice distortion effect of two-dimensional high-entropy MXene strengthens the intrinsic mechanical properties of the separator: The solid solution and distortion of multi-metal element atoms in the MXene lattice form a high-strength covalent bond network. Combining with the ordered stacking structure of two-dimensional sheets, it endows the composite separator with excellent puncture and deformation resistance capabilities, significantly inhibits the risk of separator penetration caused by the growth of lithium dendrites, and at the same time maintains the lightweight characteristics of the separator.

[0017] (2) The high-viscosity colloid hot pressing integrated structure accelerates the desolvation transport of lithium ions: The seamless interfacial bonding between the separator coating and the negative electrode current collector is realized through the high-viscosity colloid and the soft-pack process of hot pressing first and then injecting electrolyte, eliminating the ion transport barrier caused by the traditional physical contact gap. This integrated design forces lithium ions to quickly desolvate during cross-interfacial transport, greatly improving the ion migration efficiency, and guiding the uniform deposition of lithium ions along the MXene interlayer channels.

[0018] (3) Inducing the construction of stable SEI chemical components by fluorinated terminations on the MXene surface: The fluorinated functional groups in-situ generated by the etching process react with lithium preferentially in the initial stage of battery cycling, forming an SEI film dominated by lithium fluoride with high ionic conductivity. This SEI component effectively passivates the electrode interface, reduces the kinetic barrier of lithium deposition, and simultaneously inhibits the side reactions of the electrolyte, realizing highly reversible lithium metal deposition / stripping behavior.

[0019] Through the structure strengthening of high-entropy MXene, interfacial integrated bonding, and in-situ regulation of fluorinated SEI, the present invention synergistically solves the core problems of dendrite growth, ion transport retardation, and interface instability in anode-free batteries, providing an innovative technical path for high-safety and high-energy-density lithium metal batteries.

[0020] The technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0021] Figure 1 is the XRD pattern of high-entropy MAX and high-entropy MXene in Example 1 of the present invention; Figure 2 is the density of states diagram of unit MXene in Comparative Example 1 of the present invention; Figure 3 is the density of states diagram of high-entropy MXene in Example 1 of the present invention; Figure 4 is the SEM and EDS diagrams of high-entropy MXene in Example 1 of the present invention; Figure 5 is the AFM diagram of high-entropy MXene in Example 1 of the present invention; Figure 6 is the TEM diagram of high-entropy MXene in Example 1 of the present invention; Figure 7 is the peel force diagram after hot pressing of modified PP separator I and copper foil in Example 1 of the present invention; Figure 8 is the peel force diagram after hot pressing of modified PP separator II and copper foil in Comparative Example 1 of the present invention; Figure 9 is the contact angle comparison diagram between modified PP separator I in Example 1 and modified PP separator II in Comparative Example 1 of the present invention; Figure 10 is the fracture energy comparison diagram among modified PP separator I in Example 1, modified PP separator II in Comparative Example 1, and modified PP separator III in Comparative Example 2 of the present invention; Figure 11 is the lithium ion transference number comparison diagram among modified PP separator I in Example 1, modified PP separator II in Comparative Example 1, and modified PP separator III in Comparative Example 2 of the present invention; Figure 12It is a comparative diagram of the cyclic stability performance of lithium symmetric batteries assembled in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention; Figure 13 It is a comparative diagram of the cyclic curves of non-anode button batteries assembled in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention.

[0022] Figure 14 It is a comparative diagram of the cyclic rate curves of non-anode button batteries assembled in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention. Detailed implementation manners

[0023] In order to better understand the above technical solutions, the above technical solutions will be described in detail below in conjunction with the accompanying drawings of the specification and specific implementation manners. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0024] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "the", and "said" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. "Plural" generally includes at least two.

[0025] It should also be noted that the term "comprises", "comprising", or any other variation thereof is intended to cover a non-exclusive inclusion, such that a commodity or device including a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such commodity or device. Without further limitation, an element defined by the phrase "comprising an..." does not exclude the presence of additional identical elements in the commodity or device including the said element.

[0026] The present invention provides a design method for a high-entropy MXene-high-viscosity colloid composite coating battery separator, including the following steps: S1. Place the multi-layer high-entropy MAX phase raw material, namely TiVNbMoAlC3, in a mixed solution of lithium fluoride and hydrochloric acid for etching treatment. After washing with deionized water until neutral, cycle stripping is carried out through a high-pressure homogenizer, and high-entropy MXene nanosheets rich in fluorinated functional groups on the surface, namely TiVNbMoC3 nanosheets, are obtained by centrifugal separation; S2. Dissolve polyacrylamide (PAM) colloid in deionized water and stir evenly to form a homogeneous adhesive solution; S3. Disperse the high-entropy MXene nanosheets in S2's PAM colloid and mix them with a high-speed homogenizer to form a high-entropy MXene / PAM hybrid slurry; S4. Uniformly coat the hybrid slurry in S3 on the surface of a polypropylene (PP) separator using a wire bar coating process, and then dry it by gradient heating to form a dense composite coating; S5. Bond the coated separator in S4 with a copper current collector through a soft-pack process of first hot pressing and then injecting electrolyte to form an integrated interface structure.

[0027] Preferably, in the above design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator, in S1, the composition of the lithium fluoride and hydrochloric acid mixed solution is: 1 g of lithium fluoride, the hydrochloric acid concentration is 12 mol / L, and the hydrochloric acid usage is 40 mL; the high-entropy MAX raw material is 1 g; the etching temperature for the etching treatment is 45 °C, and the treatment time is 72 h; the working pressure of the high-pressure homogenizer is 1100 - 1200 MPa, and the number of circulation treatments is 10 - 15 times.

[0028] Preferably, in the above design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator, in S1, the single-layer thickness of the high-entropy MXene nanosheets is 1 - 2 nm, and the number of layers is 3 - 5 layers.

[0029] Preferably, in the above design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator, in S2, the stirring time for generating the homogeneous adhesive solution is 4 - 6 h, and the mass concentration of the adhesive solution is 8% - 12%.

[0030] Preferably, in the above design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator, in S3, the rotation speed of the high-speed homogenizer is 2000 r / min, the mixing time is 30 - 60 min, and the slurry viscosity is controlled at 500 - 800 mPa·s.

[0031] Preferably, in the above design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator, in S3, the mass ratio of high-entropy MXene to polyacrylamide in the high-entropy MXene / PAM hybrid slurry is 8:1, and the solid content of the slurry is 25%.

[0032] Preferably, in the above design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator, in S4, the wire bar coating process uses an OSP-1.5 type wire bar, the coating speed is 0.5 - 1.5 m / min, and the thickness of the dried coating is 4 - 5 μm.

[0033] Preferably, in the above-mentioned design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator, in S4, the thickness of the PP separator substrate is 12-16 μm, and the drying conditions are pre-baking at 40 °C for 1 h and final baking at 60 °C for 6 h.

[0034] Preferably, in the above-mentioned design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator, in S5, the hot pressing temperature of the hot pressing process is 80 °C, the pressure is 0.5 MPa, and the pressure holding time is 30-60 s.

[0035] Preferably, for the composite coating separator prepared by the above-mentioned design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator, the lithium ion transference number is 0.76, and the fracture energy is 50.15 J / m 3 , and the capacity retention rate is 82.6% after 100 cycles in a non-aqueous cathode soft-pack battery.

[0036] In order to introduce the design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator provided by the embodiments of the present invention more clearly and in detail, the following will be described in combination with specific embodiments.

[0037] Example 1 S1. Place 1 g of multi-layer high-entropy MAX phase raw material (TiVNbMoAlC3) in a mixed solution of 1 g of lithium fluoride and 40 mL of 12 mol / L hydrochloric acid, and etch it at a constant temperature of 45 °C for 72 h, and then wash it with deionized water until neutral; subject the etched product to cyclic peeling 10-15 times by a high-pressure homogenizer under a pressure of 1100-1200 MPa, and centrifuge it at a speed of 6000 r / min to obtain high-entropy MXene (TiVNbMoC3) nanosheets with a single-layer thickness of 1-2 nm and 3-5 layers, and the surface is rich in fluorinated functional groups.

[0038] S2. Dissolve polyacrylamide (PAM) colloid in deionized water, and stir it evenly at a speed of 500 r / min for 4-6 h to prepare a homogeneous binder solution with a mass concentration of 8%-12%.

[0039] S3. Disperse the high-entropy MXene nanosheets in S1 in the PAM colloid in S2 according to a mass ratio of 8:1, and mix them at a speed of 8000-12000 r / min for 30-60 min by a high-speed homogenizer, and control the slurry viscosity to be 500-800 mPa·s to form a high-entropy MXene / PAM mixed slurry with a solid content of 25%.

[0040] S4. The mixed slurry in S3 is uniformly coated on the surface of a polypropylene (PP) separator with a thickness of 12 - 16 μm at a coating speed of 0.5 - 1.5 m / min using an OSP-1.5 type wire bar for thickness control screening; subsequently, it undergoes a gradient drying process of pre-drying at 40°C for 1 h and final drying at 60°C for 6 h to form a dense composite coating.

[0041] S5. The lithium metal soft-pack battery without a negative electrode assembled from the coated separator in S4 and a copper current collector is placed in a hot press and kept under pressure at 80°C and 0.5 MPa for 30 - 60 s to form an integrated interfacial structure with a seamless bond between the coating and the current collector, and then the liquid injection operation is carried out in a vacuum glove box.

[0042] Comparative Example 1 S1. 1 g of the unit MAX phase raw material (Ti3AlC2) is placed in a mixed solution of 1 g of lithium fluoride and 40 mL of 12 mol / L hydrochloric acid, and etched at a constant temperature of 45°C for 24 h, and then washed with deionized water until neutral; the etched product is ultrasonically exfoliated to obtain unit MXene (Ti3C2) nanosheets with a single-layer thickness of 1 - 2 nm and 8 - 10 layers.

[0043] S2. Sodium carboxymethyl cellulose (CMC) colloid is dissolved in deionized water and stirred at a constant speed of 500 r / min for 4 - 6 h to prepare a homogeneous binder solution with a mass concentration of 8% - 12%, and magnetically stirred and mixed with the unit MXene nanosheets in S1 in a ratio of 8:1 for 1 h to obtain a mixed slurry.

[0044] S3. The mixed slurry in S2 is coated on the surface of a polypropylene (PP) separator with a thickness of 12 - 16 μm using a doctor blade and dried at 40°C for 6 h to form a composite coating.

[0045] Comparative Example 2 S1. 1 high-entropy MAX phase raw material (TiVNbMoAlC3) is placed in a mixed solution of 1 g of lithium fluoride and 40 mL of 12 mol / L hydrochloric acid, and etched at a constant temperature of 45°C for 72 h, and then washed with deionized water until neutral; the etched product is ultrasonically exfoliated to obtain high-entropy MXene (TiVNbMoC3) nanosheets with a single-layer thickness of 1 - 2 nm and 8 - 10 layers.

[0046] S2. Polyacrylamide (PAM) colloid is dissolved in deionized water and stirred at a constant speed of 500 r / min for 4 - 6 h to prepare a homogeneous binder solution with a mass concentration of 8% - 12%.

[0047] S3. Dispersed the high-entropy MXene nanosheets in S1 in the PAM colloid of S2 at a mass ratio of 8:1, and mixed them for 30 - 60 min at a rotation speed of 8000 - 12000 r / min by a high-speed homogenizer to form a high-entropy MXene / PAM mixed slurry with a solid content of 25%.

[0048] S4. The mixed slurry in S3 was uniformly coated on the surface of a polypropylene (PP) diaphragm with a thickness of 12 - 16 μm at a coating speed of 0.5 - 1.5 m / min using an OSP-1.5 type wire bar for thickness control screening; subsequently, it underwent a gradient drying process of pre-drying at 40°C for 1 h and final drying at 60°C for 6 h to form a dense composite coating.

[0049] Test Example 1 a. Characterization by X-ray diffractometer (XRD) Figure 1 It is the XRD pattern of the high-entropy MAX and high-entropy MXene in Example 1 of the present invention. The results are as Figure 1 shown. After etching, compared with the high-entropy MAX raw material, an obvious (002) characteristic peak appeared in the etched high-entropy MXene product, proving the successful etching of the material.

[0050] b. Density of states (DOS) calculation Figure 2 It is the density of states diagram of the unit MXene in Comparative Example 1 of the present invention; Figure 3 It is the density of states diagram of the high-entropy MXene in Example 1 of the present invention. Through comparison, it can be seen that the density of states of the high-entropy MXene is closer to the 0 eV Fermi level, which is more conducive to the migration of electrons in terms of structure.

[0051] c. Characterization by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) Figure 4 It is the SEM and EDS diagrams of the high-entropy MXene in Example 1 of the present invention. As Figure 4 shown, the etched high-entropy MXene product presents an obvious layered peeling structure, and various metal elements are uniformly distributed therein. At the same time, fluorine elements attached to the surface of the high-entropy MXene are observed.

[0052] d. Characterization by atomic force electron microscope (AFM) Figure 5 It is the AFM diagram of the high-entropy MXene in Example 1 of the present invention. As Figure 5 shown, the stack thickness of the high-entropy MXene prepared in Example 1 is 4 - 7 nm.

[0053] e. Characterization by transmission electron microscope (TEM) Figure 6It is the TEM image of the high-entropy MXene in Example 1 of the present invention. The high-entropy MXene prepared in Example 1 of the present invention was characterized by TEM, and the results are as Figure 6 shown.

[0054] f. Peel force test The modified PP separator I in Example 1 and the modified PP separator II in Comparative Example 1 were subjected to a peel force test. Figure 7 It is the peel force diagram of the modified PP separator I in Example 1 of the present invention. Figure 8 It is the peel force diagram of the modified PP separator II in Comparative Example 1 of the present invention. It can be seen that the modified PP separator I in Example 1 has a greater peel force with the copper current collector compared to the modified PP separator in Comparative Example 1, proving that the modified PP separator I prepared in Example 1 can more effectively achieve the integrated structure of the separator and the negative electrode interface from a mechanical perspective.

[0055] g. Contact angle test The modified PP separator I in Example 1 and the modified PP separator II in Comparative Example 1 were subjected to a contact angle test. Figure 9 It is the contact angle comparison diagram of the modified PP separator I in Example 1 and the modified PP separator in Comparative Example 1 of the present invention. The results are as Figure 9 shown. It can be seen that the modified PP separator I in Example 1 has a smaller electrolyte contact angle compared to the modified PP separator II in Comparative Example 1. Due to the addition of PAM containing polar amide groups, it is proved that the modified PP separator I prepared in Example 1 has better wettability to the electrolyte.

[0056] h. Fracture energy test The modified PP separator I in Example 1, the modified PP separator II in Comparative Example 1, and the modified PP separator III in Comparative Example 2 were subjected to stress-strain tests. Figure 10 It is the stress-strain curve comparison diagram of the modified PP separator I in Example 1, the modified PP separator II in Comparative Example 1, and the modified PP separator III in Comparative Example 2 of the present invention. The area integral of the curve was performed to obtain the fracture energy data, and the results are as Figure 10 shown. By comparison, it can be seen that the mechanical properties of the modified PP separator I in Example 1 have been greatly improved.

[0057] Test Example 2 a. Lithium ion transference number test (i-t) Figure 11It is a comparison chart of the ion transference numbers of the traditional PP separator, the modified PP separator I in Example 1, the modified PP separator II in Comparative Example 1, and the modified PP separator III in Comparative Example 2. It can be seen from the comparison that the lithium ion transference number (0.76) of the modified PP separator I in Example 1 is greater than that of the modified PP separator II in Comparative Example 1 (0.56) and that of the modified PP separator III in Comparative Example 2 (0.63).

[0058] b. Electrochemical performance test Figure 12 It is a comparison chart of the cycling stabilities of lithium symmetric batteries assembled respectively with the modified PP separator I in Example 1, the modified PP separator II in Comparative Example 1, and the modified PP separator III in Comparative Example 2. As Figure 12 shown, compared with the two groups of comparative examples, the polarization voltage of the modified PP separator I in Example 1 decreases significantly, and the stable cycling time increases greatly.

[0059] Assemble non-negative electrode soft-pack batteries respectively with the modified PP separator I in Example 1, the modified PP separator II in Comparative Example 1, and the modified PP separator III in Comparative Example 2 and a lithium iron phosphate positive electrode. Figure 13 It is a comparison chart of the cycling curves of non-negative electrode button batteries assembled respectively in Example 1, Comparative Example 1, and Comparative Example 2; Figure 14 It is a comparison chart of the cycling rate curves of non-negative electrode button batteries assembled respectively in Example 1, Comparative Example 1, and Comparative Example 2. As can be seen from Figure 13 and 14 it, the modified PP separator I prepared in Example 1 has better capacity retention rate and rate performance.

[0060] Through the systematic comparison between the examples and the comparative examples, it can be known that the high-entropy MXene-based composite separator proposed by the present invention shows significant performance advantages in non-negative electrode lithium metal batteries. Compared with the traditional single-metal MXene-coated separator or the pure polymer coating scheme, the present invention induces the lattice distortion effect through the atomic-level solid solution design of multi-metal elements (Ti / V / Nb / Mo), so that while maintaining the ultra-thin thickness (16 - 20 μm), the mechanical strength of the composite separator is also significantly improved, completely solving the short-circuit hidden danger caused by dendrite piercing. Further, due to the in-situ conversion characteristics of the high-density fluorinated functional groups on the surface of high-entropy MXene, the formed lithium fluoride-rich SEI film during the cycling process significantly inhibits the side reaction of electrolyte decomposition, making the Coulomb efficiency stable above 99%. The comparative experiment shows that the non-negative electrode battery adopting this scheme has a capacity retention rate exceeding 80% after cycling 100 times at a rate of 0.5C, far exceeding 59.1% and 21.3% of the comparative example batteries, verifying its long cycling stability.

[0061] The core innovation of the present invention lies in the realization of multi-dimensional performance co-optimization through materials gene design and interface engineering. First, the lattice distortion effect and strong covalent bond network of high-entropy MXene endow the separator with ceramic-like mechanical rigidity, while its two-dimensional sheet structure constructs continuous lithium-ion transport channels through ordered stacking, breaking through the mutually exclusive bottleneck between the mechanical strength and ion flux of traditional modified separators. Second, the synergistic effect of highly viscous PAM colloid and thermocompression bonding process enables the separator coating to form an integrated interface with the copper current collector, completely eliminating the ion transport barrier caused by the traditional physical contact gap, forcing the lithium ions to quickly desolvate during cross-interface migration, and the transference number reaches 0.76. In addition, the fluorinated terminals (-F, -O-F) introduced in-situ during the MXene etching process react with lithium preferentially in the initial stage of the electrochemical cycle to form a SEI film dominated by highly ion-conductive lithium fluoride. Its dense passivation characteristics not only reduce the lithium polarization voltage but also block the continuous decomposition path of the electrolyte, achieving an interface dynamic stability of up to 900 h.

[0062] Based on the above technical innovations, the composite separator of the present invention has successfully overcome the core problems such as dendrite runaway, interface failure, and short cycle life that have long existed in the field of lithium metal batteries without a negative electrode. Its ultra-thin and lightweight characteristics are expected to enable the battery energy density to exceed 400 Wh / kg, an increase of more than 40% compared with the traditional graphite negative electrode system; at the same time, the integrated interface design is compatible with the existing roll-to-roll manufacturing process, making large-scale mass production feasible. This technology not only provides a reliable technical path for the commercialization of high-energy-density lithium metal batteries but also can be extended to emerging fields such as sodium metal batteries and solid-state batteries, promoting the innovation process of the next-generation energy storage system.

[0063] Therefore, the present invention adopts the above-mentioned design method of a high-entropy MXene-highly viscous colloid composite coating battery separator. The lattice distortion effect of two-dimensional high-entropy MXene strengthens the intrinsic mechanical properties of the separator: the solid solution and distortion of multi-metal element atoms in the MXene lattice form a high-strength covalent bond network, combined with the ordered stacking structure of two-dimensional sheets, endowing the composite separator with excellent puncture resistance and anti-deformation ability, significantly inhibiting the risk of separator penetration caused by lithium dendrite growth, while maintaining the lightweight characteristics of the separator.

[0064] The high-viscosity glue thermocompression integrated structure accelerates the desolvation transport of lithium ions: the seamless interface bonding between the separator coating and the negative electrode current collector is realized through the highly viscous colloid and the soft-packaging process of thermocompression first and then liquid injection, eliminating the ion transport barrier caused by the traditional physical contact gap. This integrated design forces the lithium ions to quickly desolvate during cross-interface transport, greatly improving the ion migration efficiency, and guiding the lithium ions to deposit uniformly along the MXene interlayer channels.

[0065] Fluorinated Terminals on the MXene Surface Induce the Formation of a Stable SEI Chemical Composition: The fluorinated functional groups in-situ generated by the etching process react with lithium preferentially at the initial stage of battery cycling to form an SEI film dominated by lithium fluoride with high ionic conductivity. This SEI composition effectively passivates the electrode interface, reduces the kinetic barrier of lithium deposition, and simultaneously inhibits side reactions of the electrolyte, enabling highly reversible lithium metal deposition / stripping behavior.

[0066] Through the structural strengthening of high-entropy MXene, interfacial integrated bonding, and in-situ regulation of the fluorinated SEI, the present invention synergistically solves the core problems of dendrite growth, sluggish ion transport, and interface instability in anode-free batteries, providing an innovative technical path for high-safety and high-energy-density lithium metal batteries.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements do not make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. Design method of high-entropy MXene-high-viscosity colloid composite coating battery separator, characterized in that, It includes the following steps: S1. Place the multi-layer high-entropy MAX phase raw material, i.e., TiVNbMoAlC3, in a mixed solution of lithium fluoride and hydrochloric acid for etching treatment. After washing with deionized water until neutral, cycle stripping is carried out through a high-pressure homogenizer, and high-entropy MXene nanosheets rich in fluorinated functional groups on the surface, namely TiVNbMoC3 nanosheets, are obtained by centrifugal separation; S2. Dissolve polyacrylamide colloid in deionized water and stir evenly at a constant speed to form a homogeneous adhesive solution; S3. Disperse the high-entropy MXene nanosheets in S1 in the polyacrylamide colloid in S2 and mix through a high-speed homogenizer to form a high-entropy MXene / polyacrylamide mixed slurry; S4. Uniformly coat the mixed slurry in S3 on the surface of the polypropylene separator by the wire bar coating process, and then form a dense composite coating through gradient temperature drying; S5. Bond the coated separator in S4 and the copper current collector through a soft-pack process of first hot pressing and then injecting liquid to form an integrated interface structure.

2. The design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator according to claim 1, wherein In S1, the composition of the mixed solution of lithium fluoride and hydrochloric acid is: 1 g of lithium fluoride, the concentration of hydrochloric acid is 12 mol / L, and the usage amount of hydrochloric acid is 40 mL; the high-entropy MAX raw material is 1 g; The etching temperature for the etching treatment is 45 °C, and the treatment time is 72 h; the working pressure of the high-pressure homogenizer is 1100 - 1200 MPa, and the number of cycle treatments is 10 - 15 times.

3. The design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator according to claim 1, wherein In S1, the single-layer thickness of the high-entropy MXene nanosheets is 1 - 2 nm, and the number of layers is 3 - 5 layers.

4. The design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator according to claim 1, characterized in that, In S2, the stirring time for generating the homogeneous adhesive solution is 4 - 6 h, and the mass concentration of the adhesive solution is 8% - 12%.

5. The design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator according to claim 1, wherein In S3, the rotation speed of the high-speed homogenizer is 2000 r / min, the mixing time is 30 - 60 min, and the viscosity of the slurry is controlled at 500 - 800 mPa·s.

6. The design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator according to claim 1, wherein In S3, the mass ratio of high-entropy MXene to polyacrylamide in the high-entropy MXene / polyacrylamide mixed slurry is 8:1, and the solid content of the slurry is 25%.

7. The design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator according to claim 1, characterized in that In S4, the wire bar coating process uses an OSP-1.5 type wire bar, the coating speed is 0.5 - 1.5 m / min, and the thickness of the dried coating is 4 - 5 μm.

8. The design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator according to claim 1, wherein In S4, the thickness of the polypropylene separator substrate is 12 - 16 μm, and the drying conditions are pre-baking at 40 °C for 1 h and final baking at 60 °C for 6 h.

9. The design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator according to claim 1, characterized in that In S5, the hot pressing temperature of the hot pressing process is 80 °C, the pressure is 0.5 MPa, and the pressure holding time is 30 - 60 s.

10. The composite coating separator prepared by the design method of the high-entropy MXene-high-viscosity colloid composite coating battery separator according to any one of claims 1-9, characterized in that, The lithium ion transference number of the separator is 0.76, and the fracture energy is 50.15 J / m 3 , and the capacity retention rate is 82.6% after 100 cycles in the non-anode soft-pack battery.

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