CN117936889A

CN117936889A - Asymmetric composite electrolyte and preparation method and application thereof

Info

Publication number: CN117936889A
Application number: CN202410009020.9A
Authority: CN
Inventors: 卢侠; 杜光远; 卢学毅; 钱果裕
Original assignee: Sun Yat Sen University
Current assignee: Sun Yat Sen University
Priority date: 2024-01-03
Filing date: 2024-01-03
Publication date: 2024-04-26

Abstract

The invention belongs to the technical field of batteries, and particularly discloses an asymmetric composite electrolyte and a preparation method and application thereof. The composite electrolyte has an asymmetric double-layer structure, wherein the upper layer is a matrix rich in polymer, and the lower layer is a filler rich in organic metal frame material. The invention adopts a natural gravity sedimentation method to construct an asymmetric composite electrolyte structure at one time, thereby reducing the microcosmic interface of the electrolyte and improving the ion conductivity of the electrolyte; meanwhile, compared with layered composite electrolyte, the one-piece structure constructed at one time has better mechanical strength and toughness, and can effectively inhibit puncture of lithium dendrite. The ionic conductivity of the prepared composite electrolyte at room temperature is up to 8mS/cm, the electrochemical stability can be up to 4.75V, the tensile deformation can be up to 758 percent, and the composite electrolyte is suitable for various commercial anodes.

Description

Asymmetric composite electrolyte and preparation method and application thereof

Technical Field

The invention belongs to the technical field of batteries, and particularly relates to an asymmetric composite electrolyte, a preparation method and application thereof.

Background

Since commercialization, lithium ion batteries have taken the dominant role in the field of mobile energy storage, and are applied to mobile phones, notebook computers, electric automobiles, electric ships and the like. Through continuous optimization and iteration, the main components of the lithium ion battery, such as anode and cathode materials, a diaphragm, a current collector and even a battery module form are all close to the optimal, so that the energy density of the lithium ion battery is continuously approaching the theoretical limit. Nevertheless, the energy density of the traditional lithium ion battery still cannot meet the requirement of people on long endurance, for example, the theoretical energy density of a lithium iron phosphate battery is about 200Wh kg ^-1, and the theoretical energy density of a ternary lithium battery is about 300Wh kg ^-1. As a solution for replacing the graphite cathode, a new combination mode of the lithium metal cathode and the high-energy anode is expected to make a great breakthrough in energy density. However, if the battery is considered as an energy-containing system, the higher the energy, the higher the risk and the irreconcilable nature of the contradiction between high energy content and high safety.

Currently, commercial lithium ion batteries are mostly built based on liquid organic electrolyte. However, the inflammable and leaking property of the organic electrolyte of the liquid leads to serious safety problems of commercial lithium ion batteries, and the commercial lithium ion batteries are difficult to cope with severe working conditions. And when lithium metal is used as the negative electrode and a high-energy material is used as the positive electrode, serious safety problems such as short circuit, thermal runaway and explosion can be caused due to long dendrite of the negative electrode. The use of a solid electrolyte instead of a liquid organic electrolyte is expected to substantially improve the safety of the battery. Generally, solid electrolytes can be divided into three general categories, respectively: polymer electrolytes, inorganic solid electrolytes, and composite electrolytes. The polymer electrolyte is soft in texture, easy to form good interface contact with the electrode, and good in processability. However, the electrochemical stability is insufficient, the high-voltage positive electrode material is difficult to match, the texture is soft and difficult to resist dendrite penetration, and more importantly, the room-temperature ionic conductivity is low, so that the room-temperature operation of the solid-state battery is difficult to ensure. In contrast, the inorganic solid electrolyte has good electrochemical stability and room temperature ionic conductivity, but is hard and brittle in texture, difficult to process, low in matching degree with the existing lithium ion battery production line in the preparation process, and can influence the capacity exertion of the battery due to huge interface impedance after being assembled into a solid battery. As a new choice of 'hardness and softness and combination', the composite electrolyte has the advantages of polymer electrolyte and inorganic solid electrolyte, is easy to process, has good comprehensive performance, and can form effective interface contact with electrodes, so the composite electrolyte is considered as the solid electrolyte with the most application prospect at the present stage.

As a core component of a solid-state battery, good interfacial compatibility and interfacial stability between the solid-state electrolyte and the anode and cathode materials will directly determine the capacity exertion and cycle life of the battery. The positive electrode material particles undergo volume expansion and contraction during cycling, which causes the positive electrode-electrolyte interface to be detached, degrading the ion transport path, and further affecting the battery performance. Lithium metal anodes can cause uneven deposition of lithium metal during cycling due to uneven ion flow or surface topography and thereby induce dendrite growth. It follows that in solid state lithium metal batteries, the starting point and requirements for interface modification are different, in particular to the positive and negative electrode side. Therefore, the development of the composite electrolyte with the asymmetric structure, which is simple and convenient to prepare and low in cost, and can be respectively matched with the interface requirements of the anode and the cathode and the electrolyte, is very necessary. In addition, lithium, sodium and potassium are in the same main group of the periodic table of elements and have similar physicochemical properties, so that the development of solid-state sodium metal batteries and potassium metal batteries based on successful experience is also a necessary choice and optimal approach for eliminating anxiety of lithium resources.

Disclosure of Invention

The present invention aims to solve at least one of the technical problems in the prior art described above. Therefore, the invention provides an asymmetric composite electrolyte, a preparation method and application thereof, wherein the composite electrolyte has high room-temperature ionic conductivity and excellent mechanical properties, has wide adaptability and can be simultaneously applied to solid-state lithium metal batteries, solid-state sodium metal batteries and solid-state potassium metal batteries; the preparation method is simple and easy to implement, and is suitable for large-scale production.

The invention is characterized in that: according to the invention, the polymer is taken as a matrix, the organic metal frame material is taken as a filler, the filler is dispersed in a polymer solution for pouring, and filler particles naturally settle to the bottom under the action of gravity in the solvent evaporation process, so that an asymmetric structure with the upper layer rich in the polymer matrix and the lower layer rich in filler particles is formed. Wherein: one side rich in polymer (such as polyvinylidene fluoride-hexafluoropropylene, PVDF-HFP) is more soft and elastic, so that the interface contact with the positive electrode material can be improved, the interface contact between the positive electrode material and the positive electrode material can be dynamically maintained in the circulation process, and a certain buffer effect can be provided when the positive electrode material expands or contracts; the cathode side is rich in organic metal frame material (such as copper-based microporous metal skeleton, HKUST-1) so that the cathode side has higher mechanical strength and better dendrite penetration resistance, and the ion flow can be regulated through a special pore channel structure of the organic metal frame material, thereby achieving the purpose of uniform deposition of alkali metal and further fundamentally eliminating hidden danger of dendrite growth.

To solve the above technical problem, a first aspect of the present invention provides a composite electrolyte having an asymmetric bilayer structure, wherein an upper layer is a polymer-rich matrix, and a lower layer is a filler rich in an organometallic framework material.

Specifically, the composite electrolyte of the invention consists of a polymer-rich matrix and a filler rich in an organometallic framework material, and the two materials form an asymmetric double-layer structure. Wherein: the organic metal frame material can reduce the crystallinity of the polymer matrix and improve the ion conductivity of the composite electrolyte; at the same time, the uniform ion flow can be induced by the special pore structure to induce the uniform deposition of lithium/sodium metal, thus eliminating dendrite growth. The polymer can improve the interface contact with the positive electrode material, dynamically maintain the interface contact between the positive electrode material and the polymer in the circulation process, and provide a certain buffer function when the positive electrode material expands or contracts. The combined action of the two materials gives the electrolyte high ionic conductivity and excellent mechanical properties.

Preferably, the polymer comprises polyvinylidene fluoride-hexafluoropropylene.

Preferably, the organic metal framework material is a copper-based microporous metal framework, and the particle size of the organic metal framework material is 300-500nm.

Preferably, the mass ratio of the matrix to the filler is (1-100): 1, a step of; further preferably, the mass ratio of the matrix to the filler is (1-50): 1, a step of; still more preferably, the mass ratio of the matrix to the filler is (1-25): 1.

Preferably, the thickness of the composite electrolyte is 1-50 μm; further preferably, the thickness of the composite electrolyte is 1 to 25 μm; still more preferably, the thickness of the composite electrolyte is 15-25 μm.

The second aspect of the present invention provides a method for preparing the above composite electrolyte, comprising the steps of:

(1) Providing or preparing an organometallic framework material;

(2) Adding the organic metal frame material into the polymer solution under the condition of stirring, and dispersing to obtain a composite electrolyte solution;

(3) Pouring the composite electrolyte solution into a mould, evaporating the solvent, and obtaining the composite electrolyte with an asymmetric double-layer structure under the action of gravity.

Specifically, when the composite electrolyte is prepared, an asymmetric composite electrolyte structure is constructed at one time by adopting a natural gravity sedimentation method, so that a microscopic interface of the asymmetric composite electrolyte structure only exists between a polymer matrix and a filler. Since mutations in physical/chemical properties usually occur at the "interfaces", the presence of interfaces should be reduced as much as possible under conditions where the electrolyte is able to achieve the intended purpose of concern, the more interfaces the more instability factors. Therefore, the composite electrolyte prepared by the invention has more efficient ionic conduction compared with electrolytes with interfaces of multiple types because of only one type of interface. Meanwhile, the composite electrolyte prepared by the invention is of an integrated structure constructed at one time, and has better mechanical strength and toughness and better advantage in the aspect of inhibiting dendrite penetration compared with layered composite electrolytes.

Preferably, the mass concentration of the composite electrolyte solution is 20-80%; further preferably, the mass concentration of the composite electrolyte solution is 40 to 60%. The invention controls the thickness of the composite electrolyte by controlling the dosage of the composite electrolyte solution.

Preferably, the solvent of the polymer solution is N, N-Dimethylformamide (DMF); further preferably, the water content of the solvent is 4 to 6wt%.

Preferably, in the step (2), the stirring speed is 8000-10000 rpm.

Preferably, in the step (2), the dispersion is magnetic stirring at a rotational speed of 8000-10000 rpm.

Preferably, the material of the mold is polytetrafluoroethylene.

Preferably, in step (3), the solvent evaporates at a temperature of 50-200 ℃; further preferably, the solvent evaporates at a temperature of 50-150 ℃.

Preferably, in step (3), the solvent is evaporated for a period of 0.5 to 3 hours; further preferably, the solvent is evaporated for a time of 0.5 to 1.5 hours.

As a further improvement of the above solution, the preparation of the organometallic framework material comprises the steps of:

mixing copper salt solution and organic ligand solution, and standing to obtain a reaction product; and then separating, washing and drying the reaction product to obtain the organic metal framework material.

Preferably, the copper salt solution is a copper nitrate solution.

Preferably, the organic ligand solution is a1, 3, 5-benzene-trimethyl acid solution.

Preferably, in the solution obtained by mixing the copper salt solution and the organic ligand solution, the concentration of the copper salt is 1-4mmol/L, the concentration of the organic ligand is 5-7mmol/L, and the solvent is methanol.

Preferably, the time of the standing is 10 to 14 hours.

Preferably, the reaction product is separated and washed by suction filtration and the detergent is methanol.

Preferably, the drying temperature is 140-160 ℃, the drying time is 10-14 hours, and the drying is mainly used for removing the residual solvent in the pore canal of the material.

A third aspect of the present invention provides a solid-state battery comprising the above-described composite electrolyte; or a composite electrolyte prepared by the preparation method of the composite electrolyte.

Preferably, the solid-state battery further comprises a positive electrode and a negative electrode, the active material of the positive electrode is an organic positive electrode material, and the organic positive electrode material is perylene-3, 4,9, 10-tetracarboxylic dianhydride (PTCDA). The organic positive electrode material is easy to dissolve in the electrolyte, and the problem of capacity fading caused by the organic positive electrode material can be overcome by using the composite electrolyte and greatly reducing the electrolyte consumption, so that the stable circulation of the organic positive electrode material in the solid-state alkali metal battery is realized.

Preferably, the solid-state battery is a solid-state lithium metal battery, a solid-state sodium metal battery or a solid-state potassium metal battery.

Compared with the prior art, the technical scheme of the invention has at least the following technical effects or advantages:

(1) The composite electrolyte has an asymmetric double-layer structure, wherein the upper layer is a matrix rich in polymer, and the lower layer is a filler rich in organic metal frame material, and the composite electrolyte comprises: the organic metal frame material (such as HKUST-1) has a multifunctional function, on one hand, the crystallinity of the polymer matrix can be reduced, and the ion conductivity of the composite electrolyte can be improved; on the other hand, the uniform ion flow can be induced by the special pore structure to induce the uniform deposition of lithium/sodium metal, thereby eliminating dendrite growth. The "soft-elastic" properties of the polymer (e.g., PVDF-HFP) are effective in improving interfacial contact with the positive electrode material and dynamically maintaining interfacial contact therebetween during cycling, providing a cushioning effect as the positive electrode material expands or contracts.

(2) The invention adopts a natural gravity sedimentation method to construct an asymmetric composite electrolyte structure at one time, thereby reducing the microcosmic interface of the electrolyte and improving the ion conductivity of the electrolyte; meanwhile, compared with layered composite electrolyte, the one-piece structure constructed at one time has better mechanical strength and toughness, and can effectively inhibit the penetration of dendrites.

(3) The preparation method of the composite electrolyte is simple and feasible, does not need expensive preparation equipment and severe preparation conditions, and can realize rapid production in a large scale at low cost. Meanwhile, the effective thickness adjustment can be performed by controlling the dosage of the composite electrolyte solution so as to further reduce the thickness of the electrolyte and improve the energy density of the solid-state battery.

(4) The ionic conductivity of the composite electrolyte prepared by the invention at room temperature is up to 8mS/cm, the electrochemical stability can be up to 4.75V, the tensile deformation can be up to 758 percent, and the composite electrolyte is suitable for various commercial anodes.

Drawings

FIG. 1 is an SEM image of HKUST-1 prepared in example 1;

FIG. 2 is an XRD pattern of HKUST-1 prepared in example 1;

FIG. 3 is a physical diagram of the composite electrolyte prepared in example 2;

FIG. 4 is a graph of the ionic conductivity at room temperature of the composite electrolytes prepared in examples 2-6 at different filler levels;

FIG. 5 is a graph showing electrochemical stability tests of the composite electrolytes of examples 2 to 6 having different filler contents and the electrolyte of comparative example 1;

FIG. 6 is a graph showing the wettability of the composite electrolyte prepared in example 5 to an electrolyte;

FIG. 7 is a graph showing the wettability of the electrolyte of comparative example 2 with respect to the electrolyte;

Fig. 8 is a cycle performance and rate performance of a solid lithium metal battery assembled from the composite electrolyte prepared in example 5;

Fig. 9 is a cycle performance and corresponding charge-discharge curve, rate performance and corresponding charge-discharge curve of a solid state sodium metal battery assembled from the composite electrolyte prepared in example 5;

Fig. 10 is a cycle performance and rate performance of a solid state potassium metal battery assembled from the composite electrolyte prepared in example 5;

fig. 11 is a stress-strain curve of the composite electrolyte prepared in example 5.

Detailed Description

The present invention is described in detail below with reference to examples to facilitate understanding of the present invention by those skilled in the art. It is specifically pointed out that the examples are given solely for the purpose of illustration of the invention and are not to be construed as limiting the scope of the invention, since numerous insubstantial modifications and variations of the invention will be within the scope of the invention, as described above, will become apparent to those skilled in the art. Meanwhile, the raw materials mentioned below are not specified, and are all commercial products; the process steps or preparation methods not mentioned in detail are those known to the person skilled in the art.

Example 1

A method of preparing a metal organic framework material comprising the steps of:

Copper nitrate (Cu (NO ₃)₂·3H₂ O) and 1,3, 5-benzene-tricarboxylic acid are dissolved in 100mL of methanol solution, the molar concentration of copper nitrate is 3mmol/L, the molar concentration of 1,3, 5-benzene-tricarboxylic acid is 6mmol/L in the obtained mixed solution, the mixed solution is stirred and mixed uniformly, the mixture is stood for 12 hours to obtain HKUST-1 particles as a reaction product, then the reaction product is separated and washed, the used washing solution is methanol, finally the mixture is dried for 12 hours at the vacuum of 150 ℃ to remove residual solvent in a pore canal of the HKUST-1, and the metal organic frame material is recorded as HKUST-1.

FIG. 1 is a SEM morphology of HKUST-1 particles prepared in example 1. As can be seen from FIG. 1, HKUST-1 particles are uniform in size and about 300-500nm in particle size, and some degree of agglomeration occurs between the particles due to large surface area.

FIG. 2 is an XRD pattern of HKUST-1 particles prepared in example 1, wherein: the abscissa 2θ represents the diffraction angle, and the ordinate Intensity represents the Intensity of the diffraction peak. As can be seen from FIG. 2, HKUST-1 was prepared with good crystallinity.

Example 2

A method for preparing a composite electrolyte, comprising the steps of:

Dissolving PVDF-HFP of a polymer matrix in DMF (dimethyl formamide) by stirring (the rotation speed is 10000 revolutions per minute) to obtain a polymer solution; deionized water (5 wt% of the polymer solution) was then added thereto and stirring continued; adding HKUST-1 prepared in example 1 (the mass fraction of HKUST-1 in the polymer solution is 1.5 wt%) under stirring, and continuously stirring at the same rotating speed for 3 hours to obtain a composite electrolyte solution with the mass concentration of 50%; then, the composite electrolyte solution was poured into a polytetrafluoroethylene mold, dried at 120℃for 3 hours, and the solvent was evaporated, and under the action of gravity, the composite electrolyte having the asymmetric bilayer structure of this example was prepared, which was designated as PH-1.5HK.

Fig. 3 is a physical diagram of the composite electrolyte prepared in example 2, in which: FIG. 3a is a lower layer of a composite electrolyte, i.e., HKUST-1 enriched fraction, showing a blue color; FIG. 3b shows the upper layer of the composite electrolyte, i.e., the PVDF-HFP rich portion, which appears white, and is slightly blue due to the too thin thickness of the composite electrolyte and the blue color transmission of the lower layer; thus, the composite electrolyte prepared by the invention has an asymmetric double-layer structure.

Example 3

Referring to the preparation method of the composite electrolyte of example 1, only the mass fraction of HKUST-1 in the polymer solution was changed to 3wt%, and the composite electrolyte having an asymmetric bilayer structure of this example was prepared, which was designated as PH-3HK.

Example 4

Referring to the preparation method of the composite electrolyte of example 1, only the mass fraction of HKUST-1 in the polymer solution was changed to 4.5wt%, and the composite electrolyte having the asymmetric bilayer structure of this example was prepared, which was designated as PH-4.5HK.

Example 5

Referring to the preparation method of the composite electrolyte of example 1, only the mass fraction of HKUST-1 in the polymer solution was changed to 6wt%, and the composite electrolyte having an asymmetric bilayer structure of this example was prepared, which was designated as PH-6HK.

Example 6

Referring to the preparation method of the composite electrolyte of example 1, only the mass fraction of HKUST-1 in the polymer solution was changed to 7.5wt%, and the composite electrolyte having the asymmetric bilayer structure of this example was prepared, which was designated as PH-7.5HK.

Comparative example 1

A method of preparing an electrolyte comprising the steps of:

Dissolving PVDF-HFP of a polymer matrix in DMF (dimethyl formamide) by stirring (the rotation speed is 10000 revolutions per minute) to obtain a polymer solution; then deionized water (the addition amount is 5wt percent of the polymer solution) is added into the solution, and stirring is continued to obtain electrolyte solution with the mass concentration of 50 percent; subsequently, the electrolyte solution was poured into a polytetrafluoroethylene mold, and dried at 120℃for 3 hours, and the solvent was evaporated to prepare an electrolyte of this example, which was designated as pure PH.

Comparative example 2

Commercial battery separator Celgard-2500.

Performance testing

1. Ion conductivity

The composite electrolyte prepared in examples 2-6 was clamped by two stainless steel blocking electrodes, assembled into a CR2032 button cell, and tested for room temperature ionic conductivity, the composite electrolyte was first subjected to an electrolyte [ NaPF ₆ electrolyte with a concentration of 1mol/L ] prior to testing, and the solvent was a volume ratio of 1:1 (EC)/dimethyl carbonate (DMC) was soaked in the mixed solvent of EC/DMC) for 1 minute. The test results are shown in FIG. 4, and the content of HKUST-1 is indicated by the Filler content on the abscissa in FIG. 4; as can be seen from FIG. 4, when the content of HKUST-1 filler was 6wt%, the sodium ion conductivity at room temperature corresponding to the composite electrolyte reached a peak value exceeding 8mS/cm.

2. Electrochemical stability

The composite electrolytes prepared in examples 2 to 6 and comparative example 1 were assembled into CR2032 button cells, respectively, and linear sweep voltammetry was performed, the test results are shown in fig. 5, the abscissa Potential in fig. 5 represents voltage, and the ordinate Current represents Current; as can be seen from FIG. 5, the electrochemical stability of each composite electrolyte can reach 4.75V (vs. Na ⁺/Na).

3. Wettability by water

Electrolyte wettability experiments were performed on the composite electrolyte prepared in example 5 and the commercial battery separator Celgard-2500 of comparative example 2, respectively, as follows:

5 mu L of electrolyte (NaPF ₆ electrolyte with 1mol/L concentration) is respectively taken, and the volume ratio of the solvent is 1:1 Ethylene Carbonate (EC)/dimethyl carbonate (DMC) mixed solvent the composite electrolyte prepared in example 5 and the commercial battery separator Celgard-2500 of comparative example 2 were dropped and photographed immediately, and the results are shown in fig. 6 to 7. As can be seen from fig. 6 to 7, the electrolyte was dropped on the composite electrolyte prepared in example 5 to exhibit a contact angle of 29.7 °/26.2 °; whereas the electrolyte was dripped onto the commercial battery separator Celgard-2500 of comparative example 2, exhibited a contact angle of 75.2 °/74.4 °. Therefore, the wettability of the asymmetric structure composite electrolyte prepared by the invention to electrolyte is obviously better than that of a common commercial Celgard-2500 diaphragm.

4. Cycling stability and rate capability of solid state lithium metal batteries

The lithium metal negative electrode, the composite electrolyte prepared in example 5, and the PTCDA positive electrode were assembled into a solid-state lithium metal battery in an argon glove box, and cycle performance and rate performance tests were performed, the results of which are shown in fig. 8, in which: fig. 8a is a Cycle performance, fig. 8b is a rate performance, the abscissa indicates the number of cycles, the left ordinate SPECIFIC CAPACITY indicates a specific capacity, the right ordinate Coulombic efficiency indicates coulombic efficiency, charge indicates Charge, and Discharge indicates Discharge. As can be seen from fig. 8a, after 10 weeks of current activation at 0.1C, the test was continued at a current density of 0.5C, with little capacity decay and stable coulombic efficiency during the 70 week cycle. As can be seen from fig. 8b, the specific capacity of about 110mAh/g is still obtained when the current density is increased to 1C, and the capacity is restored when the current density is restored to 0.5C. Therefore, the solid-state lithium metal battery based on the asymmetric structure composite electrolyte and the PTCDA positive electrode has good cycle stability and rate capability.

Wherein: the PTCDA positive electrode was prepared using a knife coating method: namely PTCDA, conductive carbon black and binder polyvinylidene fluoride (PVDF) at 7:2:1 in N-methylpyrrolidone (NMP) to obtain an electrode slurry, then knife-coating it on an aluminum foil, and drying at 120 ℃ to obtain a PTCDA positive electrode.

5. Cycling stability and rate capability of solid state sodium metal batteries

The sodium metal negative electrode, the composite electrolyte prepared in example 5 and the PTCDA positive electrode were assembled into a solid sodium metal battery in an argon glove box, and the cycle performance and the rate performance were tested, and the preparation method of the PTCDA positive electrode was the same as in the performance test of the solid lithium metal battery, and the test results are shown in fig. 9. Wherein: fig. 9a and 9b are respectively cycle performance and corresponding charge-discharge graphs; fig. 9c and 9d are the rate performance and the corresponding charge-discharge curves, respectively. As can be seen from fig. 9a, the solid sodium metal battery has a specific capacity of about 140mAh/g at a current density of 0.2C, and the capacity remains stable during the 50 week cycle. As can be seen from fig. 9b, the charge-discharge curve at week 20 and the charge-discharge curve at week 40 overlap well, indicating that the reaction occurring in the solid sodium metal battery is stable and highly reversible, and the battery capacity remains good during cycling. As can be seen from fig. 9C and 9d, the solid sodium metal battery still has a specific capacity of about 130mAh/g when the current density is increased by 1C, and the polarization change between the charge and discharge curves is small during the current density increase. From this, it is shown that the solid state sodium metal battery based on the asymmetric structured composite electrolyte and PTCDA positive electrode has good rate performance.

6. Cycling stability and rate capability of solid state potassium metal batteries

The potassium metal negative electrode, the composite electrolyte prepared in example 5 and the PTCDA positive electrode were assembled into a solid-state potassium metal battery in an argon glove box, and the cycle performance and the rate performance were tested, the preparation method of the PTCDA positive electrode was the same as in the performance test of the solid-state lithium metal battery described above, and the test results are shown in fig. 10, wherein: fig. 10a shows cycle performance, and fig. 10b shows rate performance. As can be seen from fig. 10a, after 10 weeks of current activation at 0.1C, the test was continued at a current density of 0.5C, with little capacity decay and stable coulombic efficiency during the 60 week cycle. As can be seen from fig. 10b, the specific capacity of more than 130mAh/g is still provided when the current density is increased to 0.5C, and the rate performance is good; as the current density increases to 1C, the specific capacity approaches 120mAh/g and when the current density is restored, the specific capacity is restored accordingly. Therefore, the solid-state potassium metal battery based on the asymmetric structure composite electrolyte and the PTCDA positive electrode has good cycle stability and rate capability.

7. Mechanical strength

Fig. 11 is a Stress-Strain graph of the composite electrolyte prepared in example 5, and in fig. 11, stress represents tensile deformation and Stress represents pressure. As can be seen from FIG. 11, the asymmetric structure composite electrolyte prepared by the invention has tensile deformation as high as 758%, has excellent toughness and can effectively inhibit dendrite penetration.

It will be apparent to those skilled in the art that several simple deductions or substitutions may be made without departing from the inventive concept. Accordingly, it is intended that all such modifications as would be within the scope of this invention be included within the scope of this invention. The above embodiments are preferred embodiments of the present invention, and all similar processes and equivalent modifications are intended to fall within the scope of the present invention.

Claims

1. The composite electrolyte is characterized by having an asymmetric double-layer structure, wherein the upper layer is a polymer-rich matrix, and the lower layer is a filler rich in an organometallic framework material.

2. The composite electrolyte of claim 1 wherein the polymer comprises polyvinylidene fluoride-hexafluoropropylene.

3. The composite electrolyte of claim 1, wherein the organometallic framework material is a copper-based microporous metal framework, and the organometallic framework material has a particle size of 300-500nm.

4. The composite electrolyte of claim 1, wherein the mass ratio of the matrix to the filler is (1-100): 1.

5. The composite electrolyte of claim 1, wherein the composite electrolyte has a thickness of 1-50 μm.

6. A method for producing the composite electrolyte according to any one of claims 1 to 5, comprising the steps of:

(1) Providing or preparing an organometallic framework material;

7. The method of preparing a composite electrolyte according to claim 6, wherein the preparation of the organometallic framework material comprises the steps of:

8. The method for producing a composite electrolyte according to claim 7, wherein the copper salt solution is a copper nitrate solution; and/or the organic ligand solution is a1, 3, 5-benzene-trimethyl acid solution.

9. The method for producing a composite electrolyte according to claim 6, wherein the mass concentration of the composite electrolyte solution is 20 to 80%.

10. A solid-state battery comprising the composite electrolyte according to any one of claims 1 to 5; or a composite electrolyte produced by the production method comprising the composite electrolyte according to any one of claims 6 to 9.