Organic-inorganic composite solid electrolyte as well as preparation method and application thereof

Abstract

The invention discloses an organic-inorganic composite solid electrolyte as well as a preparation method and application thereof. The solid electrolyte comprises polyethylene oxide, lithium salt and semiconductor nanocrystals. According to the invention, the semiconductor nanocrystal is used as an inorganic filler to be compounded with the PEO-based organic polymer solid electrolyte, the adjustability of the semiconductor nanocrystal component and structure and the flexibility of surface modification are utilized, the crystallization of PEO at normal temperature is obviously inhibited, and a high ionic conductance interface is formed. Through surface ligand modification, the semiconductor nanocrystal can obtain good dispersibility in a PEO matrix, so that dissociation and transmission of lithium ions in a lithium salt are effectively promoted, and the organic-inorganic composite solid electrolyte membrane has relatively high ionic conductivity. Through cladding treatment, the stability of the semiconductor nanocrystal in the PEO can also be remarkably improved. The solid electrolyte can effectively improve the ion transmission performance of the PEO-based solid electrolyte at the conventional working temperature of the lithium ion battery.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and particularly to an organic-inorganic composite solid electrolyte, a preparation method thereof, and an application thereof. Background Art

[0002] Driven by the increasing global energy demand, the development of safe and reliable high-energy and high-power energy storage devices has become a research hotspot in the energy field. Due to their high energy density and recyclability, lithium-ion batteries have been the main energy storage solution for portable electronic devices and electric vehicles since their inception. However, traditional lithium-ion batteries use organic liquid electrolytes, which have a relatively high flammability during battery operation, posing a safety hazard. In addition, during the charge and discharge cycle process, the solid electrolyte interface film will be repeatedly broken down and regenerated, resulting in the loss of liquid electrolyte. Therefore, traditional lithium-ion batteries usually contain additional electrolytes to compensate for the loss of electrolyte during long-cycle operation, but this increases the manufacturing cost of lithium-ion batteries.

[0003] In response to the limitations of organic liquid electrolytes, researchers have developed all-solid-state batteries prepared using solid electrolytes, lithium metal anodes, and high-voltage cathodes. Because most solid electrolytes are non-flammable and have a wider operating temperature range, all-solid-state batteries are much safer than liquid batteries in the event of a battery short circuit. Reported solid electrolytes include inorganic solid electrolytes and organic solid electrolytes. Compared with inorganic solid electrolytes, organic solid electrolytes have better processability, higher wettability with electrodes, and smaller contact resistance generated, thus attracting the attention of many researchers. Among organic solid electrolytes, polyethylene oxide (PEO) has become the most intensively studied material in organic solid electrolytes because it has a relatively high dielectric constant and strong lithium-ion solvation performance, and its chain segments have a relatively high lithium-ion donor number and flexibility, which can promote the transport of lithium ions. However, so far, PEO-based solid electrolytes have not reached the performance for full commercial application. This is mainly because PEO contains a large number of crystalline regions at room temperature, resulting in serious inhibition of ion transport performance and limiting the application of such materials in solid-state lithium-ion batteries.

[0004] Therefore, how to improve the ion transport performance of PEO-based solid electrolytes at the conventional operating temperature of lithium-ion batteries has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] In order to improve the above technical problems, the present invention provides a solid electrolyte, which comprises polyethylene oxide (PEO), a lithium salt, and semiconductor nanocrystals.

[0006] According to an embodiment of the present invention, the mass ratio of semiconductor nanocrystals, lithium salt, and PEO in the solid electrolyte is (0.01 - 0.2):(0.15 - 1):1, and examples are 0.05:0.3:1, 0.1:0.3:1, 0.1:0.3:1, 0.01:0.15:1, 0.01:0.5:1, 0.01:1:1, 0.2:0.15:1, 0.2:0.5:1, 0.2:1:1.

[0007] According to an embodiment of the present invention, the solid electrolyte is in the form of a film. For example, the thickness of the solid electrolyte film is 1 - 100 μm, and examples are 1 μm, 2 μm, 5 μm, 10 μm, 20 μm, 50 μm, 80 μm, 100 μm.

[0008] According to an embodiment of the present invention, the molecular weight of the PEO is 500,000 - 700,000, and examples are 500,000, 550,000, 600,000, 650,000, 700,000.

[0009] According to an embodiment of the present invention, the lithium salt is selected from one or more of lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(oxalato)borate.

[0010] According to an embodiment of the present invention, the semiconductor nanocrystals can be at least one of II-VI group nanocrystals such as CdSe, III-V group nanocrystals such as InP, I-III-VI group nanocrystals such as Cu-In-Se, and single-element nanocrystals such as carbon, phosphorus, sulfur, silicon, and germanium.

[0011] According to an embodiment of the present invention, the size of the semiconductor nanocrystals is 1 - 100 nm, and examples are 1 nm, 2 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm.

[0012] According to an embodiment of the present invention, the semiconductor nanocrystals are semiconductor nanocrystals with ligands on the surface and / or semiconductor nanocrystals with a core-shell structure.

[0013] For example, the ligand is coordinated and bound to the semiconductor nanocrystals through one or more of carboxyl, phosphonic acid group, sulfonic acid group, amine group, phosphine group, and phosphine oxide group to the metal ions on the surface of the semiconductor nanocrystals.

[0014] For example, the shell layer of the semiconductor nanocrystals with a core-shell structure is bonded to the semiconductor nanocrystal core through a covalent bond or an ionic bond.

[0015] According to an embodiment of the present invention, the ligand is an organic ligand. Preferably, the organic ligand has one or more of a carboxyl group, a phosphonic acid group, a sulfonic acid group, an amine group, a phosphine group, and a phosphine oxide group. According to an embodiment of the present invention, the organic ligand is an organic ligand having one or more functional groups selected from a carboxyl group, a phosphonic acid group, a sulfonic acid group, an amine group, a phosphine group, and a phosphine oxide group and having 4 to 20 carbon atoms. Exemplarily, the organic ligand may be methanesulfonic acid or hexamethylenediaminetetramethylenephosphonic acid.

[0016] According to an embodiment of the present invention, the organic ligand is a monodentate ligand (one ligand molecule contains one coordination functional group) or a polydentate ligand (one ligand molecule contains two or more coordination functional groups). Preferably, the number of coordination functional groups on the surface of each semiconductor nanocrystal can be 1 to 8, exemplarily 1, 2, 3, 4, 5, 6, 7, 8.

[0017] According to an embodiment of the present invention, the ratio of the number of the organic ligands to the surface area of the semiconductor nanocrystals is 0.2 to 4 molecules per square nanometer. In the present invention, the surface area of the semiconductor nanocrystals is determined by measuring the length, width, height, or diameter of the nanocrystals through transmission electron microscopy.

[0018] According to an embodiment of the present invention, the semiconductor nanocrystals having a core-shell structure are prepared by coating the semiconductor nanocrystals. For example, the shell material used for the coating treatment is one or more of oxides, sulfides, selenides, and halides. For example, the shell material may be silicon oxide or titanium oxide.

[0019] According to an embodiment of the present invention, the thickness of the shell material used for the coating treatment is 0.5 to 50 nm.

[0020] According to an embodiment of the present invention, the method for ligand exchange or coating treatment of the semiconductor nanocrystals includes mixing the semiconductor nanocrystals with a ligand or a precursor of the shell material and reacting to obtain the semiconductor nanocrystals.

[0021] Preferably, the reaction is carried out in the presence of a solvent. For example, the solvent is n-hexane. Also, for example, the semiconductor nanocrystals are first dissolved in the solvent to obtain a nanocrystal colloidal solution, and then mixed with the ligand or the precursor of the shell material.

[0022] In one embodiment of the present invention, the concentration of the nanocrystal colloidal solution can be 0.5 to 2 M, exemplarily 0.5 M, 1 M, 2 M.

[0023] In one embodiment of the present invention, the molar ratio of the semiconductor nanocrystals to the ligand or the precursor of the shell material is 1:(0.01 to 0.2), exemplarily 1:0.01, 1:0.05, 1:0.1, 1:0.2.

[0024] In one embodiment of the present invention, the shell material precursor can be, for example, tetraethyl orthosilicate or titanium tetrachloride.

[0025] According to an embodiment of the present invention, the synthesis method of the semiconductor nanocrystals is an oil-phase method or a water-phase method.

[0026] According to an exemplary embodiment of the present invention, the preparation method of the semiconductor nanocrystal CdSe includes the following steps:

[0027] (1) Prepare a Cd precursor solution: Add a Cd source to an organic coating agent and a co-solvent, and heat to dissolve it to obtain a Cd precursor solution;

[0028] (2) Prepare a Se precursor solution: Add Se powder to trioctylphosphine and mix, and heat to dissolve it to obtain a Se precursor solution;

[0029] (3) Mix the Cd precursor solution and the Se precursor solution, heat and react, and then cool to obtain CdSe semiconductor nanocrystals.

[0030] In one embodiment of the present invention, the molar ratio of the Cd source to the organic coating agent is 1:0.5 - 1:2, and exemplarily it is 1:1.

[0031] In one embodiment of the present invention, the concentration of Cd ions in the co-solvent is 0.01 - 1.0 mol / L, and exemplarily it is 0.1 mol / L.

[0032] In one embodiment of the present invention, the Cd source is CdO, cadmium acetate, cadmium oxalate, cadmium myristate or cadmium stearate, and preferably it is CdO.

[0033] In one embodiment of the present invention, the organic coating agent is one or a combination of several of oleic acid, stearic acid, erucic acid, trioctylphosphine oxide, dodecylamine, hexadecylamine and octadecylamine.

[0034] In one embodiment of the present invention, in step (1), the heating temperature is 120 - 200 °C.

[0035] In one embodiment of the present invention, the molar ratio of Se powder to trioctylphosphine (TOP) is 1:0.5 - 1:2, and exemplarily it is 1:1.

[0036] In one embodiment of the present invention, in step (2), the heating temperature is 100 - 120 °C.

[0037] In one embodiment of the present invention, the molar ratio of the Cd precursor solution to the Se precursor solution is 1:0.5 - 1:2, and exemplarily it is 1:1.

[0038] In one embodiment of the present invention, in step (3), the heating temperature is 200 - 300 °C, exemplarily 280 °C; the heating time is 0.5 - 5 minutes, exemplarily 0.5 minute, 1 minute, 2 minutes, 3 minutes, 5 minutes.

[0039] In one embodiment of the present invention, the preparation method further includes purifying the prepared CdSe semiconductor nanocrystals. For example, the prepared stock solution of semiconductor nanocrystals is centrifuged, filtered, and subjected to anti-solvent precipitation - redispersion to obtain semiconductor nanocrystal powder. Exemplarily, the obtained stock solution of CdSe semiconductor nanocrystals is centrifuged, petroleum ether is added to the precipitate, the precipitate is dispersed by ultrasonic treatment, and vacuum drying is carried out to obtain CdSe semiconductor nanocrystal powder.

[0040] According to an embodiment of the present invention, the preparation method of the semiconductor nanocrystal Cu - In - Se includes the following steps:

[0041] (1) Prepare a Se precursor solution: Add Se powder to diphenylphosphine (DPP) and a co - solvent, and dissolve it by ultrasonic treatment to obtain a Se precursor solution;

[0042] (2) Prepare a metal precursor solution: Add a Cu source and an In source to a co - solvent, heat to dissolve them to obtain a metal precursor solution;

[0043] (3) Mix the metal precursor solution and the Se precursor solution, heat for reaction, and then cool to obtain Cu - In - Se semiconductor nanocrystals.

[0044] In one embodiment of the present invention, the molar volume ratio of Se powder to diphenylphosphine (DPP) is 1 mmol:(0.1 - 1) mL, exemplarily 1 mmol:0.5 mL.

[0045] In one embodiment of the present invention, the concentration of Se in the co - solvent is 0.5 - 2 mol / L, exemplarily 1 mol / L.

[0046] In one embodiment of the present invention, the molar ratio of the In source to the Cu source is 1:0.1 - 1:1, exemplarily 1:0.7.

[0047] In one embodiment of the present invention, the concentration of Cu ions in the co - solvent is 0.1 - 0.2 mol / L, exemplarily 0.14 mol / L.

[0048] In one embodiment of the present invention, the concentration of In ions in the co - solvent is 0.1 - 0.5 mol / L, exemplarily 0.2 mol / L.

[0049] In one embodiment of the present invention, the Cu source is cuprous iodide.

[0050] In one embodiment of the present invention, the In source is indium acetate.

[0051] In one embodiment of the present invention, the co-solvent is one or a combination of several of oleylamine, oleic acid, stearic acid, erucic acid, trioctylphosphine oxide, dodecylamine, hexadecylamine, and octadecylamine.

[0052] In one embodiment of the present invention, in step (2), the heating temperature is 120 - 200 °C, and exemplarily it is 180 °C.

[0053] In one embodiment of the present invention, the molar ratio of In ions in the metal precursor solution to the Se precursor solution is 1:0.5 - 1:2, and exemplarily it is 1:1.

[0054] In one embodiment of the present invention, in step (3), the heating temperature is 120 - 200 °C, and exemplarily it is 180 °C; the heating time is 0.5 - 5 seconds, and exemplarily it is 1 second, 3 seconds, 5 seconds.

[0055] In one embodiment of the present invention, the preparation method further includes purifying the prepared Cu-In-Se semiconductor nanocrystals. For example, the original solution of the prepared semiconductor nanocrystals is centrifuged, filtered, and subjected to anti-solvent precipitation - redispersion to obtain semiconductor nanocrystal powder. Exemplarily, the original solution of the obtained Cu-In-Se semiconductor nanocrystals is centrifuged, petroleum ether is added to the precipitate, the precipitate is dispersed by ultrasonic treatment, and then vacuum dried to obtain Cu-In-Se semiconductor nanocrystal powder.

[0056] According to an embodiment of the present invention, the solid electrolyte is an organic-inorganic composite solid electrolyte.

[0057] According to an embodiment of the present invention, the solid electrolyte is prepared by mixing semiconductor nanocrystals, a lithium salt, and PEO in proportion.

[0058] The present invention also provides a preparation method for the above solid electrolyte, including mixing semiconductor nanocrystals, a lithium salt, and PEO in proportion.

[0059] According to an embodiment of the present invention, the preparation method includes the following steps:

[0060] S1. Prepare the original solution of semiconductor nanocrystals;

[0061] S2. Purify and / or perform ligand exchange reaction or encapsulation treatment on the original solution of semiconductor nanocrystals to prepare semiconductor nanocrystals in the form of powder or colloidal solution;

[0062] S3. Dissolve a lithium salt, PEO, and semiconductor nanocrystals in the form of semiconductor nanocrystal powder or colloidal solution in a solvent to obtain a mixed solution, heat and stir to obtain a solid electrolyte slurry, pour the slurry into a mold, and evaporate the solvent to form a film to prepare the solid electrolyte.

[0063] According to an embodiment of the present invention, in step S2, the method for preparing the semiconductor nanocrystal colloidal solution is to disperse semiconductor nanocrystal powder in water or an organic solvent.

[0064] According to an embodiment of the present invention, in step S3, the solvent is acetonitrile.

[0065] According to an embodiment of the present invention, in step S3, the temperature of the heating and stirring is 50 - 80 °C, for example, 50 °C, 60 °C, 70 °C, 80 °C; the time of the heating and stirring is 12 - 48 h, for example, 24 h.

[0066] According to an embodiment of the present invention, the thickness of the solid electrolyte is 1 - 100 μm, for example, 1 μm, 2 μm, 5 μm, 10 μm, 20 μm, 50 μm, 80 μm, 100 μm.

[0067] The present invention also provides the application of the above solid electrolyte in energy storage devices; preferably, the energy storage device is a battery; more preferably, it is a solid-state battery, and still more preferably, it is a solid-state lithium-ion battery.

[0068] The present invention also provides a battery containing the above solid electrolyte. Preferably, the battery is a solid-state battery. More preferably, it is a solid-state lithium-ion battery.

[0069] According to an embodiment of the present invention, the battery contains a negative electrode and / or a positive electrode. For example, the negative electrode and / or the positive electrode are selected from stainless steel.

[0070] Advantages of the present invention:

[0071] The present invention uses semiconductor nanocrystals as inorganic fillers to be compounded with a PEO-based organic polymer solid electrolyte to prepare an organic-inorganic composite solid electrolyte membrane. By utilizing the tunability of the semiconductor nanocrystal composition and structure and the flexibility of surface modification, the crystallization of PEO at room temperature is significantly inhibited, forming a high ion-conducting interface. Functional groups (such as carboxylic acid, phosphonic acid, amine, phosphine, etc.) on the surface of the semiconductor nanocrystals can effectively promote the dissociation and transport of lithium ions in the lithium salt, enabling the prepared organic-inorganic composite solid electrolyte membrane to have a high ionic conductivity. In addition, through surface ligand modification, the semiconductor nanocrystals can achieve good dispersion in the PEO matrix. Through encapsulation treatment, the stability of the semiconductor nanocrystals in PEO can also be significantly improved. The organic-inorganic composite solid electrolyte of the present invention can effectively improve the ionic transport performance of the PEO-based solid electrolyte at the conventional operating temperature of a lithium-ion battery. Description of the Drawings

[0072] Figure 1 TEM image of the CdSe semiconductor nanocrystals synthesized in Example 1.

[0073] Figure 2 TEM image of the CdSe semiconductor nanocrystals synthesized in Example 2.

[0074] Figure 3 TEM image of the Cu-In-Se semiconductor nanocrystals synthesized in Example 8. Detailed Description of the Invention

[0075] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0076] Example 1:

[0077] A method for preparing an organic-inorganic composite solid electrolyte membrane, comprising the following steps:

[0078] (1) Preparation of CdSe semiconductor nanocrystals

[0079] 1 mmol of cadmium oxide and 1 mmol of oleic acid are added to 10 mL of 1-octadecene solvent. The mixture is stirred and heated to 120 °C under an inert atmosphere and continuously heated until the solution becomes completely clear and transparent. Then the solution is cooled to 120 °C, and the vacuum is pumped to volatilize impurities such as generated water. After the bubbles disappear, the solution is heated to 280 °C again under an inert atmosphere to obtain a cadmium oleate solution.

[0080] Mix 1 mmol of Se powder with 1 mmol of trioctylphosphine oxide (TOP) under an inert atmosphere. Stir and heat the mixture to 120 °C and continue heating until the solution becomes completely clear and transparent to prepare the TOP-Se solution.

[0081] Quickly inject the TOP-Se solution into the cadmium oleate solution at 280 °C mentioned above, heat for 1 minute under rapid stirring, and then quickly cool it down through a 25 °C water bath to obtain the stock solution of CdSe semiconductor nanocrystals.

[0082] (2) Purification of the stock solution of CdSe semiconductor nanocrystals

[0083] Centrifuge the stock solution of CdSe semiconductor nanocrystals obtained in step (1) at 5000 rpm for 30 minutes, discard the supernatant, add 1 mL of petroleum ether to the precipitate, disperse the precipitate evenly by ultrasonic treatment, and then centrifuge again at 5000 rpm for 30 minutes. Repeat the above steps 3 times. Finally, vacuum-dry the CdSe semiconductor nanocrystal precipitate to obtain CdSe semiconductor nanocrystal powder with a particle size of about 3.2 nm.

[0084] (3) Preparation of the organic-inorganic composite solid electrolyte membrane

[0085] Add 5 g of the CdSe semiconductor nanocrystal powder obtained in step (2), 30 g of lithium perchlorate, and 100 g of PEO (with a molecular weight of 600,000) powder to 1000 g of acetonitrile, stir at 80 °C for 24 hours under an inert atmosphere to obtain an organic-inorganic composite solid electrolyte slurry. Then pour the slurry into a Teflon mold and vacuum-dry to remove the solvent to prepare an organic-inorganic composite solid electrolyte membrane with a thickness of 30 μm. Finally, carefully peel off the thin film with tweezers to obtain the organic-inorganic composite solid electrolyte membrane composed of CdSe semiconductor nanocrystals and PEO.

[0086] Example 2:

[0087] Prepare the organic-inorganic composite solid electrolyte membrane according to the method of Example 1, except that in step (1): quickly inject the TOP-Se solution into the cadmium oleate solution at 280 °C mentioned above, heat for 3 minutes, and then quickly cool it down through a water bath to obtain the stock solution of CdSe semiconductor nanocrystals with a particle size of about 4.6 nm. The extended heating time is to obtain larger-sized CdSe semiconductor nanocrystals.

[0088] Example 3

[0089] Prepare the organic-inorganic composite solid electrolyte membrane according to the method of Example 1, except that the purified CdSe semiconductor nanocrystal powder in step (2) is dispersed in n-hexane to obtain a 1M nanocrystal colloidal solution, and then phenylsulfonic acid is added thereto to make the concentration of phenylsulfonic acid 0.1M. Stir the solution at room temperature for 0.5 h, then centrifuge at 5000 rpm for 20 min, and vacuum-dry the precipitate to obtain phenylsulfonic acid-modified CdSe semiconductor nanocrystal powder.

[0090] Example 4

[0091] Prepare the organic-inorganic composite solid electrolyte membrane according to the method of Example 1, except that the purified CdSe semiconductor nanocrystal powder in step (2) is dispersed in n-hexane to obtain a 1M nanocrystal colloidal solution, and then diethylenetriamine pentamethylenephosphonic acid is added thereto to make the concentration of diethylenetriamine pentamethylenephosphonic acid 0.1M. Stir the solution at room temperature for 0.5 h, then centrifuge at 5000 rpm for 20 min, and vacuum-dry the precipitate to obtain diethylenetriamine pentamethylenephosphonic acid-modified CdSe semiconductor nanocrystal powder.

[0092] Example 5:

[0093] Prepare the organic-inorganic composite solid electrolyte membrane according to the method of Example 1, except that the purified CdSe semiconductor nanocrystal powder in step (2) is dispersed in n-hexane to obtain a 1M nanocrystal colloidal solution, and then tetraethyl orthosilicate is added thereto to make the concentration of tetraethyl orthosilicate 0.1M. Stir the solution at room temperature for 24 h, then centrifuge at 5000 rpm for 20 min, and vacuum-dry the precipitate to obtain CdSe semiconductor nanocrystal powder coated with a silica shell layer.

[0094] Example 6:

[0095] Prepare the organic-inorganic composite solid electrolyte membrane according to the method of Example 1, except that the purified CdSe semiconductor nanocrystal powder in step (2) is dispersed in n-hexane to obtain a 1M nanocrystal colloidal solution, and then titanium tetrachloride is added thereto to make the concentration of titanium tetrachloride 0.1M. Stir the solution at room temperature for 24 h, then centrifuge at 5000 rpm for 20 min, and vacuum-dry the precipitate to obtain CdSe semiconductor nanocrystal powder coated with a titanium oxide shell layer.

[0096] Example 7:

[0097] Prepare the organic-inorganic composite solid electrolyte membrane according to the method of Example 1, except that in step (3): the material ratio for preparing the organic-inorganic composite solid electrolyte slurry is to add 10 g of CdSe semiconductor nanocrystal powder, 30 g of lithium perchlorate, and 100 g of PEO (molecular weight: 6 million) powder into 1000 g of acetonitrile.

[0098] Example 8:

[0099] Prepare the organic-inorganic composite solid electrolyte membrane according to the method of Example 1, except that the synthesized semiconductor nanocrystals are Cu-In-Se semiconductor nanocrystals. The preparation method is as follows.

[0100] (1) Preparation of Cu-In-Se semiconductor nanocrystals

[0101] Mix 1 mmol of Se powder with 0.5 mL of diphenylphosphine (DPP) and 1 mL of oleylamine, and ultrasonically dissolve at room temperature to obtain a clear and transparent DPP-Se solution. Add 0.7 mmol of cuprous iodide and 1 mmol of indium acetate to 5 mL of oleylamine, heat the mixture to 180 °C under an inert atmosphere to form a clear and transparent pale yellow solution, quickly inject the above-prepared DPP-Se solution into it, heat for 5 seconds, and cool naturally to obtain the Cu-In-Se semiconductor nanocrystal stock solution.

[0102] (2) Purification of Cu-In-Se semiconductor nanocrystal stock solution

[0103] Centrifuge the Cu-In-Se semiconductor nanocrystal stock solution at 5000 rpm for 30 minutes, discard the supernatant, add 1 mL of petroleum ether to the precipitate, and ultrasonically disperse the precipitate evenly. Repeat the above steps 3 times, and finally vacuum-dry the Cu-In-Se semiconductor nanocrystal precipitate to obtain Cu-In-Se semiconductor nanocrystal powder with a particle size of about 4.0 nm.

[0104] Comparative Example 1:

[0105] Prepare the organic-inorganic composite solid electrolyte membrane according to the method of Example 1, except that it does not contain CdSe semiconductor nanocrystals.

[0106] Comparative Example 2:

[0107] Prepare the organic-inorganic composite solid electrolyte membrane according to the method of Example 1, except that the material ratio for preparing the organic-inorganic composite solid electrolyte slurry is to add 50 g of CdSe semiconductor nanocrystal powder, 30 g of lithium perchlorate, and 100 g of PEO (molecular weight: 6 million) powder into 1000 g of acetonitrile.

[0108] Figure 1TEM image of the CdSe semiconductor nanocrystals synthesized in Example 1. Figure 2 TEM image of the CdSe semiconductor nanocrystals synthesized in Example 2. Figure 3 TEM image of the Cu-In-Se semiconductor nanocrystals synthesized in Example 8. It can be seen from the figure that the semiconductor nanocrystals prepared by the present invention have high size uniformity, which is beneficial to their controllable composite with PEO. Moreover, the ultra-large specific surface area and rich surface atomic species of the semiconductor nanocrystals are beneficial to modifying different organic ligands on their surfaces to meet the performance requirements of different solid electrolytes.

[0109] The organic-inorganic composite solid electrolyte membranes prepared in Examples 1-8 and Comparative Examples 1-2 were cut into discs and assembled into symmetric coin cells of stainless steel 304||stainless steel 304 (Keluode CR20 gasket) in a glove box, and their ionic conductivities at 25 °C were tested by electrochemical impedance spectroscopy. The test results are shown in Table 1.

[0110] Table 1

[0111] Example <![CDATA[Ionic conductivity (S / cm -1 )]]> Example 1 <![CDATA[4.60×10 -4 > Example 2 <![CDATA[4.43×10 -4 > Example 3 <![CDATA[5.09×10 -4 > Example 4 <![CDATA[6.62×10 -4 > Example 5 <![CDATA[5.93×10 -4 > Example 6 <![CDATA[6.33×10 -4 > Example 7 <![CDATA[4.72×10 -4 > Example 8 <![CDATA[4.81×10 -4 > Comparative Example 1 <![CDATA[4.10×10 -4 > Comparative Example 2 <![CDATA[4.23×10 -4 >

[0112] The above results show that the composite of semiconductor nanocrystals and PEO solid electrolyte can improve the ionic conductivity of the solid electrolyte, and by ligand exchange of the semiconductor nanocrystals with ligands having multiple functional groups or coating the semiconductor nanocrystals in the present invention, the ionic conductivity of the solid electrolyte can be improved.

[0113] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A solid electrolyte, characterized in that, The solid electrolyte includes poly(ethylene oxide) (PEO), a lithium salt, and semiconductor nanocrystals. Preferably, the mass ratio of semiconductor nanocrystals, lithium salt, and PEO in the solid electrolyte is (0.01 - 0.2):(0.15 - 1):

1. Preferably, the solid electrolyte is in the form of a film. For example, the thickness of the solid electrolyte film is 1 - 100 μm.

2. The solid electrolyte according to claim 1, characterized in that, The molecular weight of the PEO is 500,000 - 700,000. Preferably, the lithium salt is selected from one or more of lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(oxalato)borate. Preferably, the semiconductor nanocrystals are at least one of II-VI group nanocrystals such as CdSe, III-V group nanocrystals such as InP, I-III-VI group nanocrystals such as Cu-In-Se, and single-element nanocrystals such as carbon, phosphorus, sulfur, silicon, and germanium. Preferably, the size of the semiconductor nanocrystals is 1 - 100 nm.

3. The solid electrolyte according to claim 1, wherein The semiconductor nanocrystals are semiconductor nanocrystals with ligands on the surface and / or semiconductor nanocrystals with a core-shell structure. Preferably, the ligand is coordinated and bonded to the semiconductor nanocrystals through one or more of carboxyl, phosphonic acid, sulfonic acid, amine, phosphine, and phosphine oxide groups with metal ions on the surface of the semiconductor nanocrystals. Preferably, the shell layer of the semiconductor nanocrystals with a core-shell structure is bonded to the semiconductor nanocrystal core through covalent bonds or ionic bonds. Preferably, the ligand is an organic ligand. Preferably, the organic ligand has one or more of carboxyl, phosphonic acid, sulfonic acid, amine, phosphine, and phosphine oxide groups. Preferably, the organic ligand is an organic ligand containing one or more of carboxyl, phosphonic acid, sulfonic acid, amine, phosphine, and phosphine oxide functional groups with C4 - C20. Preferably, the organic ligand can be methanesulfonic acid or hexamethylenediaminetetramethylenephosphonic acid. Preferably, the organic ligand is a monodentate ligand (one ligand molecule contains one coordination functional group) or a polydentate ligand (one ligand molecule contains two or more coordination functional groups). Preferably, the number of coordination functional groups on the surface of each semiconductor nanocrystal can be 1 - 8. Preferably, the ratio of the number of organic ligands to the surface area of the semiconductor nanocrystals is 0.2 - 4 molecules per square nanometer.

4. The solid electrolyte according to claim 2, wherein The semiconductor nanocrystals with a core-shell structure are prepared by coating the semiconductor nanocrystals. Preferably, the shell layer material used for the coating treatment is one or more of oxides, sulfides, selenides, and halides. Preferably, the shell layer material can be silicon oxide or titanium oxide. Preferably, the thickness of the shell layer material used for the coating treatment is 0.5 - 50 nm. Preferably, the method for ligand exchange or coating treatment of the semiconductor nanocrystals includes mixing the semiconductor nanocrystals with a ligand or a precursor of the shell layer material, and reacting to obtain the semiconductor nanocrystals.

5. The solid electrolyte according to any one of claims 1-4, characterized in that, The solid electrolyte is prepared by mixing semiconductor nanocrystals, a lithium salt, and PEO in proportion.

6. The method for preparing a solid electrolyte according to any one of claims 1-5, characterized in that, The preparation method includes mixing semiconductor nanocrystals, a lithium salt, and PEO in proportion.

7. The preparation method according to claim 6, characterized in that, The preparation method includes the following steps: S1. Prepare a stock solution of semiconductor nanocrystals; S2. Purify the semiconductor nanocrystal stock solution and / or conduct ligand exchange reaction or encapsulation treatment to obtain semiconductor nanocrystals in the form of semiconductor nanocrystal powder or colloidal solution; S3. Dissolve a lithium salt, PEO, and semiconductor nanocrystals in the form of semiconductor nanocrystal powder or colloidal solution in a solvent to obtain a mixed solution, heat and stir to obtain a solid electrolyte slurry, pour the slurry into a mold, and evaporate the solvent to form a film to obtain the solid electrolyte.

8. The preparation method according to claim 7, characterized in that, In step S2, the method for preparing the semiconductor nanocrystal colloidal solution is to disperse the semiconductor nanocrystal powder in water or an organic solvent. Preferably, in step S3, the solvent is acetonitrile. Preferably, in step S3, the temperature of the heating and stirring is 50 - 80 °C; the time of the heating and stirring is 12 - 48 h. Preferably, the thickness of the solid electrolyte is 1 - 100 μm.

9. Application of the solid electrolyte according to any one of claims 1 - 5 in an energy storage device; preferably, the energy storage device is a battery; more preferably a solid-state battery, and still more preferably a solid-state lithium-ion battery.

10. A battery, characterized in that, It contains the above solid electrolyte. Preferably, the battery is a solid-state battery, and more preferably a solid-state lithium-ion battery. Preferably, the battery contains a negative electrode and / or a positive electrode.

Images