Solid electrolyte composite material and preparation method and application thereof

Abstract

The invention discloses a solid electrolyte composite material as well as a preparation method and application thereof. The solid electrolyte composite material comprises an oxide solid electrolyte with a porous structure and an electron conduction material, wherein the electron conduction material comprises granular thermal decomposition carbon and reduced graphene oxide; wherein the electron conduction material is distributed in pores of the oxide solid electrolyte, and / or, at least part of the electron conduction material is embedded in the oxide solid electrolyte, and / or, the electron conduction material is distributed on part of the surface of the oxide solid electrolyte. High-conductivity reduced graphene oxide is obtained through heat treatment reduction, the material has the effect of conducting lithium ions and electrons at the same time, the porous oxide solid electrolyte material with the high specific surface can increase the contact area and increase a conduction path for ion migration, and the electrode reaction kinetics is effectively accelerated through the combined action of the two materials; and meanwhile, good rate capability and low-temperature performance are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery materials, and in particular relates to a solid electrolyte composite material and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries are widely used in mobile communications, electric vehicles and other fields due to their advantages such as high energy density, long cycle life and no memory effect. Among them, oxide solid electrolytes are used as electrode additives due to their advantages such as high stability, high ionic conductivity and high mechanical strength to enhance the ion conduction path inside the electrode and improve the ionic conductivity of the electrode. Oxide solid electrolytes can also enhance the mechanical strength of the electrode, thereby improving the cycle life. However, the electronic conductivity of oxide solid electrolytes is extremely low. When added to the electrode as an electrode additive, it will block the electron conduction and lead to increased polarization. Therefore, how to make oxide solid electrolytes have high electronic conductivity and ionic conductivity at the same time is an important direction of current technical research. Summary of the Invention

[0003] The main purpose of the present invention is to provide a solid electrolyte composite material and its preparation method and application, aiming to provide a solid electrolyte with good electronic conductivity and ionic conductivity.

[0004] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0005] An embodiment of the present invention provides a solid electrolyte composite material, which includes an oxide solid electrolyte with a porous structure and an electron-conducting material, wherein the electron-conducting material includes granular thermally decomposed carbon and reduced graphene oxide;

[0006] The electron-conductive material is distributed in the pores of the oxide solid electrolyte, and / or the electron-conductive material is at least partially embedded in the oxide solid electrolyte, and / or the electron-conductive material is distributed on part of the surface of the oxide solid electrolyte.

[0007] An embodiment of the present invention further provides a method for preparing the aforementioned solid electrolyte composite material, which comprises:

[0008] Mixing a first mixed solution comprising at least a titanium source, a readily hydrolyzable and difficultly complexing raw material, and a complexing agent with a second mixed solution comprising at least a lithium source, a phosphorus source, and a non-hydrolyzable and easily complexing raw material, and then adding a graphene oxide solution to obtain a third mixed solution;

[0009] Furthermore, the third mixed solution is freeze-dried and subjected to heat treatment in a non-oxidizing atmosphere to obtain a solid electrolyte composite material.

[0010] An embodiment of the present invention further provides an electrode additive, which includes the aforementioned solid electrolyte composite material, or includes the solid electrolyte composite material prepared by the aforementioned preparation method.

[0011] An embodiment of the present invention further provides an electrode, which includes the aforementioned electrode additive, and the electrode is a positive electrode or a negative electrode.

[0012] An embodiment of the present invention further provides a lithium-ion battery, characterized in that it includes the aforementioned electrode.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] (1) The oxide solid electrolyte material in the solid electrolyte composite material of the present invention can absorb more electrolyte due to the high porosity structure brought about by the nanoporous morphology, thereby optimizing ion transport. At the same time, thanks to the electronic conductive material distributed therein, especially the reduced graphene oxide, it can have excellent electronic conductivity, thereby forming an electron-ion mixed conductivity, which helps to improve the charge transfer dynamics; the ion conductivity of the solid electrolyte material and the electronic conductivity of the graphene material are less affected by low temperature, so that this material maintains the advantage of lithium ion electron mixed conductor at low temperature, providing a rapid ion and electron migration channel for the electrode;

[0015] (2) Graphene materials have ultra-high thermal conductivity. Their honeycomb structure and high lattice ordering properties accelerate the transfer of heat energy from the electrode active material to the outside, reduce the risk of local overheating, and effectively reduce the heat accumulation inside the battery. Therefore, the solid electrolyte composite material prepared by the present invention can be applied to the positive electrode of lithium-ion batteries to improve the battery rate performance, low-temperature performance and thermal safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 1 is a schematic diagram of a preparation process of a solid electrolyte composite material in a typical embodiment of the present invention;

[0018] Figure 2 This is the XRD result of the sample in Example 1 of the present invention;

[0019] Figure 3 This is a high-resolution SEM photograph of the sample material of Example 3 of the present invention;

[0020] Figure 4This is a high-resolution SEM photograph of the sample material of Example 4 of the present invention;

[0021] Figure 5 This is a thermogravimetric test curve of the sample of Example 3 of the present invention;

[0022] Figure 6 This is a thermogravimetric test curve of the sample of Example 4 of the present invention;

[0023] Figure 7 Schematic diagram of the morphology of a solid electrolyte composite material in a typical embodiment of the present invention. DETAILED DESCRIPTION

[0024] In view of the shortcomings of the prior art, the inventors of this case, after long-term research and extensive practice, have proposed the technical solution of the present invention. The technical solution of the present invention will be clearly and completely described below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making any creative effort shall fall within the scope of protection of the present invention.

[0025] Specifically, as one aspect of the technical solution of the present invention, a solid electrolyte composite material includes an oxide solid electrolyte with a porous structure and an electron-conducting material, wherein the electron-conducting material includes granular thermally decomposed carbon and reduced graphene oxide;

[0026] The electron-conductive material is distributed in the pores of the oxide solid electrolyte, and / or the electron-conductive material is at least partially embedded in the oxide solid electrolyte, and / or the electron-conductive material is distributed on part of the surface of the oxide solid electrolyte.

[0027] In some preferred embodiments, the mass fraction of the electron conductive material is 10-38%.

[0028] In some preferred embodiments, the reduced graphene oxide has a sheet-like structure.

[0029] In some preferred embodiments, the oxide solid electrolyte includes any one or more combinations of LLTO, LATP, and LLZO, but is not limited thereto.

[0030] In some preferred embodiments, the pore volume of the oxide solid electrolyte is 0.05-0.55 cm 3 / g.

[0031] In some preferred embodiments, the pores contained in the oxide solid electrolyte have a pore diameter of 10-200 nm.

[0032] In some preferred embodiments, the specific surface area of ​​the oxide solid electrolyte is 15-200 m 2 / g.

[0033] In some preferred embodiments, the particle size of the oxide solid electrolyte is 120 to 900 nm.

[0034] In some preferred embodiments, the purity of the solid electrolyte composite material is 90%-100%.

[0035] In some preferred embodiments, the reduced graphene oxide is distributed in the form of flakes on the surface of the oxide solid electrolyte material and / or in the pores contained therein.

[0036] Specifically, the solid electrolyte composite material of the present invention includes a porous oxide solid electrolyte material and an electron conductive material contained on the surface or in the pores and / or inside the oxide solid electrolyte, wherein the oxide solid electrolyte includes any one of LLTO, LATP, and LLZO;

[0037] The volume distribution particle size Dv50 of the oxide solid electrolyte material ranges from 120 to 900 nm, preferably from 250 to 700 nm.

[0038] The electron-conducting material consists of two components: reduced graphene oxide (ROG), followed by carbon formed by the thermal decomposition of an organic complexing agent. In thermogravimetric testing in an oxidizing atmosphere, the material experienced a weight loss percentage ranging from 10-38% at temperatures between 30°C and 900°C. This indicates that both the RGO and the carbon formed by the thermal decomposition of the organic complexing agent undergo oxidation, and this weight loss percentage corresponds to the oxidation weight loss of the two carbon materials (electron-conducting materials).

[0039] The solid electrolyte composite material of the present invention comprises a porous oxide solid electrolyte and an electron-conducting material contained on the surface or within the pores of the oxide solid electrolyte material, the electron-conducting material comprising granular thermally decomposed carbon and a thin layer of reduced graphene oxide. The size of the solid electrolyte composite material is generally nanoscale, with particle size measurements combined with electron microscopy showing a range of 140-800 nm. This coating structure can significantly increase the contact area between the solid electrolyte and the positive electrode active material, as well as the electrolyte, effectively accelerating the electron and ion migration kinetics on the surface of the composite positive electrode material, thereby improving rate and low-temperature performance. Due to the formation of reduced graphene oxide, the electronic conductivity of the material is greatly improved compared to solid electrolytes containing only organic chelating agents and decomposed carbon. Conventional solid electrolytes are only good lithium ion conductors. The solid electrolyte composite material of the present invention can simultaneously conduct electrons in addition to effectively conducting lithium ions, i.e., it is a mixed good lithium ion and electron conductor. The electron-conducting material and the oxide solid electrolyte in this type of mixed good lithium ion and electron conductor solid electrolyte contain a certain ratio. The raw materials prepared contain an organic chelating agent for complexing metal ions, and the non-oxidizing atmosphere serves to prevent oxidation of the carbon material. Furthermore, the specific heat treatment temperature and holding time are intended to obtain the target oxide solid electrolyte material, thereby achieving high lithium ion conductivity. Simultaneously, the organic complexing agent undergoes thermal decomposition to form carbon, which remains within the material, and the graphene oxide undergoes thermal reduction to form reduced graphene oxide, which remains within the material. Under the required process conditions, this heat treatment can yield a solid electrolyte composite material exhibiting both high lithium ion conductivity and high electronic conductivity.

[0040] The sol-gel process is a novel method for preparing porous materials. Based on the sol-gel principle, this method utilizes the accumulation of colloidal particles during the gelation process to form a porous structure. The solution filling the pores is expelled during the gelation and heat treatment processes, leaving behind small pores. These small pores are mostly nanoscale, but they can collapse during the drying process due to capillary forces, temperature gradients, or material shrinkage. Therefore, the present invention uses freeze-drying to freeze the water at low temperatures and then rapidly sublime it, preserving the material's porous morphology.

[0041] The surface of graphene oxide contains a large number of oxygen-containing functional groups (such as epoxy, hydroxyl, and carboxyl groups), which destroy the sp 2 conjugated structure, forming sp 3 Hybridized regions lead to the interruption of π electron delocalization and extremely low electrical conductivity (~10-5S / m), which is usually insulating or semiconductor. Graphene oxide can be reduced to graphene by thermal reduction. After graphene oxide is reduced, most of the oxygen-containing groups are removed and sp 2Hybrid network, after reduction, carbon atoms reform into a six-membered ring conjugated structure, and the π electrons are delocalized. Even after reduction, there are still defects such as vacancies and five / seven-membered rings, which will scatter carriers, but the overall conductivity is significantly improved (10 2 -10 4 s / m), several orders of magnitude higher than graphene oxide. Furthermore, graphene also has higher thermal conductivity than graphene oxide, with thermal conductivity performance several orders of magnitude higher than that of graphene oxide. Therefore, in the present invention, in conjunction with a specific process, graphene oxide is first used to prepare a sol-gel precursor solution, and then the graphene oxide is thermally reduced using a heat treatment. This thermally reduced graphene oxide is also referred to as reduced graphene oxide.

[0042] The present invention utilizes a sol-gel method to prepare a porous solid electrolyte composite material. In addition to adding basic raw materials, the sol-gel synthesis process also utilizes graphene oxide as a nucleating agent, as its high surface energy can provide more active attachment sites for metal ions. Furthermore, the abundant functional groups on the surface of graphene oxide have a strong attraction to metallic lithium, facilitating the in-situ growth of oxide solid electrolytes on the graphene oxide surface. Subsequently, drying is performed, and the solvent in the pores of the wet gel evaporates upon heating, leaving pores and thus achieving a porous morphology. Finally, the dried gel is heat-treated in a non-oxidizing atmosphere to obtain a carbon component formed by the complexing agent. The graphene oxide is then reduced to graphene with higher electronic conductivity through the heat treatment, resulting in a porous solid electrolyte composite material having excellent electronic conductivity. Subsequently, the porous solid electrolyte composite material is prepared into a powder of a specific nanoparticle size through mechanical methods such as ball milling and grinding, and applied as an additive to the positive electrode of a lithium-ion battery.

[0043] In the present invention, graphene oxide is introduced in the process of preparing solid electrolyte. When the content of graphene oxide is too little, the high electronic conductivity and high thermal conductivity reduced graphene oxide content generated in the solid electrolyte after thermal reduction are insufficient, resulting in the electronic conductivity of the entire material not being high enough, so its surface reaction kinetics improvement effect on the positive electrode is limited, and thermal conductivity is not high enough; at the same time, because graphene does not have ion conduction function, introducing too much graphene oxide will hinder the ion conduction path in the material, and there is an upper limit to the amount introduced, so the amount of graphene oxide introduced has a preferred range value. In addition, the solid content of the graphene oxide solution needs to be set in a smaller range, because the smaller the solid content, the more conducive to the uniform dispersion of graphene oxide in the solution, so as to effectively realize the effect of the graphene oxide material as a nucleating agent.

[0044] The role of organic complexing agents in the sol-gel method is to combine with metal ions through coordination bonds, reduce their activity, slow down the hydrolysis rate, and avoid precipitation caused by local supersaturation. For example, citric acid can be combined with Al 3+Forming a stable complex prevents premature precipitation of Al(OH)3. In addition, the complexing agent also has the effect of electrostatic / steric stabilization: the complex may be charged (such as citrate anions), which prevents the aggregation of sol particles through electrostatic repulsion or steric hindrance, thereby extending the storage time of the sol. Insufficient addition of the complexing agent will cause the metal ions to hydrolyze too quickly to form a precipitate, resulting in an uneven sol; secondly, it will lead to a lack of electrostatic / steric hindrance of the complexing agent, and the sol particles will easily aggregate through van der Waals forces, resulting in flocculation or sedimentation, shortening the storage time of the sol; in addition, insufficient complexing agent may lead to uneven pore size distribution, and the sol will quickly condense to form large pores or cracks, reducing the specific surface area and mechanical strength of the material. However, if too much complexing agent is added, it will bind too strongly to the metal ions, and the hydrolysis-condensation reaction will be excessively delayed, resulting in the sol being unable to gel within a reasonable time (such as not gelling for several days). In addition, excessive complexing agent leads to excessive carbon formed by thermal decomposition. Since the electronic conductivity of this thermally decomposed carbon is not high, it will affect the electronic conductivity in the solid electrolyte composite material. Therefore, the amount of complexing agent introduced also has an optimal range of values.

[0045] An embodiment of the present invention further provides a method for preparing the aforementioned solid electrolyte composite material, which comprises:

[0046] Mixing a first mixed solution comprising at least a titanium source, a readily hydrolyzable and difficultly complexing raw material, and a complexing agent with a second mixed solution comprising at least a lithium source, a phosphorus source, and a non-hydrolyzable and easily complexing raw material, and then adding a graphene oxide solution to obtain a third mixed solution;

[0047] Furthermore, the third mixed solution is freeze-dried and subjected to heat treatment in a non-oxidizing atmosphere to obtain a solid electrolyte composite material.

[0048] In some preferred embodiments, the titanium source comprises C 16 H 36 O4Ti and / or Ti4(OCH3) 16 , and are not limited to this.

[0049] In some preferred embodiments, the easily hydrolyzed and difficult to complex raw materials include Al(NO3)3·9H2O, C9H 21 Any one or more combinations of AlO3, Al(NO3)3, ZrO(NO3)2, (C2H5O)4Si, Sr(NO3)2, Ca(NO3)2, Ba(NO3)2, La(NO3)3, La2O3, but not limited thereto.

[0050] In some preferred embodiments, the complexing agent includes any one or more combinations of citric acid, citric acid monohydrate, malic acid, malonic acid, succinic acid, succinic acid, lactic acid, and ethylenediaminetetraacetic acid, but is not limited thereto.

[0051] In some preferred embodiments, the lithium source includes any one or more combinations of LiOH, Li2CO3, and LiNO3, but is not limited thereto.

[0052] In some preferred embodiments, the phosphorus source includes any one or more combinations of NH4H2PO4, Li3PO4, and LiH2PO4, but is not limited thereto.

[0053] In some preferred embodiments, the raw materials that are not easily hydrolyzed and easily complexed include but are not limited to NaNO3, LiF, etc.

[0054] In some preferred embodiments, the first mixed solution further includes a first solvent, and the first solvent includes any one or more combinations of anhydrous ethanol, isopropyl alcohol, and methanol, but is not limited thereto.

[0055] In some preferred embodiments, the second mixed solution further includes a second solvent, and the second solvent includes any one or more combinations of anhydrous ethanol, isopropyl alcohol, and methanol, but is not limited thereto.

[0056] In some preferred embodiments, the molar ratio of the complexing agent to the sum of the molar numbers of metal ions other than lithium ions in the easily hydrolyzed and difficult to complex raw materials is 0.7-3:1.

[0057] In some preferred embodiments, the solid content of the graphene oxide solution is 0.5-5 wt%.

[0058] In some preferred embodiments, the mass ratio of graphene oxide to lithium source in the graphene oxide solution is 2-50:100.

[0059] In some preferred embodiments, the molar ratio of the titanium source to the easily hydrolyzed and difficultly complexed raw material is (0.4:2)-(1.7:0.725).

[0060] In some preferred embodiments, the molar ratio of the titanium source to the raw material that is not easily hydrolyzed and easily complexed is (0.4:4.4)-(1.7:4.3).

[0061] In some preferred embodiments, the molar ratio of the titanium source to the lithium source is (0.4:1.4)-(1.7:1.3).

[0062] In some preferred embodiments, the molar ratio of the titanium source to the phosphorus source is 0.4-1.7:3.

[0063] In some preferred embodiments, the non-oxidizing atmosphere heat treatment is performed at a temperature of 500 to 1200° C. for a time of 4 to 15 hours.

[0064] In some preferred embodiments, the non-oxidizing atmosphere used in the non-oxidizing atmosphere heat treatment includes any one or more combinations of nitrogen, argon, helium, and argon-hydrogen mixed gas, but is not limited thereto.

[0065] In some preferred embodiments, the preparation method further comprises: crushing the solid electrolyte composite material by grinding.

[0066] In some more specific embodiments, the method for preparing the porous solid electrolyte composite material comprises the following steps:

[0067] Step 1: dissolving the easily hydrolyzed and difficult to complex raw material and the complexing agent in a solvent to obtain a first mixed solution;

[0068] Step 2: dissolving the non-hydrolyzable and easily complexing raw material in a solvent to obtain a second mixed solution;

[0069] Step 3: mixing the first mixed solution and the second mixed solution, and adding the graphene oxide solution to obtain a third mixed solution;

[0070] Step 4: freeze-drying the third mixed solution to obtain a dried powder;

[0071] Step 5: heat-treating the dried powder to obtain a solid electrolyte composite material;

[0072] Step 6: Grind the material into nanoparticles.

[0073] The solid electrolyte component includes one or more NASICON solid electrolyte types.

[0074] Optionally, in some embodiments of the present application, the third mixed solution includes: LiNO3, Al(NO3)·9H2O, NH4H2PO4 and C 16 H 36 O4Ti.

[0075] Optionally, in some embodiments of the present application, the complexing agent is one or more of citric acid, citric acid monohydrate, malic acid, malonic acid, succinic acid, succinic acid, lactic acid, and ethylenediaminetetraacetic acid.

[0076] Optionally, in some embodiments of the present application, freeze drying is used to prepare the third mixed solution in step 4, so that the solid electrolyte composite material can obtain a porous morphology.

[0077] Optionally, in some embodiments of the present application, the holding temperature of the heat treatment ranges from 500°C to 1200°C; the holding time of the heat treatment ranges from 4h to 15h, and the heat treatment adopts a nitrogen atmosphere.

[0078] In the present invention, under appropriate heat treatment conditions (temperature, time, atmosphere), in the solid electrolyte composite material with relatively excellent comprehensive performance, the addition amount of reduced graphene oxide has a certain optimal range, and the mass ratio of the graphene oxide to the lithium source is 2%-50%.

[0079] In some preferred embodiments, the preparation process diagram of the solid electrolyte composite material of the present invention is as follows Figure 1 shown.

[0080] Another aspect of the embodiments of the present invention further provides an electrode additive, which includes the aforementioned solid electrolyte composite material, or includes the solid electrolyte composite material prepared by the aforementioned preparation method.

[0081] Another aspect of an embodiment of the present invention further provides an electrode, which includes the aforementioned electrode additive, and the electrode is a positive electrode or a negative electrode.

[0082] Another aspect of the embodiments of the present invention further provides a lithium-ion battery comprising the aforementioned electrode.

[0083] The present invention primarily prepares a porous solid-state electrolyte composite material. First, a porous oxide solid-state electrolyte material is prepared using a sol-gel method. This method utilizes graphene oxide as a nucleating agent, leveraging its high specific surface area and abundant surface functional groups to provide more attachment sites for metal ions. This promotes the in-situ growth of the oxide solid-state electrolyte on its surface, achieving uniform mixing of the raw materials and synthesizing a high-purity oxide solid-state electrolyte. The porous oxide solid-state electrolyte material is prepared by gel drying, and a high-conductivity graphene material is simultaneously formed and composited therewith, resulting in an excellent ionic-electronic mixed conductor material.

[0084] In the present invention, reduced graphene oxide is reduced to high conductivity through heat treatment, so that the material has the function of conducting lithium ions and electrons at the same time. The porous oxide solid electrolyte material with high specific surface area can increase the contact area and increase the conduction path for ion migration. The two work together to effectively accelerate the electrode reaction kinetics while having good rate performance and low-temperature performance. At the same time, the introduced reduced graphene oxide can also promote thermal conductivity, effectively reducing the temperature rise of the battery during discharge.

[0085] The technical solution of the present invention is further described in detail below in conjunction with several preferred embodiments and the accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0086] Unless otherwise specified, the experimental materials used in the following examples can be purchased from conventional biochemical reagent companies.

[0087] Example 1

[0088] Step 1: First, add 150 mL of anhydrous ethanol into a beaker and add a magnetic stirrer. Then, add 2.72 g of Ti(OC4H9)4, 0.75 g of Al(NO3)3·9H2O, and 0.938 g of malic acid in sequence. After the previous raw material is fully dissolved, add the next raw material to obtain a first mixed solution.

[0089] Step 2: First, add 150 mL of anhydrous ethanol into a beaker, and then add 0.48 g of LiNO3 and 1.72 g of NH4H2PO4 to obtain a second mixed solution.

[0090] Step 3: The second mixed solution and the first mixed solution were mixed, 3.04 g of a 0.5% solid content graphene oxide aqueous solution was added, and the mixture was stirred thoroughly to obtain a third mixed solution.

[0091] Step 4: freeze-dry the third mixed solution, first freezing the solution with liquid nitrogen, and then drying it using a freeze dryer to obtain a dry powder.

[0092] Step 5: The dried powder is heat-treated at 600 degrees Celsius for 15 hours in a nitrogen atmosphere to obtain a solid electrolyte composite material.

[0093] Step 6: The prepared solid electrolyte powder is subjected to alcohol wet high-speed planetary ball milling, with a mass ratio of grinding medium isopropyl alcohol to solid electrolyte composite material of 3:1, a rotation speed of 1200 rpm, a grinding time of 6 hours, and then dried at 70 degrees to obtain the ground nanopowder.

[0094] Example 2

[0095] Step 1: First, add 150 mL of anhydrous ethanol into a beaker and add a magnet for magnetic stirring. Then, add 2.72 g of Ti(OC4H9)4, 0.75 g of Al(NO3)3·9H2O, and 3.12 g of malonic acid in sequence. After the previous raw material is fully dissolved, add the next raw material to obtain the first mixed solution.

[0096] Step 2: First, add 150 mL of anhydrous ethanol into a beaker, and then add 0.48 g of LiNO3 and 1.72 g of NH4H2PO4 to obtain a second mixed solution.

[0097] Step 3: The second mixed solution and the first mixed solution were mixed, 1.29 g of a 3% solid content graphene oxide aqueous solution was added, and the mixture was stirred thoroughly to obtain a third mixed solution.

[0098] Step 4: freeze-dry the third mixed solution, first freezing the solution with liquid nitrogen, and then drying it using a freeze dryer to obtain a dry powder.

[0099] Step 5: The refined powder is heat-treated at 900 degrees for 8 hours in a nitrogen atmosphere to obtain a solid electrolyte composite material.

[0100] Step 6: The prepared solid electrolyte powder is subjected to alcohol wet high-speed planetary ball milling, with a mass ratio of grinding medium isopropyl alcohol to solid electrolyte composite material of 3:1, a rotation speed of 1200 rpm, a grinding time of 6 hours, and then dried at 70 degrees to obtain the ground nanopowder.

[0101] Example 3

[0102] Step 1: First add 150 mL of anhydrous ethanol into a beaker, add a magnet for magnetic stirring, then add 2.72 g of Ti(OC4H9)4, 0.75 g of Al(NO3)3·9H2O and 1.18 g of succinic acid in sequence, and add the next raw material after the previous raw material is fully dissolved to obtain the first mixed solution.

[0103] Step 2: First, add 150 mL of anhydrous ethanol into a beaker, and then add 0.48 g of LiNO3 and 1.72 g of NH4H2PO4 to obtain a second mixed solution.

[0104] Step 3: The second mixed solution and the first mixed solution were mixed, 4.83 g of a 5% solid content graphene oxide aqueous solution was added, and the mixture was stirred thoroughly to obtain a third mixed solution.

[0105] Step 4: freeze-dry the third mixed solution, first freezing the solution with liquid nitrogen, and then drying it using a freeze dryer to obtain a dry powder.

[0106] Step 5: The refined powder is heat-treated at 1100 degrees for 4 hours in a nitrogen atmosphere to obtain a solid electrolyte composite material.

[0107] Step 6: The prepared solid electrolyte powder is subjected to alcohol wet high-speed planetary ball milling, with a mass ratio of grinding medium isopropyl alcohol to solid electrolyte composite material of 3:1, a rotation speed of 1200 rpm, a grinding time of 6 hours, and then dried at 70 degrees to obtain the ground nanopowder.

[0108] Example 4

[0109] Step 1: First, add 150 mL of anhydrous ethanol into a beaker and add a magnet for magnetic stirring. Then, add 2.72 g of Ti(OC4H9)4, 0.75 g of Al(NO3)3·9H2O, and 1.92 g of citric acid in sequence. After the previous raw material is fully dissolved, add the next raw material to obtain a first mixed solution.

[0110] Step 2: First, add 150 mL of anhydrous ethanol into a beaker, and then add 0.48 g of LiNO3 and 1.72 g of NH4H2PO4 to obtain a second mixed solution.

[0111] Step 3: The second mixed solution and the first mixed solution were mixed, 3.62 g of a 2% solid content graphene oxide aqueous solution was added, and the mixture was stirred thoroughly to obtain a third mixed solution.

[0112] Step 4: freeze-dry the third mixed solution, first freezing the solution with liquid nitrogen, and then drying it using a freeze dryer to obtain a dry powder.

[0113] Step 5: The refined powder is heat-treated at 950 degrees for 6 hours in a nitrogen atmosphere to obtain a solid electrolyte composite material.

[0114] Step 6: The prepared solid electrolyte powder is subjected to alcohol wet high-speed planetary ball milling, with a mass ratio of grinding medium isopropyl alcohol to solid electrolyte composite material of 3:1, a rotation speed of 1200 rpm, a grinding time of 6 hours, and then dried at 70 degrees to obtain the ground nanopowder.

[0115] Example 5

[0116] Step 1: First, add 150 mL of anhydrous ethanol into a beaker and add a magnet for magnetic stirring. Then, add 1.70 g of Ti(OC4H9)4, 1.21 g of La(NO3)3·6H2O, and 1.50 g of citric acid in sequence. After the previous raw material is fully dissolved, add the next raw material to obtain a first mixed solution.

[0117] Step 2: First add 150 mL of anhydrous ethanol into a beaker, and then add 0.11 g of LiNO3 to obtain a second mixed solution.

[0118] Step 3: The second mixed solution and the first mixed solution were mixed, 0.85 g of a 2% solid content graphene oxide aqueous solution was added, and the mixture was stirred thoroughly to obtain a third mixed solution.

[0119] Step 4: freeze-dry the third mixed solution, first freezing the solution with liquid nitrogen, and then drying it using a freeze dryer to obtain a dry powder.

[0120] Step 5: The refined powder is heat-treated at 750 degrees for 6 hours in a nitrogen atmosphere to obtain a solid electrolyte composite material.

[0121] Step 6: The prepared solid electrolyte powder is subjected to alcohol wet high-speed planetary ball milling, with a mass ratio of grinding medium isopropyl alcohol to solid electrolyte composite material of 3:1, a rotation speed of 1200 rpm, a grinding time of 6 hours, and then dried at 70 degrees to obtain the ground nanopowder.

[0122] Comparative Example 1

[0123] Step 1: First, add 150 mL of anhydrous ethanol into a beaker and add a magnet for magnetic stirring. Then, add 2.72 g of Ti(OC4H9)4, 0.75 g of Al(NO3)3·9H2O, and 1.92 g of citric acid in sequence. After the previous raw material is fully dissolved, add the next raw material to obtain a first mixed solution.

[0124] Step 2: First, add 150 mL of anhydrous ethanol into a beaker, and then add 0.48 g of LiNO3 and 1.72 g of NH4H2PO4 to obtain a second mixed solution.

[0125] Step 3: The second mixed solution and the first mixed solution were mixed, 0.24 g of a 2% solid content graphene oxide aqueous solution was added, and the mixture was stirred thoroughly to obtain a third mixed solution.

[0126] Step 4: freeze-dry the third mixed solution, first freezing the solution with liquid nitrogen, and then drying it using a freeze dryer to obtain a dry powder.

[0127] Step 5: The refined powder is heat-treated at 950 degrees for 6 hours in a nitrogen atmosphere to obtain a solid electrolyte composite material.

[0128] Step 6: The prepared solid electrolyte powder is subjected to alcohol wet high-speed planetary ball milling, with a mass ratio of grinding medium isopropyl alcohol to solid electrolyte composite material of 3:1, a rotation speed of 1200 rpm, a grinding time of 6 hours, and then dried at 70 degrees to obtain the ground nanopowder.

[0129] Comparative Example 2

[0130] Step 1: First, add 150 mL of anhydrous ethanol into a beaker and add a magnet for magnetic stirring. Then, add 2.72 g of Ti(OC4H9)4, 0.75 g of Al(NO3)3·9H2O, and 1.92 g of citric acid in sequence. After the previous raw material is fully dissolved, add the next raw material to obtain a first mixed solution.

[0131] Step 2: First, add 150 mL of anhydrous ethanol into a beaker, and then add 0.48 g of LiNO3 and 1.72 g of NH4H2PO4 to obtain a second mixed solution.

[0132] Step 3: The second mixed solution and the first mixed solution were mixed, 13.27 g of a 2% solid content graphene oxide aqueous solution was added, and the mixture was stirred thoroughly to obtain a third mixed solution.

[0133] Step 4: freeze-dry the third mixed solution, first freezing the solution with liquid nitrogen, and then drying it using a freeze dryer to obtain a dry powder.

[0134] Step 5: The refined powder is heat-treated at 950 degrees for 6 hours in a nitrogen atmosphere to obtain a solid electrolyte composite material.

[0135] Step 6: The prepared solid electrolyte powder is subjected to alcohol wet high-speed planetary ball milling, with a mass ratio of grinding medium isopropyl alcohol to solid electrolyte composite material of 3:1, a rotation speed of 1200 rpm, a grinding time of 6 hours, and then dried at 70 degrees to obtain the ground nanopowder.

[0136] Comparative Example 3

[0137] Step 1: First, add 150 mL of anhydrous ethanol into a beaker and add a magnet for magnetic stirring. Then, add 2.72 g of Ti(OC4H9)4, 0.75 g of Al(NO3)3·9H2O, and 1.92 g of citric acid in sequence. After the previous raw material is fully dissolved, add the next raw material to obtain a first mixed solution.

[0138] Step 2: First, add 150 mL of anhydrous ethanol into a beaker, and then add 0.48 g of LiNO3 and 1.72 g of NH4H2PO4 to obtain a second mixed solution.

[0139] Step 3: The second mixed solution and the first mixed solution were mixed, 3.62 g of a 2% solid content graphene oxide aqueous solution was added, and the mixture was stirred thoroughly to obtain a third mixed solution.

[0140] Step 4: freeze-dry the third mixed solution, first freezing the solution with liquid nitrogen, and then drying it using a freeze dryer to obtain a dry powder.

[0141] Step 5: The refined powder is heat-treated at 950 degrees in an air atmosphere for 6 hours to obtain a solid electrolyte composite material.

[0142] Step 6: The prepared solid electrolyte powder is subjected to alcohol wet high-speed planetary ball milling, with a mass ratio of grinding medium isopropyl alcohol to solid electrolyte composite material of 3:1, a rotation speed of 1200 rpm, a grinding time of 6 hours, and then dried at 70 degrees to obtain the ground nanopowder.

[0143] Comparative Example 4

[0144] Step 1: First, add 150 mL of anhydrous ethanol into a beaker and add a magnet for magnetic stirring. Then, add 2.72 g of Ti(OC4H9)4, 0.75 g of Al(NO3)3·9H2O, and 1.92 g of citric acid in sequence. After the previous raw material is fully dissolved, add the next raw material to obtain a first mixed solution.

[0145] Step 2: First, add 150 mL of anhydrous ethanol into a beaker, and then add 0.48 g of LiNO3 and 1.72 g of NH4H2PO4 to obtain a second mixed solution.

[0146] Step 3: The second mixed solution and the first mixed solution were mixed, 3.62 g of 2% graphene oxide aqueous solution was added, and the mixture was stirred thoroughly to obtain a third mixed solution.

[0147] Step 4: freeze-dry the third mixed solution, first freezing the solution with liquid nitrogen, and then drying it using a freeze dryer to obtain a dry powder.

[0148] Step 5: The refined powder is heat-treated at 400 degrees for 6 hours in a nitrogen atmosphere to obtain a solid electrolyte composite material.

[0149] Step 6: The prepared solid electrolyte powder is subjected to alcohol wet high-speed planetary ball milling, with a mass ratio of grinding medium isopropyl alcohol to solid electrolyte composite material of 3:1, a rotation speed of 1200 rpm, a grinding time of 6 hours, and then dried at 70 degrees to obtain the ground nanopowder.

[0150] Comparative Example 5

[0151] Step 1: First, add 150 mL of anhydrous ethanol into a beaker and add a magnet for magnetic stirring. Then, add 2.72 g of Ti(OC4H9)4, 0.75 g of Al(NO3)3·9H2O, and 1.92 g of citric acid in sequence. After the previous raw material is fully dissolved, add the next raw material to obtain a first mixed solution.

[0152] Step 2: First, add 150 mL of anhydrous ethanol into a beaker, and then add 0.48 g of LiNO3 and 1.72 g of NH4H2PO4 to obtain a second mixed solution.

[0153] Step 3: The second mixed solution and the first mixed solution were mixed, 3.62 g of 2% graphene oxide aqueous solution was added, and the mixture was stirred thoroughly to obtain a third mixed solution.

[0154] Step 4: freeze-dry the third mixed solution, first freezing the solution with liquid nitrogen, and then drying it using a freeze dryer to obtain a dry powder.

[0155] Step 5: The refined powder is heat-treated at 1200 degrees for 6 hours in a nitrogen atmosphere to obtain a solid electrolyte composite material.

[0156] Step 6: The prepared solid electrolyte powder is subjected to alcohol wet high-speed planetary ball milling, with a mass ratio of grinding medium isopropyl alcohol to solid electrolyte composite material of 3:1, a rotation speed of 1200 rpm, a grinding time of 6 hours, and then dried at 70 degrees to obtain the ground nanopowder.

[0157] Comparative Example 6

[0158] Step 1: First, add 150 mL of anhydrous ethanol into a beaker and add a magnet for magnetic stirring. Then, add 2.72 g of Ti(OC4H9)4, 0.75 g of Al(NO3)3·9H2O, and 1.92 g of citric acid in sequence. After the previous raw material is fully dissolved, add the next raw material to obtain a first mixed solution.

[0159] Step 2: First, add 150 mL of anhydrous ethanol into a beaker, and then add 0.48 g of LiNO3 and 1.72 g of NH4H2PO4 to obtain a second mixed solution.

[0160] Step 3: Mix the second mixed solution and the first mixed solution, and stir them thoroughly to obtain a third mixed solution.

[0161] Step 4: freeze-dry the third mixed solution, first freezing the solution with liquid nitrogen, and then drying it using a freeze dryer to obtain a dry powder.

[0162] Step 5: The refined powder is heat-treated at 950 degrees for 6 hours in a nitrogen atmosphere to obtain a solid electrolyte composite material.

[0163] Step 6: The prepared solid electrolyte powder is subjected to alcohol wet high-speed planetary ball milling, with a mass ratio of grinding medium isopropyl alcohol to solid electrolyte composite material of 3:1, a rotation speed of 1200 rpm, a grinding time of 6 hours, and then dried at 70 degrees to obtain the ground nanopowder.

[0164] Comparative Example 7

[0165] Step 1: First add 150 mL of anhydrous ethanol into a beaker, add a magnet for magnetic stirring, then add 2.72 g of Ti(OC4H9)4 and 0.75 g of Al(NO3)3·9H2O in sequence. After the previous raw material is fully dissolved, add the next raw material to obtain the first mixed solution.

[0166] Step 2: First, add 150 mL of anhydrous ethanol into a beaker, and then add 0.48 g of LiNO3 and 1.72 g of NH4H2PO4 to obtain a second mixed solution.

[0167] Step 3: Mix the second mixed solution and the first mixed solution, and stir them thoroughly to obtain a third mixed solution.

[0168] Step 4: freeze-dry the third mixed solution, first freezing the solution with liquid nitrogen, and then drying it using a freeze dryer to obtain a dry powder.

[0169] Step 5: The refined powder is heat-treated at 950 degrees for 6 hours in a nitrogen atmosphere to obtain a solid electrolyte composite material.

[0170] Step 6: The prepared solid electrolyte powder is subjected to alcohol wet high-speed planetary ball milling, with a mass ratio of grinding medium isopropyl alcohol to solid electrolyte composite material of 3:1, a rotation speed of 1200 rpm, a grinding time of 6 hours, and then dried at 70 degrees to obtain the ground nanopowder.

[0171] The following describes a method for manufacturing a battery using the solid electrolyte composite material of the present application.

[0172] Button half-cell production:

[0173] NCM9055, solid electrolyte powder, conductive agent, and binder were mixed uniformly in a mass ratio of 90.16:1.38:5:3, with the ratio of NCM9055 to solid electrolyte being 98.5%:1.5%. This was then coated onto an aluminum foil current collector and vacuum-dried at 200°C to form the positive electrode sheet. In a glove box, the lithium sheet, separator, and positive electrode sheet were assembled using a button-type battery case. The electrolyte was then added dropwise, sealed, and pressurized to create the assembled CR2032 button-type half-cell.

[0174] Soft pack battery production:

[0175] The NCM9055 positive electrode, solid electrolyte powder, conductive agent, and binder were mixed uniformly in a mass ratio of 95.8:1:2:1.2 to prepare the positive electrode nmp slurry, which was coated on Al foil and vacuum dried to prepare the positive electrode. The artificial graphite material, dispersant, binder, and conductive agent were mixed uniformly in a mass ratio of 95.4:1.4:2:1.2 to prepare the negative electrode aqueous slurry, which was coated on Cu foil and vacuum dried to prepare the negative electrode. The above positive and negative electrode sheets were assembled into soft-pack batteries using commercial electrolytes.

[0176] The following describes the preparation of the solid electrolyte coated on the surface of the graphite negative electrode material of the present application and the testing method of its performance parameters.

[0177] Ionic conductivity test:

[0178] Preparation of solid electrolyte sheets: First, the obtained solid electrolyte powder material is kept at 600 degrees Celsius in air for 5 hours to remove the carbon material in the powder and prevent it from affecting the ionic conductivity test. 1g of powder is pressed into a mold with a diameter of 1 / 2 inch and a manual press is used for tableting at a pressure of 300MPa. The pressed electrolyte sheet is then heat-treated in an air atmosphere in a box furnace at 850 degrees Celsius for 10 hours, with a heating rate of 2 degrees per minute and a cooling phase. After heat treatment, a densely sintered solid electrolyte sheet is obtained.

[0179] The EIS test was conducted using an electrochemical workstation with a test voltage of 50mV and a frequency range of 300mHz-7MHz. After the test, an equivalent fitting circuit was used. R B and R GB The sum of the two is the total resistance R, ionic conductivity: σ = d / (R × S), where d is the thickness of the solid electrolyte sheet (cm); R is the total resistance of the solid electrolyte (Ω), and S is the effective area of ​​the electrode (cm 2 ).

[0180] Electronic conductivity test:

[0181] The powder used to test electronic conductivity is a solid electrolyte powder, and the measurement method follows the relevant provisions of GB / T 40007-2021, "Nanotechnology and Nanomaterials - General Rules for Contact Measurement of Resistivity." The test result is the electronic conductivity of the material when the pressure is equal to 4 kN.

[0182] Purity test:

[0183] X-ray diffractometer analysis was performed in accordance with the requirements of GB / T 24533-2019, "Graphite Anode Materials for Lithium-ion Batteries." The purity of the solid electrolyte phase was calculated by dividing the strongest peak of the solid electrolyte phase in the XRD pattern by the sum of the strongest peaks of all fitted phases. It is worth noting that carbon materials do not exhibit distinct crystalline peaks in XRD and are therefore not included in the purity calculation.

[0184] Particle size test:

[0185] The particle size of the prepared solid electrolyte was tested using a Malvern 3000 laser particle size analyzer. The dispersant was water, and the measurement method was carried out in accordance with the relevant provisions of GB / T19077.

[0186] Specific surface area test:

[0187] The determination method is in accordance with the relevant provisions of GB / T19587 Gas Adsorption BET Method for Determination of Specific Surface Area of ​​Solid Matter.

[0188] Pore ​​volume test:

[0189] The specific surface area and pore size analyzer was used, and the determination method was carried out in accordance with the relevant provisions of GB / T 21650.2-2008 Determination of pore size distribution and porosity of solid materials by mercury intrusion and gas adsorption method Part 2: Analysis of mesopores and macropores by gas adsorption method.

[0190] Thermogravimetric test:

[0191] The test was carried out in accordance with GB / T 27761-2011 test method for weight loss and residual amount by thermogravimetric analyzer.

[0192] Button battery test:

[0193] Capacity and initial efficiency: CR2032 button-type semi-solid-state batteries were assembled and the battery cycle performance was tested. For the NCM9055-Li system, the voltage range was 3.0-4.3V and the current was 0.1C. The initial discharge capacity and charge and discharge efficiency were compared.

[0194] Soft pack battery test:

[0195] Rate discharge test: (1) The soft-pack battery was first charged to 4.35V at 0.5C constant current, with a cutoff current of 0.05C, and allowed to stand for 5 minutes. It was then discharged to 3V at 1C constant current and allowed to stand for 5 minutes. (2) The battery was then charged to 4.35V at 0.5C constant current, with a cutoff current of 0.05C, and allowed to stand for 5 minutes. It was then discharged to 3V at 3C constant current and allowed to stand for 5 minutes. The ratio of the 3C discharge capacity to the 1C discharge capacity was calculated and compared.

[0196] Rate charging temperature rise test: (1) The soft-pack battery is first charged to 4.35V at 0.2C constant current, with a cut-off current of 0.05C, and allowed to stand for 5 minutes. It is then discharged to 3V at 0.5C constant current and allowed to stand for 5 minutes. (2) The battery is then charged to 4.35V at 3C constant current, with a cut-off current of 0.05C, and allowed to stand for 5 minutes. It is then discharged to 3V at 0.5C constant current and allowed to stand for 5 minutes. The temperature change during the 3C step charging process is tested.

[0197] 0 degree low temperature cycle: A soft pack battery is used to test the battery cycle performance. For the NCM9055-graphite system, the voltage range is 3-4.35V, the current is 0.2C, the temperature is 0 degrees, and the capacity retention rate is calculated for 50 cycles.

[0198] Low-temperature lithium deposition at -10 degrees Celsius: (1) The soft-pack battery is first placed in a constant temperature box at 10 degrees Celsius for 5 minutes, then discharged at a constant current of 1C to 3V and placed for 4 hours; (2) Placed for 5 minutes, then charged at a constant current and constant voltage of 2C to 4.35V, with a cut-off current of 50mA, continued to place for 5 minutes, and discharged at a constant current of 2C to 3V; (3) Repeat step (2) for 10 cycles of 2C charge and discharge; (4) Disassemble the battery in a glove box, remove the negative electrode, and observe the lithium deposition. If the electrode is golden and free of black matter, there is no lithium deposition; if black matter appears on the electrode, there is lithium deposition.

[0199] The solid electrolyte composite materials of Examples 1 to 4 and Comparative Examples 1 to 5 were subjected to relevant tests, and the test results are shown in Tables 1 to 4. The preparation process of the solid electrolyte composite material in the present invention is as follows: Figure 1 shown.

[0200] Figure 2 The XRD result diagram of the sample in Example 1 is given. When the graphene oxide and complexing agent are added in the amounts in Example 1, no obvious characteristic peaks related to the carbon material are found in the XRD, which may be related to the content and crystallinity of the carbon material.

[0201] Figure 3 and Figure 4 They are high-resolution SEM photos of the sample materials of Example 3 and Example 4 of the present invention, in which the porous LATP material and the flaky reduced graphene oxide material can be seen very clearly.

[0202] Figure 5 and Figure 6 Thermogravimetric test curves of samples from Examples 3 and 4 of the present invention are shown, respectively. The test temperature range is 30-900 degrees Celsius, and the test atmosphere is air. The total weight loss of Example 3 is approximately 16.18%, and the total weight loss of Example 4 is approximately 21.27%. The total weight loss here is mainly due to the oxidation of the carbon material (including reduced graphene oxide and pyrolyzed carbon).

[0203] Figure 7 The figure is a schematic diagram of the powder morphology of the example sample, which mainly includes a porous material portion and flaky reduced graphene oxide. The porous material portion consists of a porous solid electrolyte with pyrolyzed carbon mixed therein. The flaky reduced graphene oxide is mainly present on the surface, pores, and inside the porous material. Compared to simply coating the graphene material on the surface of the solid electrolyte, this method of adding graphene oxide during the sol-gel synthesis process can better combine the solid electrolyte and graphene, and can realize the three-dimensional structure of the electronic conduction network in the composite material. At the same time, the porous morphology of the solid electrolyte is achieved. When added to the positive electrode side, it greatly increases the contact area between the electrolyte and the solid electrolyte, increases the transmission path for the conduction of lithium ions, and accelerates ion migration. The pyrolyzed carbon and graphene in the material can be identified by combining high-power electron microscopy morphology observation and element distribution. The graphene morphology is clearly layered and has a distribution of C and O elements. The pyrolyzed carbon is contained in the porous solid electrolyte and has a distribution of C and O elements. In order to better identify the two carbon materials, material cross-sections can be prepared for characterization.

[0204] Table 1 Material properties of different embodiments and comparative examples

[0205]

[0206] As shown in Table 1, the ionic conductivity, electronic conductivity, particle size, specific surface area, and total weight loss of the materials of four examples and five comparative examples are summarized. Examples 1-4 use different amounts of graphene oxide to prepare solid electrolytes. The temperature and time of the heat treatment affect the crystallinity and grain size of the solid electrolyte. Higher temperatures are beneficial for improving the crystallinity of the material, promoting grain growth and ionic conduction, but the loss of lithium at high temperatures may generate impurities without ionic conductivity. Graphene oxide can promote material nucleation and increase the purity of the solid electrolyte. In Comparative Example 6, no graphene oxide was added, and its purity was only 89%. Due to the influence of impurities, the ionic conductivity of the corresponding material is also low. In addition, the heat treatment temperature and time also affect the reduction effect of graphene oxide. Generally, the higher the reduction temperature, the better the electronic conductivity of the reduced graphene oxide. Therefore, there is a certain temperature range in which solid electrolyte composite materials with high ionic and electronic conductivity can be obtained simultaneously. Heat treatment temperature: Example 1 < Example 2 < Example 4 < Example 3. The ionic conductivity obtained from the solid electrolyte tests in these four examples first increases and then decreases, while the corresponding electronic conductivity continues to increase. The powders in the examples and comparative examples are broken into comparable particle sizes by mechanical grinding. The heat treatment temperature used in comparative example 4 is too low, only 400 degrees, which hinders the phase formation of the solid electrolyte and makes it difficult to obtain the target crystal structure. Therefore, the ionic conductivity is very low. In addition, the thermal reduction of graphene oxide at low temperatures is insufficient, resulting in its very low electronic conductivity. The heat treatment temperature used in comparative example 5 is 1200 degrees. Although the thermal reduction of graphene oxide is good and the electronic conductivity is good, it causes the solid electrolyte to decompose at high temperature and produce impurities. Such impurities do not have ionic conductivity, and therefore also affect the ionic conductivity of the material. The specific surface area of ​​reduced graphene oxide is very high. Under the same process conditions, the specific surface area characteristics of the example / comparative example materials are mainly affected by the proportion of reduced graphene oxide in the material. The thermal weight loss of the examples / comparative examples is affected by the proportion of carbon material. The higher the proportion of reduced graphene oxide and thermally decomposed carbon, the greater the thermal weight loss.

[0207] Comparative Example 3, due to the use of air for heat treatment, oxidation of the carbon material occurred, leading to graphite oxidation loss. The resulting material primarily consisted of a solid electrolyte powder free of pyrolyzed carbon and graphene. Consequently, the electronic conductivity of this material was very low. Specific test results showed that under a pressure of 4 kN, the corresponding electronic conductivity was only 7.76E-08 S / cm, significantly lower than that of the other examples and comparative examples.

[0208] In Comparative Example 6, no graphene oxide solution was added, so the electronic conductivity of the synthesized material was low, only 3.50E-05S / cm, which was much lower than that of the other embodiments and comparative examples. In Comparative Example 7, due to the lack of the introduction of the complexing agent, the complexation of the LATP raw material was affected, and it was difficult to obtain the target product LATP. Therefore, the ionic conductivity was very low, only 2.10E-06S / cm.

[0209] Table 2 shows the results of the charge-withdrawal test of different embodiments and comparative examples, mainly including the first capacity and first efficiency of the charge-withdrawal test. The solid electrolyte powders of different embodiments and comparative examples are introduced into the positive electrode material in the form of additives. At the same blending amount, the solid electrolyte with higher electronic conductivity and ion conductivity is more conducive to the positive electrode capacity. Comparing Example 2 with Example 1, it can be found that the mixed conductivity of the material is improved and the charge-withdrawal capacity is improved.

[0210] It is worth mentioning that the surface area of ​​graphene oxide is very large. Excessive introduction will cause the surface of the LATP material to be wrapped, and the conduction path of lithium ions will be blocked. At the same time, it will increase the irreversible reaction between the electrolyte and graphene, affecting the first efficiency of the charge-off. Therefore, the charge-off capacity and the first efficiency of Comparative Example 2 have both decreased significantly. The graphene content in Comparative Example 1 is low, and the electronic conductivity of the material is limited; the solid electrolyte used in Comparative Example 3 does not contain any carbon material, and the electronic conductivity of the material itself is very low; Comparative Example 6 has no graphene and only relies on thermal decomposition of carbon to provide electronic conductivity. Therefore, the charge-off capacity of Comparative Examples 1, 3 and 6 is poor, but it is not affected by the graphene material, and the first efficiency is still relatively high. Comparative Examples 4-5 and 7 have poor ion conductivity of the material, which affects the charge-off capacity.

[0211] Table 2. Test results of different examples and comparative examples

[0212]

[0213] As shown in Table 3, the discharge and discharge temperature rise performance of the solid electrolyte containing graphene and pyrolyzed carbon are significantly improved compared with the comparative example, which is mainly due to the high ionic and electronic conductivity of the solid electrolyte containing graphene and pyrolyzed carbon. Example 4 has relatively optimal ionic and electronic conductivity, and its corresponding discharge performance is the best. Thanks to the improved kinetic performance, in the low temperature test, the corresponding minus 0 degrees 50 cycle capacity retention rate and minus 10 degrees lithium plating rate of the embodiment also showed good results.

[0214] Furthermore, thanks to the ultrafast thermal conductivity of reduced graphene oxide, its inclusion can accelerate heat dissipation and improve the battery's rate-discharge temperature rise. At the appropriate amount, increasing the graphene oxide content can effectively reduce the battery's rate-discharge temperature rise. Comparative Example 1 has a low graphene content, while Comparative Examples 3 and 6 contain no graphene, resulting in a relatively large battery discharge temperature rise.

[0215] Table 3 Test results of soft-pack batteries made of different examples and comparative examples

[0216]

[0217] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments using other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0218] It should be understood that the technical solution of the present invention is not limited to the above-mentioned specific implementation cases. Any technical variations made according to the technical solution of the present invention without departing from the scope of protection of the purpose of the present invention and the claims shall fall within the scope of protection of the present invention.

Claims

1. A solid electrolyte composite material, characterized in that: It includes an oxide solid electrolyte with a porous structure and an electron-conducting material, wherein the electron-conducting material includes granular thermally decomposed carbon and reduced graphene oxide; The electron-conductive material is distributed in the pores of the oxide solid electrolyte, and / or the electron-conductive material is at least partially embedded in the oxide solid electrolyte, and / or the electron-conductive material is distributed on part of the surface of the oxide solid electrolyte.

2. The solid electrolyte composite material according to claim 1, characterized in that: The mass fraction of the electron conductive material is 10-38%; And / or, the reduced graphene oxide has a flaky structure.

3. The solid electrolyte composite material according to claim 1, characterized in that: The pore volume of the oxide solid electrolyte is 0.05-0.55 cm 3 / g; And / or, the pores contained in the oxide solid electrolyte have a pore diameter of 10-200 nm; And / or, the oxide solid electrolyte includes any one or more combinations of LLTO, LATP, and LLZO; And / or, the specific surface area of ​​the oxide solid electrolyte is 15-200m 2 / g; and / or, the particle size of the oxide solid electrolyte is 120 to 900 nm; And / or, the purity of the solid electrolyte composite material is 90%-100%.

4. The method for preparing a solid electrolyte composite material according to any one of claims 1 to 3, wherein: include: Mixing a first mixed solution comprising at least a titanium source, a readily hydrolyzable and difficultly complexing raw material, and a complexing agent with a second mixed solution comprising at least a lithium source, a phosphorus source, and a non-hydrolyzable and easily complexing raw material, and then adding a graphene oxide solution to obtain a third mixed solution; Furthermore, the third mixed solution is freeze-dried and subjected to heat treatment in a non-oxidizing atmosphere to obtain a solid electrolyte composite material.

5. The preparation method according to claim 4, characterized in that: The titanium source includes C 16 H 36 O4Ti and / or Ti4(OCH3) 16 ; And / or, the easily hydrolyzed and difficult to complex raw materials include Al(NO3)3·9H2O, C9H 21 Any one or more combinations of AlO3, Al(NO3)3, ZrO(NO3)2, (C2H5O)4Si, Sr(NO3)2, Ca(NO3)2, Ba(NO3)2, La(NO3)3, La2O3; And / or, the complexing agent includes any one or more combinations of citric acid, citric acid monohydrate, malic acid, malonic acid, succinic acid, succinic acid, lactic acid, and ethylenediaminetetraacetic acid; And / or, the lithium source includes any one or more combinations of LiOH, Li2CO3, and LiNO3; And / or, the phosphorus source includes any one or more combinations of NH4H2PO4, Li3PO4, and LiH2PO4; And / or, the raw material that is not easily hydrolyzed and easily complexed includes any one or more combinations of NaNO3 and LiF; And / or, the first mixed solution further comprises a first solvent, and the first solvent comprises any one or more combinations of anhydrous ethanol, isopropanol, and methanol; And / or, the second mixed solution further includes a second solvent, and the second solvent includes any one or more combinations of anhydrous ethanol, isopropanol, and methanol.

6. The preparation method according to claim 4, wherein: The molar ratio of the complexing agent to the sum of the molar numbers of metal ions other than lithium ions in the easily hydrolyzed and difficult to complex raw materials is 0.7-3:1; And / or, the solid content of the graphene oxide solution is 0.5-5wt%; And / or, the mass ratio of graphene oxide to lithium source in the graphene oxide solution is 2-50:100; and / or, the molar ratio of the titanium source to the easily hydrolyzed and difficultly complexed raw material is (0.4:2)-(1.7:0.725); and / or, the molar ratio of the titanium source to the raw material that is not easily hydrolyzed and easily complexed is (0.4:4.4)-(1.7:4.3); And / or, the molar ratio of the titanium source to the lithium source is (0.4:1.4)-(1.7:1.3); And / or, the molar ratio of the titanium source to the phosphorus source is 0.4-1.7:

3.

7. The preparation method according to claim 4, characterized in that: The non-oxidizing atmosphere heat treatment is performed at a temperature of 500 to 1200° C. for a time of 4 to 15 hours; And / or, the non-oxidizing atmosphere used in the non-oxidizing atmosphere heat treatment includes any one or more combinations of nitrogen, argon, helium, and argon-hydrogen mixed gas.

8. An electrode additive, characterized in that The invention comprises the solid electrolyte composite material according to any one of claims 1 to 3, or comprises the solid electrolyte composite material prepared by the preparation method according to any one of claims 4 to 7.

9. An electrode, characterized in that The electrode additive according to claim 8 is included, and the electrode is a positive electrode or a negative electrode.

10. A lithium ion battery, characterized in that: Comprising the electrode according to claim 9.

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