Partially-coated lithium lanthanum zirconium oxide type solid electrolyte as well as preparation method and application thereof

Abstract

The invention provides a partially coated lithium lanthanum zirconium oxide solid electrolyte and a preparation method and application thereof, and the preparation method comprises the following steps: A) aging lithium lanthanum zirconium oxide in an air atmosphere to generate Li2CO3 on the surface to obtain aged ceramic powder; b) pickling the aged ceramic powder in a dilute acid solution, and drying to obtain dry powder after pickling; c) mixing the dry powder with an organic carbon source solution, and carrying out polymerization reaction to obtain an intermediate partially coated with an organic carbon source; and D) calcining the intermediate partially coated with the organic carbon source in an inert atmosphere to obtain the partially coated lithium lanthanum zirconium oxide type solid electrolyte. By controlling the coating process, LLZO nano powder materials with different coating areas can be obtained, and then electrolyte materials with different electronic conductivities are obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries, and in particular relates to a partially coated lithium lanthanum zirconium oxygen solid electrolyte, a preparation method and application thereof. Background Art

[0002] For decades, lithium-ion batteries (LIBs) have been used as a common power source for portable electronic devices, electric vehicles, and grid-level energy storage. However, since this type of battery usually uses organic liquid electrolytes, it has great safety and environmental issues, and its energy density has almost been developed to the limit, which limits the development of the new energy industry. In recent years, the electric vehicle market has developed rapidly, and mobile power is one of the most critical components of electric vehicles. Its performance directly determines whether it can replace fuel vehicles. The development of batteries with high specific energy, long cycle life, high safety, low cost and environmental friendliness has become the focus of the development of the new energy industry.

[0003] Compared with traditional organic liquid electrolytes, solid electrolyte lithium batteries have the characteristics of high safety, high electrochemical stability, high chemical stability, low cost, and environmental friendliness. They are considered to be ideal candidates for the next generation of lithium-ion battery electrolyte materials and are expected to completely replace organic electrolytes. However, there are still many challenges in realizing the large-scale application of all-solid-state lithium batteries. For example, the voltage polarization problem and poor rate performance caused by battery charging and discharging are caused by the low electronic conductivity of the solid electrolyte itself. Solid electrolytes usually have high lithium ion conductivity, which can meet the use requirements, but the low electronic conductivity seriously hinders the embedding and de-embedding of lithium ions on the positive and negative electrode surfaces, resulting in high interface resistance and lithium dendrites caused by uneven lithium plating.

[0004] At present, the most common improvement process for improving electronic conductivity is to carbon-coat the surface to prepare a solid electrolyte powder material with a coated structure. However, the powder materials prepared by most processes have a fully coated surface structure. While the electronic conductivity is significantly improved, the channels for lithium ions to enter and exit are greatly reduced, which significantly reduces the ion conductivity of the material, making it impossible to have both high electronic conductivity and high ion conductivity. Summary of the invention

[0005] The object of the present invention is to provide a partially coated garnet-type lithium lanthanum zirconium oxide (LLZO) solid electrolyte, a preparation method and an application thereof. The lithium lanthanum zirconium oxide solid electrolyte of the present invention has a local point coating feature. The presence of conductive carbon improves the electronic conduction of the grains, and the local coating reduces the coverage of the carbon layer on the surface of the grains, so that the lithium ion transmission channels on the surface are more exposed to the outside, and the ions are embedded and extracted faster, thereby maintaining the original conductivity level to the greatest extent and reducing the influence of the surface coating on the inherent ionic conductivity.

[0006] The present invention provides a method for preparing a partially coated lithium lanthanum zirconium oxygen solid electrolyte, comprising the following steps:

[0007] A) aging lithium lanthanum zirconium oxide in an air atmosphere to generate Li2CO3 on the surface to obtain an aged ceramic powder;

[0008] B) pickling the aged ceramic powder in a dilute acid solution, and drying after pickling to obtain dry powder;

[0009] C) mixing the dry powder with an organic carbon source solution to perform a polymerization reaction to obtain an intermediate partially coated with the organic carbon source;

[0010] D) calcining the intermediate partially coated with the organic carbon source under an inert atmosphere to obtain a partially coated lithium lanthanum zirconium oxygen type solid electrolyte.

[0011] Preferably, the aging temperature is 0 to 60° C.; and the aging time is 24 to 48 hours.

[0012] Preferably, the concentration of the dilute acid solution is 0.05-0.2 mol / L.

[0013] The pickling time is 10 to 60 seconds.

[0014] Preferably, the organic carbon source includes one or more of dopamine, tannic acid, aniline, furfural, phenol, formaldehyde, urea, furfural and furfuryl alcohol.

[0015] Preferably, the polymerization reaction temperature in the step C) is 0 to 60° C.; the polymerization reaction time in the step C) is 2 to 8 hours.

[0016] Preferably, the calcination holding temperature in step B) is 700-900° C.; the calcination time in step B) is 2-3 hours.

[0017] Preferably, the lithium lanthanum zirconium oxide is prepared according to the following steps:

[0018] 1) dissolving a lithium source, a lanthanum source and a zirconium source in water, heating to form a gel-like solid, drying the gel and then grinding it to obtain a precursor powder;

[0019] 2) calcining the precursor powder to obtain lithium lanthanum zirconium oxide.

[0020] The present invention provides a partially coated lithium lanthanum zirconium oxide type solid electrolyte, which is prepared according to the preparation method described above, and comprises a lithium lanthanum zirconium oxide body and a carbon coating layer on the surface of the lithium lanthanum zirconium oxide body, wherein the carbon coating layer presents a local point coating.

[0021] Preferably, in the partially coated lithium lanthanum zirconium oxygen type solid electrolyte, the mass fraction of the carbon coating layer is 1 to 20%.

[0022] The present invention provides a lithium ion battery, comprising the partially coated lithium lanthanum zirconium oxygen type solid electrolyte according to claim 8 or 9.

[0023] The invention provides a method for preparing a partially coated lithium lanthanum zirconium oxide (LLZO) solid electrolyte, comprising the following steps: A) aging lithium lanthanum zirconium oxide in an air atmosphere to generate Li2CO3 on the surface to obtain an aged ceramic powder; B) pickling the aged ceramic powder in a dilute acid solution, and drying after pickling to obtain a dry powder; C) mixing the dry powder with an organic carbon source solution, performing a polymerization reaction, and obtaining an intermediate partially coated with an organic carbon source; D) calcining the intermediate partially coated with an organic carbon source in an inert atmosphere to obtain a partially coated lithium lanthanum zirconium oxide solid electrolyte. The present invention first utilizes the presence of uneven Li on the surface of LLZO grains and the irregular shape of the grains through aging to generate a Li2CO3 coating layer with uneven thickness, and utilizes the difference in alkalinity between Li2CO3 on the surface of LLZO grains and LLZO itself, as well as the difference in adsorption capacity for specific organic molecules, to control the organic carbon source molecules to achieve different degrees of polymerization and uneven attachment polymerization on the surface of the grains without Li2CO3 coverage, and finally achieve the effect of local coating after calcination.

[0024] Furthermore, by controlling the coating process, LLZO nanopowder materials with different coating areas can be obtained, and thus electrolyte materials with different electronic conductivities can be obtained. Different electronic conductivities enable targeted applications according to actual needs, and in different blending systems, electronic conductivity can be adjusted to better adapt to different positive and negative electrode systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0026] Figure 1 This is a TEM image of the partially carbon-coated LLZO powder material prepared in Example 1 of the present invention;

[0027] Figure 2 1 and 2 are the physical phases of LLZO with different carbon coating amounts in the embodiments of the present invention. DETAILED DESCRIPTION

[0028] The present invention provides a method for preparing a partially coated lithium lanthanum zirconium oxygen type solid electrolyte, comprising the following steps:

[0029] A) aging lithium lanthanum zirconium oxide in an air atmosphere to generate Li2CO3 on the surface to obtain an aged ceramic powder;

[0030] B) pickling the aged ceramic powder in a dilute acid solution, and drying after pickling to obtain dry powder;

[0031] C) mixing the dry powder with an organic carbon source solution to perform a polymerization reaction to obtain an intermediate partially coated with the organic carbon source;

[0032] D) calcining the intermediate partially coated with the organic carbon source under an inert atmosphere to obtain a partially coated lithium lanthanum zirconium oxygen type solid electrolyte.

[0033] The present invention has no particular limitation on the source of the lithium lanthanum zirconium oxide, and the garnet-type lithium lanthanum zirconium oxide (Li7La3Zr2O 12 , LLZO), the lithium lanthanum zirconium oxide used can be an undoped tetragonal LLZO structure or a cubic LLZO structure doped with an element M (the M element includes Al, Ca, Fe, Ga, Nb, Ta, Ti, Sr, W, Y, etc.), and can be a conventional commercial product or homemade; in the present invention, it is preferably prepared by a sol-gel method, and the specific steps are as follows:

[0034] 1) dissolving a lithium source, a lanthanum source, a zirconium source and an optional M source in water, heating to form a gel-like solid, drying the gel and then grinding it to obtain a precursor powder;

[0035] 2) calcining the precursor powder to obtain lithium lanthanum zirconium oxide.

[0036] In the present invention, the types of the lithium source, lanthanum source and zirconium source can be the types of lithium source, lanthanum source and zirconium source commonly used in the art, such as lithium nitrate, lanthanum nitrate and zirconium oxynitrate used in the present invention; the M source can be a nitrate, oxide, etc. of the M element, such as lithium carbonate, aluminum nitrate, tantalum oxide, etc. used in the present invention. The lithium source, lanthanum source and zirconium source are selected according to Li7La3Zr2O 12 The stoichiometric ratio was weighed, wherein the Li source was a volatile element during the calcination process and therefore had an excess of 10%.

[0037] The invention adds weighed lithium source, lanthanum source and zirconium source into water, ultrasonically disperses them for 10 to 15 minutes, and then places them on a magnetic stirrer to fully stir and dissolve them, and finally forms a clear and transparent solution.

[0038] After obtaining the mixed solution, the present invention preferably heats the transparent solution under stirring conditions to volatilize the solvent to form a gel-like solid.

[0039] In the present invention, the heating temperature is preferably 70-90° C., more preferably 75-80° C.; the present invention has no particular limitation on the heating time, as long as the solvent is mixed completely to form a gel-like solid.

[0040] After obtaining the gel, the present invention dries and grinds the gel to obtain a dry precursor powder.

[0041] In the present invention, the drying temperature is preferably 130 to 160° C., more preferably 140 to 150° C.; the drying time is preferably 12 to 24 hours.

[0042] After obtaining the precursor, the present invention calcines the precursor to remove impurity elements such as carbon and nitrogen therein; and grinds the precursor after taking it out to obtain amorphous intermediate phase nano-ceramic powders such as Li-La-O, Li-Zr-O, La-Zr-O and Li-La-Zr-O.

[0043] The present invention places the ceramic powder obtained above in an air atmosphere with a certain humidity, fully exposes it, and ages it to generate Li2CO3 on its surface. In order to ensure that the reaction is sufficient and controllable, the relative humidity range should be within 10% to 90% and remain unchanged during the aging process. The presence of uneven Li on the surface of the original electrolyte material and the irregular shape of the grains cause the formation of a Li2CO3 coating layer of uneven thickness. The relative humidity range is preferably 20% to 80%, more preferably 30% to 70%, such as 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, preferably a range value with any of the above values ​​as the upper or lower limit.

[0044] In the present invention, the aging temperature is preferably 0-60° C., more preferably an ambient temperature of 10-40° C., more preferably 20-30° C. The aging time is preferably 24-48 hours, more preferably 30-40 hours, such as 24 hours, 26 hours, 28 hours, 30 hours, 32 hours, 34 hours, 36 hours, 38 hours, 40 hours, 42 hours, 44 hours, 46 hours, 48 ​​hours, preferably a range value with any of the above values ​​as the upper or lower limit.

[0045] After obtaining the aged ceramic powder, the present invention uses a dilute acid solution to pickle the aged mesophase ceramic powder material to remove the Li2CO3 coating layer on the surface. By controlling the pickling process parameters, the removal area of ​​the Li2CO3 coating layer is controlled. After pickling, the slurry is filtered and quickly dried to obtain a dry powder.

[0046] In the present invention, the acid in the dilute acid solution is preferably hydrochloric acid, the concentration of the dilute acid solution is preferably 0.05-0.2 mol / L, more preferably 0.1-0.15 mol / L, the pickling time is preferably 10-60 s, more preferably 20-50 s, such as 10 s, 15 s, 20 s, 25 s, 30 s, 35 s, 40 s, 45 s, 50 s, 55 s, 60 s, preferably a range value with any of the above values ​​as the upper or lower limit.

[0047] The present invention preferably mixes the acid-washed powder material with an organic carbon source solution, performs sufficient reaction polymerization under stirring conditions, and after the reaction is complete, performs drying to obtain an organic carbon source-coated LLZO mesophase ceramic powder.

[0048] In the present invention, the organic carbon source solution includes an organic carbon source and a solvent. The organic carbon source can be one or more of the monomers such as dopamine, tannic acid, aniline and furfural; it can also be one or more of the mixed monomers such as phenol and formaldehyde, urea and formaldehyde, furfural and furfuryl alcohol. The organic carbon source in the present invention can diffuse preferentially on the exposed LLZO original grain substrate surface rather than the Li2CO3 surface through chemical adsorption such as good metal coordination with La and Zr and physical adsorption such as hydrogen bonding, and form a strong adhesion layer to achieve local attachment. And it can automatically undergo polymerization (self-polymerization, polycondensation, condensation, addition polymerization, etc.) reaction in an alkaline environment with a pH greater than 7 using oxygen in the environment as an initiator, and the large difference in the alkalinity of the LLZO surface and Li2CO3 causes a large amount of organic monomers to attach and polymerize on the grain surface without Li2CO3 coverage.

[0049] In the present invention, the solvent in the organic carbon source is preferably an alcohol solvent, such as methanol, ethanol, etc.; the mass fraction of the organic carbon source solution is preferably 5-45%, more preferably 10-40%, such as 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, preferably a range value with any of the above values ​​as the upper or lower limit.

[0050] In the present invention, the polymerization reaction temperature is preferably 0-60°C, more preferably 20-40°C, such as 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, preferably a range value with any of the above values ​​as the upper or lower limit; the polymerization reaction time is preferably 2-8 hours, more preferably 3-6 hours.

[0051] In the present invention, the drying temperature is preferably 80 to 120° C., more preferably 90 to 110° C., most preferably 100 to 105° C., and the drying time is preferably 4 to 8 hours, more preferably 5 to 6 hours.

[0052] The present invention calcines the LLZO mesophase ceramic powder coated with an organic carbon source under an inert atmosphere, takes it out and grinds it to obtain a partially carbon-coated LLZO powder material.

[0053] In the present invention, the inert atmosphere is preferably nitrogen and / or argon; the calcination temperature is preferably 700-900°C, which can ensure that the residual Li2CO3 on the surface is completely reacted and decomposed, and the carbon source is completely carbonized, more preferably 750-850°C, such as 700°C, 720°C, 750°C, 780°C, 800°C, 820°C, 850°C, 880°C, 900°C, preferably a range value with any of the above values ​​as the upper or lower limit; the calcination time is preferably 2-3 hours.

[0054] The present invention also provides a partially coated lithium lanthanum zirconium oxide solid electrolyte, which is prepared according to the preparation method described above, and comprises a lithium lanthanum zirconium oxide body Li7La3Zr2O 12 and a carbon coating layer on the surface of the lithium lanthanum zirconium oxide body, wherein the carbon coating layer is partially dotted. In the partially coated lithium lanthanum zirconium oxide type solid electrolyte, the mass of the carbon coating layer accounts for 1 to 20% of the mass of the lithium lanthanum zirconium oxide, more preferably 5 to 15%, wherein when the mass fraction of the carbon coating layer is 10% or more, it indicates a fully coated material.

[0055] The present invention also provides a lithium-ion battery, comprising the partially coated lithium lanthanum zirconium oxygen type solid electrolyte described above

[0056] The invention provides a method for preparing a partially coated lithium lanthanum zirconium oxide type solid electrolyte, comprising the following steps: A) aging lithium lanthanum zirconium oxide in an air atmosphere to generate Li2CO3 on the surface to obtain an aged ceramic powder; B) pickling the aged ceramic powder in a dilute acid solution, and drying after pickling to obtain a dry powder; C) mixing the dry powder with an organic carbon source solution, performing a polymerization reaction, and obtaining an intermediate partially coated with an organic carbon source; D) calcining the intermediate partially coated with an organic carbon source in an inert atmosphere to obtain a partially coated lithium lanthanum zirconium oxide type solid electrolyte. The present invention first utilizes the presence of uneven Li on the surface of LLZO grains and the irregular shape of the grains through aging to generate a Li2CO3 coating layer with uneven thickness, and utilizes the difference in alkalinity between Li2CO3 on the surface of LLZO grains and LLZO itself, as well as the difference in adsorption capacity for specific organic molecules, to control the organic carbon source molecules to achieve different degrees of polymerization and uneven attachment polymerization on the surface of the grains without Li2CO3 coverage, and finally achieve the effect of local coating after calcination.

[0057] Furthermore, by controlling the coating process, LLZO nanopowder materials with different coating qualities (corresponding to different coating areas) can be obtained, and thus electrolyte materials with different electronic conductivities can be obtained. Different electronic conductivities enable targeted applications according to actual needs, and in different blending systems, electronic conductivity can be adjusted to better adapt to different positive and negative electrode systems.

[0058] In order to further illustrate the present invention, a partially coated lithium lanthanum zirconium oxygen type solid electrolyte provided by the present invention, its preparation method and application are described in detail below in combination with embodiments, but it should not be understood as limiting the scope of protection of the present invention.

[0059] Example 1

[0060] 1. First, lithium nitrate, lanthanum nitrate and zirconium nitrate are mixed according to Li7La3Zr2O 12 The stoichiometric ratio is weighed, wherein the Li element is 10% in excess. The weighed lithium source, lanthanum source, and zirconium source are added to a beaker containing an appropriate amount of deionized water in sequence, and ultrasonically dispersed for 15 minutes, and then placed on a magnetic stirrer to fully stir and dissolve, and finally a clear and transparent solution is formed. Then, heating and stirring are continued at 80°C to evaporate the solvent and form a gel-like solid; the gel is further placed in a 150°C forced air drying oven for 12 hours, and then taken out and ground to obtain a completely dry precursor powder.

[0061] 2. Pre-sintering: calcine the precursor in a muffle furnace at 500°C for 2 hours to remove impurity elements such as carbon and nitrogen; take it out and grind it to obtain amorphous intermediate phase nano-ceramic powders such as Li-La-O, Li-Zr-O, La-Zr-O and Li-La-Zr-O.

[0062] 3. Aging: Place the above powder in air with constant humidity and expose it for 24 hours to generate Li2CO3 on its surface.

[0063] 4. Pickling: Place the aged mesophase ceramic powder material in a solution with a concentration of 0.1 mol·L -1 The surface of the samples was pickled in dilute hydrochloric acid for 55 s to remove the Li2CO3 coating.

[0064] 5. Coating: Dopamine (DA) is selected as the organic coating carbon source. The acid-washed powder material is placed in a 5% mass fraction dopamine methanol solution and stirred for 2 hours to allow it to fully react and polymerize. After the reaction is complete, it is placed in a blast drying oven at 100°C for 4 hours to obtain LLZO mesophase ceramic powder coated with polydopamine (PDA).

[0065] 6. Calcination: The above powder is placed in a tubular furnace filled with inert gas such as nitrogen and argon and calcined for 3 hours at a holding temperature of 700°C. After taking out, it is ground to obtain a partially carbon-coated LLZO powder material.

[0066] Example 2

[0067] 1. First, lithium nitrate, lanthanum nitrate, aluminum nitrate, and zirconium oxynitrate were mixed according to Li 6.4 Al 0.3 La3Zr2O 12 The stoichiometric ratio is weighed, in which the Li element is 10% in excess. The weighed lithium source, aluminum source, lanthanum source, and zirconium source are added to a beaker containing an appropriate amount of deionized water in sequence, and ultrasonically dispersed for 15 minutes, and then placed on a magnetic stirrer to fully stir and dissolve, and finally a clear and transparent solution is formed. Then, heating and stirring are continued at 80°C to evaporate the solvent and form a gel-like solid; the gel is further placed in a 150°C forced air drying oven for 12 hours, and then taken out and ground to obtain a completely dry precursor powder.

[0068] 2. Pre-sintering: calcine the precursor in a muffle furnace at 500°C for 2 hours to remove impurity elements such as carbon and nitrogen; take it out and grind it to obtain amorphous intermediate phase nano-ceramic powders such as Li-La-O, Li-Zr-O, La-Zr-O and Li-La-Zr-O.

[0069] 3. Aging: Place the above powder in air with constant humidity and expose it for 30 hours to generate Li2CO3 on its surface.

[0070] 4. Pickling: Place the aged mesophase ceramic powder material in a solution with a concentration of 0.1 mol·L -1 The surface was pickled in dilute hydrochloric acid for 50 s to remove the Li2CO3 coating.

[0071] 5. Coating: Tannic acid (TA) is selected as the organic coating carbon source. The acid-washed powder material is placed in a 20% mass fraction tannic acid methanol solution and stirred for 3 hours to allow it to fully react and polymerize. After the reaction is complete, it is placed in a blast drying oven at 100°C for 4 hours to obtain LLZO mesophase ceramic powder coated with polytannic acid (PTA).

[0072] 6. Calcination: The above powder is placed in a tubular furnace filled with inert gas such as nitrogen and argon and calcined for 3 hours at a holding temperature of 800°C. After being taken out and ground, a partially carbon-coated LLZO powder material is obtained.

[0073] Example 3

[0074] 1. First, lithium nitrate, lanthanum nitrate, zirconium nitrate and lithium carbonate were mixed according to Li7La3Zr 1.5 Ta 0.5O 12 The stoichiometric ratio is weighed, in which the Li element is 10% in excess. The weighed lithium source, lanthanum source, zirconium source, and tantalum source are added to a beaker containing an appropriate amount of deionized water in sequence, and ultrasonically dispersed for 10 minutes and then placed on a magnetic stirrer to fully stir and dissolve, eventually forming a clear and transparent solution. Then continue heating and stirring at 80°C to evaporate the solvent and form a gel-like solid; the gel is further placed in a 150°C forced air drying oven for 12 hours, then taken out and ground to obtain a completely dry precursor powder.

[0075] 2. Pre-sintering: calcine the precursor in a muffle furnace at 500°C for 2 hours to remove impurity elements such as carbon and nitrogen; take it out and grind it to obtain amorphous intermediate phase nano-ceramic powders such as Li-La-O, Li-Zr-O, La-Zr-O and Li-La-Zr-O.

[0076] 3. Aging: Place the above powder in air with constant humidity and expose it for 48 hours to generate Li2CO3 on its surface.

[0077] 4. Pickling: Place the aged mesophase ceramic powder material in a solution with a concentration of 0.1 mol·L -1 The surface of the samples was pickled in dilute hydrochloric acid for 60 s to remove the Li2CO3 coating.

[0078] 5. Coating: Aniline is selected as the organic coating carbon source. The acid-washed powder material is placed in a 30% mass fraction aniline methanol solution and stirred for 4 hours to fully react and polymerize into polyaniline (PANI). After the reaction is complete, it is placed in a blast drying oven at 100°C for 4 hours to obtain LLZO mesophase ceramic powder coated with phenolic resin.

[0079] 6. Calcination: The above powder is placed in a tubular furnace filled with inert gas such as nitrogen and argon and calcined for 3 hours at a holding temperature of 900°C. After taking out, the partially carbon-coated LLZO powder material is obtained by grinding.

[0080] Example 4

[0081] 1. First, lithium nitrate, lanthanum nitrate and zirconium nitrate are mixed according to Li7La3Zr 1.5 Nb 0.5 O 12 The stoichiometric ratio is weighed, in which the Li element is 10% in excess. The weighed lithium source, lanthanum source, zirconium source, and niobium source are added to a beaker containing an appropriate amount of deionized water in sequence, and ultrasonically dispersed for 10 minutes, and then placed on a magnetic stirrer to fully stir and dissolve, and finally a clear and transparent solution is formed. Then, heating and stirring are continued at 80°C to evaporate the solvent and form a gel-like solid; the gel is further placed in a 150°C forced air drying oven for 16 hours, and then taken out and ground to obtain a completely dry precursor powder.

[0082] 2. Pre-sintering: calcine the precursor in a muffle furnace at 600°C for 2 hours to remove impurity elements such as carbon and nitrogen; take it out and grind it to obtain amorphous intermediate phase nano-ceramic powders such as Li-La-O, Li-Zr-O, La-Zr-O and Li-La-Zr-O.

[0083] 3. Aging: Place the above powder in air with constant humidity and expose it for 30 hours to generate Li2CO3 on its surface.

[0084] 4. Pickling: Place the aged mesophase ceramic powder material in a solution with a concentration of 0.1 mol·L -1 The slurry was pickled in dilute hydrochloric acid for 40 seconds to remove the Li2CO3 coating layer on the surface. The removal area of ​​the Li2CO3 coating layer was controlled by controlling the pickling time. After pickling, the slurry was filtered and quickly dried to obtain dry powder.

[0085] 5. Coating: Urea and formaldehyde are selected as organic coating carbon sources. The acid-washed powder material is placed in a mixed methanol solution of urea and formaldehyde with a concentration of 10% by mass and a molar ratio of 1:1, and stirred for 5 hours to fully react and polymerize into urea-formaldehyde resin (UF). After the reaction is complete, it is placed in a blast drying oven at 100°C for 4 hours to obtain LLZO mesophase ceramic powder coated with urea-formaldehyde resin.

[0086] 6. Calcination: The above powder is placed in a tubular furnace filled with inert gas such as nitrogen and argon and calcined for 3 hours at a holding temperature of 700°C. After taking out, it is ground to obtain a partially carbon-coated LLZO powder material.

[0087] Example 5

[0088] 1. First, lithium nitrate, lanthanum nitrate and zirconium nitrate are mixed according to Li7La3Zr2O 12 The stoichiometric ratio is weighed, in which the Li element is 10% in excess. The weighed lithium source, lanthanum source, and zirconium source are added to a beaker containing an appropriate amount of deionized water in sequence, and ultrasonically dispersed for 12 minutes and then placed on a magnetic stirrer to fully stir and dissolve, eventually forming a clear and transparent solution. Then continue heating and stirring at 80°C to evaporate the solvent and form a gel-like solid; the gel is further placed in a 150°C forced air drying oven for 16 hours, then taken out and ground to obtain a completely dry precursor powder.

[0089] 2. Pre-sintering: calcine the precursor in a muffle furnace at 600°C for 2 hours to remove impurity elements such as carbon and nitrogen; take it out and grind it to obtain amorphous intermediate phase nano-ceramic powders such as Li-La-O, Li-Zr-O, La-Zr-O and Li-La-Zr-O.

[0090] 3. Aging: Place the above powder in air with constant humidity and expose it for 42 hours to generate Li2CO3 on its surface.

[0091] 4. Pickling: Place the aged mesophase ceramic powder material in a solution with a concentration of 0.1 mol·L -1 The surface was pickled in dilute hydrochloric acid for 50 s to remove the Li2CO3 coating.

[0092] 5. Coating: A mixture of phenol and formaldehyde is selected as an organic coating carbon source. The acid-washed powder material is placed in a methanol solution containing 15% mass fraction of phenol and formaldehyde in a molar ratio of 1:1, and stirred for 4 hours to fully react and polymerize into phenolic resin (PF). After the reaction is complete, it is placed in a blast drying oven at 100°C for 4 hours to obtain LLZO mesophase ceramic powder coated with phenolic resin.

[0093] 6. Calcination: The above powder is placed in a tubular furnace filled with inert gas such as nitrogen and argon and calcined for 3 hours at a holding temperature of 800°C. After being taken out and ground, a partially carbon-coated LLZO powder material is obtained.

[0094] Example 6

[0095] 1. First, lithium nitrate, lanthanum nitrate, zirconium oxynitrate and lithium tantalate are mixed according to Li7La3Zr 1.5 Ta 0.5 O 12 The stoichiometric ratio is weighed, in which the Li element is 10% in excess. The weighed lithium source, lanthanum source, zirconium source, and tantalum source are added to a beaker containing an appropriate amount of deionized water in sequence, and ultrasonically dispersed for 12 minutes and then placed on a magnetic stirrer to fully stir and dissolve, eventually forming a clear and transparent solution. Then continue heating and stirring at 80°C to evaporate the solvent and form a gel-like solid; the gel is further placed in a 150°C forced air drying oven for 16 hours, then taken out and ground to obtain a completely dry precursor powder.

[0096] 2. Pre-sintering: calcine the precursor in a muffle furnace at 600°C for 2 hours to remove impurity elements such as carbon and nitrogen; take it out and grind it to obtain amorphous intermediate phase nano-ceramic powders such as Li-La-O, Li-Zr-O, La-Zr-O and Li-La-Zr-O.

[0097] 3. Aging: Place the above powder in air with constant humidity and expose it for 36 hours to generate Li2CO3 on its surface.

[0098] 4. Pickling: Place the aged mesophase ceramic powder material in a solution with a concentration of 0.1 mol·L -1 The surface of the samples was pickled in dilute hydrochloric acid for 40 s to remove the Li2CO3 coating.

[0099] 5. Coating: Dopamine (DA) is selected as the organic coating carbon source. The acid-washed powder material is placed in a 25% mass fraction dopamine methanol solution and stirred for 6 hours to allow it to fully react and polymerize. After the reaction is complete, it is placed in a blast drying oven at 100°C for 6 hours to obtain LLZO mesophase ceramic powder coated with polydopamine (PDA).

[0100] 6. Calcination: The above powder is placed in a tubular furnace filled with inert gas such as nitrogen and argon and calcined for 3 hours at a holding temperature of 900°C. After being taken out and ground, a partially carbon-coated LLZO powder material is obtained.

[0101] Example 7

[0102] 1. First, lithium nitrate, lanthanum nitrate and zirconium nitrate are mixed according to Li7La3Zr2O 12 The stoichiometric ratio is weighed, in which the Li element is 10% in excess. The weighed lithium source, lanthanum source, and zirconium source are added to a beaker containing an appropriate amount of deionized water in sequence, and ultrasonically dispersed for 15 minutes, and then placed on a magnetic stirrer to fully stir and dissolve, and finally a clear and transparent solution is formed. Then, heating and stirring are continued at 80°C to evaporate the solvent and form a gel-like solid; the gel is further placed in a 150°C forced air drying oven for 16 hours, and then taken out and ground to obtain a completely dry precursor powder.

[0103] 2. Pre-sintering: calcine the precursor in a muffle furnace at 450°C for 2 hours to remove impurity elements such as carbon and nitrogen; take it out and grind it to obtain amorphous intermediate phase nano-ceramic powders such as Li-La-O, Li-Zr-O, La-Zr-O and Li-La-Zr-O.

[0104] 3. Aging: Place the above powder in air with constant humidity for 48 hours to generate Li2CO3 on its surface.

[0105] 4. Pickling: Place the aged mesophase ceramic powder material in a solution with a concentration of 0.1 mol·L -1 The surface was pickled in dilute hydrochloric acid for 50 s to remove the Li2CO3 coating.

[0106] 5. Coating: Aniline is selected as the organic coating carbon source. The acid-washed powder material is placed in a 35% mass fraction aniline methanol solution and stirred for 7 hours to fully react and polymerize into polyaniline (PANI). After the reaction is complete, it is placed in a blast drying oven at 100°C for 6 hours to obtain LLZO mesophase ceramic powder coated with phenolic resin.

[0107] 6. Calcination: The above powder is placed in a tubular furnace filled with inert gas such as nitrogen and argon and calcined for 2 hours at a holding temperature of 700°C. After being taken out and ground, a partially carbon-coated LLZO powder material is obtained.

[0108] Example 8

[0109] 1. First, lithium nitrate, lanthanum nitrate, gallium nitrate and zirconium oxynitrate are mixed according to Li 6.4 Ga 0.3 La3Zr2O 12 The stoichiometric ratio is weighed, wherein the Li element is 10% in excess. The weighed lithium source, lanthanum source, gallium source, and zirconium source are added to a beaker containing an appropriate amount of deionized water in sequence, and after ultrasonic separation for 15 minutes, they are placed on a magnetic stirrer to be fully stirred and dissolved, and finally a clear and transparent solution is formed. Then, heating and stirring are continued at 80°C to evaporate the solvent and form a gel-like solid; the gel is further placed in a 150°C forced air drying oven for 20 hours, and then taken out and ground to obtain a completely dry precursor powder.

[0110] 2. Pre-sintering: calcine the precursor in a muffle furnace at 450°C for 3 hours to remove impurity elements such as carbon and nitrogen; take it out and grind it to obtain amorphous intermediate phase nano-ceramic powders such as Li-La-O, Li-Zr-O, La-Zr-O and Li-La-Zr-O.

[0111] 3. Aging: Place the above powder in air with constant humidity and expose it for 30 hours to generate Li2CO3 on its surface.

[0112] 4. Pickling: Place the aged mesophase ceramic powder material in a solution with a concentration of 0.1 mol·L -1 The surface of the samples was pickled in dilute hydrochloric acid for 30 s to remove the Li2CO3 coating.

[0113] 5. Coating: Dopamine (DA) is selected as the organic coating carbon source. The acid-washed powder material is placed in a 45% mass fraction dopamine methanol solution and stirred for 8 hours to allow it to fully react and polymerize. After the reaction is complete, it is placed in a blast drying oven at 100°C for 6 hours to obtain LLZO mesophase ceramic powder coated with polydopamine (PDA).

[0114] 6. Calcination: The above powder is placed in a tubular furnace filled with inert gas such as nitrogen and argon and calcined for 2 hours at a holding temperature of 900°C. After being taken out and ground, a partially carbon-coated LLZO powder material is obtained.

[0115] Example 9

[0116] 1. First, lithium nitrate, lanthanum nitrate and zirconium nitrate are mixed according to Li7La3Zr2O 12The stoichiometric ratio is weighed, wherein the Li element is 10% in excess. The weighed lithium source, lanthanum source, and zirconium source are added to a beaker containing an appropriate amount of deionized water in sequence, and ultrasonically dispersed for 10 minutes, and then placed on a magnetic stirrer to fully stir and dissolve, and finally a clear and transparent solution is formed. Then, heating and stirring are continued at 80°C to evaporate the solvent and form a gel-like solid; the gel is further placed in a 150°C forced air drying oven for 20 hours, and then taken out and ground to obtain a completely dry precursor powder.

[0117] 2. Pre-sintering: calcine the precursor in a muffle furnace at 450°C for 3 hours to remove impurity elements such as carbon and nitrogen; take it out and grind it to obtain amorphous intermediate phase nano-ceramic powders such as Li-La-O, Li-Zr-O, La-Zr-O and Li-La-Zr-O.

[0118] 3. Aging: Place the above powder in air with constant humidity and expose it for 42 hours to generate Li2CO3 on its surface.

[0119] 4. Pickling: Place the aged mesophase ceramic powder material in a solution with a concentration of 0.1 mol·L -1 The surface of the samples was pickled in dilute hydrochloric acid for 40 s to remove the Li2CO3 coating.

[0120] 5. Coating: Tannic acid (TA) is selected as the organic coating carbon source. The acid-washed powder material is placed in a 5% mass fraction tannic acid methanol solution and stirred for 4 hours to allow it to fully react and polymerize. After the reaction is complete, it is placed in a blast drying oven at 100°C for 6 hours to obtain LLZO mesophase ceramic powder coated with polytannic acid (PTA).

[0121] 6. Calcination: The above powder is placed in a tubular furnace filled with inert gas such as nitrogen and argon and calcined for 2 hours at a holding temperature of 800°C. After being taken out and ground, a partially carbon-coated LLZO powder material is obtained.

[0122] Example 10

[0123] 1. First, lithium nitrate, lanthanum nitrate, lithium tantalate, and zirconium oxynitrate are mixed according to Li7La3Zr 1.5 Ta 0.5 O 12 The stoichiometric ratio is weighed, in which the Li element is 10% in excess. The weighed lithium source, lanthanum source, zirconium source and tantalum source are added to a beaker containing an appropriate amount of deionized water in sequence, and ultrasonically dispersed for 12 minutes and then placed on a magnetic stirrer to fully stir and dissolve, eventually forming a clear and transparent solution. Then continue heating and stirring at 80°C to evaporate the solvent and form a gel-like solid; the gel is further placed in a 150°C forced air drying oven for 20 hours, then taken out and ground to obtain a completely dry precursor powder.

[0124] 2. Pre-sintering: calcine the precursor in a muffle furnace at 550°C for 3 hours to remove impurity elements such as carbon and nitrogen; take it out and grind it to obtain amorphous intermediate phase nano-ceramic powders such as Li-La-O, Li-Zr-O, La-Zr-O and Li-La-Zr-O.

[0125] 3. Aging: Place the above powder in air with constant humidity and expose it for 24 hours to generate Li2CO3 on its surface.

[0126] 4. Pickling: Place the aged mesophase ceramic powder material in a solution with a concentration of 0.1 mol·L -1 The surface of the samples was pickled in dilute hydrochloric acid for 30 s to remove the Li2CO3 coating.

[0127] 5. Coating: Aniline is selected as the organic coating carbon source. The acid-washed powder material is placed in a 10% mass fraction aniline methanol solution and stirred for 4 hours to fully react and polymerize into polyaniline (PANI). After the reaction is complete, it is placed in a blast drying oven at 100°C for 6 hours to obtain LLZO mesophase ceramic powder coated with phenolic resin.

[0128] 6. Calcination: The above powder is placed in a tubular furnace filled with inert gas such as nitrogen and argon and calcined for 2 hours at a holding temperature of 900°C. After being taken out and ground, a partially carbon-coated LLZO powder material is obtained.

[0129] Embodiment 11

[0130] 1. First, lithium nitrate, lanthanum nitrate and zirconium nitrate are mixed according to Li7La3Zr2O 12 The stoichiometric ratio is weighed, in which the Li element is 10% in excess. The weighed lithium source, lanthanum source, and zirconium source are added to a beaker containing an appropriate amount of deionized water in sequence, and ultrasonically dispersed for 12 minutes and then placed on a magnetic stirrer to fully stir and dissolve, eventually forming a clear and transparent solution. Then continue heating and stirring at 80°C to evaporate the solvent and form a gel-like solid; the gel is further placed in a 150°C forced air drying oven for 20 hours, then taken out and ground to obtain a completely dry precursor powder.

[0131] 2. Pre-sintering: calcine the precursor in a muffle furnace at 550°C for 3 hours to remove impurity elements such as carbon and nitrogen; take it out and grind it to obtain amorphous intermediate phase nano-ceramic powders such as Li-La-O, Li-Zr-O, La-Zr-O and Li-La-Zr-O.

[0132] 3. Aging: Place the above powder in air with constant humidity for 48 hours to generate Li2CO3 on its surface.

[0133] 4. Pickling: Place the aged mesophase ceramic powder material in a solution with a concentration of 0.1 mol·L -1 The surface of the samples was pickled in dilute hydrochloric acid for 40 s to remove the Li2CO3 coating.

[0134] 5. Coating: Tannic acid (TA) is selected as the organic coating carbon source. The acid-washed powder material is placed in a 15% mass fraction tannic acid methanol solution and stirred for 8 hours to allow it to fully react and polymerize. After the reaction is complete, it is placed in a blast drying oven at 100°C for 8 hours to obtain LLZO mesophase ceramic powder coated with polytannic acid (PTA).

[0135] 6. Calcination: The above powder is placed in a tubular furnace filled with inert gas such as nitrogen and argon and calcined for 2 hours at a holding temperature of 700°C. After being taken out and ground, a partially carbon-coated LLZO powder material is obtained.

[0136] Example 12

[0137] 1. First, lithium nitrate, lanthanum nitrate, lithium tantalate, and zirconium oxynitrate are mixed according to Li7La3Zr 1.5 Ta 0.5 O 12 The stoichiometric ratio is weighed, wherein the Li element is 10% in excess. The weighed lithium source, lanthanum source, and zirconium source are added to a beaker containing an appropriate amount of deionized water in sequence, and ultrasonically dispersed for 15 minutes, and then placed on a magnetic stirrer to fully stir and dissolve, and finally a clear and transparent solution is formed. Then, heating and stirring are continued at 80°C to evaporate the solvent and form a gel-like solid; the gel is further placed in a 150°C forced air drying oven for 20 hours, and then taken out and ground to obtain a completely dry precursor powder.

[0138] 2. Pre-sintering: calcine the precursor in a muffle furnace at 550°C for 3 hours to remove impurity elements such as carbon and nitrogen; take it out and grind it to obtain amorphous intermediate phase nano-ceramic powders such as Li-La-O, Li-Zr-O, La-Zr-O and Li-La-Zr-O.

[0139] 3. Aging: Place the above powder in air with constant humidity and expose it for 36 hours to generate Li2CO3 on its surface.

[0140] 4. Pickling: Place the aged mesophase ceramic powder material in a solution with a concentration of 0.1 mol·L -1 The surface of the samples was pickled in dilute hydrochloric acid for 20 s to remove the Li2CO3 coating.

[0141] 5. Coating: Dopamine (DA) is selected as the organic coating carbon source. The acid-washed powder material is placed in a 20% mass fraction dopamine methanol solution and stirred for 6 hours to allow it to fully react and polymerize. After the reaction is complete, it is placed in a blast drying oven at 100°C for 8 hours to obtain LLZO mesophase ceramic powder coated with polydopamine (PDA).

[0142] 6. Calcination: The above powder is placed in a tubular furnace filled with inert gas such as nitrogen and argon and calcined for 2 hours at a holding temperature of 800°C. After being taken out and ground, a partially carbon-coated LLZO powder material is obtained.

[0143] Example 13

[0144] 1. First, lithium nitrate, lanthanum nitrate, lithium tantalate, and zirconium oxynitrate are mixed according to Li7La3Zr 1.5 Ta 0.5 O 12 The stoichiometric ratio is weighed, in which the Li element is 10% in excess. The weighed lithium source, lanthanum source, and zirconium source are added to a beaker containing an appropriate amount of deionized water in sequence, and ultrasonically dispersed for 15 minutes, and then placed on a magnetic stirrer to fully stir and dissolve, and finally a clear and transparent solution is formed. Then, heating and stirring are continued at 80°C to evaporate the solvent and form a gel-like solid; the gel is further placed in a 150°C forced air drying oven for 24 hours, and then taken out and ground to obtain a completely dry precursor powder.

[0145] 2. Pre-sintering: calcine the precursor in a muffle furnace at 500°C for 3 hours to remove impurity elements such as carbon and nitrogen; take it out and grind it to obtain amorphous intermediate phase nano-ceramic powders such as Li-La-O, Li-Zr-O, La-Zr-O and Li-La-Zr-O.

[0146] 3. Aging: Place the above powder in air with constant humidity for 48 hours to generate Li2CO3 on its surface.

[0147] 4. Pickling: Place the aged mesophase ceramic powder material in a solution with a concentration of 0.1 mol·L -1 The surface of the samples was pickled in dilute hydrochloric acid for 30 s to remove the Li2CO3 coating.

[0148] 5. Coating: Aniline is selected as the organic coating carbon source. The acid-washed powder material is placed in a 25% mass fraction aniline methanol solution and stirred for 6 hours to fully react and polymerize into polyaniline (PANI). After the reaction is complete, it is placed in a blast drying oven at 100°C for 8 hours to obtain LLZO mesophase ceramic powder coated with phenolic resin.

[0149] 6. Calcination: The above powder is placed in a tubular furnace filled with inert gas such as nitrogen and argon and calcined for 2 hours at a holding temperature of 900°C. After being taken out and ground, a partially carbon-coated LLZO powder material is obtained.

[0150] Embodiment 14

[0151] 1. First, lithium nitrate, lanthanum nitrate, lithium tantalate, and zirconium oxynitrate are mixed according to Li7La3Zr 1.5 Ta 0.5 O 12 The stoichiometric ratio is weighed, in which the Li element is 10% in excess. The weighed lithium source, lanthanum source, and zirconium source are added to a beaker containing an appropriate amount of deionized water in sequence, and ultrasonically dispersed for 15 minutes, and then placed on a magnetic stirrer to fully stir and dissolve, and finally a clear and transparent solution is formed. Then, heating and stirring are continued at 80°C to evaporate the solvent and form a gel-like solid; the gel is further placed in a 150°C forced air drying oven for 24 hours, and then taken out and ground to obtain a completely dry precursor powder.

[0152] 2. Pre-sintering: calcine the precursor in a muffle furnace at 500°C for 3 hours to remove impurity elements such as carbon and nitrogen; take it out and grind it to obtain amorphous intermediate phase nano-ceramic powders such as Li-La-O, Li-Zr-O, La-Zr-O and Li-La-Zr-O.

[0153] 3. Aging: Place the above powder in air with constant humidity and expose it for 48 hours to generate Li2CO3 on its surface.

[0154] 4. Pickling: Place the aged mesophase ceramic powder material in a solution with a concentration of 0.1 mol·L -1 The surface of the samples was pickled in dilute hydrochloric acid for 10 s to remove the Li2CO3 coating.

[0155] 5. Coating: Dopamine (DA) is selected as the organic coating carbon source. The acid-washed powder material is placed in a 30% mass fraction dopamine methanol solution and stirred for 8 hours to allow it to fully react and polymerize. After the reaction is complete, it is placed in a blast drying oven at 100°C for 8 hours to obtain LLZO mesophase ceramic powder coated with polydopamine (PDA).

[0156] 6. Calcination: The above powder is placed in a tubular furnace filled with inert gas such as nitrogen and argon and calcined for 3 hours at a holding temperature of 700°C. After being taken out and ground, a partially carbon-coated LLZO powder material is obtained.

[0157] Embodiment 15

[0158] 1. First, lithium nitrate, lanthanum nitrate and zirconium nitrate are mixed according to Li7La3Zr2O 12The stoichiometric ratio is weighed, in which the Li element is 10% in excess. The weighed lithium source, lanthanum source, and zirconium source are added to a beaker containing an appropriate amount of deionized water in sequence, and ultrasonically dispersed for 15 minutes, and then placed on a magnetic stirrer to fully stir and dissolve, and finally a clear and transparent solution is formed. Then, heating and stirring are continued at 80°C to evaporate the solvent and form a gel-like solid; the gel is further placed in a 150°C forced air drying oven for 24 hours, and then taken out and ground to obtain a completely dry precursor powder.

[0159] 2. Pre-sintering: calcine the precursor in a muffle furnace at 500°C for 3 hours to remove impurity elements such as carbon and nitrogen; take it out and grind it to obtain amorphous intermediate phase nano-ceramic powders such as Li-La-O, Li-Zr-O, La-Zr-O and Li-La-Zr-O.

[0160] 3. Aging: Place the above powder in air with constant humidity and expose it for 48 hours to generate Li2CO3 on its surface.

[0161] 4. Pickling: The aged mesophase ceramic powder material is pickled without using dilute hydrochloric acid to retain the Li2CO3 coating layer on the surface.

[0162] 5. Coating: Dopamine (DA) is selected as the organic coating carbon source. The acid-washed powder material is placed in a 30% mass fraction dopamine methanol solution and stirred for 8 hours to allow it to fully react and polymerize. After the reaction is complete, it is placed in a blast drying oven at 100°C for 8 hours to obtain LLZO mesophase ceramic powder coated with polydopamine (PDA).

[0163] 6. Calcination: The above powder is placed in a tubular furnace filled with inert gas such as nitrogen and argon and calcined for 3 hours at a holding temperature of 900°C. After being taken out and ground, a completely carbon-coated LLZO powder material is obtained.

[0164] Comparative Example 1

[0165] Carbon-free coated Al-LLZO was prepared using a sol-gel method.

[0166] 1. First, lithium nitrate, aluminum nitrate, lanthanum nitrate and zirconium oxynitrate were mixed according to Li 6.4 Al 0.3 La3Zr2O 12The stoichiometric ratio is weighed, in which the Li element is 10% in excess. The weighed lithium source, lanthanum source, and zirconium source are added to a beaker containing an appropriate amount of deionized water in sequence, and ultrasonically dispersed for 15 minutes, and then placed on a magnetic stirrer to fully stir and dissolve, and finally a clear and transparent solution is formed. Then, heating and stirring are continued at 80°C to evaporate the solvent and form a gel-like solid; the gel is further placed in a 150°C forced air drying oven for 24 hours, and then taken out and ground to obtain a completely dry precursor powder.

[0167] 2. Pre-sintering: calcine the precursor in a muffle furnace at 500°C for 3 hours to remove impurity elements such as carbon and nitrogen; take it out and grind it to obtain amorphous intermediate phase nano-ceramic powders such as Li-La-O, Li-Zr-O, La-Zr-O and Li-La-Zr-O.

[0168] 3. Grinding: Grind and crush the mesophase ceramics in a mortar to facilitate further calcination.

[0169] 4. Calcination: The above powder was placed in a tubular furnace with an argon gas atmosphere and calcined for 3 hours at a holding temperature of 900° C. After being taken out and ground, an uncoated (i.e., 0% coating area) LALZO powder material was obtained.

[0170] Comparative Example 2

[0171] Preparation of Carbon-coated Ta-LLZO by Solid-state Reaction Method

[0172] 1. Lithium hydroxide monohydrate, tantalum oxide, lanthanum hydroxide and zirconium oxide are mixed according to Li7La3Zr 1.5 Ta 0.5 O 12 The stoichiometric ratio is weighed, wherein the Li element is 10% in excess. The weighed lithium source, lanthanum source, zirconium source, and tantalum source are added to the ball mill in sequence, and an alcohol dispersant is added. Then, a planetary ball mill is used to grind for 24 hours at a speed of 500 rpm; the precursor slurry is placed in a 150°C forced air drying oven for 24 hours, and then taken out and ground to obtain a completely dry precursor powder.

[0173] 2. Calcination: The precursor powder is placed in a muffle furnace and calcined for 6 hours at a holding temperature of 900°C. After being taken out and ground, the uncoated LLZTO powder material is obtained.

[0174] 3. Coating: Add LLZTO and citric acid into a ball mill, where the amount of citric acid added is 10% of the mass of the electrolyte powder, and mix them with a planetary ball mill under alcohol dispersant conditions. The speed is 500 rpm and the ball milling time is 24 hours. After ball milling, place the slurry in a 150°C forced air drying oven for 24 hours, then take it out and grind it to obtain a completely dry organic carbon source coated precursor powder material.

[0175] 4. Second calcination: The above precursor powder is placed in a tubular furnace with an argon gas atmosphere and calcined for 6 hours at a holding temperature of 700°C. After being taken out and ground, a completely carbon-coated LLZTO powder material is obtained.

[0176] Comparative Example 3

[0177] Preparation of carbon-coated LLZO by solid phase reaction method

[0178] 1. Lithium hydroxide monohydrate, lanthanum hydroxide and zirconium oxide are mixed according to Li7La3Zr2O 12 The stoichiometric ratio is weighed, in which the Li element is 10% in excess. The weighed lithium source, lanthanum source, and zirconium source are added to the ball mill in sequence, as well as 30% relative mass fraction of glucose. Using alcohol dispersant, grind with a planetary ball mill at a speed of 500rpm for 24h; place the mixed precursor slurry in a 150℃ forced air drying oven for 24h, then take it out and grind it manually to obtain a completely dry precursor powder.

[0179] 2. Calcination: The precursor powder is placed in a tubular furnace with an argon gas atmosphere and calcined for 6 hours at a holding temperature of 900°C. After being taken out and ground, a carbon-free coated LLZO powder material is obtained.

[0180] The carbon-coated LLZO materials prepared in the above examples and comparative examples were subjected to phase structure characterization tests using a powder X-ray diffraction method. The test equipment was an X-ray diffractometer. The test results are shown in FIG. Figure 2 As shown. The results show that after element doping, the LLZO powder material embodiments with different carbon coating amounts all show the cubic phase structure of garnet LLZO, including the doped comparative example 1; while the undoped carbon-coated LLZO comparative example 3 shows the original garnet tetragonal phase structure, indicating that the crystal structure of the LLZO material will not be changed after the carbon coating process. Due to the relatively low content of carbon source, large calcination mass loss, and the influence of carbonization degree, it is difficult to be detected in the physical phase test.

[0181] Take some of the carbon-coated LLZO powder materials prepared in the above examples and use the four-probe method to test the electronic conductivity. The testing equipment is a resistivity meter. LLZO powders with different carbon coating amounts were tested respectively, and the carbon coating areas were defined as 0-100% C-LLZO from low to high. Among them, 0% C-LLZO is a powder material that has not been carbon-coated, and 100% C-LLZO is a powder material with a completely carbon-coated surface. The test results are shown in Table 1 below. It can be observed from the examples that as the carbon coating area gradually increases, the ionic conductivity of the powder shows a trend of gradually decreasing, while the electronic conductivity of the powder shows a trend of gradually increasing. The ionic conductivity of the minimum coating area of ​​10% in Example 2 is the highest, which is close to the ionic conductivity of the uncoated powder in Comparative Example 1, and Example 15 has the lowest ionic conductivity among the cubic phase structure powders, indicating that too much coating will have an adverse effect on ionic conductivity. This is because the carbon coating on the surface of LLZO powder hinders the embedding / ejection of lithium ions on the surface of LLZO crystal, thus affecting the ion conductivity. Too little or too much carbon coating cannot meet the ideal use requirements. Therefore, the appropriate carbon coating amount should be selected according to the actual application to achieve the best comprehensive index requirements.

[0182] Table 1 Electronic conductivity test results of powders with different carbon coating amounts

[0183] sample Carbon coating area Ionic conductivity (S / cm) Electronic conductivity (S / cm) Example 2 10％ <![CDATA[5.758×10 -4 ]]> <![CDATA[5.103×10 -3 ]]> Example 4 20％ <![CDATA[2.910×10 -4 ]]> <![CDATA[2.072×10 -2 ]]> Example 6 30％ <![CDATA[1.414×10 -4 ]]> <![CDATA[8.627×10 -2 ]]> Example 10 50％ <![CDATA[8.774×10 -5 ]]> <![CDATA[9.997×10 -1 ]]> Example 12 70％ <![CDATA[4.383×10 -5 ]]> <![CDATA[1.140×10 -1 ]]> Embodiment 14 90％ <![CDATA[2.627×10 -5 ]]> <![CDATA[9.703×10 -1 ]]> Embodiment 15 100％ <![CDATA[1.159×10 -5 ]]> <![CDATA[1.427×10 0 ]]> Comparative Example 1 0％ <![CDATA[6.478×10 -4 ]]> <![CDATA[1.506×10 -8 ]]> Comparative Example 2 100％ <![CDATA[1.477×10 -5 ]]> <![CDATA[7.435×10 -1 ]]> Comparative Example 3 100％ <![CDATA[8.547×10 -7 ]]> <![CDATA[8.663×10 -1 ]]>

[0184] Some of the carbon-coated LLZO powder materials prepared in the above examples were used to verify the performance of the positive electrode mixed battery. The performance was verified using a CR2032 button battery, and its preparation process used conventional industry processes, including slurry coating and other processes, slurry ratio formula and battery testing procedures.

[0185] Specifically, the positive electrode active material is high-voltage lithium cobalt oxide, and the positive electrode slurry includes LCO, binder PVDF, conductive carbon black SP and garnet electrolyte LLZO, with a mass ratio of 90:5:4:1, and is prepared as a 50% solid NMP oil-based slurry; the slurry is coated on an aluminum foil current collector to form a positive electrode sheet with a thickness of 200um; the electrode sheet is dried in an oven at 120°C for 24 hours, taken out after cooling, and cut into a circular electrode sheet with a diameter of 10mm using a cutting machine for preparation. Use; the button battery assembly is carried out in an argon glove box with a water and oxygen content of less than 0.01ppm, wherein the diaphragm is a 9um thick PE diaphragm, the electrolyte is a 1MLiPF6 dissolved in ethylene carbonate (EC) / dimethyl carbonate (DMC) / diethyl carbonate (EMC) (the volume ratio is 1:1:1) electrolyte, and the negative electrode is a lithium metal sheet. The positive electrode sheet, diaphragm, electrolyte, and lithium sheet are assembled in the order of assembly, and then taken out and left to stand for 24 hours before use.

[0186] Use the battery testing system to activate the button battery. The test procedure is: the charge and discharge voltage range is 3 to 4.5V, and two charge and discharge cycles are performed using a current density of 0.1C. After each charge and discharge, let it stand for 5 minutes.

[0187] The room temperature rate performance test was carried out using a battery test system. The test procedure was as follows: the charge and discharge voltage range was 3 to 4.5 V, and the charge and discharge capacity was tested in sequence at 0.2C, 0.3C, 0.5C, 1C, 2C, 3C, and 0.2C. Each rate cycle was 5 cycles, and each charge and discharge was left to stand for 2 minutes. The specific performance of different batteries is shown in Table 2.

[0188] The results of the charge-off performance test show that when LLZO is used in the positive electrode blend, regardless of whether it is carbon-coated or not, and whether the carbon coating amount is the same, its first-cycle performance difference is small, the initial discharge capacity is 187.8-193.7mAh / g, and the first-cycle coulomb efficiency is 93.5-94.8%. Under high-rate charge and discharge conditions, the performance is quite different. When the carbon coating amount is less than or equal to 50%, it has a higher discharge capacity and coulomb efficiency, which are 146.3-153.7mAh / g and 93-95%, respectively. When the coating amount is greater than 50% or no carbon coating is performed, its discharge capacity and coulomb efficiency remain at a lower level, which are 135.3-142.4mAh / g and 85-91%. It shows that an appropriate amount of carbon coating can not only compensate for the negative impact caused by the decrease in ionic conductivity, but also significantly increase the oxidation / reduction rate of lithium ions on the surface of LLZO crystals by increasing electronic conductivity, thereby indirectly improving the transmission of lithium ions, while alleviating the polarization effect during high-rate charging and discharging of the battery, and ultimately improving the rate performance.

[0189] Table 2 The buckling performance of LLZO powder cathode blended with different carbon coating amounts

[0190]

[0191]

[0192] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a partially coated lithium lanthanum zirconium oxygen solid electrolyte, comprising the following steps: A) aging lithium lanthanum zirconium oxide in an air atmosphere to generate Li2CO3 on the surface to obtain an aged ceramic powder; B) pickling the aged ceramic powder in a dilute acid solution, and drying after pickling to obtain dry powder; C) mixing the dry powder with an organic carbon source solution to perform a polymerization reaction to obtain an intermediate partially coated with the organic carbon source; D) calcining the intermediate partially coated with the organic carbon source under an inert atmosphere to obtain a partially coated lithium lanthanum zirconium oxygen type solid electrolyte.

2. The preparation method according to claim 1, characterized in that: The aging temperature is 0 to 60° C.; the aging time is 24 to 48 hours.

3. The preparation method according to claim 1, characterized in that: The concentration of the dilute acid solution is 0.05-0.2 mol / L. The pickling time is 10 to 60 seconds.

4. The preparation method according to claim 1, characterized in that: The organic carbon source includes one or more of dopamine, tannic acid, aniline, furfural, phenol, formaldehyde, urea, furfural and furfuryl alcohol.

5. The preparation method according to claim 1, characterized in that: The polymerization reaction temperature in the step C) is 0 to 60° C.; the polymerization reaction time in the step C) is 2 to 8 hours.

6. The preparation method according to claim 1, characterized in that: The calcination holding temperature in step D) is 700-900° C.; the calcination time in step D) is 2-3 hours.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The lithium lanthanum zirconium oxide is prepared according to the following steps: 1) dissolving a lithium source, a lanthanum source and a zirconium source in water, heating to form a gel-like solid, drying the gel and then grinding it to obtain a precursor powder; 2) calcining the precursor powder to obtain lithium lanthanum zirconium oxide.

8. A partially coated lithium lanthanum zirconium oxide type solid electrolyte, prepared according to the preparation method described in any one of claims 1 to 7, comprising a lithium lanthanum zirconium oxide body and a carbon coating layer on the surface of the lithium lanthanum zirconium oxide body, wherein the carbon coating layer presents a local point coating.

9. The partially coated lithium lanthanum zirconium oxygen type solid electrolyte according to claim 8, characterized in that In the partially coated lithium lanthanum zirconium oxygen type solid electrolyte, the mass fraction of the carbon coating layer is 1-20%.

10. A lithium ion battery, characterized in that: Comprising the partially coated lithium lanthanum zirconium oxygen type solid electrolyte as described in claim 8 or 9.

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