Modified solid electrolyte, preparation method thereof and all-solid-state lithium ion battery

Abstract

The invention discloses a modified solid electrolyte, a preparation method thereof and an all-solid-state lithium ion battery, and belongs to the field of all-solid-state lithium ion batteries. The modified solid electrolyte comprises an inner core and a coating layer coating the surface of the solid electrolyte, the inner core comprises an inorganic solid electrolyte, the coating layer comprises at least one of a first main group nitride and a third main group nitride, and the thickness of the coating layer is smaller than or equal to 100 nm. The inorganic solid electrolyte is coated with the first main group nitride and / or the third main group nitride, the air stability of the inorganic solid electrolyte can be effectively improved, a good ion conduction function is achieved, the inorganic solid electrolyte can be coated and isolated through the coating layer, and the service life of the inorganic solid electrolyte is prolonged. The problem that side reaction is easy to occur after the inorganic solid electrolyte is in direct contact with the active material is solved, and the cycle performance of the all-solid-state lithium ion battery is improved through comprehensive action.

Description

Technical Field

[0001] The present application relates to the field of all-solid-state lithium-ion batteries, and more specifically, to a modified solid-state electrolyte, a preparation method thereof, and an all-solid-state lithium-ion battery. Background Art

[0002] In the existing technology, all-solid-state electrolytes have received widespread attention due to their advantages such as high safety, high energy density, long cycle life, and a wide temperature range of application. However, inorganic solid electrolytes in all-solid-state electrolytes still have some problems in their application. For example, sulfide solid electrolytes and halide solid electrolytes in inorganic solid electrolytes both have poor air stability. Under the action of voltage and current, sulfide solid electrolytes are prone to failure when in contact with positive electrode active materials, and halide solid electrolytes are prone to failure when in contact with negative electrode active materials, resulting in poor battery cycle performance. Summary of the Invention

[0003] The present application provides a modified solid electrolyte, a preparation method thereof, and an all-solid-state lithium-ion battery, which can effectively isolate the inorganic solid electrolyte from contact with water or active materials by introducing a coating layer, thereby improving the battery cycle performance.

[0004] The embodiment of the present application is implemented as follows:

[0005] In the first aspect, the present application provides an example of a modified solid electrolyte, which includes a core and a coating layer coated on the surface of the solid electrolyte; wherein the core includes an inorganic solid electrolyte; the coating layer includes at least one of a Group I nitride and a Group III nitride, and the thickness of the coating layer is ≤100nm.

[0006] The modified solid electrolyte provided in the present application, when coated with at least one of Group I nitrides and Group III nitrides as an inorganic solid electrolyte, can not only effectively improve the air stability of the inorganic solid electrolyte, but also the thickness of the coating layer is ≤100nm, the modified solid electrolyte has better ion conduction function, and the coating layer can achieve coating and isolation of the inorganic solid electrolyte, thereby improving the problem of side reactions that are prone to occur after direct contact between the inorganic solid electrolyte and the active material. The combined effect improves the cycle performance of the all-solid-state lithium-ion battery.

[0007] In some optional embodiments, the Group I nitride includes lithium nitride, and the Group III nitride includes at least one of boron nitride, aluminum nitride, gallium nitride, and indium nitride.

[0008] The use of the above-mentioned Group I and Group III nitrides to coat the inorganic solid electrolyte can more effectively improve the air stability of the inorganic solid electrolyte, so that the corresponding all-solid-state lithium-ion battery has better cycle performance.

[0009] In some optional embodiments, the coating layer has a thickness of 0.1 nm-50 nm.

[0010] Since the coating of Group I and Group III nitrides will affect the ionic conductivity of the modified solid electrolyte, the thickness of the coating layer is controlled to be thinner to reduce the impact of Group I and Group III nitrides on the ionic conductivity, so that the coated solid electrolyte has better ionic conductivity.

[0011] In some optional embodiments, the coating layer has a thickness of 1 nm-10 nm.

[0012] By controlling the thickness within the above range, on the basis of having a good isolation effect, the influence of the main group I and III nitrides on the ionic conductivity can be effectively reduced, so that the coated solid electrolyte has a more ideal ionic conductivity.

[0013] In some optional embodiments, the inorganic solid electrolyte is selected from at least one of a sulfide solid electrolyte and a halide solid electrolyte.

[0014] The coating layer provided in the embodiments of the present application can be well adapted to sulfide solid electrolytes and halide solid electrolytes.

[0015] In some optional embodiments, the inorganic solid electrolyte is a sulfide solid electrolyte, and the material of the sulfide solid electrolyte is Li6PS5Cl.

[0016] In some optional embodiments, the inorganic solid electrolyte is a halide solid electrolyte, and the material of the halide solid electrolyte is Li3InCl6.

[0017] In a second aspect, the present application provides an example of a method for preparing a modified solid electrolyte, comprising: obtaining an inorganic solid electrolyte, and preparing a coating layer on the surface of the inorganic solid electrolyte by atomic layer deposition.

[0018] The preparation method provided in this application uses atomic layer deposition to prepare the coating layer, which is conducive to obtaining a coating layer with relatively uniform thickness, high density and high coverage rate of the core, which can better isolate the inorganic solid electrolyte from contact with water or active materials, etc., and is conducive to improving the battery cycle performance.

[0019] In some optional embodiments, the atomic layer deposition is performed under vacuum conditions, and the processing temperature of the atomic layer deposition is 80° C.-400° C.

[0020] By carrying out the above-mentioned process under vacuum conditions and at the above-mentioned temperature, a coating layer can be prepared on the surface of the inorganic solid electrolyte by atomic layer deposition.

[0021] A third aspect of the present application provides an all-solid-state lithium-ion battery, which includes a positive electrode sheet, a solid electrolyte membrane and a negative electrode sheet, wherein the solid electrolyte membrane is located between the positive electrode sheet and the negative electrode sheet.

[0022] Among them, at least one of the positive electrode plate, the solid electrolyte membrane and the negative electrode plate includes the modified solid electrolyte provided in the embodiment of the first aspect of the present application. DETAILED DESCRIPTION

[0023] The embodiments of the present application will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0024] Both sulfide solid electrolytes and halide solid electrolytes in inorganic solid electrolytes have the problem of poor air stability. Under the action of voltage and current, sulfide solid electrolytes are prone to failure when in contact with positive electrode active materials (such as NCM), and halide solid electrolytes are prone to failure when in contact with negative electrode active materials, etc., resulting in poor battery cycle performance.

[0025] In view of this, the present application provides a modified solid electrolyte, a preparation method thereof, and an all-solid-state lithium-ion battery.

[0026] A first embodiment of the present application provides a modified solid electrolyte, which includes a core and a coating layer coated on the surface of the solid electrolyte.

[0027] The core includes an inorganic solid electrolyte, the coating layer includes at least one of a Group I nitride and a Group III nitride, and the thickness of the coating layer is ≤100 nm.

[0028] At least one of Group I nitride and Group III nitride means: the coating layer is Group III nitride, or the coating layer is Group I nitride, or the coating layer is a stacked arrangement of Group III nitride and Group I nitride.

[0029] Group I nitrides and Group III nitrides have good air stability and can effectively isolate inorganic solid electrolytes (such as Li6PS5Cl) from contact with moisture in the air, thereby absorbing moisture and decomposing. In addition, due to the presence of the Group I nitride and Group III nitride coating layers, sulfide solid electrolytes, for example, can be used in the negative electrode sheet to prevent the sulfide solid electrolyte Li6PS5Cl material from undergoing oxidation reaction and failure at high potential.

[0030] Furthermore, since the thickness of the coating layer is ≤100 nm, that is, the coating layer is relatively thin, its influence on the ion conduction function can be reduced, so that the modified solid electrolyte has better ion conduction function.

[0031] The modified solid electrolyte provided in the present application, when coated with at least one of Group I nitrides and Group III nitrides as an inorganic solid electrolyte, can not only effectively improve the air stability of the inorganic solid electrolyte, but also the thickness of the coating layer is ≤100nm, the modified solid electrolyte has better ion conduction function, and the coating layer can achieve coating and isolation of the inorganic solid electrolyte, thereby improving the problem of side reactions that are prone to occur after direct contact between the inorganic solid electrolyte and the active material. The combined effect improves the cycle performance of the all-solid-state lithium-ion battery.

[0032] In some embodiments, the Group I nitride includes lithium nitride, and the Group III nitride includes at least one of boron nitride, aluminum nitride, gallium nitride, and indium nitride.

[0033] It should be noted that when the Group III nitrides include two or more of boron nitride, aluminum nitride, gallium nitride and indium nitride, the coating layer can be prepared by stacking different nitrides in sequence, or it can be a layer doped with two or more components, for example, the material is indium gallium nitride.

[0034] In this embodiment, the use of the above-mentioned Group I and Group III nitrides to coat the inorganic solid electrolyte can more effectively improve the air stability of the inorganic solid electrolyte, so that the corresponding all-solid-state lithium-ion battery has better cycle performance.

[0035] Illustratively, the Group III nitride is aluminum nitride.

[0036] In some embodiments, the coating layer has a thickness of 0.1 nm to 50 nm.

[0037] Since the coating of Group I and Group III nitrides will affect the ionic conductivity of the modified solid electrolyte, the thickness of the coating layer is controlled to be thinner to reduce the effect of Group III nitrides on the ionic conductivity, so that the coated solid electrolyte has better ionic conductivity.

[0038] Illustratively, the thickness of the coating layer is any value among 0.1 nm, 1 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, or between any two values.

[0039] In some embodiments, the coating layer has a thickness of 1 nm to 10 nm.

[0040] By controlling the thickness within the above range, on the basis of having a good isolation effect, the influence of the I and III main group nitrides on the ionic conductivity can be further effectively reduced, so that the coated solid electrolyte has a more ideal ionic conductivity.

[0041] Illustratively, the thickness of the coating layer is any value of 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, or between any two values.

[0042] In some embodiments, the inorganic solid electrolyte is selected from at least one of a sulfide solid electrolyte and a halide solid electrolyte.

[0043] In this embodiment, the coating layer provided in the embodiment of the present application can be well adapted to the sulfide solid electrolyte and the halide solid electrolyte.

[0044] It should be noted that the types of sulfide solid electrolytes and halide solid electrolytes are not limited and can be set according to conventional selection in the field. For example, the sulfide solid electrolyte is selected from Li3PS4, Li 10 GeP2S 12 , at least one of Li6PS5Br, Li6PS5I and Li6PS5Cl; for example, the halide solid electrolyte is selected from at least one of Li3InCl6, Li3ScCl6, Li2ZrCl6 and Li3YCl6.

[0045] In some embodiments, the inorganic solid electrolyte is a sulfide solid electrolyte, and the material of the sulfide solid electrolyte is Li6PS5Cl.

[0046] In some embodiments, the inorganic solid electrolyte is a halide solid electrolyte, and the material of the halide solid electrolyte is Li3InCl6.

[0047] In this embodiment, the coating layer provided in the embodiment of the present application can be well adapted to Li6PS5Cl and Li3InCl6.

[0048] It should be noted that any structural or functional units not specifically described or limited in the modified solid electrolyte may be arranged according to conventional selections in the art.

[0049] A second embodiment of the present application provides a method for preparing a modified solid electrolyte, comprising:

[0050] Obtain an inorganic solid electrolyte.

[0051] A coating layer is prepared on the surface of the inorganic solid electrolyte by atomic layer deposition.

[0052] The inorganic solid electrolyte includes at least one of a sulfide solid electrolyte and a halide solid electrolyte.

[0053] Atomic layer deposition (ALD) is a thin film deposition technology based on surface self-limiting reactions, which can precisely control the thickness and composition of the film at the atomic scale.

[0054] In this application, atomic layer deposition is used to prepare the coating layer, which is beneficial to obtaining a coating layer with relatively uniform thickness, high density and high coverage rate of the core, which can better isolate the inorganic solid electrolyte from contact with water or active materials, etc., and is beneficial to improving the battery cycle performance.

[0055] In some embodiments, the atomic layer deposition is performed under vacuum conditions, and the processing temperature of the atomic layer deposition is 80° C.-400° C.

[0056] The processing temperature of atomic layer deposition refers to the temperature in the atomic layer deposition chamber. By performing the process at the above temperature under vacuum conditions, a coating layer can be prepared on the surface of an inorganic solid electrolyte by atomic layer deposition.

[0057] Illustratively, the process temperature of the atomic layer deposition is any one of 80° C., 100° C., 150° C., 200° C., 250° C., 300° C., 350° C., and 400° C., or between any two values.

[0058] Exemplarily, the steps of atomic layer deposition include:

[0059] S1. Placing an inorganic solid electrolyte in a reaction chamber of an atomic layer deposition device, wherein the reaction chamber is in a vacuum state and the temperature is maintained at 80-400°C.

[0060] S2. The gaseous Group III compound is transported into the reaction chamber for sealing treatment, so that the gaseous Group III compound is adsorbed on the surface of the inorganic solid electrolyte to form a precursor layer.

[0061] S3. Purge the reaction chamber with an inert gas to remove residual gaseous Group III compounds in the reaction chamber.

[0062] S4. Transporting a gaseous nitrogen source into the reaction chamber to allow the gaseous nitrogen source to react with the precursor layer to generate a Group III nitride.

[0063] S5. Purging the reaction chamber with an inert gas to remove residual gaseous nitrogen source in the reaction chamber;

[0064] S6. Repeat steps S2 to S5 multiple times to form a modified solid electrolyte with a core-shell structure.

[0065] It should be noted that in step S1, the vacuum degree in the reaction chamber can be set according to conventional selections in the art, for example, the vacuum degree can be (1 to 10)×10 -5 mTorr, for example but not limited to, the vacuum degree can be 1×10 -5 mTorr, 2×10 -5 mTorr, 4×10 -5 mTorr, 6×10 -5 mTorr, 8×10 -5 mTorr and 10×10 -5 A range of values ​​between at least one or any two of mTorr.

[0066] In this embodiment, the preparation is carried out according to the above process, and a Group III nitride coating layer with relatively uniform thickness, high density and high coverage of the core can be formed on the surface of the inorganic solid electrolyte core; wherein the temperature of the reaction chamber is maintained within the above range so that the gaseous metal compound always remains in a gaseous state before being loaded onto the core, thereby facilitating the gasification of the Group III compound to be more fully loaded onto the surface of the inorganic solid electrolyte to form a precursor layer.

[0067] It should be noted that at the beginning of the first cycle, since there is no coating layer on the surface of the inorganic solid electrolyte core, the formed precursor layer is directly coated on the surface of the inorganic solid electrolyte core. However, after the first cycle, the surface of the inorganic solid electrolyte core already has a single layer of Group III nitride. Therefore, starting from the second cycle, the formed precursor layer will be coated on the surface of the Group III nitride single layer formed in the previous cycle. By repeating this cycle, a Group III nitride coating layer of the target thickness is finally prepared.

[0068] As an example, steps S2 to S5 are repeated 10 to 50 times, for example but not limited to, the number of times is at least one of 10 times, 20 times, 30 times, 40 times and 50 times, or a range value between any two of them.

[0069] As an example, the step of purging the reaction chamber with an inert gas to remove residual gaseous metal compounds in the reaction chamber includes:

[0070] S31 delivers an inert gas into a reaction chamber in a vacuum state, wherein the pulse gas pressure of the delivered inert gas is 8000-9000 mTorr (for example, but not limited to, the pulse gas pressure is at least one of or a range between any two of 8000 mTorr, 8100 mTorr, 8200 mTorr, 8300 mTorr, 8400 mTorr, 8500 mTorr, 8600 mTorr, 8700 mTorr, 8800 mTorr, 8900 mTorr, and 9000 mTorr); S32 vacuums the reaction chamber to remove the inert gas in the reaction chamber; S33 repeats steps S31-S32 multiple times.

[0071] It should be noted that in step S31, if the reaction chamber is already in a vacuum state, there is no need to perform vacuuming in advance; if the reaction chamber is not in a vacuum state, it is necessary to perform vacuuming in advance, and the specific process can be adaptively adjusted according to actual conditions.

[0072] It should be noted that, in the step of vacuuming, the vacuum degree in the reaction chamber is maintained consistent with the vacuum degree in step S1.

[0073] In this embodiment, by repeatedly purging the reaction chamber with an inert atmosphere and limiting the pulse pressure of the inert gas delivered each time to within the above range, the gaseous metal compounds remaining in the reaction chamber and some gaseous impurities that may be generated can be effectively removed.

[0074] As an example, steps S31 to S33 are repeated 3 to 5 times.

[0075] In this embodiment, steps S31 to S32 are repeated 3 to 5 times, which can more thoroughly remove the gaseous metal compounds remaining in the reaction chamber.

[0076] It should be noted that step S5 can be performed with reference to step S3.

[0077] As an example, the step of transporting the gaseous Group III compound into the reaction chamber for sealing treatment so that the gaseous Group III compound is adsorbed on the surface of the inorganic solid electrolyte to form a precursor layer includes: S21 transporting the gaseous Group III compound into the reaction chamber for sealing treatment, wherein the pulse gas pressure of the gaseous Group III compound is 200 to 400 mTorr (for example, but not limited to, the pulse gas pressure is 200 mTorr, 250 mTorr, 300 mTorr, 350 mTorr and 40 0 mTorr), the sealing treatment time is 0.5 to 2 min (for example, but not limited to, the time is at least one of 0.5 min, 1 min, 1.5 min and 2 min or a range of values ​​between any two), so that the gaseous Group III compound is adsorbed on the surface of the inorganic solid electrolyte to form a precursor layer; S22 uses an inert gas to purge the reaction chamber to remove the gaseous metal compound remaining in the reaction chamber; S23 repeats steps S21 to S22 multiple times.

[0078] In this embodiment, a precursor layer is formed on the surface of the inorganic solid electrolyte by repeated deposition, and in each deposition process, the pulse gas pressure for delivering the gaseous Group III compound and the time of the sealing treatment are respectively limited within the above-mentioned ranges, so that the gaseous Group III compound can be more saturatedly covered on the entire surface of the core, thereby allowing the coating layer formed by the subsequent reaction to more completely and evenly cover the entire core.

[0079] As an example, in step S22, the step of purging the reaction chamber with an inert gas includes: first evacuating the reaction chamber, then delivering an inert gas into the reaction chamber, and then evacuating the reaction chamber again, wherein the pulse gas pressure of the delivered inert gas is 8000-9000 mTorr, for example, but not limited to, the pulse gas pressure is at least one of 8000 mTorr, 8100 mTorr, 8200 mTorr, 8300 mTorr, 8400 mTorr, 8500 mTorr, 8600 mTorr, 8700 mTorr, 8800 mTorr, 8900 mTorr and 9000 mTorr, or a range value between any two thereof; in the step of evacuating the reaction chamber, the vacuum level in the reaction chamber is consistent with the vacuum level in step S1.

[0080] It should be noted that the number of times step 22 is performed is not limited. For example, it can be performed only once or repeatedly for multiple times. The specific number of times can be adaptively adjusted according to actual conditions.

[0081] As an example, the step of delivering a gaseous nitrogen source into a reaction chamber so that the gaseous nitrogen source reacts with the precursor layer to generate metal sulfide includes:

[0082] S41 transports a gaseous nitrogen source into a reaction chamber for a sealed treatment, wherein a pulse gas pressure of the gaseous nitrogen source is 200-400 mTorr (for example, but not limited to, a pulse gas pressure of at least one of 200 mTorr, 250 mTorr, 300 mTorr, 350 mTorr and 400 mTorr, or a range value between any two thereof), and a reaction time is 0.5-2 min (for example, but not limited to, a reaction time of at least one of 0.5 min, 1 min, 1.5 min and 2 min, or a range value between any two thereof), so that the gaseous nitrogen source reacts with the precursor layer to generate metal sulfide; S42 uses an inert gas to purge the reaction chamber to remove the residual gaseous nitrogen source in the reaction chamber; S43 repeats steps S41-S42 multiple times.

[0083] In this embodiment, during the process of the gaseous nitrogen source and the precursor layer reacting to generate Group III nitrides, the gaseous nitrogen source is repeatedly delivered to the reaction chamber, and the pulse gas pressure and reaction time of each delivery of the gaseous nitrogen source are respectively limited within the above-mentioned ranges, so that the precursor layer can fully contact and react with the gaseous sulfur source, thereby allowing the shell formed by the reaction to relatively completely and evenly cover the entire core.

[0084] Exemplarily, the material of the gaseous Group III compound can be selected according to the composition of the Group III nitride, including but not limited to tris(diethylamino)aluminum, trimethylindium and at least one of trimethylaluminum, triethylboron, diborane, gallium chloride, and LiN(SiMe3)2.

[0085] Exemplarily, the nitrogen source includes but is not limited to any one of N2, NH3, N2H4, and can also be a mixture of H2 and N2, or a mixture of the above nitrogen sources and an inert gas.

[0086] In this embodiment, there are many types of gaseous metal compounds that are applicable to the embodiments of the present application, and more feasible implementation plans can be provided, thereby facilitating the promotion and application of the technical solutions provided by the embodiments of the present application.

[0087] A third aspect of the present application provides an all-solid-state lithium-ion battery, which includes a positive electrode sheet, a solid electrolyte membrane and a negative electrode sheet, wherein the solid electrolyte membrane is located between the positive electrode sheet and the negative electrode sheet.

[0088] Among them, at least one of the positive electrode plate, the solid electrolyte membrane and the negative electrode plate includes the modified solid electrolyte provided in the embodiment of the first aspect of the present application.

[0089] In the present application, the functional unit in the all-solid-state lithium-ion battery (at least one of the positive electrode plate, solid electrolyte membrane and negative electrode plate) includes the modified solid electrolyte provided in the first embodiment. Since the modified solid electrolyte has relatively ideal air stability and relatively suitable ionic conductivity, the corresponding all-solid-state battery has relatively excellent cycle performance.

[0090] It should be noted that each functional unit in the all-solid-state lithium-ion battery can be configured according to conventional selections in the art and is not specifically limited in the embodiments of the present application.

[0091] As an example, the positive electrode plate includes NCM622 (positive electrode active material), super-P (conductive agent), CNT (conductive agent), Li6PS5Cl (sulfide solid electrolyte) and PVDF (binder) in a mass ratio of 87:1.5:0.3:10:1.2; the negative electrode plate includes graphite (negative electrode active material), conductive carbon black (conductive agent), Li6PS5Cl (sulfide solid electrolyte) carboxymethyl cellulose, sodium cellulose (binder) and styrene-butadiene rubber (binder) in a mass ratio of 85.6:2:10:1.2:2.2.

[0092] In other possible implementations, Li6PS5Cl (sulfide solid electrolyte) can be completely replaced with Li3InCl6 (halide solid electrolyte); similarly, the types and amounts of other functional components in the positive and negative electrode sheets can also be adaptively adjusted.

[0093] It should be noted that the solid electrolytes of the positive electrode plate and the negative electrode plate can be either one of them using the modified solid electrolyte provided in the embodiment of the present application, or both of them using the modified solid electrolyte provided in the embodiment of the present application, and specific adaptive adjustments can be made according to actual needs.

[0094] The modified solid electrolyte, preparation method thereof, and all-solid-state lithium-ion battery of the present application are further described in detail below with reference to the embodiments.

[0095] Example 1

[0096]

Preparation of modified solid electrolyte

[0097] S1 placed 1 kg of Li6PS5Cl in the reaction chamber of the atomic layer deposition equipment, where the reaction chamber was in a vacuum state (vacuum degree of 7.5×10 -5 mTorr) and the temperature was maintained at 180°C.

[0098] S2 transports gaseous AlMe3 (trimethylaluminum) into the reaction chamber for sealing treatment, so that the gaseous AlMe3 is adsorbed on the surface of the inorganic solid electrolyte to form a precursor layer. Specifically, the pulse gas pressure for transporting the gaseous AlMe3 is 300mTorr, and the sealing treatment is 1 minute after transporting. This standard is repeated 5 times; and, after each treatment, the reaction chamber needs to be purged once with an inert gas to remove the residual gaseous AlMe3 that has not been adsorbed. The standard is: first vacuum the reaction chamber, and then transport an inert gas (nitrogen) into the reaction chamber, and then vacuum the reaction chamber again. Among them, the pulse gas pressure for transporting the inert gas is 8500mTorr. In the vacuum treatment step, the vacuum degree in the reaction chamber is consistent with the vacuum degree in step S1.

[0099] In step S3, the reaction chamber is purged with an inert gas to remove residual gaseous trimethylaluminum in the reaction chamber. Specifically, nitrogen is delivered to the vacuum reaction chamber at a pulsed gas pressure of 8500 mTorr, and then the reaction chamber is evacuated until the vacuum level in the reaction chamber is consistent with the vacuum level in step S1. This process is repeated three times according to this standard.

[0100] S4 delivers gaseous NH3 (ammonia) into the reaction chamber to allow NH3 to react with the precursor layer to generate aluminum nitride. Specifically, the pulse pressure of the NH3 delivered is 300mTorr, and the reaction is sealed for 1 minute after delivery. This standard is repeated 5 times. Moreover, after each completion, the reaction chamber needs to be purged once with an inert gas to remove unreacted residual NH3. The standard is: first vacuum the reaction chamber, then deliver inert gas (nitrogen) into the reaction chamber, and then vacuum the reaction chamber again. The pulse pressure of the inert gas delivered is 8500mTorr. During the vacuum treatment step, the vacuum degree in the reaction chamber is consistent with the vacuum degree in step S1.

[0101] In step S5, the reaction chamber is purged with an inert gas to remove residual NH3 in the reaction chamber. Specifically, nitrogen gas is delivered into the vacuum reaction chamber at a pulsed gas pressure of 8500 mTorr, and then the reaction chamber is evacuated until the vacuum level in the reaction chamber is consistent with the vacuum level in step S1. This process is repeated three times according to this standard.

[0102] S6: Repeat steps S2 to S5 20 times to form a modified solid electrolyte with a core-shell structure, wherein the core is Li6PS5Cl and the coating layer is AlN, wherein the thickness of the coating layer is 1.2 nm.

[0103]

All-solid-state lithium-ion battery preparation

[0104] Preparation of positive electrode sheet: NCM622 (positive electrode active material), super-P (conductive agent), CNT (conductive agent), the modified solid electrolyte prepared above and PVDF (binder) were stirred and mixed with N-methylpyrrolidone (NMP) in a vacuum mixer in a mass ratio of 87:1.5:0.3:10:1.2 to obtain positive electrode sheet slurry; the positive electrode sheet slurry was evenly coated on both sides of the aluminum foil (thickness 13μm) current collector, and the positive electrode sheet was obtained after drying, cold pressing and die-cutting.

[0105] Preparation of negative electrode sheet: Graphite (negative electrode active material), conductive carbon black (conductive agent), Li6PS5Cl (uncoated sulfide solid electrolyte), carboxymethyl cellulose, sodium cellulose (binder) and styrene-butadiene rubber (binder) are mixed evenly with deionized water in a vacuum mixer in a mass ratio of 85.6:2:10:1.2:2.2 to obtain negative electrode sheet slurry; the negative electrode sheet slurry is evenly coated on both sides of the copper foil (thickness 8μm) current collector, and the negative electrode sheet is obtained after drying, cold pressing and die-cutting.

[0106] A 20μm thick sulfide solid electrolyte membrane (Li6PS5Cl) was placed between the positive and negative electrodes, and a bare cell was prepared by lamination. A packaging bag was made of an aluminum-plastic film composite material, and the bare cell was placed in the packaging bag and packaged to obtain a dry cell. The dry cell was baked to remove water to reduce the water content to less than 250ppm. Then, the dry cell was subjected to isostatic pressing, sealing, standing, formation, degassing packaging, and capacity division to obtain a soft-pack all-solid-state lithium-ion battery.

[0107] Example 2

[0108] The only difference between it and Example 1 is:

[0109] In the preparation process of [Preparation of modified solid electrolyte], LiN(SiMe3)2 is used to replace AlMe3.

[0110] That is, the prepared modified solid electrolyte includes a core and a coating layer coated on the surface of the solid electrolyte; wherein the core is Li6PS5Cl and the coating layer is Li3N.

[0111] Example 3

[0112] The only difference between it and Example 1 is:

[0113] In the preparation process of [Preparation of modified solid electrolyte], GaMe3 is used to replace AlMe3.

[0114] That is, the prepared modified solid electrolyte includes a core and a coating layer coated on the surface of the solid electrolyte; wherein the core is Li6PS5Cl and the coating layer is GaN.

[0115] Example 4

[0116] The only difference between it and Example 1 is:

[0117] In [Preparation of Modified Solid Electrolyte], S6 repeated steps S2 to S5 40 times to form a modified solid electrolyte with a core-shell structure having a core of Li6PS5Cl and a coating layer of AlN, wherein the thickness of the coating layer was 2.44 nm.

[0118] Example 5

[0119] The only difference from Example 1 is that in [Preparation of Modified Solid Electrolyte], Li3InCl6 is used instead of Li6PS5Cl.

[0120] Comparative Example 1

[0121] The only difference between this embodiment and Example 1 is that the sulfide solid electrolyte Li6PS5Cl used is not coated.

[0122] Comparative Example 2

[0123] The only difference between this embodiment and Example 5 is that the halide solid electrolyte Li3InCl6 used is not coated.

[0124] Test example

[0125] 1. Air stability test of solid electrolyte

[0126] The modified solid electrolytes of Examples 1-5 and Comparative Examples 1-2 were divided into two groups according to the solid electrolyte material, and then the air stability of the prepared solid electrolyte samples was tested respectively, and the test results were statistically summarized in Table 1.

[0127] The test steps for air stability are as follows:

[0128] The lithium ion conductivity of the solid electrolyte powder was tested before and after being exposed to moisture at a relative humidity of 5% for 24 hours, and the retention rate of the lithium ion conductivity was calculated.

[0129] Table 1

[0130]

[0131] It should be noted that in Table 1, the ionic conductivity retention rate of Comparative Examples 1 and 2 is 0. This is because there is no coating layer on the internal surface of the solid electrolyte, and the reaction activity of the material is high, resulting in severe decomposition of the material after exposure to moisture with a relative humidity of 5% for 24 hours.

[0132] It can be seen from Table 1 that the modified solid electrolyte provided in the present application has excellent air stability by providing a nitride coating layer outside the inner core of the inorganic solid electrolyte.

[0133] 2. Cycle performance test of all-solid-state lithium-ion batteries

[0134] The solid-state lithium-ion batteries prepared in Examples 1-5 and Comparative Examples 1-2 were divided into two groups according to the solid electrolyte material, and the cycle performance of each battery sample in the two groups was tested respectively. The test results are then statistically summarized in Table 2.

[0135] Among them, the test parameters of the battery cycle performance are as follows: the obtained all-solid-state lithium-ion battery is subjected to a charge and discharge cycle test, with a charging current of 0.8A, a cut-off voltage of 4.9V, a discharge current of 0.8A, a cut-off voltage of 2.5V, and a test environment temperature of 25°C. The number of cycles when the battery capacity decays to 80% is counted.

[0136] Table 2

[0137] Sample Battery cycle number Example 1 1466 Example 2 1052 Example 3 1736 Example 4 1644 Example 5 1524 Comparative Example 1 528 Comparative Example 2 492

[0138] It can be seen from Table 2 that whether it is a sulfide solid electrolyte or a halide solid electrolyte, the cycle performance of the all-solid-state lithium-ion battery can be effectively improved by coating a nitride coating layer on its surface. The embodiments described above are part of the embodiments of this application, not all of them. The detailed description of the embodiments of this application is not intended to limit the scope of the application for protection, but merely represents the selected embodiments of this application. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

Claims

1. A modified solid electrolyte, characterized in that comprising a core and a coating layer coated on the surface of the solid electrolyte; wherein the core comprises an inorganic solid electrolyte; The coating layer includes at least one of Group I nitride and Group III nitride, and the thickness of the coating layer is ≤100nm.

2. The modified solid electrolyte according to claim 1, characterized in that The Group I nitride includes lithium nitride, and the Group III nitride includes at least one of boron nitride, aluminum nitride, gallium nitride and indium nitride.

3. The modified solid electrolyte according to claim 1, characterized in that The coating layer has a thickness of 0.1 nm to 50 nm.

4. The modified solid electrolyte according to claim 1, characterized in that The coating layer has a thickness of 1 nm to 10 nm.

5. The modified solid electrolyte according to any one of claims 1 to 4, characterized in that The inorganic solid electrolyte is selected from at least one of a sulfide solid electrolyte and a halide solid electrolyte.

6. The modified solid electrolyte according to claim 5, characterized in that The inorganic solid electrolyte is a sulfide solid electrolyte, and the material of the sulfide solid electrolyte is Li6PS5Cl.

7. The modified solid electrolyte according to claim 5, characterized in that The inorganic solid electrolyte is a halide solid electrolyte, and the material of the halide solid electrolyte is Li3InCl6.

8. A method for preparing a modified solid electrolyte according to any one of claims 1 to 7, characterized in that: include: Obtaining an inorganic solid electrolyte; The coating layer is prepared on the surface of the inorganic solid electrolyte by atomic layer deposition.

9. The preparation method according to claim 8, characterized in that The atomic layer deposition is performed under vacuum conditions, and the processing temperature of the atomic layer deposition is 80° C.-400° C.

10. An all-solid-state lithium-ion battery, characterized in that: The all-solid-state lithium-ion battery comprises a positive electrode sheet, a solid electrolyte membrane and a negative electrode sheet, wherein the solid electrolyte membrane is located between the positive electrode sheet and the negative electrode sheet; Wherein, at least one of the positive electrode sheet, the solid electrolyte membrane and the negative electrode sheet comprises the modified solid electrolyte according to any one of claims 1 to 7.

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