A method for improving the surface and interface properties of garnet-type solid electrolytes and preparing composite solid electrolytes by plasma technology

Abstract

The present invention belongs to the field of energy materials and discloses a technology for improving the interface properties of garnet-type inorganic solid electrolytes by using plasma, thereby optimizing the interface between electrolyte fillers and polymer matrix in composite solid electrolytes. The present invention uses plasma technology to effectively convert the air pollution layer on the surface of garnet-type inorganic solid electrolytes into a fast ion conductor layer, thereby improving the air stability of the electrolyte. Through this technology, the uniform distribution between the active filler and the polymer matrix and the rapid Li+ transfer at the interface are greatly promoted. + The filler effectively inhibits the dehydrofluorination of polyvinylidene fluoride-co-hexafluoropropylene-based polymer materials, thereby improving the mechanical properties of the electrolyte and its compatibility with the electrodes. The present invention has the advantages of simple processing method and low cost, and has good commercial application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of energy materials, and in particular relates to a method for preparing a solid electrolyte in a lithium metal solid-state battery. Background Art

[0002] Since the 21st century, humanity has achieved remarkable progress and development in all fields. However, the environmental problems brought about by social development have become increasingly serious, forcing people to seek more clean and efficient emerging energy sources. Among them, lithium-ion batteries, as a clean energy and efficient energy storage device, have received widespread attention and development.

[0003] Conventional commercial lithium-ion batteries typically utilize liquid organic electrolytes for ion conduction, enabling energy storage and conversion. However, their poor thermal and electrochemical stability are significant drawbacks. In recent years, numerous reports have highlighted serious safety incidents involving lithium-ion batteries due to thermal runaway caused by electrolyte decomposition. Consequently, the safety of lithium-ion batteries has drawn significant attention.

[0004] In order to meet people's demand for higher energy density batteries, metallic lithium has a high capacity of 3960 mAh g -1 Due to its high theoretical specific capacity, it is considered a new generation of negative electrode materials. However, in conventional batteries with organic liquid electrolyte systems, short circuits occur during charge and discharge due to the uncontrolled growth of lithium dendrites, significantly reducing the battery's cycle life and increasing safety risks. In light of this, solid-state electrolytes, as an emerging technology, can effectively inhibit the growth of lithium dendrites, thereby resolving the short circuit problem.

[0005] In general, solid electrolytes exhibit the following advantages: (1) The high thermal stability of solid electrolytes allows them to be used in a wider operating temperature range. (2) The high electrochemical stability window of solid electrolytes allows them to be matched with high-voltage cathode materials to improve the energy density of solid electrolytes. (3) Solid electrolytes with high Young's modulus can effectively inhibit the growth of lithium dendrites due to their high mechanical strength. Therefore, the development of high-performance solid electrolytes is of far-reaching significance for the construction of high-energy-density lithium metal batteries. Summary of the Invention

[0006] To address these issues, the present invention discloses a method for plasma interface modification of the surface of a garnet-type solid electrolyte filler, as well as a process for preparing a composite solid electrolyte. This interface modification technique is simple, efficient, and low-cost, effectively removing the passivation layer on the surface of the electrolyte powder, enabling it to perform better as an active filler in the composite electrolyte.

[0007] To achieve the above object, the technical solution of the present invention is as follows:

[0008] The present invention provides a method for preparing a composite solid electrolyte treated by plasma reaction, comprising the following steps:

[0009] S01. Preparation of a garnet-type solid electrolyte filler: lanthanum oxide, tantalum pentoxide, zirconium oxide, and a predetermined lithium source material are weighed in a certain molar ratio, ball-milled, and sintered at a predetermined temperature for a predetermined time by a solid-phase sintering method to obtain a garnet-type solid electrolyte filler;

[0010] S02. Plasma interface modification: Plasma reaction treatment is performed on the garnet-type solid electrolyte powder to obtain a surface-modified garnet-type solid electrolyte filler.

[0011] S03. Preparation of a composite solid electrolyte: Weigh a polymer, a lithium salt, and a garnet-type solid electrolyte filler according to a predetermined ratio. Dissolve the polymer and lithium salt in an organic solvent and magnetically stir for a second predetermined time to obtain a mixed solution from the first step. Add the surface-modified garnet-type solid electrolyte filler to the mixed solution from the first step and magnetically stir for a third predetermined time to obtain a mixed solution from the second step. Cast the mixed solution into a polytetrafluoroethylene mold and dry in a vacuum oven for a fourth predetermined time to obtain a composite solid electrolyte with uniform thickness.

[0012] Compared with the existing interface modification technology, in the above-mentioned method of plasma treatment of garnet-type solid electrolyte powder, the treated garnet-type solid electrolyte filler effectively removes the passivation layer on the surface and suppresses the dehydrofluorination phenomenon that occurs in the composite solid electrolyte. The composite solid electrolyte prepared using the treated garnet-type solid electrolyte filler exhibits lower interface impedance and better matching with the metal lithium negative electrode, thereby extending its cycle life. Moreover, due to its excellent mechanical properties, it also performs well in resisting lithium dendrite growth. In addition, the above-mentioned method has a simple process flow and is green and environmentally friendly. The prepared composite solid electrolyte also has excellent flexibility, so it also has good application prospects in flexible devices.

[0013] Furthermore, in step S01, the molar ratio of lanthanum oxide, tantalum pentoxide, zirconium oxide, and a predetermined lithium source is 1.5:3:1.4:7.04-7.68. To compensate for lithium source loss during the sintering process, the lithium source is overdosed to a ratio ranging from 10% to 20% of the original molar weight of the lithium source.

[0014] Furthermore, in step S01, the preset temperature is 900-950° C., and the first preset time is 4-6 hours. The first preset time can fully sinter the raw materials to obtain a pure phase garnet-type solid electrolyte filler.

[0015] Furthermore, in step S01, the lithium source is one or more of lithium hydroxide monohydrate and lithium carbonate, and different lithium sources are used as raw materials to obtain garnet-type solid electrolyte powder through solid-phase sintering.

[0016] Furthermore, in step S02, plasma interface modification specifically includes the following steps: using preset parameters to uniformly perform plasma reaction treatment on the surface of the garnet-type solid electrolyte filler prepared in step S01, the preset parameters include a preset plasma treatment atmosphere, a preset treatment power, and a preset treatment time, the preset plasma treatment atmosphere is one of ammonium fluoride and urea, the preset treatment power range is 100-300 W, and the preset treatment time is 3-20 min.

[0017] The surface modification treatment of the garnet-type solid electrolyte filler using the above-mentioned preset parameters can effectively treat the passivation layer on the surface of the garnet-type solid electrolyte, so that it can be dissolved in the polymer as an active filler to form a continuous ion transmission path, thereby improving the mechanical properties, conductivity and long cycle performance of the composite solid electrolyte.

[0018] Furthermore, in step S03, the preset ratio is: the mass percentage of lithium salt to polymer is 50 wt%~110 wt%, the mass percentage of garnet solid electrolyte filler to polymer is 10 wt%~60 wt%, and the mass percentage of solvent to polymer is 280 wt%~370 wt%.

[0019] Following the above-mentioned preset ratio, the crystallinity of the polymer matrix can be effectively reduced, the glass transition temperature can be lowered, the ion transport capacity of the polymer chain segments can be effectively improved, and the ionic conductivity and ion transference number of the composite solid electrolyte can be improved. Secondly, the addition of garnet-type solid electrolyte fillers can also effectively increase the mechanical properties of the electrolyte, thereby improving its ability to resist lithium dendrite growth, so that the battery can exhibit better cycle performance.

[0020] Furthermore, in step S03, the polymer and lithium salt are dissolved in an organic solvent and uniformly stirred for a second preset time of 6-12 hours to obtain the mixed solution of the first step. The step includes: using magnetic stirring to obtain the mixed solution of the first step. Specifically, magnetic stirring has the advantages of uniform stirring, simple operation, and high controllability, so that the stirring condition of the mixed solution can be observed. The second preset time can achieve a sufficient stirring effect to obtain a uniform first-step mixed solution.

[0021] Furthermore, in step S03, the garnet-type solid electrolyte filler is dissolved in the first mixed solution and magnetically stirred for a third preset time of 6-12 h to obtain a mixed solution of the second step, and the step includes: uniformly stirring by magnetic stirring to obtain a mixed solution of the second step. Specifically, magnetic stirring can make the garnet-type solid electrolyte filler uniformly dispersed in the mixed solution of the first step, and the method is simple and convenient to obtain a uniform mixed solution. The third preset time can effectively disperse the garnet-type solid electrolyte filler in the mixed solution of the first step, so that the mixed solution of the second step exhibits a better microstructure.

[0022] Furthermore, in step S03, the fourth preset time is 12-24 hours. Using the fourth preset time can produce a composite solid electrolyte with excellent mechanical properties and a dense structure.

[0023] Furthermore, in step S03, the polymer is one or more of polyethylene oxide and poly(vinylidene fluoride-co-hexafluoropropylene), the solvent contains one or more of N,N-dimethylformamide and acetonitrile; the lithium salt is one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium perchlorate (LiClO4), and lithium hexafluorophosphate (LiFP6).

[0024] The polymer matrix has excellent film-forming properties, electrochemical stability, and thermodynamic stability, and its polymer segments can rapidly transport lithium ions. As a result, the resulting composite solid-state electrolyte exhibits excellent electrical conductivity and mechanical properties, a wide electrochemical stability window, and a high operating temperature range.

[0025] Furthermore, in step S03, the thickness of the composite solid electrolyte membrane is 20-100 μm. The composite solid electrolyte having a thickness of 20-100 μm can exhibit excellent ion transport performance and good mechanical properties, and the thin thickness of the composite solid electrolyte makes it have good application prospects.

[0026] The present invention also provides a garnet-type composite solid electrolyte prepared by the above-mentioned preparation method.

[0027] The beneficial effects of the present invention are:

[0028] The interface modification of the garnet-type solid electrolyte filler by plasma can effectively remove the passivation layer on the filler surface. When it is used as an active filler in a composite solid electrolyte, the following performance will be achieved: (1) The garnet-type solid electrolyte filler can be evenly distributed in the composite solid electrolyte and in close contact with the polymer matrix, so that the interface compatibility between the composite solid electrolyte and the metal lithium negative electrode is increased, the interface impedance is reduced, and the battery polarization is reduced. However, if the composite solid electrolyte is interface modified, the uniform distribution of the garnet-type solid electrolyte filler in the polymer matrix cannot be adjusted. The composite solid electrolyte after interface modification still maintains a porous and loose morphology, so its interface compatibility with the metal lithium negative electrode is poor, which has a disadvantageous performance in resisting lithium dendrite growth. (2) The effective removal of the lithium carbonate passivation layer on the surface of the garnet-type solid electrolyte can effectively alleviate the occurrence of dehydrofluorination, avoid the gelation of the polymer composite solid electrolyte, and significantly improve its electrochemical stability, so it also has good performance in matching high-voltage positive electrodes. (3) The lithium fluoride interface layer formed in situ on the surface of the garnet-type solid electrolyte filler can effectively regulate the SEI layer components between the electrolyte and the metal lithium negative electrode, thereby improving the stability of the electrolyte to the metal lithium negative electrode. Therefore, the solid-state battery using the above-mentioned composite solid electrolyte can obtain excellent cycle performance. (4) In addition, the CEI layer enriched with inorganic components can effectively protect the cathode material to avoid irreversible structural degradation. Therefore, by regulating the CEI layer components on the cathode side and the SEI layer components on the anode side, the cycle performance of the cathode|SPE|Li full battery can be effectively improved, so that the composite solid electrolyte has good performance when matching various cathode materials.

[0029] In summary, the above-mentioned process of plasma interface modification of garnet-type solid electrolyte powder has the advantages of simple method and low cost, and the treatment process is safe and environmentally friendly, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A flow chart of the method for plasma interface modification of garnet-type solid electrolyte filler and the preparation process of the composite solid electrolyte provided by the present invention;

[0031] Figure 2 X-ray diffraction patterns (XRD) of the garnet-type solid electrolyte powders obtained in Examples 2 and 6 of the present invention before and after plasma interface modification;

[0032] Figure 3 This is a scanning electron microscope image (SEM) of the PVDF-HFP-LLZTO composite solid electrolyte obtained in Example 2 of the present invention;

[0033] Figure 4This is a scanning electron microscope image (SEM) of the PVDF-HFP-LLZTO(P) composite solid electrolyte obtained in Example 6 of the present invention;

[0034] Figure 5 This is a scanning electron microscope image (SEM) of the [PVDF-HFP-LLZTO](P) composite solid electrolyte obtained in Example 10 of the present invention;

[0035] Figure 6 Electrochemical impedance spectroscopy (EIS) diagrams of the PVDF-HFP-LLZTO composite solid electrolyte, the PVDF-HFP-LLZTO(P) composite solid electrolyte, and the [PVDF-HFP-LLZTO](P) composite solid electrolyte obtained in Examples 2, 6, and 10 of the present invention;

[0036] Figure 7 is the activation energy of the PVDF-HFP-LLZTO composite solid electrolyte and the PVDF-HFP-LLZTO(P) composite solid electrolyte obtained in Example 2 and Example 6 of the present invention;

[0037] Figure 8 This is the electrochemical impedance spectroscopy diagram of the PEO-LLZTO composite solid electrolyte obtained in Example 11 of the present invention;

[0038] Figure 9 This is the electrochemical impedance spectroscopy diagram of the PEO-LLZTO(P) composite solid electrolyte obtained in Example 12 of the present invention;

[0039] Figure 10 This is a long cycle performance diagram of a symmetrical (Li / CPE / Li) battery with a PVDF-HFP-LLZTO(P) composite solid electrolyte obtained in Example 6 of the present invention;

[0040] Figure 11 This is a long cycle performance diagram of a symmetrical (Li / CPE / Li) battery with a PVDF-HFP-LLZTO composite solid electrolyte obtained in Example 2 of the present invention;

[0041] Figure 12 This is a long cycle performance diagram of a full cell (LFP / CPE / Li) with a PVDF-HFP-LLZTO(P) composite solid electrolyte obtained in Example 6 of the present invention;

[0042] Figure 13 This is a long cycle performance diagram of a full battery (LFP / CPE / Li) with a PVDF-HFP-LLZTO composite solid electrolyte obtained in Example 2 of the present invention;

[0043] Figure 14This is a rate performance diagram of a full cell (LFP / CPE / Li) of the PVDF-HFP-LLZTO(P) composite solid electrolyte obtained in Example 6 of the present invention;

[0044] Figure 15 This is a rate performance diagram of a full battery (LFP / CPE / Li) of the PVDF-HFP-LLZTO composite solid electrolyte obtained in Example 2 of the present invention. DETAILED DESCRIPTION

[0045] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0046] The development of new solid-state electrolytes currently faces numerous scientific and technological challenges: for example, the large interfacial impedance caused by the solid-solid contact between the electrolyte and the lithium metal anode; the room-temperature ionic conductivity still cannot match that of liquid electrolytes; and the long-term cycling performance is poor. Therefore, in response to the above-mentioned issues, the present invention aims to perform plasma interface modification on the active filler of a garnet-type solid electrolyte, thereby improving the room-temperature ionic conductivity of the composite solid electrolyte while also improving the interfacial contact with the lithium metal anode and enhancing the stability of the solid electrolyte to the electrode.

[0047] PVDF-HFP-LLZTO composite solid electrolyte (untreated PVDF-HFP-based composite solid electrolyte);

[0048] PVDF-HFP-LLZTO(P) composite solid electrolyte (PVDF-HFP-based composite solid electrolyte that undergoes plasma interface modification treatment and then composite);

[0049] [PVDF-HFP-LLZTO](P) composite solid electrolyte (PVDF-HFP-based composite solid electrolyte that is first composited and then subjected to plasma interface modification treatment);

[0050] PEO-LLZTO composite solid electrolyte (untreated PEO-based composite solid electrolyte);

[0051] PEO-LLZTO(P) composite solid electrolyte (PEO-based composite solid electrolyte that undergoes plasma interface modification treatment and then composite). Example 1

[0052] Preparation of the garnet-type solid electrolyte filler: Lanthanum oxide, zirconium oxide, tantalum pentoxide, and a predetermined lithium source were weighed according to the predetermined amounts. The predetermined amounts were 0.015 mol of lanthanum oxide, 0.014 mol of zirconium oxide, 0.03 mol of tantalum pentoxide, and 0.0736 mol of the lithium source. The predetermined lithium source was lithium hydroxide monohydrate, and an excess amount was used to compensate for the loss of the lithium source during the sintering process. The raw materials were ball-milled at 400 rpm for 10 hours and then prepared using a solid-phase sintering method. The sintering temperature was 950°C and the sintering time was 6 hours. Example 2

[0053] Preparation of PVDF-HFP-LLZTO composite solid electrolyte

[0054] Preparation steps: Weigh poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), lithium salt LiTFSI, and garnet-type solid electrolyte active filler (product prepared in Example 1) according to the preset mass. The preset mass is 0.5 g PVDF-HFP, 0.55 g LiTFSI, and 0.15 g garnet-type solid electrolyte active filler. Add 15 mL N,N-dimethylformamide (DMF) and stir magnetically for 24 hours to obtain a uniform polymer slurry. Pour the polymer slurry into a polytetrafluoroethylene mold and dry it in a vacuum oven for 20-24 hours to obtain a composite solid electrolyte membrane with a thickness of 20-100 μm. Example 3

[0055] Preparation of PVDF-HFP-LLZTO(P) composite solid electrolyte

[0056] Preparation steps: Weigh 0.5 g of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and 0.55 g of LiTFSI according to the preset mass. Add 15 mL of N,N-dimethylformamide (DMF) and magnetically stir for 12 hours to obtain a uniform polymer slurry.

[0057] Plasma surface modification treatment of the garnet-type solid electrolyte active filler (product prepared in Example 1): The surface of the garnet-type solid electrolyte powder is uniformly modified by plasma, and the preset plasma atmosphere is ammonium fluoride. The preset power range is 150 W. The preset treatment time is 3 minutes.

[0058] A garnet-type solid electrolyte active filler, which has undergone plasma interface modification, was added to a polymer slurry at a ratio of 15 wt%. The mixture was magnetically stirred for 12 hours to obtain a uniformly mixed slurry. The polymer slurry was then cast into a polytetrafluoroethylene mold and dried in a vacuum oven for a predetermined time, typically 20-24 hours, to form a composite solid electrolyte membrane with a thickness of 20-100 μm. Example 4

[0059] Preparation of PVDF-HFP-LLZTO(P) composite solid electrolyte

[0060] Preparation steps: Weigh 0.5 g of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and 0.55 g of LiTFSI according to the preset mass. Add 15 mL of N,N-dimethylformamide (DMF) and magnetically stir for 12 hours to obtain a uniform polymer slurry.

[0061] Plasma interface modification treatment of the garnet-type solid electrolyte active filler: Uniformly modify the surface of the garnet-type solid electrolyte powder with plasma, wherein the preset plasma atmosphere is ammonium fluoride. The preset power range is 300 W. The preset treatment time is 3 minutes.

[0062] A garnet-type solid electrolyte active filler, which has undergone plasma interface modification, was added to a polymer slurry at a ratio of 15 wt%. The mixture was magnetically stirred for 12 hours to obtain a uniformly mixed slurry. The polymer slurry was then cast into a polytetrafluoroethylene mold and dried in a vacuum oven for a predetermined time, typically 20-24 hours, to form a composite solid electrolyte membrane with a thickness of 20-100 μm. Example 5

[0063] Preparation of PVDF-HFP-LLZTO(P) composite solid electrolyte

[0064] Preparation steps: Weigh 0.5 g of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and 0.55 g of LiTFSI according to the preset mass. Add 15 mL of N,N-dimethylformamide (DMF) and magnetically stir for 12 hours to obtain a uniform polymer slurry.

[0065] Plasma interface modification treatment of the garnet-type solid electrolyte active filler: Uniformly modify the surface of the garnet-type solid electrolyte powder with plasma, wherein the preset plasma atmosphere is ammonium fluoride. The preset power range is 300 W. The preset treatment time is 5 minutes.

[0066] A garnet-type solid electrolyte active filler, which has undergone plasma interface modification, was added to a polymer slurry at a ratio of 15 wt%. The mixture was magnetically stirred for 12 hours to obtain a uniformly mixed slurry. The polymer slurry was then cast into a polytetrafluoroethylene mold and dried in a vacuum oven for a predetermined time, typically 20-24 hours, to form a composite solid electrolyte membrane with a thickness of 20-100 μm. Example 6

[0067] Preparation of PVDF-HFP-LLZTO(P) composite solid electrolyte

[0068] Preparation steps: Weigh 0.5 g of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and 0.55 g of LiTFSI according to the preset mass. Add 15 mL of N,N-dimethylformamide (DMF) and magnetically stir for 12 hours to obtain a uniform polymer slurry.

[0069] Plasma interface modification treatment of the garnet-type solid electrolyte active filler: Uniformly modify the surface of the garnet-type solid electrolyte powder with plasma, wherein the plasma is pre-set in an atmosphere of ammonium fluoride. The pre-set power range is 300 W, and the pre-set treatment time is 10 minutes.

[0070] A garnet-type solid electrolyte active filler, which has undergone plasma interface modification, was added to a polymer slurry at a ratio of 15 wt%. The mixture was magnetically stirred for 12 hours to obtain a uniformly mixed slurry. The polymer slurry was then cast into a polytetrafluoroethylene mold and dried in a vacuum oven for a predetermined time, typically 20-24 hours, to form a composite solid electrolyte membrane with a thickness of 20-100 μm. Example 7

[0071] Preparation of PVDF-HFP-LLZTO(P) composite solid electrolyte

[0072] Preparation steps: Weigh 0.5 g of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and 0.55 g of LiTFSI according to the preset mass. Add 15 mL of N,N-dimethylformamide (DMF) and magnetically stir for 12 hours to obtain a uniform polymer slurry.

[0073] Plasma surface modification treatment of the garnet-type solid electrolyte active filler: Uniformly modify the surface of the garnet-type solid electrolyte powder with plasma, using an ammonium fluoride atmosphere. The preset power is 300 W, and the preset treatment time is 15 minutes.

[0074] A plasma-modified garnet-type solid electrolyte active filler was added to a polymer slurry at a ratio of 15 wt%. The mixture was magnetically stirred for 12 hours to obtain a uniform slurry. The polymer slurry was then poured into a polytetrafluoroethylene mold and dried in a vacuum oven for a predetermined time, typically 20-24 hours, to form a composite solid electrolyte membrane with a thickness of 20-100 μm. Example 8

[0075] Preparation of PVDF-HFP-LLZTO(P) composite solid electrolyte

[0076] Preparation steps: Weigh 0.5 g of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and 0.3 g of LiTFSI according to the preset mass. Add 15 mL of N,N-dimethylformamide (DMF) and magnetically stir for 12 hours to obtain a uniform polymer slurry.

[0077] Plasma surface modification treatment of the garnet-type solid electrolyte active filler: Uniformly modify the surface of the garnet-type solid electrolyte powder with plasma, wherein the plasma is pre-set in an atmosphere of ammonium fluoride. The pre-set power range is 300 W, and the pre-set treatment time is 10 minutes.

[0078] A plasma-modified garnet-type solid electrolyte active filler was added to a polymer slurry at a ratio of 60 wt%. The mixture was magnetically stirred for 12 hours to obtain a uniform slurry. The polymer slurry was then poured into a polytetrafluoroethylene mold and dried in a vacuum oven for a predetermined time, typically 20-24 hours, to form a composite solid electrolyte membrane with a thickness of 20-100 μm. Example 9

[0079] Preparation of PVDF-HFP-LLZTO(P) composite solid electrolyte

[0080] Preparation steps: Weigh 0.5 g of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and 0.55 g of LiTFSI according to the preset mass. Add 15 mL of N,N-dimethylformamide (DMF) and magnetically stir for 12 hours to obtain a uniform polymer slurry.

[0081] Plasma surface modification treatment of the garnet-type solid electrolyte active filler: Uniformly modify the surface of the garnet-type solid electrolyte powder using plasma, wherein the plasma is pre-set to a urea atmosphere. The pre-set power range is 300 W, and the pre-set treatment time is 10 minutes.

[0082] A plasma-modified garnet-type solid electrolyte active filler was added to a polymer slurry at a ratio of 15 wt%. The mixture was magnetically stirred for 12 hours to obtain a uniform slurry. The polymer slurry was then poured into a polytetrafluoroethylene mold and dried in a vacuum oven for a predetermined time, typically 20-24 hours, to form a composite solid electrolyte membrane with a thickness of 20-100 μm. Example 10

[0083] Preparation of [PVDF-HFP-LLZTO](P) composite solid electrolyte

[0084] Preparation steps: The surface of the PVDF-HFP-LLZTO composite solid electrolyte (product prepared in Example 2) was uniformly plasma-modified, with the plasma atmosphere set to ammonium fluoride. The preset power was 300 W, and the preset treatment time was 10 minutes. Example 11

[0085] Preparation of PEO-LLZTO composite solid electrolyte

[0086] Preparation steps: Weigh polyethylene oxide (PEO), lithium salt (LITFSI), and garnet-type solid electrolyte active filler according to the preset mass. The preset mass is 0.5 g PEO, 0.181 g LiTFSI, and 0.1 g garnet solid electrolyte active filler. Add 15 mL acetonitrile and stir magnetically for 24 hours to obtain a uniform polymer slurry. The polymer slurry is poured into a polytetrafluoroethylene mold under an argon atmosphere, dried at room temperature for a preset time, and then dried in a vacuum oven to obtain a composite solid electrolyte membrane with a thickness of 80-100 μm. The preset time is 12 hours. Example 12

[0087] Preparation of PEO-LLZTO(P) composite solid electrolyte

[0088] Preparation steps: Weigh 0.5 g of polyethylene oxide (PEO) and 0.181 g of lithium ion battery (LITFSI) according to the preset mass, add 15 mL of acetonitrile, and stir magnetically for 12 hours to obtain a uniform polymer slurry.

[0089] Plasma surface modification treatment of the garnet-type solid electrolyte active filler: Uniformly modify the surface of the garnet-type solid electrolyte powder with plasma, wherein the plasma is pre-set in an atmosphere of ammonium fluoride. The pre-set power range is 300 W, and the pre-set treatment time is 10 minutes.

[0090] A plasma-modified garnet-type solid electrolyte active filler was added to the polymer slurry at a ratio of 15 wt% and magnetically stirred for 12 hours to obtain a uniformly mixed slurry. The polymer slurry was then cast into a polytetrafluoroethylene mold under an argon atmosphere, dried at room temperature for a preset time, and then dried in a vacuum oven to produce a composite solid electrolyte membrane with a thickness of 80-100 μm.

[0091] The method for plasma interface modification of garnet-type solid electrolyte filler and the process for preparing composite solid electrolyte provided by the present invention are shown in the flowchart as follows: Figure 1 shown.

[0092] The X-ray diffraction patterns (XRD) of the garnet-type solid electrolyte powders obtained in Example 1 and Example 6 of the present invention before and after plasma interface modification treatment are as follows: Figure 2 As shown in the figure, the lithium carbonate passivation layer on the surface of the garnet-type solid electrolyte powder is completely treated, and a new lithium fluoride characteristic peak appears, which proves that the plasma technology proposed in this paper has a good interface modification effect.

[0093] The scanning electron microscope image (SEM) of the untreated PVDF-HFP-LLZTO composite solid electrolyte obtained in Example 2 of the present invention is as follows: Figure 3 As shown, the surface of the PVDF-HFP-LLZTO composite solid electrolyte doped with garnet-type solid electrolyte powder presents a porous morphology, which has an adverse effect on resisting lithium dendrite growth.

[0094] The scanning electron microscope image (SEM) of the PVDF-HFP-LLZTO (P) composite solid electrolyte obtained in Example 6 of the present invention is as follows: Figure 4As shown, the density of the PVDF-HFP-LLZTO(P) composite solid electrolyte that is first subjected to plasma interface modification treatment and then composited is greatly improved, and has a better effect in resisting lithium dendrite growth.

[0095] The scanning electron microscope image (SEM) of the [PVDF-HFP-LLZTO] (P) composite solid electrolyte obtained in Example 10 of the present invention is as follows: Figure 5 As shown, after the interface modification of the composite solid electrolyte surface, the electrolyte exhibits a porous and loose morphology, and has poor performance in resisting lithium dendrite growth.

[0096] The electrochemical impedance spectroscopy of the PVDF-HFP-LLZTO composite solid electrolyte, PVDF-HFP-LLZTO (P) composite solid electrolyte and [PVDF-HFP-LLZTO] (P) composite solid electrolyte obtained in Example 2, Example 6 and Example 10 of the present invention is shown in FIG. Figure 6 As shown in Figure 2, the room temperature ionic conductivity of the PVDF-HFP-LLZTO(P) composite solid electrolyte is 7.26×10 -4 S cm -1 , which is twice that of the electrolyte without interface modification and is also much higher than the ionic conductivity of the [PVDF-HFP-LLZTO](P) composite solid electrolyte obtained in Example 10 (4.22×10 -4 S cm -1 ).

[0097] The activation energy of the PVDF-HFP-LLZTO(P) composite solid electrolyte obtained in Example 6 of the present invention is as follows: Figure 7 As shown in the figure, the PVDF-HFP-LLZTO(P) composite solid electrolyte that was first treated with plasma interface modification and then composited showed a smaller migration activation energy, which was beneficial to the Li + Migration movement.

[0098] The electrochemical impedance spectroscopy of the PEO-LLZTO composite solid electrolyte obtained in Example 11 of the present invention is as follows: Figure 8 As shown in Figure 2, under room temperature conditions, the room temperature ionic conductivity of the untreated PEO-LLZTO composite solid electrolyte is 1.31×10 -5 Scm -1 . ;

[0099] The electrochemical impedance spectroscopy of the PEO-LLZTO(P) composite solid electrolyte obtained in Example 12 of the present invention is as follows: Figure 9 As shown in the figure, the room temperature ionic conductivity of the PEO-LLZTO(P) composite solid electrolyte, which was first treated with plasma interface modification and then composited, was 2.2×10 -5S cm -1 .

[0100] The long cycle performance diagram of the symmetrical (Li / CPE / Li) battery of the PVDF-HFP-LLZTO(P) composite solid electrolyte obtained in Example 6 of the present invention is as follows: Figure 10 As shown in the figure, the PVDF-HFP-LLZTO(P) composite solid electrolyte that is first subjected to plasma interface modification treatment and then composited has good anti-lithium dendrite performance and cycle stability, and can be stably cycled for more than 900 h.

[0101] The long cycle performance of the symmetrical (Li / CPE / Li) battery of the untreated PVDF-HFP-LLZTO composite solid electrolyte membrane obtained in Example 2 of the present invention is shown in FIG. Figure 11 As shown in Figure 3, the PVDF-HFP-LLZTO composite solid electrolyte failed rapidly after 200 h of cycling due to the problems of lithium dendrite growth and poor interface stability.

[0102] The long cycle performance of the full battery (LFP / CPE / Li) of the PVDF-HFP-LLZTO(P) composite solid electrolyte obtained in Example 6 of the present invention is shown in FIG. Figure 12 As shown in the figure, the PVDF-HFP-LLZTO(P) composite solid electrolyte, which was first treated with plasma interface modification and then composited, has a good match with the LFP positive electrode material. It can be stably cycled for 200 cycles at a rate of 0.5 C, with a capacity retention rate of 94.2%.

[0103] The long cycle performance of the full battery (LFP / CPE / Li) of the untreated PVDF-HFP-LLZTO composite solid electrolyte membrane obtained in Example 2 of the present invention is shown in FIG. Figure 13 As shown in Figure 3, the capacity of the untreated PVDF-HFP-LLZTO composite solid electrolyte rapidly decays after 100 cycles.

[0104] The rate performance of the full battery (LFP / CPE / Li) of the PVDF-HFP-LLZTO(P) composite solid electrolyte obtained in Example 6 of the present invention is shown in FIG. Figure 14 As shown in Figure 2, the PVDF-HFP-LLZTO(P) composite solid electrolyte, which was first treated with plasma interface modification and then composited, maintained good cycling stability at different discharge rates. When the current density returned from 5 C to 0.1 C, the discharge capacity was 152.1 mAh g -1 , which is 98.6% of the initial discharge capacity.

[0105] The rate performance of the full cell (LFP / CPE / Li) of the PVDF-HFP-LLZTO composite solid electrolyte membrane obtained in Example 2 of the present invention is shown in FIG. Figure 15 As shown in Figure 2, the rate performance of the untreated PVDF-HFP-LLZTO composite solid electrolyte is poor, especially at a high current density of 5 C, where the discharge capacity is only 42.6 mAh g -1 .

[0106] It should be noted that the above content merely illustrates the technical idea of ​​the present invention and cannot be used to limit the scope of protection of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a garnet-type composite solid electrolyte treated by plasma reaction, characterized in that: The following steps are involved: S01 Preparation of garnet-type solid electrolyte filler: lanthanum oxide, tantalum pentoxide, zirconium oxide and lithium source are ball-milled and mixed, and sintered at a preset temperature for a first preset time by a solid-phase sintering method to obtain a garnet-type solid electrolyte filler; S02 plasma interface modification, plasma reaction treatment of the prepared garnet-type solid electrolyte filler; Preparation of S03 garnet-type composite solid electrolyte: dissolving the polymer and lithium salt in a solvent and uniformly stirring for a second preset time to obtain a mixed solution of the first step; adding the treated garnet-type solid electrolyte filler to the mixed solution of the first step and uniformly stirring for a third preset time to obtain a mixed solution of the second step; Then, the mixed solution obtained in the second step is poured into a polytetrafluoroethylene mold, and dried in a vacuum oven for a fourth preset time to obtain a composite solid electrolyte; In step S02, plasma interface modification specifically includes the following steps: using preset parameters to perform plasma reaction treatment on the surface of the garnet-type solid electrolyte filler prepared in step S01, the preset parameters include a preset plasma treatment atmosphere, a preset treatment power, and a preset treatment time, the preset plasma treatment atmosphere is ammonium fluoride, the preset treatment power range is 100-300 W, and the preset treatment time is 3-20 min.

2. The method for preparing a garnet-type composite solid electrolyte treated by plasma reaction according to claim 1, characterized in that: In step S01, the molar ratio of lanthanum oxide, tantalum pentoxide, zirconium oxide, and lithium source is 1.5:3:1.4:7.04-7.

68.

3. The method for preparing a garnet-type composite solid electrolyte treated by plasma reaction according to claim 1, characterized in that: In step S01, the preset temperature is 900-950° C., and the first preset time is 4-6 hours; the lithium source is one or more of lithium hydroxide monohydrate and lithium carbonate.

4. The method for preparing a garnet-type composite solid electrolyte treated by plasma reaction according to claim 1, characterized in that: In step S03 , the mass percentage of the lithium salt and the polymer is 50 wt % to 110 wt %, the mass percentage of the garnet-type solid electrolyte filler and the polymer is 10 wt % to 60 wt %, and the mass percentage of the solvent and the polymer is 280 wt % to 370 wt %.

5. The method for preparing a garnet-type composite solid electrolyte treated by plasma reaction according to claim 1, characterized in that: In step S03, the second preset time is 6-12 hours, the third preset time is 6-12 hours, and the fourth preset time is 12-24 hours.

6. The method for preparing a garnet-type composite solid electrolyte treated by plasma reaction according to claim 1, characterized in that: In step S03, the polymer is one or more of polyethylene oxide and poly(vinylidene fluoride-co-hexafluoropropylene), the solvent contains one or more of N,N-dimethylformamide and acetonitrile; and the lithium salt is one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, and lithium hexafluorophosphate.

7. The method for preparing a garnet-type composite solid electrolyte treated by plasma reaction according to claim 1, characterized in that: In step S03, the thickness of the composite solid electrolyte membrane is obtained to be 20-100 μm.

8. A garnet-type composite solid electrolyte prepared by the preparation method according to any one of claims 1 to 7.

Images