Solid-state battery and preparation method thereof

Abstract

The invention provides a solid-state battery and a preparation method thereof. The solid-state battery comprises a positive electrode, a solid-state electrolyte layer and a composite negative electrode which are sequentially stacked, the composite negative electrode comprises a negative electrode and a Li3N modified carbon source layer, and the Li3N modified carbon source layer is located between the negative electrode and the solid electrolyte layer. Functional layers for improving lithium ion transmission efficiency are constructed on the surface of the carbon material and in pores, and are used as a modification layer between a solid electrolyte and a negative electrode interface, so that rapid transmission of lithium ions at the interface is improved; the solid electrolyte is prepared into uniform slurry and then is directly coated on the surface of the silver-carbon composite negative plate of the solid battery, so that the interface contact between the negative plate and an electrolyte layer is greatly enhanced compared with a bonding transfer printing mode; the battery structure that the double-layer composite negative electrode is integrated with the electrolyte and then attached to the positive electrode is beneficial to improving rapid transmission of lithium ions on a negative electrode interface and in the negative electrode and promoting uniform and rapid deposition of lithium on the current collector side, so that the stability of the battery is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of negative electrode sheets, and in particular relates to a solid-state battery and a preparation method thereof. Background Art

[0002] In all-solid-state lithium-ion batteries, the interface between the electrolyte and the negative electrode is a solid-solid contact, with an uneven interface and poor contact. Therefore, during the charge and discharge process, the current density distribution at the interface is uneven, the lithium-ion transmission rate is slow, and it is easy to deposit at the interface, react with the electrolyte to produce side reactions or form lithium dendrites, which may pierce the electrolyte and cause battery short circuit. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a solid-state battery and a preparation method thereof. The composite negative electrode sheet used in this solid-state battery can improve the rapid transfer of lithium ions at the interface, promote the uniform and rapid deposition of lithium on the current collector side, and improve the stability and reversible specific capacity of the battery.

[0004] The present invention provides a solid-state battery, comprising:

[0005] A positive electrode, a solid electrolyte layer, and a composite negative electrode stacked in sequence;

[0006] The composite negative electrode includes a negative electrode and a LiN 3 modified carbon source layer, and the LiN 3 modified carbon source layer is located between the negative electrode and the solid electrolyte layer.

[0007] Preferably, the composite negative electrode has a bilayer structure, and the negative electrode is a carbon-based negative electrode, a silicon-based negative electrode, or an alloyed negative electrode;

[0008] LiN 3 The preparation raw materials of the modified carbon source layer include a carbon source, a nitrogen source, and a lithium molten salt system;

[0009] The carbon source is selected from one or more of hard carbon, graphite, graphene, carbon black, carbon nanofibers, carbon nanotubes, and mesophase carbon microspheres;

[0010] The nitrogen source is selected from one or more of melamine, dihydrodiamine, urea, and ammonium chloride.

[0011] Preferably, the lithium molten salt system is selected from one or more of LiCl, LiF, LiI, LiBr, LiNO 3 , LiCl-LiF, LiCl-LiBr, and LiCl-LiI.

[0012] Preferably, the mass ratio of the carbon source, the nitrogen source, and the lithium molten salt system is 1:(0.95-1.05):(1.9-2.1).

[0013] Preferably, the method for preparing the composite negative electrode comprises the following steps:

[0014] Disperse a lithium molten salt system, a nitrogen source, and a carbon source into a solvent, stir evenly to obtain a precursor dispersion;

[0015] After subjecting the precursor dispersion to sanding treatment, evaporate the solvent, grind it, and calcine it in an inert atmosphere to obtain a calcined product;

[0016] Wash the calcined product and dry it to obtain Li 3 N-carbon material;

[0017] Mix the Li 3 N-carbon material with a colloidal solution by ball milling to form a slurry, coat it on the surface of the negative electrode sheet, and dry it to obtain a composite negative electrode.

[0018] Preferably, the negative electrode sheet is a silver-carbon negative electrode sheet;

[0019] The silver-carbon negative electrode sheet is prepared by the following method:

[0020] Mix silver powder and C65, and ball mill them in a PAALi-H 2 O colloidal solution to obtain a slurry;

[0021] Coat the slurry on the surface of the current collector and vacuum dry it to obtain a silver-carbon negative electrode sheet.

[0022] Preferably, the temperature of the calcination is 500-600 °C, the heating rate of the calcination is 4-5 °C / min, and the time of the calcination is 3.5-4.5 h.

[0023] The present invention provides a method for preparing the solid-state battery according to the above technical solution, comprising the following steps:

[0024] Coat the electrolyte slurry on the surface of the negative electrode of the composite negative electrode according to the above technical solution, dry it, and integrate the composite negative electrode with the electrolyte layer;

[0025] Then, after die-cutting with the positive electrode sheet, scrape off the material coated on the tab, bond it, encapsulate it, perform warm isostatic pressing, weld the tab, and encapsulate it again to obtain a solid-state battery.

[0026] Preferably, the conditions of the warm isostatic pressing are: the pressure is 300-500 MPa, the temperature is 80-120 °C, and the time is 9-11 min.

[0027] Preferably, when the solid-state battery is subjected to performance testing, the pressure applied to the battery is 4 MPa, and the testing temperature is 55 °C. The present invention provides a solid-state battery, comprising a positive electrode, a solid electrolyte layer, and a composite negative electrode stacked in sequence; the composite negative electrode comprises a negative electrode and a Li 3 N-modified carbon source layer, the LiN 3The modified carbon source layer is located between the negative electrode and the solid electrolyte layer. In the present invention, a functional layer for improving the lithium ion transmission efficiency is constructed on the surface and inside the pores of the carbon material and used as a modification layer between the solid electrolyte and the negative electrode interface to enhance the rapid transmission of lithium ions at the interface. After the solid electrolyte is made into a uniform slurry, it is directly coated on the surface of the composite negative electrode. Compared with the use of the lamination transfer method, the interface contact between the negative electrode sheet and the electrolyte layer is greatly enhanced. This battery structure in which the double-layer composite negative electrode integrates the electrolyte and then is laminated with the positive electrode is beneficial to enhancing the rapid transmission of lithium ions at the negative electrode interface and inside, promoting the uniform and rapid deposition of lithium on the current collector side, and thus improving the stability of the battery. Description of the Drawings

[0028] Figure 1 SEM characterization and elemental analysis diagram of the raw hard carbon used in Example 1;

[0029] Figure 2 For Li in Example 1 3 SEM characterization and Mapping analysis diagram of N-carbon material;

[0030] Figure 3 In a and b are the surface and cross-sectional views of the composite electrode sheet respectively;

[0031] Figure 4 For AgC-Li 3 Structural diagram after N@hard carbon composited with P04H electrolyte layer;

[0032] Figure 5 For AgC-hard carbon and AgC-Li 3 Charge and discharge cycle performance diagram of the battery assembled with N@hard carbon-P04H-NCM H3 at 0.1C / 0.2C;

[0033] Figure 6 SEM characterization and Mapping analysis diagram of the carbon fiber in Example 2;

[0034] Figure 7 For Li in Example 2 3 SEM characterization and Mapping analysis diagram of N-carbon material;

[0035] Figure 8 Surface and cross-sectional views of the composite electrode sheet in Example 2;

[0036] Figure 9 Charge and discharge cycle performance diagram of VGCF before and after modification at 0.1C / 0.2C in Example 2. Detailed Description of the Invention

[0037] The present invention provides a solid-state battery, comprising:

[0038] A positive electrode, a solid electrolyte layer, and a composite negative electrode stacked in sequence;

[0039] The composite negative electrode includes a negative electrode and a Li 3 N-modified carbon source layer, and the Li 3 N-modified carbon source layer is located between the negative electrode and the solid electrolyte layer.

[0040] In the present invention, a functional layer for improving the lithium ion transport efficiency is constructed on the surface and inside the pores of the carbon material and used as a modification layer between the solid electrolyte and the negative electrode interface to enhance the rapid transfer of lithium ions at the interface; after the solid electrolyte is made into a uniform slurry, it is directly coated on the surface of the silver-carbon composite negative electrode of the solid state battery. Compared with the method of using lamination transfer, the interface contact between the negative electrode and the electrolyte layer is greatly enhanced. This battery structure in which the double-layer composite negative electrode integrates the electrolyte and then is laminated with the positive electrode is beneficial to improving the rapid transfer of lithium ions at the negative electrode interface and inside, and promoting the uniform and rapid deposition of lithium on the current collector side.

[0041] In the solid state battery provided by the present invention, the positive electrode, the solid electrolyte layer, and the composite negative electrode are stacked in sequence.

[0042] The solid state battery provided by the present invention includes a positive electrode; the positive electrode is obtained by coating a positive electrode slurry on a positive electrode substrate; the positive electrode slurry is preferably prepared by a two-step wet mixing method; the positive electrode slurry is preferably prepared according to the following method:

[0043] C45, LPSCl electrolyte, p-xylene, and a sizing agent are degassed and mixed; then they are further degassed and mixed with NCM H3, p-xylene, and a sizing agent to obtain the positive electrode slurry.

[0044] The sizing agent in the positive electrode slurry is a PIB-p-xylene sizing agent, and the concentration is preferably 7.5-8.5 wt%.

[0045] The solid state battery provided by the present invention includes a solid electrolyte; the solid electrolyte is selected from one or more of LPSCl electrolytes with a particle size of ~1 μm for vehicle power, LPSCl electrolytes with a particle size of ~3 μm, LIC electrolytes, and Ganfeng electrolytes, and is preferably an LPSCl electrolyte with a particle size of ~3 μm; in a specific embodiment, the solid electrolyte is P04H electrolyte powder, which belongs to the category of LPSCl electrolytes.

[0046] The solid state battery provided by the present invention includes a composite negative electrode, the composite negative electrode includes a negative electrode, and the negative electrode includes a carbon-based negative electrode, a silicon-based negative electrode, or an alloyed negative electrode; among them, the carbon-based negative electrode includes a silver-carbon negative electrode, a graphite negative electrode, or a silicon-carbon negative electrode; the alloyed negative electrode includes a lithium metal negative electrode.

[0047] Among them, the silver-carbon negative electrode is prepared according to the following method:

[0048] Mix silver powder with C65 and ball mill in 1 wt% PAALi-H 2 O glue solution to obtain a slurry;

[0049] Coat the slurry on the surface of the current collector and dry it under vacuum to obtain a silver-carbon negative electrode.

[0050] The ball milling time is 2.5 - 3.5 h, preferably 3 h. The particle size of the silver powder is 20 - 60 μm; specifically 20 μm, 30 μm, 40 μm, 50 μm or 60 μm.

[0051] The composite negative electrode in the present invention further includes a Li 3 N-modified carbon source layer, and the Li 3 N-modified carbon source layer is located between the negative electrode and the solid electrolyte layer. The Li 3 N-modified carbon source layer is obtained by calcining raw materials, and the raw materials include a carbon source, a nitrogen source and a lithium molten salt system.

[0052] The carbon source in the present invention is selected from one or more of hard carbon, graphite, graphene, carbon black, carbon nanofibers, carbon nanotubes and mesophase carbon microspheres; preferably hard carbon or carbon nanofibers are used as the carbon source. As a buffer layer, the hard carbon can fill the interfacial gaps generated when the electrolyte contacts the negative electrode and alleviate the problem of poor interfacial compatibility. The presence of Li 3 N can effectively improve the rapid transport of lithium ions between the solid-solid interfaces.

[0053] The nitrogen source in the present invention is selected from one or more of melamine, dihydrodiamine, urea and ammonium chloride, preferably melamine.

[0054] The lithium molten salt system in the present invention is selected from one or more of LiCl, LiF, LiI, LiBr, LiNO 3 , LiCl-LiF, LiCl-LiBr and LiCl-LiI, preferably LiCl. The lithium molten salt system used in the present invention is inexpensive and can still be recycled during the subsequent suction filtration process.

[0055] The mass ratio of the carbon source, nitrogen source and lithium molten salt system in the present invention is 1:(0.95 - 1.05):(1.9 - 2.1), preferably 1:1:2.

[0056] In a specific embodiment of the present invention, hard carbon is used as the carbon source, lithium chloride (LiCl) is used as the molten salt system and lithium source, and melamine is used as the nitrogen source. After being dissolved and dispersed in ethanol and then sanded, the solvent is then evaporated to dryness. After grinding evenly, it is calcined at high temperature. During the calcination process, LiCl turns into a molten state and has a very strong polarization ability, which can be used as a structure-directing agent (template) to adjust the structural properties (particle size and morphology) of the product. The ionized cations and anions can be used as ionic templates to promote the high dispersion of the precursor. Finally, the solidification process is beneficial to stabilizing the product structure and effectively alleviates the shrinkage and collapse problems of carbonaceous materials. Adding melamine forms a Li 3 N functional layer, which improves the ionic conductivity and promotes the rapid transfer of lithium ions at the interface. The modified carbon material used as the negative electrode interface modification layer can play a buffering role, effectively alleviating the problem of poor solid-solid interface contact. At the same time, the Li 3 N functional layer has high ionic conductivity characteristics and can effectively accelerate the lithium ion transport rate, reducing the generation of lithium deposition. The electrolyte slurry is directly coated on the surface of the silver-carbon-Li 3 N-hard carbon negative electrode, enhancing the interface contact between the negative electrode and the electrolyte layer. The battery structure with the composite negative electrode integrating the electrolyte and the positive electrode is beneficial to improving the rapid transfer of lithium ions at the negative electrode interface and inside, promoting the uniform and rapid deposition of lithium on the current collector side, and further enhancing the stability of the battery system.

[0057] In the present invention, the preparation method of the composite negative electrode includes the following steps:

[0058] Disperse the lithium molten salt system, nitrogen source and carbon source into a solvent, stir evenly to obtain a precursor dispersion;

[0059] After sanding the precursor dispersion, evaporate the solvent to dryness, grind and then calcine in an inert atmosphere to obtain a calcined product;

[0060] Wash and dry the calcined product to obtain Li 3 N-carbon material;

[0061] Mix the Li 3 N-carbon material with a colloidal solution by ball milling to make a slurry, coat it on the surface of the negative electrode sheet, and dry to obtain the composite negative electrode.

[0062] In the present invention, the lithium molten salt system, nitrogen source and carbon source are dispersed into a solvent, stirred evenly to obtain a precursor dispersion. The solvent is anhydrous ethanol; preferably, magnetic stirring is used to stir evenly.

[0063] After obtaining the precursor dispersion, the present invention sands the precursor dispersion, evaporates the solvent to dryness, grinds and then calcines in an inert atmosphere to obtain a calcined product. The present invention is placed in a corundum boat for calcination after sufficient grinding, and the material is placed in a tubular furnace for calcination; the calcination uses N 2As an inert atmosphere; the calcination temperature is 500 - 600 °C, the heating rate of calcination is 4 - 5 °C / min, and the calcination time is 3.5 - 4.5 h.

[0064] After obtaining the calcined product, the present invention washes the calcined product with water and dries it to obtain Li 3 N-carbon material. The present invention washes away the excess lithium molten salt by washing with water, performs suction filtration and drying, and places it in an oven for drying and standby.

[0065] After obtaining the Li 3 N-carbon material, the present invention ball-mills the Li 3 N-carbon material with a colloidal solution to make a slurry, coats it on the surface of the negative electrode sheet, and dries it to obtain a composite negative electrode.

[0066] In the present invention, the negative electrode is selected from a carbon-based negative electrode, a silicon-based negative electrode, or an alloyed negative electrode; the silicon-based negative electrode is a silver-carbon negative electrode, a graphite negative electrode, or a silicon-carbon negative electrode; the alloyed negative electrode is a lithium-metalized negative electrode.

[0067] When the negative electrode sheet is a silver-carbon negative electrode sheet, the silver-carbon negative electrode sheet is prepared by the following method:

[0068] Mix silver powder and C65, and ball-mill in a PAALi-H 2 O colloidal solution to obtain a slurry;

[0069] Coat the slurry on the surface of the current collector and vacuum-dry it to obtain a silver-carbon negative electrode sheet.

[0070] In the present invention, the concentration of the PAALi-H 2 O colloidal solution is 1 wt%; the ball-milling time is 10 - 14 h. The slurry is coated on the surface of a copper foil current collector or a stainless steel foil; the thickness of the current collector is 12 μm; it is preferably vacuum-dried overnight to obtain a silver-carbon negative electrode sheet.

[0071] The present invention preferably ball-mills the Li 3 N-carbon material with a PVDF-NMP colloidal solution; the concentration of the PVDF-NMP colloidal solution is 2 wt%. The coating method and thickness are four-sided knife coating, and the thickness is 30 - 60 μm.

[0072] The present invention provides a preparation method for an all-solid-state battery, comprising the following steps:

[0073] Coat the electrolyte slurry on the surface of the negative electrode of the composite negative electrode described in the above technical solution, dry it, and integrate the composite negative electrode with the electrolyte layer;

[0074] Then, after die-cutting with the positive electrode sheet, scrape off the material coated on the tab, bond, encapsulate, perform warm isostatic pressing, weld the tab, and encapsulate again to obtain an all-solid-state battery.

[0075] The present invention coats an electrolyte slurry on the negative electrode sheet described in the above technical solution, dries it, and integrates the composite negative electrode with the electrolyte layer. In the present invention, the electrolyte slurry includes 5 wt% IBIB-NBR colloidal solution, P04H electrolyte powder, and IBIB solvent, and their mass ratio is 4:4:3.3. After the solid electrolyte is prepared into a uniform slurry, it is directly coated on the negative electrode surface of the composite negative electrode sheet, greatly enhancing the interfacial contact between the composite negative electrode sheet and the electrolyte layer, and further improving the stability of the battery system. When preparing the electrolyte slurry, zirconium beads are used for ball milling; the diameter of the zirconium beads is 3 mm. After ball milling, it is defoamed, coated on the negative electrode sheet, and vacuum dried overnight.

[0076] After the composite negative electrode and the electrolyte layer are integrated, the present invention die-cuts it with the positive electrode sheet, scrapes off the material coated on the tab, fits it, encapsulates it, performs warm isostatic pressing, welds the tab, and encapsulates it again to obtain a all-solid-state battery.

[0077] In the present invention, the positive electrode sheet is prepared into a slurry by using a two-step wet mixing method; in the first step, C45, LPSCl electrolyte powder, p-xylene, and 8 wt% PIB-p-xylene colloidal solution are mixed and ball milled, defoamed, and then NCM H3, p-xylene, and 8 wt% PIB-p-xylene colloidal solution are added, defoamed again, coated, and dried to obtain the positive electrode sheet. The present invention preferably coats it on a 20-μm-thick aluminum foil current collector with a coating thickness of 400 μm by a four-sided knife coater, and vacuums it overnight for standby.

[0078] The present invention die-cuts the positive electrode sheet into a size of 2 cm × 3 cm, and the size of the composite negative electrode sheet is 2.5 cm × 3.5 cm. Scrapes off the material coated on the positive and negative tabs, then weighs and records the mass of the positive electrode sheet, and uses a 5 cm × 6 cm PET board for electrode sheet fitting.

[0079] After the fitting is completed, the present invention preferably uses an aluminum foil bag for vacuum packaging, and then performs warm isostatic pressing to make the electrode sheets fit tightly; the conditions of the warm isostatic pressing are: the pressure is 300-500 MPa, the temperature is 80-120 °C, and the time is 9-11 min.

[0080] After warm isostatic pressing, the tab is welded, and it is vacuum packaged with an aluminum foil bag. Finally, it is fixed with a stainless steel plate fixture, and 4 layers of sulfuric acid paper and a layer of silica gel pad are placed between the soft-pack battery and the clamping plate as a buffer layer. Thus, the soft-pack battery assembly is completed.

[0081] The present invention conducts battery performance testing in an oven. The applied pressure of the battery is 4 MPa, and the test temperature is 55 °C.

[0082] The present invention modifies carbon sources such as hard carbon and uses them as a negative electrode modification layer to enhance the rapid transfer of lithium ions at the solid-state interface, and constructs a layer containing Li at the interface between the negative electrode and the electrolyte 3The N-modified hard carbon layer fills the interfacial voids between the electrolyte and the anode, effectively improving the interfacial contact problem; the in-situ formed Li 3 3N is conducive to promoting the uniform deposition of lithium and plays a role in inhibiting lithium dendrites; the battery structure with a composite anode integrated electrolyte greatly enhances the interfacial contact between the anode and the electrolyte layer, improving the stability of the battery system.

[0083] From the perspective of improving the rapid transfer of lithium ions at the interface and thus inhibiting the growth of lithium dendrites, the present invention coats a layer of Li 3 3N-modified hard carbon layer between the electrolyte and the anode. As a buffer layer, hard carbon can effectively improve the interfacial contact between the electrolyte and the anode, making the two interfaces closely combined. Li 3 3N promotes the transmission speed of lithium ions, reduces the deposition of lithium ions at the interface, and effectively inhibits the generation of lithium dendrites. After preparing the solid electrolyte into a uniform slurry, it is directly coated on the surface of the modified silver-carbon anode. The method of integrating the electrolyte into the composite anode greatly enhances the interfacial contact between the anode and the electrolyte layer. This battery structure is conducive to improving the rapid transfer of lithium ions at and inside the anode interface. The two interact with each other to jointly improve the stability of the battery system.

[0084] To further illustrate the present invention, the following describes in detail a solid-state battery and its preparation method provided by the present invention in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0085] Example 1

[0086] 1) 20 g of LiCl, 1.5 g of melamine, and 5 g of hard carbon are dispersed in 300 mL of absolute ethanol. After ultrasonic dispersion for 5 min and magnetic stirring for 2 h, a precursor dispersion is obtained.

[0087] 2) The above dispersion is subjected to sanding treatment. The sanding beads are 0.3 - 0.4 mm Zr 2 spherical beads, the rotation speed is 2000 r / min, and the sanding time is 3 h. After completion, the solvent is evaporated by stirring at 600 r / min in an oil bath at 100 °C;

[0088] 3) The material after evaporation is thoroughly ground and placed in a tube furnace. N 2 is used as an inert atmosphere for high-temperature calcination. The heating rate is 5 °C / min, and it is calcined at 800 °C for 2 h;

[0089] 4) After calcination, it is washed under the conditions of 80 °C - 600 r / min - 5 h, filtered by suction, and then placed in an oven at 60 °C overnight to dry, obtaining Li 3 3N-carbon material, that is, modified hard carbon;

[0090] 5) C65 and silver powder are mixed at a mass ratio of 3:1. The sanding solvent is ethylene glycol. ZrO spherical beads with a diameter of 0.3 - 0.4 mm are selected, the rotation speed is 2000 r / min, and the sanding time is 3 h. After completion, suction filtration is carried out, and it is dried overnight for standby. The preparation of silver-carbon powder is completed; 2 After completion, suction filtration is carried out, and it is dried overnight for standby. The preparation of silver-carbon powder is completed;

[0091] 6) During ball milling, the mass ratio of silver-carbon powder to 1 wt% PAALi-H2O colloidal solution is 1:3.5. The ball milling beads selected are 4 ZrO spherical beads with a diameter of 10 mm, 6 with a diameter of 8 mm, and 24 with a diameter of 6 mm. The rotation speed is 300 r / min, and the ball milling time is 12 h. After completion, a coating thickness of 60 μm is applied with a four-sided scraper on a copper foil current collector with a thickness of 12 μm to prepare a silver-carbon negative electrode sheet, which is dried overnight for standby; 2 During ball milling, the mass ratio of silver-carbon powder to 1 wt% PAALi-H2O colloidal solution is 1:3.5. The ball milling beads selected are 4 ZrO spherical beads with a diameter of 10 mm, 6 with a diameter of 8 mm, and 24 with a diameter of 6 mm. The rotation speed is 300 r / min, and the ball milling time is 12 h. After completion, a coating thickness of 60 μm is applied with a four-sided scraper on a copper foil current collector with a thickness of 12 μm to prepare a silver-carbon negative electrode sheet, which is dried overnight for standby; 2 After completion, a coating thickness of 60 μm is applied with a four-sided scraper on a copper foil current collector with a thickness of 12 μm to prepare a silver-carbon negative electrode sheet, which is dried overnight for standby;

[0092] 7) The modified hard carbon in step 4) and 2%-PVDF-NMP colloidal solution are ball milled into a slurry at a mass ratio of 1:5.5. A coating thickness of 30 μm is applied with a four-sided scraper and coated on the surface of the AgC negative electrode sheet. After vacuum drying overnight, the composite negative electrode is prepared;

[0093] 8) 4.0 g of 5 wt% IBIB-NBR colloidal solution, 4.0 g of P04H electrolyte powder, 3.3 g of IBIB solvent and 20 ZrO spherical beads with a diameter of 3 mm are placed in a 50 mL degassing tank to prepare an electrolyte slurry. The slurry is prepared by running the program of the degassing machine at 300 rpm - 900 rpm - 120 s, 600 rpm - 900 rpm - 600 s (rotation speed - revolution speed - time (seconds)) twice. A coating thickness of 100 μm is applied with a four-sided scraper and coated on the silver-carbon negative electrode sheet surface of the composite electrode sheet. The integration of the composite negative electrode and the electrolyte layer is completed and dried overnight in a vacuum for standby; 2 After completion, a coating thickness of 100 μm is applied with a four-sided scraper and coated on the silver-carbon negative electrode sheet surface of the composite electrode sheet. The integration of the composite negative electrode and the electrolyte layer is completed and dried overnight in a vacuum for standby;

[0094] 9) The positive electrode sheet is prepared by ball milling in a two-step wet mixing method. 0.4 g of C45, 2.8 g of LPSCl electrolyte powder, 10 g of p-xylene and 4 g of 8 wt% PIB-p-xylene colloidal solution are added with 4 8 mm and 16 6 mm ball milling beads, and mixed through a degassing process of 200 rpm - 900 rpm - 900 s once and 300 rpm - 900 rpm - 900 s twice. After completion, 16 g of NCMH3, 2 g of p-xylene and 6 g of 8 wt% PIB-p-xylene colloidal solution are added, and the mixing is continued by the above two-step degassing and mixing method. After completion, a coating thickness of 400 μm is applied with a four-sided scraper on an aluminum foil current collector with a thickness of 20 μm. The positive electrode sheet is prepared and dried overnight in a vacuum oven for standby;

[0095] 10) Die-cut the prepared composite negative electrode and positive electrode sheets. The size of the positive electrode is 2cm*3cm, and the size of the negative electrode is 2.5cm×3.5cm. Scrape off the materials coated on the positive and negative electrode tabs, then weigh and record the mass of the positive electrode sheet, and use a 5cm×6cm PET plate for electrode sheet bonding;

[0096] 11) After the bonding is completed, vacuum packaging is performed in an aluminum foil bag, followed by warm isostatic pressing at 300Mpa-80℃-10min, so that the pole pieces are tightly bonded under high temperature and high pressure;

[0097] 12) After warm isostatic pressing, the pole ears are welded and vacuum packaged with aluminum foil bags. Finally, they are fixed with stainless steel plate clamps. Four layers of sulfuric acid paper and one layer of silicone pad are placed between the soft-pack battery and the clamp as a buffer layer. At this point, the soft-pack battery assembly is completed;

[0098] 13) When the battery performance test is carried out in the oven, the pressure applied to the battery is 4Mpa and the test temperature is 55°C.

[0099] The present invention performs SEM characterization and mapping analysis on the raw material hard carbon used to observe its morphology and element distribution. The results are as follows: Figure 1 As shown, it can be seen that hard carbon is an irregular block structure with uneven size, a particle size of about 2 to 3 μm, and contains two elements, C and O.

[0100] The present invention is to prepare Li 3 N-Carbon Materials (LiN 3 Modified hard carbon) was subjected to SEM characterization and mapping analysis to observe its morphology and element distribution. The results are as follows Figure 2 As shown. It can be seen that after sand grinding, the particle size of hard carbon becomes significantly smaller (about 0.2-0.5 μm), and it still has an irregular small block structure. Mapping shows that it contains C, Cl, N, Zr (ZrO 2 Bead residue) four elements.

[0101] The present invention will Li 3 The N-carbon material was coated on the surface of the silver-carbon negative electrode as a modification layer. After the composite electrode was made, SEM characterization was performed. The results are as follows: Figure 3 As shown, Figure 3 Figures a and b are the surface and cross-sectional views of the composite electrode, respectively. It can be seen from the figure that the electrode surface is in good condition and has uniform thickness. From the element distribution diagram of Ag and C, it can be seen that hard carbon has been successfully integrated into the surface of the silver-carbon negative electrode.

[0102] Integrate with the electrolyte, and after the electrode is dried, attach the positive electrode to assemble the soft-pack battery for performance verification. Figure 4 AgC-Li 3Structural diagram after the hard carbon is compounded with the P04H electrolyte layer: It can be seen that the solid electrolyte is prepared into a uniform slurry and directly coated on the surface of the silver-carbon negative electrode. After drying, its thickness is about 50 μm, and the interfacial contact between the composite negative electrode and the electrolyte layer is very good; and a schematic diagram of the soft-pack battery after being attached to the NCM H3 positive electrode. It can be seen that the interfaces are well attached to each other, and the battery can perform normal charge and discharge cycles without short circuit.

[0103] Before and after the hard carbon is modified, the charge and discharge cycle performance at 0.1C / 0.2C is as Figure 5 , Figure 5 In a, it is the cycle performance diagram of the AgC-unmodified hard carbon-P04H-NCM H3 soft-pack battery. It can be seen that after the battery undergoes 50 charge and discharge cycles, the reversible specific capacity drops to 63.2 mAh g -1 , and the capacity retention rate compared with the first cycle is 45.2%, showing a relatively fast decay. Figure 5 In b, it is the charge and discharge cycle performance diagram of the AgC-Li 3 N@hard carbon-P04H-NCM H3 soft-pack battery at 0.1C / 0.2C. It can be seen that the cycle stability and reversible specific capacity of the modified soft-pack battery have been greatly improved. After 50 charge and discharge cycles, the reversible specific capacity drops to 108.6 mAhg -1 , and the capacity retention rate compared with the first cycle is 72.4%, indicating that the Li 3 N modification layer plays a positive role.

[0104] Example 2

[0105] 1) Disperse 6 g of LiCl, 1.5 g of ammonium chloride, and 1.5 g of carbon nanofibers (VGCF) into 300 mL of absolute ethanol. After ultrasonic dispersion for 5 min and magnetic stirring for 2 h, a precursor dispersion is obtained. After that, in an oil bath at 100 °C, stir and evaporate the solvent at 600 r / min;

[0106] 2) Grind the evaporated material thoroughly and place it in a tube furnace. Use N 2 as an inert atmosphere for high-temperature calcination. The heating rate is 5 °C / min, and calcine at 800 °C for 2 h;

[0107] 3) After calcination, perform water washing under the conditions of 80 °C - 600 r / min - 5 h. After suction filtration, place it in an oven at 60 °C and dry overnight to obtain Li 3 N-carbon material, that is, modified hard carbon;

[0108] 4) Mix C65 and silver powder in a mass ratio of 3:1. The sanding solvent is ethylene glycol. Select ZrO 2 spherical beads with a diameter of 0.3 - 0.4 mm, rotate at 2000 r / min, and sand for 3 h. After that, perform suction filtration, dry overnight and set aside. The silver-carbon powder preparation is completed;

[0109] 5) Silver carbon powder and 1wt% PAALi-H during ball milling 2 The mass ratio of ZrO gel was 1:3.5, and the ball milling beads were 4 with a diameter of 10 mm, 6 with a diameter of 8 mm, and 24 with a diameter of 6 mm. 2 Spherical beads, rotating speed of 300r / min, ball milling time of 12h. After finishing, a four-sided scraper is used to coat the 60μm coating thickness on a 12μm thick copper foil current collector to prepare a silver-carbon negative electrode sheet, which is dried overnight for use;

[0110] 6) The hard carbon modified in step 3) and 2%-PVDF-NMP glue were ball-milled at a mass ratio of 1:5.5, and coated on the surface of the silver-carbon negative electrode with a coating thickness of 30 μm using a four-sided scraper. After vacuum drying overnight, the composite negative electrode was prepared;

[0111] 7) 4.0 g 5 wt% IBIB-NBR glue, 4.0 g LPSCl electrolyte powder, 3.3 g IBIB solvent and 20 ZrO particles with a diameter of 3 mm were used. 2 The spherical beads are placed in a 50 mL degassing tank to prepare electrolyte slurry, and the degassing machine is run twice at 300 rpm-900 rpm-120 s and 600 rpm-900 rpm-600 s to make slurry, and a four-sided scraper is used to coat the surface of the silver-carbon negative electrode sheet of the composite negative electrode sheet with a coating thickness of 100 μm. The composite negative electrode and the electrolyte layer are integrated, and vacuum dried overnight for use;

[0112] 8) The positive electrode sheet is slurried by a two-step wet mixing method. 0.4g C45, 2.8g LPSCl electrolyte powder, 10g p-xylene and 4g 8wt% PIB-p-xylene glue are added with 4 8mm and 16 6mm ball mills, and mixed by a degassing procedure of 200rpm-900rpm-900s once and 300rpm-900rpm-900s twice. After the degassing, 16g NCMH3, 2g p-xylene and 6g 8wt% PIB-p-xylene glue are added, and the slurry is continued by the above two-step degassing and mixing method. After the degassing, a four-sided scraper is used to apply a coating thickness of 400μm on a 20μm thick aluminum foil current collector. The positive electrode sheet is prepared and dried in a vacuum oven overnight for use;

[0113] 9) Die-cut the prepared composite negative electrode and positive electrode sheets. The size of the positive electrode is 2cm*3cm, and the size of the negative electrode is 2.5cm×3.5cm. Scrape off the materials coated on the positive and negative electrode tabs, then weigh and record the mass of the positive electrode sheet, and use a 5cm×6cm PET plate for electrode sheet bonding;

[0114] 10) After the bonding is completed, vacuum packaging is performed in an aluminum foil bag, followed by warm isostatic pressing at 300Mpa-80℃-10min, so that the pole pieces are tightly bonded under high temperature and high pressure;

[0115] 11) After warm isostatic pressing, the pole ears are welded and vacuum packaged with aluminum foil bags. Finally, they are fixed with stainless steel plate clamps. Four layers of sulfuric acid paper and one layer of silicone pad are placed between the soft-pack battery and the clamp as a buffer layer. At this point, the soft-pack battery assembly is completed;

[0116] 12) When the battery performance test is carried out in the oven, the pressure applied to the battery is 4Mpa and the test temperature is 55°C.

[0117] The present invention performs SEM characterization and mapping analysis on the raw material carbon nanofiber (VGCF) used to observe its morphology and element distribution. The results are as follows Figure 6 As shown, it can be seen that the carbon fiber is a linear structure with a diameter of about 50-100nm, a length of about 4-7μm, and contains two elements, C and O.

[0118] The present invention is to prepare Li 3 N-Carbon Materials (LiN 3 The modified VGCF) was subjected to SEM characterization and mapping analysis to observe its morphology and element distribution. The results are as follows Figure 7 As shown in the figure, it can be seen that the morphology of carbon fiber has not changed and it is still a linear structure. Mapping shows that it contains four elements: C, Cl, N, and O.

[0119] The present invention will Li 3 The N-carbon material was coated on the surface of the silver-carbon negative electrode as a modification layer. After the composite electrode was made, SEM characterization was performed. The results are as follows: Figure 8 As shown, they are the surface and cross-sectional views of the composite electrode, respectively; it can be seen from the figure that the surface condition of the electrode is good, the VGCF is evenly distributed, the thickness is uniform, and it has been successfully integrated into the surface of the silver-carbon negative electrode.

[0120] Integrate with the electrolyte, and after the electrode is dried, attach the positive electrode to assemble the soft-pack battery for performance verification. Figure 9 The 0.1C / 0.2C charge-discharge cycle performance diagram before and after VGCF modification shows that before VGCF modification, the reversible specific capacity of the battery dropped to 108 mAh g after 40 cycles of charge-discharge. -1 Compared with the first cycle, the capacity retention rate was 67.5%, which decayed faster. The modified soft-pack battery has improved cycle stability and reversible specific capacity. After 37 cycles of charge and discharge, the reversible specific capacity is 117.5 mAh g -1 Compared with the first cycle, the capacity retention rate is 73.6%, indicating that Li 3The N modification layer plays a positive role.

[0121] As can be seen from the above embodiments, the present invention provides a solid-state battery, including a positive electrode, a solid electrolyte layer, and a composite negative electrode stacked in sequence; the composite negative electrode includes a negative electrode and a Li 3 N-modified carbon source layer, and the LiN 3 modified carbon source layer is located between the negative electrode and the solid electrolyte layer. The present invention constructs a functional layer on the surface and inside the pores of the carbon material to improve the lithium ion transport efficiency, and uses it as a modification layer between the solid electrolyte and the negative electrode interface to enhance the rapid transfer of lithium ions at the interface; after the solid electrolyte is made into a uniform slurry, it is directly coated on the surface of the silver-carbon composite negative electrode of the solid-state battery. Compared with the method of using lamination and transfer, the interface contact between the negative electrode sheet and the electrolyte layer is greatly enhanced. This battery structure in which the double-layer composite negative electrode integrates the electrolyte and then is laminated with the positive electrode is beneficial to improving the rapid transfer of lithium ions at the negative electrode interface and inside, and promoting the uniform and rapid deposition of lithium on the current collector side. Together, they improve the stability of the battery.

[0122] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A solid-state battery, characterized in that: include: A positive electrode, a solid electrolyte layer and a composite negative electrode stacked in sequence; The composite negative electrode comprises a negative electrode and a Li3N-modified carbon source layer, wherein the Li3N-modified carbon source layer is located between the negative electrode and the solid electrolyte layer.

2. The solid-state battery according to claim 1, characterized in that: The composite negative electrode has a double-layer structure, and the negative electrode is a carbon-based negative electrode, a silicon-based negative electrode or an alloyed negative electrode; The raw materials for preparing the LiN3-modified carbon source layer include a carbon source, a nitrogen source and a lithium molten salt system; The carbon source is selected from one or more of hard carbon, graphite, graphene, carbon black, carbon nanofibers, carbon nanotubes and mesophase carbon microspheres; The nitrogen source is selected from one or more of melamine, dihydrogen diamine, urea and ammonium chloride.

3. The solid-state battery according to claim 2, characterized in that: The lithium molten salt system is selected from one or more of LiCl, LiF, LiI, LiBr, LiNO3, LiCl-LiF, LiCl-LiBr and LiCl-LiI.

4. The solid-state battery according to claim 2, characterized in that: The mass ratio of the carbon source, the nitrogen source and the lithium molten salt system is 1:(0.95-1.05):(1.9-2.1).

5. The solid-state battery according to claim 2, wherein the method for preparing the composite negative electrode comprises the following steps: Dispersing the lithium molten salt system, the nitrogen source and the carbon source in a solvent, and stirring evenly to obtain a precursor dispersion; The precursor dispersion is sand-milled to evaporate the solvent, and then calcined in an inert atmosphere to obtain a calcined product. The calcined product is washed with water and dried to obtain a Li3N-carbon material; The Li3N-carbon material and the colloid solution are ball-milled into a slurry, coated on the surface of the negative electrode sheet, and dried to obtain a composite negative electrode.

6. The solid-state battery according to claim 5, characterized in that: When the negative electrode is a silver-carbon negative electrode sheet, the silver-carbon negative electrode sheet is prepared according to the following method: Silver powder and C65 are mixed and ball-milled in PAALi-H2O gel to obtain a slurry; The slurry is coated on the surface of the current collector and vacuum dried to obtain a silver-carbon negative electrode sheet.

7. The solid-state battery according to claim 5, characterized in that: The calcination temperature is 500-600° C., the calcination heating rate is 4-5° C. / min, and the calcination time is 3.5-4.5 h.

8. A method for preparing the all-solid-state battery according to claim 1, characterized in that: The following steps are involved: The electrolyte slurry is coated on the negative electrode surface of the composite negative electrode, dried, and the composite negative electrode is integrated with the electrolyte layer; After die-cutting with the positive electrode sheet, the material coated on the tab is scraped off, the tabs are bonded, packaged, warm isostatically pressed, the tabs are welded, and packaged again to obtain a solid-state battery.

9. The preparation method according to claim 8, characterized in that: The conditions of the warm isostatic pressing are: pressure of 300-500 MPa, temperature of 80-120° C., and time of 9-11 min.

10. The preparation method according to claim 8, characterized in that: During the performance test of the all-solid-state battery, the pressure applied to the battery was 4MPa and the test temperature was 55°C.

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