Integrated electrode / electrolyte composite material and in-situ preparation method thereof

Abstract

The invention discloses an integrated electrode / electrolyte composite material and an in-situ preparation method thereof, and belongs to the technical field of solid-state batteries. The technical problem that the electrochemical performance of the solid-state battery is affected due to large interface impedance between the electrode and electrolyte of the existing solid-state battery body is solved. The in-situ preparation method comprises the following steps: step 1, preparing precursor slurry of the composite solid electrolyte; 2, preparing a composite positive pole piece material and a composite negative pole piece material; and 3, forming a lamination structure by using the precursor slurry of the composite solid electrolyte, the composite positive pole piece material and the composite negative pole piece material, and then carrying out in-situ thermal initiation polymerization to obtain the integrated electrode / electrolyte composite material. According to the invention, the solid-solid interface contact and compatibility of the solid-state battery are improved, and the interface impedance is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and particularly to an integrated electrode / electrolyte composite material and an in-situ preparation method thereof. Background Art

[0002] As an energy application terminal, lithium-ion batteries will embrace significant development opportunities. It has characteristics such as low maintenance requirements and no memory effect. Based on the advantages in terms of safety and energy density, solid-state batteries have become the inevitable path for the future development of lithium-ion batteries.

[0003] Compared with traditional organic electrolytes, solid electrolytes have many advantages such as low flammability, high stability, high mechanical strength, and the ability to inhibit lithium dendrites. It is expected to alleviate the safety problems of traditional lithium metal batteries in liquid electrolytes and at the same time increase the overall energy density of the battery. Solid electrolytes and electrodes usually have a rigid point contact with a large interfacial resistance, while traditional liquid electrolytes can completely wet the electrode material. The solid-solid interface contact performance and compatibility have become the key factors hindering the practical application of solid-state lithium metal batteries. Therefore, there is an urgent need to increase the solid-solid interface contact, reduce the interfacial resistance, and improve the stability of the solid-state interface.

[0004] To alleviate the above problems, researchers usually construct a "soft wetting layer" between the solid-solid interface of the electrode / electrolyte, including methods such as adding trace electrolytes and ionic liquids, constructing an artificial interface buffer layer, alloying the lithium negative electrode, and heat / pressure treatment. These strategies have improved the point contact and high impedance problems at the interface to a certain extent.

[0005] Polymer electrolytes have the characteristics of softness and high flexibility, which are beneficial to the full interface contact between the electrode / solid electrolyte. Currently, polymer electrolytes generally adopt the traditional preparation process of solution casting into films, and the preparation process is time-consuming and uses toxic and polluting low-boiling solvents. These non-in-situ film-forming methods are not only cumbersome to prepare but also cause a large solid-solid interface contact impedance between the electrolyte / electrode when assembling solid-state batteries, affecting the electrochemical performance of the batteries.

[0006] The prior art does not integrate the preparation of the electrolyte and the positive and negative electrode materials, and secondary matching and assembly of the electrolyte and the positive and negative electrode materials are still required later. Summary of the Invention

[0007] In view of the above analysis, the present invention aims to provide an integrated electrode / electrolyte composite material and an in-situ preparation method thereof to solve the technical problem that the interfacial impedance between the electrode / electrolyte of the existing solid-state battery body is large, affecting the electrochemical performance of the battery.

[0008] The purpose of the present invention is mainly achieved through the following technical solutions:

[0009] On the one hand, the present invention provides an in-situ preparation method of an integrated electrode / electrolyte composite material, comprising the following steps:

[0010] Step 1, prepare a precursor slurry of a composite solid electrolyte;

[0011] Step 2, prepare a composite positive electrode sheet material and a composite negative electrode sheet material;

[0012] Step 3, place the composite negative electrode sheet material on a clean glass plate, coat the surface of the composite negative electrode sheet material with the precursor slurry of the composite solid electrolyte prepared in Step 1, and then lay the composite positive electrode sheet material flat on the surface of the precursor slurry of the composite solid electrolyte to form a laminated structure of the composite negative electrode sheet material / composite solid electrolyte / composite positive electrode sheet material. Place the laminated structure on a magnetic stirring heater in a glove box for in-situ thermal-initiated polymerization to obtain an integrated electrode / electrolyte composite material.

[0013] Further, in Step 1, the process of preparing the precursor slurry of the composite solid electrolyte includes: mixing an acrylate polymer monomer with an inorganic solid electrolyte and an electrolyte salt with a certain mass fraction, adding an initiator after mixing evenly, and obtaining the precursor slurry of the composite solid electrolyte after mixing evenly.

[0014] Further, in Step 1, the mixing time of the acrylate polymer monomer with the inorganic solid electrolyte and the electrolyte salt is 0.5 h - 2 h.

[0015] Further, in Step 1, the inorganic solid electrolyte is at least one of garnet type, perovskite type, NASICON type, LISICON type, LiPON type, and sulfide.

[0016] Further, in Step 2, the process of preparing the composite positive electrode sheet material includes: mixing a positive electrode active material, conductive carbon black, a PVDF binder, and an inorganic solid electrolyte according to a certain mass ratio to form a mixed slurry; adding an NMP solution dropwise according to the viscosity of the mixed slurry, fully grinding it to form a uniform slurry, and then coating it on an aluminum foil and drying it in vacuum to obtain the composite positive electrode sheet material.

[0017] Further, in Step 2, the process of preparing the composite negative electrode sheet material includes: mixing a negative electrode active material, conductive carbon black, a PVDF binder, and an inorganic solid electrolyte powder according to a certain mass ratio to form a mixed slurry; adding an NMP solution dropwise according to the viscosity of the mixed slurry, fully grinding it to form a uniform slurry, and then coating it on a copper foil and drying it in vacuum to obtain the composite negative electrode sheet material.

[0018] Further, in Step 2, the positive electrode active material is at least one of lithium iron phosphate, ternary material, lithium cobaltate, and lithium manganate.

[0019] Further, in step 2, the ternary material is nickel cobalt manganese or nickel cobalt aluminum.

[0020] Further, in step 2, the negative electrode active material is at least one of graphite, silicon-based material, metal oxide material, and carbon-based composite material.

[0021] On the other hand, the present invention also provides an integrated electrode / electrolyte composite material, which is prepared by the in-situ preparation method of the above integrated electrode / electrolyte composite material.

[0022] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0023] (1) By introducing the positive and negative electrode active materials while in-situ synthesizing the composite solid electrolyte, the present invention maximally improves the interfacial contact and compatibility between the composite solid electrolyte and the electrode, and finally obtains the integrated electrode / electrolyte composite material. This method is an innovative preparation of electrolyte / electrode materials. The electrode / electrolyte / electrode in-situ polymerization process used in the method can effectively improve the solid-solid interfacial contact and compatibility, and provide an overall design for the solid-state battery system that meets the requirements of high specific energy, high safety, and long life performance.

[0024] (2) By adopting the in-situ thermal-initiated radical polymerization and the integrated electrode / electrolyte preparation process, the present invention coats the solid electrolyte on the positive and negative electrode carriers with a controllable thickness, constructs a "super conformal" interface between the electrode and the electrolyte, greatly improves the solid-solid interfacial contact and compatibility, reduces the interfacial impedance, enhances the interfacial stability, and alleviates the relatively intractable interfacial problems in the solid-state battery system.

[0025] In the present invention, the above technical solutions can also be combined with each other to achieve more preferred combination schemes. Other features and advantages of the present invention will be described in the subsequent description. Moreover, some advantages can be made obvious from the description, or can be understood by implementing the present invention. The objectives and other advantages of the present invention can be realized and obtained from the content specifically pointed out in the embodiments of the description and the drawings. Description of the Drawings

[0026] The drawings are only for the purpose of showing specific embodiments, and are not considered as a limitation to the present invention. Throughout the drawings, the same reference signs represent the same components.

[0027] Figure 1 Schematic diagram of the in-situ preparation of the integrated electrode / electrolyte according to Embodiments 1-4 of the present invention;

[0028] Figure 2Schematic diagram of the assembly of the solid-state soft-pack battery based on integrated electrode / electrolyte according to Examples 1-4 of the present invention;

[0029] Figure 3 Schematic diagram of the process for in-situ preparation of the integrated electrode / electrolyte composite material of the present invention. DETAILED DESCRIPTION

[0030] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0031] In one aspect, the present invention provides an in-situ preparation method for an integrated electrode / electrolyte composite material, such as Figure 3 As shown, the following steps are included:

[0032] Step 1: mixing an acrylic polymer monomer with a certain mass fraction of an inorganic solid electrolyte and an electrolyte salt, and adding an initiator at a certain mass ratio after mixing evenly to obtain a precursor slurry of a composite solid electrolyte;

[0033] Step 2: The positive electrode active material or the negative electrode active material, conductive carbon black (Super P), PVDF binder and a small amount of inorganic solid electrolyte powder are mixed in a certain mass ratio to form a mixed slurry. NMP solution is added dropwise according to the viscosity of the mixed slurry, and the slurry is fully ground to form a uniform slurry. The slurry is coated on an aluminum foil (copper foil for the negative electrode) with a doctor blade with controllable thickness. After vacuum drying, a composite positive electrode sheet material or a composite negative electrode sheet material is obtained. The composite negative electrode sheet material can also be a metal lithium strip (lithium foil);

[0034] That is, in step 2, the process of preparing the composite positive electrode sheet material includes: mixing the positive electrode active material or the negative electrode active material, conductive carbon black (Super P), PVDF binder and inorganic solid electrolyte powder in a certain mass ratio to form a mixed slurry; adding NMP solution according to the viscosity of the mixed slurry, grinding it thoroughly to form a uniform slurry, and then coating it on aluminum foil, and vacuum drying to obtain a composite positive electrode sheet material or a composite negative electrode sheet material. Similarly, the process of preparing the composite negative electrode sheet material includes: mixing the negative electrode active material, conductive carbon black (Super P), PVDF binder and inorganic solid electrolyte powder in a certain mass ratio to form a mixed slurry; adding NMP solution according to the viscosity of the mixed slurry, grinding it thoroughly to form a uniform slurry, and then coating it on copper foil, and vacuum drying to obtain a composite positive electrode sheet material or a composite negative electrode sheet material.

[0035] Step 3: Place the composite negative electrode sheet material on a clean glass plate. Use a doctor blade with a controllable thickness to evenly coat the precursor slurry of the composite solid electrolyte prepared in Step 1 on the surface of the composite negative electrode sheet material, and lay the composite positive electrode sheet material flat on the surface of the electrolyte to form a laminated structure of composite negative electrode sheet material / composite solid electrolyte / composite positive electrode sheet material (i.e., negative electrode / electrolyte / positive electrode) (as Figure 1 shown). Place the laminated structure on a magnetic stirring heater in a glove box for in-situ thermal-initiated polymerization, and obtain an integrated electrode / electrolyte composite material after polymerization.

[0036] In the above Step 1, the role of adding the inorganic solid electrolyte is as follows: First, the inorganic solid electrolyte can plasticize the acrylate polymer monomer (polymer electrolyte), which is equivalent to preparing an organic-inorganic composite solid electrolyte, and the ionic conductivity of the composite solid electrolyte is improved, which is a very critical performance requirement for the inorganic solid electrolyte; Second, after the inorganic solid electrolyte is added, it can improve the mechanical strength of the composite solid electrolyte membrane, making it easy to form a complete and smooth-surfaced solid electrolyte membrane, which helps to form a good solid interface; while the pure acrylate polymer membrane has poor mechanical strength and is easy to tear, and the film-forming effect is not ideal.

[0037] In the prior art, ionic conductivity and solid-solid interface are the two most critical factors affecting the performance of solid-state batteries and restricting the development of solid-state battery systems. Based on these two key factors, the present invention can improve the ionic conductivity of the composite solid electrolyte and form a good solid interface by adding an inorganic solid electrolyte.

[0038] In the above Step 1, the mixing time of the acrylate polymer monomer with the inorganic solid electrolyte and the electrolyte salt at room temperature is 0.5 h - 2 h (for example, 1 h). Since different addition amounts of the inorganic solid electrolyte and the electrolyte salt will affect the viscosity of the precursor slurry of the composite solid electrolyte, the corresponding uniform mixing time also varies.

[0039] In terms of the material addition sequence, the present invention first mixes the acrylate polymer monomer with the inorganic solid electrolyte and the electrolytic salt, and then adds the initiator after mixing evenly. The reason for designing this specific material addition sequence is that: the mixture of the acrylate polymer monomer, the inorganic solid electrolyte and the electrolyte salt is equivalent to a polymerization precursor, and the addition amount of the initiator needs to be added according to a certain ratio based on the total mass of the polymerization precursor. In addition, if the initiator is added in advance, it may cause partial micro-polymerization of the acrylate polymer monomer to become viscous under a relatively high external environmental temperature, which is not conducive to the full mixing with the inorganic solid electrolyte and the electrolyte salt in the later stage.

[0040] In the above step 1, the inorganic solid electrolyte is at least one of garnet, perovskite, NASICON, LISICON, LiPON and sulfide. The inorganic solid electrolyte is a nano-scale material with a particle size range of 200-500 nm.

[0041] In the above step 2, the solid-liquid ratio of the NMP solution is 0.1g / mL-1g / mL (for example, 0.5g / mL); the NMP solution is mainly used to dilute the mixed slurry to facilitate the coating of the mixed slurry on the positive and negative electrode active material matrix. If the mixed slurry is too thin, the positive and negative electrode active materials loaded on the electrode sheet will be too little during scraping. On the contrary, if the mixed slurry is too thick, the positive and negative electrode active materials scraped on the electrode sheet will be too thick and easily lead to unevenness. Later, the positive and negative electrode sheets will be vacuum dried. After the NMP evaporates, the positive and negative electrode materials that are too thick will fall off, while those that are too thin will result in too low active load or even exposure of the electrode matrix.

[0042] In the above step 2, the PVDF binder is prepared by dissolving 5 mg of PVDF powder in 100 μL of NMP solution.

[0043] In the above step 2, the grinding time is greater than or equal to 30 minutes.

[0044] In the above step 2, the original positive or negative electrode active material and the inorganic solid electrolyte are all nano-scale materials, and the particle size range after grinding is 100nm to 500nm (for example, 200nm); the mixed slurry is added to the NMP solution and then fully ground, the purpose of which is to reduce the particle size of the positive or negative electrode active material, improve the dispersion and uniformity of the granular active material, and facilitate subsequent smearing.

[0045] In the above step 2, the coating thickness of the composite positive electrode sheet material and the composite negative electrode sheet material is 25μm-300μm (for example, 100μm); the thicker the coating, the more positive or negative electrode active material is loaded; the coating thickness is equal to the controllable thickness of the scraper. Controlling the coating thickness within the range of 25μm-300μm helps to reasonably control the load of positive and negative electrode active materials, which not only avoids the low battery energy density caused by low load, but also avoids the problems of difficult battery ion transmission and poor rate performance caused by high load. In addition, by regulating the thickness and size of the solid electrolyte and electrode coating, and then regulating the size and weight of the solid-state battery, the application range of the battery is broadened.

[0046] It should be noted that in the above step 2, the composite cathode electrode material and the composite anode electrode material prepared by the present invention are designed for a solid-state battery system, mainly to enhance the ion transport performance inside the positive and negative active materials. Compared with the traditional liquid electrolyte that can completely wet the positive and negative electrode materials and the ion transport between the internal particles of the materials is smooth, the solid-state electrolyte and the positive and negative electrode materials are in solid-solid contact, and the solid-state electrolyte layer cannot penetrate deep into the positive and negative electrodes for ion transport. At this time, adding a certain mass fraction of inorganic solid electrolyte to the positive active material to prepare the composite cathode electrode material can increase the interfacial contact between the solid electrolyte and the positive active material particles and improve the ion transport inside the composite cathode electrode material; similarly, adding a certain mass fraction of solid electrolyte to the negative active material to prepare the composite anode electrode material can increase the interfacial contact between the solid electrolyte and the negative active material particles and improve the ion transport inside the composite anode electrode material.

[0047] In the above step 2, the positive active material is at least one of lithium iron phosphate, ternary materials (such as nickel cobalt manganese and nickel cobalt aluminum), lithium cobalt oxide, and lithium manganese oxide. For example, the positive active material is a ternary material, such as nickel cobalt manganese.

[0048] In the above step 2, the negative active material is at least one of graphite, silicon-based materials, metal oxide materials, and carbon-based composite materials.

[0049] In the above step 2, the thickness of the above composite cathode electrode material or composite anode electrode material is 40-50 μm.

[0050] In the above step 2, the mass ratio of the positive (or negative) active material, inorganic solid electrolyte, conductive carbon black (Super P), and PVDF binder is (70:10-79:1):10:10.

[0051] It should be explained that the positive (or negative) composite material of the present invention is a composite material formed by mixing the positive (negative) active material with a small amount of inorganic solid electrolyte, and its total proportion is 80; positive (or negative) composite material: conductive carbon black (Super P) and PVDF binder = 80:10:10; among them, the ratio of the positive (or negative) active material to the inorganic solid electrolyte is 70:10-79:1.

[0052] In the above step 2, the mass ratio of the positive or negative active material, inorganic solid electrolyte, conductive carbon black (Super P), and PVDF binder is 75:5:10:10.

[0053] In the above step 2, during vacuum drying, it is placed in a vacuum constant temperature drying oven at 80 °C and dried for 24 h. After drying is completed, it is taken out and reserved.

[0054] In the above step 3, the thermal initiation polymerization temperature is 65°C to 85°C; for example, the thermal initiation polymerization temperature is 70°C, 75°C or 80°C.

[0055] In the above step 3, the coating thickness range of the precursor slurry of the composite solid electrolyte is 150 - 250 μm (for example, 200 μm). If the coating is too thin, the slurry is not easily attached to the substrate and the film formation is uneven; if the coating is too thick, the solid electrolyte film of the integrated electrode / electrolyte material after polymerization is too thick, the ion transport path is extended, and the ion transport resistance increases.

[0056] In the above step 3, during the in-situ thermal initiation polymerization process, it is necessary to ensure the oxygen and water content (H2O < 0.1 ppm, O2 < 0.1 ppm), that is, because the electrolyte contains lithium salt and is extremely easy to absorb, so the in-situ thermal initiation polymerization is carried out in a glove box protected by an argon atmosphere.

[0057] In the above step 3, the rotation speed of the magnetic stirring is 300 - 320 r / min, and the stirring time is 30 min - 40 min.

[0058] Compared with the prior art, the present invention mixes poly(ethylene glycol) methyl ether methacrylate, lithium bis(trifluoromethanesulfonyl)imide, nano-scale inorganic solid electrolyte powder and initiator uniformly to prepare a precursor slurry of a composite solid electrolyte. Among them, the polymer (poly(ethylene glycol) methyl ether methacrylate) provides a flexible matrix, and the flexibility and three-dimensional cross-linked network structure of the polymer can provide certain elastic deformation. During the lithium metal electroplating / stripping process, volume expansion is likely to occur, resulting in insufficient solid-solid interface contact. The polymer electrolyte with high flexibility and high elastic deformation can adapt to the lithium volume expansion, maintain good contact at the lithium negative electrode interface, and promote interface stability. In addition, the synergistic effect between organic particles and inorganic particles reduces the polymer crystallinity and promotes the dissociation of lithium salt and the conduction of lithium ions. Among them, the functions of the inorganic solid electrolyte include three aspects: on the one hand, the inorganic solid electrolyte LAGP is a single-ion fast ion conductor and only allows lithium ions to pass through. On the second hand, the inorganic solid electrolyte LAGP acts as an inorganic filler to inhibit the crystallization of PEGMA and reduce the polymer crystallinity, thereby increasing more amorphous regions for the transport of lithium ions. On the third hand, the Lewis acid-base interaction between the inorganic filler and the polymer surface promotes the transport of lithium ions. These factors work together synergistically to promote the rapid migration of lithium ions. The lithium salt plays a plasticizing role. The polar functional groups in the lithium salt have an electron-withdrawing effect, which can improve the dissolution and dissociation ability of lithium ions and increase the ionic conductivity.

[0059] On the other hand, the present invention also provides an integrated electrode / electrolyte composite material, which is prepared by using the in-situ preparation method provided above.

[0060] In a third aspect, the present invention also provides a high specific energy and high safety solid-state battery, including the above-mentioned integrated electrode / electrolyte composite material.

[0061] Compared with the prior art, the present invention adopts an in-situ thermal-initiated free radical polymerization and an integrated electrode / electrolyte preparation process, coats the solid electrolyte on the positive and negative electrode carriers with a controllable thickness, constructs a "super conformal" interface between the electrode and the electrolyte, greatly improves the solid-solid interface contact and compatibility, reduces the interface impedance, has strong interface stability, and alleviates the relatively intractable interface problems in the solid-state battery system.

[0062] It should be noted that the high specific energy and high safety solid-state battery of the present invention has the following advantages compared with the existing lithium-ion battery with a liquid electrolyte:

[0063] (1) The solid-state battery of the present invention has good safety.

[0064] The liquid electrolyte is flammable and explosive, and the growth of lithium dendrites during the charging process is likely to pierce the diaphragm, causing battery short circuit and posing a safety hazard. While the solid electrolyte can inhibit lithium dendrites, is not easy to burn, is not easy to explode, has no electrolyte leakage, and does not undergo side reactions at high temperatures, etc. That is, the solid-state battery will not be short-circuited due to the piercing of the diaphragm by lithium dendrites when working at a large current, will not undergo side reactions at high temperatures, and will not catch fire due to the generation of gas. Therefore, safety is considered to be one of the most fundamental driving forces for the development of solid-state batteries.

[0065] (2) The solid-state battery of the present invention has a high energy density.

[0066] The highest energy density of the existing liquid electrolyte battery can reach 300 Wh / kg, but it is considered impossible to exceed 500 Wh / kg. The present invention adopts an all-solid electrolyte, and the solid-state battery can directly use metallic lithium as the negative electrode instead of using a lithium-inserted graphite negative electrode, which can greatly reduce the amount of negative electrode material used, resulting in a significant increase in the energy density of the entire solid-state battery. The energy density that the solid-state battery can provide can reach 300 - 400 Wh / kg.

[0067] (3) The solid-state battery of the present invention has strong cycle performance.

[0068] The solid electrolyte solves the problems of the solid electrolyte interface film formed during the charge and discharge process of the liquid electrolyte and the lithium dendrite phenomenon, greatly improves the cycle performance and service life of the lithium battery, and shows excellent cycle performance under ideal conditions, capable of reaching about 1000 cycles.

[0069] (4) The applicable range of the solid-state battery of the present invention is expanded.

[0070] The solid electrolyte of the present invention endows the solid-state lithium battery with characteristics such as a compact structure, adjustable scale, and large design flexibility, and can be applied to drive microelectronic devices as well as the power and energy storage fields. In addition, the solid-state battery also has a wider operating temperature range, which is -25°C to 60°C.

[0071] Fourthly, the present invention also provides a method for preparing a high specific energy and high safety solid-state battery, including assembling the polymerized integrated electrode / electrolyte composite material into a solid-state battery and performing battery charge and discharge cycle tests.

[0072] It should be noted that the solid-state battery of the present invention includes a solid-state button battery and a solid-state soft-pack battery; among them, the assembly method of the solid-state button battery includes the following process:

[0073] Cut the integrated electrode / electrolyte into a 19-mm diameter circular piece with a punching machine, use a CR2016 type battery case, and assemble it into a Li|in-situ PEGMA-LAGP|Li and LiFePO4|in-situ PEGMA-LAGP|Li solid-state button battery in a glove box (H2O < 0.1 ppm, O2 < 0.1 ppm) protected by an argon atmosphere.

[0074] In addition, the assembly method of the solid-state soft-pack battery includes the following process:

[0075] Assemble the integrated electrode / electrolyte material into an electrode core, weld the tab, then shape and package the aluminum-plastic film, and put the electrode core into a bag, evacuate and package to complete the assembly of the LiFePO4|in-situ PEGMA-LAGP|Li solid-state soft-pack battery.

[0076] It should be noted that both the solid-state button battery and the solid-state soft-pack battery are left standing for 12 h and then tested on a LAND CT2001A tester.

[0077] Compared with the prior art, the method provided by the present invention for in-situ preparing an integrated electrode / electrolyte for a high specific energy and high safety solid-state battery does not increase the burden on battery components, the preparation method is convenient, and the battery assembly method is flexible.

[0078] Compared with the prior art, the present invention realizes the quantitative compounding of the electrode / solid electrolyte through a compounding technology, constructs a composite positive / negative electrode material, enhances the interfacial contact between particles inside the electrode, and promotes the ionic and electronic conductive transport inside the composite electrode.

[0079] Example 1

[0080] This example is used to illustrate a method for in-situ preparing an integrated electrode / electrolyte for a high specific energy and high safety solid-state battery according to the present invention.

[0081] Step 1: Prepare the precursor of the composite solid electrolyte;

[0082] Weigh a certain amount (0.2871 g) of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and dissolve it in 1 mL of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA, Mn = 475 g mol -1 ) solution to make the concentration of LiTFSI 1 mol L -1 . Magnetically stir the above mixed solution (rotation speed 300 r / min) for 0.5 h, then add nanoscale inorganic ceramic electrolyte LAGP with a mass fraction of 25 wt.% and a particle size of 200 - 500 nm, and magnetically stir for 2.5 h. Then add 0.003 - 0.004 g of AIBN initiator to obtain a uniformly mixed white electrolyte precursor slurry.

[0083] Step 2: Prepare the composite positive electrode sheet material;

[0084] Mix the positive electrode active material lithium iron phosphate (LiFePO4), inorganic solid electrolyte LAGP, conductive carbon black (Super P), and PVDF binder (prepared by dissolving 5 mg of PVDF powder in 100 μL of NMP solution) according to a mass ratio of 75:5:10:10, and grind them in a mortar (grind for at least 30 min). Drop an appropriate amount of NMP solution according to the viscosity and grind thoroughly to make a uniform slurry; coat the electrode sheet with a 75 μm doctor blade, and then place it in a vacuum constant temperature drying oven at 80 °C for 24 h. After drying is completed, take out the coated sheet for standby.

[0085] Step 3: Prepare the negative electrode sheet: Select a 50 μm thick lithium foil, cut it into a lithium strip with a width of (5 cm) × length of (15 cm), and place it on a clean and dry glass plate;

[0086] Step 4: Prepare the integrated electrode / electrolyte: Uniformly coat the electrolyte precursor slurry in Step 1 on the surface of the lithium foil with a doctor blade (coating thickness 150 μm). Place the lithium foil coated with the solid electrolyte slurry on a magnetic stirring heater at 70 °C in a glove box and preheat it for 5 min. Then stack a composite positive electrode sheet of similar size on the surface of the solid electrolyte and conduct thermal-initiated polymerization for 2 h;

[0087] Step 5: Assemble the solid-state button battery: Cut the integrated electrode / electrolyte into circular pieces with a diameter of 19 mm using a punching machine, use a CR2016 type battery case, and assemble Li|in-situ PEGMA-LAGP|Li and LiFePO4|in-situ PEGMA-LAGP|Li solid-state button batteries in a glove box under argon atmosphere protection (H2O < 0.1 ppm, O2 < 0.1 ppm);

[0088] Step 6. Assembly of solid-state soft-pack battery: Assemble the integrated electrode / electrolyte material into an electrode core, weld the tab, then shape and encapsulate the aluminum-plastic film, and place the electrode core into the bag, evacuate the air, and complete the assembly of the LiFePO4|in-situ PEGMA-LAGP|Li solid-state soft-pack battery (as Figure 2 shown);

[0089] Step 7. Both the solid-state button battery and the solid-state soft-pack battery are left standing for 12 h and then tested on a LAND CT2001A tester.

[0090] Example 2

[0091] This example is used to illustrate a method for in-situ preparation of an integrated electrode / electrolyte for a high specific energy and high safety solid-state battery.

[0092] According to the method described in Example 1, the difference is that in step (2), the positive electrode active material is changed to lithium cobalt oxide (LiCoO2), and LiCoO2|in-situ PEGMA-LAGP|Li solid-state button and solid-state soft-pack batteries are assembled respectively.

[0093] Example 3

[0094] This example is used to illustrate a method for in-situ preparation of an integrated electrode / electrolyte for a high specific energy and high safety solid-state battery.

[0095] According to the method described in Example 1, the difference is that in step (2), the positive electrode active material is changed to the ternary layered positive electrode LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM 811 ), and NCM 811 |in-situ PEGMA-LAGP|Li solid-state button and solid-state soft-pack batteries are assembled respectively.

[0096] Example 4

[0097] This example is used to illustrate a method for in-situ preparation of an integrated electrode / electrolyte for a high specific energy and high safety solid-state battery.

[0098] According to the method described in Example 1, the difference is that in step (3), the negative electrode active material is changed to silicon carbide (SiC), and LiFePO4|in-situ PEGMA-LAGP|SiC solid-state button and solid-state soft-pack batteries are assembled respectively.

[0099] Comparative Example 1

[0100] This comparative example is used to illustrate the differences in the electrochemical performance of solid-state batteries under non-in-situ composite solid electrolyte / electrode assembly, mainly comparing the deposition polarization voltage and cycle life of the lithium metal anode.

[0101] (1) According to the method described in step 1 of Example 1, the prepared white electrolyte precursor slurry was directly cast into a polytetrafluoroethylene mold and placed on a magnetic stirring heater at 70 °C for thermal-initiated polymerization for 2 h to obtain a composite solid electrolyte membrane.

[0102] (2) According to the methods described in steps 2 and 3 of Example 1, the composite positive and negative electrode sheets were prepared, and the positive electrode (LiFePO4) sheet, negative electrode (Li) sheet, composite solid electrolyte, and gasket were assembled into Li|ex-situ PEGMA-LAGP|Li and LiFePO4|ex-situ PEGMA-LAGP|Li coin cells in a glove box protected by an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm).

[0103] Comparative Example 2

[0104] This comparative example is used to illustrate the differences in the electrochemical performance of solid-state batteries with polymer electrolytes lacking inorganic filler composites, that is, under in-situ polymer electrolyte / electrode assembly, and also mainly compares the deposition polarization voltage and cycle life of the lithium metal anode.

[0105] (1) According to the method described in step 1 of Example 1, the difference is that the inorganic ceramic electrolyte LAGP is not added to the electrolyte precursor slurry, which is the PEGMA polymer electrolyte precursor.

[0106] (2) According to the methods described in steps 2, 3, 4, and 5 of Example 1, an integrated electrode / electrolyte without inorganic filler LAGP was prepared in-situ and assembled into Li|in-situ PEGMA|Li and LiFePO4|in-situ PEGMA|Li solid coin cells.

[0107] Table 1 Polarization voltage values and cycle life table of solid Li|Li symmetric batteries in Examples and Comparative Examples at a current density of 0.1 mA cm –2 under

[0108] Polarization voltage value (mV) Cycle life (h) Examples 1 - 4 ～25 ＞3500 Comparative Example 1 ～300 ＜700 Comparative Example 2 ～100 ＜2100

[0109] Table 2 Polarization voltage values and cycle life table of solid Li|Li symmetric batteries in Examples and Comparative Examples at a current density of 0.2 mA cm –2 under

[0110] Polarization voltage value (mV) Cycle life (h) Examples 1 - 4 ～100 ＞2100 Comparative Example 1 400～1000 ＜450 Comparative Example 2 ～250 ＜1600

[0111] From the results of Examples 1-4 and Comparative Example 1, it can be seen that at the same current density and cycle capacity, the solid-state Li|ex-situ PEGMA-LAGP|Li symmetric battery under the non-in-situ electrode / electrolyte assembly in Comparative Example 1 exhibited a relatively large polarization voltage (~300 mV) and a limited cycle life, and the battery short-circuited after 700 h of cycling. While for Examples 1-4 of the present invention, i.e., the solid-state Li|in-situ PEGMA-LAGP|Li symmetric battery based on in-situ integrated electrode / electrolyte assembly, the polarization overpotential was only 25 mV, and it stably cycled for up to 3500 h. This shows that the in-situ preparation process of the solid electrolyte has an important impact on the electrochemical performance of the battery. Compared with the traditional non-in-situ solid electrolyte preparation method, in-situ synthesis of the solid electrolyte can effectively reduce the solid / solid interface contact impedance, improve the interface compatibility, reduce the lithium deposition overpotential, and achieve uniform lithium deposition.

[0112] From the results of Examples 1-4 and Comparative Example 2, it can be seen that at the same current density and cycle capacity, the polarization voltage of the solid-state Li|in-situ PEGMA|Li symmetric battery under the non-inorganic filler composite in-situ electrode / electrolyte assembly in Comparative Example 2 was about ~100 mV, and it could stably cycle for about 2100 h. While for Examples 1-4 of the present invention, i.e., the solid-state Li|in-situ PEGMA-LAGP|Li symmetric battery based on in-situ integrated electrode / electrolyte assembly, the polarization overpotential was significantly less than that of Comparative Example 2, and the stable cycle duration of the battery in the examples was significantly longer than that of Comparative Example 2. This shows that under the same in-situ polymerization process, the PEGMA-LAGP composite solid electrolyte has a higher ionic conductivity than the pure PEGMA polymer electrolyte, can achieve rapid transport of bulk and interfacial lithium ions, reduce the internal polarization of the battery, and improve the lithium cycling stability.

[0113] Through the preliminary safety test of Examples 1-4, that is, subjecting the battery to abnormal operating conditions such as bending, shearing, and tearing, the results show that the solid-state soft-pack battery can still continuously and normally light up the LED lamp board, having high safety.

[0114] As mentioned above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. An in-situ preparation method of an integrated electrode / electrolyte composite material, characterized in that, It includes the following steps: Step 1: Prepare a precursor slurry of a composite solid electrolyte; Step 2: Prepare a composite positive electrode sheet material and a composite negative electrode sheet material; Step 3: Use the precursor slurry, the composite positive electrode sheet material and the composite negative electrode sheet material to prepare an integrated electrode / electrolyte composite material.

2. The in-situ preparation method of the integrated electrode / electrolyte composite material according to claim 1, characterized in that In the Step 1, the process of preparing the precursor slurry of the composite solid electrolyte includes: mixing acrylate polymer monomers with an inorganic solid electrolyte and an electrolyte salt with a certain mass fraction, adding an initiator after mixing evenly to obtain the precursor slurry of the composite electrolyte.

3. The in-situ preparation method of the integrated electrode / electrolyte composite material according to claim 2, wherein In the Step 1, the mixing time of the acrylate polymer monomers with the inorganic solid electrolyte and the electrolyte salt is 0.5h - 2h.

4. The in-situ preparation method of the integrated electrode / electrolyte composite material according to claim 2, characterized in that, In the Step 1, the inorganic solid electrolyte is at least one of garnet type, perovskite type, NASICON type, LISICON type, LiPON type and sulfide.

5. The in-situ preparation method of the integrated electrode / electrolyte composite material according to claim 1, characterized in that, In the Step 2, the process of preparing the composite positive electrode sheet material includes: Mixing a positive electrode active material, conductive carbon black, a PVDF binder and an inorganic solid electrolyte according to a certain mass ratio, forming a mixed slurry after mixing; dropping NMP solution according to the viscosity of the mixed slurry, fully grinding it to make it a uniform slurry and then coating it on aluminum foil, and obtaining the composite positive electrode sheet material after vacuum drying.

6. The in-situ preparation method of the integrated electrode / electrolyte composite material according to claim 1, characterized in that, In the Step 2, the process of preparing the composite negative electrode sheet material includes: Mixing a negative electrode active material, conductive carbon black, a PVDF binder and an inorganic solid electrolyte powder according to a certain mass ratio, forming a mixed slurry after mixing; dropping NMP solution according to the viscosity of the mixed slurry, fully grinding it to make it a uniform slurry and then coating it on copper foil, and obtaining the composite negative electrode sheet material after vacuum drying.

7. The in-situ preparation method of the integrated electrode / electrolyte composite material according to claim 5, characterized in that, In the Step 2, the positive electrode active material is at least one of lithium iron phosphate, ternary materials, lithium cobalt oxide and lithium manganate.

8. The in-situ preparation method of the integrated electrode / electrolyte composite material according to claim 7, characterized in that, In the Step 2, the ternary material is nickel cobalt manganese or nickel cobalt aluminum.

9. The in-situ preparation method of the integrated electrode / electrolyte composite material according to claim 6, wherein, In the Step 2, the negative electrode active material is at least one of graphite, silicon-based materials, metal oxide materials and carbon-based composite materials.

10. An integrated electrode / electrolyte composite material, characterized in that, It is prepared by using the in-situ preparation method of the integrated electrode / electrolyte composite material according to any one of claims 1 to 9.

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