阅读说明：本技术 一种用于固态锂电池的复合正极及其制备方法和应用 (Composite positive electrode for solid lithium battery and preparation method and application thereof ) 是由 熊岳平 金英敏 宗鑫 张雪柏 于 2021-07-27 设计创作，主要内容包括：一种用于固态锂电池的复合正极及其制备方法和应用,它涉及复合正极及其制备方法和应用。它是要解决现有固态锂电池中正极与固体电解质界面接触差、正极内部离子/电子传导不连续、以及活性物质载量过低的技术问题。本发明的复合正极由多孔正极骨架和填充的聚合物电解质组成。制法：采用静电纺丝技术制备三维互联的多孔正极骨架；将含有聚合物单体、锂盐和引发剂的聚合物电解质前驱液,滴在多孔正极表面,静置后将极片加热聚合固化,得到复合正极。组装成固态锂电池在2.8～4.3V电压区间内循环,正极活性材料负载量为9.28mg/cm～(2)时首圈放电比容量为128.0mAh/g,52圈循环内循环稳定,可用于固态锂电池领域。(A composite anode for a solid-state lithium battery and a preparation method and application thereof relate to a composite anode and a preparation method and application thereof. The solid-state lithium battery aims to solve the technical problems that the interface contact between a positive electrode and a solid electrolyte in the existing solid-state lithium battery is poor, the ion/electron conduction in the positive electrode is discontinuous, and the active substance loading capacity is too low. The composite positive electrode of the invention is composed of a porous positive electrode framework and a filled polymer electrolyte. The preparation method comprises the following steps: preparing a three-dimensional interconnected porous positive electrode framework by adopting an electrostatic spinning technology; and dripping polymer electrolyte precursor liquid containing polymer monomers, lithium salt and an initiator on the surface of the porous positive electrode, standing, and heating, polymerizing and curing the pole piece to obtain the composite positive electrode. The solid lithium battery assembled by the lithium ion battery can circulate in a voltage range of 2.8-4.3V, and the loading capacity of the positive active material is 9.28mg/cm 2 The discharge specific capacity of the first circle is 128.0mAh/g, the internal circulation is stable in 52 circles of circulation, and the lithium ion battery can be used in the field of solid lithium batteries.)

1. A composite positive electrode for a solid lithium battery is characterized in that the composite positive electrode is composed of a porous positive electrode framework and a filled polymer electrolyte; wherein the porous positive electrode framework consists of a positive electrode active material, a conductive agent and a binder; wherein the mass of the conductive agent accounts for 10-12.5% of the mass of the positive active material; the mass of the binder accounts for 10-12.5% of that of the positive active material; the filled polymer electrolyte consists of lithium salt, polymer monomer and initiator; wherein the mass of the lithium salt accounts for 10-16% of the mass of the polymer monomer, and the mass of the initiator accounts for 0.5-1% of the mass of the polymer monomer; the positive active material in the porous positive electrode framework is lithium cobaltate, lithium manganate, lithium iron phosphate or lithium nickel cobalt manganese.

2. The composite positive electrode for a solid lithium battery as claimed in claim 1, wherein the conductive agent is one or a combination of several of conductive carbon black, carbon nanotubes, carbon fibers and graphene.

3. A composite positive electrode for a solid state lithium battery as claimed in claim 1 or 2, wherein the binder in the porous positive electrode matrix is polyvinylidene fluoride.

4. A composite positive electrode for a solid state lithium battery as claimed in claim 1 or 2, wherein the lithium salt in the filled polymer electrolyte is one or a combination of several of lithium difluorooxalato borate, lithium perchlorate, lithium hexafluorophosphate, lithium bis (oxalato) borate and lithium bis (fluorosulfonylimide).

5. The composite positive electrode for a solid lithium battery as claimed in claim 1 or 2, wherein the polymer monomer in the filled polymer electrolyte is one or a combination of vinylene carbonate, methyl methacrylate, butyl acrylate and triethylene glycol diacrylate.

6. The composite positive electrode for a solid lithium battery as claimed in claim 1 or 2, wherein the initiator in the filled polymer electrolyte is azobisisobutyronitrile or azobisisoheptonitrile.

7. A method of preparing a composite positive electrode for a solid state lithium battery as claimed in claim 1, characterized in that the method is carried out by the steps of:

firstly, dissolving nitrate in a solvent I, and stirring at room temperature to form a uniform solution; adding a high molecular polymer into the obtained solution, and stirring at room temperature to obtain uniform and viscous electrostatic spinning precursor solution; wherein the nitrate is a nitrate of a metal element in the positive electrode active material; the positive active material is lithium cobaltate, lithium manganate, lithium iron phosphate or lithium nickel cobalt manganese;

secondly, adding the electrostatic spinning precursor solution prepared in the first step into an injector, adopting a stainless steel flat-head needle as a spinning nozzle, adopting a nickel net as a spinning receiving net, and forming an electrostatic field of electrostatic spinning by using an external direct-current power supply mode to obtain an electrostatic spinning fiber membrane;

thirdly, placing the electrostatic spinning fiber membrane prepared in the second step into a box-type muffle furnace, and sintering at constant temperature in air atmosphere to obtain a three-dimensional interconnected anode active material;

weighing the positive electrode active material prepared in the step three, a conductive agent accounting for 10-12.5% of the mass of the positive electrode active material and a binder accounting for 10-12.5% of the mass of the positive electrode active material, sequentially dissolving the positive electrode material, the conductive agent and the binder in a solvent II, and stirring uniformly at room temperature to form viscous positive electrode slurry;

fifthly, uniformly blade-coating the anode slurry prepared in the step four on the surface of an aluminum foil, and performing vacuum drying to obtain a pole piece coated with a porous anode framework;

weighing lithium salt accounting for 10-16% of the mass of the polymer monomer and initiator accounting for 0.5-1% of the mass of the polymer monomer, sequentially dissolving the lithium salt and the initiator in the polymer monomer, and uniformly stirring to form polymer electrolyte precursor liquid;

and seventhly, dripping the polymer electrolyte precursor liquid prepared in the step six on the surface of the pole piece prepared in the step five, standing, and heating, polymerizing and curing the pole piece to obtain the composite anode for the solid-state lithium battery.

8. The method of claim 7, wherein the solvent I is N, N-dimethylformamide, acetonitrile or N-methylpyrrolidone.

9. The method according to claim 7, wherein the polymer in the first step is polyvinylpyrrolidone, polyacrylonitrile or polyvinylidene fluoride.

10. A solid lithium battery is characterized in that the solid lithium battery is assembled by a metallic lithium cathode, a solid electrolyte and a composite anode for the solid lithium battery; the solid electrolyte is a composite solid electrolyte film compounded by polyvinylidene fluoride, lithium aluminum titanium phosphate and lithium salt.

Technical Field

The invention relates to a composite anode and a preparation method thereof, belonging to the field of solid-state lithium batteries.

Background

The solid-state lithium battery has the advantages of high energy density, safety, reliability and the like, has become one of the research hotspots in the field of energy storage nowadays, and is paid much attention by researchers. In recent years, various solid electrolytes with high ionic conductivity and wide electrochemical window are developed, but the power density and the cycle life of the solid-state lithium battery are still away from practical application. The reason for this is that the solid-solid interface formed between the electrode and the solid electrolyte in the solid lithium battery has higher contact resistance than the solid-liquid interface in the conventional liquid lithium ion battery due to non-wettability of the solid electrolyte. Meanwhile, according to a great deal of research on failure mechanisms in the aspects of chemistry, electrochemistry and mechanics, the charge transfer resistance is increased due to the incompatibility of the electrode/solid electrolyte interface and the accumulation of the interface stress of the electrode caused by volume change. Therefore, solving the interface problem in the solid-state lithium battery is a key factor for achieving fundamental breakthrough of battery performance.

At present, researches on the interface problem of the solid lithium battery are mostly focused on improving the interlayer interface contact and electrochemical stability of the electrode and the electrolyte, and the researches on the interface improvement and mechanism among the particles in the electrode material are less. In addition, most studies adopt low-loading active materials, and more conductive agents and solid electrolytes are added in the electrodes, so that the solid lithium battery loses the advantage of high specific energy density. Therefore, the performance requirements of the fields of new energy power vehicles and the like on the solid-state lithium battery can be met only by regulating and controlling the solid-solid interface between the solid electrolyte/the electrode and the solid-solid interface between particles in the electrode and developing and researching a high-capacity electrode material.

Disclosure of Invention

The invention provides a composite positive electrode for a solid-state lithium battery and a preparation method thereof, aiming at solving the technical problems of poor interface contact between a positive electrode and a solid electrolyte, discontinuous ion/electron conduction in the positive electrode and low active substance loading capacity in the existing solid-state lithium battery.

The composite positive electrode for the solid lithium battery consists of a porous positive electrode framework and a filled polymer electrolyte; wherein the porous positive electrode framework consists of a positive electrode active material, a conductive agent and a binder; wherein the mass of the conductive agent accounts for 10-12.5% of the mass of the positive active material; the mass of the binder accounts for 10-12.5% of that of the positive active material; the filled polymer electrolyte consists of lithium salt, polymer monomer and initiator; wherein the mass of the lithium salt accounts for 10-16% of the mass of the polymer monomer, and the mass of the initiator accounts for 0.5-1% of the mass of the polymer monomer; the positive active material in the porous positive electrode framework is lithium cobaltate, lithium manganate, lithium iron phosphate or lithium nickel cobalt manganese.

Further, the conductive agent in the porous positive electrode skeleton is one or more of conductive carbon black, carbon nanotubes, carbon fibers and graphene.

Further, the binder in the porous positive electrode skeleton is polyvinylidene fluoride.

Further, the lithium salt in the filled polymer electrolyte is one or a combination of several of lithium difluoro oxalate borate, lithium perchlorate, lithium hexafluorophosphate, lithium bis (oxalato) borate and lithium bis (fluorosulfonyl) imide.

Furthermore, the polymer monomer in the filled polymer electrolyte is one or a combination of several of vinylene carbonate, methyl methacrylate, butyl acrylate and triethylene glycol diacrylate.

Further, the initiator in the filled polymer electrolyte is azobisisobutyronitrile or azobisisoheptonitrile.

Furthermore, the mass of the porous positive electrode framework is 90-95% of the mass of the composite positive electrode, and the mass of the filled polymer electrolyte is 5-10% of the mass of the composite positive electrode.

The preparation method of the composite positive electrode for the solid-state lithium battery comprises the following steps:

firstly, dissolving nitrate in a solvent I, and stirring at room temperature to form a uniform solution; adding a high molecular polymer into the obtained solution, and stirring at room temperature to obtain uniform and viscous electrostatic spinning precursor solution; wherein the nitrate is a nitrate of a metal element in the positive electrode active material; the positive active material is lithium cobaltate, lithium manganate, lithium iron phosphate or lithium nickel cobalt manganese;

secondly, adding the electrostatic spinning precursor solution prepared in the first step into an injector, taking a stainless steel flat-head needle as a spinning nozzle, taking a nickel net as a spinning receiving net, and forming an electrostatic field of electrostatic spinning by using an external direct-current power supply mode, wherein the spinning nozzle is connected with the positive pole of the direct-current power supply, the receiving net is connected with the negative pole of the direct-current power supply, and electrostatic spinning is carried out to obtain an electrostatic spinning fiber membrane;

thirdly, placing the electrostatic spinning fiber membrane prepared in the second step into a box-type muffle furnace, and sintering at constant temperature in air atmosphere to obtain a three-dimensional interconnected anode active material;

weighing the positive electrode active material prepared in the step three, a conductive agent accounting for 10-12.5% of the mass of the positive electrode active material and a binder accounting for 10-12.5% of the mass of the positive electrode active material, sequentially dissolving the positive electrode material, the conductive agent and the binder in a solvent II, and stirring uniformly at room temperature to form viscous positive electrode slurry;

fifthly, uniformly blade-coating the anode slurry prepared in the step four on the surface of an aluminum foil, and performing vacuum drying to obtain a pole piece coated with a porous anode framework;

weighing lithium salt accounting for 10-16% of the mass of the polymer monomer and initiator accounting for 0.5-1% of the mass of the polymer monomer, sequentially dissolving the lithium salt and the initiator in the polymer monomer, and uniformly stirring to form polymer electrolyte precursor liquid;

and seventhly, dripping the polymer electrolyte precursor liquid prepared in the step six on the surface of the pole piece prepared in the step five, standing, and heating, polymerizing and curing the pole piece to obtain the composite anode for the solid-state lithium battery.

Further, in the first step, the nitrate is nickel nitrate, cobalt nitrate, manganese nitrate and/or lithium nitrate;

further, in the first step, the solvent I is N, N-dimethylformamide, acetonitrile or N-methylpyrrolidone;

furthermore, the high molecular polymer in the step one is polyvinylpyrrolidone, polyacrylonitrile or polyvinylidene fluoride;

furthermore, the injector in the step two is a 5mL injector, and the spinning nozzle adopts a stainless steel flat-head needle head with the inner diameter of 0.51 mm;

further, the voltage applied by the direct current power supply in the second step is 30 kV;

furthermore, the distance between the spinning receiving net and the spinning nozzle in the second step is 15-30 cm;

furthermore, the sintering temperature in the third step is 900 ℃, the heating rate is 3 ℃/min, and the sintering time is 5 h;

furthermore, the positive active material in the third step is a lithium cobaltate, lithium manganate, lithium iron phosphate or lithium nickel cobalt manganese oxide ternary material;

furthermore, the conductive agent in the fourth step is conductive carbon black, carbon nanotubes, carbon fibers or graphene;

further, the adhesive in the fourth step is polyvinylidene fluoride;

furthermore, the solvent II in the fourth step is N-methylpyrrolidone, N-dimethylformamide or acetonitrile;

furthermore, the temperature of the vacuum drying in the fifth step is 60-80 ℃, and the time is 24-48 h;

further, the lithium salt in the sixth step is lithium difluorooxalato borate, lithium perchlorate, lithium hexafluorophosphate, lithium bis (oxalato) borate or lithium bis (fluorosulfonyl) imide;

further, the polymer monomer in the sixth step is vinylene carbonate, methyl methacrylate, butyl acrylate or triethylene glycol diacrylate;

further, the initiator in the sixth step is azobisisobutyronitrile or azobisisoheptonitrile;

further, the standing temperature in the seventh step is 25-30 ℃, and the time is 15-30 min;

furthermore, the heating temperature in the seventh step is 60-80 ℃, and the time is 1-2 hours; in the preparation process, polymerization and solidification are carried out at a lower temperature, so that part of unpolymerized monomers still remain on the surface of the composite anode, and the binding force between the composite anode and the solid electrolyte layer in the subsequent battery preparation process is enhanced.

The invention provides a solid-state lithium battery, which is assembled by a metal lithium cathode, a solid-state electrolyte and a composite anode for the solid-state lithium battery; the solid electrolyte is a composite solid electrolyte film compounded by polyvinylidene fluoride, lithium aluminum titanium phosphate and lithium salt.

The invention also provides a preparation method of the solid-state lithium battery, which comprises the following steps:

firstly, soaking a composite solid electrolyte film compounded by polyvinylidene fluoride, lithium aluminum titanium phosphate and lithium salt in an organic electrolyte, taking out and sucking to dry for later use;

and secondly, stacking the composite anode, the solid electrolyte film and the metal lithium cathode for the solid lithium battery in sequence, packaging the stacked composite anode, the solid electrolyte film and the metal lithium cathode in a button-type battery case, and heating the button-type battery case to obtain the solid lithium battery.

Further, the stepsThe soaking time in the first step is 10-20 min, and the adopted organic electrolyte is 1M lithium hexafluorophosphate (LiPF)₆) Ethylene carbonate/dimethyl carbonate (EC/DMC) solution.

Furthermore, the method for preparing the composite solid electrolyte film by using the polyvinylidene fluoride, the lithium aluminum titanium phosphate and the lithium salt in the first step is carried out according to the following steps:

(1) dispersing lithium aluminum titanium phosphate particles in an N, N-dimethylformamide solvent, and performing ultrasonic dispersion to form a dispersion liquid homogeneous phase solution;

(2) weighing polyvinylidene fluoride accounting for 15-40% of the mass of lithium aluminum titanium phosphate and lithium salt accounting for 33-67% of the mass of polyvinylidene fluoride, sequentially dissolving the polyvinylidene fluoride and the lithium salt in an N, N-dimethylformamide solvent, and uniformly stirring to form a polymer solution with the polymer concentration of 0.15-0.25 g/mL;

(3) dissolving the dispersion liquid of lithium aluminum titanium phosphate particles in a polymer solution, and uniformly stirring to obtain a composite solid electrolyte solution;

(4) and uniformly coating the composite solid electrolyte solution on a flat substrate, and vacuum drying at 80 ℃ for 48h to obtain the composite solid electrolyte film.

Furthermore, the heating temperature in the second step is 60-80 ℃, and the heating time is 0.5-1 h.

The composite positive electrode is prepared by filling polymer electrolyte precursor liquid into the positive electrode by adopting a three-dimensional interconnected lithium cobaltate, lithium manganate, lithium iron phosphate or lithium nickel cobalt manganese oxide ternary material as a positive electrode framework, and carrying out in-situ polymerization and solidification. The beneficial effects are as follows:

(1) according to the composite anode provided by the invention, the anode framework is formed by stacking nano fibers, and each fiber is formed by mutually connecting nano nickel cobalt lithium manganate particles. The active material particles are connected with each other on a one-dimensional scale, so that the interface contact among the particles in the electrode material is effectively improved. Meanwhile, the nano active substance particles can shorten the diffusion distance of lithium ions and electrons and increase the contact area of an electrode/electrolyte, and the three-dimensional interconnected fiber structure forms a continuous electron transmission channel in the composite anode, thereby being beneficial to realizing the optimization of the rate capability of the material.

(2) The polymer electrolyte in the composite anode is formed by in-situ polymerization and solidification of polymer monomers filled in the anode framework. The polymer monomer with high fluidity can be easily filled into the interior and the depth of an electrode, uniform filling between active substances can be realized after polymerization and solidification, the interface contact area of a positive electrode material and a solid electrolyte is obviously increased, the polarization of a solid lithium battery is reduced, the interface impedance is reduced, the problem that the solid electrolyte is difficult to infiltrate the pores of the electrode due to poor fluidity is avoided, and the utilization rate of the active substances can be obviously improved.

(3) The composite positive electrode provided by the invention is flat and smooth due to the fact that the surface is covered with the polymer electrolyte layer, solid-solid point contact of an electrode/solid electrolyte interface in a traditional solid-state battery is improved into surface contact, interface contact of an electrode layer and the solid electrolyte layer can be obviously enhanced, and polarization of the battery is reduced. Meanwhile, the polymer electrolyte in the composite anode can relieve the volume change of an electrode material, avoid the mechanical contact failure caused by stress accumulation and improve the structural integrity of the composite anode. Lithium salt in the polymer electrolyte can generate beneficial components such as lithium fluoride and lithium carbonate on the surface of the active material, and the dynamic performance and high voltage tolerance of the electrode material can be improved. In addition, the carbonyl functional group in the polymer has higher electrochemical stability, and can generate intermolecular interaction with a solid electrolyte layer, so that the electrochemical stability and interlayer bonding force of an electrode/electrolyte interface are enhanced, and interlayer stripping in the battery cycle process is avoided.

(4) The polymer electrolyte in the composite anode only accounts for 5-10% of the total mass of the composite anode, and compared with the conventional composite anode, the composite anode can obviously reduce the filling amount of the solid electrolyte and avoid the reduction of the specific energy density of a solid battery. Meanwhile, the high-porosity positive electrode framework and the high-fluidity polymer monomer ensure that the polymer electrolyte can fill the whole composite positive electrode from top to bottom after being heated, polymerized and cured, on the premise of ensuring the specific capacity of the positive electrode active material,can increase the loading capacity of the active material to 8-12 mg/cm²The technical problem that the loading capacity of the anode of the traditional solid-state lithium battery is too low is solved, and the method has practical application and popularization values.

Drawings

FIG. 1 is a scanning electron microscope photograph of a fibrous electrode material in example 1.

FIG. 2 is a transmission electron microscope photograph of the fibrous electrode material in example 1.

FIG. 3 shows the X-ray diffraction pattern and refinement calculation of the fibrous electrode material in example 1.

FIG. 4 is a scanning electron microscope photograph of the surface of the porous positive electrode in example 1.

FIG. 5 is a scanning electron microscope photograph of the surface of the composite positive electrode in example 1.

FIG. 6 is a scanning electron microscope photograph of a cross section of the porous positive electrode in example 1.

FIG. 7 is a scanning electron microscope photograph of a cross section of the composite positive electrode in example 1.

Fig. 8 is a fourier infrared spectroscopy test curve of the surface of the porous positive electrode and the composite positive electrode in example 1.

Fig. 9 is an X-ray photoelectron diffraction pattern of the surface of the porous positive electrode in example 1.

Fig. 10 is an X-ray photoelectron diffraction pattern of the surface of the composite positive electrode in example 1.

Fig. 11 is a thermogravimetric analysis test curve of the composite positive electrode and the porous positive electrode in example 1.

Fig. 12 is a fourier infrared spectroscopy test curve of the surface of the solid electrolyte in example 1.

Fig. 13 is a rate capability and voltage curve of the solid-state lithium battery of example 1.

Fig. 14 is a graph showing cycle performance and voltage curve of the solid lithium battery of example 1.

Fig. 15 is an X-ray photoelectron diffraction pattern of the surface of the positive electrode after cycling of the solid-state lithium battery in example 1.

Fig. 16 is a graph showing high voltage cycle performance and voltage curve of the solid lithium battery of example 1.

Fig. 17 is a graph showing cycle performance and voltage curve of the solid lithium battery in example 2.

Fig. 18 is a graph showing cycle performance and voltage curve of the solid lithium battery in example 3.

Fig. 19 is a graph showing cycle performance and voltage curve of the solid lithium battery in example 4.

Detailed Description

The following examples are used to demonstrate the beneficial effects of the present invention.

Example 1: the preparation method of the composite positive electrode for the solid-state lithium battery of the embodiment is carried out according to the following steps:

one, will meet LiNi_0.5Co_0.2Mn_0.3O₂Of (2) is Ni (NO)₃)₂·6H₂O、Co(NO₃)₂·6H₂O，Mn(CH₃COO)₂·4H₂O and LiNO₃Dissolving in N, N-dimethylformamide, and stirring at room temperature for 2h to form a uniform solution; adding polyvinylpyrrolidone into the solution and continuously stirring for 8 hours to obtain uniform and viscous electrostatic spinning precursor solution; wherein the addition amount of the polyvinylpyrrolidone accounts for 12 wt% of the total mass of the electrostatic spinning precursor solution;

secondly, adding the electrostatic spinning precursor solution prepared in the first step into a 5mL injector, and forming an electrostatic field of electrostatic spinning by using a stainless steel flat-head needle with the inner diameter of 0.51mm as a spinning spray head and a nickel net as a spinning receiving net in an external direct-current power supply manner, wherein the spinning spray head is connected with the anode of the direct-current power supply, and the receiving net is connected with the cathode of the direct-current power supply; adjusting the angle of the injector to make the liquid drops hung on the spray head hang and not fall, and controlling the electrostatic spinning conditions: carrying out electrostatic spinning at the temperature of 25 ℃, the humidity of 20 percent and the voltage of 30kV, wherein the distance between a spray head and a receiving net is 15cm, so as to obtain an electrostatic spinning fiber membrane;

thirdly, placing the electrostatic spinning fiber membrane prepared in the second step into a box-type muffle furnace, and sintering the electrostatic spinning fiber membrane at the constant temperature of 900 ℃ for 5 hours at the heating rate of 3 ℃/min in the air atmosphere to obtain a three-dimensional interconnected fibrous ternary positive electrode active material;

fourthly, weighing 0.8g of the fibrous ternary positive electrode active material prepared in the first step, 0.1g of conductive carbon black and 0.1g of polyvinylidene fluoride binder, sequentially dissolving the materials in N-methyl pyrrolidone, and stirring the materials at room temperature for 8 hours to obtain viscous positive electrode slurry;

fifthly, uniformly scraping the anode slurry prepared in the step four on the surface of an aluminum foil, and drying the aluminum foil in vacuum at 80 ℃ for 24 hours to obtain a porous anode piece coated with a fibrous ternary material, wherein the loading capacity of the ternary anode active material is 2mg/cm²；

Sixthly, 0.17g of lithium difluoro (oxalato) borate is weighed and dissolved in 1mL of vinylene carbonate, the mixture is stirred at room temperature for 30min, then azodiisobutyronitrile initiator accounting for 0.5 percent of the weight of the vinylene carbonate is added, and the mixture is continuously stirred at room temperature for 1h to obtain uniform polymer electrolyte precursor solution;

seventhly, absorbing the polymer electrolyte precursor liquid to drop on the surface of the porous positive pole piece, so that the ratio of the volume of the polymer electrolyte precursor liquid to the loading capacity of the porous positive pole active substance is 1 mu L/mg; and standing at room temperature for 30min, placing the porous anode dripped with the polymer electrolyte precursor solution on a heating table at 70 ℃, and heating in a glove box filled with argon for 1h to obtain the composite anode for the solid-state lithium battery.

Fig. 1 is a scanning electron microscope image of the three-dimensionally interconnected fibrous ternary positive electrode active material obtained in step three of example 1, and it can be seen that the ternary positive electrode active material prepared by the electrospinning technique has an obvious fibrous micro-morphology. The nanometer active particles are closely connected and grow on the one-dimensional fibers, so that the lithium ion/electron transmission path can be shortened, the multiplying power performance of the material is improved, the contact area of an electrode/electrolyte can be increased, and the polarization of the battery is reduced. The stacking of the fibers forms the mutual cross-linking of the active materials in a three-dimensional space, the unique micro-morphology forms a continuous lithium ion/electron conduction path, and the loose and porous electrode skeleton structure is used as a host, so that a large number of pores can be provided for the infiltration of polymer electrolyte, and the contact area of the electrode/electrolyte is increased.

Fig. 2 is a transmission electron microscope image of the three-dimensionally interconnected fibrous ternary positive electrode active material obtained in step three of example 1, and it can be seen that active particles having a diameter of 200nm are grown closely on one-dimensional fibers, and a 0.47nm lattice fringe may correspond to the (003) plane of the ternary material.

FIG. 3 is a graph showing the X-ray diffraction pattern and refinement calculation result of the three-dimensionally interconnected fibrous ternary positive electrode active material obtained in step three of example 1, in which a represents the pattern of the three-dimensionally interconnected fibrous ternary positive electrode active material obtained in step three, and b represents a hexagonal system α -NaFeO₂The standard diffraction spectrum of the layered structure, c is the deviation of a and b, and figure 3 shows that the X-ray diffraction spectrum of the ternary material prepared by the electrostatic spinning technology can well match with the hexagonal system alpha-NaFeO₂The standard diffraction patterns of the layered structure correspond. The combination of the distinct peak splitting phenomena at the (006)/(102) and (108)/(110) planes, the high c/a value (4.9643), and the high peak intensity ratio (1.5200) of the (003) to (104) planes indicates that the fibrous ternary cathode active material prepared in example 1 has a good layered structure and a low degree of lithium-nickel rearrangement.

Fig. 4 is a scanning electron microscope photograph of the porous positive electrode sheet coated with the fibrous ternary material obtained in step five of example 1, and fig. 5 is a scanning electron microscope photograph of the composite positive electrode surface for a solid-state lithium battery obtained in step seven. As can be seen from fig. 4 and 5, the composite positive electrode filled with the polymer electrolyte can completely cover the surface of the porous positive electrode, so that the surface of the electrode becomes flat and smooth, which is beneficial to enhancing the interlayer contact between the electrode and the electrolyte.

FIG. 6 is a scanning electron microscope image of a cross section of a porous positive electrode sheet coated with a fibrous ternary material obtained in step five of example 1; and 7, a scanning electron microscope image of the cross section of the composite anode for the solid-state lithium battery obtained in the seventh step is shown in fig. 6 and 7, and it can be seen from fig. 6 and 7 that the polymer monomer precursor liquid with strong fluidity can fill the pores inside the porous anode, and a compact and pore-free electrode/electrolyte integrated structure is formed in the composite anode after polymerization and solidification, so that the utilization rate of active materials in the solid-state battery is improved. The filled polymer electrolyte not only provides a continuous lithium ion transmission channel in the composite anode, enhances the electrochemical reaction rate of the electrode, but also can relieve the volume change of the active material and avoid contact failure in the circulating process.

Fig. 8 is a fourier infrared spectroscopy test curve of the porous positive electrode sheet coated with the fibrous ternary material obtained in step five of example 1 and the composite positive electrode surface for a solid-state lithium battery obtained in step seven, and it can be found by comparison that vibration peaks representing C ═ O and C-O-C in the polyvinyl carbonate are detected on the composite positive electrode surface, and the presence of the polyvinyl carbonate-based polymer electrolyte on the surface of the electrode sheet can be proved.

Fig. 9 and 10 are X-ray photoelectron diffraction patterns of the surface of the porous positive electrode sheet coated with the fibrous ternary material obtained in step five of example 1, respectively, fig. 10 is an X-ray photoelectron diffraction pattern of the surface of the composite positive electrode for a solid lithium battery obtained in step seven, and as can be seen from fig. 10, peaks representing lithium difluorooxalato borate are detected in the B1s orbital of the composite positive electrode surface, and peaks representing O ═ C-O, C-O-C/C ═ O and C-O in polyvinyl carbonate are detected in the C1s orbital, which can prove the presence of the polyvinyl carbonate-based polymer electrolyte on the surface of the sheet. Meanwhile, the comparison of an X-ray photoelectron diffraction spectrogram on the surface of the porous anode can find that a Co 2p orbit on the surface of the composite anode cannot detect a signal peak, and the fact that the surface of the pole piece is completely covered by the polymer electrolyte is proved.

Fig. 11 is a thermogravimetric analysis test curve of the porous positive electrode sheet coated with the fibrous ternary material obtained in step five and the composite positive electrode for the solid-state lithium battery obtained in step seven in example 1, and it can be calculated that the mass of the filled polymer electrolyte accounts for 8% of the total mass of the composite positive electrode, and the influence on the energy density of the solid-state battery is small.

The solid-state lithium battery assembled by using the composite positive electrode for a solid-state lithium battery prepared in the embodiment 1 includes the following specific steps:

firstly, compounding polyvinylidene fluoride, lithium aluminum titanium phosphate and lithium salt: the specific compounding method is as follows:

(1) dispersing lithium titanium aluminum phosphate particles in an N, N-dimethylformamide solvent, and performing ultrasonic dispersion to form homogeneous lithium titanium aluminum phosphate particle dispersion liquid;

(2) weighing polyvinylidene fluoride accounting for 20% of the mass of the lithium aluminum titanium phosphate and lithium bistrifluoromethanesulfonimide accounting for 40% of the mass of the polyvinylidene fluoride, sequentially dissolving the polyvinylidene fluoride and the lithium bistrifluoromethanesulfonimide in an N, N-dimethylformamide solvent, and uniformly stirring to form a polymer solution with the polymer concentration of 0.20 g/mL;

(3) adding the lithium aluminum titanium phosphate particle dispersion liquid into the polymer solution, and uniformly stirring to obtain a composite solid electrolyte solution;

(4) uniformly blade-coating the composite solid electrolyte solution on a flat substrate, and vacuum-drying at 80 ℃ for 48h to obtain a composite solid electrolyte film; then placing the composite solid electrolyte film in 1M LiPF₆Soaking the EC/DMC electrolyte (EC/DMC is 1: 1) for 10min, and sucking the electrolyte with dust-free paper to obtain a solid electrolyte film;

and secondly, stacking the composite anode for the solid lithium battery, the solid electrolyte film and the metal lithium cathode prepared in the embodiment 1 in sequence, packaging the stacked composite anode in a button-type battery shell, and heating the shell at 70 ℃ for 1 hour to obtain the solid lithium battery.

A solid lithium battery is disassembled, a fourier infrared spectrum test curve of the surface of the solid electrolyte after being heated and attached to the composite positive electrode is tested, as shown in fig. 12, it can be seen from fig. 12 that a vibration peak belonging to a group C ═ O can be detected on the surface of the solid electrolyte after being heated and attached to the composite positive electrode, which indicates that the solid electrolyte layer after being heated and attached has strong adhesion to the composite positive electrode layer. Meanwhile, the compound can also be found to represent-CH in polyvinylidene fluoride₂The oscillating peak of-undergoes a blue shift, which indicates that-CH is paired with C ═ O group₂The bond can generate an electron-withdrawing effect, the polyvinyl carbonate on the surface of the composite positive electrode and the polyvinylidene fluoride in the solid electrolyte generate intermolecular interaction, and the special electrode/electrolyte interfacial force can enhance the interface adhesion and avoid the occurrence of an interlayer peeling phenomenon.

The solid-state lithium battery is subjected to constant-current charge-discharge cycle test (1C: 170mAh/g) in a voltage range of 2.8-4.3V by a NEWARE CT-4008T-5V10mA-164 multichannel battery tester, and the test temperature is room temperature. The solid state lithium battery is 2The room temperature multiplying power performance of 0.1-1C and the corresponding voltage curve in the voltage interval of 8-4.3V are shown in FIG. 13, and it can be seen from FIG. 13 that the loading amount of the active material is 2mg/cm²The solid lithium battery assembled by the composite positive electrode has specific discharge capacities of 146.1, 123.4, 114.2, 104.0 and 92.7mAh/g at the multiplying power of 0.1, 0.2, 0.3, 0.5 and 1C respectively. Meanwhile, the degree of voltage polarization increase is slower along with the increase of the multiplying power, and the solid-state battery is proved to have more excellent multiplying power performance.

Fig. 14 shows the 0.1C room temperature cycle performance and the corresponding voltage curve of the solid-state lithium battery prepared in example 1 in the voltage range of 2.8 to 4.3V. The loading of the active material is 2mg/cm²The first circle of the solid-state lithium battery assembled by the composite anode has the specific discharge capacity of 143.2mAh/g, and the first circle still has the specific discharge capacity of 106.0mAh/g after 80 circles of circulation, which shows that the structural design of the composite anode is beneficial to improving the utilization rate of the active material of the anode and maintaining the circulation stability of the solid-state battery.

Fig. 15 is an X-ray photoelectron diffraction pattern of the positive electrode surface after cycling of the solid-state lithium battery prepared in example 1, and the presence of chemical bonds C-O, O ═ C-O and B-F demonstrates that the polymer electrolyte layer still remains on the composite positive electrode surface after cycling. In addition, the O1 s orbital can be detected as representing LiNi_0.5Co_0.2Mn_0.3O₂And Li₂CO₃The F1 s orbitals detected peaks of polyvinylidene fluoride and LiF, indicating that there was partial decomposition of lithium difluorooxalato borate with concomitant thinning of the polymer electrolyte layer as the cell cycles progressed. After the surface of the composite anode is subjected to argon ion etching for 200s, LiF and Li can be found to represent₂CO₃The phenomenon of peak intensity enhancement occurs. Meanwhile, the peak intensity of C-O and O ═ C-O is weakened. These show that the addition of polymer electrolyte to the composite positive electrode helps to form LiF and Li on the surface of the active material, which have high lithium ion conductivity and high voltage tolerance₂CO₃The substance can obviously improve the electrochemical stability of the electrode material in the circulating process.

The battery is subjected to a constant current charge-discharge cycle test (1C: 170mAh/g) in a voltage range of 2.8-4.5V by a NEWARE CT-4008T-5V10mA-164 multichannel battery tester, and the test temperature is room temperature. Fig. 16 shows the 0.1C room temperature cycle performance and the corresponding voltage curve of the solid-state lithium battery in example 2 in the voltage range of 2.8 to 4.5V. It can be seen that the first circle of the solid-state battery has a specific discharge capacity of 160.0mAh/g, and can still be maintained at 106.0mAh/g after 53 cycles of cycling, which indicates that the composite positive electrode has excellent high-voltage performance and the electrode/electrolyte interface has high electrochemical stability.

Example 2: the preparation method of the composite positive electrode for the solid-state lithium battery of the embodiment is carried out according to the following steps:

one, one according to LiNi_0.5Co_0.2Mn_0.3O₂Stoichiometric ratio of (2) to Ni (NO)₃)₂·6H₂O、Co(NO₃)₂·6H₂O、Mn(CH₃COO)₂·4H₂O and LiNO₃Dissolving in N, N-dimethylformamide and stirring for 2 h; adding polyvinylpyrrolidone into the solution and continuously stirring for 8 hours to obtain uniform and viscous electrostatic spinning precursor solution; wherein the mass of the polyvinylpyrrolidone accounts for 12 wt% of the total mass of the electrostatic spinning precursor solution;

and secondly, adding the electrostatic spinning precursor solution prepared in the step one into a 5mL injector, adopting a stainless steel flat-head needle with the inner diameter of 0.51mm as a spinning spray head, adopting a nickel net as a spinning receiving net, and forming an electrostatic field of electrostatic spinning by utilizing an external direct-current power supply mode, wherein the spinning spray head is connected with the anode of the direct-current power supply, and the receiving net is connected with the cathode of the direct-current power supply. Adjusting the angle of the injector to make the liquid drops hung on the spray head hang and not fall, and controlling the electrostatic spinning conditions: carrying out electrostatic spinning at the temperature of 30 ℃, the humidity of 25%, the voltage of 30kV and the distance between a spray head and a receiving net of 15cm to obtain an electrostatic spinning fiber membrane;

thirdly, placing the electrostatic spinning fiber membrane prepared in the second step into a box-type muffle furnace, and sintering the electrostatic spinning fiber membrane at the constant temperature of 900 ℃ for 5 hours at the heating rate of 3 ℃/min in the air atmosphere to obtain a three-dimensional interconnected fibrous ternary positive electrode active material;

fourthly, weighing 0.8g of the fibrous ternary positive electrode active material prepared in the first step, 0.1g of conductive carbon black and 0.1g of polyvinylidene fluoride binder, sequentially dissolving the materials in N-methyl pyrrolidone, and stirring the materials at room temperature for 8 hours to obtain viscous positive electrode slurry;

fifthly, uniformly blade-coating the anode slurry prepared in the step four on the surface of an aluminum foil, and vacuum-drying at 80 ℃ for 24 hours to obtain the porous anode coated with the fibrous ternary anode active material, wherein the loading capacity of the anode active material is 7.57mg/cm²；

Sixthly, 0.17g of lithium difluoro (oxalato) borate is weighed and dissolved in 1mL of vinylene carbonate, the mixture is stirred at room temperature for 30min, then azodiisobutyronitrile initiator accounting for 0.5 percent of the weight of the vinylene carbonate is added, and the mixture is continuously stirred at room temperature for 1h to obtain uniform polymer electrolyte precursor solution;

seventhly, absorbing the polymer electrolyte precursor liquid to drop on the surface of the porous positive pole piece, so that the ratio of the volume of the polymer electrolyte precursor liquid to the loading capacity of the porous positive pole active substance is 1 mu L/mg; and standing at room temperature for 30min, placing the porous anode dripped with the polymer electrolyte precursor solution on a heating table at 70 ℃, and heating in a glove box filled with argon for 1h to obtain the composite anode for the solid-state lithium battery.

The solid-state lithium battery assembled by using the composite positive electrode for a solid-state lithium battery prepared in this example 2 includes the following specific steps:

firstly, compounding polyvinylidene fluoride, lithium aluminum titanium phosphate and lithium salt, wherein the specific compounding method comprises the following steps:

(1) dispersing lithium titanium aluminum phosphate particles in an N, N-dimethylformamide solvent, and performing ultrasonic dispersion to form homogeneous lithium titanium aluminum phosphate particle dispersion liquid;

(2) weighing polyvinylidene fluoride accounting for 30% of the mass of lithium aluminum titanium phosphate and lithium bis (trifluoromethanesulfonyl) imide accounting for 50% of the mass of polyvinylidene fluoride, sequentially dissolving the polyvinylidene fluoride and the lithium bis (trifluoromethanesulfonyl) imide in an N, N-dimethylformamide solvent, and uniformly stirring to form a polymer solution with the polymer concentration of 0.20 g/mL;

(3) adding the lithium aluminum titanium phosphate particle dispersion liquid into the polymer solution, and uniformly stirring to obtain a composite solid electrolyte solution;

(4) compound solid state electricityUniformly blade-coating the electrolyte solution on a flat substrate, and vacuum-drying at 80 ℃ for 48h to obtain a composite solid electrolyte film; then placing the composite solid electrolyte film in 1M LiPF₆Soaking the EC/DMC electrolyte (EC/DMC is 1: 1) for 10min, and sucking the electrolyte with dust-free paper to obtain a solid electrolyte film;

and secondly, stacking the composite anode for the solid lithium battery, the solid electrolyte film and the metal lithium cathode prepared in the embodiment 2 in sequence, packaging the stacked composite anode in a button-type battery shell, and heating the obtained product at 70 ℃ for 1 hour to obtain the solid lithium battery.

The battery is subjected to a constant current charge-discharge cycle test (1C: 170mAh/g) in a voltage range of 2.8-4.3V by a NEWARE CT-4008T-5V10mA-164 multichannel battery tester, and the test temperature is room temperature.

FIG. 17 shows the loading of the active material of the positive electrode of the solid-state lithium battery of example 2 at 7.57mg/cm²Cycling performance and voltage profile. Thanks to the three-dimensional structure design of the composite anode, the solid-state lithium battery can still keep excellent gram capacity exertion when the load of the active material is high. The solid lithium battery assembled by the high-capacity composite anode has the maximum discharge specific capacity of 133.3mAh/g, which is equivalent to 1.01mAh/cm²The surface capacity of the lithium battery is good, the cycle stability is good in 27 cycles, and the lithium battery can assist the research and development design of the solid lithium battery with high specific energy.

Example 3: the preparation method of the composite positive electrode for the solid-state lithium battery of the embodiment is carried out according to the following steps:

one, one according to LiNi_0.5Co_0.2Mn_0.3O₂Stoichiometric ratio of (2) to Ni (NO)₃)₂·6H₂O、Co(NO₃)₂·6H₂O、Mn(CH₃COO)₂·4H₂O and LiNO₃Dissolving in N, N-dimethylformamide and stirring for 2 h; adding polyvinylpyrrolidone into the solution and continuously stirring for 8 hours to obtain uniform and viscous electrostatic spinning precursor solution; wherein the addition amount of the polyvinylpyrrolidone accounts for 12 wt% of the total mass of the electrostatic spinning precursor solution;

and secondly, adding the electrostatic spinning precursor solution prepared in the step one into a 5mL injector, adopting a stainless steel flat-head needle with the inner diameter of 0.51mm as a spinning spray head, adopting a nickel net as a spinning receiving net, and forming an electrostatic field of electrostatic spinning by utilizing an external direct-current power supply mode, wherein the spinning spray head is connected with the anode of the direct-current power supply, and the receiving net is connected with the cathode of the direct-current power supply. Adjusting the angle of the injector to make the liquid drops hung on the spray head hang and not fall, and controlling the electrostatic spinning conditions: carrying out electrostatic spinning at the temperature of 25 ℃, the humidity of 20 percent and the voltage of 30kV, wherein the distance between a spray head and a receiving net is 15cm, so as to obtain an electrostatic spinning fiber membrane;

thirdly, placing the electrostatic spinning fiber membrane prepared in the second step into a box-type muffle furnace, and sintering the electrostatic spinning fiber membrane at the constant temperature of 900 ℃ for 5 hours at the heating rate of 3 ℃/min in the air atmosphere to obtain a three-dimensional interconnected fibrous ternary positive electrode active material;

fourthly, weighing 0.8g of the fibrous ternary positive electrode active material prepared in the first step, 0.1g of conductive carbon black and 0.1g of polyvinylidene fluoride binder, sequentially dissolving the materials in N-methyl pyrrolidone, and stirring the materials at room temperature for 8 hours to obtain viscous positive electrode slurry;

fifthly, uniformly blade-coating the anode slurry prepared in the step four on the surface of an aluminum foil, and vacuum-drying at 80 ℃ for 24 hours to obtain the porous anode coated with the fibrous ternary anode active material, wherein the loading capacity of the anode active material is 9.28mg/cm²；

Sixthly, 0.17g of lithium difluoro (oxalato) borate is weighed and dissolved in 1mL of vinylene carbonate, the mixture is stirred at room temperature for 30min, then azodiisobutyronitrile initiator accounting for 0.5 percent of the weight of the vinylene carbonate is added, and the mixture is continuously stirred at room temperature for 1h to obtain uniform polymer electrolyte precursor solution;

seventhly, absorbing the polymer electrolyte precursor liquid to drop on the surface of the porous positive pole piece, so that the ratio of the volume of the polymer electrolyte precursor liquid to the loading capacity of the porous positive pole active substance is 1 mu L/mg; and standing at room temperature for 30min, placing the porous anode dripped with the polymer electrolyte precursor solution on a heating table at 70 ℃, and heating in a glove box filled with argon for 1h to obtain the composite anode for the solid-state lithium battery.

The solid-state lithium battery assembled by using the composite positive electrode for a solid-state lithium battery prepared in this example 3 includes the following specific steps:

firstly, compounding polyvinylidene fluoride, lithium aluminum titanium phosphate and lithium salt, wherein the specific compounding method comprises the following steps:

(1) dispersing lithium titanium aluminum phosphate particles in an N, N-dimethylformamide solvent, and performing ultrasonic dispersion to form homogeneous lithium titanium aluminum phosphate particle dispersion liquid;

(2) weighing polyvinylidene fluoride accounting for 15% of the mass of the lithium aluminum titanium phosphate and lithium bis (trifluoromethanesulfonyl) imide accounting for 30% of the mass of the polyvinylidene fluoride, sequentially dissolving the polyvinylidene fluoride and the lithium bis (trifluoromethanesulfonyl) imide in an N, N-dimethylformamide solvent, and uniformly stirring to form a polymer solution with the polymer concentration of 0.20 g/mL;

(3) adding the lithium aluminum titanium phosphate particle dispersion liquid into the polymer solution, and uniformly stirring to obtain a composite solid electrolyte solution;

(4) uniformly blade-coating the composite solid electrolyte solution on a flat substrate, and vacuum-drying at 80 ℃ for 48h to obtain a composite solid electrolyte film; then placing the composite solid electrolyte film in 1M LiPF₆Soaking the EC/DMC electrolyte (EC/DMC is 1: 1) for 10min, and sucking the electrolyte with dust-free paper to obtain a solid electrolyte film;

and secondly, stacking the composite anode for the solid lithium battery, the solid electrolyte film and the metal lithium cathode prepared in the embodiment 3 in sequence, packaging the stacked composite anode in a button-type battery shell, and heating the obtained product at 70 ℃ for 1 hour to obtain the solid lithium battery.

The battery is subjected to a constant current charge-discharge cycle test (1C: 170mAh/g) in a voltage range of 2.8-4.3V by a NEWARE CT-4008T-5V10mA-164 multichannel battery tester, and the test temperature is room temperature.

FIG. 18 shows the loading of the positive active material of the solid lithium battery prepared in example 3 at 9.28mg/cm²Cycling performance and voltage profile. Thanks to the three-dimensional structure design of the composite anode, the solid-state lithium battery can still keep excellent gram capacity exertion when the load of the active material is high. The first circle of the solid lithium battery assembled by the high-capacity composite anode has the specific discharge capacity of 128.0mAh/g, which is equivalent to 1.19mAh/cm²Has good circulation stability within 52 cycles,can assist the research and development design of the solid-state lithium battery with high specific energy.

Example 4: the preparation method of the composite positive electrode for the solid-state lithium battery of the embodiment is carried out according to the following steps:

one, one according to LiNi_0.5Co_0.2Mn_0.3O₂Stoichiometric ratio of (2) to Ni (NO)₃)₂·6H₂O、Co(NO₃)₂·6H₂O、Mn(CH₃COO)₂·4H₂O and LiNO₃Dissolving in N, N-dimethylformamide and stirring for 2 h; adding polyvinylpyrrolidone into the solution and continuously stirring for 8 hours to obtain uniform and viscous electrostatic spinning precursor solution; wherein the addition amount of the polyvinylpyrrolidone accounts for 12 wt% of the total mass of the electrostatic spinning precursor solution;

and secondly, adding the electrostatic spinning precursor solution prepared in the step one into a 5mL injector, adopting a stainless steel flat-head needle with the inner diameter of 0.51mm as a spinning spray head, adopting a nickel net as a spinning receiving net, and forming an electrostatic field of electrostatic spinning by utilizing an external direct-current power supply mode, wherein the spinning spray head is connected with the anode of the direct-current power supply, and the receiving net is connected with the cathode of the direct-current power supply. Adjusting the angle of the injector to make the liquid drops hung on the spray head hang and not fall, and controlling the electrostatic spinning conditions: carrying out electrostatic spinning at the temperature of 25 ℃, the humidity of 20 percent and the voltage of 30kV, wherein the distance between a spray head and a receiving net is 15cm, so as to obtain an electrostatic spinning fiber membrane;

thirdly, placing the electrostatic spinning fiber membrane prepared in the second step into a box-type muffle furnace, and sintering the electrostatic spinning fiber membrane at the constant temperature of 900 ℃ for 5 hours at the heating rate of 3 ℃/min in the air atmosphere to obtain a three-dimensional interconnected fibrous ternary positive electrode active material;

fourthly, weighing 0.8g of the fibrous ternary positive electrode active material prepared in the first step, 0.1g of conductive carbon black and 0.1g of polyvinylidene fluoride binder, sequentially dissolving the materials in N-methyl pyrrolidone, and stirring the materials at room temperature for 8 hours to obtain viscous positive electrode slurry;

fifthly, uniformly blade-coating the anode slurry prepared in the step four on the surface of an aluminum foil, and vacuum-drying at 80 ℃ for 24 hours to obtain a porous anode coated with a fibrous ternary anode active material, wherein the anode is activeThe loading amount of the material is 2mg/cm²；

Sixthly, 0.17g of lithium difluoro (oxalato) borate is weighed and dissolved in 1mL of methyl methacrylate, the mixture is stirred at room temperature for 30min, azodiisobutyronitrile initiator accounting for 0.5 percent of the weight of vinylene carbonate is added, and the mixture is continuously stirred at room temperature for 1h to obtain uniform polymer electrolyte precursor solution;

seventhly, absorbing the polymer electrolyte precursor liquid to drop on the surface of the porous positive pole piece, so that the ratio of the volume of the polymer electrolyte precursor liquid to the loading capacity of the porous positive pole active substance is 1 mu L/mg; and standing at room temperature for 30min, placing the porous anode dripped with the polymer electrolyte precursor solution on a heating table at 70 ℃, and heating in a glove box filled with argon for 1h to obtain the composite anode for the solid-state lithium battery.

The solid-state lithium battery assembled by using the composite positive electrode for a solid-state lithium battery prepared in this example 4 includes the following specific steps:

firstly, compounding polyvinylidene fluoride, lithium aluminum titanium phosphate and lithium salt, wherein the specific compounding method comprises the following steps:

(1) dispersing lithium titanium aluminum phosphate particles in an N, N-dimethylformamide solvent, and performing ultrasonic dispersion to form homogeneous lithium titanium aluminum phosphate particle dispersion liquid;

(2) weighing polyvinylidene fluoride accounting for 40% of the mass of the lithium aluminum titanium phosphate and lithium bis (trifluoromethanesulfonyl) imide accounting for 60% of the mass of the polyvinylidene fluoride, sequentially dissolving the polyvinylidene fluoride and the lithium bis (trifluoromethanesulfonyl) imide in an N, N-dimethylformamide solvent, and uniformly stirring to form a polymer solution with the polymer concentration of 0.20 g/mL;

(3) adding the lithium aluminum titanium phosphate particle dispersion liquid into the polymer solution, and uniformly stirring to obtain a composite solid electrolyte solution;

(4) uniformly blade-coating the composite solid electrolyte solution on a flat substrate, and vacuum-drying at 80 ℃ for 48h to obtain a composite solid electrolyte film; then placing the composite solid electrolyte film in 1M LiPF₆Soaking the EC/DMC electrolyte (EC/DMC is 1: 1) for 10min, and sucking the electrolyte with dust-free paper to obtain a solid electrolyte film;

and secondly, stacking the composite anode for the solid lithium battery, the solid electrolyte film and the metal lithium cathode prepared in the embodiment 4 in sequence, packaging the stacked composite anode in a button-type battery shell, and heating the obtained product at 70 ℃ for 1 hour to obtain the solid lithium battery.

The battery is subjected to a constant current charge-discharge cycle test (1C: 170mAh/g) in a voltage range of 2.8-4.3V by a NEWARE CT-4008T-5V10mA-164 multichannel battery tester, and the test temperature is room temperature.

Fig. 19 shows the 0.1C room temperature cycle performance and the corresponding voltage curve of the solid-state lithium battery in example 4 in the voltage range of 2.8 to 4.3V. The loading of the active material is 2mg/cm²The solid-state lithium battery assembled by the composite anode has the first circle of discharge specific capacity of 151.5mAh/g, still has the discharge specific capacity of 103.5mAh/g after 50 circles of circulation, and has better circulation stability.