A novel one-step method for the preparation of flexible self-supporting electrodes

Abstract

The present application relates to a kind of novel one-step method for preparing flexible self-supporting electrode, and the technical field is electrochemistry field.The method includes: preparing mixed binder for the preparation of flexible self-supporting electrode;Mixed binder is mixed with a certain proportion with conductive agent and active material and is mixed and beaten, and active material slurry is prepared;Slurry is coated on glass plate, and flexible electrode with self-supporting structure is obtained after heat drying, and the electrode is pretreated by electrolyte solvent before use, and the porous structure of electrode is constructed, and the electrode has strong flexibility and electrochemical performance.

Description

TECHNICAL FIELD

[0001] The application relates to a novel one-step method for preparing a flexible self-supporting electrode, and belongs to the field of electrochemistry. BACKGROUND

[0002] Lithium ion batteries (LIBs) are one of the most promising conversion and energy storage devices due to their low cost, long cycle life, and high energy density. The latest development of LIBs is the development of flexible LIBs, which need to be foldable, lightweight, stretchable, and implantable compared with traditional LIBs due to the demand for portable and wearable electronic devices. The loading amount of active materials and the amount of electrolyte leakage are also key factors affecting the performance of flexible lithium ion batteries. Reliable electrode materials need reasonable electrolyte, separator, and packaging materials to match. How to efficiently mass-produce flexible LIBs to reduce their cost is the key. In recent years, great efforts have been made to solve these problems; however, the development of flexible LIBs is still in its infancy.

[0003] Currently, there are mainly two ways to study flexible batteries, 1. using a flexible current collector to coat active materials on a flexible base to realize the flexibility of the electrode, mainly including coating on a flexible skeleton such as carbon cloth, carbon fiber copper mesh, etc.; 2. in-situ composite preparation of flexible electrodes, mainly mixing active materials with CNT, GO, electrospun carbon fiber, etc. with strong flexible collective materials to prepare flexible electrodes. Method 1 is similar to traditional coating, and the energy density is sacrificed compared with method 2. In method 2, the active material content is low, the electrode material preparation technology is complex, and it has selectivity to electrode materials, and cannot realize the universality of the method.

[0004] Based on this, the application reports a method for preparing a flexible self-supporting electrode which is universal to current commercial materials, using a mixed binder which has both rigid skeleton and flexible segment, even in the case of a high active material ratio, the construction of a flexible self-supporting structure can still be realized.

[0005] The innovation utilizes the instability of the flexible segment in the electrolyte environment to form a large number of pores on the surface of the active material, which is beneficial to the effective contact of the electrolyte and the active material, and further improves the charge transfer between the active materials. The prepared flexible positive electrode has excellent cycle stability and rate performance, and shows great application potential in flexible lithium ion batteries. SUMMARY

[0006] In view of the problems existing in the prior art preparation technology, the application aims to provide a novel one-step method for preparing a flexible self-supporting electrode. The flexible electrode preparation method is simple and easy to implement.

[0007] In the present application, a preparation method of a flexible self-supporting electrode is provided, which comprises: mixing a new type of mixed binder with a conductive agent and an active material in a certain proportion and distributing them in a solvent; adjusting the proportion of each component and the solid content of the slurry, and fully stirring to ensure the uniformity of the slurry; uniformly coating the prepared slurry on a glass plate according to a certain thickness; and performing heat drying on the coated sample, and then cleaning it using an electrolyte solvent to obtain a flexible self-supporting electrode.

[0008] Preferably, the new type of mixed binder is a PAN / TPU, PAN / PVDF, PAN / PEO or the like mixed binder, and the proportion between the mixed binders is 10:0-0:10.

[0009] Preferably, the solvent used for dispersion is an organic solvent such as DMF, NMP, hydrazine hydrate or the like.

[0010] Preferably, the active material is a positive electrode powder that can be used in a lithium ion battery, and a negative electrode powder material that can be used in a lithium ion battery.

[0011] Preferably, the heat drying method of the sample comprises vacuum heat drying, air blowing drying, natural drying or the like.

[0012] Preferably, the conductive agent material comprises super p, carbon black, KB, CNT, CNF or the like high-activity conductive material.

[0013] Preferably, the electrolyte solvent can comprise an organic solvent such as DME, DMC, EMC, EC or the like.

[0014] Preferably, the heat drying stability is 50-80℃ for the volatilization temperature of the organic solvent.

[0015] Preferably, the coating thickness can be controlled by controlling the solid content of the slurry and the thickness of the scraper used for coating, and the thickness range is 50-300μm.

[0016] The method of the present application is simple and easy to implement. According to the preparation method of the present application, the preparation method of the flexible self-supporting electrode does not need to use additional current collector material, and a mixed binder with a rigid skeleton and a flexible unit is used to prepare an electrode with a flexible self-supporting structure. The electrode active material is uniformly dispersed in the conductive skeleton, which guarantees the electrochemical reaction kinetics of the electrode, and the flexible conductive matrix can relieve the volume effect in the electrochemical process, which is beneficial to maintaining the stability of the electrode structure. The electrode shows high discharge capacity, stable cycle performance, high energy density and high mechanical performance. BRIEF DESCRIPTION OF DRAWINGS

[0017] The preferred embodiments of the present application will be described below with reference to the accompanying drawings, in which:

[0018] Figure 1 Bending digital photo of flexible self-supporting electrode

[0019] Figure 2 Internal porous structure diagram of flexible self-supporting electrode

[0020] Figure 3 Cycle performance diagram of flexible self-supporting electrode at 0.2C current density DETAILED DESCRIPTION

[0021] The present application will be further described below in conjunction with the accompanying drawings and the following detailed description. It should be understood that the following embodiments and / or drawings are merely used to illustrate the present application, but not to limit the present application.

[0022] The above inventive objectives of the present application are preferably achieved by the following technical solutions:

[0023] a) mixing and distributing the active material, the conductive agent and the new mixed binder in a certain proportion in DMF solvent to prepare a coating electrode slurry.

[0024] b) uniformly coating the prepared slurry on a glass plate according to a certain thickness.

[0025] c) heat drying the coated sample, and then cleaning with an electrolyte solvent.

[0026] As preferred, the new mixed binder in step a) can be a mixed binder of PAN / TPU, PAN / PVDF, PAN / PEO, etc., and the proportion between the mixed binders is 10:1-1:1.

[0027] As preferred, the solvent used for dispersion in step a) is an organic solvent such as DMF, NMP, hydrazine hydrate, etc.

[0028] As preferred, the active material in step a) is a positive electrode powder that can be used for lithium ion batteries, and a negative electrode powder material that can be used for lithium ion batteries.

[0029] As preferred, the mass ratio of the electrode active material to the conductive agent and the mixed binder in step a) is 1:1-9:1.

[0030] As preferred, the conductive agent material in step a) includes high-activity conductive materials such as super p, carbon black, KB, CNT, CNF, etc.

[0031] As preferred, the coating thickness in step b) can be controlled by controlling the solid content of the slurry and the thickness of the coating scraper, and the thickness range is 50-300 μm.

[0032] Preferably, the heat drying in step c) is stabilized at an organic solvent evaporation temperature of 50-80°C.

[0033] Preferably, the electrolyte solvent in step c) includes organic solvents such as DME, DMC, EMC, and EC.

[0034] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific active materials, conductive agents, types of mixed binders, solid content of the slurry, and coating thicknesses in the following examples are merely examples within a suitable range; that is, those skilled in the art can select from the suitable range described herein, and are not intended to be limited to the specific values ​​in the examples below.

[0035] Example 1

[0036] 1) Using PAN / TPU as the mixed adhesive, with a ratio of PAN:TPU = 8:2 and DMF as the solvent, the mixture was magnetically stirred at room temperature for 12 hours to obtain 10 wt% P8T2 adhesive.

[0037] 2) Commercially available NCM523 electrode material was used as the active material (AM) for mixing. The material was dispersed in DMF solution at a mass ratio of AM:P8T2:KB:CNF = 89:7:2:2 and magnetically stirred for 24 hours to prepare the electrode slurry.

[0038] 3) The active material slurry is coated onto ordinary glass, and the DMF solvent is dried to prepare a flexible self-supporting electrode, such as... Figure 1 .

[0039] 4) Immerse the flexible self-supporting electrode in DMC solvent to remove free TPU and form a porous structure, ensuring electrolyte wetting. Figure 2 .

[0040] The obtained electrode film was cut into circular pieces with a diameter of 10 mm. Using the cut electrode pieces as the positive electrode, a lithium metal sheet as the negative electrode, a polypropylene microporous membrane (Celgard 2400) as the separator, and a 1 M LiPF6 EC / DEC / DMC solution (volume ratio 1:1:1) as the electrolyte, a coin cell was assembled. Its electrochemical performance was tested, and the charge-discharge cycle performance was as follows: Figure 3 The first reversible specific capacity is 149.26 mAh g. -1 After 100 cycles, the discharge specific capacity is 148.98 mAh g. -1 It has a reversible capacity retention rate of 99.81% and good cycle stability.

[0041] Example 2

[0042] 1) PAN / TPU as mixed binder, ratio of PAN:TPU=8:2, solvent of DMF, magnetic stirring for 12 hours at room temperature, 10wt% of P8T2 binder was obtained.

[0043] 2) Commercialized LCO electrode material as active material (AM) was mixed. AM: P8T2: KB: CNF=89:7:2:2 in mass ratio, the material was dispersed into DMF solution, magnetic stirring for 24 hours, electrode slurry was prepared.

[0044] 3) The active material slurry was coated on ordinary glass, and the DMF solvent was dried to prepare a flexible self-supporting electrode.

[0045] 4) The flexible self-supporting electrode was placed in DMC solvent for soaking, and free TPU was removed to form a porous structure to ensure electrolyte infiltration.

[0046] Example 3

[0047] 1) PAN / TPU as mixed binder, ratio of PAN:TPU=8:2, solvent of DMF, magnetic stirring for 12 hours at room temperature, 10wt% of P8T2 binder was obtained.

[0048] 2) Commercialized MCMB electrode material as active material (AM) was mixed. AM: P8T2: KB: CNF=89:7:2:2 in mass ratio, the material was dispersed into DMF solution, magnetic stirring for 24 hours, electrode slurry was prepared.

[0049] 3) The active material slurry was coated on ordinary glass, and the DMF solvent was dried to prepare a flexible self-supporting electrode.

[0050] 4) The flexible self-supporting electrode was placed in DMC solvent for soaking, and free TPU was removed to form a porous structure to ensure electrolyte infiltration.

[0051] Example 4

[0052] 1) PAN / TPU as mixed binder, ratio of PAN:PVDF=8:2, solvent of DMF, magnetic stirring for 12 hours at room temperature, 10wt% of P8V2 binder was obtained.

[0053] 2) Commercialized LCO electrode material as active material (AM) was mixed. AM: P8V2: KB: CNF=89:7:2:2 in mass ratio, the material was dispersed into DMF solution, magnetic stirring for 24 hours, electrode slurry was prepared.

[0054] 3) The active material slurry is coated on common glass, and the DMF solvent is dried to prepare a flexible self-supporting electrode.

[0055] 4) The flexible self-supporting electrode is placed in a DMC solvent for soaking, and free TPU is removed to form a porous structure, so that the electrolyte is infiltrated.

[0056] Finally, it should be noted that the above examples are only used to further illustrate the present application, and cannot be understood as limiting the scope of protection of the present application. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present application are within the scope of protection of the present application.

Claims

1. A method for fabricating a flexible self-supporting electrode in one step, characterized in that, include: The mixed binder is mixed with conductive agent and electrode active material in a certain proportion and distributed in solvent; Adjust the proportions of each component and the solid content of the slurry, and stir thoroughly to ensure the homogeneity of the slurry; The prepared slurry is evenly coated onto a glass plate to a certain thickness. The coated sample is heat-dried and then cleaned with an electrolyte solvent. The mixed adhesive is PAN / TPU, and the ratio of PAN to TPU in the mixed adhesive is 10:1 to 1:1; The solvent is any one of DMF, NMP, and hydrazine hydrate; The active material is a positive electrode powder used in lithium-ion batteries, or a negative electrode powder material used in lithium-ion batteries. The heat drying method includes any one of vacuum heat drying, forced air drying, and natural drying. The electrolyte solvent includes DMC.

2. The method according to claim 1, characterized in that, The mass ratio of the electrode active material to the conductive agent and the mixed binder is 1:1 to 9:

1.

3. The method according to claim 1, characterized in that, The conductive agent includes one or more of the highly active conductive materials selected from super p, KB, CNT, and CNF.

4. The method according to claim 1, characterized in that, The conductive agent includes carbon black.

5. The method according to claim 1, characterized in that, The coating thickness is controlled by adjusting the solid content of the slurry and the thickness of the doctor blade used for coating, and the coating thickness ranges from 50 to 300 μm.

6. The method according to claim 1, characterized in that, The heat drying stability is at the organic solvent evaporation temperature of 50-80 ℃.

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