Novel one-step method for preparing flexible self-supporting electrode

Abstract

The invention relates to a novel method for preparing a flexible self-supporting electrode by a one-step method, and belongs to the technical field of electrochemistry. The method comprises the following steps: preparing a mixed binder for preparing a flexible self-supporting electrode; mixing and pulping the mixed binder, a conductive agent and an active material according to a certain proportion to prepare active material slurry; a glass plate is coated with the slurry, a flexible electrode with a self-supporting structure is obtained through thermal drying, the electrode is pretreated through an electrolyte solvent before being used, an electrode porous structure is constructed, and the electrode has high flexibility and electrochemical performance.

Description

Technical Field

[0001] The invention discloses a novel one-step method for preparing a flexible self-supporting electrode, belonging to the field of electrochemistry. Background Art

[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 progress in LIBs is the development of flexible LIBs, which need to be foldable, lightweight, stretchable, and implantable due to the demand for portable and wearable electronic devices compared to traditional LIBs. The loading amount of active materials and electrolyte leakage are also key factors affecting the performance of flexible lithium-ion batteries. Reliable electrode materials require reasonable electrolytes, separators, 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] At present, there are two main methods for flexible battery research: 1. Use a flexible current collector to coat the active material on a flexible base to achieve the flexibility of the electrode, mainly including coating on flexible skeletons such as carbon cloth and carbon fiber copper mesh; 2. In-situ composite preparation of flexible electrodes, mainly mixing active materials with CNT, GO, electrospun carbon fiber and other highly flexible collective materials to prepare flexible electrodes. Method 1 is similar to traditional coating, and the energy density is somewhat lower than that of Method 2. Method 2 has a low content of active materials, complex electrode material preparation technology, and selectivity for electrode materials, which cannot achieve the universality of the method.

[0004] Based on this, the present invention reports a method for preparing flexible self-supporting electrodes that is universal to current commercial materials. By using a mixed binder having both a rigid skeleton and a flexible chain segment, the construction of a flexible self-supporting structure can be achieved even when the proportion of active substances is relatively high.

[0005] The innovative use of the instability of the flexible chain segments in the electrolyte environment will form a large number of holes on the surface of the active material, which is conducive to the effective contact between 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, showing great application potential in flexible lithium-ion batteries. Summary of the invention

[0006] In view of the problems existing in the existing preparation technology, the purpose of the present invention is to propose a new one-step method for preparing a flexible self-supporting electrode. The flexible electrode preparation method is simple and easy to implement.

[0007] Here, the present invention provides a method for preparing a flexible self-supporting electrode, comprising: using a new mixed binder to mix 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; thermally drying the coated sample, and then washing it with an electrolyte solvent to obtain a flexible self-supporting electrode.

[0008] Preferably, the novel mixed binder is a mixed binder such as PAN / TPU, PAN / PVDF, PAN / PEO, etc., and the ratio between the mixed binders is 10:0-0:10.

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

[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 method of thermal drying of the sample includes vacuum thermal drying, forced air drying, natural drying and the like.

[0012] Preferably, the conductive agent material includes highly active conductive materials such as super p, carbon black, KB, CNT, and CNF.

[0013] Preferably, the electrolyte solvent may include organic solvents such as DME, DMC, EMC, EC, etc.

[0014] Preferably, the thermal drying is stabilized at an organic solvent volatilization temperature of 50-80°C.

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

[0016] The method of the present invention is simple and easy to implement. According to the preparation method of the present invention, the method for preparing a flexible self-supporting electrode does not need to use additional current collector materials, and a mixed binder having both a rigid skeleton and a flexible element is used to prepare an electrode with a flexible self-supporting structure. The electrode active material is evenly dispersed in the conductive skeleton to ensure the electrochemical reaction kinetics of the electrode. The flexible conductive matrix can alleviate the volume effect in the electrochemical process, which is conducive to maintaining the stability of the electrode structure; the electrode shows high discharge capacity, stable cycle performance, high energy density and high mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings, in which:

[0018] Figure 1 This is a digital photo of the bending of a flexible self-supporting electrode.

[0019] Figure 2 This is the porous structure inside the flexible self-supporting electrode

[0020] Figure 3 This is the cycling performance diagram of the flexible self-supporting electrode at a current density of 0.2C. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with the accompanying drawings and the following specific embodiments. It should be understood that the following embodiments and / or drawings are only used to illustrate the present invention rather than to limit the present invention.

[0022] The above-mentioned invention object of the present invention is preferably achieved through the following technical solutions:

[0023] a) Active materials, conductive agents and novel mixed binders are mixed and distributed in a DMF solvent in a certain proportion to prepare electrode slurry for coating.

[0024] b) The prepared slurry is evenly coated on a glass plate at a certain thickness.

[0025] c) The coated sample is thermally dried and then cleaned with an electrolyte solvent.

[0026] Preferably, the novel mixed binder in step a) may be a mixed binder such as PAN / TPU, PAN / PVDF, PAN / PEO, etc., and the ratio between the mixed binders is 10:1-1:1.

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

[0028] Preferably, the active material in step a) is a positive electrode powder that can be used in a lithium ion battery, or a negative electrode powder material that can be used in a lithium ion battery.

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

[0030] Preferably, the conductive agent material in step a) includes highly active conductive materials such as super p, carbon black, KB, CNT, CNF, etc.

[0031] Preferably, the coating thickness in step b) can be adjusted by controlling the solid content of the slurry and the thickness of the scraper used for coating, and the thickness ranges from 50 to 300 μm.

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

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

[0034] The following further examples are given to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention. The following examples of specific active materials, conductive agents, types of mixed binders, solid content of slurry, coating thickness, etc. are also only examples within a suitable range, that is, those skilled in the art can choose within a suitable range according to the description of this article, and are not limited to the specific values ​​​​exemplified below.

[0035] Example 1

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

[0037] 2) The commercial NCM523 electrode material was mixed as the active material (AM). The material was dispersed in a DMF solution at a mass ratio of AM: P8T2: KB: CNF = 89: 7: 2: 2, and magnetic stirring was performed for 24 hours to prepare an electrode slurry.

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

[0039] 4) Soak the flexible self-supporting electrode in DMC solvent to remove free TPU to form a porous structure and ensure electrolyte infiltration, such as Figure 2 .

[0040] The obtained electrode film was cut into discs with a diameter of 10 mm, and button cells were assembled with the cut electrode pieces as the positive electrode, the metal lithium sheet as the negative electrode, the polypropylene microporous membrane (Celgard 2400) as the separator, and 1M LiPF6 EC / DEC / DMC (volume ratio of 1:1:1) solution as the electrolyte. The electrochemical properties of the cells were tested, and the charge and discharge cycle performance was shown in Figure 2. Figure 3 The first reversible specific capacity is 149.26 mAh g -1 After 100 cycles, the discharge capacity is 148.98 mAh g -1 The reversible capacity retention rate is 99.81%, which has good cycle stability performance.

[0041] Example 2

[0042] 1) PAN / TPU was used as a mixed binder with a ratio of PAN:TPU=8:2 and a solvent of DMF. The mixture was magnetically stirred at room temperature for 12 hours to obtain a 10 wt% P8T2 binder.

[0043] 2) Commercial LCO electrode materials were mixed as active materials (AM). The materials were 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 electrode slurry.

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

[0045] 4) The flexible self-supporting electrode is immersed in a DMC solvent to remove free TPU to form a porous structure and ensure electrolyte infiltration.

[0046] Example 3

[0047] 1) PAN / TPU was used as a mixed binder with a ratio of PAN:TPU=8:2 and a solvent of DMF. The mixture was magnetically stirred at room temperature for 12 hours to obtain a 10 wt% P8T2 binder.

[0048] 2) The commercial MCMB electrode material was mixed as the active material (AM). The material was dispersed in a DMF solution at a mass ratio of AM: P8T2: KB: CNF = 89: 7: 2: 2, and magnetically stirred for 24 hours to prepare an electrode slurry.

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

[0050] 4) The flexible self-supporting electrode is immersed in a DMC solvent to remove free TPU to form a porous structure and ensure electrolyte infiltration.

[0051] Example 4

[0052] 1) PAN / TPU was used as a mixed binder with a ratio of PAN:PVDF=8:2 and a solvent of DMF. The mixture was magnetically stirred at room temperature for 12 hours to obtain a 10 wt% P8V2 binder.

[0053] 2) Commercial LCO electrode materials were mixed as active materials (AM). The materials were dispersed in DMF solution at a mass ratio of AM: P8V2: KB: CNF = 89: 7: 2: 2, and magnetically stirred for 24 hours to prepare electrode slurry.

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

[0055] 4) The flexible self-supporting electrode is immersed in a DMC solvent to remove free TPU to form a porous structure and ensure electrolyte infiltration.

[0056] Finally, it should be noted that the above embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by technicians in this field based on the above contents of the present invention all fall within the scope of protection of the present invention.

Claims

1. A novel one-step method for preparing a flexible self-supporting electrode, characterized in that: include: A new type of mixed binder is used to mix with a conductive agent and an electrode active material in a certain proportion and distribute them in a solvent; Adjust the proportion of each component and the solid content of the slurry, and stir it thoroughly to ensure the uniformity of the slurry; The prepared slurry is evenly coated on the glass plate according to a certain thickness; The coated samples are heat dried and then cleaned with electrolyte solvent; The novel mixed binder is a mixed binder such as PAN / TPU, PAN / PVDF, PAN / PEO, etc., and the ratio between the mixed binders is 10:0-0:10; The solvent used for the dispersion is an organic solvent such as DMF, NMP, hydrazine hydrate, etc. The active material is a positive electrode powder that can be used in lithium ion batteries, and a negative electrode powder material that can be used in lithium ion batteries; The thermal drying methods of the sample include vacuum thermal drying, forced air drying, natural drying and the like.

2. The preparation 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 1:1-9:

1.

3. The preparation method according to claim 1, characterized in that: The conductive agent material includes highly active conductive materials such as super p, carbon black, KB, CNT, CNF, etc.

4. The preparation method according to claim 1, characterized in that: The prepared mixed adhesive comprises various hard segment polymers with supporting structures and polymers with flexible segment structures, and the ratio between the two is 10:0-0:

10.

5. The preparation method according to claim 1, characterized in that: The coating thickness can be adjusted by controlling the solid content of the slurry and the thickness of the scraper used for coating, and the thickness range is 50-300 μm.

6. The preparation method according to claim 1, characterized in that: The thermal drying is stable at the organic solvent volatilization temperature of 50-80°C.

7. The preparation method according to claim 1, characterized in that: The electrolyte solvent includes organic solvents such as DME, DMC, EMC, EC, etc.

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