Stretchable current collector, preparation method thereof and application of stretchable current collector in omnidirectional stretchable zinc-manganese microbattery

Abstract

The invention discloses a stretchable current collector, a preparation method thereof and an application of the stretchable current collector in an omnidirectional stretchable zinc-manganese microbattery, and the stretchable current collector is prepared by compounding a conductive composite filler and an elastic polymer to prepare a high-modulus conductive nano-material, and then laser engraving a snake-shaped interdigital pattern on the surface of the conductive nano-material. By compounding the modulus-enhanced snakelike interdigital pattern with the soft substrate rubber, a certain modulus gradient is formed at an interface, the deformation resistance of the current collector is enhanced, the strain can be buffered in any stretching direction through the backing-off motion of the snakelike wire and a modulus-regulated strain redistribution mechanism, and the high deformability is achieved. According to the current collector, high loading capacity of an active material can be achieved, a stretchable micro battery with excellent stretchability and excellent electrochemical performance is prepared, stretching at any angle in a two-dimensional plane can be achieved, the current collector can still be tightly attached to the skin in the movement process of a human body, and the current collector has remarkable advantages in the aspect of long-term wearing and using.

Description

Technical Field

[0001] The present invention belongs to the field of flexible electronic technology, and particularly relates to a stretchable current collector, a preparation method thereof, and an application in an omnidirectionally stretchable zinc-manganese microbattery. Background Art

[0002] With the rapid development of wearable electronic devices towards the directions of being thin, light, flexible and intelligent, and their extensive applications in the fields of medical monitoring, motion sensing, human-computer interaction, etc., higher requirements are put forward for the mechanical adaptability and electrochemical performance of micro energy storage devices. Flexible microbatteries, with their miniaturization characteristics, high energy density and easy integration, are regarded as one of the most potential power supply devices. The core structure of a flexible microbattery usually consists of key components such as a flexible current collector, electrode active materials, an electrolyte and a packaging layer. According to the different arrangements of the components, flexible microbatteries are mainly divided into two structures: the laminated structure and the planar structure. The laminated structure is difficult to be efficiently integrated with flexible electronic devices due to its large size and poor mechanical flexibility. While the planar structure, with the positive and negative electrodes arranged in parallel, not only reduces the risk of short circuit, but also improves the integration safety, and is more suitable for the design of flexible microbatteries. When constructing a new type of microbattery, the flexible current collector plays a crucial role: it not only needs to conduct electrons efficiently, but also maintain stable electrochemical performance under mechanical deformation conditions.

[0003] Currently, commercially available batteries generally use aluminum foil or copper foil as the current collector. The inherent rigidity characteristics of these traditional metal materials severely restrict the deformability of the battery and are difficult to meet the requirements of flexible electronic devices. In response to this technical bottleneck, researchers have proposed a variety of innovative solutions, but each has its limitations, and most flexible batteries focus on the research in a single stretching direction, having excellent energy storage performance in a specific stretching direction, but the energy storage performance of the battery may rapidly decay and deteriorate in other stretching directions.

[0004] Patent CN 116053611 A uses 3D printing technology to precisely deposit the positive and negative electrode inks according to a preset serpentine curve pattern by extrusion printing, and combines the lamination process to assemble the battery. The assembled battery can be stably charged and discharged at a current density of 0.1 to 2.0 A g -1 and has good rate performance. Although this method realizes the patterned design of the electrode structure and enables the battery to have certain stretching performance, it has the following deficiencies: First, the three-dimensional laminated structure limits the overall strain range of the battery; Second, during the stretching process, the electrodes and the separator are prone to relative displacement, which may lead to internal short circuit; Finally, the laminated structure is not conducive to the integrated design of the battery and is difficult to be effectively compatible with flexible electronic devices.

[0005] Patent CN 202210818724.1 proposes a method for preparing a stretchable current collector based on an SEBS elastic substrate. This method introduces conductive carbon black and carbon nanotubes as conductive fillers, uses a solution casting process to prepare a flexible current collector, and optimizes the deformation performance by regulating the parameters of the electrode paste. Although this method improves the mechanical properties of the current collector, there are still obvious defects: the carbon-based current collector prepared with carbon materials as fillers exhibits low conductivity, which easily leads to excessive overpotential of the battery during charge and discharge, affecting the specific capacity of the battery; at the same time, under large mechanical strain conditions, the microstructure of the current collector is easily damaged, and the resistance increases significantly, resulting in rapid decay of battery performance.

[0006] Patent CN 111477838 A uses electrospinning technology to uniformly deposit the electrode paste on a stretchable current collector, significantly improving the interfacial bonding strength. Tests show that the battery assembled with this current collector can achieve a capacity retention rate of over 70% after 100 stretching-release cycles under 50% strain conditions. However, this method still has two key limitations: firstly, the strain range of 50% is difficult to meet the requirements of long-term skin contact use of wearable devices (usually requiring a strain capacity of >100%); secondly, the strain direction of the current collector is single and cannot adapt to the multi-directional random stretching requirements in practical applications.

[0007] In summary, it is difficult for the existing technologies to simultaneously achieve the key performance indicators of high stretchability (>100% strain), high conductivity (>1000 S / cm), and multi-directional deformation ability. Therefore, it is urgent to develop a new patterned current collector design strategy through material innovation and structural optimization to ensure that secondary batteries can still maintain stable electrochemical performance under complex mechanical deformation conditions and provide a reliable energy solution for the next generation of flexible electronic devices. Summary of the Invention

[0008] The purpose of this section is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this section, the abstract, and the title, and such simplifications or omissions shall not be used to limit the scope of the present invention.

[0009] In view of the above and / or problems existing in the prior art, the present invention is proposed.

[0010] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a stretchable current collector.

[0011] To solve the above technical problems, the present invention provides the following technical solutions: including,

[0012] The carbon-based conductive nano-fillers are dispersed in the elastic polymer solution I to obtain the mixed slurry I, which is scrape-coated onto the glass surface treated with oxygen plasma and dried to form a stretchable conductive nano-layer;

[0013] The metal nano-wire fillers and the elastomer particles are dispersed in the organic solvent to obtain the mixed slurry II, which is sprayed onto the surface of the stretchable conductive nano-layer. Through the interfacial action of the carbon-based conductive nano-materials and the metal nano-wire fillers and the elastic polymer, a conductive composite nano-layer with a high Young's modulus is obtained;

[0014] A serpentine interdigital pattern is engraved on the surface of the conductive composite nano-layer with a high Young's modulus by laser processing, and then the elastic polymer solution II is spin-coated to form a low-modulus stretchable base layer embedded therein, thus obtaining a micro-battery current collector with omnidirectional stretchability.

[0015] As a preferred embodiment of the preparation method of the stretchable current collector described in the present invention, wherein: the elastic polymer solution I is obtained by dissolving the elastic polymer in the organic solvent, wherein the elastic polymer includes one or more of styrene thermoplastic elastomer, polydimethylsiloxane, and polyurethane, and the concentration is 10-30 wt%.

[0016] As a preferred embodiment of the preparation method of the stretchable current collector described in the present invention, wherein: the mass fraction of the carbon-based conductive nano-fillers in the mixed slurry I is 15%-25%, wherein the carbon-based conductive nano-fillers include one or more of carbon nanotubes (MWCNTs), carbon black (Super P), and graphene.

[0017] As a preferred embodiment of the preparation method of the stretchable current collector described in the present invention, wherein: the drying temperature after the mixed slurry I is scrape-coated is 60-80 °C, the time is 20-40 min, and the thickness of the formed stretchable conductive nano-layer is 40-60 μm.

[0018] As a preferred embodiment of the preparation method of the stretchable current collector described in the present invention, wherein: the metal nano-wire fillers include one or more of gold nano-wires (AuNWs), copper nano-wires (CuNWs), and silver nano-wires (AgNWs), and the elastomer particles include one or more of styrene thermoplastic elastomer, polydimethylsiloxane, and polyurethane.

[0019] As a preferred embodiment of the preparation method of the stretchable current collector described in the present invention, wherein: the concentration of the metal nano-wire fillers in the mixed slurry II is 2 mg / ml, and the concentration of the elastomer particles is 1 mg / ml.

[0020] As a preferred scheme of the preparation method of the stretchable current collector described in the present invention, the gas pressure of the spraying is 0.1-0.2 MPa, the distance between the lower end of the nozzle and the surface of the carbon-based material layer is 8-12 cm, the liquid feeding speed is 1-4 mm / min, and the thickness of the highly conductive composite nanolayer formed by spraying is 10-20 μm.

[0021] As a preferred solution of the method for preparing a microbattery current collector with omnidirectional stretchability described in the present invention, the laser processing is performed by a 1064nm infrared laser marking device, and selective ablation is performed according to the designed snake-shaped interdigitated pattern.

[0022] Another object of the present invention is to provide a stretchable current collector.

[0023] In order to solve the above technical problems, the present invention provides the following technical solutions: comprising:

[0024] The structure of the stretchable current collector from bottom to top is:

[0025] A high modulus conductive composite nanolayer engraved with a snake-like interdigitated pattern and a low modulus stretchable substrate layer embedded therein. The modulus difference between the snake-like interdigitated pattern and the flexible substrate results in an inhomogeneous local modulus distribution during the subsequent stretching process. The strain is concentrated in the soft rubber substrate. Combined with the orderly expansion of the structure when the snake-like conductor is stretched, the stretchable current collector with a heterogeneous structure can bear deformation in any direction.

[0026] The serpentine interdigitated pattern is designed as 4 to 6 interlaced serpentine wires, the width of the interdigitated fingers is 500 to 1000 μm, and the ratio of the interdigitated distance to the interdigitated fingers is 1:1 to 4:1.

[0027] Another object of the present invention is to provide an omnidirectionally stretchable zinc-manganese microbattery.

[0028] In order to solve the above technical problems, the present invention provides the following technical solution: comprising a positive electrode and a negative electrode,

[0029] Wherein, the positive electrode and / or the negative electrode is made of the microbattery current collector-loaded active material with omnidirectional stretchability as claimed in claim 9, and further comprises:

[0030] an electrolyte layer formed of a gel electrolyte applied by blade coating to the surfaces of the positive electrode and the negative electrode; and,

[0031] The encapsulation layer is formed of an acrylic elastomer encapsulated outside the electrolyte layer.

[0032] Beneficial effects of the present invention:

[0033] (1) By introducing carbon nanotubes and silver nanowires to construct a composite conductive nanomaterial for the current collector, high conductivity and a wide electrochemical window are ensured, which can be adapted to a variety of electrochemical reaction systems. Moreover, the filling of the composite conductive nanomaterial can enhance the modulus of the elastic polymer, exerting a strong mechanical constraint on the interdigital structure current collector and enhancing the mechanical stability against deformation.

[0034] (2) The current collector material components are prepared from the same type of polymer elastomer, significantly improving the interfacial bonding strength and effectively suppressing the interlayer desorption phenomenon under mechanical stress, thereby enhancing the overall stability of the current collector and the battery.

[0035] (3) The current collector is designed based on a coplanar structure and a serpentine pattern, which can reduce the local strain of the electrode during the stretching process, significantly reducing the failure risk such as electrode layer peeling, and effectively improving the loading amount and energy density of the microbattery electrode material.

[0036] (4) The microbattery constructed with the omnidirectionally stretchable microbattery current collector prepared by the present invention has excellent electrochemical performance under deformation in any direction through a unique serpentine structure design and modulus gradient regulation. The strain is concentrated in the spacer rubber where no electrochemical reaction occurs through the inhomogeneous modulus distribution, and the strain is buffered through the extension of the serpentine wire structure and the opening of the arc, so that the microbattery with an isomeric pattern design can have stable electrochemical performance under strain in any direction, greatly promoting the development of stretchable batteries and overcoming the defect that existing stretchable microbatteries are usually limited to single-direction stretching. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. Among them:

[0038] Figure 1 It is a schematic diagram of the omnidirectionally stretchable microbattery current collector in Embodiment 1 of the present invention.

[0039] Figure 2 It is the resistance value of the double-layer composite material in different stretching ranges in Embodiment 1 of the present invention.

[0040] Figure 3 It is the stress-strain curve of the stretchable microelectrode assembly in Embodiment 1 of the present invention.

[0041] Figure 4 It is a comparison diagram of the local strain of the interdigital electrode with modulus regulation in Embodiment 1 of the present invention.

[0042] Figure 5 These are the constant current charge-discharge curves of the stretchable zinc-manganese battery in Example 1 of the present invention at different current densities.

[0043] Figure 6 These are the constant current charge-discharge curves of Example 1 of the present invention under different stretching states, with the stretching direction along the x-axis.

[0044] Figure 7 These are the constant current charge-discharge curves of Example 1 of the present invention under different stretching states, with the stretching direction along the y-axis.

[0045] Figure 8 This is the display diagram of the stretching angle of the microelectrode in Example 1 of the present invention.

[0046] Figure 9 These are the constant current charge-discharge curves and capacity retention rates of the microbattery in Example 1 of the present invention at different stretching angles.

[0047] Figure 10 This is the display diagram of lighting the LED lamp array at different stretching angles in Example 1 of the present invention.

[0048] Figure 11 These are the local strains of different parts of the stretchable microelectrode under different stretching states in Comparative Example 2 of the present invention.

[0049] Figure 12 This is a schematic diagram of the traditional parallel straight line interleaved pattern. Detailed implementation manners

[0050] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following detailed description of the specific implementation manners of the present invention is provided in conjunction with the embodiments of the specification.

[0051] In the following description, many specific details are set forth to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0052] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that can be included in at least one implementation manner of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that mutually excludes other embodiments.

[0053] Unless otherwise specified, the raw materials used in the present invention are all commonly available in the market for ordinary use in the art.

[0054] The elastic polymer used in the specific embodiments of the present invention is styrene thermoplastic elastomer (SEBS), which is from Asahi Kasei Corporation, with a Young's modulus of 1.3 Mpa and an elongation at break of 900%.

[0055] The silver nanowires (AgNWs) used in the present invention were synthesized with reference to the literature "Investigation on the Preparation of Silver Nanowires by Alcohol Reduction Method and Their Growth Mechanism", in which the molar ratio of PVP to AgNO3 is 6:1 and the length is 60 microns.

[0056] Example 1

[0057] This example provides a micro-battery current collector with omnidirectional stretchability. Specifically:

[0058] 1) SEBS rubber particles were dissolved in toluene at a mass ratio of 1:4 to form a homogeneous solution, which was placed on a magnetic stirrer and heated and stirred at 50 °C until the rubber was completely dissolved to obtain an elastic polymer solution I (20 wt% SEBS solution) with a concentration of 20 wt%;

[0059] Carbon nanotubes (MWCNTs) were mixed with the 20 wt% SEBS solution and mechanically stirred evenly at a speed of 2000 rpm to obtain a mixed slurry I (MWCNTs / SEBS slurry) with a carbon nanotube content of 15%;

[0060] The MWCNTs / SEBS slurry was scrape-coated onto the glass surface treated with oxygen plasma and placed on a heating table at 80 °C to be heated and dried for 30 min to volatilize the solvent to form a MWCNTs / SEBS layer, that is, a stretchable conductive nano-layer with a thickness of 50 μm.

[0061] 2) Silver nanowires (AgNWs) and SEBS rubber particles were dispersed in chloroform at a mass ratio of 2:1 to obtain a mixed slurry II (AgNWs / SEBS slurry) with a silver nanowire concentration of 2 mg / ml;

[0062] The AgNWs / SEBS was sprayed onto the surface of the MWCNTs / SEBS layer, the air pressure was set at 0.1 MPa, the distance between the bottom of the nozzle and the surface of the MWCNTs / SEBS layer was 12 cm, the liquid supply speed was 2 mm / min, and the drying temperature was 60 °C to form an AgNWs layer, that is, a highly conductive composite nano-layer with a thickness of 12 μm.

[0063] 3) According to Figure 1 The designed pattern was used to perform laser engraving processing on the highly conductive composite current collector layer. Figure 1The middle serpentine interdigital pattern is designed with 6 mutually interleaved serpentine wires. The width of the interdigital fingers is 1000μm, and the finger spacing is set at 1200μm to isolate the electron transfer between the positive and negative electrodes. The width ratio is 1:1.2. Laser processing uses a 1064nm laser engraving machine. The power of the laser engraving machine is 35%, and the number of times is 15 times, and it is selectively ablated into a serpentine interdigital pattern.

[0064] Subsequently, a 20wt% SEBS solution was spin-coated, and after natural drying for 6h, the serpentine interdigital current collector of this example was obtained, that is, a micro-battery current collector with omnidirectional stretchability. The prepared interdigital current collector was peeled off from the glass, flipped, and pasted onto another glass plate for standby.

[0065] Tensile property test

[0066] A Keithley digital multimeter was used to measure the resistance of the double-layer composite current collector, and the four-probe method was used to reduce the influence of contact resistance on the test results.

[0067] Figure 2 This is a schematic diagram of the resistance change of the current collector prepared in this example during stretching in the strain range of 0% to 100%. It can be seen that the initial sheet resistance of the conductive current collector is 0.08Ω / sq., and the sheet resistance is 7.2Ω / sq. when the strain is stretched to 100%.

[0068] Figure 3 To test the stress-strain curve of the stretchable electrode using a universal tensile testing machine, the results show that the Young's modulus of the single flexible SEBS substrate is only 1.3MPa. After being enhanced by carbon nanotubes and silver nanowire fillers, the Young's modulus of the double-layer composite current collector reaches 61.1Mpa. The 47-fold modulus difference forms a discontinuous modulus gradient at the interface, which helps to enhance the ability of the current collector to resist external deformation.

[0069] As Figure 4 shown, when the macroscopic strain applied to the serpentine interdigital current collector reaches 200%, the actual strain borne by the interdigital current collector is only 64%. The strain is concentrated in the soft elastic substrate, and the strain gap indicates the effective implementation of the strain redistribution mechanism of modulus regulation.

[0070] Example 2

[0071] This example provides a stretchable zinc-manganese battery applying the stretchable current collector of Example 1. Specifically:

[0072] 1) Preparation of stretchable electrodes loaded with positive and negative electrode materials

[0073] 350mg of α-MnO2, 100mg of carbon black, and 50mg of PVDF were added to 1ml of N,N-dimethylformamide (DMF) to prepare a positive electrode slurry;

[0074] The positive electrode slurry was blade-coated onto the surface of the stretchable current collector using the template printing method, and after sufficient drying, a stretchable positive electrode was obtained with a loading amount of 18.91 mg cm -2 .

[0075] Zinc powder and SEBS were added to toluene at a mass ratio of 30:1 to obtain the negative electrode slurry;

[0076] The negative electrode slurry was blade-coated onto the surface of the stretchable current collector using the template printing method to obtain Zn / SEBS. Subsequently, metallic zinc was deposited onto the surface of Zn / SEBS by a three-electrode constant current method to prepare a stretchable negative electrode.

[0077] 2) Preparation of the stretchable zinc-manganese microbattery

[0078] An aqueous solution with a solute concentration of 10 wt% trifluoroacetamide, 2 M ZnSO4, and 0.1 M MnSO4 was prepared, and 0.1 wt% xanthan gum was added. The solvent was deionized water, and after complete dissolution, a gel electrolyte was obtained;

[0079] The gel electrolyte was blade-coated onto the surfaces of the Zn negative electrode and the MnO2 positive electrode using a spatula, and then encapsulated with an acrylic elastomer. Finally, a stretchable Zn-MnO2 microbattery was obtained

[0080] Figure 5 For the prepared intrinsically stretchable microbattery, the constant current charge-discharge curves at 0.5 - 5 mA cm -2 current density are shown. It can be found that when the current density increases, there is a slight decrease in the discharge plateau, which is considered to be due to the increase in polarization and the slowdown of the diffusion rate of Zn 2+ in MnO 2 . At a current density of 0.5 mA cm -2 , the microbattery capacity is as high as 1.5 mAh cm -2 . Even at current densities as high as 4 mA cm -2 and 5 mA cm -2 , the microbattery still maintains a discharge capacity of 0.35 mAh cm -2 and 0.32 mAh cm -2 . The excellent discharge capacity of the microbattery at different current densities indicates that the battery has excellent power supply capabilities and rate performance.

[0081] As Figure 6 shown, the constant current charge-discharge test of the microbattery was carried out at a current density of 3 mA cm -2 . The charge-discharge voltage plateau was set to 0.8 - 1.8 V, and the initial areal specific capacity was 0.52 mAh cm -2, the direction along the interdigital electrodes is defined as the x-axis. In the x-direction, the zinc-manganese microbattery effectively absorbs strain through the extension of the serpentine wire structure and the opening of the arc. When the tensile range in the x-direction reaches 200%, it still has a capacity of 0.41 mAh cm -2 and has a capacity retention rate of up to 80%.

[0082] As Figure 7 shown, the direction orthogonal to the x-axis is defined as the y-direction. In the y-direction, the microbattery concentrates the strain at the spacing rubber where no electrochemical reaction occurs through the modulus gradient difference, thereby protecting the electrode area. When the tensile range in the y-direction reaches 200%, it still has a capacity of 0.34 mAh cm -2 , indicating that the strain on the designed serpentine interdigital electrode is effectively regulated, and the prepared Zn-MnO₂ microbattery exhibits excellent electrochemical performance under tensile deformation.

[0083] The prepared stretchable zinc-manganese microbattery is placed on an electric sliding table to test the electrochemical energy storage performance at different stretching angles. As Figure 8 shown, the stretchable zinc-manganese microbattery is verified at stretching angles of 0°, 30°, 60°, 90° and a 100% stretching state respectively.

[0084] As Figure 9 shown, it can be found that with the change of the angle, the stretchable microbattery can be charged and discharged stably, and maintain a stable charge-discharge platform, demonstrating a good balance ability between the electrochemical performance and the stretching performance of the stretchable microbattery.

[0085] The energy supply ability of the microbattery in series integration at different stretching angles is tested. The results are as Figure 10 shown. It can stably light up the LED array, proving its excellent omnidirectional stretchability and stable and continuous power supply ability.

[0086] Example 3

[0087] The difference between this example and Example 1 is that the conductive filler carbon nanotubes are adjusted to carbon nanotubes + carbon black. Specifically, step 1) of Example 1 is adjusted as follows:

[0088] 1) SEBS rubber particles are dissolved in toluene at a mass-volume ratio of 1:4 to form a homogeneous solution, which is placed on a magnetic stirrer and heated and stirred at 50 °C until the rubber is completely dissolved to obtain an elastic polymer solution I (20 wt% SEBS solution) with a concentration of 20 wt%;

[0089] Multi-walled carbon nanotubes (MWCNTs) and carbon black were added to the elastic polymer solution at a ratio of 1:1, such that the mass fraction of the carbon-based conductive nano-fillers was 20%. The mixture was mechanically stirred at 2000 rpm for 3 h to obtain a homogeneous MWCNTs / SEBS / carbon black slurry.

[0090] The MWCNTs / SEBS / carbon black slurry was deposited on the glass surface by spraying. The air pressure was set at 0.2 MPa, the distance between the bottom of the nozzle and the elastic rubber mold was 15 cm, the liquid supply rate was 4 mm / min, and the drying method was natural drying. The cumulative deposition thickness reached 30 μm.

[0091] All other process steps were the same as in Example 1 to obtain the stretchable composite current collector of this example.

[0092] The composite current collector was tested in the tensile range of 0% to 100%. The initial sheet resistance of the conductive current collector was 0.67 Ω / sq., and the sheet resistance was 10 Ω / sq. when the strain was stretched to 100%. This indicates that the prepared composite current collector still maintains good conductivity even under a large tensile deformation of 100%, meeting the requirements of the flexible electronics field.

[0093] Example 4

[0094] The difference between this example and Example 1 is that the concentration of carbon nanotubes in the MWCNTs / SEBS slurry in step 2) was adjusted to 20% and 25% respectively. All other process steps were the same as in Example 1 to obtain the conductive composite current collector of this example.

[0095] After testing, in the tensile range of 0% to 100%, there was no phenomenon of fracture and delamination on the surface of the current collector, and the conductive path remained intact, indicating that it can be applied to the flexible electronics field.

[0096] Example 5

[0097] The difference between this example and Example 1 is that the concentration of AgNWs in the metal nanowire solution in step 5) was adjusted to 1 mg / ml -1 、3 mg / ml -1 、4 mg / ml -1 , and all other process steps were the same as in Example 1 to obtain the conductive composite current collector of this example.

[0098] After testing, in the tensile range of 0% to 100%,

[0099] When the concentration of silver nanowires was 1 mg / ml -1 , the initial resistance of the prepared composite current collector was relatively large, which was not conducive to the subsequent assembly and application of the battery.

[0100] When the concentration of silver nanowires was 3 mg / ml -1and 4 mg / ml -1 When the concentration is 4 mg / ml, the initial resistance of the prepared composite current collector is maintained at a relatively low level. After assembling the micro-battery, the battery can exhibit excellent charge and discharge platforms.

[0101] Comparative Example 1

[0102] The difference between this comparative example and Example 1 is that the width of the interdigital fingers in the serpentine pattern designed in step 6) is adjusted to 1000 microns, and the finger spacings are set to 500 microns, 800 microns, 1000 microns, and 1500 microns respectively, and the width ratios are 1:0.5, 1:0.8, 1:1, and 1:1.5 respectively, to obtain different composite current collectors in this comparative example.

[0103] Tests found that when the composite current collectors are prepared based on the ratios of 1:0.5, 1:0.8, and 1:1 and are subjected to external stress along the y-axis, the interdigital parts of the current collector are subjected to relatively serious stress concentration, and the deformation amount is relatively high, higher than the design ratio applied in Example 1. This shows that when the spacing distance of the interdigital fingers is not wide enough compared to the designed width, the buffering effect of the current collector on stress during deformation is not obvious. And the interdigital parts of the serpentine interdigital current collector are responsible for loading the active material to prepare the positive and negative electrodes. Therefore, when the interdigital parts are subjected to relatively serious stress concentration, it is easy to cause the shedding of the active material, affecting the energy storage performance of the battery.

[0104] When the composite current collector is prepared based on the width ratio of 1:1.5, when the current collector is subjected to external stress, the buffering effect on stress is significantly improved, protecting the structural integrity at the interdigital part. However, the increased distance between the positive and negative electrodes increases the ion transport path and reduces the transport efficiency, resulting in a decrease in the electrochemical performance of the battery.

[0105] Comparative Example 2

[0106] The difference between this comparative example and Example 1 is that only the template printing method is used to print the serpentine interdigital pattern on the SEBS substrate, and the coating used for printing is a mixture of SEBS rubber solution (20 wt%) and an appropriate amount of organic dye indigo, that is, the serpentine interdigital pattern and the composite substrate have the same rubber modulus, and there is no modulus gradient at the interface.

[0107] The same strain is applied to the methods of Example 1 and Comparative Example 1 respectively, and the strain range is from 0% - 200%, and the responses of these two electrodes to macroscopic strain are tested. As Figure 11As shown, by analyzing the results of Example 1 and this comparative example, it can be found that when the current collector regulated by modulus is subjected to 100% external tensile strain in the y direction, the adjacent interdigital finger spacing bears 235% strain, while the current collector itself only bears 41% tensile strain. The current collector and finger spacing rubber that have not been regulated by modulus are both subjected to 100% strain, indicating that the strain of the current collector as a functional area is not buffered, showing the same stretching amount as the external tensile strain, and the strain buffering effect of the current collector that has not been regulated by modulus is not good. When the external tensile strain increases to 200%, the adjacent interdigital finger spacing bears 415% strain, while the current collector itself only bears 41% tensile strain. The current collector and finger spacing that have not been regulated by modulus have both suffered a large strain of 200%. Similarly, when external strain is applied in the x-axis direction, the serpentine interdigital current collector regulated by modulus shows a better strain absorption effect. When the active material is subsequently loaded, the ability of the current collector to buffer strain can enhance the adhesion of the active material and reduce the occurrence of delamination. Figure 11 The results show that the effective implementation of the modulus-regulated strain distribution mechanism is beneficial to enhancing the mechanical stability of the electrode. The electrode without modulus regulation exhibits poor stretchability, a greater degree of strain within the same stretching range, and no buffering effect on the macroscopic strain.

[0108] Comparative Example 3

[0109] The difference between this comparative example and Example 1 is that the pattern used for laser engraving is a traditional parallel straight line staggered pattern, the finger width is set to 1000 microns, and the finger spacing is set to 1200 microns, to obtain the linear finger collector of this comparative example.

[0110] The stretchable battery was prepared based on the linear interdigital current collector of this comparative example and the serpentine interdigital current collector of Example 1. The results showed that when the serpentine interdigital current collector was subjected to external strain along the x-axis, it buffered the strain by unwinding movement similar to a spring, protected the microstructure of the battery, and exhibited excellent electrochemical performance under mechanical deformation of 0%-200%. When the linear interdigital current collector was subjected to external stress, the battery assembly was directly subjected to tensile strain, the resistance increased significantly, and the electrochemical performance of the stretchable battery rapidly decayed and deteriorated.

[0111] In summary, the preparation method of the serpentine interdigitated composite current collector provided by the present invention introduces composite conductive nanofillers into elastic polymers to construct a high modulus composite nanoconductor with high electrical conductivity, mechanical stretchability and a wide electrochemical window.

[0112] After being processed into a serpentine interdigital structure, the nano-composite conductor is embedded in a rubber substrate and assembled to form a stretchable current collector. The excellent deformation ability of the current collector enables it to effectively buffer the mechanical deformation through the unwinding movement of the serpentine wire and the modulus gradient regulation in any direction, ensuring the structural integrity of the nano-composite conductor and maintaining the charge transport ability under macroscopic large tensile deformation conditions.

[0113] This current collector can be loaded with a high loading of electrode materials to construct a stretchable secondary battery with high energy density. The high-modulus conductive nano-composite material exerts a strong mechanical constraint on the interdigital electrodes, effectively reducing the local strain of the electrodes, enabling the electrodes to have the adaptive ability to redistribute strain, and greatly regulating the balance between the stretchable performance and the electrochemical performance of the electrode materials, thereby solving the problems of insufficient tensile deformation ability and deteriorated electrochemical performance under deformed conditions of traditional secondary batteries.

[0114] The stretchable battery prepared based on the serpentine interdigital current collector can achieve stretching at any angle in a two-dimensional plane, and can still maintain close contact with the skin during human movement, having significant advantages in long-term wearable use.

[0115] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A preparation method of a stretchable current collector, characterized in that: including Disperse carbon-based conductive nano-fillers in elastic polymer solution I to obtain mixed slurry I, scrape-coat it onto glass whose surface has been treated with oxygen plasma, and dry it to form a stretchable conductive nano-layer; Disperse metal nanowire fillers and elastomer particles in an organic solvent to obtain mixed slurry II, spray it onto the surface of the stretchable conductive nano-layer, and through the interfacial action of the carbon-based conductive nano-material and the metal nanowire fillers and the elastic polymer, obtain a conductive composite nano-layer with a high Young's modulus; Engrave a serpentine interdigital pattern on the surface of the conductive composite nano-layer with a high Young's modulus by laser processing, and then spin-coat elastic polymer solution II to form a low-modulus stretchable base layer embedded therein, thus obtaining a micro-battery current collector with omnidirectional stretchability.

2. The preparation method of the stretchable current collector according to claim 1, wherein: Elastic polymer solution I is obtained by dissolving an elastic polymer in an organic solvent. Among them, the elastic polymer includes one or more of styrene thermoplastic elastomer, polydimethylsiloxane, and polyurethane, and the concentration is 10-30 wt%.

3. The preparation method of the stretchable current collector according to claim 1 or 2, characterized in that: The mass fraction of the carbon-based conductive nano-fillers in the mixed slurry I is 15%-25%. Among them, the carbon-based conductive nano-fillers include one or more of carbon nanotubes, carbon black, and graphene.

4. The preparation method of the stretchable current collector according to claim 3, wherein: The drying temperature after the mixed slurry I is scrape-coated is 60-80 °C, the time is 20-40 min, and the thickness of the formed stretchable conductive nano-layer is 40-60 μm.

5. The preparation method of the stretchable current collector according to claim 1, 2 or 4, characterized in that: The metal nanowire fillers include one or more of gold nanowires, copper nanowires, and silver nanowires, and the elastomer particles include one or more of styrene thermoplastic elastomer, polydimethylsiloxane, and polyurethane.

6. The preparation method of the stretchable current collector according to claim 1, 2 or 4, characterized in that: The concentration of the metal nanowire fillers in the mixed slurry II is 2 mg / ml, and the concentration of the elastomer particles is 1 mg / ml.

7. The preparation method of the stretchable current collector according to claim 6, wherein: The air pressure for the spraying is 0.1-0.2 MPa, the distance between the bottom end of the nozzle and the surface of the carbon-based material layer is 8-12 cm, the liquid supply speed is 1-4 mm / min, and the thickness of the formed highly conductive composite nano-layer is 10-20 μm.

8. The preparation method of the stretchable current collector according to claim 1, 2, 4 or 7, characterized in that: The laser processing is carried out by a 1064 nm infrared laser marking device and selectively ablated according to the designed serpentine interdigital pattern.

9. The stretchable current collector prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The structure of the stretchable current collector from bottom to top is successively A high-modulus conductive composite nano-layer engraved with a serpentine interdigital pattern and a low-modulus stretchable base layer embedded therein; Among them, the serpentine interdigital pattern is designed as 4-6 mutually staggered serpentine wires, the width of the interdigital fingers is 500-1000 μm, and the ratio of the finger spacing to the interdigital fingers is 1:1-4:

1.

10. An omnidirectional stretchable zinc-manganese micro-battery, characterized in that: including a positive electrode and a negative electrode Among them, the positive electrode and / or the negative electrode is made of the micro-battery current collector with omnidirectional stretchability described in claim 9 loaded with active materials, and further includes an electrolyte layer, which is formed by scrape-coating a gel electrolyte on the surfaces of the positive electrode and the negative electrode; and A packaging layer, which is formed by an acrylic elastomer encapsulated outside the electrolyte layer.

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