Preparation method of electrode, electrode and metal-based flow battery

Abstract

The invention relates to a preparation method of an electrode, the electrode and a metal-based flow battery. The preparation method of the electrode comprises the following steps: S100, cleaning and drying a carbon felt; s200, preparing an MXene colloidal solution; and S300, loading the MXene colloid on the surface of the carbon felt in situ by adopting an electrochemical deposition method to form the MXene-coated CF composite electrode. Through the arrangement, the high-zinc-ion-concentration IHP layer is constructed on the negative electrode of the battery by using MXene to inhibit dendritic crystal formation and reduce polarization loss, and the high-current-density performance and cycling stability of the zinc-bromine flow battery are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrochemistry, in particular to a preparation method of electrode, electrode and metal-based flow battery. BACKGROUND

[0002] In recent years, with the transformation of global energy structure to low carbonization, large-scale application of renewable energy has become an inevitable trend. However, renewable energy represented by wind energy and solar energy has significant intermittency and volatility, which causes impact on the stability of the grid after being connected to the grid, and causes more than 20% of energy waste. In order to alleviate this problem, it is essential to develop efficient, safe and low-cost large-scale energy storage technology. Zinc-bromine flow battery (ZBFBs) is considered as one of the most potential energy storage technologies due to its high safety, long cycle life and low material cost. However, its practical application faces severe challenges: under high current density (> 20 mA cm- 2 ) and long cycle conditions, the zinc negative electrode interface causes dendrite growth due to uneven distribution of zinc ions (Zn 2+ ), accompanied by serious polarization loss (including ohmic polarization, activation polarization and concentration polarization), which leads to significant decrease of energy efficiency (EE) of the electrode.

[0003] The electrode, as the core component of ZBFBs, directly determines the polarization characteristics and cycle stability of the battery. Although the carbon felt (CF) electrode widely used at present has high conductivity and chemical stability, its surface is rough and has poor zinc affinity, which leads to the following problems: 1) high nucleation barrier of zinc ions on the electrode surface, causing activation polarization; 2) large interfacial resistance, aggravating ohmic polarization; 3) rapid consumption of zinc ions in the double layer (IHP), forming a concentration gradient and inducing concentration polarization. In addition, the defect area on the surface of CF is easy to form local electric field distortion, leading to preferential nucleation of zinc at the "tip" and growth into dendrites, which eventually causes short circuit or capacity decay of the battery. SUMMARY

[0004] In order to solve the above defects, the present application proposes a preparation method of electrode, electrode and metal-based flow battery. The present application aims to inhibit dendrite formation and reduce polarization loss by constructing a high zinc ion concentration IHP layer at the negative electrode of the battery using MXene through electrode interface engineering strategy, and to improve the high current density performance and cycle stability of zinc-bromine flow battery.

[0005] The technical scheme adopted by the present application is a preparation method of electrode, comprising the following steps:

[0006] S100, cleaning and drying the carbon felt;

[0007] S200, preparing a MXene colloidal solution;

[0008] S300, loading the MXene colloid on the surface of the carbon felt in situ by an electrochemical deposition method to form a MXene@CF composite electrode.

[0009] Preferably, the S300 specifically comprises:

[0010] S310, immersing the platinum sheet and the carbon felt into the MXene colloid solution;

[0011] S320, continuously applying a voltage with the carbon felt as the positive electrode and the platinum sheet as the negative electrode to obtain the carbon felt loaded with MXene;

[0012] S330, cleaning and drying the carbon felt loaded with MXene to obtain the MXene@CF composite electrode.

[0013] Preferably, the concentration of the MXene colloid prepared in the S200 is between 3 mg / mL and 4 mg / mL, and the pH is greater than 6.

[0014] Preferably, the voltage applied in the S320 is between 5 V and 20 V, and the duration is between 5 min and 15 min.

[0015] Preferably, in the S320, the voltage is first applied at 5 V for 5 min, and then applied at 10 V for 5 min, with the carbon felt as the positive electrode and the platinum sheet as the negative electrode.

[0016] Preferably, the MXene is one of Ti3C2Tx, Ti2C, or Nb2C. x

[0017] Preferably, the S200 specifically comprises:

[0018] S210, etching the Ti3AlC2 MAX phase by using a LiF and HCl solution, and obtaining the few-layer Ti3C2Tx MXene nanosheet after water bath;

[0019] S220, after cleaning, purifying and drying the Ti3C2Tx MXene nanosheet, the MXene colloid is obtained.

[0020] The application also discloses a MXene@CF composite electrode prepared by the above method.

[0021] The application also discloses a metal-based flow battery comprising the above MXene@CF composite electrode as the negative electrode, and the active substance of the negative electrode of the metal-based flow battery is zinc ion.

[0022] Preferably, the metal-based flow battery is a zinc-bromine flow battery, and the metal-based flow battery further comprises:

[0023] ​a positive electrode, which is carbon felt;

[0024] a separator, which is a porous polyolefin membrane;

[0025] an electrolyte, which includes 2M ZnBr2, 1M KCl and 0.4M MEP, and the flow rate of the electrolyte is 50 mL / min.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] The present application constructs a composite electrode with a "zinc ion reservoir" function by in-situ electrochemical deposition of MXene nanosheets (MXene@CF) on the surface of three-dimensional carbon felt (CF), optimizes the zinc ion adsorption, migration and deposition behavior of the negative electrode of zinc-bromine flow battery (ZBFBs), thereby inhibiting dendrite growth and reducing polarization, and improving the cycle life and energy efficiency of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0028] The present application will be described in detail below in conjunction with the embodiments and drawings, in which:

[0029] Figure 1 is a flow chart of the preparation method of the electrode;

[0030] Figure 2 is a scanning electron microscope (SEM) image of CF and MXene@CF before and after MXene deposition;

[0031] Figure 3 is a TEM image of Ti3C2T x MXene;

[0032] Figure 4 is a schematic diagram of (a) cyclic voltammetry, (b) voltage-time curve and (c) relative ion concentration of CF and MXene@CF;

[0033] Figure 5 is a SEM image of CF and MXene@CF after cyclic deposition;

[0034] Figure 6 is a schematic diagram of (a) rate performance and (b) cycle performance of CF and MXene@CF;

[0035] Figure 7 is a polarization curve and polarization loss schematic diagram of CF and MXene@CF. DETAILED DESCRIPTION

[0036] In order to make the objects, technical solutions and advantages of the present application clearer, the embodiments of the present application will be further described in detail below with reference to the drawings. The examples of the embodiments are shown in the drawings, wherein the same or similar notations represent the same or similar parts or parts having the same or similar functions throughout. The embodiments described below by reference to the drawings are exemplary and are only used to explain the present application, but cannot be explained as a limitation of the present application.

[0037] Under high rate and long time operation conditions, the zinc ions of the negative electrode of the zinc-bromine flow battery (ZBFBs) are unevenly distributed in the inner Helmholtz layer (IHP), which leads to zinc dendrite growth, polarization accumulation (including ohmic polarization, activation polarization, and concentration polarization), thereby reducing the cycle life, energy efficiency, and safety of the battery. To solve this problem, the present application provides the following electrode preparation method, and the electrode prepared by the following method has high zinc ion adsorption capacity, fast charge transport characteristics, and excellent structural stability.

[0038] In one embodiment, a method for preparing an electrode, as shown in Figure 1 , includes the following steps:

[0039] S100, cleaning and drying the carbon felt.

[0040] This is a pretreatment of the carbon felt, specifically including: after ultrasonic cleaning of the carbon felt with deionized water and ethanol, vacuum drying at 80°C to ensure that the surface is free of impurities, providing a clean substrate for MXene loading.

[0041] S200, preparing a MXene colloidal solution, the MXene being Ti3C2T x , Ti2C, or Nb2C, etc.

[0042] Specifically, it can include:

[0043] S210, etching the Ti3AlC2 MAX phase with a LiF and HCl solution, and obtaining few-layer Ti3C2Tx MXene nanosheets after water bath. More specifically, 2g of Ti3AlC2 MAX phase is etched with 1.98g of LiF + 40ml of 9M HCl solution, and the few-layer Ti3C2Tx MXene nanosheets are obtained after 40° water bath for 24h. The 40°C water bath for 24 hours can ensure that the Al layer is completely etched, while avoiding excessive etching that causes damage to the structure of the MXene. After etching, 3-5 layers of Ti3C2Tx nanosheets are obtained, and the specific surface area is greatly increased, providing abundant sites for zinc ion adsorption. After etching, -OH, -O, -F, and other functional groups are generated on the surface of the MXene, enhancing the hydrophilicity and zinc ion binding capacity (such as -OH forming a coordination bond with Zn 2+ ).

[0044] S220, after washing, purifying and drying the Ti3C2Tx MXene nanosheet, the MXene colloid is obtained. More specifically, the MXene colloid is dispersed at a concentration of 3 mg / mL to 4 mg / mL after repeated deionized water washing, 3500 rpm centrifugal purification to pH>6, and vacuum drying. Repeated deionized water washing + 3500 rpm centrifugation (5-8 times) removes unreacted LiF, HCl and etching byproducts (such as AlF3), avoiding battery side reactions caused by electrolyte contamination. When purified to pH>6, the surface negative charge density of MXene is maximized (-O-, -OH ionization), providing conditions for subsequent electrochemical deposition (negative MXene migrates to the positive electrode). MXene colloid concentration that is too low (<3 mg / mL) will result in insufficient MXene loading, and too high (>4 mg / mL) will easily agglomerate; a concentration of 3 mg / mL to 4 mg / mL allows a continuous MXene layer to be formed on the carbon felt surface (SEM observation shows no exposed carbon felt fibers) within 10 minutes of electrochemical deposition, with high deposition efficiency.

[0045] S300, the MXene colloid is loaded on the surface of the carbon felt in situ by electrochemical deposition to form a MXene@CF composite electrode.

[0046] Unlike wet forming, vapor deposition and other composite technologies, the electrochemical deposition process takes advantage of the negative charge-rich characteristics of the MXene nanosheet surface. The negative MXene nanosheet is driven by the electric field and migrates directionally to the positive carbon felt surface, forming a highly uniform and continuous coating (coverage>95%), which avoids the agglomeration that occurs in wet coating and the local thickness unevenness of vapor deposition. During the electrochemical deposition process, the -OH / -O functional groups of MXene form chemical bonds with the oxygen-containing groups on the surface of the carbon felt, which is significantly better than the physical adsorption of wet forming, and the MXene shedding rate is <5% after 1000 cycles (wet>30%). Without high temperature (<60°C) or vacuum environment, the MXene can be directly deposited in situ on the carbon felt substrate, simplifying the process flow (5 fewer processes than vapor deposition), avoiding damage to the substrate caused by high temperature, and being suitable for large-scale production, with better comprehensive performance than traditional composite technologies.

[0047] The S300 specifically includes:

[0048] S310, immerse the platinum sheet and the carbon felt in the MXene colloid solution. The porous structure (porosity>90%) of the carbon felt is fully penetrated by the MXene colloid, ensuring that the MXene can enter the surface of the internal fibers of the carbon felt during subsequent deposition.

[0049] S320, continuously apply voltage with the carbon felt as the positive electrode and the platinum sheet as the negative electrode, and the MXene nanosheet with a surface rich in negative charges migrates directionally and adheres tightly to the surface of the carbon felt fiber, obtaining the carbon felt loaded with MXene.

[0050] S330, washing and drying the load MXene carbon felt to obtain a MXene@CF composite electrode.

[0051] In this embodiment, MXene nanosheets are used to modify carbon felt (MXene@CF) electrodes. In-situ electrochemical deposition is used to uniformly load MXene nanosheets on the surface of carbon felt to form a continuous conductive network. A zinc ion storage layer is constructed, and high-concentration Zn 2+ is enriched in the double-layer (IHP) by using the layered structure and pseudo-capacitance characteristics of MXene. -1 The interface is synergistically optimized, combining the high electrical conductivity (6255 S cm -1 ), low activation energy (12.15 kJ mol 2+ ) and high concentration of Zn 2 IHP structure of MXene, which simultaneously reduces the polarization loss.

[0052] In one embodiment, the voltage applied in S320 is between 5V and 20V, and the duration is between 5min and 15min. By adjusting the voltage (5-20V) and time (5-15min), the MXene loading (1-3mg / cm 2 ) and interlayer arrangement (such as vertical orientation induced by high voltage) can be precisely controlled, and the ion transport channel can be optimized (interlayer spacing 1.0-1.2nm adjustable), while wet and gas phase processes are difficult to achieve nanoscale structure regulation.

[0053] In one embodiment, in S320, the carbon felt is used as the positive electrode and platinum sheet is used as the negative electrode. First, a voltage of 5V is applied for 5min. The weak electric field drives MXene to slowly approach the surface of CF, and the MXene nanosheets are arranged in parallel orientation with uniform interlayer spacing, reducing stacking defects and increasing the density of zinc ion adsorption sites. Then, a voltage of 10V is applied for 5min. The strong electric field enhances the electrostatic adsorption force, and the MXene layers are tightly anchored in the CF fiber grooves, enhancing the stability of the electrode-electrolyte interface and prolonging the cycle life.

[0054] In one embodiment, a MXene@CF composite electrode is prepared by the method described in the above embodiments. The MXene@CF composite electrode is prepared by in-situ introducing MXene nanosheets (MXene@CF) on the surface of carbon felt (CF), constructing a "zinc ion reservoir" structure by using the pseudo-capacitance characteristics of MXene, and constructing a high-concentration zinc ion storage layer and a multifunctional electrode interface to achieve the following goals: suppressing dendrites by uniformly distributing Zn 2+ and regulating the electric field to eliminate the local "tip effect"; reducing polarization to synergistically reduce ohmic, activation and concentration polarization; and improving performance at high current density (>20mA cm- 2) and maintain high energy efficiency (EE>85%) under long cycle (>1000 hours) conditions.

[0055] In one embodiment, a metal-based liquid flow battery includes the MXene@CF composite electrode in the above embodiment as a negative electrode, and the active material of the negative electrode of the metal-based liquid flow battery is zinc ions, such as a zinc-bromine liquid flow battery, a zinc-iodine battery, etc.

[0056] Furthermore, the metal-based flow battery further comprises:

[0057] a positive electrode, which is carbon felt;

[0058] a separator, which is a porous polyolefin membrane;

[0059] The electrolyte includes 2M ZnBr2, 1M KCl and 0.4M MEP, and the flow rate of the electrolyte is 50mL / min.

[0060] In this embodiment, MXene@CF electrode is prepared by in-situ loading MXene nanosheets on the surface of carbon felt by electrochemical deposition. The interlayer embedding and surface adsorption characteristics of MXene are used to construct a zinc ion reservoir, achieving high-density storage of zinc ions in the inner Helmholtz layer (IHP), thereby inhibiting the growth of zinc dendrites from the root. At the same time, the MXene@CF electrode reduces ohmic resistance with high conductivity and accelerates reaction kinetics with low activation energy. The reservoir stabilizes ion concentration to alleviate concentration polarization, forming a multi-dimensional synergistic mechanism, so that the battery can achieve a high charge and discharge rate of 20mA / cm 2 After 1000 hours of cycling at the current density, the energy efficiency remains above 85%, and the zinc deposition overpotential is reduced by 50%, effectively solving the problems of dendrite growth and polarization accumulation under high-rate and long-term operation.

[0061] In one embodiment, it is verified by experiments.

[0062] See also Figure 2 , these two scanning electron microscope (SEM) images show the microstructure of carbon felt (CF) before and after MXene deposition. Figure 2 Left side): Only carbon felt (CF) is shown, the surface is relatively smooth and flat, the fiber structure is clearly visible, and no other substances are attached. This represents the original state of carbon felt. After deposition ( Figure 2 Right side): The carbon felt surface is evenly covered with a layer of MXene, which becomes rough with obvious texture changes. This intuitively demonstrates that MXene is successfully loaded on the carbon felt to form a MXene@CF composite electrode. MXene has pseudocapacitive properties. After being loaded on the carbon felt surface, it can build an inner Helmholtz layer (IHP layer) at the electrode interface, which is similar to a "zinc ion reservoir" and enriches high concentrations of Zn. 2+In this way, during the charging and discharging process of the battery, the concentration polarization caused by uneven ion transmission can be significantly reduced, the driving force for the growth of zinc dendrites is reduced, the formation of dendrites is inhibited, and the performance and stability of the battery are improved.

[0063] Referring to Figure 3 , it is shown that Tact x Microstructure characteristics of MXene. When the scale is 500 nm, the image presents the two-dimensional sheet morphology of MXene nanosheets, the nanosheets are distributed in the field of view, the size of the nanosheets is large, and the thickness is thin, which indicates that MXene has typical layered two-dimensional structure characteristics. This large-size thin sheet structure provides a large specific surface area, which is beneficial to subsequent ion adsorption and transmission functions.

[0064] When the scale is 10 nm, it is a high-resolution TEM image, focusing on the local area of the MXene nanosheet, and clearly showing that the MXene nanosheet has an ordered layered arrangement structure. The interlayer boundary can be seen, and the interlayer spacing is relatively uniform. The interlayer space can accommodate ions (such as Zn 2+ ) intercalation and deintercalation, which plays a key role in building a "zinc ion reservoir" and other functions, and provides a structural basis for its pseudocapacitance characteristics and related electrochemical performance.

[0065] Referring to Figure 4 , (a) cyclic voltammetry, (b) voltage-time curve and (c) relative ion concentration comparison diagram of MXene@CF and CF under the condition of electrodeposition 10V-10min. Figure 4 The left part (label a, electrochemical test), the horizontal coordinate is voltage (V), and the vertical coordinate is current density (mA / cm 2 ), the blue curve represents CF (carbon felt), and the red curve represents MXene@CF. The CV curve of MXene@CF shows obvious and larger redox peaks, and the peak current is about 3 times higher than that of CF. This proves that MXene@CF has pseudocapacitance characteristics, the introduction of MXene increases the active sites for fast and reversible redox reactions on the electrode surface, so that the electrode can store and release more electric charge during the charging and discharging process, which reflects the promoting effect of MXene on the pseudocapacitance behavior in the electrode.

[0066] Figure 4The middle part (label b), the horizontal coordinate is time (s), and the vertical coordinate is voltage (V). The light blue area represents Zn@CF (zinc deposited on carbon felt), and the light red area represents Zn@MXene@CF (zinc deposited on MXene@CF composite electrode). The voltage change curve of Zn@MXene@CF is different from that of Zn@CF, which not only reflects the pseudo-capacitance behavior of MXene@CF (different voltage response reflects different charge storage and release characteristics), but also implies that the ion concentration in the inner Helmholtz layer (IHP layer) of MXene@CF has changed. It shows that MXene@CF can affect the behavior of zinc ions at the electrode interface, and then affect the change of voltage with time, which indirectly proves the effect of MXene@CF on the ion concentration in the IHP layer.

[0067] Figure 4 The right part (label c), the horizontal coordinate is CF and MXene@CF respectively, and the vertical coordinate is relative ion concentration. The relative ion concentration of MXene@CF is 237, which is about 128 times higher than that of CF (2). This directly and powerfully proves that MXene@CF has built a "zinc ion reservoir" structure, stably enriched a large amount of zinc ions in the IHP layer, greatly increased the zinc ion concentration at the electrode interface, effectively avoided the interface concentration polarization problem caused by uneven ion concentration, and provided an important guarantee for the improvement of battery performance.

[0068] Referring to Figure 5 , SEM images of CF and MXene@CF after cyclic deposition. Figure 5 The upper middle part (label a), from the left low magnification image (scale 400 μm), the surface of pure CF after zinc deposition shows a disordered morphology with many sharp and irregular protrusions. The right high magnification image (scale 40 μm) further shows that these protrusions are obvious zinc dendrites with different growth morphologies, uneven thickness and rough surface. The existence of zinc dendrites will bring many problems in the battery cycling process, such as piercing the separator to cause short circuit of the battery, reducing the safety and cycle life of the battery.

[0069] Figure 5 The lower middle part (label b), the left low magnification image (scale 40 μm) shows that the zinc deposition on the surface of MXene@CF is relatively uniform, without the disordered dendrite structure on the surface of CF. The right high magnification image (scale 10 μm) further confirms that the zinc layer on the surface of MXene@CF is dense and uniform, and the zinc deposition is relatively flat without sharp dendrite growth. This is due to the fact that MXene@CF provides uniform nucleation sites, so that zinc ions can be more orderly arranged during deposition, thereby inhibiting the growth of dendrites, ensuring the stability of the electrode structure, and improving the cycle performance and safety of the battery.

[0070] Referring toFigure 6 , Figure 6 are (a) rate performance, (b) cycle performance of CF and MXene@CF. Figure 6 The left part (labeled as a), the horizontal coordinate is the cycle number, and the vertical coordinate is the efficiency (%), including coulomb efficiency (CE, blue), voltage efficiency (VE, yellow) and energy efficiency (EE, red) (93.4, 23.9, 22.3% (CF) respectively at 100ma cm-2; 94.3, 54.9, 51.8). Different symbols represent different electrodes, triangles represent CF, and circles represent MXene@CF. Different color background areas correspond to different current densities (mA / cm 2 ). As the current density gradually increases from 10mA / cm 2 to 100mA / cm 2 , the energy efficiency (EE) of the CF electrode (triangle) decreases significantly, while the energy efficiency of the MXene@CF electrode (circle) decreases relatively small. At 100mA / cm 2 , the EE of MXene@CF can still reach 60%, while the EE of CF electrode is far below this value (traditional CF electrode EE < 60%). This indicates that the MXene@CF electrode can better maintain the efficiency of the battery at different current densities, has better rate performance, and can adapt to different power demand scenarios.

[0071] Figure 6 The right part (labeled as b), the horizontal coordinate is time (h), and the vertical coordinate is voltage (V). Blue represents the CF electrode, and red represents the MXene@CF electrode. Under the condition of 20mAcm -2 , 20mAhcm -2 , the voltage of the MXene@CF electrode (red) remains relatively stable during the 1000h cycle process, and the cumulative capacity reaches 11Ahcm -2 after 1000h of battery cycle, and the energy efficiency (EE) is stable at 85%. While the CF electrode (blue) has large voltage fluctuation and cannot maintain long-term stable cycle (traditional CF electrode cycle < 100h). The construction of "zinc ion reservoir" significantly inhibits the growth of zinc dendrites, and the cycle time of MXene@CF is increased from 196h of CF to more than 1000h, which fully embodies the excellent cycle stability of MXene@CF electrode, which can be stably operated for a long time, and meets the application demand of long life of the battery.

[0072] Referring to Figure 7 , Figure 7are the polarization curve and polarization loss diagram of CF and MXene@CF. Due to the construction of the "zinc ion reservoir", the concentration polarization of MXene@CF is significantly reduced; at the same time, combined with the high conductivity and low nucleation barrier of MXene, the ohmic polarization and activation polarization are also reduced, and the overall voltage polarization of the battery is reduced.

[0073] Figure 7 The left and middle parts show the polarization curve, and the open circuit voltage (OCV) is 1.771 V. Different colored areas in the figure represent different polarization losses, blue for concentration loss, yellow for activation loss, and red for ohmic loss. Figure 7 The left part represents the CF electrode, Figure 7 The middle part represents the MXene@CF electrode. As the current density increases, the three polarization losses (concentration, activation, and ohmic) of the CF electrode all increase significantly, leading to a rapid drop in voltage; while the polarization loss of the MXene@CF electrode increases at a smaller rate, especially the ohmic loss and concentration loss are significantly lower than the CF electrode. Decoupling analysis of the polarization curve shows that the ohmic polarization of MXene@CF is reduced by 0.15 V at 100 mA / cm 2 , which indicates that the MXene@CF electrode can effectively suppress the polarization phenomenon, reduce the polarization loss, and improve the battery performance.

[0074] Figure 7 The right part shows the polarization loss, with the horizontal axis as the current density (mA / cm 2 ) and the vertical axis as the voltage (V). Different colored columns represent different polarization losses, blue for concentration loss, yellow for activation loss, and red for ohmic loss. Blue column superposition represents the CF electrode, and red column superposition represents the MXene@CF electrode. At each current density, the concentration polarization voltage loss of the MXene@CF electrode is significantly lower than that of the CF electrode, with a reduction of 46% (0.036 V vs. 0.056 V), and the concentration polarization accounts for <10%. This further indicates that the MXene@CF electrode effectively reduces the polarization loss by suppressing concentration polarization, etc., improves the working stability and efficiency of the battery at different current densities, and reflects its significant advantages in optimizing the performance of the battery.

[0075] Strong process compatibility: suitable for flow battery systems, meeting the demand for high power density.

[0076] In the description of the specification, if the terms "embodiment one", "this embodiment", "in one embodiment", etc. are described, it means that the specific features, structures, materials or characteristics described in conjunction with this embodiment or example are included in the invention or at least one embodiment or example of the invention. In this specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example; moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in an appropriate manner.

[0077] In the description of the specification, the terms "connection", "installation", "fixation", "setting", "have" and the like are understood in a broad sense, for example, "connection" can be fixed connection, or detachable connection, or integral connection; can be mechanical connection, or electrical connection; can be directly connected, or indirectly connected through intermediate medium, can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0078] In the description of the specification, the relationship terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, article or device. Without more limitations, the element defined by the statement "including a" does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0079] The above description of the embodiments is to facilitate the understanding and application of the present technology for those skilled in the art, and those skilled in the art can easily make various modifications to these examples and apply the general principles described herein to other embodiments without creative labor. Therefore, the present application is not limited to the above embodiments, and the following modifications should be within the scope of protection: ① new technical solutions based on the technical solutions of the present application and combined with existing common knowledge, the technical effects produced by the new technical solutions do not exceed the technical effects of the present application; ② equivalent replacement of part of the features of the technical solutions of the present application using known technology, the technical effects produced are the same as the technical effects of the present application; ③ expandable based on the technical solutions of the present application, the essential content of the expanded technical solutions does not exceed the technical solutions of the present application; ④ equivalent transformation using the contents of the present application specification and drawings, direct or indirect application in other related technical fields.

Claims

1. A method for preparing an electrode, characterized in that: The following steps are involved: S100, cleaning and drying the carbon felt; S200, preparing a MXene colloidal solution; S300, in situ loading the MXene colloid on the carbon felt surface by electrochemical deposition to form a MXene@CF composite electrode.

2. The preparation method according to claim 1, characterized in that The S300 specifically includes: S310, immersing the platinum sheet and the carbon felt in the MXene colloidal solution; S320, continuously applying voltage with the carbon felt as the positive electrode and the platinum sheet as the negative electrode to obtain a carbon felt loaded with MXene; S330, washing and drying the MXene-loaded carbon felt to obtain a MXene@CF composite electrode.

3. The preparation method according to claim 2, characterized in that The concentration of the MXene colloid prepared by S200 is between 3 mg / mL and 4 mg / mL, and the pH is greater than 6.

4. The preparation method according to claim 3, characterized in that The voltage applied in S320 is between 5V and 20V, and the duration is between 5min and 15min.

5. The preparation method according to claim 3, characterized in that In the S320 , the carbon felt is used as the positive electrode and the platinum sheet is used as the negative electrode. A voltage of 5 V is first applied for 5 minutes, and then a voltage of 10 V is applied for 5 minutes.

6. The preparation method according to any one of claims 1 to 5, characterized in that The MXene is Ti3C2T x , Ti2C, or Nb2C.

7. The preparation method according to claim 6, characterized in that The S200 specifically includes: S210, using LiF and HCl solution to etch the Ti3AlC2 MAX phase, and obtaining few-layer Ti3C2Tx MXene nanosheets after water bath; S220, after washing, purifying and drying the Ti3C2Tx MXene nanosheets, the MXene colloid is obtained.

8. A MXene@CF composite electrode, characterized in that: The method is prepared according to any one of claims 1 to 7.

9. A metal-based liquid flow battery, characterized in that: The MXene@CF composite electrode according to claim 8 is used as a negative electrode, and the active material of the negative electrode of the metal-based liquid flow battery is zinc ions.

10. The battery according to claim 9, characterized in that The metal-based liquid flow battery is a zinc-bromine liquid flow battery, and the metal-based liquid flow battery further comprises: a positive electrode, which is carbon felt; a separator, which is a porous polyolefin membrane; The electrolyte includes 2M ZnBr2, 1M KCl and 0.4M MEP, and the flow rate of the electrolyte is 50mL / min.

Images