Preparation method of ALD modified graphite felt applied to aqueous flow battery
By depositing a thin layer of alumina on the surface of graphite felt to form a nano-island structure, the problem of insufficient catalytic activity of graphite felt electrodes was solved, thereby improving the electrochemical performance and energy efficiency of flow batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- INST OF COAL CHEM CHINESE ACAD OF SCI
- Filing Date
- 2026-01-20
- Publication Date
- 2026-04-10
AI Technical Summary
Existing graphite felt electrodes have limited catalytic activity, resulting in high electrochemical polarization impedance. Furthermore, the low solubility of organic molecules makes them prone to clogging, affecting the operational activity and stability of flow batteries.
Alumina thin layers are deposited on the surface of graphite felt using ALD technology to form nano-island structures, increasing the contact area between the electrode material and the electrolyte, providing more reaction sites, and constructing composite electrodes to improve electrochemical performance.
By coating modified graphite felt with alumina, side reactions are suppressed, the integrity of the electrode structure is protected, the reactive surface area is increased, the redox reaction rate and battery voltage efficiency are improved, and the energy efficiency is increased.
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Figure CN121839718A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of redox flow battery technology, specifically relating to a method for preparing ALD-modified graphite felt for use in aqueous flow batteries. Background Technology
[0002] Against the backdrop of global energy decarbonization, clean energy is gradually replacing traditional fossil fuels. While new energy sources like wind and nuclear power generate large amounts of electricity, their inherent intermittency leads to a mismatch between power generation and demand, making the development of long-duration energy storage technology a key solution. Flow batteries, with their inherent safety, adjustable structure, and long lifespan, have become an ideal choice for long-duration energy storage. Electrode materials, as a core component, significantly influence the operational activity, stability, and efficiency of flow batteries. Electrodes are crucial components of flow batteries, providing the reaction site for redox reactions during charging and discharging and facilitating the transport of internal active materials. Although they account for only 10% of the cost of flow batteries, almost all flow batteries utilize carbon electrodes, indicating a promising research prospect. Currently, the most widely used carbon electrode material is graphite felt (GF), which possesses excellent conductivity, a large specific surface area, good stability, high mechanical strength, and low cost. However, graphite felt has limited catalytic activity, resulting in significant electrochemical polarization resistance. Therefore, surface modification has become a key research focus for improving its electrochemical performance.
[0003] Previous studies have mainly used methods such as heat treatment, doping with heteroatoms such as nitrogen and phosphorus, and single-atom modification to modify electrode materials, focusing on improving conductivity and catalytic performance, with less attention paid to electrode stability. At the same time, organic molecules have low solubility and are prone to local precipitation on the surface of graphite felt electrodes, clogging the electrodes and leading to capacity loss and hindered charge and discharge.
[0004] Metal oxides offer advantages in dielectric constant, thermal stability, and electrical conductivity, while ALD technology allows for the deposition of amorphous atomic layers under highly conformal conditions. Currently, oxides are widely used as active coating materials in heterogeneous catalysis and electrochemistry. Summary of the Invention
[0005] To improve electrode material performance, this invention discloses a modified graphite felt for flow batteries with oxide thin-layer coating. Firstly, the small size of the nano-island-like oxide particles increases the contact area between the electrode material and the electrolyte, providing more sites for electrochemical reactions and leveraging the synergistic effect of the composite electrode material. Secondly, metal oxides, due to their excellent electrical conductivity and unique physical and chemical properties, are used to construct composite electrodes such as nanomaterials / graphite fibers to improve electrochemical performance. Furthermore, the coated metal oxides provide a large number of active sites, further enhancing material performance.
[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:
[0007] A method for preparing ALD-modified graphite felt for use in aqueous flow batteries.
[0008] Step 1, graphite felt pretreatment: The graphite felt is ultrasonically cleaned with organic cleaning agent and deionized water respectively to remove surface impurities, and then thoroughly dried.
[0009] Step 2, Activation of graphite felt; The pretreated graphite felt is placed in a vacuum tube furnace filled with carrier gas for calcination to activate it, and the activated graphite felt is obtained.
[0010] Step 3, Preparation of alumina thin layer: The activated graphite felt is placed in the ALD reactor, nitrogen is used as the carrier gas, the set temperature of the raw material bottle and the cavity is maintained, the precursor is introduced, the pulse, exposure and purging time of the precursor are set, and then atomic layer deposition is performed; the furnace is cooled to room temperature to obtain the modified flow battery graphite felt coated with alumina thin layer after low temperature treatment.
[0011] Furthermore, in step 3, the precursor includes precursor 1 and precursor 2; precursor 1 is selected from at least one of trimethylaluminum, aluminum isopropoxide, aluminum chloride, and aluminum oxide.
[0012] The precursor 2 is selected from at least one of ozone, a mixture of hydrogen and argon, and water vapor.
[0013] Furthermore, the pulse, exposure, and purge times of the precursors are specifically set as follows: the pulse, exposure, and purge times of the precursor 1 are 0.01~5, 10~50, and 10~50 seconds; the pulse, exposure, and purge times of the precursor 2 are 0.1~10, 10~50, and 10~80 seconds.
[0014] Furthermore, maintaining the set temperature of the raw material bottle and the cavity specifically involves maintaining the temperature of the raw material bottle at 25~150℃ and maintaining the temperature of the cavity at 100~300℃.
[0015] Furthermore, the atomic deposition cycle is 10 to 40 layers.
[0016] Furthermore, the reaction time for atomic deposition is 4–8 h.
[0017] Furthermore, the activation process in step 2, which involves calcining in a vacuum tube furnace with carrier gas, specifically involves raising the temperature from 25°C to 500°C within 60-120 minutes in an air atmosphere, calcining for 300-900 minutes, and then naturally cooling to room temperature before removal.
[0018] Furthermore, the ultrasonic cleaning time in step 1 is 0.5~3 hours.
[0019] Furthermore, the organic cleaning agent in step 1 is selected from at least one of methanol, ethanol, propanol, and isopropanol.
[0020] Preferably, in step S3, the deposition time varies depending on the required thin-layer thickness. After purging in an inert gas atmosphere, the modified flow battery graphite felt with alumina thin-layer coating can be obtained.
[0021] This invention provides an application of alumina-coated modified graphite felt, wherein the alumina-coated modified graphite felt prepared by the above-described method is applied to a redox flow battery.
[0022] Compared with the prior art, the present invention has the following advantages:
[0023] 1. The present invention coats and fixes aluminum oxide onto the surface of graphite felt fibers by depositing an aluminum oxide atomic layer on the surface of graphite felt, forming a passivation protective layer, which inhibits the occurrence of side reactions, protects the structural integrity of the graphite felt fiber surface, and reduces capacity decay.
[0024] 2. This invention loads alumina onto graphite felt using a low-temperature atomic layer deposition method to form a nano-island structure. The alumina coating retains the porous morphology, increasing the reactive area of the graphite felt and providing sufficient reactive sites for redox reactions. This can effectively improve the redox reaction rate, increase battery voltage efficiency, and thus improve energy efficiency. Attached Figure Description
[0025] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0026] Figure 1 This is a schematic diagram of the preparation method of alumina-coated modified graphite felt according to this application;
[0027] Figure 2 Cyclic voltammetry curves of Comparative Example 1 and the modified graphite felts of Examples 1, 2, 3, and 4 of this application are shown.
[0028] Figure 3 This is a battery cycle diagram of the modified graphite felt in Comparative Example 1 and Examples 1, 2, 3, and 4 of this application under different current densities.
[0029] Figure 4 This is a battery cycling diagram of the modified graphite felt in Comparative Example 1 and Examples 1, 2, 3, and 4 of this application at low current density;
[0030] Figure 5 This is a long-cycle diagram of the battery under high current density for Comparative Example 1 and Examples 1, 2, 3, and 4 of this application using modified graphite felt.
[0031] Figure 6 This is a battery cycle diagram of the modified graphite felt of Comparative Example 1 and Example 3 of this application. The negative electrode was removed, cleaned and put back after every 50 cycles. Detailed Implementation
[0032] To gain a deeper understanding of this invention, we will provide a comprehensive and detailed description. However, this invention has various implementations and is not limited to the specific examples listed herein. These examples are presented to enhance a full understanding of the disclosure of this invention.
[0033] Example 1: The following technical solution is adopted.
[0034] Step S1: Pretreatment of graphite felt. The graphite felt was ultrasonically cleaned with isopropanol and deionized water for 1.5 h respectively to remove surface impurities, and then thoroughly dried;
[0035] Step S2: Activation of graphite felt. The pretreated graphite felt is placed in a vacuum tube furnace and, under air atmosphere, the temperature is raised from 25°C to 500°C within 120 min, and calcined for 420 min to activate it, thereby obtaining activated graphite felt;
[0036] Step S3: Preparation of the alumina thin layer. The method for preparing the alumina thin layer includes the following steps:
[0037] The activated graphite felt was placed in an ALD reactor, with nitrogen as the carrier gas, and the precursor trimethylaluminum (TMA) and water vapor were introduced. The temperature of the raw material bottle was maintained at 100°C, and the temperature of the chamber was maintained at 150°C. The pulse, exposure, and purging times were 0.06, 18, and 35 seconds and 1, 18, and 50 seconds, respectively, and the number of atomic deposition cycles was 10 layers. The reaction was carried out in the ALD reactor for 4 hours, followed by purging with nitrogen and cooling to room temperature to obtain the modified flow battery graphite felt with alumina thin-layer coating after low-temperature treatment.
[0038] Example 2:
[0039] The preparation method is the same as in Example 1, except that the atomic deposition cycle is 20 layers.
[0040] Example 3:
[0041] The preparation method is the same as in Example 1, except that the atomic deposition cycle is 30 layers.
[0042] Example 4:
[0043] The preparation method is the same as in Example 1, except that the atomic deposition cycle is 40 layers.
[0044] Example 5:
[0045] Step S1: Pretreatment of graphite felt. The graphite felt was ultrasonically cleaned with methanol and deionized water for 0.5 h respectively to remove surface impurities, and then thoroughly dried;
[0046] Step S2: Activation of graphite felt. The pretreated graphite felt is placed in a vacuum tube furnace and, under air atmosphere, the temperature is raised from 25°C to 500°C within 60 minutes and calcined for 300 minutes to activate it, thereby obtaining activated graphite felt;
[0047] Step S3: Preparation of the alumina thin layer. The method for preparing the alumina thin layer includes the following steps:
[0048] The activated graphite felt was placed in an ALD reactor, with nitrogen as the carrier gas. A mixture of aluminum isopropoxide precursor, ozone, hydrogen, and argon was introduced. The temperature of the raw material bottle was maintained at 25 °C, and the temperature of the chamber was maintained at 100 °C. The pulse, exposure, and purging times were 0.01, 10, 10 seconds and 0.1, 10, 10 seconds, respectively, and the atomic deposition cycle was 20 layers. The reaction was carried out in the ALD reactor for 8 h, followed by purging with nitrogen and cooling to room temperature to obtain alumina-coated modified flow battery graphite felt after cryogenic treatment.
[0049] Example 6:
[0050] Step S1: Pretreatment of graphite felt. The graphite felt was ultrasonically cleaned with ethanol and deionized water for 3 hours respectively to remove surface impurities, and then thoroughly dried.
[0051] Step S2: Activation of graphite felt. The pretreated graphite felt is placed in a vacuum tube furnace and, under air atmosphere, the temperature is raised from 25°C to 500°C within 120 min, and calcined for 900 min to activate it, thereby obtaining activated graphite felt;
[0052] Step S3: Preparation of the alumina thin layer. The method for preparing the alumina thin layer includes the following steps:
[0053] The activated graphite felt was placed in an ALD reactor, with nitrogen as the carrier gas. A mixture of aluminum isopropoxide precursor, ozone, hydrogen, and argon was introduced. The temperature of the raw material bottle was maintained at 150 °C, and the temperature of the chamber was maintained at 300 °C. The pulse, exposure, and purging times were 5, 50, and 50 seconds and 10, 50, and 80 seconds, respectively, and the atomic deposition cycle was 30 layers. The reaction was carried out in the ALD reactor for 5 h, followed by purging with nitrogen and cooling to room temperature to obtain alumina-coated modified flow battery graphite felt after cryogenic treatment.
[0054] Example 7:
[0055] Step S1: Pretreatment of graphite felt. The graphite felt was ultrasonically cleaned with isopropanol and deionized water for 2 hours respectively to remove surface impurities, and then thoroughly dried.
[0056] Step S2: Activation of graphite felt. The pretreated graphite felt is placed in a vacuum tube furnace and, under air atmosphere, the temperature is raised from 25°C to 500°C within 100 min, and calcined for 600 min to activate it, thereby obtaining activated graphite felt;
[0057] Step S3: Preparation of the alumina thin layer. The method for preparing the alumina thin layer includes the following steps:
[0058] The activated graphite felt was placed in an ALD reactor, with nitrogen as the carrier gas. A mixture of aluminum chloride precursor, ozone, hydrogen, and argon was introduced. The temperature of the raw material bottle was maintained at 90 °C, and the temperature of the chamber was maintained at 200 °C. The pulse, exposure, and purging times were 1, 5, and 20 seconds and 5, 25, and 45 seconds, respectively, and the atomic deposition cycle was 30 layers. The reaction was carried out in the ALD reactor for 6 hours, followed by purging with nitrogen and cooling to room temperature to obtain alumina-coated modified flow battery graphite felt after cryogenic treatment.
[0059] Example 8:
[0060] Step S1: Pretreatment of graphite felt. The graphite felt was ultrasonically cleaned with isopropanol and deionized water for 3 hours respectively to remove surface impurities, and then thoroughly dried.
[0061] Step S2: Activation of graphite felt. The pretreated graphite felt is placed in a vacuum tube furnace and, under air atmosphere, the temperature is raised from 25°C to 500°C within 90 minutes and calcined for 500 minutes to activate it, thereby obtaining activated graphite felt;
[0062] Step S3: Preparation of the alumina thin layer. The method for preparing the alumina thin layer includes the following steps:
[0063] The activated graphite felt was placed in an ALD reactor. Nitrogen was used as the carrier gas, and a mixture of aluminum chloride precursor, ozone, hydrogen, and argon was introduced. The temperature of the raw material bottle was maintained at 120 °C, and the temperature of the chamber was maintained at 260 °C. The pulse, exposure, and purging times were 2, 20, and 30 seconds and 8, 38, and 60 seconds, respectively, and the number of atomic deposition cycles was 30 layers. The reaction was carried out in the ALD reactor for 7 hours, followed by purging with nitrogen and cooling to room temperature to obtain alumina-coated modified flow battery graphite felt after cryogenic treatment.
[0064] Example 9:
[0065] Step S1: Pretreatment of graphite felt. The graphite felt was ultrasonically cleaned with methanol and deionized water for 0.5 h respectively to remove surface impurities, and then thoroughly dried;
[0066] Step S2: Activation of graphite felt. The pretreated graphite felt is placed in a vacuum tube furnace and, under air atmosphere, the temperature is raised from 25°C to 500°C within 100 min, and calcined for 800 min to activate it, thereby obtaining activated graphite felt;
[0067] Step S3: Preparation of the alumina thin layer. The method for preparing the alumina thin layer includes the following steps:
[0068] The activated graphite felt was placed in an ALD reactor, with nitrogen as the carrier gas, and alumina precursor and water vapor were introduced. The temperature of the raw material bottle was maintained at 50 °C, and the temperature of the chamber was maintained at 150 °C. The pulse, exposure, and purging times were 5, 50, 50 seconds and 10, 50, 80 seconds, respectively, and the number of atomic deposition cycles was 30 layers. After reacting in the ALD reactor for 8 hours, it was purged with nitrogen and cooled to room temperature to obtain alumina thin-layer-coated modified flow battery graphite felt after low-temperature treatment.
[0069] Comparative Example 1:
[0070] The steps S1 and S2 in Example 1 are used, but step S3 is not included.
[0071] Test process and data:
[0072] The modified graphite felts prepared in the examples and comparative examples were cut into 5 mm * 5 mm pieces, and the electrochemical impedance was tested using an electrochemical workstation to fit the contact resistance.
[0073] The modified graphite felt prepared in the examples and comparative examples was used as the negative electrode, and the untreated graphite felt was used as the positive electrode. Cells were assembled using cation exchange membranes of the same thickness. A negative electrode electrolyte was prepared using 0.1 mol / L 2,6-N-TSAQ and 1 mol / L sodium hydroxide, and a positive electrode electrolyte was prepared using 0.4 mol / L sodium ferrocyanide and 1 mol / L sodium hydroxide. The cells were tested at 40 mA / cm under the same conditions. 2 and 120 mA / cm 2 Constant current density charge-discharge test. After the charge-discharge test, the battery coulombic efficiency, voltage efficiency, and energy efficiency were recorded. The test results are shown in Table 1.
[0074] Table 1 Test results of modified graphite felt
[0075]
[0076] As shown in Table 1, Comparative Example 1, as a blank sample, only underwent pretreatment and activation, resulting in lower voltage and energy efficiencies. The results indicate that among all oxides, loaded alumina exhibits the best performance. The greater the amount of alumina layer attached to the graphite felt substrate, the higher the coverage, and the greater the alteration in interface structure and properties. When assembled into a single cell, the modified graphite felt exhibits higher energy efficiency compared to untreated graphite felt, indicating enhanced electrochemical activity. Overall, redox flow batteries using alumina-coated modified graphite felt as the negative electrode achieve higher energy efficiency, and the modified graphite felt with a surface alumina layer significantly improves the performance of single cells.
[0077] Contents not described in detail in this specification are prior art known to those skilled in the art. Although illustrative specific embodiments of the invention have been described above to facilitate understanding by those skilled in the art, it should be understood that the invention is not limited to the scope of the specific embodiments. Various modifications are readily apparent to those skilled in the art as long as they fall within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of this invention are protected.
Claims
1. A method for preparing ALD-modified graphite felt for use in aqueous flow batteries, characterized in that: Step 1, graphite felt pretreatment: The graphite felt is ultrasonically cleaned with organic cleaning agent and deionized water respectively to remove surface impurities, and then thoroughly dried. Step 2, Activation of graphite felt; The pretreated graphite felt is placed in a vacuum tube furnace filled with carrier gas for calcination to activate it, and the activated graphite felt is obtained. Step 3, Preparation of alumina thin layer: The activated graphite felt is placed in the ALD reactor, nitrogen is used as the carrier gas, the set temperature of the raw material bottle and the cavity is maintained, the precursor is introduced, the pulse, exposure and purging time of the precursor are set, and then atomic layer deposition is performed; the furnace is cooled to room temperature to obtain the modified flow battery graphite felt coated with alumina thin layer after low temperature treatment.
2. The method for preparing ALD-modified graphite felt for use in aqueous flow batteries according to claim 1, characterized in that: In step 3, the precursor includes precursor 1 and precursor 2; precursor 1 is selected from at least one of trimethylaluminum, aluminum isopropoxide, aluminum chloride, and aluminum oxide. The precursor 2 is selected from at least one of ozone, a mixture of hydrogen and argon, and water vapor.
3. The method for preparing ALD-modified graphite felt for use in aqueous flow batteries according to claim 2, characterized in that: The pulse, exposure, and purge times of the precursors are specifically set as follows: for the precursor 1, the pulse, exposure, and purge times are 0.01~5, 10~50, and 10~50 seconds; for the precursor 2, the pulse, exposure, and purge times are 0.1~10, 10~50, and 10~80 seconds.
4. The method for preparing ALD-modified graphite felt for use in aqueous flow batteries according to claim 3, characterized in that: Maintaining the set temperature of the raw material bottle and the cavity specifically means maintaining the temperature of the raw material bottle at 25~150℃ and the temperature of the cavity at 100~300℃.
5. The method for preparing ALD-modified graphite felt for use in aqueous flow batteries according to claim 1, characterized in that: The number of atomic deposition cycles is 10 to 40 layers.
6. The method for preparing ALD-modified graphite felt for use in aqueous flow batteries according to claim 1, characterized in that: The reaction time for atomic deposition is 4–8 h.
7. The method for preparing ALD-modified graphite felt for use in aqueous flow batteries according to claim 1, characterized in that: The activation process in step 2, which involves calcining in a vacuum tube furnace with carrier gas, specifically involves raising the temperature from 25°C to 500°C within 60-120 minutes in an air atmosphere, calcining for 300-900 minutes, and then allowing it to cool naturally to room temperature before removing it.
8. The method for preparing ALD-modified graphite felt for use in aqueous flow batteries according to claim 1, characterized in that: The ultrasonic cleaning time in step 1 is 0.5~3 hours.
9. The method for preparing ALD-modified graphite felt for use in aqueous flow batteries according to claim 1, characterized in that: In step 1, the organic cleaning agent is selected from at least one of methanol, ethanol, propanol, and isopropanol.