Pseudocapacitors by Unknown

Author:Unknown
Language: eng
Format: epub
ISBN: 9783031454301
Publisher: Springer Nature Switzerland

2.2 MXenes/polymer Composites

Compared with other pseudocapacitive materials, conductive polymers exhibit additional advantages in supercapacitors due to simple synthesis, good conductivity, good flexibility, and high redox activity [12]. Many conductive polymers can achieve high capacitance in acidic electrolytes, as can MXenes/conductive polymer composites. At present, many conductive polymers, such as polyaniline (PANI), poly (3,4-ethylenedioxythiophene) (PEDOT), polypyridine (PPy), and polydopamine (PDA), combine with MXenes to prepare composites with excellent electrochemical performance [12]. Gogotsi et al. prepared a high-performance 3D PANI@M-Ti3C2Tx composites by casting homogeneous polyaniline layer on 3D porous Ti3C2Tx MXene in Fig. 5a–b [37]. The compact and highly integrated PANI@MXene heterostructure possesses a larger work function, so they have high anodic oxidation electrochemical stability and can be used as stable positive terminals. This electrode synergistically utilizes the high capacitance of PANI at a positive potential and the high-speed capability of MXene, which allows the PANI@M-Ti3C2Tx electrode to have a high specific capacitance of 1632 F/cm3, and a high-capacity retention of 827 F/cm3 at a scanning rate of up to 5000 mV/s in Fig. 5c. The asymmetric supercapacitors device assembled based on this material achieves a volumetric energy density of 50.6Wh/L. Yuan et al. proposed high conductivity PANI nanoparticles (PANI-NPs, ~10 nm) as intercalation agents, and adjusted MXene nanoflake interlayer by self-assembly method [38]. PANI-NPs not only inhibit the self-stacking of MXene, but also provides more ion transfer pathways. In addition, conductive PANI-NPs filled between MXene layers can construct interconnected conductive channels in the form of nanoparticles. Meanwhile, PANI-NPs will slightly change the thickness of the MX/PANI-NPs mixed film, resulting in higher volumetric capacitance. The capacitance of the MX/PANI NPs-10% electrode is 1885 mF/cm2 (377 F/g), which can maintain a high capacitance of 873 F/cm3 even when the MXene load reaches 5 mg/cm2. In addition, the symmetrical supercapacitors assembled based on MX/PANI NPs hybrid films have a bulk energy density (20.9 Wh/L). Zhang et al. established a simple and effective method for preparing Ti3C2Tx/PEDOT: PSS hybrid membranes, which involves filtering Ti3C2Tx/Levios PH1000 composite ink, and then treating by H2SO4 in Fig. 5d–e [39]. The process of H2SO4 treatment can remove some insulating PSS on the Ti3C2Tx/PEDOT: PSS hybrid film, thereby significantly improving the conductivity of the composites. In addition, conductive PEDOT can not only serve as a pillar between Ti3C2Tx sheets, exposing more electroactive surfaces and reducing ion diffusion pathways but also serve as a conductive bridge to form multidimensional electron transfer channels for accelerating the electrochemical reaction process. The specific surface area of Ti3C2Tx/PEDOT: PSS (Ti3C2Tx/P-100-H) hybrid film treated with H2SO4 increased by 4.5 times, and the capacity reached 1065 F/cm3 at 2 mV/s, demonstrating excellent rate performance in 1 M H2SO4 electrolyte in Fig. 5f. The asymmetric supercapacitors based on the materials show an energy density of 23mWh/cm3 and a power density of 7659 mW/cm3. Ma et al. prepared MXene/PPy (M-PPy) composite films using MXene nanosheets and PPy nanofibers as raw materials by vacuum-assisted filtration in Fig. 5g [40]. By introducing PPy nanofibers, the layer spacing of MXene nanosheets is expanded in Fig.

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