Polypyrrole Nanopipes as a Promising Cathode Material for Li-ion Batteries and Li-ion Capacitors : Two-in-One Approach

Lithium ion capacitor (LIC) is a promising energy storage system that can simultaneously provide high energy with high rate (high power). Generally, LIC is fabricated using capacitive cathode (activated carbon, AC) and insertion-type anode (graphite) with Li-ion based organic electrolyte. However, the limited specific capacities of both anode and cathode materials limit the performance of LIC, in particular energy density. In this context, we have developed "two in one" synthetic approach to engineer both cathode and anode from single precursor for high performance LIC. Firstly, we have engineered a low cost 1D polypyrrole nanopipes (PPy-NPipes), which was utilized as cathode material and delivered a maximum specific capacity of 126 mAh/g, far higher than that of conventional AC cathodes (35 mAh/g). Later, N doped carbon nanopipes (N-CNPipes) was derived from direct carbonization of PPy-NPipes and successfully applied as anode material in LIC. Thus, a full LIC was fabricated using both pseudo-capacitive cathode (PPy-NPipes) and anode (N-CNPipes) materials, respectively. The cell delivered a remarkable specific energy of 107 Wh/kg with maximum specific power of 10 kW/kg and good capacity retention of 93 % over 2000 cycles. Thus, this work provide a new approach of utilization of nanostructured conducting polymers as a promising pseudocapacitive cathode for high performance energy storage systems

Improvement in performance of inverted organic solar cell by rare earth element lanthanum doped ZnO electron buffer layer

In the past decade of robust innovation, the inverted organic solar cells (IOSCs) have been considered as a substitute photovoltaic technology with the potential to provide comparable power conversion efficiencies (PCEs) combined with low processing cost and ease in fabrication. The doping of metal oxides is an expedient technique for controlling the electronic band gap configurations of the electron buffer layer (EBL) in inverted organic solar cells for better performance. In addition, the sol-gel method is utilized for doping various functional materials as EBLs in IOSCs due to its cost effectiveness and uniform nanoscale film deposition. In this report, we analyzed the sol-gel-based ZnO films as EBLs for P3HT: PCBM based IOSCs. The ZnO film thickness was optimized and we studied the effect of lanthanum doping into the ZnO films by measuring the power conversion efficiency of the devices. In our study, lanthanum nitrate hexahydrate was selected as a potential lanthanum dopant. The IOSC device made with 1.57 atomic.%-lanthanum-doped ZnO (La-ZnO B) EBL showed a PCE of 4.34%, which is an increment of 12% as compared to the reference cell device containing a pure ZnO EBL. Therefore, we demonstrated that the lanthanum doping enhanced the interfacial electrical properties in terms of conductivity and carrier density

Improvement in performance of inverted polymer solar cells by interface engineering of ALD ZnS on ZnO electron buffer layer

Atomic layer deposition (ALD) is an effective coating technique for angstrom- to nanometer-scale film deposition; its advantages include uniform and conformal coverage, controlled thickness, high reproducibility, and facile synthesis of various functional materials. In this study, we analyzed sol???gel-processed ZnO films coupled with interface-engineered ALD ZnS as electron buffer layers (EBLs) for inverted polymer solar cells (IPSCs). The thickness of the ZnO film was optimized to 10 nm by adjusting the solution concentration. Subsequently, we investigated the effect of the thickness of the ALD ZnS (formed on top of the ZnO film using diethyl zinc and H 2 S gas) on the photovoltaic properties of the IPSCs. The IPSC device fabricated with 1.8 nm-thick ALD ZnS on ZnO EBL (ZnS C) exhibited a power conversion efficiency (PCE) of 3.17%, which represents a 22% increase over that of equivalent reference cell devices containing only a pristine ZnO EBL. Characterization of the ZnO and ALD ZnS on the ZnO films revealed that the ALD ZnS films reduced the electron resistivity and surface defects of the ZnO films; this in turn reduced the interfacial carrier recombination in the IPSCs. Overall, we demonstrated that the interface engineering of ALD ZnS favorably influenced the electrical properties of the ZnO films

High performance inverted polymer solar cells using ultrathin atomic layer deposited TiO2 films

Photovoltaic properties of inverted type polymer solar cells (PSCs) using ultrathin TiO2 layers as an adjuvant electron collecting layer were investigated. To prepare the ultrathin (2.5 nm) TiO2 layers on top of TiO2 nanoparticles, atomic layer deposition (ALD) process was conducted at 125, 175, and 200 degrees C. The addition of ALD TiO2 on nanoparticulated TiO2 effectively enhanced the photovoltaic performances of inverted organic solar cells. The inverted PSC device with the thin 200 degrees C-ALD TiO2 layers showed the highest power conversion efficiency of 3.50%, which is an enhancement of approximately 30% compared to the cells without the ALD TiO2 layer (PCE = 2.72%). This work demonstrates that the ALD process plays a critical role in the enhancement of electron extraction efficiency with treating the surface defects of the TiO2 nanoparticles

Towards flexible solid-state supercapacitors for smart and wearable electronics

Flexible solid-state supercapacitors (FSSCs) are frontrunners in energy storage device technology and have attracted extensive attention owing to recent significant breakthroughs in modern wearable electronics. In this study, we review the state-of-the-art advancements in FSSCs to provide new insights on mechanisms, emerging electrode materials, flexible gel electrolytes and novel cell designs. The review begins with a brief introduction on the fundamental understanding of charge storage mechanisms based on the structural properties of electrode materials. The next sections briefly summarise the latest progress in flexible electrodes (i.e., freestanding and substrate-supported, including textile, paper, metal foil/wire and polymer-based substrates) and flexible gel electrolytes (i.e., aqueous, organic, ionic liquids and redox-active gels). Subsequently, a comprehensive summary of FSSC cell designs introduces some emerging electrode materials, including MXenes, metal nitrides, metal–organic frameworks (MOFs), polyoxometalates (POMs) and black phosphorus. Some potential practical applications, such as the development of piezoelectric, photo-, shape-memory, self-healing, electrochromic and integrated sensor-supercapacitors are also discussed. The final section highlights current challenges and future perspectives on research in this thriving field

Self-assembled nickel pyrophosphate-decorated amorphous bimetal hydroxides 2D-on-2D nanostructure for high-energy solid-state asymmetric supercapacitor

To obtain a supercapacitor with a remarkable specific capacitance and rate performance, a cogent design and synthesis of the electrode material containing abundant active sites is necessary. In present work, a scalable strategy is developed for preparing 2D‐on‐2D nanostructures for high‐energy solid‐state asymmetric supercapacitors (ASCs). The self‐assembled vertically aligned microsheet‐structured 2D nickel pyrophosphate (Ni2P2O7) is decorated with amorphous bimetallic nickel cobalt hydroxide (NiCo‐OH) to form a 2D‐on‐2D nanostructure arrays electrode. The resulting Ni2P2O7/NiCo‐OH 2D‐on‐2D array electrode exhibits peak specific capacity of 281 mA hg−1 (4.3 F cm−2), excellent rate capacity, and cycling stability over 10 000 charge–discharge cycles in the positive potential range. The excellent electrochemical features can be attributed to the high electrical conductivity and 2D layered structure of Ni2P2O7 along with the Faradic capacitance of the amorphous NiCo‐OH nanosheets. The constructed Ni2P2O7/NiCo‐OH//activated carbon based solid‐state ASC cell operates in a high voltage window of 1.8 V with an energy density of 78 Wh kg−1 (1.065 mWh cm−3) and extraordinary cyclic stability over 10 000 charge–discharge cycles with excellent energy efficiency (75%–80%) over all current densities. The excellent electrochemical performance of the prepared electrode and solid‐state ASC device offers a favorable and scalable pathway for developing advanced electrodes

Self‐Assembled Nickel Pyrophosphate‐Decorated Amorphous Bimetal Hydroxides 2D‐on‐2D Nanostructure for High‐Energy Solid‐State Asymmetric Supercapacitor

To obtain a supercapacitor with a remarkable specific capacitance and rate performance, a cogent design and synthesis of the electrode material containing abundant active sites is necessary. In present work, a scalable strategy is developed for preparing 2D‐on‐2D nanostructures for high‐energy solid‐state asymmetric supercapacitors (ASCs). The self‐assembled vertically aligned microsheet‐structured 2D nickel pyrophosphate (Ni2P2O7) is decorated with amorphous bimetallic nickel cobalt hydroxide (NiCo‐OH) to form a 2D‐on‐2D nanostructure arrays electrode. The resulting Ni2P2O7/NiCo‐OH 2D‐on‐2D array electrode exhibits peak specific capacity of 281 mA hg−1 (4.3 F cm−2), excellent rate capacity, and cycling stability over 10 000 charge–discharge cycles in the positive potential range. The excellent electrochemical features can be attributed to the high electrical conductivity and 2D layered structure of Ni2P2O7 along with the Faradic capacitance of the amorphous NiCo‐OH nanosheets. The constructed Ni2P2O7/NiCo‐OH//activated carbon based solid‐state ASC cell operates in a high voltage window of 1.8 V with an energy density of 78 Wh kg−1 (1.065 mWh cm−3) and extraordinary cyclic stability over 10 000 charge–discharge cycles with excellent energy efficiency (75%–80%) over all current densities. The excellent electrochemical performance of the prepared electrode and solid‐state ASC device offers a favorable and scalable pathway for developing advanced electrodes