Molecular Structure Tailoring of Organic Spacers for High‑Performance Ruddlesden–Popper Perovskite Solar Cells

Layer-structured Ruddlesden–Popper(RP)perovskites(RPPs)with decent stability have captured the imagination of the photovoltaic research community and bring hope for boosting the development of perovskite solar cell(PSC)technology.However,two-dimensional(2D)or quasi-2D RP PSCs are encountered with some challenges of the large exciton binding energy,blocked charge transport and poor film quality,which restrict their photovoltaic performance.Fortunately,these issues can be readily resolved by rationally designing spacer cations of RPPs.This review mainly focuses on how to design the molecular structures of organic spacers and aims to endow RPPs with outstanding photovoltaic applications.We firstly elucidated the important roles of organic spacers in impacting crystallization kinetics,charge transporting ability and stability of RPPs.Then we brought three aspects to attention for designing organic spacers.Finally,we presented the specific molecular structure design strategies for organic spacers of RPPs aiming to improve photovoltaic performance of RP PSCs.These proposed strategies in this review will provide new avenues to develop novel organic spacers for RPPs and advance the development of RPP photovoltaic technology for future applications.

Dual carbon Li-ion capacitor with high energy density and ultralong cycling life at a wide voltage window

Using the same materials for the cathode and anode in energy storage devices could greatly simplify the technological process and reduce the device cost significantly.In this paper,we assemble a dual carbon-based Li-ion capacitor with the active materials derived entirely from a single precursor,petroleum coke.For the anode,petroleum cokederived carbon(PCC)is prepared by simple ball milling and carbonization,having a massive tap density(1.80 g cm^(-3))and high electrical conductivity(11.5 S cm^(-1)).For the cathode,the raw petroleum coke is activated by KOH(petroleum cokeactivated carbon(PC-AC)sample)to achieve a well-developed pore structure to meet a rapid capacitive behavior.As a result,in addition to the robust structural stability of both the anode and cathode,the assembled dual carbon Li-ion capacitor shows a high energy density(231 W h kg^(-1)/206 W h L^(-1))and ultralong cycling life(up to 3000/10,000 cycles)at a wide voltage window.The excellent electrochemical response and simple production process make the PCC materials have great potential for practical application.

Realizing the Long Lifespan of Molybdenum Trioxide in Aqueous Aluminum Ion Batteries Through Potential Regulation

MoO_(3) is one of the most promising anode materials for aqueous aluminum batteries due to its high theoretical capacity and suitable aluminum insertion/de-insertion potential.However,the inferior cycling stability limits its further application,and the failure mechanism is still unclear.In this article,we provide a straightforward potential regulation technique to manage phase evolution during the charge/discharge process,which ultimately results in a markedly enhanced MoO_(3) electrode cycling stability.The failure mechanism study reveals that the excessive oxidation of the electrode during charge/discharge generates the H_(0.34)MoO_(3) phase,which has high solubility and is the primary cause of MoO_(3) deactivation.Although the dissolved Mo species will be deposited onto the electrode sheet again,the deposition is not electrochemically active and cannot contribute to the capacitance.Controlling the cutoff potential prevented the production of H_(0.34)MoO_(3),resulting in excellent cycling performance(80.1% capacity retention after 4000 cycles).The as-assembled α-MoO_(3)//MnO_(2) full battery exhibits high discharge plateaus(1.4 and 0.9 V),large specific capacity(200 mAhg^(-1) at 2 Ag^(-1)),and ultra-high coulombic efficiency(99%).The research presented here may contribute to the development of highly stable electrode materials for aqueous batteries.

Construction of Frame-Structured Flexible MXene Film Electrode to Achieve High Areal Capacitance Micro-Supercapacitor

Two-dimensional MXene-based film materials as flexible electrodes have been widely studied in wearable microsupercapacitors(MSCs).However,the existence of strong van derWaals interactions leads to serious self-stacking ofMXene layers,resulting in poor ionic dynamics and loss of active sites,which causes MXene film electrodes to exhibit low capacitance and poor rate performance in practical studies.To solve this,a frame-structured hybrid film(labeled as CN-MX hybrid film)is constructed by introducing intercalating agents(nanometer g-C_(3)N_(4))into MXene layers.In this unique hybrid film,the g-C_(3)N_(4)nanoparticles rationally occupy the interspace between MXene layers so as to alleviate layer stacking,thus effectively expanding the electrochemically active surface and promoting proton transfer.Synergistic pseudocapacitance inducted by g-C_(3)N_(4)surface groups,consequently,the CN-MX hybrid film electrode achieves an enhanced capacitive capability.In the three-electrode system,this frame-structured film electrode exhibits an ultra-high areal capacitance of 1932.8 mF cm^(−2).The assembled symmetry flexible MSC device based on CN-MX hybrid film can achieve an energy density of 2.28μWh cm^(−2)at 0.075 mW cm^(−2),as well as a superior cyclic stability with 90.4%retention after 700 cycles in alternating 90o bending and releasing states,revealing its potential in practical applications.

High-performance aluminum-polyaniline battery based on the interaction between aluminum ion and-NH groups

Aluminum-ion batteries(AIBs)are a type of promising energy storage device due to their high capacity,high charge transfer efficiency,low cost,and high safety.However,the most investigated graphitic and metal dichalcogenide cathodes normally possess only a moderate capacity and a relatively low cycling stability,respectively,which limit the further development of high-performance AIBs.Here,based on the results of first principles calculations,we developed a polyaniline/graphene oxide composite that exhibited outstanding performances as a cathode material in AIBs(delivering 180 mA h g^−1 after 4000 cycles),considering both the discharge capacity and the cycling performance.Ex-situ characterizations verified that the charge storage mechanism of polyaniline depended on the moderate interactions between−NH in the polyaniline chain and the electrolyte anions,such as AlCl4^−.These findings lay the foundation of the development of high-performance AIBs based on conducting polymers.