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Developing ionogel electrolytes based on ionic liquid instead of volatile liquid in gel polymer electrolytes is regarded to be effective to diminish safety concerns in terms of overheating and fire. Herein, a zwitterion‐based copolymer matrix based on the copolymerization of trimethylolpropane ethoxylate triacrylate (ETPTA) and 2‐methacryloyloxyethylphosphorylcholine (MPC, one typical zwitterion) is developed. It is shown that introducing zwitterions into ionogel electrolytes can effectively optimize local lithium‐ion (Li+) coordination environment to improve Li+ transport kinetics. The interactions between Li+ and bis(trifluoromethanesulfonyl)imide (TFSI−)/MPC lead to the formation of Li+ coordination shell jointly occupied by MPC and TFSI−. Benefiting from the competitive Li+ attraction of TFSI− and MPC, the energy barrier of Li+ desolvation is sharply decreased and thus the room‐temperature ionic conductivity can reach a value of 4.4 × 10−4 S cm−1. Besides, the coulombic interaction between TFSI− and MPC can greatly decrease the reduction stability of TFSI−, boosting in situ derivation of LiF‐enriched solid electrolyte interface layer on lithium metal surface. As expected, the assembled Li||LiFePO4 cells deliver a high reversible discharge capacity of 139 mAh g−1 at 0.5 C and good cycling stability. Besides, the pouch cells exhibit a steady open‐circuit voltage and can operate normally under abuse testing (fold, cut), showing its outstanding safety performance. [ABSTRACT FROM AUTHOR]

Ameliorating round‐trip efficiency and mitigating parasitic reaction play a key role in enhancing the activity and durability of lithium–oxygen batteries. Herein, it is first reported that Ti3C2 MXene quantum dot clusters full of rich crystal defects anchored on N‐doped carbon nanosheets (Ti3C2 QDC/N‐C) can operate well as bifunctional catalyst for Li–O2 batteries. The well‐defined grain boundary and edge defects make crucial contributions in modulating the local unsaturated coordination state of active titanium atoms and thus the electronic structure of Ti3C2 QDC/N‐C, greatly enhancing the catalytic capability. Furthermore, density functional theory calculations disclose that the fruitful crystal defects governed catalytic centers endow substantial benefits for inducing charge density delocalization, regulating the LixOy intermediate adsorption and reducing the oxidation‐reduction energy barriers. The geometric morphology and distribution of final Li2O2 accommodations are distinctly altered with optimized decomposition reversibility, which strengthens electro‐catalytic kinetics and lowers redox voltage gaps. As expected, Li–O2 cells based on Ti3C2 QDC/N‐C show favorable long‐period stability (240 cycles at 200 mA g−1) with minimal side reactions and distinguished discharge/charge overpotential (0.62 V). Critically, this crystal defect strategy paves a new way for expanding the active sites in MXenes for catalytic applications. [ABSTRACT FROM AUTHOR]

Rechargeable Li–O2 batteries are promising due to their superior high energy density but subject to sluggish oxygen reduction/evolution kinetics. Developing highly efficient catalysts to improve catalytic activity and alleviate oxidation–reduction overpotential of Li–O2 batteries is of great challenge and importance. Herein, a CO2‐assisted thermal‐reaction strategy is developed to fabricate isolated semi‐metallic selenium single‐atom‐doped Ti3C2 MXene catalyst (SASe‐Ti3C2) as cathodes for high‐performance Li–O2 batteries. The isolated moieties of single Se atom catalysis centers can function as active catalytic centers to drastically enhance the intrinsic LiO2‐absorption ability and thus fundamentally modulate the formation/decomposition mechanism of lithium peroxide (Li2O2) discharge product, thus demonstrating greatly enhanced redox kinetics and efficiently ameliorated overpotentials. Theoretical simulations reveal that the interaction between Se‐involved moieties and Ti3C2 substrate greatly enhances the intrinsic LiO2‐absorption ability and fundamentally promotes the charge transfer between electrode and Li2O2 product, deeply ameliorating the round‐trip overpotential. The well‐designed SASe–Ti3C2 electrode exhibits decreased charge/discharge polarization (1.10 V vs Li/Li+), ultrahigh discharge capacity (17 260 mAh g−1 at 100 mA g−1), and superior durability (170 cycles at 200 mA g−1) as cathode for Li–O2 batteries. The promising results will shed light on the design of highly efficient catalysts for oxygen‐involved systems of future investigation. [ABSTRACT FROM AUTHOR]

Silicon is attracting enormous attention due to its theoretical capacity of 4200 mAh g−1 as an anode for Li‐ion batteries (LIBs). It is of fundamental importance and challenge to develop low‐temperature reaction route to controllably synthesize Si/Ti3C2 MXene LIBs anodes. Herein, a novel and efficient strategy integrating in situ orthosilicate hydrolysis and a low‐temperature reduction process to synthesize Si/Ti3C2 MXene composites is reported. The hydrolysis of tetraethyl orthosilicate leads to homogenous nucleation and growth of SiO2 nanoparticles on the surface of Ti3C2 MXene. Subsequently, SiO2 nanoparticles are reduced to Si via a low‐temperature (200 °C) reduction route. Importantly, Ti3C2 MXene not only provides fast transfer channels for Li+ and electrons, but also relieves volume expansion of Si during cycling. Moreover, the characteristics of excellent pseudocapacitive performance and high conductivity of Ti3C2 MXene can synergistically contribute to the enhancement of energy storage performance. As expected, Ti3C2/Si anode exhibits an outstanding specific capacity of 1849 mAh g−1 at 100 mA g−1, even retaining 956 mAh g−1 at 1 A g−1. The low‐temperature synthetic route to Si/Ti3C2 MXene electrodes and involved battery‐capacitive dual‐model energy storage mechanism has potential in the design of novel high‐performance electrodes for energy storage devices. [ABSTRACT FROM AUTHOR]

Owing to their well-defined crystalline pore structures and ordered functional ionic groups along the skeleton, ionic covalent organic frameworks (iCOFs) exhibit excellent performance and have significant potential for use in energy storage and conversion devices. Herein, we for the first time developed cationic phosphonium COFs with high hydroxide conduction even with low ion exchange capacity (IEC). Specifically, we synthesized COFs containing quaternary phosphonium groups as excellent ion transport moieties. Then, we fabricated freestanding phosphonium membranes through a vapor-assisted method, which exhibited high hydroxide conductivity of 126 mS cm-1 at 80 °C from a minimal IEC of 1.17 mmol g-1. The resulting film was successfully applied to zinc-air batteries, demonstrating energy density of 96.1 mW cm-2, specific capacity of 95.0 mAh cm-2, and stable operation over 2,300 min. Overall, in addition to investigating a novel cationic functional group, we demonstrated a freestanding film formation method of COF-based materials. The findings can provide a solid foundation for advancing the field of iCOFs to ion transport and promoting electrochemical applications., (© 2024 Wiley‐VCH GmbH.)

Developing ionogel electrolytes based on ionic liquid instead of volatile liquid in gel polymer electrolytes is regarded to be effective to diminish safety concerns in terms of overheating and fire. Herein, a zwitterion-based copolymer matrix based on the copolymerization of trimethylolpropane ethoxylate triacrylate (ETPTA) and 2-methacryloyloxyethylphosphorylcholine (MPC, one typical zwitterion) is developed. It is shown that introducing zwitterions into ionogel electrolytes can effectively optimize local lithium-ion (Li + ) coordination environment to improve Li + transport kinetics. The interactions between Li + and bis(trifluoromethanesulfonyl)imide (TFSI - )/MPC lead to the formation of Li + coordination shell jointly occupied by MPC and TFSI - . Benefiting from the competitive Li + attraction of TFSI - and MPC, the energy barrier of Li + desolvation is sharply decreased and thus the room-temperature ionic conductivity can reach a value of 4.4 × 10 -4 S cm -1 . Besides, the coulombic interaction between TFSI - and MPC can greatly decrease the reduction stability of TFSI - , boosting in situ derivation of LiF-enriched solid electrolyte interface  layer on lithium metal surface. As expected, the assembled Li||LiFePO 4 cells deliver a high reversible discharge capacity of 139 mAh g -1 at 0.5 C and good cycling stability. Besides, the pouch cells exhibit a steady open-circuit voltage and can operate normally under abuse testing (fold, cut), showing its outstanding safety performance., (© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.)

The commercialization of MXenes as anodes for lithium-ion batteries is largely impeded by low initial coulombic efficiency (ICE) and unfavorable cycling stability, which are closely associated with defects such as Ti vacancies (V Ti ) in Ti 3 C 2 MXenes. Herein, an effective strategy is developed to deactivate V Ti defects by in situ growing Al 2 O 3 nanoclusters on MXenes to alleviate the irreversible electrolyte decomposition and Li dendrites formation trend induced by defects, improving ICE and cycling stability. Furthermore, it is revealed that excessively lithiophilic V Ti defects would impede Li ions diffusion due to their strong adsorption, leading to a locally nonuniform Li flux to these "hot spots," setting scene for the formation of Li dendrites. The Al 2 O 3 nanoclusters anchored on V Ti sites can not only improve Li diffusion kinetics but also promote the homogeneous solid electrolyte interphase formation with small charge transfer resistance, achieving uniform Li deposition in a smaller overpotential without formation of Li dendrites. As expected, Ti 3 C 2 @Al 2 O 3 -11 electrode delivers a high ICE of 76.6% and an outstanding specific capacity of 285.5 mAh g -1 after 500 cycles, which is much higher than that of pristine Ti 3 C 2 sample. This work sheds light on modulating defects for high-performance energy storage materials., (© 2021 Wiley-VCH GmbH.)

Taking into consideration the advantages of the highly theoretical capacity of antimony (Sb) and abundant surface redox reaction sites of Na + pre-intercalated 3D porous Ti 3 C 2 T x (Na-Ti 3 C 2 T x ) architectures, we elaborately designed the Sb/Na-Ti 3 C 2 T x hybrid with Sb nanoparticles homogeneously distributed in 3D porous Na-Ti 3 C 2 T x architectures through a facile electrostatic attraction and carbothermic reduction process. Na-Ti 3 C 2 T x architectures with more open structures and larger active specific surface area not only could certainly alleviate volume changes and hinder the aggregation of Sb nanoparticles in the cycling process to improve the structural stability but also significantly strengthen the electron-transfer kinetics and provide unblocked K + diffusion channels to promote ionic/electronic transport rate. Furthermore, the ultrafine Sb nanoparticles could efficiently shorten K + transport distance and expose more accessible active sites to improve capacity utilization. DFT calculations further indicate that the Sb/Na-Ti 3 C 2 T x anode effectively decreases the adsorption energy of K + and accelerates the potassiation process. Benefiting from the synergistic effect, it exhibits an outstanding specific capacity of 392.2 mAh g -1 at 0.1 A g -1 after 450 cycles and a stable capacity reservation with a capacity fading rate of 0.03% per cycle at 0.5 A g -1 . Our work may encourage further research on advanced MXene-based hybrid materials for high-performance PIBs.