Interfacial built-in electric field and crosslinking pathways enabling WS_(2)/Ti_(3)C_(2)T_(x) heterojunction with robust sodium storage at low temperature

Developing efficient energy storage for sodium-ion batteries(SIBs)by creating high-performance heterojunctions and understanding their interfacial interaction at the atomic/molecular level holds promise but is also challenging.Besides,sluggish reaction kinetics at low temperatures restrict the operation of SIBs in cold climates.Herein,cross-linking nanoarchitectonics of WS_(2)/Ti_(3)C_(2)T_(x) heterojunction,featuring built-in electric field(BIEF),have been developed,employing as a model to reveal the positive effect of heterojunction design and BIEF for modifying the reaction kinetics and electrochemical activity.Particularly,the theoretical analysis manifests the discrepancy in work functions leads to the electronic flow from the electron-rich Ti_(3)C_(2)T_(x) to layered WS_(2),spontaneously forming the BIEF and“ion reservoir”at the heterogeneous interface.Besides,the generation of cross-linking pathways further promotes the transportation of electrons/ions,which guarantees rapid diffusion kinetics and excellent structure coupling.Consequently,superior sodium storage performance is obtained for the WS_(2)/Ti_(3)C_(2)T_(x) heterojunction,with only 0.2%decay per cycle at 5.0 A g^(-1)(25℃)up to 1000 cycles and a high capacity of 293.5 mA h g^(-1)(0.1A g^(-1)after 100 cycles)even at-20℃.Importantly,the spontaneously formed BIEF,accompanied by“ion reservoir”,in heterojunction provides deep understandings of the correlation between structure fabricated and performance obtained.

Two-step carbon modification of NaTi_2(PO_4)_3 with improved sodium storage performance for Na-ion batteries

NASICON-type structured NaTi2(PO4)3 has been regarded as a promising anode material for non-aqueous and aqueous Na-ion batteries,whereas its sodium storage performance was greatly restricted by its inherent inferior electronic conductivity.In the present work,a two-step carbon modification method using prefabricated carbon spheres as support and phenolic resin as carbon source was proposed to prepare advanced NaTi2(PO4)3/C.The as-prepared composite with carbon spheres displayed a much higher reversible capacity(126.7 mA?h/g vs 106.7 mA?h/g at 0.5C)than the control sample without carbon spheres.Superior rate capability with discharge capacities of 115.1,95.5,80.8 mAh/g at 1C,10C,20C,respectively and long-term cycling stability with capacity retention of 92.4%after 1000 cycles at 5C were also observed.Owing to the designing of two-step carbon modification,although the as-prepared sample shows much smaller surface area,it possesses much better conductive network and more uniform particle distribution,resulting in higher electronic conductivity and faster ionic conductivity,thereby superior sodium storage ability at high rate.

3D Graphene Nanosheets Crosslinked Core-Shell FeS_(2)@N,S Co-Doped Porous Carbon for Improved Lithium/Sodium Storage Performance

Transition metal sulfides(TMS)hold great promise as anode materials for Li^(+)/Na^(+)storage.However,their practical application still faces several challenges,such as inadequate electrical conductivity,substantial volume changes and a propensity for agglomeration.To tackle these challenges,a 3D composite structure composed of graphene nanosheets crosslinked core−shell FeS_(2)@N,S co−doped porous carbon(FeS_(2)@NSC/GNs)is created by combining self−template polymerization with the graphene encapsulation technique.Systematic characterization and analysis demonstrate the effectiveness of the self−template polymerization strategy in generating a porous core−shell structure,which facilitates the uniform dispersion and optimal contact of the FeS_(2) core within the carbon shell.Concurrently,the integration of graphene,alongside the porous carbon shell,introduces a sophisticated dual−protection mechanism against volume expansion and undesirable FeS_(2) aggregation.Furthermore,the resulting 3D architecture enables efficient electron/ion transport and provides abundant sites for Li^(+)/Na^(+)storage.Leveraging these inherent benefits,the FeS_(2)@NSC/GNs composite exhibits significantly improved lithium/sodium storage performance in comparison to the counterparts.Evidently,our proposed approach offers valuable guidance for the construction of advanced anodes for lithium/sodium−ion batteries.