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Tin dioxide (SnO 2 ) is a promising alternative material to graphite anode, but the large volume change induced electrode pulverization issue has limited its application in lithium-ion batteries (LIBs). In contrast, titanium dioxide (TiO 2 ) anode shows high structure stability upon lithium insertion/extraction, but with low specific capacity. To overcome their inherent disadvantages, combination of SnO 2 with TiO 2 and highly conductive carbon material is an effective way. Herein, we report a facile fabrication method of carbon-coated SnO 2 /TiO 2 nanowires (SnO 2 /TiO 2 @C) using tin titanate nanowires as precursor, which are prepared by reacting SnCl 2 ·2H 2 O with layered sodium titanate (Na 2 Ti 3 O 7 ) nanowires in the aqueous solution though the ion exchange between Sn 2+ and Na + . After annealing under argon atmosphere, the hydrothermally carbon-coated tin-titanate nanowires decompose, forming a unique hybrid structure, where ultrafine SnO 2 nanoparticles are uniformly embedded within the TiO 2 substrate with carbon coating. Consequently, the SnO 2 /TiO 2 @C nanowires demonstrate excellent lithium storage capacity with high pseudocapacitance contribution, excellent reversible capacity, and long-term cycling stability (673.7/510.5 mAh/g at 0.5/1.0 A/g after 250/800 cycles), owing to the unique hybrid structure, as the well-dispersion of ultra-small SnO 2 within TiO 2 nanowire substrate with simultaneous carbon coating efficiently suppresses the volume changes of SnO 2 , provides abundant reactive sites for lithium storage, and enhances the electrical conductivity with shortened ion transport distance., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Ti 2 Nb 10 O 29 , as one of the most promising anode materials for lithium-ion batteries (LIBs), possesses excellent structural stability during lithiation/delithiation cycling and higher theoretical capacity. However, Ti 2 Nb 10 O 29 faces some challenges, such as insufficient ion diffusion coefficient and poor electronic conductivity. To overcome these problems, this study investigates the effect of applying nanostructure engineering on Ti 2 Nb 10 O 29 and the lithium storage behaviors. We successfully synthesized hollow Ti 2 Nb 10 O 29 nanospheres (h-TNO NSs) via solvothermal method using phenolic resin nanospheres as the template. The effects of using a template or not and the annealing atmospheres on the microstructures of the as-prepared Ti 2 Nb 10 O 29 are investigated. Different nanostructures (porous Ti 2 Nb 10 O 29 nanoaggregates (p-TNO NAs) without a template and core-shelled Ti 2 Nb 10 O 29 @C nanospheres (cs-TNO@C NSs)) were formed through annealing in Ar. When examined as anodes for LIBs, the h-TNO NSs electrode with hollow spherical structure displayed a better lithium storage performance. Compared to its counterparts, p-TNO NAs and cs-TNO@C NSs, h-TNO NSs electrode exhibited a higher reversible capacity of 282.5 mAh g -1 at 1C, capacity retention of 79.5% (i.e., 224.6 mAh g -1 ) after 200 cycles, and a higher rate capacity of 173.1 mAh g -1 at 10C after 600 cycles. The excellent electrochemical performance of h-TNO NSs is attributed to the novel structure. The hollow nanospheres with cavities and thin shells not only exposed more active sites and improved ion diffusion, but also buffered the volume variation upon cycling and facilitated electrolyte penetration. This consequently enhanced the lithium storage performance of the electrode and its high pseudocapacitive contribution (90% at 1.0 mV s -1 )., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Transition metal oxides as potentialanodes of lithium-ion batteries (LIBs) possess high theoretical capacity but suffer from large volume expansion and poor conductivity. To overcome these drawbacks, we designed and fabricated polyphosphazene-coated yolk-shelled CoMoO 4 nanospheres, in which polyphosphazene with abundant C/P/S/N species was readily converted into carbon shells and provided P/S/N dopants. This resulted in the formation of P/S/N co-doped carbon-coated yolk-shelled CoMoO 4 nanospheres (PSN-C@CoMoO 4 ). The PSN-C@CoMoO 4 electrode exhibits superior cycle stability of 439.2 mA h g -1 at 1000 mA g -1 after 500 cycles and rate capability of 470.1 mA h g -1 at 2000 mA g -1 . The electrochemical and structural analyses reveal that PSN-C@CoMoO 4 with yolk-shell structure, coated with carbon and doped with heteroatom not only greatly enhances the charge transfer rate and reaction kinetics, but also efficiently buffers the volume variation upon lithiation/delithiation cycling. Importantly, the use of polyphosphazene as coating/doping agent can be a general strategy for developing advanced electrode materials., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

We report the fabrication of well-defined phase-pure Mn 2 V 2 O 7 hollow microspheres (h-MVO), assembled from the porous plate-like building blocks, via a facile solvothermal method followed by annealing, with the assistance of polyvinylpyrrolidone (PVP) as the structure-regulating agent. The microstructure dependent electrochemical properties of h-MVO as anode materials for lithium ion batteries (LIBs) are investigated, and excellent lithium storage performance is obtained with a reversible capacity of 1707 mAh g -1 after 700 cycles at 0.5 A g -1 , revealing that the unique hierarchical framework of the h-MVO microspheres with hollow interiors and porous building blocks could not only accelerate the transport of Li + ions and electrolyte, but also efficiently suppress the electrode pulverization upon cycling. More importantly, we demonstrate that PVP can be an effective agent to tune the microstructures, which would be promising for the development of high-performance energy storage devices., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

TiNb 2 O 7 (TNO) as a promising candidate anode for lithium-ion batteries (LIBs) shows obvious advantages in terms of specific capacity and safety, but which undergoes the intrinsic poor electrical and ionic conductivity. Herein, we propose a simple synthesis strategy of mesoporous TNO via a polymeric surfactant-mediated evaporation-induced sol-gel method, using polyvinylpyrrolidone (PVP) with different molecular weights (average Mw: 10000/58000/1300000) as the regulating agent, which greatly affects the lithium storage performance of the as-prepared TNO. The optimized TNO (i.e., PVP of 58000) delivers a high reversible capacity of 303.1 mAh/g at 1 C, with a retention rate of 73.4% (222.5 mAh/g) after 300 cycles. Even at 5 C, a high reversible capacity of 185.6 mAh/g can be achieved, with a retention rate of 72.3% after 1000 cycles. The superior lithium storage behavior is attributed to the fine mesoporous framework consisting of interconnected TNO nanocrystallites with high specific surface area and high mesoporosity, which greatly increases the active sites, improves the Li + diffusion kinetics and alleviates volume fluctuation induced by the repetitive Li + insertion-extraction processes., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Metal oxides are prospective alternative anode materials to the commercial graphite for lithium ion batteries (LIBs), while their practical application is seriously hampered by their poor conductivities and large volume changes. Herein, we report the controllable synthesis of amorphous/crystalline MnCo 2 O x nanoparticles within porous carbon nanofibers (marked as MCO@CNFs) through a facile electrospinning strategy and subsequent annealing reactions. The phase structures from Co/MnO X to amorphous MnCo 2 O x and crystalline MnCo 2 O 4.5 can be readily tuned by thermal reduction/oxidation under controlled atmosphere and temperature. When examined as anode for LIBs, the optimized MCO@CNFs delivers a high stable capacity of 780.3 mA h g -1 at 200 mA g -1 after 250 cycles, which is attributed to the synergistic effect of the distinctive amorphous structure and defective carbon nanofiber matrices. Specifically, the amorphous structure with rich defects offers more reactive sites and multiple pathways for the Li + diffusion, while carbon hybridization sufficiently improves the electrode conductivities as well as buffers the volume changes. More importantly, we demonstrate a convenient synthesis strategy to control the metal-to-oxide structure evolution within carbon matrices, which is of great importance in exploring high-performance electrodes for next generation LIBs., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Titanium dioxide (TiO 2 ) as a potential anode material for sodium-ion batteries (SIBs) suffers from the intrinsic poor electronic conductivity and sluggish ionic diffusivity, thus usually leading to the inferior electrochemical performance. Herein, we demonstrate a facile strategy to enhance the sodium storage performance of TiO 2 via vanadium (V) doping, using the pre-synthesized V-doped Ti-based metal-organic framework (MOF, MIL-125) as the precursor, which can be converted into the V-doped TiO 2 with simultaneous carbon hybridization and controlled V-doping amount (denote as V x TiO 2 @C, where × represents the V/Ti molar ratio (R V/Ti )). V-doping not only affects the morphology of the MIL-125 changing from thick to thin nanotablets, but also greatly enhances the electrochemical performance of the V x TiO 2 @C. When used as an anode for SIBs, the V 0.1 TiO 2 @C exhibits a much higher reversible capacity of 211 mAh/g than that for the undoped TiO 2 @C (only 156 mAh/g) after 150 cycles at 100 mA/g. Even after high-rate long-term cycling, the V 0.1 TiO 2 @C can still display a capacity of 180 mAh/g with a high capacity retention of 137% at 1000 mA/g after 4500 cycles. Structural/electrochemical measurements reveal that V-doping induces the formation of oxygen vacancies as well as Ti 3+ species, which efficiently improve the electric conductivity and the ion diffusivity of the electrode. Meanwhile, the thinner V 0.1 TiO 2 @C nanotablets with porous structure and carbon hybridization could facilitate the ion/electron transfer with shortened diffusion pathways., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Transition metal oxides/selenides as anodes for sodium-ion batteries (SIBs) suffer from the insufficient conductivity and large volumetric expansion, which leads to the poor electrochemical performance. To address these issues, we herein demonstrate a facile selenization method to enhance the sodium storage capability of CoMoO 4 nanoparticles which are encapsulated into the electrospun carbon nanofibers (CMO@carbon for short). The partially and fully selenized CoMoO 4 within carbon nanofibers (denote as CMOS@carbon and CMS@carbon, respectively) can be readily obtained by controlling the annealing temperature (at 400 and 600 °C, correspondingly). When examined as anode materials for SIBs, the CMOS@carbon nanofibers display an outstanding electrochemical performance with a higher reversible capacity of 396 mA h g -1 after 200 cycles at 0.2 A g -1 and a high-rate capacity of 365 mA h g -1 at 2 A g -1 , as compared with the CMO@carbon and CMS@carbon counterparts. The enhanced sodium storage performance of the CMOS@carbon can be owing to the partial selenization of the CoMoO 4 nanoparticles which are rooted into the porous electrospun carbon nanofibers, thus endowing them with superior ionic/electronic charge transfer efficiencies and a cushion against the electrode pulverization during cycling. Moreover, this work proposed a useful strategy to enhance the sodium storage performance of metal oxides via controlled selenization, which is promising for exploiting the advanced anode materials for SIBs., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

We design and fabricate a novel hybrid with amorphous lithium vanadate (LiV 3 O x , LVO for short) uniformly encapsulated into carbon nanofibers (denoted as LVO@CNFs) via an easy electrospinning strategy followed by proper postannealing. When examined for use as anode materials for lithium-ion batteries (LIBs), the optimized LVO@CNFs present a high discharge capacity of 603 mAh g -1 with a capacity retention as high as 90% after 200 cycles at 0.5 A g -1 and a high rate capacity of 326 mAh g -1 after 400 cycles even at a high rate of 5 A g -1 . The superior electrochemical performance with excellent cycling stability and rate capability is attributed to the full encapsulation of the amorphous LVO into the conductive carbon nanofibers, which hold enlarged electrochemically active sites for lithium storage, facilitate the charge transfer, and efficiently alleviate the volume changes upon lithium insertion/extraction. More importantly, the current synthesis can be a general strategy to fabricate various alkaline earth metal vanadates, which is promising for developing advanced electrochemical energy storage devices., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Alloy-/conversion-type metal oxides usually exhibit high theoretical lithium storage capacities but suffer from the large volume change induced electrode pulverization and the poor electric conductivity, which limit their practical applications. Hybrid/mixed metal oxides with different working mechanisms/potentials can display advantageous synergistic enhancement effect if delicate structure engineering is performed. Herein, atomically hybridized SnO 2 /Co 3 O 4 nanocomposites with amorphous nature are successfully cast onto the porous N-doped carbon (denoted as NC) nanoflakes through facile pyrolysis of the tin (II) 2-ethylhexanoate (C 16 H 30 O 4 Sn) and cobalt (II) 2-ethylhexanoate (C 16 H 30 O 4 Co) mixture within NC nanoflakes in air at 300 °C for 1 h. The Sn/Co atomic ratio and the loading amount of SnO 2 /Co 3 O 4 can be readily controlled, whose effect on lithium storage are investigated as anodes for lithium ion batteries (LIBs). Notably, SnO 2 /Co 3 O 4 @NC (R Sn/Co  = 1.25) nanoflakes exhibit the most excellent lithium storage properties, delivering a reversible capacity of 1450.3 mA h g -1 after 300 cycles at 200 mA g -1 , which is much higher than that of the single metal oxide SnO 2 @NC and Co 3 O 4 @NC electrodes., (Copyright © 2019 Elsevier Inc. All rights reserved.)

CoMoO 4 nanoparticles have been successfully in-situ formed and simultaneously embedded within the porous carbon nanofibers (CoMoO 4 /CNFs) via a facile electrospinning-annealing strategy. The porous CoMoO 4 /CNFs exhibit a specific surface area of 255.3 m 2 /g and a pore volume of 0.52 cc/g with average pore diameter of 43.5 nm. The carbon content in the CoMoO 4 /CNFs can be readily controlled by adjusting the annealing temperature. When examined as anode materials for lithium ion batteries (LIBs), the CoMoO 4 /CNFs demonstrate superior electrochemical performance, delivering a high reversible capacity of 802 mA h/g after 200 cycles at 200 mA/g and a high-rate capacity of 574 mA h/g at 2000 mA/g. The excellent lithium storage behavior can be attributed to the incorporation of CoMoO 4 nanoparticles into the porous N-doped graphitic carbon nanofibers, which efficiently buffer the volume changes of CoMoO 4 upon lithiation/delithiation and maintain the overall electrode conductivity/integrity., (Copyright © 2019 Elsevier Inc. All rights reserved.)

We report an amorphorization-hybridization strategy to enhance lithium storage by casting atomically mixed amorphorized SnO 2 /MoO 3 into porous foam-like carbon nanoflakes (denote as SnO 2 /MoO 3 @CNFs, or SMC in short), which are simply prepared by annealing tin(II)/molybdenum(IV) 2-ethylhexanoate within CNFs under ambient atmosphere at a low temperature (300 °C). The SnO 2 /MoO 3 loading amount within CNFs can be easily adjusted by controlling the Sn/Mo/C precursors. When examined as lithium ion battery (LIB) anode materials, the amorphorized SnO 2 /MoO 3 @CNFs with carbon content of 32 wt% (also denote as SMC-32, in which the number represents the carbon content) deliver a high reversible capacity of 1120.5 mA h/g after 200 cycles at 200 mA/g and then 651.5 mA h/g after another 300 cycles at 2000 mA/g, which is much better than that of the crystalline SnO 2 /CNFs (carbon content of 34 wt%), MoO 3 /CNFs (carbon content of 22.7 wt%), or SnO 2 /MoO 3 @CNFs (with lower carbon contents of 11 and 25 wt%). The electrochemical measurements as well as the ex situ structure characterization clearly suggest that combination of amorphorization and hybridization of SnO 2 /MoO 3 with CNFs synergistically contributes to the superior lithium storage performance with high pseudocapacitive contribution., (Copyright © 2019 Elsevier Inc. All rights reserved.)