Facile Fabrication of Fe2 O3 Nanoparticles Anchored on Carbon Nanotubes as High-Performance Anode for Lithium-Ion Batteries

Fe2O3/MoO3@NG Heterostructure Enables High Pseudocapacitance and Fast Electrochemical Reaction Kinetics for Lithium-Ion Batteries

Transition metal oxides (TMOs) hold great potential for lithium-ion batteries (LIBs) on account of the high theoretical capacity. Unfortunately, the unfavorable volume expansion and low intrinsic electronic conductivity of TMOs lead to irreversible structural degradation, disordered particle agglomeration, and sluggish electrochemical reaction kinetics, which result in perishing rate capability and long-term stability. This work reports an Fe₂O₃/MoO₃@NG heterostructure composite for LIBs through the uniform growth of Fe₂O₃/MoO₃ heterostructure quantum dots (HQDs) on the N-doped rGO (NG). Due to the synergistic effects of the "couple tree"-type heterostructures constructed by Fe₂O₃ and MoO₃ with NG, Fe₂O₃/MoO₃@NG delivers a prominent rate performance (322 mA h g^-1 at 20 A g^-1, 5.0 times higher than that of Fe₂O₃@NG) and long-term cycle stability (433.5 mA h g^-1 after 1700 cycles at 10 A g^-1). Theoretical calculations elucidate that the strong covalent Fe-O-Mo, Mo-N, and Fe-N bonds weaken the diffusion energy barrier and promote the Li⁺-ion reaction to Fe₂O₃/MoO₃@NG, thereby facilitating the structural stability, pseudocapacitance contribution, and electrochemical reaction kinetics. This work may provide a feasible strategy to promote the practical application of TMO-based LIBs.

Bulk-Like SnO2-Fe2O3@Carbon Composite as a High-Performance Anode for Lithium Ion Batteries

Boosted power handling and the reduced charging duration of Li ion cells critically rests with ionic/electronic mobility. Ion mobility in electrochemically relevant grains normally stands for an essential restriction of the velocity at which the energy of a cell can be stored/released. To offset sluggish solid-state ionic transport and achieve a superior power/energy density rating, electroactive grains often need exquisite nanoscaling, harming crucial virtues on volumetric packing density, tractability, sustainability, durability, and cost. Unlike elaborate nanostructuring, here we describe that a SnO₂-Fe₂O₃@carbon composite—which adopts a metal oxide particles-intercalated bulk-like configuration—can insert many Li⁺ ions at elevated speeds, despite its micro-dimensionality. Analysis of charge transport kinetics in this tailor-made architecture unveils both much improved ion travel through compact monolithic substances and the greatly enhanced ion access to surfaces of SnO₂/Fe₂O₃ grains. According to the well-studied battery degradation mechanism, it is that both the effective stress management and internal electric field in our as-prepared sample that result in recommendable capacity, rate behavior, and cyclic lifespan (exhibiting a high reversible capacity of 927 mAh g⁻¹ at 0.2 A g⁻¹ with a capacity retention of 95.1% after 100 cycles and an ultra-stable capacity of 429 mAh g⁻¹ even over 1800 cycles at 3 A g⁻¹). Unique materials and working rationale which ensure the swift (de)lithiation of such micrometer-dimensional monoliths may open a door for various high-power/density usages.

Micro/Nanoengineered α-Fe2 O3 Nanoaggregate Conformably Enclosed by Ultrathin N-Doped Carbon Shell for Ultrastable Lithium Storage and Insight into Phase Evolution Mechanism

The Fe-based transition metal oxides are promising anode candidates for lithium storage considering their high specific capacity, low cost, and environmental compatibility. However, the poor electron/ion conductivity and significant volume stress limit their cycle and rate performances. Furthermore, the phenomena of capacity rise and sudden decay for α-Fe₂ O₃ have appeared in most reports. Here, a uniform micro/nano α-Fe₂ O₃ nanoaggregate conformably enclosed in an ultrathin N-doped carbon network (denoted as M/N-α-Fe₂ O₃ @NC) is designed. The M/N porous balls combine the merits of secondary nanoparticles to shorten the Li⁺ transportation pathways as well as alleviating volume expansion, and primary microballs to stabilize the electrode/electrolyte interface. Furthermore, the ultrathin carbon shell favors fast electron transfer and protects the electrode from electrolyte corrosion. Therefore, the M/N-α-Fe₂ O₃ @NC electrode delivers an excellent reversible capacity of 901 mA h g^-1 with capacity retention up to 94.0 % after 200 cycles at 0.2 A g^-1 . Notably, the capacity rise does not happen during cycling. Moreover, the lithium storage mechanism is elucidated by ex situ XRD and HRTEM experiments. It is verified that the reversible phase transformation of α↔γ occurs during the first cycle, whereas only the α-Fe₂ O₃ phase is reversibly transformed during subsequent cycles. This study offers a simple and scalable strategy for the practical application of high-performance Fe₂ O₃ electrodes.

NiMoS4 nanocrystals anchored on N-doped carbon nanosheets as anode for high performance lithium ion batteries

Owing to the excellent electrical conductivity and high theoretical capacity, binary transition metal sulfides have attracted extensive attention as promising anodes for lithium ion batteries (LIBs). However, the relatively poor electrical conductivity and serious capacity fading originated from large volume change still hinder their practical applications. Herein, binary NiMoS₄ nanoparticles are deposited on N doped carbon nanosheets (NC@NiMoS₄) through a facile hydrothermal method. The N doped carbon nanosheets and the strong chemical bonding between NC and NiMoS₄ can accommodate the volume change, keep the structural integrity and promote the ion/electron transfer during electrochemical reaction. The extra voids between NiMoS₄ nanoparticles enlarge the contact area and reduce the lithium migration barriers. As anode for LIBs, the NC@NiMoS₄ exhibits the excellent cycle stability with 834 mAh g^-1 after 100 cycles at the current density of 100 mA g^-1. Even at high rate of 2000 mA g^-1, the specific capacity of 544 mAh g^-1 can be achieved after 500 cycles.

Hierarchical non-woven fabric NiO/TiO2 film as an efficient anode material for lithium-ion batteries

Positive synergistic effect of TiO₂ and NiO of NiO/TiO₂ non-woven fabric electrode improves the electrochemical performance.