SnO2@C@VO2 Composite Hollow Nanospheres as an Anode Material for Lithium-Ion Batteries

Critical Review of Emerging Pre-metallization Technologies for Rechargeable Metal-Ion Batteries

Low Coulombic efficiency, low-capacity retention, and short cycle life are the primary challenges faced by various metal-ion batteries due to the loss of corresponding active metal. Practically, these issues can be significantly ameliorated by compensating for the loss of active metals using pre-metallization techniques. Herein, the state-of-the-art development in various pr-emetallization techniques is summarized. First, the origin of pre-metallization is elaborated and the Coulombic efficiency of different battery materials is compared. Second, different pre-metallization strategies, including direct physical contact, chemical strategies, electrochemical method, overmetallized approach, and the use of electrode additives are summarized. Third, the impact of pre-metallization on batteries, along with its role in improving Coulombic efficiency is discussed. Fourth, the various characterization techniques required for mechanistic studies in this field are outlined, from laboratory-level experiments to large scientific device. Finally, the current challenges and future opportunities of pre-metallization technology in improving Coulombic efficiency and cycle stability for various metal-ion batteries are discussed. In particular, the positive influence of pre-metallization reagents is emphasized in the anode-free battery systems. It is envisioned that this review will inspire the development of high-performance energy storage systems via the effective pre-metallization technologies.

Boosting Reversibility and Stability of Li Storage in SnO2 -Mo Multilayers: Introduction of Interfacial Oxygen Redistribution

Among the promising high-capacity anode materials, SnO₂ represents a classic and important candidate that involves both conversion and alloying reactions toward Li storage. However, the inferior reversibility of conversion reactions usually results in low initial Coulombic efficiency (ICE, ≈60%), small reversible capacity, and poor cycling stability. Here, it is demonstrated that by carefully designing the interface structure of SnO₂ -Mo, a breakthrough comprehensive performance with ultrahigh average ICE of 92.6%, large capacity of 1067 mA h g^-1 , and 100% capacity retention after 700 cycles can be realized in a multilayer Mo/SnO₂ /Mo electrode. Furthermore, high capacity retentions are also achieved in pouch-type Mo/SnO₂ /Mo||Li half cells and Mo/SnO₂ /Mo||LiFePO₄ full cells. The amorphous SnO₂ /Mo interfaces, which are induced by redistribution of oxygen between SnO₂ and Mo, can precisely adjust the reversible capacity and cycling stability of the multilayers, while the stable capacities are parabolic with the interfacial density. Theoretical calculations and in/ex situ investigation reveal that oxygen redistribution in SnO₂ /Mo heterointerfaces boosts Li-ion transport kinetics by inducing a built-in electric field and improves the reaction reversibility of SnO₂ . This work provides a new understanding of interface-performance relationship of metal-oxide hybrid electrodes and pivotal guidance for creating high-performance Li-ion batteries.

Emerging of Heterostructure Materials in Energy Storage: A Review

With the ever-increasing adaption of large-scale energy storage systems and electric devices, the energy storage capability of batteries and supercapacitors has faced increased demand and challenges. The electrodes of these devices have experienced radical change with the introduction of nano-scale materials. As new generation materials, heterostructure materials have attracted increasing attention due to their unique interfaces, robust architectures, and synergistic effects, and thus, the ability to enhance the energy/power outputs as well as the lifespan of batteries. In this review, the recent progress in heterostructure from energy storage fields is summarized. Specifically, the fundamental natures of heterostructures, including charge redistribution, built-in electric field, and associated energy storage mechanisms, are summarized and discussed in detail. Furthermore, various synthesis routes for heterostructures in energy storage fields are roundly reviewed, and their advantages and drawbacks are analyzed. The superiorities and current achievements of heterostructure materials in lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), lithium-sulfur batteries (Li-S batteries), supercapacitors, and other energy storage devices are discussed. Finally, the authors conclude with the current challenges and perspectives of the heterostructure materials for the fields of energy storage.

Highly conductive triple-layered hollow MnO2@SnO2@NHCS nanospheres with excellent lithium storage capacity for high performance lithium-ion batteries

Multilayered hollow MnO2@SnO2@NHCS nanospheres incorporate the merits of highly conductive N-doping and the synergistic effect of metal oxides.

VO2 Nanostructures for Batteries and Supercapacitors: A Review

Vanadium dioxide (VO₂ ) received tremendous interest lately due to its unique structural, electronic, and optoelectronic properties. VO₂ has been extensively used in electrochromic displays and memristors and its VO₂ (B) polymorph is extensively utilized as electrode material in energy storage applications. More studies are focused on VO₂ (B) nanostructures which displayed different energy storage behavior than the bulk VO₂ . The present review provides a systematic overview of the progress in VO₂ nanostructures syntheses and its application in energy storage devices. Herein, a general introduction, discussion about crystal structure, and syntheses of a variety of nanostructures such as nanowires, nanorods, nanobelts, nanotubes, carambola shaped, etc. are summarized. The energy storage application of VO₂ nanostructure and its composites are also described in detail and categorically, e.g. Li-ion battery, Na-ion battery, and supercapacitors. The current status and challenges associated with VO₂ nanostructures are reported. Finally, light has been shed for the overall performance improvement of VO₂ nanostructure as potential electrode material for future application.

Rapid preparation of ultra-fine and well-dispersed SnO2 nanoparticles via a double hydrolysis reaction for lithium storage

An efficient and rapid method is reported for preparing ultra-fine and well-dispersed SnO₂ nanoparticles in a large scale. A simple double hydrolysis reaction between SnO₃^2- and Fe³⁺ ions was masterly used to form a stable colloid system, in which colloidal particles of H₂SnO₃ with negative charges and Fe(OH)₃ with positive charges electrostatically interact with each other and form honeycomb-like "core-shell" units. Through the hydrothermal reaction, the units are easily transformed into SnO₂@FeO(OH) structures. Ultra-fine and well-dispersed SnO₂ particles with less than 6 nm diameter were finally obtained with a high yield by further etching using hydrochloric acid. When used as anode materials for lithium ion batteries, the ultra-fine SnO₂ particles can be easily dispersed into the carbon networks originating from the carbon source of glucose during the hydrothermal reaction. Electrochemical tests confirmed that these ultra-fine SnO₂/C materials were endowed with excellent cyclic stability and C-rate performance. Even at a 1.56 A g^-1 (2C) high current density, the reversible capacity could be maintained at 710 mA h g^-1 after 100 cycles owing to the ultra-fine particle size of SnO₂ and the rich carbon networks.

Superior and Reversible Lithium Storage of SnO2/Graphene Composites by Silicon Doping and Carbon Sealing

The poor cycle stability and reversibility seriously hinder the widespread application of SnO₂ materials as anodes for lithium-ion batteries (LIBs). A novel sandwich-architecture composite of Si-doped SnO₂ nanorods and reduced graphene oxide with carbon sealing (Si-SnO₂@G@C) is engineered and fabricated by a facile two-step hydrothermal process and subsequent annealing treatment, which exhibit not only extraordinary rate performance and ultrahigh reversible capacity but also excellent cycle stability and high electrical conductivity as the anode of LIBs. The Si-doped SnO₂ nanoparticles on the surface of graphene were firmly wrapped in the C-coating and formed a porous sandwich structure, which can efficiently prevent the Sn nanoparticles from aggregation and provide more extra space for accommodating the volume variations and more active sites for reactions. The carbon layer also blocks the direct contact of the SnO₂ nanorods with electrolyte and prevents the graphene nanosheets from the restacking. More importantly, the reversibility of lithiation/delithiation reactions can be remarkably improved by the doping silicon. The doped Si not only accelerates the diffusion of Li⁺ but also brings a significant increase in the specific capacity. As a consequence, the Si-SnO₂@G@C nanocomposite can maintain a high capacity of 654 mAh/g at 2 A/g even after 1200 cycles with negligible capacity loss and excellent reversibility with a Coulombic efficiency retention over 99%, which can be capable of the alternative to commercial graphite anodes. This work provides a new strategy for the reasonable design of advanced anode materials with superior and reversible lithium storage capacity.

Integrated Design of Hierarchical CoSnO3@NC@MnO@NC Nanobox as Anode Material for Enhanced Lithium Storage Performance

Transition-metal oxides (TMOs) are potential candidates for anode materials of lithium-ion batteries (LIBs) due to their high theoretical capacity (∼1000 mA h/g) and enhanced safety from suppressing the formation of lithium dendrites. However, the poor electron conductivity and the large volume expansion during lithiation/delithiation processes are still the main hurdles for the practical usage of TMOs as anode materials. In this work, the CoSnO3@NC@MnO@NC hierarchical nanobox (CNMN) is then proposed and fabricated to solve those issues. The as-prepared nanobox contains hollow cubic CoSnO3 as a core and dual N-doped carbon-"sandwiched" MnO particles as a shell. As anode materials of LIBs, the hollow and carbon interlayer structures effectively accommodate the volume expansion while dual active TMOs of CoSnO3 and MnO efficiently increase the specific capacity. Notably, the dual-layer structure of N-doped carbons plays a critical functional role in the incorporated composites, where the inner layer serves as a reaction substrate and a spatial barrier and the outer layer offers electron conductivity, enabling more effective involvement of active anode materials in lithium storage, as well as maintaining their high activity during lithium cycling. Subsequently, the as-prepared CNMN exhibits a high specific capacity of 1195 mA h/g after the 200th cycle at 0.1C and an excellent stable reversible capacity of about 876 mA h/g after the 300th cycle at 0.5C with only 0.07 mA h/g fade per cycle after 300 cycles. Even after a 250 times fast charging/discharging cycle both at 5C, it still retains a reversible capacity of 422.6 mA h/g. We ascribe the enhanced lithium storage performances to the novel hierarchical architectures achieved from the rational design.

MoS2 nanoflowers encapsulated into carbon nanofibers containing amorphous SnO2 as an anode for lithium-ion batteries

SnO₂ with high abundance, large theoretical capacity, and nontoxicity is considered to be a promising candidate for use as advanced electrodes. However, the poor electronic conductivity and large volume variations hinder the practical applications of SnO₂-based electrodes for use in lithium-ion batteries (LIBs). Herein, the MoS₂-SnO₂ heterostructures were encapsulated into carbon nanofibers (CNFs) via facile solvothermal and electrospinning methods. Remarkably, when the binder-free and robust MoS₂-SnO₂@CNF is employed as the anode for LIBs, such a clever structure yields a discharge capacity of 983 mA h g^-1 at a current density of 200 mA g^-1 after 100 cycles and a capacity of 710 mA h g^-1 after 800 cycles at a current density of 2000 mA g^-1. Moreover, full cells and flexible full cells were constructed, which exhibited high flexibility and delivered a high reversible capacity of 463 mA h g^-1 after 100 cycles at 500 mA g^-1. The exceptional performance of MoS₂-SnO₂@CNF could be attributed to the rational design of the electrode structure. On one hand, the robust structure of the amorphous SnO₂ and MoS₂ nanoflowers in the conductive carbon network not only provides direct current pathways, but also enhances electron transfer. On the other hand, the abundance of p-n heterogeneous interfaces considerably reduces the charge transfer resistance and enhances the surface reaction kinetics. This work proposes a feasible strategy to enhance the capacity and stability of SnO₂-based electrodes and opens up a new avenue for the potential applications of SnO₂ anode materials.

Tin Oxide Based Nanomaterials and Their Application as Anodes in Lithium-Ion Batteries and Beyond

Herein, recent progress in the field of tin oxide (SnO2 )-based nanosized and nanostructured materials as conversion and alloying/dealloying-type anodes in lithium-ion batteries and beyond (sodium- and potassium-ion batteries) is briefly discussed. The first section addresses the importance of the initial SnO2 micro- and nanostructure on the conversion and alloying/dealloying reaction upon lithiation and its impact on the microstructure and cyclability of the anodes. A further section is dedicated to recent advances in the fabrication of diverse 0D to 3D nanostructures to overcome stability issues induced by large volume changes during cycling. Additionally, the role of doping on conductivity and synergistic effects of redox-active and -inactive dopants on the reversible lithium-storage capacity and rate capability are discussed. Furthermore, the synthesis and electrochemical properties of nanostructured SnO2 /C composites are reviewed. The broad research spectrum of SnO2 anode materials is finally reflected in a brief overview of recent work published on Na- and K-ion batteries.

A one-step synthesis of porous V2O3@C hollow spheres as a high-performance anode for lithium-ion batteries

V₂O₃@C hollow spheres with a large specific surface area exhibited high reversible capacity for LIBs.