CoTe nanorods/rGO composites as a potential anode material for sodium-ion storage

Confining Co1.11Te2 nanoparticles within mesoporous hollow carbon combination sphere for fast and ultralong sodium storage

Co1.11Te2 nanoparticles are in-situ uniformly grown within mesoporous hollow carbon combination sphere (MHCCS@Co1.11Te2) using a hard-template and spray drying process, solution impregnation and pyrolysis tellurization. Material characterizations reveal that Co1.11Te2, with a diameter of ∼ 20 nm, is attached to the internal walls of the unit spheres or embedded in the mesopore shells of the unit spheres, presenting a distinctive "ships-in-combination-bottles" nanoencapsulation structure. In sodium-ion half-cells, MHCCS@Co1.11Te2 exhibits excellent cycling stability, achieving reversible capacities of 257 mAh/g at 0.5 A/g after 250 cycles, 235 mAh/g at 1.0 A/g after 300 cycles and 161 mAh/g at 10.0 A/g after 1900 cycles. Electrochemical kinetic analyses and ex-situ characterizations reveal rapid electron/Na+ transport kinetics, prominent surface pseudocapacitive behavior, robust nanocomposite structure, and multi-step conversion reactions of sodium polytellurides. In sodium-ion full-cells, MHCCS@Co1.11Te2 still demonstrates stable cycling performance at 1.0 and 5.0 A/g and excellent rate capability. The superior electrochemical performance is associated with the nanoencapsulation structure based on mesoporous hollow carbon combination spheres, which promotes electron conduction and Na+ transport. The space-confined effect maintains the high electrochemical activity and cycling stability of Co1.11Te2.

Sandwich-type N-C@CoTe2@C anode: a stress-buffer nanostructure for stable sodium-ion storage

Transition metal tellurides (TMTes) have received extensive attention for high specific energy sodium-ion batteries (SIBs) due to their high volumetric specific capacity. However, the continuous capacity attenuation arising from the huge volumetric strain during sodiation/desodiation impedes practical applications. Here, we report a "sandwich-type" carbon confinement strategy that entraps cobalt ditelluride (CoTe2) nanocrystals between two carbon layers. Porous cellulose-derived fibres were employed as the inner carbon framework to construct fast conductive circuits and provide an abundant site for anchoring CoTe2 nanocrystals. Polyvinylpyrrolidone (PVP)-derived carbon layers act as carbon armour to encapsulate CoTe2 nanocrystals, inhibiting their volume change and structural pulverization during repeated sodium intercalation/deintercalation. Benefiting from the exquisite structural design, the N-C@CoTe2@C electrode exhibits excellent cycling stability for over 3000 cycles at 2.0 A g-1 and rate performance (113.8 mA h g-1 at 5.0 A g-1). Moreover, ex situ XRD/TEM and kinetic tests revealed a multistep conversion reaction mechanism and a battery-capacitive dual-model Na-storage process. This work provides a new perspective on the development of low-cost and straightforward techniques for fabricating long-life commercial SIB anode materials.

Boosting cobalt ditelluride quantum-rods anode materials for excellent potassium-ion storage via hierarchical physicochemical encapsulation

The exploration of anode materials that can store large-sized K-ion to solve the poor kinetics and large volume expansion issues has become the key scientific bottlenecks hindering the development of potassium-ion batteries (PIBs). Herein, ultrafine CoTe₂ quantum rods physiochemically encapsulated by graphene and nitrogen-doped carbon (CoTe₂@rGO@NC) are regarded as anode electrodes for PIBs. Dual physicochemical confinement and quantum size effect not only enhance electrochemical kinetics but also restrain large lattice stress during repeated K-ion insertion/extraction process. Superior electronic conductivity, K-ion adsorption, and diffusion ability can be acquired for CoTe₂@rGO@NC, confirmed through first-principles calculations and kinetics study. K-ion insertion/extraction proceeds via a typical conversion mechanism relying on Co as the redox site, where the robust chemical bond of COCo plays an important role in maintaining the electrode stability. Accordingly, CoTe₂@rGO@NC contributes a high initial capacity of 237.6 mAh·g^-1 at 200 mA·g^-1, a long lifetime over 500 cycles with low-capacity decay of 0.10% per cycle. This research will lay the materials science foundation for the construction of quantum-rod electrodes.

Dual-Type Carbon Confinement Strategy: Improving the Stability of CoTe2 Nanocrystals for Sodium-Ion Batteries with a Long Lifespan

Sodium-ion batteries have great potential to become large-scale energy storage devices due to their abundant and low-cost resources. However, the lack of anode and cathode materials with both high energy density and long-term cycling performance significantly affects their commercial applications. In this work, uniform CoTe₂ nanoparticles are generated from the tellurization of Co nanoparticles, which were coated with polyvinylpyrrolidone in a three-dimensional (3D) porous carbon matrix (CoTe₂@3DPNC). Finally, a dual-type carbon confinement structure is formed after tellurization during which citric acid is adopted as the source of the inner carbon scaffold. The hierarchical carbon matrix not only builds a robust and fast ion/electronic conductive 3D architecture but also mitigates the volume expansion and aggregation of CoTe₂ during sodium insertion/extraction. Remarkably, the CoTe₂@3DPNC electrode displays a high reversible capacity (216.5 mAh g^-1/627.9 mAh cm^-3 at 0.2 A g^-1 after 200 cycles) and outstanding long-term cycling performance (118.1 mAh g^-1/342.5 mAh cm^-3 even at 5.0 A g^-1 after 2500 cycles). Kinetics tests and capacitance calculations clearly reveal a battery-capacitive dual-model Na-storage mechanism. Furthermore, ex situ XRD/SEM/TEM demonstrate superior stability during sodium insertion/extraction. This work provides a valuable strategy for the rational structural design of long-life electrodes for advanced rechargeable batteries.

Recent advances of metal telluride anodes for high-performance lithium/sodium-ion batteries

Metal tellurides (MTs) have emerged as highly promising candidate anode materials for state-of-the-art lithium-ion batteries (LIBs) and sodium ion batteries (SIBs). This is owing to the unique crystal structure, high intrinsic conductivity, and high trap density of such materials. The present work delivers a detailed discussion on the latest research and progress associated with the use of MTs for LIBs/SIBs with a focus on reaction mechanisms, challenges, electrochemical performance, and synthesis strategies. Further, the prospects and future development of MT anode materials are discussed in terms of strategies to overcome the existing limitations. This review provides both an in-depth understanding of MTs and provides the driving force for expanding research on MTs for energy storage and conversion applications.

Pseudocapacitance-boosted ultrafast and stable Na-storage in NiTe2 coupled with N-doped carbon nanosheets for advanced sodium-ion half/full batteries

Developing high-rate and durable anode materials for sodium-ion batteries (SIBs) is still a challenge because of the larger ion radius of sodium compared with the lithium ion during charge-discharge processes. Herein, NiTe₂ coupled with N-doped carbon (NiTe₂/NC) hexagonal nanosheets has been fabricated through a solvothermal and subsequent carbonisation strategy. This unique hexagonal nanosheet structure offers abundant active sites and contact area to the electrolyte, which could shorten the Na⁺ diffusion path. The heterostructured N-doping carbon improves the electrochemical conductivity and accelerates the kinetics of Na⁺ transportation. Electrochemical analysis shows that the charge-discharge process is controlled by the pseudocapacitive behavior thus leading to high-rate capability and long lifespan in half batteries. As expected, high capacities of 311 mA h g^-1 to 217 mA h g^-1 at 5 A g^-1 to 10 A g^-1 are maintained after 800 and 1200 cycles, respectively. Furthermore, a full battery equipped with a Na₃V₂(PO₄)₂O₂F cathode and a NiTe₂/NC anode offers a maximum energy density of 104 W h kg^-1 and a maximum power density of 9116 W kg^-1. The results clearly show that the NiTe₂/NC hexagonal nanosheet with superior Na storage properties is an advanced new material for energy storage systems.

Orthorhombic Cobalt Ditelluride with Te Vacancy Defects Anchoring on Elastic MXene Enables Efficient Potassium-Ion Storage

The fast and reversible potassiation/depotassiation of anode materials remains an elusive yet intriguing goal. Herein, a class of the P-doping-induced orthorhombic CoTe₂ nanowires with Te vacancy defects supported on MXene (o-P-CoTe₂ /MXene) is designed and prepared, taking advantage of the synergistic effects of the conductive o-P-CoTe₂ arrays with rich Te vacancy defects and the elastic MXene sheets with self-autoadjustable function. Consequently, the o-P-CoTe₂ /MXene superstructure exhibits boosted potassium-storage performance, in terms of high reversible capacity (373.7 mAh g^-1 at 0.2 A g^-1 after 200 cycles), remarkable rate capability (168.2 mAh g^-1 at 20 A g^-1 ), and outstanding long-term cyclability (0.011% capacity decay per cycle over 2000 cycles at 2 A g^-1 ), representing the best performance in transition-metal-dichalcogenides-based anodes to date. Impressively, the flexible full battery with o-P-CoTe₂ /MXene anode achieves a satisfying energy density of 275 Wh kg^-1 and high bending stability. The kinetics analysis and first-principles calculations reveal superior pseudocapacitive property, high electronic conductivity, and favorable K⁺ ion adsorption and diffusion capability, corroborating fast K⁺ ion storage. Especially, ex situ characterizations confirm o-P-CoTe₂ /MXene undergoes reversible evolutions of initially proceeding with the K⁺ ion insertion, followed by the conversion reaction mechanism.

Rational Design of Embedded CoTe2 Nanoparticles in Freestanding N-Doped Multichannel Carbon Fibers for Sodium-Ion Batteries with Ultralong Cycle Lifespan

Although sodium-ion batteries (SIBs) have high potential for applications in large-scale energy storage, their limited cycle life and unsatisfactory energy density hinder their commercial applications. Here, a superior stable CoTe₂/carbon anode, in which CoTe₂ nanoparticles are embedded in freestanding N-doped multichannel carbon fiber (CoTe₂@NMCNFs), with ultralong cycle life for SIBs, is reported. Specifically, CoTe₂ nanoparticles are uniformly dispersed in the carbon matrix to inhibit its volume expansion and agglomeration during the desodiation/sodiation process, enabling a high-capacity and stable energy storage (retains 204.3 mAh g^-1/612.9 mAh cm^-3 at 1 A g^-1 after 2000 cycles with an ultralow capacity decay of 0.016% per cycle). Moreover, a CoTe₂@NMCNFs electrode exhibits a pseudocapacitive-dominated behavior, enabling the high-rate performance (152.4 mAh g^-1/457.2 mAh cm^-3 at 10 A g^-1). The battery-capacitive dual-model reaction mechanism and outstanding reversibility of the CoTe₂@NMCNFs composite are systematically investigated by ex situ XRD/SEM/TEM and a galvanostatic intermittent titration technique test, as well as surface capacitance calculations. More importantly, the fabricated sodium-ion CoTe₂@NMCNFs//P2-NaNMMT-4 full cell delivers a stable reversible capacity of 445 Wh kg^-1_anode at 0.2 A g^-1 and an excellent rate performance. The facile synthetic approach together with unique nanostructural design, provides a meaningful reference for the rational design of next-generation ultralong cycle-life SIBs anodes.

Co-Vacancy, Co1−xS@C flower-like nanosheets derived from MOFs for high current density cycle performance and stable sodium-ion storage

A non-stoichiometric cobalt–sulfur compound anode material with excellent electrochemical properties was prepared, and the first principles simulation described the effect of Co-vacancy on electrode reaction.

Tailored polyimide as positive electrode and polyimide-derived carbon as negative electrode for sodium ion full batteries

Organic electrode materials have secured a distinctive place among the auspicious choices for modern energy storage systems due to their resource sustainability and environmental friendliness. Herein, a novel all-organic electrode-based sodium ion full battery is demonstrated using 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) as raw material for the assembly of positive and negative electrodes. Both the electrodes exhibit excellent cycling stability and rate performance. The fabricated organic sodium ion full battery not only displays a high initial capacity of 157 mA h g-1 with an average battery voltage of 1.47 V under the current density of 100 mA g-1, but also delivers a high energy density of 254 W h kg-1 and a high power density of 614 W kg-1. These sodium ion batteries with organic positive and negative electrode materials can provide a new way for energy storage devices.

Construction of well-designed 1D selenium–tellurium nanorods anchored on graphene sheets as a high storage capacity anode material for lithium-ion batteries

The graphical illustration of the preparation of the SeTe@rGO composite material and its electrochemical application in Li-ion batteries.

Ultrafine Co1-xS Attached to Porous Interconnected Carbon Skeleton for Sodium-Ion Batteries

Carbon-based materials are effective carriers of metal sulfides because of their good volume stability and chemical stability, which can reduce volume expansion of materials and can also inhibit the interfacial reaction. In this study, Co_1-xS incorporated into three-dimensional porous biomass carbon skeleton were synthesized by a template method. The three-dimensional porous carbon with large surface area is favorable for the electrolyte infiltration. The uniform distribution of Co_1-xS nanoparticles results in a high reversible electrochemical reaction. The well-designed Co_1-xS/three-dimensional porous carbon structure exhibits outstanding performance when used as an anode for sodium-ion batteries (SIBs). The results show that the transition mental sulfide/three-dimensional porous carbon structure has broad application prospects in SIBs.

Designed synthesis of porous NiMoO4/C composite nanorods for asymmetric supercapacitors

Porous and carbon composited binary transition metal oxide nanomaterials provide high ionic conductivity and electronic conductivity.