Intercalation-type Anode Material Research Articles

Enhanced lithium-ion storage through anchoring nanocrystalline MoO2/C microspheres in rGO nanosheets: Boosting pseudocapacitance and facilitating rapid conversion

Both crystalline and amorphous MoO2 exhibit distinct advantages for lithium-ion battery applications, with the former favoring lithium-ion intercalation and the latter undergoing complete lithiation via a conversion reaction. However, their sluggish lithium-ion insertion rates and inadequate charge transfer kinetics hinder their full potential. To address these challenges, we have developed a controllable approach that integrates liquid-phase dispersion of the HxMoO3/C and graphene oxides (GO) precursors followed by freeze-drying and low-temperature calcinations, aiming to merit the ionic conductivity of MoO2/C nanocrystallite and the electronic conductivity of reduce graphene oxides (rGO), respectively. This facile method yields bubble-sheet-like MoO2/C@rGO composites, where the quantitatively strategic incorporation of rGO can effectively mitigate recrystallization and surface oxidation of MoO2 nanocrystals. Furthermore, the approximately 70 % volume shrinkage of HxMoO3/C precursors into MoO2/C can create a flexible void space between the microspheres and the rGO coating for better accommodating volume variations during lithiation. Electrochemical measurements show that MoO2/C@rGO delivers high initial coulombic efficiency (ICE, e.g., up to 71.3 % at 100 mA g⁻¹), impressive rate performance (e.g., achieving 60 mA h g⁻¹ at 1 A g⁻¹, and 34.1 % retention from 0.1 to 2 A g⁻¹) and excellent cyclability (e.g., retaining 98.9 % of its capacity after 200 cycles) when employed as an intercalation-type anode material above 1.00 V (vs. Li/Li⁺). Remarkably, electrochemical analysis indicates that the capacitive contribution is dominant during high-rate applications (e.g., up to 73.06 % ratio at a scan rate of 0.50 mV s⁻¹), exhibiting a pseudocapacitive behavior. Additionally, MoO2/C@rGO exhibits enhanced ICE (e.g., up to 76.9 % at 100 mA g⁻¹), accelerated activation (e.g., achieving peak performance within 10 cycles at 100 mA g⁻¹), superior rate performance (e.g., achieving 446 mA h g⁻¹ at 2 A g⁻¹), and remarkable cyclability (e.g., maintaining 510 mA h g⁻¹ with 88.9 % capacity retention over 600 cycles at 1 A g⁻¹) when applied as a conversion-type anode material at between 1.00 and 3.00 V (vs. Li/Li⁺). To elucidate the mechanisms underlying the high-rate performance and the increased capacity, ex-situ XRD, ex-situ SEM, ex-situ TEM, and electrochemical analysis were carried out. No evident phase transition or material pulverization can be observed upon cycling above 1.00 V; therefore, the structural evolution is entirely single-phase or solid-solution, which accompanies with pseudocapacitive characteristic. However, the diffraction peaks downshift, the eminent of LixMoO2+δ, the pulverization, and the gradual amorphization of MoO2 can be observed upon cycling, indicating an sequential intercalation-to-conversion activation from a crystalline state to an amorphous state.

Ultrafast Knock-Off Li+ Diffusion and Subtle Structural Evolution of Li5V3O8 Anode in Lithium-Ion Batteries.

Li5V3O8, a lithiation product derived from the LiV3O8 cathode, has emerged as a promising intercalation-type anode material, boasting a theoretical capacity of 256 mA h g-1. Through a comprehensive combination of experimental and theoretical approaches, we demonstrate its capability to intercalate a substantial amount of Li+ at extremely high rates. Experimental findings reveal that Li5V3O8 exhibits outstanding high-rate capability (with a specific capacity of 152 mA h g-1, 60% of the theoretical capacity at 40 C) and exceptional cyclability (with a capacity retention of 80% after 11,000 cycles at 20 C). The structural changes in Li5V3O8 during the lithiation/delithiation cycles are subtle and reversible. First-principles calculations highlight a knock-off mechanism in Li+ diffusion within Li5V3O8, with an estimated energy barrier ranging from 0.16 to 0.38 eV, considerably lower than that of a direct hopping mechanism (0.62-1.44 eV). These ultrafast ion diffusion properties are attributed to interlock interactions among interstitial tetrahedral Li+ and neighboring octahedral lattice Li+, facilitating long-distance and chain-like Li+ diffusion. This study not only introduces an influential vanadium-based anode material with practical implications for fast-charging lithium-ion batteries but also provides fundamental insights into solid state Li+ diffusion kinetics.

Phase Engineering of Nonstoichiometric Cu2-xSe as Anode for Aqueous Zn-Ion Batteries.

Aqueous zinc-ion batteries (AZIBs) are receiving widespread attention due to their abundant resources, low material cost, and high safety. However, the susceptibility of Zn metal anodes to corrosion and hydrogen evolution limits their further practical applications. Replacing Zn metal with intercalation-type anode material and constructing rocking-chair-type batteries could be an effective way to significantly prolong the cycle life of AZIBs. Herein, we present copper selenide with different crystal phase structures through a facile redox reaction as an anode for AZIBs. By comparing and analyzing different copper selenide phases, it is found that the cubic Cu2-xSe shows superior structural stability and highly reversible Zn2+ storage. Theoretical calculation results further demonstrate that the cubic Cu2-xSe possesses an increased electrical conductivity, higher Zn2+ adsorption energy, and reduced diffusion barrier, thereby promoting the storage reversibility and (de)intercalation kinetics of the Zn2+ ion. Thus, the Cu2-xSe anode delivers a long-term service life of over 15 000 cycles and impressive cumulative capacity. Furthermore, the full-cells assembled with the MnO2/CNT cathode operate stably for over 1500 cycles at 6 mA cm-2 at a negative/positive (N/P) capacity ratio of ∼1.53. This work provides a more ideal Zn-metal-free anode, which helps to push the practical applications of AZIBs.

Atomic Layer Deposition of SnO2-Based Composite Anodes for Thin-Film Lithium-Ion Batteries

Transition metal oxides are promising anode materials for lithium-ion batteries thanks to their good electrochemical reversibility, high theoretical capacities, high abundance, and low cost. The mechanism of lithium insertion or deintercalation into or from these metal oxides can be different depending upon their lattice structure or chemical nature. Synergistic effects obtained from mixing different metal oxides with (dis)similar lithiation/delithiation mechanisms (intercalation, conversion and alloying) can significantly improve the device performances. In this research, we systematically investigate the impact on electrochemical properties of SnO2 thin-films upon mixing with TiO2, Fe2O3 and ZnO. In these pure thin-films, SnO2 displays conversion- as well as alloying-type lithiation and serves as the host material, whereas TiO2 represents an intercalation-type anode material, Fe2O3 exhibits conversion reactions and ZnO expresses alloying during lithiation-delithiation processes. Importantly, all the composite thin-films have an intermixed structure at the atomic scale, as they are precisely prepared by the atomic layer deposition method. The electrochemical properties demonstrate that the composite thin-films show better performance, either higher capacities or better cycling retentions, than the individual constituent material (SnO2, TiO2, Fe2O3 or ZnO). Overall cycling stability improves to a great extent along with a slight increase in capacity with the addition of TiO2. The supplement of Fe2O3 in the SnO2–Fe2O3 composite thin-films moderately improves both capacity and retention, while the SnO2–ZnO composite electrodes demonstrate a good cyclability and stabilize at a relatively high capacity. The systematic investigation of synergistic effects on the different types (intercalation, conversion and alloying) of metal oxide composites is expected to provide guidance towards the development of composite anode materials for lithium-ion batteries.

In situ XRD and electrochemical investigation on a new intercalation-type anode for high-rate lithium ion capacitor

A new intercalation-type anode material is reported herein to improve the lithium storage kinetics for high-rate lithium ion capacitors. The crystal structure of orthorhombic NaNbO3 indicates two possible tunnels for lithium ions insertion into NaNbO3 host along the <101> and <141> directions. Moreover, in situ XRD is conducted to investigate the lithium storage mechanism and structural evolution of the NaNbO3 anode, demonstrating its intercalation behavior through (101) and (141) planes. Furthermore, the rGO nanosheets are introduced to facilitate the charge transfer, which also effectively prevent the aggregation of NaNbO3 nanocubes. As expected, the NaNbO3/rGO nanocomposites possess remarkable reversible capacity (465 mA h g−1 at 0.1 A g−1), superior rate capability (325 mA h g−1 at 1.0 A g−1) and cycling stability, attributed to their synergistic effect and high Li+ diffusion coefficient DLi [D(NaNbO3/rGO)/D(NaNbO3) ≈ 31.54]. Remarkably, the NaNbO3/rGO-based LIC delivers a high energy density of 166.7 W h kg−1 at 112.4 W kg−1 and remains 24.1 W h kg−1 at an ultrahigh power density of 26621.2 W kg−1, with an outstanding cycling durability (90% retention over 3000 cycles at 1.0 A g−1). This study provides new insights on novel intercalation-type anode material to enrich the materials system of LICs.

A highly Li+-conductive HfNb24O62 anode material for superior Li+ storage.

Highly Li+-conductive HfNb24O62 is explored as a new intercalation-type niobium-based oxide anode material for superior Li+ storage. HfNb24O62 owns a Wadsley-Roth shear structure with a large unit-cell volume, leading to a large Li+ diffusion coefficient. HfNb24O62 shows a large capacity, safe operating potential, high rate performance and good cyclability.

Crystalline iceplant-like nano-NaVPO4F@graphene as an intercalation-type anode material for sodium-ion batteries.

A crystalline iceplant-like nano-NaVPO4F@graphene composite is successfully synthesized by a freeze-drying process. Graphene forms a lamellar structure wherein NaVPO4F nanoparticles are uniformly adhered to the surface of graphene. The composite displays an intercalation-type reaction mechanism and excellent cycling and rate performance.

Constructing a buffering and conducting carbon nanotubes-interweaved layer on graphite flakes for high-rate and long-term K-storage properties

Graphite, as a typical carbon allotrope, is demonstrated as an available intercalation-type anode material for potassium-ion batteries (PIBs). The main challenges associated with graphite anodes are structural pulverization and instability of the solid electrolyte interphase (SEI) resulting from the repeated volume change during charge/discharge. In this work, a layer of interweaved carbon nanotubes (CNTs) are grown on the surface of micro-size graphite flakes through controllable in-situ catalytic chemical vapor deposition method (CCVD), and the CNTs content can be easily adjusted by varying the deposition time. The CNTs-interweaved layer can not only stabilize the graphite structure but also enhance the diffusion kinetics of K+ during cycling. Furthermore, CNTs also provide a certain amount of capacity. The composite material of in situ growing carbon nanotubes and modified graphite flakes (CNTs-MG) exhibit a reversible capacity of 234 mAh g−1 at 2 A g−1 after 1500 cycles, which is obviously better than that of counterpart graphite flakes. Besides, the K storage mechanism and the effect of the contents of CNTs are also investigated systemically by in-situ Raman spectra and electrochemical characterizations.

Hierarchical Porous Intercalation-Type V2 O3 as High-Performance Anode Materials for Li-Ion Batteries.

As intercalation-type anode materials for Li-ion batteries (LIBs), the commercially used graphite and Li4 Ti5 O12 exhibit good cycling and rate properties, but their theoretical specific capacities are too low to meet the ever-growing demands of high-energy applications such as electric vehicles. Therefore, the development of new intercalation-type anode materials with larger capacity is very desirable. Herein, we design and synthesize novel 3 D hierarchical porous V2 O3 @C micro/nanostructures consisting of crumpled nanosheets, through self-reduction under annealing from the structurally similar VO2 (B)@C precursors without the addition of any other reducing reagent or gas. Excitingly, it is found for the first time through ex situ XRD technology that V2 O3 is a new, promising intercalation-type anode material for LIBs with a high capacity. V2 O3 @C micro/nanostructures can deliver a large capacity of 732 mAh g-1 without capacity loss at 100 mA g-1 even after 136 cycles, as well as exhibiting excellent cycling and rate performances. The application of V2 O3 for Na-ion batteries (NIBs) is elaborated for the first time, and excitingly, it is found that V2 O3 @C micro/nanostructures may be promising anode materials for NIBs.

Cr0.5Nb24.5O62 Nanowires with High Electronic Conductivity for High-Rate and Long-Life Lithium-Ion Storage.

Intercalation-type TiNbxO2+2.5x (x = 2, 5, and 24) anode materials have recently become more interesting for lithium-ion batteries (LIBs) due to their large theoretical capacities of 388-402 mAh g-1. However, the Ti4+/Nb5+ ions in TiNbxO2+2.5x with empty 3d/4d orbitals usually lead to extremely low electronic conductivity of <10-9 S cm-1, greatly restricting their practical capacity and rate capability. Herein, we report a class of highly conductive Cr0.5Nb24.5O62 nanowires as an intercalation-type anode material for high-performance LIBs. The as-made Cr0.5Nb24.5O62 nanowires show an open shear ReO3 crystal structure (C2 space group) with 4% tetrahedra and a conducting characteristic with ultrahigh electronic conductivity of 3.6 × 10-2 S cm-1 and a large Li+-ion diffusion coefficient of 2.19 × 10-13 cm2 s-1. These important characteristics make them deliver outstanding electrochemical properties in term of the largest reversible capacity (344 mAh g-1 at 0.1 C) in all the known niobium- and titanium-based anode materials, safe working potential (∼1.65 V vs Li/Li+), high first-cycle Coulombic efficiency (90.8%), superior rate capability (209 mAh g-1 at 30 C), and excellent cycling stability, making them among the best for LIBs in niobium- and titanium-based anode materials.

Enhanced Electrochemical Properties of Li3 VO4 with Controlled Oxygen Vacancies as Li-Ion Battery Anode.

Li3 VO4 , as a promising intercalation-type anode material for lithium-ion batteries, features a desired discharge potential (ca. 0.5-1.0 V vs. Li/Li+ ) and a good theoretical storage capacity (590 mAh g-1 with three Li+ inserted). However, the poor electrical conductivity of Li3 VO4 hinders its practical application. In the present work, various amounts of oxygen vacancies were introduced in Li3 VO4 through annealing in hydrogen to improve its conductivity. To elucidate the influence of oxygen vacancies on the electrochemical performances of Li3 VO4 , the surface energy of the resulting material was measured with an inverse gas chromatography method. It was found that Li3 VO4 annealed in pure hydrogen at 400 °C for 15 min exhibited a much higher surface energy (60.7 mJ m-2 ) than pristine Li3 VO4 (50.6 mJ m-2 ). The increased surface energy would lower the activation energy of phase transformation during the charge-discharge process, leading to improved electrochemical properties. As a result, the oxygen-deficient Li3 VO4 achieved a significantly improved specific capacity of 495 mAh g-1 at 0.1 Ag-1 (381 mAh g-1 for pristine Li3 VO4 ) and retains 165 mAh g-1 when the current density increases to 8 Ag-1 .

Cu3 V2 O8 Nanoparticles as Intercalation-Type Anode Material for Lithium-Ion Batteries.

Cu3 V2 O8 nanoparticles with particle sizes of 40-50 nm have been prepared by the co-precipitation method. The Cu3 V2 O8 electrode delivers a discharge capacity of 462 mA h g(-1) for the first 10 cycles and then the specific capacity, surprisingly, increases to 773 mA h g(-1) after 50 cycles, possibly as a result of extra lithium interfacial storage through the reversible formation/decomposition of a solid electrolyte interface (SEI) film. In addition, the electrode shows good rate capability with discharge capacities of 218 mA h g(-1) under current densities of 1000 mA g(-1) . Moreover, the lithium storage mechanism for Cu3 V2 O8 nanoparticles is explained on the basis of ex situ X-ray diffraction data and high-resolution transmission electron microscopy analyses at different charge/discharge depths. It was evidenced that Cu3 V2 O8 decomposes into copper metal and Li3 VO4 on being initially discharged to 0.01 V, and the Li3 VO4 is then likely to act as the host for lithium ions in subsequent cycles by means of the intercalation mechanism. Such an "in situ" compositing phenomenon during the electrochemical processes is novel and provides a very useful insight into the design of new anode materials for application in lithium-ion batteries.

Ru0.01Ti0.99Nb2O7 as an intercalation-type anode material with a large capacity and high rate performance for lithium-ion batteries

Ru0.01Ti0.99Nb2O7, with a much larger capacity than Li4Ti5O12, fulfils the requirements of high power and energy density for electric vehicles.

Li 3V 2(PO 4) 3/C composite as an intercalation-type anode material for lithium-ion batteries

The carbon coated monoclinic Li 3V 2(PO 4) 3 (LVP/C) powder is successfully synthesized by a carbothermal reduction method using crystal sugar as the carbon source. Its structure and physicochemical properties are investigated using X-ray diffraction (XRD), scanning electron microscopy, high-resolution transmission electron microscopy and electrochemical methods. The LVP/C electrode exhibits stable reversible capacities of 203 and 102 mAh g −1 in the potential ranges of 3.0–0.0 V and 3.0–1.0 V versus Li +/Li, respectively. It is identified that the insertion/extraction of Li + undergoes a series of two-phase transition processes between 3.0 and 1.6 V and a single phase process between 1.6 and 0.0 V. The ex situ XRD patterns of the electrodes at various lithiated states indicate that the monoclinic structure can still be retained during charge–discharge process and the insertion/deinsertion of lithium ions occur reversibly, which provides an excellent cycling stability with high energy efficiency.