N-Doped Carbon Nanonecklaces with Encapsulated BiOCl Nanoparticles as High-Rate Anodes for Lithium-Ion Batteries.

The unique two-dimensional layered structure of BiOCl makes it highly promising for energy storage applications. In this study, we successfully synthesized BiOCl nanoparticles encapsulated in N-doped carbon nanonecklaces (BiOCl NPs/N-CNNs) using well-established electrospinning and solvothermal substitution. As an anode material for lithium-ion batteries, BiOCl NPs/N-CNNs exhibited enhanced rate performance, delivering a capacity of 220.2 mA h g-1 at 8 A g-1. Furthermore, it demonstrated remarkable long cycle stability, retaining a capacity of 200.5 mA h g-1 after 9000 cycles with a discharge rate of 8.0 A g-1. The superior electrochemical performance can be attributed to the stacked layered structure of BiOCl, facilitated by van der Waals force, as well as the ingenious nanonecklace structures. These structures not only provide fast ion diffusion pathways but also enhance electrolyte penetration and offer more active sites for Li+ insertion and extraction. Additionally, the nanonecklace structure prevents the aggregation of nanopolyhedra, promoting the complete reaction of BiOCl with Li+. Moreover, the unique nanopolyhedron structure alleviates the stress caused by the volume expansion of Bi nanoparticles during cycling and reduces the internal resistance of the electrode.

Insights into the multi-functional lithium difluoro(oxalate)borate additive in boosting the Li-ion reaction kinetics for Li3VO4 anodes.

The rational design of a solid electrolyte interphase (SEI) with high ionic conductivity and high electrochemical stability is significantly important in improving the electrochemical performance of anode materials. Herein, lithium difluoro(oxalate)borate (LiDFOB) is used as an electrolyte additive to generate protective SEI films on Li3VO4 (LVO) anodes. The addition of LiDFOB is beneficial to form a dense, uniform, stable and LiF-richer SEI, which is helpful to boost the Li-ion storage kinetics. In addition, the generated SEI can inhibit the further decomposition of electrolytes and maintain the morphology of LVO anodes during charge/discharge processes. As a result, LVO-based anodes exhibit a much higher capacity (769.5 mA h g-1 at 0.5 A g-1), enhanced rate performance (243.3 mA h g-1 at 5.0 A g-1) and excellent long-term cycling stability (209.9 mA h g-1 after 5000 cycles) when cycled in 1 wt% LiDFOB addition electrolyte. This work confirms that LiDFOB is a promising multi-functional additive for LiPF6 electrolytes and provides new insights into SEI construction towards high-performance LVO anodes.

C-Doped LiVO3 Honeycombs Derived from the Biomass Template Strategy for Superior Lithium Storage.

LiVO3 as a prospective anode for lithium-ion batteries has drawn considerable focus based on its superior ion transfer capability and relatively elevated specific capacity. Nevertheless, the inherent low electrical conductivity and sluggish reaction kinetics hindered its commercial application. Herein, C-doped LiVO3 honeycombs (C-doped LiVO3 HCs) are designed via introducing low-cost and scalable biomass carbon as a template, and the influence of the structure on the lithium storage property is systematically studied. The prepared C-doped LiVO3 HC electrode delivers a high reversible capacity of 743.7 mA h g-1 at 0.5 A g-1 after 400 cycles and superior high-rate performance with an average discharge capacity of 420.8 mA h g-1 even at 5.0 A g-1. The remarkable comprehensive electrochemical performance is attributed to the high electrical conductivity caused by carbon doping and rapid ion transport triggered by the honeycomb structure. This work may offer a rational design on both the hierarchical structure and doping engineering of future battery electrodes.

Activation-Assisted High-Concentration Phosphorus-Doping to Enhance the Electrochemical Performance of Cobalt Carbonate Hydroxide Hydrate.

P-doping into metal oxides has been demonstrated as a valid avenue to ameliorate electrochemical performance because it can tune the electronic structures and increase the active sites for an electrochemical reaction. However, it usually results in a low P-doping concentration via the commonly used gas phosphorization method. In this work, an activation-assisted P-doping strategy was explored to significantly raise the P-doping concentration in cobalt carbonate hydroxide hydrate (CCHH). The activation treatment increased active sites for electrochemical reaction and endowed the sample with a high P content in the subsequent gas phosphorization process, thereby greatly enhancing the conductivity of the sample. Therefore, the final CCHH-A-P electrode exhibited a high capacitance of 6.62 F cm-2 at 5 mA cm-2 and good cyclic stability. In addition, the CCHH-A-P//CC ASC with CCHH-A-P as the positive electrode and carbon cloth as the negative electrode provided a high energy density of 0.25 mWh cm-2 at 4 mW cm-2 as well as excellent cycling performance with capacitance retention of 91.2% after 20,000 cycles. Our work shows an effective strategy to acquire Co-based materials with high-concentration P-doping that holds great potential in boosting the electrochemical performance of electrode materials via P-doping technology.

Heterostructured Li3VO4-Ga2O3-embedded porous carbon nanofibers as advanced anode materials for lithium-ion batteries.

The development of lithium-ion batteries (LIBs) is still facing challenges due to the design and optimization of anode materials and their Li-ion storage mechanisms. In this study, we aimed to address this issue by constructing three-dimensional hierarchical heterojunction structures using a double needle electrospinning strategy. The heterostructure was composed of insertion-type Li3VO4 and conversion/alloying-type Ga2O3 embedded porous carbon nanofibers (Li3VO4-Ga2O3@PCNF). The designed heterostructured Ga2O3 and Li3VO4 materials were found to effectively enhance charge transfer dynamics, thereby improving capacity and rate capability. Additionally, the facilitated efficient contact between the electrode and electrolyte, enabling the diffusion of ions and electrons. When applied as an anode material in LIBs, the Li3VO4-Ga2O3@PCNF composite achieved a high capacity of 630.0 mA h g-1 at 0.5 A g-1, and full capacity recovery after 6 periods of rate testing over 480 cycles. When simulating the practical application under a high discharge current of 6.0 A g-1, the Li3VO4-Ga2O3@PCNF could still deliver a high discharge capacity of 322.0 mA h g-1 after 2000 cycles. Furthermore, the composite exhibited a remarkable capacity retention of 77.2% after 2000 cycles at 6.0 A g-1. This research provides valuable guidance for the design of high-performance Li3VO4-based anodes, particularly in addressing the issue of inferior electronic conductivity.

Optimized Kinetics Match and Charge Balance Toward Potassium Ion Hybrid Capacitors with Ultrahigh Energy and Power Densities.

Potassium ion hybrid capacitors (PIHCs) are of particular interest benefiting from high energy/power densities. However, challenges lie in the kinetic mismatch between battery-type anode and capacitive-type cathode, as well as the difficulty in achieving optimized charge/mass balance. These significantly sacrifice the electrochemical performance of PIHCs. Here, strategies including charge/mass balance pursuance, electrolyte optimization, and tailored electrode design, are employed, together, to address these challenges. The key parameters determining the energy storage properties of PIHCs are identified. Specifically, i) the good kinetic match between anode and cathode translates into the very small variation of cathode/anode mass ratio at various rates. This sets general rules for the pursuance of charge balance, and to maximize the electrochemical performance of hybrid devices. ii) A potassium bis(fluoroslufonyl)imide (KFSI)-based electrolyte promotes better electrode kinetics and allows for the formation of more stable and intact solid electrolyte interphase layer, with respect to potassium hexafluorophosphate (KPF6 )-based electrolyte. And iii) hierarchically porous N/O codoped carbon nanosheets (NOCSs) with enlarged interlayer spacing, disordered structure, and abundant pyridinic-N functional groups are advantageous in terms of high electronic/ionic transport dynamics and structural stability. All these together, contribute to the high energy/power density of the activated carbon//NOCSs PIHCs (113.4 Wh kg-1 , at 17,000 W Kg-1 ).

The charge/discharge mechanism and electrochemical performance of CuV2O6 as a new anode material for Li-ion batteries.

The charge/discharge mechanism of CuV2O6 as the anode for Li-ion batteries is studied for the first time, suggesting a phase transition in discharging, which initially involves the formation of LiV2O5 and Cu3V2O8, the subsequent transition from Cu3V2O8 to LixV2O5 and CuO, the insertion of lithium ions into LiV2O5, and later the reduction of CuO into Cu. The phase transition of Cu3V2O8 is accompanied by an amorphization process, which is maintained in the subsequent discharging and charging processes. The CuV2O6/natural graphite electrode with a sodium alginate binder is prepared, which shows superior electrochemical performance. At a specific current of 110 mA g(-1), it delivers initial discharge and charge capacities of 725 and 453 mA h g(-1), respectively, maintaining 537 and 533 mA h g(-1) after 200 cycles.

Lithium Polyacrylate as Lithium and Carbon Source in the Synthesis of Li3 VO4 for High-Rate and Long-Life Li-Ion Batteries.

Li3 VO4 is a promising anode material for use in lithium-ion batteries, however, the conventional synthesis methods for Li3 VO4 anodes involve the separate use of lithium and carbon sources, resulting in inefficient contact and low crystalline quality. Herein, lithium polyacrylate (LiPAA) was utilized as a dual-functional source and an in-situ polymerization followed by a spray-drying method was employed to synthesize Li3 VO4 . LiPAA serves a dual purpose, acting as both a lithium source to improve the crystal process and a carbon source to confine the particle size within a desired volume during high-temperature treatment. Additionally, the in-situ synthesis of a porous carbon decorating skeleton prevents the growth and agglomeration of Li3 VO4 particles and provides abundant ion/electron diffusion channels and contact areas. Based on the synthesis route and the constructed primary-secondary structure, the Li3 VO4 anodes obtained in this study exhibit an impressive capacity of 596.2 mAh g-1 . Moreover, they demonstrate enhanced rate performance over 600 cycles during 10 periods of rate testing, as well as a remarkably long lifespan of 5000 cycles at high currents. The utilization of LiPAA as a dual-functional source represents a broad approach that holds great potential for future research on high-performance electrodes requiring both lithium and carbon sources.

Hierarchical Self-Assembly Strategy for Scalable Synthesis of Li3VO4/N Doped C Nanosheets for High-Rate Li-Ion Storage.

While the comprehensive merits of high safety and high capacity make Li3VO4 (LVO) a potential anode material for lithium-ion batteries, the practical application of LVO was severely impeded by the unfavorable high-rate capability and unscalable preparation. Here, LVO/N doped C nanosheets (LVO@NC NSs) assembled from primary LVO@NC nanoparticles are prepared via a scalable and concise spray drying approach. The 2D morphology and the interconnected LVO@NC constituents endow the LVO@NC NSs with continuously excellent reaction activity, leading to prominent rate performance. When cycling at 0.2 A g-1, the obtained LVO@NC NSs exhibit a high charge capacity of 628.4 mAh g-1 after 300 cycles, showing little improvement compared with the initial charge capacity. After 9 periods of rate testing ranging from 0.1 to 6.0 A g-1 for 460 cycles, a high charge capacity of 610.3 mAh g-1 remains. It also exhibits an outstanding long lifespan at the charge/discharge currents of 3.0/6.0 A g-1, delivering a high charge capacity of 277.0 mAh g-1 in the 5000th cycle. The scalable and concise preparation as well as the enhanced high-rate capability of the LVO@NC NSs make them hold great promise as an anode candidate for high-power lithium-ion storage devices.

Enhanced electrochemical performance of the cobalt chloride carbonate hydroxide hydrate via micromorphology and phase transformation.

Micromorphology and conductivity are two vital factors for the practical capacitance of the electrode materials for supercapacitors. In this work, a novel two-step electrochemical activation method involving a cyclic voltammetry (CV) treatment within 0-0.7 V followed by a CV treatment within -1.2-0 V is explored to induce the micromorphology and phase transformation of the cobalt chloride carbonate hydroxide hydrate (CCCH) nanoneedle arrays. The first-step activation transforms the CCCH to Co(OH)2 and then the reversible transformation between Co(OH)2 and CoOOH generates plenty of pores in the sample, thereby increasing the specific capacitance from 0.54 to 1.74 F cm-2 at the current density of 10 mA cm-2. The second-step activation inducing the reversible transformation between Co(OH)2 and Co not only endows the final sample with a nanosheets-assembled fasciculate structure but also decreases the internal resistance via generating Co0 in the final sample (CCCH-P75N50). Consequently, the CCCH-P75N50 shows a high specific capacitance of 3.83 F cm-2 at the current density of 10 mA cm-2. Besides, the aqueous asymmetric supercapacitor assembled with CCCH-P75N50 and commercial conductive carbon cloth (CC) delivers a high energy density of 2.75 mWh cm-3 at a power density of 37.5 mW cm-3. This work provides a novel, facile and promising method to optimize the micromorphology and conductivity of Co-based electrodes.

Superior Li-ion storage of VS4 nanowires anchored on reduced graphene.

Research on VS4 is lagging due to the difficulty in its tailored synthesis. Herein, unique architecture design of one-dimensional VS4 nanowires anchored on reduced graphene oxide is demonstrated via a facile solvothermal synthesis. Different amounts of reduced graphene oxide with VS4 are synthesized and compared regarding their rate capability and cycling stability. Among them, VS4 nanowires@15 wt% reduced graphene oxide present the best electrochemical performance. The superior performance is attributed to the optimal amount of reduced graphene oxide and one-dimensional VS4 nanowires based on (i) the large surface area that could accommodate volume changes, (ii) enhanced accessibility of the electrolyte, and (iii) improvement in electrical conductivity. In addition, kinetic parameters derived from electrochemical impedance spectroscopy spectra and sweep rate dependent cyclic voltammetry curves such as charge transfer resistances and Li+ ion apparent diffusion coefficients both support this claim. The diffusion coefficient is calculated to be 1.694 × 10-12 cm2 s-1 for VS4 nanowires/15 wt% reduced graphene oxide, highest among all samples.

Excellent electrochemical performance of NiV3O8/natural graphite anodes via novel in situ electrochemical reconstruction.

A novel in situ electrochemical reconstruction occurs in NiV3O8/natural graphite electrodes, which results in excellent electrochemical performance. After repeated rate performance from 0.16 to 3.1 A g(-1) over 320 cycles, the specific capacity can restore well and shows no obvious attenuation in the subsequent 360 cycles.

Systematic investigation on Cadmium-incorporation in Li2FeSiO4/C cathode material for lithium-ion batteries.

Cadmium-incorporated Li2FeSiO4/C composites have been successfully synthesized by a solid-state reaction assisted with refluxing. The effect and mechanism of Cd-modification on the electrochemical performance of Li2FeSiO4/C were investigated in detail by X-ray powder diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, Raman spectra, transmission electron microscopy, positron annihilation lifetime spectroscopy and Doppler broadening spectrum, and electrochemical measurements. The results show that Cd not only exists in an amorphous state of CdO on the surface of LFS particles, but also enters into the crystal lattice of LFS. Positron annihilation lifetime spectroscopy and Doppler broadening spectrum analyses verify that Cd-incorporation increases the defect concentration and the electronic conductivity of LFS, thus improve the Li(+)-ion diffusion process. Furthermore, our electrochemical measurements verify that an appropriate amount of Cd-incorporation can achieve a satisfied electrochemical performance for LFS/C cathode material.

Reduced graphene oxide modified Li2FeSiO4/C composite with enhanced electrochemical performance as cathode material for lithium ion batteries.

Reduced graphene oxide modified Li2FeSiO4/C (LFS/(C+rGO)) composite is successfully synthesized by a citric-acid-based sol-gel method and evaluated as cathode material for lithium ion batteries. The LFS/(C+rGO) shows an improved electronic conductivity due to the conductive network formed by reduced graphene oxide nanosheets and amorphous carbon in particles. Electrochemical impedance spectroscopy results indicate an increased diffusion coefficient of lithium ions (2.4 × 10(-11) cm(2) s(-1)) for LFS/(C+rGO) electrode. Compared with LFS with only amorphous carbon, the LFS/(C+rGO) electrode exhibits higher capacity and better cycling stability. It delivers a reversible capacity of 178 mAh g(-1) with a capacity retention ratio of 94.5% after 40 cycles at 0.1 C, and an average capacity of 119 mAh g(-1) at 2 C. The improved performance can be contributed to the reduced crystal size, good particle dispersion, and the improved conductive network between LFS particles.

W18O49 Nanowires as Ultraviolet Photodetector.

Photodetectors in a configuration of field effect transistor were fabricated based on individual W18O49 nanowires. Evaluation of electrical transport behavior indicates that the W18O49 nanowires are n-type semiconductors. The photodetectors show high sensitivity, stability and reversibility to ultraviolet (UV) light. A high photoconductive gain of 104 was obtained, and the photoconductivity is up to 60 nS upon exposure to 312 nm UV light with an intensity of 1.6 mW/cm2. Absorption of oxygen on the surface of W18O49 nanowires has a significant influence on the dark conductivity, and the ambient gas can remarkably change the conductivity of W18O49 nanowire. The results imply that W18O49 nanowires will be promising candidates for fabricating UV photodetectors.