RESUMEN
NiCo2 S4 is an attractive anode for sodium-ion batteries (SIBs) due to its high capacity and excellent redox reversibility. Practical deployment of NiCo2 S4 electrode in SIBs, however, is still hindered by the inferior capacity and unsatisfactory cycling performance, which result from the mismatch between the electrolyte chemistry and electrode. Herein, a functional electrolyte containing 1.0 m NaCF3 SO3 in diethylene glycol dimethyl ether (DEGDME) (1.0 m NaCF3 SO3 -DEGDME) is developed, which can be readily used for NiCo2 S4 anode with high initial coulomb efficiency (96.2%), enhanced cycling performance, and boosted capacities (341.7 mA h g-1 after 250 continuous cycles at the current density of 200 mA g-1 ). The electrochemical tests and related phase characterization combined with density functional theory (DFT) calculation indicate the ether-based electrolyte is more suitable for the NiCo2 S4 anode in SIBs due to the formation of a stable electrode-electrolyte interface. Additionally, the importance of the voltage window is also demonstrated to further optimize the electrochemical performance of the NiCo2 S4 electrode. The formation of sulfide intermediates during charging and discharging is predicted by combining DFT and verified by in situ XRD and HRTEM. The findings indicate that electrolyte engineering would be an effective way of performance enhancement for sulfides in practical SIBs.
RESUMEN
Hexagonal BCN (h-BCN) is considered to be a promising dielectric ceramic material with a hybrid B-C-N structure and an electromagnetic wave (EMW) absorbing material with tenable properties. H-BCN bulk and microtube architectures are simultaneously synthesized by precursor pyrolysis method using BCl3, aniline (AN) and diethylenetriamine (DETA) as the raw material. By analyzing its electromagnetic parameters, the effective absorption bandwidth of the sample cracking at 900 °C with the proportion of raw materials (DETA:AN = 1:1) can be up to 7.2 GHz, and the minimum reflection loss can reach -43.6 dB at 7.92 GHz with a thickness of 3.5 mm. Moreover, the EMW absorbing property of the ceramic can be tuned by adjusting the ratio of monomers, pyrolysis temperature, and cooling rates.
RESUMEN
Electromagnetic wave (EMW) induction of shape memory polymer (SMP) composites with multifunctional inorganic fillers is a high efficiency, uniform, and non-contact method. Herein, the shape memory effect of ternary BCN/Fe3O4/PCL composites induced by EMWs are explored. The components of Fe3O4 and the BCN nanotubes serve as wave-absorbing materials. The electromagnetic properties and EMW absorption performance of BCN/Fe3O4/PCL are discussed in detail. The EMWs absorbed by BCN/Fe3O4/PCL are dissipated by dielectric loss and magnetic loss. The shape memory mechanism of BCN/Fe3O4/PCL is based on the Fe3O4 and BCN nanotubes dissipating absorbed EMW energy into heat to boost the temperature of the composites, thereby responding to EMW remote control. This work introduces a new direction for SMPs induced by EMWs as potential candidates in the application of shape recovery in a restricted space.
RESUMEN
The development of high-performance electrode materials is crucial for the advancement of sodium ion batteries (SIBs), and NiCo2 S4 has been identified as a promising anode material due to its high theoretical capacity and abundant redox centers. However, its practical application in SIBs is hampered by issues such as severe volume variations and poor cycle stability. Herein, the Mn-doped NiCo2 S4 @graphene nanosheets (GNs) composite electrodes with hollow nanocages were designed using a structure engineering method to relieve the volume expansion and improve the transport kinetics and conductivity of the NiCo2 S4 electrode during cycling. Physical characterization and electrochemical tests, combined with density functional theory (DFT) calculations indicate that the resulting 3 % Mn-NCS@GNs electrode demonstrates excellent electrochemical performance (352.9â mAh g-1 at 200â mA g-1 after 200â cycles, and 315.3â mAh g-1 at 5000â mA g-1 ). This work provides a promising strategy for enhancing the sodium storage performance of metal sulfide electrodes.
RESUMEN
The solid-state method is extensively applied to the synthesis of electrode materials for its simplicity and low cost. However, particles obtained using the traditional solid-state method exhibited a large, uneven particle size and a severe aggregation phenomenon, leading to an unsatisfactory electrochemical performance. Here, spinel LiNi0.5Mn1.5O4 (LNMO) with good dispersion was synthesized using the solid-state method with the addition of N,N-dimethylpyrrolidone (NMP). During the LNMO preparation process, NMP is effective in refining and optimizing the particle size and suppressing the aggregation phenomenon. Meanwhile, the N element migration phenomenon was also observed in the bulk of LNMO, and it was beneficial for extending solid-solute reactions as demonstrated by in situ X-ray diffraction. LNMO prepared with NMP (LNMO-N-x) exhibited a higher discharge voltage and capacity (115.3 mA h g-1 at 2 C) compared with LNMO (105.8 mA h g-1). These results reveal the function of NMP in the preparation of LNMO and the effect of the physical characteristic changes on structure and phase transition in a working battery, and it can be easily incorporated into other electrode materials; if well engineered, it will contribute a lot to the further applications of lithium ion batteries.