Electrolyte Engineering on Performance Enhancement of NiCo2 S4 Anode for Sodium Storage.

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.

Wavelength selection of dual-mechanism LiDAR with reflection and fluorescence spectra for plant detection.

With the continuous expansion and refinement in plant detection range, reflection, and fluorescence spectra present great research potentials and commercial values. Referring technical advantages with hyperspectral and fluorescence lidar for monitoring plants, the synchronous observation with reflection and fluorescence signals achieved by one lidar system has attracted wide attention. This paper plans to design and construct a dual-mechanism lidar system that can obtain spatial information, reflection, and fluorescence signals simultaneously. How to select the optimal detected bands to the dual-mechanism lidar system for monitoring plants is an essential step. Therefore, this paper proposes a two-step wavelength selection method to determine the optimal bands combination by considering the spectral characteristic of reflection and fluorescence signals themselves, and the hardware performance of lidar units comprehensively. The optimal bands combination of 4 reflection bands of 481 nm, 541 nm, 711.5 nm, 775.5 nm, and 2 fluorescence bands of 686.5 nm, 737 nm was determined. Besides, compared with the original reflection or fluorescence bands, the overall accuracy and average accuracy of the optimal band combination were respectively improved by 2.51%, 15.45%, and 7.8%, 29.06%. The study demonstrated the reliability and availability of the two-step wavelength selection method, and can provide references for dual-mechanism lidar system construction.

Optimization of Sodium Storage Performance by Structure Engineering in Nickel-Cobalt-Sulfide.

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 (352.9 mAh g-1 at 200 mA g-1 after 200 cycles, and 315.3 mAh g-1 at 5000 mA g-1 ). This work provides a promising strategy for enhancing the sodium storage performance of metal sulfide electrodes.

Insights for the New Function of N,N-Dimethylpyrrolidone in Preparation of a High-Voltage Spinel LiNi0.5Mn1.5O4 Cathode.

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.