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The spinel LiNi0.5Mn1.5O4 (LNMO) has been attracted great attention as lithium ion cathode material due to its high voltage and large energy density. However, the practical application of LNMO is still limited by poor cycling stability. Herein, to improve the cycling stability of spinel LNMO, it was treated with anneal process at 900 °C for 2 h after prepared by traditional solid-state method (LNMO-A). LNMO-A sample presented better electrochemical property especially under high rate, with capacity of 91.2 mAh g−1 after 1000 cycles under 10 C. Its superior electrochemical property was ascribed to the anneal process, resulting a stable crystal structure, indicated by XRD and Raman results of electrodes after 1000 cycles under 10 C and the longer solid-solution reaction, revealed by in-situ XRD. In addition, the optimized particle size, micro morphology and the larger BET area surface induced by the recrystallization in anneal process also contributes to its superior electrochemical property. What's more, the thin layer, which interacted LNMO-A particles with each other, induced by particles remelting in anneal process is also beneficial for its excellent electrochemical property. This study not only improved the electrochemical properties by anneal process, but also revealed the origins and mechanisms for its improvement.

The hollow microspherical structure cathode materials of bimetallic disulfide CoxNi1-xS2 (x varied from 0.1 to 0.5) for lithium thermal battery were synthesized by hydrothermal method. The structure, morphology, and composition of the hollow CoxNi1-xS2 were evaluated by field emission scanning electron microscope (FESEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The thermal stability was assessed by differential thermal analyzer (DTA). The thermal battery fabricated with CoxNi1-xS2 as cathode active material and LiB as anode exhibits the good electrochemical performance at 450 °C. Especially when x = 0.1, the initial discharge voltage reached 2.037 V, and specific capacity was 297.4 mA h g−1 at cut-off voltage of 1.5 V during constant current discharge. The bimetal disulfide material also presented advantages of reducing the internal resistance of the single cell.

Li7La3Zr2O12 (LLZO) has been considered as one of the most promising electrolytes for lithium batteries due to its high safety and wide electrochemical window. However, few reports were observed for the application of LLZO on lithium thermal batteries. In this paper, LLZO was studied as the electrolyte of lithium thermal battery. To further improve the performance of LLZO, LLZO-LiCl-LiBr-LiF composite electrolyte was designed by mechanical mixing LiCl-LiBr-LiF eutectic salt with LLZO. The doping content of LiCl-LiBr-LiF was also investigated, and the results showed that the optimize content was 15% (in weight) LiCl-LiBr-LiF. For instance, the specific capacity of the battery using LLZO-(LiCl-LiBr-LiF)x (x = 15%) as electrolyte was 224.6 mAh g−1, the active material utilization rate was 85.08%, and the service life of lithium thermal battery can be extended to 25 min under 80 mA cm−2 at 550 °C. The superior electrochemical properties of LLZO-(LiCl-LiBr-LiF)x (x = 15%) were ascribed to the larger ionic conductivity (2.802 × 10−2 S cm−1 at 550 °C). Our study not only successfully improves the electrochemical properties of LLZO by compositing with LiCl-LiBr-LiF electrolyte but also paves the way for the practical application of LLZO-LiCl-LiBr-LiF composite in the lithium thermal batteries.

In this paper, LiNi0.5Mn1.5O4 (LNMO) coated with various amount of RGO (0, 0.5, 1, and 2 wt%) were successfully synthesized by solid-state assembly method. The physical properties of LNMO and RGO-LNMO were investigated by x-ray diffraction (XRD), Raman spectra, scanning electron microscopy (SEM), and transmission electron microscope (TEM). XRD and Raman spectrum exhibit all samples that are well crystallized in P4332 space group; SEM and TEM results show the uniform size of the particles is 1 ~ 2 μm with octahedral structure, and LNMO is successfully wrapped by RGO. The electrochemical properties of RGO-LNMO visibly improved compared with the bared LNMO, especially at high current rate, which has been proven by galvanostatic charge-discharge test, cycle performance test, and rate capacity test. For example, the bared LNMO delivers a discharge capacity of 39.2 mAh g−1 at 10 C rate, while that of 1-wt% RGO-LNMO was 86.2 mAh g−1, which was approximately 2.5 times more than that of the bared LNMO. At 10 C rate after 1000 cycles, 2-wt% RGO-LNMO delivers a discharge capacity of 50.6 mAh g−1 with a capacity retention of 86.7%, while the bared LNMO delivers a discharge capacity of 27.6 mAh g−1 with a capacity retention of 52.5%, only about 54% of the 2-wt% RGO-LNMO. EIS results show the charge transfer resistance of LNMO decreased after coating with RGO, which was favorable for improving electrochemical performance.

Micronanosized LiNi0.5Mn1.5O4 nanorods coated with reduced graphene oxide is successfully synthesized by a hydrothermal-assembly method. The as-prepared samples are characterized by X-ray diffraction, Raman spectroscopy, field emission scanning electron microscope, and electrochemical tests. The XRD and Raman results show that the LiNi0.5Mn1.5O4 nanorods have disordered structure of Fd-3m space group. The SEM characterization exhibits that LiNi0.5Mn1.5O4 nanorods are about 200–400 nm in diameter, and the RGO is well dispersed on the surface of LiNi0.5Mn1.5O4 nanorods. Moreover, a RGO layer coated on the surface of LiNi0.5Mn1.5O4 can suppress the interfacial side reactions. The electrochemical tests show that the RGO-LNMO composites reveal high specific capacity and excellent cyclic stability at high rates. The 1%-RGO-LNMO composite can still possess the capacity of 71.4 mAh g−1 and excellent capacity retention about 99% after 1000 cycles at 10 C rate. The excellent performance of RGO-LNMO composites makes it a promising candidate as lithium-ion battery cathode materials.

The three-dimensional network structure of NiCo2S4@CNTs electrode materials for LIBs and SIBs composing NiCo2S4 nanoflakes anchored on the surface of carbon nanotubes (CNTs), which was prepared by electrostatic adsorption through a two-step solvothermal method. This composite structure is helpful to alleviate the volume expansion effect of NiCo2S4 materials and enhance the conductivity of composite electrode materials. Therefore, NiCo2S4@CNTs anode materials exhibit good cycle stability (after 80 cycles, the NiCo2S4@CNTs electrodes deliver the capacities of 783.17 mAh g−1 for LIBs and 291.10 mAh g−1 for SIBs) and rate performance (the NiCo2S4@CNTs electrodes show 517.64 mAh g−1 in LIBs and 169.29 mAh g−1 in SIBs at 1000 mA g−1). Moreover, the conversion mechanism of NiCo2S4@CNTs electrode materials was revealed combined with in-situ XRD, ex-situ XRD, ex-situ Raman spectrum and HRTEM. The cycle reversibility of conversion products in lithium and sodium storage process were also proved. Furthermore, the energy storage behavior of NiCo2S4@CNTs electrodes (the combination of capacitance and diffusion) during the process of charge and discharge both in LIBs and SIBs was indicated by CV curves of different scanning scans. Such conversion reaction mechanism provides a reference for the research of this kind of materials in other alkali metal ion batteries.

Nickel(II) chloride materials were synthesized via a novel two-step variable-temperature method for the use as a cathode material in Li-B/NiCl2 cells with the LiCl-LiBr-LiF electrolyte. The influence of temperature on its structure, surface morphology, and electrochemical performance was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical measurements of single cells. XRD results showed that after pre-dehydration for 2 h at 270°C followed by sintering for 5 h at 600°C, the crystal water in nickel chloride hexahydrate could be removed effectively. The SEM results showed that particles recombined to form larger coarse particles and presented a layered structure. Discharge tests showed that the 600°C-treated materials demonstrated remarkable specific capacities of 210.42 and 242.84 mA h g−1 at constant currents of 0.5 and 2.0 A, respectively. Therefore, the Li-B/NiCl2 thermal battery showed excellent discharge performance. The present work demonstrates that NiCl2 is a promising cathode material for thermal batteries and this two-step variable-temperature method is a simple and useful method for the fabrication of NiCl2 materials.

LiNi0.5Mn1.5− x Sn x O4 (0 ≤ x ≤ 0.1) cathode materials with uniform and fine particle sizes were successfully synthesized by a two-step calcination of solid-state reaction method. As the cathode materials for lithium ion batteries, the LiNi0.5Mn1.48Sn0.02O4 shows the highest specific capacity and cycle stability. In the potential range of 3.5–4.9 V at room temperature, LiNi0.5Mn1.48Sn0.02O4 composite material shows a discharge capacity of more than 117 mA h g−1 at 0.1 C, while the corresponding discharge capacity of undoped LiNi0.5Mn1.5O4 is only 101 mA h g−1. Moreover, in cycle performance, all the LiNi0.5Mn1.5− x Sn x O4 (0 ≤ x ≤ 0.1) samples show better capacity retention than the undoped LiNi0.5Mn1.5O4 at 1 C rate after 100 cycles. Especially, for the LiNi0.5Mn1.5O4, the discharge capacity after 100 cycles is 90 mA h g−1, while the corresponding discharge capacities of the undoped LiNi0.5Mn1.5O4 is only 56.1 mA h g−1. The significantly enhanced D Li+ and the enlarged electronic conductivity make the Sn-doped spinel LiNi0.5Mn1.5O4 material present even more excellent electrochemical performances. These results reveal that Sn-doping is an effective way to improve electrochemical performances of LiNi0.5Mn1.5O4.

In this work, the 3D macroscopic graphene hydrogels (MGHs) with a high capacitor performance were easily prepared by a one-step hydrothermal method from graphene oxide (GO) dispersions. A very small amount of 1,4-butanediamine was employed to realize the partial reduction of GO, modification of the 3D structure of MGHs, and nitrogen doping of graphene, at the same time. The synthesized MGH-6 sample in the wet state exhibit a high specific capacitance of 268.8 Fg −1 at 0.3 A g −1 in 6 M KOH electrolyte, and this capacitance can be maintained for 84.9% even as the discharging current density was increased up to 10 A g −1 . The MGH-6 sample also shows good cycle stability along with a 1.03% increase of its initial specific capacitance after 10000 cycles at current density of 10 Ag −1 . These remarkable properties are ascribed to the both nitrogen- and oxygen-containing functional groups, modified macroporous 3D framework, and the high specific surface area of the graphene. Combining with the economical and easy path toward mass production, the present MGH-6 can be expected as a promising candidate for high-performance supercapacitors.

Nanosized Li 4 Ti 5 O 12 /graphene(LTO/graphene) materials have been successfully synthesized by a sol-gel method. The LTO/graphene composites exhibit a well-defined cubic spinel structure with an average particle size of approximately 200–500 nm. Compared with pure Li 4 Ti 5 O 12 , LTO/graphene composites show higher specific capacity, much improved rate capability and better cycle stability when used as anode materials for lithium ion batteries. The initial capacity of the LTO/graphene composite(0.5 wt%) reaches 170.7 mAh g −1 at 1C, which slightly decreases to 168.5 mAh g −1 after 100 cycles with a capacity loss of 1.3%. More importantly, the resulting LTO/graphene (0.5 wt%) sample demonstrates remarkable rate capability in that it delivers a reversible capacity of 108.4 mAh g −1 in the 1000th cycle at 10C charge-discharge rate, about 2.5 times that of pristine Li 4 Ti 5 O 12 particles (44.1 mAh g −1 ). The improved high-rate capability, cycling stability, fast charge-discharge performance of LTO/graphene composites can be ascribed to the improvement of lithium ion diffusion and ionic conductivity by graphene-coating.

Nanosized Li 4 Ti 5 O 12 /graphene materials have been successfully synthesized by a solid state-assembly method. As the anode materials for lithium ion batteries, nanosized Li 4 Ti 5 O 12 /graphene exhibits higher specific capacity, much improved rate capability, and better cycle stability than the pure Li 4 Ti 5 O 12 . In the potential range of 1.0-2.0 V at room temperature, Li 4 Ti 5 O 12 /graphene with weight ratio of LTO:GO to 1000:5 shows discharge capacities of more than 144 and 96.2 mAh g −1 after 100 cycles at 1C and 3C charge-discharge rates, while the correspond discharge capacities of pure Li 4 Ti 5 O 12 are only 108 and 75.4 mAh g −1 , respectively. The resulting Li 4 Ti 5 O 15 /graphene (1000:5) sample demonstrates remarkable rate capability in that it delivers a reversible capacity of 53.4 mAh g −1 in the 1000th cycle at 10C charge-discharge rate, about 240% that of pristine Li 4 Ti 5 O 12 particles (22.2 mAh g −1 ). The low charge-transfer resistance and large lithium ion diffusion coefficients confirmed that Li 4 Ti 5 O 12 /graphene materials possessed better electronic conductivity and lithium ion mobility. The present work demonstrates that Li 4 Ti 5 O 12 /graphene composite is a promising anode material for high-rate and long life lithium ion batteries and this simple preparation method makes its production on a large scale.

The effects of organic additive, 3-S isothiuronium propyl sulfonate (UPS) on bath stability, deposition rate, reaction activation energy, and Ni-P coating composition in acidic electroless nickel (EN) plating were investigated. The study was performed by measuring the polarization curves and X-ray fluorescence spectrometer (XRF) in combination with X-ray photoelectron spectroscopy (XPS) analysis. The results show that UPS improves bath stability and increases the reaction activation energy. At lower concentration, UPS is an effective accelerator for EN deposition; whereas, at higher concentration, it decreases deposition rate. It also reveals that UPS inhibits the anodic oxidation of hypophosphite and accelerates the cathodic reduction. In addition, UPS decreases the phosphorus content in Ni-P deposit and can be adsorbed on the deposit surface and compound with Ni2+. On the basis of these results, the effect mechanism of UPS on electroless nickel deposition was deduced.

Li3V2-xSnx(PO4)3/C (x = 0, 0.01, 0.02, 0.05, 0.10) cathode materials are synthesized by a microwave-assisted solid state reaction starting with mixtures of LiOH·H2O, V2O5, NH4H2PO4, SnO2, and sucrose (Ar flow, 300 °C for 3 h followed by microwave heating at 750 °C for 15 min).

An immersion gold-plating process on electroless nickel substrate was investigated. The effects of gold salt, trisodium citrate, bath temperature, and pH on the gold-immersion-deposition process are also discussed. The study was performed by measuring the mixed potential-time curves in situ and electrochemical impedance spectroscopy in combination with X-ray fluorescence spectrometry (XRF) and atomic force microscopy (AFM) surface analysis. Electrochemical measurements and XRF results show that both the deposition rate and the mixed potential changed during the gold-deposition process. These variations reflect the change of electrode surface state. AFM analysis shows that the morphology of nickel surface changed greatly at the initial stage of gold deposition. A model for understanding the gold-immersion-deposition process was proposed based on the experimental data. The effects of KAu(CN) 2 , trisodium citrate, pH, and temperature on gold-immersion deposition are significant, via affecting the gold film formation and the deposition rate. The optimal conditions of aqueous solution for the gold-immersion plating were determined. The experimental results support the explanation of the proposed model.