Polydopamine coated TiO2 nanofiber fillers for polyethylene oxide hybrid electrolytes for efficient and durable all solid state lithium ion batteries.

The polyethylene oxide (PEO) solid electrolyte is a promising candidate for all solid state lithium-ion batteries (ASSLIBs), but its low ionic conductivity and poor interfacial compatibility against lithium limit the rate and cycling performance of the cell. Herein, the novel and efficient TiO2@polydopamine (PDA) fillers have been synthesized by coating PDA onto the surface of the TiO2 nanofibers, which are then incorporated into PEO matrices to form the composite electrolyte. The composite electrolyte displays a higher ionic conductivity of 4.36 × 10-4 S cm-1, a wider electrochemical window up to about 5 V and a higher tLi+ of 0.190 at 55 °C compared to the PEO electrolyte. Additionally, the Li/composite electrolyte/Li batteries show a stable Li plating/stripping cycle performance, indicating good interfacial compatibility between the composite electrolyte and lithium. Thus, the LiFePO4/Li ASSLIBs display a fantastic rate performance and cycling stability, and deliver superior discharge specific capacities of 153.83 and 136.45 mA h g-1 at current densities of 0.5C and 2C, achieving good capacity retentions of 93.27% and 91.23% at 0.5C and 1C after 150 cycles, respectively. Therefore, the PEO-TiO2@PDA composite electrolyte is a potential solid electrolyte for ASSLIBs.

Bagasse as a carbon structure with high sulfur content for lithium-sulfur batteries.

A bagasse-based 3D carbon matrix (BC) with high specific surface area and high conductivity was obtained by carbonization and pore-forming processes with bagasse as the carbon precursor and K2FeO4 as the pore-former. The microporous structure and nitrogenous functional groups were determined in the prepared carbon matrix, which could allow high sulfur loading and improve the polysulfide absorption capacity during cycling. After sulfur infusion, the S/BC composite with 68.8% sulfur content was obtained. The lithium-sulfur (Li-S) battery with the S/BC cathode shows high specific capacity and good cycling performance. It delivers a specific capacity of 1360 mA h g-1 at 0.2C and remains at 790 mA h g-1 after 200 cycles. At 1C, the Li-S with this composite cathode exhibits 601 mA h g-1 after 150 cycles. This work offers a new kind of green material and a new method for Li-S batteries.

Carbon nanotube hollow polyhedrons derived from ZIF-8@ZIF-67 coupled to electro-deposited gold nanoparticles for voltammetric determination of acetaminophen.

A comparative study was carried out on the electrochemical behavior of three carbonized zeolitic imidazolate frameworks (ZIFs) synthesized through solvothermal pyrolysis. An electrochemical sensor for acetaminophen (ACT) was subsequently developed. The sensor was made by coating the glassy carbon electrode (GCE) with cobalt-nitrogen co-doped carbon nanotube hollow polyhedron (Co-NCNHP), which was prepared from core shell ZIF-8@ZIF-67, before electrodeposition of gold nanoparticles. Due to the high specific surface area, good electrical conductivity and stability of both Co-NCNHP and the gold nanoparticles, the resultant sensor displayed excellent electrocatalytic activity towards ACT with the catalytic rate constant Kcat of 4.9 × 105 M-1 s-1, diffusion coefficient D of 1.8 × 10-6 cm2 s-1, high sensitivity of 1.75 µA µM-1 cm-2, and best at a working voltage of 0.35 V (vs. Ag/AgCl). Benefitting from the synergistic effect of both Co-NCNHP and gold nanoparticles, the modified GCE had a linear response in the 0.1 µM-250 µM ACT and detection limit of 0.05 µM (at S/N = 3). The sensor was successfully applied to quantify ACT in tablets and spiked urine samples with recoveries ranged between 96.0% and 105.2%. Graphical abstractSchematic representation of cobalt-nitrogen co-doped carbon nanotube hollow polyhedrons (Co-NCNHP) exhibiting superior electrocatalytic activity to carbonized ZIF-8 and carbonized ZIF-67. Co-NCNHP were coupled to electrodeposition gold nanoparticles to modify glassy carbon electrode for improving acetaminophen (ACT) redox.

Separation and recovery of carbon powder in anodes from spent lithium-ion batteries to synthesize graphene.

Based on the structural characteristics of the anodes of lithium-ion batteries, an improved Hummers' method is proposed to recycle the anode materials of spent lithium-ion batteries into graphene. In order to effectively separate the active material from the copper foil, water was selected as an ultrasonic solvent in this experiment. In order to further verify whether lithium ions exist in the active material, carbon powder, it was digested by microwave digestion. ICP-AES was then used to analyse the solution. It was found that lithium ions were almost non-existent in the carbon powder. In order to further increase the added value of the active material, graphene oxide was obtained by an improved Hummers' method using the carbon powder. The graphene material was also reduced by adding vitamin C as a reducing agent through a chemical reduction method using graphene oxide. Meanwhile, the negative graphite, graphite oxide and graphene samples were characterized by XRD, SEM, FTIR and TEM. The conductivity of the negative graphite, graphite oxide and graphene was tested. The results show that graphene prepared by a redox method has a better layered structure, less impurities and oxygen groups in its molecular structure, wider interlayer spacing and smaller resistivity.

Analysis of nanofiber-based La0.2Sr0.8TiO3-Gd0.2Ce0.8O1.9 electrode kinetics.

For the sake of comparison, a single cell with nanofiber-based LST-GDC composite anode (Cell-1) and a single cell with nanoparticle-based LST-GDC composite anode (Cell-2) are fabricated, respectively. The electrolyte ohmic resistances of the LST-GDC composite anode side half-cells are determined by an AC resistance measurement. Current interrupt is applied to measure the ohmic resistance of the half-cells. Combined with V-I characteristics, the influences of the potential drops caused by electrolyte ohmic resistance, electrode ohmic resistance and electrode electrochemical reaction on the cell kinetics are investigated. Under a current density of 0.6 A cm-2 at 850 °C, for the nanofiber-based LST-GDC composite anode (NF-LST-GDC), the electrode ohmic potential drop is 0.007 V and the potential drop caused by the electrode electrochemical reaction is 0.080 V. While for the nanoparticle-based LST-GDC composite anode (NP-LST-GDC), the corresponding potential drops are 0.159 V and 0.246 V, respectively. Both the potential drops of the former are lower than those of the latter. The kinetics of Cell-1 is greater than Cell-2, i.e., the kinetics of NF-LST-GDC is greater than that of NP-LST-GDC.