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High nickel content in LiNixCoyMnzO2 (NCM, x ≥ 0.8, x + y + z = 1) layered cathode material allows high specific energy density in lithium-ion batteries (LIBs). However, Ni-rich NCM cathodes suffer from performance degradation, mechanical and structural instability upon prolonged cell cycling. Although the use of single-crystal Ni-rich NCM can mitigate these drawbacks, the ion-diffusion in large single-crystal particles hamper its rate capability. Herein, we report a strategy to construct an in situ Li1.4Y0.4Ti1.6(PO4)3 (LYTP) ion/electron conductive network which interconnects single-crystal LiNi0.88Co0.09Mn0.03O2 (SC-NCM88) particles. The LYTP network facilitates the lithium-ion transport between SC-NCM88 particles, mitigates mechanical instability and prevents detrimental crystalline phase transformation. When used in combination with a Li metal anode, the LYTP-containing SC-NCM88-based cathode enables a coin cell capacity of 130 mAh g−1 after 500 cycles at 5 C rate in the 2.75-4.4 V range at 25 °C. Tests in Li-ion pouch cell configuration (i.e., graphite used as negative electrode active material) demonstrate capacity retention of 85% after 1000 cycles at 0.5 C in the 2.75-4.4 V range at 25 °C for the LYTP-containing SC-NCM88-based positive electrode. Single-crystal Ni-rich cathodes suffer from side reactions with the electrolyte and slow Li-ion transport during high-voltage cycling. Herein, a Li1.4Y0.4Ti1.6(PO4)3 coating is applied to facilitate the Li-ion transport and improve the cycling life of the cell. [ABSTRACT FROM AUTHOR]

A novel catalyst of platinum nanoparticles (PtNPs) decorated on polydiallyldimethylammonium chloride (PDDA) functionalized polypyrrole nanospheres (PNS) has been prepared by simple wet-chemical method. PNS with large surface area and high dispersion was prepared by chemical polymerization of pyrrole. PtNPs with uniformed size and high dispersion have been successfully decorated on PDDA functionalized PNS via a sodium borohydride reduction process. The PNS/PtNPs is characterized by transmission electron microscopy, high resolution transmission electron microscopy, energy-dispersive X-ray, X-ray diffraction, X-ray photoelectron spectroscopy and inductively coupled plasma spectrum instrument. The results show that the PtNPs with sizes of approximate 5-6 nm are uniformly dispersed on the surface of PNS. Compared to Vulcan XC-72 carbon black supported same mass PtNPs (XC-72/PtNPs), PNS/PtNPs show larger mass activity (374 mA mg) and stronger poisoning-tolerance (I/I = 2.85) due to high dispersion of PtNPs on large surface of PNS. The performance indicates that PNS/PtNPs may be an excellent anode catalyst for methanol oxidation reaction. [ABSTRACT FROM AUTHOR]

A simple and cost-effective electrochemical method synthesized platinum nanoparticles on graphene nanosheet (PtNPs@GNS) is reported, and the Pt loading of the PtNPs@GNS can be controlled by electrodeposition. The structure and element analysis of the PtNPs@GNS have been investigated by scanning electron microscopy (SEM), Raman spectrum, X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The electrochemical measurement including electrochemical active surface area, current density, mass activity, oxidation peak potential,shows the PtNPs@GNS have more performance electrocatalytic properties for methanol oxidation reaction (MOR) compared to Vulcan XC-72 carbon (XC-72) supported PtNPs electrocatalysts. Probably, the cause which may be attributes to no aggregation of PtNPs and the well-dispersion on surface of GNS, so PtNPs@GNS show large electrochemically active surface area, highly electrocatalytic activity and stability in direct methanol fuel cells. [ABSTRACT FROM AUTHOR]

In this study, the new electrocatalyst of platinum support on polypyrrole-functionalized graphene (GNS-PPy/PtNPs) is reported. The polypyrrole-functionalized graphene (GNS-PPy) is constructed first with graphene nanosheets (GNS) and polypyrrole (PPy) particles by constant potential deposition. And then PtNPs are deposited on the surface of GNS-PPy by cyclic voltammetry. The as-prepared GNS-PPy/PtNPs is characterized by scanning electron microscopy, energy-dispersive spectroscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. The prepared GNS-PPy/PtNPs catalyst is employed for methanol oxidation reactions. Compared with GNS/PtNPs and PPy/PtNPs, the GNS-PPy/PtNPs has higher catalytic activity (508 mA/mg), better stability, and stronger poisoning-tolerance ( I/ I = 4.18) due to high dispersion of PtNPs on large surface of GNS-PPy as well as synergic effect among the GNS, PPy particles, and PtNPs. The experimental results indicate that GNS-PPy/PtNPs may be an ideal candidate catalyst for direct methanol fuel cell. [ABSTRACT FROM AUTHOR]