One-Step Synthesis of Co@C Composite as High-Performance Anode Material for Lithium-ion Batteries

A carbon-coated cobalt (Co@C) composite was synthesized by a one-step method using ionic liquid as carbon source and reducing agent. The Co@C composite exhibited a core-shell structure, in which the cobalt nanoparticles uniformly embedded in the carbon matrix. When used as the anode material for lithium ion batteries, the cobalt nanoparticles enhanced the kinetics of Li+ and electronic transport during the charge/discharge process. The Co@C composite material delivered a reversible capacity of 657.3 mAh g-1 after 60 cycles at a current density of 0.1C and exhibits improved rate performance when compared with pure carbon

A BOUNDARY-PARTITION-BASED DIAGRAM OF D-DIMENSIONAL BALLS: DEFINITION, PROPERTIES AND APPLICATIONS

In computational geometry, different ways of space partitioning have been developed, including the Voronoi diagram of points and the power diagram of balls. In this article, a generalized Voronoi partition of overlapping d-dimensional balls, called the boundary-partition-based diagram, is proposed. The definition, properties and applications of this diagram are presented. Compared to the power diagram, this boundary-partition-based diagram is straightforward in the computation of the volume of overlapping balls, which avoids the possibly complicated construction of power cells. Furthermore, it can be applied to characterize singularities on molecular surfaces and to compute the medial axis that can potentially be used to classify molecular structures

Nitrogen–Sulfur Co-Doped Porous Carbon Prepared Using Ionic Liquids as a Dual Heteroatom Source and Their Application for Li-Ion Batteries

Nitrogen–sulfur co-doped porous carbon (NSPC) were prepared by using ionic liquids as both nitrogen and sulfur source. The as-obtained NSPC exhibits open pore structure with thin carbon walls and nitrogen (2.32 wt%) and sulfur (0.91 wt%) doping. When used as lithium-ion batteries (LIBs), NSPC shows a high reversible capacity of 821 mAh g−1 at 0.1 A g−1 after 50 cycles. Even after 1000 cycles, the NSPC exhibits a stable reversible capacity of 533 mAh g−1 at current density of 1.5 A g−1. The excellent electrochemical performance of NSPC is attributed to two points: (1) interconnected three-dimensional pore structure; (2) Nitrogen and sulfur doping and the synergic effect of dual-doping heteroatoms. This work provides new ideas for the development of new anode materials for LIBs

A Simple Synthesis of Nitrogen-Sulfur Co-Doped Porous Carbon Using Ionic Liquids as Dopant for High Rate Performance Li-Ion Batteries

A novel nitrogen‑sulfur co-doped porous carbon (NSPC) material was synthesized by using ionic liquids as the nitrogen and sulfur precursor. This material exhibited porous structure with high specific surface area (701 m2 g−1) and superior nitrogen and sulfur co-doping (4.66 and 1.83 wt%, respectively), The materials was used as anode materials for Lithium-ion batteries and showed a high reversible capacity of 987.7 mAh g−1 at a current density of 0.1 A g−1 and a good long cycle performance (337.5 mAh g−1 at 5 A g−1 after 5000 cycles). The NSPC\u27s superior electrochemical performance can be attributed to three points: (1) Excellent pore structure (surface area is 701 m2 g−1). (2) Nitrogen and sulfur co-doping (4.66 and 1.83 wt%, respectively). (3) Higher rate of capacitance contribution during process of charge and discharge

Carbon Modified Porous Scale-like γ-Fe2O3 as Anode for High Performance Li-ion Batteries

Carbon modified porous γ-Fe2O3 particles (PFe2O3–C) are synthesized by a high temperature calcination method using sodium chloride as a template. During the nucleation and carbonation process, the Fe(NO3)3–C10H15N5 complex uniformly dispersed on the surface of NaCl particles which can limit its longitudinal growth, thus forming independent and homogeneous nanoparticles with a diameter of about 30 nm. Because of this special structure, the γ-Fe2O3 particles have a sufficient interspace between them, which can not only provide a large number of active sites for storing lithium ions, but also shorten diffusion length for lithium ion transport. The introduction of carbon can offer additional lithium ion storage and improve overall electrical conductivity. This PFe2O3–C electrode exhibits excellent rate performance (1139, 1067, and 972 mAh g−1 at 2, 5, and 10 C, respectively, 1 C = 924 mAh g−1) and cycle performance (up to 2100 mAh g−1 after 200 cycles at 0.3 C)

Nitrogen Doped Porous Onion Carbon Derived from Ionic Liquids as the Anode Materials for Lithium Ion Batteries with High Performance

A novel nitrogen doped porous onion carbon (NDPOC) material was prepared by using [HMIm]N(CN)2 as carbon and nitrogen source. The transmission electron microscopy (TEM) and scanning electron microscopy (SEM) revealed that the NDPOC had a uniform porous structure and was wrapped by onion structured carbon. When used as the anode material for lithium ion batteries, this material not only prevented the collapse and breakage of the pores, but also facilitated the lithium ion migration and electron transfer. The NDPOC anode showed excellent discharge specific capacity (805 mAh g−1 of 0.1C after 50 cycles), rate performance, and cycle stability (306 and 267 mAh g−1 at 5 and 10C after 300 and 500 cycles, respectively)

Preparation of Carbon Encapsulated Core-Shell Fe@ CoFe2O4 Particles Through the Kirkendall Effect and Application as Advanced Anode Materials for Lithium-Ion Batteries

Carbon encapsulated core-shell Fe@CoFe2O4 nanoparticles (Fe@CoFe2O4@C) are produced by using Kirkendall effect method and used as the anode material for lithium-ion batteries. During the discharge process, Fe and Co particles are synthesized at the shell of the nanoparticles and are pulverized to smaller grains in the low potential regions. These pulverized particles not only increase the contact area between electrolyte and active materials, but also shortens the transfer distance of Li+ and electron, leading to an enhanced capacity. In addition, the structure stability and electrical conductivity of CoFe2O4 (CFO) shell are improved by the thin carbon layer coated on the surface of the shell. Due to this special structure, the Fe@CoFe2O4@C electrode exhibits excellent cycle performance, delivering a capacity of 1911 mA h g−1 after 500 cycles at 0.3 C (1 C = 1000 mA g−1). It also shows superior rate capacities of 760.8, 735.6, 672.2, and 596.5 mA h g−1 at the current densities of 1.0, 2.0, 5.0, and 10.0 C, respectively