An Advanced Lithium Ion Battery Based on a Sulfur-Doped Porous Carbon Anode and a Lithium Iron Phosphate Cathode

Coaxial spinning fabricated high nitrogen-doped porous carbon walnut anchored on carbon fibers as anodic material with boosted lithium storage performance

Commercial graphite with low theoretical capacity cannot meet the ever-increasing requirement demands of lithium-ion batteries (LIBs) caused by the rapid development of electric devices. Rationally designed carbon-based nanomaterials can provide a wide range of possibilities to meet the growing requirements of energy storage. Hence, the porous walnut anchored on carbon fibers with reasonable pore structure, N-self doping (10.2 at%) and novel structure and morphology is designed via interaction of inner layer polyethylene oxide and outer layer polyacrylonitrile and polyvinylpyrrolidone during pyrolysis of the obtained precursor, which is fabricated by coaxial electrospinning. As an electrode material, the as-made sample shows a high discharge capacity of 965.3 mA h g^-1 at 0.2 A g^-1 in the first cycle, retains a capacity of 819.7 mA h g^-1 after 500 cycles, and displays excellent cycling stability (475.2 mA h g^-1 at 1 A g^-1 after 1000 cycles). Moreover, the capacity of the electrode material still keeps 260.5 mA h g^-1 at 5 A g^-1 after 1000 cycles. Therefore, the obtained sample has a bright application prospect as a high performance anode material for LIBs. Besides, this design idea paves the way for situ N-enriched carbon material with novel structure and morphology by coaxial electrospinning.

Deciphering the Structural, Textural, and Electrochemical Properties of Activated BN-Doped Spherical Carbons

In this study, the effect of K₂CO₃ activation on the structural, textural, and electrochemical properties of carbon spheres (CSs) and boron and nitrogen co-doped carbon spheres (BN-CSs) was evaluated. Activation of the CSs and BN-CSs by K₂CO₃ resulted in increased specific surface areas and I_D/I_G ratios. From the X-ray photoelectron spectroscopy (XPS) results, the BN-CSs comprised of 64% pyridinic-N, 24% pyrrolic-N and 7% graphitic-N whereas the activated BN-CSs had 19% pyridinic-N, 40% pyrrolic-N and 22% graphitic-N displaying the effect of activation on the type of N configurations in BN-CSs. A possible BN-co-doping and activation mechanism for the BN-CSs is proposed. Electrochemical analysis of the electrode materials revealed that BN doping, carbon morphology, structure, and porosity played a crucial role in enhancing the capacitive behavior of the CSs. As a proof of concept, a symmetric device comprising the activated BN-CSs displayed a specific power of 800 W kg⁻¹ at a specific current of 1 A g⁻¹ within an operating cell potential of 1.6 V in a 3 M KNO₃ electrolyte. The study illustrated for the first time the role of K₂CO₃ activation in influencing the physical and surface properties of template-free activated BN-CSs as potential electrode materials for energy storage systems.

Ultrathin Nitrogen-Doped Carbon Layer Uniformly Supported on Graphene Frameworks as Ultrahigh-Capacity Anode for Lithium-Ion Full Battery

The designable structure with 3D structure, ultrathin 2D nanosheets, and heteroatom doping are considered as highly promising routes to improve the electrochemical performance of carbon materials as anodes for lithium-ion batteries. However, it remains a significant challenge to efficiently integrate 3D interconnected porous frameworks with 2D tunable heteroatom-doped ultrathin carbon layers to further boost the performance. Herein, a novel nanostructure consisting of a uniform ultrathin N-doped carbon layer in situ coated on a 3D graphene framework (NC@GF) through solvothermal self-assembly/polymerization and pyrolysis is reported. The NC@GF with the nanosheets thickness of 4.0 nm and N content of 4.13 at% exhibits an ultrahigh reversible capacity of 2018 mA h g^-1 at 0.5 A g^-1 and an ultrafast charge-discharge feature with a remarkable capacity of 340 mA h g^-1 at an ultrahigh current density of 40 A g^-1 and a superlong cycle life with a capacity retention of 93% after 10 000 cycles at 40 A g^-1 . More importantly, when coupled with LiFePO₄ cathode, the fabricated lithium-ion full cells also exhibit high capacity and excellent rate and cycling performances, highlighting the practicability of this NC@GF.