Linlin Fan

Superior Cathode Performance of Nitrogen-Doped Graphene Frameworks for Lithium Ion Batteries

Development of alternative cathode materials is of highly desirable for sustainable and cost-efficient lithium-ion batteries (LIBs) in energy storage fields. In this study, for the first time, we report tunable nitrogen-doped graphene with active functional groups for cathode utilization of LIBs. When employed as cathode materials, the functionalized graphene frameworks with a nitrogen content of 9.26 at% retain a reversible capacity of 344 mAh g-1 after 200 cycles at a current density of 50 mA g-1. More surprisingly, when conducted at a high current density of 1 A g-1, this cathode delivers a high reversible capacity of 146 mAh g-1 after 1000 cycles. Our current research demonstrates the effective significance of nitrogen doping on enhancing cathode performance of functionalized graphene for LIBs.

An optimized Al2O3 layer for enhancing the anode performance of NiCo2O4 nanosheets for sodium-ion batteries

Herein, an ultrathin Al2O3 layer was coated onto NiCo2O4 nanosheets via an atomic layer deposition (ALD) method, and the NiCo2O4 coated with an ALD-derived Al2O3 material was successfully used as an anode material for sodium-ion batteries (SIBs). This kind of electrode exhibited enhanced cycling performance with a reversible capacity of 395 mA h g−1 after 50 cycles, and good rate capability with the discharge capacities of 350, 320, and 294 mA h g−1 at the various current densities of 100, 200, and 400 mA g−1, respectively. Interestingly, remarkable prevention of the reactions between the electrode and electrolyte was observed. The performance improvement is due to the protection of the NiCo2O4 coated with an ALD-derived Al2O3 layer from the electrochemical active materials. These results demonstrate the great potential of NiCo2O4 coated with an ALD-derived Al2O3 material as anodes in SIBs.

Promising Dual-Doped Graphene Aerogel/SnS2 Nanocrystal Building High Performance Sodium Ion Batteries

We report the effort in designing layered SnS2 nanocrystals decorated on nitrogen and sulfur dual-doped graphene aerogels (SnS2@N,S-GA) as anode material of SIBs. The optimized mass loading of SnS2 along with the addition of nitrogen and sulfur on the surface of GAs results in enhanced electrochemical performance of SnS2@N,S-GA composite. In particular, the introduction of nitrogen and sulfur heteroatoms could provide more active sites and good accessibility for Na ions. Moreover, the incorporation of the stable SnS2 crystal structure within the anode results in the superior discharge capacity of 527 mAh g-1 under a current density of 20 mA g-1 upon 50 cycles. It maintains 340 mAh g-1 even the current density is increased to 800 mA g-1. Aiming to further systematically study mechanism of composite with improved SIB performance, we construct the corresponding models based on experimental data and conduct first-principles calculations. The calculated results indicate the sulfur atoms doped in GAs show a strong bridging effect with the SnS2 nanocrystals, contributing to build robust architecture for electrode. Simultaneously, heteroatom dual doping of GAs shows the imperative function for improved electrical conductivity. Herein, first-principles calculations present a theoretical explanation for outstanding cycling properties of SnS2@N,S-GA composite.

Metal–Organic Frameworks-Derived Co2P@N-C@rGO with Dual Protection Layers for Improved Sodium Storage

The Co2P nanoparticles hybridized with unique N-doping carbon matrices have been successfully designed employing ZIF-67 as the precursor via a facile two-step procedure. The Co2P nanostructures are shielded with reduced graphene oxide (rGO) to enhance electrical conductivity and mitigate volume expansion/shrinkage during sodium storage. As anode materials for sodium-ion batteries (SIBs), the novel architectures of Co2P@N-C@rGO exhibited excellent sodium storage performance with a high reversible capacity of 225 mA h g-1 at 50 mA g-1 after 100 cycles. Our study demonstrates the significant potential of Co2P@N-C@rGO as anode materials for SIBs.

SnO2/Reduced Graphene Oxide Interlayer Mitigating the Shuttle Effect of Li–S Batteries

The short cycle life of lithium-sulfur batteries (LSBs) plagues its practical application. In this study, a uniform SnO2/reduced graphene oxide (denoted as SnO2/rGO) composite is successfully designed onto the commercial polypropylene separator for use of interlayer of LSBs to decrease the charge-transfer resistance and trap the soluble lithium polysulfides (LPSs). As a result, the assembled devices using the separator modified with the functional interlayer (SnO2/rGO) exhibit improved cycle performance; for instance, over 200 cycles at 1C, the discharge capacity of the cells reaches 734 mAh g-1. The cells also display high rate capability, with the average discharge capacity of 541.9 mAh g-1 at 5C. Additionally, the mechanism of anchoring behavior of the SnO2/rGO interlayer was systematically investigated using density functional theory calculations. The results demonstrate that the improved performance is related to the ability of SnO2/rGO to effectively absorb S8 cluster and LPS. The strong Li-O/Sn-S/O-S bonds and tight chemical adsorption between LPS and SnO2 mitigate the shuttle effect of LSBs. This study demonstrates that engineering the functional interlayer of metal oxide and carbon materials in LSBs may be an easy way to improve their rate capacity and cycling life.