Renzong Hu

Nanoscale Surface Modification of Lithium‐Rich Layered‐Oxide Composite Cathodes for Suppressing Voltage Fade

Lithium-rich layered oxides are promising cathode materials for lithium-ion batteries and exhibit a high reversible capacity exceeding 250u2005mAhu2009g(-1) . However, voltage fade is the major problem that needs to be overcome before they can find practical applications. Here, Li1.2 Mn0.54 Ni0.13 Co0.13 O2 (LLMO) oxides are subjected to nanoscale LiFePO4 (LFP) surface modification. The resulting materials combine the advantages of both bulk doping and surface coating as the LLMO crystal structure is stabilized through cationic doping, and the LLMO cathode materials are protected from corrosion induced by organic electrolytes. An LLMO cathode modified with 5u2005wtu2009% LFP (LLMO-LFP5) demonstrated suppressed voltage fade and a discharge capacity of 282.8u2005mAhu2009g(-1) at 0.1u2005C with a capacity retention of 98.1u2009% after 120 cycles. Moreover, the nanoscale LFP layers incorporated into the LLMO surfaces can effectively maintain the lithium-ion and charge transport channels, and the LLMO-LFP5 cathode demonstrated an excellent rate capacity.

Dramatically enhanced reversibility of Li2O in SnO2-based electrodes: the effect of nanostructure on high initial reversible capacity

The formation of irreversible Li2O during discharge is believed to be the main cause of large capacity loss and low Coulombic efficiency of oxide negative electrodes for Li batteries. This assumption may have misguided the development of high-capacity SnO2-based anodes in recent years. Here we demonstrated that contrary to this perception, Li2O can indeed be highly reversible in a SnO2 electrode with controlled nanostructure and achieved an initial Coulombic efficiency of ∼95.5%, much higher than that previously believed to be possible (52.4%). In situ spectroscopic and diffraction analyses corroborate highly reversible electrochemical cycling, suggesting that the interfaces and grain boundaries of nano-sized SnO2 may suppress the coarsening of Sn and enable the conversion between Li2O and Sn to amorphous SnO2 when de-lithiated. These results provide important insight into the rational design of high-performance oxide electrodes for Li-ion batteries.

V5S8–graphite hybrid nanosheets as a high rate-capacity and stable anode material for sodium-ion batteries

Here we report chemically-exfoliated V5S8 and graphite hybrid nanosheets (ce-V5S8–C) as a novel anode material for sodium-ion batteries (SIBs). It exhibits much improved sodiation capacity, rate capability, reversibility and stability compared to other major SIB anode materials.

Deformable fibrous carbon supported ultrafine nano-SnO2 as a high volumetric capacity and cyclic durable anode for Li storage

Multidimensional fibrous carbon scaffolds, derived from carbonized filter papers (CFPs), were used to support SnO2 nanocrystals (NCs, with a size of 4–5 nm) to form a free-standing SnO2NC@CFP hybrid anode for Li-ion batteries. The SnO2NC particles are well accreted on the surfaces of 1D carbon fibers and 2D ultrathin carbon sheets while maintaining 3D interconnected pores of the carbon matrices for fast ionic transport. The SnO2NC@CFP hybrid electrode exhibits long-term higher energy density than the commercial graphite anode, and excellent rate capability, mainly due to good dispersion of SnO2 in the multidimensional conductive carbon. In particular, the reversible deformation of the flexible fibrous carbon matrices, as inferred from in situ Raman spectroscopy and SEM image analysis, facilitates stress release from the active SnO2NCs during discharge–charge cycling while maintaining the structural integrity of the self-supported SnO2NC@CFP anode. These demonstrate that the rational combination of the multidimensional architecture of deformable carbon with nanoscale active materials is ideally suited for high-performance Li-ion batteries.

Sn-MoS2-C@C Microspheres as a Sodium-Ion Battery Anode Material with High Capacity and Long Cycle Life

Sodium ion batteries (SIBs) have been regarded as a prime candidate for large-scale energy storage, and developing high performance anode materials is one of the main challenges for advanced SIBs. Novel structured Sn-MoS2 -C@C microspheres, in which Sn nanoparticles are evenly embedded in MoS2 nanosheets and a thin carbon film is homogenously engineered over the microspheres, have been fabricated by the hydrothermal method. The Sn-MoS2 -C@C microspheres demonstrate an excellent Na-storage performance as an anode of SIBs and deliver a high reversible charge capacity (580.3u2005mAhu2009g-1 at 0.05u2005Ag-1 ) and rate capacity (580.3, 373, 326, 285.2, and 181.9u2005mAhu2009g-1 at 0.05, 0.5, 1, 2, and 5u2005Ag-1 , respectively). A high charge specific capacity of 245u2005mAhu2009g-1 can still be achieved after 2750 cycles at 2u2005Ag-1 , indicating an outstanding cycling performance. The high capacity and long-term stability make Sn-MoS2 -C@C composite a very promising anode material for SIBs.