Chao Lai

A porous nitrogen and phosphorous dual doped graphene blocking layer for high performance Li–S batteries

Conductive confinement of sulfur and polysulfides via carbonaceous blocking layers can simultaneously address the issues of low conductivity, volume expansion of sulfur during the charge/discharge process and the polysulfide shuttling effect in lithium–sulfur (Li–S) batteries. Herein, a conductive and porous nitrogen and phosphorus dual doped graphene (p-NP-G) blocking layer is prepared via a thermal annealing and subsequent hydrothermal reaction route. The doping levels of N and P in p-NP-G as measured by X-ray photoelectron spectroscopy are ca. 4.38% and ca. 1.93%, respectively. The dual doped blocking layer exhibits higher conductivity than N or P single doped blocking layers. More importantly, density functional theory (DFT) calculations demonstrate that P atoms and –P–O groups in the p-NP-G layer offer stronger adsorption of polysulfides than the N species. The electrochemical evaluation results illustrate that the p-NP-G blocking layer can deliver superior initial capacity (1158.3 mA h g−1 at a current density of 1C), excellent rate capability (633.7 mA h g−1 at 2C), and satisfactory cycling stability (ca. 0.09% capacity decay per cycle), which are better than those of the N or P single doped graphene. This work suggests that this synergetic combination of conductive and adsorptive confinement strategies induced by the multi-heteroatom doping scheme is a promising approach for developing high performance Li–S batteries.

A conductive interwoven bamboo carbon fiber membrane for Li–S batteries

Natural bamboo, as a sustainable precursor, is used to prepare porous bamboo carbon fibers (BCFs) that are subsequently interwoven into a BCF membrane (BCFM) as a captor interlayer for the lithium polysulfide intermediates between the sulfur cathode and the separator in Li–S batteries. On one hand, the interwoven BCFs offer efficient conductive networks. On the other hand, the pores of the BCFM facilitate fast mass transport of the electrolyte and Li ions and accommodate severe volume changes of the sulfur cathode during charge/discharge processes. Furthermore abundant macro/microporous structures of BCFs provide substantial adsorption capability to remarkably suppress the formation of the Li2S2/Li2S layer on the cathode and extend the lifetime of the electrode by successfully confining sulfur within the carbon networks. Consequently, Li–S batteries with the BCFM deliver excellent electrochemical performances with a high coulombic efficiency (ca. 98%), low capacity fade at only 0.11% per cycle, and long-term cyclability over 300 cycles at a high charge/discharge rate of 1 C. This green, low cost BCFM can provide an attractive alternative for large-scale commercialization of Li–S batteries.

Blue hydrogenated lithium titanate as a high-rate anode material for lithium-ion batteries

Blue hydrogenated lithium titanate (LTO) was prepared by treating industrial grade white LTO at 500 °C under a 40 bar H2 atmosphere. This process improves the Li-ion diffusivity and electronic conductivity, leading to enhanced specific capacity and rate capability in lithium-ion batteries.

A type of sodium-ion full-cell with a layered NaNi0.5Ti0.5O2 cathode and a pre-sodiated hard carbon anode

A new structure of sodium-ion full-cell with a layered NaNi0.5Ti0.5O2 cathode and a pre-sodiated hard carbon anode is reported. The pre-sodiation of the hard carbon anode, achieved via a facile approach in a three-electrode battery, can significantly enhance the initial coulombic efficiency of the sodium-ion full-cell. As a consequence, a much higher capacity is obtained in the hard carbon/NaNi0.5Ti0.5O2 sodium-ion battery. Based on the cathode mass, the full-cell with the pre-sodiated hard carbon anode can exhibit a reversible capacity of 93 mA h g−1.

High-performance amorphous carbon–graphene nanocomposite anode for lithium-ion batteries

An amorphous carbon–graphene nanocomposite was prepared using glucose and graphene oxide as the precursors via a facile hydrothermal route and subsequent calcination. The amorphous carbon grown on the graphene plane prevents restacking of the resultant graphene nanolayers and maintains the structural stability of the nanocomposite during the discharge–charge process in lithium-ion batteries.

Facile fabrication of three-dimensional hierarchical CuO nanostructures with enhanced lithium storage capability

Three-dimensional hierarchical CuO nanostructures with uniform flower-like and urchin-like morphologies have been successfully prepared by a facile, cheap and environmentally friendly solvothermal method. The as-prepared flower-like CuO is constructed by nanopetals, which are composed of nanoparticles, and the urchin-like CuO with a hollow structure is composed of tightly arranged nanorods. As anode materials for lithium-ion batteries, the flower-like CuO material exhibits a high initial discharge capacitance (1457.2 mA h g−1 at 100 mA g−1), good rate capability and excellent cycling stability. The superior electrochemical performance is mainly attributed to the hierarchical structure and the nanosize of the nanoparticles composing the nanopetals, which benefit electron and Li ion transportation, and provide large electrode–electrolyte contact area. The extra capacity of the samples may be due to the partial reversible formation and decomposition of the gel-like SEI film on the surface of the electrode and pseudocapacitance.

Crystalline TiO2@C nanosheet anode with enhanced rate capability for lithium-ion batteries

TiO2@C nanosheets have been obtained by a facile solvothermal method using titanate butoxide and hydrofluoric acid as precursors, followed by our novel carbon coating technique using oleic acid as the carbon source. The TiO2@C nanosheet anode shows a high discharge capacity of 145.8 mA h g−1 after 50 cycles and excellent rate capability.

Enhanced cycling performance of the Li4Ti5O12 anode in an ethers electrolyte induced by a solid–electrolyte interphase film

The generation of a uniform solid–electrolyte interphase film on the surface of the Li4Ti5O12 anode at potentials above 1.0 V in an ethers electrolyte with lithium bis(trifluoromethanesulfonyl)imide as the lithium salt is reported. A significant enhancement in the cycling life can be obtained in the ethers electrolyte compared to in the conventional carbonates electrolyte. At a rate of 2 C, the discharge capacity can be retained at a stable 155.4 mA h g−1 after 300 cycles with a high capacity retention of 97.5%, which is the best result reported for a Li4Ti5O12 anode with a particle size above 300 nm.

Titanium pyrophosphate hexagonal nanoplates for electrochemical lithium storage

Titanium pyrophosphate hexagonal nanoplates were synthesized via facile hydrothermal reaction followed by a calcination procedure. As new cathode materials for lithium-ion batteries, they demonstrate stable cycle performance and high capacity retention at various current densities.