Enhanced high-temperature electrochemical properties of in situ carbon-coated truncated octahedral LiMn2O4 cathodes.

Truncated octahedral spinel LiMn2O4 was homogenously coated by amorphous carbon layer via chemical vapor deposition (CVD) using acetylene gas (C2H2) as carbon source to ease Mn dissolution to improve high-temperature performance, delivering a capacity retention of 92.9% after 1000 cycles at 5C at 50 °C.

Rationally engineering a hierarchical porous carbon and reduced graphene oxide supported magnetite composite with boosted lithium-ion storage performances.

Ferric gallate (Fe-GA), an ancient metal-organic framework (MOF) material, has been recently employed as an eco-friendly and cost-effective precursor sample to synthesize a porous carbon confined nano-iron composite (Fe/RPC), and the Fe element in the Fe/RPC sample could be further oxidized to Fe3O4 nanocrystals in a 180 °C hydrothermal condition. On this foundation, this work reports an optimized approach to engineering a hierarchical one-dimensional porous carbon and two-dimensional reduced graphene oxide (RGO) supporting framework with Fe3O4 nanoparticles well dispersed. Under mild hydrothermal condition, the redox reaction between metal iron atoms from Fe/RPC and surface functional radicals from few-layered graphene oxide sheets (GO) is triggered. As a result, reinforced microstructure and improved atomic efficiency have been achieved for the Fe3O4@RPC/RGO sample. The homogeneously dispersed Fe3O4 nanoparticles with controlled size are anchored on the surface of the larger sized RGO coating layers while the smaller sized RPC domains are embedded between the RGO sheets as spacer. Challenges including spontaneous aggregation of RPC, over exposure of Fe3O4 nanoparticles and excessive restacking of RGO have been significantly inhibited. Furthermore, micro-sized carbon fiber (CF) is chosen as a structural reinforcement additive during electrode fabrication, and the Fe3O4@RPC/RGO sample delivers a good specific capacity of 1170.5 mAh·g-1 under a current rate of 1000 mA·g-1 for 500 cycles in the half cell form. The reasons for superior electrochemical behaviors have been revealed and the lithium-ion storage performances of the Fe3O4@RPC/RGO sample in the full cell form have been preliminarily investigated.

Copper Substitution in P2-Type Sodium Layered Oxide To Mitigate Phase Transition and Enhance Cyclability of Sodium-Ion Batteries.

Development of high-performance cathode materials is one of the key challenges in the practical application of sodium-ion batteries. Among all the cathode materials, layered sodium transition-metal oxides are particularly attractive. However, undesired phase transitions are often reported and have detrimental effects on the structure stability and electrochemical performance. Cu substitution of zinc in the P2-type Na0.6Mn0.7Ni0.15Zn0.15-xCuxO2 (x = 0, 0.075, and 0.15) composites was investigated in this study for mitigating the biphase transition and enhancing the electrochemical performance of sodium-ion batteries. The coupling effect of Zn and Cu enables an excellent capacity retention of 96.4% of the initial discharge capacity after 150 cycles at 0.1 C in the Na/Na0.6Mn0.7Ni0.15Zn0.075Cu0.075O2 cell. The biphase transition that occurred in the high voltage range has been significantly suppressed after the incorporation of Cu in Na0.6Mn0.7Ni0.15Zn0.15O2, which was confirmed by in situ X-ray diffraction studies. Moreover, the substitution of the inert element Zn with electrochemically active Cu leads to the suppression of anionic redox and the occurrence of Cu2+/3+ redox reaction, and the electrolyte decomposition is impeded after the introduction of electrochemically active Cu in the Na0.6Mn0.7Ni0.15Zn0.15-xCuxO2 composite cathode. The enhanced electrochemical performance in the Na0.6Mn0.7Ni0.15Zn0.075Cu0.075O2 electrode can be ascribed to the coexistence of Zn and Cu and alleviated volumetric change as well as suppressed electrode/electrolyte side reaction after Cu substitution.

Highly Stretchable Polymer Binder Engineered with Polysaccharides for Silicon Microparticles as High-Performance Anodes.

Silicon has been considered as a promising anode material for lithium-ion batteries owing to its extraordinarily high capacity. However, the huge volume expansion during cycling results in severe pulverization and disintegration of active materials, especially when the particle size is in microscale. This challenge can be addressed by highly stretchable polymer binders engineered with helical polysaccharides. The elaborately designed binder presents excellent stretchability and adhesive property, which can buffer the strain caused by the large volume change and coalesce the pulverized silicon fragments without disintegration. As a result, the microsized silicon electrode exhibits high initial Coulombic efficiency of 91.8 % and excellent cycling stability for 300 cycles. Importantly, when paired with a commercial LiCoO2 cathode, the full cell manifests a high areal capacity of 3.02 mAh cm-2 and superior stability for 100 cycles. Our contribution paves the way to the practical application of microsized silicon for lithium-ion batteries.

High-Energy Density Li metal Dual-Ion Battery with a Lithium Nitrate-Modified Carbonate-Based Electrolyte.

Lithium (Li) metal is a favorable anode for most energy storage equipment, thanks to its higher theoretical specific capacity. However, nonuniform Li nucleation/growth results in large-sized and irregular dendrites generated from the Li anode, which causes rapid capacity fade and serious safety hazard, hindering its widespread practical applications. In this paper, with the aid of a lithium nitrate (LiNO3) additive in a carbonate-based electrolyte, the Li anode shows low hysteresis for in excess of 1000 h at a current density of 0.5 mA cm-2. At the same time, a Li-graphite dual-ion battery exhibits an outstanding cycling stability at 5C; after 1000 cycles, 81% of the capacity is retained. After calculation, the Li-graphite dual-ion battery shows a competitive specific energy density of 243 Wh kg-1 at a power density of 234 W kg-1. Moreover, the linear sweep voltammetry test was first performed to analyze the Li nucleation/growth mechanism and explain the effect of the LiNO3 additive. The superior electrochemical properties of the Li-graphite dual-ion battery are ascribed to the formation of smooth Li composed of Li nanoparticles and a steady solid electrolyte interface film.

Enabling Lithium-Metal Anode Encapsulated in a 3D Carbon Skeleton with a Superior Rate Performance and Capacity Retention in Full Cells.

Suppressing the formation of lithium (Li) dendrites is central to implementing Li-metal anode, which has gained growing attention due to its ultrahigh specific capacity and low redox potential. Here, a novel approach is adopted to deposit Li-metal within a rigid three-dimensional (3D) carbon paper (3DCP) network, which consists of a cross-link framework of carbon fibers and graphene nanosheets (GNs). This unique structure yields a uniform distribution of Li-nuclei during the preliminary stage of Li-plating and the formation of a stable solid-electrolyte interface. The as-obtained anode can deliver a high areal capacity of 10 mAh cm-2 without the dendritic formation after 1000 cycles in a Li@3DCP/LiFePO4 full cell at 4 C. In addition, the Li@3DCP anode displays low voltage platform (<20 mV at 1 mA cm-2), high plating/stripping efficiency (99.0%), and long lifespan (>1000 h). When coupled with LiNi0.8Co0.15Al0.05O2 cathode, the Li@3DCP electrode exhibits a superior rate capability up to 10 C and high temperature performance (60 °C). The unprecedented performance is attributed to the desirable combination of micro/nanostructures in 3DCP, in which carbon fiber framework provides the mechanical stability for volume change, whereas numerous lithiophilicity sites on GNs enable the suppression of Li-dendrite growth.

Electrochemical and structural study of layered P2-type Na(2/3)Ni(1/3)Mn(2/3)O2 as cathode material for sodium-ion battery.

P2-type Na(2/3)Ni(1/3)Mn(2/3)O2 was synthesized by a controlled co-precipitation method followed by a high-temperature solid-state reaction and was used as a cathode material for a sodium-ion battery (SIB). The electrochemical behavior of this layered material was studied and an initial discharge capacity of 151.8 mA h g(-1) was achieved in the voltage range of 1.5-3.75 V versus Na(+)/Na. The retained discharge capacity was found to be 123.5 mA h g(-1) after charging/discharging 50 cycles, approximately 81.4% of the initial discharge capacity. In situ X-ray diffraction analysis was used to investigate the sodium insertion and extraction mechanism and clearly revealed the reversible structural changes of the P2-Na(2/3)Ni(1/3)Mn(2/3)O2 and no emergence of the O2-Ni(1/3)Mn(2/3)O2 phase during the cycling test, which is important for designing stable and high-performance SIB cathode materials.

Dual protection of sulfur by carbon nanospheres and graphene sheets for lithium-sulfur batteries.

Well-confined elemental sulfur was implanted into a stacked block of carbon nanospheres and graphene sheets through a simple solution process to create a new type of composite cathode material for lithium-sulfur batteries. Transmission electron microscopy and elemental mapping analysis confirm that the as-prepared composite material consists of graphene-wrapped carbon nanospheres with sulfur uniformly distributed in between, where the carbon nanospheres act as the sulfur carriers. With this structural design, the graphene contributes to direct coverage of sulfur to inhibit the mobility of polysulfides, whereas the carbon nanospheres undertake the role of carrying the sulfur into the carbon network. This composite achieves a high loading of sulfur (64.2 wt %) and gives a stable electrochemical performance with a maximum discharge capacity of 1394 mAh g(-1) at a current rate of 0.1 C as well as excellent rate capability at 1 C and 2 C. The improved electrochemical properties of this composite material are attributed to the dual functions of the carbon components, which effectively restrain the sulfur inside the carbon nano-network for use in lithium-sulfur rechargeable batteries.