In situ one-pot synthesis of Sn/lignite-based porous carbon composite for enhanced lithium storage

To expand the variety of Sn/C composites, lignite-based porous carbon was initially prepared with Baoqing lignite as the raw material and K₂CO₃ as the extractant and activator. A novel Sn/lignite-based porous carbon composite was subsequently fabricated via an in situ one-pot synthesis method. In the nanocomposite, Sn nanoparticles are uniformly distributed on lignite-based porous carbon, improving the lithium-ion storage performance of the as-prepared material. Compared with pure Sn and bare lignite-based porous carbon, Sn/lignite-based porous carbon displayed a superior electrochemical performance. The composite material exhibits a high reversible capacity of 941 mAh g^-1 after 200 cycles at 100 mA g^-1. Even after 800 charge/discharge cycles at a high current density of 1000 mA g^-1, the nanocomposite retains a reversible capacity of 573 mAh g^-1. The enhanced lithium-ion storage performance can be attributed to the combined effect of Sn and lignite-based porous carbon.

Efficient Fractionation of Graphene Oxide Based on Reversible Adsorption of Polymer and Size-Dependent Sodium Ion Storage

Graphene oxide (GO) is not only a unique class of two-dimensional (2D) materials but also an important precursor for scalable preparation of graphene. The efficient size fractionation of GO is of great importance to the fundamental and applied studies of chemically modified graphene, but remains a great challenge. Herein, we report an efficient and scalable fractionation method of GO employing reversible adsorption/desorption of temperature-responsive poly( N-isopropylacrylamide) on GO to amplify its mass difference and significantly improve the fractionation efficiency. Furthermore, size-dependent sodium ion storage of the resulting fractionated reduced GO (RGO) is revealed for the first time with high sodium storage performance achieved for the smallest RGO because of its largest d-spacing and most defect sites. This work provides valuable insights into the size fractionation and size-dependent electrochemical performance of graphene, which can be potentially extended to other 2D materials.

Sol-Gel Synthesis and in Situ X-ray Diffraction Study of Li3Nd3W2O12 as a Lithium Container

In this work, garnet-framework Li₃Nd₃W₂O₁₂ as a novel insertion-type anode material has been prepared via a facile sol-gel method and examined as a lithium container for lithium ion batteries (LIBs). Li₃Nd₃W₂O₁₂ shows a charge capacity of 225 mA h g^-1 at 50 mA g^-1, and with the current density increasing up to 500 mA g^-1, the charge capacity can still be maintained at 186 mA h g^-1. After cycling at 500 mA g^-1 for 500 cycles, Li₃Nd₃W₂O₁₂ retains about 85% of its first charge capacity changed from 190.2 to 161 mA h g^-1. Furthermore, in situ X-ray diffraction technique is adopted for the understanding of the insertion/extraction mechanism of Li₃Nd₃W₂O₁₂. The full-cell configuration LiFePO₄/Li₃Nd₃W₂O₁₂ is also assembled to evaluate the potential of Li₃Nd₃W₂O₁₂ for practical application. These results show that Li₃Nd₃W₂O₁₂ is such a promising anode material for LIBs with excellent electrochemical performance and stable structure.

Robust Strategy for Crafting Li5Cr7Ti6O25@CeO2 Composites as High-Performance Anode Material for Lithium-Ion Battery

A facile strategy was developed to prepare Li₅Cr₇Ti₆O₂₅@CeO₂ composites as a high-performance anode material. X-ray diffraction (XRD) and Rietveld refinement results show that the CeO₂ coating does not alter the structure of Li₅Cr₇Ti₆O₂₅ but increases the lattice parameter. Scanning electron microscopy (SEM) indicates that all samples have similar morphologies with a homogeneous particle distribution in the range of 100-500 nm. Energy-dispersive spectroscopy (EDS) mapping and high-resolution transmission electron microscopy (HRTEM) prove that CeO₂ layer successfully formed a coating layer on a surface of Li₅Cr₇Ti₆O₂₅ particles and supplied a good conductive connection between the Li₅Cr₇Ti₆O₂₅ particles. The electrochemical characterization reveals that Li₅Cr₇Ti₆O₂₅@CeO₂ (3 wt %) electrode shows the highest reversibility of the insertion and deinsertion behavior of Li ion, the smallest electrochemical polarization, the best lithium-ion mobility among all electrodes, and a better electrochemical activity than the pristine one. Therefore, Li₅Cr₇Ti₆O₂₅@CeO₂ (3 wt %) electrode indicates the highest delithiation and lithiation capacities at each rate. At 5 C charge-discharge rate, the pristine Li₅Cr₇Ti₆O₂₅ only delivers an initial delithiation capacity of ∼94.7 mAh g^-1, and the delithiation capacity merely achieves 87.4 mAh g^-1 even after 100 cycles. However, Li₅Cr₇Ti₆O₂₅@CeO₂ (3 wt %) delivers an initial delithiation capacity of 107.5 mAh·g^-1, and the delithiation capacity also reaches 100.5 mAh g^-1 even after 100 cycles. The cerium dioxide modification is a direct and efficient approach to improve the delithiation and lithiation capacities and cycle property of Li₅Cr₇Ti₆O₂₅ at large current densities.

A high-power and fast charging Li-ion battery with outstanding cycle-life

Electrochemical energy storage devices based on Li-ion cells currently power almost all electronic devices and power tools. The development of new Li-ion cell configurations by incorporating innovative functional components (electrode materials and electrolyte formulations) will allow to bring this technology beyond mobile electronics and to boost performance largely beyond the state-of-the-art. Here we demonstrate a new full Li-ion cell constituted by a high-potential cathode material, i.e. LiNi_0.5Mn_1.5O₄, a safe nanostructured anode material, i.e. TiO₂, and a composite electrolyte made by a mixture of an ionic liquid suitable for high potential applications, i.e. Pyr_1,4PF₆, a lithium salt, i.e. LiPF₆, and standard organic carbonates. The final cell configuration is able to reversibly cycle lithium for thousands of cycles at 1000 mAg⁻¹ and a capacity retention of 65% at cycle 2000.

Chemically Lithiated TiO2 Heterostructured Nanosheet Anode with Excellent Rate Capability and Long Cycle Life for High-Performance Lithium-Ion Batteries

A new form of dual-phase heterostructured nanosheet comprised of oxygen-deficient TiO2/Li4Ti5O12 has been successfully synthesized and used as anode material for lithium ion batteries. With the three-dimensional (3D) Ti mesh as both the conducting substrate and the Ti(3+)/Ti(4+) source, blue anatase Ti(3+)/TiO2nanosheets were grown by a hydrothermal reaction. By controlling the chemical lithiation period of TiO2 nanosheets, a phase boundary was created between the TiO2 and the newly formed Li4Ti5O12, which contribute additional capacity benefiting from favorable charge separation between the two phase interfaces. Through further hydrogenation of the 3D TiO2/Li4Ti5O12 heterostructured nanosheets (denoted as H-TiO2/LTO HNS), an extraordinary rate performance with capacity of 174 mAh g(-1) at 200 C and outstanding long-term cycling stability with only an ∼6% decrease of its initial specific capacity after 6000 cycles were delivered. The heterostructured nanosheet morphology provides a short length of lithium diffusion and high electrode/electrolyte contact area, which could also explain the remarkable lithium storage performance. In addition, the full battery assembled based on the H-TiO2/LTO anode achieves high energy and power densities.