SnSe2 Quantum Dot/rGO composite as high performing lithium anode

Due to its high working voltage (4.7 V vs. Li/Li+ for Ni2+/Ni4+ redox couple), high theoretical capacity (147 mAh/g), and inherent cyclic stability (no Jahn-Teller distortion from Mn3+), LiNi0.5Mn1.5O4 is a promising cathode material for the practical application in high energy density lithium ion batteries [1-3]. The cation ordering, the degree of presence of Mn3+ in the spinel structure, is regarded as an important factor influencing the electrochemical properties of LiNi0.5Mn1.5O4 [4, 5]. With a simply strategy of cooling rate, the degree of ordering in disordered spinel LiNi0.5Mn1.5O4-δ structure is controlled at 0.5 oC/min for slow cooled spinel and at 5 oC/min for fast cooled spinel. From XRD and FTIR analyses and charge/discharge profiles, it is confirmed that the fast cooled spinel develops more disordered structure than the slow cooled spinel, retaining more oxygen vacancies and more abundant Mn3+. Moreover, through in situ XRD analysis, the more disordered spinel follows the extended solid-solution reaction in favor of Li+transport, which results in an improved rate capability. But, the local structure information of interesting atoms without a destructive interference which can arise from long-range structural order is highly related to the electrochemical performance. Therefore, the examination in local structural variations of interesting atoms is essential for understanding their electrochemical properties. In this work, we investigate local structural changes in the vicinity of Mn and Ni cations at various C-rates by using ex situ XAS analysis and quantify the structural changes by fitting a theoretical model to the extended X-ray absorption fine structure data. This finding will propose that a change of structural distortion can be another platform to understand the enhanced Li+transport in the disordered spinel and offer valuable guidance for developing LiNi0.5Mn1.5O4, a promising cathode material with high rate capability for next generation rechargeable batteries. More detailed discussion will be presented at the 2016 IMLB meeting. [1]. X. Liu, D. Li et al., J. Alloys Compd.,2014, 609, 54-59. [2]. X.-W. Gao, Y.-F. Deng et al., J. Mater, Chem. A.,2015, 3, 404-411. [3]. H. Xia, Y.S. Meng et al., J. Electrochem. Soc., 2007, 154, A737-A743. [4]. M. Kunduraci and G.G Amatucci, J. Electrochem. Soc.,2006, 153, A1345-A1352 [5]. L. Wang, H. Li et al., Solid State Ionics., 2011, 193, 32-38

Porous ZnO/Co3O4/CoO/Co composite derived from Zn-Co-ZIF as improved performance anodes for lithium-ion batteries

Effect of niobium doping on the structure and electrochemical performance of LiNi0.5Co0.2Mn0.3O2 cathode materials for lithium ion batteries

The performance and reliability of energy storage systems largely depend on the characteristics and properties of the electrode materials that constitute the system. Nanostructured materials have greatly influenced the overall performance of these systems by enhancing surface processes and improving the transport kinetics of the ions/molecules involved. Vanadium based materials have received considerable attention, particularly as electrode materials in high energy density Lithium ion batteries (LIB) and supercapacitors because of their cost effectiveness, efficient energy utilization and special structural characteristics. In this review, the applications of vanadium based materials as electrode components in energy storage systems have been described; their utilization in LIB and supercapacitors has been particularly highlighted. Recent developments in the field of vanadium based nanoelectrode materials are also discussed.

Designing anode materials with high lithium specific capacity is crucial to the development of high energy density lithium (ion) batteries. Herein, a distinctive lithium growth mechanism, namely, the restricted multilayered growth for lithium, and a strategy for lithium storage are proposed to achieve a balance between ultrahigh specific capacity and the need to avert uncontrolled dendritic growth of lithium. In particular, based on first-principles computation, we show that the Al2C monolayer with a planar tetracoordinate carbon structure can be an ideal platform for realizing the restricted multilayered growth mechanism as a two-dimensional (2D) anode material. Furthermore, the Al2C monolayer exhibits the ultrahigh specific capacity of lithium of 4059 mAh/g, yet with a low diffusion barrier of 0.039-0.17 eV and low open circuit voltage in the range of 0.002-0.34 V. These novel properties render the Al2C monolayer a promising anode material for future lithium (ion) batteries. Our study also offers a design of promising 2D anode materials with a high specific capacity, fast lithium-ion diffusion, and safe lithium storage.

High energy nickel manganese cobalt oxide materials (HENMC) are one of the most viable cathode materials for a high energy density lithium ion battery (LIB), but they contain expensive and toxic cobalt (Co). We synthesized Co-free high energy nickel manganese oxide cathode materials (HENM) via a solid state reaction method and a coprecipitation method. Their structural and electrochemical properties were comparatively investigated using X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), inductively coupled plasma (ICP), electron probe micro-analysis (EPMA), particle size analysis (PSA) and electrochemical impedance spectroscopy (EIS). The co-precipitated HENM and the solid state fabricated HENM showed high capacities of 250 mAhg−1 and 240 mAhg−1, respectively. It suggests that the solid state fabricated method of HENM would be a good candidate for practical application as well as the co-precipitated one.

The rapid development of mobile electronics, electric-vehicles and intermittent power generation relies on the availability of advanced electrochemical energy storage systems such as high capacity lithium ion batteries (LIBs). Although the state-of-the-art commercial LIBs have impressive electrochemical performance, they are suffering from relative low capacities due to the usage of host materials for storing lithium ions safely and reproducibly. The host material for LIB anode is dominated by graphite with a theoretical capacity of 372 mAh g-1. To further improve the capacity and energy density of LIBs, revolutionary changes in electrode materials, electrolytes, additives, binders and cell design are much needed. Alloying anode materials like Si, Ge and Sn have much higher theoretical capacities (4200, 1600 and 990 mAh g-1 for Si, Ge and Sn, respectively) as compared to graphite. However, a high capacity inevitably leads to a large electrode volume change during lithiation and de-lithiation process (e.g. 300% for Si-based anodes). Such a huge volume change can cause electrode pulverization, detachment of active materials from conductive additives, unstable solid-electrolyte interphase, and eventually result in a rapid, permanent capacity loss. Although Si-based anode has caught much research attention, formidable challenges remain to develop an electrode fabrication method that is efficient, low-cost, scalable, highly reproducible, and self-assembled, thus boosting the commercialization potential of Si-based anodes. As inspired by the hollow fiber membrane technology that has been successfully commercialized in the last decades to provide billions of gallons of purified drinking water worldwide, we report the use of carbonized asymmetric membrane electrodes (fiber and thin film types) that contain silicon, silicon monoxide, germanium, tin dioxide or vanadium (V) oxide to significantly increase LIB electrode capacity while maintaining a long cycling life and an excellent rate performance. These asymmetric membrane electrodes are fabricated using a modified reverse-osmosis membrane technology, the phase-inversion method combined with dip-coating and carbonization. The asymmetric membrane electrodes have a thin, nanoporous top layer (up to several microns) and a thick, macroporous bottom layer (up to 200 µm). The top layer can prevent fractured anode materials from falling away, while the bottom layer can efficiently accommodate the large volume changes of high capacity alloying anodes. 90% capacity of thin film asymmetric membrane at 1000 mAh g-1 containing Si nanoparticles can be retained after 200 cycles with an initial capacity loss of ~ 30%. Combining phase inversion with sol-gel chemistry, this method can be extended to obtain SnO2 and V2O5 asymmetric membranes. Thin film SnO2 asymmetric membrane electrode demonstrates a specific capacity of 500 mAh g-1 a current density of 280 mA g-1 (~0.5C) with >96% capacity retention after 400 cycles. When the current density is increased from 28 to 560 mA g-1, more than 65% capacity can be retained. The V2O5 electrode can be cycled at 0.5C with a capacity of 160 mAh g-1 for 380 times with ~100% capacity retention. The same method can be employed to stabilize micron-size Ge and Si alloying anodes with >80% capacity retention in 100 cycles. Most recently, our group has successfully fabricated various fibrous Si and Sn asymmetric membrane electrodes whose electrochemical performance is compared to thin film Si and Sn asymmetric membrane electrodes. e.g. ~90 % initial capacity at ~1,200 mAh g-1 can be maintained in 300 cycles applying a current density of 400 mA g-1 with an initial capacity loss less than 15%. These asymmetric membrane electrodes have been systematically characterized using extensive instruments spanning from scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), Raman spectroscopy, powder X-ray diffractometer (PXRD), thermogravimetric analyzer (TGA), surface area analyzer (BET method) to X-ray photoelectron spectroscopy (XPS), as well as various electrochemical tests such as cycling and rate performance, cyclic voltammetry, and electrochemical impedance spectroscopy, purposing to understand the relationship between structure, chemical composition and electrochemical properties for these asymmetric membrane electrodes.

Medium‐nickel layered oxide materials are a promising positive electrode material for high energy density lithium ion batteries. These materials can suffer from surface instability at a highly de‐lithiated state and poor rate capability. Surface coatings with multiple elements are a common strategy to overcome some of these challenges, however, the rationale behind adding these elements has never been explored. Here, various mid‐nickel single crystal vendor materials are evaluated by X‐ray Photoelectron Spectroscopy (XPS) and identified various surface coating compounds that can form during synthesis. Among the many common coating elements this study primarily focuses on tungsten (W). Using the in‐house “all dry synthesis” method, single crystal Li1+x(Ni0.6Mn0.3Co0.1)1‐xO2 materials are developed, where W is added at different stages of the synthesis to generate some unique W‐based surface compounds that match with vendor materials. This study systematically evaluates different W‐based surface compounds, compares their overall effect on electrochemical performance and highlights the instability of some of them. This work demonstrates that W is an important element and can significantly improve electrochemical performance when added in a second heating step.

Realizing superior cycling stability of Ni-Rich layered cathode by combination of grain boundary engineering and surface coating

The search of new multifunctional cathode materials, with new crystal structures and compositions, for lithium ion battery is extremely important to mitigate the drawbacks associated with the current electrode materials used in rechargeable lithium ion batteries. In this paper, orthovanadate family CrVO4 has been identified and investigated as a new cathode material for high-rate and high-capacity lithium ion battery for the first time. A solution-based effective and versatile synthetic protocol has been proposed to synthesize CrVO4 nanoparticles. Physical characterizations reveal that the prepared CrVO4 consists of uniform and discreet nanoparticles of crystallite size ~ 19 nm with widespread pore diameter, enhanced conductivity and surface area. The prepared CrVO4 nanoparticles have been evaluated as a potential cathode material for lithium ion batteries, wherein the experimental results demonstrate enhanced lithium storage with high rate-capability and cyclability. The experimental results reveal that the proposed CrVO4 is working through a partial conversion reaction mechanism.

Atomic layer deposition of ZnO–SnO2 composite thin film: The influence of structure, composition and crystallinity on lithium-ion battery performance

Silicon (Si) and Tin (Sn) are promising materials for anodes in lithium-ion batteries due to their high theoretical capacity and abundance of Si on earth. Si can be derived from rice husk which is the main agricultural byproduct in Thailand. However, the challenge of using these materials in lithium-ion batteries is the large volume expansion during charge-discharge process which leads to pulverization of electrodes. The effective solution is to combine these metals as composite with carbon supporter. Nitrogen-doped reduced graphene oxide (NrGO) has been used as carbon supporter in this research because of its high surface area, electrical conductivity and rate of electron transfer. To confirm phases of products, X-rays diffraction techniques (XRD) was measured. The results show that there were peaks of Si, Sn and carbon in XRD patterns. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to illustrate the morphology of prepared composites. From SEM and TEM results, there were small-sized particles of Si and Sn dispersed randomly on NrGO sheets. Furthermore, electrochemical properties of these products were measured to confirm their efficiency as anode materials in lithium-ion batteries by coin cell assembly. The prepared composite can deliver the highest initial capacity of 1600 mA h g-1 and expected to use as anode materials in the next generation lithium-ion batteries.

Spontaneous local redox reaction to passivate CNTs as lightweight current collector for high energy density lithium ion batteries

Si Nanoparticles Intercalated into Interlayers of Slightly Exfoliated Graphite filled by Carbon as Anode with High Volumetric Capacity for Lithium-ion Battery

Carbon coated Li3VO4 microsphere: Ultrafast solvothermal synthesis and excellent performance as lithium-ion battery anode