Synthesis and characterization of LNMO cathode materials for lithium-ion batteries

Abstract Synthesis of LiNi0.5Mn1.5O4 (LNMO), a promising cathode material for next generation lithium-ion batteries, was performed via Liquid Phase Self-propagating High-temperature Synthesis (LPSHS) and Aerosol Spray Pyrolysis (ASP) techniques. In the case of the LPSHS technique, the effect of the "fuel" quantity of the precursor solution on the structure, morphology and electrochemical performance of the materials was studied, while in the case of the ASP technique the effect of eight different calcination profiles on the structure, morphology, crystalline phase and electrochemical performance of the material. Structural characterization was performed through XRD, SEM, TEM, BET and Raman spectroscopy, while the electrochemical activity was evaluated via charge/discharge galvanostatic characterization. The results showed that the optimal LPSHS material was obtained for a molar ratio of metal ions/fuel = 3:1 exhibiting stable specific capacity over the cycles even by increasing the C-rate. Τhe optimal ASP material was identified in the case of calcination at 850°C. Both materials had the disordered Fd-3m structure of the LNMO spine

Monolithic Ceramic Redox Materials for Thermochemical Heat Storage Applications in CSP Plants

AbstractThe present work relates to the investigation of cobalt and manganese oxide based compositions as candidate materials for the storage of surplus energy, available in the form of heat, generated from high temperature concentrated solar power plants (e.g. solar tower, solar dish) via a two-step thermochemical cyclic redox process under air flow. Emphasis is given on the utilization of small structured monolithic bodies (flow-through pellets) made entirely from the two aforementioned oxides. As compared to the respective powders, and in addition to the natural advantage of substantially lower pressure drop that monolithic structures can offer, this study demonstrated that structured bodies can also improve redox kinetics to a measurable extent. Cobalt oxide was found to be superior to manganese oxide both from an estimated energy density and from a redox reactions kinetics point-of-view. Among the redox conditions studied, the optimum reduction-oxidation operating window for the former oxide was determined to be in the range of 1000-800°C, while for the latter material no clear conclusion was drawn with reduction reaching its maximum extent at 1000°C and oxidation occurring in the range of 500-650°C. In both cases, no significant degradation of redox performance was observed upon cyclic operation (up to 10 cycles), however manganese oxide showed notably slower oxidation kinetics

SnO2 anode materials for high capacity Li-ion cells

Tin-based materials, especially tin oxide, have been widely investigated as potential graphite substitutes anodes"br" of Li-ion batteries. In comparison to graphite anode, the SnO2 anodes shows high theoretical capacity of 1494"br" mAhg-1 in a voltage range of 0-2 V, furthermore it is also inexpensive, exhibits low toxicity and is"br" environmentally friendly. Unfortunately, during the lithiation process (i.e. conversion and alloying reaction), tin"br" dioxide suffers of a drastic volumetric expansion, that induces surface cracking accompanied by an electrical"br" contact loss with the current collector and subsequent capacity fading. It’s well known that reducing the particle"br" size of SnO2, the surface will be increased and consequently the volume expansion during lithium"br" insertion/extraction will be reduced. For these reasons, we synthesized SnO2 particles by an aerosol method and"br" we compare the results with commercial SnO2 particles and their mixtures with different carbon sources."br" All the materials were morphological and electrochemical characterized in order to investigate the influence of"br" crystal structure, particle size, morphology and surface area on cell cyclability. Cyclic voltammetry and"br" galvanostatic discharge/charge cycling have been used to test the electrochemical behavior of SnO2 anodes

Emission reduction technologies for the future low emission rail diesel engines: EGR vs SCR

The EU emission standards for new rail Diesel engines are becoming even more stringent. EGR and SCR technologies can both be used to reduce NOx emissions; however, the use of EGR is usually accompanied by an increase in PM emissions and may require a DPF. On the other hand, the use of SCR requires on-board storage of urea. Thus, it is necessary to study these trade-offs in order to understand how these technologies can best be used in rail applications to meet new emission standards. The present study assesses the application of these technologies in Diesel railcars on a quantitative basis using one and three dimensional numerical simulation tools. In particular, the study considers a 560 kW railcar engine with the use of either EGR or SCR based solutions for NOx reduction. The NOx and PM emissions performances are evaluated over the C1 homologation cycle. The simulation results indicate that either EGR or SCR based solutions can be used to achieve Stage IIIB NOx limits for the 560 kW engine, with an acceptable trade-off regarding BSFC in the case of EGR solutions. In the case of EGR, though, a DPF is necessary to meet Stage IIIB PM limits. Furthermore, SCR based solutions have the potential to go beyond the Stage IIIB NOx limit by scaling up the size of the SCR device and the on-board urea storage. Copyright \ua9 2013 SAE International

LiNi0.5Mn1.5O4cathode materials for high-voltage, next-generation automotive Li-ion cells

The insufficient autonomy of Electric Vehicles (EVs), which is mainly due to the limited energy density of automotive batteries, can be addressed by increasing the specific energy and/or the average operating voltage of the active cell materials. LiMn1.5Ni0.5O4 (LNMO) is a top candidate active cathode material due to its access to a rare two-electron transition from Ni2+ to Ni4+ at two voltage plateaus near 4.7 V vs. Li+/Li, a theoretical capacity of 147 mAhg-1 and fast three-dimensional Li-ion diffusion paths within the cubic lattice. Furthermore, LNMO is a relatively low-cost material with fairly good charging rate capability, suitable for EV requirements. However, the employment of LNMO in next-generation Li-ion batteries is prohibited by phenomena related to structural stability due to manganese dissolution and electrolyte compatibility. Structural modification via the inclusion of suitable dopants and proper surface treatment constitute promising solutions to these problems. Materials development for more efficient automotive batteries is an urgent task. In this work, four research organizations have joined efforts to realize LNMO cathodes appropriate for EVs. Three partners in this team worked on the materials development, and the fourth partner worked on the benchmarking of the materials. We have exploited nine different synthesis technologies for the pristine LNMO. From the evaluated technologies, three have been identified as most promising and were optimized for the specific application: the co-precipitation, the sol-gel and the aerosol spray pyrolysis methods. Several calcination profile conditions of the produced powder were studied obtaining two LNMO spinel phases: the ordered (P4332) and the disordered (Fd-3m) with the latter identified as the most electrochemically active. Five dopants have been introduced into the most promising LNMO lattices with Fe and Al proven to be the best-performing ones. Twelve materials have been considered for the LNMO particle surface treatment, and the Al2O3 was evaluated as the one showing satisfactory cyclic stability. We have used Scanning and Transition Electron Microscopy (SEM/TEM), micro-Raman spectroscopy, X-Ray Powder Diffraction (XRD) and Particle Size Analysis (PSD) for the structural characterization of the products. The most promising compositions have been scaled up to quantities sufficient for the manufacture of battery cells used in the automotive sector. In this work, we will present the most significant results from the above developments including results from electrochemical performance tests of electrodes in half and full coin cells (HCC/FCC). At HCC and C/5 we managed to obtain a specific capacity of more than 130 mAh/g with about 10% irreversible capacity loss. In FCC (vs. graphite) and C/20 we have obtained materials with 118 mAh/g specific capacity and about 20 % irreversible loss. During cycling of FCCs at 1C, with the best performing material, we have attained about 80 % of the initial capacity after 100 charging/discharging cycles. Future developments should focus on increasing the cycling ability of the full-cell by optimising the active materials (both cathode and anode), the electrolyte as well as the electrode structure