Jan von Zamory

ZnFe2O4-C/LiFePO4-CNT: A Novel High-Power Lithium-Ion Battery with Excellent Cycling Performance.

An innovative and environmentally friendly battery chemistry is proposed for high power applications. A carbon-coated ZnFe2O4 nanoparticle-based anode and a LiFePO4-multiwalled carbon nanotube-based cathode, both aqueous processed with Na-carboxymethyl cellulose, are combined, for the first time, in a Li-ion full cell with exceptional electrochemical performance. Such novel battery shows remarkable rate capabilities, delivering 50% of its nominal capacity at currents corresponding to ≈20C (with respect to the limiting cathode). Furthermore, the pre-lithiation of the negative electrode offers the possibility of tuning the cell potential and, therefore, achieving remarkable gravimetric energy and power density values of 202 Wh kg−1 and 3.72 W kg−1, respectively, in addition to grant a lithium reservoir. The high reversibility of the system enables sustaining more than 10 000 cycles at elevated C-rates (≈10C with respect to the LiFePO4 cathode), while retaining up to 85% of its initial capacity.

Puzzling out the origin of the electrochemical activity of black P as a negative electrode material for lithium-ion batteries

Black phosphorus prepared via the mineralization concept displays promising characteristics with respect to Li-ion battery applications. Although the theoretical specific capacity of black phosphorus as a negative electrode material is 2596 mA h g−1, a good cycling stability at high capacities, however, is still missing. Even worse, a large capacity drop after the first cycle is present and, depending on the electrode preparation, a poor first cycle coulombic efficiency (only 8%) represents a huge challenge to overcome. Herein we report on the performances of black phosphorus as a negative electrode material and display the roles of Cu3P and the copper current collector in this context. Furthermore, a composite material prepared by reacting pristine black phosphorus particles with a copper solution under solvothermal conditions shows a first cycle coulombic efficiency of 43%. We show that the presence of copper is crucial for the electrochemical performance of black phosphorus and that also the particle size and the electrode preparation procedure play a crucial role.

Homogeneous Lithium Electrodeposition with Pyrrolidinium-Based Ionic Liquid Electrolytes

In this study, we report on the electroplating and stripping of lithium in two ionic liquid (IL) based electrolytes, namely N-butyl-N-methylpyrrolidinium bis(fluorosulfonyl) imide (Pyr14FSI) and N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14TFSI), and mixtures thereof, both on nickel and lithium electrodes. An improved method to evaluate the Li cycling efficiency confirmed that homogeneous electroplating (and stripping) of Li is possible with TFSI-based ILs. Moreover, the presence of native surface features on lithium, directly observable via scanning electron microscope imaging, was used to demonstrate the enhanced electrolyte interphase (SEI)-forming ability, that is, fast cathodic reactivity of this class of electrolytes and the suppressed dendrite growth. Finally, the induced inhomogeneous deposition enabled us to witness the SEI cracking and revealed previously unreported bundled Li fibers below the pre-existing SEI and nonrod-shaped protuberances resulting from Li extrusion.

Separators for Li-Ion and Li-Metal Battery Including Ionic Liquid Based Electrolytes Based on the TFSI⁻ and FSI⁻ Anions

The characterization of separators for Li-ion or Li-metal batteries incorporating hydrophobic ionic liquid electrolytes is reported herein. Ionic liquids made of N-butyl-N-methylpyrrolidinium (PYR14+) or N-methoxyethyl-N-methylpyrrolidinium (PYR12O1+), paired with bis(trifluoromethanesulfonyl)imide (TFSI−) or bis(fluorosulfonyl)imide (FSI−) anions, were tested in combination with separators having different chemistries and morphologies in terms of wetting behavior, Gurley and McMullin number, as well as Li/(Separator + Electrolyte) interfacial properties. It is shown that non-functionalized microporous polyolefin separators are poorly wetted by FSI−-based electrolytes (contrary to TFSI−-based electrolytes), while the ceramic coated separator Separion® allows good wetting with all electrolytes. Furthermore, by comparing the lithium solid electrolyte interphase (SEI) resistance evolution at open circuit and during cycling, depending on separator morphologies and chemistries, it is possible to propose a scale for SEI forming properties in the order: PYR12O1FSI > PYR14FSI > PYR14TFSI > PYR12O1TFSI. Finally, the impact the separator morphology is evidenced by the SEI resistance evolution and by comparing Li electrodes cycled using separators with two different morphologies.

Synthesis and characterization of carbon coated sponge-like tin oxide (SnOx) films and their application as electrode materials in lithium-ion batteries

Nanoporous metal oxides are widely used for the development of various functional nanostructures. We report on the synthesis of sponge-like tin oxide films on copper foil by anodization of electrochemically deposited tin films. The thin films are functionalized using a surface-anchoring carbon precursor-polymer (poly(acrylonitrile-b-dopamine acrylamide)) followed by annealing at elevated temperature to convert the polymer coating into a carbonaceous coating. The as prepared and the carbon coated films are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and Raman spectroscopy. Subsequently, both SnOx films are employed as anode materials in lithium ion batteries. Carbon coating has a beneficial effect on the battery performance with respect to the rate capability, increasing the capacity by 200 mA h g−1 for all applied current densities. After 20 cycles, coated samples show a reversible specific charge capacity of 497 mA h g−1. Ex situ scanning electron microscopy reveals the retention of the sponge-like morphology even after cycling.

Graphite//LiNi0.5Mn1.5O4 cells based on environmentally friendly in-water-made-electrodes.

The performance of graphite//LiNi0.5 Mn1.5 O4 (LNMO) cells, both electrodes of which are made using water-soluble sodium carboxymethyl cellulose (CMC) binder, is reported for the first time. The full cell performed outstandingly over 400 cycles in the conventional electrolyte ethylene carbonate/dimethyl carbonate-1 m LiPF6 , and the delivered specific energy at the 100th, 200th, 300th, and 400th cycle corresponded to 82, 78, 73, and 66 %, respectively, of the initial energy value of 259 Wh kg-1 (referring to the sum of the two electrode-composite weights). The good stability of high-voltage, LNMO-CMC-based electrodes upon long-term cycling is discussed and the results are compared to those of LNMO-composite electrodes with polyvinylidene fluoride (PVdF). LNMO-CMC electrodes outperformed those with PVdF binder, displaying a capacity retention of 83 % compared to 62 % for the PVdF-based electrodes after 400 cycles at 1 C. CMC promotes a more compact and stable electrode surface than PVdF; undesired interfacial reactions at high operating voltages are mitigated, and the thickness of the passivation layer on the LNMO surface is reduced, thereby enhancing its cycling stability.

Comparative Analysis of Aqueous Binders for High-Energy Li-Rich NMC as a Lithium-Ion Cathode and the Impact of Adding Phosphoric Acid

Even though electrochemically inactive, the binding agent in lithium-ion electrodes substantially contributes to the performance metrics such as the achievable capacity, rate capability, and cycling stability. Herein, we present an in-depth comparative analysis of three different aqueous binding agents, allowing for the replacement of the toxic N-methyl-2-pyrrolidone as the processing solvent, for high-energy Li1.2Ni0.16Mn0.56Co0.08O2 (Li-rich NMC or LR-NMC) as a potential next-generation cathode material. The impact of the binding agents, sodium carboxymethyl cellulose, sodium alginate, and commercial TRD202A (TRD), and the related chemical reactions occurring during the electrode coating process on the electrode morphology and cycling performance is investigated. In particular, the role of phosphoric acid in avoiding the aluminum current collector corrosion and stabilizing the LR-NMC/electrolyte interface as well as its chemical interaction with the binder is investigated, providing an explanation for the observed differences in the electrochemical performance.