Priscilla Reale

A New, Safe, High‐Rate and High‐Energy Polymer Lithium‐Ion Battery

Adv. Mater. 2009, 21, 4807–481

Microbial reductive dechlorination of trichloroethene to ethene with electrodes serving as electron donors without the external addition of redox mediators.

In situ bioremediation of industrial chlorinated solvents, such as trichloroethene (TCE), is typically accomplished by providing an organic electron donor to naturally occurring dechlorinating populations. In the present study, we show that TCE dechlorinating bacteria can access the electrons required for TCE dechlorination directly from a negatively polarized (−450 mV vs. SHE) carbon paper electrode. In replicated batch experiments, a mixed dechlorinating culture, also containing Dehalococcoides spp., dechlorinated TCE to cis‐dichloroethene (cis‐DCE) and lower amounts of vinyl chloride (VC) and ethene using the polarized electrode as the sole electron donor. Conversely, neither VC nor ethene formation occurred when a pure culture of the electro‐active microorganism Geobacter lovleyi was used, under identical experimental conditions. Cyclic voltammetry tests, carried out on the filter‐sterilized supernatant of the mixed culture revealed the presence of a self‐produced redox mediator, exhibiting a midpoint potential of around −400 mV (vs. SHE). This yet unidentified redox‐active molecule appeared to be involved in the extracellular electron transfer from the electrode to the dechlorinating bacteria. The ability of dechlorinating bacteria to use electrodes as electron donors opens new perspectives for the development of clean, versatile, and efficient bioremediation systems based on a controlled subsurface delivery of electrons in support of biodegradative metabolisms and provides further evidence on the possibility of using conductive materials to manipulate and control a range of microbial bioprocesses. Biotechnol. Bioeng. 2009;103: 85–91.

Characterization of an electro-active biocathode capable of dechlorinating trichloroethene and cis-dichloroethene to ethene

In the presence of suitable electron donors, the industrial solvent trichloroethene (TCE) is reductively dechlorinated by anaerobic microorganisms, eventually to harmless ethene. In this study we investigated the use of a carbon paper electrode, polarized to -550 mV vs. standard hydrogen electrode (SHE), as direct electron donor for the mediator-less microbial reductive dechlorination of TCE to ethene. In potentiostatic batch assays, TCE was dechlorinated to predominantly cis-dichloroethene (cis-DCE) and lower amounts of vinyl chloride (VC) and ethene, at rates falling in the range 14.2-22.4 micro equiv./Ld. When cis-DCE was spiked to the system, it was also dechlorinated, to VC and ethene, but at a much lower rate (1.5-1.7 micro equiv./Ld). Scanning electron microscopy and FISH analyses revealed that the electrode was homogeneously colonized by active bacterial cells, each in direct contact with the electrode surface. Cyclic voltammetry tests revealed the presence, at the electrode interface, of formed redox active components possibly involved in the extracellular electron transfer processes, that were however detached by a vigorous magnetic stirring. Electrochemical impedance spectroscopy (EIS) tests revealed that polarization resistances of the electrode in the presence of microorganisms (ranging from 0.09 to 0.17 k Omega/cm(2)) were one-order of magnitude lower than those measured with abiotic electrodes (ranging from 1.4 to 1.8 k Omega/cm(2)). This confirmed that attached dechlorinating microorganisms significantly enhanced the kinetics of the electron transfer reactions. Thus, for the first time, the bio-electrochemical dechlorination of TCE to ethene is obtained without the apparent requirements for exogenous or self-produced redox mediators. Accordingly, this work further expands the range of metabolic reactions and microorganisms that can be stimulated by using solid-state electrodes, and has practical implications for the in situ bioremediation of groundwater contaminated by chlorinated solvents.

A Safe, Low-Cost, and Sustainable Lithium-Ion Polymer Battery

A polymer lithium-ion battery, formed by a Li 4/3 Ti 5/3 O 4 -LiFePO 4 electrode combination and a poly(vinylidene fluoride) (PVdF)-based gel electrolyte, is presented and discussed. The electrochemical characterization demonstrates that this battery is capable of delivering appreciable capacity values at rates ranging from C/32 (160 mAh g -1 ) to 0.75C (130 mAh g -1 ), this being accompanied by a remarkable cycle life. In addition, because the two electrodes are based on common and nontoxic materials and operate within the stability window of the electrolyte, the battery is expected to be safe, inexpensive, and compatible with the environment. All these properties make the battery of prospective interest for application in the hybrid and electric vehicle field.

Recent advances in liquid and polymer lithium-ion batteries

New types of electrode and electrolyte materials have been investigated and characterized in our laboratory. These include high capacity lithium–tin alloys, high-rate lithium titanium oxide and high conductivity gel-type, polymer electrolytes. The results obtained, collected in this article, demonstrate that these materials may be combined for the development of new types of liquid and polymer lithium-ion batteries having impressive features in terms of capacity, stability, high rates and, particularly, safety. Taking this into consideration, these batteries appear suitable power sources for electric or hybrid vehicles.

Hydrated Iron Phosphates FePO4 ⋅ n H 2 O and Fe4 ( P 2 O 7 ) 3 ⋅ n H 2 O as 3 V Positive Electrodes in Rechargeable Lithium Batteries

Hydrated Fe III phosphates were investigated as positive electrode materials in lithium batteries. Reversible lithium insertion into amorphous and crystalline FePO 4 .nH 2 O and Fe 4 (P 2 O 7 ) 3 .nH 2 O compositions was found at potentials between 3.5 and 2.5 V vs. Li + /Li. The roles of (i) specific surface area, (ii) amorphous vs. crystalline state, (iii) H 2 O content, and (iv) electronic contact between particles in the composite positive electrode, on the electrochemical performances of these materials are discussed. Very stable cycling was obtained for optimized FePO 4 .1.6H 2 O and Fe 4 (P 2 O 7 ) 3 .4H 2 O electrodes at an average voltage of 3.0 and 3.2 V vs. Li + /Li, respectively.

Sustainable High-Voltage Lithium Ion Polymer Batteries

New types of polymer lithium ion batteries, formed by combining a Li 4 Ti 5 O 1 2 anode with a LiMn 2 O 4 and a LiNi 0 . 5 Mn 1 . 5 O 4 cathode, respectively, in a poly(vinylidene fluoride) PVdF-based gel electrolyte cell, arepresented and discussed. The operating voltage is around 2.5 V for the battery based on LiMn 2 O 4 and around 3.0 V for that based on LiNi 0 . 5 Mn 1 . 5 O 4 . The electrochemical characterization demonstrates that these high-voltage batteries are capable of delivering appreciable capacity values at various rates, this being accompanied by a remarkable cycle life. In addition, since the two electrodes are based on common and not toxic materials and operate within the stability window of the electrolyte, the batteries are expected to be safe, inexpensive, and compatible with the environment. All these properties make the batteries of interest for application in the hybrid and electric vehicle field.

Dechlorination of Trichloroethene in a Continuous-Flow Bioelectrochemical Reactor: Effect of Cathode Potential on Rate, Selectivity, and Electron Transfer Mechanisms

The exciting discovery that dechlorinating bacteria can use polarized graphite cathodes as direct electron donors in the reductive dechlorination has prompted investigations on the development of novel bioelectrochemical remediation approaches. In this work, we investigated the performance of a bioelectrochemical reactor for the treatment of trichloroethene (TCE). The reactor was continuously operated for about 570 days, at different potentiostatically controlled cathode potentials, ranging from -250 mV to -750 mV vs standard hydrogen electrode. The rate and extent of TCE dechlorination, as well as the competition for the available electrons, were highly dependent on the set cathode potential. When the cathode was controlled at -250 mV, no abiotic hydrogen production occurred and TCE dechlorination (predominantly to cis-DCE and VC), most probably sustained via direct extracellular electron transfer, proceeded at an average rate of 15.5 ± 1.2 μmol e(-)/L d. At this cathode, potential methanogenesis was almost completely suppressed and dechlorination accounted for 94.7 ± 0.1% of the electric current (15.0 ± 0.8 μA) flowing in the system. A higher rate of TCE dechlorination (up to 64 ± 2 μmol e(-)/L d) was achieved at cathode potentials lower than -450 mV, though in the presence of a very active methanogenesis which accounted for over 60% of the electric current. Remarkably, the bioelectrochemical reactor displayed a stable and reproducible performance even without the supply of organic carbon sources with the feed, confirming long-term viability.

In situ studies of electrodic materials in Li-ion cells upon cycling performed by very-high-energy x-ray diffraction

A very high-energy synchrotron radiation source (87 keV) was utilized for in situ sampling of the structural changes occurring in the electrodic materials of a Li-ion cell during charge–discharge cycling. The real-time evolution of their crystal lattice was obtained as a function of the degree of Li intercalation. As a result, new information on two electrodic materials, Li–Ti “zero strain” and Li–Ni–Co oxide, both of extreme interest for generation of rechargeable batteries, was gained. The actual change of the Li–Ti oxide lattice parameter upon cycling was observed in greater detail than before, and provided evidence of unexpected behavior in some intervals of the cycle. In the Li–Ni–Co sample, a new phase formed during the early stages of cycling that remained stable in the subsequent cycles was revealed.

Refined, in-situ EDXD structural analysis of the Li[Li1/3Ti5/3]O4 electrode under lithium insertion–extraction

An in-situ energy dispersive X-ray diffraction (EDXD) analysis has been run on the Li[Li1/3Ti5/3]O4 compound upon Li intercalation–deintercalation process. The results confirm that this process is accompanied by a very small variation of the host lattice parameter, i.e., confined between 1‰ over the entire cycle. This value, which agrees with previous literature information, concurs to demonstrate that Li[Li1/3Ti5/3]O4 may indeed be considered as a zero-strain intercalation compound, this being a characteristic of key technological importance since lattice strains upon cycling are among the main causes of capacity decays in lithium battery electrodes. In addition, this work confirms that EDXD is a quite convenient technique for electrochemical measurements since, allowing in-situ lattice parameter determinations, may lead to a complete evaluation of the intermediate stages of the intercalation process and, possibly, to detect differences among the various cycles.