The reaction of Fe(N(SiMe(3))(2))(3) with PH(3) in THF at 100 °C gives amorphous FeP(2) in high yield. As an anode material in a Li ion battery, this material shows remarkable performance toward electrochemical lithiation/delithation, with gravimetric discharge and charge capacities of 1258 and 766 mA h g(-1), respectively, translating to 61% reversibility on the first cycle and a discharge capacity of 906 mA h g(-1) after 10 cycles. This translates to 66% retention of the theoretical full conversion capacity of FeP(2) (1365 mA h g(-1)).

Transition-metal phosphates (TMPs) are potential materials for large-scale applications of lithium ion batteries (LIBs). Yet, high-voltage TMP cathodes have not met commercial success due to ill understood failure mechanisms. In this article we studied the surface chemistry of Li 3 V 2 (PO 4 ) 3 composite electrodes using X-ray photoelectron spectroscopy (XPS) post-electrochemical cycling in a stable electrochemical window of 3.0−4.2 V vs Li/Li + and in the wider window of 3.0−4.8 V vs Li/Li + where a dramatic fade in capacity is noted. In addition, we performed aging experiments in LiPF 6 EC/DEC electrolyte with no electrochemical bias applied to investigate a possible spontaneous solid electrolyte interphase (SEI) formation as has been described for lithium transition-metal oxide (Li x M y O z ) electrodes. An SEI was found on the Li 3 V 2 (PO 4 ) 3 composite electrodes cycled in both potential windows and after aging with similar chemical compositions including ethers, alkoxides, esters, carboxylates, and carbonates as well as decomposed salt products. Analogous experiments were performed on the individual constituents of the composite electrode (active material, binder, and carbon additive). It was determined that the carbon additive and not Li 3 V 2 (PO 4 ) 3 formed an SEI both spontaneously and electrochemically. Therefore, the carbon additive and its properties are crucial in the formation of the SEI on TMP cathodes for LIBs which directly affect its lithium intercalation performance.

Monoclinic α-Li 3 V 2 (PO 4 ) 3 has a complex 3-D metal phosphate framework that provides mobility for all three lithium ions, giving it the highest gravimetric capacity (197 mAh/g) of all the transition-metal phosphates. Along with its high gravimetric capacity, its thermal and electrochemical stability make it of great interest as a cathode material for lithium-ion energy storage devices. Raman spectroscopy has proven to be a unique analytical tool for studying electrode materials of lithium-ion batteries due to its ability to probe structural changes at the level of chemical bonds. In this work, the calculated Raman spectrum of α-Li 3 V 2 (PO 4 ) 3 provided by density functional theory is presented along with symmetry assignments for all of the calculated and observed modes through Raman microscopy. Furthermore, the phase stability of microcrystalline α-Li 3 V 2 (PO 4 ) 3 was studied as a function of irradiation power density. Follow-up thermal studies confirm that two structural phase transitions, β and γ, occur at elevated temperatures or high irradiation power density before degradation to α-LiVOPO 4 under an oxygen-rich atmosphere. Calculated and experimentally determined Raman modes for α-Li 3 V 2 (PO 4 ) 3 are in good agreement. It is also noted that careful consideration of the irradiation power density employed must be taken into account to prevent misinterpretation of Raman spectral features.

A new optically transparent thin layer electrode (OTTLE) cell and holder have been designed to facilitate spectroelectrochemical measurements in standard bench-top absorbance and fluorescence spectrophotometers. The use of rapid prototyping for the OTTLE cell holder combined with the selection of inexpensive OTE materials results in a practical, low-cost spectroelectrochemical cell. The cell was characterized by thin-layer cyclic voltammetry and coulometry of ferricyanide/ferrocyanide. Spectroelectrochemistry of tris-(2,2'-bipyridine) ruthenium(II) chloride (Ru-(bpy) 3 Cl 2 ) and 1-hydroxypyrene (1-pyOH) was done with commercially available bench-top absorbance and fluorescence spectrophotometers. The good correlation between the results obtained and the known properties of each compound demonstrate that the OTTLE cell and holder provide an effective means for making spectroelectrochemical measurements in bench-top absorbance and fluorescence spectrophotometers.

Vanadium oxide (V 2 O 5 ) is a multifaceted material possessing desirable redox properties, including accessibility to multiple valence states, which make it attractive as a cathode for lithium ion batteries and microbatteries. Studies show that performance of this electrode material is dependent on the electrolyte employed and that solid electrolyte interphase (SEI) layer formation is responsible for the fade in capacity with multiple cycling. Nanostructured V 2 O 5 thin films synthesized through reactive ballistic deposition (RBD) were studied with electrochemical methods, ex situ Raman and ex situ XPS in two widely used electrolytes: LiClO 4 /propylene carbonate (PC) and LiPF 6 / diethyl carbonate (DEC) + ethylene carbonate (EC). Films cycled in LiPF 6 /DEC+EC experienced a 32% greater capacity fade between the first and second lithiathion/delithiation cycles than those cycled in LiClO 4 /PC, due to a redox-induced change in the surface morphology and composition and an irreversible transformation into an amorphous state as monitored by ex situ Raman. From X-ray photoelectron spectroscopy (XPS), it was shown that V 2 O 5 cycled in LiPF 6 /DEC+EC contained a high atomic concentration percentage of fluoride (16.18%) in comparison with V 2 O 5 electrodes cycled in LiClO 4 /PC (3.94%). No significant amounts of carbonates, oxalates, or oxyfluorophosphates typically associated with SEI formation were found when V 2 O 5 was cycled in either electrolyte. The results obtained suggest instead that HF, formed upon water contamination of the electrolyte, reacts with V 2 O 5 through a self-catalyzed process both at open circuit and under applied potential. The formation of vanadium oxyfluorides causes active mass loss and severe capacity fade upon discharging/charging.