Borate Electrolyte Research Articles

Impact of Lithium Bis(oxalate)borate Electrolyte Additive on the Performance of High-Voltage Spinel/Graphite Li-Ion Batteries

The impact of lithium bis(oxalate)borate (LiBOB) electrolyte additive on the performance of full lithium-ion cells pairing the high-voltage spinel cathode with the graphite anode was systematically investigated. Adding 1 wt % LiBOB to the electrolyte significantly improved the cycle life and Coulombic efficiency of the full-cells at 30 and 45 °C. As the LiBOB was preferentially oxidized and reduced compared with LiBOB-free electrolyte during cycling, their relative contributions to the improved capacity retention in full-cells was gauged by pairing fresh and LiBOB-treated electrodes with various combinations. The results indicated that a solid–electrolyte interphase (SEI) film on graphite produced by the reduction of the LiBOB additive is more robust and stable against Mn dissolution problem during cycling at 45 °C compared with the SEI formed by the reduction of the base (LiBOB-free) electrolyte. In addition, a 3 wt % LiBOB-added electrolyte showed reduced Mn dissolution compared with the base electrolyte after storing the fully charged Li1–xNi0.42Fe0.08Mn1.5O4 (LNFMO) electrodes at 60 °C for one month. It is believed that LiBOB aids in stabilizing the electrolyte by trapping the PF5, i.e., sequestering the radical which tends to oxidize EC and DEC electrolyte solvents. Thus, oxidation is suppressed on the carbon black particles in the positive electrode, as evidenced by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) analyses. As a result, HF generation is suppressed, which in turn results in less Mn dissolution from the spinel cathode.

The effects of film thickness and incorporated anions on pitting corrosion of aluminum with barrier-type oxide films formed in neutral borate and phosphate electrolytes

The pitting corrosion behavior of high-purity aluminum covered with barrier-type anodic films, which are formed in neutral borate and phosphate electrolytes, has been examined in 0.5 mol dm−3 NaCl solution at an applied potential of −0.6 V versus Ag/AgCl, which is slightly nobler than the pitting potential of −0.64 V in the same solution. The pitting current density, i p, increased with time after an incubation time, t i. The double logarithmic plot of i p and polarization time, t, reveal two straight lines, which are separated at the time, τ. The slope becomes larger after τ for the specimens anodized in the phosphate electrolyte, while it becomes smaller for those in the borate electrolyte. Both the t i and τ increase with the thickness of the anodic films, and at the similar film thickness, they are much larger for the anodic films formed in the phosphate electrolyte than for those in the borate electrolyte. The corrosion process can be divided into three stages: the incubation period up to t i, the pit nucleation period before τ, and the pit growth period after τ. We have discussed the different pitting corrosion behavior of the aluminum specimens covered with the anodic films formed in the borate and phosphate electrolytes in terms of ion selectivity of the anodic films.

Intermediate-Range Structure of Self-Assembled Cobalt-Based Oxygen-Evolving Catalyst

Continual improvements in solar-to-fuels catalysis require a genuine understanding of catalyst structure-function relationships, not only with respect to local order, but also intermediate-range structure. We report the X-ray pair distribution function analysis of the nanoscale order of an oxidic cobalt-based water-splitting catalyst and uncover an electrolyte dependence in the intermediate-range structure of catalyst films. Whereas catalyst films formed in borate electrolyte (CoB(i)) exhibit coherent domains consisting of 3-4 nm cobaltate clusters with up to three layers, films deposited in phosphate electrolyte (CoP(i)) comprise significantly smaller clusters that are not coherently stacked. These structural insights are correlated with marked differences in activity between CoP(i) and CoB(i) films.

Solar water oxidation using nickel-borate coupled BiVO4 photoelectrodes

A naturally abundant nickel-borate (Ni-Bi) complex is demonstrated to successfully catalyze the photoelectrochemical (PEC) water oxidation of BiVO4 electrodes at 1.23 VRHE with nearly 100% faradaic efficiency for oxygen evolution. Ni-Bi is electrodeposited (ED) and photodeposited (PD) for varying times on BiVO4 electrodes in the 0.1 M borate electrolyte with 1 mM Ni(2+) at pH 9.2. Surprisingly, optimally deposited Ni-Bi films (ED-10 s and PD-30 min) display the same layer thickness of ca. 40 nm. Both Ni-Bi films enhance the photocurrent generation of BiVO4 at 1.23 VRHE by a factor of 3-4 under AM 1.5-light irradiation (100 mW cm(-2)) along with ca. 250% increase in the incident and absorbed photon-to-current efficiencies. Impedance analysis further reveals that the charge transfer resistance at BiVO4 is markedly decreased by Ni-Bi deposits. The primary role of Ni-Bi has been suggested to be a hole-conductor making photogenerated electrons more mobile and catalyzing a four-hole transfer to water through cyclic changes between the lower and higher Ni oxidation states. However, thick Ni-Bi films (>~40 nm) significantly reduce the PEC performance of BiVO4 due to the kinetic bottleneck and charge recombination. Under identical PEC conditions (0.1 M, pH 9.2), the borate electrolyte (good proton acceptor) is found to be better than nitrate (poor proton acceptor), indicative of a proton-coupled electron transfer pathway in PEC water oxidation.

Diffusion-Limited Aggregation in Potato Starch and Hydrogen Borate Electrolyte System

Natural growth of diffusion-limited aggregate (DLA), without any external stimuli, in boric acid doped starch system is reported here. Fractals grown were confirmed to be of diffusion-limited aggregate (DLA) pattern having fractal dimension ~1.49. Effect of substrate and humidity on growth pattern has also been discussed. The existence of a different vibration band of H3BO3in FTIR confirmed that growth structures are related to boric acid. XRD pattern has shown broad peak along with some sharp peaks. Broad peak is related to starch’s amorphous nature, as where intense sharp peaks are due to boric acid.

Delving into the Properties and Solution Structure of Nitrile-Lithium Difluoro(Oxalato)Borate (LiDFOB) Electrolytes for Li-Ion Batteries

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Delving into the Properties and Solution Structure of Nitrile-Lithium Difluoro(Oxalato)Borate (LiDFOB) Electrolytes for Li-Ion Batteries

The phase diagram of acetonitrile-LiDFOB mixtures was determined. Raman spectroscopic analysis of the DFOB- anion vibrational bands indicates that a diverse range of solvates are present in solution. As demonstrated here, an in-depth analysis of (AN)n-LiDFOB electrolyte mixtures through the combination of the phase diagram with Raman spectroscopic characterization (and known crystalline solvate structures) enables the identification of the solvate species present. This information greatly aids in understanding the link between solution structure and electrolyte properties.

The effect of electrodeposition conditions and post-annealing on nanostructure of Co–W coatings

Nanocrystalline Co–W alloys were electrodeposited at 60°C from citrate–borate electrolyte at pH 6.7 and 8.0. The effect of electrodeposition conditions in the direct (DC) and pulse (PC) current modes on tungsten content in the alloys and their structure was investigated. The tungsten content in the alloys was varied between 13 and 36at.%, and it defines the grain size of the Co–W coatings irrespectively on the deposition mode or current density allowing us to obtain this particular content of alloy. A grain size of 27–40nm was obtained for a lower content of tungsten, and 3–6nm is characteristic for as-deposited coatings containing more than 23at.% W. The formation of W solid solution in the Co and Co3W phases is discussed. The transition from nanocrystalline to polycrystalline structure of the Co–W coatings with an as-deposited grain size of 3–6nm was obtained by annealing. In coatings containing 24.5at.% W, a well developed polycrystalline structure of Co3W appears at 400°C with {200}, {201} and {220} textures which remain stable up to 1000°C. The grain size of the coatings containing 24.5at.% W increases from 3–5nm up to 26–30nm after annealing at 400°C. Whereas, Co–W coatings with a tungsten content of 34.4at.% maintain their nanocrystallinity at 400°C, and transforms to the polycrystalline structure at 600°C with an increase of grain size up to 45nm.

Structure–Activity Correlations in a Nickel–Borate Oxygen Evolution Catalyst

An oxygen evolution catalyst that forms as a thin film from Ni(aq)(2+) solutions containing borate electrolyte (Ni-B(i)) has been studied by in situ X-ray absorption spectroscopy. A dramatic increase in catalytic rate, induced by anodic activation of the electrodeposited films, is accompanied by structure and oxidation state changes. Coulometric measurements correlated with X-ray absorption near-edge structure spectra of the active catalyst show that the nickel centers in activated films possess an average oxidation state of +3.6, indicating that a substantial proportion of nickel centers exist in a formal oxidation state of Ni(IV). In contrast, nickel centers in nonactivated films exist predominantly as Ni(III). Extended X-ray absorption fine structure reveals that activated catalyst films comprise bis-oxo/hydroxo-bridged nickel centers organized into sheets of edge-sharing NiO(6) octahedra. Diminished long-range ordering in catalyst films is due to their ostensibly amorphous nature. Nonactivated films display a similar oxidic nature but exhibit a distortion in the local coordination geometry about nickel centers, characteristic of Jahn-Teller distorted Ni(III) centers. Our findings indicate that the increase in catalytic activity of films is accompanied by changes in oxidation state and structure that are reminiscent of those observed for conversion of β-NiOOH to γ-NiOOH and consequently challenge the long-held notion that the β-NiOOH phase is a more efficient oxygen-evolving catalyst.

A tetraethylene glycol dimethylether-lithium bis(oxalate)borate (TEGDME-LiBOB) electrolyte for advanced lithium ion batteries

Tetraethylene glycol dimethylether-lithium bis(oxalate)borate (TEGDME-LiBOB) electrolyte is here studied. Electrochemical impedance spectroscopy (EIS) measurements demonstrate that the electrolyte has conductivity higher than 10 − 3 S cm − 1 at room temperature and about 10 − 2 S cm − 1 at 60 °C, while thermogravimetry indicates a stability extending up to 180 °C. Sweep voltammetry of the electrolyte shows anodic stability extending over 4.6 V vs. Li and cathodic peak at about 1.5 V vs. Li/Li +, caused by a decomposition of LiBOB salt, and following prevented by using a pre-treated Sn-C anode. Furthermore, LiFePO 4 electrode is successfully used as cathode in a lithium cell using the TEGDME-LiBOB electrolyte. The promising electrochemical results, the low cost and the very high safety level candidate the electrolyte here reported as a valid alternative to the conventional electrolyte based on fluorinated salts presently used in the lithium ion battery field.

Delving into the Properties and Solution Structure of Nitrile-Lithium Difluoro(oxalate)borate (LiDFOB) Electrolytes for Li-ion Batteries

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Highly active cobalt phosphate and borate based oxygen evolving catalysts operating in neutral and natural waters

A high surface area electrode is functionalized with cobalt-based oxygen evolving catalysts (Co-OEC = electrodeposited from pH 7 phosphate, Pi, pH 8.5 methylphosphonate, MePi, and pH 9.2 borate electrolyte, Bi). Co-OEC prepared from MePi and operated in Pi and Bi achieves a current density of 100 mA cm−2 for water oxidation at 442 and 363 mV overpotential, respectively. The catalyst retains activity in near-neutral pH buffered electrolyte in natural waters such as those from the Charles River (Cambridge, MA) and seawater (Woods Hole, MA). The efficacy and ease of operation of anodes functionalized with Co-OEC at appreciable current density together with its ability to operate in near neutral pH buffered natural water sources bodes well for the translation of this catalyst to a viable renewable energy storage technology.

Application of three-electrode electrolytic cell to evaluate thin films of vegetable and mineral oils

Films (∼5μm) of rapeseed and mineral oils with or without antioxidants were coated on steel disc electrodes. Initial stages of corrosion and oxidation were monitored by potentiodynamic polarization and impedance spectroscopy in ammonium borate electrolyte at pH 9.0. Fresh films lead to spatial separation of electrochemical reactions without major changes in corrosion mechanism. However, heating in air (4h, 70°C) reduced current densities by 2 orders and produced dramatic changes in impedance and phase angle patterns. Data fitting was proposed and reasons discussed why mild heating changed the course of corrosion so strongly.

Formation of barrier-type anodic films on sputtering-deposited Al–Ti alloys

The formation of amorphous anodic films at constant current is investigated for sputtering-deposited Al–Ti alloys containing from 3–30 at.% Ti. The films were grown at high efficiency in a borate electrolyte and comprised a main region containing units of Al 2O 3 and TiO 2, with a thin surface region enriched in titanium species. The formation ratios of the films increased with increase of titanium content of the alloys. The presence of the outer region is explained by the faster migration of Ti 4+ ions relative to that of Al 3+ ions through the films.

CZE and ESI-MS of Borate-Sugar Complexes

Capillary zone electrophoresis (CZE) with electrospray ionization (ESI) mass spectrometry (MS) was used to study borate (B−1) and sugar (L) complexes (LxB−1). Boric acid was adjusted to pH 10 with ammonium hydroxide to create an ESI-MS compatible CZE background electrolyte. We show for the first time that the electrophoretic peaks for each injected sugar contained both the substrates (i.e., sugar and/or multimers) and products (i.e., LxB−1). The effects of sheath liquid, temperature, and borate concentration were studied. The molecular mass information obtained from the ESI-MS provided new evidence on the mechanisms of borate-sugar complexation. Direct infusion ESI-MS and CZE-ESI-MS experiments strongly suggest that the formation of LxB−1 was from the direct reaction of a sugar or sugar multimer (Lx) and B−1. Larger LxB−1, where x > 2 were observed. Separation in the CZE dimension allows for the simultaneous analysis of a sugar mixture and simplified the ESI-MS analysis of sugars of the same molecular mass. The increase in sugar electrophoretic mobility caused by the increase in borate concentration was discussed in terms of the formation of LxB−1 complexes. In addition, the separation of five nucleosides by CZE using a borate electrolyte and detection using ESI-MS is demonstrated.

A two-liquid electroosmotic pump using low applied voltage and power

We report the development and experimental analysis of a two-liquid electroosmotic (EO) pump. The pump uses a collapsible and impermeable membrane to separate the liquid delivered from a working electrolyte solution optimized for EO pumping. To achieve high pressures at low voltages, we use a porous glass substrate with 450 nm mean diameter pores and a 1 mM sodium borate electrolyte. Results show that the membranes add negligible pressure load and that the pump can deliver adequately stable flow rates after an initial transient period. At flow rates and pressures suitable for drug delivery (order 10 μl/min and a few kPa), the pump requires an applied voltage and power of less than 3 V and 75 μW, respectively. Based on the relative scaling of flow rate, current, and time, we hypothesize that distinct initial transients in flow rate are attributable to concentration polarization and its effects on the spatiotemporal ionic strength of the working fluid.

Nickel-borate oxygen-evolving catalyst that functions under benign conditions

Thin catalyst films with electrocatalytic water oxidation properties similar to those of a recently reported Co-based catalyst can be electrodeposited from dilute Ni2+solutions in borate electrolyte at pH 9.2 (Bi). The Ni-Bifilms can be prepared with precise thickness control and operate at modest overpotential providing an alternative to the Co catalyst for applications in solar energy conversion.

Layered structure of anodic SiO2 films doped with phosphorus or boron

It is shown that anodic silicon oxide films deposited by reanodization (repeated anodic oxidation) of p- and n-type silicon in phosphate (1.5 M H3PO4), borate (1.5 M H3BO3), and nitrate (0.04 M NH4NO3) electrolytes based on tetrahydrofurfuryl alcohol have a three- or four-layer structure both before and after high-temperature annealing. It is assumed that this circumstance accounts for the nonuniform distribution of phosphorus and boron across the thickness of anodic SiO2.

Oxide coatings on Al/SiC composite formed by plasma-electrochemical method

The processes of film growth and characteristics of film formation in an aqueous phosphate-borate or borate electrolyte are studied. After 2 h, films with thicknesses of 30–40 µm and surface microhardnesses of 9–13 GPa are obtained. The elemental and phase compositions of the films and their corrosion resistance estimated using thes drop technique are discussed.

Electrolyte-Dependent Electrosynthesis and Activity of Cobalt-Based Water Oxidation Catalysts

Electrolysis of Co(2+) in phosphate, methylphosphonate, and borate electrolytes effects the electrodeposition of an amorphous highly active water oxidation catalyst as a thin film on an inert anode. Electrodeposition of a catalytically competent species immediately follows oxidation of Co(2+) to Co(3+) in solution. Methylphosphonate and borate electrolytes support catalyst activity comparable to that observed for phosphate. Catalytic activity for O(2) generation in aqueous solutions containing 0.5 M NaCl is retained for catalysts grown from phosphate electrolyte.