Trimethylsilyl Phosphite Research Articles

In Situ Controlled Syntheses of Electrolyte Additives for High Voltage Lithium Ion Batteries

The development of cathode materials needs concomitant electrolyte developments to accommodate the high voltage to reach high energy and power densities required for electric vehicle and personal electronics. Previously we reported that aging TMSPi (trimethylsilylphosphite) additive in a standard 1.2 M LiPF6 carbonate electrolyte can generate a beneficial transient product, PF2(OSi(CH3)3), which was later proven to mitigate impedance rise during long term cycling in composite cathode-graphite cells. However, the generation of PF2(OSi(CH3)3) is spontaneous and cannot be controlled, and as aging process proceeds to a greater extent, PF2(OSi(CH3)3) disappears gradually and other transient detrimental products form along the way and eventually deteriorate the impedance.1,2 By using molecular engineering to tune functionality, ratio, and stability, we can control the in situ electrolyte additive to selectively synthesize the beneficial component in high yield (> 98%) and maximize the battery performance. The in situ method is particularly of interest to scale up electrolyte preparation since it would alleviate any requirements of extra separation and purification of the desired additives. By varying the structure of the additive precursor, we clearly see a trend that is governed by thermodynamics which determine the product ratio and composition. The electrochemistry of these additives and their application in composite cathodes will be discussed. By introducing the novel in situ synthetic method for electrolyte additive syntheses, avenues for new additives that were previously inaccessible will open up and facilitate the development of the lithium ion batteries toward high energy and high power density. References The Journal of Physical Chemistry C 2018, 122 (18), 9811-9824.RSC Advances 2016, 6 (44), 38342-38349.

Effects of Charge Cutoff Potential on an Electrolyte Additive for LiNi0.6Co0.2Mn0.2O2–Mesocarbon Microbead Full Cells

Tris(trimethylsilyl)phosphite (TMSPi) has been reported to be an excellent electrolyte additive. However, scarce reports exist on the effect of the charge cutoff potential on the cyclic stability using high‐performance LiNi0.6Co0.2Mn0.2O2 (NCM622)–mesocarbon microbead (MCMB) full cells. Herein, a high‐loading and repeatable NCM622–MCMB coin‐type full cell is successfully prepared, and the role of TMSPi on such a full cell at charge cutoff potentials of 4.25 and 4.45 V is studied. Theoretical calculations and detailed analyses reveal that it is oxidized in the first charging process due to its unsaturated P—O bonds, thus forming a stable P—O—F‐rich cathode electrolyte interphase and preventing severe decomposition of the electrolyte over NCM622 during long‐term cycling. In addition, the P—O and Si—O bonds of TMSPi both display HF‐scavenging ability. Moreover, TMSPi may react directly with the LiPF6‐based electrolyte to form some intermediate products that can be reduced on the MCMB electrode, thereby modifying the solid electrolyte interphase and improving the stability of MCMB during lithium intercalation.

Reaction of Methyl (2-Methylidene)-3-oxolup-20(29)-en-28-oate with Dimethyl Trimethylsilyl Phosphite

A method of phosphorylation of pentacyclic triterpenoids derivatives containing an α,β-unsaturated carbonyl fragment in the ring A was described by the example of the reaction of methyl (2-methylidene)-3-oxolup-20(29)-en-28-oate with dimethyl trimethylsilyl phosphite. Methyl 2-dimethoxyphosphorylmethyl-3-oxolup-20(29)-en-28-oate was obtained as two epimers in a 2: 1 ratio in a 70% yield.

Chemical “Pickling” of Phosphite Additives Mitigates Impedance Rise in Li Ion Batteries

The use of high-voltage, high-capacity positive electrodes in lithium ion batteries presents a challenge, given their tendency to degrade organic electrolytes. To prevent this damage, electrolyte additives modifying the cathode surface are required. Tris(trimethylsilyl) phosphite (TMSPi) is one such electrolyte additive. However, the mechanism for its protective action (similar to other phosphite, borate, and boroxane compounds) remains not completely understood. In LiPF6 containing carbonate electrolytes, TMSPi undergoes reactions yielding numerous products. Here we demonstrate that one of these products, PF2OSiMe3, is responsible for mitigation of the impedance rise that occurs in aged cells during charge/discharge cycling. This same agent can also be responsible for reducing parasitic oxidation currents and transition metal loss during prolonged cell cycling. Mechanistic underpinnings of this protective action are examined using computational methods. Our study suggests that this beneficial action orig...

Reactions of Disulfides with Silyl Phosphites to Generate Thiophosphates Under Neat Conditions.

An efficient procedure for the synthesis of thiophosphates is described. Without using any metallic catalyst or base, the direct sulfur-phosphorus coupling reaction of disulfides and dialkyl trimethylsilyl phosphite (DTSP) was carried out under solvent-free reaction conditions in moderate to excellent yields with good functional group compatibility. The reaction conditions represent an advance over established methods not only in omitting the need for expensive catalysts or solvents, but also in shortening the reaction time significantly.These transformations are easy to conduct and can be readily applied to gram-scale preparation.

Electrochemical study of the synergic effect of phosphorus and cerium additions on a sol-gel coating for Titanium manufactured by powder metallurgy

The goal of this work was to combine the physical barrier properties provided by the sol-gel network with an active-chemistry protection against corrosion provided by corrosion inhibitors and cross-linking agents. Sol-gel coatings, organic–inorganic hybrid materials were prepared by hydrolysis and condensation of (3-glycidyloxypropyl)trimethoxysilane (GPTMS) and tetraethylorthosilane (TEOS) in an ethanol/water solution. This coatings were satisfactorily modified by adding an inhibitor of the corrosion, namely hexahydrate cerium nitrate, and a cross-linking agent, namely tris(trimethylsilyl)phosphite (TMSP). The synergetic effect of these two compounds was evaluated by means of electrochemical characterization. The evolution rate of the hydrolysis-polycondensation reaction was monitored by Fourier-transform infrared spectroscopy and viscosity. Once the hydrolysis-polycondensation rate was reached, sols were deposited on titanium fabricated by powder metallurgy. The morphological characteristics and elemental distribution of the coatings were studied using scanning electrochemical microscopy (SEM). The solid-state of Si-NMR spectroscopy and thermogravimetric analysis (TGA) was employed in order to identify the cross-linking state of the coating by ensuring the creation of enough siloxane bonds. Impedance measurements were carried out to study the effect of cerium and TMSP on the corrosion resistance. It was observed that the coating with additions of cerium presented stable and good barrier features against 5 mM NaCl solution. The synergy between the cerium inhibitor and the TMSP cross-linking agent was found not to exert a positive effect because the electrochemical behaviour was dominated by the phosphorus compound over the cerium.

Prescribing Functional Additives for Treating the Poor Performances of High‐Voltage (5 V‐class) LiNi0.5Mn1.5O4/MCMB Li‐Ion Batteries

AbstractIn this paper, tris(trimethylsilyl) phosphite (TMSP) and 1,3‐propanediolcyclic sulfate (PCS) are unprecedentedly prescribed as binary functional additives for treating the poor performances of high‐voltage (5 V‐class) LiNi0.5Mn1.5O4/MCMB (graphitic mesocarbon microbeads) Li‐ion batteries at both room temperature and 50 °C. The high‐voltage LiNi0.5Mn1.5O4/MCMB cell with binary functional additives shows a preponderant discharge capacity retention of 79.5% after 500 cycles at 0.5 C rate at room temperature. By increasing the current intensity from 0.2 to 5 C rate, the discharge capacity retention of the high‐voltage cell with binary functional additives is ≈90%, while the counterpart is only ≈55%. By characterizations, it is rationally demonstrated that the binary functional additives decompose and participate in the modification of solid–electrolyte interface layers (both electrodes), which are more conductive, protective, and resistant to electrolyte oxidative/reductive decompositions (accompanying active‐Li+ consuming parasitic reactions) due to synergistic effects. Specifically, the TMSP additive can stabilize LiPF6 salt and scavenge erosive hydrofluoric acid. More encouragingly, at 50 °C, the high‐voltage cell with binary functional additives holds an ultrahigh discharge capacity retention of 79.5% after 200 cycles at 1 C rate. Moreover, a third designed self‐extinguishing flame‐retardant additive of (ethoxy)‐penta‐fluoro‐cyclo‐triphosphazene (PFPN) is introduced for reducing the flammability of the aforementioned binary functional additives containing electrolyte.

Tris(trimethylsilyl) Phosphite as an Efficient Electrolyte Additive To Improve the Surface Stability of Graphite Anodes.

Tris(trimethylsilyl) phosphite (TMSP) has received considerable attention as a functional additive for various cathode materials in lithium-ion batteries, but the effect of TMSP on the surface stability of a graphite anode has not been studied. Herein, we demonstrate that TMSP serves as an effective solid electrolyte interphase (SEI)-forming additive for graphite anodes in lithium-ion batteries (LIBs). TMSP forms SEI layers by chemical reactions between TMSP and a reductively decomposed ethylene carbonate (EC) anion, which is strikingly different from the widely known mechanism of the SEI-forming additives. TMSP is stable under cathodic polarization, but it reacts chemically with radical anion intermediates derived from the electrochemical reduction of the carbonate solvents to generate a stable SEI layer. These TMSP-derived SEI layers improve the interfacial stability of the graphite anode, resulting in a retention of 96.8% and a high Coulombic efficiency of 95.2%. We suggest the use of TMSP as a functional additive that effectively stabilizes solid electrolyte interfaces of both the anode and cathode in lithium-ion batteries.

Evaluating electrolyte additives for lithium-ion cells: A new Figure of Merit approach

Electrolyte additives are known to improve the performance of lithium-ion cells. In this work we examine the performance of Li1.03Ni0.5Mn0.3Co0.3O2-graphite (NMC532/Gr) cells containing combinations of lithium bis(oxalate)borate (LiBOB), vinylene carbonate (VC), trivinylcyclotriboroxane (tVCBO), prop-1-ene-1,3-sultone (PES), phenyl boronic acid ethylene glycol ester (PBE), tris(trimethylsilyl) phosphite (TMSPi), triethyl phosphite (TEPi), and lithium difluoro(oxalate)borate (LiDFOB) added to our baseline (1.2 M LiPF6 in EC:EMC, 3:7 w/w) electrolyte. In order to rank performance of the various electrolytes, we developed two separate figures of merit (FOM), which are based on the energy retention and power retention of the cells. Using these two metrics in conjunction, we show that only one of the fifteen electrolyte formulations tested significantly outperforms the baseline electrolyte: this electrolyte contains the 0.25 wt% tVCBO + 1 wt% TMSPi additive mix. Little correlation was observed between the FOMs for energy retention and power retention, which indicates that the mechanisms that govern these performance parameters are likely independent of each other. Our FOM approach has general applicability and can be used to develop electrolyte and electrode formulations that prolong the life of lithium-ion batteries.

A Combinatorial Model of the Effect of Additives in High-Voltage, NMC Cells

Coin cells containing the additives, vinylene carbonate (VC) and tris(trimethylsilyl)phosphite (TMSPi), in the range of 0 to 0.020 wt. fraction, were cycled between 3.0 and 4.4 V. The changes in C/10 and C/1 capacity and cell resistance at 60% SOC were found to follow linear-with-time kinetic rate laws. After aging, the electrodes were characterized by X-ray photoelectron spectroscopy. The concentration of some surface species correlated very strongly with changes in cell performance. Further, the cell performance data could be modeled using a statistics of mixtures approach. The modeling indicated that there was a strong, synergistic interaction between VC and TMSPi, as expected. The interaction between these additives lessened capacity fade. These results, as well as others, will be discussed. Acknowledgment The work at Argonne National Laboratory was performed under the auspices of the U.S. Department of Energy (DOE), Office of Vehicle Technologies, under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.

Addition of tris(trimethylsilyl) phosphite to quinuclidin-3-one and its carbocyclic analogs

Convenient methods of synthesis of functionalized phosphonic acids and their trimethylsilyl esters containing quinuclidine, adamantine, and bornane (camphane) moieties, involving reactions of tris(trimethylsilyl) phosphite with quinuclidin-3-one and its carbocyclic analogs.

Additive effects in high-voltage layered-oxide cells: A statistics of mixtures approach

Li1.03(Ni0.5Mn0.3Co0.2)0.97O2 (NMC)-based coin cells containing the electrolyte additives vinylene carbonate (VC) and tris(trimethylsilyl)phosphite (TMSPi) in the range of 0–2 wt% were cycled between 3.0 and 4.4 V. The changes in capacity at rates of C/10 and C/1 and resistance at 60% state of charge were found to follow linear-with-time kinetic rate laws. Further, the C/10 capacity and resistance data were amenable to modeling by a statistics of mixtures approach. Applying physical meaning to the terms in the empirical models indicated that the interactions between the electrolyte and additives were not simple. For example, there were strong, synergistic interactions between VC and TMSPi affecting C/10 capacity loss, as expected, but there were other, more subtle interactions between the electrolyte components. The interactions between these components controlled the C/10 capacity decline and resistance increase.

Aged Tris(trimethylsilyl) Phosphite (TMSPi) As a L.I.B. Electrolyte Additive

The use of electrolyte additives has been and continues to be an economical and effective approach to enhance the performance and increase the lifetime of lithium ion battery systems. In the presence of additives, the baseline performance of electrolytes can be improved due to the formation of surface films on the electrodes, HF scavenging in the bulk electrolyte, etc. However, the interaction between electrolytes and small molecule additives are rarely studied due to the assumed inertness of the system. While this inert relationship may hold true for many additives, we have found that one commonly used additive, tris(trimethylsilyl) phosphite (TMSPi), demonstrates a dynamic (reactive) relationship when used with a LiPF6-based electrolyte (1.2 M LiPF6 in EC/EMC, 3/7 wt/wt). Our findings suggest that immediately after the addition of TMSPi into the electrolyte, the nature of the electrolyte changes and the properties of the bulk electrolyte are drastically different between immediately making the solution and waiting less than a week. We present electrochemical data comparing freshly prepared (same day) and “aged” (one week) TMSPi-based electrolyte formulations. Our results indicate that the effect of electrolyte aging on cell electrochemistry (LiNi0.5Mn0.3Co0.2O2 /graphite full cells operating between 3.0-4.4 V) can be dramatic with observable differences in impedance, redox behavior, surface film formation and transition metal dissolution from the positive electrode. The data presented sheds considerable light on the possible interactions between additives and electrolyte and are of utmost importance when considering electrolyte formulations for lithium ion batteries.

Effect of Phosphorus-Based Additives on Cathode-Electrolyte Interface of Charged Ncm Surface through Potentiostatic Holds

Nickel-rich layered oxide cathode materials have seen widespread deployment due to their high gravimetric capacity and high average discharge voltage. However, achieving this high capacity requires charging voltages above the potential at which the electrolytes decompose at the cathode surface (>4.5 V vs. Li/Li+). This interfacial instability leads to impedance rise and capacity loss. One strategy to stabilize this interface is by the addition of additives to the electrolyte, in which small amounts of a new component change the interactions of the interface. Potentiostatic holds with LiNi0.5Mn0.3 Co0.2O2 (NMC) as the working electrode and Li4Ti5O12 (LTO) as the counter/reference allow a quantitative measurement of the oxidation reactions occurring at cathode. A 60 hour hold allows for concentration polarizations to relax and oxidative side reactions to dominate the current. A more stable electrolyte at the cathode/electrolyte interface would lead to a lower current during the potentiostatic hold. In this work, the performance of five phosphorus-based additive electrolyte formulations (1% wt. ratio) is evaluated against a baseline organic carbonate electrolyte in NMC (LiNi0.5Mn0.3 Co0.2O2 ) / LTO (Li4Ti5O12) full cells. These additives include triethylphosphite (TEPi), tris(2,2,2-trifluoroethyl)phosphite (TTFPi), tris(trimethylsilyl) phosphite (TMSPi), and tris(trimethyl silyl) phosphate (TMSPa). The electrochemical protocol used to evaluate these additives comprises multiple cycles up to 4.4 V vs. Li+/Li, a potentiostatic hold at 4.6 V vs. Li+/Li, followed by AC impedance spectroscopy and extended cycling. Of the formulations surveyed, only electrolytes containing TMSPa and TMSPi (aged for one week) increased the coulombic efficiency during the initial cycling. For the potentiostatic hold, only the aged TMSPi electrolyte lowered the terminal oxidation current compared to the baseline electrolyte, indicating increased stability of the cathode/electrolyte interface. AC impedance spectra indicated the aged TMSPi electrolyte had a slightly elevated high-frequency semicircle (traditionally associated with phenomena at the solid-electrolyte interphase) and a vastly decreased mid-frequency semicircle (traditionally associated with charge-transfer phenomena), compared with all other electrolytes tested. Characterization of cycled electrodes was performed with XPS and SEM will be presented. Acknowledgements The work at Argonne National Laboratory was performed under the auspices of the U.S. Department of Energy (DOE), Office of Vehicle Technologies, under Contract No. DE-AC02-06CH11357. The submitted issue has been created by the University of Chicago as Operator of Argonne National Laboratory (“Argonne”) under Contract No. W-31-109-Eng-38 with the U.S. Department of Energy. The U.S. Government retains for itself, and others acting on its behalf, a paid-up, non-exclusive, irrevocable, worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.

Synthesis of poly(oxyethylene phosphoramidate)s and glycopolymers via Staudinger reaction: Multivalent binding studies with Concanavalin A

ABSTRACTA new method for the preparation of poly(oxyethylene phosphoramidate)s and glycopolymers is developed via modification of poly(oxyethylene H‐phosphonate) which is a biodegradable, biocompatible and low toxic polymer. The phosphonate groups of the precursor are converted into tri‐coordinated phosphorus species yielding poly(oxyethylene trimethylsilyl phosphite). The latter is then reacted with different azides, including sugar azides, via Staudinger reaction to furnish the desired poly(oxyethylene phosphoramidate)s and such containing sugar moieties in the side chains attached to the P‐centers. 2002P NMR spectroscopy is applied as a powerful tool for determination of the conversion and structure of the reaction products. Studies on Concanavalin A binding to the obtained glycopolymers are performed using dynamic light scattering and analytical ultracentrifugation techniques. The viability of Human Embryonic Kidney 293 cell line is slightly affected when exposed to polyphosphoramidate glucoconjugate over a broad range of concentrations. The results obtained are encouraging for further investigations on the clustering and bio‐recognition properties of the synthesized glycopolymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1730–1741

Addition of tris(trimethylsilyl) phosphite to N-substituted 4-piperidone

Convenient methods for the synthesis of functionalized phosphonic acids containing piperidine moieties via the reaction of tris(trimethylsilyl) phosphite with N-substituted 4-piperidone derivatives have been developed.

Improved facile synthesis of α-amino phosphonates by the reaction of α-amido sulfones with dialkyl trimethyl silyl phosphites catalyzed by Fe(III) chloride

ABSTRACTAn improved efficient synthesis of α-amino phosphonates has been discovered by the reaction of N-benzyloxycarbonylamino sulfones with dialkyl trimethyl silyl phosphites in the presence of FeCl3 as a catalyst. The products were formed in high yields (86–94%) within 2–4 h. The catalyst is inexpensive, easily available, and highly active. The unreacted dialkyl trimetyl silyl phosphites can easily be removed from the products due to their low boiling points. The sulfones can conveniently be prepared and are generally stable.

Tris(trimethylsilyl) Phosphite (TMSPi) and Triethyl Phosphite (TEPi) as Electrolyte Additives for Lithium Ion Batteries: Mechanistic Insights into Differences during LiNi0.5Mn0.3Co0.2O2-Graphite Full Cell Cycling

Tris(trimethylsilyl) phosphite (TMSPi) has emerged as an useful electrolyte additive for lithium ion cells. This work examines the use of TMSPi and a structurally analogous compound, triethyl phosphite (TEPi), in LiNi0.5Mn0.3Co0.2O2-graphite full cells, containing a (baseline) electrolyte with 1.2 M LiPF6 in EC:EMC (3:7 w/w) and operating between 3.0–4.4 V. Galvanostatic cycling data reveal a measurable difference in capacity fade between the TMSPi and TEPi cells. Furthermore, lower impedance rise is observed for the TMSPi cells, because of the formation of a P- and O-rich surface film on the positive electrode that was revealed by X-ray photoelectron spectroscopy data. Elemental analysis on negative electrodes harvested from cycled cells show lower contents of transition metal (TM) elements for the TMSPi cells than for the baseline and TEPi cells. Our findings indicate that removal of TMS groups from the central P-O core of the TMSPi additive enables formation of the oxide surface film. This film is able to block the generation of reactive TM-oxygen radical species, suppress hydrogen abstraction from the electrolyte solvent, and minimize oxidation reactions at the positive electrode-electrolyte interface. In contrast, oxidation of TEPi does not yield a protective positive electrode film, which results in inferior electrochemical performance.

Synthesis of new five-membered N-heterocycle derivatives of mono- and bis-phosphonic acids

The new functionalized hydroxymethylphosphonic and methylenebis(phosphonic) acids are synthesized via reaction of tris(trimethylsilyl) phosphite and N-formyl derivatives of five-membered N-heterocycles in the presence of trimethylsilyl triflate.

Tandem Addition of Phosphite Nucleophiles Across Unsaturated Nitrogen-Containing Systems: Mechanistic Insights on Regioselectivity

The addition of phosphite nucleophiles across linear unsaturated imines is a powerful and atom-economical methodology for the synthesis of aminophosphonates. These products are of interest from both a biological and a synthetic point of view: they act as amino acid transition state analogs and Horner-Wadsworth-Emmons reagents, respectively. In this work the reaction between dialkyl trimethylsilyl phosphites and α,β,γ,δ-diunsaturated imines was evaluated as a continuation of our previous efforts in the field. As such, the first conjugate 1,6-addition of a phosphite nucleophile across a linear unsaturated N-containing system is reported herein. Theoretical calculations were performed to rationalize the observed regioselectivites and to shed light on the proposed mechanism.