Interfacial reactions in lithia-based cathodes depending on the binder in the electrode and salt in the electrolyte

Lithia (Li2O)-based cathodes, utilizing oxygen redox reactions for obtaining capacity, exhibit higher capacity than commercial cathodes. However, they are highly reactive owing to superoxides formed during charging, and they enable more active parasitic (side) reactions at the cathode/electrolyte and cathode/binder interfaces than conventional cathodes. This causes deterioration of the electrochemical performance limiting commercialization. To address these issues, the binder and salt for electrolyte were replaced in this study to reduce the side reaction of the cells containing lithia-based cathodes. The commercially used polyvinylidene fluoride (PVDF) binder and LiPF6 salt in the electrolyte easily generate such reactions, and the subsequent reaction between PVDF and LiOH (from decomposition of lithia) causes slurry gelation and agglomeration of particles in the electrode. Moreover, the fluoride ions from PVDF promote side reactions, and LiPF6 salt forms POF3 and HF, which cause side reactions owing to hydrolysis in organic solvents containing water. However, the polyacrylonitrile (PAN) binder and LiTFSI salt decrease these side reactions owing to their high stability with lithia-based cathode. Further, thickness of the interfacial layer was reduced, resulting in decreased impedance value of cells containing lithia-based cathodes. Consequently, for the same lithia-based cathodes, available capacity and cyclic performance were increased owing to the effects of PAN binder and LiTFSI salt in the electrolyte.

FOAMING AND MOISTURE CROSSLINKING OF VINYL TRIETHOXY SILANE GRAFTED ETHYLENE–PROPYLENE–DIENE TERPOLYMER

ABSTRACT Moisture crosslinking of polyolefins has attracted increasing attention because of its high efficiency, low cost, and easy processing. However, the crucial shortcoming of moisture crosslinking is that the side reaction of peroxide scorch (precrosslinking) simultaneously occurs in silane grafting. It has been recognized that making peroxide precrosslinking useful is an effective way to broaden the application of moisture crosslinking. A novel foaming process combined with moisture crosslinking is proposed. The matrix of ethylene–propylene–diene terpolymer grafted with silane vinyl triethoxysilane (EPDM-g-VTES) was prepared by melt grafting, with dicumyl peroxide as initiator. Foaming was then carried out with azodicarbonamide (AC) as the blowing agent by making use of precrosslinking. Subsequently, the EPDM-g-VTES foams were immersed in a water bath to achieve moisture crosslinking with dibutyl tin dilaurate as the catalyst. The results showed that VTES was grafted onto EPDM and the EPDM-g-VTES foams were successfully crosslinked by moisture. The EPDM-g-VTES compounds with AC obtained great cells by compression molding with the help of precrosslinking. The mechanical property of the EPDM-g-VTES foam was improved by moisture crosslinking. The moisture-cured foam with 4 wt% AC had an expansion ratio of about three times, which could bear large deformation and showed a high energy-absorption effect.

ABC-Type Triblock Copolyacrylamides via Copper-Mediated Reversible Deactivation Radical Polymerization

The aqueous Cu(0)-mediated reversible deactivation radical polymerization (RDRP) of triblock copolymers with two block sequences at 0.0 °C is reported herein. Well-defined triblock copolymers initiated from PHEAA or PDMA, containing (A) 2-hydroxyethyl acrylamide (HEAA), (B) N-isopropylacrylamide (NIPAM) and (C) N, N-dimethylacrylamide (DMA), were synthesized. The ultrafast one-pot synthesis of sequence-controlled triblock copolymers via iterative sequential monomer addition after full conversion, without any purification steps throughout the monomer additions, was performed. The narrow dispersities of the triblock copolymers proved the high degree of end-group fidelity of the starting macroinitiator and the absence of any significant undesirable side reactions. Controlled chain length and extremely narrow molecular weight distributions (dispersity ~ 1.10) were achieved, and quantitative conversion was attained in as little as 52 min. The full disproportionation of CuBr in the presence of Me6TREN in water prior to both monomer and initiator addition was crucially exploited to produce a well-defined ABC-type triblock copolymer. In addition, the undesirable side reaction that could influence the living nature of the system was investigated. The ability to incorporate several functional monomers without affecting the living nature of the polymerization proves the versatility of this approach.

Kinetic Studies of Esterification of Rosin and Pentaerythritol

Esterification of rosin with pentaerythritol produces rosin pentaerythritol ester (RPE) which is widely used in paint, coating, and pressure-sensitive and hot-melt adhesive industries. Although RPE has excellent valuable applications and has been industrially produced, studies on the reaction kinetics have not been widely reported in the present literature. This work proposed a kinetic study of RPE synthesis by including a series of consecutive reactions forming mono-, di-, tri-, and tetra-ester with decarboxylation of rosin as a side reaction in the kinetics model. For esterification, the reaction rates were determined by the second-order kinetic model. The first-order kinetic order was proposed for decarboxylation. Kinetic experiments were performed at a temperature range of 260 °C to 290 °C. The initial molar ratio of pentaerythritol to rosin (in the mole of OH/COOH) used was between 0.8 and 1.2. A small amount of samples were withdrawn in certain time interval. The sample was analyzed to evaluate their acid and saponification number. Afterward, those experimental data were used to simulate and validate the proposed kinetic model. In general, the proposed model could capture the experimental data well. The resulting activation energies ranged from 65.81 to 129.13 kJ mol−1 for esterification and 233.00 kJ mol−1 for decarboxylation. This model also offers a new insight that correlates well with tetra-ester formation and the softening point.

Modelling competition between the siderophore ferrioxamine B and humic like binding sites in seawater v1

Here we archive a protocol that can be used to determine competition between a siderophore (ferrioxamine B) and humic like binding sites that are present in marine DOM. We use the NICA-Donnan model to describe binding by humic like binding sites in DOM. Constants for Fe binding to marine DOM are taken from Zhu et al., (2021). Thermodynamic constants describing binding between major ions, iron and ferrioxamine B are taken from Schijf and Burns, (2016). References Schijf, J., Burns, S.M., 2016. Determination of the Side-Reaction Coefficient of Desferrioxamine B in Trace-Metal-Free Seawater. Front. Mar. Sci. 3, 117. https://doi.org/10.3389/fmars.2016.00117 Zhu, K., Birchill, A.J., Milne, A., Ussher, S.J., Humphreys, M.P., Carr, N., Mahaffey, C., Lohan, M.C., Achterberg, E.P., Gledhill, M., 2021a. Equilbrium calculations of iron speciation and apparent iron solubility in the Celtic Sea at ambient pH using the NICA-Donnan model. Mar. Chem

Influence of the Substituents on the Opening of Silylepoxy Alcohols: 5-exo-Cyclization towards Tetrahydrofurans vs. Unexpected Side Reaction Leading to Tetrahydropyrans

The regioselective ring opening of epoxy alcohols is an effective method for the synthesis of different types of oxacycles. The 5-exo opening being preferred vs. the 6-endo mode, according to Baldwin rules, the use of silyl-substituted oxiranes has been reported as a possible method to favor the 6-endo cyclization. However, there is a need for a detailed study on the different factors (structural factors, catalyst nature or conditions) that influence this process. In this paper, the acid-catalyzed cyclization of epoxysilyl alcohols was studied, focusing on the effect of substituents and reaction conditions on the outcome of the process. Two types of heterocycles (tetrahydrofurans or tetrahydropyrans) were selectively obtained depending on the structure of the initial epoxysilyl alcohol. Interestingly, cyclization of hindered epoxysilyl alcohols mainly proceeds through an unexpected side reaction, which implies a previous isomerization to an aldehyde. A mechanistic proposal for the formation of the different products is presented.

Suzuki–Miyaura Catalyst-Transfer Polycondensation of Triolborate-Type Carbazole Monomers

Herein, we report the Suzuki–Miyaura catalyst-transfer polycondensation (SCTP) of triolborate-type carbazole monomers, i.e., potassium 3-(6-bromo-9-(2-octyldodecyl)-9H-carbazole-2-yl)triolborate (M1) and potassium 2-(7-bromo-9-(2-octyldodecyl)-9H-carbazole-2-yl) triolborate (M2), as an efficient and versatile approach for precisely synthesizing poly[9-(2-octyldodecyl)-3,6-carbazole] (3,6-PCz) and poly[9-(2-octyldodecyl)-2,7-carbazole] (2,7-PCz), respectively. The SCTP of triolborate-type carbazole monomers was performed in a mixture of THF/H2O using an initiating system consisted of 4-iodobenzyl alcohol, Pd2(dba)3•CHCl3, and t-Bu3P. In the SCTP of M1, cyclic by-product formation was confirmed, as reported for the corresponding pinacolboronate-type monomer. By optimizing the reaction temperature and reaction time, we successfully synthesized linear end-functionalized 3,6-PCz for the first time. The SCTP of M2 proceeded with almost no side reaction, yielding 2,7-PCz with a functional initiator residue at the α-chain end. Kinetic and block copolymerization experiments demonstrated that the SCTP of M2 proceeded in a chain-growth and controlled/living polymerization manner. This is a novel study on the synthesis of 2,7-PCz via SCTP. By taking advantage of the well-controlled nature of this polymerization system, we demonstrated the synthesis of high-molecular-weight 2,7-PCzs (Mn = 5–38 kg mol−1) with a relatively narrow ÐM (1.35–1.48). Furthermore, we successfully synthesized fluorene/carbazole copolymers as well as 2,7-PCz-containing diblock copolymers, demonstrating the versatility of the present polymerization system as a novel synthetic strategy for well-defined polycarbazole-based materials.

Interfacial reactions in lithia-based cathodes depending on the binder in the electrode and salt in the electrolyte

Lithia (Li2O)-based cathodes, utilizing oxygen redox reactions for obtaining capacity, exhibit higher capacity than commercial cathodes. However, they are highly reactive owing to superoxides formed during charging, and they enable more active parasitic (side) reactions at the cathode/electrolyte and cathode/binder interfaces than conventional cathodes. This causes deterioration of the electrochemical performance limiting commercialization. To address these issues, the binder and salt for electrolyte were replaced in this study to reduce the side reaction of the cells containing lithia-based cathodes. The commercially used polyvinylidene fluoride (PVDF) binder and LiPF6 salt in the electrolyte easily generate such reactions, and the subsequent reaction between PVDF and LiOH (from decomposition of lithia) causes slurry gelation and agglomeration of particles in the electrode. Moreover, the fluoride ions from PVDF promote side reactions, and LiPF6 salt forms POF3 and HF, which cause side reactions owing to hydrolysis in organic solvents containing water. However, the polyacrylonitrile (PAN) binder and LiTFSI salt decrease these side reactions owing to their high stability with lithia-based cathode. Further, thickness of the interfacial layer was reduced, resulting in decreased impedance value of cells containing lithia-based cathodes. Consequently, for the same lithia-based cathodes, available capacity and cyclic performance were increased owing to the effects of PAN binder and LiTFSI salt in the electrolyte.