Eliminating H_(2)O/HF and regulating interphase with bifunctional tolylene-2,4-diisocyanate(TDI)additive for long life Li-ion battery

Lithium-ion batteries(LIBs)featuring a Ni-rich cathode exhibit increased specific capacity,but the establishment of a stable interphase through the implementation of a functional electrolyte strategy remains challenging.Especially when the battery is operated under high temperature,the trace water present in the electrolyte will accelerate the hydrolysis of the electrolyte and the resulting HF will further erode the interphase.In order to enhance the long-term cycling performance of graphite/LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)LIBs,herein,Tolylene-2,4-diisocyanate(TDI)additive containing lone-pair electrons is employed to formulate a novel bifunctional electrolyte aimed at eliminating H_(2)O/HF generated at elevated temperature.After 1000 cycles at 25℃,the battery incorporating the TDI-containing electrolyte exhibits an impressive capacity retention of 94%at 1 C.In contrast,the battery utilizing the blank electrolyte has a lower capacity retention of only 78%.Furthermore,after undergoing 550 cycles at 1 C under45℃,the inclusion of TDI results in a notable enhancement of capacity,increasing it from 68%to 80%.This indicates TDI has a favorable influence on the cycling performance of LIBs,especially at elevated temperatures.The analysis of the film formation mechanism suggests that the lone pair of electrons of the isocyanate group in TDI play a crucial role in inhibiting the generation of H_(2)O and HF,which leads to the formation of a thin and dense interphase.The existence of this interphase is thought to substantially enhance the cycling performance of the LIBs.This work not only improves the performance of graphite/NCM811 batteries at room temperature and high temperature by eliminating H_(2)O/HF but also presents a novel strategy for advancing functional electrolyte development.

An efficient green route for hexamethylene-1,6-diisocyanate synthesis by thermal decomposition of hexamethylene-1,6-dicarbamate over Co3O4/ZSM-5 catalyst： An indirect utilization of CO2

The utilization of CO2 as raw material for chemical synthesis has the potential for substantial economic and green benefits. Thermal decomposition of hexamethylene-1,6-dicarbamate （HDC） is a promising approach for indirect utilization of CO2 to produce hexamethylene-1,6-diisocyanate （HDI）. In this work, a green route was developed for the synthesis of HD1 by thermal decomposition of HDC over Co3O4/ZSM-5 catalyst, using chlorobenzene as low boiling point solvent. Different metal oxide supported catalysts were prepared by incipient wetness impregnation （IWI）, PEG-additive （PEG） and deposition precipitation with ammonia evaporation （DP） methods. Their catalytic performances for the thermal decomposition of HDC were tested. The catalyst screening results showed that Co3O4/ZSM-525 catalysts prepared by different methods showed different performances in the order of Co3O4/ZSM-5 25（PEG） 〉 Co3O4/ZSM-525（IWI） 〉 Co3O4/ZSM-525（DP）. The physicochemical properties of Co3O4/ZSM- 52s catalyst were characterized by XRD, FTIR, N2 adsorption-desorption measurements, NH3-TPD and XPS. The superior catalytic performance of Co3O4/ZSM-52S（PEG） catalyst was attributed to its relative surface content of Co3 ＋, surface lattice oxygen content and total acidity. Under the optimized reaction conditions： 6.5% HDC concentration in chlorobenzene, 1 wt% Co3O4/ZSM-525（PEG） catalyst, 250℃ temperature, 2.5 h time, 800 ml.min 1 nitrogen flow rate and 1.0 MPa pressure, the HDC conversion and HDI yield could reach 100% and 92.8% respectively. The Co3O4/ZSM-525（PEG） catalyst could be facilely separated from the reaction mixture, and reused without degradation in catalytic performance. Furthermore, a possible reaction mechanism was proposed based on the physicochemical properties of the Co3O4/ZSM-5 25 catalysts.

Non-phosgene synthesis of hexamethylene-1,6-diisocyanate from thermal decomposition of hexamethylene-1,6-dicarbamate over Zn–Co bimetallic supported ZSM-5 catalyst

A non-phosgene route for the synthesis of hexamethylene-1,6-diisocyanate(HDI) was developed via catalytic decomposition of hexamethylene-1,6-dicarbamate(HDC) over Zn–Co bi-metallic supported ZSM-5 catalyst.The catalyst was characterized by FTIR and XRD analyses. Three solvents dioctyl sebacate(DOS), dibutyl sebacate(DBS) and 1-butyl-3-methylimidazolium tetrafluoroborate(BMIMBF_4) were investigated and compared; DOS gave better performance. The catalytic performances for thermal decomposition of HDC to HDI using DOS as solvent were then investigated, and the results showed that, under the optimized reaction conditions, i.e.,10 wt%concentration of HDC in DOS, 250 °C temperature, 60 min reaction time, 83.8% yield of HDI had been achieved over Zn–Co/ZSM-5. Decomposition of the intermediate hexamethylene-1-carbamate-6-isocyanate(HMI) over Zn–Co/ZSM-5 in DOS solvent was further studied and the results indicated that yield of HDI from HMI reached to 69.6%(98.6% HDI selectively) at 270 °C, which further increased the yield of the total HDI(HDI_(tol)) to as high as 95.0%. Recycling of catalyst showed that HDI and HMI yield slightly decreased, and by-product yield increased after the catalyst was reused for 4 times. At last possible reaction mechanism was proposed.

~1H NMR analysis of the tolylene-2,4-diisocyanate-methanol reaction

Tolylene-2,4-diisocyanate（2,4-TDI） 1 reacts with methanol through two simultaneous paths in the polyurethane reaction,which involve two different intermediates-tolylene-4-carbamatic-2-isocyanate 2 and tolylene-2-carbamatic-4-isocyanate 3,and the final product is tolylene-2,4-dicarbamate 4.The-CH_3 chemical shifts in benzene ring in compounds 1,2,3 and 4 can be easily tested and well distinguished,through which those four compounds are quantified and their kinetics are investigated.It shows that four rate constants for the tolylene-2,4-diisocyanate-methanol reaction in CCl_4 at 50℃are k_1=9.6×10^（-2）h^（-2）mol^（-2）min^（-1）, k_2=1.4×10^（-2）h^（-2）mol^（-2）min^（-1）,k_3=4.0×10^（-3）h^（-2）mol^（-2）min^（-1）,k_4=1.4×10^（-3）h^（-2）mol^（-2）min^（-1）.（k_1 is the reaction rate constant from compounds 1 to 2;k_2 is the reaction rate constant from compounds 1 to 3;k_3 is the reaction rate constant from compounds 3 to 4;k_4 is the reaction rate constant from compounds 2 to 4）.

Selective derivatization of oxime-blocked tolylene-2,4-diisocyanate

A selective reaction of cyclohexanone oxime-blocked tolylene-2,4-diisocyanate（2,4-TDI）with amino siloxane was observed,in which amines were capable of discriminating two reactive groups in the 2,4-TDI molecule.Thus,tolylene-2-tert-butyldimethylsilyloxyethyl carbamide-4-cyclohexanone oxime carbamate was synthesized and its precise structure was determined by single-crystal X-ray diffraction.Moreover,it was found that oxime-blocked isocyanate could react selectively with the–NH2group with the–OH group unprotected in ethanolamine.

Study on ternary polymerization of toluene diisocyanate

For the production of reactive polyurethane cross-linkinger and curing agents, 2, 4-diisocyanate toluene （TDI） terpolymer, which possesses the rigid structures of hexatomic ring and three reactive functional groups, was synthesized and characterized by the Fourier transform infrared （FFIR）, the gel permeation chromatography （GPC） and the chemical analysis methods. The reaction conditions were studied and optimized. A tracking research on the polymerization process of TDI was taken by using the GPC. The formation processes of the terpolymer, oligomers and higher-polymers were also dealt with. Results show that the TDI terpolymer can be prepared in the presence of Cat-3 catalyst and at the reaction temperature of （60 ±2）℃. The reaction time is short, its outcomes have narrow molecular weights distribution, namely molecular weights from 530 to 550, Mw/Mn =1.10, and the mass fraction of NCO is （25. 0 ± 0. 5）%. With the reaction time prolonging, however, TDI can be further higher-polymedzed to form higher-polymers. Benzoyl chloride （0. 4%, mass fraction）, as the stabilizing agent, can effectively inhibit the occurrence of higher-polymerization. The obtained TDI terpolymer can be stable for more than half a year.

Synthesis and characterization of asymmetric substituted dicarbamates

Several new asymmetric substituted dicarbamates were synthesized with a convenient route.Firstly,tolylene-2,4-diisocyanate dimmer was obtained from monomer with tributylphosphine as catalyst.Then,the dimmer reacted with alcohol（R^1OH） to prepare carbamate substituted uretidione.Finally,uretidione ring was opened and the released isocyanate reacted with another alcohol （R^2OH,R^1≠R^2）.