A Series of Novel Flame Retardants Produced with Nanosilica, Melamine, and Aluminum Diethylphosphinate to Improve the Flame Retardancy of Phenolic Resin.

To facilitate the flame retardancy of phenolic resin (PF), a series of novel flame retardants with nano-SiO2, melamine, and aluminum diethylphosphinate (ADP) were freshly prepared and tested. A thermogravimetric analysis, cone calorimeter, and scanning electron microscopy were employed to determine the thermal decomposition, flame retardancy, combustion properties, and structure of the carbon residue layer of PF. The pyrolysis kinetic parameters of modified PF were then computed, and the pyrolysis process was appraised. The results indicated that when 1.5 wt % of nano-SiO2, 3 wt % of melamine, and 15 wt % of ADP were added to PF, the limiting oxygen index value reached 39.6%, and UL-94 passed the V-0 level. A substantial synergistic effect was also observed. The thermogravimetric analysis revealed that the char residue at 800 °C reached 59.93 wt %. Furthermore, in the cone calorimeter test, the total thermal release and thermal release rate decreased to 30.7 MJ/m2 and 105.7 kW/m2, respectively.

Thermal hazard evaluation on spontaneous combustion characteristics of nitrocellulose solution under different atmospheric conditions.

Nitrocellulose (NC) is widely used in both military and civilian fields. Because of its high chemical sensitivity and low decomposition temperature, NC is prone to spontaneous combustion. Due to the dangerous properties of NC, it is often dissolved in other organic solvents, then stored and transported in the form of a solution. Therefore, this paper took NC solutions (NC-S) with different concentrations as research objects. Under different atmospheric conditions, a series of thermal analysis experiments and different reaction kinetic methods investigated the influence of solution concentration and oxygen concentration on NC-S's thermal stability. The variation rules of NC-S's thermodynamic parameters with solution and oxygen concentrations were explored. On this basis, the spontaneous combustion characteristics of NC-S under actual industrial conditions were summarized to put forward the theoretical guidance for the spontaneous combustion treatment together with the safety in production, transportation, and storage.

Synergistic Flame Retardancy of Microcapsules Based on Ammonium Polyphosphate and Aluminum Hydroxide for Lithium-Ion Batteries.

Flame retardants have important theoretical research and applied value for lithium-ion battery safety. Microcapsule flame retardants based on ammonium polyphosphate (APP) and aluminum hydroxide (ATH) were synthesized for application in lithium-ion batteries. First, the ATH-APP was prepared by coating a layer of ATH on the surface of the core APP. Then, the ATH-APP was encapsulated by poly(urea-formaldehyde) (PUF) to obtain en-ATH-APP. The structure and flame-retardant property of en-ATH-APP, the influence of en-ATH-APP on the thermal stability of the electrode, and the electrochemical performance of the battery were studied. The results of Fourier transform infrared and scanning electron microscope experiments indicated that APP was coated with ATH and PUF in turn. The results of differential scanning calorimetry and the fire extinguishing test for electrodes manifested that en-ATH-APP had better flame-retardant property than APP because of the synergistic effect between APP and ATH. Moreover, the flame-retardant efficiency of en-ATH-APP was comparable to that of ATH-APP, indicating that the presence of PUF had almost no effect on the flame-retardant property. The results of electrochemical experiments indicated that en-ATH-APP had the best electrochemical compatibility for the battery compared with APP and ATH-APP. The research lights the way to improve inherent safety of lithium-ion batteries by adding en-ATH-APP to the cathode.

Thermal Effect and Mechanism Analysis of Flame-Retardant Modified Polymer Electrolyte for Lithium-Ion Battery.

In recent years, the prosperous electric vehicle industry has contributed to the rapid development of lithium-ion batteries. However, the increase in the energy density of lithium-ion batteries has also created more pressing safety concerns. The emergence of a new flame-retardant material with the additive ethoxy (pentafluoro) cyclotriphosphazene can ameliorate the performance of lithium-ion batteries while ensuring their safety. The present study proposes a new polymer composite flame-retardant electrolyte and adopts differential scanning calorimetry (DSC) and accelerating rate calorimetry to investigate its thermal effect. The study found that the heating rate is positively correlated with the onset temperature, peak temperature, and endset temperature of the endothermic peak. The flame-retardant modified polymer electrolyte for new lithium-ion batteries has better thermal stability than traditional lithium-ion battery electrolytes. Three non-isothermal methods (Kissinger; Kissinger-Akahira-Sunose; and Flynn-Wall-Ozawa) were also used to calculate the kinetic parameters based on the DSC experimental data. The apparent activation energy results of the three non-isothermal methods were averaged as 54.16 kJ/mol. The research results can provide valuable references for the selection and preparation of flame-retardant additives in lithium-ion batteries.

Thermal Stability Analysis of Lithium-Ion Battery Electrolytes Based on Lithium Bis(trifluoromethanesulfonyl)imide-Lithium Difluoro(oxalato)Borate Dual-Salt.

Lithium-ion batteries with conventional LiPF6 carbonate electrolytes are prone to failure at high temperature. In this work, the thermal stability of a dual-salt electrolyte of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium difluoro(oxalato)borate (LiODFB) in carbonate solvents was analyzed by accelerated rate calorimetry (ARC) and differential scanning calorimetry (DSC). LiTFSI-LiODFB dual-salt carbonate electrolyte decomposed when the temperature exceeded 138.5 °C in the DSC test and decomposed at 271.0 °C in the ARC test. The former is the onset decomposition temperature of the solvents in the electrolyte, and the latter is the LiTFSI-LiODFB dual salts. Flynn-Wall-Ozawa, Starink, and autocatalytic models were applied to determine pyrolysis kinetic parameters. The average apparent activation energy of the dual-salt electrolyte was 53.25 kJ/mol. According to the various model fitting, the thermal decomposition process of the dual-salt electrolyte followed the autocatalytic model. The results showed that the LiTFSI-LiODFB dual-salt electrolyte is significantly better than the LiPF6 electrolyte in terms of thermal stability.