A new synthetic strategy is developed for the synthesis of polyphosphazene bearing stable nitroxide radicals as a pendant group. The resulting material is investigated as a cathode‐active material for rechargeable lithium–ion batteries that performs 80 mAh g−1 capacities at a C/2 current density over 50 cycles. Thus, the inorganic–organic hybrid system can be proposed as an alternative cathode‐active material with improved performance.

Novel, eco‐friendly, and halogen‐free polyphosphazene‐based flame retardant (FR) cathodes for Li–S batteries are prepared by the inverse vulcanization of elemental sulfur with polybis(2‐acrylamidoethoxy)phosphazene (poly(AAE)) resulting in the covalently bonded different wt% sulfur content polymers. Due to the polar amide groups, poly(AAE)‐xS (x refer to the wt% of sulfur) composites assist in anchoring intermediate lithium polysulfide species. The structural characterizations of the poly(AAE)‐xS polymers are conducted by elemental analysis, Fourier‐transform infrared spectroscopy, differential scanning calorimeter, thermogravimetric analysis, and scanning electron microscopy. Their FR properties are elevated by calculation of the limiting oxygen index values and burning tests. Later, lithium‐ion storage mechanism of poly(AAE)‐55S polymer is evaluated, including cyclic voltammetry, rate performance tests and electrochemical impedance spectroscopy measurements. To compare with the electrochemical performance of poly(AAE)‐55S, a noncovalent blend polymer mixture and bare sulfur are also tested. It is found that covalently bonded poly(AAE)‐55S obtained by the inverse vulcanization of elemental sulfur and poly(AAE) results much pronounced capacities. Herein, new insights into the design and development of alternative cathode materials for safer Li–S batteries, both providing FR properties and good lithium polysulfides adsorption capabilities, are offered.

A cathode material based on polyphosphazene with pyrene-4,5,9,10-tetraone (PTO) units as electroactive groups with a high specific capacity in the side chain, poly­[(bis­(2-amino-4,5,9,10-pyrenetetraone)]­phosphazene (PPAPT), is synthesized. The structural characterization of PPAPT is carried out by using appropriate standard spectroscopic methods such as 31P NMR spectroscopy, FT-IR, DSC, and TGA. The material is found to be an insoluble and halogen-free flame retardant in accordance with the results of the simple flame test and solubility control in electrolyte solutions accompanied by UV–vis analysis. The electrochemical performance of PPAPT is evaluated as a Li–ion battery cathode material. The fabricated cells demonstrate immensely good capacity retention with 72% after 500 discharge–charge cycles at a high current density of 20 C. In comparison with the pristine PTO, introducing a PTO unit into the side chain of the polyphosphazene leads to substantially improved performance because of the lowered LUMO energy levels of PPAPT. In order to investigate the reversibility of carbonyl groups as an electroactive side with respect to their chemical composition, complementary chemical post-mortem analyses are performed by FT-IR, X-ray photoelectron spectroscopy (XPS) analysis. Density functional theory (DFT) calculations are also proposed to determine HOMO–LUMO levels and investigate the lithiation mechanism of PPAPT.

Novel insoluble star-shaped hexa-branched polymeric materials based on cyclotriphosphazene core are prepared by the inverse vulcanization of sulfur with hexakis(styreneoxy)cyclotriphosphazene and tested as cathode for lithium–sulfur (Li–S) batteries.

A novel polyphosphazene carrying stable nitroxide aromatic radical groups as a pendant with four electrons involvement per repeating unit is synthesized. To do so, series of macromolecular substitution reactions of poly (dichlorophosphazene) with 3,5-dibromophenol, 2-methyl-2-nitrosopropane, and lead oxide, respectively, are performed. After characterization of the newly synthesized polymers by standard spectroscopic techniques (such as Fourier transform infrared [FT-IR], nuclear magnetic resonance [NMR], or electron paramagnetic resonance [EPR]), the targeted polymer is further investigated as a cathode-active material for rechargeable lithium-ion batteries (LIBs). The cell delivered a good rate performance with a discharge capacity of 100 mAh/g at a C/2 current density over 500 cycles.