A review on functional applications of polyphosphazenes as multipurpose material for lithium-ion batteries

Polyphosphazenes, which are inorganic-organic hybrid polymers with PN as the skeleton, are well-known for their unique physicochemical properties stemming from their backbone structure and highly active PCl bonds. The diverse functional properties of polyphosphazene make it a promising research prospect in many fields, including solid polymer electrolytes, anode materials, diaphragms and so on. This review discusses the main synthesis routes, modifications for a variety of functions, as well as template precipitation self-assembly polymerization. Among them, template-induced precipitation self-assembly is an outstanding strategy for polyphosphazene to form nanospheres, nanosheets, and nanotubes. Solid state lithium batteries are promising energy storage candidates, but the Li+ conductivity of the commonly used PEO electrolytes is limited to 10−6 S·cm−1 at room temperature. Polyphosphazenes-based electrolytes with an ether oxygen side tend to possess better ionic conductivity and are flame retardant. The polyphosphazenes organic polymer is also an attractive carbon material precursor and a good choice for anode electrodes. After high-temperature carbonization, N, P heteroatoms doped in-situ on the carbon matrix can change carbon neutrality and endow charged sites, further improving the lithium storage ability. In addition, polyphosphazene has potential for use on the diaphragm and other battery systems.