Polyphosphoesters are environmentally friendly and multifunctional materials. They were noted for their special properties, i.e. fire resistance, plasticity, lubricity, high physical-mechanical performance, thermal stability, and as degradable biopolymers which properties can be modified specifically to desired application in medicine, biology and agriculture. They have a wide range of application as: flame retardants, scaffolds for tissue engineering, gene carriers, drug delivery, carriers for the sustained release of nerve growth factor, pH/thermoresponsive materials, or as solid polymer electrolytes. In this paper we present our researches concerning the synthesis and application of polyphosphates, and polyphosphonates using different modern methods. Different approaches were used. These polyphosphoesters were used as solid polymer electrolytes for lithium polymer batteries by complexation of polyphosphoesters obtained from different phospho(n)ric dichlorides and aliphatic or aromatic diols with lithium salts. These polymers present two important features: they have good conductivity, around 10(-6) S/cm, and are fire proof.