In this review, latest updates in the poly (ethylene oxide) based electrolytes are summarized. The ultimate goal of researchers globally is towards the development of free standing solid polymeric separator for energy storage devices. This single free standing solid polymeric separator may replace the liquid and separator (organic/Inorganic) used in existing efficient/smart energy technology. As an example polyethylene oxide (PEO) consist of an electron donor rich group which provides coordinating sites to the cation for migration. Owing to this exclusive structure PEO exhibits some remarkable properties such as; low glass transition temperature, excellent flexibility and ability to make complexation with various metal salts which are unattainable by another polymer host. Hence, the PEO is the most emerging candidate that have been examined or is currently under audition for application in energy storage devices. So, this review article first provides the detailed study of the PEO properties, characteristic of constituents of polymer electrolyte and suitable approaches for the modification of polymer electrolytes. Then, the synthesization and characterizations techniques are outlined. The structures, characteristics, and performance during charge-discharge of four types of electrolyte/separators which are Liquid, Plasticized, and dispersed/intercalated electrolyte are highlighted. The suitable ion transport mechanism proposed by researchers in different renowned group have been discussed for better understanding of the ion dynamics in such systems.Keywords: polyethylene oxide, constituents of polymer electrolytes, structural and microstructural properties, electrochemical properties summarizes the requirements for selection of electrolyte cum separator for efficient lithium-ion battery system [4].At, present, LIB is the ideal choice for the automotive sector by Companies including Tesla Inc. and Volkswagen AG due to ease of transportation, environmentally friendly, less cost [5]. Allied Market Research published a report entitled, "World Lithium-Ion Battery Market: Opportunities and Forecasts, 2015-2022" and the main point was that the global LIB market is expected to generate revenue of $46.21 billion by 2022, with a CAGR of 10.8% during the forecast period (2016)(2017)(2018)(2019)(2020)(2021)(2022). At a 37 percent revenue share, Li-ion is the battery of choice for portable devices and the electric vehicles. There are no other systems till now that threaten the market of LIB today [figure 2].Recently in 2017, John Goodenough, inventor of Li-ion battery has developed the first all-solid-state battery cells using sodium-or lithium-coated glass electrolyte and claimed that new battery cells have three times more energy density (1,200 charge-discharge cycles) in comparison to existing rechargeable batteries. He concluded that they store and transmit energy at temperatures (-20 o C to 60 o C) lower than traditional lithium-ion packs and can be made using globally abundant supplies of sodium. One advantage of this...