INTRODUCTIONLithium-ion batteries (LIBs) is a rigid battery type which is common in the small power-source due to their environmentally friendly operation, energy density, stability, absence of memory effect, and high voltage output.Flexible Lithium ion battery is similar to LIBs but it is a very thin type of the Lithium-ion batteries (LIBs) that has the ability of retaining their original power characteristics after undergoing repeated physical but not permanent deformation. The research on flexible lithium ion battery is still at the infant stage but with promising future applications due to the emergence of increase in the number of small, light and flexible electronics which requires energy storage devices for its smooth operation.How does Flexible lithium ion Battery Works?The Flexible LIBs works on the same principle as the rigid LIBs only for the bendability characteristics that make it flexible and different from the rigid lithium ion battery. Flexible Lithium ion batteries are made up of some components, namely; positive electrode material, negative electrode material, current collector, electrolytes and separator. Lithium ions are extracted electrochemically from positive electrode during the charge of a cell in electrolytes and are doped into a negative electrode. During discharge, lithium ions are extracted from the negative electrode and doped back into positive electrode. Electrons are concurrently extracted from one electrode and transported into another electrode. Materials are oxidized or reduced in positive and negative electrodes during storing and delivering of electrical energy. The challenges of flexible LIBs are high capacity and fast charge and discharge rates, electrode materials design (Cathode and anode), stable electrolyte. However, the fabrication of such an energy storage device remains a great challenge owing to the lack of reliable materials that combine superior electron and ion conductivity, robust mechanical flexibility, and excellent corrosion resistance in electrochemical environments 1.Present work on Flexible Lithium Ion BatteryA lot of research work has been trying to address the challenges being faced with the emerging flexible Lithium ion battery. Studies using graphene-introduced LiFePO4 cathode which gives a better charge/discharge performance to lithium ion battery as compared with other conventional additives such as carbon nanotubes suggested that this promising performance of graphene will possibly find early application as a flexible and planar conductive additive in high performance flexible lithium ion battery 2. Also, some new approach developed uses high energy density inorganic thin films that can be treated at high temperatures, resulting in the highest-performance of flexible lithium-ion batteries. The mechanical flexibility studies using paper batteries reported that using paper as separators and free-standing carbon nanotube thin films as both current collectors gives a very light weight of 0.2mg/cm2 and excellent flexibility and higher energy density (108 mWh/g) 3. Improved round-trip efficiency and good cycling ability of flexible lithium ion battery can also be achieved with the use of catalytic materials and amorphous material which aid the electron transfer efficiency. Cross-linked gel polymer electrolytes (C-GPEs) improve the stability and excellent elasticity, with almost full strain recovery after 100% stretch of flexible lithium ion battery 4.Future Perspective for Improved Efficiency and Durability of Flexible Lithium ion BatteryIf the cathode defects of flexible Lithium ion battery will have to be fully addressed, materials that will be able to withstand the temperature at which the cathode will be required to operate effectively for better performance must be a point of call. This will reduce the storage loses and improve the specific capacity. This is believed will excellently prolong the life cycle of flexible lithium ion batteries. Also, separator material that will be stable in high temperature will improve the life cycle of the battery.