Preparation And Properties Of Flexible Lithium Ion Battery Based On Block Copolymer

The emergence of flexible wearable,implantable communication,display,sensing,medical and other electronic devices has placed new demands on the energy storage device.At present,the rigid materials used in most lithium ion batteries limit the ability of the battery to be flexibly deformed.Therefore,in order to prepare a flexible battery,it is necessary to prepare a flexible material instead of the conventional rigid material to prepare a battery.Employing flexible current collector as the supporting for active material is important to realizethe flexibility of the lithium ion battery.When the conventional lithium ion battery experiences a large deformation,the electrode active material may fall off from the surface of the metal current collector,resulting in a decrease in battery performance.In order to make lithium ion batteries flexible,electrolytes and packaging materials also need to be studied.The liquid electrolyte used in the conventional lithium ion battery has a risk of liquid leakage.The ester or ether compound contained in the liquid electrolyte is extremely flammable.Once the liquid leakage occurs,the battery is a great safety hazard.At present,the stainless steel casing of the cylinder or square type lithium ion battery has almost no flexibility.The aluminum plastic film packaging material used in the soft lithium ion battery can satisfy the bending performance to a certain extent,but its tensile performance is almost zero,so the use of flexible batteries is limited to a certain extent.In order to solve the problems of current collector and electrolyte,polystyrene-polybutyl acrylate-polystyrene(SBAS)and polystyrene-polymethyl acrylate-polystyrene(SMAS)with different molecular weights were synthesized by reversible addition fragmentation chain transfer radical polymerization(RAFT).The SBAS/SWCNTs composite elastomer was prepared based on the above polymer and used as a flexible lithium ion battery current collector.The resistivity can reach 23.43Ω cm-1 in the unstretched state.The SMAS swelling electrolyte can be used to prepare the gel electrolyte.Its ionic conductivity can reach 3.54×10-4 cm-1.The battery prepared from the above flexible material still exhibited good battery performance under the condition that the electrode active material content reached 95%.There is still a certain gap between the SBAS/SWCNTs composite flexible current collector and the metal current collector.The application of the flexible current collector to the flexible battery has a great influence on the impedance performance of the battery.In this work,AgNWs with better conductivity are coated on the surface of the flexible current collector,which changes the transmission path of electrons from the external circuit to the active material.It greatly reduces the impedance of the flexible battery.Most modified lithium ion batteriesstill retainperfect battery performance while bending,except that when the bending radius was reduced to 5 mm,the battery performance degraded due to the limitation of the battery outer packaging material.In order to overcome the limitations of the outer packaging material,it is attempted to prepare a stretchable battery by using a flexible and stretchable PDMS as an outer package.The battery can be successfully charged/discharged and illuminate the LED bulb,but its electrochemical performance is poor due to the limited airtightness of the outer packaging material.Its discharge specific capacity decreases to near 0 after the battery was cycled at 0.2 C for about 10 times.