The Application Of CO₂ Derived Carbon In Lithium/Sodium Ion Batteries

Molten salt electrochemical technology is a pollution-free method with strong driving force and fast reaction rate.CO₂ can be directly converted into carbon material in the high temperature carbonate-containing molten salt.Making realization of CO₂ emission reduction and at the same time storing the chemical energy in carbon,which can be reused as available materials in the field of energy and environment.As an advanced energy storage technique with high energy density,long cycle life and non-pollution,Li-ion batteries?LIBs?have been widely used in the portable electronic equipment and electric vehicles.However,the increasing price and resource consumption worried people to looking for alternatives of lithium-ion batteries.Benefiting from rich resource distribution in earth and similarity of properties with lithium,sodium ion battery?SIBs or NIBs?gain increasing attention.Although the energy density of SIBs is lower than LIBs',it is more attractive for its application to larger grid-level energy storage where low cost occupies the main superiority.Carbon is an important electrode material for lithium/sodium ion batteries.Making use of the CO₂ derived carbon for secondary batteries not only increases the added value of products derived from CO₂,but also guarantees the sustainable supply of high-capacity low-cost electrode materials.Herein,carbon materials,prepared by electrochemical conversion of greenhouse gas,CO₂,in Li-Na-K carbonate molten salts,are tested as electrode materials for lithium/sodium ion batteries.The effects of electrolysis temperature and cell voltage on the morphology and structure of the CO₂ derived carbon as well as electrochemical performance were systematically investigated.The relationship between morphology and electrochemical properties was established to obtain the optimal electrode materials.Detailed work were described as follows:?1?The lithium storage performance of CO₂ derived carbon prepared at different electrolytic conditions was researched.Systematically summarizing the effects of molten salt temperature and electrolytic voltage on the morphology,size,specific surface area and pore structure of carbon materials.The cyclic voltammetry inferred that the mechanism of the CO₂ derived carbon for Li storage involves both intercalation/deintercalation and surface adsorption/desorption.The small particle size and suitable surface area were contributed to the excellent performance of T450-4.5V?deposited at the temperature of 450? and at the voltage of 4.5V?:a high reversible capacity of 798 mAh g-1?more than two times of graphites' theoretical capacity?at 50 mA g-1 and 266 mAh g-1 with a stable cyclability over 500 cycles at a current density up to 500 mAg-1.?2?The sodium storage performance of CO₂ derived carbon deposited at different molten salt temperature and the effect of activation to electrochemical performance were studied.The results proved that the storage of Na+ in the carbon material mainly derived from adsorption/desorption process,the sample of T450-4.5V showed the highest capacity and good cycling stability,attributed to the advantage of abundant pores and high specific surface area.A specific capacity of 146.7 mAh g-1 was obtained after 600 cycles at 500 mA g-1 in the voltage range of 0?3V.The activation process have significantly increased the capacity to 188.2 mAh g-1 obtained at 500 mA g-1 after 1000 cycles.?3?The feasibility of CO₂ derived carbon prepared at different molten salt temperature used as conductive additive for cathode material of lithium ion battery was explored.Comparing with Super P,the capacity,the reversibility and the electrochemical impedance of LiFePO4/C electrodes were evaluated.The LiFePO4/C electrode exhibited higher capacity?more than 120 mAh g-1 after 60 cycles?when T550-4.5V and T650-4.5V used as the conductive additives.However,the reversibility and electrochemical impedance remained to be improved.