Synthesis Of Cobalt Tetrapyridinoporphyrazine/Carbon Nanocomposites For Catalytic Performance Of Lithium/Thionyl Chloride Battery

Lithium/thionyl chloride（Li/SOCl₂）battery is a kind of inorganic non-aqueous electrolyte primary battery,which has a stable voltage platform,wide operating temperature range,long storage life and no heavy metal elements.At present,Li/SOCl₂ battery has two problems to be solved.The first is high-current to meet military equipment.The continuous high-current operation of the battery requires that the reduction rate of the SOCl₂ be accelerated.The second is that during the discharge process,the surface of the cathode is gradually covered by bulk lithium chloride particles.Lithium chloride particles are the insulating layer on the carbon cathode,leading to the termination of the chemical reaction inside the battery.In this article,five kinds of catalytic materials were designed.Catalysts can not only increase the reduction rate of SOCl₂,but also cause the rapid nucleation of the discharge product lithium chloride,thereby minimizing the size of lithium chloride particles.At the same time,two methods of adding catalyst were studied:injection method to electrolyte and roll forming method to carbon cathode.The specific work is as follows:A hovenia acerba-like assembly constructed with cobalt tetrapyridinoporphyrazine of thickness of 5～15 nm is anchored on acid-functionalized multi-walled carbon nanotubes（CoTAP/MWCNTs）,which were prepared using an in situ solid synthesis process.The discharge time of Li/SOCl₂ batteries with a voltage greater than 3.15 V catalyzed by CoTAP/MWCNTs is found to be 11 minutes longer than batteries without catalysts and 4 minutes longer than those catalyzed by CoTAP alone.The impedance analysis demonstrates that the assembly of CoTAP/MWCNTs can benefit the diffusion of SOCl₂ via the passive cathode film,enhancing the voltage platform of the battery.The bulk cobalt tetrapyridinoporphyrazine was recrystallized on the surface of graphene by prefabrication method.The graphene-supported cobalt tetrapyridinoporphyrazine（CoTAP/Gr）nanocomposites were prepared.The size of cobalt tetrapyridinoporphyrazine nanoparticles about 50 nm are uniformly anchored on the surface of graphene through physical adsorption.The discharge time of the Li/SOCl₂ battery catalyzed by the CoTAP/Gr nanocomposites is about 38 minutes,and the voltage platform is 0.40 V higher than the battery without the catalyst.The cobalt tetrapyridinoporphyrazine nanoparticles accelerate the reduction of SOCl₂,thereby increasing the battery’s discharge time and voltage platform.At the same time,graphene composed of six-membered carbon ring has a catalytic performance on SOCl₂.Space-confined construction of cobalt tetrapyridinoporphyrazine nanoparticles anchored on functional-activated carbon（NCA）composites were prepared by in situ solid phase synthesis as catalysts of carbon cathode.On the molecular level,the π-π conjugate system is further enhanced by forming C-O-Co bond between the Co atoms of cobalt tetrapyridinoporphyrazine and the oxygen-containing functional groups of functional-activated carbon.On the structure of carbon electrode,the pore volume with NCA composites is 0.70 mL/g more than without catalysts,and the range of pore size is 2 nm～2 μm,mainly because of bulk activated carbon.The resulting NCA composites exhibit the longest time about 43 minutes,and the capacity is the largest up to 21.67 mAh,almost 2 times that of the battery without catalysts.Meanwhile,the internal resistance of the battery catalyzed by the NCA composites（24.06 Ω）is 0.40 times lower than that without catalysts,and the reduction peak of cyclic voltammetry is the largest about 2.357 V,moving towards high potential.Copper-doped cobalt tetrapyridinoporphyrazine（Co/CuTAP）nanocomposites were prepared by recrystallization method.The discharge time of the battery catalyzed by Co/CuTAP nanocomposites is the longest,about 38 minutes.The average voltage platform of the Co/CuTAP nanocomposites added to the battery is 0.20 V higher than that of the copper tetrapyridinoporphyrazine.The battery with Co/CuTAP nanocomposites has the largest reduction potential,about 2.398 V,indicating that the electrode has good catalytic activity.Due to the copper tetrapyridinoporphyrazine in the Co/CuTAP nanocomposites hinders the orderly arrangement of the cobalt tetrapyridinoporphyrazine,defects such as vacancies and doping are formed.The defects lead to an increase in the number of active sites exposed by the Co/CuTAP nanocomposites,which can speed up the reduction of SOCl₂.Space-confined construction of copper doped cobalt tetrapyridinoporphyrazine nanoparticulates anchored on activated carbon（Co/CuTAP-AC）were prepared by an in situ solid synthesis method.Large-size LiCl particles deposited on the carbon cathode of lithium thionyl chloride battery during discharge are mainly limited by the sluggish kinetics,decreasing the voltage platform and service life.After discharge,the surface of the carbon cathode with Co/CuTAP-AC composites displays LiCl particles approximately 200 nm,which is only a fifth of the size without catalysts.Moreover,a large number of nano LiCl particles appear inside compared to the catalyst free.The fast reaction kinetics of SOCl₂ with Co/CuTAP-AC composites is favorable for the nucleation of LiCl particles.Meanwhile,the electrolyte resistance,the surface film resistance and the charge transfer resistance of the battery are reduced to approximately 77%,and the discharge time is 37 minutes higher than that without catalysts.