High-Mass-Loading And High-Areal-Capacity LiFePO₄ And Li₄Ti₅O₁₂ Electrodes For Lithium Ion Batteries

With a dual crisis of energy shortage and deteriorating living environment,it is urgent to find new alternative energy sources.Lithium ion batteries?LIBs?are outstanding in new energy field,which have the advantages of high energy density,long cycling life,less environmental pollution,and no memory effect.LIBs have been widely used in some smart portable electronic devices,but they are still necessary to achieve higher energy density to meet higher demand.In addition to exploring active electrode materials with higher specific capacity,the energy density of LIBs could also be improved by increasing the loading of active materials.Although lithium iron phosphate?LiFePO₄?and lithium titanate composite?Li4Ti5O12?with high stability and excellent chemical properties have been widely reported and applied in practice,there are few reports on LiFePO₄ cathode and Li₄Ti₅O₁₂ anode with high mass loading and high areal capacity.Because in the electrodes prepared by traditional coating method,conductive agents usually do not have good mechanical properties,and binders usually do not have any electronic conductivity,which leads to the failure to obtain high-mass-loading thick electrodes with excellent performance.Aiming at the key technical problems of thick electrodes,this paper adopts three-dimensional integration strategy,chooses three different dimensions of carbon materials and active materials to composite,and studies their electrochemical performance.The main contents and results are as follows:?1?A 3D LiFePO₄ composite thick electrode with high mass loading was prepared using carbon fibers,graphene oxide,and Ketjen black.The interaction between heterogeneous charge materials and solution ultrasonic dispersion apparently increased the active material loading,which could reach up to 40 mg/cm².When the current density is500 mA/g,composite electrodes with an active material loading of 10 mg/cm² deliver a discharge specific capacity of 120 mAh/g after 100 cycles,which demonstrates good rate capability and cycling stability.Under the same current density,the discharge specific capacity of composite electrodes with an active material loading of 20 mg/cm² is stable around 80 mAh/g after 50 cycles.?2?3D Li₄Ti₅O₁₂ electrodes with different active materials loading?10,20 and 40mg/cm²?were prepared using carbon fibers,graphene oxide,and Ketjen black through interaction between them.When the current density is 100 mA/g,composite electrodes with different active materials loading?10,20 and 40 mg/cm²?delivered initial specific discharge capacity of 175.9,171.1,and 77.5 mAh/g respectively.The 3D composite electrode with active materials loading of 10 mg/cm² showed high capacity,good cycling stability,and rate capability,whose electrochemical performances are better than those of ordinary Li4Ti5O12electrodes.We further assemble full LIBs with 3D LiFePO₄ composite electrodes and Li₄Ti₅O₁₂ composite electrodes.The full lithium ion batteries have an initial discharge capacity of 150 mAh/g and an initial coulombic efficiency of 85.5%.Besides,the full lithium ion batteries show a good cycling stability.In conclusion,LiFePO₄ cathode and Li₄Ti₅O₁₂ anode with high mass loading and high areal capacity have been successfully fabricated in this paper.Moreover,the preparation process of the electrodes is simple and feasible,also it can be produced on a large scale and has great application prospects.