Preparation And Properties Of Novel Organic Cathode Based On Naphthalimide For Lithium-ion Batteries

Organic carbonyl compounds are considered to be promising electrodes materials of secondary batteries for their outstanding properties of high specific capacity, low-cost, easily accessible and recyclable. However, to become ideals electrode materials, the organic carbonyl compound should overcome two serious problems. One is the easily dissolve in the solvent of common electrolyte, which could serious affect the electrochemical property of the compound and lead to a fast capacity decay of batteries; the other is the inherent insulativity of these compounds, with low electroconductivity, lithium ions transfer in electrode materials are difficult and the structure of compound could be destroy when charge and discharge with high rate current. In this paper, we choose organic carbonyl compounds of 1,8-naphthalene anhydride and 3,4,9,10-Perylenetetracarboxylic acid anhydride as research object, through functional group substitute and molecular structure design to optimizing the compounds and preparing electrode materials of lithium batteries with excellent electrochemistry property. Constant current charging-discharging method and cyclic voltammetry were used to test the electrochemistry property of the organic carbonyl compounds. The main contents of our work are as follow:(1) The carbonyl compound of 1,8-naphthalimide (NI) was easy prepared by substituted the anhydride group of 1,8-naphthalene anhydride with imide group. Both of the electrochemistry property of these two compounds were test. The result reveal that the electrochemistry property of carbonyl compound 1,8-naphthalimide were better than that of 1,8-naphthalene anhydride.1,8-naphthalimide displayed a initial capacity of 230 mAh/g and a better rate capacity. While the dissolve problem of the compound still serious.(2) To solve the problem of dissolution, dimer of 1,8-naphthalimide which name ethidene-naphthalimide (ENI2) and N-N-diamido-naphthalimides (NI2) respectively, with different molecular structure were prepared. The dimer ENI2 with coplanar structure presented a moderate discharge potential (2.2 V) and a higher initial capacity of 280 mAh/g. This compound retain half of its initial capacity after 45 cycles at a current density of 0.25 C (1 C=250 mA/g), which is much better than its monomer NI and other dimer NI2 (nonplanar structure) while these two compounds almost lost their capacity under the same conditions. Furthermore, after charge/discharge at high current density (e.g. at the current density of 2 C) the capacity recover of the cathode can reaches to 170 mAh/g, which indicated high capacity restorability. The excellent electrochemistry property of ENI2 could be ascribed to the coplanar construction of this molecular, which could enhance the intermolecular interactions.(3) Organic carbonyl polymer of triethylamine-perylene were prepared with carbonyl compound of 3,4,9,10-Perylenetetracarboxylic acid anhydride. The result of electrochemical test reveal that the polymer presented a high initial capacity of 160 mAh/g at a charge/discharge current density of 10 mA/g, after 50 cycle the specific capacity still retain 132 mAh/g. Furthermore, after charge/discharge at high current density (e.g.1000 mA/g) the capacity recover of the cathode can reaches to 125 mAh/g, which indicated high capacity restorability. Cyclic voltammetry test of the compound presented a fast reaction kinetics.