Ling Yulin

Electrochemical Study of Monoclinic Li3V2(PO4)3 in the Voltage Range of 1.5∼3.0 V

Abstract The electroactive lithium vanadium phosphate, monoclinic Li 3 V 2 (PO 4 ) 3 [space group 14(P21/n)] has been synthesized by a solution route. The microstructure and electrochemical properties of the samples were characterized through combination of X-ray diffraction and galvanostatical discharge/discharge. Preliminary electrochemical evaluation indicates that this phosphate undergoes reversible lithium insertion reactions at average potentials of 1.81 and 3.77 V, and a complex series of two-phase transitions were observed during lithium extraction and insertion in the voltage range of 1.5∼4.3 V. Constant current cycling conducted at C/5 and in the voltage range of 1.5∼3.0 V is indicative of the longer term stability of the lithium insertion reactions evidenced by minimal capacity fade over the first 50 charge-discharge cycles. Therefore Li 3 V 2 (PO 4 ) 3 maybe used as both cathode and anode for fabrication of a symmetric lithium-ion battery, and the lithium insertion in the voltage region of 1.5∼3.0 V could serve as a built-in overdischarge safety valve.

Synthesis and Viscosity Behavior of Poly(diallylmethylbenzylammonium chloride)

Poly(diallylmethylbenzylammonium chloride)(PDAMABC) was synthesized using methylamine,allyl chloride,NaOH,benzyl chloride and 2,2′-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride as raw materials.The structure of PDAMABC was characterized by FT-IR,1H NMR and elemental analysis.The viscosity behaviors of the polymer in sodium chloride,potassium chloride,potassium bromide,calcium chloride,magnesium chloride,magnesium sulfate and sodium sulfate solutions were investigated.The results show that the yield of diallylmethylamine increases from 72.79% to 83.41% by reusing the water phase and the collected distillate with low boiling point;the yield of diallylmethylbenzylammonium chloride is high and the product has a good water-solubility using the mixed solvents with a volume ratio in the range of 1∶3～2∶3 as solvents.The reduced viscosity of PDAMABC decreases with increasing the concentration of added salt.In 0.1 mol/L NaCl solution,it behaves as a polyelectrolyte with a mass concentration below 0.03125 g/L,and a neutral polymer when the concentration is above 0.125 g/L.The influence order of added salts is as follows:Na2SO4NaClKClMgSO4MgCl2CaCl2KBr.The shielding effect of anion to quaternary ammonium cation is the main reason for the decrease of reduced viscosity.