He Zeqiang

Thin-film lithium-ion battery derived from Li1.3Al0.3Ti1.7(PO4)3 sintered pellet

Abstract Thin-film lithium-ion battery of LiMn 2 O 4 Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 /LiMn 2 O 4 was fabricated using Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 sintered pellet as both substrate and electrolyte. Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 sintered pellet was prepared by sol-gel technique, and the thin-film battery was heat-treated by rapid thermal annealing. Phase identification, morphology and electrochemical properties of the components and thin-film battery were investigated by X-ray diffractometry, scanning electron microscopy, electrochemical impedance spectroscopy and galvanostatic charge-discharge experiments. The results show that Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 possesses a electrochemical window of 2.4 V and an ionic conductivity of 1.2 ×10 −4 S/cm. With Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 sintered pellet as both substrate and solid electrolyte, the fabricated thin-film battery with an open circuit voltage of 1.2V can be easily cycled.

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.

Characterization of rapid thermally processed LiMn2O4 thin films derived from solution deposition

Abstract Cathode material LiMn 2 O 4 thin films were prepared through solution deposition followed by rapid thermal annealing. The phase identification and surface morphology were studied by X-ray diffraction and scanning electron microscopy. Electrical and electrochemical properties were examined by four-probe method, cyclic voltammetry and galvanostatic charge-discharge experiments. The results show that the film prepared by this method is homogeneous, dense and crack-free. As the annealing temperature and annealing time increase, the electronic resistivity decreases, while the capacity of the films increases generally. For the thin films annealed at different temperatures for 2 min, the thin film annealed at 800 °C has the best cycling behavior with the capacity loss of 0.021% per cycle. While for the thin films annealed at 750 °C for different times, the film annealed for 4 min possesses the best cycling performance with a capacity loss of 0.025% per cycle. For the lithium diffusion coefficient in LiMn 2 O 4 thin film, its magnitude order is 10 −11 cm 2 ·s −1 .

Characterization and electrochemical properties of LiMn2O4 thin films prepared by solution deposition

LiMn2O4 thin films were prepared by solution deposition using lithium acetate and manganese acetate as raw materials. The phase constitution and surface morphology were observed by X-ray diffraction and scanning electron microscopy. The electrochemical properties of the thin films were studied by cyclic voltammetry, charge-discharge experiments and impedance spectroscopy in 1 mol·L−1 LiPE6/EC-DMC solution using lithium metal as both the counter and reference electrodes. The films prepared by this method are of spinel phase. The lattice parameter increases with the annealing temperature and annealing time. The film annealed at 750°C for 30 minutes has the highest capacity of 34.5 μAh·cm−2·μm−1, and its capacity loss per cycle is 0.05% after being cycled 100 times.

Electrochemical Performance of LiMnBO3/C Composite Synthesized by Wet Impregnating Method

Abstract Hexagonal-LiMnBO 3 /C composite was prepared by a wet impregnating method using the 3D-network ketchen black (KB) as both a temple and a conductive framework. The crystal structure, morphology and specific surface area were characterized by X-ray diffraction, scanning electron microscopy and nitrogen sorption measurements, respectively. The electrochemical properties of the composite were studied by galvanostatic charge/discharge and cyclic voltammetry measurements. Results show that when tested at C/20 rate for Li ion insertion/extraction properties, LiMnBO 3 /C composite exhibits good cycle capability with discharge capacity retention of 87.4% at the 30th cycle. As the current rate increases from C/20, C/10 to C/5, good rate capability is obtained for all rates with initial discharge specific capacities of 138.8, 124.5 and 100.5 mAh·g −1 , respectively.