Key Engineering Materials Vol. 566

Abstract: LiFePO₄/C powders were synthesized by ultrasonic spray pyrolysis using carbon powder instead of organic substances as the carbon source. LiFePO₄ (LFP) powders containing different types of carbon powders were prepared and used as cathode active materials in lithium ion batteries. The charge-discharge properties of lithium ion batteries with LFP, LFP/AB, and LFP/CNT powders as the cathode material were worse than those of the battery with LFP/sucrose powder as the cathode active material.

Abstract: Plate-like LiMnPO₄ particles were prepared by polyol method. The chemical and physical properties of plate-like LiMnPO₄ particles were characterized by XRD and SEM. The thickness of plate-like LiMnPO₄ particles was approximately 35 nm. XRD pattern of plate-like LiMnPO₄ was good agreement with orthorhombic olivine structure. The first discharge capacity of C/LiMnPO₄ cathode was approximately 95 mAh/g. 99.9 % of initial discharge capacity was maintained after 100 cycles.

Abstract: Lithium nickel manganese oxide, LiNi_0.5Mn_1.5O₄, a cathode material for lithium-ion batteries was synthesized by a microwave heating method. Synthesized samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical properties. The results revealed that spinel LiNi_0.5Mn_1.5O₄ powders can be directly synthesized by microwave heating. The precursor prepared using 48 to 64 g of PVA solution would be best to synthesize LiNi_0.5Mn_1.5O₄ successfully by microwave heating.

Abstract: SnO₂/Fe₂O₃ nanocomposites were successfully synthesized by microwave heating. SEM-EDX and XRD analyses and Raman spectroscopy revealed that nanosized SnO₂ was deposited on rod-shaped α-Fe₂O₃ crystals. The SnO₂/Fe₂O₃ nanocomposites worked as a rechargeable electrode material. The initial insertion capacity of the SnO₂/Fe₂O₃ nanocomposites achieved 1522 mAh/g that is larger than the theoretical capacity, and the rechargeable capacity at 10 cycles was 862 mAh/g. The initial charge-discharge reaction of the SnO₂/Fe₂O₃ nanocomposites was caused by the redox reactions of SnO₂ and Fe₂O₃ and alloying-dealloying reaction of Sn with Li.

Abstract: Li₄Ti₅O₁₂ powders were synthesized via the solid state reaction of Li₂CO₃ and spherical composite powders of carbon and TiO₂ (denoted by C/TiO₂) with different microstructures. These C/TiO₂ powders were synthesized by spray pyrolysis using various organic acid aqueous solutions. The particle characteristics of the resulting carbon composite Li₄Ti₅O₁₂ (denoted by C/Li₄Ti₅O₁₂) powders were determined using SEM, XRD, and DTA-TG. DTA-TG showed that the carbon content of all Li₄Ti₅O₁₂ powders. was around 3 wt%. XRD revealed that the spinel structure (Fd3m) was obtained by heating at 750 °C under N₂ atmosphere. The initial rechargeable capacity of the C/Li₄Ti₅O₁₂ powders formed using citric acid was approximately 170 mAh/g at 1 C. The rechargeable capacity of the C/Li₄Ti₅O₁₂ powders decreased with an increase in the rechargeable rate. The anodes maintained over 90% of their initial discharge capacity after 200 cycles at 1 C. The C/Li₄Ti₅O₁₂ powders also demonstrated high cycle stability at 50 °C. It was found that rechargeable capacity was influenced by the particles microstructure, but cycle stability did not depend on the microstructure.

Abstract: A porous titania was synthesized by spray-drying of titania nanosheets exfoliated by (C₄H₉)₄NOH. Nitrogen adsorption-desorption isotherms showed that the porous titania has a mesoporous structure composed of slit-shaped pores. The porous titania acted as a rechargeable active material in a liquid organic electrolyte lithium cell. An initial lithium insertion capacity was about 150 mAh/g (cut-off voltage of 1.0 V), which approximately correspond to the composition of Li_0.45TiO₂.

Abstract: Electrochemical properties of restacked nanosheets (RS-LDH) of nickel-aluminum layered double hydroxide were investigated for the first time. RS-LDH was prepared by delaminating nickel-aluminum layered double hydroxide powder (powder LDH) into nanosheets and restacking them. RS-LDH and powder LDH showed same discharge capacity of 230 mAhg¹ at a current density of 500 mAg¹, but RS-LDH showed a larger capacity than powder LDH at a large current density of 1000 mAg¹. This increase in capacity was assumed to be attributed to the increased specific surface area and ion conductivity.

Abstract: Fe₂O₃/Ga₂O₃ composite and GaFeO₃ electrodes worked as rechargeable electrode materials for lithium-ion batteries, whereas their capacities were gradually decreased with increasing of cycle number. The initial Li insertion capacities (cut-off voltage: 0.01 V) were 1643 mAh/g for Fe₂O₃/Ga₂O₃ composite and 1196 mAh/g for GaFeO₃, respectively. Despite same Fe/Ga atomic ratio, Fe₂O₃/Ga₂O₃ composite showed a higher capacity than that of GaFeO₃ over the 50 cycles.

Abstract: Li_0.55Na_0.03Mn_0.5Ni_0.25Ti_0.25O₂ was prepared via Na/Li ion exchange from Na_0.7Mn_0.5Ni_0.25Ti_0.25O₂ as a starting compound. Li_0.55Na_0.03Mn_0.5Ni_0.25Ti_0.25O₂ is a layered rocksalt-type oxide with the O3 structure. The electrochemical lithium insertion/extraction properties of O3-Li_0.55Na_0.03Mn_0.5Ni_0.25Ti_0.25O₂ exhibits a reversible capacity of approximately 190 mAh g^-1 in the voltage range between 2.0 and 4.8 V. The voltage profile consists of two plateaus around 4.0 and 3.0 V. The layered structure remains unchanged and does not transform to the spinel structure during cycling.

Abstract: Spherical Li₂Ti₃O₇ precursor powders were successfully prepared by spray pyrolysis. X-ray diffraction analysis revealed that the ramsdellite phase was obtained by calcining at 1100 °C for 3 h under an argon/hydrogen (95/5 %) atmosphere. The Li₂Ti₃O₇ anode exhibited higher rechargeable capacity and excellent cycle stability. The rechargeable capacity of the Li₂Ti₃O₇ anode was approximately 168 mAh/g at 0.1 C. The discharge capacity of the Li₂Ti₃O₇ anode after 100 cycles was approximately 90% of the initial discharge capacity.