Preparation of Li4Mn5O12 on Porous Li0.29La0.57TiO3 via Liquid Sintering for Oxide-based All-solid-state Li-ion Secondary Battery

This paper presents a technique to form an electrochemically active interface between the oxides in an all-solid-state Li secondary battery (ASSB), via liquid sintering. Spinel-type Li4Mn5O12 (LMO) is formed on a perovskite-type Li0.29La0.57TiO3 (LLTO) solid electrolyte by heating Mn(NO3)2·6H2O, LiNO3 and LiCl. The resultant LMO, when evaluated as a positive electrode in an ASSB, exhibits a reversible capacity of 100 mAh g−1, good cyclability, and typical charge/discharge curves. LiCoO2 (LCO) is also prepared similarly, using molten salts, and a full ASSB is assembled with LCO as the positive electrode, LLTO as the solid electrolyte, and LMO as the negative electrode. The full ASSB exhibits a plateau at 1 V and discharge capacity of 60 mAh g−1 at a C-rate of C/100. When the C-rate is increased to 1 C, the capacity retention decreases below 20 % after 40 cycles; however, when the C-rate is returned to C/100, the retention recovers to 100 %. The porous LLTO supporting Li-ion conduction improves the performance of the ASSB. The effective formation of electrodes on LLTO using molten salts can facilitate the creation of ASSBs comprising oxides alone

Preparation of LiCoO2 by Molten Salts on Li0.29La0.57TiO3 Solid Electrolyte and Electrochemical Performances of the All-solid-state Li Secondary Battery

An LiCoO2 (LCO) phase is prepared on a perovskite type Li0.29La0.57TiO3 (LLTO) solid electrolyte by heating mixed lithium salts of LiNO3 and LiCl with Co(NO3)2·6H2O at 700 °C for 1 h. The resultant LCO is evaluated as a positive electrode in an all-solid-state Li secondary battery. Liquid-phase sintering using molten salts has been effective for the formation of a favorable interface between oxides in which lithium ions migrate electrochemically with reversibility. The fracture surface revealed by field emission scanning electron microscopy observation shows that the microscopic texture of the LCO consists of a dense 1 to 2 µm thick layer closely attached to the solid electrolyte over a wide area, as well as LCO spherical particles with sizes of several micrometers. The former growth has superior electrochemical activity compared to the latter. Additionally, a preferential growth plane of the LCO on LLTO is analyzed by transmission electron microscopy and the process of formation with heating is described