Effect of Li salts on the properties of Li1.5Al0.5Ti1.5(PO4)3 solid electrolytes prepared by the co-precipitation method

Abstract

In this study, Li1.5Al0.5Ti1.5(PO4)3 (LATP) solid electrolyte is prepared through co-precipitation using Li3PO4 and Li2C2O4 salts. The co-precipitates are heated at 800°C to obtain precursor powders. The precursor powders are then ball-milled to reduce the particle size to prepare dense LATP pellets. Li salts significantly influence the morphology and crystallinity of the precursor powders. The precursor powder prepared from Li3PO4 possesses a smaller particle size and lower crystallinity of LATP compared with Li2C2O4. The soft, low-crystallinity powder from Li3PO4 is easily crushed by the ball-milling. The average particle size is reduced to 30 nm, while the average size of particles from Li2C2O4 is 120 nm after the ball-milling. The small particle size promotes sintering of LATP pellets. As a result, LATP pellets prepared from Li3PO4 show higher Li ion conductivity than those from Li2C2O4 due to their high sinterability and large grain size (low grain-boundary resistance). The Li ion conductivity is 2.0 × 10−4 S cm−1 after sintering at 1050°C for 6 h. It is concluded that the Li source used to form the co-precipitate greatly influences the properties of sintered LATP pellet. The Li source is one key to obtain LATP with high Li ion conductivity.