Stability, morphological transformation and flocculability investigation of planar tridecameric Al13(OH)24(H2O)2415+

•Transformation from P-Al13 to K-Al13 in aqueous solution is temperature-dependent.•Transformation from P-Al13 to K-Al13 can completely be inhibited at temperature below 5°C.•Flocculability of P-Al13 dramatically decline after transforming to K-Al13.•P-Al13 is a promising and highly efficient coagulant for water purification.•Stability of P-Al13 is crucial for its practical application for water treatment.