This study aims to develop aluminum ammonium sulfate dodecahydrate (NH4Al(SO4)(2)center dot 12H(2)O, AASD)-based novel composite phase change materials (CPCMs) for thermal energy storage. Forty types of AASD-based CPCMs were developed by mixing AASD with 1 wt % CF (calcium fluoride) (or 2 wt % CF), 2 wt % xanthan gum (XG), and nanoparticles (alpha-ION, gamma-ION, TDN, CN, or MWCNTs-OH; the mass ratios of the nanoparticles to XG were 1:8, 2:8, 3:8, or 4:8). The effect of multiple additives on the heat storage/release performance of AASD was observed and analyzed by the melting and solidification experiment (MSE). CPCMs with good heat storage/release performance were achieved, which were further characterized by the thermal cycling test. It was shown that the optimal formulation of the CPCM with good thermal reliability was AASD/2 wt % XG/2 wt % CF/4:8 TDN:XG. The structure of AASD was not destroyed by the addition of the above additives. During the process of 30 thermal cycles, the melting temperature, crystallization temperature, and latent heat were 89.4-91.5 degrees C, 56.6-69.2 degrees C, and 180.9-220.9 J/g, respectively. The thermogravimetric (TG) test demonstrated that the novel CPCM possessed excellent thermal stability during the operating temperature. The novel CPCM obtained with this simple preparation method and with excellent thermal performance can be used in applications such as solar thermal storage and waste heat recovery.