Multilayered 1T-MoS2 nanosheets are desired as an electrode material for supercapacitors. There is no effective way to synthesize pure, clean, highly ambient-stable, multilayered 1T-MoS2 which results in the absence of intrinsic electrochemical storage mechanisms. Here, we report the intrinsic electrochemical storage mechanisms in three types of multilayered MoS2 nanosheets including 2H-MoS2, MoS2-CTAB and highly ambient-stable pure 1T-MoS2 nanosheets by magneto-hydrothermal synthesis. We reveal that layer spacing enhancement leads to an obvious improvement in specific capacitance (20 F g-1 increased to 173 F g-1) and enhanced hydrophilicity as well as metallic characteristics can further improve the specific capacitance (173 F g-1 increased to 320 F g-1). Furthermore, ex situ XRD tests show the expansion of interlayer spacing during charging of 1T-MoS2 electrodes, suggesting the advantages of multilayered nanosheets used as electrodes for supercapacitors due to the enhanced capacitance from intercalation. All-solid-state flexible supercapacitors assembled with 1T-MoS2 obtained by magneto-hydrothermal synthesis exhibit a high areal capacitance of 310 mF cm-2 at 1 mA cm-2, excellent flexibility and outstanding cycle stability, and the capacitance retention can remain above 97.3% and 84.1% after 10000 and 30000 cycles, respectively. These results unveil the electrochemical storage mechanisms in pure, clean, highly ambient-stable 1T-MoS2 multilayered nanosheets, serving as promising supercapacitor electrodes for all-solid-state supercapacitors with excellent performance.