Composite materials for energy storage such as powders, electrodes or battery stack often require probing their bulk chemical/morphological properties, which remains challenging so far with conventional analytical methods. In this work, Ar + milling cross-section is proposed to reveal the intrinsically buried bulk information of three different composites without physical/chemical change. Then, nano-Auger/scanning electron microscopy (SEM) analysis is proposed to investigate their bulk properties at both micro-and nano-scales. For MnCo-based powders with micrometric particles, it allowed revealing the bulk porosity and the bulk nano-or micro-Mn/Co distribution. For micrometer thick TiSnSb-based electrodes, it allowed proving the conversion reaction over long term cycling (i.e. the participation of the electrochemically inactive Ti) while revealing the TiSnSb particles morphological evolution (shell to core spreading/pulverization into porous structure) and SEI formation inside the porous TiSnSb. For PEO-based solid battery stacks, the cross-section allowed revealing well-defined interfaces so that reliable interfaces analysis can thus be perform. Advantage/limitation of this cross-section nano-Auger/SEM approach are also discussed. Overall, this work opens the door for future development of Ar + milling cross-section and Auger analysis as powerful tools to reveal/study buried chemical/morphological properties at micro-and nano-scales even beyond the energy storage field.