This work describes a new strategy to achieve both safe and energy-dense battery (SEB) cells, as schematically sketched in Fig. 1, where the cell resistance is plotted against the inverse of temperature. First, a passivated cell is judiciously designed and built by using highly stable materials and by creating exceptionally stable EEIs, as characterized by higher charge-transfer resistance (Rct) and higher direct-current resistance (DCR). This is illustrated in Fig. 1 by the line from point a (the conventional Li-ion cell design) to point b (the SEB cell design). It follows that these resistive SEB cells are inherently stable and safe, as demonstrated by nail penetration, short circuiting, and high-temperature storage. Second, in order for SEB cells to deliver high power during operation, they are heated instantaneously before operation, say from room temperature to 60°C, so as to recover acceptable operational DCR and ultimately battery power, going from point b (at room temperature) to point c (at an elevated temperature such as 60°C) in Fig. 1. This power on demand through rapid thermal stimulation is opposed to standby power in the present-day LIB cells, where the high-power EEIs need to be ever present. Rapid cell heating at a speed of 1° to 5°C/s has been made possible by a self-heating structure discovered by Wang et al. (1), in which a micrometer-thick nickel foil is inserted in a stack of anode-separator-cathode assemblies for uniform and internal heating. Thus, heating from room temperature to 60°C for battery operation conveniently takes only 10 to 20 s.