Methods and systems for depowering a rechargeable battery in a rapid, yet controlled, manner. The methods comprise (i) providing a depowering medium comprising expanded graphite (and optionally, one or more dispersible non-ionic electric conductors) dispersed in a substantially non-ionic aqueous medium; (ii) contacting terminals of the battery with the depowering medium; and (iii) maintaining contact between the depowering medium and terminals for a period of time sufficient to depower the battery. The systems comprise (i) the depowering medium; and (ii) a container configured to receive a battery and the depowering medium such that the battery body is contacted with the depowering medium prior to the terminals.