NOTE: this question is intended to give you a broader scope on electrochemistry applications and consequences. It should not take more than ~20 minutes to complete. The effective and sustainable construction of batteries in an important part of the global technology landscape. Look up the standard (nominal) voltage of a "double A" battery and suggest a redox reaction that could achieve that (or close to that) voltage. Look up the toxicity of the metals you suggested, and briefly discuss the balance between effectiveness, sustainability, and safety when designing practical chemical systems such as batteries