<human>:  What is the difference between a lithium ion battery and a lead acid battery?
<bot>: The main difference between a lithium ion battery and a lead acid battery is the composition of their electrodes. Lithium ion batteries use lithium as their positive electrode, while lead acid batteries use lead dioxide for the positive electrode and sponge lead for the negative electrode. Additionally, lithium ion batteries are more efficient and have a higher energy density than lead acid batteries.