Children's education AND Rechargeable lantern

Prof Vijay Modi at Columbia has come up with a rechargeable lantern.
http://www.columbia.edu/cu/mechanical/modi/ColumbiaUniversityLanternBrochure.pdf

The idea he has is that a child will carry this like a lunch box to school.
At school it will get plugged into a charging unit. For 8 hours.
When the pack is taken back home, it can power a lantern for up to 7 hours.
Cost 25-30$
http://www.columbia.edu/cu/mechanical/modi/ColumbiaUniversityLanternBrochure.pdf
Modi says it would encourage children to come to school and encourage parents to send them to school.

Modi is connected with Sachs' Earthwatch Institute at Columbia.

I wondered if we could come up with something better, one that would not have the weight of a lead-acid battery; and one that is more benign at the end of its useful life.