Disclosed are batteries and methods of manufacturing batteries with improved energy densities. In some embodiments, a first cathode current collector and a first anode current collector are provided on a first side of a substrate. A second cathode current collector and a second anode current collector are provided on a second side of the substrate. A laser is used to form: a first channel through the substrate between the first cathode current collector and the second cathode current collector, and a second channel through the substrate between the first anode current collector and the second anode current collector. A cathode interconnection is formed, via the first channel, between the first cathode current collector and the second cathode current collector. An anode interconnection is formed, via the second channel, between the first anode current collector and the second anode current collector.