Lithium ion research continues in the R&D labs of many consumer-battery makers. And university labs across the country have churned out paper after paper on the possibilities of graphene, a single-atom-thick sheet of graphite that has the potential to store and transmit energy (though any use of graphene for consumer batteries is still a long way off). But the U.S. government (like many other national governments) has provided almost no funding for consumer battery research, instead putting money into research for vehicle and military-use batteries.
It's Not Just the Battery, Though
Designing a mobile device is no longer just about perfecting its computing power, design, and user interface; it's about doing all those things with far less power. At some point, consumers' desire for faster data plans and monster multitasking capabilities will be overtaken by the simple need for a device that can remain in operation for at least one full workday.
Smartphone screens are getting larger and supporting higher resolutions, both of which suck power like crazy. Lowering your screen's brightness might help eke a few extra minutes out of your battery, but Apple, HTC, Motorola, and other major phone manufacturers are unlikely to move to smaller or duller screens anytime soon. Nevertheless, some (including Samsung and LG Electronics) are focusing on making new types of displays that are no dimmer but use less power.
Another major power drain relates to increasingly complex apps, which impose ever-steeper processing requirements. Most smartphones contain Bluetooth, Wi-Fi, and GPS radios inside, and in many instances these components operate simultaneously. The GPS radio, in particular, is a notorious battery killer: You can see the battery bar getting shorter as you run your navigation app. Newer phones add a 4G radio chipset, which requires a lot more processing power to decode far greater amounts of data encoded in the LTE wireless spectrum. On top of all that, new 4G phones have two different chip sets, to connect with a 4G spectrum and with the carrier's older 3G network. As a result, you can count on your battery to deliver only about a day of juice to your phone, if you're lucky.
One consequence of runaway power consumption is that the makers of mobile processors are feeling a lot of pressure to produce more-efficient chips for phones.