LG already has the claim as being the first manufacturer to market with a curved battery, which will be found in the LG G Flex; but, that doesn't mean it will be the only manufacturer or device to feature a curved battery. Samsung has the Galaxy Round with its curved screen, but it doesn't use a curved battery. However, it sounds like future curved Samsung smartphones may come with curved batteries...
Source: http://www.phonearena.com/news/Samsung-may-be-ready-to-mass-produce-curved-batteries_id48917
Source: http://www.phonearena.com/news/Samsung-may-be-ready-to-mass-produce-curved-batteries_id48917