An implantable medical device (IMD) including a nonhermetic battery is described. The IMD includes components and a power source module that includes the nonhermetic battery. The IMD also includes a barrier to substantially impede movement of substances from the nonhermetic battery to the components. The barrier may include a hermetic feedthrough, a gel, a polymer, or a solid electrolyte within the nonhermetic battery, and a seal member. The barrier may also be a material that encapsulates the nonhermetic battery and a getter within the IMD. In some embodiments, the IMD comprises a modular IMD including an interconnect member. In that case, the barrier may include a material that fills at least a portion of a void defined by the interconnect member. A length and a cross-sectional area of the interconnect member may also act as a barrier.