Low-Duty-Cycle (LDC) is the most important technique in increasing the lifecycle of wireless sensor networks. This paper imports low duty cycle technology into opportunistic networks to extend the lifecycle of opportunistic networks effectively. However, the existing routing algorithms for opportunistic networks perform poorly in LDC environment. To solve this problem, this paper proposes an erasure-coding algorithm based on energy-aware (E-EC) for LDC opportunistic networks. Simulation results show that, compared with existing classical algorithms, E-EC algorithm achieves significant performance improvement in terms of life cycle and data success rate.