A lot of people complain about short battery lifetime of their smartphones. Therefore, power-banks are very popular and even cases with power-bank are available. The biggest power-bank from Xiaomi has 20 000 mAh capacity. However, what would you say about a smartphone with 10 000 mAh battery?
Most of power-banks available on the market has capacity between 5 000 mAh and 12 000 mAh. However, Oukitel company has produced a smartphone called K10000 with 10 000 mAh battery! It can also be used as power-bank, so you can charge e.g. your iPhone 6s Plus and you still will remain 90% of battery. The full charging will take about 3.5 hours, however you will have to do this one time per 10-15 days, so it will not be burdensome.
Unfortunately specification is not so powerful, the smartphone will have 5.5 inch HD screen, quad-core MediaTek MT6735 1.0 GHz processor, 2 GB of RAM, 16 GB of internal storage, two cameras (8 MP and 2 MP). The mobile will be dual-sim and it will support LTE technology. The phone will be available in India for about Rs. 16 000 (this is an expected price).