One of the greatest challenges besetting the development of Lithium (Li) ion battery technologies these days is the difficulty of fast charging.
It is even more difficult to maintain a high energy density battery within a flexible and compact design. An energy dense battery within a small, confined space runs a higher risk of explosion due to volumetric expansions within the anode material, which is traditionally graphite. However, given the strong demand for electric vehicles and wearable electronics, it is crucial that we surmount this challenge.
You can find more details at https://www.sutd.edu.sg/Research/Research-News/2016/1/Low-dimensional-nanomaterials-for-energy-storage-a