As the Earth warms, we will need to curb our dependence on fossil fuels and switch to renewable energy. But the availability of renewable energy fluctutates through the day. So, batteries are needed to make it reliable. A recent NPR investigation found that a new type of battery technology -- vanadium redox flow battery -- that was developed in the US a decade ago, fell into China's hands due to US negligence. Now China has become the world leader in the manufacture of vanadium redox flow batteries. More in this episode