Lithium-ion batteries continue to improve in all respects: Capacity, charge rate, cost, and safety.
Safety has been a vexing issue, since failure of these types of batteries can be dangerous. This concern, as well as the cost, has been limiting the wide-spread adoption of this technology in electric vehicles. That is changing.
A promising trend is toward Lithium Titanate batteries. This technology has made great strides in resolving many of the issues common to other types of Li-ION batteries. They can be charged very quickly (at a rate of 50C for example). According to one manufacturer: In testing, a 35 kWh battery pack was charged in ten minutes. They also provide advantages in longer life with up to 25,000 deep cycles, higher power density than other nanostructured cells, wider operating temperatures, and most importantly, greater stability under electrical and mechanical stress (it is said that the cells cannot catch fire). Naturally, they are also more expensive.The advances don't just apply to the automotive industry. If the trend continues, in the near future, we may be designing circuits powered by Li-ION clothing.