"Achieving the new outer coating required a set time of soaking. The accident occurred when Wang and Li forgot to remove one batch of the nanoparticles from the soaking process. That batch ended up soaking for several hours longer than intended with the result being the sulfuric acid and titanium oxysulfate mix leaked into the 50nm nanoparticles and dissolved some of the aluminum inside. What this left was a nanoparticle with a 4nm outer shell of titanium hydroxide and an inner 30nm "yolk" of aluminum.
Rather than discarding this forgotten batch, they decided to test it by building batteries using these particles. It turns out they have potentially solved the problem of using aluminum for the anodes in the battery. The extra long soak meant the anodes did not expand and contract, in fact they created a battery that over 500 charge/discharge cycles retained up to four-times the capacity of the equivalent graphite anode batteries. These batteries last considerably longer in terms of usable lifespan and, according to MIT, can hold up to three-times the energy."