jan_jes writes: A new "yolk-and-shell" nanoparticle created by researchers at MIT and Tsinghua University in China could boost the capacity and power of lithium-ion batteries. The researchers have created an electrode made of nanoparticles with a solid shell, and a "yolk" inside that can change size again and again without affecting the shell. The new findings, which use aluminum as the key material for the lithium-ion battery's negative electrode, or anode, are reported in the journal Nature Communications. The use of nanoparticles with an aluminum yolk and a titanium dioxide shell has proven to be "the high-rate champion among high-capacity anodes." The linked article goes into much more detail about the (serendipitous) discovery.