Fusing semiconductor and nonmetal into a high conductive wide-range solid solution alloy for Li-ion batteries

Abstract Developing large capacity electrode with fast charging capability has always been our goal for high-energy Li-ion batteries. To design a superior electrode, large enough capacity, suitable voltage plateau and good ionic/electronic conductivity need to be taken into account at the same time. Herein, by fusing the semiconductor Ge into nonmetal P, a novel metallic GexP60-x solid solution with wide range tuneable region is proposed, which is proved a kind of Ge-P binary alloy instead of typical ionic/covalent compound. The synthesized GexP60-x is not a metal phophide, which is in contradictory to our conventional view. Attributed from its unique phosphorus-like layered structure, those GexP60-x alloys possess a high conductivity (∼2.4 × 106 S/m). More specially, the Ge-P interaction is not a strong covalent bond like metal phosphides and thereby, the conversion reaction process based on chemical bond breaking in metal phosphides would not take place in those GexP60-x alloys, being replaced by alloying-type mechanism only. Therefore, such GexP60-x alloys are the first ones which can simultaneously exhibit both large capacity (>1800 mAh/g), unexpected high reversibility (ICE>90%) and suitable voltage plateau (∼0.5 V), delivering 770 mAh/g within 15 min with low yet safe voltage for fast-charging battery. This discovery that nonmetallic and semiconductor elements can form conductive alloys based on solid solution chemistry injects fresh blood into high-performanced anode families and offers a new strategy for material design toward advanced fast charging electrodes for energy storage.