Reversible lithium ions stored by lithium clusters

• A new Li + storage mechanism based on Li clusters is proposed firstly. • The anode shows highest specific capacities but low volume expansion. • The anode shows low voltage but hinders growth of Li dendrites. • The new mechanism is revealed by experiments and DFT calculations. Solving the “capacity-volume expansion” and “low voltage-safety” contradictions in extant reacting mechanisms of lithium-ion batteries (LIBs) anodes is a challenge. Herein, a new Li + storage behaviour based on reversible Li clusters is proposed firstly by designing an anode with high Li + affinity and spatially dispersed atomic nucleation sites. Due to the well-designed atomic nucleation sites, the Li + would grow into Li clusters (below 4 nm) above 0 V, which restrains the formation of Li dendrites, suggesting that the anode provides low operating voltage while ensuring safety. The Li clusters contain a large amount of Li + , so the anode shows the highest specific capacities in reported carbonaceous anodes (∼2100 mA h g -1 at 0.2 A/g) but merely presents slight volume expansion (∼12%). The Li + storage mechanism is revealed by experiments and density functional theory. The new Li + storage mechanism solves the two above-mentioned contradictions, and may open an opportunity to design and prepare new generation anodes for LIBs.