Tailoring hierarchical porous core–shell SnO2@Cu upon Cu–Sn alloys through oxygen binding energy difference for high energy density lithium-ion storage

Rational design and construction of self-supporting anodes with high energy density is an essential part of research in the field of lithium-ion batteries. Tin oxide (SnO₂) is restricted in application as a prospective high energy density anode due to inherent low conductivity and huge volume expansion of the charge/discharge process. A new strategy that combines high energy ball milling and nonsolvent induced phase separation (NIPS) method was employed to synthesize self-supporting electrodes in which porous SnO₂ was encapsulated in a three-dimensional hierarchical porous copper (Cu) shell structure (3DHPSnO₂@Cu). This unique structure was constructed due to the different binding energy of the alloy with oxygen, which are −0.91 eV for Cu₄₁Sn₁₁ and −1.17 eV for Cu_5.6Sn according to the density functional theory calculation. 3DHPSnO₂@Cu electrodes exhibited excellent discharge capacity with an initial reversible capacity of 4.35 mAh cm⁻² and a reversible capacity of 3.13 mAh cm⁻² after 300 cycles at a current density of 1.4 mA cm⁻². It is attributed that the porous Cu shell encapsulated with porous SnO₂ provides buffer volume. Among them, the SnO₂-Cu-SnO₂ interface increases the electrical conductivity and the porous structure provides ion transport channels. This strategy opens a new pathway in the development of self-supporting electrode materials with high energy density.