Interconnected Ni(HCO₃)₂ Hollow Spheres Enabled by Self-Sacrificial Templating with Enhanced Lithium Storage Properties

Interconnected nickel bicarbonate (Ni(HCO 3 ) 2 ) hollow spheres were produced and exploited for the first time as an anode of lithium ion batteries, delivering the 80th reversible capacity of 1442 mAh g –1 at a current rate of 100 mA g –1, which is 3.9 times the theoretical capacity of commercial anode graphite. The time-dependent study suggested a self-sacrificial templating formation mechanism that yielded intriguing interconnected hollow structures. X-ray photoelectron spectroscopy measurements on cycled electrodes indicated that both the deep oxidation of Ni 2+ into Ni 3+ and the reversible reactions in HCO 3 – accounted for the ultrahigh capacity of Ni(HCO 3 ) 2 in comparison to its generally accepted theoretical capacity of 297 mAh g –1 . Morphological characterizations revealed that the interconnected hollow structures enabled the enhanced rate performance and cycling stability, compared to those of the solid counterpart, because of their larger contact areas with electrolyte and better buffering effect to accommodate the volume change.