Hierarchical multi-yolk-shell copper oxide@copper-1, 3, 5-benzenetricarboxylate as an ultrastable anode for lithium ion batteries

The capacity attenuation of transition metal oxides (TMOs) and metal-organic frameworks (MOFs) is the obstacle for practical application in lithium ion batteries, due to the extensive volume variation upon charge/discharge cycles. Herein, a hierarchical composite material with copper oxide (CuO) multi-yolks and copper-1, 3, 5-benzenetricarboxylate (Cu-BTC) shell is synthesized by a facile method to study the effect of the hierarchical structure on the electrochemical performance. The porosity and pore volume of CuO@Cu-BTC composites are optimized to buffer the volume change and facilitate the infiltration of electrolytes by altering reaction conditions. The CuO@Cu-BTC (20 h) with the largest surface area and pore volume delivers an excellent reversible capacity of 780.7 mAh g-1 at 200 mA g-1 after 100 cycles, and ultrastable long-term performance with a specific capacity of 569 mAh g-1 at a current density of 1000 mA g-1 after 900 cycles. The corresponding full battery shows moderate capacity retention from 149.4 to 125.8 mAh g-1 after 70 cycles, with a specific capacity retention of 84.2%, based on the mass of lithium iron phosphate (LiFePO4) at 0.2 C (1 C = 170 mA g-1). This strategy applies copper oxide as the metal source of the coordination compound, as well as the internal yolks, which can be extended to the in-situ construction of other hierarchical composites, providing a new avenue for practical application of TMOs and MOFs as anode materials.