A lean-zinc anode battery based on metal-organic framework-derived carbon

Improving zinc metal (Zn-0) reversibility and minimizing the N/P ratio are critical to boosting the energy density of Zn-0 batteries. However, in reality, an excess Zn source is usually adopted to offset the irreversible zinc loss and guarantee sufficient zinc cycling, which sacrifices the energy density and leads to poor practicability of Zn-0 batteries. To address the above conundrum, here, we report a lean-Zn and hierarchical anode based on metal-organic framework (MOF)-derived carbon, where trace Zn-0 is pre-reserved within the anode structure to make up for any irreversible zinc source loss. This allows us to construct low N/P ratio Zn-0 full cells when coupling the lean-Zn anode with Zn-containing cathodes. Impressively, high Zn-0 reversibility (average Coulombic efficiency of 99.4% for 3000 cycles) and long full-cell lifetime (92% capacity retention after 900 cycles) were realized even under the harsh lean-Zn condition (N/P ratio: 1.34). The excellent Zn reversibility is attributed to the hierarchy structure that homogenizes zinc ion flux and electric field distribution, as confirmed by theoretical simulations, which therefore stabilizes Zn-0 evolution. The lean-Zn anode design strategy will provide new insights into construction of high-energy Zn-0 batteries for practical applications.

Automated summary

A lean-Zn and hierarchical anode design strategy, based on metal-organic framework-derived carbon, is reported here to improve Zn-0 reversibility and minimize zinc loss. This design allows for the construction of low N/P ratio Zn-0 full cells, resulting in high Zn-0 reversibility and long full-cell lifetime even under harsh lean-Zn conditions.