Calcium-based metal–organic framework as an optimized anode material for Li-ion batteries

Abstract

Metal–organic frameworks (MOFs) as attracting electrode materials for lithium-ion batteries (LIBs) suffer seriously from structural instability, leading to the fast decay of capacity. Introducing insolvable metal ion bonding strongly with functional groups into MOF may effectively stabilize the electrode and improve the Li+ ion reaction stability during the electrochemical processes. In this work, a calcium-based metal–organic framework (Ca2PMA) is synthesized by a cation exchange method and explored as an anode material for LIBs. Ca2PMA exhibits a large reversible capacity of 673.9 mAh g−1 (100 mA g−1) as well as good cycle performance. Upon activation from the first cycle to the 320th cycle at 500 mA g−1, an extremely large reversible capacity of ∼360 mAh g−1 is achieved and there is almost no capacity fading until the 800th cycle. During the activation stage, the crystalline structure of Ca2PMA deteriorates quickly to be amorphous, while the capacity continuously increases. A 14-electron redox chemistry is proposed for the Ca2PMA monomer, and the high cycle stability is attributed to the insolvable Ca2+ stabilized functional groups.