A novel anode with improved electrochemical performance based on cobalt squarate for lithium-ion batteries

Organics matter squaric acid with small molecules and multiple active sites are of great potential to obtain a high theoretical specific capacity. However, square acids are easily dissolved in the electrolyte, causing it to exhibit characteristics of low capacity and poor cycling performance. Metal ions are introduced to create metal–organic frameworks (MOFs), which is one of the efficient solutions for the aforementioned problems. MOFs based on π-d systems can improve stabilities and inhibit the dissolution of organic ligands. Meanwhile, different metal ions can modify its electrochemical properties, especially those with redox activity, which can significantly improve the capacity and stability of the MOFs. In this paper, the M−SQ (M = Co, Ni, Mn) based on square acid was synthesized, compare to Ni-SQ and Mn-SQ, Co-SQ with multiple redox-active centers shown greater reversible capacity and cycle stability, which has 1242.2 mA h g−1 at 0.1 A g−1, it is present an excellent capacity, and Co-SQ also has good rate capacity, when current density added to 2 A g−1, it has 807.9 mA h g−1. Meanwhile, Co-SQ showing an outstanding long cycle life with 481.8 mA h g−1 after 700 cycles at 1 A g−1. In addition, Co-SQ with a porous structure has a higher capacity than Co-SQ-NaOH with rod-like structure. Further, the Li+ storage advantage of the porous structure Co-SQ was revealed by kinetic studies. The strategy though tunable active sites of metals and carbonyl is great potential for obtaining high-performance energy storage materials.