Aluminum fumarate-based metal organic frameworks with tremella-like structure as ultrafast and stable anode for lithium-ion batteries

Metal organic frameworks (MOFs) with the unique advantages of high surface area and easily controllable structure have attracted significant attention as electrode materials for various batteries. In this work, aluminum fumarate-based MOFs are prepared through complexation of fumaric acid with different aluminum salts. Interestingly, hierarchical tremella-like structured aluminum fumarates composed of intertangled ultrathin nanosheets are obtained using Al(NO₃)₃·9H₂O and AlCl₃·6H₂O as aluminum salts. When being used as the anode material for lithium-ion batteries, the aluminum fumarates MOFs deliver a considerably improved performance compared to the pristine organic fumaric acid. Excellent high-rate behavior and long-term cycling stability are obtained for the aluminum fumarate electrodes. At a current density of 37.5 mA g⁻¹, a reversible capacity of 392 mA h g⁻¹ is obtained without any capacity-fading up to 100 cycles. Even at an extremely high current density of 37.5 A g⁻¹, aluminum fumarate retains a capacity of 258 mA h g⁻¹. The electrochemical process of aluminum fumarate electrode is elucidated through in-depth electrochemical and spectroscopic studies. The low impedance, reversible lithiation/delithiation process, and structural stability of aluminum fumarate electrode during electrochemical cycling are found to be the main factors for its excellent lithium storage performance.