Organic Dicarboxylate Negative Electrode Materials with Remarkably Small Strain for High- Voltage Bipolar Batteries

As advanced negative electrodes for powerful and useful high-voltage bipolar batteries, an intercalated metal-organic framework (iMOF), 2,6-naphthalene dicarboxylate dilithium, is described which has an organic-inorganic layered structure of -stacked naphthalene and tetrahedral LiO4 units. The material shows a reversible two-electron-transfer Li intercalation at a flat potential of 0.8V with a small polarization. Detailed crystal structure analysis during Li intercalation shows the layered framework to be maintained and its volume change is only 0.33%. The material possesses two-dimensional pathways for efficient electron and Li+ transport formed by Li-doped naphthalene packing and tetrahedral LiO3C network. A cell with a high potential operating LiNi0.5Mn1.5O4 spinel positive and the proposed negative electrodes exhibited favorable cycle performance (96% capacity retention after 100 cycles), high specific energy (300Whkg(-1)), and high specific power (5kWkg(-1)). An 8V bipolar cell was also constructed by connecting only two cells in series.