Lithium salt of biphenyl tetracarboxylate as an anode material for Li/Na-ion batteries

Electrochemical lithiation/delithiation and sodiation/desodiation studies are carried out on lithium [1,1′-biphenyl]-3,3′,4,4′-tetracarboxylate (Li ₄ -BPTC). Although four Li ⁺ can be inserted, only two Li ⁺ was reversible yielding a capacity of 110, 122 and 107 mAh g ⁻¹ (after 50 cycles) at a current density of 40, 80 and 160 mA g ⁻¹ respectively. As sodium analog of Li ₄ -BPTC is unstable in the ambient conditions, Li ₄ -BPTC was tested in sodium half-cell and a reversible capacity of 107 mAh g ⁻¹ was obtained even after 200 cycles at 160 mA g ⁻¹ rate. The exchange of Li ⁺ by Na ⁺ in Li ₄ -BPTC electrode during the electrochemical sodiation/desodiation was confirmed by ICP-OES and XPS studies.