High-Performance Polymeric Lithium Salt Electrode Material from Phenol–Formaldehyde Condensation

In spite of the recent progress made in organic electrode materials, high-performance candidates are still lacking, especially when taking affordability into account. Herein, we report a novel polymeric lithium salt, namely dilithium salt of poly(2,5-dihydroxy-1,4-benzoquinone-3,6-methylene) (Li2PDBM), which can be easily synthesized by phenol–formaldehyde condensation, followed by lithiation in LiOH solution to eliminate the negative effect of phenol groups in PDBM. Benefiting from a high theoretical capacity (327 mA h g–1), structure stability, insolubility, and redox reversibility, Li2PDBM exhibits superior electrochemical performance as a cathode for rechargeable lithium batteries, including a high reversible capacity (256 mA h g–1), a high rate capability (79% @ 2000 mA g–1), and a high cycling stability (77% @ 2000th cycle). Besides the cost-effective electrode material synthesis approach, this work also provides an important mechanistic understanding of the structure–performance relationship of carbonyl-based electrode materials, especially those with −OH or −OM (M = Li, Na, and K) substituents.