Synergistic valorization of spent lithium-ion battery electrodes: anode graphite derived lamellar graphene oxide membranes for selective lithium recovery from cathode leachate

Abstract

The independent recycling of anode and cathode materials from spent lithium-ion batteries (LIBs) misses a crucial opportunity for synergistic valorization. Herein, we establish a closed-loop recycling paradigm that transforms spent anode graphite into high-performance graphene oxide (GO)-polyethyleneimine (PEI) nanofiltration membranes for the selective recovery of lithium from cathode leachates. Comprehensive characterization confirms the successful regeneration of monolayer GO nanosheets from spent graphite, utilizing the material's expanded lattice to facilitate exfoliation. The subsequent assembly into GO-PEI laminate membranes creates a robust dual-sieving mechanism governed by precise size exclusion and strong electrostatic repulsion. This architecture enables the ultrafast permeation of monovalent Li⁺ while imposing a severe kinetic and energetic barrier to divalent transition metal ions M²⁺ (e.g., Mg²⁺, Ni²⁺, Co²⁺, Mn²⁺). Consequently, the optimized membrane achieves a high Li⁺/M²⁺ selectivity (>24 000), with a peak Li⁺/Mn²⁺ separation factor exceeding 52 856, alongside a commercially relevant lithium flux. This work demonstrates that low-value waste graphite can be upcycled into advanced separation materials, offering a sustainable, chemical-efficient pathway for closing the loop on critical battery metals.