Synergistic conversion of spent mobile phone batteries and industrial lignin into the NiCo2S4/Co9S8@LC composite with enhanced sodium storage performance

This study systematically investigated the NiCo2S4/Co9S8@LC composite synthesized from spent mobile phone batteries and industrial lignin, focusing on its sodium storage characteristics. A hydrothermal method was employed to successfully fabricate NCS/CS@LC50, exhibiting a honeycomb-like morphology through the precise control of lignin content. This composite integrated the high electrochemical activity of NiCo2S4 and Co9S8 with the superior conductivity of carbon materials, demonstrating promising sodium storage performance. The results indicated that NCS/CS@LC50 exhibited a high specific discharge capacity, i.e., an initial discharge specific capacity of 1,062.8 mAh g−1, and outstanding cycling stability. The unique architecture of NCS/CS@LC50 facilitated the effective insertion and extraction of Na+, allowing the material to preserve its structural stability throughout repeated charge-discharge processes, which in turn greatly improved the battery's cycling performance. At elevated current densities, such as 2.0 A g−1, NCS/CS@LC50 continued to exhibit a high specific discharge capacity (208.7 mAh g−1), demonstrating excellent rate performance. This research introduces an innovative approach to effectively recycle and reuse spent mobile phone batteries and industrial lignin, while also providing new insights into the design of electrode materials for sodium-ion batteries.