The resulting material, NiCo₂S₄/Co₉S₈@LC50, combines electroactive metal sulfides with lignin-derived carbon in a honeycomb-like architecture that improves conductivity, structural stability, and ion transport. The study suggests a practical route to lower-cost, more sustainable battery materials while reducing waste and creating new value from discarded consumer electronics and industrial biomass residues.
Discarded mobile phone batteries are growing rapidly and can release hazardous substances while wasting recoverable metals if not properly recycled. At the same time, industrial lignin is produced in huge quantities, yet only a small fraction is converted into high-value products, with most still burned or discarded. Sodium-ion batteries are attracting attention as alternatives to lithium-ion systems because sodium is more abundant and potentially cheaper, but their anode materials still need better cycling stability, rate capability, and cost effectiveness. Although NiCo₂S₄ is a promising anode candidate, its performance is limited in its pure form, and previous carbon modifications have usually relied on conventional industrial carbon sources rather than waste-derived ones. This created the need for a “waste-to-waste” strategy that could upgrade both e-waste and lignin into a better-performing sodium storage material.
A study (DOI:10.48130/bchax-0026-0005) published in Biochar X on 10 February 2026 by Rui Liang’s & Yuebin Xi’s team, Henan Normal University & Qilu University of Technology, reports that controlled co-conversion of battery-derived NiCo₂S₄ and lignin produced a composite with a honeycomb-like structure, fast Na⁺ transport, and markedly improved capacity, rate performance, and cycling stability.
The researchers first recovered and synthesized NiCo₂S₄ from spent Nokia mobile phone batteries through a hydrothermal route. They then purified industrial lignin, mixed it with the recovered sulfide precursor at different ratios, and subjected the composites to alkaline treatment, precipitation, activation with K₂CO₃, and stepwise carbonization under nitrogen. This yielded three comparison samples with different lignin contents, among which NCS/CS@LC50 proved optimal. Structural analysis showed that lignin addition did more than provide carbon: during carbonization it also promoted partial formation of a new Co₉S₈ phase, creating a dual-sulfide composite wrapped by lignin-derived carbon. Raman, XRD, XPS, SEM, and TEM analyses together confirmed the coexistence of NiCo₂S₄, Co₉S₈, and carbon, as well as the formation of a mesoporous honeycomb-like morphology when the lignin ratio reached 50%. The material also achieved a favorable balance of specific surface area and pore size, which the authors linked to improved electrolyte access and sodium-ion movement. Electrochemical testing showed that this structure translated into strong battery behavior. NCS/CS@LC50 delivered an initial discharge specific capacity of 1,062.8 mAh g⁻¹ and retained 244.5 mAh g⁻¹ after 100 cycles, outperforming the comparison samples. It also showed an initial Coulombic efficiency of 65.61%, higher than that of the unmodified material. In rate tests, it maintained average discharge capacities of 548.2, 423.3, 328.1, 247.1, and 208.7 mAh g⁻¹ at 0.1, 0.2, 0.5, 1, and 2 A g⁻¹, respectively, and still preserved 207 mAh g⁻¹ after 300 cycles at 0.5 A g⁻¹. Impedance analysis further showed that this sample had the lowest charge-transfer resistance and the highest Na⁺ diffusion coefficient among the tested materials. Additional pseudocapacitive analysis indicated that rapid surface-controlled storage contributed substantially to performance, while density functional theory calculations suggested that the NiCo₂S₄/Co₉S₈ heterostructure improved electronic conductivity and facilitated charge transfer.
Overall, the study presents a convincing example of circular materials design: one waste stream supplies metals, another supplies carbon, and together they form a high-performance sodium-ion battery anode. By showing that recycled feedstocks can produce competitive electrochemical performance, the work points toward greener and potentially more economical battery manufacturing for future grid storage, electric vehicles, and portable electronics.
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References
DOI
10.48130/bchax-0026-0005
Original Source URL
https://doi.org/10.48130/bchax-0026-0005
Funding information
This research was supported by the Postdoctoral Research Funds from Henan Province (Grant No. 5101039470652); collaborative scientific research projects with Henan Nuofei Biotechnology Co., Ltd (Grant Nos 5201039160188 and 5201039160224); National Natural Science Foundation of China (Grant No. 22108135); Natural Science Foundation of Shandong Province (Grant Nos ZR2024MB12 and ZR2020QB197); Shandong University youth innovation team (Grant No. 2023KJ137).
About Biochar X
Biochar X is an open access, online-only journal aims to transcend traditional disciplinary boundaries by providing a multidisciplinary platform for the exchange of cutting-edge research in both fundamental and applied aspects of biochar. The journal is dedicated to supporting the global biochar research community by offering an innovative, efficient, and professional outlet for sharing new findings and perspectives. Its core focus lies in the discovery of novel insights and the development of emerging applications in the rapidly growing field of biochar science.