In a groundbreaking demonstration of circular economy principles applied to energy storage technology, researchers from Henan Normal University and Qilu University of Technology have unveiled a novel composite material that transforms waste products into a high-performance sodium-ion battery anode. By ingeniously synergizing spent mobile phone batteries and industrial lignin, the team developed a NiCo₂S₄/Co₉S₈@LC composite with a distinctive honeycomb-like architecture that markedly enhances electrochemical performance, conductivity, and structural stability.
With electronic waste expanding at an alarming rate globally, particularly from discarded mobile phone batteries, the associated environmental risks and resource wastage are critical concerns. These spent batteries not only harbor hazardous substances but also contain valuable metals such as nickel and cobalt that remain underutilized post-disposal. Meanwhile, lignin, a biopolymer abundantly generated as a by-product in the pulp and paper industries, often ends up incinerated or discarded, despite its potential as a carbon resource. Addressing these parallel challenges, the research team embarked on a pioneering “waste-to-waste” upcycling strategy designed to transform both e-waste and lignin into a value-added energy storage material.
Sodium-ion batteries have gained traction as an alternative to lithium-ion technology due to sodium’s abundant availability and cost advantages. However, current anode materials face limitations including suboptimal cycling stability and insufficient rate capability. NiCo₂S₄ has emerged as a promising electrode material due to its high theoretical capacity and favorable electrochemical characteristics. Yet, in its pristine form, its practical application is hindered by poor conductivity and structural degradation during battery operation. Previous studies aimed at carbon modification of NiCo₂S₄ predominantly utilized conventional carbon sources, missing opportunities to integrate sustainable waste-derived carbons.
Capitalizing on this insight, the researchers recovered NiCo₂S₄ from spent Nokia mobile phone batteries via a hydrothermal synthesis method, thereby reclaiming critical metals and converting them into an electroactive sulfide precursor. Industrial lignin was purified and then blended with this precursor in varying ratios. The mixture underwent a meticulous sequence of chemical treatments including alkaline treatment, precipitation, activation with potassium carbonate, and stepwise carbonization under an inert nitrogen atmosphere. This process yielded a series of composites with distinct lignin content, among which the sample designated NCS/CS@LC50 showcased exceptional performance.
Structural investigation using Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) revealed the formation of an intricate dual-phase composite. The presence of NiCo₂S₄ and a newly formed Co₉S₈ phase was encapsulated within a mesoporous network of lignin-derived carbon, fostering a honeycomb-like morphology. This unique structure was attributed to the 50% lignin proportion, which balanced the specific surface area and pore size distribution. The morphology not only improved electrolyte infiltration but also facilitated expedited sodium-ion transport, crucial for battery efficiency.
Electrochemical performance assessments demonstrated that NCS/CS@LC50 exhibited a remarkable initial discharge specific capacity of 1,062.8 mAh g⁻¹, which is notably higher than many comparable anode materials reported in literature. After 100 charge-discharge cycles, the composite retained a capacity of 244.5 mAh g⁻¹, signaling improved cycling stability—an essential factor for practical applications. The initial Coulombic efficiency, reflecting reversible capacity utilization, was significantly enhanced to 65.61%, surpassing that of unmodified NiCo₂S₄, showcasing the favorable interplay between the dual sulfide phases and carbon matrix.
Rate performance analyses under increasing current densities from 0.1 to 2 A g⁻¹ further confirmed superior capabilities. The composite steadily maintained high average discharge capacities across the range, preserving 207 mAh g⁻¹ even after an extended 300 cycles at 0.5 A g⁻¹. Electrochemical impedance spectroscopy highlighted a reduction in charge-transfer resistance, indicating facilitated electron flow at the electrode-electrolyte interface. Additionally, the composite exhibited the highest sodium ion diffusion coefficient among tested variants, supporting rapid ion mobility critical for high-rate applications.
Pseudocapacitive behavior analysis illuminated that rapid surface-controlled reactions substantially contributed to the measured capacity, distinguishing this material from conventional intercalation-type electrodes. Complementing experimental results, density functional theory (DFT) calculations elucidated the electronic structure of the NiCo₂S₄/Co₉S₈ heterostructure. The calculations revealed that the dual-phase interface enhanced electronic conductivity and lowered energy barriers for charge transfer, mechanistically underpinning the improved electrochemical responses observed.
By elegantly harnessing waste streams from consumer electronics and biomass industries to produce a composite with superior sodium storage performance, this study exemplifies innovative circular materials design. It paves the way for greener synthesis routes in battery manufacturing by integrating sustainability with advanced functionality. The work holds promise not only for grid-scale energy storage solutions but also for electrification of portable devices and electric vehicles, where cost-effective and durable batteries are paramount.
This research also underscores the critical role of interdisciplinary collaboration spanning materials science, environmental chemistry, and electrochemistry, leveraging advanced characterization tools and theoretical modeling to drive technological breakthroughs. Importantly, it establishes a replicable model for converting other waste combinations into high-value functional materials, potentially catalyzing circular economy approaches across multiple sectors.
Further research could expand on scaling the synthesis method, optimizing processing parameters, and integrating such composites into full-cell configurations to fully evaluate lifetime and safety performance. Nonetheless, the impressive balance of capacity, stability, and rate capability achieved signals a significant advance in sodium-ion battery anode development and sustainability-driven materials engineering.
Subject of Research:
Not applicable
Article Title:
Synergistic conversion of spent mobile phone batteries and industrial lignin into the NiCo2S4/Co9S8@LC composite with enhanced sodium storage performance
News Publication Date:
10-Feb-2026
References:
DOI: 10.48130/bchax-0026-0005
Keywords:
Sodium-ion batteries, waste upcycling, NiCo₂S₄, Co₉S₈, lignin-derived carbon, battery anode, electrochemical performance, circular economy, dual-phase composite, honeycomb structure, electrochemical impedance, density functional theory
