Scientists in China have turned discarded mobile phone batteries and industrial lignin waste into a sodium-ion battery anode material with improved energy storage performance, offering a possible low-cost alternative to conventional lithium-ion battery components.

The team developed a composite called NiCo₂S₄/Co₉S₈@LC50 by combining recovered metals from spent Nokia phone batteries with carbon derived from lignin, a byproduct generated in large quantities by the paper and biomass industries.

Researchers said the resulting honeycomb-like structure improved conductivity, sodium-ion transport, and structural stability during battery operation.

Sodium-ion batteries are gaining attention as cheaper alternatives to lithium-ion systems because sodium is more abundant and easier to source. However, many sodium-ion anode materials still struggle with poor cycling stability and limited rate performance, limiting their commercial viability.

Waste powers battery design

To address this, researchers from Henan Normal University and Qilu University of Technology developed what they described as a “waste-to-waste” strategy that converts both electronic waste and industrial biomass residue into a functional battery material.

The researchers first extracted and synthesized NiCo₂S₄ from discarded mobile phone batteries using a hydrothermal process. They then purified industrial lignin and combined it with the recovered sulfide precursor before carrying out alkaline treatment, activation, and carbonization under nitrogen.

Tests showed that adding lignin did more than simply introduce carbon into the material. During carbonization, it also helped generate a secondary Co₉S₈ phase, forming a dual-sulfide structure wrapped in lignin-derived carbon.

Microscopy and spectroscopy analysis confirmed the formation of a mesoporous honeycomb-like architecture that improved electrolyte access and accelerated sodium-ion movement within the electrode.

Electrochemical testing showed the optimized material delivered an initial discharge capacity of 1,062.8 mAh g⁻¹ and retained 244.5 mAh g⁻¹ after 100 charge-discharge cycles. It also maintained 207 mAh g⁻¹ after 300 cycles at 0.5 A g⁻¹.

Honeycomb structure boosts flow

The material also demonstrated improved charge-transfer behavior and sodium-ion diffusion compared to other tested samples, according to impedance analysis.

Researchers said rapid surface-controlled sodium storage contributed significantly to the material’s performance. Computational modeling further suggested that the NiCo₂S₄/Co₉S₈ heterostructure improved electronic conductivity and facilitated charge transfer.

The work highlights growing efforts to develop battery materials from recycled feedstocks as the energy storage industry searches for lower-cost and more sustainable alternatives to conventional lithium-based systems.

Discarded batteries continue to pose environmental challenges because they contain recoverable metals that are often wasted when not recycled properly. Industrial lignin faces a similar issue, with much of it still burned or discarded despite being produced in massive quantities worldwide.

By combining both waste streams into a single sodium-ion battery material, the researchers believe the approach could support greener battery manufacturing for future grid storage systems, electric vehicles, and portable electronics.

The study was published in the journal Biochar X.