Valorization of graphite tailings into high-value silicon-carbon anodes: A spray-drying strategy for superior lithium storage

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Abstract The large dimensional variation of silicon during lithiation/delithiation usually causes electrode pulverization and unstable cycling behavior, which restricts the use of silicon-based anodes in lithium-ion batteries. Herein, a graphite tailing-derived silicon-carbon anode was designed by using natural graphite spheronization tailings (NGST) as a low-cost conductive matrix. SiNPs were incorporated with NGST through sucrose-assisted spray drying to obtain composite microspheres, followed by pitch carbonization to generate a continuous outer carbon layer. The resulting C@NGST-Si composite exhibits an integrated structure in which NGST provides a conductive and buffering skeleton, while the carbon coating improves surface protection and interparticle electrical contact. In addition, the formation of Si-O-C linkages between SiNPs and the carbonaceous phase strengthens the interfacial coupling, thereby suppressing structural deterioration during cycling. As a result, the optimized electrode presents an initial discharge capacity of 622.36 mAh/g at 0.2 A/g and maintains 80.6% capacity retention after 100 cycles at 1.0 A/g. The C@NGST-Si‖NCM811 full cell also shows stable operation at high rates, retaining 85.94% of its capacity after 50 cycles at 3C and delivering reversible capacity even at 5C. This work verifies the feasibility of converting NGST waste into functional anode components and provides a practical strategy for developing silicon-carbon anodes with improved cycling and rate performance.

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