Recycling of Lignin and Si Waste for Advanced Si/C Battery Anodes

The ever-increasing silicon photovoltaics industry produces a huge annual production of silicon waste (2.03 × 10⁵ tons in 2019), while lignin is one of the main waste materials in the traditional paper industry (7.0 × 10⁷ tons annually), which lead to not only enormous wastage of resources but also serious environment pollution. Lithium-ion batteries (LIBs) are the dominating power sources for portable electronics and electric vehicles. Silicon (Si)-based material is the most promising anode choice for the next-generation high-energy-density LIBs due to its much higher capacity than the commercial graphite anode. Here, we proposed the use of these silicon and lignin waste as sustainable raw materials to fabricate high-capacity silicon/carbon (Si/C) anode materials for LIBs via a facile coprecipitation method utilizing electrostatic attracting force, followed by a thermal annealing process. The as-achieved Si/C composite featured an advanced material structure with micrometer-sized secondary particles and Si nanoparticles embedded in the carbon matrix, which could tackle the inherent challenges of Si materials, including low conductivity and large volume change during the lithiation/delithiation processes. As expected, the obtained Si/C composite displayed an initial charge capacity of 1016.8 mAh g^-1, which was 3 times that of a commercial graphite anode in the state-of-the-art LIBs, as well as a high capacity retention of 74.5% at 0.2 A g^-1 after 100 cycles. In addition, this Si/C composite delivered superior rate capability with a high capacity of 575.9 mAh g^-1 at 2 A g^-1, 63.4% of the capacity at 0.2 A g^-1. The utilization of industrial Si and lignin waste provides a sustainable route for the fabrication of advanced high-capacity anode materials for the next-generation LIBs with high economic and environmental feasibility.