Simple Construction of Multistage Stable Silicon–Graphite Hybrid Granules for Lithium‐Ion Batteries

Abstract

volume change (≈300%) during the lithiation process causes severe electrode pulverization. [7] On the contrary, graphite offers high initial Coulombic efficiency (ICE), good electrical conductivity, and structural stability. [8][9][10] The synergy of graphite and Si not only significantly improves the energy density, but ensures long battery life by effectively alleviating the lithiation-induced volumetric expansion of Si. [11] The main challenge of SGC is the large difference between Si and graphite in volume change, causing an electrical contact loss of graphite in composite easily. [12] More seriously, the intrinsic disparity between Si and graphite anodes (including the anodic potential peak range and lithium-ion diffusion kinetics) causes extremely continuous stress on graphite during the cycle process. [13][14][15] To solve this problem, commercial SGC anodes are typically prepared by a twosection process that first preparing a modified Si seed and then combining it with graphite. [4,16] Many researches focus on the preparation of modified silicon with promising results. [17][18][19] Xu et al. prepared a fullerene carbon layer coating on the surface of Si nanoparticles (Si NPs) by controlling the association of polyaromatic molecules, effectively alleviating the volume changes of Si. [20] Yang et al. created a polyaniline layer coating on Si NPs by aniline bridge and assisted self-assembly. [21] Modified Si NPs possessed competitive electrochemical performance with a reversible capacity over 1000 mAh g −1 after 300 cycles. Although these modified Si composites greatly improve electrochemical stability, the complex modification process severely limits their industrial production when cost effectiveness is taken into account. On the other hand, many combining methods, such as mechanical mixing, [22,23] high energy ball milling, [24][25][26] liquid solidification, [27,28] and spray drying, [29,30] are commonly used to produce commercial SGC electrodes. [3,4,31] However, the above methods cannot guarantee uniform dispersion of Si in the graphite matrix. The stress concentration caused by aggregated Si domains will lead to the generation and propagation of cracks in composite electrodes, eventually resulting in electrode failure. Therefore, it is critical to design a cost-effective route to improve the dispersion of Si and fabricate SGC with a stable structure.Because of its high specific capacity, the silicon-graphite composite (SGC) is regarded as a promising anode for new-generation lithium-ion batteries. However, the frequently employed two-section preparation process, including the modification of silicon seed and followed mixture with graphite, cannot ensure the uniform dispersion of silicon in the graphite matrix, resulting in a stress concentration of aggregated silicon domains and cracks in composite electrodes during cycling. Herein, inspired by powder engineering, the two independent sections are integrated to construct multistage stable silicon-graphite hybrid granules (SGHGs) through wet granulation...

Regulating oxygen functionalities of cellulose-derived hard carbon toward superior sodium storage

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Lithiophilic SiO2 nanoparticle pillared MXene nanosheets for stable and dendrite-free lithium metal anodes

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