ConspectusWith the escalating demands of portable electronics, electric vehicles, and grid-scale energy storage systems, the development of next-generation rechargeable batteries, which boasts high energy density, cost effectiveness, and environmental sustainability, becomes imperative. Accelerating these advancements could substantially mitigate detrimental carbon emissions. The pursuit of main objectives has kindled interest in pure silicon as a high-capacity electroactive material, capable of further enhancing the gravimetric and volumetric energy densities compared with traditional graphite counterparts. Despite such promising attributes, pure silicon materials face significant hurdles, primarily due to their drastic volumetric changes during the lithiation/delithiation processes. Volume changes give rise to severe side effects, such as fracturing, pulverization, and delamination, triggering rapid capacity decay. Therefore, mitigating silicon particle fracture remains a primary challenge. Importantly, nanoscale silicon (below 150 nm in size) has shown resilience to stresses induced by repeated volume changes, thereby highlighting its potential as an anode-active material. However, the volume expansion stress not only affects the internal structure of the particle but also disrupts the solid-electrolyte interphase (SEI) layer, formed spontaneously on the outer surface of silicon, causing adverse side reactions. Therefore, despite silicon nanoparticles offering new opportunities, overcoming the associated issues is of paramount importance.Thus, this Account aims to spotlight the significant strides made in the development of pure silicon anodes with particular attention to feature size. From the emergence of nanoscale silicon, the following nanotechnology played a crucial role in growing the particle through nano/microstructuring. Similarly, bulk silicon microparticles gradually surfaced with the post-engineering methods owing to their practical advantages. We briefly discuss the special characteristics of representative examples from bulk silicon engineering and nano/microstructuring, all aimed at overcoming intrinsic challenges, such as limiting large volume changes and stabilizing SEI formation during electrochemical cycling. Subsequently, we outline guidelines for advancing pure silicon anodes to incorporate high mass loading and high energy density. Importantly, these advancements require superior material design and the incorporation of exceptional battery components to ensure compatibility and yield synergistic effects. By broadening the cooperative strategies at the cell and system levels, we anticipate that this Account will provide an insightful analysis of pure silicon anodes and catalyze their practical applications in real battery systems.

High-theoretical capacity and low working potential make silicon ideal anode for lithium ion batteries. However, the large volume change of silicon upon lithiation/delithiation poses a critical challenge for stable battery operations. Here, we introduce an unprecedented design, which takes advantage of large deformation and ensures the structural stability of the material by developing a two-dimensional silicon nanosheet coated with a thin carbon layer. During electrochemical cycling, this carbon coated silicon nanosheet exhibits unique deformation patterns, featuring accommodation of deformation in the thickness direction upon lithiation, while forming ripples upon delithiation, as demonstrated by in situ transmission electron microscopy observation and chemomechanical simulation. The ripple formation presents a unique mechanism for releasing the cycling induced stress, rendering the electrode much more stable and durable than the uncoated counterparts. This work demonstrates a general principle as how to take the advantage of the large deformation materials for designing high capacity electrode.

Silicon nanosheets have attracted much attention owing to their novel electronic and optical properties and compatibility with existing silicon technology. However, a cost-effective and scalable technique for synthesizing these nanosheets remains elusive. Here, we report a novel strategy for producing silicon nanosheets on a large scale through the simultaneous molten-salt-induced exfoliation and chemical reduction of natural clay. The silicon nanosheets thus synthesized have a high surface area, are ultrathin (~5 nm) and contain mesoporous structures derived from the oxygen vacancies in the clay. These advantages make the nanosheets a highly suitable photocatalyst with an exceptionally high activity for the generation of hydrogen from a water–methanol mixture. Further, when the silicon nanosheets are combined with platinum as a cocatalyst, they exhibit high activity in KOH (15.83 mmol H₂ per s per mol Si) and excellent photocatalytic activity with respect to the evolution of hydrogen from a water–methanol mixture (723 μmol H₂ per h per g Si).