Emerging Organic Surface Chemistry for Si Anodes in Lithium‐Ion Batteries: Advances, Prospects, and Beyond

Abstract

To date, lithium-ion batteries (LIBs) as one of the most promising means of energy storage have witnessed progressive upgrades of cell energy density and cost reduction, enabling, for example, longer EVs travel ranges (>300 km/charge) and deeper penetration of renewables into grid electricity. Despite the fast growing market of LIBs [3] and the worldwide conspicuous rise in LIBs production, the practical specific energy density of prevailing LIBs adopting graphite anode is approaching its theoretical limit, that is, ≈250 Wh kg −1 when paired with high-energy ceramic cathode such as nickel cobalt manganese oxides. Nevertheless, to meet the everpresent relentless demand from end-users such as portable electronics and EVs, the battery ought to be upgraded to provide 400-500 Wh kg −1 , 700-800 Wh L −1 with lower cost (<9.5 US cents/Wh, expected in 2030), and fast charge capabilities (>2C, i.e., fully charged within 1/2 h). [4] To achieve these goals, the core strategy for developing next-generation LIBs is to exploit higher-capacity battery materials that are cheap and abundant.Silicon (Si) is recognized to be one of the most appealing choices of anode materials due to its inherent low-cost, natural abundance, and the ultrahigh theoretical capacity of 3590 mAh g −1 (based on Li 15 Si 4 ) at low potential (<0.4 V vs Li/ Li + ). [5] Pioneering battery manufacturers like CATL and Tesla have Due to its uniquely high specific capacity and natural abundance, silicon (Si) anode for lithium-ion batteries (LIBs) has reaped intensive research from both academic and industrial sectors. This review discusses the ongoing efforts in tailoring Si particle surfaces to minimize the cycle-induced changes to the integral structure of particles or electrodes. As an upgrade or alternative to conventional coatings (e.g., carbons), the emerging organic moieties on Si offer new avenues toward tuning the interactions with various battery components that are key to electrochemical performances. The recent progress on understanding Si surfaces is reviewed with an emphasis on newly emerged diagnostic tools, which increasingly points to the critical role of organic components in stabilizing Si. The detailed analysis on the chemistry-structure-performance relationships in Si surface are discussed and the successful cases demonstrating the functions of the organic layers are provided, that is, via tailored interactions toward electrolyte or binder or conductive agents, are recapped. Various synthetic strategies for designing the surface organic layers are discussed and compared, highlighting the versatility and tunability of surface organic chemistry. The holistic considerations and promising research directions are summarized, shedding light on in-depth understanding and engineering Si surface chemistry toward practical LIBs application.

Spatially Confined Silicon Nanoparticles Anchored in Porous Carbon as Lithium-Ion-Battery Anode Materials

“…Moreover, Figure f shows a decrease of the CO 3 2– and C–O contents, indicating that the proportion of Li 2 CO 3 as a constituent of the SEI is reduced in Si@C-PAM. Meanwhile, the much lower concentration of organic CO in Si@C-PAM indicates that well C coating inhibits the formation of electrolyte reduction products . The formation of more LiF in the SEI layer and fewer Li 2 CO 3 , which originates from the reduction of organic Li salts, is beneficial to the formation of a thin and robust SEI layer of Si@C-PAM so that the sample can promote Li + transport, suppress further electrolyte decomposition, and lessen side reactions to boost the Coulombic efficiency …”

“…Meanwhile, the much lower concentration of organic C�O in Si@C-PAM indicates that well C coating inhibits the formation of electrolyte reduction products. 58 The formation of more LiF in the SEI layer and fewer Li 2 CO 3 , which originates from the reduction of organic Li salts, is beneficial to the formation of a thin and robust SEI layer of Si@C-PAM so that the sample can promote Li + transport, suppress further electrolyte decomposition, and lessen side reactions to boost the Coulombic efficiency. 59 To intuitively display the effect of Si@C-PAM, with the hierarchically and orderly porous structure in inhibiting the volume variation of Si, the morphology of the electrode sheet before and after cycling was further characterized.…”

Challenges and Developments of High Energy Density Anode Materials in Sulfide‐Based Solid‐State Batteries

“…In addition, these deficiencies are exacerbated by the continuous SEI formation between LEs and highly reactive LiÀ Si alloy, and the poor electrical conductivity of semiconductor Si particles ( � 3 × 10 À 5 S cm À 1 ). [151] In 2009, Lee's group [152] first reported the application of Si nanoparticles in sulfide-based ASSBs, and the Si anodes delivered a more stable cycle performance with sulfide SEs than in the LEs system. Subsequently, Various strategies have been made to address these issues for silicon-based anodes in ASSBs, ranging from material engineering (Si morphology control, [153] electrolytes modification, [79] binder matrix enhancement [154] ) to system optimization (cutoff voltage, [155] external pressure [156] ).…”

Prefabrication of “Trinity” Functional Binary Layers on a Silicon Surface to Develop High-Performance Lithium-Ion Batteries

“…Silicon (Si) remains a flourishing alternative anode material in lithium-ion batteries (LIBs) owing to the high theoretical capacity, appropriate operating voltage, and abundant reserves. − Nevertheless, it undergoes a huge volume change up to 300% once it stores Li to form Li x Si y by alloying reactions, resulting in the collapse of particle structure and disintegration of the integral electrode. Nanostructure engineering has been widely regarded as an available strategy to suppress the huge volume change, such as nanoparticles, nanotubes, nanosheets, and three-dimensional porous Si materials .…”