Irrigation System-Inspired Open-/Closed-Pore Hybrid Porous Silicon-Carbon Materials for Lithium-Ion Battery Anodes

Porous silicon-carbon (Si-C) nanocomposites exhibit high specific capacity and low electrode strain, positioning them as promising next-generation anode materials for lithium-ion batteries (LIBs). However, nanoscale Si's poor dispersibility and severe interfacial side reactions historically hamper battery performance. Inspired by irrigation systems, this study employs a charge-driven Si dispersion and stepwise assembly strategy to fabricate an open-/closed-pore hybrid porous Si-C composite. Polydimethyl diallyl ammonium chloride (PDDA) is used to functionalize Si nanoparticles, inducing strong electrostatic repulsion for uniform dispersion. Subsequently, the PDDA functional layer on Si nanoparticle surfaces facilitates the stepwise self-assembly of acetic acid and chitosan, resulting in Si nanoparticles encapsulated within closed pores during carbonization. Simultaneously, the PDDA functional layers transform into a graphene coating on the Si nanoparticles. Conversely, regions of homogeneous acetic acid/chitosan, distant from the PDDA-functionalized Si nanoparticles, form an open-pore structure. The dual shielding effect of closed carbon pores and the graphene coating effectively isolates Si from the electrolyte, preventing interfacial side reactions. Open carbon pores enhance electrolyte-active material contact, reducing Li+ transport distances. The resulting composite material (PDDA@Si/C) demonstrated excellent cycling stability and superior rate performance as a LIB anode.

A Review on Recent Advances for Boosting Initial Coulombic Efficiency of Silicon Anodic Lithium Ion batteries

Rechargeable silicon anode lithium ion batteries (SLIBs) have attracted tremendous attention because of their merits, including a high theoretical capacity, low working potential, and abundant natural sources. The past decade has witnessed significant developments in terms of extending the lifespan and maintaining high capacities of SLIBs. However, the detrimental issue of low initial Coulombic efficiency (ICE) toward SLIBs is causing more and more attention in recent years because ICE value is a core index in full battery design that profoundly determines the utilization of active materials and the weight of an assembled battery. Herein, a comprehensive review is presented of recent advances in solutions for improving ICE of SLIBs. From design perspectives, the strategies for boosting ICE of silicon anodes are systematically categorized into several aspects covering structure regulation, prelithiation, interfacial design, binder design, and electrolyte additives. The merits and challenges of various approaches are highlighted and discussed in detail, which provides valuable insights into the rational design and development of state-of-the-art techniques to deal with the deteriorative issue of low ICE of SLIBs. Furthermore, conclusions and future promising research prospects for lifting ICE of SLIBs are proposed at the end of the review.

Eco-Friendly Water-Processable Polyimide Binders with High Adhesion to Silicon Anodes for Lithium-Ion Batteries

Silicon is an attractive anode material for lithium-ion batteries (LIBs) because of its natural abundance and excellent theoretical energy density. However, Si-based electrodes are difficult to commercialize because of their significant volume changes during lithiation that can result in mechanical damage. To overcome this limitation, we synthesized an eco-friendly water-soluble polyimide (W-PI) precursor, poly(amic acid) salt (W-PAmAS), as a binder for Si anodes via a simple one-step process using water as a solvent. Using the W-PAmAS binder, a composite Si electrode was achieved by low-temperature processing at 150 °C. The adhesion between the electrode components was further enhanced by introducing 3,5-diaminobenzoic acid, which contains free carboxylic acid (-COOH) groups in the W-PAmAS backbone. The -COOH of the W-PI binder chemically interacts with the surface of Si nanoparticles (SiNPs) by forming ester bonds, which efficiently bond the SiNPs, even during severe volume changes. The Si anode with W-PI binder showed improved electrochemical performance with a high capacity of 2061 mAh g^-1 and excellent cyclability of 1883 mAh g^-1 after 200 cycles at 1200 mA g^-1. Therefore, W-PI can be used as a highly effective polymeric binder in Si-based high-capacity LIBs.

Challenges and prospects of nanosized silicon anodes in lithium-ion batteries

Batteries are commonly considered one of the key technologies to reduce carbon dioxide emissions caused by the transport, power, and industry sectors. We need to remember that not only the production of energy needs to be realized sustainably, but also the technologies for energy storage need to follow the green guidelines to reduce the emission of greenhouse gases effectively. To reach the sustainability goals, we have to make batteries with the performances beyond their present capabilities concerning their lifetime, reliability, and safety. To be commercially viable, the technologies, materials, and chemicals utilized in batteries must support scalability that enables cost-effective large-scale production. As lithium-ion battery (LIB) is still the prevailing technology of the rechargeable batteries for the next ten years, the most practical approach to obtain batteries with better performance is to develop the chemistry and materials utilized in LIBs-especially in terms of safety and commercialization. To this end, silicon is the most promising candidate to obtain ultra-high performance on the anode side of the cell as silicon gives the highest theoretical capacity of the anode exceeding ten times the one of graphite. By balancing the other components in the cell, it is realistic to increase the overall capacity of the battery by 100%-200%. However, the exploitation of silicon in LIBs is anything else than a simple task due to the severe material-related challenges caused by lithiation/delithiation during battery cycling. The present review makes a comprehensive overview of the latest studies focusing on the utilization of nanosized silicon as the anode material in LIBs.

The Study of the Binder Poly(acrylic acid) and Its Role in Concomitant Solid-Electrolyte Interphase Formation on Si Anodes

We use neutron reflectometry to study how the polymeric binder, poly(acrylic acid) (PAA), affects the in situ formation and chemical composition of the solid-electrolyte interphase (SEI) formation on a silicon anode at various states of charge. The reflectivity is correlated with electrochemical quartz crystal microbalance to better understand the viscoelastic effects of the polymer during cycling. The use of model thin films allows for a well-controlled interface between the amorphous Si surface and the PAA layer. If the PAA perfectly coats the Si surface and standard processing conditions are used, the binder will prevent the lithiation of the anode. The PAA suppresses the growth of a new layer formed at early states of discharge (open circuit voltage to 0.8 V vs Li/Li⁺), protecting the surface of the anode. At 0.15 V, the SEI layer underneath the PAA changes in chemical composition as indicated by an increase in the scattering length density and thickness as the layer incorporates components from the electrolyte, most likely the salt. At lithiated and delithiated states, the SEI layer changes in chemical composition and grows in thickness with delithiation and shrinks during lithiation.

Designing superior solid electrolyte interfaces on silicon anodes for high-performance lithium-ion batteries

The solid electrolyte interface (SEI) is a passivation layer formed on the surface of lithium-ion battery (LIB) anode materials produced by electrolyte decomposition. The quality of the SEI plays a critical role in the cyclability, rate capacity, irreversible capacity loss and safety of lithium-ion batteries (LIBs). The stability of the SEI is especially important for Si anodes which experience tremendous volume changes during cycling. Therefore, in this review we discuss the effect of the SEI on Si anodes. Firstly, the mechanism of formation, composition, and component properties of solid electrolyte interfaces (SEIs) are introduced, and the SEI of native-oxide-terminated Si is emphasized. Then the growth model and mechanical failure of SEIs are analyzed in detail, and the challenges facing SEIs of Si anodes are proposed. Moreover, we highlight several modification methods for SEIs on Si anodes, including electrolyte additives, surface-functionalization of Si, coating artificial SEIs or protective layers, and the structural design of Si-based composites. We believe that designing a high-quality SEI is of great significance and is beneficial for the improved electrochemical performance of Si anodes.

Stable Silicon Anode for Lithium-Ion Batteries through Covalent Bond Formation with a Binder via Esterification

Silicon (Si) is considered to be one of the most promising anode candidates for next-generation lithium-ion batteries because of its high theoretical specific capacity and low discharge potential. However, its poor cyclability, caused by tremendous volume change during cycling, prevents commercial use of the Si anode. Herein, we demonstrate a high-performance Si anode produced via covalent bond formation between a commercially available Si nanopowder and a linear polymeric binder through an esterification reaction. For efficient ester bonding, polyacrylic acid, composed of -COOH groups, is selected as the binder, Si is treated with piranha solution to produce abundant -OH groups on its surface, and sodium hypophosphite is employed as a catalyst. The as-fabricated electrode exhibits excellent high rate capability and long cycle stability, delivering a high capacity of 1500 mA h g^-1 after 500 cycles at a high current density of 1000 mA g^-1 by effectively restraining the susceptible sliding of the binder, stabilizing the solid electrolyte interface layer, preventing the electrode delamination, and suppressing the Si aggregation. Furthermore, a full cell is fabricated with as-fabricated Si as an anode and commercially available LiNi_0.6Mn_0.2Co_0.2O₂ as a cathode, and its electrochemical properties are investigated for the possibility of practical use.

Surface-Functionalized Silicon Nanoparticles as Anode Material for Lithium-Ion Battery

An epoxy group was successfully attached to the surface of silicon nanoparticle (SiNPs) via a silanization reaction between silanol-enriched SiNPs and functional silanes. The epoxy-functionalized SiNPs showed a much improved cell performance compared with the pristine SiNPs because of the increased stability with electrolyte and the formation of a covalent bond between the epoxy group and the polyacrylic acid binder. Furthermore, the anode laminate made from epoxy-SiNPs showed much enhanced adhesion strength. Post-test analysis shed light on how the epoxy-functional group affects the physical and electrochemical properties of the SiNP anode.

FePO4 as an anode material to obtain high-performance sodium-based dual-ion batteries

Herein, FePO₄ was for the first time proposed to serve as an anode material (the sodium intercalation host), to obtain novel sodium-based dual-ion batteries.

Si nanorod arrays modified with metal–organic segments as anodes in lithium ion batteries

Metal–organic segments (MOSs) were synthesized to composite with Si nanorod (NR) arrays as electrodes in lithium ion batteries (LIBs).