Liquid Processing of Interfacially Grown Iron‐Oxide Flowers into 2D‐Platelets Yields Lithium‐Ion Battery Anodes with Capacities of Twice the Theoretical Value

Abstract

papers have shown that converting bulk powder to 2D nanosheets yields significant capacity increases. [18][19][20] In addition, 2D platelet-shaped nanoparticles show great potential for use in battery electrodes due to shorter solid state diffusion lengths which can yield improved rate performance. [21] However, high aspect ratio 2D nanosheets can reduce the diffusion coefficient associated with ion transport within the electrolyte filled pores. [21] To avoid slow liquid phase diffusion while maintaining short solid state diffusion times, quasi-2D platelets with reduced aspect ratio are required. [21] This suggests that when using Fe 2 O 3 for battery applications there would be significant advantages to producing it in the form of quasi-2D platelets.Several synthetic routes have been proposed to generate nanoscale α-Fe 2 O 3 of various geometries including 2D platelets. [22][23][24][25] However, current methods are expensive to implement and typically include multiple complex steps which require high temperatures as well as templates or solid supports. A simpler alternative is to use a controllable, soft interfacial method to self-assemble well-defined and mesoporous nanostructures at an immiscible aqueous/organic interface. [26] The interface provides a defect-free, dimensionally-confined space to self-assemble unique 2D nanomaterials in a single step with perfect reproducibility. This can yield nanomaterials, potentially including quasi-2D materials, that are inaccessible in bulk solution. [27,28] Furthermore, certain interfaces between two immiscible electrolyte solutions (ITIES) may be electrochemically polarized, providing a driving force that may influence the kinetics of self-assembly or even enable electrosynthesis of interfacial thin films of materials. [29,30] Another consideration involves electrode architecture and the need to include conductive additives. For Fe 2 O 3 , a number of carbon-based additives including 2D graphene, 1D carbon (nanofibers/nanotubes), and 0D nanocarbon has been extensively explored. [10,[31][32][33][34] We believe significant advantages are to be had from using carbon nanotubes (CNTs) as the conductive additive. We and others have shown that incorporating CNTs in electrodes based on both 2D [35][36][37] and 3D [38] materials allows them to approach their theoretical capacity. This is because the high conductivity of the CNTs allows effective charge distribution increasing both initial capacity, stability, and rate performance. [38][39][40] In addition, CNTs provide mechanical reinforcement to the electrode without the need for any additional binder. [38] This is particularly important for iron oxide-based anodes, where a large volume expansion is often observed upon lithiation which leads to particle de-cohesion and poor cycling performance. [7] We have shown previously that nanotubes lead to electrode toughening which imparts stability even in silicon anodes which display very high volume expansion. [38] In this paper we will combine the advantages associated with quasi-2D...

Carbon Microstructure Dependent Li‐Ion Storage Behaviors in SiOx/C Anodes

“…Abundant pore distributions and relatively disordered structure of carbon have positive effects on the Li‐ion diffusion in the electrode. [ 19 ] Such enhancement is benefit for the rate performance. Under current densities of 0.1C, 0.2C, 0.5C, 1C, and 2C (Figure 3d), the HCSP electrode presents the best rate performance, SCSP the second, and GrSP the third.…”

Epitaxial growth of hexahedral Fe2O3@SnO2 nano-heterostructure for improved lithium-ion batteries

“…S3a,† the reduction peak at 0.56 V and the oxidation peak at 1.65 V are visible in the initial cycle, which suggested that lithium ions were inserted into the Fe 2 O 3 to generate the solid electrolyte interface (SEI) layer (eqn (4)) 24 and invertible conversion of Fe and Fe 2 O 3 to each other (eqn (1)–(3)). 25,26 Fe 2 O 3 + x Li + + x e − ↔ Li x Fe 2 O 3 Li x Fe 2 O 3 + (2 − x )Li + + (2 − x )e − ↔ Li 2 Fe 2 O 3 Li 2 Fe 2 O 3 + 4Li + + 4e − ↔ 2Fe 0 + 3Li 2 OLi + + e − + electrolyte → SEI (Li)…”

“…S3a, † the reduction peak at 0.56 V and the oxidation peak at 1.65 V are visible in the initial cycle, which suggested that lithium ions were inserted into the Fe 2 O 3 to generate the solid electrolyte interface (SEI) layer (eqn (4)) 24 and invertible conversion of Fe and Fe 2 O 3 to each other (eqn (1)-( 3)). 25,26 Fe…”

Design of Gradient Ti Reconstituted Fe2O3 Anodes with Enhanced Lithium Affinity Modulated Electronic Structures: First-Principles Calculations and Experiment Verification

“…Conversion-type Fe 2 O 3 -based electrodes have received extensive attention due to their high theoretical capacity (1007 mAh g –1 ), environmental friendliness, and wide source of raw materials. − However, Fe 2 O 3 , similar to other conversion anodes, has poor electrical conductivity (less than 10 –38 S cm –1 at 300 K), resulting in disappointing rate properties, and suffers from large volume changes (∼75%) during battery operation, making it difficult to maintain long life . Strategies such as heteroatomic doping, − introducing conductive carbon, , and constructing nanostructures − are widely employed to address these issues. Reducing the particle size to the nanometer scale can effectively shorten the Li + ion diffusion path, buffer the volume change, ease the release stress, and thus promote the electrochemical properties .…”