Amorphous Si1-yCy composite anode materials: ab initio molecular dynamics for behaviors of Li and Na in the framework

Although amorphous Si/C composite anode materials with various types of nanostructures Si/C materials have been experimentally proposed for rechargeable ion batteries for their structural durability, the atomistic mechanism primarily suggesting Li and Na monovalent ion intercalation into an amorphous Si/C composite matrix has not theoretically been understood to explore the thermodynamic and kinetic features of the a-Si/C composite phase regarding the effects on the carbon addition to an amorphous Si matrix. In this work, systematic ab initio molecular dynamics calculations (AIMDs) were conducted to identify electrochemical intercalation reactions involved in nanostructure evolutions, which correspond to favorable ion-intercalated formations, volume expansions, pair correlations, charge transfers, and diffusion behaviors of metals in a-M_xSi_1-yC_y (M_x: Li_x and Na_x) alloys with increasing x contents of atomic concentrations. AIMDs using the a-Si_1-yC_y composite phase might allow one to have an atomic-level understanding of the composite phase and further insightful comprehension of any implementations such as the controlled ratio of the Si_1-yC_y composite and multivalent ions inserted into the framework.

Modified SiO hierarchical structure materials with improved initial coulombic efficiency for advanced lithium-ion battery anodes

Silicon-based anode materials are indispensable components in developing high energy density lithium-ion batteries, yet their practical application still faces great challenges, such as large volume change during the lithiation and delithiation process that causes the pulverization of silicon particles, and continuous formation and reformation of the solid electrolyte interfaces (SEI) which results in a low initial coulombic efficiency. As an endeavor to address these problems, in this study, Si/SiO/Li₂SiO₃@C structures were prepared via a facile method using SiO, pitch powder and Li₂CO₃/PVA solution followed by annealing treatment. The Si/SiO/Li₂SiO₃@C composite shows a great improvement in lithium storage where a high discharge capacity of 1645.47 mA h g⁻¹ was delivered with the 1^st C.E. of 69.05% at 100 mA g⁻¹. These results indicate that the designed method of integrating prelithiation and carbon coating for SiO and the as-prepared macro scale Si/SiO/Li₂SiO₃@C structures are practical for implementation in lithium-ion battery technology.

A simple method of prelithiation of SiO along with carbon coating to achieve high performance SiO-based materials.

Scalable synthesis of carbon stabilized SiO/graphite sheets composite as anode for high-performance Li ion batteries

Various carbon coated SiO/graphite composites are fabricated through in situ polymerization and followed by annealing for high-performance Li-ion batteries.

Nanoporous silicon from low-cost natural clinoptilolite for lithium storage

Nanoporous silicon is derived from extremely low-cost natural clinoptilolite by using magnesiothermic reduction method. After surface carbon coating, it exhibits good cycling stability and is of tremendous potential for its practical application.

Graphite/silicon hybrid electrodes using a 3D current collector for flexible batteries

A flexible hybrid anode from graphite and thin film silicon is realized by the concept of a 3D sandwich current collector by the combination of micro-contact printing and RF magnetron sputtering. Flexible lithium-ion batteries with a new hybrid anode demonstrate not only enhanced specific capacity but also improved rate capability compared to that of a conventional graphite anode under bending deformation.

Si-Mn/reduced graphene oxide nanocomposite anodes with enhanced capacity and stability for lithium-ion batteries

Although Si is a promising high-capacity anode material for Li-ion batteries (LIB), it suffers from capacity fading due to excessively large volumetric changes upon Li insertion. Nanocarbon materials have been used to enhance the cyclic stability of LIB anodes, but they have an inherently low specific capacity. To address these issues, we present a novel ternary nanocomposite of Si, Mn, and reduced graphene oxide (rGO) for LIB anodes, in which the Si-Mn alloy offers high capacity characteristics and embedded rGO nanosheets confer structural stability. Si-Mn/rGO ternary nanocomposites were synthesized by mechanical complexation and subsequent thermal reduction of mixtures of Si nanoparticles, MnO2 nanorods, and rGO nanosheets. Resulting ternary nanocomposite anodes displayed a specific capacity of 600 mAh/g with ∼90% capacity retention after 50 cycles at a current density of 100 mA/g. The enhanced performance is attributed to facilitated Li-ion reactions with the MnSi alloy phase and the formation of a structurally reinforced electroconductive matrix of rGO nanosheets. The ternary nanocomposite design paradigm presented in this study can be exploited for the development of high-capacity and long-life anode materials for versatile LIB applications.

CoxP compounds: electrochemical conversion/partial recombination reaction and partially disproportionated nanocomposite for Li-ion battery anodes

In this report, Co_xP binary compounds and their nanocomposites were synthesized using simple solid-state synthetic routes, and their potential as anode materials for Li-ion batteries was investigated.

Caramel popcorn shaped silicon particle with carbon coating as a high performance anode material for Li-ion batteries

Silicon is a very promising anode material for lithium ion batteries. It has a 4200 mAh/g theoretical capacity, which is ten times higher than that of commercial graphite anodes. However, when lithium ions diffuse to Si anodes, the volume of Si will expand to almost 400% of its initial size and lead to the crack of Si. Such a huge volume change and crack cause significant capacity loss. Meanwhile, with the crack of Si particles, the conductivity between the electrode and the current collector drops. Moreover, the solid electrolyte interphase (SEI), which is generated during the cycling, reduces the discharge capacity. These issues must be addressed for widespread application of this material. In this work, caramel popcorn shaped porous silicon particles with carbon coating are fabricated by a set of simple chemical methods as active anode material. Si particles are etched to form a porous structure. The pores in Si provide space for the volume expansion and liquid electrolyte diffusion. A layer of amorphous carbon is formed inside the pores, which gives an excellent isolation between the Si particle and electrolyte, so that the formation of the SEI layer is stabilized. Meanwhile, this novel structure enhances the mechanical properties of the Si particles, and the crack phenomenon caused by the volume change is significantly restrained. Therefore, an excellent cycle life under a high rate for the novel Si electrode is achieved.