Carbon-free high-loading silicon anodes enabled by sulfide solid electrolytes.

The development of silicon anodes for lithium-ion batteries has been largely impeded by poor interfacial stability against liquid electrolytes. Here, we enabled the stable operation of a 99.9 weight % microsilicon anode by using the interface passivating properties of sulfide solid electrolytes. Bulk and surface characterization, and quantification of interfacial components, showed that such an approach eliminates continuous interfacial growth and irreversible lithium losses. Microsilicon full cells were assembled and found to achieve high areal current density, wide operating temperature range, and high areal loadings for the different cells. The promising performance can be attributed to both the desirable interfacial property between microsilicon and sulfide electrolytes and the distinctive chemomechanical behavior of the lithium-silicon alloy.

In Situ Construction of High-Performing Compact Si-SiOx-CNx Composites from Polyaminosiloxane for Li-Ion Batteries.

Great efforts have been made to design high-performing Si/C composite anodes for Li-ion batteries to improve their energy density and cycling life. However, challenges remain in achieving fast electrical conductivity while accommodating significant electrode volumetric changes. Here, we report a unique Si/C-based anode architecture, a Si-SiOx-CNx composite, which is simultaneously constructed via the pyrolysis of a polyaminosiloxane precursor. The obtained structure features high-purity Si nanocrystals embedded in an amorphous silica matrix and then embraced by N-doped carbon layers. Notably, in this structure, all three components derived from the polyaminosiloxane precursor are linked by chemical bonding, forming a compact Si-SiOx-CNx triple heterostructure. Because of the improvement in the volumetric efficiency for accommodating Si active materials and electrical properties, this anode design enables promising electrochemical performance, including excellent cycle performance (830 mAh g-1 after 100 cycles at 0.1 A g-1) and outstanding rate performance (400 mAh g-1 at 5 A g-1). Moreover, this composite anode demonstrates great potential for high-energy Li-ion batteries, where a Si-SiOx-CNx//LiNi0.9Co0.1O2 full-cell shows a high capacity of 180 mAh g-1 as well as stable cycle performance (150 mAh g-1 after 200 cycles at 0.19 A g-1).

Toward Mechanically Stable Silicon-Based Anodes Using Si/SiO x@C Hierarchical Structures with Well-Controlled Internal Buffer Voids.

Low conductivity and structural degradation of silicon-based anodes lead to severe capacity fading, which fundamentally hinders their practical application in Li-ion batteries. Here, we report a scalable Si/SiO x@C anode architecture, which is constructed simultaneously by sintering a mixture of SiO/sucrose in argon atmosphere, followed by acid etching. The obtained structure features highly uniform Si nanocrystals embedded in silica matrices with well-controlled internal nanovoids, with all of them embraced by carbon shells. Because of the improvement of the volumetric efficiency for accommodating Si active spices and electrical properties, this hierarchical anode design enables the promising electrochemical performance, including a high initial reversible capacity (1210 mAh g-1), stable cycling performance (90% capacity retention after 100 cycles), and good rate capability (850 mAh g-1 at 2.0 A g-1 rate). More notably, the compact heterostructures derived from micro-SiO allow high active mass loading for practical applications and the facile and scalable fabrication strategy makes this electrode material potentially viable for commercialization in Li-ion batteries.

Scalable Preparation of Ternary Hierarchical Silicon Oxide-Nickel-Graphite Composites for Lithium-Ion Batteries.

Silicon monoxide is a promising anode candidate because of its high theoretical capacity and good cycle performance. To solve the problems associated with this material, including large volume changes during charge-discharge processes, we report a ternary hierarchical silicon oxide-nickel-graphite composite prepared by a facile two-step ball-milling method. The composite consists of nano-Si dispersed silicon oxides embedded in nano-Ni/graphite matrices (Si@SiOx /Ni/graphite). In the composite, crystalline nano-Si particles are generated by the mechanochemical reduction of SiO by ball milling with Ni. These nano-Si dispersed oxides have abundant electrochemical activity and can provide high Li-ion storage capacity. Furthermore, the milled nano-Ni/graphite matrices stick well to active materials and interconnect to form a crosslinked framework, which functions as an electrical highway and a mechanical backbone so that all silicon oxide particles become electrochemically active. Owing to these advanced structural and electrochemical characteristics, the composite enhances the utilization efficiency of SiO, accommodates its large volume expansion upon cycling, and has good ionic and electronic conductivity. The composite electrodes thus exhibit substantial improvements in electrochemical performance. This ternary hierarchical Si@SiOx /Ni/graphite composite is a promising candidate anode material for high-energy lithium-ion batteries. Additionally, the mechanochemical ball-milling method is low cost and easy to reproduce, indicating potential for the commercial production of the composite materials.