Designed Formation of Yolk–Shell-Like N-Doped Carbon-Coated Si Nanoparticles by a Facile Method for Lithium-Ion Battery Anodes

Abstract

Silicon (Si) is considered as a promising anode material for lithium-ion batteries (LIBs) because of its ultrahigh capacity (3579 mA h g–1, Li15Si4). However, the irreversible huge volume change during cycling and poor conductivity hinder its practical application. Nanoscale shortens electron and ion transport paths and provides more active sites. To solve these problems, yolk–shell-like N-doped carbon-coated Si nanoparticles (Si@void@NC) were designed and prepared by a simple solution coating method and a high-temperature calcination process. Si@void@NC exhibits two advantages: First, the prepared hollow structure is favorable for buffering the volume expansion. Second, the N-doped carbon layer coating on Si can improve the conductivity and reduce the volume change during cycling. The as-prepared sample exhibits 697.7 mA h g–1 at 0.2 A g–1 after 100 cycles and a capacity retention of 475.1 mA h g–1 at 0.5 A g–1 after 400 cycles. This strategy of designation and preparation of yolk–shell-like N-doped carbon-coated Si nanoparticles provides a way to construct ideal Si-based composite materials for LIBs.

Synthetic Strategy of Si@void@C Nanoparticles for High-Performance Lithium-Ion Battery Anodes

“…As seen in Figure a, the peaks at 28, 47, 56, 69, 76, and 88° represent the (1 1 1), (2 2 0), (3 1 1), (4 0 0), (3 1 1), and (4 2 2) planes of silicon, which is consistent with the above HRTEM result. − A weak and broad peak can be observed at 23°, which indicates that the carbon layer is amorphous with a low graphitization degree . No existence of unknown peak demonstrates the high purity of the prepared material.…”

Ultrathin Carbon Sheet Obtained by Self-Template Method toward Highly Effective Charge Transfer for Si-Based Anodes

“…Nevertheless, these strategies are often costly, environmentally unfriendly, and not suitable for scalable production. Additionally, the spherical or polyhedral morphologies of as-synthesized composites make it difficult to ensure effective electrical contact between nanoconductive additives and active materials, which is mainly initiated by the agglomeration of conductive agents and the limited contact area. , This will further aggravate the formation of two-phase interface stress during the uneven lithiation process . Concomitantly, the fatal electric disconnection issues are triggered by inevitable expansion and slip of the composites, leading to electric isolated and failed charge transfer .…”

Facile Synthesis of Ultrasmall SnO2/Sn Nanoparticles Grown on the N-Doped Carbon Framework as a Long-Life Anode Material

“…Reducing the particle size is an effectual strategy. Smaller particle size can help diminish the volume variation in the Li + insertion and release process and shorten the lithium ion diffusion distance. − Integrating SnO 2 with N-doped carbon is another effectual strategy, which can further dramatically mute the volume variation in the Li + insertion and release process and quicken the lithium ion and electron transfer speed. − Introducing an appropriate amount of Sn is also an effectual strategy to suppress the volume change in the lithium insertion and release process and improve cyclic stability, − which could be interpreted by the two-stage electrochemical reaction process of SnO 2 : a conversion process (converting SnO 2 into Sn) and an alloying process of Sn. During the conversion reaction stage, the introduced Sn can be a buffer for volume change; in the alloying reaction stage, the formed Li 2 O in the first stage can also relieve the volume change and protects active materials from aggregating.…”