Nitrogen, Oxygen‐Codoped Vertical Graphene Arrays Coated 3D Flexible Carbon Nanofibers with High Silicon Content as an Ultrastable Anode for Superior Lithium Storage

Abstract

Free‐standing and foldable electrodes with high energy density and long lifespan have recently elicited attention on the development of lithium‐ion batteries (LIBs) for flexible electronic devices. However, both low energy density and slow kinetics in cycling impede their practical applications. In this work, a free‐standing and binder‐free N, O‐codoped 3D vertical graphene carbon nanofibers electrode with ultra‐high silicon content (VGAs@Si@CNFs) is developed via electrospinning, subsequent thermal treatment, and chemical vapor deposition processes. The as‐prepared VGAs@Si@CNFs electrode exhibits excellent conductivity and flexibility because of the high graphitized carbon nanofiber network and abundant vertical graphene arrays. Such 3D all‐carbon architecture can be fabulous for providing a conductive and mechanically robust network, further improving the kinetics and restraining the volume expansion of Si NPs, especially with an ultra‐high Si content (>90 wt%). As a result, the VGAs@Si@CNFs composite demonstrates a superior specific capacity (3619.5 mAh g−1 at 0.05 A g−1), ultralong lifespan, and outstanding rate capability (1093.1 mAh g−1 after 1500 cycles at 8 A g−1) as a free‐standing anode for LIBs. It is believed that this work offers an exciting method for developing free‐standing and high‐energy‐density electrodes for other energy storage devices.

Fe/Fe3C modification to effectively achieve high-performance Si–C anode materials

“…3a, in which diffraction peaks reecting silicon were detected at 28.4 , 47.3 , 56.1 , 69.1 , and 76.4 (JCPDS# 27-1402), corresponding to the (111), ( 220), ( 311), (400), and (331) planes, and the diffraction peak representing the CNFs was at $26 . 16,17 In addition, Fe/Fe 3 C-Si@CNFs shows obvious diffraction peaks of Fe 3 C (JCPDS# 89-2867), which is the main component in the high-temperature annealing process, 39,40 and weak diffraction peaks of Fe (JCPDS# 89-7194). 32 In short, it is further demonstrated that Fe/Fe 3 C with a modied interface is successfully doped in Fe/Fe 3 C-Si@CNFs.…”

Constructing a Yolk–Shell Structure SiOx/C@C Composite for Long-Life Lithium-Ion Batteries

“…Therefore, improving the conductivity of silicon electrodes is necessary even if this strategy may offset the superiority of high capacity. 14,15 In order to overcome the above problems and effectively boost the electrochemical performance of silicon-based electrodes, researchers have paid lots of effort. A series of modification methods has been developed, including nanocrystallization, 16,17 surface coating, 18,19 and structure design, 20,21 to heighten the conductivity of silicon-based anodes.…”

“…Energy depletion and environmental pollution have gradually become major problems that cannot be ignored in today’s world, while the pursuit of sustainable development is meaningful. − At present, consumers focus on green new energy storage technologies and devices represented by lithium-ion batteries (LIBs), which are usually used in 3C electronics on account of their advantages of high operating voltage, long service life, and environmental friendliness. − Conventional commercial LIBs based on graphite anodes are unable to match the need for high energy density, which suffer from limited theoretical specific capacity (372 mAh g –1 ). − On this basis, silicon-based anodes have become the most potential substitute for commercial graphite anodes in the future because of their high theoretical specific capacity (∼4200 mAh g –1 ) and suitable operating voltage (<0.5 V vs Li/Li + ). , Nevertheless, the enormous volume changes of silicon materials in repeated galvanostatic discharge/charge processes lead to the rapid attenuation of capacity and even cause safety problems, which seriously restricts the commercial application of silicon-based LIBs. , In addition, silicon-based materials are a common semiconductor material which has poor electrical conductivity. Therefore, improving the conductivity of silicon electrodes is necessary even if this strategy may offset the superiority of high capacity. , …”

Realizing the high energy density and flexibility of a fabric electrode through hierarchical structure design

“…So far, various hybrid flexible electrodes with 1D building blocks have been reported, including MoS 2 /C, phosphide/C and Si/C. 13–22 Although certain flexibility can be achieved, the active materials are usually loaded on the surface of the flexible carbon substrates, which may fall off during the bending process due to structural rigidity and the lack of protection, leading to rapid capacity decay. 23 The encapsulation of active materials within the carbon matrix is one possible way to avoid these issues.…”