Harvesting Interconductivity and Intraconductivity of Graphene Nanoribbons for a Directly Deposited, High-Rate Silicon-Based Anode for Li-Ion Batteries

Abstract

Batteries for high-rate applications such as electric vehicles need to be efficient at mobilizing charges (both electrons and ions). To this end, choice of the conductive carbon in the electrode can make a significant difference in the performance of the electrode. In this work, graphene nanoribbons (GNRs) are explored as conductive pathways for a silicon-based anode. Water-based electrospinning is employed to directly deposit poly(vinyl alcohol) (PVA)−silicon−graphene nanoribbon composite fibers on a copper current collector. The size of the employed GNRs dictates their placement: either inside each fiber (small GNRs) or as a bridge between multiple fibers (large GNRs). Galvanostatic charge/discharge cycles reveal that fibers with GNRs have higher capacity and overall retention compared to those with corresponding precursor carbon nanotubes (CNTs). To further distinguish the effectiveness of GNRs as the conductive agent, samples with two GNRs and their parent CNTs were subject to rate-capability tests. Fibers with large GNR inclusions exhibit an excellent performance at fast rates (1400 mAh g −1 at 12.6 A g −1 ). For both pairs, enhancement in the performance of GNRs over CNTs grows with increasing rates. Finally, a small amount of large GNRs (1 wt %) is blended with small GNRs in the fibers to create synergy between intra-and interconductivity provided by small and large GNRs, respectively. The resulting fiber mat exhibits the same capacity as that of only small GNRs, even at a current rate that is 4 times higher (300 mAh g −1 at 21 A g −1 ).

Mitigation and In Situ Probing of Volume Expansion in Silicon/Graphene Hybrid Anodes for High‐Capacity, High‐Rate‐Capable Lithium‐Ion Batteries

“…The high capacity is obtained due to the enhanced activation of silicon due to the presence of GNR. [38] The initial columbic efficiency for both Si/Gr/GNR with and without pores is very similar, 74.25 and 74.5, respectively, giving another confirmation of similar composition leading to similar electrochemical reactions and inline with our CV results. The loss of initial columbic efficiency is due to several factors such as 1) formation of SEI layer on SiNp, 2) high surface area of graphene sheets leading to the irreversible reactions, and 3) electrochemical activity of polyimide.…”

“…Third, the added graphene nanoribbon (GNR), which is obtained from chemically unzipping carbon nanotube (CNT), acts as a conductive pathway to ensure that the silicon inside the voids is electronically connected to the graphene sheets and offers a pathway for shorter transport of the lithium ions. [37,38] To prove our hypothesis of mitigation of silicon volume expansion via the creation of internal pores, we also carry out in situ volume expansion measurements of small pouch cells via a dilatometer and compare the resulting mitigation of volume expansion for Si/Gr/GNR anode with pores and that without pores, finding a reduction of almost 50% in the volume expansion. To the best our knowledge, the interplay of creation of pores and the resulting mitigation of volume expansion over a number of charge/discharge cycles via in situ measurement have never been quantitatively probed before.…”

Ultrahigh Malleability of the Lithiation-Induced LixSi Phase

“…Previous experiments have already demonstrated that the Si–C composite is one of the best solutions for high-performance anodes in many cases. For instance, the C-coated Si materials, such as Si–C yolk–shell, − Si particles in C fiber matrix, − C-coated mesoporous Si, and graphene/Si composite anode − exhibit much less volume expansion during lithiation and stable cycling performance.…”

Polymer reinforced carbon fiber interfaces for high energy density structural lithium-ion batteries

“…Along the theme of structural batteries and supercapacitors, recent studies have also made signicant progress designing electrode architectures that can be drop-in components to multifunctional or structural battery design and sustain mechanical stress independent of interface coupling challenges. [51][52][53][54][55] With this said, with a growing broad research interest in studying structural supercapacitors and batteries that require stable energy storage operation under mechanical loading, there surprisingly have been little to no studies studying interfaces and interface design in these systems.…”