Silicon Nanowires and Lithium Cobalt Oxide Nanowires in Graphene Nanoribbon Papers for Full Lithium Ion Battery

Abstract

a few examples have attained small increments of capacity or higher voltage operation >5 V versus Li/Li + . [5][6][7] An exception is sulfur, which has an outstanding capacity of 1675 mA h g −1 , but a lower voltage of operation of 2.1 V. [8] On the other hand, several high capacity alternatives, such as Li metal, Si, and other alloying metals (Sn, Sb, Al) are possible in anode applications. [9] This higher capacity can decrease the total amount of anode mass necessary to compose the batteries, increasing the energy density. In this sense, Si is particularly attractive due to its practical capacity of ≈3500 mA h g −1 (the theoretical capacity is 3579 mA h g −1 at room temperature, based on Li 15 Si 4 alloy), [10] its earth abundance, environmental friendliness, stability at ambient atmosphere and its average delithiation potential of ≈0.4 V, which is similar to graphite's of 0.15 V versus Li/Li + . Hence, Si is compatible with the same high voltage operation of ≈3.7 V when combined with commercial cathodes. [11] The hurdles associated with Si anodes, such as its large volume expansion of up to 300%, low electronic conductivity and high reactivity with common electrolytes, can compromise its stability and capacity. [12] This has been previously addressed by employing capped Si nanostructures to prevent pulverization, [13,14] by using Si/C nanocomposites, [15] by limiting the extension of Li reaction with Si [16] and by using specifically designed electrolytes to control the solid electrolyte interphase (SEI) formation. [17,18] The SEI should be stable and it is especially important in materials that develop high volume expansion during Li uptake, or else the cracking can result in electrolyte decomposition over the bare Si surface. These strategies have generated anodes that deliver gravimetric capacities much higher than those seen in graphite. However, a higher gravimetric or specific capacity is by no means the most important factor to outperform graphite as an anode in LIBs. [19,20] A material with a higher specific capacity must also be distributed over a small area because of the limited size of LIB electrodes, displaying a competitive areal and volumetric capacity that at least meets current industry standards for graphite, which is 2-4 mA h cm −2 and >600 Wh L −1 . Most Si anode half-cells have been reported to have high specific capacities of 1000-3000 mA h g −1 , but there is limited information regarding their areal capacity. [20] Noting that cycle life and electrode thickness are inversely proportional, [21,22] a reliable comparison among electrodes becomes exceedingly difficult without fully understanding the gravimetric, areal, and volumetric capacities.Described here is the production and characterization of a scalable method to produce 3D structured lithium ion battery anodes using free-standing papers of porous silicon nanowires (Si-NW) and graphene nanoribbons (GNRs). Using simple filtration methods, GNRs and Si-NWs can be entangled into a mat thereby forming Si-NW GNR papers. This produces anode...

High areal capacity battery electrodes enabled by segregated nanotube networks

“…5f (see calculations and literatures in Supplementary Table 6−7). 9,[32][33][34]36 This plot shows that our high-C/A full-cells delivered much higher ESP (up to 401 Wh kg -1 ) than any other reports (<261 Wh kg -1 , open symbols), highlighting their superlative performance. We note that, after calendaring to increase the density of both electrodes by ~60% and so decrease electrolyte mass, we could increase the energy density up to 480 Wh kg -1 , a value which is nearly twice the state-of-the-art (see Supplementary Table 7).…”

“…Standard additives such as carbon black (CB) yield low, inhomogeneous and unstable electrode conductivity, [3][4][5] limiting electrochemical performance, especially for very thick electrodes. 6 While a number of methods have been suggested to maximize C/A, [7][8][9][10][11][12][13][14][15][16] none are scalable. We aim to develop a general, materials science-based strategy that allows the production of very thick electrodes which retain almost all of their theoretical capabilities.…”

“…To demonstrate that high C/A can be achieved using SNCs, we produced sets of 2 m Table 3−5). [9][10][11][24][25][26][27][28][29] The disconnection of silicon from the electrode due to crack-formation is a known capacityloss mechanism in Si-based LiBs. 30 These extremely thick electrodes are relatively stable ( Fig.…”

Advanced 3D Current Collectors for Lithium‐Based Batteries

“…In addition, the aspect ratio of the nanowires has an important influence on the physical properties of the freestanding stacked nanowires papers. It is reported that nanowires of a larger aspect ratio result in nanowire papers of higher free volume fraction so that higher mass loading of the active materials can be enabled . Durstock and co‐workers reported an assembly consisting of interconnect Ni nanofibers of diameters of 100–1000 nm ( Figure a) .…”

Group IVA Element (Si, Ge, Sn)‐Based Alloying/Dealloying Anodes as Negative Electrodes for Full‐Cell Lithium‐Ion Batteries

“…Salvatierra et al prepared a free‐standing nanocomposite paper of porous Si‐NWs and graphene nanoribbons (GNRs) by a cofiltration method . The interconnected Si‐NWs and GNRs formed a stable conductive path across the paper, which made it more robust and flexible.…”