Superior Storage Performance of a Si@SiO_x/C Nanocomposite as Anode Material for Lithium‐Ion Batteries

Abstract

Rechargeable lithium-ion batteries are essential to portable electronic devices. Owing to the rapid development of such equipment there is an increasing demand for lithium-ion batteries with high energy density and long cycle life. For high energy density, the electrode materials in the lithium-ion batteries must possess high specific storage capacity and coulombic efficiency. Graphite and LiCoO 2 are normally used and have high coulombic efficiencies (typically >90%) but rather low capacities (372 and 145 mAhg -1 , respectively). [1][2][3][4][5] Various anode materials with improved storage capacity and thermal stability have been proposed for lithium-ion batteries in the last decade. Among these, silicon has attracted great interest as a candidate to replace commercial graphite materials owing to its numerous appealing features: it has the highest theoretical capacity (Li 4.4 Siº4200 mAhg ) of all known materials, and is abundant, inexpensive, and safer than graphite (it shows a slightly higher voltage plateau than that of graphite as shown in Figure S1, and lithiated silicon is more stable in typical electrolytes than lithiated graphite [6]).The practical use of Si powders as a negative electrode in lithium-ion batteries is, however, still hindered by two major problems: the low intrinsic electric conductivity and severe volume changes during Li insertion/extraction processes, leading to poor cycling performance. [7][8][9][10][11][12][13][14][15][16][17][18][19][20] Tremendous efforts have been made to overcome these problems by decreasing the particle size, [7, 8a,b] using silicon-based thin films and silicon-metal alloys, [9,10, 20] dispersing silicon into an inactive/ active matrix, [11][12][13][14][15][16][17][18][19] and coating with carbon as well as using different electrolyte systems. [15, 20] In these approaches a variety of composites of active and inactive materials have been widely exploited in which the inactive component plays a structural buffering role to minimize the mechanical stress induced by huge volume change of active silicon, thus preventing the deterioration of the electrode integrity. [11][12][13][14][15][16][17][18][19] Recent work has demonstrated that anodes made of silicon/ carbon composites can combine the advantageous properties of carbon (long cycle life) and silicon (high lithium-storage capacity) to improve the overall electrochemical performance of the anode for lithium-ion batteries. [8c,9b, 11-13,15-17] In contrast to these rather complicated high-temperature processes we report here a new, simple, and green methodology for the simultaneous coating of preformed silicon nanoparticles in a one-step procedure with a thin layer of SiO x and carbon by the hydrothermal carbonization of glucose. This Si@SiO x /C nanocomposite with a typical core/shell structure, which was further modified by electrochemical in situ generation of a passivated layer, shows remarkably improved lithium-storage performance in terms of high reversible lithium-storage capacity (º1100 mAhg -1 ), ex...

Surface Modification of CNTs with N-Doped Carbon: An Effective Way of Enhancing Their Performance in Supercapacitors

“…18 This also includes coating of various pre-formed nanostructures. 19 We have used preformed carbon nanotubes and coated them with a thin layer of glucosamine-derived hydrothermal carbons and studied the performance of the resulting carbon-carbon composite in supercapacitors. A 3-to 4-fold increase in specific capacitance per surface area was registered at low current densities and sweep rates, and a 2-fold increase in energy density, while keeping the power density.…”

Silicon-based nanomaterials for lithium-ion batteries

“…In addition to the utilization of conductive carbonaceous materials to combine with Si, core/shell structure with Si core were utilized for the formation of stable SEI via pyrolysis of organic precursors [33][34][35][36]. For example, Si nanoparticles were coated with carbon by the hydrothermal carbonization of glucose to obtain Si@SiO x /C nanocomposite [34].…”

“…For example, Si nanoparticles were coated with carbon by the hydrothermal carbonization of glucose to obtain Si@SiO x /C nanocomposite [34]. The reversible capacity of Si@SiO x /C nanocomposite was as high as 1100 mAh g -1 under a current density of 150 mA g -1 with no further decay of capacity even after 60 cycles in the electrolyte of 1 mol/L LiPF 6 in EC/DMC (1:1, v/v) containing 2 wt% VC.…”

“…low Coulombic efficiency) and short cycle life. Except for the stable coating layer on the surface of Si [18,39], the electrolyte containing VC with 1 mol/L LiPF 6 in EC/DMC solution has been recognized to favor the formation of stable SEI [34]. Furthermore, sodium alginate, polyacrylic acid and sodium carboxymethylcellulose with carboxyl groups are potential binders for Sibased electrodes compared with the commonly used poly (vinylidene fluoride) for Si-based electrode materials [40][41][42][43].…”

Cellulose/Polysulfonamide Composite Membrane as a High Performance Lithium-Ion Battery Separator

“…The surface morphology of cellulose/PSA composite membrane was observed by a Hitachi S-4800 field emission scanning electron microscope (SEM). The air permeability of the membrane was examined with a Gurley densometer (4110N, Gurley) by measuring the time for air to pass through a determined volume (100 cm 3 ). The porosity of the membrane was measured using the method of n-butyl alcohol immersion by immersing in n-butanol 1 h, and then calculating the porosity using the equation: porosity = (m a /ρ a )/(m a /ρ a + m b /ρ b ) × 100%, where m a and m b are the mass of n-butanol and the membrane and ρ a and ρ b are the density of n-butanol and the membrane, respectively.…”