Anode For Rechargeable Lithium Batteries Research Articles

Development of Aluminum-Foil Anodes for Rechargeable Lithium Batteries

Alloy anode materials, such as silicon, tin, and aluminum, are expected to be used in rechargeable lithium batteries owing to high theoretical capacities, compared to conventional carbonaceous anodes. However, the high capacities inevitably cause drastic volume change (+100~300%) of the anode materials during battery reactions (i.e., lithium insertion and extraction), which usually leads to fatal structural degradation.[1,2] Although downsizing the anode materials into fine particles is an effective way to endure the huge volume change,[3] the complicated preparation process raise the production costs, and the indispensable supporting substance (e.g. polymer binder, current collector) for the active material particles decreases the practical capacity of the total anode. Therefore, easy-to-manufacture strategy is still strongly demanded for practical application of alloy anode materials towards high energy-density and low-cost rechargeable lithium batteries.Recently, we have reported a metallurgical approach which stabilizes the structure change of Al foils during repeated lithiation and delithiation. By adjusting the composition and hardness of the Al matrix, a homogeneous in-plane lithiation and an out-of-plane (one-dimensional) volume expansion (+100%) are achieved during lithiation.[4] Because the LiAl phase has a certain tolerance to off-stoichiometry composition, a concentration gradient can be formed from the surface to the inside of Al foils, driving the interdiffusion of Al and Li. During delithiation, the Al matrix is recrystallized and self-organized to pillar/porous structure, which can tolerant the volume changes in subsequent cycles. The reversible structure changes allow the Al foils to work as self-contained anodes. The Al-foil anodes can be divided into a surface layer that alloys Li, and a base layer that maintains the structural stability and electric conductivity. However, during cycling, the electrolyte exhibits a significant impact on the structure stability of the Al-foil anodes. The decomposition products of the conventional carbonate-based electrolytes, such as 1 M LiPF6 in EC-DMC, easily passivate the surface of Al-foil anodes. As a result, the base layer is gradually consumed during cycling accompanied with the pulverization of the surface layer. The electrolyte permeates the fresh Al surface would further passivate the Al surface. Eventually, the capacity would be vanished, when the Al-foil anodes are completely pulverized, or the electrolytes are completely decomposed.To extend the cycle life of Al-foil anodes, in this presentation, we summarize the degradation mechanism of the Al-foil anodes and introduce the improvement strategies from various perspectives, including alloy additions, electrolyte selection and the structural design. Appropriate alloy additions can moderate the surface formation of Al matrix during delithiation, which prevent the electrolyte permeation. In addition, salt concentrations, anion and solvent combinations markedly affects the electrolyte compatibility with the Al-foil anodes, where the cyclability can be significantly improved with electrolytes that are less susceptible to passivating the Al surface. Furthermore, introducing distinct thermodynamic and kinetic characteristics between the surface and base layers, such as cladding Al foils,[5] can effectively prevent the electrolyte permeation and Li penetration consume the base layer.[1] T. Ichitsubo et al, J. Mater. Chem. A 21, 2701 (2011).[2] T. Ichitsubo et al, J. Electrochem. Soc. 159, A14 (2012).[3] T. Wada, T. Ichitsubo et al, Nano Lett. 14, 4505 (2014).[4] H. Li, T. Ichitsubo et al, Nat. Commun. 11, 1584 (2020).[5] H. Li, T. Ichitsubo et al, J. Mater. Chem. A 11, 23311 (2023).

Utilizing Cladding Processes to Enhance Structural Stability of Aluminum-Foil Anodes for Rechargeable Lithium Batteries

Al-foil anodes are attractive candidate materials for rechargeable lithium batteries owing to their high theoretical capacities (993 mAh g-1, Al+Li++e -=LiAl) and low production costs. Within appropriate hardness and composition, the Al foils can work as self-standing anodes, where the surface layer reacts with Li as the active material, and the base layer remain unreacted to hold the structural stability as the current collector. However, during battery cycling, the base layer of Al foils is prone to be consumed due to surface passivation by cathodic decomposition products of electrolyte species. Eventually, the Al-foil anodes are totally pulverized, and the reversible capacity is completely diminished.To limit the reaction depth and protect the base layer, we combine Al foils with various alloy additions (such as Si, Mn, and Mg) by roll-bonding processes to prepare clad foils. [2] The alloy additions change the mechanical properties of Al matrix and affect the lithiation potentials.[3] Thus, the clad Al foils with different alloy additions can create lithiation potential gaps to prevent the Li penetration into the base layer. In particular, the lithiation potentials of 99.99%Al, Al-1%Si, Mn-based A3003 and Mg-based A5052 foils are compared using galvanostatic intermittent titration technique (GITT) measurements. Among the various Al foils, A5052 shows lowest lithiation potential close to 0 V vs Li, where the hard matrix significantly retards the lithiation reaction. The clad foils of Al / A5052 and Al-1%Si / A5052 exhibit a lithiation potential gap up to 0.15 V. By setting the appropriate cutoff potential to utilize the lithiation potential gap, the Li penetration to the base layer is successfully blocked and the structural stability is enhanced.[1] H. Li, T. Ichitsubo et al, Nat. Commun. 11, 1584 (2020).[2] H. Li, T. Ichitsubo et al, J. Mater. Chem. A 11, 23311 (2023).[3] T. Ichitsubo et al, J. Electrochem. Soc. 159, A14 (2011).

Tuning wettability of gallium-based liquid metal anode for lithium-ion battery via a metal mixing strategy

Exploring highly stable alloy-type anodes for rechargeable lithium batteries is urgent with the ever-increasing demands for high energy density batteries. The liquid metal (LM)-based anodes demonstrate great potential in advanced lithium-ion batteries due to their high energy densities and self-healing performance. However, its high surface tension leads to poor wettability towards the current collector and higher interfacial contact resistance. In this study, we developed a new free-standing LM-based anode LM-W10/Cu foil with good wettability and machinability by mixing high-melting-point tungsten (W) nanoparticles. It greatly improves the inherent defects of poor interfacial contact and lithium diffusion kinetics between the LM and current collectors, reduces the tedious and costly electrode manufacturing process, and regulates lithium deposition behaviors. And this metal mixing strategy has a negligible effect on the self-healing nature of LM. Symmetric cells of LM-W10/Cu foil anodes displayed a low overpotential (~13 mV) and cycled stably for more than 8,000 h (4,000 cycles) at 0.5 or 1 mA/cm2; full cells coupled with LiFePO4 cathode showed a high capacity retention of 95.15% after 150 cycles.

Solid electrolyte interphase on anodes in rechargeable lithium batteries

Solid electrolyte interphase on anodes in rechargeable lithium batteries

Rational Synthesis of "Grape-like" Ni2 V2 O7 Microspheres as High-capacity Anodes for Rechargeable Lithium Batteries.

Vanadates have received booming attention recently as promising materials for extensive electrochemical devices such as batteries and electrocatalysis. However, the enormous difficulties of achieving pure-phase transition metal vanadates, especially for nickel-based, hinder their exploitations. Herein, for the first time, by controlling the amount of ethylene glycol (EG) and reaction time, grape-like Ni2 V2 O7 (or V2 O5 /Ni2 V2 O7 ) microspheres were rationally fabricated. It is demonstrated that the EG can chelate both Ni2+ and VO3 - to form organometallic precursors. As anode in lithium-ion batteries (LIBs), it could deliver superior reversible capacity of 1050 mAh/g at 0.1 A/g and excellent rate capability of 600 mAh/g at 4 A/g. The facile hydrothermal synthesis broadens the material variety of nickel vanadates and offers new opportunities for their wider applications in electrochemistry.

A low-cost and high-loading viologen-based organic electrode for rechargeable lithium batteries.

Organic active materials are regarded as a very promising choice for lithium batteries because of several outstanding advantages such as low-cost, flexible tunability and pollution-free sources. Viologen compounds are attractive two-electron storage materials with low redox potentials, which are mainly used as anolytes in redox flow batteries (RFBs) considering their high solubility in electrolytes. However, due to their relatively large molecular weight and low density, it is difficult to prepare high-loading and stable-cycling electrodes for lithium battery application. In this research, by adopting 4,4′-bipyridine as the raw material and combining salification with a high-energy ball milling method, a low-solubility and high-stability viologen carbon-coated composite, ethyl viologen dihexafluorophosphate-Ketjen black (EV-KB), is synthesized. Then, by optimizing the electrode preparation process, a high-loading viologen-based electrode is successfully prepared. Salification effectively reduces the solubility of viologen compounds in the electrolyte so that the EV-KB composite can be used in lithium batteries. At the same time, it is pointed out that current collectors and slurry solvents play an important role in achieving the high-loading electrode. By deliberately selecting carbon paper as the current collector and ethanol as the solvent, the EV-KB composite organic electrode with a loading up to 1.5–9 mg cm−2 can achieve a specific capacity of 106–79 mA h g−1 for 400 stable cycles with a coulombic efficiency of 96% as well as a good rate capability. The synthesis method and electrode preparation optimization process introduced in this paper provide a reference for other types of organic active materials to be used in high-loading lithium batteries.

Inducing uniform lithium nucleation by integrated lithium-rich li-in anode with lithiophilic 3D framework

Lithium metal has been regarded as the most ideal choice to be anode for rechargeable lithium batteries. However, lithium dendrites growth and unstable interface between lithium and electrolyte result in security risk and poor cyclic performance, hindering practical applications of lithium anode. By analyzing kinetic parameters and the morphology of initial lithium deposition, we find that In3Li13 substrate exhibits excellent lithiophilic nature with extremely small nucleation barrier of lithium. Thus, an integrated Li-rich Li-In anode with lithiophilic In3Li13 framework was designed and prepared by a facile one-step vacuum evaporation approach. The framework reduces the local current density and accommodates lithium in the interior space. Most importantly, the lithiophilic In3Li13 can guide uniform Li nucleation. Via the synergy of lithiophilic framework in structure and interface, the designed integrated Li-In anode exhibits excellent electrochemical performance. Symmetric cells with the Li-In anode stably cycle for over 230 hours, about four times the lifespan of the cell with the pure lithium anode. In the full cells with LiFePO4 cathode, the capacity retention is improved from 83.6% to 97.7% after 160 cycles with the Li-In anode. These attempts deepened the understanding of Li nucleation on lithiophilic substrate and provide new insight for designing high-performance lithium anode.

Toward high lithium conduction in solid polymer and polymer–ceramic batteries

Summary High-energy-density batteries use lithium electrodes because they provide the highest theoretical capacity and widest electrochemical potential window of all the possible anodes for rechargeable lithium batteries. However, adoption of metallic lithium leads to safety problems and low cycling performance due to the reactivity of lithium with standard liquid electrolytes (LEs). Solid electrolytes (SEs) are a promising solution to replace LEs due to their high thermal and chemical stability. They also possess numerous other advantages such as light-weight, flexibility, low-cost and a high operating window voltage. The aim of this review is to present a summary of recent advances in polymer and inorganic SEs for all-solid lithium metal batteries (LMBs). We will discuss the replacement of polyethylene oxide (PEO) and the crucial parameters for achieving a suitable combination of polymer matrix with inorganic ceramic fillers to obtain viable SE composites for high-voltage and high-capacity cell.

Synthesis and Electrochemical Reaction of Tin Oxalate-Reduced Graphene Oxide Composite Anode for Rechargeable Lithium Batteries.

Unlike for SnO2, few studies have reported on the use of SnC2O4 as an anode material for rechargeable lithium batteries. Here, we first introduce a SnC2O4-reduced graphene oxide composite produced via hydrothermal reactions followed by a layer-by-layer self-assembly process. The addition of rGO increased the electric conductivity up to ∼10-3 S cm-1. As a result, the SnC2O4-reduced graphene oxide electrode exhibited a high charge (oxidation) capacity of ∼1166 mAh g-1 at a current of 100 mA g-1 (0.1 C-rate) with a good retention delivering approximately 620 mAh g-1 at the 200th cycle. Even at a rate of 10 C (10 A g-1), the composite electrode was able to obtain a charge capacity of 467 mAh g-1. In contrast, the bare SnC2O4 had inferior electrochemical properties relative to those of the SnC2O4-reduced graphene oxide composite: ∼643 mAh g-1 at the first charge, retaining 192 mAh g-1 at the 200th cycle and 289 mAh g-1 at 10 C. This improvement in electrochemical properties is most likely due to the improvement in electric conductivity, which enables facile electron transfer via simultaneous conversion above 0.75 V and de/alloy reactions below 0.75 V: SnC2O4 + 2Li+ + 2e- → Sn + Li2C2O4 + xLi+ + xe- → LixSn on discharge (reduction) and vice versa on charge. This was confirmed by systematic studies of ex situ X-ray diffraction, transmission electron microscopy, and time-of-flight secondary-ion mass spectroscopy.

Characterization and Electrochemical Properties of Nanostructured Zr-Doped Anatase TiO2 Tubes Synthesized by Sol–Gel Template Route

A series of nanostructured Zr-doped anatase TiO2 tubes with the Zr/Ti molar ratio of 0.01, 0.02, 0.03, and 0.09 were prepared by a sol–gel technology on a carbon fiber template. The electrochemical performance of Zr-doped anatase TiO2 as anodes for rechargeable lithium batteries was investigated and compared with undoped titania. Tests represented that after 35-fold charge/discharge cycling at C/10 the reversible capacity of Zr-doped titania (Zr/Ti = 0.03) reaches 135 mA h g−1, while the capacity of undoped titania (Zr/Ti = 0) yielded only 50 mA h g−1. Based on the results of the physicochemical investigation, three reasons of improving electrochemical performance of Zr-doped titania were suggested. According to the scanning electron microscopy and transmission electron microscopy, Zr4+ doping induces a decrease in nanoparticle size, which facilitates the Li+ diffusion. The Raman investigations show the more open structure of Zr-doped TiO2 as compared to undoped titania due to changing of the unit cell parameters, that significantly affects on the reversibility of the insertion/extraction process. The electrochemical impedance spectroscopy results indicate that substitution of Zr4+ for Ti4+ into anatase TiO2 has favorable effects on the conductivity.

Accommodating Lithium into a Three-Dimensional Carbon Framework As the Anode for Rechargeable Lithium Batteries

Introduction Lithium has drawn great attentions for its unprecedentedly high theoretical specific capacity (3860 mAh g-1) and low redox potential (-3.04V vs NHE). However, the growth of lithium dendrites will cause security problems which restrict the application of lithium metal. It has been proved that the current collector could play an important role in the protection of the lithium metal. In this work, we report a kind of carbon paper which can effectively relieve the growth of lithium dendrites as a three-dimensional (3D) current collector. This 3D-network material, which is constructed with carbon nanotube fibers, can provide a conductive network and a large specific surface area for lithium deposition. The lithium-ions can deposit on the fiber surface uniformly which confines lithium metal deposition within the 3D current collectors. Therefore, this 3D current collector gives a good result to suppress the growth of lithium dendrites. Result and Discussion Fig. 1 (a) and (d) show the SEM images of the original carbon paper before charge-discharge cycles. The carbon paper is consisted of interwoven carbon fibers, which provide much larger specific surface area and more internal spaces than lithium foil to confine lithium deposition inside the 3D-structured current collectors. Fig. 1 (b), (c) and (e) show the SEM images of the carbon paper after cycles. We can obviously see that lithium metal deposits on the surface of carbon paper and no lithium dendrites can be observed. As a comparison, after the same charge-discharge cycles, a lot of lithium dendrites can be found on the surface of the lithium foil and the surface becomes very rough (Fig 1 (f)). Fig.1 (g) shows the galvanostatic discharge/charge voltage profiles of lithium anode with the carbon paper as current collector. The lithium deposition process exhibits a low overpotential of 20 mV at 0.4 mA cm-2. Fig.1 (h) shows the cycling performance of the Li/carbon paper electrode. We can see that the Li/carbon paper electrode exhibits stable voltage profiles at 0.4 mA cm-2 even after more than 570 hours charge-discharge cycles which proves that this 3D current collector exhibits an outstanding cycling stability. In this work, we use a commercial carbon paper as a 3D current collector to suppress the growth of lithium dendrites. Benefitting from the three-dimensional conductive framework which can provide electronic conduction channel to ensures the lithium ion deposit more uniformly. And this 3D current collector can also provide sufficient internal space for lithium metal deposition. Therefore, this 3D carbon current collector gives good results to inhibit the growth of the lithium dendrite. Fig. 1 (a), (d) SEM images of the original carbon paper; (b), (e) SEM images of carbon paper after lithium deposition; (c) SEM image of carbon paper (cross-section) after cycles. (f) SEM image of lithium foil (top) after cycles. (g) Galvanostatic discharge/charge voltage profile of the Li/carbon paper electrode at 0.4mA cm-2. (h) Voltage profiles of Li plating/stripping at 0.4mA cm-2 in the Li/carbon paper electrode. Figure 1

Nickel Oxalate Dihydrate Nanorods Attached to Reduced Graphene Oxide Sheets As a High Capacity Anode for Rechargeable Lithium Batteries

In the search for high capacity anode materials, a facile hydrothermal route has been developed to synthesize phase-pure NiC2O4·2H2O nanorods, which were crystallized to orthorhombic structure without using templates. To ensure the electric conductivity of the nanorods, the produced NiC2O4·2H2O nanorods were attached to reduced graphene oxide sheets via self-assembly layer-by-layer processes utilizing the electrostatic adsorption that occurs in a poly(diallyldimethylammonium chloride) solution. High electric conductivity aided by the presence of reduced graphene oxide (rGO) significantly improved the electrochemical properties: 933 mAh g-1 for the charge capacity (oxidation), which showed 87.5% efficiency at the first cycle with its retention approximately 85% for 100 cycles, and 586 mAh g-1 at 10 C-rates (10 A g-1) for the NiC2O4·2H2O/rGO electrode were measured. We determined the details of the lithium storage processes involved with the conversion reaction, which were fairly reversible via a transformation to Ni metal accompanied by the formation of a lithium oxalate compound on discharge (reduction) and restoration to the original NiC2O4·2H2O on charge (oxidation); this was confirmed via X-ray diffraction, transmission electron microscopy, X-ray photoelectron microscopy, and time-of-flight secondary ion mass spectroscopy. We believe that the high rate capacity and rechargeability upon cycling are a result of the unique features of the highly crystalline NiC2O4·2H2O nanorods assisted by conducting rGOs.

Nickel oxalate dihydrate nanorods attached to reduced graphene oxide sheets as a high-capacity anode for rechargeable lithium batteries

In the search for high-capacity anode materials, a facile hydrothermal route has been developed to synthesize phase-pure NiC2O4·2H2O nanorods, which were crystallized into the orthorhombic structure without using templates. To ensure the electrical conductivity of the nanorods, the produced NiC2O4·2H2O nanorods were attached to reduced graphene oxide (rGO) sheets via self-assembly layer-by-layer processes that utilize the electrostatic adsorption that occurs in a poly(diallyldimethylammonium chloride) solution. The high electrical conductivity aided by the presence of rGO significantly improved the electrochemical properties: 933 mAh g−1 for the charge capacity (oxidation), which showed 87.5% efficiency at the first cycle with a retention of approximately 85% for 100 cycles, and 586 mAh g−1 at 10 C-rates (10 A g−1) for the NiC2O4·2H2O/rGO electrode. The lithium storage processes were involved in the conversion reaction, which were fairly reversible via a transformation to Ni metal accompanied by the formation of a lithium oxalate compound upon discharge (reduction) and restoration to the original NiC2O4·2H2O upon charging (oxidation); this was confirmed via X-ray diffraction, transmission electron microscopy, X-ray photoelectron microscopy and time-of-flight secondary ion mass spectroscopy. We believe that the high rate capacity and rechargeability upon cycling are the result of the unique features of the highly crystalline NiC2O4·2H2O nanorods assisted by conducting rGOs.

SiOx/C composite from rice husks as an anode material for lithium-ion batteries

SiOx/C composite material derived directly from agricultural rice husk byproducts through an economically viable and environmentally benign approach has been explored to be used as an anode for rechargeable lithium batteries. Rice husks were converted into a SiOx/C composite directly by heat treatment under argon/hydrogen atmosphere, at a temperature of 900°C. The composite contains SiOx surrounded by an amorphous carbon matrix. A steady state reversible capacity of nearly 600mAhg−1 was delivered at 100mAg−1 current density after 100 cycles. The improved performance of the SiOx/C composite anode over other agricultural byproduct derived carbon materials is believed to be due to the presence of low valence silicon. The filth-to-wealth conversion of rice husks to battery material is a highly energy efficient process with great economic and environmental benefits.

Role of 1,3-Dioxolane and LiNO3 Addition on the Long Term Stability of Nanostructured Silicon/Carbon Anodes for Rechargeable Lithium Batteries

In order to utilize silicon as alternative anode for unfavorable lithium metal in lithium – sulfur (Li–S) batteries, a profound understanding of the interfacial characteristics in ether-based electrolytes is required. Herein, the solid electrolyte interface (SEI) of a nanostructured silicon/carbon anode after long-term cycling in an ether-based electrolyte for Li–S batteries is investigated. The role of LiNO3 and 1,3-dioxolane (DOL) in dimethoxy ethane (DME) solutions as typically used electrolyte components on the electrochemical performance and interfacial characteristics on silicon are evaluated. Because of the high surface area of our nanostructured electrode owing to the silicon particle size of around 5 nm and the porous carbon scaffold, the interfacial characteristics dominate the overall electrochemical reversibility opening a detailed analysis. We show that the use of DME/DOL solutions under ambient temperature causes higher degradation of electrolyte components compared to carbonate-based electrolytes used for Li–ion batteries (LIB). This behavior of DME/DOL mixtures is associated with different SEI component formation and it is demonstrated that LiNO3 addition can significantly stabilize the cycle performance of nanostructured silicon/carbon anodes. A careful post-mortem analysis and a discussion in context to carbonate-based electrolyte solutions helps to understand the degradation mechanism of silicon-based anodes in rechargeable lithium-based batteries.

Carbothermal synthesis of molybdenum(IV) oxide as a high rate anode for rechargeable lithium batteries

MoO2 is synthesized via carbothermal reduction, using pitch, of hydrothermally produced MoO3 nanobelts. X-ray diffraction (XRD) and electron microscopic data indicate that the MoO3 is readily reduced to MnO2 and the smooth surfaces are modified by carbon products after the heat treatment in reduction atmosphere. The produced carbon-coated MoO2 lengthened a few micrometers is ball-milled to reduce the particle size below 100 nm. Electrochemical tests of the milled carbon-coated MoO2 electrode demonstrate a high discharge (reduction) capacity approximately 248 mAh (g-MoO2)−1 at 150 mA g−1 (0.5 C-rate) with an average operation voltage of 1.3 V, and the resulting charge (oxidation) capacity approximates to 208 mAh g−1. The charge capacity is retained about 98.6% upon cycling. The carbon-coated MoO2 electrode is also suitable for high rate charge and discharge, reaching 129 mAh g−1 for charge and 146 mAh g−1 for discharge even at 30 C-rates (9 A g−1), suggesting feasibility of the MoO2 as the anode material suitable for high rate applications.

One‐Step Solvothermal Synthesis of Nanostructured Manganese Fluoride as an Anode for Rechargeable Lithium‐Ion Batteries and Insights into the Conversion Mechanism

A nanostructured manganese fluoride is successfully synthesized for the first time through a facile one‐step solvothermal method. Ionic liquid (IL) 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BmimBF4) as fluorine source and manganese (II) acetate tetrahydrate (Mn(CH3COO)2·4H2O) as manganese source are used. By controlling the amount of manganese source and both the reaction time and temperature, pure phase tetragonal MnF2 with a uniformly distributed nanocrystalline of 100–300 nm can be obtained. A possible formation mechanism related to the role of the IL is proposed. Electrochemical performance of MnF2 nanocrystals as anodes for rechargeable lithium batteries is investigated. A low discharge plateau around 0.6 V at 0.1 C of the first cycle is obtained for lithium uptake reactions with a reversible discharge capacity as high as 300 mAh g−1. The new MnF2 anode is found to deliver significantly improved cycling performance than conventional conversion reaction electrodes with a capacity retention of 237 mAh g−1 at 10 C even after 5000 cycles, indicating its promising utilization as anode material for future lithium‐ion batteries with long cycle life. High‐resolution transmission electron microscopy and X‐ray photoelectron spectroscopy analyses for lithiated and delithiated MnF2 electrodes are used to reveal the conversion mechanism for the reversible electrochemical reaction of MnF2 with Li.

Nitrogen containing bio-carbon as a potential anode for lithium batteries

Nitrogen containing porous carbon, derived from human hair through an economically viable and an environmentally benign approach has been explored for the first time as an anode for rechargeable lithium batteries. Such a human hair derived carbon (HHC) is found to be mesoporous with an appreciable BET surface area of 1617m2g−1. HHC, when explored as a lithium intercalating anode exhibits excellent electrochemical properties upon moderate (100mAg−1) and high rate (3800mAg−1) discharge conditions. A steady state reversible capacity of 700 and 610mAhg−1 has been delivered against 50 and 100mAg−1 current density. Further, an acceptable capacity of 181mAhg−1 has been exhibited at 10.21C rate, by withstanding a current density of 3800mAg−1. The superior electrochemical properties of HHC anode over other biomass derived carbons are believed to be due to the presence of nitrogen containing mesoporous carbon with a high surface area. The study demonstrates the exploitation of a universal waste material, viz., human hair, as a potential anode for the most sought after energy storage application. Further, the process of filth-to-wealth conversion is bestowed with economic and environmental benefits, thus qualifying itself as an energy efficient process.

High-Performance Artificial SEI-Capped Nano-SiO x /Graphite Anode for Rechargeable Lithium Batteries

Carbon composites of silicon (Si), silicon monoxide (SiO) or silicon suboxide (SiO x ) are considered as alternative anode materials to graphite for rechargeable lithium batteries, due to the high theoretical capacity of 3579 mAh/g for Si at room temperature and safer operation voltage above lithium. The Si, however, suffers from capacity fade due to large volume change upon lithiation and delithiation during cycling. This leads to electrochemical and mechanical particle disintegration. SiO and SiO x are favored with respect to cycling stability despite sacrificing the capacity, as lithium oxide (Li2O) and lithium silicates formed during initial lithiation better accommodates significant volume change of Si.Interfacial processes for Si anode with LiPF6-containing electrolyte, which is another cause for particle disintegration and performance fade, have been established as LiPF6 decompose and produce Lewis acids (PF5, PF3O) and HF (LiPF6 → LiF + PF5; PF5 + H2O → PF3O + 2HF) that can undergo electrophilic attack to the surface of Si anode and participate in electrochemical reduction leading to Si deactivation. This restricts the formation of a stable SEI and charge-discharge cycling stability. Extensive research efforts have been made to improve interfacial stability and cycling performance of SiOx-based carbon composite.We have been developing a new synthetic method and mechanistic investigation of surface-protected SiO x , (x < 0.5) nanoparticles and their carbon composites for attaining stabilized electrode performance. Here we report a facile preparation, and material and electrochemical characterization of amorphous nano-SiO x and its graphite composite with homogeneous compositional distribution.Artificial SEI-capped SiO x nanoparticles were synthesized by a chemical reduction of silicon tetrachloride and in-situ capping with a surface protective hydrophobic layer. The hydrophobic surface nature led to an easy and homogeneous dispersion of SiO x nanoparticles with graphite powders in n-methylpyrrolidinone (NMP) just by room temperature mixing for the preparation of slurry. Artificial SEI-capped nano-SiO x /graphite (50:50 wt%) electrodes consisted of the active material (70 wt%), carbon black (15 wt%) and binder (15 wt%) were fabricated onto a copper foil, followed by vacuum drying at 110 °C overnight. Cycling ability of the composite electrode was evaluated using coin half-cell cells with a lithium foil as a counter electrode and the baseline electrolyte of 1M LiPF6/EC:EMC (3:7 volume ratio) or that with a new carbonate-based solvent, and polyethylene separator, between 0.01 to 1.5 V at a constant current density of 300 mA/g (~0.3C).SEM and elemental mapping images (Figure 1A) of nano-SiOx/graphite reveal a uniform distribution of carbon (green) and silicon (red) atoms over bulk composite. Large micron carbon particles are of graphite and relatively small ones are of carbon black, respectively. Figure 1B shows the voltage profiles of nano-SiO x /graphite electrode measured at 0.3C. The initial charge and discharge capacity are 1370 and 1010 mAh/g, respectively, resulting in the initial coulombic efficiency of 74 %. Coulombic efficiency increases to higher than 98 % after the fifth cycle. Discharge capacity is retained as 931 mAh/g after 100 cycles (Figure 1C), corresponding to capacity retention of 91%. The excellent cycling stability is ascribed to homogenous dispersion of SiO x and graphite powders, accommodation of volume change of SiO x by oxygen and graphite, and enhanced interfacial stability by artificial SEI. Further discussion of the high-rate capability, and the SEI formation and stability and their correlation to cycling performance would be presented in the meeting. Acknowledgments This work was supported partly by the Korean Ministry of Education and National Research Foundation through the Human Resource Training Project for Regional Innovation (2012026203) and partly by the Converging Research Center Program (2013K000214) through the Ministry of Science, ICT & Future Planning.

Role of surface functionality in the electrochemical performance of silicon nanowire anodes for rechargeable lithium batteries.

We report the synthesis of silicon nanowires using the supercritical-fluid-liquid-solid growth method from two silicon precursors, monophenylsilane and trisilane. The nanowires were synthesized at least on a gram scale at a pilot scale facility, and various surface modification methods were developed to optimize the electrochemical performance. The observed electrochemical performance of the silicon nanowires was clearly dependent on the origination of the surface functional group, either from the residual precursor or from surface modifications. On the basis of detailed electron microscopy, X-ray photoelectron spectroscopy, and confocal Raman spectroscopy studies, we analyzed the surface chemical reactivity of the silicon nanowires with respect to their electrochemical performance in terms of their capacity retention over continuous charge-discharge cycles.