Anodes For Rechargeable Li-ion Batteries Research Articles

Anthracite coal from Vang Danh – Quang Ninh as anode material for rechargeable Li-ion batteries

This study investigated the structure of anthracite material (ATC) exploited from the Vang Danh mine (Quang Ninh) and its application as an anode for rechargeable Li-ion batteries. After the chemical treatment, the material was heated at 800 oC, 1000 oC, or 1200 oC for 2 hours, 3 hours, or 4 hours, respectively. Scanning electron microscopy (SEM) confirms that the raw material was polyhedral and sharp particles. The impurities in raw material, especially the metal compounds, was significantly reduced after the chemical-treated process. As a result, the carbon content increased from 78.91% in raw material to 86.94% in the chemical-treated sample. Regarding the structure, the Raman spectra showed that the AD/AG ratio decreased with increasing temperature and heating time. This confirmed that the more disordered structures were obtained at low temperatures and heating times. In addition, the interlayer spacing (d002) between the aromatic layers in the crystalline regions varied from 0.35 to 0.36 nm, while the lateral sizes (La) were 3.0-4.1 nm, and the stacking heights (Lc) were 1.4-2.0 nm. The ATC materials can serve as anode for rechargeable Li-ion batteries with high Coulombic efficiency (nearly 100%) and impressing capacity retention (nearly 100% after 40 cycles). Among the investigated samples, ATC 8002 delivers the highest capacity of 286.3 mAh/g with a high capacity retention of 88.5% after 40 cycles.

Co(BO2)2 supported on MIL-101 as high-performance anode material for Li-ion battery

In this work, via a simple liquid impregnation method, Co(BO2)2 nanoparticles are successfully loaded on the surface of Cr-based metal organic frameworks MIL-101 without destroying the three-dimensional organic frameworks. As received Co(BO2)2@MIL-101 composite shows the improved cyclability when serves as anode for rechargeable Li-ion batteries. The obtained Co(BO2)2@MIL-101 electrode demonstrates high reversible capacity of 810 mA h g−1 after 100 cycles at a current density of 200 mA g−1 and shows stable cycle performance (coulombic efficiency remains above 95%). The improvement could be attributed to MIL-101, which provides effective barrier spaces for Co(BO2)2 to relax the volumetric variation and maintains superior conductivity during the charge and discharge process.

Graphitic N-CMK3 pores filled with SnO2 nanoparticles as an ultrastable anode for rechargeable Li-ion batteries

The incorporation of ultrafine SnO2 particles inside N-doped ordered mesoporous carbon (N-CMK3) is suggested as a method to prepare an ultrastable anode material for Li-ion batteries. Sn nanoparticles formed by chemical reduction of SnCl4 inside N-CMK3 pores are spontaneously reoxidised by dissolved oxygen, resulting in the formation of ultrafine SnO2 inside N-CMK3 pores. This SnO2@N-CMK3 exhibits superior capacity, cyclability, and rate capability. Over 100 cycles at a rate of 0.1C, SnO2@N-CMK3 maintains a specific capacity of 635 mAh g−1, corresponding to a capacity retention of 86.6%. Over 1000 cycles at the rate of 0.5C, SnO2@N-CMK3 can deliver a capacity of 433 mAh g−1. At an ultrahigh rate of 5C, SnO2@N-CMK3 still delivers a capacity higher than that of commercial graphite. The full cell, composed of an SnO2@N-CMK3 anode, LiCoO2 cathode, and sacrificial Li electrode, presents excellent performance, better than previous reports of Li-ion cells. By employing a sacrificial Li electrode, the issue related to the low Coulombic efficiency of SnO2@N-CMK3 in the first few cycles and the pre-lithiation SnO2@N-CMK3 electrode can be successfully addressed.

Developing the processing stages of carbon fiber composite paper as efficient materials for energy conversion, storage, and conservation

Carbon is a wonder material and has served the mankind since the inception of civilization in a variety of ways. Among its different forms, carbon fibers are especially known for their conductivity and favorable strength to weight ratio. Here the development of PAN based carbon fibers embedded in a matrix material followed by pyrolysis to form a fibrous C/C composite has been discussed. The processing of carbon paper has been divided into four steps, with the product of each stage used separately for different energy applications. (1) Carbon fiber preform has been used as a filler to achieve high strength in bipolar plates for PEM Fuel cells (energy conversion). Flexural strength of nearly 80 MPa has been achieved as compared to 40 MPa of the commercially available Schunk plate, Germany. (2) Resin impregnated preform, i.e. the Green composite paper has been employed as an energy efficient heating element (energy conservation). This has been further fabricated as a room heater, which works at <200 W of power as compared to 1–2 kW ingested by the commercial heaters. (3) The Carbonized paper, worked well as a free standing anode for rechargeable Li-ion batteries (energy storage). It delivers a discharge capacity of 225 mAh/g @ 0.2C rate with excellent cycling performance (>500 cycles). The (4) Graphitized carbon paper has proved to be an excellent electrode (anode and cathode) backing material for PEM Fuel cell. 25% hike in the peak power density of unit PEM FC has been achieved while employing CNT incorporated NPL carbon paper as compared to while using Toray carbon paper of Japan and tested under similar conditions. This in turn is attributed to the unique properties acquired by the material with subsequent processing at each stage which has been discussed in detail.

Intercalation chemistry of graphite: alkali metal ions and beyond.

Reversibly intercalating ions into host materials for electrochemical energy storage is the essence of the working principle of rocking-chair type batteries. The most relevant example is the graphite anode for rechargeable Li-ion batteries which has been commercialized in 1991 and still represents the benchmark anode in Li-ion batteries 30 years later. Learning from past lessons on alkali metal intercalation in graphite, recent breakthroughs in sodium and potassium intercalation in graphite have been demonstrated for Na-ion batteries and K-ion batteries. Interestingly, some significant differences proved to exist for the intercalation of Na+ and K+ into graphite compared with the Li+ case. Such different host-guest interactions are unique depending on the host materials and electrolytes, which greatly contribute to a deeper understanding of intercalation-type electrode materials for next generation alkali metal ion batteries. This review summarizes significant advances from both experimental and theoretical calculations with a focus on comparing the intercalation of three alkali metal ions (Li+, Na+, K+) into graphite and aims to clarify the intimate host-guest relationships and the underlying mechanisms. New approaches developed to achieve favorable intercalation coupled with the challenges in this field are also discussed. We also extrapolate alkali metal ion intercalation in graphite to mono-/multi-valent ions in layered electrode materials, which will deepen the understanding of intercalation chemistry and provide guidance to explore new guests and hosts.

Swift Combustion Synthesis of PbLi2Ti6O14 Anode for Lithium-Ion Batteries: Diffusional and Electrochemical Investigation

Lead lithium titanate (PbLi2Ti6O14) was synthesized by combustion route restricting the annealing at 900°C to just 1 minute. Rietveld analysis confirmed orthorhombic (Cmca) product phase with an average particle size ∼200 nm and surface area of 2 m2/g forming secondary porous particles. From bond valence site energy (BVSE) calculations, 1 D ionic conduction was found along c axis with low activation energy (0.23 eV). AC conductivity analysis revealed a bulk conductivity of 2 × 10−7 S.cm−1 at room temperature and 1 × 10−4 S.cm−1 at 200°C with a switch from extrinsic 1D to intrinsic 2D mechanism at 150°C. Li+ diffusion coefficient was calculated to be in the order of 10−12 cm2.s−1. More than 4 lithium (per f.u.) could be reversibly (de)inserted delivering capacity over 160 mAh/g with good cycling retention over 1000 cycles. With a feasible rapid synthesis, good diffusional and electrochemical behavior especially high rate capability, PbLi2Ti6O14 can act as a safe 1.35 V anode for rechargeable Li-ion batteries.

Fe3O4 nanoparticles produced by mechanochemical transformation: A highly reversible electrode material for Li-ion batteries

Well-dispersed Fe3O4 nanoparticles (around 10–20nm) were simply produced by mechanochemical transformation of iron oxyhydroxides (FeO(OH)). When the Fe3O4 nanoparticles were applied as anodes for rechargeable Li-ion batteries (LIBs), excellent electrochemical performance was observed with highly reversible capacities of 914mAhg−1 over 120 cycles and fast rate capability. The metal oxides produced by mechanochemical transformation of metal oxyhydroxides will be highly applicable to electrodes for high-performance LIBs.

Ambient-Air Stable Lithiated Anode for Rechargeable Li-Ion Batteries with High Energy Density.

An important requirement of battery anodes is the processing step involving the formation of the solid electrolyte interphase (SEI) in the initial cycle, which consumes a significant portion of active lithium ions. This step is more critical in nanostructured anodes with high specific capacity, such as Si and Sn, due to their high surface area and large volume change. Prelithiation presents a viable approach to address such loss. However, the stability of prelithiation reagents is a big issue due to their low potential and high chemical reactivity toward O2 and moisture. Very limited amount of prelithiation agents survive in ambient air. In this research, we describe the development of a trilayer structure of active material/polymer/lithium anode, which is stable in ambient air (10-30% relative humidity) for a period that is sufficient to manufacture anode materials. The polymer layer protects lithium against O2 and moisture, and it is stable in coating active materials. The polymer layer is gradually dissolved in the battery electrolyte, and active materials contact with lithium to form lithiated anode. This trilayer-structure not only renders electrodes stable in ambient air but also leads to uniform lithiation. Moreover, the degree of prelithiation could vary from compensating SEI to fully lithiated anode. With this strategy, we have achieved high initial Coulombic efficiency of 99.7% in graphite anodes, and over 100% in silicon nanoparticles anodes. The cycling performance of lithiated anodes is comparable or better than those not lithiated. We also demonstrate a Li4Ti5O12/lithiated graphite cell with stable cycling performance. The trilayer structure represents a new prelithiation method to enhance performance of Li-ion batteries.

Partially reversible Li2O formation in ZnO: A critical finding supporting realization of highly reversible metal oxide electrodes

The electrochemical reaction mechanism of ZnO is investigated to understand its Li insertion/extraction behavior using ex situ X-ray diffraction, extended X-ray absorption fine structure, and high-resolution transmission electron microscopy. Based on these analyses, an interesting partial recombination reaction of ZnO is discovered, which demonstrates that Li2O formed during Li insertion is partially reversible. Additionally, we discover that the control of the partial recombination reaction of the metal oxide is very important for improving reversibility in the first cycle, which is a key finding for realization of highly reversible oxide-based electrode materials. In addition, to enhance the electrochemical performance of the ZnO electrode, a nanostructured ZnO/C composite is prepared by a simple high-energy mechanical milling process. This process allows the electrochemical performance of the ZnO electrode to be evaluated as an anode for rechargeable Li-ion batteries. Electrochemical tests show that the nanocomposite electrode exhibits a high initial charge capacity of 682 mAh g−1, fast rate capability of 371 mAh g−1 at 2 C, and excellent cyclability over 200 cycles.

Designing Microstructure with Voids of Si-Based Anode Materials for Li-Ion Batteries

Silicon has been regarded as one of the most promising anode materials for Li-ion batteries because of its higher specific capacity than carbon anodes. However, there is a fatal problem that Si undergoes massive volumetric change (about 400%) during lithiation/delithiation process. This large volume change results in the following sequential processes; pulverization, breakage of solid electrolyte interface (SEI), creation of new surface for SEI formation, continuous exhaustion of electrolyte, and finally sudden capacity fade. Among many attempts to solve these problems, the microstructure control with voids showed notable progress in improving the cycle performance. But the synthetic methods adopted so far were too complicate to apply to large scale commercial processes. Here, we introduce a microstructure of Si-based anode materials with voids using water-soluble compounds. The role of water-soluble compounds is to create enough spaces within the anode agglomerate particles, so that they can expand without generating excessive crack on the surface during the electrochemical reaction. We synthesized active anode materials using ball-milled ferrosilicon alloy and fine water-soluble compound mixtures as starting materials. After coating with carbon precursor followed by carbonization heat treatment, they were washed with distilled water to remove the water-soluble compounds which create void structure in anode particles. The evidences of the removal of the water-soluble compounds were provided by X-ray diffraction, FIB cross-section/EDS analysis, and BET analysis. From the electrochemical cell test, significant improvement of battery performance including coulombic efficiency, irreversible capacity were observed, especially at the beginning of the cycles, compared to that of anode materials without void structure. The present study shows the simple and practical approach to realize an ideal microstructure of Si-based anode for rechargeable Li-ion batteries.

Co–Sb intermetallic compounds and their disproportionated nanocomposites as high-performance anodes for rechargeable Li-ion batteries

A simple, fast, and straightforward method for synthesizing Co–Sb intermetallic compounds based on nanocomposites is proposed for obtaining high-performance anode materials for rechargeable Li-ion batteries.

Facile synthesis of Si/TiO2 (anatase) core–shell nanostructured anodes for rechargeable Li-ion batteries

A nano-Si/TiO2 core–shell nanostructured electrode was synthesized using sol–gel method. The TiO2 shells were made with 10-nm thickness, and were structurally stable upon the intercalation/deintercalation of Li+, improve the cyclability of the Si electrode during cycling. The nano-Si/TiO2 core–shell nanostructured electrode showed a reversible capacity of ca. 1250mA hg−1 over 50 cycles. The reaction mechanism between the nano-Si/TiO2 core–shell nanostructured electrode and Li was investigated by ex situ analyses.

Preparation and study of carbon nano-onion for lithium storage

Carbon nano-onions were prepared by burning castor oil. The as-prepared carbon nano-onions were characterized by scanning electron microscopy and transmission electron microscope to confirm the nano-onion structures. The carbon nano-onions were used as anodes for rechargeable Li-ion batteries and demonstrated high reversible capacity and relatively good rate capability. The electrochemical performance can be attributed to the unusual surface properties and unique structural features of the carbon nano-onion anode, which amplify both surface area and extensive intermingling between curved graphite layer over small length scales, thereby leading to fast kinetics and short pathways for both Li ions and electrons.

Enhanced performance of SiO/Fe2O3 composite as an anode for rechargeable Li-ion batteries

Iron oxide (Fe2O3) was utilized to enhance the electrochemical properties of SiO as a promising anode for Li-ion batteries. An SiO/Fe2O3 composite, composed of SiO coated with Fe2O3 nanoparticles, was synthesized by mechanical milling and characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The electrochemical properties of the SiO/Fe2O3 composite, SiO, and mechanically milled SiO as anodes for Li-ion batteries were then investigated. The SiO/Fe2O3 composite showed superior performance compared with the two Fe2O3-free SiO samples, including an increased initial coulombic efficiency, enhanced rate capability, and better capacity retention.

Nanostructured Zn-based composite anodes for rechargeable Li-ion batteries

The mechanism of the electrochemical reaction of Zn with Li was investigated by ex situ X-ray diffraction (XRD) analysis combined with a differential capacity plot of the Zn electrode at a low current of 10 mA g−1. The pure Zn electrode showed a high reactivity with Li, with first discharge and charge capacities of 574 and 351 mA h g−1, respectively. In addition, Zn–C and Zn–Al2O3–C composites prepared by simple high-energy mechanical milling were evaluated for use as anode materials in rechargeable Li-ion batteries. The Zn–C nanocomposite was composed of nanosized Zn in an amorphous C matrix, while the Zn–Al2O3–C nanocomposite (obtained by the mechanochemical reduction of ZnO and Al) was composed of nanocrystalline Zn and amorphous Al2O3 in the amorphous C matrix. Electrochemical tests showed that the Zn–Al2O3–C nanocomposite electrode exhibited a high volumetric capacity of more than 1800 mA h cm−3 over 100 cycles.

Designing Si-based nanowall arrays by dynamic shadowing growth to tailor the performance of Li-ion battery anodes

To target the low conductance and stress issues of Si anodes for rechargeable Li-ion batteries, we have systematically designed four unique Si nanorod-based anodes using a dynamic shadowing growth method. Multilayer Cu/Si and Cu side-coated Si nanorods serve to improve the conductance, meanwhile, uniform CuSi and composition-graded CuSi nanocomposites serve to relax the stress and increase the conductance. Under the identical charge/discharge conditions, both the uniform and graded CuSi composite nanostructures exhibit the best cycling performance with capacity retention of 60–80% after 100 cycles of Li-ion insertion and extraction. The morphology evolution reveals that the nanorod wall-like structures remain intact in the uniform and graded CuSi composite anodes, while they have peeled off from the current collectors in the intrinsic Si, multilayer Cu/Si, and Cu side-coated Si samples. The morphological changes of different Si-based nanoanodes have also been modeled by a beam network, revealing that Si-based composite nanostructures generate a low yield stress which could be the key to developing high performance Li-ion battery anodes.

Electrochemical Characteristics of TiSb2 and Sb/TiC/C Nanocomposites as Anodes for Rechargeable Li-Ion Batteries

Intermetallic and Sb/TiC/C nanocomposites were prepared by alloying and dealloying reactions, respectively, and their potential as anode materials for rechargeable Li-ion batteries was investigated. The Sb/TiC/C nanocomposite was composed of nanocrystalline Sb and TiC, which were distributed uniformly in an amorphous carbon matrix. The reaction mechanism of intermetallic with Li was examined by ex situ X-ray diffraction and high resolution transmission electron microscopy. The Sb/TiC/C nanocomposite exhibited good electrochemical performance, such as a high initial coulombic efficiency of 87% and a long cycle retention of 83% after 100 cycles.