A review of the electrochemical performance of alloy anodes for lithium-ion batteries

Alloy anodes are promising anode materials for lithium-ion batteries due to their high-energy capacity and safety characteristics. However, the commercial use of alloy anodes has been hindered to date by their low cycle life and high initial capacity loss. This review highlights the recent progress in improving and understanding the electrochemical performance of various alloy anodes. The approaches used for performance improvement are summarized, and the causes of first-cycle irreversible capacity loss are discussed. The capacity retentions and irreversible capacity losses of various alloy anodes are compared. Several alloy anodes exhibited excellent cycle life (up to 300 cycles) with high initial coulombic efficiency (80-90%) and large reversible capacity (500-700 mAh g⁻¹).     

Surface-modified silicon nanowire anodes for lithium-ion batteries

Silicon nanowires with hydride, methyl and siloxane surfaces terminations were evaluated as anodes in lithium-ion half cells using LiPF₆ in EC/DMC electrolytes. Voltammetry, FT-IR and XPS analyses show hydride-terminated nanowires react with the electrolyte and methyl termination tends to passivate silicon surfaces. Silicon anodes pretreated with trimethoxymethylsilane show decreased lithium capacities similar to methylated anodes; however, the addition of 5% trimethoxymethylsilane as an electrolyte additive resulted in the formation of significantly more OPFx compounds while improving capacity retention relative to hydride-terminated nanowires (2348 mAh g⁻¹ at 15 cycles at C/10 rates). FTIR analysis show trimethoxymethylsilane additives covalently bond silicon surfaces and other SEI components. AFM nano-indentation tests also suggest the alkoxy silane additives in the electrolyte function as a binder to improve silicon's ability to withstand the large reversible volume changes. The results indicate silicon surface terminations play a key role in chemical and mechanical behaviors that control reversibility.     

Nano- and bulk-silicon-based insertion anodes for lithium-ion secondary cells

The increase in energy density and power density requirements for lithium-ion secondary cells for commercial applications has led to a search for higher capacity electrode materials than those available today. Silicon would seem to be a possible alternative for the graphite or carbon anode because its intercalation capacity is the highest known. However, the large capacity fade observed during initial cycling has prevented the silicon anode from being commercialized. Here we present a review of methodologies adopted for reducing the capacity fade observed in silicon-based anodes, discuss the challenges that remain in using silicon and silicon-based anodes, and propose possible approaches for overcoming them.     

Lithium insertion/extraction mechanism in alloy anodes for lithium-ion batteries

The electrochemical performance of alloy anodes has been reviewed in a previous paper [1]. In this work, the fundamental understanding of lithium-insertion/extraction mechanism in alloy anodes is discussed. The article summarizes the different types of lithium-reaction processes observed in Si, Sn, Sb, Al, Mg and their alloys, with particular emphasis on the characteristics unique to alloy anodes, including the sloping voltage profiles, lithiation amorphization, cycling hysteresis and reaction-potential depression. These unique characteristics are discussed with respect to the effect of interface and surface energies on the phase transformation and thermodynamic stability of fine alloy particles.     

Practical silicon-based composite anodes for lithium-ion batteries: Fundamental and technological features

Despite recent worldwide research efforts, composite silicon-based anodes remain at the centre of debate in the field of lithium-ion batteries. Here, we demonstrated that successful development of composite silicon-based anodes requires the simultaneous consideration of two equally important features: fundamental and technological. The fundamental feature dictates that the in situ formed amorphous phase should remain in its amorphous state in order to achieve a long-lasting reversible electrode, while the technological feature implies that the complex active material–binder interactions have to be numerically evaluated in order to tailor the electrode properties in an appropriate way. Only the harmonic consideration of both aspects allows creation of a long-lasting reversible silicon electrode. Examples demonstrating these features are considered and lithium-ion batteries employing hybrid silicon-based electrodes are proposed.     

Electrochemical characterizations of multi-layer and composite silicon-germanium anodes for Li-ion batteries using magnetron sputtering

To improve the electrochemical performance of Si film, we investigate the addition of two film forms of Ge. Si/Ge multi-layered and Si-Ge composite electrodes that are fabricated by magnetron sputtering onto Cu current collector substrates are investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and extended X-ray absorption fine structure (EXAFS) are employed to analyze the structures of the Si-Ge electrodes. When used as an anode electrode for a lithium ion battery, the first discharge capacity of a Si/Ge 150 multi-layer cell with a ratio of Si 15 nm/Ge 3 nm is 2099 mAh g⁻¹ between 1.1 and 0.01 V. A stable reversible capacity of 1559 mAh g⁻¹ is maintained after 100 cycles with a capacity retention rate of 74.25%. Additionally, the Si_0.84Ge_0.16 composite has an initial discharge capacity of 1915 mAh g⁻¹ and a capacity retention of 74.25%. In full cell tests of Si-Ge electrodes, the Si_0.84Ge_0.16/LiCoO₂ cell delivers a specific capacity of approximatly 160 mAh g⁻¹ and a capacity retention of 52.4% after 100 cycles. The results reveal that these two systems of sputtered Si-Ge electrodes can be used as anodes in lithium ion batteries with higher energy densities.     

Nano-sized LiMn2O4 spinel cathode materials exhibiting high rate discharge capability for lithium-ion batteries

Nano-sized LiMn₂O₄ spinel with well crystallized homogeneous particles (60 nm) is synthesized by a resorcinol-formaldehyde route. Micro-sized LiMn₂O₄ spinel with micrometric particles (1 μm) is prepared by a conventional solid-state reaction. These two samples are characterized by XRD, SEM, TEM, BET, and electrochemical methods. At current rate of 0.2C (1C = 148 mA g⁻¹), a discharge capacity of 136 mAh g⁻¹ is obtained on the nano-sized LiMn₂O₄, which is higher than that of micro-sized one (103 mAh g⁻¹). Furthermore, compared to the micro-sized sample, nano-sized LiMn₂O₄ shows much better rate capability, i.e. a capacity of 85 mAh g⁻¹, 63% of that at 0.2C, is realized at 60C. The excellent high rate performance of nano-sized LiMn₂O₄ spinel may be attributed to its impurity-free nano-sized particles, higher surface area and well crystalline. The outstanding electrochemical performances demonstrate that the nano-sized LiMn₂O₄ spinel will be the promising cathode materials for high power lithium-ion batteries used in hybrid and electric vehicles.     

Surface chemistry and morphology of the solid electrolyte interphase on silicon nanowire lithium-ion battery anodes

Silicon nanowires (SiNWs) have the potential to perform as anodes for lithium-ion batteries with a much higher energy density than graphite. However, there has been little work in understanding the surface chemistry of the solid electrolyte interphase (SEI) formed on silicon due to the reduction of the electrolyte. Given that a good, passivating SEI layer plays such a crucial role in graphite anodes, we have characterized the surface composition and morphology of the SEI formed on the SiNWs using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). We have found that the SEI is composed of reduction products similar to that found on graphite electrodes, with Li₂CO₃ as an important component. Combined with electrochemical impedance spectroscopy, the results were used to determine the optimal cycling parameters for good cycling. The role of the native SiO₂ as well as the effect of the surface area of the SiNWs on reactivity with the electrolyte were also addressed.     

C-rate performance of silicon oxycarbide anodes for Li+ batteries enhanced by carbon nanotubes

We show that employing single wall carbon nanotubes (CNTs) as the conducting agent significantly increases the capacity of silicon oxycarbide anodes at high C-rates. In these anodes 515 mAh g⁻¹ can be extracted in just over 3 min. The capacity decreases to 300 mAh g⁻¹ at the same extraction rate when carbon black is used as the conducting agent. The CNT anodes have good cyclic stability, retaining 89.2% of initial capacity after 40 cycles. The coulombic efficiency ranges from 95% to 100%.     

Oxygen deficiency,a key factor in controlling the cycle performance of Mn-spinel cathode for lithium-ion batteries

Several series of Li_1±xMn_2−yO_4±δ and Li_1.05Al_yMn_1.95−yO_4±δ samples with different oxygen defect degree have been synthesized by controlling synthesis temperature and procedures. The cycle performance of spinel as cathode in lithium batteries has been correlated with oxygen deficiency. The structure change of spinel during charge has also been investigated with respect with oxygen deficiency.     

Fabrication and electrochemical properties of lithium-ion batteries for power tools

204056-Type prismatic lithium-ion battery for power tools was developed by using LiMn₂O₄ as cathode and CMS (carbonaceous mesophase spheres) as anode. The performance of batteries and their electrodes were characterized by SEM, ac impedance and electrochemical tests. The bulk density of cathode after pressing was selected as a main factor and it effects on high current rate capability and discharge plateau distinctly, which were investigated in details. Being charged/discharged in the voltage range of 2.5–4.2 V, the normal LiMn₂O₄ battery with cathode bulk density of 2.7 g cm⁻³ shows excellent electrochemical performances. The discharge capacity at 20C rate is 94.1% of that at 1C rate, and the capacity retention ratio charged at 1C and discharged at 5C is 91.7% after 100 cycles at 25 °C. While modified LiMn₂O₄ is used as the cathode material, the cycling performance of batteries is better than that of batteries made from normal LiMn₂O₄. The capacity retention ratios of modified LiMn₂O₄ batteries after 100 cycles at 25 °C and 55 °C are 95.0% and 85.3%, respectively. The discharge capacity at low temperature was tested both at 1C rate and 5C rate, and the capacities discharged at −20 °C were 96.3% and 94.2% of that at 1C at 25 °C. Furthermore, the batteries also show good safety in the test of short circuit, overcharge, and nail penetration.     

Influence of lithium content on high rate cycleability of layered Li1+xNi0.30Co0.30Mn0.40O2 cathodes for high power lithium-ion batteries

Layered Li_1+xNi_0.30Co_0.30Mn_0.40O₂ (x = 0, 0.05, 0.10, 0.15) materials have been synthesized using citric acid assisted sol-gel method. The materials with excess lithium showed distinct differences in the structure and the charge and discharge characteristics. The rate capability tests were performed and compared on Li_1+xNi_0.30Co_0.30Mn_0.40O₂ (x = 0, 0.05, 0.10, 0.15) cathode materials. Among these materials, Li_1.10Ni_0.30Co_0.30Mn_0.40O₂ cathode demonstrated higher discharge capacity than that of the other cathodes. Upon extended cycling at 1C and 8C, Li_1.10Ni_0.30Co_0.30Mn_0.40O₂ showed better capacity retention when compared to other materials with different lithium content. Li_1.10Ni_0.30Co_0.30Mn_0.40O₂ exhibited 93 and 90% capacity retention where as Li_1.05Ni_0.30Co_0.30Mn_0.40O₂, Li_1.15Ni_0.30Co_0.30Mn_0.40O₂, and Li_1.00Ni_0.30Co_0.30Mn_0.40O₂ exhibited only 84, 71, and 63% (at 1C), and 79, 66 and 40% (at 10C) capacity retention, respectively, after 40 cycles. The enhanced high rate cycleability of Li_1.10Ni_0.30Co_0.30Mn_0.40O₂ cathode is attributed to the improved structural stability due to the formation of appropriate amount of Li₂MnO₃-like domains in the transition metal layer and decreased Li/Ni disorder (i.e., Ni content in the Li layer).     

Novel lithium titanate hydrate nanotubes with outstanding rate capabilities and long cycle life

Novel lithium titanate hydrate nanotubes for lithium ion batteries have been easily prepared via a hydrothermal method. This material demonstrates high energy density, outstanding rate capabilities and a very long cycle life comparable to those of supercapacitors. At a rate equivalent to a 10-min total charge/discharge, the as-prepared lithium titanate hydrate nanotubes exhibit a life of over 5000 charge/discharge cycles while still retaining up to 86.3% of its original capacity. The abilities of lithium titanate hydrate nanotubes to fully charge within minutes for thousands of times and still retain a large capacity may find promising applications in hybrid and plug-in hybrid electric vehicles.     

Improvement of cyclic behavior of a ball-milled SiO and carbon nanofiber composite anode for lithium-ion batteries

The cyclic performance of a composite SiO and carbon nanofiber (CNF) anode was examined for lithium-ion batteries. SiO powder of several micrometers was pulverized using high energy mechanical milling. The SiO was ball-milled for 12 h with CNF to produce a composite electrode material that exhibited excellent cycling performance. A reversible capacity of approximately 700 mAh g⁻¹ was observed after 200 cycles. The excellent cyclic performance was discussed with respect to the change of the valence state of Si by ball-milling. A large irreversible capacity at the first cycle for the SiO/CNF composite electrode was reduced to 2% by chemically pre-charging with a lithium film attached to the rim of the electrode.     

Computer simulation of a porous positive electrode for lithium batteries

The discharge characteristics of a Li/Li_yCoO₂ cell were simulated by numerical calculations. Based on the program proposed by Newman's group, the change in entropy due to lithium-ion insertion into the active materials was introduced into the open-circuit potential (OCP) for more practical applications. The OCP of LiCoO₂ (y = 1) at a full-discharge state was 3.82 V, which was determined from the original program. However, it should show a rapid decrease to minus infinity when discharge is complete (y = 1), which is due to the introduced entropy term. In addition, the local use of active materials across the Li_yCoO₂ electrode was not uniform, whereas the original program showed a constant value throughout the electrode. Based on the present results, the introduction of an entropy term to the OCP of Li_yCoO₂ works reasonably well for more practical applications.     

Electrochemical characterization of thermally oxidized natural graphite anodes in lithium-ion batteries

Natural graphite, which is used as an anode material in lithium-ion batteries, is thermally treated to improve its cycleability and reduce irreversible reactions with the electrolyte. Natural graphite is treated in air at 550 °C. The weight loss increases when the thermal oxidation time is increased. The BET surface area of the graphite decreases with increasing weight loss. The cycleability and efficiency of the thermally oxidized natural graphite improves significantly. Thermal oxidation decreases the irreversible capacity for side-reactions with the electrolyte on the first cycle. By contrast, it does not change the reversible capacity and rate capability. The improvement in the cycleability after thermal oxidation may be due to the removal of imperfect sites on the graphite.     

Rapid test and non-linear model characterisation of solid-state lithium-ion batteries

This paper describes a rapid test-procedure that can be used to derive parameters of a proposed battery model. The battery model is a non-linear dynamic equivalent circuit model, which is based on Randle’s model for electrochemical impedance [J. Power Sources 54 (1995) 393]. The level of sophistication has been selected such that it gives a satisfactory prediction of battery performance, but simple enough to enable on-line identification and adaptation of model parameters based on measurements of terminal voltage, current and temperature during usage. The paper also presents test data for a commercial 100 Ah battery including ageing effects.     

A review of processes and technologies for the recycling of lithium-ion secondary batteries

The purpose of this paper is to review the current status of the recycling technologies of spent lithium-ion secondary batteries. It introduced the structure and components of the lithium-ion secondary batteries, summarized all kinds of single recycling processes from spent lithium-ion secondary batteries and presented some examples of typical combined recycling processes. Also, the problems and prospect of the studies of their recycling technologies have been put forward.     

Synthesis of carbon coated Fe3O4/SnO2 composite beads and their application as anodes for lithium ion batteries

Abstract

Two metal oxide materials, namely, Fe₃O₄ and SnO₂, were combined into one specially designed nanostructure for lithium ion battery application. Hollow and porous Fe₃O₄ beads with an average size of ～700 nm were first synthesised through a one-step solvothermal route, followed by the decoration of SnO₂ nanoparticles via a hydrothermal method. A thin carbon layer was coated to further enhance the overall electrochemical performances. Under the current density of 100 mA g^?1, the first reversible capacity of such composite beads reached 834·7 mA h g^?1. While being tested at a higher current density of 500 mA g^?1, carbon coated Fe₃O₄/SnO₂ delivered steady reversible capacities with 569·5 mA h g^?1 at two hundredth cycle. Such performances were attributed to the high theoretical capacities of the metal oxides, desired morphology in nanoscale, carbon coating layer and the synergistic effect between Fe₃O₄ and SnO₂.     

Fabrication and characterization of three-dimensional carbon electrodes for lithium-ion batteries

This paper presents fabrication and testing results of three-dimensional carbon anodes for lithium-ion batteries, which are fabricated through the pyrolysis of lithographically patterned epoxy resins. This technique, known as Carbon-MEMS, provides great flexibility and an unprecedented dimensional control in shaping carbon microstructures. Variations in the pattern density and in the pyrolysis conditions result in anodes with different specific and gravimetric capacities, with a three to six times increase in specific capacity with respect to the current thin-film battery technology. Newly designed cross-shaped Carbon-MEMS arrays have a much higher mechanical robustness (as given by their moment of inertia) than the traditionally used cylindrical posts, but the gravimetric analysis suggests that new designs with thinner features are required for better carbon utilization. Pyrolysis at higher temperatures and slower ramping up schedules reduces the irreversible capacity of the carbon electrodes. We also analyze the addition of Meso-Carbon Micro-Beads (MCMB) particles on the reversible and irreversible capacities of new three-dimensional, hybrid electrodes. This combination results in a slight increase in reversible capacity and a big increase in the irreversible capacity of the carbon electrodes, mostly due to the non-complete attachment of the MCMB particles.