Status of rechargeable positive electrodes for ambient temperature lithium batteries

There have been striking advances in the technology of ambient temperature rechargeable lithium cells during the middle and late 1970s. Discoveries of new and attractive cathode systems, along with developmental efforts on some, have contributed significantly to this. A survey of the status of the positive electrodes is presented. Insoluble solid cathodes which undergo intercalation or topochemical electrode reactions appear to be the most promising for immediate application in practical cells. There are presently available several such materials suitable for fabricating cells with high energy density, rate capability, and rechargeability. It is hoped that this account will direct the attention of investigators in this area to promising systems with the result that research and developmental efforts on practical rechargeable Li batteries will be accelerated.     

Status of rechargeable positive electrodes for ambient temperature lithium batteries

There have been striking advances in the technology of ambient temperature rechargeable lithium cells during the middle and late 1970s. Discoveries of new and attractive cathode systems, along with developmental efforts on some, have contributed significantly to this. A survey of the status of the positive electrodes is presented. Insoluble solid cathodes which undergo intercalation or topochemical electrode reactions appear to be the most promising for immediate application in practical cells. There are presently available several such materials suitable for fabricating cells with high energy density, rate capability, and rechargeability. It is hoped that this account will direct the attention of investigators in this area to promising systems with the result that research and developmental efforts on practical rechargeable Li batteries will be accelerated.     

Lithium reserves and resources

As a result of accelerating research efforts in the fields of secondary batteries and thermonuclear power generation, concern has been expressed in certain quarters regarding the availability, in sufficient quantities, of lithium.As part of a recent study by the National Research Council on behalf of the Energy Research & Development Administration, a subpanel was formed to consider the outlook for lithium. Principal areas of concern were reserves, resources and the “surplus” available for energy applications after allowing for the growth in current lithium applications. Reserves and resources were categorized into four classes ranging from fully proved reserves to resources which are probably dependent upon the marketing of co-products to become economically attractive.Because of the proprietary nature of data on beneficiation and processing recoveries, the tonnages of available lithium are expressed in terms of plant feed. However, highly conservative assumptions have been made concerning mining recoveries and these go a considerable way to accounting for total losses. Western World reserves and resources of all classes are estimated at 10.6 million tonnes Li of which 3.5 million tonnes Li are located in the United States. Current United States capacity, virtually equivalent to Western World capacity, is 4700 tonnes Li and production in 1976 approximated to 3500 tonnes Li. Production for current applications is expected to grow to approx. 10,000 tonnes in year 2000 and 13.00 tonnes a decade later.The massive excess of reserves and resources over that necessary to support conventional requirements has limited the amount of justifiable exploration expenditures; on the last occasion, there was a major increase in demand (by the USAEA) reserves and capacity were increased rapidly. There are no foresceable reasons why this shouldn't happen again when the need is clear.Resources not included in the estimates are discussed. Some have great promise should their development ever prove necessary.     

Geochemical evidence of chemical equilibria in the South Meager Creek geothermal system, British Columbia, Canada

Meager geothermal reservoir appears to be in “thermochemical” equilibrium as indicated by constant ion-concentration ratios (B/Li, B/K, Na/Li, Na/CI etc.). The Na/Li ratio describes the thermal conditions of the first and the deepest equilibrium reached by the thermal waters, whereas the Na/K indicates a secondary and shallower equilibrium. Analysis of the correlations between K, Na and CI indicate that discharge from well MC1 is probably a mixture between a single brine and high-chloride cool waters.     

Investigation and production control of Li/SO2 cells by the galvanostatic pulse method

A fast and nondestructive method for production control and development research on Li/SO₂, Li/SOCl₂, and Li/SO₂Cl₂ cells is described.     

Electrochemical behavior of a lithium-pre-doped carbon-coated silicon monoxide anode cell

Owing to high energy density, silicon monoxide is an attractive anode material for lithium ion secondary batteries. However, its huge irreversible capacity during initial cycling makes it difficult to use in lithium secondary batteries. A new technique for lithiation in the silicon monoxide has been developed using Li powders. The electrochemical behavior of the lithium powder pre-doped carbon-coated silicon monoxide (OG) anode cell was studied. The cells showed reduced initial irreversibility and enhanced coulombic efficiency. The behavior of the cells was analyzed by X-ray diffraction and electrochemical testing methods.     

Investigation and production control of Li/SO2 cells by the galvanostatic pulse method

A fast and nondestructive method for production control and development research on Li/SO₂, Li/SOCl₂, and Li/SO₂Cl₂ cells is described. Employing the galvanostatic pulse technique, the method yields useful data for the IR drop in the cell, the passivation state of the Li anode, and eventual cathode defects. It can also be applied to the study of the effect of variations in the electrolyte and the cathode on the performance characteristics of cells during storage under various conditions. The applicability of the method is exemplified by data on fresh and stored Li/SO₂ cells.     

The effect of a concentration graded cathode for organic solar cells

We present the effects of a concentration graded Li:Al cathode when it is made by one-step evaporation method using single alloy sources on the performance of organic solar cells. The concentration profile of the Li:Al cathode and related interface energy levels were investigated by means of secondary ion mass spectroscopy and ultraviolet photoelectron spectroscopy, in comparison with those of a common Al cathode. The results indicate that interfacial lithium accumulation introduces a cascade decrease of the work function (WF) of the cathode. The WF graded cathode applied to bulk heterojunction solar cells resulted in increased short circuit current and power conversion efficiency. Furthermore, the Li:Al cathode avoids the formation of interface Al-C complex, which may cause disruption of electron transport.     

Prospects,challenges, and latest developments in lithium–air batteries

Metal–air batteries are being envisioned as a clean and high energy fuel for the modern automotive industry. The lithium–air battery has been found most promising among the various practically applicable metal–air systems, that is, Al–air, Li–air, Mg–air, Fe–air, and Zn–air. The theoretical specific energy of the Li–air battery is ~12 kWh/kg, excluding the oxygen mass. This is comparable with the energy density of gasoline, which is ~13 kWh/kg. It has been hypothesized that the Li–air battery could supply an energy ~1.7 kWh/kg after losses from over potentials to run a vehicle ~300 miles on a single charge. During the first decade of this century, a fair amount of research has been conducted on Li–air battery system. Yet, Li–air batteries could not make an industrial breakthrough, and are still in the laboratory phase since their birth. In this article, we technically evaluated the recent developments, and the inferences have been analyzed from the practical/commercial point of view. The study concludes that low discharge rate, lower number of cycles, oxidation of lithium anode, discharge products at the cathode, and side reactions inside the battery are the key limiting factors in the slow progress of Li–air batteries on an industrial scale. The ongoing researches to overcome these hurdles have also been discussed. This analysis will help the reader to understand the current standing of the lithium–air battery technology. Copyright © 2014 John Wiley & Sons, Ltd.     

Electrochemical behavior of Al in a non-aqueous alkyl carbonate solution containing LiBOB salt

Aluminum was studied as a current collector for rechargeable lithium batteries to understand electrochemical and passivation behavior. Electrochemical polarization tests, in situ scratch polarization tests and time-of-flight secondary ion mass spectroscopy (ToF-SIMS) analysis in lithium bis-oxalato borate (LiBOB)-containing alkyl carbonate solution were conducted. The Al foil did not follow the alloy and de-alloy process with the LiBOB salt in electrolyte at 0 V vs. Li/Li⁺ in the cathodic sweep. During the anodic scan to the noble direction, the absence of an oxidation peak up to 3 V vs. Li/Li⁺ indicated that the air-formed oxide layer of Al was not reduced to metal. Oxide-free Al surfaces made by the in situ scratch test during the electrochemical polarization resulted in abrupt alloy formation with Li at 0 V vs. Li/Li⁺, but the newly formed surface formed passive films at higher potential with oxygen, namely, Al-O compound, as confirmed by ToF-SIMS.     

Electrochemical performance of lithium ion capacitors using high-capacitance Li2NiO2/AC as the negative electrode

兼具锂离子电池高能量密度和双电层电容器高功率特性的锂离子电容器成为了现今超级电容器性能提升的重点发展方向。本工作以高富锂金属氧化物Li2NiO2为锂离子电容器用负极锂源,将其与活性物复合组成正极电极,并制备出“无金属锂片”预嵌锂过程的300 F锂离子电容器,考察了金属氧化物Li2NiO2的理化性能与电化学特性、不同Li2NiO2添加量对锂离子电容器样品的电化学性能影响。结果表明,Li2NiO2材料具有398 mA·h/g的首次不可逆容量,首次放电不可逆率为94.8%。添加15%～20% Li2NiO2的样品在10 A电流下具有大于75%倍率特性以及91%的容量保持率。当Li2NiO2添加量为20%时,样品在1 A条件下具有400 F的容量,15.5 W·h/kg的能量密度以及11.3 kW/kg的功率密度,是一种制备工艺简单、性能优异的新型锂离子电容器。     

Characterization of all-solid-state secondary batteries with LiCoO2 thin films prepared by ECR sputtering as positive electrodes

We fabricated all-solid-state lithium secondary batteries consisting of LiCoO₂ thin films prepared by electron cyclotron resonance (ECR) sputtering LiPON and metallic lithium films, and investigated the influence of the sputtering target composition on the performance of the batteries and LiCoO₂ films. We found that the LiCoO₂ film sputtered with a stoichiometric LiCoO₂ target included many impurities (mainly Co₃O₄) and these impurities were eliminated by adding an excess of Li source to the sputtering target to achieve a Li/Co atomic ratio of 2.0 elsewhere. The LiCoO₂ film sputtered with a Li2.0 target exhibited a larger discharge capacity and a high performance level for large current operation. However, the capacity of a battery employing LiCoO₂ film sputtered with a Li2.0 target decreased more rapidly than that with a Li1.0 or Li1.7 target in a charge–discharge cycle test. We also investigated the cycle performance of LiCoO₂ films in an ordinary liquid electrolyte by using beaker type cells. We found that the decrease in capacity during the cycle tests was caused by the deterioration of the LiCoO₂ film, because the dependence of the target composition on the cycle performance in the beaker type cells was similar to that in the all-solid-state cells. We consider the capacity decrease to be caused by the deterioration in the crystallinity of the LiCoO₂ film when using the Li2.0 target and caused by the formation of a Co₃O₄ layer on the surface of the LiCoO₂ film when using a Li1.7 target on basis of the results of X-ray diffraction analysis and Raman spectroscopy.     

Ethylene carbonate/ether solvents for electrolytes in lithium secondary batteries

An examination has been made of the effectiveness of ethylene carbonate(EC)/2-methyltetrahydrofuran(2-MeTHF) solvents incorporating LiAsF₆ as the solute as electrolytes in secondary lithium batteries. From —10 to 30 °C, the conductivities of EC/2-MeTHF are higher than those of 2-MeTHF and EC/propylene carbonate (PC). For lithium-on-lithium cycling in a half cell, the FOM (figure of merit) of lithium in EC/2-MeTHF has a value 2.2 to 2.7 times higher than that in 2-MeTHF and EC/PC. A coin cell of Li/amorphous V₂O ₅-P₂O₅ with EC/2-MeTHF clearly exhibits higher capacity and longer cycle life than cells with 2-MeTHF or EC/PC. It is concluded that EC/2-MeTHF is a promising electrolyte system for secondary lithium battery applications.     

Density functional theory study of reversible hydrogen storage in monolayer beryllium hydride by decoration with boron and lithium

The hydrogen storage capacity of M-decorated (M = Li and B) 2D beryllium hydride is investigated using first-principles calculations based on density functional theory. The Li and B atoms were calculated to be successfully and chemically decorated on the Surface of the α-BeH₂ monolayer with a large binding energy of 2.41 and 4.45eV/atom. The absolute value was higher than the cohesive energy of Li and B bulk (1.68, 5.81eV/atom). Hence, the Li and B atoms are strongly bound on the beryllium hydride monolayer without clustering. Our findings show that the hydrogen molecule interacted weakly with B/α-BeH₂(B-decorated beryllium hydride monolayer) with a low adsorption energy of only 0.0226 eV/H₂ but was strongly adsorbed on the introduced active site of the Li atom in the decorated BeH₂ with an improved adsorption energy of 0.472 eV/H₂. Based on density functional theory, the gravimetric density of 28H₂/8li/α-BeH₂) could reach 14.5 wt.% higher than DOE's target of 6.5 wt. % (the criteria of the United States Department of Energy). Therefore, our research indicates that the Li-decorated beryllium hydride monolayer could be a candidate for further investigation as an alternative material for hydrogen storage.     

The progress of novel binder as a non‐ignorable part to improve the performance of Si‐based anodes for Li‐ion batteries

In this review, we highlight recent achievements of polymer binders used for Si‐based anodes in Li‐ion batteries. We classify the polymer binders, depending on their polymer structures and the function on performances of Si‐based anodes, into 3 types: cellulose‐type, conductive‐type and self‐healing‐type binders. The relationship between polymer structures and enhanced electrochemical performances of Si‐based anodes is discussed in details. We investigate how the binders make an extraordinary improvement on the specific capacity, cycling stability and rate performances of Si‐based anodes. The reasons of the noticeable effect on Si‐based anodes especially the controlling of swelling during cycling are also researched. In a word, the main aim of this review is to analyze recent research achievements and propose perspectives of polymer binders used for Si‐based anodes in promising Li‐ion batteries.     

New glyme-cyclic imide lithium salt complexes as thermally stable electrolytes for lithium batteries

New glyme-Li salt complexes were prepared by mixing equimolar amounts of a novel cyclic imide lithium salt LiN(C₂F₄S₂O₄) (LiCTFSI) and a glyme (triglyme (G3) or tetraglyme (G4)). The glyme-Li salt complexes, [Li(G3)][CTFSI] and [Li(G4)][CTFSI], are solid and liquid, respectively, at room temperature. The thermal stability of [Li(G4)][CTFSI] is much higher than that of pure G4, and the vapor pressure of [Li(G4)][CTFSI] is negligible at temperatures lower than 100 °C. Although the viscosity of [Li(G4)][CTFSI] is high (132.0 mPa s at 30 °C), because of its high molar concentration (ca. 3 mol dm⁻³), its ionic conductivity at 30 °C is relatively high, i.e., 0.8 mS cm⁻¹, which is slightly lower than that of a conventional organic electrolyte solution (1 mol dm⁻³ LiTFSI dissolved in propylene carbonate). The self-diffusion coefficients of a Li⁺ cation, a CTFSI⁻ anion, and a glyme molecule were measured by the pulsed gradient spin-echo NMR method (PGSE-NMR). The ionicity (dissociativity) of [Li(G4)][CTFSI] at 30 °C is ca. 0.5, as estimated from the PGSE-NMR diffusivity measurements and the ionic conductivity measurements. Results of linear sweep voltammetry revealed that [Li(G4)][CTFSI] is electrochemically stable in an electrode potential range of 0-4.5 V vs. Li/Li⁺. The reversible deposition-stripping behavior of lithium was observed by cyclic voltammetry. The [LiCoO₂|[Li(G4)][CTFSI]|Li metal] cell showed a stable charge-discharge cycling behavior during 50 cycles, indicating that the [Li(G4)][CTFSI] complex is applicable to a 4 V class lithium secondary battery.     

Camphor-based carbon nanotubes as an anode in lithium secondary batteries

Camphor vapour is pyrolysed in the presence of Fe, Ni and Co powder under a dinitrogen atmosphere at different temperatures (750–1050 °C). While Fe and Ni catalyse the formation of carbon nanotubes (CNs), Co facilitates carbon nanobead growth. The CNs, obtained using a Fe catalyst at 950 °C, are utilised as the anode in Li secondary batteries. The capacity of the batteries constructed in this way is as good as those prepared by graphitic carbon formed in the arc process.     

An investigation of Li-decorated N-doped penta-graphene for hydrogen storage

By making use of first principles calculations, lithium-decorated (Li-decorated) and nitrogen-doped (N-doped) penta-graphene (PG) was investigated as a potential material for hydrogen storage. The geometric and electronic structures of two types of N-doped PG were studied, and the band gaps were 1.86 eV and 2.06 eV, respectively, depending on the positions of the substitution. The probable adsorption sites for Li atoms on topside and downside were calculated. Hydrogen molecules were added one by one to Li-decorated N-doped PG to research the maximum hydrogen gravimetric density. It is found that up to 5 hydrogen molecules on topside and 8 hydrogen molecules on downside can be adsorbed around a Li atom, and the average adsorption energies are in the range of physical adsorption processes (0.1–0.4 eV). The gravimetric densities can reach 7.88 wt% for N-doped PG with Li decoration. Our results suggest that Li-decorated N-doped PG is a significantly promising material for hydrogen storage.     

A review of cells based on lithium negative electrodes (anodes)

This review traces the development of lithium cells from their inception to the present day: about 500 references are included. Primary and secondary cells are dealt with and the most useful anode/cathode combinations, in both fields, are noted. Electrolytes and separators are also discussed, as are the effects of film formation and the charge/discharge mechanisms.Shortcomings are emphasised where they are known to exist and attention is drawn to some areas where the present authors consider advances may be made.