Preparation of LiCoO2 cathode materials from spent lithium–ion batteries

Preparation of LiCoO₂ cathode materials from spent lithium–ion batteries are presented. It started with the reclaim/recycle of metal values from spent lithium–ion batteries, which involves the separation of electrode materials by ultrasonic treatment, acid dissolution, precipitation of cobalt and lithium, followed by the preparation of LiCoO₂ cathode materials. Co (99.4%) and Li (94.5%) were recovered from spent lithium–ion batteries. The LiCoO₂ cathode materials prepared from the reclaimed cobalt and lithium compounds showed good elecrtochemical performance. The reclaiming of cobalt and lithium has a promising outlook for the recycling of cobalt and lithium from spent Li–ion batteries, thus reducing the cost of Li–ion batteries.     

Critical review on lithium-ion batteries: are they safe? Sustainable?

The goal of this critical review is to explain why the safety problem raised by the lithium batteries must be considered. The performance of the batteries with different chemistries is compared and analyzed, with emphasis on the safety aspects, in addition to the electrochemical properties of the cells. Problems encountered with cathode materials (layered compounds, spinel and olivine), anode materials (graphite and lithium titanate), electrolytes, lithium salts, and separators are pointed out. In this critical review, we also discuss the place of the lithium batteries in the context of sustainable energies (electric vehicles, smart grid).     

Iron doped lithium cobalt oxides as lithium intercalating cathode materials

Layered transition metal oxides of the formula LiMO₂ have good lithium insertion properties for which reason LiCoO₂ and LiNiO₂ have been exploited in practical lithium rocking chair batteries. Another member of the LiMO₂ series, LiFeO₂, should be an attractive cathode material considering the cheapness and environment-friendliness of iron compounds. Its rock-salt structure, however, does not allow significant amounts of lithium to be reversibly intercalated in its structure. Synthesis of layered LiFeO₂ and study of its lithium intercalating properties have been of limited success. Therefore, an attempt has been made here to study LiCo_1−yFe_yO₂ solid solutions (0 ≤ y ≤ 0.4) as prospective cathode materials. XRD, FTIR, Atomic absorption spectroscopy, Particle size and Surface area analysis were carried out in this regard towards the physical characterization of the entire series of LiCo_1−yFe_yO₂ compounds. The electrochemical discharge capacity of these materials is explained as a function of the iron content.     

Experimental routes to in situ characterization of the electronic structure and chemical composition of cathode materials for lithium ion batteries during lithium intercalation and deintercalation using photoelectron spectroscopy and related techniques

Three different experimental routes to in situ characterization of electronic structure and chemical composition of thin film cathode surfaces used in lithium ion batteries are presented. The focus is laid on changes in electronic structure and chemical composition during lithium intercalation and deintercalation studied by photoelectron spectroscopy and related techniques. At first, results are shown obtained from spontaneous intercalation into amorphous or polycrystalline V₂O₅ thin films after lithium deposition. Although this technique is simple and clean, it is nonreversible and only applicable to the first lithium intercalation cycle into the cathode only to be applied to host materials stable in the delithiated stage. For other cathode materials, as LiCoO₂, a real electrochemical setup has to be used. In our second approach, the experiments are performed in a specially designed electrochemical cell directly connected to the vacuum system. First experimental results of RF magnetron sputtered V₂O₅ and LiCoO₂ thin film cathodes are presented. In the third approach, an all solid-state microbattery cell must be prepared inside the vacuum chamber, which allows electrochemical processing and characterization by photoelectron spectroscopy in real time. We will present our status and experimental difficulties in preparing such cells.     

Electrochemical characteristics of transition-metal trichalcogenides in the secondary lithium battery

Transition-metal trichalcogenides have been investigated as cathode materials in the lithium electrochemical cell. Three lithium ions per TiS₃ molecule have been found to be marginally reversible, while only one lithium is reversible in TaSe₃. This difference may be related to exfoliation of these substances due to the progress of lithium intercalation.     

A new approach to synthesize LiAsF6 and other lithium based fluorochemicals for rechargeable lithium cells

A new method to synthesize inorganic lithium based fluorinated compounds like LiAsF₆ (Lithium hexafluoro arsenate) has been developed by a low temperature solid state procedure. LiAsF₆ is used extensively in the lithium cells because of its stability to withstand high voltages during cycling. The procedure developed to synthesize lithium based fluorinated compounds is a single step procedure and fluorination is done in-situ. This is an environmentally friendly method and is less expensive than the other known procedures.     

锂电池发展简史

由于具有很高的能量密度，锂金属在1958年被引入电池领域，1970年进入锂一次电池的商业研发阶段。自1990年以来，随着正极材料、负极材料与电解质的革新，可充放二次锂电池不断发展并实现商品化。如今锂电池技术仍在继续发展并将进一步改善人类生活。文章对40多年来锂电池技术发展历程进行了简单的回顾。     

新型锂离子电池正极材料LiMPO_4(M=Fe,Mn)的谱学和电化学研究

采用固相反应与液相反应,合成了新型锂离子电池正极材料LiMPO4(M=Fe,Mn)。粉末X光衍射表明材料均为纯相。对材料的显微拉曼光谱和红外光谱进行了研究和指认。循环伏安研究表明,含锂磷酸盐是一类有潜力的锂离子电池正极材料。     

Phosphate materials for cathodes in lithium ion secondary batteries

Olivine phosphates of general formula LiMPO₄ (M=Fe, Co, Ni) were prepared and characterised in order to evaluate new potential cathode materials for secondary lithium ion batteries. The synthesis was performed by soft chemistry methods to avoid problematical and energetic expensive solid state reactions. In all the compounds no secondary phase was detected and the powder morphology was found to be suitable for cathode layers preparation. Only LiFePO₄ and LiCoPO₄ showed reversible lithium deintercalation-intercalation at 3.5 and 4.8 V vs. Li⁺/Li, respectively. The LiCoPO₄ high potential makes this compound very attractive for high energy batteries, but unfortunately its lifetime appears to be too poor. Paper presented at the Patras Conference on Solid State Ionics — Transport Properties, Patras, Greece, Sept. 14 – 18, 2004.     

Strategies to curb structural changes of lithium/transition metal oxide cathode materials & the changes' effects on thermal & cycling stability

Structural transformation behaviors of several typical oxide cathode materials during a heating process are reviewed in detail to provide in-depth understanding of the key factors governing the thermal stability of these materials. We also discuss applying the information about heat induced structural evolution in the study of electrochemically induced structural changes. All these discussions are expected to provide valuable insights for designing oxide cathode materials with significantly improved structural stability for safe, long-life lithium ion batteries, as the safety of lithium-ion batteries is a critical issue; it is widely accepted that the thermal instability of the cathodes is one of the most critical factors in thermal runaway and related safety problems.     

Square model for charge and discharge behavior of cathode electrode materials

The shape of cathode electrode affects severely the potential curves of charge/discharge process of lithium ion cells. In this paper, we take LiFePO₄ for an example. The square model is presented to predict the concentration of lithium on the cathode electrode under some simplified conditions. With the square model as a tool, effects of shape and position are determined and analyzed. Meanwhile, the lithium transportation, Gibbs free energy, and battery potential are proved to be different from that of sphere models. It shows that asymmetry of electrode materials makes a great impact on the performance of charge or discharge process.     

Compatibility study of oxide and olivine cathode materials with lithium aluminum titanium phosphate

The compatibility of the solid electrolyte Li_1.5Al_0.5Ti_1.5(PO₄)₃ (LATP) with the cathode materials LiCoO₂, LiMn₂O₄, LiCoPO₄, LiFePO₄, and LiMn_0.5Fe_0.5PO₄ was investigated in a co-sintering study. Mixtures of LATP and the different cathode materials were sintered at various temperatures and subsequently analyzed by thermal analysis, X-ray diffraction, and electron microscopy. Oxide cathode materials display a rapid decomposition reaction with the electrolyte material even at temperatures as low as 500 °C, while olivine cathode materials are much more stable. The oxide cathode materials tend to decompose to lithium-free compounds, leaving lithium to form Li₃PO₄ and other metal phosphates. In contrast, the olivine cathode materials decompose to mixed phosphates, which can, in part, still be electrochemically active. Among the olivine cathode materials, LiFePO₄ demonstrated the most promising results. No secondary phases were detected by X-ray diffraction after sintering a LATP/LiFePO₄ mixture at temperatures as high as 700 °C. Electron microscopy revealed a small secondary phase probably consisting of Li₂FeTi(PO₄)₃, which is ionically conductive and should be electrochemically active as well.     

Recent developments in the doping and surface modification of LiFePO4 as cathode material for power lithium ion battery

Lithium ion batteries have become attractive for portable devices due to their higher energy density compared to other systems. With a growing interest to develop rechargeable batteries for electric vehicles, lithium iron phosphate (LiFePO₄) is considered to replace the currently used LiCoO₂ cathodes in lithium ion cells. LiFePO₄ is a technically important cathode material for new-generation power lithium ion battery applications because of its abundance in raw materials, environmental friendliness, perfect cycling performance, and safety characteristics. However, the commercial use of LiFePO₄ cathode material has been hindered to date by their low electronic conductivity. This review highlights the recent progress in improving and understanding the electrochemical performance like the rate ability and cycling performance of LiFePO₄ cathode. This review sums up some important researches related to LiFePO₄ cathode material, including doping and coating on surface. Doping elements with coating conductive film is an effective way to improve its rate ability.     

基于材料基因组方法的锂电池新材料开发

近年来,在锂二次电池新材料的研发过程中逐渐建立了基于材料基因组思想的高通量计算理论工具与研究平台.在该平台上,通过将不同精度的计算方法组合,实现了基于离子输运性质的材料筛选;通过将信息学中数据挖掘算法引入高通量计算数据的分析,证实了材料大数据解读的可行性.上述平台实现了在锂电池固体电解质的高通量筛选、优化和设计上进行新材料研发的示范应用,通过高通量计算筛选获得了两种可用于富锂正极包覆材料的化合物Li_2SiO_3和Li2SnO_3,有效改善了富锂正极的循环稳定性;通过对掺杂策略的高通量筛选,获得了提高固体电解质β-Li_3PS_4离子电导率和稳定性的方案;通过高通量结构预测设计了全新的氧硫化物固体电解质LiAlSO;并在零应变电极材料结构与性能的构效关系研究中进行了大数据分析的尝试,分析了零应变电极材料的设计依据.上述材料基因组方法在锂电池材料研发中的应用为在其他类型材料研发中推广这种新的研发模式提供了可能.     

Characterisation of the oxygen transfer in BIMEVOX membranes under applied current conditions

Oxygen isotopic exchange has been studied for a number of materials in the BIMEVOX family of compounds. The exchanges were undertaken at 620 °C with gold grid electrodes on the samples and with a constant current flowing through the samples during the exchange anneals. These conditions simulate those used when these materials are employed in oxygen separation devices where substantial oxygen fluxes can be sustained using such simple gold grid electrodes.The results showed that samples exchanged under current flow conditions exhibit substantial oxygen exchange at the cathode, in contrast to samples where no electrical bias is applied. This effect was sustained in regions remote from the sputtered gold electrode. Complementary studies of the samples using X-ray diffraction revealed subtle changes in the diffraction patterns following experiments with current flow. These changes are ascribed to a reduction of V⁵⁺ to V⁴⁺ at the cathode locally transforming the BIMEVOX material into a mixed conducting material, and hence enhancing the oxygen isotopic exchange process.     

First-principles study of LiMPO4 compounds (M=Mn,Fe, Co,Ni) as electrode material for lithium batteries

The intercalation voltages of cathode materials for rechargeable lithium-ion batteries are calculated for lithium-orthophosphate oxides LiMPO₄ (M=Mn, Fe, Co and Ni) using density-functional theory within the local-density (LDA) and LDA?+?U approximations. We show that the LDA?+?U approximation is able to reproduce the experimental volumes as well as the experimentally observed magnetic structures of the lithiated and non-lithiated compounds for which LDA qualitatively fail. Moreover, we find that, using the LDA?+?U approach, the experimental evolution of the lithium intercalation voltage along the series can be reproduced accurately.     

Studies on the effect of titanium addition on LiCoO2

The lithiated transition metal oxide has been used as the cathode materials for lithium ion rechargeable batteries. Among the various cathode materials, LiCoO₂ has been widely used. There are lot of reports on the substituted LiCoO₂ replacing small amount of Cobalt with other transition and nontransitional metals. Here, we focus on to a tetravalent transition metal atom such as titanium, as an addition in LiCoO₂ and studied its performance. The titled cathode material was synthesized by solid-state reaction method. Thermogravimetric/differential thermal analysis, X-ray diffraction, X-ray fluorescence, scanning electron microscopy, and particle size analysis were carried out to assess the effect of addition of titanium on LiCoO₂. Electrochemical studies were carried out by cyclic voltammetry and life cycle analyzer.     

Morphological changes in polymer electrolyte cells

Rechargeable solid state batteries utilizing lithium anodes, V₆O₁₃ composite cathodes and polymer electrolytes made from polyethylene oxide - LiCF₃SO₃ complex - were investigated at 100°C. The cells exhibited good cycling and reversibility. Optical and scanning electron microscopy were used to study the morphological changes taking place at the electrodes and electrolyte as a function of cycle number. Post-mortem examination of the cell materials indicated that the structures of lithium, electrolyte and cathode become finer grained and hence smoother. In addition the structures were more coherent. The cathode appeared to undergo a re-healing process during the early stage of cycling. The results indicate that the structures are consistent with one another and that long cycle life can be obtained with these types of cells.     

Advanced lithium ion battery materials

Although a commercial reality, the lithium ion battery is still the object of intense R&D aimed to further improve its performance. In this paper we review the activities in progress in our laboratory for the characterization of novel, not-carbonaceous anode materials, high-voltage cathode materials and composite polymer electrolytes.     

Synthesis and characterization of mixed vanadium oxide cathode materials for lithium-ion batteries

A family of mixed vanadium oxides LiCo_yNi_(1−y)VO₄ (x=0.2, 0.5 and 0.8) of potential use as high voltage cathode materials in lithium batteries, has been synthesized and characterized. In general the x-ray diffraction analysis showed that these compounds have an inverse spinel structure where about 85 % of the Ni²⁺ and Co²⁺ ions occupies octahedral sites and the rest tetrahedral sites along with the V⁵⁺ ions. Moreover, the annealing temperature plays a key role in determining the particle size, as demonstrated by scanning electron microscope analysis. Cycling voltammetry tests showed that the lithium insertion-extraction process in the LiCo_yNi_(1−y)VO₄ electrode materials occurs reversibly at around 4.3–4.4 V vs. Li and these results are confirmed by cycling tests. The cycling capacity is modest; however the trend of the cycling curves leads to foresee that an increase in capacity may be obtained by extending the charging process beyond 4.6 V vs. Li, once a stable electrolyte will be available. Paper presented at the 6th Euroconference on Solid State Ionics, Cetraro, Calabria, Italy, Sept. 12–19, 1999.