1,721,014 research outputs found
LiBH4 as a Solid-State Electrolyte for Li and Li-Ion Batteries: A Review
Full text linkIn this paper, the methods used to enhance the conductivity of LiBH4, a potential electrolyte for the construction of solid-state batteries, are summarized. Since this electrolyte becomes conductive at temperatures above 380 K due to a phase change, numerous studies have been conducted to lower the temperature at which the hydride becomes conductive. An increase in conductivity at lower temperatures has generally been obtained by adding a second component that can increase the mobility of the lithium ion. In some cases, conductivities at room temperature, such as those exhibited by the liquid electrolytes used in current lithium-ion batteries, have been achieved. With these modified electrolytes, both lithium metal and lithium-ion cells have also been constructed, the performances of which are reported in the paper. In some cases, cells characterized by a high capacity and rate capability have been developed. Although it is still necessary to confirm the stability of the devices, especially in terms of cyclability, LiBH4-based doped electrolytes could be employed to produce solid-state lithium or lithium-ion batteries susceptible to industrial development
Electrical system research: The electrochemical storage sub-program
No full textThe electrochemical storage sub-program is a part of a larger program, The Electrical System Research, aimed at developing technical and technological innovation of general interest for the Italian electricity sector. The sub-program is finalized to find new electrochemical energy storage technologies suitable for stationary applications. It intends to study innovative active material with the aim of reducing the preparation costs. To increase the energy density of lithium-ion battery, a combined approach is proposed, which synergistically exploits the properties of salts based on orthoborate anions and ionic liquids. Advanced computational modeling will enable rapid prototyping and screening of materials. At the same time, the replacing of the intercalation materials with materials capable of reacting with lithium by alloying or conversion processes will allow to increase the energy density of the devices. In order to improve the thermal stability and wettability of the separators the use of polymeric non-woven fabrics will be investigated. To foster the development of sodium ion battery study and development of cathode and anode materials that have a high specific capacity, good cyclic stability and high energy density will be carried out. As regards the electrolyte for sodium ion batteries, electrolyte systems based on organic and/or aqueous solvents will be designed. Innovative lithium metal batteries will be also investigated: the key to solving the problem of dendrite formation is reputed be the protection of the lithium anode. The basic idea is to develop a coating material or a gelled polymer electrolyte that can protect the surface of the lithium metal and make the deposition of lithium ions uniform, avoiding their preferential growth in some places. This would allow the development of technologies based on Li-metal/X electrochemical pairs in which X could be represented by S or O2
Crystal Group Prediction for Lithiated Manganese Oxides Using Machine Learning
Full text linkThis work aimed to predict the crystal structure of a compound starting only from the knowledge of its chemical composition. The method was developed to select new materials in the field of lithium-ion batteries and tested on Li-Fe-O compounds. For each testing compound, the correspondence with respect to the training compounds was evaluated simply by calculating the Euclidean distance existing between the stoichiometric coefficients of the elements constituting the two compounds. At the compound under test was assigned the crystal structure of the training compound for which the distance value was minimum. The results showed that the model can predict the crystalline group of the test compound with an accuracy higher than 80% and a precision higher than 90%, for a cut-off distance higher than four. The method was then used to predict the crystalline group of manganese-based compounds (Li-Mn-O). The analysis conducted on twenty randomly selected compounds showed an accuracy of 70%. Out of ten valid predictions, nine were true positives, with a precision of 90%
Exploitation of the Concept of Vicariance to Predict the Space Group of Lithiated Manganese or Cobalt Oxides
Full text linkIn this work, a machine learning program was used to predict the crystal structure of lithiated manganese or cobalt oxides based only on their chemical composition. The composition and crystal structure of lithiated iron oxides were used as trial matrix. To assign the crystal structure, the Euclidean distance between the stoichiometric coefficients of the elements of the compound under testing and the trial compound was calculated. The softmax function was used to convert this distance into a probability distribution. The compound under test was assigned the space group of the training compound that appeared with the highest percentage. The logarithmic cross-entropy loss was used in evaluating the forecast results. The results showed that the program, for logarithmic cross-entropy loss values between 0.2 and 0.3, can predict the crystalline group with an accuracy of about 0.67. In the same range, sensitivity and precision values are placed in a range between 0.6 and 0.8, respectively, and the F1_Score reaches values above 0.62
Improved Electrochemical Performance of a LiFePO4-Based Composite Cathode
No full textLiFePO4 was synthesized in the presence of high-surface area carbon-black. The carbon was added to the precursors before the formation of the crystalline phase. SEM micrographs confirmed that the addition of the fine carbon powder reduces the LiFePO4 grain size. The carbon is uniformly dispersed between the grains, ensuring a good electronic contact. Electrochemical tests showed that the material obtained by adding 10 wt.% of carbon gives enhanced performance in terms of improved practical capacity and charge/discharge rate. The specific capacity was seen to increase on increasing temperatures. The full capacity (170 mA h g− 1) was delivered when discharging the cell at 80 °C and C/10 rate. The cyclability of the material was tested at room temperature and C/2 rate. The cell was cycled for over 230 cycles with an average specific capacity of about 95 mA h g− 1. © 2001 Elsevier Science Ltd. All rights reserved
Hard carbon for sodium batteries: Wood precursors and activation with first group hydroxide
No full textThis manuscript contains a survey of composite anodes for sodium ion batteries based on hard carbon obtained from different wood precursors. The hard carbon was activated with various metal hydroxide (MeOH with Me = Na, K, Rb, Cs). A commercially available carbon was also tested to compare the performance of the hard carbon so prepared. Electrochemical tests have shown that anodes prepared with different hard carbons have different specific capacities. The different capacity was related both to the type of wood used as the precursor and to the metal hydroxide used as the activation agent. The cycling tests indicated that KOH activated hard carbons show the best performance in terms of specific capacity and rate capability. The effect of the cation size on the carbon activation process can be explained considering that the alkali metal acts through a mechanism combined which on the one hand determines an increase in the porosity of the carbon and on the other one, an increase in the inter-atomic distance of the carbon structure
Easy and Scalable Syntheses of Li1.2Ni0.2Mn0.6O2
Full text linkSolid-state and sol-gel syntheses were selected as easy and scalable methods to prepare a lithium-rich cathode material for lithium-ion batteries. Among the extended family of layered oxides, Li1.2Ni0.2Mn0.6O2 was chosen for its low nickel content and the absence of cobalt. Both synthesis methods involved two heating steps at different temperatures, 600 and 900 °C. The first step is needed to decompose the metal acetates, which were selected as precursors, and the second step is needed to crystallise the material. To obtain a material with well-defined defects, the rate of heating and cooling was carefully controlled. The materials were characterised by X-ray diffraction, SEM coupled with EDS analysis, and thermal analysis and were finally tested as cathodes in a lithium semi cell. The solid-state synthesis allowed us to obtain better structural characteristics with respect to the sol-gel one in terms of a well-formed hexagonal layer structure and a reduced Li+/Ni2+ disorder. On the other hand, the sol-gel method produced a material with a higher specific capacity. The performance of this latter material was then evaluated as a function of the discharge current, highlighting its good rate capabilities
Determination of Chemical Diffusion Coefficient of Lithium in LiFePO4
No full textThe lithium insertion in the ordered olivine-type structure of LiFePO4 was analyzed as an insertion process with a Frumkin- type sorption isotherm. A minimum in the chemical diffusion coefficient of lithium (DLi) was predicted by the model for strong attractive interactions between the intercalation species and the host matrix. The DLi in the material was measured as a function of the lithium content by using the galvanostatic intermittent titration technique (GITT). The diffusion coefficient was found 1.8 10 14 and 2.2 10 16 cm2 s 1 for LiFePO4 and FePO4, respectively, with a minimum in correspondence of the peak of the differential capacity. The DLi has also been measured by AC impedance method for various lithium contents. The calculated values are in very good agreement with the previous calculated ones. D 2002 Elsevier Science B.V. All rights reserved
X-Ray microscopy: a non-destructive multi-scale imaging to study the inner workings of batteries
No full textX-ray microscopy (XRM) is a non-destructive characterization technique that provides quantitative information regarding the morphology/composition of the specimen and allows to perform multiscale and multimodal 2D/3D experiments exploiting the radiation-matter interactions. XRM is particularly suitable to afford in situ images of inner parts of a battery and for the early diagnosis of its degradation in a non-invasive way. Since traditional characterization techniques (SEM, AFM, XRD) often require the removal of a component from the encapsulated device that may lead to non-desired contamination of the sample, the non-destructive multi-scale potential of XRM represents an important improvement to batteries investigation. In this work, we present the advanced technical features that characterize a sub-micron X-ray microscopy system, its use for the investigation of hidden and internal structures of different types of batteries and to understand their behavior and evolution after many charge/discharge cycles
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