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Petzl M.,Helmholtz Institute Ulm | Danzer M.A.,Helmholtz Institute Ulm | Danzer M.A.,Center for Solar Energy and Hydrogen Research
Journal of Power Sources | Year: 2014

Lithium plating is a typical aging mechanism of lithium-ion (Li-ion) batteries at low temperatures and high charge rates. Therefore an instant detection method is needed for safe battery operation and to increase the life time. Detection of lithium plating during operation is only possible by nondestructive analysis of short-term plating effects. In this study, we present a new approach to detect, characterize, and quantify lithium plating in a commercial graphite/LiFePO4 battery. This is crucial for battery management systems (BMS) in real-world applications. The method is based on a high voltage plateau in the discharge profile after charging at plating conditions. This voltage plateau corresponds to the stripping of plated lithium from the graphite surface. It is shown that differential analysis of such voltage profiles provides a quantitative estimation of lithium plating. The correlation between lithium plating and stripping necessitates a distinction of reversible and irreversible plating. Effects of various operating conditions, i.e. charge temperature, state-of-charge (SOC), and charge current, on the plating behavior are investigated in order to elucidate this degradation mode. Furthermore, the presented approach allows for determination of the reversibility of lithium plating. © 2013 Elsevier B.V. All rights reserved. Source


Witte W.,Center for Solar Energy and Hydrogen Research
Vakuum in Forschung und Praxis | Year: 2014

This contribution provides an overview of current activities in the area of alternative buffer layers for Cu(In,Ga)(S,Se)2 (CIGS) thin-film solar cells. Good cell and module results were achieved by replacing the standard Cds buffer with Zn(O,S), In2S3, (Zn,Sn)O y or (Zn,Mg)O grown by various methods like chemical bath deposition (CBD), thermal evaporation, sputtering, atomic layer deposition, and spray ion layer gas reaction. The "dry" deposition methods like sputtering and thermal evaporation could be favorable in an industrial environment on glass substrates or application in a roll-to-roll coater. Significant progress was made within the last two years for various Cd-free CIGS devices. We list current records for cells with alternative buffers, e. g. Zn(O,S)-buffered champion cells with efficiencies between 18 - 20 % and In2S 3-buffered cells with 16 - 17 %. Both materials have the potential to substitute CdS with efficiencies approaching the 20 % mark already surpassed by CIGS cells with CBD CdS buffers. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Petzl M.,Helmholtz Institute Ulm | Danzer M.A.,Center for Solar Energy and Hydrogen Research
IEEE Transactions on Energy Conversion | Year: 2013

Incremental open-circuit voltage (OCV) curves and low-current charge/discharge voltage profiles of a lithium-ion (Li-ion) battery are compared and evaluated for optimizing measurement time and resolution. Since these curves are often used for further analysis, minimizing kinetic contributions is crucial for approximating battery OCV behavior. In this context, an incremental OCV measurement is characterized by state of charge (SOC) intervals and relaxation times. Various constant low C-rates, SOC intervals, and relaxation times are tested for approximating OCV behavior. Differential capacity and voltage analysis is used to check whether the main electrode features can be resolved satisfactorily. An interpolation method yields additional data points for the differential analysis of incremental OCV curves. It is shown that incremental OCV measurements are suitable for an approximation of battery OCV behavior, rather than low current-voltage profiles. Furthermore, extrapolation of voltage relaxation enables the estimation of fully relaxed OCV. © 1986-2012 IEEE. Source


Grant
Agency: Cordis | Branch: H2020 | Program: RIA | Phase: GV-1-2014 | Award Amount: 5.93M | Year: 2015

The FiveVB project will develop a new cell technology based on innovative materials such as high capacity anodes, high voltage cathodes and stable, safe and environmentally friendly electrolytes. Since main European industry partners representing the value chain from materials supplier to car manufacturer are involved, this program will support and enable the development of a strong and competitive European battery industry. The multidisciplinary project team will also assure not only early technology integration between materials, cells, batteries and application requirements, but also a subsequent industrialization of the developed technology. With an integrated trans-disciplinary cell development approach we will also realize an early feedback loop from battery and vehicle level to material suppliers and a feed-forward of relevant information to industrial scale cell production. Through an iterative and holistic approach two generations of cell chemistries (anode, cathode, binder and electrolyte) will be evaluated and optimized to improve electrochemical performance of active materials and related new cell technology in terms of energy density, lifetime, safety and costs. Furthermore, we will address early development and validation of test procedures for the reduction of development time from material to cell by e.g. accelerated test procedures. Among other objectives, in particular the lifetime and aging aspects will be addressed in depth in FiveVB, but also input for future European and International standardization will be provided. Thus, one major result of FiveVB is a hard case prismatic cell in PHEV1 format, developed according to automotive requirements and produced on a representative prototype facility.


Grant
Agency: Cordis | Branch: H2020 | Program: RIA | Phase: LCE-02-2014 | Award Amount: 6.15M | Year: 2015

Prime objective of the Sharc25 project is to develop super-high efficiency Cu(In,Ga)Se2 (CIGS) solar cells for next generation of cost-beneficial solar module technology with the world leading expertise establishing the new benchmarks of global excellence. The project partners ZSW and EMPA hold the current CIGS solar cell efficiency world records of 21.7% on glass and 20.4% on polymer film, achieved by using high (~650C) and low (~450C) temperature CIGS deposition, respectively. Both have developed new processing concepts which open new prospects for further breakthroughs leading to paradigm shift for increased performance of solar cells approaching to the practically achievable theoretical limits. In this way the costs for industrial solar module production < 0.35/Wp and installed systems < 0.60/Wp can be achieved, along with a reduced Capex < 0.75/Wp for factories of >100 MW production capacity, with further scopes for cost reductions through production ramp-up. In this project the performance of single junction CIGS solar cells will be pushed from ~21% towards 25% by a consortium with multidisciplinary expertise. The key limiting factors in state-of-the-art CIGS solar cells are the non-radiative recombination and light absorption losses. Novel concepts will overcome major recombination losses: combinations of increased carrier life time in CIGS with emitter point contacts, engineered grain boundaries for active carrier collection, shift of absorber energy bandgap, and bandgap grading for increased tolerance of potential fluctuations. Innovative approaches will be applied for light management to increase the optical path length in the CIGS absorber and combine novel emitter, front contact, and anti-reflection concepts for higher photon injection into the absorber. Concepts of enhanced cell efficiency will be applied for achieving sub-module efficiencies of >20% and industrial implementation strategies will be proposed for the benefit of European industries.

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