A Novel Technique for Estimation of the Solid Electrolyte Interphase Film Resistance for Li-Ion Batteries

2018 ◽  
Author(s):  
Shashank Arora
Keyword(s):  
Solid Electrolyte ◽  
Solid Electrolyte Interphase ◽  
Carbon Film ◽  
Open Circuit ◽  
Film Resistance ◽  
Battery Cell ◽  
Average Value ◽  
Sei Film ◽  
Li Ion ◽  
The Difference

Solid electrolyte interphase (SEI) film resistance is an important parameter in the study of charge transfer kinetics of a Li-ion battery. The passive film affects diffusion process of Li-ions. As such, it becomes essential to include film resistance in battery modelling. However, the traditional method of estimating the SEI film resistance is costly and time consuming. An indirect approach based on Ohm’s law is thus presented in this paper. It relies on determining the interfacial polarisation from the difference of open-circuit voltage measured immediately after switching off the applied current and the equilibrium voltage. The technique is simple, easy to implement and can be used for a quick estimation of SEI film resistance with reasonable accuracy. For instance, average value of SEI film resistance for commercial LFP battery cell is measured as 0.004 Ohm · m2 , which was found to be consistent with the values determined using the impedance spectroscopy techhnique in the published literature for lithium-carbon film electrodes.

Influence of VC and FEC Additives on Interphase Properties of Carbon in Li-Ion Cells Investigated by Combined EIS & EQCM-D

2020 ◽  
Author(s):  
Paul Kitz ◽  
Matthew Lacey ◽  
Petr Novák ◽  
Erik Berg
Keyword(s):  
Electrochemical Impedance ◽  
Solid Electrolyte Interphase ◽  
Electrochemical Quartz Crystal Microbalance ◽  
Gas Analysis ◽  
Side Reactions ◽  
Ion Diffusion ◽  
Battery Cell ◽  
Anode Passivation ◽  
Order Of Magnitude ◽  
Li Ion

<div>The electrolyte additives vinylene carbonate (VC) and fluoroethylene carbonate (FEC) are well known for increasing the lifetime of a Li-ion battery cell by supporting the formation of an effective solid electrolyte interphase (SEI) at the anode. In this study combined simultaneous electrochemical impedance spectroscopy (EIS) and <i>operando</i> electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D) are employed together with <i>in situ</i> gas analysis (OEMS) to study the influence of VC and FEC on the passivation process and the interphase properties at carbon-based anodes. In small quantities both additives reduce the initial interphase mass loading by 30 to 50 %, but only VC also effectively prevents continuous side reactions and improves anode passivation significantly. VC and FEC are both reduced at potentials above 1 V vs. Li<sup>+</sup>/Li in the first cycle and change the SEI composition which causes an increase of the SEI shear storage modulus by over one order of magnitude in both cases. As a consequence, the ion diffusion coefficient and conductivity in the interphase is also significantly affected. While small quantities of VC in the initial electrolyte increase the SEI conductivity, FEC decomposition products hinder charge transport through the SEI and thus increase overall anode impedance significantly. </div>

scholarly journals A ΔSOC-based equalization strategy applied to industry

2020 ◽  
Author(s):  
Maonan Wang ◽  
Chun Chang ◽  
Feng Ji
Keyword(s):  
Open Circuit ◽  
Battery Pack ◽  
Battery Management System ◽  
Battery Management ◽  
Battery Cell ◽  
New Strategy ◽  
The Difference ◽  
Relative Errors ◽  
The Relationship ◽  
Battery Cells

Abstract The voltage-based equalization strategy is widely used in the industry because the voltage (U) of the battery cell is very easy to obtain, but it is difficult to provide an accurate parameter for the battery management system (BMS). This study proposes a new equalization strategy, which is based on the difference between the state of charge (SOC) of any two battery cells in the battery pack, that is, a ΔSOC-based equalization strategy. The new strategy is not only as simple as the voltage-based equalization strategy, but it can also provide an accurate parameter for the BMS. Simply put, using the relationship between the open circuit voltage and the SOC of the battery pack, the proposed strategy can convert the difference between the voltage of the battery cells into ΔSOC, which renders a good performance. Additionally, the required parameters are all from the BMS, and no additional calculation is required, which makes the strategy as simple as the voltage-based balancing strategy. The four experiments show that the relative errors of ΔSOC estimated by the ΔSOC-based equalization strategy are 0.37%, 0.39%, 0.1% and 0.17%, and thereby demonstrate that the ΔSOC-based equalization strategy proposed in this study shows promise in replacing the voltage-based equalization strategy within the industry to obtain better performance.

Capacity losses due to solid electrolyte interphase formation and sodium diffusion in sodium-ion batteries

2021 ◽  
Author(s):  
Le Anh Ma ◽  
Alexander Buckel ◽  
Leif Nyholm ◽  
Reza Younesi
Keyword(s):  
Carbon Black ◽  
Solid Electrolyte ◽  
Solid Electrolyte Interphase ◽  
Open Circuit ◽  
Sodium Ion ◽  
Sodium Ion Batteries ◽  
Electrochemical Testing ◽  
Capacity Loss ◽  
Sei Layer ◽  
Sodium Diffusion

Abstract Knowledge about capacity losses due to the formation and dissolution of the solid electrolyte interphase (SEI) layer in sodium-ion batteries (SIBs) is still limited. One major challenge in SIBs is the fact that the SEI generally contains more soluble species than the corresponding SEI layers formed in Li-ion batteries. By cycling carbon black electrodes against Na-metal electrodes, to mimic the SEI formation on negative SIB electrodes, this study studies the associated capacity losses in different carbonate electrolyte systems. Using electrochemical testing and synchrotron-based X-ray photoelectron (XPS) experiments, the capacity losses due to changes in the SEI layer and diffusion of sodium in the carbon black electrodes during open circuit pauses of 50 h, 30 h, 15 h and 5 h are investigated in nine different electrolyte systems. The different contributions to the open circuit capacity loss were determined using a new approach involving different galvanostatic cycling protocols. It is shown that the capacity loss depends on the interplay between the electrolyte chemistry and the thickness and stability of the SEI layer. The results show, that the Na-diffusion into the bulk electrode gives rise to a larger capacity loss than the SEI dissolution. Hence, Na-trapping effect is one of the major contribution in the observed capacity losses. Furthermore, the SEI formed in NaPF6-EC:DEC was found to become slightly thicker during 50 h pause, due to self-diffused deintercalation of Na from the carbon black structure coupled by further electrolyte reduction. On the other hand, the SEI in NaTFSI with the same solvent goes into dissolution during pause. The highest SEI dissolution rate and capacity loss was observed in NaPF6-EC:DEC (0.57 μAh/hpause) and the lowest in NaTFSI-EC:DME (0.15 μAh/hpause).

NMR quantitative analysis of solid electrolyte interphase on aged Li-ion battery electrodes

2015 ◽  
Vol 155 ◽  
pp. 391-395 ◽  
Author(s):  
Rémi Castaing ◽  
Philippe Moreau ◽  
Yvan Reynier ◽  
Donald Schleich ◽  
Séverine Jouanneau Si Larbi ◽  
...  
Keyword(s):  
Quantitative Analysis ◽  
Solid Electrolyte ◽  
Solid Electrolyte Interphase ◽  
Li Ion Battery ◽  
Li Ion
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