Influences of Instant Voltage Drop Occurring during Insulation Test on

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Influences of instant voltage drop occurred during insulation test on the performance of lithium ion batteries Po-Han Lee, Shun-Shiang Hsu, Po-Han Huang, Han-Jen Tseng, Shuo-Chieh Chang, and She-huang Wu ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.7b04351 • Publication Date (Web): 28 Feb 2018 Downloaded from http://pubs.acs.org on March 2, 2018

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ACS Sustainable Chemistry & Engineering

Influences of instant voltage drop occurred during insulation test on the performance of lithium ion batteries Po-Han Leea, Shun-Shiang Hsua, Po-Han Huanga, Han-Jen Tsengb, Shuo-Chieh Changb, She-huang Wua,c* a

Department of Materials Engineering, Tatung University, No.40, Sec. 3, Zhongshan N. Rd., Taipei

City 104, Taiwan b

Product Marketing Department, Test & Measurement BU, Chroma ATE Inc., 66 Huaya 1st Road,

Guishan, Taoyuan 333, Taiwan c

Battery Research Center of Green Energy, Ming Chi University of Technology, 84 Gungjuan Rd.,

Taishan Dist., New Taipei City 24301, Taiwan Corresponding Author *E-mail: [email protected] ABSTRACT Effects of partial discharge during insulation test were investigated with jelly rolls of a single electrode-pair and 500 mAh stacking-type cells by inspecting the separator and studying the capacity fade of the cells prepared with the tested 500 mAh jelly rolls. For comparison, 500 mAh cells with jelly rolls without insulation test or with separator having laser-engraved holes are also prepared. The cells prepared with jelly rolls with insulation test show higher capacity fading rate than cells comprised with jelly rolls without insulation test and lower fading rate than those assembled with jelly rolls with laser-engraved separator. Dark spots were observed on the negative

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electrodes at the corresponding position facing the defect spots on separator caused by partial discharge or the laser-engraved holes in a glove box and became white after being moved into air in company with temperature rise. Li2O was also detected with XPS in additional to Li2CO3 and higher Li content was found by LIBS at the spots. These results recommend there is residual Li at the spots when cells were discharged due to local over-lithiation. The accumulated residual Li at the spots may cause imbalanced lithium inventory and enhance capacity fade of the cells. KEYWORDS: partial discharge, insulation test, separator defects, Li deposition, internal short circuit INTRODUCTION Internal short circuit (ISC) can not only affect coulombic efficiency and life of lithium ion batteries, but also a key factor of field failures and safety hazards. It can occur between negative and positive electrodes, Al current collector and negative electrode, Cu current collector and positive electrode, or Al and Cu current collectors.1, 2 ISCs can be developed from various sources, such as manufacturing defects, dissolution/deposition of positive electrode materials and current collectors, lithium plating and dendrite formation. Though the probability of these failure incidents is estimated to be very low (1 in 5~10 million), the consequences of a failure caused by ISC in a Li-ion battery system can be catastrophic because they are difficult to detect and predict.1 Most of the reports are focused on the electrochemical-thermal models of the forced ISCs created by mechanical deformation of the cell, such as small nail penetration,3-5 indentation,4,

6

surface

indentation or pinch test.4, 7 It had been manifested that electrodeposited metallic lithium is a major


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cause of failure in lithium batteries,8, 9 which may be caused by overcharging or charging cell at high rates especially at low temperature since the working potential of graphite is very close to that of metallic Li deposition.10, 11 In order to screen out the potential ISC risks due to manufacturing defects, such as impurities on electrodes or separator, pin holes and thickness non-uniformity of separator, insulation test is commonly carried out for the prepared dry jelly rolls by applying a high voltage for several hundred milliseconds. Jelly rolls can retain insulation after the test will go for follow-up process, while those can’t retain insulation are considered as unqualified and have to be re-assembled. In our preliminary experiments, instant voltage drop or so-called partial discharge might be detected from the V-t curves collected with a digital oscilloscope during the jelly rolls were charged to a high voltage for 200 milliseconds and retained insulation after the test. According to the current screening criteria, these jelly rolls will be considered as passing the insulation test and can be moved to subsequent processes. In this study, the effects of the partial discharge on the separators and the cycling performance of the cells were investigated with single electrode-pair cells and 500 mAh NMC//MCMB pouch-type cells, respectively. EXPERIMENTAL SECTION LiNi0.5Mn0.3Co0.2O2 (NMC532, Umicore Korea Ltd., Korea) and mesocarbon microbeads (MCMB, China Steel Chemical Co., Taiwan) were selected as cathode and anode materials in this study by mixing with Super P (Timcal Co. Ltd., Switzerland), Vapor Grown Carbon Fiber (VGCF, Yonyu Co. Ltd., Taiwan), and Kynar PVDF (Arkema Inc., USA) in adequate amount of NMP (Mitsubishi Chemical Co., Japan) at weight ratios of 92 : 3 : 1 : 4 for cathode and 92 : 2 : 0 : 6 for



anode, respectively. The slurry of NMC was coated on aluminum foil, whereas the slurry of MCMB was coated on copper foil with a continuous coater, followed by drying under 120oC for 24 hours. According to the specific capacities of MCMB and NMC determined with coin-type cells and the negative/positive (N/P) loading ratio of 1.1:1 in capacity, the loadings of MCMB and NMC per cm2 were calculated and used for preparing negative and positive electrode tapes. Single-side coated tapes were used for preparing single electrode-pair cells, while double-side coating was applied for electrodes of 500 mAh cells. After compression with high pressure for densification, the coated tapes were punch into sizes of 3.2 x 5.7 and 3.1 x 5.6 cm2 with terminal film for negative and positive electrodes, respectively. Single electrode-pair cells were assembled with a single side coated negative electrode, a single side coated positive electrode, and a piece of separator (micro porous polyethylene separators, Asahi Kasei, Japan). After being sealed in Al laminated pouches, these cells were tested with a insulation tester (Model 11210-K, Chroma ATE Inc., Taiwan) by charging them with a testing voltage increasing from 200 V with an incremental of 50 V until partial discharge is detected with a digital oscilloscope (TDS-2022B or TDS1002B, Tektronix Inc., USA) within testing duration of 200 ms. Then the separators obtained from the tested cells were observed with an optical microscope (OM, Nikon OPTIPHOT-100, Japan) and a scanning electron microscopy (SEM, SU8020, Hitachi Ltd., Japan). For 500 mAh cells, 13 pieces of double side coated negative electrodes and 12 pieces of double side coated positive electrodes were sandwiched together with a folded separator on a home-made stacking machine, followed by welding the positive and negative terminals separately


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with nickel tabs and sealing with a preformed housing of Al laminated film to become a dry cell. 5 of the prepared 500 mAh dry cells were used for insulation test by charging them up to a voltage higher than 500 V for 200 ms and increasing by 50 V each time until partial discharge being detected with a digital oscilloscope but they all retain insulation after test. After insulation test, two of them were disassembled for separator examination with an optical microscopy, while another three dry cells were opened for filling electrolyte of 1M LiPF6 in EC/DEC = 1 : 1 (vol.) and sealed with hot pressing after 24 h rest in an Ar-filled glove box to ensure complete wetting of the cells. The prepared pouch-type cells were connected with a battery tester (Model 17011, Chroma ATE Inc., Taiwan) for formation with 50 mA (C/10 rate) between 3.0 and 4.2 V at room temperature for 2 cycles, then the cells were cycled at 0.5C rate by charging with constant current (CC) mode followed by constant (CV) mode with current limit of C/25 and discharging at CC mode between 3.0 and 4.2 V at 10oC for 200 cycles. 3 reference cells containing a 500 mAh jelly roll without being insulation tested and 6 cell consisting with a 500 mAh jelly roll with a piece of defective separator between the 13th anode/cathode pair, 3 laser-engraved 30 or 50 µm holes at the apex of a triangle, as shown in Figure 1, were also prepared for comparison. After cycling, the aged cells were disassembled at their discharged state in a glove box. The collected negative electrodes were inspected carefully before and after removing from glove box, and then they were studied with a scanning electron microscopy, an X-ray photoelectron spectrometer (VG Scientific ESCALAB 250), and a laser-induced breakdown spectroscopy (J200 LIBS system, Applied Spectra, USA).



Figure 1. (a) Typical photo of a piece of separator with 3 laser-engraved holes in diameter of 50 µm taken with back lighting, (b) and (c) OM photos of the upper and lower left holes, and (d) SEM photo with inset of OM photo of lower right hole. RESULTS AND DISCUSSION From the results of insulation test for the dry single electrode-pair cells, 5 cells displayed 2 to 8 partial discharges and retained insulation after being charged to 700 V and keep at the voltage for 200 ms, but 4 cells did not show any partial discharge after being charged to 800 V for 200 ms. Figure 2 shows a typical example of a cell with 2 partial discharges been detected. 3 black spots were observed on its separator as the illustration shown as Figure 2(b), the photos of the spot no. 2 observed with OM and SEM are shown in Figure 2(c) and 2(d), respectively. Carbonization seems to occur at the black spots caused by partial discharge. Black spots can be found with OM on the


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separators of the cells displayed partial discharge, whereas no damage can be observed on the separators of the dry cells those didn’t show any partial discharge after being charged to 800V. These results may suggest that a partial discharge may induce at least one black spot on separator.

Figure 2. (a) Typical partial discharges recorded with a digital oscilloscope during insulation test of a single electrode-pair cell at 700 V, (b) illustration of the black spots on the separator, (c) OM and (d) SEM photos of the black spot No. 2. Figure 3 (a) and (b) show two partial discharges and their enlargement recorded with a digital oscilloscope during insulation test on a 500 mAh cell at 550 V. Figure 3(c) illustrates the distribution of the black spots on the separator between various pairs of negative/positive electrodes, shown with different symbols, observed with an optical microscope. The diameters of the black spots are range between 7 and 18 µm. It is also found that most of the black spots are located near to the edge of the electrode probably due to the potentially lower resistance for partial discharge at the bare cutting surface of Al current collector than any other part because the positive electrodes are ACS Paragon Plus Environment


slightly smaller in size than the negative electrodes. Figure 3(d) and (e) are typical photos of OM of the two black spots on the separator between the 1st negative/positive electrode pair.

Figure 3. (a) Screenshot of the partial discharges pattern with (b) the enlarge image recorded with a digital oscilloscope during insulation test on a 500 mAh cell at 550V, (c) illustration of the black spots distribution on separators, (d) and (e) the OM photos of the spots on separator between the 1st negative/positive electrode pair. Figure 4 exhibits the average of the capacity retention studies at 0.5C rate within cut-off voltages of 3.0 and 4.2 V at 10oC after formation for three 500 mAh NMC//MCMB cells with partial discharge being detected during insulation test. For comparison, the average of cycling studies of 3 reference cells without insulation test and those of 6 cells prepared with jelly roll ACS Paragon Plus Environment

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containing a piece of separator with 3 laser-engraved holes of diameter of 30 or 50 µm are also shown in the figure. It can be found that these cells show good reproducibility up to 200 cycles except the cells prepared with jelly roll assembling with a piece of separator with 3 laser-engraved 50 µm holes manifest significant discrepancy from each other after being cycled more than 150 cycles. The results recommend that cells with larger holes show higher capacity fading rate and worse reproducibility. The insulation-tested cells manifest capacity fading rate higher than the reference cells and lower than those cells with a piece of separator with 3 laser-engraved 30 µm holes. It can be attributed to the defect holes caused by partial discharge show diameters range between 7 and 18 µm, are smaller than 30 µm.

Figure 4. Averaged results of the capacity retention studies at 10oC at 0.5C rate after formation for ACS Paragon Plus Environment


the 500 mAh pouch-type cells comprised jelly rolls with or without insulation test and jelly rolls prepared with a piece of separator having 3 laser-engraved 30 or 50 µm holes, respectively. After 200 cycles, the cells been insulation-tested were disassembled at their discharged state in an Ar-filled glove box for inspection carefully. Dark spots were observed on the negative electrodes at the corresponding positions facing the black spots on separators caused by partial discharge. Figure 5(a) shows a typical example of the dark spots on a piece of negative electrode at the corresponding positions facing the black spots on the neighboring separator caused by partial discharge during insulation test. When the negative electrodes were taken from the glove box to atmosphere, the black spots turn into white gradually, as shown in Figure 5(b). One of the spots was observed with SEM with different magnifications and shown in Figure 5(c) and (d). Burst can be found at the white spot and can be differentiate from other part of the negative electrode easily. It may be attributed to the oxidation of the residual lithium at the dark spot due to lithium plating or over-lithiation caused by the higher local current density during cycling at the carbonized spots than other parts of separator.


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Figure 5. Typical photos of a negative electrode with (a) dark spots token in an argon-filled glove box and (b) after it was removed into atmosphere. (c) and (d) SEM photos of a white spot under different magnifications. For comparison, the cells prepared with a piece of separator with 3 laser-engraved 50 µm holes were also disassembled in an Ar-filled glove box at their discharged state after 200 cycles. Dark spots on the negative electrode at the corresponding position facing the laser-engraved holes of the defective separator can be observed. In addition to the color changes of the dark spots into white, exothermic temperature rises were also detected when the negative electrodes were removed from glove box. A typical case of quick temperature rises from a temperature near room temperature (23.6oC) to 27.5oC had been recorded by a thermal couple fixed on the back of the electrode near the spot when an anode was removed from an argon-filled glove box. Figure 6(a) shows a typical photo of the negative electrode next to the separator with the laser-engraved holes (Figure 2(a)). ACS Paragon Plus Environment


The color change and heat evolution can be attributed to the reaction between residual lithium on anode and oxygen. It suggests lithium plating might occur on the anode next to the defects of separator after charging/discharging cycling because of the relative higher local charging current densities at these sites than other sites next to the non-defective separator and accumulation of residual dead lithium. Cells prepared with jelly roll containing a piece of separator with 3 laser-engraved 50 µm holes show higher capacity deviation after 150 cycles than those prepared with jelly rolls assembled with a piece of separator with 3 laser-engraved 30 µm holes or been insulation-tested can be due to the cells with 50 µm laser-engraved holes have larger defect area on separator, higher deviation of defect areas since the laser-engraved holes are not perfect circles, and potentially higher variation in morphology of the accumulated dead lithium next to the holes than the other two kinds of cells. Whereas cells prepared with insulation-tested jelly rolls manifest higher capacity deviation than cells prepared with jelly rolls containing a piece of separator with 3 laser-engraved 30 µm holes can be attributed to the high variations in number, size, and degree of defect spots caused by partial discharge. However, the defect area of the separator caused by partial discharge is much lower than those of 3 laser-engraved 30 or 50 µm holes, such that cells prepared with jelly rolls with insulation test show lower capacity fading rates than those prepared with jelly rolls containing a piece of separator with 3 laser-engraved holes.


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Figure 6. (a) Typical photo of the negative electrode next to the defective separator collected from a cell prepared with a piece of separator with 3 laser-engraved 50 µm holes after been cycled 200 cycles. SEM photos of the white spots: (b) upper, (c) lower left, and (d) lower right. From the XPS study for the site near a white spot and other parts far from it of the negative electrode next to the separator with 3 laser-engraved 50 µm holes, as shown in Figure 7, it can be found that Li2O is also detected in additional to Li2CO3 at the sites around the white spot, such as point 3, 4, and 5 on illustration Figure 7(a), while only Li2CO3 which exists in the SEI layer can be found at the sites far from the white spots. The results of LIBS, shown in Figure 8, also manifest higher Li concentration at the site of the white spot than sites far from it. These results recommend that there is residual lithium, becomes Li2O after moving from Ar-filled glove box, on the negative electrode at the corresponding position of laser-engraved holes of the defective separator after



cycling can be attributed to the accumulation of dead lithium due to higher local charging/discharging current densities at the holes than other sites. Residual lithium on anode may induce imbalance of lithium inventory upon cycling and enhance capacity fade.

Figure 7. (a) Illustration of the sites for XPS study and (b) XPS spectra of Li1s at the site near the white spot and other part of the negative electrode next to the separator with 3 laser-engraved 50µm holes from the cell being cycled 200 cycles.


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Figure 8. Li LIBS mapping of a cycled anode next to the defective separator: (a) sites far from the white spot and (b) the site of white spot, (c) and (d) are the surface layer of the depth profile of 3D mapping of (a) and (b). CONCLUSION Partial discharge occurred during insulation test will caused black spots or local carbonization on separator with diameter range between 7 and 18 µm near the edge of the cathode. The cells prepared with dry jelly rolls showing partial discharge during insulation test exhibits higher capacity fading rate than those without being insulation-tested, but lower than those assembled with jelly rolls containing a piece of separator with three laser-engraved 30 µm or 50 µm holes. From the observation of the color change of the dark spots on the anodes next to the defective separator ACS Paragon Plus Environment


collected from the cells prepared with jelly rolls with partial discharge during insulation test and with a piece of laser engraved separator in company with the results of SEM, XPS, and LIBS studies, it can be suggested that the defects caused by partial discharge during insulation test can induce accumulation of dead lithium at the corresponding sites of the anodes next to the damaged separator due to relative higher current density at these sites. The accumulation of dead lithium will lead to imbalance of lithium inventory and increased capacity fading rate. Furthermore, the accumulated lithium may result in internal short of the cell after long-term cycling. AUTHOR INFORMATION Corresponding author *E-mail: [email protected] (S.H. Wu), Tel: 886-919045888 ACKNOWLEDGEMENT The authors are thankful for financial support from the Chroma ATE Inc. and instrumental support from the Instrumentation Center, National Taiwan University for ESCA analyses, and the LIBS study from Applied Spectra, USA and Rightek, Tawian. REFERENCES 1. Orendorff, C. J.; Roth, E. P.; Nagasubramanian, G., Experimental triggers for internal short circuits in lithium-ion cells. J. Power Sources 2011, 196 (15), 6554-6558, DOI: https://doi.org/10.1016/j.jpowsour.2011.03.035. 2. Abada, S.; Marlair, G.; Lecocq, A.; Petit, M., Sauvant-Moynot, V., Huet, F., Safety focused modeling of lithium-ion batteries: A review. J. Power Sources 2016, 306, 178-192, DOI:


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https://doi.org/10.1016/j.jpowsour.2015.11.100. 3. Wu, M.-S.; Chiang, P.-C. J.; Lin, J.-C.; Jan, Y.-S., Correlation between electrochemical characteristics and thermal stability of advanced lithium-ion batteries in abuse tests—short-circuit

tests.

Electrochim.

Acta

2004,

49

(11),

1803-1812,

DOI:

https://doi.org/10.1016/j.electacta.2003.12.012. 4. Maleki, H.; Howard, J. N., Internal short circuit in Li-ion cells. J. Power Sources 2009, 191 (2), 568-574, DOI: https://doi.org/10.1016/j.jpowsour.2009.02.070. 5. Zhao, R.; Liu, J.; Gu, J., Simulation and experimental study on lithium ion battery short circuit.

Appl. Energy 2016, 173, 29-39, DOI: https://doi.org/10.1016/j.apenergy.2016.04.016. 6. Sahraei, E.; Campbell, J.; Wierzbicki, T., Modeling and short circuit detection of 18650 Li-ion cells under mechanical abuse conditions. J. Power Sources 2012, 220, 360-372, DOI: https://doi.org/10.1016/j.jpowsour.2012.07.057. 7. Cai, W.; Wang, H.; Maleki, H.; Howard, J.; Lara-Curzio, E., Experimental simulation of internal short circuit in Li-ion and Li-ion-polymer cells. J. Power Sources 2011, 196 (18), 7779-7783, DOI: https://doi.org/10.1016/j.jpowsour.2011.04.024. 8. Agubra, V.; Fergus, J., Lithium Ion Battery Anode Aging Mechanisms. Materials 2013, 6 (4), 1310-1325, DOI: 10.3390/ma6041310. 9. Eastwood, D. S.; Bayley, P. M.; Chang, H. J.; Taiwo, O. O.; Vila-Comamala, J.; Brett, D. J. L.; Rau, C.; Withers, P. J.; Shearing, P. R.; Grey, C. P.; Lee, P. D., Three-dimensional characterization of electrodeposited lithium microstructures using synchrotron X-ray phase



contrast imaging. Chem. Commun. 2015, 51 (2), 266-268, DOI: 10.1039/C4CC03187C. 10. Aurbach, D.; Zinigrad, E.; Cohen, Y.; Teller, H., A short review of failure mechanisms of lithium metal and lithiated graphite anodes in liquid electrolyte solutions. Solid State Ionics 2002,

148 (3-4), 405-416, DOI: 10.1016/S0167-2738(02)00080-2. 11. Li, Z.; Huang, J.; Liaw, B. Y.; Metzler, V.; Zhang, J., A review of lithium deposition in lithium-ion and lithium metal secondary batteries. J. Power Sources 2014, 254, 168-182, DOI: https://doi.org/10.1016/j.jpowsour.2013.12.099.


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Highlights The effects of partial discharge on separator occur during insulation test. Defect spots are observed on separator of cell showing partial discharge during insulation test. Existence of defective separator can cause residual dead lithium on graphite anode.



Abstract Graphic

Brief Synopsis: The novel phenomena of partial discharge during insulation test may cause imbalance of lithium inventory.


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Influences of Instant Voltage Drop Occurring during Insulation Test on

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