Influence of lithium hexafluorophosphate/ethylene carbonate/dimethyl carbonate electrolyte soaking on heat seal strength of polyamide 6/aluminum/cast-polypropylene laminates used as lithium-ion battery packaging

Abstract

The heat-seal strength of polymer–metal–polymer laminates, widely used in the packaging industry and more recently for pouch lithium-ion batteries, is a critical factor for the integrity of flexible package structures during service. The influences of lithium hexafluorophosphate/ethylene carbonate/dimethyl carbonate (LiPF₆/EC/DMC) electrolyte soaking time and storage temperature on heat-seal strength were investigated through T-peel testing using a universal testing machine. Sealed multilayer laminates’ heat-seal strength and their failure modes were measured for specimens sealed at various heat-sealing temperatures and dwell times before and after exposure to room temperature and 60℃ soaking conditions. The soaking condition significantly influences heat-seal strength, especially for the packages heat-sealed at low temperatures and short heat-sealing times. Higher storage temperature during electrolyte-soaking accelerates the heat-seal strength decrease. Failure modes are affected by the soaking conditions and become more complicated than the packages without soaking. The optimized heat-sealing processing window is obtained under a certain soaking condition. The electrolyte hydrogen ion concentration (pH) decreases with longer soaking time and higher storage temperature, indicating that acidification may also contribute to decreased heat-seal strength. The results are important for understanding how stored lithium-ion batteries deteriorate and can help to guide battery design to maximize their shelf life.

Keywords

Polymer–metal–polymer laminates heat-seal strength electrolyte soaking time and storage temperature failure mode pH value

Get full access to this article

View all access options for this article.

References

Yam

. The Wiley encyclopedia of packaging technology, 3rd ed. Hoboken, NJ: Wiley, 2009.

Marouani

. Investigation of the resistance welding of multilayers aluminum-coated polymer complexes used as envelope of vacuum insulation panels. Mater Des 2012; 36: 546–556.

Tetsuya

Ishiaku

Mizoguchi

et al.

The effect of heat sealing temperature on the properties of OPP/CPP heat seal. I. mechanical properties. J Appl Poly Sci 2005; 97: 753–760.

Hashimoto

Ishiaku

Leong

et al.

Effect of heat-sealing temperature on the failure criteria of oriented polypropylene/cast polypropylene heat seal. Poly Eng Sci 2006; 46: 205–214.

Planes

Marouani

Flandin

. Optimizing the heat sealing parameters of multilayers polymeric films. J Mater Sci 2011; 46: 5948–5958.

Liang

et al.

Effect of modified polypropylene on the interfacial bonding of polymer-aluminum laminated films. Mater Des 2015; 81: 141–148.

Xia

. Effect of surface pre-treatment on the hydrophilicity and adhesive properties of multilayered laminate used for lithium battery packing. Appl Surf Sci 2013; 268: 337–342.

Devisme

Haudin

Agassant

et al.

Chopinez Adhesion in polypropylene/aluminum laminates made by extrusion coating. J Appl Polym Sci 2009; 112: 2609–2624.

Guo

Fan

. Heat seal properties of polymer–aluminum–polymer composite films for application in pouch lithium-ion battery. RSC Adv 2016; 6: 8971–8979.

10.

Jang

Ahn

. Numerical and experimental analysis of heat sealing of multi-layered laminate films used in lithium polymer battery packaging. J Plastic Film Sheet 2016; 33: 142–167.

11.

Wang

Dong

Huang

et al.

Chen. Impacts of electrolyte solvent soakage on structure and electrochemical performance of LiCoO₂ for lithium-Ion batteries. Electrochem Solid-State Lett 2004; 7: 353–357.

12.

Wang

Dong

Huang

et al.

Characterization of spontaneous reactions of LiCoO₂with electrolyte solvent for lithium-ion batteries. J Electrochem Soci 2004; 151: 1641–1652.

13.

Liu

. Improving the performances of LiCoO₂ cathode materials by soaking nano-alumina in commercial electrolyte. J Electrochem Soc 2007; 154: 55–63.

14.

Wang

Srinivasan

. Corrosion behaviour of AB5-type hydride electrodes in alkaline electrolyte solution. J Appl Electrochem 2003; 33: 325–331.

15.

Mancinia

Mehrens

. Study on the stability of Li₂MnSiO₄ cathode material in different electrolyte systems for Li-ion batteries. Electrochimica Acta 2015; 176: 679–688.

16.

Feng

Yang

et al.

Study on surface corrosion behavior of non-charge-discharge LiMn₂O₄ in LiPF₆-based electrolyte. Inter J Electrochem Sci 2012; 7: 8299–8308.

17.

Kitta

Kohyama

. Stability of the LiMn₂O₄ surface in a LiPF₆-based non-aqueous electrolyte studied by in-situ atomic force microscopy. Japan J Appl Phys 2016; 55: 065801–1-6.

18.

Rohan

Rohit

Balaji

. Modeling the effect of acid attack on the capacity fading in lithium-ion batteries. J Electrochem Soc 2016; 163: 1214–1218.

19.

Cannarella

Liu

Leng

et al.

Arnold Mechanical properties of a battery separator under compression and tension. J Electrochem Soc 2014; 161: 3117–3122.

20.

Gor

Cannarella

Prévost

et al.

Arnold. A model for the behavior of battery separators in compression at different strain/charge rates. J Electrochem Soc 2014; 161: 3065–3071.

21.

Gor

Cannarella

Leng

et al.

Swelling and softening of lithium-ion battery separators in electrolyte solvents. J Power Source 2015; 294: 167–172.

22.

Yan

Xiao

Huang

et al.

Unveiling the environment-dependent mechanical properties of porous polypropylene separators. Polymer 2014; 55: 6282–6292.

23.

Mihindukulasuriya

Lim

. Effects of liquid contaminants on heat seal strength of low-density polyethylene film. Pack Tech Sci 2012; 25: 271–284.

24.

Mihindukulasuriya

Lim

. Heat sealing of LLDPE films: Heat transfer modeling with liquid presence at film-film interface. J Food Eng 2013; 116: 532–540.

25.

GB/T 22638.7-2008. Test methods for aluminum and aluminum alloy foils. Part 7: Determination of heat seal strength. (in Chinese).

26.

ASTM F88/F88M-09. Standard test method for seal strength of flexible barrier materials.

27.

Olafsson

Jägerstad

Öste

et al.

Delamination of polyethylene and aluminum foil layers of laminated packaging material by acetic-acid. J Food Sci 1993; 58: 215–219.

28.

Olafsson

Jägerstad

Öste

et al.

Effects of different organic-acids on the adhesion between polyethylene film and aluminum foil. Food Chem 1993; 47: 227–233.

29.

Olafsson

Hildingsson

. Sorption of fatty-acids into low-density polyethylene and its effect on adhesion with aluminum foil in laminated packaging material. J Agri Food Chem 1995; 43: 306–312.

30.

Nielsen

Olafsson

. Sorption of p-carotene from solutions of a food colorant powder into low-density polyethylene and its effect on the adhesion between layers in laminated packaging material. Food Chem 1995; 54: 255–260.

31.

Korpås O. Investigation of a package laminate by nanoindentation – a study of polymer-aluminum adhesion and the effect of free fatty acids. Thesis. Lund University, 2016.