Elsevier

Journal of Power Sources

Volume 189, Issue 1, 1 April 2009, Pages 315-323
Journal of Power Sources

New gel-type polyolefin electrolyte film for rechargeable lithium batteries

https://doi.org/10.1016/j.jpowsour.2008.08.074Get rights and content

Abstract

A random poly(ethylene-co-acrylic acid) (PE-A) with an acrylic acid (AA) content of 5.0–20 mol% was functionalized by esterifying acrylic acid group with poly(ethylene glycol) monomethyl ether. Polyethylene oxide functional groups such as a pendant were introduced into the polyethylene backbone chain. The resulting polymer (PEGM-g-EAA) can be easily formed to a thin sheet and possesses the adhesion property such as gluing. Its thin film could absorb and hold a large quantity of the electrolyte solutions employed for the lithium batteries. The ionic conductivity of the PEGM-g-EAA gel electrolyte obtained with the starting PE-A with acrylic acid content of 9.0 mol% was a value of around 1.5 × 10−3 S cm−1 at 20 °C. The ionic conductivity results obtained for the network type gel, which was entangled with the present PE-A-based polymer, were 1.1 × 10−3 S cm−1 and 5.5 × 10−3 S cm−1 at 0 °C and 80 °C, respectively. The characteristics of good thermostability, transparency and good adhesion to the electrodes have also been demonstrated. As an example, the test cell consisted of the proposed polyolefin gel electrolyte, a LiCoO2 cathode and a lithium anode showed excellent charge/discharge characteristics.

Introduction

Polymer electrolytes have been actively studied in an attempt to develop safer and thinner rechargeable lithium batteries. Solid polymer electrolytes (SPEs) proposed by Wright [1] have been extensively studied by Armand and Duclot [2]. Although much research effort has been devoted to the development of SPEs, conductivity of SPE such as a poly(ethylene oxide) (PEO) [1] remains too low for practical batteries operating at room temperature. In order to overcome the disadvantage for practical usage, in the last two decades, so-called polymer gel electrolytes (PGEs) that are capable of holding stably a considerable amount of electrolyte solution within polymer matrices have attracted both basic research and industry attentions, as more promising materials for the practical use. The various PGEs based on polyethylene oxide (PEO) [2], polyacrylonitrile (PAN) [3], [4], [5], [6], [7], poly(methacrylate) (PMA) [8], [9], [10] and polyvinylidene fluoride (PVdF) [11] with ionic conductivities of 10−3 S cm−1 at room temperature have been initially prepared and applied for lithium batteries. However, their thermostabilities of traditional PGEs were not sufficient for the practical usage in a wide temperature range. Frequently, it was found that poor interaction of a polymer matrix and solvent cannot prevent completely the solvent leakage. One of the procedures to advance their properties and functions is an introduction of suitable functional groups to side chains on a backbone polymer.

A new challenge in the development of polymers used for PGEs is the preparation of sticky film such as post-it®. Such polymer adheres easily to the electrode, separator and package, so that the physical adhesion at the interface between the polymer electrolyte and electrode expect to be improved.

In this work, we introduce a sticky self-standing film of an ethyleneoxide side chain modified polyethylene-based PGE applied for lithium battery. As well known, polyolefin material is used as a chief component of a separator in lithium batteries, but it is not so far regarded as a PGE material, because a polyolefin does not absorb and hold organic solvents used for lithium batteries. Even if polyethylene contains a functional group of acrylic acid (AA), this polymer does not possess the property of gelation. Therefore, by using the functional group of acrylic acid on a poly(ethylene-co-acrylic acid) (PE-A), we try to alter the PE-A to a polyolefin-based PGE in this study. The acrylic acid group on the PE-A is esterified with a poly(ethyleneglycol)monomethyl ether (PEGM) and thus oligo(ethyleneoxide) side chains of the single bondO(CH2CH2O)nCH3 type is introduced on the polyethylene, being like pendants dangling from the polyethylene backbone. The synthesis method for such a grafted copolymer has been reported by Hallden and Wesslen in order to improve the adhesion properties such as painting, printing and gluing [12]. We are interested in whether the resulting graft copolymers (PEGM-g-EAA) can be expected to form a self-standing film which absorbs a large quantity of electrolyte solutions, since an ethylene oxide functional group grafted on a polyethylene backbone takes a behavior of the polar one. The PE-A with acrylic acid group of the content of around 10 mol% will be selected as the best reactant base polymer for the synthesis at the present research. Here, we report that new non-halogen polyolefin films make it possible to provide as a PGE for a Li secondary cell.

Furthermore, to improve the mechanical and thermal properties of the present PGE we introduce a polymer network having probably a three-dimensional structure that includes the PE-A within the crosslinked polymer network matrix. The resulting PGE possesses not only a high thermostability at 80 °C but also a high flexibility, adhesion and transparency properties. Therefore, the present polyolefine-based material is very promising one to be used as a PGE in battery, electrochemical capacitor, dye-sensitized solar cell and electrochromic device.

Section snippets

Materials

PE-A was a random polyethylene-poly(acrylic acid) copolymer with an acrylic acid content of 9.0 mol%, produced by Du Pont–Mitsui Polychemicals Co., Ltd. Its number-average molecular weight (Mn) was estimated to be 10,500, unless otherwise stated, using GPC with o-dichlorobenzene at 135 °C according to a standard procedure with use of polystyrene. (However, the PE-A having an acrylic acid content of 10.0 mol% and the weight-average molecular weight (Mw) of 50,000 was used in Table 3, Table 4.) PEGM

Ionic conductivity

A TEFLON spacer having a square shape of 3.5 cm × 3.5 cm with a thickness of 300 μm (and having a hole of 2 cm × 2 cm made at its center) was placed on a lithium metal foil having a square shape of 3 cm × 3 cm with a thickness of 100 μm. Then, the gel film having a described thickness of 80 μm, 100 μm or 300 μm was set in the center hole, and another metallic lithium foil similar to the above was laid upon it. On both sides, stainless (SUS304) foils having a thickness of 100 μm were, respectively attached as

Synthesis and characterization of PEGM-g-EAA

A novel polyolefin-type gel electrolyte synthesized in the present paper was based on a graft copolymer PEGM-g-EAA with a polyethylene backbone grafted with polyethylene oxide. By changing the reactants, the amount of reagents and the synthesized conditions such as temperature and reaction time, polymer materials with various compositions and a variety of properties were obtained. However, PEGM-g-EAA synthesized from PE-A with an acrylic acid content of less than 5.0 mol% and more than 20 mol%

Conclusion

New PGE composed of polyolefin derivatives and organic electrolyte solution was prepared and applied as electrolyte materials for lithium secondary cells. The introduction of about 9.0% by ethylene mol unit of oligo(oxyethylene) group grafted into the polyethylene induced to exhibit the properties absorbing and holding a large amount of the organic electrolyte solution. The ionic conductivity of the resulting PGE was a high value of 1.1 × 10−3 S cm−1, even when at 0 °C. The PEGM-g-EAA synthesized at

Acknowledgements

The authors wish to express their gratitude for the experimental assistance of Mr. S. Miyagawa. This work was partially supported in part by Shirouma Science Co., Ltd.

References (20)

  • T. Sotomura et al.

    Electrochim. Acta

    (1992)
  • T. Tatsuma et al.

    J. Electroanal. Chem.

    (1999)
  • T. Sotomura et al.

    J. Power Sources

    (1999)
  • H. Inaba et al.

    Electrochim. Acta

    (1995)
  • M. Morita et al.

    Solid State Ionics

    (1998)
  • J.-M. Tarascon

    Solid State Ionics

    (1996)
  • S.G. Greenbaum et al.

    Solid State Ionics

    (1988)
  • P.V. Wright

    Br. Polym.

    (1975)
  • M.B. Armand, M. Duclot, US Patent 4,303,748...
  • G. Feuillade et al.

    J. Appl. Electrochem.

    (1975)
There are more references available in the full text version of this article.

Cited by (17)

  • Cellulose/Poly(vinylidene fluoride hexafluoropropylene) composite membrane with titania nanoparticles for lithium-ion batteries

    2020, Materials Chemistry and Physics
    Citation Excerpt :

    Fig. S6 of the Supplementary information shows that PP separator is unable to offer sufficient protection to the anode and smooth surface of anode convert into a needle-like surface which cause a short circuit and performance decay [57]. On the other hand, the titania nanoparticles create a network of lithium ions on the surface of anode due to its abundant hydroxyl group and offer high safety and minimize the possibility of dendrite production on it which prolongs the life period of lithium-ion battery [58]. In this work, the Cellulose/PVDF-HFP membrane with the incorporation of titania nanoparticles has been designed and prepared via an ecofriendly phase-inversion-method followed by hydrolysis.

  • Composite of polyvinylidene fluoride–cellulose acetate with Al(OH)<inf>3</inf> as a separator for high-performance lithium ion battery

    2017, Journal of Membrane Science
    Citation Excerpt :

    There are many polar groups on the surface of Al(OH)3 particles which can disperse the lithium ions on the anode surface so that the lithium ions are deposited on the anode surface evenly, which contributes to prevent the growth of lithium dendrites. According to the reports, the PVDF-CA matrix with the Al(OH)3 fillers may function as a kind of gel polymer electrolyte which can minimize the dendrite growth [35,36]. For high power applications, the batteries should meet the requirement of good rate capability.

  • Porous cellulose diacetate-SiO<inf>2</inf> composite coating on polyethylene separator for high-performance lithium-ion battery

    2016, Carbohydrate Polymers
    Citation Excerpt :

    Overall, the unstable SEI decays the cell capacity (Ryou et al., 2012), which is in agreement with the cycle performance in Fig. 5. The CDA coating and CDA-SiO2 coatings soaked electrolyte may function as a kind of gel polymer electrolytes (GPEs) which can minimize the dendrite growth (Belov, Yarmolenko, Peng, & Efimov, 2006; Choi, Lee, Park, & Park, 2003; Jeong & Kim, 2005; Oyama et al., 2009), by reducing the reaction with Li metal and enhancing the adhesive properties to Li surfaces (Ryou et al., 2012). It is clear that the needle-like Li dendrites exist on the image (a) of Fig. 7, the image (b)–(e) have no needle-like Li dendrites, because the CDA-SiO2 functioned as a gel polymer electrolyte and limited the growth of needle-like Li dendrites during cycling.

  • Novel cross-linked copolymer gel electrolyte supported by hydrophilic polytetrafluoroethylene for rechargeable lithium batteries

    2014, Journal of Membrane Science
    Citation Excerpt :

    Gel polymer electrolytes (GPEs) are just good alternatives between all-solid-state polymer electrolytes and conventional liquid electrolytes. Various polymers including PEO [4], poly(propylene oxide) (PPO) [5], poly(methylmethacrylate) (PMMA) [6], poly(acrylonitrile) (PAN) [7] and poly(vinylidene fluoride) (PVdF) [8] have been investigated as GPE matrices and high ionic conductivity with other desirable properties have been achieved by incorporation of ceramic fillers and polar plasticizer [9,10]. For example, Oh and Amine [11] prepared a poly(ethylene oxide)-co-poly(propylene oxide) random copolymer (abbr.

  • Enhanced performance of modified HDPE separators generated from surface enrichment of polyether chains for lithium ion secondary battery

    2013, Journal of Membrane Science
    Citation Excerpt :

    The authors have successfully prepared hydrophilic PE/poly(ethylene-block-ethylene glycol) (PE-b-PEG) blend membranes via TIPS process for water filtration [18,19]. Given the excellent property of PEG chains in increasing membrane surface energy [20,21] and their advantageous functions in polymer electrolytes for LIBs [22–25], the preparation and the electrochemical properties of HDPE/PE-b-PEG blend separators for LIBs are studied in this work. HDPE, PE-b-PEG and LP with a designed ratio (Table 1) were added into a flask equipped with a stirrer.

  • Preparation and properties of poly(ethylene oxide) gel filled polypropylene separators and their corresponding gel polymer electrolytes for Li-ion batteries

    2011, Electrochimica Acta
    Citation Excerpt :

    Due to polymer electrolytes acting as the key materials for lithium-ion batteries, the ever works were mainly focused on exploration of polymer electrolytes with improved performance in ionic conductivity, chemical, thermal and electrochemical stability, and mechanical strength [1–4]. Though various polymers including poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO) poly(methylmethacrylate) (PMMA), poly(acrylonitrile) (PAN), and poly(vinylidene fluoride) (PVdF) etc. have been investigated as GPE matrixs by addition of ceramic fillers/additives and polar plasticizers to fabricate the promising GPEs with high ionic conductivity and other desirable properties [5,6], the crosslinked polyether systems are approved one of the most potential gel bases for GPEs because of ideal interaction between lithium ion and ethylene oxide (EO) or propylene oxide (PO) unit. Generally, the polyether gel base was formed from the precursors containing one or two methacrylate groups.

View all citing articles on Scopus
View full text