Influence of MOF ligands on the electrochemical and interfacial properties of PEO-based electrolytes for all-solid- state lithium batteries
Introduction
Although lithium-ion batteries (LIBs) were commercialized in 1991 by Sony, Japan for consumer electronics (e.g. laptop, mobile) their applications in hybrid electric vehicles still require improvements in terms of energy density, cycle life and better safety [1,2]. LIBs also face critical safety issues since it contains organic liquid electrolytes which have low thermal stability and flash point that lead to poor safety issues [3]. In order to overcome these challenges, new types of solid electrolytes with better safety, excellent flexibility and outstanding electrochemical properties are being explored [4].
Advancement in lithium battery technology in terms of energy density can be achieved only by replacing the conventional liquid electrolyte by solid polymer electrolytes (SPE) in conjunction with Li- metal anode [4]. Although inorganic solid electrolyte possesses high thermal stability the poor electrode/electrolyte contact hampers it from practical application [5,6]. Obviously, by virtue of its advantages, SPEs have been identified as a potential candidate for all-solid-state lithium batteries. The basic requirements for solid polymer electrolyte are; (i) high ionic conductivity (10−4 S cm−1 at ambient temperature) with negligible electronic conductivity, (ii) appreciable mechanical integrity and compatibility with electrodes and (iii) chemical and electrochemical stability. However, identifying a SPE with appreciable ionic conductivity at ambient temperature remains as a great challenge [7].
Although low molecular weight liquid plasticizers such as ethylene carbonate, propylene carbonate, diethyl carbonate etc. added to PEO- based electrolytes increase the ionic conductivity, it adversely affects the mechanical integrity and safety of the electrolyte membrane. Composite polymer electrolyte (CPE), on the other hand, is a sub- set of polymer electrolytes for electrochemical devices in which nanofiller is introduced to promote the ionic conductivity and interfacial properties. So far, several polymeric hosts have been explored. However, poly (ethylene oxide) (PEO) has been extensively studied due its advantages such as high salt content/complexation, acceptable cost, mechanical integrity and good corrosion resistance [8].
The crystalline structure plays a key role on the ionic conductivity of PEO which can be modified by adding ceramic additives [8,9]. Additionally, the electrochemical and interfacial properties of polymer electrolytes are mainly influenced by the nature of ceramic fillers added and are broadly classified into two main categories as active (LiAl2O3) and passive (SiO2, TiO2) [10]. Recently, incorporation of superionic conductors such as Li1.4Al0.4Ti1.6 (PO4)3 (LATP) [11,12], Li7La3Zr2O12 (LLZO) [13], Li6.75La3Zr1.75Ta0.25O12 (LLZTO) [14], Li1.4Al0.4Ge1.6 (PO4)3 (LAGP) [15] in a PEO matrix has been considered as an efficient way to enhance the ionic conductivity of polymer electrolytes. Nan et al. have added Li0.3La0.557TiO3 (LLTO) in a PEO matrix and achieved an ionic conductivity as high as 1.8 × 10−4 S cm−1 at room temperature [16].
MOFs are class of crystalline porous materials having metal ions and clusters linked by organic units [17] through metal- ligand coordination bonds. Recently, MOFs are widely used in diverse technological and industrial applications in areas such as catalysis [18], sensors [19], proton conduction [20], gas storage, purification, separation [21,22] and sequestration [23,24] due to its outstanding structural properties. It also finds applications in emerging technologies such as drug delivery [25], light harvesting [26] and nanofluids [27]. Very recently Wu et al. [28] reported the enhanced performance of PEO based polymer electrolytes with the addition of MOF-derived nanoporous multifunctional fillers. The PEO-n-UIO solid electrolytes showed an increased conductivity by a factor of ∼37 to1.3 × 10−4 S cm−1 at 30 °C.
The lithium ion migration in a SPE is generally influenced by the environment of polymeric host which can be tailored by the added fillers. Numerous reports describe the electrochemical and interfacial properties of CPE with inorganic fillers [29]. However, reports on CPE with MOFs having different organic ligands are scanty. Therefore, in the present work the influence of organic ligands that present in Mg-TPA and Mg-TMA on the electrochemical and interfacial properties of PEO containing LiTFSI as salt is studied and compared.
Section snippets
Materials
Materials PEO (Mw = 3 × 105, Aldrich, USA) and lithium bis(trifluoromethane)sulfonimide, LiTFSI (Aldrich, USA), were dried under vacuum for 48 h at 45 and 90 °C respectively. The MOF magnesium 1,4-benzenedicarboxylic acid (Terephthalic acid- TPA) and magnesium 1,3,5-benzene tricarboxylic acid (Trimesic acid- TMA) were also vacuum dried at 80 °C for 3 days prior to use. The synthesis and characterization of MOFs are discussed in the supporting information (SI-1).
Preparation of composite polymer electrolyte
Composite polymer electrolytes
Results and discussion
Fig. 1 (a and b) depicts the surface morphology of composite polymer electrolyte (Sample S4) containing Mg-TPA and Mg-TMA respectively. The SEM images show a smooth surface morphology and a uniform distribution of MOF particles throughout the membrane. However, small pores are also observed on its surface and are attributed to non- uniform evaporation of solvent at the time of casting the membrane [33]. The size distributions of MOFs were calculated by considering the diameter of more than 100
Conclusions
PEO based composite polymer electrolytes were prepared by the incorporation of Mg-TPA and Mg-TMA MOFs independently as filler and their electrochemical and interfacial properties were analysed. The CPE containing MOF filler (Mg-TPA/Mg-TMA) and LiTFSI salt above 10 wt% was found to be optimal in terms of ionic conductivity and compatibility points of view. Comparing the ionic conductivity of samples, Mg-TPA (Sample S4) offered highest ionic conductivity and was attributed to the lesser amount of
Acknowledgement
The authors gratefully acknowledge the UGC, New Delhi for the financial support.
References (51)
- et al.
Review on solid electrolytes for all-solid-state lithium-ion batteries
J. Pow. Sour.
(2018) Entropy effects on conductivity of the blend-based and composite polymer solid electrolytes
Solid State Ionics
(1992)- et al.
Li1.4Al0.4Ti1.6(PO4)3 nanoparticle-reinforced solid polymer electrolytes for all-solid-state lithium batteries
Solid State Ionics
(2019) - et al.
Synthesis , characterization and hydrogen adsorption on metal-organic frameworks Al , Cr , Fe and Ga-BTB
Chem. Eng. J.
(2011) - et al.
Metal-organic heat carrier nanofluids
Nanomater. Energy
(2013) - et al.
Electrochemical measurement of transference numbers in polymer electrolytes
Polym. J.
(1987) - et al.
Solid polymer electrolytes based on poly ( vinylchloride )
– lithium sulfate
(2005) - et al.
Poly (ethylene oxide) and its blends with sodium alginate
Polym. J.
(2005) - et al.
Structural and thermal studies of PVA:NH4I
J. Phys. Chem. Solids
(2009) - et al.(2000)
Kinetics and stability of the lithium electrode in poly ( methylmethacrylate ) -based gel electrolytes
Electrochim. Acta
FTIR study of ion-pairing effects in polymer
Electrochim. Acta
Spectrochimica Acta Part A : molecular and Biomolecular Spectroscopy FT-IR and FT-Raman spectra , normal coordinate analysis and ab initio computations of Trimesic acid
Spectrochim. Acta Part A Mol. Biomol. Spectrosc.
Electrochemically lithiated graphite characterised by photoelectron spectroscopy
J. Power Sources
Electrochemical control of lithium-ion batteries
IEEE Control Syst.
Challenges for rechargeable Li batteries
Chem. Mater.
Issues and challenges facing rechargeable lithium batteries
Nature
Solid polymer electrolytes-fundamentals and technological applications
Lithium-ion conducting oxide single crystal as solid electrolyte for advanced lithium battery application
Sci. Rep.
High-power all-solid-state batteries using sulfide superionic conductors
Nature Ener
Review on composite polymer electrolytes for lithium batteries
Polym. J.
Effect of fillers on composite polymer electrolytes- a study
Int. J. Appl. Eng. Res.
A high-performance and durable Poly(ethylene oxide)-based composite solid electrolyte for all solid-state lithium battery
J. Phys. Chem. C
Space-charge effects at the Li7La3Zr2O12/Poly(ethylene oxide) interface
ACS Appl. Mater. Interfaces
Synergistic coupling between Li6.75La3Zr1.75Ta0.25O12 and Poly(vinylidene fluoride) induces high ionic conductivity, mechanical strength, and thermal stability of solid composite electrolytes
J. Am. Chem. Soc.
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2022, Journal of Energy ChemistryCitation Excerpt :ADP containing Al and P elements has been proved to enable modification and optimization of the SEI layer [31], and the 3DPA can well avoid the accumulation of ADP particles while providing mechanical support and increasing flame retardancy [30,32,33]. As a new filler [34], MOF can greatly improve the ionic conductivity of SPEs, whether directly adding [35] or combining with Li+-containing ionic liquids, and then adding to PEO matrix [36,37]. Crystalline microporous zeolitic imidazolate framework-8 (ZIF-8) is a kind of MOF material with large specific surface area, highly uniform pore structure and abundant Lewis acid sites on the surface [38], which can encapsulate ionic liquids and promote lithium ion transmission.