Microporous organic polymer-based lithium ion batteries with improved rate performance and energy density
Graphical abstract
Introduction
Rechargeable batteries have been playing a key role in power source for portable consumer electronics, tools and electric vehicles. Among various rechargeable batteries, lithium ion batteries (LIBs) are undoubtedly one of the most popular and promising energy storage devices because of their high energy density and cyclability [1], [2], [3], [4]. Currently, the leading technology of LIBs is based on the combination of lithium metal oxide or phosphate (e.g. LiCoO2, LiMn2O4, LiFePO4) cathode [3], [5], [6] and carbon anode. However, as a result of relatively slow intercalation kinetics of Li+ in the inorganic cathode materials, most of these conventional inorganic cathodes exhibited low rate performance, which is one of the most important challenges for practical applications. To achieve a sustainable and environmentally acceptable energy storage process, it is desirable to develop fast, high energy density and heavy metal-free cathode materials for the next generation of “green battery” [2], [6], [7], [8]. Recent studies have revealed that organic cathode materials including organic molecules and polymers could be promising for LIBs because of their high energy/power densities, environmental friendliness, structural diversity and controllability, and resource renewability [2], [9], [10]. These organic compound-based cathode materials for LIBs mainly include organosulfur compounds [11], [12], [13], organic carbonyl compounds [14], [15], conducting polymers [9], [16], [17], [19], and organic free radical compounds [10], [18], [21].
However, the dissolution of small organic molecules in non-aqueous electrolyte will lead to the fast fading of electrochemical capacity, which is one of the most problems in practical applications. Some strategies have been developed to overcome this issue [8], [15], [22], [23]. Among various approaches, it is a common and efficient strategy to design active materials with intrinsic insolubility, which mainly includes metal organic salts [22], [24], [25], [26] and organic polymers [8], [10], [13], [28]. Although utilization of metal organic salts and polymers can decrease the dissolution in electrolytes, organic salts bulk [24], [26] and dense packed polymers [21] hinder the contact between active sites within the organic materials and electrolyte, resulting in low utilization ratio of active materials and slowing the diffusion of Li+, which sequentially decreases the practical specific capacity and seriously compromises their advantage of intrinsic fast reaction kinetics on rate performance of LIBs [21], [24], [26], [29], [30], [31]. High surface area of active materials allows for improved contact area with the electrolyte, more surface sites available for reversible reactions with Li+ and shorter Li+ diffusion pathways, which in turn lead to enhanced battery kinetics and specific capacity [26], [27], [29], [30]. For example, Zhang et al. [27] reported that the P-doped Li2.05Mn0.95P0.05Si0.95O4/C sample showed smaller particle size, higher surface area and electrochemical performances compared to LiMnSiO4/C. Wang et al. [26] reported that the croconic acid disodium salt (CADS) nanowire with smaller size and higher surface area showed higher specific capacity and rate performance than CADS micropillar and CADS microwire. Chen et al. [24] synthesized organic tetralithium salts of 2, 5-dihydroxyterephthalic acid (Li4C8H2O6, Li4DHTPA) with different morphology (bulk, nanoparticles and nanosheets) and surface area, and Li4DHTPA nanosheets with the highest surface area exhibited the best electrochemical performance among these materials. Zhang et al. [21] synthesized a polytriphenylamine terminated with ferrocene, the introduction of ferrocene segment hindered the dense packing of the resulting polymer, leading to the improved specific capacity and rate performance of LIBs.
Microporous organic polymers (MOPs), as a kind of advanced porous materials, show some features such as large specific surface area, high chemical and thermal stability, insolubility in most solvents, and synthetic diversity. These advantages make MOPs broad potentials in a variety of applications, such as gas adsorption [32], [33], [34], light emitting [35], [36], energy storage [28], [37], [38], [39], [40], [41], [42] and heterogeneous catalysis [43], [44], [45], [46]. There are, however, only a few reports on MOPs applied as electrode materials of LIBs. Jiang et al. [28] synthesized hexaazatrinaphthalene conjugated microporous polymers with built-in redox-active skeletons and permanent nanopores for cathode materials of LIBs. Sakaushi et al. [41] obtained high power and long life all-organic energy storage devices by employing bipolar porous polymeric frameworks. Yang et al. [39] investigated the lithium storage of conjugated microporous polymers based on carbazole and benzothiadiazole. Chang et al. [47] developed a promising energy-storage system of porous polyimides as cathode materials for LIBs. These results demonstrated that MOPs could be promising candidates of electrode materials for the new generation of “green battery”.
Recently, we reported two microporous organic polymers (SPTPA and YPTPA) based on triphenylamine (TPA) for gas adsorption [33]. In this work, we employed both of the polymers as cathode materials for LIBs since both polymers combine high surface area with redox-active TPA units, which will lead to the improvement of electrochemical performances of LIBs. For comparison, another polymer of OPTPA was also synthesized via ferric chloride-catalyzed oxidative coupling reaction of N, N, N′, N′-tetraphenylbenzidine. The three porous polymer networks possess the same repeating units (TPA), and thus the equal theoretical capacity, although they were produced from different polymerizations. Owing to the higher surface area, SPTPA and YPTPA display higher rate performance and energy density over a wide range of power density compared with OPTPA. In addition, YPTPA with higher surface area exhibits better electrochemical properties than SPTPA, indicating that increasing surface area of polymer cathodes by interweaving the redox-active units into microporous polymer skeleton is an efficient way to develop advanced polymer cathode materials with outstanding electrochemical performances.
Section snippets
Materials and synthesis
Ferric chloride (FeCl3, analytical grade), methanol, chloroform and N-methylpyrrolidone (NMP, analytical grade) were purchased from Sinopharm Chemical Reagent Co. Ltd. Acetylene black and polyvinylidenefluoride (PVDF) are commercially available. The monomers of N4, N4, N4′, N4′-tetrakis(4-bromophenyl)biphenyl-4,4′-diamine [48] and tris(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)amine were synthesized according to the literature [49].
OPTPA was prepared by FeCl3-catalyzed oxidative
Results and discussion
Scheme 1 shows the synthetic route for the porous polymer networks and the notional molecular structures. SPTPA and YPTPA were synthesized by Suzuki cross-coupling polycondensation and nickel-catalyzed Yamamoto-type Ullmann cross-coupling reaction, respectively [33]. For comparison, OPTPA was also synthesized via ferric chloride-catalyzed oxidative coupling reaction of N, N, N′, N′-tetraphenylbenzidine. Thermogravimetric analysis indicated that SPTPA and YPTPA were thermally stable in nitrogen
Conclusion
In summary, triphenylamine-based microporous organic polymers with high surface area were employed as cathode materials for lithium ion batteries. The charge–discharge performance of the polymers was investigated by galvanostatic charge–discharge testing. The high structural stability, insolubility in organic solvents, high surface area as well as the inherent fast redox kinetics and high redox potential of TPA units in the polymer network endow the microporous polymers high discharge capacity,
Acknowledgment
J.-X. J. thanks the National Natural Science Foundation of China (21304055 & 21574077), Shaanxi Innovative Team of Key Science and Technology (2013KCT-17), and the Fundamental Research Funds for the Central Universities (GK201501002). Y. W. thanks the National Natural Science Foundation of China (No. 51402302), F. S. thanks the National Natural Science Foundation of China (No. 51272252, 51402302, 51402299) and Hundred Talents Program of the Chinese Academy of Sciences for financial support. We
References (57)
- et al.
J. Alloys Compd.
(2010) - et al.
J. Power Sources
(2008) - et al.
Polymer
(2015) - et al.
Electrochim. Acta
(2013) - et al.
Polymer
(2015) - et al.
Prog. Polym. Sci.
(2012) - et al.
J. Power Sources
(2014) - et al.
J. Power Sources
(2012) - et al.
Synth. Met.
(2003) - et al.
Nature
(2001)
Nature
Adv. Mater.
J. Solid State Electrochem.
Nat. Mater.
J. Am. Chem. Soc.
J. Am. Chem. Soc.
Chem. Rev.
Adv. Mater.
Mol. Cryst. Liq. Cryst.
Nature
Adv. Energy Mater.
Angew. Chem. Int. Ed.
Chem. Soc.
Chem. Commun.
Chem. Rev.
J. Mater. Chem. A
J. Mater. Chem.
Energy Environ. Sci.
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