A Pyrazine‐Based Polymer for Fast‐Charge Batteries

Abstract

The lack of high-power and stable cathodes prohibits the development of rechargeable metal (Na, Mg, Al) batteries.Herein, poly(hexaazatrinaphthalene)(PHATN), an environmentally benign, abundant and sustainable polymer, is employed as auniversal cathode material for these batteries. In Na-ion batteries (NIBs), PHATN delivers ar eversible capacity of 220 mAh g À1 at 50 mA g À1 ,c orresponding to the energy density of 440 Wh kg À1 ,and still retains 100 mAh g À1 at 10 Ag À1 after 50 000 cycles,w hich is among the best performances in NIBs.S uch an exceptional performance is also observed in more challenging Mg and Al batteries.P HATN retains reversible capacities of 110 mAh g À1 after 200 cycles in Mg batteries and 92 mAh g À1 after 100 cycles in Al batteries. DFT calculations,X -ray photoelectron spectroscopy, Raman, and FTIR showt hat the electron-deficient pyrazine sites in PHATN are the redoxc enters to reversibly react with metal ions.

Rational Molecular Design of Benzoquinone‐Derived Cathode Materials for High‐Performance Lithium‐Ion Batteries

“…Constructing polymers is also deemed as an effective way to enhance the cycling stability of organic electrode materials [ 6,26–29 ] and improved performance has been reported. [ 30–34 ] However, due to the introduction of electron donating groups and redox‐inactive portion, the BQ‐derived polymer electrode materials are often reported with decreased discharge voltages (1.7–2.5 V) or greatly reduced capacity (<300 mAh g −1 ). [ 30–32,35,36 ] Apparently, new molecular structure design strategies are needed to achieve largely enhanced electrochemical performance of BQ‐derived electrode materials in organic liquid electrolytes.…”

Dense‐Stacking Porous Conjugated Polymer as Reactive‐Type Host for High‐Performance Lithium Sulfur Batteries

“…HATN polymer features two reversible redox couples located at 1.8/ 2.05 Va nd 2.4/2.65 Vw ithin the sulfur redox potential window,w hereas polymer/S exhibits an enhanced sulfur redox behavior with diminishing polarization of anodic and cathodic peaks,s uggesting strong interaction between the polymer and sulfur.T he electrochemical behavior of HATN polymer/S is distinct from compounds like CuO, [28] VO 2 , [28,29] MoO 3 , [30] and Mo 6 S 8 [18] that were previously used as Li 2 S x immobilizers within the sulfur electrochemical window, because these host materials and sulfur show independent redox behaviors in their CV curves.F urther investigation of the Li 2 S x -reactive type process is needed to understand the role of HATN polymer.H ere we used an electrolyte of 1M Li 2 S 6 in dioxolane/dimethoxyethane(DOL/DME) as the sole Li + source to study the discharge/charge behaviour of the polymer,w hich is shown in Figure 2c.F irst, HATN polymer has as pecific capacity of 700 mAh g polymer À1 at the first discharge,w hich is much higher than the capacity of super P (400 mAh g super P À1 ;Supporting Information, Figure S7a). This indicates the efficient deposition of Li 2 S x onto the polymer matrix to form Li 2 S. Secondly,t he first charge delivers amatching capacity with the plateau capacity during the first discharge in the profile,suggesting that the as-formed Li 2 Sin the polymer can be completely oxidized into Li 2 S x ,a nd only Angewandte Chemie Forschungsartikel these strongly bound Li 2 S x continue to be oxidized into S excluding outer Li 2 S 6 from oxidizing in the polymer.C ompared to super P, the polymer presents longer discharge plateaus with high CE (Supporting Information, Figure S7a), which indicates the effective suppression of polysulfides owing to the strong binding of Li 2 S x to the redox-active polymer.F urthermore,H ATNp olymer shows declining voltage overshoot related to easier Li 2 Sactivation (Figure 2c, inset) suggesting good reaction kinetics.M oreover,t he lithiation reaction of the polymer by Li 2 S x is verified from the evolution of the different chemical states in the N1s XPS signals (Figure 2d)c orresponding to the different discharge states in Figure 2c.T he XPS signal of C=Na t3 99.02 eV [25] vanishes along with the formation of C À Na t4 00.02 eV [23] owing to polymer lithiation, and the C = Npeak restores after delithiation. Thep resence of nitrogen oxide derivatives indicates as olvent decomposition-derived solid-electrolyteinterface (SEI) on the polymer.…”

“…[20][21][22] To overcome these drawbacks, we have selected Hexaazatrinaphthylene (HATN) as the redox-active core since it boasts 6bidentate Natoms that are able to undergo lithiation/delithiation during dischargecharge,p resenting multi-electron redox capability within the Selectrochemical window. [20,22] To avoid the formation of low density polymer products prepared with solution-based methods, [23][24][25] we performed catalyzed melting polymerization by high temperature annealing to prepare densely stacked polymer (Figure 1a;S upporting Information, Figure S1). Details on the synthesis of both the monomer and HATN polymer are provided in the Supplementary.C haracterization studies revealed that HATN polymer is bulky and dense compared to nanosheets of the monomer with low bulk density (Supporting Information, Figures S2 and S3).…”

Covalent Organic Frameworks for Next‐Generation Batteries

“…Therefore, rechargeable magnesium ion batteries (MIBs) are very promising for large-scale energy storage. [120][121][122] More importantly, unlike Li and Na anodes, Mg anodes have no dendrites during long-term Mg plating and stripping, making MIBs an inherently high-security battery system. All these advantages make MIBs promising in the market of low-cost and sustainable energy storage equipment.…”

“…Because magnesium (Mg) metal not only is abundant in the ambient atmosphere, cheap and extremely safe but also has a volume capacity (3833 mAh cm −3 ) that is almost twice that of lithium (2046 mAh cm −3 ). Therefore, rechargeable magnesium ion batteries (MIBs) are very promising for large‐scale energy storage . More importantly, unlike Li and Na anodes, Mg anodes have no dendrites during long‐term Mg plating and stripping, making MIBs an inherently high‐security battery system.…”