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• Ti 3 C 2 T x -PPy/Bi 2 S 3 enabled the voltage window of AZIC-TPB//ZnSO 4 //Zn to 2.1 V. • Ti 3 C 2 T x served as the expansion joint in voltage-window-expansion engineering. • Bi 2 S 3 and PPy offered pseudocapacitance and widened the voltage window laterally. • The energy density of AZIC-TPB//ZnSO 4 //Zn was elevated to 269.09 Wh Kg−1. • DFT calculations revealed the origins of enhanced electrochemical properties. Although increasing the voltage window should be more effective by square rewarding than the specific capacitance for enhancing the energy density of zinc-ion hybrid capacitors (ZIC), the lack of an ideal cathode has hindered its realization. Herein, Ti 3 C 2 T x -PPy/Bi 2 S 3 composite was fabricated through voltage-window-expansion engineering, where Ti 3 C 2 T x layers were covered by a tremella-like network of PPy through hydrogen bonds (-N H···O- and -N H···F-), and then compounded with pseudocapacitive Bi 2 S 3. Due to the redox reactions of Bi 2 S 3 and PPy at low and high potentials, the working voltage window of AZIC-TPB//ZnSO 4 //Zn was elevated up to 2.1 V with low-cost electrolyte ZnSO 4 , exhibiting a high energy density comparable to that of batteries (269.09 Wh Kg−1 with a power density of 1564.73 W Kg−1). Even at a power density of 12947.15 W Kg−1, the energy density of AZIC kept as high as 107 Wh Kg−1, far exceeding the common level. Density functional theory (DFT) calculation demonstrated the obvious electron transfer between Ti 3 C 2 T x and PPy (or Bi 2 S 3) and advanced conductivity, which promoted the redox reaction and facilitate the charge transfer in the electrochemical process. The strategy of voltage-window-expansion engineering here can be further extended to aqueous energy storage devices, offering a viable path to enhancing energy density. [ABSTRACT FROM AUTHOR]

• A new pizza-like ternary heterostructure Ti 3 C 2 T x /Bi 2 S 3 @N-C was fabricated by in-situ growth. • The introduction of dopamine has played an important role in the construction of the ternary composite material. • Ti 3 C 2 T x /Bi 2 S 3 @N-C delivered high specific capacitance of 653 F g-1 at 1 A g-1 in three electrode system. • Ti 3 C 2 T x /Bi 2 S 3 @N-C served as electrode material both for SSC and ZIHC and showed energy density of 46.98 W h kg-1 in ZIHC. The aqueous zinc-ion hybrid supercapacitor (ZIHC) has become an emerging energy storage device due to its safety and low cost. Herein, a new pizza-like heterostructure of Ti 3 C 2 T x intercalated by N-doped-carbon-wrapped Bi 2 S 3 is fabricated by in-situ growth. The specific capacitance of Ti 3 C 2 T x /Bi 2 S 3 @N-C electrode is as high as 653 F g−1 at 1 A g−1, which is significantly higher than other binary composites or similar MXene-based materials in literature. The ZIHC are assembled with Ti 3 C 2 T x /Bi 2 S 3 @N-C and Zn foil as electrodes, possessing high specific capacitance of 150.33 F g−1 at 1 A g−1, and a maximum energy density of 46.98 W h kg−1 at a power density of 750 W kg−1. The excellent performance of Ti 3 C 2 T x /Bi 2 S 3 @N-C is mainly attributed to the synergistic effect of the three components: (a) highly conductive Ti 3 C 2 T x as the substrate shortens the electron transport path; (b) the in-situ growth of Bi 2 S 3 on Ti 3 C 2 T x layers makes full use of Bi 2 S 3 active sites; (c) the innovative introduction of dopamine can not only make Bi(NO) 3 evenly dispersed, but also form the "cross-bridge" N-C film, which further improves the binding between Ti 3 C 2 T x substrate and Bi 2 S 3 and reduces the internal resistance greatly. This study proposes a new in-situ growth strategy for a ternary heterostructure, which may offer a new avenue for the development of high-performance electrode materials. [ABSTRACT FROM AUTHOR]

Hybrid electrode materials with superior electrochemical performance are highly desired to fulfil the ever-increasing energy-density demands of supercapacitors. Herein, a facile and efficient ion-attraction strategy is demonstrated for the construction of a uniform heterostructure of Bi 2 S 3 /Ti 3 C 2 T x (BSTC) nanocomposites, in which fallen leaf-like Bi 2 S 3 nanopieces are firstly planted on the surface of Ti 3 C 2 T x due to the local-repulsion of Ti atoms and the macroscopic attraction of functional groups (OH/O/F) to Bi3+. The DFT calculation was conducted to explain the morphology transformation mechanism from nanoparticles to nanopieces and the enhancement of the electrical conductivity of Bi 2 S 3 is due to the incorporation of Ti 3 C 2 T x. When used as a supercapacitor electrode, the BSTC-29 (Ti 3 C 2 T x content: 29 wt.%) nanocomposite exhibits a superior electrochemical performance with an enhanced capacity of 615 C g-1 at a high discharge current density of 3 A g-1, and a high capacitance retention up to 91% is also obtained due to the enhanced structural stability. Furthermore, the assembled symmetrical supercapacitor exhibits both a high energy density of 27.6 Wh kg-1 and a power density of 24.3 kW kg-1, respectively, surpassing those of Bi 2 S 3 and Ti 3 C 2 T x in this study and many other related composites in literature. This study presents a new promising strategy for the synthesis of high-performance supercapacitor electrode materials. [ABSTRACT FROM AUTHOR]