CNT@MnO₂ composite ink toward a flexible 3D printed micro‐zinc‐ion battery

Abstract

Flexible energy storage devices have played a significant role in multiscenario applications, while flexible zinc-ion batteries (ZIBs), as an essential branch, have developed rapidly in recent years. Three-dimensional (3D) printing is an extremely advanced technology to design and modify the structure of batteries and provides unlimited possibilities for the diversified development of energy storage equipment. Herein, by utilizing 3D printing technology, carbon nanotube (CNT) is coated by MnO 2 to form a flexible CNT@MnO 2 ink as a cathode for flexible aqueous micro-ZIBs for the first time and zinc powder ink is used as an anode due to its high flexibility and bendability. The Zn//CNT@MnO 2 flexible battery shows a stable capacity of 63 μAh cm −2 at 0.4 mA cm −2 . When the battery is bent in different states, the maximum capacity loss compared with the initial value is only 2.72%, indicating its stability. This study shows the potential of 3D printing technology in the development of flexible manganese-based ZIBs.

High Pseudocapacitance‐Driven CoC2O4 Electrodes Exhibiting Superior Electrochemical Kinetics and Reversible Capacities for Lithium‐Ion and Lithium–Sulfur Batteries

“…The surround area of each curve is related to the total amount of charge storage deriving from the capacitive and faradaic processes, which can be identified by the relationship between redox peak current ( i ) and scan rate (υ) according to the following equations: $$\[ \begin{array}{*{20}{c}}{i = a{v^b}}\end{array} \]$$ $$\[ \begin{array}{*{20}{c}}{\log i = \log a + b\log v}\end{array} \]$$where “ a ” and “ b ” are variable parameters, and the b ‐value can be determined from the slope of linear fitting of log i against log υ. Theoretically, if the b ‐value approaches to 0.5, the electrode material follows a battery‐type mechanism, and the electrochemical contribution mostly comes from diffusion‐controlled process; meanwhile, if the b ‐value approaches to 1.0, the electrode material demonstrates a capacitive‐controlled behavior. [ 60,61 ] The b ‐values obtained for peaks 1, 2 and 3 are 0.841 and 0.844 and 0.972, respectively, signifying that the lithium storage for CoC 2 O 4 ‐HK is primarily dominated by the capacitive‐controlled behavior (Figure 5b). In addition, the relative contributions of diffusion‐ and capacitive‐controlled processes at various scan rates were quantitatively determined by Equation (): $$\[ \begin{array}{*{20}{c}}{i = {i_{{\rm{cap}}}} + {i_{{\rm{diff}}}} = {k_1}v + {k_2}{v^{1/2}}}\end{array} \]$$…”

“…where "a" and "b" are variable parameters, and the b-value can be determined from the slope of linear fitting of log i against log υ. Theoretically, if the b-value approaches to 0.5, the electrode material follows a battery-type mechanism, and the electrochemical contribution mostly comes from diffusioncontrolled process; meanwhile, if the b-value approaches to 1.0, the electrode material demonstrates a capacitive-controlled behavior. [60,61] The b-values obtained for peaks 1, 2 and 3 are 0.841 and 0.844 and 0.972, respectively, signifying that the lithium storage for CoC 2 O 4 -HK is primarily dominated by the capacitive-controlled behavior (Figure 5b). In addition, the relative contributions of diffusion-and capacitive-controlled processes at various scan rates were quantitatively determined by Equation ( 8):…”

Boosting the Cycling Stability of Aqueous Zinc-Ion Batteries through Nanofibrous Coating of a Bead-like MnOx Cathode

“…Despite these merits, the practical application of AZIBs has been halted by the lack of suitable cathode materials. To date, only a limited pool of compounds, mainly including Mn-based compounds, − V-based compounds, , Prussian blue analogues, and organic compounds, have been identified as promising cathode materials for AZIBs. In particular, manganese oxides show great potential due to the advantages of natural abundance, low toxicity, diverse crystal structures, and high theoretical energy density. , However, the poor conductivity, manganese dissolution, and inferior structural stability of manganese oxides result in fast capacity fading and inferior electrochemical performance. , …”

Atomic Mechanisms of Cation Adsorption/Exchange in Octahedral Molecular Sieves

“…Octahedral molecular sieves (OMSs), with the general formula of MnO 2 , are constructed by core-/edge-sharing [MnO 6 ] structural units in an ordered fashion, via which a microporous one-dimensional tunnel framework is established. The pore size is typically on a scale of angstroms, which is appropriate for the adsorption of a wide variety of cations (H + , Li + , Na + , K + , Ag + , Zn 2+ , Mg 2+ , Ba 2+ , and Pb 4+ ) and thus allows OMSs to be widely applied in fields of deionization, catalysis, and energy storage. − These cation dopants not only affect the physical configuration of the OMS framework but also modulate the host’s chemical properties by charge redistribution across the Mn 4+/3+ mixed-valence framework. Besides cation adsorption, a cation exchange reaction could also occur within the OMS tunnels when two or more cations are present surrounding the host, which significantly affects the associated functionality in various applications. − With the natural existence of OMSs in marine sediments and terrestrial Mn ore deposits, the cation–OMS interaction also functions to balance the trace-metal cycling in seawater and underground soil, which has aroused substantial research interest in geochemistry (Figure ).…”