Ultrafast Carrier Transport through an Advanced Thick Electrode with a High Areal Capacity for Aqueous Lithium‐Ion Batteries

Abstract

Thick electrode design holds great promise to render the aqueous lithium ion battery more cost effective by boosting the packing density of the electroactive materials to enhance the energy delivery at the device level. However, a thick electrode faces the concomitant challenge of the sluggish transport of electrons and, importantly, the Li ions. To address this issue, numerous 3 D shortcuts that include a conductive percolation network and well‐interconnected mesoporous channels were established in the 330 μm thick V2O5⋅H2O/CC monolithic electrode developed here. In this way, electron transfer and ion transport were favored, which accounts for the outstanding charge‐storage capacity that exceeded 2 mA h cm−2 and the exceptional energy and power densities of 1.38 mW h cm−2 and 34.1 mW cm−2, respectively, measured at the electrode and the device scale within a short subhour timeframe. Such a remarkable high rate performance is better than that of electrodes reported previously for commercial lithium‐ion microbatteries, advanced aqueous batteries, and state‐of‐the‐art supercapacitors designed for high‐power applications.

Dual-Ion Co-intercalation Mechanism on a Na2V6O16·3H2O Cathode with a Commercial-Level Mass Loading for Aqueous Zinc-Ion Batteries with High Areal Capacity

“…Along with this reaction process is the intercalation/deintercalation of cations to compensate for the negative charge of the electrons stored/released by Na 2 V 6 O 16 ·3H 2 O. Such argumentation is well supported in view of the kinetic analysis of the CV curves using the following equations: which is derived from the power law shown below: wherein i p refers to the current response measured for the most intense redox peaks at different scan rates (ν). ,,, By plotting log­( i p ) as a function of log­( ν ), to which the linear regression is further applied, b = 0.47 and b = 0.60 are determined for the strongest anodic and cathodic peaks, respectively, and more importantly, these values are highly close to 0.50, suggesting the charge storage kinetics being predominately controlled by the solid-state diffusion rate of cations in Na 2 V 6 O 16 ·3H 2 O (Figure b and Supplementary Note 2). ,,, Their diffusion coefficient ( D ion ) is additionally estimated from the GITT plot collected via first applying a constant current flux I = 0.05 A g –1 to discharge the Na 2 V 6 O 16 ·3H 2 O/ACC//Zn/In cell for a limited time period τ = 20 min, at the end of which I is interrupted to allow this ZIB to relax for 120 min to a new steady state potential ( E s ), using the formula shown below: wherein m B /g denotes the mass loading of Na 2 V 6 O 16 ·3H 2 O, M B /g mol –1 represents the molecular weight of Na 2 V 6 O 16 ·3H 2 O, V M /cm 3 mol –1 stands for the molar volume of Na 2 V 6 O 16 ·3H 2 O, A refers to the contact area of Na 2 V 6 O 16 ·3H 2 O/ACC with the electrolyte, and Δ E τ and Δ E s are related to the transient cell voltage change during the current pulse for a given time τ and change in E s after full relaxation over a single galvanostatic titration step, respectively (Figure c). ,− Equation is derived from which is valid when τ is shorter than the diffusion time constant ( L 2 / D ion ) of cations in the host materials through a simple approximation in view of the linear dependency of E τ on square root of time √τ . ,− Of particular note is D ion in the order of 10 –8 to 10 –10 cm 2 s –1 , far above that (10 –10 to 10 –11 cm 2 s –1 ) reported for V 2 O 5 in the literature by more than one order of magnitude, which is attributed to the interlamellar Na + and structural water that functioned as not only pillars to expand the interplanar distance between adjacent V 3 O 8 layers but also lubricants to screen the charge density of inserted cations to thus attenuate their strong interaction with the V 3 O 8 slabs (inset in Figure e and Figure…”

“…3b and Supplementary Note 2). 10,25,51,52 Their diffusion coefficient (D ion ) is additionally estimated from the GITT plot collected via first applying a constant current flux I = 0.05 A g −1 to discharge the Na 2 V 6 O 16 •3H 2 O/ACC//Zn/In cell for a limited time period τ = 20 min, at the end of which I is interrupted to allow this ZIB to relax for 120 min to a new steady state potential (E s ), using the formula shown below:…”

“…ACC then served as the working electrode and was coupled with a platinum (Pt) foil (1.5 cm × 1.5 cm) as the counter electrode and a Ag/AgCl reference electrode in 3 M KCl (0.207 V vs the standard hydrogen electrode, SHE) to build a three-electrode cell. An aqueous solution consisting of 0.1 M NH 4 VO 3 and 2 M Na 2 SO 4 was used as the electrolyte, from which Na 2 V 6 O 16 ·3H 2 O was electrodeposited on ACC by applying a constant current of 2 mA cm –2 for 3 h at 70 °C. − As-obtained Na 2 V 6 O 16 ·3H 2 O NBs/ACC was thoroughly washed with distilled water to remove the precursor residues and naturally dried under ambient conditions.…”

“…In the current era of lithium ion batteries (LIBs), the burgeoning popularity of electric vehicles (EVs) and Internet of Things (IoT) devices, among others, has led to the increasing demand of the modern society for LIBs. − As a result of such growing dependency on LIBs is, however, the lithium price inevitably soaring, over which the unevenly distributed lithium resources and the flammable nature of organic electrolytes are also ever-increasing public concerns, not to mention the energy density of present LIBs being still inadequate to power mobile electronics with augmented energy consumption and to well extend the driving mileages of EVs. − The aforementioned issues have in turn stimulated tremendous research into a wide range of post-lithium and post-lithium-ion batteries, among which aqueous zinc ion batteries (ZIBs) particularly stand out due to their several advantageous characteristics including high capacity (820 mAh g –1 /5855 mAh cm –3 ), low cost, safety, and environmental abundance and friendliness. − A variety of cathode materials have further been put forward, including manganese dioxide (MnO 2 ), lithium vanadium phosphate (Li 3 V 2 (PO 4 ) 3 ), etc., among which vanadium-based cathodes, e.g., hydrated layered vanadium oxide (V 5 O 12 ·6H 2 O), show outstanding capacity, excellent long cycling stability, and remarkable rate capability. − However, their outstanding electrochemical properties have hardly been translated to device performance due to their poor packing density in ZIBs, which is usually no more than 2 mg cm –2 and far below that (∼20 mg cm –2 ) in commercial LIBs by more than one order of magnitude. − To tackle this challenge, massive Barnesite (Na 2 V 6 O 16 ·3H 2 O), which is employed in the present contribution as an electroactive material, is embedded particularly in the highly interconnected macropores of activated carbon cloth (ACC) as an alternative current collector to the conventional metal foil to thus take full advantage of the confinement effect of these porous channels to not only prevent the detachment of Na 2 V 6 O 16 ·3H 2 O from ACC but also mitigate the pulverization of Na 2 V 6 O 16 ·3H 2 O resulting from the huge volume change upon charging/discharging. − Herein, Na 2 V 6 O 16 ·3H 2 O is preferentially chosen in view of its layered crystal structure favorable to the intercalation/deintercalation of zinc ions (Zn 2+ ), leading to its gravimetric capacity amounting to 383 mAh g –1 , well outperforming those reported in the literature, as well as the interlamellar sodium ions (Na + ) and water molecules (H 2 O), which have been reported to function as pillars to enhance the structural stability of Na 2 V 6 O 16 ·3H 2 O. , More importantly, a strong electric field is further applied to the intrapore Na 2 V 6 O 16 ·3H 2 O to induce not only their morphologic evolution into a belt-like nanostructure to a...…”

“…10,25,51,52 By plotting log(i p ) as a function of log(ν), to which the linear regression is further applied, b = 0.47 and b = 0.60 are determined for the strongest anodic and cathodic peaks, respectively, and more importantly, these values are highly close to 0.50, suggesting the charge storage kinetics being predominately controlled by the solid-state diffusion rate of cations in Na 2 V 6 O 16 •3H 2 O (Figure…”