Depth Of Discharge Research Articles

Bifunctional Ion Rectification Layer Separators Toward Superior Reversible Dendrite‐Free Zinc Metal Anodes

AbstractThe slow transport dynamics and poor dendritic growth significantly hinder the performance of zinc metal batteries. Here, a unique difunctional ion rectification strategy is developed using vacuum evaporation technology to design a coated separator for efficient ion transport. The highly conductive Cu‐coated separator acts as an ion redistributor, ensuring homogenized electric field distribution. The excellent znophilicity of the copper coating acts as an ion accelerator, promoting ion transport and facilitating face‐to‐face zinc deposition on the separator. Consequently, this synergy enables stable battery operation at high current densities (cumulative capacity up to 10 800 mAh cm−2 at 8 mA cm−2) and high depth of discharge (over 200 h at 94% DOD). The Cu‐coated separator exhibits a reversible plating/stripping life of over 2400 h with an average coulombic efficiency of 99.88%. Notably, the Cu‐coated separator significantly enhances the rate performance and cycle capacity of Zn||V6O13 and Zn||MnO2 full cells. This functional separator with a difunctional ion rectification strategy presents a promising solution to the challenge of zinc metal anodes.

Highly Reversible Zn Anode Design Through Oriented ZnO(002) Facets.

The practical implementation of aqueous Zn-ion batteries presents formidable hurdles, including uncontrolled dendrite growth, water-induced side reactions, suboptimal Zn metal utilization, and intricate Zn anode manufacturing. Here, large-scale construction of a highly oriented ZnO(002) lattice plane on Zn anode (ZnO(002)@Zn) with thermodynamic inertia and kinetic zincophilicity is designed to address such problems. Both theoretical calculations and experiment results elucidate that the ZnO(002)@Zn possesses high Zn chemical affinity, hydrogen evolution reaction suppression, and dendrite-free deposition ability due to the abundant lattice oxygen species in ZnO(002) and its low lattice mismatch with Zn(002). These features synergistically promote ion transport and enable homogeneous Zn deposition. Consequently, the ZnO(002)@Zn anode displays a stable and prolonged cycling lifespan exceeding 500h even under a larger depth of discharge (85.6%) and realizes an impressive average Coulombic efficiency of 99.7%. Moreover, its efficacy is also evident in V2O5-cathode coin cells and pouch cells with not only high discharge capacity but also exceptional cycling stability. This integrated approach presents a promising avenue for addressing the challenges associated with Zn metal anodes, thereby advancing the prospects of aqueous Zn-ion battery technologies.

Formulating Self-Repairing Solid Electrolyte Interface via Dynamic Electric Double Layer for Practical Zinc Ion Batteries.

Zinc ion batteries (ZIBs) encounter interface issues stemming from the water-rich electrical double layer (EDL) and unstable solid-electrolyte interphase (SEI). Herein, we propose the dynamic EDL and self-repairing hybrid SEI for practical ZIBs via incorporating the horizontally-oriented dual-site additive. The rearrangement of distribution and molecular configuration of additive constructs the robust dynamic EDL under different interface charges. And, a self-repairing organic-inorganic hybrid SEI is constructed via the electrochemical decomposition of additive. The dynamic EDL and self-repairing SEI accelerate interfacial kinetics, regulate deposition and suppress side reactions in the both stripping and plating during long-term cycles, which affords high reversibility for 500 h at 42.7 % depth of discharge or 50 mA ⋅ cm-1. Remarkably, Zn//NVO full cells deliver the impressive cycling stability for 10000 cycles with 100 % capacity retention at 3 A ⋅ g-1 and for over 3000 cycles even at lean electrolyte (7.5 μL ⋅ mAh-1) and high loading (15.26 mg ⋅ cm-2). Moreover, effectiveness of this strategy is further demonstrated in the low-temperature full cell (-30 °C).

Nitrogen and Oxygen Co‐Doped Graphene Quantum Dots as a Trace Amphipathic Additive for Dendrite‐Free Zn Anodes

AbstractThe practical implementation of aqueous zinc‐ion batteries (AZIBs) has encountered obstacles stemming from the limited reversibility of the zinc anode, primarily due to dendrite proliferation and water‐induced reactions occurring. In this investigation, a novel bifunctional interphase is proposed by integrating nitrogen and oxygen group graphene quantum dot (N‐O‐GQD) additives into the electrolyte. Experimental results and theoretical calculations demonstrate that the amphipathic N‐O‐GQD additive enhances the stability of the electrode by forming a protection layer on Zn surface. The zincophilic and hydrophobic nitrogen function groups stick to the surface of Zn electrodes to form a hydrophobic layer that shields water molecules from the electrode and promotes the uniform deposition of Zn. The hydrophilic hydroxyl function groups are exposed to the electrolyte to improve the compatibility at the electrode/electrolyte interface. As a result, the amphipathic N‐O‐GQD additive enables a robust cycling performance at high depth of discharge (DOD). Significantly, cells incorporating N‐O‐GQDs demonstrate a remarkable Coulombic efficiency of 99.7% over 900 cycles and sustain dendrite‐free cycling for 564 h (DOD = 51%). Particularly noteworthy is the performance of the modified Zn||ZnVO full cell with robust cycling behavior, enduring 4 000 cycles at 10 A g−1.

Anion Receptor-manipulated solvation chemistry and electric double layer enables high Zn-Utilization rate and lean Zn metal batteries

The practical application of aqueous Zn metal batteries (AZMBs) is impeded by inferior reversibility and stability of Zn metal anode (ZMA) originated from side reactions and dendrite growth. Herein, anion receptor l-Proline (LP) is selected to simultaneously manipulate solvation chemistry and electric double layer (EDL) for constructing dendrite-free and stable AZMBs with an ultra-high depth of discharge (DOD of 100 %) and low negative/positive capacity ratio (N/P of 1.1). Experimental and computational results demonstrate that the strong interaction between −SO32- group from OTf- anion and LP promotes the coordination effect of cation and solvent, which improves the stability of electrolyte and induces fine and uniform Zn nucleus formation. Meanwhile, the preferential reduction of OTf- and adsorption of LP establish an anion-derived ZnF2-rich solid electrolyte interface by altering EDL structure, which enhances the mechanical stability and Zn2+ diffusion kinetics of the interface and prevents the contact of H2O molecules. Consequently, ZMA in LP/Zn(OTf)2 electrolyte delivers a satisfactory cycling lifespan under DOD of 100 % and an outstanding Coulombic efficiency of 99.93 % for 10,000 cycles at 10 mA cm−2. Moreover, Zn||Od-NH4V4O10 full cells with LP/Zn(OTf)2 electrolyte demonstrate excellent cycle stability at high cathode loading (20.412 mg), low N/P (1.1), and high temperature (50 °C).

УПРАВЛІННЯ ГІБРИДНОЮ СИСТЕМОЮ ЕЛЕКТРОЖИВЛЕННЯ ТВАРИННИЦЬКОЇ ФЕРМИ З ВІДНОВЛЮВАЛЬНИМИ ДЖЕРЕЛАМИ ТА ЕЛЕКТРОТРАНСПОРТОМ

The article considers the improvement of the control with using the generation of renewable energy sources forecast for a grid-connected a hybrid power supply system of a livestock farm with electric transport and a gas generator. The task is to form a graph of the state of charge of the main battery with a limitation of the depth of discharge with the maximum use of renewable sources energy. The calculation method of the state of charge of a battery and power consumption graph when working with the grid and in autonomous mode has been improved, with the definition of recommendations for charging electric transport. A mechanism has been developed for correcting the power consumption based on the deviation of the battery charge state relative to the specified value, with the correction disabled to implement the function of eliminating the export of excess energy to the grid or gas generator. This ensures the limitation of the gas generator power within certain limits and helps to limit the influence of generation and load deviations relative to the forecast on the battery discharge depth. The structure of the energy processes model in the system for the daily operation cycle has been developed. In the process of modeling, the deviation of renewable energy generation up to 20% and 10% was studied simultane-ously with a 10% increase in load.

Thin Zinc Electrodes Stabilized with Organobromine-Partnered H2O-Zn-MeOH Cluster Ions for Practical Zinc-Metal Pouch Cells.

The utilization of thin zinc (Zn) anodes with a high depth of discharge is an effective strategy to increase the energy density of aqueous Zn metal batteries (ZMBs), but challenged by the poor reversibility of Zn electrode due to the serious Zn-consuming side reactions at the Zn||electrolyte interface. Here, we introduce 2-bromomethyl-1,3-dioxolane (BDOL) and methanol (MeOH) as electrolyte additive into aqueous ZnSO4 electrolyte. In the as-formulated electrolyte, BDOL with a strong electron-withdrawing group (-CH2Br) tends to pair with the H2O-Zn-MeOH complex, leading to the formation of organobromine-partnered H2O-Zn-MeOH cluster ions. During the Zn electrodeposition process, the formed ZnO-dominated by-products induce the polymerization of BDOL monomers, which are previously adsorbed on the electrode. As a result, a uniform dual-layer SEI with ZnO-dominated outer layer and polyether-dominated inner layer is built on the surface of Zn electrode. With such an in-situ formed dual-layer SEI, the Zn||Mg0.9Mn3O7·2.7H2O pouch cell using a 10-um Zn anode (corresponding to a low negative to positive areal capacity ratio of 3.56) successfully operated for 300 cycles with a high capacity retention of 86%, promising a high practical energy density of > 120 Wh/kg (based on the total mass of Zn and Mg0.9Mn3O7·2.7H2O).

Supervisory control strategy for dual battery assisted solar water pumping using a 3-stage interleaved boost converter

This article proposes effective power management and battery protection strategies for a solar photovoltaic (SPV) powered dual-battery supported standalone water pumping approach propelled by a permanent magnet brushless direct current (PMBLDC) motor. A drift-avoidance perturb and observe MPPT algorithm is employed in conjunction with a 3-stage interleaved boost converter (TSIBC) and proposes a switching control scheme to enable double-stage solar photovoltaic generation system (SPGS) to operate at its maximum accessible power point (MPP) irrespective of any variation in climatic condition. The proposed dual battery control scheme (DBCS), which integrates a primary battery with an auxiliary battery, is connected to the 310 V DC link. This dual battery setup utilizes a parallel-active configuration facilitated by two bidirectional DC-DC converters (BDCs). The core idea behind dualization aims to maintain the state of charge (SoC) of the primary battery within upper and lower limits with the help of an auxiliary battery unit and regulate the DC link voltage at 310 V during fluctuations generated in the protection period. This scheme significantly extends the battery's lifespan, achieving an estimated 800 to 1000 cycles by maintaining its depth of discharge (DoD) at a level of 70 %. A centralized power handling unit (CPHU) is integrated for both the BDCs to facilitate the operating mode selection and regulate DC link voltage by alternatively charging/discharging both batteries. This approach enhances overall system efficiency by eliminating the need to oversize the solar array by up to 46 %, which would have been necessary to fully charge both batteries simultaneously. Previously, the DC link voltage regulation relied solely on MPPT control, resulting in significant deviations (up to ±38.43 %) during battery overcharging/deep-discharging (SoC ≥ 90 %/SoC ≤ 20 %). This work proposes a solution using an auxiliary battery controller within the DBCS, achieving near-zero (±0.5 %) DC link voltage deviation under all operating conditions. The effectiveness of the suggested DBCS controller is validated through a time-domain simulation conducted in MATLAB/Simulink, alongside real-time hardware-in-the-loop (HIL) digital simulator using the OPAL-RT platform. The acquired results corroborate enhanced performance for the standalone water pumping system (WPS) and demonstrate a seamless shift from the normal operational mode to battery protection mode, while ensuring steady regulation of the DC link voltage.

High-Entropy-Inspired Multicomponent Electrical Double Layer Structure Design for Stable Zinc Metal Anodes.

Regulating the electrical double layer (EDL) structure can enhance the cycling stability of Zn metal anodes, however, the effectiveness of this strategy is significantly limited by individual additives. Inspired by the high-entropy (HE) concept, we developed a multicomponent (MC) EDL structure composed of La3+, Cl-, and BBI anions by adding dibenzenesulfonimide (BBI) and LaCl3 additives into ZnSO4 electrolytes (BBI/LaCl3/ZnSO4). Specifically, La3+ ions accumulate within EDL to shield the net charges on the Zn surface, allowing more BBI anions and Cl- ions to enter this region. Consequently, this unique MC EDL enables Zn anodes to simultaneously achieve uniform electric field, robust SEI layer, and balanced reaction kinetics. Moreover, the synergistic parameter - a novel descriptor for quantifying collaborative improvement - was first proposed to demonstrates the synergistic effect between BBI and LaCl3 additives. Benefitting from these advantages, Zn metal anodes achieved a high reversibility of 99.5 % at a depth of discharge (DoD) of 51.3 %, and Zn|MnO2 pouch cells exhibited a stable cycle life of 100 cycles at a low N/P ratio of 2.9.

An efficient two-stage heating strategy for embedded heat pipe system considering power and energy requirements from battery

The battery thermal management system (BTMS) embedded heat pipe system cannot only quickly heat the battery, but also improve its temperature consistency. In order to accurate predict the electro-thermal performance of the battery pack with such a BTMS, an electro-thermal model integrating heat pipe model is established for the pack. This model extends the traditional RC model to a dual-RC model at the cell level for predicting the cell anode potential, which clearly senses the status of lithium plating during the heating process. At the pack level, a distributed electro-thermal model combined with a thermal resistance network-based heat pipe model is proposed for the precise determination of the overall pack temperature. To further enhance the accurate monitoring of lithium plating status and control of the heating process for each cell within the pack, the control criterion is based on the terminal voltage rather than the state of charge (SOC). Additionally, an absolute SOC is defined to unify the SOC calculation across different low-temperature scenarios. With the assistance of the model frameworks above, a two-stage heating strategy is proposed for the BTMS, including the power requirement stage to ensure the heating rate and energy requirement for more available depth of discharge (DoD). In the stage of power requirement, air parameters are determined as Vair = 9 m/s and Tair = 60 °C, and the corresponding temperature rising rates are 1.05 °C/min under discharge and 1.08 °C/min under charge condition, respectively. Additionally, in order to ensure the high heating rate and 98 % available DoD, the second stage heats the pack with the air parameters of Vair = 5 m/s and Tair = 60 °C, with the temperature rising rates of 1.02°C/min under discharge and 1.74°C/min under charge condition. Unlike the air parameters used in the first phase, those in second phase also considers the energy conservation of the BTMS and temperature homogeneity inside the pack. The energy consumptions of BTMS are 0.323 kW·h for the discharging and 0.133 kW·h for the charging. Moreover, the tested temperature difference among cells in the whole heating process is no more than 1.3 °C.

Data-driven state-of-charge estimation of a lithium-ion battery pack in electric vehicles based on real-world driving data

State-of-charge (SOC) is one of the most important indicators in the battery management system (BMS) of electric vehicles (EVs). Accurate online estimation of battery pack SOC is essential for ensuring safety by preventing overcharging and overdischarging, as well as for facilitating proper operation and efficient energy utilization. This paper proposes a deep learning model, CNN-BiLSTM-Attention, to drive the battery pack SOC estimation by datasets collected from actual operating EVs. Multivariate time series (MVTS) signals such as vehicle speed, battery voltage, current and temperature are carefully selected as inputs to the model. Additionally, a three-parameter Weibull probability model is used to model the terminal voltage distribution of all cells within the investigated battery pack, and the evolution of cell terminal voltage inconsistency concerning depth of discharge (DOD) is described from the perspective of dispersion and symmetry. By adding these distribution features to the input dimension of the CNN-BiLSTM-Attention model, the estimation accuracy of battery pack SOC has been further improved. Experimental results indicate that when the window length (WL) is set to 25 sampling time steps and the window overlap rate is >72 %, the SOC estimation error is <3 % and the root mean square error (RMSE) is <1.12 % within the maximum DOD variation range experienced by the battery pack. Especially when the battery pack is in the discharge platform period of 30 %–100 % SOC, the SOC estimation error is reduced to <2 %. After adding the Weibull distribution features that reflect the cell inconsistency evolution into the model's input dimensions, the overall SOC estimation RMSE is reduced by about 31 %, especially by about 51 % at lower SOC levels (below 31 %).

Refined air-cooled battery sizing process for conceptual design of eVTOL aircraft

Recently, electric vertical takeoff and landing (eVTOL) aircraft have garnered significant interest as a primary mode of transportation in advanced air mobility (AAM). For the conceptual design of eVTOL aircraft, where a broad design space must be explored rapidly, a practical and reliable battery sizing process is essential. This process needs to employ models with low computational cost while comprehensively considering two key factors: voltage drop characteristics and thermal effects. However, existing research on battery sizing mainly relies on constant specific energy or power, neglecting these factors. This oversight can lead to significant discrepancies in battery sizing between the conceptual and detailed design phases. To address these limitations, this paper introduces a refined battery sizing process. Our approach incorporates models for battery voltage drop, heat generation, and a cooling system. A Thevenin equivalent circuit is used to model voltage drop and heat generation, with a novel calibration method developed for accurate predictions of voltage and temperature profiles. An air cooling system is adopted for its simplicity and lightweight design, and a corresponding model is constructed. Applying our process to eVTOL aircraft sizing revealed that incorporating temperature, along with the depth of discharge (DoD) and C-rate, as constraints in battery sizing led to a 4.6 % decrease in specific energy and a 4.2 % decrease in specific power. These findings underscore the importance of considering temperature in battery sizing. Additionally, sensitivity analyses provided insights into which thermal management system, air-cooled or liquid-cooled, is more appropriate for the battery under various operating conditions.

Emulating "Curvature-Enhanced Adsorbate Coverage" for Superconformal and Orientated Zn Electrodeposition in Zinc-ion-Batteries.

Uneven Zn deposition and unfavorable side reactions have prevented the reversibility of the Zn anode. Herein, we design a rearranged (002) textured Zn anode inspired by a traditional curvature-enhanced adsorbate coverage (CEAC) process to realize the highly reversible Zn anode. The rearranged (002) textured structure orientates the superconformal Zn deposition owing to the spatial deposition rate of the rearranged crystal planes, promoting bottom-up "superfilling" of the 3D Zn skeletons. Meanwhile, our designed anode also induces the epitaxial Zn deposition, alleviating the parasitic reactions owing to the lowest surface energy of the (002) plane. Attributed to these superiorities, uniform and oriented Zn deposition can be obtained, exhibiting an ultra-long lifespan over 479 hrs at an ultrahigh depth of discharge (DOD) of 82.12%. The Zn|Na2V6O16·3H2O battery delivers an improved cycling performance, even at a high area capacity of 5.15 mAh/cm2 with a low negative/positive (N/P) capacity ratio of 1.63. The superconformal deposition approach for Zn anodes paves the way for the practical application of high-performance zinc-ion batteries.

Emulating “Curvature‐Enhanced Adsorbate Coverage” for Superconformal and Orientated Zn Electrodeposition in Zinc‐ion‐Batteries

Uneven Zn deposition and unfavorable side reactions have prevented the reversibility of the Zn anode. Herein, we design a rearranged (002) textured Zn anode inspired by a traditional curvature‐enhanced adsorbate coverage (CEAC) process to realize the highly reversible Zn anode. The rearranged (002) textured structure orientates the superconformal Zn deposition owing to the spatial deposition rate of the rearranged crystal planes, promoting bottom‐up “superfilling” of the 3D Zn skeletons. Meanwhile, our designed anode also induces the epitaxial Zn deposition, alleviating the parasitic reactions owing to the lowest surface energy of the (002) plane. Attributed to these superiorities, uniform and oriented Zn deposition can be obtained, exhibiting an ultra‐long lifespan over 479 hrs at an ultrahigh depth of discharge (DOD) of 82.12%. The Zn|Na2V6O16·3H2O battery delivers an improved cycling performance, even at a high area capacity of 5.15 mAh/cm2 with a low negative/positive (N/P) capacity ratio of 1.63. The superconformal deposition approach for Zn anodes paves the way for the practical application of high‐performance zinc‐ion batteries.

Understanding the heat generation mechanisms and the interplay between joule heat and entropy effects as a function of state of charge in lithium-ion batteries

The thermal performance of lithium-ion battery cells is critical for ensuring their safe and reliable operation across various applications. In this study, we employed an isothermal calorimetry method to investigate the heat generation of commercial 18650 lithium-ion battery fresh cells during charge and discharge at different current rates, ranging from 0.05C to 0.5C, and across various temperatures: 20 °C, 30 °C, 40 °C, and 50 °C. Our findings revealed a direct correlation between heat generation and current rates, indicating that higher current rates lead to increased heat generation within the cells. Conversely, we observed that heat generation remained relatively stable as the temperature rose, suggesting that temperature changes within this range may not significantly impact the heat generation of fresh cells during typical operations. Furthermore, our study explored irreversible heat generation, which depends on the applied current and overpotential, using the galvanostatic intermittent titration technique at 0.05C–0.5C and 30 °C. Additionally, electrochemical impedance spectroscopy was performed on the same cells during charge and discharge at 20 °C, 30 °C, and 40 °C to analyze cell impedance. Our results indicated a consistent dependence of impedance on the state of charge and depth of discharge, with a significant increase in impedance observed at the end of the discharge process.

An interfacial dual-regulation strategy for ultra-stable 3D Zn metal anodes

The development of Zn metal-batteries, which are viewed as one of the most potential alternatives to lithium ion batteries, is severely hindered by sluggish ion diffusion kinetics and uncontrollable dendritic growth for anodes. Herein, we propose an interfacial dual-regulation strategy for the fabrication of 3D Zn anode through the direct in-situ treatment of benchmark Zn foil. Both rapid ion migration dynamics and homogeneous bottom-up Zn2+ deposition are achieved due to the unique open nanoarray structure with superhydrophilic and zincophilic interface to the electrolyte. Theoretical calculations and finite element simulations reveal this design can effectively redistribute Zn2+ and increase ion flux with a long-lasting 3D diffusion mode, enabling exceptional reversibility during Zn plating/stripping. The as-prepared anode therefore achieves an ultralong lifespan over 3000 h along with high rate capability even at 40 mA cm−2 (depth of discharge ≈ 68.4%). Furthermore, its practical feasibility is validated by a superior capacity retention of 92.5% after 1000 cycles for full cell and high capacity of 112.2 mAh g−1 for pouch cell. This study opens up new opportunities for the development of dendrite-free anodes for aqueous metal batteries.

High gravimetric energy density lead acid battery with titanium-based negative grids employing expanded mesh sandwich structure

Addressing the low gravimetric energy density issue caused by the heavy grid mass and poor active material utilization, a titanium-based, sandwich-structured expanded mesh grid (Ti/Cu/Pb) for lead-acid battery negative electrode is introduced. Titanium was chosen for its advantageous properties such as low density, high mechanical strength, and good electrical conductivity, which reduces the electrode mass and enhances battery gravimetric energy density. However, titanium's use in battery negative grids is limited due to its passivation in sulfuric acid and poor adhesion to the active material. To overcome these drawbacks, a copper layer is added to prevent passivation, and a lead layer is applied to improve the adhesion between the titanium matrix and the active material. This innovative Ti/Cu/Pb negative grid reduces electrode mass and increases current density, boosting active material utilization. Electrode with Ti/Cu/Pb negative grid achieves an gravimetric energy density of up to 163.5 Wh/kg, a 26 % increase over conventional lead-alloy electrode. With Ti/Cu/Pb negative grid, battery cycle life extends to 339 cycles under a 0.5C 100 % depth of discharge, marking a significant advance over existing lightweight negative grid batteries. This research not only demonstrates a significant step in lead-acid battery enhancement but also proposes a methodological approach for future high gravimetric energy density battery design.

Experimental Investigations into a Hybrid Energy Storage System Using Directly Connected Lead-Acid and Li-Ion Batteries

This paper presents experimental investigations into a hybrid energy storage system comprising directly parallel connected lead-acid and lithium batteries. This is achieved by the charge and discharge cycling of five hybrid battery configurations at rates of 0.2–1C, with a 10–50% depth of discharge (DoD) at 24 V and one at 48 V. The resulting data include the overall round-trip efficiency, transient currents, energy transfers between the strings, and the amount of energy discharged by each string across all systems. The general observation is that the round-trip efficiency drops from a maximum of around 94–95% in the first stages of the charge/discharge process, when only the Li-ion strings are active, to around 82–90% when the lead-acid strings reach a DoD of up to 50%. The most important parameters in the round-trip efficiency function are the ratio between the Li-ion and lead-acid energy available and the charge/discharge current. The energy transfer between the strings, caused by the transient currents, is negligible in the first stages of the discharge and then grows, with the DoD peaking at around 60% DoD. Finally, during the first stage of discharge, when only the Li-ion strings are active, the amount of energy discharged varies with the discharge C rate, decreasing to almost half at between 0.2 and 1C.

Improving diffusion kinetics of zinc ions/stabilizing zinc anode by molecular slip mechanism and anchoring effect in supramolecular zwitterionic hydrogels

The severe hydrogen evolution reaction and parasitic side reaction on Zn anode are the key issues which hinder the development of aqueous Zn-based energy storage devices. Herein, a polyacrylamide/carboxylated cellulose nanofibers/betaine citrate supramolecular zwitterionic hydrogels with molecular slip effects are proposed for enhancing Zn2+ diffusion and protecting Zn anodes. Non-covalent interactions within supramolecular hydrogels forms the skeleton for molecular slip and the strong coordination of carboxyl and amino groups with Zn2+ further facilitates the rapid Zn2+ transfer. Additionally, anchoring carboxyl and amino groups at the anode promotes the uniform deposition of Zn2+and protects Zn anode. On the basis of molecular slip mechanism and anchoring effect in the supramolecular zwitterionic hydrogels, Zn||Zn symmetric batteries undergo 800 h of stable electroplating stripping at a depth of discharge of 80 %. Zn||Cu asymmetric batteries exhibit an impressive average coulombic efficiency of 99.4 % over a remarkable span of 900 cycles at a current density of 15 mA cm−2. Furthermore, Zn||NH4V4O10 batteries successfully undergo over 1,000 cycles at a current density of 0.5 A g−1. Intrinsic ion diffusion mechanism of supramolecular hydrogel electrolytes provides an original strategy for the application of high-performance Zn-based energy storage devices.

Zn-anode stability in additive added perchlorate electrolyte for aqueous Zn-MnO2 battery

Extensive research has been conducted on aqueous Zn-MnO2 batteries in the most common ZnSO4 electrolyte. However, the present study focuses on Zn anode stability and subsequent pairing with the commonly utilized MnO2 cathode in a low-concentration aqueous Zn (ClO4)2 electrolyte containing an organic additive, triethyl phosphate (TEP). The structural stability of Zn anodes in optimized additive-added and additive-free electrolytes is analyzed by assembling series of Zn∥Zn symmetry cells under various electrochemical conditions with varying depth of discharges between 20 and 60 %. As such, additive added electrolyte stabilizes the Zn anode over 250 h under high areal capacity/low areal current density of 38.3 mAh cm−2/11.3 mA cm−2 with 60 % depth of discharge at long half-cycle time of 29.5 h. The Zn-MnO2 paired cells in the Zn (ClO4)2 electrolyte with and without additives registered reversible capacities of 262 and 247 mAh g−1, respectively, at 0.05 A g−1. These electrochemical features are completely different from those of the common ZnSO4 electrolyte, whose electrochemical mechanism is still a subject of debate.