Cathodic Dissolution Research Articles

Synergistic Regulation of Anode and Cathode Interphases via an Alum Electrolyte Additive for High‐Performance Aqueous Zinc‐Vanadium Batteries

AbstractA zinc (Zn) metal anode paired with a vanadium oxide (VOx) cathode is a promising system for aqueous Zn–ion batteries (AZIBs); however, side reactions proliferating on the Zn anode surface and the infinite dissolution of the VOx cathode destabilise the battery system. Here, we introduce a multi‐functional additive into the ZnSO4 (ZS) electrolyte, KAl(SO4)2 (KASO), to synchronise the in situ construction of the protective layer on the surface of the Zn anode and the VOx cathode. Theoretical calculations and synchrotron radiation have verified that the high‐valence Al3+ plays dual roles of competing with Zn2+ for solvation and forming a Zn−Al alloy layer with a homogeneous electric field on the anode surface to mitigate the side reactions and dendrite generation. The Al‐containing cathode–electrolyte interface (CEI) considerably alleviates the irreversible dissolution of the VOx cathode and the accumulation of byproducts. Consequently, the Zn||Zn cell with KASO exhibits an ultra‐long cycle of 6000 h at 2 mA cm−2. Importantly, the VOx cathodes (VO2, V2O5 and NH4V4O10) in the ZS−KASO electrolyte showed excellent cycling stability, including Zn powder||VO2 cells and Zn||VO2 pouch cells. Even better, the full cell exhibits excellent cycling stability at low negative/positive (N/P) ratio of 2.83 and high mass loading (~16 mg cm−2). This study offers a straightforward and practical reference for concurrently addressing challenges at the anode and cathode of AZIBs.

Highly efficient Mn2+ deposition induced by H-vacancies of NiMn-LDH nanosheets for durable zinc ion batteries

The dissolution of Mn-based oxides cathodes is an urgent issue, as it leads to electrochemically irreversible byproducts and, finally, battery failure. In this work, activated NiMn-LDHv nanosheets with H vacancies are proposed as the cathode material for durable zinc ion batteries. The H vacancies promote Mn2+ deposition by redistributing the electron density and building strong Mn-O bonds, as a result, endowing NiMn-LDHv with the ability of controllable back-deposition of Mn2+. It's verified that MnO2 is deposited on the NiMn-LHDv substrate during charging, the dissolution and the Zn2+/H+ co-intercalation of MnO2 have a combined contribution to the discharge capacity. The full battery with NiMn-LDHv cathode delivers rate capacity of 258 mAh g−1 at 0.3 A g−1, and even 90 mAh g−1 at 11.0 A g−1. Furthermore, the irreversible Mn-based byproducts are inhibited, resulting in durable cycling performance. After 2500 charge/discharge cycles, the initial capacity remains 91%. This work provides an important strategy to utilize Mn2+ efficiently and develop a robust Mn-based cathode, which could greatly prompt the practical application of aqueous zinc ion batteries.

A Dynamically Ion‐Sieved Electrolyte towards Ultralong‐Lifespan Zn‐Ion Batteries

AbstractThe practical deployment of Zn‐ion batteries faces challenges such as dendrite growth, side reactions and cathode dissolution in traditional electrolytes. Here, we develop a highly conductive and dynamically ion‐sieved electrolyte to simultaneously enhance the Zn metal reversibility and suppress the cathode dissolution. The dynamic ion screen at the electrode/electrolyte interface is achieved by numerous pyrane rings with a radius of 3.69 Å, which can selectively facilitate the plating/stripping and insertion/extraction process of [Zn(H2O)6]2+ and Zn2+ on the anode and cathode surfaces. As a proof of concept, Zn//Zn symmetric cells deliver exceptional cyclic stability for over 6,800 h and ultrahigh cumulative plated capacity of 1.95 Ah cm−2. Zn//Na2Mn3O7 cells exhibit satisfactory cycling performance with capacity retention of 82.7 % after 4,000 cycles, and the assembled pouch cells achieve excellent stability and durability. This work provides valuable insights into the development of electrolytes aimed at enhancing the interface stability of aqueous batteries.

α-MnO2 with a cryptomelane structure for the non-enzymatic glucose electrooxidation in a neutral medium

A high demand for non-enzymatic glucose sensors and continuous glucose monitoring systems encourages the development of stable and active catalysts for the enzymeless anodic oxidation of glucose in the neutral medium. In regard to this reaction, we analyze the prospects of alpha manganese dioxide with a cryptomelane structure synthesized via an aqueous chemical route. To provide various specific surface area, the hydrated α-MnO2 oxide is annealed in a wide temperature range from 60 to 700 °C. Furthermore, we investigate the influence of the oxide annealing temperature on the amount of crystal water, chemical composition, morphology, electrochemical recharging behavior, electrocatalytic activity and stability in the glucose oxidation carried out in an isotonic NaCl-based phosphate-buffered saline (pH 7.40). To solidly determine potentials of the irreversible cathodic dissolution of α-MnO2 as well as O2/Cl2 evolution on α-MnO2, a rotating ring-disk electrode is applied. For the most active α-MnO2 sample with the 100 μg cm−2geo loading the glucose oxidation current of ca. 40 μA cm−2geo after 1 h at +0.8 V (SCE) for 7 mM of glucose is achieved. The linear concentration dependence in a physiological glucose range (1–30 mM) with the sensitivity of ca. 17.8 μA mM−0.5 cm−2geo at 25 °C is observed. Finally, glucose selectivity of α-MnO2 in relation to fructose, galactose, xylose, ribose, urea, lactic acid, acetone, ascorbic acid and paracetamol is revealed.

Layered MnO2@PDA as cathode material toward high-performance aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) can benefit from a deep understanding of the electrochemical reaction mechanism of cathode materials, which can assist in resolving issues such as cathode dissolution and electrostatic interactions. We reported a straightforward two-step synthesis of polydopamine coated MnO2 (MnO2@PDA) and revealed the energy storage mechanisms in AZIBs. The layered structure of MnO2 creates a generous passage for the insertion of H+/Zn2+ ions. Simultaneously, the plethora of functional groups within PDA exerts a robust desolvation effect, bolstering the transfer rate of H+/Zn2+. This effect significantly enhances the overall efficiency and performance of cathode. The AZIBs, incorporating MnO2@PDA cathode material, consequently exhibit a satisfactory cycling capacity (412 mAh g−1 at 0.1 A g−1) and a superb specific energy (561.6 Wh kg−1 at 136.34 W kg−1). This work provides a new path for design strategies and catalytic mechanisms of MnO2@PDA cathode.

Reductive Dissolution of NCM Cathode through Anaerobic Respiration by Shewanella putrefaciens.

The consumption of lithium-ion batteries (LIBs) has considerably increased over the past decade, leading to a rapid increase in the number of spent LIBs. Exposing spent LIBs to the environment can cause serious environmental harm; however, there is a lack of experimentally obtained information regarding the environmental impacts of abandoned cathode materials. Here, we report the interactions between Shewanella putrefaciens, a microorganism commonly found in diverse low-oxygen natural settings, and LiNi0.6Co0.2Mn0.2O2 (NCM622) under anaerobic conditions. We present compelling evidence that the anaerobic respiration of Shewanella putrefaciens triggers ∼59 and ∼78% dissolution of 0.2 g/L pristine and spent NCM622, respectively. We observed that Shewanella putrefaciens interacted with the pristine and the spent NCM622 under anaerobic conditions at a neutral pH and room temperature and induced the reduction of Ni, Co, and Mn, resulting in the subsequent dissolution of Li, Ni, Co, and Mn. Moreover, we found that secondary mineralization occurred on the surface of reacted NCM622. These findings not only shed light on the substantial impact of microbial respiration on the fate of discarded cathode materials in anaerobic environments but also reveal the potential for sustainable bioleaching of cathodes in spent LIBs.

Synergistic Regulation of Anode and Cathode Interphases via an Alum Electrolyte Additive for High-Performance Aqueous Zinc-Vanadium Batteries.

A zinc (Zn) metal anode paired with a vanadium oxide (VOx) cathode is a promising system for aqueous Zn-ion batteries (AZIBs); however, side reactions proliferating on the Zn anode surface and the infinite dissolution of the VOx cathode destabilise the battery system. Here, we introduce a multi-functional additive into the ZnSO4 (ZS) electrolyte, KAl(SO4)2 (KASO), to synchronise the in situ construction of the protective layer on the surface of the Zn anode and the VOx cathode. Theoretical calculations and synchrotron radiation have verified that the high-valence Al3+ plays dual roles of competing with Zn2+ for solvation and forming a Zn-Al alloy layer with a homogeneous electric field on the anode surface to mitigate the side reactions and dendrite generation. The Al-containing cathode-electrolyte interface (CEI) considerably alleviates the irreversible dissolution of the VOx cathode and the accumulation of byproducts. Consequently, the Zn||Zn cell with KASO exhibits an ultra-long cycle of 6000 h at 2 mA cm-2. Importantly, the VOx cathodes (VO2, V2O5 and NH4V4O10) in the ZS-KASO electrolyte showed excellent cycling stability, including Zn powder||VO2 cells and Zn||VO2 pouch cells. Even better, the full cell exhibits excellent cycling stability at low negative/positive (N/P) ratio of 2.83 and high mass loading (~16 mg cm-2). This study offers a straightforward and practical reference for concurrently addressing challenges at the anode and cathode of AZIBs.

"Water-in-Salt" Electrolyte Suppressed MnVOPO4·2H2O Cathode Dissolution for Stable High-Voltage Platform and Cycling Performance for Aqueous Zinc Metal Battery.

Vanadium-based materials have the advantages of abundant valence states and stable structures, having great application potential as cathode materials in metal-ion batteries. However, their low voltage and vanadium dissolution in traditional water-based electrolytes greatly limit their application and development in aqueous zinc metal batteries (AZMBs). Herein, phosphate- and vanadium-based cathode materials (MnVOPO4·2H2O) with stacked layers and few defects were prepared via a condensation reflux method and then combined with a high-concentration electrolyte (21 m LiTFSI + 1 M Zn(CF3SO3)2) to address these limitations. The specific capacity and cycle stability accompanying the stable high voltage of 1.39 V were significantly enhanced compared with those for the traditional electrolyte of 3 M Zn(CF3SO3)2, benefiting from the suppressed vanadium dissolution. The cathode materials of MnVOPO4·2H2O achieved a high specific capacity of 152 mAh g-1 at 0.2 A g-1, with a retention rate of 86% after 100 cycles for AZMBs. A high energy density of 211.78 Wh kg-1 was also achieved. This strategy could illuminate the significance of electrolyte modification and provide potential high-voltage cathode materials for AZMBs and other rechargeable batteries.

A Dynamically Ion-Sieved Electrolyte towards Ultralong-Lifespan Zn-Ion Batteries.

The practical deployment of Zn-ion batteries faces challenges such as dendrite growth, side reactions and cathode dissolution in traditional electrolytes. Here, we develop a highly conductive and dynamically ion-sieved electrolyte to simultaneously enhance the Zn metal reversibility and suppress the cathode dissolution. The dynamic ion screen at the electrode/electrolyte interface is achieved by numerous pyrane rings with a radius of 3.69 Å, which can selectively facilitate the plating/stripping and insertion/extraction process of [Zn(H2O)6]2+ and Zn2+ on the anode and cathode surfaces. As a proof of concept, Zn//Zn symmetric cells deliver exceptional cyclic stability for over 6,800 h and ultrahigh cumulative plated capacity of 3.9 Ah cm-2. Zn//Na2Mn3O7 cells exhibit satisfactory cycling performance with capacity retention of 82.7% after 4,000 cycles, and the assembled pouch cells achieve excellent stability and durability. This work provides valuable insights into the development of electrolytes aimed at enhancing the interface stability of aqueous batteries.

Simultaneous Inhibition of Vanadium Dissolution and Zinc Dendrites by Mineral‐Derived Solid‐State Electrolyte for High‐Performance Zinc Metal Batteries

Designing solid electrolyte is deemed as an effective approach to suppress the side reaction of zinc anode and active material dissolution of cathodes in liquid electrolytes for zinc metal batteries (ZMBs). Herein, kaolin is comprehensively investigated as raw material to prepare solid electrolyte (KL‐Zn) for ZMBs. As demonstrated, KL‐Zn electrolyte is an excellent electronic insulator and zinc ionic conductor, which presents wide voltage window of 2.73 V, high ionic conductivity of 5.08 mS cm‐1, and high Zn2+ transference number of 0.79. For the Zn//Zn cells, superior cyclic stability lasting for 2200 h can be achieved at 0.2 mA cm‐2. For the Zn//NH4V4O10 batteries, stable capacity of 245.8 mAh g‐1 can be maintained at 0.2 A g‐1 after 200 cycles along with high retention ratio of 81%, manifesting KL‐Zn electrolyte contributes to stabilize the crystal structure of NH4V4O10 cathode. These satisfying performances can be attributed to the enlarged interlayer spacing, zinc (de)solvation‐free mechanism and fast diffusion kinetics of KL‐Zn electrolyte, availably guaranteeing uniform zinc deposition for zinc anode and reversible zinc (de)intercalation for NH4V4O10 cathode. Additionally, this work also verifies the application possibility of KL‐Zn electrolyte for Zn//MnO2 batteries and Zn//I2 batteries, suggesting the universality of mineral‐based solid electrolyte.

Simultaneous Inhibition of Vanadium Dissolution and Zinc Dendrites by Mineral-Derived Solid-State Electrolyte for High-Performance Zinc Metal Batteries.

Designing solid electrolyte is deemed as an effective approach to suppress the side reaction of zinc anode and active material dissolution of cathodes in liquid electrolytes for zinc metal batteries (ZMBs). Herein, kaolin is comprehensively investigated as raw material to prepare solid electrolyte (KL-Zn) for ZMBs. As demonstrated, KL-Zn electrolyte is an excellent electronic insulator and zinc ionic conductor, which presents wide voltage window of 2.73 V, high ionic conductivity of 5.08 mS cm-1, and high Zn2+ transference number of 0.79. For the Zn//Zn cells, superior cyclic stability lasting for 2200 h can be achieved at 0.2 mA cm-2. For the Zn//NH4V4O10 batteries, stable capacity of 245.8 mAh g-1 can be maintained at 0.2 A g-1 after 200 cycles along with high retention ratio of 81%, manifesting KL-Zn electrolyte contributes to stabilize the crystal structure of NH4V4O10 cathode. These satisfying performances can be attributed to the enlarged interlayer spacing, zinc (de)solvation-free mechanism and fast diffusion kinetics of KL-Zn electrolyte, availably guaranteeing uniform zinc deposition for zinc anode and reversible zinc (de)intercalation for NH4V4O10 cathode. Additionally, this work also verifies the application possibility of KL-Zn electrolyte for Zn//MnO2 batteries and Zn//I2 batteries, suggesting the universality of mineral-based solid electrolyte.

PH Dependence of Noble Metals Dissolution: Gold

AbstractThe electrochemical applications of gold span the entire pH spectrum. Recently, gold dissolution in acidic and alkaline media has been studied, but less attention has been given to electrolytes at intermediate pH values. To address this gap, this work uses on‐line electrochemical dissolution inductively coupled plasma mass spectrometry (ICP‐MS) to examine gold dissolution across a pH range of 1 to 12.7 using phosphate buffer solutions. All experimental parameters, except pH, are kept constant, enabling a clear investigation of pH effects on anodic (gold oxidation) and cathodic (gold oxide reduction) dissolution processes. Results show that dissolution amounts are lowest at neutral pH values between 3 and 7, varying with the applied potential and exposure time. Anodic and cathodic dissolution dominate in acidic and alkaline electrolytes, respectively. Depending on the highest applied potentials and time exposure, the main dissolution mechanism shifts at pH=5, 7, and 9. The pH dependence of Au dissolution is proposed to be linked to the nature of gold oxides formed, the kinetics of oxide formation/reduction, gold ion redeposition, and the influence of the oxygen evolution reaction (OER) on dissolution. These results provide fundamental insights into gold dissolution under neutral pH conditions.

Dual Functional Propylene Carbonate Co-Solvent for High Performance Aqueous Zinc-Ion Batteries

In response to the global rise in energy demand, extensive research has spurred the development of batteries with high energy density, affordable cost, and safety. The present Li-ion batteries are attractive due to their high energy density, but their cost and geopolitical accessibility of raw materials, along with safety-related issues, have led researchers to shift their attention towards aqueous batteries.1,2 In aqueous systems, zinc metal has been regarded as the most promising candidate due to its high specific capacity, low redox potential of Zn-metal, environmental friendliness, and low cost. However, challenges such as the dendritic growth of zinc, hydrogen evolution, corrosion, structural degradation and dissolution of oxide cathodes, and poor coulombic efficiencies (CEs) limit their scope. To address these issues, various studies demonstrate the usage of organic co-solvents and additives such as DMSO3, DMC4, etc. at different concentrations in the electrolytes. However, the overall efficiency of the battery performance is hindered due to the large amount requirements of these additives.Along this line, we have studied the electrochemical properties of a hybrid water-highly polar propylene carbonate-based electrolyte, which suppresses water-derived parasitic reactions occurring at both the Zn anode and the V2O5 cathode.5 We have observed a significant enhancement in the battery characteristics, such as high coulombic efficiency and stable capacity, merely by tuning the solvation structure of the electrolyte. Upon a small addition of PC (20 wt.%) in 1M Zn(OTf)2 electrolyte, water molecules solvating Zn2+ ions are replaced by carbonate and triflate anions. The solvated Zn-ion species were further electrochemically reduced to form a ZnF2-rich solid electrolyte interphase (SEI), as demonstrated by post-cycling XPS studies. Moreover, the spectroscopy studies suggest the strong interaction of highly basic carbonyl oxygen of PC with water molecules, which in turn suppresses the dissolution of the cathode, enabling exceptional capacities of ∼300 mAh g−1 over 900 cycles at 1 A g−1. We further demonstrate the significance of the dielectric constant and polarity of an additive or cosolvent in the aqueous zinc ion battery electrolyte by contrasting the performance of cyclic propylene carbonate with acyclic dimethyl carbonate.Reference O. Schmidt, A. Hawkes, A. Gambhir, and I. Staffell, Nature Energy, 2, 1–8 (2017)M. M. Thackeray, C. Wolverton, and E. D. Isaacs, Energy Environ. Sci., 5, 7854–7863 (2012)L. Cao ,D. Li, E. Hu, J. Xu, T. Deng, L. Ma, Y. Wang, X. Q. Yang, and C. Wang, J. Am. Chem. Soc., 142, 21404–21409 (2020)Y. Dong, L. Miao, G. Ma, S. Di, Y. Wang, L. Wang, J. Xua, and N. Zhang, Chem. Sci., 12, 5843–5852 (2021)B. Kakoty, R. Vengarathody, S. Mukherji, V. Ahuja, A. Joseph, C. Narayana, S. Balasubramanian, and P. Senguttuvan, J. Mater. Chem. A, 10, 12597–12607 (2022)

A Self‐Assembled Hybrid Electrode with Efficient Tandem Electrochemistry for Dissolution‐Shielding, Ultrafast‐Charging, and Record‐Lifespan Zinc‐Ion Batteries

AbstractThe design of electrode compatible with wide‐temperature, fast‐charging, and long‐lifespan aqueous zinc‐ion batteries is a great challenge that urgently needs addressing. However, the mismatch between runaway host dissolution and high interfacial hydrophilicity within electrode is a contradictory problem that restricts their electrochemical performance. In this report, take the typical vanadium diselendie (VSe2) host for example, by employing the natural polymer bacterial cellulose (BC) as the multifunctional mediator, a design paradigm of self‐assembly hybrid electrode with efficient tandem electrochemistry is presented. Theoretical and experimental research confirmed that such BC‐mediated hybrid structure exhibits multiple functions to well balance the cathode dissolution and storage kinetics. Impressively, such an electrode displayed an excellent rate capability (1–50 A g−1), and an unexpected record‐lifespan of 45 000 cycles. Beyond that, it also shows a good temperature‐tolerance ability, remaining the high specific capacities of 120 and 288 mAh g−1 (at 10 A g−1) after 3000 cycles at −25 and 50 °C, respectively. Note that such approach is also applicable to the high‐voltage platform MnO2 and I2 hosts, demonstrating its potential for universality. This discovery can provide a new design principle of robust electrode for advanced aqueous zinc‐ion batteries.

Boosting anion-cation coordination by anti-solvents towards durable hydrous organic zinc batteries

Hydrated fluoroborates offer excellent nonflammability and their spontaneous hydrolysis can generate a ZnF2-based solid electrolyte interphase (SEI) on Zn anodes in hydrous organic Zn batteries. However, uncontrolled hydrolysis can lead to thick and uneven SEI, as well as cathode collapse. Here, we propose using anti-solvents to regulate the hydrolysis of fluoroborate anions via facilitating anion-cation coordination, resulting in a thin but compact ZnF2 SEI. Consequently, Zn anodes maintain stable cycling for over 1400 h at 1 mA cm−2, a high Coulombic efficiency (CE) of 99.4 % and high-rate capability up to 15 mA cm−2. Even at a challenging temperature of 60 °C, the Zn anode demonstrates over 1000 h of stable cycling with a CE of 98.0 %. Furthermore, the modified electrolyte alleviates V2O5 cathode dissolution, enabling extended cycling lifespan with a high CE close to 100 % in Zn||V2O5 full cells at room and high temperatures. Our findings suggest an avenue toward electrolyte design for developing high-performance Zn batteries and beyond.

Capacity Fade of Graphite/NMC811: Influence of Particle Morphology, Electrolyte, and Charge Voltage

LiNi0.8Mn0.1Co0.1O2 (NMC811) is an important Li-ion battery cathode material; however, there is a tradeoff between delivered capacity and capacity retention. As the charge potential increases the capacity rises but at the expense of capacity retention. The decrease in capacity retention has been ascribed to several factors including particle cracking, surface reconstruction, transition metal dissolution, and electrolyte reactivity. The present study compares 4.1 and 4.3 V charging limits in commercially relevant graphite/NMC811 pouch cells for single crystal (SC) and polycrystalline (PC) NMC811 with ethylene carbonate (EC)-containing or EC-free electrolytes. The electrochemistry is rationalized through analysis of electrochemical impedance spectroscopy, positive electrode X-ray photoelectron spectroscopy, soft X-ray absorption spectroscopy, X-ray diffraction, and negative electrode mapping by X-ray fluorescence. Graphite/SC-NMC811 cells show high-capacity retention at 4.1 V but exhibit degradation at 4.3 V charging potentials. The EC-free electrolyte cells led to higher capacity fade, especially when charged to 4.3 V. Cathode dissolution and deposition on the negative electrode from PC-NMC811 cells was higher than for samples from SC-NMC811 cells. This study reveals the impact of material type, charge voltage, and electrolyte composition on the reactions at the positive electrode, their influence on the negative electrode, and evolution with cycle number.

PH dependence of noble metals dissolution: Platinum

Obtaining new information about the dissolution behavior of platinum in different pH conditions can help understand the stability of this metal in a wide variety of electrochemical devices. In this work, Pt dissolution is investigated in a pH range from 0 to 12.7 applying on-line inductively coupled plasma mass spectrometry (ICP-MS) with phosphate buffer solutions in an electrochemical scanning flow cell (SFC). Various electrochemical protocols are employed, including slow cyclic voltammetries at 5 mV s-1 and potential steps up to 1.2 and 1.6 VRHE. Results for total Pt dissolution show an inverted volcano dependence with pH in all cases, with the minimum dissolution located at pH = 7. Dissolution for pH = 0 is considerably higher than for pH = 1. In the case of the cyclic voltammetry experiments, the changes in dissolution are mainly due to the cathodic dissolution contribution. Interestingly, when phosphoric acid is used for the electrolyte with pH = 1, cathodic dissolution is higher than for the perchloric acid case. When comparing a slow reductive ramp to a direct potential jump after holding the electrode at oxidative potential, the results point out that dissolution is much higher for the slow reductive ramp in the case of acidic pH values. The results presented in this work can help improve the fundamental understanding of Pt dissolution since it is the first time such an exhaustive pH study has been carried out for on-line potential resolved experiments.

Constructing Gradient Separator to Stabilize Bi‐electrodes Toward High‐Performance Zn Metal Batteries

AbstractAqueous zinc (Zn) metal batteries have considerable potential as large‐scale energy storage systems. However, cathodic metal ions dissolution and anodic dendrite growth constrain their further development. Here, an ion gradient separator is proposed to stabilize the bi‐electrodes of Zn metal batteries. The results show that the constructed low Zn2+ concentration region in the separator helps the NH4V4O10 (NVO) model cathode to maintain good electrolyte wettability and form a N/ZnS/ZnF2‐rich cathode‐electrolyte interphase (CEI), exhibiting a low vanadium (V) dissolution behavior. Meanwhile, the high Zn2+ concentration region in the separator and the flexible solid electrolyte interphase (SEI) inhibit the dendrite growth and parasitic reactions of the Zn metal anode and further prevent the diffusion of V ions. As a proof‐of‐concept, the NVO||Zn battery with gradient separator can achieve 88.1% capacity retention even after cycling over 800 cycles at 1 A g−1, while the ordinary separator only maintains 14.8%. This work presents an innovative gradient separator strategy for achieving high‐performance Zn metal batteries and sheds light on other rechargeable batteries.

Model-based electrolyte design for near-neutral aqueous zinc batteries with manganese-oxide cathodes

Most modern zinc-ion batteries (ZIBs) with MnO2 cathodes utilize near-neutral aqueous electrolytes based on a zinc sulfate (ZnSO4) salt. They achieve good cycling stabilities with high intrinsic safety, employ environmentally friendly materials, and deliver competitive volumetric energy densities. However, the limited solubility of zinc-sulfate species influences the performance and cycling mechanism of these cells. We examine the speciation and solubility limits of ZnSO4, zinc chloride (ZnCl2), and zinc triflate (Zn(CF3SO3)2) in aqueous solutions and simulate their intrinsic transport properties. We use our earlier developed and validated full-cell model to investigate the effects of several electrolytes on the two-phase cycling behavior. Previously, we reported that the origin of the second phase is based on an interaction mechanism between cathodic dissolution and a precipitation reaction at the cathode. We investigate this interplay between electrolyte stability and cathodic dissolution based on electrolyte choice. Our theory-based approach allows us to identify performance indicators of aqueous electrolytes and draws a consistent pathway to optimize electrolyte design for manganese-based ZIBs.

Lattice modulation improving surface passivation of LiMnPO4 for stable cycling at high temperatures

The undesirable capacity degradation of LiMnPO4 upon cycling at high temperatures is a challenge to its practical application. Herein, a lattice doping strategy is adopted to improve the high-temperature cycling stability of LiMnPO4, and the comparative study reveals that Al3+ doping into LiMnPO4 in a form of Li0.98Al0.02MnPO4 is highly beneficial to the cycling performance of LiMnPO4 and the capacity retention can be significantly improved from 67.4 % to 93.4 % after 100 cycles at 1C at 60 °C, because Al3+ doping can effectively reduce passivation products deposition on the cathode and manganese dissolution in the electrolyte, which thus improve the cathode/electrolyte interface and stabilize the structure of LiMnPO4 at high temperatures.