Prevent Dendrite Formation Research Articles

Study of the Lithium/Polymer Interface and Conductive Deposits on Lithium Metal Used for Lithium Metal Polymer Batteries.

Lithium metal anode has recently regained tremendous attention in the frame of the development of higher power and energy density lithium batteries for automotive industry. Lithium metal is indeed an ideal anode for lithium batteries due to its high capacity (3860 mAh/g). However, upon high discharge currents, the growth of dendrites leads to cell short cuts and limited coulombic efficiency.This issue had first restrained its practical application in rechargeable batteries for high power applications until the use of solid polymer electrolytes that could mechanically prevent the dendrites from crossing the electrolyte. Among the different families of polymer electrolytes, polyethylene oxide-based (PEO-based) electrolytes have been established as the reference thanks to a reasonable conductivity above 60oC and its ability to form a stable solid electrolyte interphase (SEI) with lithium. Nevertheless, due to the low transference number of POE/LiTFSI electrolytes (t+≈0.15), dendrites or uneven lithium plating are still susceptible to form. Nowadays, many efforts are dedicated to solve these problems by focusing either on the improvement of the electrolyte or on the modification of the lithium-electrolyte interface. Gold layers have been proposed as an alternative to prevent dendrite formation; these gold coatings are used mainly together with ceramic electrolytes in order to improve the interface between Li metal anode and electrolyte. However, their use with polymer electrolytes where dendrite formation is favorable due to low transference number and mechanical strength have not being widely studied. In this presentation, three different coatings will be considered; aluminum (Al), gold (Au) and lithium fluoride (LiF). The choice of Al and Au is based on their ability to form Li-rich alloys while LiF is known to act as an artificial ion conducting SEI. The morphology and physico-chemical properties of the coatings are first characterized by Atomic Force Microscopy (AFM), X-Ray Diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) before evaluation of the interface between POE-based electrolyte and coated Lithium. Eventually stability during long-term cycling in Lithium Metal Polymer batteries is performed and compared to that of cells made using bare Lithium.

Universal chemomechanical design rules for solid-ion conductors to prevent dendrite formation in lithium metal batteries.

Dendrite formation during electrodeposition while charging lithium metal batteries compromises their safety. Although high-shear-modulus (Gs) solid-ion conductors (SICs) have been prioritized to resolve the pressure-driven instabilities that lead to dendrite propagation and cell shorting, it is unclear whether these or alternatives are needed to guide uniform lithium electrodeposition, which is intrinsically density-driven. Here, we show that SICs can be designed within a universal chemomechanical paradigm to access either pressure-driven dendrite-blocking or density-driven dendrite-suppressing properties, but not both. This dichotomy reflects the competing influence of the SIC's mechanical properties and the partial molar volume of Li+ ([Formula: see text]) relative to those of the lithium anode (GLi and VLi) on plating outcomes. Within this paradigm, we explore SICs in a previously unrecognized dendrite-suppressing regime that are concomitantly 'soft', as is typical of polymer electrolytes, but feature an atypically low [Formula: see text] that is more reminiscent of 'hard' ceramics. Li plating (1 mA cm-2; T = 20 °C) mediated by these SICs is uniform, as revealed using synchrotron hard X-ray microtomography. As a result, cell cycle life is extended, even when assembled with thin Li anodes (~30 µm) and either high-voltage NMC-622 cathodes (1.44 mAh cm-2) or high-capacity sulfur cathodes (3.02 mAh cm-2).

Metal‐Organic Framework Integrated Anodes for Aqueous Zinc‐Ion Batteries

AbstractZinc‐based batteries have a high capacity and are safe, cost‐effective, environmentally‐friendly, and capable of scalable production. However, dendrite formation and poor reversibility hinder their performance. Metal‐organic framework (MOF)‐based Zn anodes are made by wet chemistry to address these issues. These MOF‐based anodes exhibit high efficiency during Zn plating‐stripping and prevent dendrite formation, as shown by ex situ SEM analysis. The practicality of the MOF‐based anodes is demonstrated in aqueous Zn ion batteries, which show improved performance including specific capacity, cycle life, and safety relative to the pristine Zn anode due to their hydrophilic and porous surface. These results, along with the easy scalability of the process, demonstrate the high potential of MOF‐modified Zn anodes for use in dendrite‐free, higher‐performance, Zn‐based energy storage systems.

A Sodiophilic Interphase‐Mediated, Dendrite‐Free Anode with Ultrahigh Specific Capacity for Sodium‐Metal Batteries

Despite efforts to stabilize sodium metal anodes and prevent dendrite formation, achieving long cycle life with high areal capacities remains difficult owing to a combination of complex failure modes that involve retardant uneven sodium nucleation and subsequent dendrite formation. Now, a sodiophilic interphase based on oxygen-functionalized carbon nanotube networks is presented, which concurrently facilitates a homogeneous sodium nucleation and a dendrite-free, lateral growth behavior upon recurring sodium plating/stripping processes. This sodiophilic interphase renders sodium anodes with an ultrahigh capacity of 1078 mAh g-1 (areal capacity of 10 mAh cm-2 ), approaching the theoretical capacity of 1166 mAh g-1 of pure sodium, as well as a long cycle life up to 3000 cycles. Implementation of this anode allows for the construction of a sodium-air battery with largely enhanced cycling performance owing to the oxygen functionalization-mediated, dendrite-free sodium morphology.

A Sodiophilic Interphase‐Mediated, Dendrite‐Free Anode with Ultrahigh Specific Capacity for Sodium‐Metal Batteries

AbstractDespite efforts to stabilize sodium metal anodes and prevent dendrite formation, achieving long cycle life with high areal capacities remains difficult owing to a combination of complex failure modes that involve retardant uneven sodium nucleation and subsequent dendrite formation. Now, a sodiophilic interphase based on oxygen‐functionalized carbon nanotube networks is presented, which concurrently facilitates a homogeneous sodium nucleation and a dendrite‐free, lateral growth behavior upon recurring sodium plating/stripping processes. This sodiophilic interphase renders sodium anodes with an ultrahigh capacity of 1078 mAh g−1 (areal capacity of 10 mAh cm−2), approaching the theoretical capacity of 1166 mAh g−1 of pure sodium, as well as a long cycle life up to 3000 cycles. Implementation of this anode allows for the construction of a sodium–air battery with largely enhanced cycling performance owing to the oxygen functionalization‐mediated, dendrite‐free sodium morphology.

Effect of Sodium Fluoride and Sodium Lignosulphonate Additives on Performance of the Soluble Lead Redox Flow Battery

Soluble lead redox flow battery (SLRFB) is a flow battery with a common electrolyte and can be developed in undivided, divided and semi-divided configurations [1]. At present, the development of SLRFB is hindered mainly due to (i) the formation of lead dendrites at anode, (ii) oxygen evolution reaction (OER) at cathode and (iii) accumulation of PbO2 due to poor electrode kinetics [2]. In an earlier study, we have reported a study on extending the cycle-life of SLRFB using an auxiliary electrode concept [3]. In the present study, we report the independent and combined effects of adding sodium lignosulfonate (SLS) and sodium fluoride (NaF) to the electrolyte as anode and cathode benefitting additives, respectively. The study reveals that adding 4.2 gm/L NaF alone improves the kinetics of both electrode reactions as compared to that with no additive but fails to prevent dendrite formation. Adding 1 gm/L SLS alone has beneficial effect on anode by preventing dendrite formation but the concentration of SLS gradually decreases with the cycling of the battery. The combined effect of adding SLS and NaF depends on the concentration of SLS. It is observed that adding low concentration of SLS 0.2 gm/L along with 4.2 gm/L NaF has beneficial effect on both the anode and cathode reactions and hence maintaining this concentration would help extending the cycle-life of SLRFB. The individual as well as combined effects of these additives on the reaction products is studied by quasi in situ XRD and FESEM techniques. The effect on electrode kinetics and cycle life are also reported.

Self-smoothing anode for achieving high-energy lithium metal batteries under realistic conditions.

Despite considerable efforts to stabilize lithium metal anode structures and prevent dendrite formation, achieving long cycling life in high-energy batteries under realistic conditions remains extremely difficult due to a combination of complex failure modes that involve accelerated anode degradation and the depletion of electrolyte and lithium metal. Here we report a self-smoothing lithium-carbon anode structure based on mesoporous carbon nanofibres, which, coupled with a lithium nickel-manganese-cobalt oxide cathode with a high nickel content, can lead to a cell-level energy density of 350-380 Wh kg-1 (counting all the active and inactive components) and a stable cycling life up to 200 cycles. These performances are achieved under the realistic conditions required for practical high-energy rechargeable lithium metal batteries: cathode loading ≥4.0 mAh cm-2, negative to positive electrode capacity ratio ≤2 and electrolyte weight to cathode capacity ratio ≤3 g Ah-1. The high stability of our anode is due to the amine functionalization and the mesoporous carbon structures that favour smooth lithium deposition.

The surface-modified effects of Zn anode with CuO in Zn-air batteries

Copper oxide nanoparticles (CuO-NPs) can be used to prevent dendrite formation and increase the reversibility of Zn anode. The zinc surface was modified with CuO and the Cu source used was copper nitrate. It also contained 0.1 wt%, 0.5 wt%, 1.0 wt%, and 3.0 wt% CuO by weight of zinc. The morphologies of the Zn surfaces modified by CuO-NPs were observed by scanning electron microscopy (SEM). The structures of the surface-modified and bare zinc powders showed that the modification did not affect the crystal structure, but Cu 2p details from XPS were detected in the form of a satellite peak of CuO. SEM images of CuO modified on the zinc particles revealed homogeneous modification on the Zn surface. The use of an appropriate CuO particle can prevent direct contact with Zn and KOH electrolyte, and minimize side reactions within the batteries. In a DC-cycling test, the 0.1 wt% CuO-modified Zn anode powder provided the best cycle performance up to 24 h. A surface-modified zinc electrode can increase reversibility and reduce self-discharge with electrochemical stability. The results suggest that surface modification is effective for improving the comprehensive properties of Zn anode materials for Zn-air batteries.

(Invited) Improvements in High Energy Density Silver-Zinc Button Cells for Wearable Devices

The silver (Ag)-zinc (Zn) system has the highest theoretical specific (Wh/kg) and volumetric energy density (Wh/L) amongst all rechargeable batteries with the added benefit of safety and non-flammability compared to lithium-ion or lithium metal batteries, which makes it a good and ideal candidate for portable applications like hearing-aids. However, historically, the Ag-Zn battery has suffered from poor rechargeability and low energy utilization. At ZPower, we have tailored the chemistry and engineered a new Ag-Zn battery system, which is highly energy dense and rechargeable, thus making it possible to use it portable applications and giving more power to the consumer to allow them to contribute to a greener future. As aforementioned, enhancing the capacity of the active materials is paramount for high energy density, which we achieved by developing proprietary additives and methods. For the cathode, silver oxide (AgO) was used in our system. We developed novel proprietary conductive coatings for AgO, which allowed high capacity utilization and retention for many cycles. We conducted gassing tests, where we found the coatings considerably reduced oxygen generation. The role of these coatings was further studied through charge algorithm cycling, where we found that it reduced AgO cathode’s impedance compared to the control tests and maintained its active surface area. More importantly, we found that the morphology of the proprietary conductive coatings played a crucial role in efficiently utilizing the AgO cathode’s capacity. For the anode, Zn was used, where it has a theoretical specific capacity of 820 mAh/g; however, Zn has a long history of poor rechargeability due to problems like shape change (zinc redistribution), dendrite formation and passivation. In the past, previous researchers tried altering the Zn formulation to increase utilization; however, these attempts were not fruitful. We have engineered a new Zn anode that can access 94% of its theoretical capacity in a single primary discharge and 56% of its theoretical capacity rechargeably for over 300 cycles. We achieved this breakthrough by developing proprietary additives and methods that localize the Zn to the current collector and prevent dendrite formation. We will comment on the anode performance further in the talk. Finally, we will present impedance models and data of the ZPower Ag-Zn system measured with respect to state of charge, storage time and temperature, which is vital from a manufacturing standpoint to understand cell properties and make future cell and electrode improvements. We will comment on our future work of identifying impedance contribution from the cathode and anode components of the battery and using this data as a guideline for improving electrode composition and cell performance.

Advantages of ZrO2 Composite Protection Coating on Lithium Metal Anode in Lithium Metal Battery

Lithium metal anode was regarded as holy grail due to its high theoretical capacity (3860 mAh /g) and lowest electrochemical potentials (–3.04 V vs SHE). However, the dendrite formation induces safety hazard and decomposition of liquid electrolyte, resulting in low Coulombic efficiency and short cycle life. Recently, many studies have studied approaches to suppress dendrite growth by stable SEI layer, optimization of solvents, salts, electrolyte additives, and protection layer. The protection layer was well known method to prevent dendrite growth and improve cycle stability. Here we fabricate composite protection coating on lithium metal anode to prevent dendrite formation and prevent salt dissociation. This protection layer has high ionic conductivity and superior mechanical properties. The protection layer successfully suppresses dendrite formation and improves coulombic efficiency. In this study we show potential of achieving highly safe lithium metal anode.

Surface Modification of Porous Foam Electrodes: Stabilization of Solid Electrolyte Interphase Formation in Li-Metal Batteries

The formation of the solid electrolyte interphase (SEI) is critical to stabilization of lithium metal electrodes.1,2 When the electrodes contact electrolyte, a thin solid layer is immediately deposited on the surface. Ideally, this layer should be electronically insulating, while conducting Li-ions, and only a few nanometers thick to ensure that lithium can diffuse to the electrode surface without the reduction of any electrolyte components.2 Unfortunately, much research has shown that even after initial formation, the SEI layer continues to grow, and eventually leads to cell failure by limiting the ability of lithium to diffuse to the electrode surface.3,4 In order make electrodes practical for use in lithium metal batteries, the growth of the SEI needs to be well controlled and limited in thickness. Previous work has shown that the use of high surface area porous metal anodes can prevent dendrite formation, another key barrier to commercialization of lithium metal batteries.5 However, as the number of cycles increases and the SEI layer on the electrode grows too thick, the pore network fills and lithium diffusion is limited, and plating subsequently reverts to unwanted dendritic growth. In this work, a method for improving the cycling stability of these porous foam electrodes by controlling the SEI is examined. Accordingly, the work focuses on the utilization of novel surface additives to achieve this goal. The approach has shown to greatly increase the number of achievable cycles. The engineered systems already show ~99% efficiency over 100 cycles, far better than the 70 cycles at ~95% efficiency previously obtained using unmodified foams. By controlling the initial SEI formation and limiting its thickness, saturation of the pore network can be inhibited, thus extending the stable cycling window. Acknowledgements: The authors acknowledge the financial support of DOE grant DE-EE 0007797, Edward R. Weidlein Chair Professorship funds, and the Center for Complex Engineered Multifunctional Materials (CCEMM). References Aurbach, E. Zinigrad, Y. Cohen, H. Teller, Solid State Ionics, 148, 405-416 (2002).Peled, S. Menkin, J. Electrochem. Soc., 164 (7), A1703-1719 (2017).Zheng, S. W. Lee, Z. Liang, H. Lee, K. Yan, H. Yao, H. Wang, W. Li, S. Chu, and Y. Cui, Nature Nanotech. 9, 618-623 (2014)Vetter et al., Journal of Power Sources 147, 269–281 (2005) A. Day, P. Jampani, P. M. Shanthi, B. Gattu, P. N. Kumta. ECS 232, National Harbor Maryland (2017).

Healing away the dendrites

Batteries The formation of lithium dendrites during charge-discharge cycles limits the development of lithium metal batteries, because the dendrites can cause electrical shorting of the cells. A number of tricks have been used to try to prevent dendrite formation. Li et al. took the opposite approach (see the Perspective by Mukhopadhyay and Jangid). They operated their cells at higher current densities, under which one would expect dendrites to form owing to the higher nucleation rates. However, under these conditions, the dendrites that started to form heated up and annealed, leading to their disappearance. Science , this issue p. [1513][1]; see also p. [1463][2] [1]: /lookup/doi/10.1126/science.aap8787 [2]: /lookup/doi/10.1126/science.aat2452

Effect of Material Anisotropy on the Mechanical Response of Protective Layers for Lithium Metal Anodes

A critical challenge in the development of safe, long-lasting secondary batteries with lithium metal anodes is protecting the surface of the anode to prevent dendrite formation during charging1 or to minimize interactions between the anode and active species in the electrolyte.2,3 One approach is to place a protective layer in the cell, such as a coating on the anode itself or as a free-standing membrane material, which can inhibit many of the mechanisms that lead to failure of the lithium metal anode. These layers must be mechanically robust such that they do not fail over the course of many cycles. However, these materials experience stress during cycling, which can lead to mechanical failure at high current densities. While such phenomena have been examined in certain cathode materials, such as LiCoO2,4 it has yet to be investigated in depth for anode protective layers. The stress arises from gradients in the lithium concentration that lead to the formation of eigenstrains. Here, we present a continuum-scale model to examine the effect of anisotropy in mechanical and transport properties on eigenstrains in protective layer materials. The model solves for the mechanical equilibrium of the layer, with the anisotropic linear elasticity tensor as well as the concentration-dependent anisotropic eigenstrain in the material based on the steady-state concentration profile. The von Mises stress is calculated as a function of the anisotropic properties and applied current. This stress can be compared to the yield stress of the protective layer material to determine whether it is sufficiently robust for many charge/discharge cycles of the lithium metal anode. The presented work will cover a range of cases from single-crystal domains to polycrystalline films with varying levels of anisotropy. By examining the peak von Mises stress as a function of the applied current density, the model will predict design guidelines for the relevant material parameters.

Modelling the Polymer Electrolyte/Li-Metal Interface by Molecular Dynamics simulations

Solid polymer electrolytes are considered promising candidates for application in Li-metal batteries due to their comparatively high mechanical strength, which can prevent dendrite formation. In this study, we have performed Molecular Dynamics simulations to investigate structural and dynamical properties of a common polymer electrolyte, poly(ethylene oxide) (PEO) doped with LiTFSI salt in the presence of a Li metal surface. Both a physical (solid wall) and a chemical (slab) model of the Li (100) surface have been applied, and the results are also compared with a model of the bulk electrolyte. The average coordination numbers for oxygen atoms around the Li ions are ca. 6 for all investigated systems. However, the calculated Radial Distribution Functions (RDFs) for Li+-OPEO and Li+-OTFSI show sharper peaks for the Li slab model, indicating a more well-defined coordination sphere for Li+ in this system. This is clearly a surface effect, since the RDF for Li+ in the interface region exhibits sharper peaks than in the bulk region of the same system. The simulations also display a high accumulation of TFSI anions and Li+ cations close to interface regions. This also leads to slower dynamics of the ionic transport in the systems, which have a Li-metal surface present, as seen from the calculated mean-square-displacement functions. The accumulation of ions close to the surface is thus likely to induce a polarization close to the electrode.

Stabilizing lithium metal using ionic liquids for long-lived batteries

Suppressing dendrite formation at lithium metal anodes during cycling is critical for the implementation of future lithium metal-based battery technology. Here we report that it can be achieved via the facile process of immersing the electrodes in ionic liquid electrolytes for a period of time before battery assembly. This creates a durable and lithium ion-permeable solid–electrolyte interphase that allows safe charge–discharge cycling of commercially applicable Li|electrolyte|LiFePO4 batteries for 1,000 cycles with Coulombic efficiencies >99.5%. The tailored solid–electrolyte interphase is prepared using a variety of electrolytes based on the N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide room temperature ionic liquid containing lithium salts. The formation is both time- and lithium salt-dependant, showing dynamic morphology changes, which when optimized prevent dendrite formation and consumption of electrolyte during cycling. This work illustrates that a simple, effective and industrially applicable lithium metal pretreatment process results in a commercially viable cycle life for a lithium metal battery.

Improved Cycle Life and Stability of Lithium Metal Anodes through Ultrathin Atomic Layer Deposition Surface Treatments

Improving the cycle life and failure resistance of lithium metal anodes is critical for next-generation rechargeable batteries. Here, we show that treating Li metal foil electrodes with ultrathin (∼2 nm) Al2O3 layers using atomic layer deposition (ALD) without air exposure can prevent dendrite formation upon cycling at a current density of 1 mA/cm2. This has the effect of doubling the lifetime of the anode before failure both under galvanostatic deep discharge conditions and cyclic plating/stripping of symmetric Li–Li cells. The ALD treated electrodes can be cycled for 1259 cycles before failure occurs, which is attributed to improved electrode morphology resulting from homogeneous Li ion flux across the electrode/electrolyte interface.

In Situ Solid-State NMR Spectroscopy of Electrochemical Cells: Batteries, Supercapacitors, and Fuel Cells

Electrochemical cells, in the form of batteries (or supercapacitors) and fuel cells, are efficient devices for energy storage and conversion. These devices show considerable promise for use in portable and static devices to power electronics and various modes of transport and to produce and store electricity both locally and on the grid. For example, high power and energy density lithium-ion batteries are being developed for use in hybrid electric vehicles where they improve the efficiency of fuel use and help to reduce greenhouse gas emissions. To gain insight into the chemical reactions involving the multiple components (electrodes, electrolytes, interfaces) in the electrochemical cells and to determine how cells operate and how they fail, researchers ideally should employ techniques that allow real-time characterization of the behavior of the cells under operating conditions. This Account reviews the recent use of in situ solid-state NMR spectroscopy, a technique that probes local structure and dynamics, to study these devices. In situ NMR studies of lithium-ion batteries are performed on the entire battery, by using a coin cell design, a flat sealed plastic bag, or a cylindrical cell. The battery is placed inside the NMR coil, leads are connected to a potentiostat, and the NMR spectra are recorded as a function of state of charge. (7)Li is used for many of these experiments because of its high sensitivity, straightforward spectral interpretation, and relevance to these devices. For example, (7)Li spectroscopy was used to detect intermediates formed during electrochemical cycling such as LixC and LiySiz species in batteries with carbon and silicon anodes, respectively. It was also used to observe and quantify the formation and growth of metallic lithium microstructures, which can cause short circuits and battery failure. This approach can be utilized to identify conditions that promote dendrite formation and whether different electrolytes and additives can help prevent dendrite formation. The in situ method was also applied to monitor (by (11)B NMR) electrochemical double-layer formation in supercapacitors in real time. Though this method is useful, it comes with challenges. The separation of the contributions from the different cell components in the NMR spectra is not trivial because of overlapping resonances. In addition, orientation-dependent NMR interactions, including the spatial- and orientation-dependent bulk magnetic susceptibility (BMS) effects, can lead to resonance broadening. Efforts to understand and mitigate these BMS effects are discussed in this Account. The in situ NMR investigation of fuel cells initially focused on the surface electrochemistry at the electrodes and the electrochemical oxidation of methanol and CO to CO2 on the Pt cathode. On the basis of the (13)C and (195)Pt NMR spectra of the adsorbates and electrodes, CO adsorbed on Pt and other reaction intermediates and complete oxidation products were detected and their mode of binding to the electrodes investigated. Appropriate design and engineering of the NMR hardware has allowed researchers to integrate intact direct methanol fuel cells into NMR probes. Chemical transformations of the circulating methanol could be followed and reaction intermediates could be detected in real time by either (2)H or (13)C NMR spectroscopy. By use of the in situ NMR approach, factors that control fuel cell performance, such as methanol cross over and catalyst performance, were identified.

Effects of Carbonate Solvents and Lithium Salts on Morphology and Coulombic Efficiency of Lithium Electrode

The application of lithium (Li) metal anodes in rechargeable batteries is hindered by Li dendrite growth during Li deposition and low Li Coulombic efficiency (CE), where the nonaqueous electrolyte plays a critical role. In this work, the effects of different carbonate solvents and Li salts on Li deposition morphology and CE were systematically investigated. Typically, cyclic carbonates favor the formation of uniform Li films and improve Li CE more than linear carbonates do. Several specific cyclic carbonates that are conventionally used as solid electrolyte interphase (SEI) formation additives in Li-ion batteries can also improve the CE of Li anodes. Furthermore, among the nine electrolyte salts studied, LiAsF6 and lithium bis(oxalato)borate (LiBOB) lead to the highest CE. LiBOB also leads to better uniformity of deposited Li than other salts do. Considering the better safety of LiBOB as compared to LiAsF6, LiBOB is a promising salt for rechargeable Li metal batteries with high CE. By combining the best electrolyte solvent/salt that can lead to high CE with novel electrolyte additives that can prevent dendrite formation, it is possible to find an electrolyte that not only prevents Li dendrite formation but also leads to high CE during Li deposition/stripping processes.

The influence of substituted aromatic aldehydes on Zn-Mn alloy electrodeposition

Additives are necessary in the electrodeposition of Zn-Mn alloys at high current density, in order to reduce hydrogen evolution reaction and prevent dendrite formation. The influence of two aromatic aldehydes, 4-hydroxy-benzaldehyde and 3,4-dimethoxy-benzaldehyde, as the additives in Zn-Mn plating electrolyte, is examined in this work. The coatings characterization by scanning electron microscopy and X-ray energy dispersive spectroscopy, as well as the examination of additives effect by electrochemical methods, indicate a complex involvement of additive molecules in hydrogen evolution, as well as in Zn2+ and Mn2+ reduction. Consequently, the levelling action can be achieved and the chemical composition of the Zn-Mn alloy can be tailored, by adding the proper additive type and concentration in the plating electrolyte.

Does decreasing ion–ion association improve cation mobility in single ion conductors?

We report on poly(ethylene oxide) based single ion conductors for solid polymer electrolytes. The widely agreed upon vehicle for cation movement in PEO-based solid polymer electrolytes is the single cation, in which the cation is solvated by PEO ether oxygens. Here we report a different vehicle that becomes active with strong anion-cation interactions. In the common perspective, increasing ion-ion interactions would increase ion association, decrease cation solvation, and disable cation movement. Decreasing these interactions would have the opposite effect. We vary cation-anion interaction strength, using anion charge delocalization in molecular dynamics simulations. This creates a series of systems with levels of ion aggregation from single cations (weak interaction) to mostly ion aggregates (strong interaction). Although in the weak model single cations are faster than those in ion pairs and aggregates, with stronger interactions a different mechanism emerges. Paired cations move the fastest by visiting different anion partners in succession. The importance of this observation lies in the possibility of decoupling cation movement from polymer motion, which is required to prevent dendrite formation in both Li and Na ion batteries.