Charging Protocol Research Articles

(Invited) Interfacial Dynamics of Anode-Free Solid-State Batteries

There is significant interest in solid-state batteries (SSBs) as an alternative to traditional Li-ion batteries, as they can potentially eliminate the flammable liquid electrolyte and enable Li-metal anodes. However, manufacturing of SSBs with Li metal anodes poses a significant challenge, owing to the highly reactive nature of Li metal. Therefore, there has been a recent increase in interest in “anode-free” configurations, where the Li metal anode is formed in situ using the pre-existing inventory in the cathode. In addition to manufacturing considerations, anode-free configurations also enhance energy density compared to batteries with excess Li metal in the anode. However, compared to pre-formed Li metal/solid electrolyte interfaces, the nucleation, growth, and stripping of Li metal in anode-free SSBs has not been widely studied, and poses unique electro-chemo-mechanical phenomena.To probe the dynamic interfacial evolution of anode-free SSBs, in this study, I will present results using a complimentary set of in situ/operando methodologies. First, I will describe the morphological evolution of Li nucleation and growth at garnet LLZO solid electrolytes, using a newly developed platform for operando 3-D video microscopy [1]. In particular, the influence of mechanical stresses on both the thermodynamic and kinetic properties of Li will be discussed, and unique electrochemical signatures of anode-free plating will described. A mechanistic framework for these electro-chemo-mechanics will be presented, which results in design rules for improving the homogeneity of Li plating during anode formation.To compliment this morphological information, I will also present results using operando x-ray photoelectron spectroscopy (XPS) on sulfide solid electrolytes. This allows for direct observation of SEI formation during in situ anode formation. In particular, we observe a transition in reaction pathways from SEI formation to nucleation of Li metal, which is a function of both the charging protocol and the presence of interlayer coatings [2-3]. Finally, these results will be compared and contrasted to anode-free Li plating in liquid electrolytes, and a discussion will be presented on how to optimize plating morphology and reversibility.[1] E. Kazyak, M. Wang, K. Lee, S. Yadavalli, A. J. Sanchez, M. D. Thouless, J. Sakamoto, N. P. Dasgupta, Submitted (2022).[2] A. L. Davis, R. Garcia-Mendez, K. N. Wood, E. Kazyak, K.-H. Chen, G. Teeter, J. Sakamoto, N. P. Dasgupta, J. Mater. Chem. A 8, 6291 (2020).[3] A. L. Davis, E. Kazyak, D. W. Liao, K. N. Wood, N. P. Dasgupta, J. Electrochem. Soc. 168, 070557 (2021).

Physics-Based Methods and Tools for Rapid Classification, Quantification, and Forecasting of Lithium-Ion Battery Aging Modes and Life

Physics-based methods and tools for rapid classification, quantification, and forecasting of lithium-ion battery aging modes and life Sangwook Kim,1 Zonggen Yi,1 Ross R. Kunz,1 Eric J. Dufek,1 Tanvir Tanim,1 Kevin L. Gering1, Bor-Rong Chen,1 Peter Weddle, 2 Kandler Smith, 2 1 Energy and Environmental Science and Technology, Idaho National Laboratory, Idaho Falls, Idaho 83415 USA 2 Center for Energy Conversion & Storage Systems, National Renewable Energy Laboratory, Golden, CO 80401, USA 242nd ECS Meeting, Atlanta, GA, Oct. 9 - 13, 2022 Symposium: A03 – Lithium Ion Batteries Lithium-ion batteries play a central role in powering electric vehicles, stationary energy storage systems, and consumer electronics. Lately, machine learning and deep learning (DL) has been successfully used to gain insights into battery degradation during battery operation and predict lifetime in battery research and development community. Fast and robust classification and quantification of battery aging (e.g., Loss of Lithium Inventory (LLI) and Loss of active Material (LAM)) and accurate long-term forecasting of battery life enable more proactive planning of battery management and preemptive actions of modified operating conditions to achieve safe operations and prolong battery life.Here, we present the development of Incremental Capacity (IC)-DL framework for fast charging conditions as a diagnostic tool for aging mode classification and quantification (Figure 1). The classification and quantification of dominant battery aging modes is conducted using a synthetic-data-based DL modeling framework. Over 6000 initial conditions and 26,000 different aging conditions are generated using IC model to train DL. We applied trained DL classification and quantification algorithm to 22 Gr/NMC532 pouch cells with a different loading and charging protocol tested up to 600 cycles. Besides the analysis of reference performance test data at C/20, cycle-by-cycle data at higher C-rate is analyzed. This IC-DL framework as a diagnostic tool is also used in different battery chemistries, such as Gr/NMC811and LTO/LMO. IC-DL framework enables unique, rapid identification and quantification of the dominant aging modes at different C-rates in different battery chemistries. Additionally, a prognostic tool, Sigmoidal Rate Expression (SRE)-type mathematics are employed to evaluate the capacity loss and aging mode (i.e., LLI). SREs are robust engines that contain three variables that capture the thermodynamic and kinetic “thumbprint” of the mechanism progression within the context of a batch reactor scenario [1].We show two different methods by which SRE parameters can be early assessed based on quantified values from IC-DL framework; (1) extrapolative techniques using specialized functions to determine SRE parameter convergence and (2) a technique based on deep learning and Monte Carlo framework. Overall results from both methods confirm that we can predict capacity loss and LLI at the end of test (i.e., 600 cycles) within 1-2% absolute error using three weeks of testing data (or 125 cycles). We believe the IC-DL framework combined with SRE-base prognostics will reduce lithium-ion batteries development cycle as well as shorten the turnover time for validation, fulfilling the demands of rapidly growing battery market. References K. Gering, Electrochimica Acta, 228(20), 636-651 (2017) Figure 1

State-of-Charge Distribution of Single-Crystalline NMC532 Cathodes in Lithium-Ion Batteries: A Critical Look at the Mesoscale.

The electrochemical response of layered lithium transition metal oxides LiMO2 [M=Ni, Mn, Co; e. g., Li(Ni0.5 Mn0.3 Co0.2 )O2 (NMC532)] with single-crystalline architecture to slow and fast charging protocols and the implication of incomplete and heterogeneous redox reactions on the active material utilization during cycling were the subject of this work. The role of the active material size and the influence of the local microstructural and chemical ramifications in the composite electrode on the evolution of heterogeneous state of charge (SOC) distribution were deciphered. For this, classification-single-particle inductively coupled plasma optical emission spectroscopy (CL-SP-ICP-OES) was comprehensively supplemented by various post mortem analytical techniques. The presented results question the impact of surface-dependent failure mechanisms of single crystals for the evolution of SOC heterogeneity and identify the deficient structural flexibility of the composite electrode framework as the main driver for the observed non-uniform active material utilization.

Pulsed Charging Protocols with Non-Zero Relaxation Time for Lithium-Ion Batteries

Lithium-ion batteries are commonly charged following the constant current -constant voltage (CC-CV) protocol. Current flow during charging implies an equivalent ionic flow through the battery materials. Intercalation and de-intercalation of Li+ are accompanied by concentration gradients that are reflected by the rise in the cells’ potentials that is required to maintain the constant current during the CC regime. In this work, two new pulsed charging protocols were tested. Firstly, a square current pulse is applied to the cell until the cut-off voltage is reached, followed by a pulsed square voltage protocol (PV). The second methodology keeps the same current pulse, however, after the limiting voltage was reached, the pulsing regime consisted in alternating between a maximum voltage value and a minimum, non-zero, constant current value. Different voltage pulse widths and frequencies were tested, in order to study the maximum electrodes’ capacity, the time required to reach that capacity, the contribution of each individual step (i.e. PC and PV) to the total electrodes’ capacity, and the thermal variations for each. The second pulsing mode produced capacity values 7%–8% higher than in the classical CC–CV protocol, and in charging times periods from 5%–25% faster, without compromising the batteries’ cycle life.

Modeling the effects of pulse plating on dendrite growth in lithium metal batteries

The formation of dendrites on lithium electrodes presents safety and cycling challenges for the development of high-performance, rechargeable lithium metal batteries. While a constant current (CC) charging protocol has been standard, recent studies have shown that a pulse plating (PP) charging protocol is effective at reducing dendrite growth and improving cycle life. In this study, dendrite growth at the anode-electrolyte interface was simulated using an Extended Butler-Volmer Smoothed Particle Hydrodynamics (eBV-SPH) model implemented in LAMMPS. Square waveform PP protocols were implemented and compared to CC results to understand the effect of charging protocols on lithium deposition and dendrite morphology. The charging conditions were controlled by the applied potential, as the model does not currently enforce galvanostatic conditions. Past studies compared CC and PP results at a single charging current density. In similar work on lithium-ion batteries, PP and CC results compared at the identical mean current resulted in little to no benefit to cycling performance. In this investigation, lithium anode PP protocols performed worse when compared with CC plating at the identical mean current. The PP and CC simulation results from the eBV-SPH model simulated the expected morphology and behavior found in experimental investigations and provide more detailed morphologies than previous computational simulations.

Emissions and Air Quality Implications of Enabling On-Road Vehicles as Flexible Load Through Widescale Zero Emission Vehicle Deployment in California

This study assesses the impacts of on-road light- to heavy-duty zero emission vehicle (ZEV) adoption and charging protocols on greenhouse gas emissions for the years 2030 and 2045 in California, and on air quality for the year 2045. Two scenarios are addressed: (1) a “business-as-usual” (BAU) scenario with modest ZEV adoption, and (2) a “carbon neutral” scenario that achieves carbon neutrality by 2045 with proactive ZEV adoption. Electricity load for fueling ZEVs is projected, including electricity fuel for battery electric vehicles and electrolytic hydrogen for fuel cell electric vehicles. This electric load was input into an electric grid dispatch model and electric grid and air quality analyses were conducted. The results revealed that although medium- and heavy-duty vehicles (MHDVs) are projected to have lower total electric load associated with fueling, they will require roughly double the electricity for hydrogen production of light-duty vehicles. For the electric grid scenarios examined, ZEV loads increased peak electricity demand by 3% to 6% in 2030 and 22% to 31% in 2045. MHDV time-of-use and smart charging strategies were equally able to shift charging demand to off-peak times. Higher ZEV loads under the carbon neutral scenario increased natural gas use up to 6% in 2030 and energy storage requirements up to 45% in 2045 compared with the BAU scenario. The analyses also found that achieving carbon neutrality through ZEV adoption had the cobenefit of significantly reducing ground-level ozone and PM2.5 concentrations in key regions of California, providing health savings of approximately $28 billion annually in 2045.

Modeling Fast Charge Protocols to Prevent Lithium Plating in a Lithium-Ion Battery

This paper describes a methodology to quantitatively devise a fast charge protocol to prevent lithium plating in a lithium-ion battery (LIB) cell. A lithium plating line was derived by detecting a voltage plateau that occurred during charging with a high current by differential voltage analysis (DVA). To account for the safe effects at a certain margin from the lithium plating line during fast charge, the novel index was expressed as a margin of safety (MS). Two-dimensional modeling was then performed to predict the charge curves and thermal distributions of LIB cell during various conditions according to the margin of safety. To validate the modeling approach for the design of the fast charge protocol, cycling tests were performed under five fast charge protocols and discharge. The higher the MS of the fast charge protocol, the better the performance and lifetime impact of the LIB cell.

Investigating Transport through Separator Membranes in Aqueous Organic Redox Flow Batteries Using NMR Spectroscopy

Electricity and heat generation contribute 25% of greenhouse gas emissions globally.1 Redox flow batteries (RFBs) are prospective devices for long-duration energy storage, which is required to integrate more renewable energy sources onto the electricity grid.2 RFBs have a modular design with decoupled power and energy ratings, allowing them to be scaled to suit grid-level energy storage requirements. The development of aqueous organic redox flow batteries (AORFBs), such as quinone-based systems, is gaining momentum because they are potentially cheaper, safer and more sustainable than vanadium-based RFBs.3-5 However, the crossover of redox-active species through the separator membrane can lead to irreversible capacity fade, limiting their lifetime and economic viability.6 It has previously been demonstrated that in situ spectroscopic techniques are powerful tools for determining reaction mechanisms in redox flow batteries.5,7 Here, we explore how solution-state in situ nuclear magnetic resonance (NMR) spectroscopy and solid-state NMR spectroscopy can be used to study the crossover of electrolytes in AORFBs. We demonstrate that in situ solution NMR spectroscopy can be used to characterise transport in operating AORFBs with high temporal resolution and minimal system disturbance. This method can therefore be applied to investigate how crossover is governed by structure-property relationships and the charging protocols used. Furthermore, polymer-electrolyte interactions within the membrane can be probed using complementary solid-state NMR studies. Together, these fundamental studies will ultimately advance our understanding of electrolyte crossover, so that improved separator membranes can be developed.

(Digital Presentation) Self-Discharge in Electrochemical Capacitors: Beyond Conway’s Diagnostics

Electrochemical double-layer capacitors (EDLCs), also known as supercapacitors, are energy storage devices. Charge-discharge in EDLCs occurs through electrostatic interactions between electrodes and oppositely charged ions. Self-discharge is the gradual loss of energy when a charged EDLC is left in open circuit state. A comparatively higher rate of self-discharge (SD) than in the batteries prevents the use of EDLCs in stand-alone devices or those charged only infrequently. The process of self-discharge, to the best of our knowledge, is far from being fully understood. It manifests as decrease in open-circuit potential which, depending on the charging protocol, can be dominated by charge-redistribution [1-3] induced rapid decrease in the initial stages.Conway [4] proposed model-based diagnostics to identify activation, diffusion, and leakage-resistance controlled mechanisms from voltage vs. time measurements. We show that for the limited voltage range window available, the method is subjective and ambiguous for real measurements. We have proposed and carried out an alternative set of extensive experiments to gain insights into the self-discharge process for an in-house capacitor with sulfuric acid as electrolyte and activated carbon as electrodes. We varied electrode thickness, the distance between the electrodes, and the state of mixing in the electrolyte. We also measured self-discharge of electrochemically isolated charged half-cells (Figures 1a,b). The results bring out interesting and unambiguous findings, independent of the degree of fit with the expected variations for various controlling mechanisms. They rule out leakage resistance as the cause of self-discharge and disprove the shuttle mechanism [2,3] (Figure 1c,d). The analysis of measurements with electrodes of different thicknesses establishes that activation process controlled self-discharge does not dominate either. And the predicted effect of charge-redistribution is in the opposite direction. The role of the complex interplay of diffusion and electrochemical reactions holds promise. Figure 1

Optimal Charging Protocols to Restrict Lithium-Ion Battery Degradation

Lithium-ion batteries degrade due to several mechanisms that occur during cell operation. These mechanisms can be parasitic reactions that lead to loss of lithium inventory or loss of active material. Some examples of these side reactions include the growth of the solid-electrolyte interphase (SEI) layer, transition metal dissolution and deposition, lithium plating, solvent oxidation, etc. Thermal effects and mechanical fatigue on the electrodes also lead to cell aging and capacity fade.For widespread implementation of lithium-ion batteries for electric vehicles, batteries should last approximately 10 years.1 Fast charging has also been heavily researched for accelerating this prevalent circumstance. However, charging at high currents can severely degrade the cell, affecting the cell’s lifetime. Algorithms that optimize charging can be effective to reduce cell aging. Physics-based battery models can be used to design these algorithms by restricting phenomena that occur in the cell that causes cell aging. For example, lithium plating can be prevented by restricting the overpotential of the reaction.In our previous work, we have shown optimal charging profiles where the intercalation induced stresses, lithium plating and the SEI layer growth was restricted using reformulated physics-based models using model-based control 2 - 3 In this talk, we show different optimal charging protocols for restricting different mechanisms, and analyze the interplay between them to predict optimal charging profiles. References M. T. Lawder, P. W. C. Northrop, and V. R. Subramanian, J. Electrochem. Soc., 161, A2099–A2108 (2014).B. Suthar, P. W. C. Northrop, R. D. Braatz, and V. R. Subramaniand, J. Electrochem. Soc., 161, F3144–F3155 (2014).M. Pathak, D. Sonawane, S. Santhanagopalan, R. D. Braatz, and V. R. Subramanian, ECS Trans., 75, 51–75 (2017).

Effect of charging protocol and carbon electrode selection in Na–O2 batteries

Nonaqueous sodium- and lithium-oxygen batteries are of interest because of their high theoretical specific energies relative to state-of-the-art Li-ion batteries. However, several challenges limit rechargeability, including instability of the carbon electrode and electrolyte with reactive oxygen species formed during cycling. This work investigates strategies to improve the cycling efficiency of the Na–O2 system and minimize irreversible degradation of electrolyte and electrode materials. We show that charging cells with a constant current/constant voltage (CCCV) protocol is a promising technique made possible by the slight solubility of sodium superoxide in nonaqueous electrolytes. In addition, the type of carbon electrode has a significant impact on cell performance and efficacy of the cycling protocol. Graphitic carbon electrodes coupled with CCCV charging demonstrate higher reversibility, more efficient oxygen evolution, and less outgassing than conventional cells using a porous carbon paper electrode and only a constant current charge.Graphical abstract

The Effects of Temperature and Cell Parameters on Lithium-Ion Battery Fast Charging Protocols: A Model-Driven Investigation

The risk of lithium plating is a key barrier to lithium-ion battery fast charging. Among other strategies, many alternative charging protocols have been proposed to reduce the plating propensity compared to the conventional constant current-constant voltage (CC-CV) protocol. However, conflicting results have been reported on their impacts on battery lifetime. This work investigates the performance of CC-CV and a boost charging protocol using an electrochemical-thermal model which accounts for nonlinear diffusion and reversible lithium plating. The relative performance of the protocols is found to ultimately depend on the solid phase and ion diffusion timescales. Boost charging is beneficial when both these timescales are short, i.e. in power cells in general or in energy cells at sufficiently high temperatures. The high concentration gradients that develop during the boost stage can sufficiently relax in the subsequent lower current stage to reduce the plating propensity in these cases. When the diffusion timescales are long, boost charging leads to increased plating heterogeneity (driven by the ion diffusion limitations) and slightly increased plating propensity (driven by the solid phase diffusion limitations). Our findings highlight the need to study alternative charging protocols at a wide range of conditions and on different cells before practical deployment.

Enhancement of charging performance of quantum battery via quantum coherence of bath

An open quantum battery (QB) model of a single qubit system charging in a coherent auxiliary bath (CAB) consisting of a series of independent coherent ancillae is considered. According to the collision charging protocol we derive a quantum master equation and obtain the analytical solution of QB in a steady state. We find that the full charging capacity (or the maximal extractable work (MEW)) of QB, in the weak QB-ancilla coupling limit, is positively correlated with the coherence magnitude of ancilla. Combining with the numerical simulations we compare with the charging properties of QB at finite coupling strength, such as the MEW, average charging power and the charging efficiency, when considering the bath to be a thermal auxiliary bath (TAB) and a CAB, respectively. We find that when the QB with CAB, in the weak coupling regime, is in fully charging, both its capacity and charging efficiency can go beyond its classical counterpart, and they increase with the increase of coherence magnitude of ancilla. In addition, the MEW of QB in the regime of relative strong coupling and strong coherent magnitude shows the oscillatory behavior with the charging time increasing, and the first peak value can even be larger than the full charging MEW of QB. This also leads to a much larger average charging power than that of QB with TAB in a short-time charging process. These features suggest that with the help of quantum coherence of CAB it becomes feasible to switch the charging schemes between the long-time slow charging protocol with large capacity and high efficiency and the short-time rapid charging protocol with highly charging power only by adjusting the coupling strength of QB-ancilla. This work clearly demonstrates that the quantum coherence of bath can not only serve as the role of “fuel” of QB to be utilized to improve the QB’s charging performance but also provide an alternative way to integrate the different charging protocols into a single QB.

Multistage fast charging optimization protocol for lithium-ion batteries based on the biogeography-based algorithm

Lithium-ion batteries play an important role in the application scenarios of electric vehicles and renewable energy systems. However, it is difficult to charge these batteries safely and quickly. Charging lithium-ion batteries has been the bottleneck problem affecting the large-scale application of electric vehicles. To find a balance between safety and speed, this study proposes a multistage fast charging protocol utilizing the biogeography-based optimization (BBO) algorithm. The optimization function of the charging time and the temperature rise of lithium-ion batteries are established through the thermoelectric coupling model of lumped parameters. In the example of a five-stage charging protocol, the Pareto front is obtained using the BBO algorithm and is composed of the optimal solutions of the two objectives under different weights. Subsequently, the optimal solution that minimizes the global optimization function is obtained. Compared with the multistage constant current charging protocol, the results show that the BBO charging optimization protocol shortens the battery charging time by 19.13% whereas the maximum temperature increase remains nearly identical.

Self-sufficiency and charger constraints of prosumer households with vehicle-to-home strategies

In recent years, the market of electric vehicles has been growing strongly. This growth is accompanied by discussions on vehicle-to-home strategies that allow households with a photovoltaic system and an electric vehicle both to charge the vehicle with solar energy and to supply energy from the vehicle to the household. However, vehicle-to-home technology is still not yet widely implemented in prosumer households and there is still little literature about the impact of technological constraints given by the hardware and charging protocols on prosumer energy consumption. To close this research gap, we develop heuristic vehicle-to-home charging strategies that aim to increase self-sufficiency, vehicle availability and traction battery lifetime. We discuss charging power constraints due to technical limitations measured in the laboratory and communication protocols. We investigate the impact of charging power constraints, bidirectional charger capability and forecasting algorithms on the self-sufficiency of the prosumer household. The simulation model integrates a comprehensive electric vehicle model, photovoltaic system model and historic measurement data of prosumer and driving profiles. We propose and simulate three different exemplary mobility profile scenarios. The mobility scenarios differ in their departure and arrival time distributions and are named Worker, Half-time Worker and Late Worker. The developed smart charging strategies can increase the self-sufficiency of the household by up to 16.9 percentage points in comparison to charging the vehicle with maximum power upon plug-in. Decreasing the minimum charging power constraint from 4.1kW to 1.8kW can increase self-sufficiency by up to 10.5 percentage points. Smart charging strategies, the use of a bidirectional charger, relaxation of charging power constraints and the use of forecasting algorithms increase the self-sufficiency of a prosumer household with a photovoltaic system and an electric vehicle.

Stress-regulated pulse charging protocols via coupled electrochemical-mechanical model for the mechanical stability of electrode materials in lithium-ion batteries

The effects of microstructural geometries and C-rates (charge and discharge rates) on mechanical failure have been widely studied to reduce the side reaction and capacity fade in Li–ion batteries. Recently, to achieve the maximum state of charge with least mechanical failure, stress-regulated charging protocols have been considered an emerging strategy. However, the theoretical studies of the charging protocols are limited to either using the equivalent circuit models, or considering only the active material phase. In this paper, we predict the pulse charging profiles by simultaneously controlling the stress level of the active particle and binder, to avoid mechanical failure of the particle, binder, and particle–binder interface. The charging protocol profiles are decided by controlling the stresses within a safe range. The simulations show that both the stress in the active particle and the binder stress and interfacial tractions play important roles in deciding the characteristics of pulse charging profiles, such as duty cycles and pulse frequencies. In addition, the binder constraint significantly affects the use of the pulse charging method. As the particle size and binder stiffness increase, and the binder contact angle decreases, binder stress plays a dominant role in controlling pulse charging. These new insights provide better understanding towards designing fast-charging protocols for Li–ion batteries.

An optimal thermal management system heating control strategy for electric vehicles under low-temperature fast charging conditions

• An improving fast charging protocol is proposed to avoid lithium plating. • A multi-stage heating control strategy based on the battery temperature is developed. • Dual crucial objectives, heating energy consumption and charging time are balanced. • An optimal heating control strategy for low-temperature fast charging is proposed. • The optimal control strategy can reduce heating energy consumption by 11.61%. Electric vehicle thermal management system (EVTMS) and its corresponding control strategy are essential to ensure the battery performance at low temperatures. Due to the complexity of the low-temperature fast charging process, it is necessary to comprehensively consider the battery heating and charging performance when developing the heating strategy. However, most studies only focus on the charging time. In this context, an EVTMS is investigated in this paper, and the simulation models are established. In addition, the battery heating and charging performance under low-temperature fast charging conditions are analyzed by experiment and simulation. An improved fast charging protocol for reducing the battery-lifetime degradation is proposed. Moreover, an EVTMS multi-stage heating control strategy is developed to realize the cooperative control with the improved charging strategy. Taking dual crucial yet conflicting factors, heating energy consumption and charging time, as the optimization objectives, the proposed EVTMS control strategy is optimized using genetic algorithm. And an optimal heating control strategy is obtained. The results show that compared with the strategy only considering the charging time, the optimal strategy can reduce the heating energy consumption by 11.61% and increase the charging efficiency by 1.2%, only with the increase of the charging time by 2.98 min.

In Situ Hydrogen Evolution Monitoring During the Electrochemical Formation and Cycling of Pressed‐Plate Carbonyl Iron Electrodes in Alkaline Electrolyte

AbstractInvited for this month's cover picture is the institute of Rüdiger‐A. Eichel. The cover picture illustrates the hydrogen evolution on carbonyl iron electrodes, with the latter being a resource‐efficient option to store renewable electricity for stationary applications effectively, if an appropriate charging protocol is applied. Read the full text of the Research Article at 10.1002/batt.202100415.

Quantum Charging Advantage Cannot Be Extensive without Global Operations.

Quantum batteries are devices made from quantum states, which store and release energy in a fast and efficient manner, thus offering numerous possibilities in future technological applications. They offer a significant charging speedup when compared to classical batteries, due to the possibility of using entangling charging operations. We show that the maximal speedup that can be achieved is extensive in the number of cells, thus offering at most quadratic scaling in the charging power over the classically achievable linear scaling. To reach such a scaling, a global charging protocol, charging all the cells collectively, needs to be employed. This concludes the quest on the limits of charging power of quantum batteries and adds to other results in which quantum methods are known to provide at most quadratic scaling over their classical counterparts.

New stepwise potentiostatic charge protocol for preventing dendrite formations in Li metal batteries

Here, we report a new charge protocol for dendrite-free Li-metal battery based on the understanding the effects of over-potential on Li dendritic growth. We demonstrate that when a large over-potential is applied, the deposited Li metal shows a needle-like morphology even though a current density of a cell does not reach the limiting current density. This clearly indicates over-potential leads to the early formation of space charge region near a negative electrode, and thereby the Li dendritic growth can be easily triggered. As a result, control of the over-potential is very important for dendrite-free Li metal batteries. Through this understanding, we propose a new stepwise potentiostatic charge protocol that can keep the over-potential below a certain critical value. By applying new charge protocol, we clearly demonstrate that Ni-rich layered materials can be fully utilized without triggering the Li dendritic growth. The understanding and finding provide a novel guideline and stimulate further research to develop ways to safely operate high energy density Li metal battery.