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The integration of automation and data-driven methodologies offers a promising approach to accelerating materials discovery in energy storage research. Thus far, in battery research, coin-cell assembly has advanced to become nearly fully automated but remains largely disconnected from data-driven methods. To bridge the disconnect, this work presents a self-driving laboratory framework to accelerate electrolyte discovery by integrating automated coin-cell assembly, galvanostatic cycling of LiFePO₄||Li₄Ti₅O₁₂ organic-aqueous full cells, and Bayesian optimization for selecting subsequent experiments based on prior results. The study explored an organic-aqueous hybrid electrolyte system comprising four co-solvents and two lithium-conducting salts. Using this framework, cells with an optimized electrolyte cycled with at least 94% Coulombic efficiency. Additionally, online electrochemical mass spectrometry revealed that the optimized organic co-solvents successfully mitigated the parasitic hydrogen evolution reaction. The results highlight the potential of combining Bayesian optimization with autonomous full-cell experimentation while contributing new electrolyte design insights for next-generation aqueous batteries.

Prussian blue analogues for sodium-ion battery cathodes are growing in popularity as next-generation energy storage devices. Prussian White (PW) with formula Na_xFe[Fe(CN)₆]_y•nH₂O is leading the trend, having already been commercialized. However, capacity fade (PW/electrolyte degradation) and safety concerns (cyanide/cyanogen release) still raise concerns. Online electrochemical mass spectrometry, supported by both operando Fourier transform infrared spectroscopy and Mössbauer spectroscopy, is herein used to analyze degradation processes in PW-based Na-ion full cells. Apart from the typical cell formation reactions, hydrogen is observed to evolve during cell discharge and evidenced to stem from oxidation of NaH, accumulated upon charge. Over-oxidation of PW after full desodiation releases CN, which not only forms (CN)₂ but also degrades the electrolyte. Loss of CN likely results in a nanometric (≈4 nm) surface-reconstructed passivation layer on PW, thus inhibiting further degradation. Fundamental understanding of degradation reactions in PW full-cells, as gathered herein, shows that the aforementioned capacity fade and safety concerns are wholly addressable and hence guides the further development of Na-ion batteries for wider ranges of applications.

Advanced aqueous batteries are promising solutions for grid energy storage. Compared with their organic counterparts, water-based electrolytes enable fast transport kinetics, high safety, low cost, and enhanced environmental sustainability. However, the presence of protons in the electrolyte, generated by the spontaneous ionization of water, may compete with the main charge-storage mechanism, trigger unwanted side reactions, and accelerate the deterioration of the cell performance. Therefore, it is of pivotal importance to understand and master the proton activities in aqueous batteries. This Perspective comments on the following scientific questions: Why are proton activities relevant? What are proton activities? What do we know about proton activities in aqueous batteries? How do we better understand, control, and utilize proton activities?

Metal anodes provide the highest energy density in batteries. However, they still suffer from electrode/electrolyte interface side reactions and dendrite growth, especially under fast-charging conditions. In this paper, we consider a phase-field model of electrodeposition in metal-anode batteries and provide a scalable, versatile framework for optimizing its chemical parameters. Our approach is based on Bayesian optimization and explores the parameter space with a high sample efficiency and a low computation complexity. We use this framework to find the optimal cell for suppressing dendrite growth and accelerating charging speed under constant voltage. We identify interfacial mobility as a key parameter, which should be maximized to inhibit dendrites without compromising the charging speed. The results are verified using extended simulations of dendrite evolution in charging half cells with lithium-metal anodes.

Vinylene carbonate (VC) is the most commonly applied performance-enhancing electrolyte additives in Li-ion batteries to date. Despite numerous studies, there is a lack of consensus regarding the various reaction pathways of VC and their implications. VC has primarily been observed to either polymerize forming poly(vinylene carbonate) (poly(VC)) or decompose releasing major amounts of CO2, two seemingly contradictory processes. Herein, we present evidence of additional reaction pathways of VC highlighting its role as a H2O scavenging agent. In contrast to the typical electrolyte solvent ethylene carbonate, VC reacts much more rapidly with water impurities, especially when in contact with hydroxides, forming products less likely to influence cell performance. Efficient removal of water and hydroxides is essential to preserve the stability of Li-ion electrolyte solvent and salt, hence guaranteeing a long lifetime of the battery. Model studies pinpointing reaction pathways of electrolytes and additives, as presented herein, are critical not only to improve modern Li-ion cells but also to establish design principles for future battery chemistries.

Electrolyte additives are indispensable to enhance the performance of Li-ion batteries. Lithium bis(oxalato)borate (LiBOB) has been explored for many years, as it improves both cathode and anode performance. No consensus regarding its reaction mechanisms has, however, been established. A model operando study combining attenuated total reflection infrared spectroscopy (ATR-FTIR), electrochemical quartz crystal microbalance (EQCM), and online electrochemical mass spectrometry (OEMS) is herein presented to elucidate LiBOB reduction and electrode/electrolyte interphases thus formed. Reduction of the BOB^– ion sets in at ∼1.8 V with solid lithium oxalate and soluble oxalatoborates as the main products. The reduced BOB^– ion also reacts with itself and its environment to evolve CO₂, which in turn impacts the interphase formed on the negative electrode. This study provides further insights into the reduction pathways of LiBOB and how they contribute to the interphase formation.

The development and application of Electrochemical Quartz Crystal Microbalance (EQCM) sensing to study metal electroplating, especially for energy storage purposes, are reviewed. The roles of EQCM in describing electrode/electrolyte interface dynamics, such as the electric double-layer build-up, ionic/molecular adsorption, metal nucleation, and growth, are addressed. Modeling of the QCM sensor is introduced and its importance is emphasized. Challenges of metal electrode use, including side reactions and dendrite formation, along with their mitigation strategies are reviewed. Numerous factors affecting the electroplating processes, such as electrolyte composition, additives, temperature, and current density, and their influence on the electroplated metals' mass, structural, and mechanical characteristics are discussed. Looking forward, the need for deeper fundamental understanding and advancing simulations of the QCM signal response as a result of electroplating metal nanostructures is stressed. Further development and integration of innovative EQCM-strategies will provide unique future means to fundamentally understand and optimize metal electroplating for energy storage and application alike. Quartz Crystal Microbalance (QCM) in the study of metal electroplating for energy storage is reviewed herein. QCM's historical development, sensitivity in detecting minute metal changes, and integration with other techniques for electrolyte and additive screening are discussed. Innovative metal plating strategies, recent advancements in QCM, and future applications of high-throughput, automated research in material science and electrochemistry are highlighted. image

The spinel oxide LiNi_0.5Mn_1.5O₄ (LNMO) currently competes to replace the conventional layered transition metal oxide active material in Li-ion batteries. The high average operating potential (4.8 V vs Li⁺/Li) challenges the stability of the electrolyte, which, in turn, compromises the lifetime of the Li-ion cell. Online electrochemical mass spectrometry (OEMS) is herein implemented to study the degradation processes occurring at the cathode surface. Gases continuously evolve across subsequent cycles as a result of electrolyte oxidation, a process that is found to be only potentially activated and independent of electrode surface composition. The subsequent formation of protic species autocatalyzes electrolyte salt degradation, which in turn triggers the corrosion of active material, current collector, and conductive carbons. The effectiveness of several well-known electrolyte additives, previously claimed to act as cathode electrolyte interphase (CEI) formers, was explored, revealing the efficacy of phosphorus-based additives. Our study provides a rapid and quantifiable approach to tackle the major challenge of high-voltage cathode materials, namely, their stabilization toward the electrolyte and how to identify and develop an efficient passivating CEI.

Optimization of cell formation during lithium -ion battery (LIB) production is needed to reduce time and cost. Operando gas analysis can provide unique insights into the nature, extent, and duration of the formation process. Herein we present the development and application of an Online Electrochemical Mass Spectrometry (OEMS) design capable of monitoring gas evolution and consumption in both model coin-cells (Q = 0.72 mAh) with a graphite/electrolyte weight-ratio of 1:12.5 and large-format Li -ion cells (Q = 72 Ah) with a graphite/electrolyte weight -ratio of 1:0.63 during operation. Although the composition and amounts of gas are highly comparable, even when validated against ex -situ analysis, the gas release rate is lower from the larger cell size and likely limited by gas bubble transport through the electrode stack of the cell during formation. Higher temperatures accelerate the formation process, but also alters the composition and extent of gas released. Apart from providing novel insights into the formation processes of large -format Li-ion cells, our OEMS setup offers an opportunity for the battery manufacturing and automotive industry to explore the impact of battery formation and/or operating conditions on gas evolution in next -generation Li-ion batteries of any size.

Rechargeable magnesium batteries are promising for future energy storage. However, among other challenges, their practical application is hindered by low coulombic efficiencies of magnesium plating and stripping. Fundamental processes such as the formation, structure, and stability of passivation layers and the influence of different electrolyte components on them are still not fully understood. In this work, we gain unique insights into the initial Mg plating and stripping cycles by comparing magnesium bis(trifluoromethanesulfonyl)imide (Mg(TFSI)₂)- and magnesium tetrakis(hexafluoroisopropyloxy)borate (Mg[B(hfip)₄]₂)-based electrolytes, each with and without MgCl₂, on gold electrodes by highly sensitive operando electrochemical quartz crystal microbalance with dissipation monitoring (EQCM−D) applying hydrodynamic spectroscopy. With the stable Mg[B(hfip)₄]₂-based electrolytes, highly efficient and interphase-free cycling is possible and passivation layers are attributed to electrolyte contaminants. These are forming and degrading during the so-called initial conditioning process. With the more reactive Mg(TFSI)₂-based electrolyte, thick passivation layers with small pores are growing during cycling. We demonstrate that the addition of chloride lowers the amount of passivated Mg deposits in these electrolytes and accelerates the currentless dissolution of the passivation layer. This has a positive effect since we observe the most efficient cycling and uniform deposition when no interphase is present on the electrode