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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.

Online acoustic emission (AE) sensing is a promising nondestructive technique for battery health monitoring. Herein, we report on the ability of AE sensing to differentiate among different chemomechanical degradation events in a TiS2-based model aqueous chemistry. Short and high-frequency AE signals primarily stem from fracture-related degradation of TiS2, such as layer delamination, exfoliation, and cracking. Long and lowfrequency signals originate from gas bubbles bursting when the cell is cycled outside the water stability window. The two processes demonstrate distinct AE features, allowing them to be semi-quantitatively distinguished from both time and frequency domains. Complementary physicochemical characterizations have been conducted to correlate with the AE observation, including online electrochemical mass spectrometry, operando synchrotron X-ray diffraction, and ex situ scanning electron microscopy. Our work indicates that online AE sensing holds the promise to identify complex chemomechanical degradation processes in batteries with liquid and potentially solid electrolytes.

Gas evolution is fundamentally problematic in rechargeable batteries, and may lead to swelling, smoking, and device-level failure. In laboratories, monitoring gas evolution can help understand dynamic chemical events inside battery cells, such as the formation of solid-electrolyte interphases, structural change of electrodes, and electrolyte degradation reactions. However, gassing in commercial batteries, discrete or continuous, is not monitored due to a lack of compatible sensing technologies. Here we describe the working principles of four real-time gas monitoring technologies for lithium-ion batteries. Gassing mechanisms and reaction pathways of five major gaseous species, namely H2, C2H4, CO, CO2, and O2, are comprehensively summarized. Since pertinent progress has been made on the optical fiber-based sensing of strain, pressure, and temperature of various battery cells recently, special emphasis has been given to fiber-based laser spectroscopy for gas detection. The technical details of the fiber-enhanced photothermal spectroscopy are compared with the four gas sensing technologies, and the commercialization possibilities are discussed. Owing to its small size, flexibility, and robustness, fiber-based sensing technology can be compatible with almost all kinds of battery cells, showcasing their great potential in various applications. It is envisioned that gas-event monitoring of rechargeable cells can be unlocked soon by utilizing fiber-based gas spectroscopy.

Anode-free zinc batteries offer reduced weight and simplified production compared to traditional zinc metal batteries, but challenges such as dendrite formation and parasitic reactions limit their efficiency and cycle life. In this study, we present an effective strategy to form a zincophilic interphase in situ via indium co-deposition during cycling, using InCl3 as an electrolyte additive. Zinc plating/stripping processes were investigated using operando electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D) and hydrodynamic spectroscopy, combined with other ex situ techniques. Our findings demonstrate that the indium-containing electrolyte additive has three functions: it induces oriented zinc deposition through prenucleation, suppresses the hydrogen evolution reaction by forming an indium intermediate layer, and suppresses zinc hydroxide sulfate (ZHS) formation by consuming OH– with In2O3/InOOH formation. These advantages result in a decreased overpotential and higher Coulombic efficiency, enhancing the design of highly reversible anode-free zinc batteries.

Online acoustic emission (AE) sensing is a nondestructive method that has the potential to be an indicator of battery health and performance. Rechargeable batteries exhibit complex mechano-electrochemical behaviors during operation, such as electrode expansion/contraction, phase transition, gas evolution, film formation, and crack propagation. These events emit transient elastic waves, which may be detected by a piezoelectric-based sensor attached to the battery cell casing. Research in this field is active and new findings are generated continuously, highlighting its potential and importance of further research and development. This Review provides a comprehensive analysis of AE sensing in rechargeable batteries, aiming to describe the underlying mechanisms and potential applications in battery monitoring and diagnostics.

Layered TiS₂ has been proposed as a versatile host material for various battery chemistries. Nevertheless, its compatibility with aqueous electrolytes has not been thoroughly understood. Herein, we report on a reversible hydration process to account for the electrochemical activity and structural evolution of TiS₂ in a relatively dilute electrolyte for sustainable aqueous Li-ion batteries. Solvated water molecules intercalate in TiS₂ layers together with Li⁺ cations, forming a hydrated phase with a nominal formula unit of Li_0.38(H₂O)_2−δTiS₂ as the end-product. We unambiguously confirm the presence of two layers of intercalated water by complementary electrochemical cycling, operando structural characterization, and computational simulation. Such a process is fast and reversible, delivering 60 mAh g^–1 discharge capacity at a current density of 1250 mA g^–1. Our work provides further design principles for high-rate aqueous Li-ion batteries based on reversible water cointercalation.

The practical application of lithium (Li) metal for next-generation rechargeable batteries is still hampered by uncontrolled growth of Li dendrite and severe volume change under repeated plating/stripping. Introducing a 3D structure to reserve space for Li storage and inducing uniform plating/stripping by a lithophilic interface layer are effective strategies to solve these problems. Herein, a novel 3D composite Li anode (Fe-N@SSM-Li) is constructed via an in situ reaction between Li and lithiophilic Fe2N/Fe3N (Fe-N) uniformly anchored on a stainless-steel mesh (SSM). The unique lithiophilic-conductive structure of the Fe-N@SSM-Li can stabilize the Li anode by effectively inducing uniform and dense deposition and confining Li deposition inside the Fe-N@SSM-Li to alleviate volume changes. The Fe-N@SSM-Li displays a distinguished electrochemical performance, with superior lifespan of 5000, 2250, and 1350 h under 1 mA cm−2/1 mAh cm−2, 5 mA cm−2/3 mAh cm−2, and 20 mA cm−2/3 mAh cm−2 in symmetric cells, respectively. Combined with this highly stable Fe-N@SSM-Li, the full cells using LiFePO4 (LFP) and S/C cathodes both show significantly improved electrochemical performances. This work provides a low-cost and scalable strategy for the construction of high-efficiency Li anode with a novel 3D structure, offers new insights to the research of Li metal batteries and beyond.

Battery cell assembly and testing in conventional battery research is acknowledged to be heavily time-consuming and often suffers from large cell-to-cell variations. Manual battery cell assembly and electrolyte formulations are prone to introducing errors which confound optimization strategies and upscaling. Herein we present ODACell, an automated electrolyte formulation and battery assembly setup, capable of preparing large batches of coin cells. We demonstrate the feasibility of Li-ion cell assembly in an ambient atmosphere by preparing LiFePO₄‖Li₄Ti₅O₁₂-based full cells with dimethyl sulfoxide-based model electrolyte. Furthermore, the influence of water is investigated to account for the hygroscopic nature of the non-aqueous electrolyte when exposed to ambient atmosphere. The reproducibility tests demonstrate a conservative fail rate of 5%, while the relative standard deviation of the discharge capacity after 10 cycles was 2% for the studied system. The groups with 2 vol% and 4 vol% of added water in the electrolyte showed overlapping performance trends, highlighting the nontrivial relationship between water contaminants in the electrolytes and the cycling performance. Thus, reproducible data are essential to ascertain whether or not there are minor differences in the performance for high-throughput electrolyte screenings. ODACell is broadly applicable to coin cell assembly with liquid electrolytes and therefore presents an essential step towards accelerating research and development of such systems.

The current exploration of high-energy-density cathode materials for Li-ion batteries is mainly concentrated on either so-called “Li-rich” or “Ni-rich” oxides. However, both are suffering from formidable practical challenges. Here, we combine these two concepts to obtain “Li-rich Ni-rich” oxides in pursuit of more practical high-energy-density cathodes. As a proof of concept, we synthesized an array of Li1+yNi(3−5y)/3Mo2y/3O2 oxides, whose structures were identified to be the coexistence of LiNiO2-rich and Li4MoO5-rich domains with the aid of XRD, TEM, and NMR techniques. Such an intergrowth structure of 5–20 nm size enables excellent mechanical and structural reversibility for the layered rock-salt LiNiO2-rich domain upon cycling thanks to the robust cubic rock-salt Li4MoO5-rich domain enabling an “epitaxial stabilization” effect. As a result, we achieved high capacities (>220 mA h g−1) with Ni contents as low as 80%; the Li1.09Ni0.85Mo0.06O2 member (y = 0.09) shows much improved cycling performances (91% capacity retention for 100 cycles at C/10) compared with pure LiNiO2. This work validates the feasibility of constructing Li-rich Ni-rich compounds in the form of intergrowing domains and hence unlocks vast possibilities for future cathode design.

Li[Li_xNi_yMn_zCo_{1−x−y−z}]O₂ (lithium-rich NMCs) are benchmark cathode materials receiving considerable attention due to the abnormally high capacities resulting from their anionic redox chemistry. Although their anionic redox mechanisms have been much investigated, the roles of cationic redox processes remain underexplored, hindering further performance improvement. Here we decoupled the effects of nickel and cobalt in lithium-rich NMCs via a comprehensive study of two typical compounds, Li_1.2Ni_0.2Mn_0.6O₂ and Li_1.2Co_0.4Mn_0.4O₂. We discovered that both Ni^3+/4+ and Co⁴⁺, generated during cationic redox processes, are actually intermediate species for triggering oxygen redox through a ligand-to-metal charge-transfer process. However, cobalt is better than nickel in mediating the kinetics of ligand-to-metal charge transfer by favouring more transition metal migration, leading to less cationic redox but more oxygen redox, more O₂ release, poorer cycling performance and more severe voltage decay. Our work highlights a compositional optimization pathway for lithium-rich NMCs by deviating from using cobalt to using nickel, providing valuable guidelines for future high-capacity cathode design.