Metal chloride-graphite molten salt batteries are promising for safe, low-cost energy storage at moderate temperatures (<200 degrees C). Here, we report a Zn/ZnCl2-graphite molten salt battery that integrates a solid-state Zn/ZnCl2 redox anode with a graphite cathode based on reversible C-n/C-n[AlCl4] intercalation chemistry. In an AlCl3/LiCl/NaCl molten salt electrolyte, the Zn/ZnCl2 redox couple exhibits a low equilibrium potential of 0.28 V versus Al/Al3+ and high reversibility. A ZnCl2 anode fabricated via dry-powder calendering delivers a specific capacity of 143 mAh g(-1), while the full-cell achieves 95% capacity retention over 100 cycles at 140 degrees C. Mechanistic investigations reveal that ZnCl2 undergoes a solid-state conversion to metallic Zn accompanied by NaCl crystallization during reduction, whereas the cathodic process proceeds through reversible formation of graphite intercalation compounds. This work establishes a cost-effective medium-temperature battery chemistry and provides insights into solid-state metal chloride redox processes for scalable and intrinsically safe energy storage.

Room-temperature sodium-sulfur (RT Na-S) batteries have garnered increasing attention due to their high theoretical capacity and the natural abundance of sodium resources. However, they suffer from the rapid capacity decay by the chemomechanical fatigue degradation (CFD) mechanism arising from repeated solid-state volume fluctuations and partial dissolution of sulfur species that progressively weaken the percolation network, leading to irreversible structural collapse, electrical disconnection, and eventual cell failure. To address the CFD, a rigid Na3Zr2Si2PO12 interlayer (NZSP) has been introduced for simultaneous mechanical confinement and chemical polysulfide anchoring, thus limiting volume fluctuation-induced stress, preserving the percolation network, and suppressing species-driven degradation. The NZSP-modified cathode exhibits an extremely high capacity of 1035.37 mAh g-1 (0.1 A g-1, 200 cycles), along with remarkable rate capability with a capacity of 830.56 mAh g-1 at 2 A g-1 (500 cycles), 685.18 mAh g-1 at 4 A g-1 after 500 cycles, respectively. Notably, after 2,000 cycles, the NZSP-modified cathode preserves its pristine morphology and structural integrity, whereas the unmodified counterpart suffers severe CFD-induced pulverization and delamination, failing after only 659 cycles. These findings demonstrate that integrating the NZSP interlayer effectively suppresses CFD, offering a practical materials strategy for achieving long-life, high-capacity RT Na-S batteries.

Liquid metal batteries (LMBs) have emerged as a promising technology for large-scale energy storage owing to their intrinsic safety, long cycle life, and low manufacturing cost. However, achieving further reductions in system-level cost remains challenging. We report a cost-effective Ca-Li & Vert;Pb LMB coupling a dual-active Ca-Li anode with an inexpensive Pb cathode. Synergy with a dual-cation CaCl2-LiCl (35 : 65 mol%) electrolyte enhances cycling stability. In situ EIS analysis reveals a unique discharge pathway: initial formation of CaLiPb followed by conversion to CaPb3 and LiPb. This sequence reshapes the voltage profile. Crucially, the molten LiPb phase redistributes, forming conductive networks that boost electrode kinetics. Consequently, an Ah-level battery achieves stable cycling at 100 mA cm-2 with a record-low electrode cost of 66.18 $ per kWh among all reported Ah-level LMBs. This work demonstrates a new high-performance, low-cost liquid metal battery architecture and provides fundamental design principles for next-generation economical grid-scale energy storage.

The Fe/FeCl2-graphite battery is an intermediate-temperature molten salt electrochemical system. It employs the solid Fe/Fe2+ redox couple as the negative electrode and a graphite positive electrode based on the intercalation/de-intercalation of AlCl- 4, offering high safety, low material cost and a moderate operating temperature range of 110-150 °C. However, the poor electronic conductivity and high nucleation barrier of the FeCl2 material result in limited electrochemical reversibility and reaction kinetics. Here, we demonstrate that the Fe-FeCl2 contact interface effectively enhances the redox reversibility and electrode kinetics by providing favorable sites for Fe0 nucleation and improving electronic conductivity. The prepared Fe-FeCl2-CR electrode delivers a low voltage hysteresis of 0.09 V and exhibits excellent electrochemical reversibility in the Fe/FeCl2-graphite molten salt battery, achieving a specific capacity of 162.6 mAh g-1 at 3 mA cm-2 and retaining 93% of its capacity after 200 cycles. Compared with the pure FeCl2 electrode, the Fe-FeCl2-CR electrode shows lower direct-current pulse resistance and negligible nucleation overpotential, which are primarily attributed to the Fe-philic nucleation interface. This mechanism is further confirmed by density functional theory (DFT) calculations, revealing that the (110) crystal plane of nano-Fe possesses the highest binding energy (-55.94 eV) during charging, thereby serving as the potential dominant interface for Fe0 nucleation. Additional self-discharge and capacity expansion tests further confirm the electrochemical reaction stability of the Fe-FeCl2-CR electrode in Fe/FeCl2-graphite molten salt batteries.

Calcium-based liquid metal batteries are promising for large-scale energy storage due to calcium abundance and low cost, yet their practical applications are impeded by high operating temperatures, severe self-discharge, limited coulombic efficiency, and rapid capacity fading. Here, we develop a machine learning (ML)-assisted optimization framework, integrating data-driven analysis, ML prediction, and experimental verification to design a high-performance ternary molten-salt electrolyte. Through multi-parameter evaluation of thermodynamic stability, melting behavior, density, and cost, KCl was identified as an optimal third component for CaCl2-LiCl based systems. A multidimensional descriptor-performance dataset was constructed to develop a random forest model for precise electrolyte composition optimization. Guided by this model, the KCl-CaCl2-LiCl electrolyte (13:35:52 mol%) was experimentally verified to enable stable operation at 480°C, delivering a coulombic efficiency >99.5%, an ultralow self-discharge current density of 0.31 mA cm-2, >91% capacity retention after 100 cycles, while maintaining a low material cost of 0.81$ kg-1. This optimized ternary electrolyte suppresses calcium dissolution through cooperative multi-cation effects, significantly improving low-temperature electrochemical performance and cycling stability. This work not only provides a viable pathway toward practical Ca-based LMBs but also establishes a generalizable ML-assisted paradigm for accelerated electrolyte design in advanced electrochemical energy storage.

Room temperature sodium-sulfur (RT Na-S) batteries have gained remarkable attention due to their high theoretical capacity, low cost, and rich raw material sources. Nevertheless, the shuttle effect and the low sulfur content still limit the further development of RT Na-S batteries. Here, micro-mesoporous carbon materials derived from cedarwood sawdust are synthesized through a simple annealing process with KOH activation as sulfur-carriers applied for RT Na-S batteries. The micro-mesoporous carbon materials with high specific surface area (1411.63 m2 g- 1) which achieve high sulfur content (61 wt%) and quite high sulfur loading (2.5 mg cm- 2). Micropores structure is used for inhibiting the shuttling behavior of sodium polysulfides to realize a quasi-solid reaction of sulfur. Besides, mesoporous and macropores promote the diffusion and penetration of electrolytes. The assembled Na-S battery achieves splendid initial capacity (1700.54 mAh g- 1) and exhibits fantastic cycle performance at 0.2 A g- 1 (724 mAh g- 1, 100 cycles) even at sulfur loading up to 2.5 mg cm- 2. Moreover, the Na-S battery demonstrates a retained discharge specific capacity of 497.78 mAh g- 1 (500 cycles) at current densities of 2 A g- 1. The cedarwood sawdust-derived micro-mesoporous carbon characterized by a high sulfur content offers a practicable strategy for the synthesis of promising sulfur cathodes.

Liquid metal batteries (LMBs), with low cost, long lifetime, straightforward assembly, and high safety endowed by their distinctive three-layer liquid structure, are emerging as a strong contender for large-scale energy storage. The Li||Bi cell exhibits stable cycling performance and significant potential for practical applications. However, the formation of solid Li3Bi intermetallic compounds at the electrolyte-electrode interface during discharging restrict lithium-ion transfer kinetics, resulting in high polarization and limited rate capability. To address these challenges, we developed a Bi-Cd dual-active alloy positive electrode, where the addition of Cd creates liquid pathways to enhance rate performance and improve adaptability to lower operating temperature. The Li|LiFLiCl-LiBr|Bi40Cd60 cell, operating at 500 degrees C, retained 70 % of its initial capacity even at a high current density of 800 mA cm- 2. Furthermore, when paired with the LiCl-LiBr-KBr electrolyte (Tm = 310 degrees C), the Li||Bi40Cd60 cell successfully operated at 380 degrees C and achieved 300 stable cycles with a discharge capacity of 4.31 Ah at 100 mA cm- 2. This study provides valuable insights into innovative electrode design for high-performance, grid-scale liquid metal batteries, paving the way for more efficient and adaptable energy storage solutions.

Li metal with ultra-high theoretical capacity is a promising anode for next-generation high-energy-density battery technologies. Nevertheless, the uncontrolled Li dendrite growth, continuous interfacial side reactions and irregular volume expansion bring about rapid capacity decay of Li metal anodes (LMAs). Herein, we design a bilayer host structure with an electronic conductivity gradient through a facile blade coating strategy to regulate Li deposition behavior. The electronic-insulative Si3N4 top layer prevents the apical growth of Li dendrites and promotes the penetration of electrolytes into the host so as to lower electrode polarization. The carbon black/ LiNO3 mixed bottom layer creates mixed electronic-ionic conductive network to enhance the charge transfer kinetics of Li ions and lower Li nucleation barrier. Moreover, we first discover that the Si3N4 protective layer avoids the cell failure resulting from the dissolution of LiNO3 in ether electrolytes, enabling the Si3N4-C/LiNO3 electrode to operate smoothly for over 600 cycles, delivering an average Coulombic efficiency of up to 98.65 %. Furthermore, the Si3N4-C/LiNO3-composited LMAs paired with 10.5 mg cm- 2 LiFePO4 cathodes achieve 200 stable cycles at a low N/P ratio of 1 under corrosive carbonate ester electrolytes, with an anode capacity utilization ratio as high as 50 %. This is the first report on the LiNO3-modified host materials that exhibit superior electrochemical properties in ether electrolytes, shedding a new light on the structural design of LMAs to enable high-energy-density Li metal batteries.

Liquid metal battery (LMB) is emerging as a promising solution for grid-scale energy storage, offering advantages such as low cost, long lifespan, safety, ease of configuration and scalability. However, the discharge products, consisting of solid intermetallic compounds with dense structure, suffer from insufficient ion transport, leading to high polarization and unsatisfactory rate performance. In this study, we address this challenge by implementing an alloy cathode with a networked structure formed by liquid tin (Sn), which enhances electrochemical kinetics. Notably, the bismuth-tin (Bi-Sn) alloy cathode exhibits a significantly high lithium (Li) ion diffusion coefficient, reducing polarization voltage and increasing the reaction stoichiometric ratio of Li. The Li||Bi-Sn cell achieves a high energy efficiency of 91.39 %, with enhanced material utilization of 93.91 % at 100 mA cm- 2. Additionally, it demonstrates excellent high-rate capability, with 81.87 % of capacity retention and 64.86 % of energy efficiency at 600 mA cm- 2 (3.40 C). These exceptional performance metrics, combined with a competitive cost of 88.69 $ kWh- 1, make the Li||Bi-Sn cell a highly attractive candidate for large-scale energy storage applications.

Liquid metal batteries (LMBs) are emerging as a promising energy storage solution owing to their inherent safety, low cost, and long lifespan. Bismuth (Bi) offers excellent cycle stability but is hindered by sluggish electrode kinetics due to the formation of compact and poorly conductive intermetallics at high rates. Here, we construct an electronically networked architecture to overcome this limitation by incorporating little copper (Cu) into a Bi electrode. This innovative design enhances electrical conductivity and reduces the ion diffusion energy barrier, affording dramatically improved electrochemical performance. Our Li & Vert;Bi96Cu4 cell demonstrates superior high-rate capability, delivering 85.50% of the theoretical capacity at 3C, a substantial improvement compared to 57.50% of the Li & Vert;Bi cell. Furthermore, it exhibits unprecedented cyclability without noticeable capacity degradation over 4000 cycles, a performance unparalleled by other reported LMB chemistries. This facile and effective Cu doping modification provides a transformative approach to enhance Bi electrode kinetics, offering a new paradigm for advanced electrode design for LMBs.

Recycling spent LiNi x Co y Mn1-x-y O2 cathode materials has gained significant attention, owing to its cost efficiency and environmental benefits. Nevertheless, several challenges persist, such as complex recycling processes, high costs, and the limited integration of recycling and regeneration technologies. This study proposes a solid-phase sintering approach to recycle the spent LiNi0.5Co0.2Mn0.3O2 (NCM523) material into LiNi0.8Co0.1Mn0.1O2 (NCM811) through an (NH4)2SO4-assisted calcination and coprecipitation (NS-CC) strategy. The NS-CC strategy not only simplifies recycling procedures by avoiding the complex element separation but also achieves a high material recovery rate. At a calcination temperature of 350 degrees C, recovery rates of Ni, Co, Mn, and Li reach approximately 99%. Under optimal regeneration conditions (pH 11.3 and presintering temperature of 470 degrees C), the regenerated NCM811 cathode exhibits a high specific capacity of 186.64 mAhg-1 at 0.1 C, with excellent cycling performance and capacity retention of 85 and 70% after 100 and 200 cycles, respectively. Life cycle assessment and techno-economic analysis demonstrate that the NS-CC strategy exhibits minimal energy consumption, lower CO2 emissions, and high economic viability. This work offers a practical solution for efficiently recycling the spent NCM523 cathode materials and regenerating them into nickel-rich NCM811, advancing the sustainable development of lithium-ion batteries.

Room-temperature sodium-sulfur (RT Na-S) batteries have become a strong contender in energy storage owing to their ultra-high energy density and low costs. Whereas, the practical application of RT Na-S batteries is limited by issues such as sluggish redox reactions and shuttle effects in sulfur (S) cathodes. To solve these challenges, this study introduces a novel Ni-doped MoS2/MPC/S cathode material for RT Na-S batteries, in-situ synthesized via magnetron sputtering. Compared with single MoS2 film, the introduction of Ni atoms endows the film with superb chemisorption capacity and catalytic performance for polysulfides. Meanwhile, the bio-derived porous carbon raises the electroconductivity of the sulfur cathodes and mitigates volume changes during cycling. Assembled with this as-prepared cathode, the RT Na-S batteries display remarkable specific capacity (1070.56 mAh g- 1, 100 cycles at 0.1 A g- 1) and splendid rate performance (557.24 mAh g- 1, 400 cycles at 2 A g- 1, and 467.49 mAh g- 1, 500 cycles at 3 A g- 1). The superior electrochemical performance is ascribed to the rapid polysulfides conversion catalyzed by Ni-MoS2 microspheres, as further supported by the density functional theory (DFT) calculations. The present work provides new insights into designing highly efficient catalysts with heterogeneous doping for high-performance RT Na-S batteries.

The application of rechargeable lithium metal batteries is challenged by intractable issues of uncontrollable Li dendrite growth that result in poor cycle life and safety risks. In this work, an air-stable interphase is developed to protect the lithium metal anode (LMA) via a facile solution-based approach. The Ag-embedded fluoride-rich interphase not only creates abundant lithiophilic sites for homogenizing Li nucleation and growth but also resists severe air erosion to protect the LMA beneath and enable decent cycling stability. As a result, the Ag-F-rich interphase enables flat Li deposition on LMA, which is clearly observed in the operando Li plating experiments. Paired with a LiFePO4 cathode (11.8 mg cm-2), the Ag-F-rich interphase-modified LMA enables 300 stable cycles at 0.5 C, delivering a capacity retention ratio as high as 91.4%. Even after being exposed to air for 1 h, the modified LMA still runs smoothly for over 120 cycles with ignorable capacity decay, exhibiting great air stability. This work proves the concept of functionalizing the interphase on the LMA to enable good cycling performance even under severe air erosion.

Liquid metal batteries (LMBs) are promising candidates for grid-scale energy storage due to their exceptional kinetics, scalability, and long lifespan derived from the distinctive three-liquid-layer structure. However, the positive electrode (such as Bi) suffers from insufficient wettability on the current collector, resulting in excess electrical resistance and uneven current distribution, thus deteriorating the cycling stability. Here the incorporation of 4 mol% Se into Bi-based metal is proposed producing an interface layer with highly surface-active property that decreases the electrode's contact angle with the 304 stainless-steel (SUS304) from 144.7° to 74.3°, so as to improve the wettability. The as-prepared 20 Ah Li || Bi-Se4 (the content of Se is 4 mol% of Bi) cell cycled 1200 times with capacity fade rate of merely 0.00174% per cycle. This facile and effective approach provides a pathway toward the production of stable cells with an extended lifespan and boosts the practical implementation of LMBs.

Liquid metal batteries (LMBs) hold immense promise for large-scale energy storage. However, normally LMBs are based on single type of cations (e.g., Ca2+, Li+, Na+), and as a result subject to inherent limitations associated with each type of single cation, such as the low energy density in Ca-based LMBs, the high energy cost in Li-based LMBs, and the short cycling lifespan in Na-based LMBs. Here we propose a dual-cation (Ca2+ and Li+) liquid metal battery, which allows access to, simultaneously, high energy density, prolonged cycling lifespan, reduced energy cost, and enhanced cycling stability. For this strategy to work, the main obstacle to overcome is the instability of the dual-cation system in electrochemical reactions. We have undertaken a hybrid design approach to resolve this issue, by integrating phase diagram design, first-principles calculations, and machine learning techniques. We discover that incorporating magnesium as an inert additive can effectively stabilize the cycling performance of dual-cation LMBs. Furthermore, our results reveal that specific ion ratios are required to release tailor dual-cation chemistry, to enable the designed multi-component alloy (Ca-Li-Mg in our case) electrode to function properly in LMBs. These findings are expected to have general implications for future developments of innovative LMBs with enhanced performance.