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Solid electrolyte interphase (SEI) makes the electrochemical window of aqueous electrolytes beyond the thermodynamics limitation of water. However, achieving the energetic and robust SEI is more challenging in aqueous electrolytes because the low SEI formation efficiency (SFE) only contributed from anion‐reduced products, and the low SEI formation quality (SFQ) negatively impacted by the hydrogen evolution, resulting in a high Li loss to compensate for SEI formation. Herein, we propose a highly efficient strategy to construct Spatially‐Temporally Synchronized (STS) robust SEI by the involvement of synergistic chemical precipitation‐electrochemical reduction. In this case, a robust Li3PO4‐rich SEI enables intelligent inherent growth at the active site of the hydrogen by the chemical capture of the OH− stemmed from the HER to trigger the ionization balance of dihydrogen phosphate (H2PO4−) shift to insoluble solid Li3PO4. It is worth highlighting that the Li3PO4 formation does not extra‐consume lithium derived from the cathode but makes good use of the product of HER (OH−), prompting the SEI to achieve 100 % SFE and pushing the HER potential into −1.8 V vs. Ag/AgCl. This energetic and robust SEI offers a new way to achieve anion/concentration‐independent interfacial chemistry for the aqueous batteries. [ABSTRACT FROM AUTHOR]

The desperate pursuit of high gravimetric specific energy leads to the ignorance of volumetric energy density that is one of the basic requirements for batteries. Due to the high volumetric capacity, less‐prone formation of dendrite, and low reduction potential of Mg metal, rechargeable Mg batteries are considered with innately high volumetric energy density. Nevertheless, the substantial elevation in energy density is compromised by extremely excessive Mg metal anode. Herein, the proof‐of‐concept of anode‐free Mg2Mo6S8‐MgS/Cu batteries is proposed, in which MgS as the premagnesiation additive constantly decomposes to replenish Mg loss by electrolyte corrosion over cycling, while both Mg2Mo6S8 and MgS acts as the active material to reversibly provide high capacities. Besides, Mg2Mo6S8 shows superior catalytic activity on the decomposition of MgS and provides the strong affinity to polysulfides to restrain their dissolution. Consequently, the anode‐free Mg2Mo6S8‐MgS/Cu batteries deliver a high reversible capacity of 190 mAh g−1 with the capacity retention of 92% after 100 cycles, corresponding to the highly competitive energy density of 420 Wh L−1. The proposed anode‐free Mg battery here spotlights the great promise of Mg batteries in achieving high volumetric energy densities, which will significantly expedite the advances of Mg batteries in practice. [ABSTRACT FROM AUTHOR]

Water-in-salt electrolytes (WiSEs) have attracted extensive attention as promising alternatives to organic electrolytes. The limited electrochemical stability windows (ESWs) of aqueous electrolytes are significantly widened by WiSEs. However, the actual ESWs are lower than predicted as the interphase with WiSEs is not as stable as the solid electrolyte interphase (SEI) in conventional lithium-ion batteries. Therefore, identifying the interface state in WiSEs is vital to understanding their electrochemical behavior. Here, the structure of the lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) electrolyte near the interface of the carbon electrode (Ketjen black) was evaluated by experimental methods (neutron diffraction, Raman, and nuclear magnetic resonance spectroscopy) and molecular dynamics (MD) simulations. The results reveal that the introduction of carbon electrodes increases the size of the anionic nanoclusters and enhances the microphase separation at the interface. The MD simulations show that cation–π interactions are responsible for the evolution of anionic nanoclusters at the electrode interface. Moreover, lower charge transfer resistance is achieved at carbon-based electrodes due to the specific interface state. Our findings provide a strategy for introducing cation–π interactions between electrodes and electrolytes to improve the electrochemical performance. [ABSTRACT FROM AUTHOR]

Aqueous Li‐ion batteries (ALIBs) are safe, environmentally friendly, and cost‐effective, promising for electric energy storage (EES). The high voltage ALIBs (HV‐ALIBs) supported by water‐in‐salt electrolytes are ideal for lowering the energy cost ($/Wh) of EES. However, HV‐ALIBs have been built with a high positive/negative capacity ratio (P/N ratio) to ensure their long‐term cycle life due to the irreversible Li consumption in the initial cycle induced by the solid electrolyte interface (SEI) formation and the parasitic reaction. Thus, the benefits of HV‐ALIBs in cost and energy density are mitigated inevitably. Generally, the feasible approach is adding per‐lithiation additives (PAs) to compensate for the capacity loss in the initial cycle. However, using PAs in ALIBs is challenging due to the high chemical activity of water. Here, a new strategy to achieve the pre‐lithiation by introducing manganese metal as a sacrificial PA for HV‐ALIBs that can provide over 900 mAh g−1 specific capacity without any adverse impact is proposed. The P/N ratio reduces to 1.02 by the LiMn2O4||TiO2 pouch cell using the sacrificial manganese PA. This results in a high initial energy density above 120 Wh kg−1 and outstanding cycle stability with a capacity retention of 80% after 400 cycles. [ABSTRACT FROM AUTHOR]

The high weight fraction of the electrolyte in lithium–sulfur (Li–S) full cell is the primary reason its specific energy is much below expectations. Thus far, it is still a challenge to reduce the electrolyte volume of Li–S batteries owing to their high cathode porosity and electrolyte depletion from the Li metal anode. Herein, we propose an ultralight electrolyte (0.83 g mL−1) by introducing a weakly‐coordinating and Li‐compatible monoether, which greatly reduces the weight fraction of electrolyte within the whole cell and also enables Li–S pouch cell functionality under lean‐electrolyte conditions. Compared to Li–S batteries using conventional counterparts (≈1.2 g mL−1), the Li–S pouch cells equipped with our ultralight electrolyte could achieve an ultralow electrolyte weight/capacity ratio (E/C) of 2.2 g Ah−1 and realize a 19.2 % improvement in specific energy (from 329.9 to 393.4 Wh kg−1) under E/S=3.0 μL mg−1. Moreover, more than 20 % improvement in specific energy could be achieved using our ultralight electrolyte at various E/S ratios. [ABSTRACT FROM AUTHOR]

Anode‐free lithium metal batteries can maximize the energy density at the cell level. However, without the Li compensation from the anode side, it faces much more challenging to achieve a long cycling life with a competitive energy density than Li metal‐based batteries. Here, we prolong the lifespan of an anode‐free Li metal battery by introducing Li‐rich Li2[Ni0.8Co0.1Mn0.1]O2 into the cathode as a Li‐ions extender. The Li2[Ni0.8Co0.1Mn0.1]O2 can release a large amount of Li‐ions during the first charging process to supplement the Li loss in the anode, then convert into NCM811, thus extending the lifespan of the battery without the introduction of inactive elements. By the benefit of Li‐rich cathode and high reversibility of Li metal on Cu foil, the anode‐free pouch cells enable to achieve 447 Wh kg−1 energy density and 84 % capacity retention after 100 cycles in the condition of limited electrolyte addition (E/C ratio of 2 g Ah−1). [ABSTRACT FROM AUTHOR]

Anode‐free designs can obtain the ultimate energy density of lithium metal batteries. However, without a continuous Li supply from the anode side, it is much more challenging to achieve high capacity retention with a competitive energy density. Here, the lifespan of an anode‐free Li metal battery is prolonged by applying an epitaxial induced plating current‐collector (E‐Cu). The functional layer on E‐Cu initiates Li storage by an alloying approach, forming an epitaxial induce layer, which exhibits speedy surface diffusion for of Li‐ions, resulting in the block like epitaxial growth of Li. Moreover, this alloying process also promotes the formation of a LiF‐rich solid electrolyte interphase (SEI), which is very useful for uniform Li plating. Due to the benefits of epitaxial Li plating and LiF‐rich SEI, the initial coulombic efficiency of the E‐Cu/Li asymmetric cell increases from 93.24 to 98.24%, and the capacity retention of anode‐free NCM811/E‐Cu pouch cell increases from 66 to 84% with a remarkable energy density of 420 Wh kg−1 in the condition of limited electrolyte addition (E/C ratio of 2 g Ah−1). This strategy is promising in the development of high energy batteries in extending their lifespans. [ABSTRACT FROM AUTHOR]

Nowadays, cost-efficient and high-power energy storage technologies are urgently required for extensive integration of intermittent wind and solar renewable energy. Complying with the simplification and acceleration principle, we designed a fast-charge Al organic battery in which ionic diffusion in anode materials and through the solid electrolyte interphase (SEI) process is simplified while the generation of charge-carrier ions at the cathode/anode interface and ion diffusion in cathode materials are accelerated. A prototype based on 2,3,5,6-tetraphthalimido-p-benzoquinone (TPBQ)–Al was successfully demonstrated with 100 mA h pouch cells displaying superior power capability, high energy density and excellent cycling stability. Moreover, extensive characterizations and DFT calculations predict the crystal structure and simulate the precise reaction pathway corresponding to the thermodynamic redox potential of TPBQ and consolidate our proposed AlCl2+ electrochemical surface-coordination and storage mechanism. We believe that our design philosophy by simplifying and accelerating kinetics would provide guidance for tailoring fast and affordable energy storage systems. [ABSTRACT FROM AUTHOR]

Mass dissolution is one main problems for cathodes in aqueous electrolytes due to the strong polarity of water molecules. In principle, mass dissolution is a thermodynamically favorable process as determined by the Gibbs free energy. However, in real situations, dissolution kinetics, which include viscosity, dissolving mass mobility, and interface properties, are also a critical factor influencing the dissolution rate. Both thermodynamic and kinetic dissolving factors can be regulated by the ratio of salt to solvent in the electrolyte. In this study, concentration‐controlled cathode dissolution is investigated in a susceptible Na3V2(PO4)3 cathode whose time‐, cycle‐, and state‐of‐charge‐dependent dissolubility are evaluated by multiple electrochemical and chemical methods. It is verified that the super‐highly concentrated water‐in‐salt electrolyte has a high viscosity, low vanadium ion diffusion, low polarity of solvated water, and scarce solute−water dissolving surfaces. These factors significantly lower the thermodynamic‐controlled solubility and the dissolving kinetics via time and physical space local mass interfacial confinement, thereby inducing a new mechanism of interface concentrated‐confinement which improves the cycling stability in real aqueous rechargeable sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

An aluminum‐ion battery was assembled with potassium nickel hexacyanoferrate (KNHCF) as a cathode and Al foil as an anode in aqueous electrolyte for the first time, based on Al3+ intercalation and deintercalation. A combination of ex situ XRD, X‐ray photoelectron spectroscopy (XPS), galvanostatic intermittent titration technique (GITT), and differential capacity analysis was used to unveil the crystal structure changes and the insertion/extraction mechanism of Al3+. Al3+ could reversibly insert/extract into/from KNHCF nanoparticles through a single‐phase reaction with reduction/oxidation of Fe and Ni. Over long‐term cycling, it was Fe rather than Ni that contributed to more capacity owing to the dissolution of Ni from the KNHCF structure, which could be expressed as a compensation effect of mixed redox centers in KNHCF. KNHCF delivered an initial discharge capacity of 46.5 mAh g−1. The capacity decay could be attributed to the unstable interface between Al foil and the aqueous electrolyte owing to the catalytic activity of the Ni transferring from Ni dissolution of KNHCF to the Al foil anode, rather than KNHCF structure collapse; KNHCF maintained its 3 D framework structure for 500 cycles. This work is expected to inspire more exhaustive investigations of the mechanisms that occur in aluminum‐ion batteries. [ABSTRACT FROM AUTHOR]

The lack of high‐power and stable cathodes prohibits the development of rechargeable metal (Na, Mg, Al) batteries. Herein, poly(hexaazatrinaphthalene) (PHATN), an environmentally benign, abundant and sustainable polymer, is employed as a universal cathode material for these batteries. In Na‐ion batteries (NIBs), PHATN delivers a reversible capacity of 220 mAh g−1 at 50 mA g−1, corresponding to the energy density of 440 Wh kg−1, and still retains 100 mAh g−1 at 10 Ag−1 after 50 000 cycles, which is among the best performances in NIBs. Such an exceptional performance is also observed in more challenging Mg and Al batteries. PHATN retains reversible capacities of 110 mAh g−1 after 200 cycles in Mg batteries and 92 mAh g−1 after 100 cycles in Al batteries. DFT calculations, X‐ray photoelectron spectroscopy, Raman, and FTIR show that the electron‐deficient pyrazine sites in PHATN are the redox centers to reversibly react with metal ions. [ABSTRACT FROM AUTHOR]