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Aqueous lithium‐ion batteries (ALIBs) are attracting significant attention as promising candidates for safe and sustainable energy storage systems. This paper delves into the crucial aspects of ALIB technology focusing on the interaction between LiCoO2 (lithium cobalt oxide) cathode material and water electrolytes, with a specific emphasis on the Oxygen Evolution Reaction (OER) process. Fundamental understanding of the electrochemical behavior of LiCoO2 in aqueous electrolytes is crucial for enhancing the performance, safety, and longevity of ALIBs using LiCoO2 as the cathode material. Through a comprehensive periodic density functional analysis of the LiCoO2‐water at the cathode interface, the potential catalytic contributions to the OER mechanism of LiCoO2 are explored. The catalytic properties of LiCoO2 towards OER are investigated considering different steady states of the lowest energy surfaces of LiCoO2 and three different Li concentrations. Our results do not predict the formation of oxygen gas due to the expected large overpotentials, although the exergonic water decomposition to hydroxyl by means the first proton‐electron transfer is predicted at equilibrium potential. This work contributes to the fundamental understanding of LiCoO2 as cathode for aqueous lithium‐ion batteries, reporting the pros and cons of one of the most common cathode materials for traditional non‐aqueous batteries. [ABSTRACT FROM AUTHOR]

The solid‐electrolyte interphase (SEI) is the key component of the electrochemical electrode as a passivation layer, which enables a long calendar life for commercial applications. However, owing to the poor understanding of aqueous SEI in conventional aqueous electrolytes, the adoption of aqueous Li‐ion batteries (ALIBs) has been drastically limited. Herein, the construction of a robust aqueous SEI is successfully demonstrated by introducing a ladderized heterocyclic polymer electrode into a water‐in‐salt electrolyte, leading to ultra‐stable dual‐ion storage with long‐term calendar life. The sophisticated SEI composed of fluorinated/oxygenated species is revealed. Electrochemical and structural analysis confirm that such SEI formation is characterized by a proton co‐intercalation, which consumes the water in the Li+'s solvation shell to trigger the subsequent decomposition of organic anions. This new SEI formation path is expected to broaden the horizons of aqueous SEI and open new avenues for the design of versatile electrode materials for further advances in ALIBs. [ABSTRACT FROM AUTHOR]

Heterogeneous photocatalysis utilizing TiO2 nanoarrays is one of the most promising advanced oxidation techniques for wastewater treatments. It is still challenging to effectively improve the photocatalytic activity of TiO2 nanoarrays, especially via a simple method. In this study, trace lithium ions are doped into anatase TiO2 nanowire arrays by using the operating principles of aqueous lithium-ion batteries. The doping process is simple and quite rapid. Even with trace doping amounts, the Li-doped anatase TiO2 shows high photocatalytic activity for pollutant degradation, whose rate constants are 1.8 and 1.6 times that of the pristine anatase TiO2 for the degradation of Rhodamine B and phenol, respectively. It can provide an effective route to design high-performance photocatalysts for environmental purification. [ABSTRACT FROM AUTHOR]

Durability and capacity of electrode materials, especially the anodes, are the main challenges for aqueous Li-ion batteries. In this work, MoSe2 micron flowers have been synthesized and investigated as anodes for Li+ storage in LiCl aqueous-based electrolytes. In the LiCl solution, the working potential of the MoSe2 anode can reach −1.0 V (vs Ag/AgCl). Yet, its reversible capacity is only ∼14 mAh g−1 (50 C g−1), owing to the absence of Faradaic reactions and the fast deformation of MoSe2. After gelation of the LiCl solution using poly vinyl alcohol (PVA), the activity of water is largely inhibited, and the operating potential is broadened to −1.2 V. In this gel system, the Faradaic reaction of the MoSe2 anode is triggered, and hence its capacity is largely enhanced. With a suitable amount of PVA (LiCl/PVA-20), the MoSe2 electrode can deliver reversible capacities of high as 157 mAh g−1 at 1 A g−1, and 139 mAh g−1 at 2 A g−1, and still high as 100 mAh g−1 after 50 cycles, indicating relative good stability. Using commercial LiMn2O4 as cathode, a full aqueous Li-ion battery was assembled, and a high discharge voltage of ∼1.8 V can be achieved. It is found that not only the activity of water but also the morphology change of the MoSe2 during cycling is inhibited in the gel electrolyte.

The use of conductive carbon materials in 3D‐printing is attracting growing academic and industrial attention in electrochemical energy storage due to the high customization and on‐demand capabilities of the additive manufacturing. However, typical polymers used in conductive filaments for 3D printing show high resistivity and low compatibility with electrochemical energy applications. Removal of insulating thermoplastics in as‐printed materials is a common post‐printing strategy, however, excessive loss of thermoplastics can weaken the structural integrity. This work reports a two‐step surface engineering methodology for fabrication of 3D‐printed carbon materials for electrochemical applications, incorporating conductive poly(ortho‐phenylenediamine) (PoPD) via electrodeposition. A conductive PoPD effectively enhances the electrochemical activities of 3D‐printed frameworks. When PoPD‐refilled frameworks casted with LiMn2O4 (LMO) composite materials used as battery cathode, it delivers a capacity of 69.1 mAh g−1 at a current density of 0.036 mA cm−2 (≈1.2 C discharge rate) and good cyclability with a retained capacity of 84.4% after 200 cycles at 0.36 mA cm−2. This work provides a pathway for developing electroactive 3D‐printed electrodes particularly with cost‐efficient low‐dimensional carbon materials for aqueous rechargeable Li‐ion batteries. [ABSTRACT FROM AUTHOR]

In pursuit to find stable economic anode for aqueous lithium-ion batteries, tavorite structured LiFePO 4 OH hydroxyphosphate has been investigated in aqueous battery for the first time. First, the target compound is tested with organic electrolyte, giving the highest reported discharge capacity of 140 mAh g−1 with an Fe3+/Fe2+ redox potential of 2.6 V with excellent reversibility. LiFePO 4 OH is found to work as a promising anode in aqueous electrolyte with capacity ∼153 mAh g−1 (at 0.42 V vs. Ag/AgCl) with good cycling stability. An all-phosphate LiFePO 4 | LiFePO 4 OH aqueous full cell has been fabricated having the first cycle capacity of 120 mAh g−1 (energy density ∼ 97 Wh kg−1). Tavorite LiFePO 4 OH forms an economic potential anode for aqueous Li-ion batteries. • Tavorite LiFePO 4 OH was implemented as anode material for aqueous Li-ion batteries. • It delivered 153 mAh g−1 discharge capacity at 1.0 mA cm−2 with good cyclability. • LiFePO 4 OH.| LiFePO 4 all phosphate full cell was fabricated. • A first discharge capacity of 120 mAh g−1 with 97 Wh kg−1 energy density was observed. [ABSTRACT FROM AUTHOR]

Lithium manganese silicate (Li2MnSiO4) demonstrates rich polymorphism with orthorhombic Pmn21 polymorph having better crystalline ordering over orthorhombic Pmnb and monoclinic forms. In this work, Li2MnSiO4 nanoparticles with the Pmn21 phase were synthesized by hydrothermal synthesis. Powder X-ray diffraction, HRSEM, and HRTEM as well as SAXS investigations revealed crystalline, spherical nanoparticles with average diameters between 14 and 25 nm. The binding energy of surface active Mn2+ ions in Li2MnSiO4 was observed at 642.9 eV in XPS analysis. SSNMR spectroscopic results revealed isotropic peaks at − 288.5 and 295.32 ppm which are attributed to the hyperfine coupling between the Li nuclei and the unpaired electrons of the Mn2+ ions. The electrochemical properties of Li2MnSiO4 electrode were studied in various 1 M LiX (X = SO42−, NO3− and ClO4−) aqueous electrolytes at a potential window of 0.2–1 V. Studies in the Li2SO4 aqueous electrolyte demonstrated better electrochemical properties with increasing peak current values up till the 2000th cycle. Charge and discharge capacities of 77.0 and 57.7 mAh g−1 were obtained at a scan rate of 5 mV s−1 with a Li-ion diffusion coefficient of 1.61 × 10−16 cm2 s−2. A small charge transfer resistance in the Li2SO4 electrolyte was also observed in EIS measurements indicating faster charge transfer kinetics. An aqueous Li-ion Swagelok-type full cell was assembled with microcrystalline graphite as anode and Li2MnSiO4 as the cathode. 1 M Li2SO4 was used as the electrolyte. The cell delivered a charge capacity of 61.8 mAh g−1 and a discharge capacity of 52.5 mAh g−1 at a current load of 1.2 A g−1 with good capacity retention of 94.0% and a Coulombic efficiency of 99.5% over 3300 cycles. SEM image, FTIR, XPS, and discharge capacity versus coulombic efficiency plots of Li2MnSiO4 nanoparticles [ABSTRACT FROM AUTHOR]

[Display omitted] • Surface orientation of spinel Li 1-x Mn 2 O 4 affects the interaction with H 2 O. • DFT simulations predict the partial water decomposition. • The O 2 production implies, in general, large overpotentials. • At equilibrium potential, O and OOH intermediates are anchored to the surface. Aqueous lithium-ion batteries are receiving a lot of attention as large-scale energy storage technology owing to their low-cost, environmentally friendly, and safe behavior in comparison to commercial organic Li-ion batteries. However, aqueous batteries suffer fast degradation due to the interaction of water with electrodes. The O loss has often been claimed to deteriorate the electrode materials and the voltage window accessible for the cathode and anode is limited by aqueous electrolyte decomposition through O 2 evolution at the cathode and H 2 evolution at the anode. In this work, we use density functional theory simulations to unveil the behavior of spinel Li 1-x Mn 2 O 4 as cathode material for aqueous Li-ion batteries exploring the Li 1-x Mn 2 O 4 electrode deterioration at the surface level. The surface stability, O vacancy formation, interaction with water, and oxygen evolution reaction have been investigated at different Li concentrations, suggesting that a partially lithiated (0 1 1) surface can produce O 2 at low overpotential, and (0 0 1) termination can favor the presence of O and OOH intermediates anchored to the surface at 1.23 V, without generating O 2. Our work reveals the pros and cons of this material as a cathode for aqueous electrolytes and the importance of surface termination. [ABSTRACT FROM AUTHOR]

In this paper, rutile TiO nanorod arrays are fabricated by a template-free method and proposed as a promising anode for aqueous Li-ion battery. The as-prepared TiO nanorod arrays exhibited reversible Li-ion insertion/extraction ability in aqueous LiOH electrolyte. Moreover, galvanostatic charge/discharge test results demonstrated that the reversible capacity of TiO nanorods could reach about 39.7 mC cm, and 93.8 % of initial capacity was maintained after 600 cycles at a current density of 1 mA cm (=240 C rate), indicating excellent cycling stability and rate capability. [ABSTRACT FROM AUTHOR]

Carboxymethylcellulose (CMC) has been proposed as a polymeric binder for electrodes in environmentally friendly Li-ion batteries. Its physical properties and interaction with Li+ ions in water are interesting not only from the point of view of electrode preparation-processability in water is one of the main reasons for its environmental friendliness-but also for its possible application in aqueous Li-ion batteries. We combine molecular dynamics simulations and variable-time pulsed field gradient spin-echo (PFGSE) NMR spectroscopy to investigate Li+ transport in CMC-based solutions. Both the simulations and experimental results show that, at concentrations at which Li-CMC has a gel-like consistency, the Li+ diffusion coefficient is still very close to that in water. These Li+ ions interact preferentially with the carboxylate groups of CMC, giving rise to a rich variety of coordination patterns. However, the diffusion of Li+ in these systems is essentially unrestricted, with a fast, nanosecond-scale exchange of the ions between CMC and the aqueous environment. [ABSTRACT FROM AUTHOR]

High-concentration water-in-salt (WIS) electrolytes expand the stable electrochemical window of aqueous electrolytes, leading to the advent of high-voltage (above 2 V) aqueous Li-ion batteries (ALIBs). However, the high lithium salt concentration electrolytes of ALIBs result in their high cost and deteriorate kinetic performance. Therefore, it is challenging for ALIBs to explore aqueous electrolytes with appropriate concentration to balance the electrochemical window and kinetic performance as well as the cost. In contrast to maintaining high concentrations of aqueous electrolytes (>20 m), a small number of hydrophobic cations are introduced to a much lower electrolyte concentration (13.8 m), and it is found that, compared with WIS electrolytes, ALIBs with these concentration-lowered electrolytes possess a compatible stable electrochemical window (3.23 V) and achieve better kinetic performance. These findings originate from the added cations, which form an electric-field-reinforced hydrophobic cationic sieve (HCS) that blocks water away from the anode and suppresses the hydrogen evolution reaction. Meanwhile, the lower electrolyte concentration provides significant benefits to ALIBs, including lower cost, better rate capability (lower viscosity of 18 cP and higher ionic conductivity of 22 mS cm -1 at 25 °C), and improved low-temperature performance (liquidus temperature of -10.18 °C)., (© 2022 Wiley-VCH GmbH.)

• Capacity fading of composite electrodes over cycling in Aqu-LIBs is investigated. • Water-assisted Li+ intercalation persists during cycling. • No mechanical degradation of LiCoO 2 composite electrode is observed. • Surficial evolution from LiCoO 2 to CoO results in the capacity fading. • Structural evolution of interface significantly slows down Li+ insertion kinetics. Unravelling the underlying reasons for degradation mechanism of battery materials is of great fundamental and practical importance. For a classical electrode consisting of an active material, a conductive additive, and a polymeric binder, its capacity fading is commonly related with (i) mechanical degradation of polymeric binder and/or (ii) structural and compositional degradation of active materials. The former is more relevant for electrodes showing volume expansion and represented by the progressive breakage of polymeric binder network during battery operation, leading to the dissolution of the other two components into electrolytes. The latter is generally reflected by an irreversible phase transition in active materials, which may affect the species exchanged at the electrode/electrolyte interface and their interfacial transfer dynamics. By employing a coupled methodology pairing electrochemical techniques with piezoelectric probes derived from quartz crystal microbalance (QCM), this work reports on the evolution of the interfacial processes during electrochemical cycling and correlates to the performance degradation of the electrodes. Shown on a LiCoO 2 (LCO) composite electrode as a model system, it was revealed that bare Li+ without a hydration sheath plays a dominant role in charge balance irrespective of the aging degree of the electrode under the experimental conditions of this work. However, Li+ transfer is closely accompanied with free H 2 O molecules with a Li+:H 2 O ratio around 10:1 at a polarization state close to LCO redox potential (0.65 V vs. Ag/AgCl). This ratio persists in all cycled electrodes with gradually faded interfacial transfer kinetics of Li+ and H 2 O along cycling. Such fading in species interfacial transfer kinetics driven by the surficial evolution from LiCoO 2 to CoO plays a major role in the electrode performance degradation during cycling. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, rutile TiO 2 nanorod arrays are fabricated by a template-free method and proposed as a promising anode for aqueous Li-ion battery. The as-prepared TiO 2 nanorod arrays exhibited reversible Li-ion insertion/extraction ability in aqueous LiOH electrolyte. Moreover, galvanostatic charge/discharge test results demonstrated that the reversible capacity of TiO 2 nanorods could reach about 39.7 mC cm -2 , and 93.8 % of initial capacity was maintained after 600 cycles at a current density of 1 mA cm -2 (=240 C rate), indicating excellent cycling stability and rate capability.