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In this research, we systematically examine the impact of atomic cation dopants and metal oxide coatings, including their respective oxidation states, on the electrochemical performance of Ni-rich NCA90 cathode materials. The study reveals that dopants exhibiting varied oxidation states, derived from high annealing temperatures, can efficaciously mitigate H2–H3 phase transitions, thereby amplifying the structural stability of the materials. Complementary Density Functional Theory (DFT) calculations corroborate that a judiciously selected dopant can enhance the electronic attributes of the cathode materials. Notably, the incorporation of a tungsten dopant is found to markedly modulate the kinetics of lithium transfer throughout the battery cycling process. This research provides vital insights into the role of cation dopants and metal oxide coatings in optimizing the electrochemical performance of Ni-rich cathode materials. [ABSTRACT FROM AUTHOR]

Li–S batteries with a sulphur loading content of 5 mg cm−2 were produced as large-scale 18 650 cylindrical cells. We have found that a key failure mode of cylindrical Li–S battery cells is the severe capacity fading during the galvanostatic charge–discharge process due to the corrosion of the electrodes, the electrolyte decomposition, and the severe polysulphide shuttling effect. [ABSTRACT FROM AUTHOR]

The electrochemical CO2 reduction reaction (CO2RR) is an attractive method to produce renewable fuel and chemical feedstock using clean energy sources. Formate production represents one of the most economical target products from CO2RR but is primarily produced using post‐transition metal catalysts that require comparatively high overpotentials. Here a composition of bimetallic Cu–Pd is formulated on 2D Ti3C2Tx (MXene) nanosheets that are lyophilized into a highly porous 3D aerogel, resulting in formate production much more efficient than post‐transition metals. Using a membrane electrode assembly (MEA), formate selectivities >90% are achieved with a current density of 150 mA cm−2 resulting in the highest ever reported overall energy efficiency of 47% (cell potentials of −2.8 V), over 5 h of operation. A comparable Cu‐Pd aerogel achieves near‐unity CO production without the MXene templating. This simple strategy represents an important step toward the experimental demonstration of 3D‐MXenes‐based electrocatalysts for CO2RR application and opens a new platform for the fabrication of macroscale aerogel MXene‐based electrocatalysts. [ABSTRACT FROM AUTHOR]

The electrochemical reduction of carbon dioxide (CO2) to value‐added chemicals is a promising strategy to mitigate climate change. Metalloporphyrins have been used as a promising class of stable and tunable catalysts for the electrochemical reduction reaction of CO2 (CO2RR) but have been primarily restricted to single‐carbon reduction products. Here, we utilize functionalized earth‐abundant manganese tetraphenylporphyrin‐based (Mn‐TPP) molecular electrocatalysts that have been immobilized via electrografting onto a glassy carbon electrode (GCE) to convert CO2 with overall 94 % Faradaic efficiencies, with 62 % being converted to acetate. Tuning of Mn‐TPP with electron‐withdrawing sulfonate groups (Mn‐TPPS) introduced mechanistic changes arising from the electrostatic interaction between the sulfonate groups and water molecules, resulting in better surface coverage, which facilitated higher conversion rates than the non‐functionalized Mn‐TPP. For Mn‐TPP only carbon monoxide and formate were detected as CO2 reduction products. Density‐functional theory (DFT) calculations confirm that the additional sulfonate groups could alter the C−C coupling pathway from *CO→*COH→*COH‐CO to *CO→*CO‐CO→*COH‐CO, reducing the free energy barrier of C−C coupling in the case of Mn‐TPPS. This opens a new approach to designing metalloporphyrin catalysts for two carbon products in CO2RR. [ABSTRACT FROM AUTHOR]

Although the LiMn2O4 cathode can provide high nominal cell voltage, high thermal stability, low toxicity, and good safety in Li-ion batteries, it still suffers from capacity fading caused by the combination of structural transformation and transition metal dissolution. Herein, a carbon-coated LiMn2O4 cathode with core@shell structure (LMO@C) was therefore produced using a mechanofusion method. The LMO@C exhibits higher cycling stability as compared to the pristine LiMn2O4 (P-LMO) due to its high conductivity reducing impedance growth and phase transition. The carbon shell can reduce direct contact between the electrolyte and the cathode reducing side reactions and Mn dissolution. Thus, the cylindrical cell of LMO@C//graphite provides higher capacity retention after 900 cycles at 1 C. The amount of dissoluted Mn for the LMO@C is almost 2 times lower than that of the P-LMO after 200 cycles. Moreover, the LMO@C shows smaller change in lattice parameter or phase transition than P-LMO, indicating to the suppression of λ-MnO2 phase from the mixed phase of Li1-δMn2O4 + λ-MnO2 when Li-delithiation at highly charged state leading to an improved cycling reversibility. This work provides both fundamental understanding and manufacturing scale demonstration for practical 18650 Li-ion batteries. Its high nominal voltage, thermal stability, and low toxicity render LiMn2O4 a highly promising cathode material for lithium ion batteries, but capacity fading due to unwanted side reactions during cycling remains an issue. Here, the authors show that carbon-coating a LiMn2O4 cathode reduces side reactions such as manganese dissolution and manganese oxide formation, thereby improving battery cycling stability. [ABSTRACT FROM AUTHOR]

Rechargeable aqueous Zn–MnO2 batteries have been considered as one of the promising alternative energy technologies due to their high abundance, environmental friendliness, and safety of both Zn–metal anodes and manganese oxide cathodes. Although layer-type MnO2 (δ-MnO2) is one of the most promising intercalation cathode materials, there are some critical drawbacks such as sluggish Zn2+ diffusion kinetics and a phase transition of δ-MnO2 as a result of a strong electrostatic interaction between Zn2+ and the host structure. Herein, we systematically studied the effects of the charge density of pre-intercalated cations in layered MnO2 using Li+, Ca2+, and Al3+ on its structural properties and electrochemical performance as a cathode in aqueous Zn–MnO2 batteries. The results reveal that a small amount of highly charged intercalant can effectively stabilize the MnO2 layers, facilitating the kinetics of Zn2+ intercalation/deintercalation. As a result, Al–MnO2 exhibits superior capacity and a rate capability of 210 mA h g−1 with 21% capacity retention when the current density is increased from 0.1 to 2 A g−1, while Ca–MnO2 and Li–MnO2 exhibit 189 and 160 mA h g−1 with a capacity retention of 17% and 11%, respectively. The superior capacity of Al–MnO2 is attributed to the enhanced redox activity from more Mn electrochemical utilization as confirmed by ex situ X-ray photoelectron spectroscopy. Moreover, the long-term cycling stability evaluated at 2 A g−1 shows that Al–MnO2 exhibits superior cycling stability with 84% capacity retention over 2000 cycles. As revealed by ex situ X-ray diffraction and theoretical calculations, the highly charged intercalant can minimize the binding energy between Zn2+ and the MnO2 host, alleviating the strong electrostatic attraction that can induce reversible Zn2+ insertion/extraction. [ABSTRACT FROM AUTHOR]

The safety of Li-ion batteries is one of the most important factors, if not the most, determining their practical applications. We have found that free carbonate-based solvent molecules in the hybrid electrolyte system can cause severe safety concerns. Mixing ionic liquids with a carbonate-based solvent as the co-solvent at a fixed salt concentration of 1 M LiPF6 can lead to free carbonate-based molecules causing poor charge storage performance and safety concerns. [ABSTRACT FROM AUTHOR]

Transport phenomena and the solvation structure of lithium ions (Li+) and hexafluorophosphate anions (PF6−) in electrolytes with different fluoroethylene carbonate (FEC) concentrations as well as the electrochemical performance and safety of Ni-rich Li-ion battery cells at the 18650 cylindrical cell level are investigated. We have found that the electrolyte with an optimized FEC concentration (25% v/v) can effectively enhance the transport property in terms of the Li+ transference number and contact ion pair (CIP) ratio leading to high performance and safety of practical 18650 cylindrical LIBs. [ABSTRACT FROM AUTHOR]

We have investigated the effect of ionic liquids (ILs) additives in 1 M LiTFSI in 1,3-dioxolane (DOL)/dimethyl ether (DME) (1:1, v/v) on the solid electrolyte interphase (SEI) using a combined theoretical and experimental method for next-generation Li metal batteries. Among all investigated cations of ILs including imidazolium (IMI+), pyrrolidinium (PYR+), and piperidinium (PIP+) cations, we have observed that the presence of IMI+ provides relatively larger decomposed products of the TFSI anion on the Li metal surface when compared with saturated-ring type cation ILs including PYR+- and PIP+-ILs due to its high electron affinity (EA). Furthermore, the reactive molecular dynamics results show that the SEI layer of the system using the ILs with saturated rings is significantly thin when compared to that of the ILs with aromatic-ring, which is desired for fast Li-ion diffusivity through the SEI. This finding may lead to an ideal design of electrolyte system for future Li-metal batteries. [ABSTRACT FROM AUTHOR]

Using free solar energy in oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) electrocatalysts to enhance the efficiency of zinc‐air batteries (ZABs) has not yet been widely investigated. Herein, we report a photoactive bifunctional catalyst of spinel‐type NiCo2S4 (NCS) urchin‐like structure with rich mesopores and direct band gap energies of ca. 1.4 and 2.4 eV. The NCS catalyst exhibits high catalytic activities for both OER (ɳ=338 mV at 10 mA cm−2) and ORR (ɳ=475 mV at E1/2), comparable to that of the state‐of‐the‐art counterparts (e. g. Pt/C for ORR, RuO2 for OER). Under light illumination, the p‐type photoactive NCS catalyst can absorb visible light, generating photogenerated holes and photoelectrons via the photoelectric effect for direct conversion of photoenergy into electric energy with increasing kinetics charge transfer process and provides ca. 10 and 18.5 % lower OER and ORR overpotentials, respectively than those under the dark condition. In addition, the as‐fabricated zinc‐air battery with the photoactive NCS as the cathode exhibits decrease in voltage gap from 0.82 to 0.60 V with an increasing round‐trip efficiency from 59.2 % to 68.8 % after exposed to visible light. The zinc‐air battery with a reversible redox reaction for the simultaneous conversion of chemical and photoenergy into electric energy could open a new pathway for the utilization of a single energy conversion and storage device. [ABSTRACT FROM AUTHOR]

A modified hydrolysed polyethylene with polyaniline was used as a dual functional interlayer/separator for high-performance lithium–sulphur batteries (LSBs) to reduce the migration of soluble polysulphide intermediates. Also, the sulphur cathode was encapsulated with carbon nanoparticles with a S@C core–shell structure using a solvent-free coating process. The chemical interaction between the imine group of the quinoid ring in the PANI structure and the polysulphides reducing the shuttle effect as well as the high electrical conductivity and less volume change of the carbon encapsulated sulphur can provide high-performance Li–S@C core–shell batteries. [ABSTRACT FROM AUTHOR]

The interaction between the reactive lithium metal surface and LiNO3 results in the formation of LixNOy clusters, which can protect the Li metal anode and suppress the shuttling effect of lithium polysulfides via the dipole–dipole interaction called the lithium bond. [ABSTRACT FROM AUTHOR]

Spinel-type cobalt oxide (Co3O4) was synthesized and used as a photoactive bifunctional electrocatalyst towards the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR) at the air cathode of zinc–air batteries (ZABs). The Co3O4 having direct and indirect band gap energies of ca. 2.20 eV and ca. 1.35 eV can absorb visible light, generating photogenerated carriers and photoelectrons via the photoelectric effect. Upon exposure to visible light, the Co3O4 electrode exhibits ca. 30% higher current density than that under dark conditions and provides around 10–20% lower OER and ORR overpotentials than those under the dark conditions. Under visible light, the specific capacity of the as-fabricated photoactive ZAB cell is improved by ca. 10% as compared to that under dark conditions. [ABSTRACT FROM AUTHOR]

A 3D free-standing lithiophilic silver nanowire aerogel (AgNWA) can stop the dendritic growth of lithium metal at the initial nucleation process. The 3D structure can also suppress the infinite volume expansion of lithium during cycling. The active AgNWA scaffold can serve as a Li reservoir to compensate for the irreversible consumption of Li. The lithiated AgNWA anode was coupled with a lithium iron phosphate (LFP) cathode in a full-cell configuration providing much higher performance than the Li//LFP cell. [ABSTRACT FROM AUTHOR]

The unusual intercalation phenomena of alkali cations (Li+, Na+, K+, Rb+, and Cs+) in the sulfate-based electrolyte on the electrochemical behavior of birnessite-type layered-manganese oxide nanosheets with Li-intercalated cation (Li-MnO 2) were studied by in situ electrochemical synchrotron X-ray Absorption spectroscopy. Li-MnO 2 exhibits the highest charge storage capacity in Na 2 SO 4 (aq), followed by Li 2 SO 4 , K 2 SO 4 , and Cs 2 SO 4 , respectively. Whilst, it does not exhibit the charge-storage characteristics in Rb 2 SO 4 as the solvated Rb+ could not intercalate into the lamellar structure of birnessite. Understanding unusual intercalation phenomena can be useful for further development of the electrochemical capacitors. Image 1 • Intercalation of alkali cations in sulfate electrolyte to 2D manganese oxide birnessite. • Electrochemical behavior of the birnessite depends on the solvated alkali cations. • Charge storage mechanism investigated by in situ electrochemical synchrotron XAS. • 2D manganese oxide nanosheets exhibit the highest charge storage capacity in Na 2 SO 4. • The solvated Rb+ could not intercalate into the lamellar structure of the birnessite. [ABSTRACT FROM AUTHOR]

The electrochemical reduction of carbon dioxide (CO 2 ) to value-added chemicals is a promising strategy to mitigate climate change. Metalloporphyrins have been used as a promising class of stable and tunable catalysts for the electrochemical reduction reaction of CO 2 (CO 2 RR) but have been primarily restricted to single-carbon reduction products. Here, we utilize functionalized earth-abundant manganese tetraphenylporphyrin-based (Mn-TPP) molecular electrocatalysts that have been immobilized via electrografting onto a glassy carbon electrode (GCE) to convert CO 2 with overall 94 % Faradaic efficiencies, with 62 % being converted to acetate. Tuning of Mn-TPP with electron-withdrawing sulfonate groups (Mn-TPPS) introduced mechanistic changes arising from the electrostatic interaction between the sulfonate groups and water molecules, resulting in better surface coverage, which facilitated higher conversion rates than the non-functionalized Mn-TPP. For Mn-TPP only carbon monoxide and formate were detected as CO 2 reduction products. Density-functional theory (DFT) calculations confirm that the additional sulfonate groups could alter the C-C coupling pathway from *CO→*COH→*COH-CO to *CO→*CO-CO→*COH-CO, reducing the free energy barrier of C-C coupling in the case of Mn-TPPS. This opens a new approach to designing metalloporphyrin catalysts for two carbon products in CO 2 RR., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Although cobalt hydroxide (Co(OH) 2 ) has been attracting attention in several applications, its photoelectrochemical property has not yet been fully investigated. In this work, tuning the energy band gap of Co(OH) 2 nanosheets with silver atoms and enhancing their electrical conductivity with silver nanoparticles were then focused. A Ag-doped α-Co(OH) 2 thin film was successfully synthesized via an electrodeposition method. The optical properties of the as-prepared materials were characterized by UV-vis and fluorescence lifetime spectroscopies and further confirmed by density functional theoretical calculation. It was found that Ag atoms between adjacent layers of Co(OH) 2 can reduce its electronic band gap to 2.45 eV (α-Co(OH) 2 ) as compared to 2.85 eV of β-Co(OH) 2 . In terms of electrochemical properties, silver nanoparticles (AgNPs) can enhance the electrical conductivity of Co(OH) 2 nanosheets, leading to faster charge transfer reducing the internal resistance and significantly increasing the overall charge storage performance. Interestingly, under light illumination, Ag-doped α-Co(OH) 2 exhibits ca. 0.8 times lower charge storage capacity as compared to that under the dark condition. This is because the photoelectrons can be recombined with the generated holes in the conduction band. The charge storage mechanisms of Ag-doped α-Co(OH) 2 operated under dark conditions and light irradiation were further studied and confirmed using in situ electrochemical X-ray absorption spectroscopy (XAS). Overall, the in situ XAS supports the electrochemical result. This finding may pave a way to further develop photoactive advanced functional materials of metal hydroxides and oxides., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)