Conventional cathodes of Li-ion batteries mainly operate through an insertion-extraction process involving transition metal redox. These cathodes will not be able to meet the increasing requirements until lithium-rich layered oxides emerge with beyond-capacity performance. Nevertheless, in-depth understanding of the evolution of crystal and excess capacity delivered by Li-rich layered oxides is insufficient. Herein, various in situ technologies such as X-ray diffraction and Raman spectroscopy are employed for a typical material Li Ni Mn O , directly visualizing O O (peroxo oxygen dimers) bonding mostly along the c-axis and demonstrating the reversible O /O redox process. Additionally, the formation of the peroxo OO bond is calculated via density functional theory, and the corresponding OO bond length of ≈1.3 Å matches well with the in situ Raman results. These findings enrich the oxygen chemistry in layered oxides and open opportunities to design high-performance positive electrodes for lithium-ion batteries.

Li metal can potentially deliver much higher specific capacity than commercially used anodes. Nevertheless, because of its poor reversibility, abundant excess Li (usually more than three times) is required in Li metal batteries, leading to higher costs and decreased energy density. Here, a concentrated lithium bis(trifluoromethane sulfonyl) imide (LiTFSI)–lithium nitrate (LiNO3)–lithium bis(fluorosulfonyl)imide (LiFSI) ternary‐salts electrolyte is introduced to realize a high stable Li metal full‐cell with only a slight excess of Li. LiNO3 and LiFSI contribute to the formation of stable Li2O–LiF‐rich solid electrolyte interface layers, and LiTFSI helps to stabilize the electrolyte under high concentration. Li metal in the electrolyte remains stable over 450 cycles and the average Coulombic efficiency reaches 99.1%. Moreover, with 0.5 × excess Li metal, the Coulombic efficiency of Li metal in the LiTFSI–LiNO3–LiFSI reaches 99.4%. The electrolyte also presents high stability to the LiFePO4 cathode, the capacity retention after 500 cycles is 92.0% and the Coulombic efficiency is 99.8%. A Li metal full‐cell with only 0.44 × excess Li is also assembled, it remains stable over 70 cycles and 83% of the initial capacity is maintained after 100 cycles.

The synthesis, structure, and reactivity of some organo-iron complexes with monodentate N-heterocyclic carbene (NHC) ligation were studied. Mononuclear ferrous complexes [(IEt) 2 FeR 2 ] (IEt = 2,5-diethyl-3,4-dimethylimidazol-1-ylidene, R = Me (2a), CH 2 TMS (2b)) and [(IPr)FeMes 2 ] (3, IPr = 2,5-diisopropyl-3,4-dimethylimidazol-1-ylidene) were prepared in good yields via salt elimination reactions of [(NHC) 2 FeCl 2 ] (1) with alkylation reagents. The interaction of 1 with PhLi gave a mixture of dinuclear complexes [Cl(IEt)Fe(IEt 0 ) 2 Fe(IEt)Cl] (4a) and [Ph(IEt)Fe(IEt 0 ) 2 Fe(IEt)Ph] (4b) (IEt 0 = 3-Et-4,5-Me 2 -2-ylideneimidazolyl anion), in which NÀC(ethyl) bond cleavage of the NHC ligand was involved. Complexes 2aÀ4b were characterized by 1 H NMR, elemental analyses, and single-crystal X-ray diffraction studies. Solution magnetism measurement by Evan's method revealed the high-spin electronic configuration for the mononuclear organo-iron(II) complexes 2a, 2b, and 3. Reactivity studies showed the tetrahedral complex 2a was inert toward many unsaturated organic substrates, whereas the trigonal-planar complex 3 could react with CO and carbodiimide Pr i NdCdNPr i to yield dimesityl ketone and [(IPr)Fe(Mes)(η 2 -Pr i NC(Mes)NPr i )] (5), respectively. Relevant to iron-catalyzed Kumada couplings, both complexes 2b and 3 were found reactive with PhI to yield the corresponding carbonÀcarbon bond formation products PhÀCH 2 TMS and PhÀMes.

Anionic redox reveals to be a promising strategy to effectively improve the energy density of layered metal oxide cathodes for sodium-ion batteries. However, lattice oxygen loss and derived structural distortion severely hinder its practical application. Herein, combined with anionic and cationic redox activities, we developed a layered structure P2-type Na0.66Li0.22Ti0.15Mn0.63O2 cathode, delivering an initial discharge capacity of 228 mAh g–1 and highly reversible structural evolution as well as improved cyclability. On the basis of comprehensive comparison with Ti-free P2-Na0.66Li0.22Mn0.78O2, both oxygen-related negative behaviors (irreversible O2 evolution and superoxo-related parasitic production) and Mn-related Jahn–Teller distortion have been effectively restrained by simultaneously suppressing both oxygen loss and the participation of Mn4+/Mn3+ redox. Not limited to discovering excess capacity derived from anionic oxidation up charging, our findings not only highlight an effective strategy to stabilize anionic and cationic redox activities but also pave the way for the further improvement of Na-deficient layered materials for high-energy sodium-ion batteries.

Tuning the electrochemical formation/decomposition of Li 2 O 2 from the circumscribed surface pathways to the solution ones, the dual redox mediator (RM) strategy largely promotes the discharge capacity and reduces the charge overpotential in aprotic Li−O 2 batteries, revealing a promising strategy to realize anticipated high specific energy cycling. However, both RM-induced Li degradation and electron shuttling between the cathode and anode become the become the inherent defects, resulting in poor sustainability. Here, with a narrow pore size window, a metal−organic framework (MOF)-based separator has been proposed, which acts as a RM molecule sieve to restrain the shuttling. By maximizing the advantages of the dual RM strategy, the Li−O 2 cell reveals a prolonged cycled life (100 cycles, 5000 mAh g −1 ) at high current rate (1000 mA g −1 ). Moreover, the Li−O 2 pouch cell fabricated by the flexible MOF-based separator exhibits the potential for the development of large-scale energy storage devices.

Anionic states of nucleic acid bases are involved in DNA damage by low-energy electrons and in charge transfer through DNA. Previous gas phase studies of free, unsolvated nucleic acid base parent anions probed only dipole-bound states, which are not present in condensed phase environments, but did not observe valence anionic states, which for purine bases are thought to be adiabatically unbound. Contrary to this expectation, we have demonstrated that some thus far ignored tautomers of adenine, which result from enamine-imine transformations, support valence anionic states with electron vertical detachment energies as large as 2.2 eV, and at least one of these anionic tautomers is adiabatically bound. Moreover, we predict that the new anionic tautomers should also dominate in solutions and should be characterized by larger values of electron vertical detachment energy than the canonical valence anion. All of the newfound anionic tautomers might be formed in the course of dissociative electron attachment followed by a hydrogen atom attachment to a carbon atom, and they might affect the structure and properties of DNA and RNA exposed to low-energy electrons. The new valence states observed here, unlike the dipole-bound state, could exist in condensed phases and might be relevant to radiobiological damage. The discovery of these valence anionic states of adenine was facilitated by the development of (i) an experimental method for preparing parent anions of nucleic acid bases for photoelectron experiments, and (ii) a combinatorial/quantum chemical approach for identification of the most stable tautomers of organic molecules.nucleic acid bases ͉ photoelectron spectroscopy ͉ tautomers ͉ valence anion L ow-energy electrons are produced when high-energy radiation interacts with the contents of living cells. They might become trapped on nucleic acid bases (NBs) and trigger chemical transformations leading to DNA damage. Recent experiments suggested that single-and double-strand breaks develop in the DNA exposed to low-energy electrons (1). Furthermore, charged NBs play a critical role in electron and hole transfer in DNA (ref. 2 and references therein). Anionic states of NBs have been intensively studied both experimentally and theoretically. Purine bases, i.e., adenine (A) and guanine (G), are believed to have a much smaller affinity to an excess electron than pyrimidine bases (3-7). The reduction potentials of G and A are more negative than those of pyrimidines by a few tenths of an eV (3). The group of Burrow (4) reported an electron vertical attachment energy (VAE) of Ϫ0.54 eV for A and Ϫ0.46 eV for G, but Ϫ0.22 to Ϫ0.32 eV for pyrimidine bases. The negative values of VAE indicate that anions are electronically unbound at the equilibrium geometry of the corresponding neutral. An electron binding energy (EBE) of Ϫ0.45 eV for A was the smallest measured by Periquet et al. (5) among four NBs (U, T, A, and C). Li et al. (6) and Wesolowski et al. (7) predicted a negative adiabatic electron affinity (AEA) for the canonical...

Dual‐ion batteries (DIBs) have attracted much attention owing to their low cost, high voltage, and environmental friendliness. As the source of active ions during the charging/discharging process, the electrolyte plays a critical role in the performance of DIBs, including capacity, energy density, and cycling life. However, most used electrolyte systems based on the LiPF6 salt demonstrate unsatisfactory performance in DIBs. We have successfully developed a 7.5 mol kg−1 lithium bis(fluorosulfonyl)imide (LiFSI) in a carbonate electrolyte system. Compared with diluted electrolytes, this highly concentrated electrolyte exhibits several advantages: 1) enhanced intercalation capacity and cycling stability of the graphite cathode, 2) optimized structural stability of the Al anode, and 3) significantly increased battery energy density. A proof‐of‐concept DIB based on this concentrated electrolyte exhibits a discharge capacity of 94.0 mAh g−1 at 200 mA g−1 and 96.8 % capacity retention after 500 cycles. By counting both the electrode materials and electrolyte, the energy density of this DIB reaches up to ≈180 Wh kg−1, which is among the best performances of DIBs reported to date.

A series of iron(III) chloride complexes based upon Schiff base framework have been synthesized and characterized by mass spectra, elemental analysis, and X-ray crystallography. These bench-stable complexes were for the first time capable as highly efficient catalysts for lactide and ε-caprolactone polymerization in the presence of propylene oxide (PO), greatly surpassing conventional aluminum analogies. Electron-withdrawing substituents as well as elevated temperature boosted the activity while a bulky group on salicylaldehyde moieties abnormally produces the same effect, whereas rigid backbone retarded the reactivity. Polylactide tactics ranging from isotactic to hererotactic enchainment were obtained by tuning the ligand backbone and substituents. The stereoselectivity was confirmed to proceed via a chain-end control mechanism by kinetic studies using different isomers of lactide, and the overall polymerization process was also investigated in detail by the oligomer mass spectrum as well as end group (−OCHMeCH 2 Cl) analysis of polymer via 1 H, 13 C, and two-dimensional (2-D) NMR characterizations.