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[en] In carbonate electrolytes, the organic-inorganic solid electrolyte interphase (SEI) formed on the Li-metal anode surface is strongly bonded to Li and experiences the same volume change as Li, thus it undergoes continuous cracking/reformation during plating/stripping cycles. Here, an inorganic-rich SEI is designed on a Li-metal surface to reduce its bonding energy with Li metal by dissolving 4m concentrated LiNO in dimethyl sulfoxide (DMSO) as an additive for a fluoroethylene-carbonate (FEC)-based electrolyte. Due to the aggregate structure of NO ions and their participation in the primary Li solvation sheath, abundant LiO, LiN, and LiNO grains are formed in the resulting SEI, in addition to the uniform LiF distribution from the reduction of PF ions. The weak bonding of the SEI (high interface energy) to Li can effectively promote Li diffusion along the SEI/Li interface and prevent Li dendrite penetration into the SEI. As a result, our designed carbonate electrolyte enables a Li anode to achieve a high Li plating/stripping Coulombic efficiency of 99.55 % (1 mA cm, 1.0 mAh cm) and the electrolyte also enables a Li||LiNiCoMnO (NMC811) full cell (2.5 mAh cm) to retain 75 % of its initial capacity after 200 cycles with an outstanding CE of 99.83 %. (© 2020 Wiley‐VCH GmbH)
[en] Despite of the good stability with Li-metal, LiLaZrTaO(LLZTO) suffers from large interfacial resistance and severe Li-metal penetration. Herein, a dual layer ceramic electrolyte of Ti-doped LLZTO(Ti-LLZTO)/LLZTO was developed, with the reducible Ti-LLZTO layer contacting Li-metal and the LLZTO layer contacting cathode. The identical crystal structures of Ti-LLZTO and LLZTO enables a seamless contact and a barrierless Li transport between them. The densities of Ti-LLZTO pellets are higher than that of LLZTO. With an in situ reduction of Ti-LLZTO by Li-metal, the interfacial wettability was improved and a mixed ion-electron conducting layer was created. Both features help to reduce defects/pores on interface and homogenize the interfacial ionic/electronic flux, facilitating the reduction of interfacial resistance and suppression of dendrites. With the help of Ti-LLZTO layer, long-term stable lithium plating/stripping was reached in an areal capacity of 3.0 mAh cm. (© 2020 Wiley‐VCH GmbH)
[en] Organic anodes have attracted increasing attention for alkali metal ion batteries. In this work, we discovered that cyclized polyacrylonitrile (cPAN) can serve as an excellent anode for alkali metal ion batteries. Upon activation cycling, as an anode of lithium-ion battery, cPAN exhibits a reversible capacity as high as 1238 mAh g under a current density of 50 mA g. Based on electrochemical experiments and first-principles calculations, it is demonstrated that the hexagonal carbon ring, piperidine ring, and pyridine nitrogen in ladder cPAN are the main active sites for lithium-ion storage. cPAN displays a unique potential-dependent solid electrolyte interphase formation from 0.1 to 0.01 V vs. Li/Li. It also displays decent performance as an anode in SIBs and PIBs. (© 2020 Wiley‐VCH GmbH)
[en] LiCoO is used as a cathode material for lithium-ion batteries, however, cationic/anodic-redox-induced unstable phase transitions, oxygen escape, and side reactions with electrolytes always occur when charging LiCoO to voltages higher than 4.35 V, resulting in severe capacity fade. Reported here is Mg-pillared LiCoO. Dopant Mg ions, serving as pillars in the Li-slab of LiCoO, prevent slab sliding in a delithiated state, thereby suppressing unfavorable phase transitions. Moreover, the resulting Li-Mg mixing structure at the surface of Mg-pillared LiCoO is beneficial for eliminating the cathode-electrolyte interphase overgrowth and phase transformation in the close-to-surface region. Mg-pillared LiCoO exhibits a high capacity of 204 mAh g at 0.2 C and an enhanced capacity retention of 84 % at 1.0 C over 100 cycles within the voltage window of 3.0-4.6 V. In contrast, pristine LiCoO has a capacity retention of 14 % within the same voltage window. (© 2020 Wiley‐VCH GmbH)
[en] Attributed to the realization of the multielectron transfers, with a stable 3D framework, LiV(PO)(PO) is considered an excellent cathode material, which can reversibly extract/insert nearly 5 mol Li. However, the poor intrinsic electronic conductivity and the low lithium diffusion coefficient limited its practical electrochemical ability. Considering the poor intrinsic electronic conductivity of the pristine LiV(PO)(PO) compound, the introduction of one extra electron by replacing V with aliovalent Mo ions increases the concentration of the electronic charge carriers from LiV(PO)(PO) and thus improves the electronic conductivity. At the same time, the larger ionic radius of Mo leads to the increasement of the cell volume of the LiV(PO)(PO) sample and thus facilitates Li transport into the structure. As a result, the electrochemical performances of the LiV(PO)(PO) were improved obviously by a small amount of Mo. Especially for the LiVMo(PO)(PO) (x = 0.02) sample, the electrode present the highest specific capacity herein and an excellent rate performance which is a promising cathode for lithium ion battery application.
[en] Monoclinic lithium vanadium phosphate LiV(PO) is a very promising cathode candidate for applications in Li-ion batteries, with a high operational voltage (~ 4 V vs. Li/Li) and a high theoretical capacity of 197 mAh/g. However, the underlying electrochemical mechanism of monoclinic LiV(PO) is not yet fully understood, due to its complexity. To gain more knowledge about the electrochemical performance of the monoclinic LiV(PO), we perform density functional calculations of structural, electrochemical, electronic, and magnetic properties of LiV(PO) for x = 3, 2, 1, based on the full-potential linearized augmented plane wave (FP-LAPW) method. The generalized gradient approximation corrected with the present work self-consistently calculated Hubbard parameter U (GGA+U method) shows that it can successfully reproduce the experimental average lithium intercalation voltage for the redox couple V/V within 7% error, and within 2% error for the transition x: 3 ➔ 2. The present work method is fully ab initio and without any arbitrary parameters. In the literature, the existence of charge ordering in LiV(PO) is subject to discrepancy. By analyzing the present calculated structural, magnetic, and electronic properties of LiV(PO), the existence of charge ordering had been confirmed. The present work method sets the path for accurately predicting the redox potential of future lithium and sodium phosphate compounds for the next-generation batteries technology.
[en] Aqueous rechargeable batteries are becoming increasingly important to the development of renewable energy sources, because they promise to meet cost-efficiency, energy and power demands for stationary applications. Over the past decade, efforts have been devoted to the improvement of electrode materials and their use in combination with highly concentrated aqueous electrolytes. Here the latest ground-breaking advances in using such electrolytes to construct aqueous battery systems efficiently storing electrical energy, i.e., offering improved energy density, cyclability and safety, are highlighted. This Review aims to timely provide a summary of the strategies proposed so far to overcome the still existing hurdles limiting the present aqueous batteries technologies employing concentrated electrolytes. Emphasis is placed on aqueous batteries for lithium and post-lithium chemistries, with potentially improved energy density, resulting from the unique advantages of concentrated electrolytes. (© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA)
[en] Lithium-ion batteries with routine carbonate electrolytes cannot exhibit satisfactory fast-charging performance and lithium plating is widely observed at low temperatures. Herein we demonstrate that a localized high-concentration electrolyte consisting of 1.5 M lithium bis(fluorosulfonyl)imide in dimethoxyethane with bis(2,2,2-trifluoroethyl) ether as the diluent, enables fast-charging of working batteries. A uniform and robust solid electrolyte interphase (SEI) can be achieved on graphite surface through the preferential decomposition of anions. The established SEI can significantly inhibit ether solvent co-intercalation into graphite and achieve highly reversible Li intercalation/de-intercalation. The graphite | Li cells exhibit fast-charging potential (340 mAh g at 0.2 C and 220 mAh g at 4 C), excellent cycling stability (ca. 85.5 % initial capacity retention for 200 cycles at 4 C), and impressive low-temperature performance. (© 2020 Wiley‐VCH GmbH)
[en] Layered lithium-rich cathode materials have attracted extensive interest owing to their high theoretical specific capacity (320-350 mA h g. However, poor cycling stability and sluggish reaction kinetics inhibit their practical applications. After many years of quiescence, interest in layered lithium-rich cathode materials is expected to revive in answer to our increasing dependence on high-energy-density lithium-ion batteries. Herein, we review recent research progress and in-depth descriptions of the structure characterization and reaction mechanisms of layered lithium-rich manganese-based cathode materials. In particular, we comprehensively summarize the proposed reaction mechanisms of both the cationic redox reaction of transition-metal ions and the anionic redox reaction of oxygen species. Finally, we discuss opportunities and challenges facing the future development of lithium-rich cathode materials for next-generation lithium-ion batteries. (© 2020 Wiley‐VCH GmbH)
[en] Coordination compounds are well-known compounds that are being used as new materials for lithium storage because of their unique advantages, that is, designable structures, abundant active sites, and facile as well as mild synthetic routes. However, the electrode stability, low rate performance, and cycle life of coordination compounds are currently the main issues preventing their application as electrode materials, and the lithium-storage mechanism in coordination networks is not well understood. Herein, isostructural one-dimensional coordination compounds were synthesized to study their lithium-storage performance. Co-HIPA and Ni-HIPA showed superior electrolyte stability than other M-HIPAs, and Co-HIPA displayed a superior reversible capacity and cycle stability, excellent rate performance, and clear voltage platform. DFT calculations and kinetic analysis revealed the influence of the metal center with different electronic structures on the lithium-storage mechanism. (© 2020 Wiley‐VCH GmbH)