Using ab initio calculations combined with experiments, we clarified how the kinetics of Li-ion diffusion can be tuned in LiNixMnyCozO2 (NMC, x + y + z = 1) materials. It is found that Li-ions tend to choose oxygen dumbbell hopping (ODH) at the early stage of charging (delithiation), and tetrahedral site hopping (TSH) begins to dominate when more than 1/3 Li-ions are extracted. In both ODH and TSH, the Li-ions surrounded by nickel (especially with low valence state) are more likely to diffuse with low activation energy and form an advantageous path. The Li slab space, which also contributes to the effective diffusion barriers, is found to be closely associated with the delithiation process (Ni oxidation) and the contents of Ni, Co, and Mn.

energy density, high voltage, and long cycle life. [ 2 ] As one of the most widely used cathode materials, LiNi x Mn y Co z O 2 (labeled as NMC) has been investigated extensively, due to their high reversible capacity, good environmental compatibility, and relatively high Li-ion diffusivity. In the previous works, different kinds of NMC materials with different content ratio of Ni, Co, and Mn have been developed, and their electrochemical properties have also been studied, such as Li(Ni 1/3 Mn 1/3 Co 1/3 ) O 2 (111), [ 3,4 ] Li(Ni 0.4 Mn 0.4 Co 0.2 )O 2 (442), [ 5 ] Li(Ni 0.42 Mn 0.42 Co 0.16 )O 2 (552), [ 6 ] Li(Ni 0.5 Mn 0.3 Co 0.2 )O 2 (532), [ 7 ] Li(Ni 0.6 Mn 0.2 Co 0.2 )O 2 (622), [ 8 ] and Li(Ni 0.7 Mn 0.15 Co 0.15 )O 2 (71515). [ 9 ] For example, Noh et al. compared the electrochemical properties including the Li-ion diffusion coeffi cient, capacity retention, and electrochemical stabilities (25 to 55 °C) of layered NMC cathode materials ((111), (532), (622), (71515), (811) and Li(Ni 0.85 Mn 0.075 Co 0.075 )O 2 ) at room temperature and found that the Ni content had a great infl uence on the electrochemical properties. [ 10 ] Solid phase diffusion coeffi cient ( D s ) is one of the most important parameters for the active materials of the LIBs, as it determines the charge and discharge rate capability directly. In particular, for high power density applications, fast Li-ion transport in cathode materials is a key factor and must be needed. As a result, many experimental and theoretical works have been devoted to investigating the Li-ion diffusion properties in layered cathode materials. [ 11,12 ] However, to the best of our knowledge, there is little work reported to study the relationship between the layer distance and kinetics of Li-ion diffusion in different temperatures of layered NMC cathode materials systematically, which is important for LIBs applied in multitemperature environments.At the same time, in order to measure D s accurately, many methods such as galvanostatic intermittent titration technique (GITT), [ 3,[13][14][15][16] potentiostatic intermittent titration technique (PITT), [ 14,17 ] electrochemical impedance spectroscopy, [ 18 ] and cyclic voltammetry [ 19 ] have been developed in the past decades. Although factors such as the inaccuracy of the assumptions, Understanding and optimizing the temperature effects of Li-ion diffusion by analyzing crystal structures of layered Li(Ni x Mn y Co z )O 2 (NMC) ( x + y + z = 1) materials is important to develop advanced rechargeable Li-ion batteries (LIBs) for multi-temperature applications with high power density. Combined with experiments and ab initio calculations, the layer distances and kinetics of Li-ion diffusion of LiNi x Mn y Co z O 2 (NMC) materials in different states of Li-ion de-intercalation and temperatures are investigatedsystematically. An improved model is also developed to reduce the system error of the "Galvanostatic Intermittent Titration Technique" with a correction of NMC particle size distribution. The Li-ion diff...

Aqueous zinc-ion batteries (ZIBs) have emerged as the most promising alternative energy storage system, but the development of a suitable cathode and the issues of Zn anodes have remained challenging. Herein, an effective strategy of high-capacity layered Mg0.1V2O5·H2O (MgVO) nanobelts together with a concentrated 3 M Zn­(CF3SO3)2 polyacrylamide gel electrolyte was proposed to achieve a durable and practical ZIB system. By adopting the designed concentrated gel electrolyte which not only inherits the high-voltage window and wide operating temperature of the concentrated electrolyte but also addresses the Zn dendrite formation problem, the prepared cathode exhibits an ultrahigh capacity of 470 mAh g–1 and a high rate capability of 345 mAh g–1 at 5.0 A g–1, and the assembled quasi-solid-state ZIBs achieve 95% capacity retention over 3000 cycles as well as a wide operating temperature from −30 to 80 °C, demonstrating a promising prospect for large-scale energy storage. In situ X-ray diffraction, X-ray photoelectron spectroscopy, and thermogravimetric analysis (TGA) investigations also demonstrate a complex reaction mechanism for this cathode involving the (de)­insertion of Zn2+, H+, and water molecules during cycling. The water molecules will reinsert into the interlayer and act as “pillars” to stabilize the host structure when Zn2+ is fully extracted.

and cycle life. However, LIBs suffer from issues including flammability, toxicity, cost, and scarcity of Li metal. [4,5] Rechargeable batteries based on an aqueous electrolyte and earth-abundant elements are regarded as a more sustainable alternative to the current LIBs. Aqueous metal-ion batteries are inherently safe, eco-friendly, cheap, and capable of operating at large currents. [6][7][8] Aqueous zinc-ion battery (ZIB) is one of the types and offers a high theoretical capacity (820 mAh g −1 ) and a low electrochemical potential of metallic Zinc (−0.76 V vs standard hydrogen electrode), [9][10][11][12][13] but the development of highly stable cathode for ZIBs is still challenging.Prussian blue analogues (PBAs) with a formula of A x M[Fe(CN) 6 ] y •nH 2 O (0 < x < 2, 0 < y ≤ 1, A = alkaline metal, M = transition metal) have been considered as promising cathode materials for aqueous alkali metalion batteries. The capacity of PBAs can reach more than 120 mAh g −1 [14][15][16][17] and the stability is excellent, due to the presence of two redox couples and robust 3D open-framework structures allowing the insertion of a variety of alkaline ions without distortion. [18][19][20] However, PBAs only provide a relatively low specific capacity for Zn 2+ cations (typically less than 80 mAh g −1 ), and intercalation of Zn 2+ can lead to uncontrolled phase transition and consequent performance degrading. [9,21,22] Liu et al. first proposed a ZIB using a rhombohedral Zn 3 [Fe(CN) 6 ] 2 (ZnHCF) cathode, which exhibited a low capacity of 65.4 mAh g −1 with 76% capacity retention after 100 cycles. [23] A cubic structure PBA (CuHCF) was synthesized for Zn 2+ storage, and this cathode completed 100 cycles with a capacity of 56 mAh g −1 . [24] Mantia et al. suggested that the capacity decay in CuHCF can be attributed to a phase transition to a second phase which is electrochemically less active. [25,26] To reduce the influence of phase transition resulted from Zn 2+ insertion, researchers employed electrolytes with a low or even zero Zn 2+ concentration to make NiHCF//Zn, [27] CuHCF//Zn, [28] and NaFe-PB//Zn [29] hybrid-ion batteries. Nonetheless, the storage capacities of Zn 2+ in these cathodes were still low despite that the cycle life was improved by increasing the scanning voltage. [30] In this work, we introduce a high voltage aqueous PBA-Zn hybrid-ion battery with KMnHCF (K 1.6 Mn[Fe(CN) 6 ] 0.94 •0.63H 2 O) cathode, zinc foil anode, and 30 m KFSI + 1 m Zn(CF 3 SO 3 ) 2 Prussian blue analogues (PBAs), featuring an open framework for accommodating large ions and tunable valence states, have garnered wide interest in the context of aqueous zinc-ion batteries (ZIBs). However, PBAs in ZIBs currently still suffer from low capacity and poor cycling stability due to structural instability. Here a K 2 MnFe(CN) 6 cathode achieving a very stable capacity of 100 mAh g −1 is reported in a ZIB charged/discharged to 400 cycles. Interestingly, such a stable capacity is attributed to the fact that the K 2 MnFe(CN) 6 cathode is gradually t...

A verification and validation study is carried out for a sequence of reversed shear Alfv en instability time slices. The mode frequency increases in time as the minimum (q min ) in the safety factor profile decreases. Profiles and equilibria are based upon reconstructions of DIII-D discharge (#142111) in which many such frequency up-sweeping modes were observed. Calculations of the frequency and mode structure evolution from two gyrokinetic codes, GTC and GYRO, and a gyro-Landau fluid code TAEFL are compared. The experimental mode structure of the instability was measured using time-resolved two-dimensional electron cyclotron emission imaging. The three models reproduce the frequency upsweep event within 610% of each other, and the average of the code predictions is within 68% of the measurements; growth rates are predicted that are consistent with the observed spectral line widths. The mode structures qualitatively agree with respect to radial location and width, dominant poloidal mode number, ballooning structure, and the up-down asymmetry, with some remaining differences in the details. Such similarities and differences between the predictions of the different models and the experimental results are a valuable part of the verification/validation process and help to guide future development of the modeling efforts.