Surface and Interface Issues in Spinel LiNi_0.5Mn_1.5O₄: Insights into a Potential Cathode Material for High Energy Density Lithium Ion Batteries

Spinel LiNi0.5Mn1.5O4 with high operating voltage (∼4.7 V vs Li/Li+), high theoretical capacity of 148 mAh g–1, fast lithium ion diffusion kinetics, and potentially low cost is the most potential candidate material for high energy density LIBs used in plug-in hybrid electric vehicles and pure electric vehicles. However, the high operating voltage of LiNi0.5Mn1.5O4 challenges the electrochemical stability of other components in the batteries and induces diverse interfacial side reactions, leading to irreversible capacity loss, poor cycling performance, and safety issues, especially at the elevated temperatures. Thus, a basic understanding of the intrinsic surface properties of LiNi0.5Mn1.5O4 and the mechanism of interfacial interactions between each component in the electrochemical system is a critical requirement for developing substantial enhancements of LiNi0.5Mn1.5O4-based batteries. In this review, we summarize the surface/interface reactions and challenges in the whole cell system of LiNi0.5Mn1.5O4-based LIBs. Perspectives and strategies for LiNi0.5Mn1.5O4-based high energy density batteries used in PHEV/EVs are also proposed at last

DFE-IP: Delegatable functional encryption for inner product

Functional encryption for inner product (FE-IP) allows an authorized user to obtain the inner product of the vectors embedded in his/her secret key and a ciphertext, respectively. Therefore, it is an elegant tool to implement secure computation over encrypted data. Existing FE-IP schemes mainly considered security and function privacy issues, but did not address the decryption delegation problem. However, in practice, delegating decryption is desirable when an authorized user is unavailable to access the system due to leaving, network problems, etc. In this paper, a delegatable FE-IP (DFE-IP) scheme is proposed to support decryption delegation. Our scheme provides the following important features: (1) a delegator can delegate his/her decryption power to a delegatee; (2) a proxy is not required to re-encrypt ciphertexts; (3) it supports temporary delegation and flexible revocation. We first formalize our DFE-IP scheme including definition and security model, and then describe a concrete construction. Furthermore, the implementation and evaluation are provided to show its efficiency. Finally, its security is formally proven. The novelty is to implement temporary decryption delegation in FE-IP when authorized users are unavailable to access the system

Oxidized Kinetic Normal Distribution Models for Sophisticated Electrochemical Windows

The electrochemical window (EW) of electrolytes is considered the essential bottleneck of the voltage range for lithium batteries, which is theoretically overestimated previously. In this work, we present an innovative strategy to quantify the EW without experiential parameters accurately. This strategy encompasses energy states and statistical distribution from both thermodynamic and oxidized kinetic aspects. Verified by linear sweep voltammetry, which specializes in intrinsic redox kinetics of reactants and excludes the influences of products, the most restrictive factor among the effects of condensation, thermal motion, solvent, electric field, and catalysis determines the practical EW. For polyethylene oxide (PEO) and ethylene carbonate (EC)-dimethyl carbonate (DMC) with glassy carbon, the solvent effect is the restriction, while for EC-DMC with LixCoO2, the catalysis effect of the LixCoO2 surface is the restriction. This work provides an effective criterion for accurate prediction, guiding the electrolyte system design to satisfy the expected EW

Presentation1_Karst landslides detection and monitoring with multiple SAR data and multi-dimensional SBAS technique in Shuicheng, Guizhou, China.pdf

Shuicheng District is a karst mountain area, located in Guizhou Province, China. Its fragile stratum and frequent underground mining activities makes it prone to landslides. Owning to its wide coverage and frequent revisit, the InSAR technology has advantages in potential landslide identification and deformation monitor. However, affected by dense vegetation and atmospheric delay, it is much difficult to get sufficient effective targets to derive the deformation in this area. Besides, deformation derived from single orbit SAR data can result in the missing identification of some potential landslides and the misinterpreting of the real kinematics process of landslides. In this study, the multi-source SAR data, atmospheric error correction by quadratic tree image segmentation method, and phase-stacking method were selected to derive the surface deformation of this area. Besides, DS-InSAR and MSBAS method were combined to derive the deformation of Pingdi landslide. First, the potential landslides in this area were identified, surface deformation result, optical remote sensing images and geomorphological features were jointly considered. Then, the landslide distribution characteristics was analyzed in terms of slope, elevation and stratum. After that, the deformation along the LOS direction was acquired using the DS-InSAR method. The MSBAS method was used to retrieve the two-dimensional deformation of Pingdi landslide. Finally, the comprehensive analysis of triggering factors and failure process were conducted according to the spatial-temporal deformation characteristics and field investigation. The results indicated that landslides in Shuicheng district were mostly located in the junction of T1 and P3 stratum and mining related. Mining activity was the main cause of the Pingdi landslide deformation, the precipitation was the driving factor of the landslide instability. The research provides an insight into the explore the unstable slope distribution characteristic and the failure process of the landslides.</p

Privacy-Preserving Confidential Reporting System With Designated Reporters

A confidential reporting system (CRS) allows reporters to report concerns or problems in confidence without the fear of blame or reprisals. Nevertheless, privacy has been the primary concern of reporters. In this paper, we propose a privacy-preserving confidential reporting system with designated reporters (PPCRS-DR) to protect the privacy of reporters and the confidentiality of reports. Our PPCRS-DR provides the following interesting features: (1) for an event, an auditor can designate a reporter to report; (2) an auditor can neither see the report nor know the reporter's identity from an encrypted report if the reporter is not the designated one; (3) when an auditor is unavailable, he/she can temporarily designate a delegatee to collect and review reports on behalf of him/her. We formalize both the definition and security model of our PPCRS-DR, and propose a concrete construction. Furthermore, the security of the proposed PPCRS-DR is formally proven. The implementation shows that it is efficient. The novelty is to implement flexible decryption delegation of CRSs and protect reporters' privacy

Atomic-Scale Clarification of Structural Transition of MoS₂ upon Sodium Intercalation

Two-dimensional (2D) transition-metal dichalcogenides hold enormous potential for applications in electronic and optoelectronic devices. Their distinctive electronic and chemical properties are closely related to the structure and intercalation chemistry. Herein, the controversial phase transition from semiconductive 2H to metallic 1T phase and occupancy of the intercalated sodium (Na) upon electrochemical Na intercalation into MoS₂ are clarified at the atomic scale by aberration-corrected scanning transmission electron microscope. In addition, a series of other complicated phase transitions along with lattice distortion, structural modulation, and even irreversible structural decomposition are recognized in MoS₂ depending on the content of Na ion intercalation. It is shown that <i>x</i> = 1.5 in Na_<i>x</i>MoS₂ is a critical point for the reversibility of the structural evolution. Our findings enrich the understanding of the phase transitions and intercalation chemistry of the MoS₂ and shed light on future material design and applications

Selecting Substituent Elements for Li-Rich Mn-Based Cathode Materials by Density Functional Theory (DFT) Calculations

Li₂MnO₃ is known to stabilize the structure of the Li-rich Mn-based cathode materials <i>x</i>Li₂MnO₃·(1 – <i>x</i>)­LiMO₂ (M = Ni, Co, Mn, etc.). However, its presence makes these materials suffer from drawbacks including oxygen release, irreversible structural transition, and discharge potential decay. In order to effectively address these issues by atomic substitution, density function theory (DFT) calculations were performed to select dopants from a series of transition metals including Ti, V, Cr, Fe, Co, Ni, Zr, and Nb. Based on the calculations, Nb is chosen as an dopant, because Nb substitution is predicted to be able to increase the electronic conductivity, donate extra electrons for charge compensation and postpone the oxygen release reaction during delithiation. Moreover, the Nb atoms bind O more strongly and promote Li diffusion as well. Electrochemical evaluation on the Nb-doped Li₂MnO₃ show that Nb doping can indeed improve the performances of Li₂MnO₃ by increasing its electrochemical activity and hindering the decay of its discharge potential

ZrO₂‑Nanoparticle-Modified Graphite Felt: Bifunctional Effects on Vanadium Flow Batteries

To improve the electrochemical performance of graphite felt (GF) electrodes in vanadium flow batteries (VFBs), we synthesize a series of ZrO₂-modified GF (ZrO₂/GF) electrodes with varying ZrO₂ contents via a facile immersion-precipitation approach. It is found that the uniform immobilization of ZrO₂ nanoparticles on the GF not only significantly promotes the accessibility of vanadium electrolyte, but also provides more active sites for the redox reactions, thereby resulting in better electrochemical activity and reversibility toward the VO²⁺/VO₂⁺ and V²⁺/V³⁺ redox reactions as compared with those of GF. In particular, The ZrO₂/GF composite with 0.3 wt % ZrO₂ displays the best electrochemical performance with voltage and energy efficiencies of 71.9% and 67.4%, respectively, which are much higher than those of 57.3% and 53.8% as obtained from the GF electrode at 200 mA cm^–2. The cycle life tests demonstrate that the ZrO₂/GF electrodes exhibit outstanding stability. The ZrO₂/GF-based VFB battery shows negligible activity decay after 200 cycles

Solid-State Composite Electrolyte LiI/3-Hydroxypropionitrile/SiO₂ for Dye-Sensitized Solar Cells

A new compound, LiI(3-hydroxypropionitrile)2, is reported here. According to its single-crystal structure (C2/c), this compound has 3-D transporting paths for iodine. Further ab initio calculation shows that the activation energy for diffusion of iodine (0.73 eV) is much lower than that of lithium ion (8.39 eV) within the lattice. Such a mono-ion transport feature is favorable as solid electrolyte to replace conventional volatile organic liquid electrolytes used in dye-sensitized solar cells (DSSC). LiI and 3-hydroxypropionitrile (HPN) can form a series of solid electrolytes. The highest ambient conductivity is 1.4 × 10-3 S/cm achieved for LiI(HPN)4. However, it tends to form large crystallites and leads to poor filling and contact within porous TiO2 electrodes in DSSC. Such a drawback can be greatly improved by introducing micrometer-sized and nanosized SiO2 particles into the solid electrolyte. It is helpful not only in enhancing the conductivity but also in improving the interfacial contact greatly. Consequently, the light-to-electricity conversion efficiency of 5.4% of a DSSC using LiI(HPN)4/15 wt % nano-SiO2 was achieved under AM 1.5 simulated solar light illumination. Due to the low cost, easy fabrication, and relatively high conversion efficiency, the DSSC based on this new solid-state composite electrolyte is promising for practical applications