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3D hosts are promising to extend the cycle life of lithium metal anodes but have rarely been implemented with lean electrolytes thus impacting the practical cell energy density. To overcome this challenge, a 3D host that is lightweight and easy to fabricate with optimum pore size that enables full utilization of its pore volume, essential for lean electrolyte operations, is reported. The host is fabricated by casting a VGCF (vapor-growncarbon fiber)-based slurry loaded with a sparingly soluble rubidium nitrate salt as an additive. The network of fibers generates uniform pores of ≈3 µm in diameter with a porosity of 80%, while the nitrate additive enhances lithiophilicity. This 3D host delivers an average coulombic efficiency of 99.36% at 1mA cm-2 and 1 mAh cm-2 for over 860 cycles in half-cell tests. Full cells containing an anode with 1.35-fold excess lithium paired with LiNi0.8 Mn0.1 Co0.1 O2 (NMC811) cathodes exhibit capacity retention of 80% over 176 cycles at C/2 under a lean electrolyte condition of 3g Ah-1 . This work provides a facile and scalable method to advance 3D lithium hosts closer to practical lithium-metal batteries.

Additional file 1: Table S1: Technical file for GOHI-AMR.

RGB-D object tracking has attracted considerable attention recently, achieving promising performance thanks to the symbiosis between visual and depth channels. However, given a limited amount of annotated RGB-D tracking data, most state-of-the-art RGB-D trackers are simple extensions of high-performance RGB-only trackers, without fully exploiting the underlying potential of the depth channel in the offline training stage. To address the dataset deficiency issue, a new RGB-D dataset named RGBD1K is released in this paper. The RGBD1K contains 1,050 sequences with about 2.5M frames in total. To demonstrate the benefits of training on a larger RGB-D data set in general, and RGBD1K in particular, we develop a transformer-based RGB-D tracker, named SPT, as a baseline for future visual object tracking studies using the new dataset. The results, of extensive experiments using the SPT tracker emonstrate the potential of the RGBD1K dataset to improve the performance of RGB-D tracking, inspiring future developments of effective tracker designs. The dataset and codes will be available on the project homepage: https://github.com/xuefeng-zhu5/RGBD1K.

The flow distribution of each branch of the aircraft's airborne liquid cooling cycle is a key issue to ensure refrigeration performance and improve energy utilization. Due to the correlation of multiple factors, the existing airborne liquid cooling cycle flow distribution method cannot achieve accurate flow distribution result. This paper takes the maximum maximum temperature of all equipment as the optimization goal, and the joint simulation-optimization of the AMESim software and the modeFRONTIER platform is used to solve the optimization design problem of the flow distribution scheme. The result shows that compared with traditional design methods, the use of simulation-based optimization design methods can give full play to the advantages of AMESim software in simulation and performance index calculation and modeFRONTIER software in searching for optimal allocation schemes. It can reduce the maximum temperature of each branch device and effectively improve the cooling effect.

Cation-disordered Li-excess cathodes with oxygen redox reactions are promising candidates for high-energy-density Li ion batteries. Nevertheless, the oxygen redox process that is required for the high capacity often comes with the oxygen loss, which leads to severe capacity degradation and voltage decay. In this work, we have successfully synthesized a series of Li-excess cation-disordered cathodes (Li1.2Mn0.4+xTi0.4-xO2-xFx) (0 ​≤ ​x ​≤ ​0.2) with different fluorine (F) contents. The electrochemical performance results show that the Li1.2Mn0.55Ti0.25O1.85F0.15 (LMTOF0.15) exhibits the highest reversible capacity (275 mAh g-1, under 30 ​mA ​g-1), cyclability, and voltage retentions. The mapping of resonant inelastic X-ray scattering (mRIXS) and differential electrochemical mass spectroscopy (DEMS) results reveal that the fluorination enhances the reversible lattice oxygen redox reaction while suppressing irreversible gas release and surface reactions. The X-ray Absorption Spectroscopy (XAS) during the initial two cycles shows that F-substitution alleviates the reduction of the Mn valence state during the whole (dis)charge processes in the bulk and at the surface of the material, results in higher average discharge voltage. In addition, the introduction of F improves the structural stability and suppresses local lattice distortion of the material. Therefore, LMTOF0.15 is able to cycle with smaller polarization, less interfacial side reaction and Mn dissolution, and therefore results in enhanced cyclability. This work provides a comprehensive understanding of the fluorination effect on the cationic and anionic redox activities in cation-disordered Li-excess cathodes.

Voltage decay,i.e., the voltage decrease during electrochemical cycling, has been a decade-long challenge for lithium-ion batteries. This issue not only leads to a substantial loss of energy density, but also raises challenges for the battery management system, hindering the commercial application of high capacity lithium-rich oxide. Here, we show that through a combination of electrochemical conditioning and thermal treatment, Li2MnO3, the parent compound of lithium-rich oxide, which typically displays severe voltage and capacity decay, could be converted into a new phase that essentially suppresses the voltage decay with improved capacity retention and rate performance. By combining atomic-sensitive nuclear magnetic resonance, differential electrochemical mass spectrometry and synchrotron-based resonant inelastic X-ray scattering, we disclose that treatment triggers the formation of three-coexisting phases,i.e., the lithium-rich layered, spinel and defect spinel phases, which enables improved reversibility of the oxygen redox activity and enhanced manganese redox reactions in the initial cycle. Our findings suggest the key role of the local structure in the voltage decay problem and provide insights for material optimizations towards lithium- and manganese-rich cathodes without the voltage decay.

Conversion-type transition-metal phosphide anode materials with high theoretical capacity usually suffer from low-rate capability and severe capacity decay, which are mainly caused by their inferior electronic conductivities and large volumetric variations together with the poor reversibility of discharge product (Li3P), impeding their practical applications. Herein, guided by density functional theory calculations, these obstacles are simultaneously mitigated by confining amorphous FeP nanoparticles into ultrathin 3D interconnected P-doped porous carbon nanosheets (denoted as FeP@CNs) via a facile approach, forming an intriguing 3D flake-CNs-like configuration. As an anode for lithium-ion batteries (LIBs), the resulting FeP@CNs electrode not only reaches a high reversible capacity (837 mA h g-1 after 300 cycles at 0.2 A g-1) and an exceptional rate capability (403 mA h g-1 at 16 A g-1) but also exhibits extraordinary durability (2500 cycles, 563 mA h g-1 at 4 A g-1, 98% capacity retention). By combining DFT calculations, in situ transmission electron microscopy, and a suite of ex situ microscopic and spectroscopic techniques, we show that the superior performances of FeP@CNs anode originate from its prominent structural and compositional merits, which render fast electron/ion-transport kinetics and abundant active sites (amorphous FeP nanoparticles and structural defects in P-doped CNs) for charge storage, promote the reversibility of conversion reactions, and buffer the volume variations while preventing pulverization/aggregation of FeP during cycling, thus enabling a high rate and highly durable lithium storage. Furthermore, a full cell composed of the prelithiated FeP@CNs anode and commercial LiFePO4 cathode exhibits impressive rate performance while maintaining superior cycling stability. This work fundamentally and experimentally presents a facile and effective structural engineering strategy for markedly improving the performance of conversion-type anodes for advanced LIBs.

Both powerful and unstable, practical lithium metal batteries have remained a difficult challenge for over 50 years. With severe ion depletion gradients in the electrolyte during charging, they rapidly develop porosity, dendrites, and dead Li that cause poor performance and, all too often, spectacular failure. Remarkably, incorporating a small, 100 MHz surface acoustic wave device (SAW) solves this problem. Providing acoustic streaming electrolyte flow during charging, the device enables dense Li plating and avoids porosity and dendrites. SAW-integrated Li cells can operate up to 6 mA cm-2 in a commercial carbonate-based electrolyte; omitting the SAW leads to short circuiting at 2 mA cm-2 . The Li deposition is morphologically dendrite-free and close to theoretical density when cycling with the SAW. With a 245 µm thick Li anode in a full Li||LFP (LiFePO4 ) cell, introducing the SAW increases the uncycled Li from 145 to 225 µm, decreasing Li consumption from 41% to only 8%. A closed-form model is provided to explain the phenomena and serve as a design tool for integrating this chemistry-agnostic approach into batteries whatever the chemistry within.

As a parent compound of Li-rich electrodes, Li2MnO3 exhibits high capacity during the initial charge; however, it suffers notoriously low Coulombic efficiency due to oxygen and surface activities. Here, we successfully optimize the oxygen activities toward reversible oxygen redox reactions by intentionally introducing protons into lithium octahedral vacancies in the Li2MnO3 system with its original structural integrity maintained. Combining structural probes, theoretical calculations, and resonant inelastic X-ray scattering results, a moderate coupling between the introduced protons and lattice oxygen at the oxidized state is revealed, which stabilizes the oxygen activities during charging. Such a coupling leads to an unprecedented initial Coulombic efficiency (99.2%) with a greatly improved discharge capacity of 302 mAh g-1 in the protonated Li2MnO3 electrodes. These findings directly demonstrate an effective concept for controlling oxygen activities in Li-rich systems, which is critical for developing high-energy cathodes in batteries.

In this work, we show that the well-known lithium-ion anode material, Li4Ti5O12, exhibits exceptionally high initial capacity of 310 mAh g-1 when it is discharged to 0.01 V. It maintains a reversible capacity of 230 mAh g-1, far exceeding the "theoretical" capacity of 175 mAh g-1 when this anode is lithiated to the composition Li7Ti5O12. Neutron diffraction analyses identify that additional Li reversibly enters into the Li7Ti5O12 to form Li8Ti5O12. density functional theory (DFT) calculations reveal the average potentials of the Li4Ti5O12 to Li7Ti5O12 step and the Li7Ti5O12 to Li8Ti5O12 step are 1.57 and 0.19 V, respectively, which are in excellent agreement with experimental results. Transmission electron microscopy (TEM) studies confirm that the irreversible capacity of Li4Ti5O12 during its first cycle originates from the formation of a solid electrolyte interface (SEI) layer. This work clarifies the fundamental lithiation mechanism of the Li4Ti5O12, when lithiated to 0.01 V vs Li.

In this paper, we study the maximum principle for stochastic optimal control problems of forward-backward stochastic difference systems (FBS{\Delta}Ss) where the uncertainty is modeled by a discrete time, finite state process, rather than white noises. Two types of FBS{\Delta}Ss are investigated. The first one is described by a partially coupled forward-backward stochastic difference equation (FBS{\Delta}E) and the second one is described by a fully coupled FBS{\Delta}E. By adopting an appropriate representation of the product rule and an appropriate formulation of the backward stochastic difference equation (BS{\Delta}E), we deduce the adjoint difference equation. Finally, the maximum principle for this optimal control problem with the control domain being convex is established., Comment: 26 pages. arXiv admin note: substantial text overlap with arXiv:1812.11283

Rechargeable lithium metal batteries based on organic electrolytes face challenges of both lithium metal cycling stability and the associated safety issues. Herein, we demonstrate an in situ formed polymer gel electrolyte which enables dendrite-free lithium metal cycling. Moreover, the gel electrolyte goes through further polymerization at elevated temperatures and loses its ionic conductivity, effectively shutting down the battery. When lithium iodide (LiI) is dissolved in vinylene carbonate (VC), LiI induces the polymerization of VC to form poly(vinylene carbonate) (polyVC). The electrolyte then transforms into a polymer gel electrolyte containing VC as the solvent and LiI as the salt. At room temperature, the gel electrolyte enables dendrite-free lithium metal cycling at current densities as high as 5 mA cm-2 for 500 cycles. Furthermore, a Li/Li4Ti5O12 (LTO) cell retains 50% of the initial capacity at the 700th cycle. When the cell is heated to 80 °C, the ionic resistance of the electrolyte increases by a factor of 103, resulting in the shutdown of the cell due to the complete polymerization of VC. The approach of using in situ polymerization to enable stable lithium cycling and to serve as a thermally triggered shutdown mechanism provides a new pathway for fabricating safer lithium metal batteries.

In this paper, we study the solvability problem for one kind of fully coupled forward-backward stochastic difference equations (FBS{\Delta}Es). With the help of the necessary and sufficient condition for the solvability of the linear FBS{\Delta}Es, under the monotone assumption, we obtain the existence and uniqueness theorem for the general nonlinear ones., Comment: 19 pages. arXiv admin note: text overlap with arXiv:1812.11283

In-depth analysis of the influence of mixed working fluids on the thermodynamic performance of a throttling refrigeration cycle through experimental research. After optimizing the calculation of two ternary mixed working fluids with different compositions, the charging test is carried out, and the throttle characteristic curve of the mixed working fluid the law of temperature and pressure changes in the experiment was analyzed. The results show that: a mixed working fluid with a mixing ratio of 30.39mol% R14, 10.73mol% R170 and 58.87mol% R600A, at a pressure ratio of 2.5/0.1, a low temperature of -67.7°C is obtained, and the cooling time is 113.42min. The refrigeration system COP is 0.076; the mixing ratio is 30.39mol%R14, 15.73mol%R23 and 53.87mol%R600A mixed working fluid, in the case of a pressure ratio of 2.14/0.1, a low temperature of -76.4°C is obtained, and the cooling time is 160min, the refrigeration system COP is 0.106.

Anisotropic disorder along the c-axis results from static disorder.

Spontaneous and anisotropic surface segregation of W cations in LiMn1.5Ni0.5O4 particles can alter the Wulff shape and improve surface stability, thereby significantly improving the electrochemical performance. An Auger electron nanoprobe was employed to identify the anisotropic surface segregation, whereby W cations prefer to segregate to {110} surface facets to decrease its relative surface energy according to Gibbs adsorption theory and subsequently increase its surface area according to Wulff theory. Consequently, the rate performance is improved (e.g., by ∼5-fold at a high rate of 25C) because the {110} facets have more open channels for fast lithium ion diffusion. Furthermore, X-ray photoelectron spectroscopy (XPS) depth profiling suggested that the surface segregation and partial reduction of W cation inhibit the formation of Mn3+ on surfaces to improve cycling stability via enhancing the cathode electrolyte interphase (CEI) stability at high charging voltages. This is the first report of using anisotropic surface segregation to thermodynamically control the particle morphology as well as enhancing CEI stability as a facile, and potentially general, method to significantly improve the electrochemical performance of battery electrodes. Combining neutron diffraction, an Auger electron nanoprobe, XPS, and other characterizations, we depict the underlying mechanisms of improved ionic transport and CEI stability in high-voltage LiMn1.5Ni0.5O4 spinel materials.

Let $a,b,n$ be three positive integers such that $a\equiv b\pmod 2$ and $n\geq b(a+b)(a+b+2)/(2a)$. Let $G$ be a graph of order $n$ with minimum degree at least $a+b/a-1$. We show that $G$ has an $(a,b)$-parity factor, if $max\{d_G(u),d_G(v)\}\geq \frac{an}{a+b}$ for any two nonadjacent vertices $u,v$ of $G$. It is an extension of Nishimura's results for the existence of $k$-factors (\emph{J. Graph Theory}, \textbf{16} (1992), 141--151) and generalizes Li and Cai's result in some senses (\emph{J. Graph Theory}, \textbf{27} (1998), 1--6). These conditions are tight.

The layered oxide compounds xLi2MnO3·(1 - x)LiMO2 (M=Ni, Mn, Co) are of great interest as positive electrode materials for high energy density lithium-ion batteries. In-situ neutron diffraction was carried out to compare the structural changes between the classical layered compound Li[Ni1/3Mn1/3Co1/3]O2 (x=0) and lithium-excess layered compound Li[Li0.2Ni0.18Mn0.53Co0.1]O2 (x=0.5) during electrochemical cycling. In this work, lab made pouch cells were built for the in-situ study and graphite was used as the anode material. Irreversible structural change of Li[Li0.2Ni0.18Mn0.53Co0.1]O2 during first charge (4.7 V)/discharge cycle (2.0 V) was indicated by dynamic changes in lattice d-spacing, while the Li[Ni1/3Mn1/3Co1/3]O2 showed completely reversible structural evolution between 4.4 V and 2.5 V. Ex-situ neutron powder diffraction was performed on both pristine and chemically delithiated lithium-excess layered compounds to better understand the irreversible structure change. © 2013 Published by Elsevier B.V.

Lithium-excess cation-disordered rock-salt oxides (DRXs) are investigated intensively as cathode materials for future lithium-ion batteries combining cationic and anionic redox reactions. However, the lattice oxygen redox can cause severe oxygen release resulting in rapid capacity fading. Here, we investigate a series of xLi(2)TiO(3)-(1 - x)LiMnO2 (0

In this work, Li-rich Li1.2Mn0.43+Mnx4+Ti0.4-xO2 (LMMxTO, 0