Lithium Atoms Research Articles

Continuum modeling for lithium storage inside nanotubes

Lithium storage and capture are of particular importance for the development of new technology in electric vehicles and portable electronics. Nanotubes (NTs) are among many porous nanomaterials offered as potential candidates for lithium storage. In this paper, we adopt a continuum approach together with the Lennard–Jones function to determine the minimum interaction energies for lithium atoms in boron nitride nanotubes (BNNTs) and carbon nanotubes (CNTs). By minimizing the interaction energies, we may obtain the preferred type and size of the nanotubes to encapsulate the lithium atoms. The results showed that BNNTs and CNTs are attractive candidates for lithium atom encapsulation, and the optimal nanotube to enclose lithium is the BNNT with a radius equal to 3.4 Å, and corresponding (5, 5) armchair nanotubes and (9, 0) zigzag nanotubes, where the minimum energy is obtained. The present computations observed that both nanotubes are promising candidates for lithium intercalation materials suitable for battery applications.

The Role of Conjugation in the Halogen-Lithium Exchange Selectivity: Lithiation of 4,6,7,9-Tetrabromo-1,3-dimethyl-2,3-dihydro-1H-perimidine.

The first case of successful suppression of the coordination of a lithium atom with a dialkylamino group by the effective conjugation of the latter with the aromatic core has been discovered. This effect controls regioselectivity of the bromine-lithium exchange in 4,6,7,9-tetrabromo-1,3-dimethyl-2,3-dihydro-1H-perimidine, which leads to products with the most effective conjugation. As a result, the product of this quadruple exchange demonstrates no tendency of the coordination of the NMe groups to neighboring lithium atoms despite the absence of steric restrictions. Experimental results are explained by means of quantum chemical calculations: geometry optimization, natural bond analysis and scans using the modredundant scheme.

Mechano-Electrochemically Promoting Lithium Atom Diffusion and Relieving Accumulative Stress for Deep-Cycling Lithium Metal Anodes.

Lithium metal batteries (LMBs) can double the energy density of lithium-ion batteries. However, the notorious lithium dendrite growth and large volume change are not well addressed, especially under deep cycling. Here, an in-situ mechanical-electrochemical coupling system is built, and it is found that tensile stress can induce smooth lithium deposition. Density functional theory (DFT) calculation and finite element method (FEM) simulation confirm that the lithium atom diffusion energy barrier can be reduced when the lithium foils are under tensile strain. Then tensile stress is incorporated into lithium metal anodes by designing an adhesive copolymer layer attached to lithium in which the copolymer thinning can yield tensile stress to the lithium foil. Elastic lithium metal anode (ELMA) is further prepared via introducing a 3D elastic conductive polyurethane (CPU) host for the copolymer-lithium bilayer to release accumulated internal stresses and resist volume variation. The ELMA can withstand hundreds of compression-release cycles under 10% strain. LMBs paired with ELMA and LiNi0.8 Co0.1 Mn0.1 O2 (NCM811) cathode can operate beyond 250 cycles with 80% capacity retention under practical condition of 4 mAh cm-2 cathode capacity, 2.86g Ah-1 electrolyte-to-capacity ratio (E/C) and 1.8 negative-to-cathode capacity ratio (N/P), five times of the lifetime using lithium foils.

Dopant ionization and efficiency of ion and electron ejection from helium nanodroplets.

Photoionization spectroscopy and mass spectrometry of doped helium (He) nanodroplets rely on the ability to efficiently detect ions and/or electrons. Using a commercial quadrupole mass spectrometer and a photoelectron-photoion coincidence spectrometer, we systematically measure yields of ions and electrons created in pure and doped He nanodroplets in a wide size range and in two ionization regimes-direct ionization and secondary ionization after resonant photoexcitation of the droplets. For two different types of dopants (oxygen molecules, O2, and lithium atoms, Li), we infer the optimal droplet size to maximize the yield of ejected ions. When dopants are ionized by charge-transfer to photoionized He nanodroplets, the highest yield of O2 and Li ions is detected for a mean size of ∼5×104 He atoms per nanodroplet. When dopants are Penning ionized via photoexcitation of the He droplets, the highest yield of O2 and Li ions is detected for ∼103 and ∼105 He atoms per droplet, respectively. At optimum droplet sizes, the detection efficiency of dopant ions in proportion to the number of primary photoabsorption events is up to 20% for charge-transfer ionization of O2 and 2% for Li, whereas for Penning ionization it is 1% for O2 and 4% for Li. Our results are instrumental in determining optimal conditions for mass spectrometric studies and photoionization spectroscopy of molecules and complexes isolated in He nanodroplets.

The performance of Li-modified B-doped phagraphene as a reversible hydrogen storage material in near-environmental conditions

In recent years, various applications of two-dimensional carbon nanomaterial phagraphene, whose protocells contain 5, 6 and 7 carbon rings, have been investigated. In this paper, first-principles and Grand Canonical Monte Carlo (GCMC) simulation methods are used to study the hydrogen storage properties of primitive and B-doped lithium modified phagraphene. The DFT results show that the binding energy of lithium atoms in Li-phagraphene is 2.0 eV. After B doping, the binding energy was significantly increased to 2.8 eV, and the molecular weight ratio of hydrogen was 13.07 wt%. According to the calculation of GCMC, the hydrogen storage weight ratio could reach 6.36 wt% under the environmental conditions of 298 K and 1 bar. The calculated Van't Hoff equation shows that doping B is more conducive to hydrogen desorption at atmospheric pressure. These results indicate that Li-modified B-doped phagraphene is a candidate material for realizing reversible hydrogen storage in near-environmental conditions.

Structural analysis of non-stoichiometric lithium cuprates, Li2+2xCu1-2xO2-x. Effects of lithium content and thermal treatments

Lithium cuprate (Li2CuO2) is being used for a wide range of applications due to its high lithium diffusion through the layer structure. Moreover, Li2+2xCu1-xO2-x non-stoichiometric material shows enhanced physicochemical properties. Therefore, lithium location understanding is highly important for lithium cuprate applications. This paper reports the structural coherence analysis, local and long atomic arrangement of Li2+2xCu1-xO2-x using X-ray diffraction (XRD), pair distribution function (PDF) and solid-state nuclear magnetic resonance (NMR) techniques. Li2CuO2, containing different excess quantities of lithium (from 0 to 60 at%), were synthesized by solid-state reaction. The synthesized ceramics presented nonstoichiometric structures, with Li2CuO2 type-structure. Two structural models were proposed to explain the high enhancement physicochemical properties of these ceramics; (i) the extra lithium atoms substitute copper sites, and (ii) lithium species occupy interstitial sites in the crystalline structure. Additionally, further thermal treatments rearrange the non-stoichiometric crystalline structures into the stable Li2CuO2 phase.

Rare-Earth Fluorite-like Li0.42La4.58Mo3O15.76±δF0.42±ε Molybdates: Crystal Growth and Atomic Structure

Rare-earth fluorine-containing molybdates of the Ln5Mo3O16+δ oxygen–electron conductor family with the LiLa4Mo3O15F composition were synthesized for the first time as single crystals by the flux method. An accurate X-ray diffraction analysis of the obtained crystals was carried out at 20 and −183 °C. The LiLa4Mo3O15F compound is isostructural to the fluorine-free analogue with a cubic structure (space group Pn3¯n). It is shown that lithium atoms replace one of the two positions of lanthanum in the more distorted LaO8 polyhedron. According to X-ray diffraction analysis, fluorine atoms replace the positions of over-stoichiometric oxygen located in the vast cavities of the structure. So, fluorine anions can promote the interstitial conductivity of F-containing LiLa4Mo3O15F molybdates.

Utilizing Ultra-homogeneous SiOx and Defects to Achieve Interlayer Protection for Lithium Metal Anodes.

The uncontrollable growth and uneven nucleation of lithium metal can be addressed by utilizing spatial confinement structures in conjunction with lithiophilic sites. However, their complex fabrication technique and the inhomogeneous dispersion of lithiophilic sites make the application ineffective. In this work, ultra-uniformly dispersed SiOx seeds and defects are produced in situ to achieve the spatially restricted protection within the reduced graphene oxide (rGO) layer. The in situ formed SiOx and defects during annealing double constrain lithium nucleation and growth behaviors thanks to the superlithiophilic characteristic, while both provide the fast Li+ transport channel to utilize the interlayer protection of rGO in limiting lithium dendrite growth. Furthermore, XANES and XPS analyze the SiOx seeds that are dominated by various valence states, and theoretical calculations further verify the control on the nucleation of lithium atoms. Benefiting from the optimum average valence of three for the "control site", the host realizes steady circulation. In asymmetric cells, the host demonstrates excellent coulombic efficiency of 99.1% and stable lifespans over 1250h at 1mAcm-2 . When assembled in LiFePO4 full cells, it retains a favorable capacity of 116.2mAhg-1 after 170 cycles.

Ground-state decoherence of lithium atoms by diatomic polar molecules and noble-gas atoms

Ground-state decoherence of lithium atoms by diatomic polar molecules and noble-gas atoms

High-zeta-potential accelerates interface charge transfer in lithium anodes via MXene-graphdiyne heterojunction layers

Lithium (Li) metal anodes are a crucial part of lithium-based batteries and are highly regarded as a top contender for achieving high-energy–density lithium batteries. However, the development of dendrites and other related issues have significantly impeded their practical applications. Here, we fabricated a MXene (Ti3C2Tx)-graphdiyne heterostructure layer anode with high-zeta-potential (−90 mV) using an electrostatic self-assembly method. The high-zeta-potential can accelerate the interface charge transfer in the lithium deposition process, facilitating the uniform Li nucleation on the surface of anodes. Theoretical simulations further reveal that the high-zeta-potential can not only reduce the lithium ion concentration gradient but also homogenize the electric field in the anodes. Besides, based on first-principles computation, the adsorption energy of lithium atoms on MXene-graphdiyne heterostructure is − 3.4 eV. As a result, a low overpotential of 12.4 mV has been achieved by MXene-graphdiyne layers at 0.05 mA cm−2. Additionally, MXene-graphdiyne-Li anodes display an ultralong cycle life upto 1400 h and good rate capability upto 8 mA cm−2 in symmetric cells. Full cells consisting of MXene-graphdiyne-Li anodes and LiFeO4 cathodes also show stable cyclic properties (300 cycles at 5C).

First principle modeling of a silicene-aluminum composite anode for lithium ion batteries

The creation of new environmentally friendly and portable energy sources requires the development of technology used to produce lithium-ion batteries, especially their anodes. The aim of this study was to show the possibilities of the state-of-the-art ab initio approach for modeling battery anode materials. A quantum-mechanical study of the limiting filling of a silicene/aluminum anode with lithium has been performed. In this case, the changes in the structure, energy, and electronic properties of silicene that occur upon filling the anode have been studied. Lithium atoms are deposited both inside and on top of the channel formed by two parallel silicene sheets. The ratio of lithium to silicon varies in the range of 0.1–1.5. The gap in the silicene channel increases as the channel is filled with lithium. The filling of the silicene channel with lithium is associated with an increase in the Si–Si bond length in both silicene sheets without destruction of the channel. The infiltration of lithium into the space between the aluminum substrate and silicene sheet has been determined. Our calculation of the band structure has shown that, regardless of filling with lithium, the silicene-aluminum system exhibits metallic conductivity. The storage capacity of the combined anode (729 mAh g−1) significantly exceeds the capacity of graphite anodes. It was found that the top sheet of silicene acquires a negative electric charge upon significant lithium filling of the anode, exceeding the absolute value of the negative charge of the bottom sheet in contact with the aluminum substrate. Therefore, our model study has elucidated that the new silicene-aluminum anode is a promising material for the creation of a new generation of lithium-ion batteries.

Simulation of the Adsorption and Diffusion of Lithium Atoms on Defective Graphene for a Li-Ion Battery

Simulation of the Adsorption and Diffusion of Lithium Atoms on Defective Graphene for a Li-Ion Battery

2D Hemiporphyrazine: A new nanoporous material

Crystalline microporous materials are solids formed by interconnected pores of less than 2 nm in size. Typically, they possess large surface areas desirable for versatile applications such as catalysis, gas adsorption, and energy storage. In the present work, we propose a new porphyrin-based 2D nanoporous crystal, named 2D Porphyrazine (2DP), which is formed by topological assembling H$_{5}$C$_{13}$N$_{4}$ porphyrins. We have considered its monolayer, bi-layer, and molecular crystal (bulk) arrangements. We carried out DFT calculations to investigate 2DP structural and electronic properties. Results show that 2DP is a very stable structure with a direct bandgap of 0.65 eV and significant optical absorption in the visible range. 2DP exhibited satisfactory affinity to lithium atoms. Simulations also showed the existence of proton transfer between nitrogen atoms. It is the first report on the site-specific hydrogen exchange process in 2D crystals.

A DFT study of COF-1 covalent organic framework as a disposable platform for rechargeable lithium-ion battery anodes

We considered the COF-1 covalent organic framework in the present study to develop materials with significant cell voltage in LIBs technology. Our analyses and evaluations based on the density functional study showed that the Li+ cation had a more stable interaction with the considered COF-1 than the neutral Li metal. Due to the adsorption of Li and Li+ on the surface of COF-1, the energy levels of HOMO and LUMO decreased drastically so that the adsorption of the lithium atom has a more significant influence on the energy gap of COF-1 than the adsorption of lithium cation. The value of the cell voltage was estimated to be 0.72 V. By increasing the number of Li/Li+ up to 6, a cell voltage of 3.34 V and a storage capacity of 169.68 mAhg−1 was obtained. The current study results described here may contribute to improving the cell voltage of the LIBs.

Lithium crystallization at solid interfaces

Understanding the electrochemical deposition of metal anodes is critical for high-energy rechargeable batteries, among which solid-state lithium metal batteries have attracted extensive interest. A long-standing open question is how electrochemically deposited lithium-ions at the interfaces with the solid-electrolytes crystalize into lithium metal. Here, using large-scale molecular dynamics simulations, we study and reveal the atomistic pathways and energy barriers of lithium crystallization at the solid interfaces. In contrast to the conventional understanding, lithium crystallization takes multi-step pathways mediated by interfacial lithium atoms with disordered and random-closed-packed configurations as intermediate steps, which give rise to the energy barrier of crystallization. This understanding of multi-step crystallization pathways extends the applicability of Ostwald’s step rule to interfacial atom states, and enables a rational strategy for lower-barrier crystallization by promoting favorable interfacial atom states as intermediate steps through interfacial engineering. Our findings open rationally guided avenues of interfacial engineering for facilitating the crystallization in metal electrodes for solid-state batteries and can be generally applicable for fast crystal growth.

A Highly-Lithiophilic Mn3O4/ZnO-Modified Carbon Nanotube Film for Dendrite-Free Lithium Metal Anodes

Lithium metal anode is deemed as a potential candidate for high energy density batteries, which has attracted increasing attention. Unfortunately, Li metal anode suffers from issues such as dendrite grown and volume expansion during cycling, which hinders its commercialization. Herein, we designed a porous and flexible self-supporting film comprising of single-walled carbon nanotube (SWCNT) modified with a highly-lithiophilic heterostructure (Mn3O4/ZnO@SWCNT) as the host material for Li metal anodes. The p-n-type heterojunction constructed by Mn3O4 and ZnO generates a built-in electric field that facilitates electron transfer and Li+ migration. Additionally, the lithiophilic Mn3O4/ZnO particles serve as the pre-implanted nucleation sites, dramatically reducing the lithium nucleation barrier due to their strong binding energy with lithium atoms. Moreover, the interwoven SWCNT conductive network effectively lowers the local current density and alleviates the tremendous volume expansion during cycling. Thanks to the aforementioned synergy, the symmetric cell composed of Mn3O4/ZnO@SWCNT-Li can stably maintain a low potential for more than 2500 h at 1 mA cm−2 and 1 mAh cm−2. Furthermore, the Li-S full battery composed of Mn3O4/ZnO@SWCNT-Li also shows excellent cycle stability. These results demonstrate that Mn3O4/ZnO@SWCNT has great potential as a dendrite-free Li metal host material.

Superfluid Signatures in a Dissipative Quantum Point Contact.

We measure superfluid transport of strongly interacting fermionic lithium atoms through a quantum point contact with local, spin-dependent particle loss. We observe that the characteristic non-Ohmic superfluid transport enabled by high-order multiple Andreev reflections transitions into an excess Ohmic current as the dissipation strength exceeds the superfluid gap. We develop a model with mean-field reservoirs connected via tunneling to a dissipative site. Our calculations in the Keldysh formalism reproduce the observed nonequilibrium particle current, yet do not fully explain the observed loss rate or spin current.

Anomalous loss behavior in a single-component Fermi gas close to a p -wave Feshbach resonance

We theoretically investigate three-body losses in a single-component Fermi gas near a $p$-wave Feshbach resonance in the interacting, non-unitary regime. We extend the cascade model introduced by Waseem \textit{et al.} [M. Waseem, J. Yoshida, T. Saito, and T. Mukaiyama, Phys. Rev. A \textbf{99}, 052704 (2019)] to describe the elastic and inelastic collision processes. We find that the loss behavior exhibits a $n^3$ and an anomalous $n^2$ density dependence for a ratio of elastic-to-inelastic collision rate larger and smaller than 1, respectively. The corresponding evolutions of the energy distribution show collisional cooling or evolution toward low-energetic non-thermalized steady states, respectively. These findings are particularly relevant for understanding atom loss and energetic evolution of ultracold gases of fermionic lithium atoms in their ground state.

Electronic properties and geometric structure of Li-Si/Gr system under strain

Graphene-silicon composite (Si/Gr), an excellent anode material for a lithium battery, undergoes internal stress during charging and discharging. In this paper, The effect of strain on Si/Gr system and Li-Si/Gr system are systematically investigated based on the first-principles method. It is found that both tensile strain and compressive strain can affect the electronic properties and geometric structure. Moreover, the effect of compressive strain is more obvious, and it is easy to cause structural distortion. Strain can open the band gap. The band gap widens with the increase of strain. When tensile strain reaches 6% and 8%, the Si/Gr system exists a band gap of 0.164 eV and 0.374 eV, respectively. The effect of strain on energy levels in the range of −2 eV to 2 eV is weakened due to the lithium atom being adsorbed in Si/Gr system. This study provides a theoretical basis for the subsequent research.

Hybrid Machine Learning-Enabled Potential Energy Model for Atomistic Simulation of Lithium Intercalation into Graphite from Plating to Overlithiation.

Graphite is one of the most widely used negative electrode materials for lithium ion batteries (LIBs). However, because of the rapid growth of demands pursuing higher energy density and charging rates, comprehensive insights into the lithium intercalation and plating processes are critical for further boosting the potential of graphite electrodes. Herein, by utilizing the dihedral-angle-corrected registry-dependent potential (DRIP) (Wen et al., Phys. Rev. B 2018, 98, 235404), the Ziegler-Biersack-Littmark (ZBL) potential (Ziegler and Biersack, Astrophysics, Chemistry, and Condensed Matter; 1985, pp 93-129), and the machine learning-based spectral neighbor analysis (SNAP) potential (Thompson et al., J. Comput, Phys. 2015, 285, 316-330), we have successfully trained a hybrid machine learning-enabled potential energy model capable of simulating a wide spectrum of lithium intercalation scenario from plating to overlithiation. Our extensive atomistic simulations reveal the trapping of intercalated lithium atoms close to the graphite edges due to high hopping barriers, resulting in lithium plating. Furthermore, we report a stable dense graphite intercalation compound (GIC) LiC4 with a theoretical capacity of 558 mAh/g, wherein lithium atoms occupy alternating upper/lower graphene hollow sites with a nearest Li-Li distance of 2.8 Å. Surprisingly, following the same lithium insertion manner would allow the nearest Li-Li distance to be retained until the capacity reaches 845.2 mAh/g, corresponding to a GIC of LiC2.6. Hence, the present study demonstrates that the hybrid machine learning approach could further extend the scope of machine learning energy models, allowing us to investigate the lithium intercalation into graphite over a wide range of intercalation capacity to unveil the underlying mechanisms of lithium plating, diffusion, and discovery of new dense GICs for advanced LIBs with high charging rates and high energy densities.