Formation Of Lithium Research Articles

Dead lithium formation in lithium metal batteries: A phase field model

Lithium metal batteries are the most promising choices for next-generation high-energy–density batteries. However, there is little mechanism understanding on lithium dendrite growth during lithium plating and the dead lithium (the main component of inactive lithium) formation during lithium stripping. This work proposed a phase field model to describe the lithium stripping process with dead lithium formation. The coupling of galvanostatic conditions enables the phase field method to accurately match experimental results. The factors influencing the dead lithium formation on the increasing discharge polarization are revealed. Besides, the simulation of the battery polarization curve, the capacity loss peak, and the Coulomb efficiency is realized. This contribution affords an insightful understanding on dead lithium formation with phase field methods, which can contribute general principles on rational design of lithium metal batteries.

Origin of Lithium–Potassium-Rich Brines in the Jianghan Basin, South China: Constraints by Water–Rock Reactions of Mesozoic–Cenozoic Igneous Rocks

A large number of lithium–potassium-rich brines have been found in Paleocene reservoirs in the Jianghan Basin, South China. First, the brines have exceptionally high lithium and potassium contents that are even higher than those in other closed basins on the Tibetan Plateau. Second, the enriched brines are widely distributed in the center of the basin. The Mesozoic and Cenozoic igneous rocks in the Jiangling depression are mainly basalt and granite, and their distribution area exceeds 50% of the basin. The large basalt body provided a thermal source for the water–rock reaction. The igneous rocks in the study area could have provided ore-forming elements, such as lithium and potassium, for the brine. A static immersion experiment at room temperature shows that fluids with certain salinities are more likely to activate K ions in basalt. However, weakly alkaline solutions more easily dissolve K. High-temperature water–rock experiments show that the dissolution rates of Ca, Mg, and Sr decrease with increasing temperature, while the dissolution rates of K and Li first increase and then decrease with increasing temperature. The dissolution of K and Li is easier when saline fluid reacts with volcanic rock. The dissolution rate of K is higher than that of Li in basalt, and the dissolution rate of Li is higher than that of K in granite. Compared with the results at normal temperatures, the ability of the fluid to leach elements at higher temperatures is significantly enhanced. Temperature is the main factor controlling the ability of fluid to leach elements. High-salinity fluid is the main carrier of ore-forming elements. According to the water–rock experiments, the mineral composition of the ancient brine in the Jiangling depression that formed during the Paleocene is consistent with that of the ore-rich brine found today, but different by a few orders of magnitude, indicating that the formation of lithium–potassium-rich brines requires a long time. The water–rock reaction is one of the important processes of brine formation, and surface evaporation and concentration are the main mechanisms of brine mineralization.

Regulating lithium-ion flux in the solid electrolyte interphase layer to prevent lithium dendrite growth on lithium metal anode

High theoretical capacity and lowest electrochemical potential make lithium metal anode the most suitable anode material for lithium-ion batteries (LIBs). However, Lithium dendrite growth on lithium metal anode hinders proper discharge capacity and practical cycle life of LIBs. It dues to high lithium-ion flux in the solid electrolyte interphase (SEI) layer versus low diffusion in anode structure. Herein, we employ argon and oxygen plasma to modify commercial polypropylene separator surface to negatively functionalize the separator surface and discuss the influence of increasing surface negative charge on lithium dendrite growth and formation of SEI layer. Comparing electrochemical and battery performance of unmodified and plasma modified separators demonstrates, increased negative surface charge prevents lithium dendrite growth and makes a uniform and thin SEI layer due to lowering lithium-ion flux in the SEI layer. More precisely, we conduct that coulombic interaction between plasma modified separator's surface and electrolyte's cations (anions) can regulate lithium-ion flux in the SEI layer, preventing lithium dendrite growth and making thin homogeneous SEI layer on lithium metal anode structure.

A Powerful Protocol Based on Anode-Free Cells Combined with Various Analytical Techniques.

Lithium (Li) metal is the ultimate negative electrode due to its high theoretical specific capacity and low negative electrochemical potential. However, the handling of lithium metal imposes safety concerns in transportation and production due to its reactive nature. Recently, anode-free lithium metal batteries (AFLMBs) have drawn much attention because of several of their advantages, including higher energy density, lower cost, and fewer safety concerns during cell production compared to LMBs. Pushing the reversible Coulombic efficiency (CE) of AFLMBs up to 99.98% is key to achieving their 80% capacity retention over more than 1000 cycles. However, interfacial irreversible phenomena such as electrolyte decomposition reactions on both electrodes, dead Li formation, and Li dendrite formation result in poor capacity retention and short circuits in LMBs and AFLMBs. Therefore, it is of great importance and scientific interest to explore those interfacial irreversible phenomena to improve the cell's cycle life. Although significant contributions toward mitigating electrolyte decomposition, dead lithium, and dendritic lithium formation have been reported at the lithium anode, real irreversible phenomena are usually hidden or difficult to discover due to excess lithium employed in LMBs and simultaneous events taking place in both electrodes or at the interfaces.An integrated protocol is suggested to include Li||Cu, cathode||Li, and cathode||Cu configurations to provide overall quantification and determination of various sources of irreversible Coulombic efficiency (irr-CE) in AFLMBs and LMBs. Combining Li||Cu, cathode||Li, and cathode||Cu configurations is essential for separating the root sources of the capacity loss and irr-CE in LMBs and AFLMBs. Remarkably, integrating an anode-free cell with various analytical techniques can serve as a powerful protocol to decouple and quantify those interfacial irreversible phenomena according to our recent reports.In this Account, we focus on the protocol based on an anode-free cell combined with various analytical methods to investigate interfacial irreversible phenomena. Complementary advanced tools such as transmission X-ray microscopy (visualizing Li plating/stripping mechanism), nuclear magnetic resonance spectroscopy (quantifying dead lithium), and gas chromatography-mass spectroscopy (decoupling interfacial reactions) were employed to extract the intrinsic reasons and sources of individual irreversible reactions in LMBs and AFLMBs. Quantitative evaluation of nucleation and growth of Li metal deposition are addressed, along with solid electrolyte interphase (SEI) fracture, visualization of lithium dendrite growth, decoupling of oxidative and reductive electrolyte decomposition mechanisms, and irreversible efficiency (i.e., dead Li and SEI formation) to reveal the intrinsic causes of individual irr-CE in AFLMBs. Meanwhile, an anode-free protocol can also be utilized as a powerful and multifunctional tool to develop electrolyte formulations or artificial layers for LMBs and AFLMBs. Therefore, we also suggest that the anode-free configurations with significant irreversible phenomena can effectively screen and develop new electrolytes. Finally, the concepts of the protocol with an anode-free cell combined with various advanced analytical tools can be extended to provide an in-depth understanding of other metal batteries and solid-state anode-free metal batteries.

Optimization of lithium nucleation by current density toward dendrite-free Li metal anode

The electrodeposition of lithium on heterogeneous substrates is often loose and uneven owing to the lithiophobic nature of most substrates, which causes deterioration of cell performance and ultimately cell failure. In this paper, a simple high current density induced uniform nucleation of Li on Cu substrate is presented to solve this problem. The as-obtained Li seeds with small and uniform size fully cover the surface of Cu, which is conducive to dense and even electrodeposition of Li afterwards. The LiF-rich solid electrolyte interface generated by the high current density on the Li seeds also helps to inhibit the formation of dendritic lithium. The pouch cell employing this strategy demonstrates remarkable improvement in cycling stability.

Effect of Fern-Leaf-like Lithiophilic Silver on the Lithium Metal Anode-Free Battery

The lithium metal anode-free battery is a promising energy storage device to serve electric vehicles (EVs) owing to its high energy density (40-50% greater than the lithium-ion at cell level), ease to fabricate, and low cost in manufacturing (Account for the absence of active and inactive anode material). However, the major issues, including lithium dendrite growth, volume fluctuation, poor cyclability, and low coulombic efficiency prevent the lithium metal anode-free battery from the practical implementation. Here, the coated fern-leaf-like lithiophilic silver on the Cu foil (Cu@AgDs) via an electroless method provided the uniform lithium plating and striping, minimizing the undesired lithium formation. As a result, Cu@AgDs as an anode for lithium-free batteries delivered a decent electrochemical performance with regard to pro-long cycling and coulombic efficiency. These findings shine the light on both fundamental and applied research, which may guide the model and invention of lithium metal anode-free battery at a commercial scale.

Visualizing Heterogeneous Lithium Plating and Stripping during Fast Charging

Lithium plating is an obstacle for the development of fast-charge batteries and enabling of widescale electric vehicle adoption. Synchrotron high-energy X-ray diffraction was used to directly identify and track lithium plating in a full LiNi0.5Mn0.3Co0.2O2 / graphite pouch cell operated with a 6C charge rate for greater than 1200 cycles. The magnitude and spatial distribution of lithium plating, lithium stripping, and the effect of plating on lithium intercalation into graphite were quantified. For discharged cell maps, irreversible and fully lithiated graphite (LiC6) was closely correlated with lithium plating and can be considered a highly reliable indicator of lithium plating in cases where plated lithium is below the detection sensitivity. Isolated regions of slight plating initially stripped to below the detection limit, but over time the coverage and amount of plated lithium increased while the stripping efficiency decreased. Long term monitoring of lithium formation in a fast-charge battery provides important information for a better understanding of lithium plating and stripping mechanisms in practical cells.

Understanding the Effects of Alloy Films on the Electrochemical Behavior of Lithium Metal Anodes with Operando Optical Microscopy

Uncontrolled morphological evolution of lithium metal anodes during cycling can lead to inactive lithium formation and excessive solid electrolyte interphase growth, causing capacity decay. Here, we investigate how interfacial alloy layers affect the growth and evolution of lithium metal during electrodeposition and stripping from stainless steel current collectors by combining electrochemical methods with operando optical microscopy. We find that thin silver films enable improved Coulombic efficiency for lithium cycling in multiple electrolyte systems compared to bare current collectors or other alloy layers. This is at least partially enabled by the observed larger lithium particle size when grown from alloys, as well as the mechanical integrity of the silver films. Operando optical microscopy reveals reduced growth of dendritic Li on silver-coated current collectors at high current densities compared to bare current collectors, as well as different dendrite growth and stripping dynamics. Together, these findings enhance our understanding of how alloy thin films can affect both the electrochemical behavior and morphological evolution of lithium metal electrodes, highlighting the benefits of interfacial engineering to enable the use lithium metal anodes in “anode-free” battery configurations.

Dendrite-Free and Stable Lithium Metal Battery Achieved by a Model of Stepwise Lithium Deposition and Stripping

HighlightsA facile method is adopted to obtain cucumber-like lithiophilic composite skeleton.Massive lithiophilic sites in cucumber-like lithiophilic composite skeleton can promote and guide uniform Li depositions.A unique model of stepwise Li deposition and stripping is determined.The uncontrolled formation of lithium (Li) dendrites and the unnecessary consumption of electrolyte during the Li plating/stripping process have been major obstacles in developing safe and stable Li metal batteries. Herein, we report a cucumber-like lithiophilic composite skeleton (CLCS) fabricated through a facile oxidation-immersion-reduction method. The stepwise Li deposition and stripping, determined using in situ Raman spectra during the galvanostatic Li charging/discharging process, promote the formation of a dendrite-free Li metal anode. Furthermore, numerous pyridinic N, pyrrolic N, and CuxN sites with excellent lithiophilicity work synergistically to distribute Li ions and suppress the formation of Li dendrites. Owing to these advantages, cells based on CLCS exhibit a high Coulombic efficiency of 97.3% for 700 cycles and an improved lifespan of 2000 h for symmetric cells. The full cells assembled with LiFePO4 (LFP), SeS2 cathodes and CLCS@Li anodes demonstrate high capacities of 110.1 mAh g−1 after 600 cycles at 0.2 A g−1 in CLCS@Li|LFP and 491.8 mAh g−1 after 500 cycles at 1 A g−1 in CLCS@Li|SeS2. The unique design of CLCS may accelerate the application of Li metal anodes in commercial Li metal batteries.

First principles study on formation and migration energies of sodium and lithium in graphite

Graphite is used as an anode material in conventional lithium-ion batteries owing to its ability to form stable Li-intercalated graphite intercalation compounds (Li GICs). Its application to sodium-ion batteries has long been of great interest, but the instability of Na GICs hampers its implementation. First-principles calculations were performed to gain physical insight into the intercalation process in alkali-metal (AM) GICs, where $\mathrm{AM}=\mathrm{Li}$, Na. In this study, the structure, stability, and diffusion properties of AM GICs with various in-plane AM concentrations were systematically investigated using a van der Waals density functional simulation, and the differences between Li and Na GICs were discussed. Li GICs were found to be quite stable over a wide range of in-plane Li concentrations, with a change in the favorable stacking sequence of graphite. In terms of diffusion, the migration energy for Li in graphite increases as the graphite stacking transition occurs, suggesting that hindering the stacking transition could realize fast and uniform Li diffusion. In contrast, Na GICs are less stable than Li GICs because of following two reasons: (1) interaction between Na and carbon is less stable than that between Li and carbon, and (2) a larger amount of deformation in the interlayer distance is necessary. The Na GICs tend to be stabilized by increasing the number of Na-carbon interactions. Namely, fasted Na diffusion is expected in the Na-rich phase. Our systematic simulations of the formation energy and migration energy of Na GICs with different structures and in-plane AM concentrations suggested that the expansion of graphite layers prior to Na intercalation could achieve graphite anodes for Na-ion batteries.

A multifunctional Cu6Sn5 interface layer for dendritic-free lithium metal anode

The unstable electrode/electrolyte interface of the lithium metal anode is one of the reasons that induce the formation of lithium (Li) dendrites. The Li dendrites will reduce the coulombic efficiency, and even pierce the separator to cause the safety problems. Herein, a tightly bonded and uniformly distributed Cu6Sn5 interface layer is formed on the surface of the Cu foam by a simple electroless plating method. The composite layer has multiple functions, such as high lithiophilicity, high carrier transport and high adaptability to mechanical strain. Based on the versatility of the Cu6Sn5 interface layer, the cycle life of Cu foam is increased from 150 h to 1000 h, and the deposition overpotential is as low as 18 mV. In-situ online observation proves that the existence of composite layer can make Li metal uniformly deposited to avoid the dendrites. Furthermore, Cu6Sn5@Cu foam also shows a higher capacity retention rate (increased from 65.2% to 78.6% after 300 cycles) and a more stable rate performance when it is used in full batteries. Compared with the single function improvement strategy proposed by the current lithium metal anode research. The Cu6Sn5 multifunctional composite layer modification method in this work provides a new strategy for constructing a stable electrode/electrolyte interface.

Adduct Formation of Lithium and Decaniobate

A lithium-decaniobate adduct was obtained by reacting TBA6[Nb10O28] with LiClO4 and processing the product in aprotic solvents (TBA = tetra-n-butylammonium). The adduct exhibited strong lithium-dec...

Wet-CO2 Pretreatment Process for Reducing Residual Lithium in High-Nickel Layered Oxides for Lithium-Ion Batteries.

As the push for inexpensive vehicle electrification grows, high-energy-density cathodes for lithium-ion batteries, such as high-nickel layered oxides, have received a great deal of attention in both industry and academia. These materials, however, suffer from severe residual lithium formation, which causes slurry gelation during electrode fabrication and gas evolution during cycling. Herein, a novel cobalt hydroxide coating method on wet-CO2 gas-treated LiNi0.91Mn0.03Co0.06O2 (Co-CO2-NMC91) is presented. Notably, the wet-CO2 treatment prior to a dry cobalt hydroxide coating plays a critical role in improving the coating uniformity and ultimately decreases the effective residual lithium content. Furthermore, full cells of Co-CO2-NMC91 exhibit excellent capacity retention of 91% after 200 cycles. This study highlights how a wet-CO2 treatment can be used to improve a typical dry coating and provides new insights toward the development of cathodes for high-energy-density LIBs without severe slurry gelation or gas evolution.

Electrolyte Composition Effects on the Formation of the Solid Electrolyte Interphases of Li-Metal Batteries: A Molecular Dynamics Study

We will present our recent effort to develop new materials for batteries using our nanobattery model able to simulate a much smaller battery containing all the main components of an actual size battery. We are testing Li-metal anodes with sulfur- and metal-oxide-based cathodes together with highly concentrated electrolytes as well as with localized highly concentrated electrolytes. Our approach consists on performing ab initio analysis and ab initio molecular dynamics simulations in order to determine energetics properties as well as reactive force fields to perform larger scale reactive molecular dynamics simulations that eventually will allow us to evaluate prospective battery systems based on cycling stability, formation of benign solid-electrolyte interphases, interfacial stability, ion-transport and its mechanisms, electron-transfer, output voltage, current and charge thresholds, battery capacity, ion-pairing, cluster and death lithium formation, dendrite growth, capacity fading. In the present work, we use molecular dynamics simulations to model a TMP-based electrolyte comprising TMP, lithium, and bis(fluorosulfonyl)imide (LiFSI) salt, exploring the effects of salt concentration on solvation and ion transport. A statistical analysis is performed to study ion pairing, clustering, mobility, and coordination of Li-ion with and without small amounts of diluent materials.

Viscoelastic polyborosiloxanes as artificial solid electrolyte interphase on lithium metal anodes

Lithium metal is considered as outstanding anode material due to its superior specific capacity and high redox potential, despite that non-uniform lithium deposition and dissolution upon charging and discharging yields formation of reactive high surface area lithium (HSAL) and a brittle, inhomogeneous solid electrolyte interphase (SEI). As counterstrategy, artificial SEIs such as protective polymer layers can be designed to control lithium deposition. Herein, viscoelastic polyborosiloxanes (PBS) with varying degree of cross-linking (maximum storage modulus of 0.4 MPa) are synthesized and coated on lithium metal. Operando7Li nuclear magnetic resonance spectroscopy illustrates that highly cross-linked PBS facilitates homogenous deposit morphologies, whereas merely cross-linked PBS does not show relevant effects compared to uncoated electrodes. Interphase analysis (impedance spectroscopy and distribution of relaxation times analysis) reveals increased interphase resistances for coated Li electrodes due to limited solvent uptake and provides a more detailed evaluation of resistive contributions from interphases compared to common equivalent circuit modeling. The beneficial effects of highly cross-linked PBS come at expense of higher resistance associated with a lower degree of swelling, hence emphasizing the complexity of Li deposition.

Electrochemical behavior of residual salts and an effective method to remove impurities in the formation of porous copper electrode for lithium metal batteries

Lithium is one of the most promising candidates for use as an anode in lithium rechargeable batteries owing to its high specific capacity and low redox potential. However, lithium dendritic formation during charging and discharging hinders the use of lithium metal as an anode. Herein, we introduce a porous copper electrode that mitigates dendritic lithium deposition and the formation of dead lithium. The porous Cu electrode is formed by electrodeposition, which is conducted using hydrogen bubbles as a template for the porous structure. However, CuSO4 remains in preparation for the porous copper collector. The residual salts are deposited during the charging process, decreasing the initial coulombic efficiency. To remove the salts, the structure was washed with ethanol and DI water. As a result, the initial coulombic efficiency of the Li/rinsed porous Cu cell was significantly higher than that before washing. The high surface area of porous Cu induces uniform lithium plating. Therefore, the cycle stability of the cell with Li/cleaned porous Cu improved compared with that of the flat Cu foil over 160 cycles. The improvement in stability and coulombic efficiency obtained by the adoption of this porous copper electrode supports the potential for the practical application of porous Cu electrodes in lithium metal batteries.

Chemical surface modification of lithium disilicate needles of a silica-based ceramic after HF-etching and ultrasonic bath cleaning: Impact on the chemical bonding with silane

ObjectiveRecommendations to obtain the best bonding to silica-based ceramics are to prepare its surface by hydrofluoric-acid HF etching and regular application of a silane. This study investigated how the HF-etching following by ultrasonic water bath cleaning (recommended protocol to improve the bonding with a composite resin), modifies the surface chemistry of a lithium disilicate glass-ceramic and impacts the chemical bonding with silane. MethodsLithium disilicate glass-ceramic discs (IPS Emax Press, Ivoclar Vivadent) were mirror polished, etched with 9% HF for 20 s and rinsed 1 min under water. Two post-etching cleaning were compared: (1) no additional cleaning and (2) immersion in water ultrasonic bath for 4 min. Morphology evolution of the surfaces was carried out by scanning electron microscopy. Chemical changes were studied using X-ray Photoelectron Spectroscopy and Nano Auger Electron Spectroscopy analyses. Identification of the compounds formed with fluorine was based on by High Resolution Transmission Tlectronic Microscopy . ResultsResidues left on the surface of the discs after etching, the fluorine salts, were eliminated after the ultrasonic bath cleaning. However, analyses showed presence of fluorine on the lithium disilicate needles associated among others with the lithium. HR-TEM validates the presence of Li2SiF6 crystallized phased. A mechanism to explain silane bonding when Li2SiF6 phase is formed on the Li2Si2O5 needles, is proposed. SignificanceHF-etching leads to the formation of lithium and fluorine contain LiSi2F6 nano-precipitates on the Li2Si2O5 needles which helps to improve the bonding with silane.

Transient morphology of lithium anodes in batteries monitored by in operando pulse electron paramagnetic resonance

Enhancing lithium-ion battery technology in terms of specific capacity and charging time is key for the advancement of the electrification of transportation. Particularly for fast charging, inhomogeneous deposition of metallic lithium, for example on commercial graphite or metallic lithium anodes, leads to cell degradation and safety issues. To understand the underlying mechanisms and develop counter-measures, non-invasive online detection techniques providing satisfactory time resolution are crucial. Here, we demonstrate in operando pulse electron paramagnetic resonance to observe transient processes during pulsed fast charging in cells with metallic lithium anodes. Sampling timescales of 100 ms enable real-time monitoring of the formation and evolution of porous lithium during and after charging pulses. It was observed that the generated morphology continued to evolve after the end of a charging pulse, whereby surface features were fusing with a time constant that was slower than their formation.

Unraveling the Intricacies of Residual Lithium in High-Ni Cathodes for Lithium-Ion Batteries

High-nickel layered oxide cathodes suffer seriously from the formation of residual lithium on the surface, which causes notorious issues, such as slurry gelation and gas evolution. Due to the use o...

Mixed ionic-electronic transport in the high-entropy (Co,Cu,Mg,Ni,Zn)1-xLixO oxides

A series of the high-entropy (Co,Cu,Mg,Ni,Zn)1-xLixO oxides with a lithium substitution level of x = 0, 0.05, 0.10, 0.15, 0.20, 0.25, and 0.30 is evaluated in terms of the crystal structure, morphology and transport properties, with thorough studies aimed at elucidation of the nature of different contributions to the total electrical conductivity. It is found that cubic Fm-3m structure is preserved in the whole investigated series, with (Co,Cu,Mg,Ni,Zn)0.8Li0.2O composition showing a high internal strain, supporting to some degree one of the so-called core effects, anticipated for the high-entropy materials. For samples with Li content x > 0.20 the strain is relaxed by formation of the oxygen vacancies. As unambiguously evidenced by DC polarization experiments and measured impedance spectroscopy data with ionically-blocking Au and reversible Li electrodes used, the previously reported in the literature transition to the lithium superionic conductivity in the Li-rich compounds, up to σi ≈ 1–10⋅10−3 Scm−1, is more complex, with emergence of the electronic conduction as well, reaching similar magnitude for (Co,Cu,Mg,Ni,Zn)0.7Li0.3O. The observed behavior upon increase of lithium concentration (x) can be explained by a qualitative change of the nature of the electronic and ionic defects present in (Co,Cu,Mg,Ni,Zn)1-xLixO series, with initial oxidation of 3d metals (mainly Co), followed by possible formation of the interstitial lithium, and final emergence of the oxygen vacancies. Furthermore, the recorded electrochemical properties of (Co,Cu,Mg,Ni,Zn)0.7Li0.3O lithium cell electrode, suggesting presence of intercalation-like behavior at the initial stages of lithiation, confirm the proposed mixed ionic-electronic conductivity.