Lithium Dendrite Formation Research Articles

A New Method for In-Situ Characterization of Solid-State Batteries Based on Optical Coherence Tomography.

With the in-depth study of solid-state batteries (SSBs), various in situ and ex situ characterization technologies have been widely used to study them. The performance and reliability of SSBs are limited by the formation and evolution of lithium dendrites at the interfaces between solid electrodes and solid electrolytes. We propose a new method based on optical coherence tomography (OCT) for in situ characterization of the internal state of solid-state batteries. OCT is a low-loss, high-resolution, non-invasive imaging technique that can provide real-time monitoring of cross-sectional images of internal structures of SSBs. The morphology, growth, and evolution of lithium dendrites at different stages of cycling under various conditions can be visualized and quantified by OCT. Furthermore, we validate and correlate the OCT results with scanning electron microscopy (SEM) and XPS, proving the accuracy and effectiveness of the OCT characterization method. We reveal the interfacial phenomena and challenges in SSBs and demonstrate the feasibility and advantages of OCT as a powerful tool for in situ and operando imaging of battery interfaces. This study provides new insights into the mechanisms and factors that affect SSB performance, safety, and lifetime, and suggests possible solutions for improvement and application in the field of applied energy.

Lightweight 3D Lithiophilic Graphene Aerogel Current Collectors for Lithium Metal Anodes.

Constructing three-dimensional (3D) current collectors is an effective strategy to solve the hindrance of the development of lithium metal anodes (LMAs). However, the excessive mass of the metallic scaffold structure leads to a decrease in energy density. Herein, lithiophilic graphene aerogels comprising reduced graphene oxide aerogels and silver nanowires (rGO-AgNW) are synthesized through chemical reduction and freeze-drying techniques. The rGO aerogels with large specific surface areas effectively mitigate local current density and delay the formation of lithium dendrites, and the lithiophilic silver nanowires can provide sites for the uniform deposition of lithium. The rGO-AgNW/Li symmetric cell presents a stable cycle of about 2000 h at 1 mA cm-2. When coupled with the LiFePO4 cathode, the assembled full cells exhibit outstanding cycle stability and rate performance. Lightweight rGO-AgNW aerogels, as the host for lithium metal, can significantly improve the energy density of lithium metal anodes.

Methylation enables the use of fluorine-free ether electrolytes in high-voltage lithium metal batteries.

Lithium metal batteries represent a promising technology for next-generation energy storage, but they still suffer from poor cycle life due to lithium dendrite formation and cathode cracking. Fluorinated solvents can improve battery longevity by improving LiF content in the solid-electrolyte interphase; however, the high cost and environmental concerns of fluorinated solvents limit battery viability. Here we designed a series of fluorine-free solvents through the methylation of 1,2-dimethoxyethane, which promotes inorganic LiF-rich interphase formation through anion reduction and achieves high oxidation stability. The anion-derived LiF interphases suppress lithium dendrite growth on the lithium anode and minimize cathode cracking under high-voltage operation. The Li+-solvent structure is investigated through in situ techniques and simulations to draw correlations between the interphase compositions and electrochemical performances. The methylation strategy provides an alternative pathway for electrolyte engineering towards high-voltage electrolytes while reducing dependence on expensive fluorinated solvents.

Synthesis of Graphene from Pencils Graphite Via Electrochemical Exfoliation Method as a Cu-Foil Coating on the Anode-Free Lithium-Ion Battery

The Anode-free Li-ion Battery (AFLB) is an alternative to a new Li-ion battery model that offers high energy density at the same battery size as conventional models. Uncontrolled dendrite growth inactive the lithium deposition, resulting in decreased specific capacity, shortened lifecycle, and reduced coulombic efficiency. This work reported the utilization of graphene derived from pencil graphite for coating Cu foil as a current collector in AFLBs, to mitigate the formation of lithium dendrites and enhance battery capacity. The graphene-coated Cu foil exhibits a specific capacity of 143 mAh/g, representing a 20 mAh/g increase compared to batteries lacking a graphene coating. The coulombic efficiency of the battery with graphene coating in the charging and discharging process for three cycles is 84.53% in the 1<sup>st</sup> cycle, 101.44% in the 2<sup>nd</sup> cycle, and 98.58% in the 3<sup>rd</sup> cycle.

Poly(vinylidene fluoride)-based composite membranes with continuous metal–organic framework layer for high-performance separators of lithium-ion batteries

Lithium-ion batteries (LIBs) play a critical role in modern portable electronic devices, electric vehicles, and wearable electronics. However, the formation of lithium dendrites during cycling results in serious capacity loss and safety risks owing to the heterogeneous transport and deposition of Li+. In this work, we present a poly(vinylidene fluoride) (PVDF)-based composite membrane with a continuous metal–organic framework (MOF) layer as high-performance separators in LIBs. The PVDF membranes with uniform pore structures are prepared by using superspreading strategy, facilitating the growth of continuous and controllable MOF layer inside the membranes via a simple interfacial synthesis. The as prepared PVDF-MOF composite membranes display uniform and continuous subnanochannels with connected opened metal sites (OMS), which can generate a homogeneous transport of Li+. Taking advantages of the low impedance (∼2 Ω), high ionic conductivity (0.61 mS cm−1), and high stripping peak current (0.89 mA cm−2), the PVDF-MOF composite separators efficiently prevent the uneven deposition and the generation of lithium dendrites. Moreover, the PVDF-MOF-based LIBs showed a high capacity retention rate of 81.0 % after 250 cycles. This strategy paves a new avenue for MOF-based composite separator in LIBs.

Thermal runaway of Li-ion battery with different aging histories

Safety issues associated with thermal runaway (TR) in batteries have attracted extensive research attention. However, understanding and predicting TR encounter significant challenges due to the complexities of chemical reactions, venting events, thermal stratification, multiphase interactions, and variable boundary conditions. These challenges are further complicated by intrinsic battery degradation, a phenomenon often insufficiently characterized and governed by multiple mechanisms. These primarily include the depletion of electrolyte and active materials, thickening of the solid-electrolyte-interphase (SEI), and formation of lithium plating and dendrites. Such degradation alters the battery's materials and structure, directly causing electrochemical performance penalties and potentially affecting its TR behavior. This study examines the TR behavior of commercial 18,650 cells with lithium nickel manganese cobalt oxide (NMC) cathodes, focusing on degradation associated typical usage scenarios: long-term cycling, low-temperature cycling, dynamic cycling with calendar aging. We employ Electrochemical Impedance Spectroscopy (EIS) to probe internal changes in the electrochemical properties of aged cells compared to fresh counterparts. The EIS results reveal pronounced SEI impedance and substantially increased charge transfer impedance in long-term cycled cells. TR tests were conducted using an Accelerating Rate Calorimeter (EV+ ARC, Thermal Hazard Technology) following the heat-wait-seek (HWS) strategy. Our findings indicate a significant impact of aging mechanisms on second-life battery safety. Specifically, cells subjected to low-temperature cycling demonstrated a considerably lower onset temperature for exothermic reactions, and shorter TR delay time, despite all aged cells showing similar state of health (SOH). Furthermore, the temperature corresponding to the cell voltage drop is consistently much lower for aged cells with dynamic cycling and calendar aging.

Solid Electrolyte Interphase Recombination on Graphene Nanoribbons for Lithium Anode.

The practical application of lithium metal batteries is hindered by the lithium dendrite issue, which is seriously affected by the composition and structure of the solid electrolyte interphase (SEI). Modifying the SEI can regulate lithium dendrite formation and growth. Here, we experimentally realize a Li protective layer of LiTFSI-ether electrolyte induced a natural SEI grafted on graphene nanoribbons (SEI@GNRs) via their in situ reactions. The experimental results and theoretical calculations uncover that the 3D structure of SEI@GNRs can reduce the local current density and Li+ flux. The natural SEI in SEI@GNRs, especially the rich inorganic species of LiF, Li3N, and Li2S, decreases the Li+ nucleation overpotential, makes Li+ ion deposition and nucleation uniform, and isolates electron transport. Their synergetic effect suppresses Li dendrite formation and growth, increasing the electrochemical performance of lithium metal batteries. The design strategy is beneficial for the development of lithium metal batteries.

Polymer/ceramic interfacial layer enables stable cycling of all-solid-state Li-metal batteries with sulfide electrolyte

The interfacial stability, particularly between lithium metal and the solid electrolyte, as a critical challenge in solid-state batteries leads to rapid lithium-dendrite growth and increased internal resistance. In this study, we tackled these issues by developing a stable interface between sulfide electrolytes Li5.5PS4.5Cl1.5 (LPSCl) and the metallic lithium anode, using a polyethylene oxide (PEO) layer integrated with Li-ion conducting oxide electrolyte Li1.3Al0.3Ti1.7(PO4)3 (LATP). The uniform distribution of LATP within the PEO matrix through a simple stirring process enhanced the mechanical strength of the PEO interlayer and minimizes both the interfacial reactions and lithium dendrite formation. A Li/Li symmetric cell incorporating this LATP-integrated layer exhibited a low interfacial resistance, ensuring stable cycling for 2800 h at a current density of 0.2 mA cm−2 at 60 °C.

Engineering a lithium silicate-based artificial solid electrolyte interphase for enhanced rechargeable lithium metal batteries

The main motivation for replacing lithium-ion batteries with lithium metal batteries is to achieve a higher energy density by using the metallic lithium anode. One of the major challenges with rechargeable lithium metal batteries is the formation of lithium dendrites and dead lithium during repeated cycling. Another challenge is the formation of the unstable solid electrolyte interphase (SEI) on the surface of the lithium metal electrode, which can reduce battery efficiency and cycle life. In the present work, two different lithium silicates (Li2Si2O5 and Li2SiO3) are successfully synthesized and implemented as an artificial SEI layer via a simple dry coating method. The lithium silicate coating acts as a protective barrier that prevents direct contact between the lithium metal and the electrolyte, which can cause undesirable side reactions and reduce the efficiency and lifetime of the battery. The lithium silicate artificial SEI layer improves the stability of lithium metal batteries by reducing unwanted surface reactions, optimizing ion transport kinetics, and protecting the lithium metal anode from mechanical deformation and unstable SEI formation during extended cycling. This laminated lithium anode structure can be an effective design for the future development of rechargeable lithium metal batteries.

Lithium-Plating Suppressed and Deep Deterministic Policy Gradient-Based Energy Management Strategy

Lithium plating and the formation of lithium dendrite are the main causes of battery internal short circuit and thermal runaway. This paper proposes a deep reinforcement learning-based energy management framework for power-split hybrid electric vehicles (HEVs) which effectively suppresses lithium plating inside batteries. First, single particle model with electrolyte (SPMe) and lithium-plating model are integrated into deep deterministic policy gradient based energy management strategy (DDPG-EMS) for the first time. Second, hybrid particle swarm optimization grey wolf optimizer (HPSOGWO) algorithm is applied to the parameter identification of the two models for the first time to ensure the optimal trade-off between convergence speed and identification accuracy. Third, the superiority of the control strategy is achieved by balancing among fuel consumption, lithium plating occurrence, and SOC sustainability effect under different initial cell temperatures, and verified by comparison with deep Q-network (DQN). The training and validation results both show that the proposed strategy with lithium plating considered not only slows down battery degradation by redressing the charging current in time before the negative overpotential drops to zero, but also reduces the fuel consumption cost as well as total cost.

RETRACTED: The three-dimensional porous mesh structure of Cu-based metal-organic-framework - Aramid cellulose separator enhances the electrochemical performance of lithium metal anode batteries

Lithium metal, due to its advantages of high theoretical capacity, low density and low electrochemical reaction potential, is used as a negative electrode material for batteries and brings great potential for the next generation of energy storage systems. However, the production of lithium metal dendrites makes the battery life low and poor safety, so lithium dendrites have been the biggest problem of lithium metal batteries. This study shows that the larger specific surface area and more pore structure of Cu-based metal-organic-framework - aramid cellulose (CuMOF-ANFs) composite separator can help to inhibit the formation of lithium dendrites. After 110 cycles at 1 mA/cm2, the discharge capacity retention rate of the Li-Cu battery using the CuMOF-ANFs separator is about 96 %. Li-Li batteries can continue to maintain low hysteresis for 2000 h at the same current density. The results show that CuMOF-ANFs composite membrane can inhibit the generation of lithium dendrites and improve the cycle stability and cycle life of the battery. The three-dimensional (3D) porous mesh structure of CuMOF-ANFs separator provides a new perspective for the practical application of lithium metal battery.

Macroscale Inhomogeneity in Electrochemical Lithium‐Metal Plating Triggered by Electrolyte‐Dependent Gas Phase Evolution

AbstractPromoting homogeneous electrode reactions is crucial for mitigating premature electrode degradation and achieving enhanced cycle stability. This is particularly important for lithium‐metal electrodes that undergo drastic morphological change during electrochemical cycles, as their failure can result in dendritic lithium growth and safety hazards. Extensive prior studies have focused on managing the nano‐/micro‐scale dendritic lithium formations, and proposed the importance of the electrolyte engineering in tailoring the solid‐electrolyte interphase. Herein, this study demonstrates, for the first time, that the macroscale inhomogeneity during lithium plating, comparable to the size of electrode, is also governed by the electrolyte, but, strikingly, this phenomenon stands independent of the propensity of the electrolyte to promote growth of nano‐/micro‐scale lithium dendrites. In situ probe reveals that this electrode‐level inhomogeneity, which occurs irrespective of lithium dendrite formation, is triggered by gas‐generating reactions influenced by the electrolyte composition, and the subsequent gas‐phase (i.e., bubble) evolution causes localized lithium growth. The restricted lithium‐ion mass transport through these bubbles increases the overpotential, which exacerbates the macroscale inhomogeneity, as supported by experimental results and continuum model simulations. The observation of electrolyte‐dependent macroscale lithium inhomogeneity highlights the importance of adopting a multi‐scale perspective when considering control strategies for achieving homogeneity during lithium deposition/stripping processes.

A Study on Long-Term Cycling Performance by External Pressure Change for Pouch-Type Lithium Metal Batteries

<p>Lithium dendrite formation is one of the most significant problems with lithium metal batteries. The lithium dendrite reduces the lithium metal batteries’ cycling life and safety. To apply consistent external pressure to a lithium metal pouch cell, we design a press jig in this study. External pressure creates dense lithium morphology by preventing lithium dendrite formation. After 300 cycles at 1 C, the cells with the external pressure perform far better than the cells without it, with a cycling retention of 97.8%. The formation of stable lithium metal is made possible by external pressure, which also enhances safety and cyclability.</p>

Enhancing Li-S Battery Performance with Limiting Li[N(SO2F)2] Content in a Sulfolane-Based Sparingly Solvating Electrolyte.

By enhancing the stability of the lithium metal anode and mitigating the formation of lithium dendrites through electrolyte design, it becomes feasible to extend the lifespan of lithium-sulfur (Li-S) batteries. One widely accepted approach involves the utilization of Li[N(SO2F)2] (Li[FSA]), which holds promise in stabilizing the lithium anode by facilitating the formation of an inorganic-dominant solid electrolyte interface (SEI) film. However, the use of Li[FSA] encounters limitations due to inevitable side reactions between lithium polysulfides (LiPSs) and [FSA] anions. In this study, our focus lies in precisely controlling the composition of the SEI film and the morphology of the deposited lithium, as these two critical factors profoundly influence lithium reversibility. Specifically, by subjecting an initial charging process to an elevated temperature, we have achieved a significant enhancement in lithium reversibility. This improvement is accomplished through the employment of a LiPS sparingly solvating electrolyte with a restricted Li[FSA] content. Notably, these optimized conditions have resulted in an enhanced cycling performance in practical Li-S pouch cells. Our findings underscore the potential for improving the cycling performance of Li-S batteries, even when confronted with challenging constraints in electrolyte design.

Suppressing the Growth of Dendrites On Ultrathin Lithium Metal Anodes by an Amide Electrolyte Additive

The practical applications of high energy density lithium (Li) metal rechargeable batteries are hindered by the formation of lithium dendrites. Besides, using the thick Li anodes (typically 50 μm to 750 μm) provide more Li inventory than is needed in the cell as well as disappears the advantage of high energy density of Li metal over Li-ion batteries.Therefore, in this study, N-N-diallyl-2,2,2-trifluoroacetamide (NDT) is proposed as an electrolyte additive to inhibit the growth of dendrites on the ultrathin Li anode (20 μm). By virtue of its preferential reduction as well as its participation in the primary Li+ solvation shell, NDT contributes to the formation of a Li3N-contained uniform SEI layer on the Li metal, leading to a low polarization in LillLi cells. Be benefited, the LillLFP cell, utilizing a carbonate-based electrolyte containing 2 wt% NDT, exhibits a prolonged life-span, an enhanced reversibility, along with a retention capacity of 72% after 75 cycles, while the cell using baseline electrolyte shows a retention capacity of 68% after 50 cycles at 0.3 C. Additionally, NDT improves the ionic conductivity, and wettability of the electrolyte to the separator. These significant findings provide valuable insights for designing electrolyte additives to stabilize ultrathin Li metal anodes.

Niobium-Based Oxide for Anode Materials for Lithium-Ion Batteries.

Recently, it has become imperative to develop high energy density as well as high safety lithium-ion batteries (LIBS) to meet the growing energy demand. Among the anode materials used in LIBs, the currently used commercial graphite has low capacity and is a safety hazard due to the formation of lithium dendrites during the reaction. Among the transition metal oxide (TMO) anode materials, TMO based on the intercalation reaction mechanism has a more stable structure and is less prone to volume expansion than TMO based on the conversion reaction mechanism, especially the niobium-based oxide in it has attracted much attention. Niobium-based oxides have a high operating potential to inhibit the formation of lithium dendrites and lithium deposits to ensure safety, and have stable and fast lithium ion transport channels with excellent multiplicative performance. This review summarizes the recent developments of niobium-based oxides as anode materials for lithium-ion batteries, discusses the special structure and electrochemical reaction mechanism of the materials, the synthesis methods and morphology of nanostructures, deficiencies and improvement strategies, and looks into the future developments and challenges of niobium-based oxide anode materials.

Anchoring Carbon Spheres on Titanium Dioxide Modified Commercial Polyethylene (PE) Separator to Suppress Lithium Dendrites for Lithium Metal Batteries.

Lithium dendrites are easily generated for excessively-solved lithium ions (Li+) inside the lithium metal batteries, which will lead serious safety issues.In this experiment, carbon spheres (CS) are successfully anchored on TiO2(CS@TiO2) in the hydrothermal polymerization, which is filtrated on the commercial PE separator (CS@TiO2@PE). Thenegative charge in CS can suppress random diffusion of anions through electrostatic interactions. Density functional theory (DFT) calculations show that CS contributes to the desolvation of Li+, thereby increasing the migration rate of Li+. Furthermore, TiO2exhibits high affinity to liquid electrolytes and acts as a physical barrier to lithium dendrite formation. CS@TiO2 is a combination of the advantages of CS and TiO2. As results, the Li+transference number of the CS@TiO2@PE separator can be promoted to 0.63. The Li||Li cell with the CS@TiO2@PE separator exhibits a stable cycle performance for more than 600h and lower polarization voltage (17mV) at 1mA cm-2. The coulombic efficiency (CE) of the Li||Cu cells employe the CS@TiO2@PE separator is 81.63% over 130 cycles. The discharge capacity of LiFePO4||Li cells based on the CS@TiO2@PE separator is 1.73 mAh (capacity retention = 91.53% after 260 cycles). Thus, the CS@TiO2 layer inhibits lithium dendrite formation.

Remarkably improved ionic conductivity and lithium metal compatibility of LLZTO-Li4(BH4)3I composite solid-state electrolyte

With superior ionic conductivity and (electro)chemical stability, garnet-type oxide Li6.4La3Zr1.4Ta0.6O12 (LLZTO) has been extensively studied and explored as advanced solid-state electrolyte (SSEs) for lithium ion batteries (LIBs). However, high-temperature sintering treatment at ∼1200 °C to fabricate dense sheets is necessary to attain high ionic conductivity, whereas at the expense of degraded mechanical properties and poor contact with electrodes. Herein, we demonstrate a novel LLZTO-Li4(BH4)3I composite solid electrolyte prepared by mechanical milling, which features a bilayer coating structure where LiBO2 in the inner layer and Li4(BH4)3I in the outer layer. The electrolyte pellets fabricated by a simple cold pressing treatment deliver an ionic conductivity of 3.69 × 10−5 S cm−1 at 30 °C and a Li+ transference number of 0.9999, which successfully prevents the formation of lithium dendrites. Using this electrolyte, Li|Li symmetric batteries can work continuously for more than 2200 h at 35 and 60 °C. Such performance improvement is ascribed to the sharp reduction in porosity, the enhanced mechanical properties and the improved interface contact after cold pressing the Li4(BH4)3I-modified LLZTO composite to form an electrolyte pellet.

3D Pathways Enabling Highly-Efficient Lithium Reservoir for Fast-Charging Batteries.

Enhancing the mobility of lithium-ions (Li+) through surface engineering is one of major challenges facing fast-charging lithium-ion batteries (LIBs). In case of demanding charging conditions, the use of a conventional artificial graphite (AG) anode leads to an increase in operating temperature and the formation of lithium dendrites on the anode surface. In this study, a biphasic zeolitic imidazolate framework (ZIF)-AG anode, designed strategically and coated with a mesoporous material, is verified to improve the pathways of Li+ and electrons under a high charging current density. In particular, the graphite surface is treated with a coating of a ZIF-8-derived carbon nanoparticles, which addresses sufficient surface porosity, enabling this material to serve as an electrolyte reservoir and facilitate Li+ intercalation. Moreover, the augmentation in specific surface area proves advantageous in reducing the overpotential for interfacial charge transfer reactions. In practical terms, employing a full-cell with the biphasic ZIF-AG anode results in a shorter charging time and improved cycling performance, demonstrating no evidence of Li plating during 300 cycles under 3.0C-charging and 1.0C-discharging. The research endeavors to contribute to the progress of anode materials by enhancing their charging capability, aligning with the increasing requirements of the electric vehicle applications.

Binary anion and cation co-doping enhance sulfide solid electrolyte performance for all-solid-state lithium batteries

Sulfide solid electrolytes are regarded as a pivotal component for all-solid-state lithium batteries (ASSLBs) due to their inherent advantages, such as high ionic conductivity and favorable mechanical properties. However, persistent challenges related to electrochemical stability and interfacial compatibility have remained significant hurdles in their practical application. To address these issues, we propose an anion-cation co-doping strategy for the optimization of Li7P3S11 (LPS) through chemical bonding and structural modifications. The co‐doping effects on the structural and electrochemical properties of SiO2-, GeO2-, and SnO2-doped sulfide electrolytes were systematically investigated. Cations are found to preferentially substitute the P5+ of the P2S74- unit within the LPS matrix, thereby expanding the Li+ diffusion pathways and introducing lithium defects to facilitate ion conduction. Concurrently, oxygen ions partially substitute sulfur ions, leading to improved electrochemical stability and enhanced interfacial performance of the sulfide electrolyte. The synergistic effects resulting from the incorporation of oxides yield several advantages, including superior ionic conductivity, enhanced interfacial stability, and effective suppression of lithium dendrite formation. Consequently, the application of oxide-doped sulfide solid electrolytes in ASSLBs yields promising electrochemical performances. The cells with doped-electrolytes exhibit higher initial coulombic efficiency, superior rate capability, and cycling stability when compared to the pristine LPS. Overall, this research highlights the potential of oxide-doped sulfide solid electrolytes in the development of advanced ASSLBs.