Density Lithium Metal Batteries Research Articles

Mg Doped Li-LiB Alloy with In Situ Formed Lithiophilic LiB Skeleton for Lithium Metal Batteries.

High energy density lithium metal batteries (LMBs) are promising next‐generation energy storage devices. However, the uncontrollable dendrite growth and huge volume change limit their practical applications. Here, a new Mg doped Li–LiB alloy with in situ formed lithiophilic 3D LiB skeleton (hereinafter called Li–B–Mg composite) is presented to suppress Li dendrite and mitigate volume change. The LiB skeleton exhibits superior lithiophilic and conductive characteristics, which contributes to the reduction of the local current density and homogenization of incoming Li+ flux. With the introduction of Mg, the composite achieves an ultralong lithium deposition/dissolution lifespan (500 h, at 0.5 mA cm−2) without short circuit in the symmetrical battery. In addition, the electrochemical performance is superior in full batteries assembled with LiCoO2 cathode and the manufactured composite. The currently proposed 3D Li–B–Mg composite anode may significantly propel the advancement of LMB technology from laboratory research to industrial commercialization.

Self‐Healable Solid Polymeric Electrolytes for Stable and Flexible Lithium Metal Batteries

AbstractThe key issue holding back the application of solid polymeric electrolytes in high‐energy density lithium metal batteries is the contradictory requirements of high ion conductivity and mechanical stability. In this work, self‐healable solid polymeric electrolytes (SHSPEs) with rigid‐flexible backbones and high ion conductivity are synthesized by a facile condensation polymerization approach. The all‐solid Li metal full batteries based on the SHSPEs possess freely bending flexibility and stable cycling performance as a result of the more disciplined metal Li plating/stripping, which have great implications as long‐lifespan energy sources compatible with other wearable devices.

Self-Healable Solid Polymeric Electrolytes for Stable and Flexible Lithium Metal Batteries.

The key issue holding back the application of solid polymeric electrolytes in high-energy density lithium metal batteries is the contradictory requirements of high ion conductivity and mechanical stability. In this work, self-healable solid polymeric electrolytes (SHSPEs) with rigid-flexible backbones and high ion conductivity are synthesized by a facile condensation polymerization approach. The all-solid Li metal full batteries based on the SHSPEs possess freely bending flexibility and stable cycling performance as a result of the more disciplined metal Li plating/stripping, which have great implications as long-lifespan energy sources compatible with other wearable devices.

Single‐Ion Conducting Poly(Ethylene Oxide Carbonate) as Solid Polymer Electrolyte for Lithium Batteries

AbstractSingle‐ion conducting polymer electrolytes (SIPE) have attracted a lot of interest for application in high energy density lithium metal batteries. SIPEs possess lithium transport numbers close to unity, which does not provoke concentration gradients and holds the promise of limiting lithium dendrite formation. In this article, we have optimized a single‐ion polymer incorporating the most successful chemical units in polymer electrolytes, such as ethylene oxide, carbonate, and a lithium sulfonimide. This single‐ion poly(ethylene oxide carbonate) copolymer was synthesized by polycondensation between polyethylene glycol, dimethyl carbonate, and a functional diol including the pendant sulfonamide anionic group and the lithium counter‐cation. By playing with the monomer stoichiometry, the crystallinity and ionic conductivity were optimized. The best copolymer showed high ionic conductivity values of 1.2×10−4 S cm−1 at 70 °C. Lithium interactions and mobility were studied by lithium‐pulsed field gradient, lithium diffusion, NMR relaxation time measurements, and FTIR‐ATR analysis. High lithium mobility is observed, which is due to the weakly coordinating chemical environment in the polymer and also that the sulfonamide in the SIPE adopts to a greater extent the cis conformation, which is known to promote lithium mobility. Finally, the performance of the singe‐ion conducting poly(ethylene oxide carbonate) was compared in lithium symmetric cells versus an analogous conventional salt in polymer electrolyte, showing improved performance in lithium plating and stripping.

Taming Interfacial Instability in Lithium–Oxygen Batteries: A Polymeric Ionic Liquid Electrolyte Solution

AbstractThere is a growing concern about the cyclability and safety, in particular, of the high‐energy density lithium–metal batteries. This concern is even greater for Li–O2 batteries because O2 that is transported from the cathode to the anode compartment, can exacerbate side reactions and dendrite growth of the lithium metal anode. The key to solving this dilemma lays in tailoring the solid electrolyte interphase (SEI) formed on the lithium metal anode in Li–O2 batteries. Here it is reported that a new electrolyte, formed from LiFSI as the salt and a mixture of tetraethylene glycol dimethyl ether and polymeric ionic liquid of P[C5O2NMA,11]FSI as the solvent, can produce a stable electrode (both cathode and anode)|electrolyte interface in Li–O2 batteries. Specifically, this new electrolyte, when in contact with lithium metal anodes, has the ability to produce a uniform SEI with high ionic conductivity for Li+ transport and desired mechanical property for suppression of dendritic lithium growth. Moreover, the electrolyte possesses a high oxidation tolerance that is very beneficial to the oxygen electrochemistry on the cathode of Li–O2 batteries. As a result, enhanced reversibility and cycle life are realized for the resultant Li–O2 batteries.

Cementation Reaction of Lithium Powder Electrodes for Improving the Electrochemical Performances of Lithium-Metal Batteries

Lithium metal is of particular interest for higher energy density Lithium Metal Batteries (LMBs) for example all-solid-state batteries, lithium/sulfur or lithium/oxygen batteries.1 Furthermore, there are several challenges to overcome, such as lithium dendrite growth, volume changes of the electrodes or low Coulombic efficiency, before reaching commercialization. With respect to these points, the initial morphology of the lithium metal could play an important role in suppressing the formation of lithium dendrites. However, the use of lithium powder is mainly limited to the prelithiation of high capacity electrodes.2 Using a common slurry casting method with polyisobutylene (PIB) as a binder3 allows the preparation of electrodes that preserve the spherical shape of lithium-powder particles. However, these lithium-powder electrodes suffer from poor active material utilization which is caused by the electronic isolation of such particles during lithium electrodissolution. In literature, studies could show an increase in mechanical surface stability after implementation of Li-rich composite alloy films on lithium electrodes.4 This approach (cementation reaction with ZnI2) was adapted to be suitable for lithium powder modification with the goal of the improvement of active lithium loss. The resulted growth of a Li-Zn alloy phase within the bulk lithium-powder electrodes and on their surface was found to improve the electronic contact between the lithium-powder particles. With this method, an increase in active material utilization could be achieved, resulting in enhanced cycling performances of LMBs with lithium powder anodes. Betz, J.; Bieker, G.; Meister, P.; Placke, T.; Winter, M.; Schmuch, R. Advanced Energy Materials 2018, 1803170.Holtstiege, F.; Schmuch, R.; Winter, M.; Brunklaus, G.; Placke, T. Power Sources 2018, 378, 522.Heine, J.; Rodehorst, U.; Qi, X.; Badillo, J. P.; Hartnig, C.; Wietelmann, U.; Winter, M.; Bieker, P. Electrochimica Acta 2014, 138, 288.Liang, X.; Pang, Q.; Kochetkov, I. R.; Sempere, M. S.; Huang, H.; Sun, X.; Nazar, L. F. Nature Energy 2017, 2, 17119.

Heterogeneous Nucleation and Interfacial Modification of Electrodeposited Lithium

There has been a recent resurgence in research on high energy density lithium metal batteries (LMBs). The successful commercialization of rechargeable LMBs requires an improved understanding of the fundamental nucleation and growth processes for electrodeposited lithium metal. These fundamental studies necessitate the use of anode-free or nearly-anode-free cells which are able to deliver the maximum theoretical capacity of lithium. Past reports in the literature tend to use significantly excess lithium, which is not representative of a practical lithium metal cell. In this work, we examine the electrodeposition of thin film (< 30 um) uniform columnar lithium directly on various current collectors. We determine the effect of both the substrate and the electrolyte interface which allow us to control the length scales of the electrodeposited lithium. The substrate overpotential has an inverse relation to the columnar diameters, but it appears that the most dominant effect comes from the composition and distribution of solid-electrolyte-interphase (SEI) components. We find that for thin film electrodeposited lithium, the columnar length scale has a minor effect on the cycling performance, whereas increasing the thickness from 5 to 10 um and fluorinating the interface appear to improve cycling performance. This work presents improved cycling performance and morphological control (via modification of bulk interfaces) of electrodeposited columnar lithium. Figure 1

Efficient Li‐Ion‐Conductive Layer for the Realization of Highly Stable High‐Voltage and High‐Capacity Lithium Metal Batteries

AbstractRecently, a consensus has been reached that using lithium metal as an anode in rechargeable Li‐ion batteries is the best way to obtain the high energy density necessary to power electronic devices. Challenges remain, however, with respect to controlling dendritic Li growth on these electrodes, enhancing compatibility with carbonate‐based electrolytes, and forming a stable solid–electrolyte interface layer. Herein, a groundbreaking solution to these challenges consisting in the preparation of a Li2TiO3 (LT) layer that can be used to cover Li electrodes via a simple and scalable fabrication method, is suggested. Not only does this LT layer impede direct contact between electrode and electrolyte, thus avoiding side reactions, but it assists and expedites Li‐ion flux in batteries, thus suppressing Li dendrite growth. Other effects of the LT layer on electrochemical performance are investigated by scanning electron microscopy, electrochemical impedance spectroscopy, and galvanostatic intermittent titration technique analyses. Notably, LT layer‐incorporating Li cells comprising high‐capacity/voltage cathodes with reasonably high mass loading (LiNi0.8Co0.1Mn0.1O2, LiNi0.5Mn1.5O4, and LiMn2O4) show highly stable cycling performance in a carbonate‐based electrolyte. Therefore, it is believed that the approach based on the LT layer can boost the realization of high energy density lithium metal batteries and next‐generation batteries.

Facet selectivity of Cu current collector for Li electrodeposition

Fabricating a uniform thin-film Li metal anode on a heterogeneous Cu substrate is a critical step toward high energy density lithium metal batteries. Here, we explore a facet selective lithium (Li) nucleation and growth phenomenon on copper (Cu) substrate and demonstrate that controlling the facet structure can improve the uniformity in electro-deposition of Li and the electrochemical performances of the resulting thin Li electrode. Preferential Li deposition on the Cu(100) plane is demonstrated by electrochemical analysis of the Cu single crystal surfaces and by electron-backscatter diffraction analysis of the Li-deposited Cu surfaces. DFT calculations show that a difference in the Li adsorption energy among the Cu facets during the initial Li deposition process is responsible for the facet selectivity. A majorly (100) plane-orientated Cu foil fabricated by a simple annealing method exhibits more uniform Li nucleation and leads to a 10-fold higher nuclei density and a two-fold enhancement in the Li cycling stability compared with a conventional Cu foil with randomly oriented surface facets. The control of the surface facet provides a new design principle for the thin-film Li metal anode used in lithium metal batteries.

Chemical Energy Release Driven Lithiophilic Layer on 1 m2 Commercial Brass Mesh toward Highly Stable Lithium Metal Batteries.

It is imperative to explore practical methods and materials to drive the development of high energy density lithium metal batteries. The constuciton of nanostructure electrodes and surface engineering on the current collectors are the two most effective strategies to regulate the homogeneous Li plating/stripping to relieve the Li dendrites and infinite volume change problems. Based on thelow stacking fault energy of the Cu-Zn alloy, we present a novel chemical energy release induced surface atom diffusion strategy, which is achieved by the negative Gibbs free energy from the surface oxidation reaction and subsequent replacement reaction under thermal treatment in air, to realize a uniform upper ZnO nanoparticles coating. Furthermore, we apply the modified brass mesh as a lithiophilic current collector to decrease the Li deposition nucleation overpotential and effectively restrain the Li dendrite growth. The modified brass current collector achieves a long-term cycling stability of 500 cycles at 2.0 mA cm-2. We have verified the effectiveness of our chemical energy release modification strategy on a 1 m2 brass mesh and other Cu alloy (Tin bronze mesh), which demonstrates its great opportunities for scalable and safe lithium metal batteries.

Poly(ethylene oxide)‐based block copolymer electrolytes for lithium metal batteries

AbstractNanostructured block copolymer electrolytes (BCEs) based on poly(ethylene oxide) (PEO) are considered as promising candidates for solid‐state electrolytes in high energy density lithium metal batteries (LMBs). Because of their self‐assembly properties, they confer on electrolytes both high mechanical strength and sufficient ionic conductivity, which linear PEO cannot provide. Two types of PEO‐based BCEs are commonly known. There are the traditional ones, also called dual‐ion conducting BCEs, which are a mixture of block copolymer chains and lithium salts. In these systems, the cations and anions participate in the conduction, inducing a concentration polarization in the electrolyte, thus leading to poor performances of LMBs. The second family of BCEs are single‐lithium‐ion conducting BCEs (SIC‐BCEs), which consist of anions being covalently grafted to the polymer backbone, therefore involving conduction by lithium ions only. SIC‐BCEs have marked advantages over dual‐ion conducting BCEs due to a high lithium ion transference number, absence of anion concentration gradients as well as low rate of lithium dendrite growth. This review focuses on the recent developments in BCEs for applications in LMBs with particular emphasis on the physicochemical and electrochemical properties of these materials. © 2018 Society of Chemical Industry

Hybrid electrolytes for lithium metal batteries

This perspective article discusses the most recent developments in the field of hybrid electrolytes, here referred to electrolytes composed of two, well-defined ion-conducting phases, for high energy density lithium metal batteries. The two phases can be both solid, as e.g., two inorganic conductors or one inorganic and one polymer conductor, or, differently, one liquid and one inorganic conductor. In this latter case, they are referred as quasi-solid hybrid electrolytes. Techniques for the appropriate characterization of hybrid electrolytes are discussed emphasizing the importance of ionic conduction and interfacial properties. On this view, multilayer systems are also discussed in more detail. Investigations on Lewis acid-base interactions, activation energies for lithium-ion transfer between the phases, and the formation of an interphase between the components are reviewed and analyzed. The application of different hybrid electrolytes in lithium metal cells with various cathode compositions is also discussed. Fabrication methods for the feasibility of large-scale applications are briefly analyzed and different cell designs and configurations, which are most suitable for the integration of hybrid electrolytes, are determined. Finally, the specific energy of cells containing different hybrid electrolytes is estimated to predict possible enhancement in energy with respect to the current lithium-ion battery technology.