A computational approach to characterize formation of a passivation layer in lithium metal anodes

Li metal anode is the “Holy Grail” material of advanced Lithium-ion-batteries (LIBs). However, it is plagued by uncontrollable dendrite growth resulting in poor cycling efficiency and short-circuiting of batteries. This has spurred a plethora of research to understand the underlying mechanism of dendrite formation. While experimental studies suggest that there are complex physical and chemical interactions between heterogeneous solid-electrolyte interphase (SEI) and dendrite growth, most of the studies do not reveal the mechanisms triggering these interactions. To deal with this knowledge gap, we propose a multiscale modeling framework which couples kinetic Monte Carlo and Molecular Dynamics simulations. Specifically, the model has been developed to account for (a) heterogeneous SEI, (b) dendrite-SEI interactions, and (c) effect of electrolyte on Li electrodeposition and potential dendrite formation. This allows the proposed computational model to be extended to various electrolytes and SEI species and generate results consistent with previous experimental studies.     

In Situ Artificial Hybrid SEI Layer Enabled High-Performance Prelithiated SiOx Anode for Lithium-Ion Batteries

Considered the promising anode material for next-generation high-energy lithium-ion batteries, SiO_x has been slow to commercialize due to its low initial Coulombic efficiency (ICE) and unstable solid electrolyte interface (SEI) layer, which leads to reduced full-cell energy density, short cycling lives, and poor rate performance. Herein, a novel strategy is proposed to in situ construct an artificial hybrid SEI layer consisting of LiF and Li₃Sb on a prelithiated SiO_x anode via spontaneous chemical reaction with SbF₃. In addition to the increasing ICE (94.5%), the preformed artificial SEI layer with long-term cycle stability and enhanced Li⁺ transport capability enables a remarkable improvement in capacity retention and rate capability for modified SiO_x. Furthermore, the full cell using Li(Ni_0.8Co_0.1Mn_0.1)O₂ and a pre-treated anode exhibits high ICE (86.0%) and capacity retention (86.6%) after 100 cycles at 0.5 C. This study provides a fresh insight into how to obtain stable interface on a prelithiated SiO_x anode for high energy and long lifespan lithium-ion batteries.     

ZrO2-8mol%Dy2O3固体电解质燃料电池性能

将强碱介质中用水热法合成的立方相ZrO2-8mol％Dy2O3纳米晶在较低的温度（1400℃）下烧结,制得了导电性固体电解质陶瓷样品。以该陶瓷作为固体电解质,Pt作电极材料组成氢．空气燃料电池,测定了不同pH介质中水热反应产物纳米晶的陶瓷样品在800～1000℃下的燃料电池性能。结果表明,该系列陶瓷样品的燃料电池均具有稳定的放电性能,燃料电池的短路电流密度随着水热反应介质pH值的减小而增大。在该系列陶瓷中,水热反应介质pH=9．95的陶瓷样品的燃料电池性能最高,在1000℃下,其短路电流密度为320mA／cm^2。     

A closed-host bi-layer dense/porous solid electrolyte interphase for enhanced lithium-metal anode stability

Thanks to its high specific capacity and low electrochemical potential, lithium metal is an ideal anode for next-generation high-energy batteries. However, the unstable heterogeneous surface of lithium gives rise to safety and efficiency concerns that prevent it from being utilized in practical applications. In this work, the formation of a closed-host bi-layer solid electrolyte interphase (SEI) improves the stability of lithium metal anode. This is successfully realized by forming an interconnected porous LiF-rich artificial SEI in contact with Li metal, and a dense, stable in-situ formed upper layer SEI. The porous layer increases the number of Li/LiF interfaces, which reduces local volume fluctuations and improves Li⁺ diffusion along these interfaces. Additionally, the tortuous porous structure guides uniform Li⁺ flux distribution and mechanically suppresses dendrite propagation. The dense upper layer of the SEI accomplishes a closed-host design, preventing continuous consumption of active materials. The duality of a dense top layer with porous bottom layer led to extended cycle life and improved rate performance, evidenced with symmetric cell testing, as well as full cell testing paired with sulfur and LiFePO₄ (LFP) cathodes. This work is a good example of a rational design of the SEI, based on comprehensive consideration of various critical factors to improve Li-metal anode stability, and highlights a new pathway to improve cycling and rate performances of Li metal batteries.     

An “Ether-In-Water” Electrolyte Boosts Stable Interfacial Chemistry for Aqueous Lithium-Ion Batteries

Aqueous batteries are promising devices for electrochemical energy storage because of their high ionic conductivity, safety, low cost, and environmental friendliness. However, their voltage output and energy density are limited by the failure to form a solid-electrolyte interphase (SEI) that can expand the inherently narrow electrochemical window of water (1.23 V) imposed by hydrogen and oxygen evolution. Here, a novel (Li₄(TEGDME)(H₂O)₇) is proposed as a solvation electrolyte with stable interfacial chemistry. By introducing tetraethylene glycol dimethyl ether (TEGDME) into a concentrated aqueous electrolyte, a new carbonaceous component for both cathode−electrolyte interface and SEI formation is generated. In situ characterizations and ab initio molecular dynamics (AIMD) calculations reveal a bilayer hybrid interface composed of inorganic LiF and organic carbonaceous species reduced from Li⁺₂(TFSI⁻) and Li⁺₄(TEGDME). Consequently, the interfacial films kinetically broaden the electrochemical stability window to 4.2 V, thus realizing a 2.5 V LiMn₂O₄−Li₄Ti₅O₁₂ full battery with an excellent energy density of 120 W h kg⁻¹ for 500 cycles. The results provide an in-depth, mechanistic understanding of a potential design of more effective interphases for next-generation aqueous lithium-ion batteries.     

A review on the development of electrolytes for lithium-based batteries for low temperature applications

The aerospace industry relies heavily on lithium-ion batteries in instrumentation such as satellites and land rovers. This equipment is exposed to extremely low temperatures in space or on the Martian surface. The extremely low temperatures affect the discharge characteristics of the battery and decrease its available working capacity. Various solvents, cosolvents, additives, and salts have been researched to fine tune the conductivity, solvation, and solid-electrolyte interface forming properties of the electrolytes. Several different resistive phenomena have been investigated to precisely determine the most limiting steps during charge and discharge at low temperatures. Longer mission lifespans as well as self-reliance on the chemistry are now highly desirable to allow low temperature performance rather than rely on external heating components. As Martian rovers are equipped with greater instrumentation and demands for greater energy storage rise, new materials also need to be adopted involving next generation lithium-ion chemistry to increase available capacity. With these objectives in mind, tailoring of the electrolyte with higher-capacity materials such as lithium metal and silicon anodes at low temperatures is of high priority. This review paper highlights the progression of electrolyte research for low temperature performance of lithium-ion batteries over the previous several decades.     

Controlling Solvation and Solid-Electrolyte Interphase Formation to Enhance Lithium Interfacial Kinetics at Low Temperatures

Operation of lithium-based batteries at low temperatures (<0 °C) is challenging due to transport limitations as well as sluggish Li⁺ kinetics at the electrode interface. The complicated relationships among desolvation, charge transfer, and transport through the solid electrolyte interphase (SEI) at low temperatures are not well understood, hindering electrolyte development. Here, an ether/hydrofluoroether and fluoroethylene carbonate (FEC)-based ternary solvent electrolyte is developed to improve Li cycling at low temperatures (Coulombic efficiency of 93.3% at -40 °C), and the influence of the local solvation structure on interfacial Li⁺ kinetics and SEI chemistry is further revealed. The hydrofluoroether cosolvent allows for modulation of the solvation structure, thereby enabling facile Li⁺ desolvation while forming an inorganic-rich SEI, which are both beneficial for lowering Li⁺ kinetic barriers at the interface. This cosolvent also increases the oxidative stability of the electrolyte to over 4.0 V versus Li/Li⁺, thereby enabling cycling of NMC-based full cells at −40 °C. This study advances the understanding of the influence of Li⁺ solvation structure, SEI chemistry, and interfacial Li⁺ kinetics on Li electrochemistry at low temperatures, providing new design considerations for creating effective low-temperature electrolyte systems.     

Switching characteristics of copper-doped GexTe1−x solid electrolyte films incorporated by nitrogen for programmable metallization cell memory applications

The switching characteristics of PMC devices (device diameter =0.5 μm) with copper-doped Ge_xTe_1−xN electrolyte films were investigated as a function of the Te composition of the electrolyte films. Nitrogen doped in order to increase the crystallization temperature of GeTe chalcogenide films was incorporated into the Ge lattice alone, and copper in Ge_xTe_1−xN films was incorporated into the Te lattice. The copper concentration in copper-doped Ge_xTe_1−xN layers is directly related to the Te concentration in GeTeN films. PMC devices with copper-doped Ge₇₅Te₂₅N electrolytes were swept at a threshold voltage of 1.0 V and showed stable switching characteristics with a switching time of 1 μs with a set voltage of 2.5 V and a reset voltage of −4.0 V.     

Dynamical SEI Reinforced by Open-Architecture MOF Film with Stereoscopic Lithiophilic Sites for High-Performance Lithium–Metal Batteries

A vulnerable solid–electrolyte interphase (SEI) layer cannot retard Li dendrite growth, electrolyte consumption, and anode volumetric expansion, which seriously hinders the development of high-safety Li-metal batteries (LMBs). Herein, a dynamical SEI reinforced by an open-architecture metal–organic framework (OA-MOF) film characterized by elastic expansion and contraction of the volume of stereoscopic lithiophilic sites, is designed. The self-adjustment distribution of lithiophilic sites on vertically grown Cu₂(BDC)₂ nanosheets enables the homogenization of Li-ion flux, smart control of Li mass transport, and compaction of Li deposition. The trapped N, N-dimethylformamide molecules in the open framework structure are favorable for the better wetting and dissolution effect of Li-ions accessing to Cu₂(BDC)₂. Combining these advantages, the featured OA-MOF/Cu@Li anode enables a high coulombic efficiency and low voltage hysteresis in Li||Cu cells even at an ultrahigh current density of 15 mA cm⁻².     

Ce0.8Gd0.2O1.9-δ氧离子固体电解质的制备

掺杂CeO2基复合氧化物是一种很有应用前景的中温固体电解质材料.以Ce(NO3)3·6H2O、Gd(NO3)3·6H2O为原料,NH4HCO3为沉淀剂,采用雾化共沉淀工艺合成了Ce0.8Gd0.2O1.9-δ粉体.XRD测定表明,Ce0.8Gd0.2O1.9-δ粉体及其烧结体均为立方萤石结构,符合电解质材料的要求.TEM图片显示所得粉体呈近球形,分散性较好且具有较高的烧结活性.将所合成的粉体在1 400℃下烧结制得了较致密的固体氧化物电解质陶瓷样品,此烧结温度比普通粉体的烧结温度(>1 600℃)低了200℃以上.不同温度下所得烧结样品的Arrhenius曲线研究表明,提高致密度对提高电导率具有重要意义.