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Lithium metal has been considered the "holy grail" anode material for rechargeable batteries despite the fact that its dendritic growth and low Coulombic efficiency (CE) have crippled its practical use for decades. Its high chemical reactivity and low stability make it difficult to explore the intrinsic chemical and physical properties of the electrochemically deposited lithium (EDLi) and its accompanying solid electrolyte interphase (SEI). To prevent the dendritic growth and enhance the electrochemical reversibility, it is crucial to understand the nano- and mesostructures of EDLi. However, Li metal is very sensitive to beam damage and has low contrast for commonly used characterization techniques such as electron microscopy. Inspired by biological imaging techniques, this work demonstrates the power of cryogenic (cryo)-electron microscopy to reveal the detailed structure of EDLi and the SEI composition at the nanoscale while minimizing beam damage during imaging. Surprisingly, the results show that the nucleation-dominated EDLi (5 min at 0.5 mA cm -2 ) is amorphous, while there is some crystalline LiF present in the SEI. The EDLi grown from various electrolytes with different additives exhibits distinctive surface properties. Consequently, these results highlight the importance of the SEI and its relationship with the CE. Our findings not only illustrate the capabilities of cryogenic microscopy for beam (thermal)-sensitive materials but also yield crucial structural information on the EDLi evolution with and without electrolyte additives.

This review focuses on the promising technology of solid-state batteries (SSBs) that utilize lithium metal and solid electrolytes. SSBs offer significant advantages in terms of high energy density and enhanced safety. This review categorizes solid electrolytes into four classes: polymer, oxide, hybrid, and sulfide solid electrolytes. Each class has its own unique characteristics and benefits. By exploring these different classes, this review aims to shed light on the diversity of materials and their contributions to the advancement of SSB technology. In order to gain insights into the latest technological developments and identify potential avenues for accelerating the progress of SSBs, this review examines the intellectual property landscape related to solid electrolytes. Thus, this review focuses on the recent SSB technology patent filed by the main companies in this area, chosen based on their contribution and influence in the field of batteries. The analysis of the patent application was performed through the Espacenet database. The number of patents related to SSBs from Toyota, Samsung, and LG is very important; they represent more than 3400 patents, the equivalent of 2/3 of the world's patent production in the field of SSBs. In addition to focusing on these three famous companies, we also focused on 15 other companies by analyzing a hundred patents. The objective of this review is to provide a comprehensive overview of the strategies employed by various companies in the field of solid-state battery technologies, bridging the gap between applied and academic research. Some of the technologies presented in this review have already been commercialized and, certainly, an acceleration in SSB industrialization will be seen in the years to come. [ABSTRACT FROM AUTHOR]

Thin intermetallic Li2Te–LiTe3 bilayer (0.75 µm) derived from 2D tellurene stabilizes the solid electrolyte interphase (SEI) of lithium metal and argyrodite (LPSCl, Li6PS5Cl) solid‐state electrolyte (SSE). Tellurene is loaded onto a standard battery separator and reacted with lithium through single‐pass mechanical rolling, or transferred directly to SSE surface by pressing. State‐of‐the‐art electrochemical performance is achieved, e.g., symmetric cell stable for 300 cycles (1800 h) at 1 mA cm−2 and 3 mAh cm−2 (25% DOD, 60 µm foil). Cryo‐stage focused ion beam (Cryo‐FIB) sectioning and Raman mapping demonstrate that the Li2Te–LiTe3 bilayer impedes SSE decomposition. The unmodified Li–LPSCl interphase is electrochemically unstable with a geometrically heterogeneous reduction decomposition reaction front that extends deep into the SSE. Decomposition drives voiding in Li metal due to its high flux to the reaction front, as well as voiding in the SSE due to the associated volume changes. Analysis of cycled SSE found no evidence for pristine (unreacted) lithium metal filaments/dendrites, implying failure driven by decomposition phases with sufficient electrical conductivity that span electrolyte thickness. DFT calculations clarify thermodynamic stability, interfacial adhesion, and electronic transport properties of interphases, while mesoscale modeling examines interrelations between reaction front heterogeneity (SEI heterogeneity), current distribution, and localized chemo‐mechanical stresses. [ABSTRACT FROM AUTHOR]

Lithium metal is regarded as the most promising anode material for next generation high energy density lithium batteries due to its high theoretical capacity and lowest potential versus standard hydrogen electrode. However, lithium dendrite growth and huge volume change during cycling hinder its practical application. It is of great importance to design advanced Li metal anodes to solve these problems. Herein, we report a ZnO-coated Zn foam as the host matrix to pre-store lithium through thermal infusing, achieving a Zn@ZnO foam supported Li composite electrode (LZO). Needlelike ZnO nanofibers grown on the Zn foam greatly increase the surface area and enhance the lithiophilicity of the Zn foam. In situ formed synaptic LiZn layer after lithium infusion can disperse local current density and lower Li diffusion barrier effectively, leading to homogeneous Li deposition behavior, thus suppressing dendrite formation. The porous Zn foam skeleton can accommodate volume variation of the electrode during long-term cycling. Benefiting from these merits, the LZO anode exhibits much better cycle stability and rate capability in both symmetrical and full cells with low voltage hysteresis than the bare Li anode. This work opens a new opportunity in designing high performance composite Li anode for lithium-metal batteries. [ABSTRACT FROM AUTHOR]

Lithium metal anodes may allow the energy density limit of rechargeable lithium batteries to be pushed higher. However, simple and efficient processing technologies for thin Li metal are lacking, which has significantly limited its applications. Herein, the feasibility of engineering Li metal by compositing it with ferromagnetic particles (termed magnetic Li, abbr. M‐Li) is reported. Due to its magnetic response, straightforward processing of M‐Li on diverse substrates with customized patterns and desired thickness is realized. Moreover, when a garnet‐type solid‐state electrolyte Li6.5La3Zr1.5Ta0.5O12 (LLZTO) is the substrate, intimate contact between M‐Li and LLZTO is obtained, with a low interfacial resistance of ≈11 Ω cm2. In addition to facilitating movement and wetting on various substrates, magnetic transfer of M‐Li sheets to designated locations is also enabled. The intriguing and brand‐new method for Li metal engineering via magnetic actuation may be adopted by the industrial system for the fabrication of Li metal batteries, extended to other alkali metals and promises further progress. [ABSTRACT FROM AUTHOR]

Silicon (Si) is one of the most promising anode candidates to further push the energy density of lithium ion batteries. However, its practical usage is still hindered by parasitic side reactions including electrolyte decomposition and continuous breakage and (re‐)formation of the solid electrolyte interphase (SEI), leading to consumption of active lithium. Pre‐lithiation is considered a highly appealing technique to compensate for active lithium losses. A critical parameter for a successful pre‐lithiation strategy by means of Li metal is to achieve lithiation of the active material/composite anode at the most uniform lateral and in‐depth distribution possible. Despite extensive exploration of various pre‐lithiation techniques, controlling the lithium amount precisely while keeping a homogeneous lithium distribution remains challenging. Here, the thermal evaporation of Li metal as a novel pre‐lithiation technique for pure Si anodes that allows both, that is, precise control of the degree of pre‐lithiation and a homogeneous Li deposition at the surface is reported. Li nucleation, mechanical cracking, and the ongoing phase changes are thoroughly evaluated. The terms dry‐state and wet‐state pre‐lithiation (without/with electrolyte) are revisited. Finally, a series of electrochemical methods are performed to allow a direct correlation of pre‐SEI formation with the electrochemical performance of pre‐lithiated Si. [ABSTRACT FROM AUTHOR]

Solid‐electrolytes (SEs) can provide a pathway to increase energy‐density in lithium metal batteries. However, lithium metal penetration through garnet based LLZO solid electrolytes has been identified as a critical failure process. This phenomenon is related to chemo‐mechanical processes which are difficult to probe. In particular, characterizing the dynamic mechanical deformations that occur in electrode‐SE structures is very challenging. This study reports in situ curvature measurements that are thus designed to probe chemo‐mechanical phenomena that occur during lithium plating. The novel experimental cell configuration created for this work shows that pressure builds up in the Li metal during plating, up until the point where short circuits occur. The resulting data are analyzed with a detailed finite element model (FEM) to quantitatively evaluate stress evolution. The results show that Li metal plating within a surface flaw can produce stress build‐up prior to short‐circuiting. The combined results from both the experiments and the FEM suggest that it is critical to minimize surface defects and flaws during the manufacturing processes. [ABSTRACT FROM AUTHOR]

The realization of anode-free lithium metal batteries (AFMBs) is limited owing to low Coulombic efficiency derived from the formation of uneven lithium plating at the anode side. Here, we induce the uniform deposition of lithium by an Au predeposited three-dimensional (3D) anodic current collector with an ether-based electrolyte. At the modified anodic current collector, the over-potential generated during the initial deposition of lithium converged to 6 mV, and stable cycling was achieved with an extremely high Coulombic efficiency of 99 % over 100 cycles. Furthermore, when compared to two-dimensional (2D) bare copper foil (LiFePO 4 /2D Cu), AFMBs using LiFePO 4 cathode with Au predeposited 3D anodic current collector (LiFePO 4 /Au-3D Cu) show better rate performance and longer cycle life. This improvement in electrochemical performance is derived from the regulation of lithium deposition and inhibition of electrolyte decomposition due to the local current density through the predeposition of Au and 3D structure. This study provides a new path to realizing AFMBs. ● Lithiophilic Au reduce nucleation overpotential and induce uniform deposition of lithium. ● A regulated lithium plating and growth direction with dense morphology is obtained. ● Large surface area of 3D network suppress volume exchange. ● Low activation energy and high binding energy improve the electrochemical performance. [ABSTRACT FROM AUTHOR]

All-solid-state lithium metal batteries (ASSLMBs) have attracted significant attention due to their superior safety and high energy density. However, little success has been made in adopting Li metal anodes in sulfide electrolyte (SE)-based ASSLMBs. The main challenges are the remarkable interfacial reactions and Li dendrite formation between Li metal and SEs. In this work, a solid-state plastic crystal electrolyte (PCE) is engineered as an interlayer in SE-based ASSLMBs. It is demonstrated that the PCE interlayer can prevent the interfacial reactions and lithium dendrite formation between SEs and Li metal. As a result, ASSLMBs with LiFePO4 exhibit a high initial capacity of 148 mAh g-1 at 0.1 C and 131 mAh g-1 at 0.5 C (1 C = 170 mA g-1), which remains at 122 mAh g-1 after 120 cycles at 0.5 C. All-solid-state Li-S batteries based on the polyacrylonitrile-sulfur composite are also demonstrated, showing an initial capacity of 1682 mAh g-1. The second discharge capacity of 890 mAh g-1 keeps at 775 mAh g-1 after 100 cycles. This work provides a new avenue to address the interfacial challenges between Li metal and SEs, enabling the successful adoption of Li metal in SE-based ASSLMBs with high energy density. [ABSTRACT FROM AUTHOR]

Abstract Lithium (Li) metal is considered to be one of the most promising anode materials for rechargeable batteries in the future. Unfortunately, the unavoidable Li dendrites are the biggest obstacle to realize the commercial application of Li metal. Herein, we employ a lithium-aluminum (Li-Al) alloy and lithium nitride (Li 3 N) composite coating layer to achieve the dendrite-free for the Li metal anode. This alloy/Li 3 N layer is acquired by the reaction of a nanosized nitride material (aluminum nitride; AlN) and Li metal in a tetrahydrofuran (THF) solution. This stable composite layer provides a fast ion migration channel and an electronic insulation passivating layer for the surface of Li metal. As a result, the modified Li anode maintains uniform and stable electrodeposition without the formation of dendrites for 200 h at 5 mA cm−2. More importantly, when, the dendrite-free Li anodes are fabricated by spraying the AlN solution onto the large Li foil and the NCM-alloy/Li 3 N-Li pouch cells show significantly improved cycle performance against the NCM-Li cells. This strategy may offer a great possibility for the commercial application of Li metal anode. [ABSTRACT FROM AUTHOR]

The development of safe lithium‐metal anodes is crucial for the next‐generation rechargeable batteries. To stabilize Li metal anodes, pre‐planting Li nucleation seeds on lithiophilic substrates is an efficient strategy to regulate initial nucleation process of Li metal. Now, activated ultrathin layered double hydroxide (U‐LDHs) are reported as a promising lithiophilic 2D material to realize the uniform deposition of Li metal. The experimental studies and DFT calculations reveal that the active oxygen on U‐LDHs provides abundant atomic‐scale active sites for Li homogeneous nucleation and plating. Moreover, the lithiophilic properties of active oxygen is also related to its coordination environments. This work opens up an opportunity to more accurate regulation and understanding of Li nucleation from atomic‐scale based on 2D ultrathin materials. Li is like oxygen: Active‐oxygen‐enriched layered double hydroxide (LDH) constructed by a facile electrochemical strategy has been proven to be an ideal lithiophilic 2D material, which realizes the uniform deposition of Li metal. This work opens up an opportunity for more accurate regulation and understanding of Li nucleation at the atomic scale based on 2D ultrathin materials. [ABSTRACT FROM AUTHOR]

Lithium (Li) metal anode has attracted extensive research interest, while lithium dendrites and the resulting irreversible effects have restricted its development. In this study, a thin and dense solid electrolyte interface is constructed by introducing 3-(1-pyridinio)-1-propane sulfonate (PPS), a pyridine functional groups additive in DME/DOL based electrolyte to inhibit the lithium dendrite growth. The preferential decomposition of PPS has resulted in a reduction of gas generation. Subsequently, this process leads to forming of an N-rich solid electrolyte interface, which has been found to cause a decrease in polarization potential and change the behavior of lithium deposition from dendrites to a more cellular Li metal surface. As a result, our proposed electrolyte provides multiple functionalities, including remarkable rate capability, cyclic stability, and coulombic efficiency. Significantly, Li | Li symmetrical cells exhibited a stable cycle over 1200 h at a high current density and capacity of 5 mA cm−2/15 mAh cm−2. We are optimistic that our proposed method can be employed in future research to identify electrolytes appropriate for use in lithium metal anodes. A thin and dense solid electrolyte interface was grown by introducing a pyridine functional groups electrolyte additive, exhibiting an excellent cycling performance for lithium metal batteries. [Display omitted] • PPS reduces gas production resulting in thin and dense N-rich SEI film. • The N-rich SEI alters the deposition behavior of lithium. • Li.| Li symmetrical cells display a stable cycle over 1200h at 5 mA/cm2. [ABSTRACT FROM AUTHOR]

Lithium metal has been considered the "holy grail" anode material for rechargeable batteries despite the fact that its dendritic growth and low Coulombic efficiency (CE) have crippled its practical use for decades. Its high chemical reactivity and low stability make it difficult to explore the intrinsic chemical and physical properties of the electrochemically deposited lithium (EDLi) and its accompanying solid electrolyte interphase (SEI). To prevent the dendritic growth and enhance the electrochemical reversibility, it is crucial to understand the nano- and mesostructures of EDLi. However, Li metal is very sensitive to beam damage and has low contrast for commonly used characterization techniques such as electron microscopy. Inspired by biological imaging techniques, this work demonstrates the power of cryogenic (cryo)-electron microscopy to reveal the detailed structure of EDLi and the SEI composition at the nanoscale while minimizing beam damage during imaging. Surprisingly, the results show that the nucleation-dominated EDLi (5 min at 0.5 mA cm-2) is amorphous, while there is some crystalline LiF present in the SEI. The EDLi grown from various electrolytes with different additives exhibits distinctive surface properties. Consequently, these results highlight the importance of the SEI and its relationship with the CE. Our findings not only illustrate the capabilities of cryogenic microscopy for beam (thermal)-sensitive materials but also yield crucial structural information on the EDLi evolution with and without electrolyte additives. [ABSTRACT FROM AUTHOR]

[Display omitted] • The SEI with rich organic and inorganic components exhibits high Li+ conductivity and mechanical strength. • The organic-inorganic interlayer prevents the serious reaction between Li metal and PVDF-HFP which maintains as the compact coating layer. • The organic-inorganic interlayer favor the stable Li+ plating/stripping in long-term. • The PVDF-HFP assisted by organic-inorganic interlayer enable high performance of Li-oxygen battery. PVDF-HFP layer has been used in lithium (Li) metal-based batteries for its high Li-ion conductivity, excellent mechanical strength and water-proof property. Moreover, the layer reacts with Li metal and improves the performance of solid electrolyte interphase (SEI) by introducing the additional component of LiF. Herein, we further allow an organic molecular (11-mercaptoundecanoic acid, MUA) to involve in the reaction between the PVDF-HFP layer and Li metal, which results in an organic–inorganic SEI interlayer consisting of Li 2 S, LiF, lithium alkyl carbonate (RCOOLi), and MUA-Li etc. This interlayer shows the high Li+ transfer number (0.62) and Young's modulus (6.17 GPa), which also serves to increase the adhesion between PVDF-HFP and Li metal. By using the organic–inorganic interlayer enhanced PVDF-HFP coated Li metal, the Li/Li symmetric cells can run for at least 2190 h steadily, and the Li-oxygen batteries can operate for 214 cycles, demonstrating the improved protection and ionic conductivity of Li metal anodes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Track-etched polyimide separator with vertically-aligned nanochannels is designed. • Vertically-aligned nanochannels of the separator allow a fast Li+ migration. • Hydrophilic polyvinylpyrrolidone can regulate Li+ flux uniformly during cycling. The practical application of Li metal is hampered by critical obstacles, such as the indiscriminate dendritic growth of metallic Li and severe dimensional changes during cycling. Effective surface engineering is necessary to stabilize the interfacial reactions of Li metal to resolve these technical issues. Many strategies have been proposed to mitigate this inherent limitation of Li metal. The interfacial stabilization using an electrolyte additive or polymer coating is the most common approach to enable the uniform distribution of Li+ on the surface of Li metal. In parallel, the development of functional separators is also considered a promising alternative strategy for effective suppression of the fatal growth of Li dendrites because it promotes Li+ transfer at the interfaces. The synergistic effect of regulating Li+ flux and promoting Li+ transfer is expected to effectively prohibit the dendritic growth of metallic Li. Herein, we report a track-etched polyimide (TEPI) separator with vertically aligned nanochannels decorated with polyvinylpyrrolidone (PVP) that enables a self-assembled robust protective layer on the surface. From a structural viewpoint, the vertically aligned nanochannels of the TEPI separator allow for fast Li+ migration. Additionally, hydrophilic PVP can regulate Li+ flux uniformly through the nanochannels by forming a stable Li 3 N-dominant solid electrolyte interphase (SEI) layer, thereby enhancing interfacial kinetics and suppressing the Li dendrite growth during cycling. We demonstrate that the TEPI separator decorated with PVP is effective in securing high reversibility and the improved cycle performance of Li-metal batteries (LMBs). [ABSTRACT FROM AUTHOR]

The recent impressive growth of Li-ion batteries (LIBs) production infrastructures is related to the surge of electric automotive industry. However, the current performance of LIBs is limited by the intrinsic capacity of graphite anodes, the use of organic solvents and by the limited wettability of the separator. In this review, we aim at demonstrating the grade of advance that can be expected for the performances of Li-ion batteries in the short term (roughly, 5–10 years) thanks to introduction of smart materials and interfaces. This temporal limit reflects the need of maintaining the current production chain of LIBs and optimizing the relative investments. In particular, we analyze and discuss the most recent scientific findings on: (i) the solvent, focusing our attention on deep eutectic solvents and ionic liquids (ILs) as an alternative to the currently adopted organic solvents; (ii) tuning the wettability of the separator, thanks to the optimization of the material, its porosity and its surface features; (iii) the anodic materials, according to the different proposed mechanism for Li storage and classifying them into different categories (i.e. carbon-based, Si, perovskites). Finally, we must recognize that, among the so-called "post LIBs" batteries, Li metal batteries can also play a key role in the near future: this type of battery is currently under production for primary cells but requires a smart cathode|electrolyte interface to avoid Li dendrite growth during charge/discharge cycles in their future as secondary systems. [ABSTRACT FROM AUTHOR]

Li7La3Zr2O12 (LLZO) garnet‐based materials doped with Al, Nb, or Ta to stabilize the Li+‐conductive cubic phase are a particularly promising class of solid electrolytes for all‐solid‐state lithium metal batteries. Understanding of the intrinsic reactivity between solid electrolytes and relevant electrode materials is crucial to developing high voltage solid‐state batteries with long lifetimes. Using a novel, surface science‐based approach to characterize the intrinsic reactivity of the Li–solid electrolyte interface, it is determined that, surprisingly, some degree of Zr reduction takes place for all three dopant types, with the extent of reduction increasing as Ta < Nb < Al. Significant reduction of Nb also takes place for Nb‐doped LLZO, with electrochemical impedance spectroscopy (EIS) of Li||Nb–LLZO||Li symmetric cells further revealing significant increases in impedance with time and suggesting that the Nb reduction propagates into the bulk. Density functional theory (DFT) calculations reveal that Nb‐doped material shows a strong preference for Nb dopants toward the interface between LLZO and Li, while Ta does not exhibit a similar preference. EIS and DFT results, coupled with the observed reduction of Zr at the interface, are consistent with the formation of an "oxygen‐deficient interphase" (ODI) layer whose structure determines the stability of the LLZO–Li interface. Understanding reactivity at buried interfaces is crucial to developing next‐generation solid‐state batteries. A novel, surface science‐based approach reveals that contact with Li metal yields Zr reduction in Nb‐, Ta‐, and Al‐doped Li7La3Zr2O12, with reduction increasing as Ta < Nb < Al. This Zr reduction indicates the formation of an "oxygen‐deficient interphase," whose composition determines the stability of the Li– Li7La3Zr2O12 interface. [ABSTRACT FROM AUTHOR]