An Encapsulation-Based Sodium Storage via Zn-Single-Atom Implanted Carbon Nanotubes.

Lithium metal batteries (LMBs) hold great promise for next-generation energy storage due to the ultrahigh theoretical capacity of lithium metal. However, an unstable solid electrolyte interphase (SEI) remains a critical challenge as these interfaces govern lithium diffusion during plating and stripping and prevent electrolyte degradation during cycling. Understanding the SEI's chemical composition and evolution is crucial for improving LMB performance.This study investigates the impact of different lithium salts on SEI formation in ether-based electrolytes using in-operando Fourier Transform Infrared (FTIR) spectroscopy. Three electrolytes were studied: 1M LiTFSI, 1M LiClO4, and 1M LiDFOB in DME: DOL. In-operando FTIR measurements were conducted on Li ||Li symmetric cells during plating and stripping at a current density of 3 mA/cm2. The results reveal distinct differences in SEI kinetics, composition, formation, and evolution depending on the salt used. In-operando FTIR in tandem with post-mortem X-ray Photoelectron Spectroscopy (XPS) reveals different compounds forming on the lithium surface. LiTFSI-based electrolytes showed an instantaneous interaction with the Li surface forming both organic and inorganic SEI components. In contrast, LiClO4 showed a delayed Li-salt interaction started after minutes into plating. The LiDFOB electrolyte resulted in an organic dominated SEI with limited inorganic compounds leading to an unstable SEI. These differences in SEI chemistry correlate with electrochemical performance, with LiTFSI exhibiting superior performance.This study provides direct spectroscopic evidence of SEI formation and evolution in LMBs, highlighting the critical role of electrolyte salt chemistry in determining interfacial properties and battery performance.

The cycling lifespan of Li-metal batteries is compromised by the unstable solid electrolyte interphase (SEI) and the continuous Li dendrites, restricting their practical implementations. Given these challenges, establishing an artificial SEI holds promise. Herein, a trinitarian gradient interphase is innovatively designed through composite coatings of magnesium fluoride (MgF2), N-hexadecyltrimethylammonium chloride (CTAC), and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) on Li-metal anode (LMA). Specifically, the MgF2/CTAC/PVDF-HFP SEI spontaneously forms a lithium fluoride (LiF)-rich PVDF-HFP-based SEI, along with lithium-magnesium (Li-Mg) alloy substrate as lithiophilic electronic conductor and positively charged CTAC during plating. Noticeably, the Li-Mg alloy homogenizes the distribution of electric field and reduce the internal resistance, while the electronically insulated LiF/PVDF-HFP composite SEI offers fast ion-conducting and mechanical flexibility, accommodating the volumetric expansion and ensuring stable Li-ion flux. Additionally, CTAC at the dendritic tip is pivotal for mitigating dendrites through its electrostatic shield mechanism. Innovatively, this trinitarian synergistic mechanism, which facilitates colossal granular Li deposits, constructs a dendrite-free LMA, leading to stable cycling performances in practical Li||LFP, popular Li||NCM811, and promising Li||S full cells. This work demonstrates the design of multifunctional composite SEI for comprehensive Li protection, thereby inspiring further advancements in artificial SEI engineering for alkali-metal batteries.

Lithium metal battery systems (LMBs) are being sought as an ultimate replacement to LIBs, potentially increasing the cell energy by over fifty percent due to the high capacity and low voltage of the metal anode. Analogous improvement in energy is possible with sodium metal batteries (NMBs) and with potassium metal batteries (KMBs), where existing ion insertion anodes can be replaced by plating/stripping metal. However, in all three cases safety and performance are compromised by an unstable solid electrolyte interphase (SEI) that consumes metal ions and electrolyte, and ultimately leads to dendrites. This presentation provides a series of case studies derived from the group's LMB, NMB and KMB research on the microstructural design principles that provide for long-term cycling and fast-charge stability of metal anodes. The approaches may be categorized as the following: a) design of plating/stripping supports and templates with tuned geometry and functionality; b) design of secondary interlayers placed between the metal anode and the separator; and c) design of multifunctional hybrid separators to replace the conventional polymer separators employed with LIBs. It is demonstrated that despite appearing distinct, the efficacy of each in enabling electrochemical stability originates from three fundamental features that are directly interrelated. The wetting behavior of the electrolyte on the anode must be optimized, the wetting/stripping behavior of the metal anode on the current collector must be controlled, and a geometrically and chemically modified SEI must be established. Simultaneously achieving all three leads to stable plating/stripping, while missing even one leads to rapid dendrite growth. There seems to be no exceptions to these rules with either Li, Na or K. In parallel this presentation will discuss fundamental insights into the role of surface modification on cycling stability and fast charge performance of ceramic LIB cathodes. Advanced transmission electron microscopy (TEM) was the primary tool employed, combined with various syntheses, analytical and electroanalytical methods. For example, analysis is performed on the role of Zr surface modification on the electrochemical performance of Li and Mn-rich (LMR) cathodes. The capacity-voltage fade phenomenon in LFP cathodes is not understood, with this study providing the first atomic-scale description of the process. It is demonstrated how a pyrrole coating suppresses the dissolution of Fe and allows for extended retention of the Olivine structure. It also reduces the level of crossover of iron to the metal anode and stabilizes its solid electrolyte interphase, thus also contributing to the half-cell cycling stability. These findings were recently published in Advanced Materials, Energy & Environmental Science, Advanced Energy Materials and Chemistry of Materials.

Traditional ethylene carbonate (EC)-based electrolytes constrain the applications of silicon carbon (Si-C) anodes under fast-charging and low-temperature conditions due to sluggish Li+ migration kinetics and unstable solid electrolyte interphase (SEI). Herein, inspired by the efficient water purification and soil stabilization of aquatic plants, a stable SEI with a 3D desolvation interface is designed with gel polymer electrolyte (GPE), accelerating Li+ desolvation and migration at the interface and within stable SEI. As demonstrated by theoretical simulations and experiment results, the resulting poly(1,3-dioxolane) (PDOL), prepared by in situ ring-opening polymerization of 1,3-dioxolane (DOL), creates a 3D desolvation area, improving the Li+ desolvation at the interface and yielding an amorphous GPE with a high Li+ ionic conductivity (5.73 mS cm-1). Furthermore, more anions participate in the solvated structure, forming an anion-derived stable SEI and improving Li+ transport through SEI. Consequently, the Si-C anode achieves excellent rate performance with GPE at room temperature (RT) and low temperature (-40°C). The pouch full cell coupled with LiFePO4 cathode obtains 97.42 mAh g-1 after 500 cycles at 5 C/5 C. This innovatively designed 3D desolvation interface and SEI represent significant breakthroughs for developing fast-charging and low-temperature batteries.

Lithium (Li)-metal anode has attracted extensive attention owing to its high theoretical specific capacity (3860 mAh/g), which is more than ten times to that of graphite anode (372 mAh/g). However, the notorious reactivity of Li-metal prevents their practical applications due to undesired Li dendrite growth and unstable solid electrolyte interphase (SEI) formation. Here, we developed a facile, cost-effective and one-step approach for creating an artificial Li-metal/electrolyte interface by treating Li metal anode with an electrolyte containing SnF2. As a result, the artificial SEI composed of LiF, Sn and Sn-Li alloy was formed with higher ionic conductivity and increased Young’s modulus. The higher ionic conductivity and larger Young’s modulus of the artificial layer facilitate fast Li-ion diffusion and suppress Li dendrite growth, respectively. The hybrid artificial SEI showed a synergistic effect of storing Li by a reversible Sn-Li alloy formation and Li plating underneath the SEI. The artificial SEI treated Li symmetrical cells showed outstanding plating/stripping cycles (~2325 hrs) with reduced overpotential compared to the bare Li. Coupled with a high-loading (11.88 mg.cm-2) LiNi1/3Co1/3Mn1/3O2 (NMC111) cathode, the SEI protected Li full cells exhibited remarkable performance such as longer stable cycling, higher capacity retention and higher capacity at higher rates compared to the bare Li anode.

The increasing demand for high-specific-energy lithium batteries has stimulated extensive research on the lithium metal anode owing to its high specific capacity and low electrode potential. However, the lithium metal will irreversibly react with the electrolyte during the first cycling process, forming an uneven and unstable solid electrolyte interphase (SEI) layer, which results in the non-uniform deposition of Li ions and thus the formation of lithium dendrites. This could cause a battery short circuit, resulting in safety hazards such as thermal runaway. In addition, the continuous rupture and repair of the SEIs during the repeated charge/discharge processes will constantly consume the active lithium, which leads to a significant decrease in battery capacity. An effective strategy to address these challenges is to design and construct ideal artificial SEIs on the surface of the lithium metal anode. This review analyzes and summarizes the mathematical modeling of SEI, the functional characteristics of SEIs with different components, and finally discusses the challenges faced by artificial SEIs in practical applications of lithium metal batteries and future development directions.

As a high‐capacity anode for lithium‐ion batteries (LIBs), MoS2 suffers from short lifespan that is due in part to its unstable solid electrolyte interphase (SEI). The cycle life of MoS2 can be greatly extended by manipulating the SEI with a fluoroethylene carbonate (FEC) additive. The capacity of MoS2 in the electrolyte with 10 wt % FEC stabilizes at about 770 mAh g−1 for 200 cycles at 1 A g−1, which far surpasses the FEC‐free counterpart (ca. 40 mAh g−1 after 150 cycles). The presence of FEC enables a robust LiF‐rich SEI that can effectively inhibit the continual electrolyte decomposition. A full cell with a LiNi0.5Co0.3Mn0.2O2 cathode also gains improved performance in the FEC‐containing electrolyte. These findings reveal the importance of controlling SEI formation on MoS2 toward promoted lithium storage, opening a new avenue for developing metal sulfides as high‐capacity electrodes for LIBs.

Controlling Zinc (Zn) nucleation and subsequent crystal growth are critical for long lifespan aqueous zinc metal batteries. However, the concurrent side reactions and unstable solid-electrolyte interphase (SEI) formations impedes the continuous Zn metal electrodeposition. Herein, induced by a well-designed organic/inorganic dual-phase SEI, we realize ordered zinc electrodeposition of polycrystalline stackings from single-crystal building blocks. The uncommon SEI with appropriate ion transport kinetics and thermodynamic stability protects deposited zinc from side reactions of hydrogen evolution and metal corrosion, enabling rapid and long single crystal Zn nucleation, followed by mitigated crystal growth, and ultimately dense polycrystalline stacking without dendrites. Benefited from the above advantages, the Zn | |Zn symmetric batteries exhibit long lifespan exceeding 5600 h and high depth of discharge of 85.0 %, and the Zn | |I2 full cell delivers a high capacity of 201.9 mAh g-1 at -30 oC. Furthermore, the practical 0.1 Ah Zn | |I2 bilayer pouch cell can stably operate for 113 cycles with a high specific energy of 122.1 Wh kg-1 with a low N/P capacity ratio of 1.5. Our findings advance the understanding of critical roles of SEI on zinc electrodeposition behaviors and provide valuable insights into crystal structure regulation during electrodeposition in other metal batteries.

Solid-state lithium metal batteries equipped with solid polymer electrolytes (SPEs) are recognized as promising energy storage devices due to their excellent safety and good interfacial contact. However, unstable solid electrolyte interphase (SEI) and sluggish Li+ transport kinetics inhibit their practical application. Herein, a bromine-modified covalent organic framework (Br-COF) with donor (D)-acceptor (A) characteristics is designed and incorporated into PVDF-HFP-based SPEs to regulate electron density for promoting Li+ migration and high stability LiF-rich SEI formation to solve these problems. The D and A units of Br-COF are confined in particular locations to create independent electron-hole transference channels, achieving rapid electron transfer dynamics, thereby promoting TFSI- decomposition to obtain high LiF content SEI. Meanwhile, the strong electron-withdrawing Br-group can adsorb the electron from tetra(p-amino-phenyl)porphyrin (TAPP) to create an electron-rich environment, resulting in the regulation of the Li+ local coordination environment to facilitate Li+ transference. Consequently, Br-COF@PVDF-HFP exhibits high ionic conductivity (9.2×10-4 S cm-1) and Li+ transference number (0.78). Li|Br-COF@PVDF-HFP|Li cells achieve excellent cycling life (3000 h) at 0.1 mA cm-2, and LFP|Br-COF@PVDF-HFP|Li and NCM90|Br-COF@PVDF-HFP|Li cells can cycle steadily over 2000 cycles and 250 cycles, respectively. This study provides a reference basis for regulating the electron density of PVDF-HFP-based SPEs to enhance the performance of solid-state LMBs.

The lithium metal anode is the holy grail of the battery field due to its lowest reduction potential and high specific capacity; however, its application is hindered by severe safety hazards and inferior cyclic stability due to dendrites and unstable solid electrolyte interphase (SEI). Aiming at these problems, a coiled Li anode with a unique upright structure is proposed. The upright structure endows coiled Li anode with abundant inner reaction interface/space/mass for lithium deposit/storage/transport, which can induce the inner growth of Li dendrites and SEI. The Li+ transport/deposit behavior and mechanism of coiled Li anode are clarified via in situ observation and numerical simulation. Benefiting from the small volume expansion and sufficient Li+ transport, the coiled Li anodes combined with Li4Ti5O12 cathodes achieve a long life of over 2000 cycles at 5C with a reversible capacity of 129 mAh g−1 and 100% Coulombic efficiency.

Practical applications of lithium metal batteries are limited by unstable solid electrolyte interphase (SEI) and uncontrollable dendrite Li deposition. Regulating the solvation structure of Li+ via modifying electrolyte components enables optimizing the structure of the SEI and realizing dendrite-free Li deposition. In this work, it is found that the ionic-dipole interactions between the electron-deficient B atoms in lithium oxalyldifluoro borate (LiDFOB) and the O atoms in the DME solvent molecule can weaken the interaction between the DME molecule and Li+, accelerating the desolvation of Li+. On this basis, the ionic-dipole interactions facilitate the entry of abundant anions into the inner solvation sheath of Li+, which promotes the formation of inorganic-rich SEI. In addition, the interaction between DFOB- and DME molecules reduces the highest occupied molecular orbital energy level of DME molecules in electrolytes, which improves the oxidative stability of the electrolytes system. As a result, the Li||Li cells in LiDFOB-containing electrolytes exhibit an excellent cyclability of over 1800h with a low overpotential of 18.2mV, and the Li||LiFePO4 full cells display a high-capacity retention of 93.4% after 100 cycles with a high Coulombic efficiency of 99.3%.

Potassium-ion batteries (PIBs) have emerged as a promising next-generation energy storage technology due to the abundance of potassium resources, low redox potential of K+/K, and compatibility with aluminum current collectors. Graphite, as a cost-effective and structurally stable anode, exhibits considerable potential for practical PIB applications. However, challenges such as sluggish K+ diffusion kinetics, significant volume expansion, and unstable solid electrolyte interphase (SEI) hinder the full utilization of the graphite anode. This review systematically summarizes recent advances in understanding the K+ intercalation behavior and storage mechanism of graphite. Key strategies for enhancing graphite performance, including interlayer spacing regulation, morphological engineering, defect and heteroatom doping, and coating design, are thoroughly discussed. In addition, interface engineering approaches involving electrolyte component optimization, artificial SEI construction, and binder design are highlighted to address SEI instability. This review also compares the potassium storage characteristics of graphite with those in lithium/sodium systems and outlines current challenges under extreme conditions. Finally, future perspectives are provided to guide the rational design of graphite-based anodes for high-performance PIBs. This work aims to offer a comprehensive reference for the development of advanced graphite anode materials in emerging potassium-ion battery technologies.

To meet the rapidly growing market in electrical vehicles (EVs) and portable electronic devices, a battery with high energy density is required. In order to reach this goal, Li metal, is considered as the most promising candidate as anode. However, the dendrite forming, low Coulombic efficiency (CE), and unstable solid electrolyte interphase (SEI) pose big challenges in applying Li metal in batteries. Here we introduce a dual-layer coated Li metal surface, which consists a lithium carboxylate organic layer and a doped MXene layer. The porous organic layer increases the wetting of electrolyte and forms a thin solid electrolyte interface (SEI). While the doped MXene leads to about 50% reduced thickness of inorganic-rich components among the SEI layer. A low overpotential of less than 30 mV over 1000 h cycling in symmetric cells was received. The functional groups along with the good electronic conductivity and smooth surface of the MXene greatly reduce the lithium plating/stripping energy barrier, enabling a dendrite-free lithium metal anode. The battery paired with NMC811 exhibited a high initial CE of 82.1%. A high capacity-retention of 175.4 mAh/g at 1.0 C was achieved after 350 cycles. After long 500 cycles, a reliable capacity was still remained while the cell with un-modified Li metal quickly dropped to below 74.2 mAh/g. In a 475 mAh pouch cell, the battery still exhibited a high discharge capacity of 165.6 mAh/g with a capacity retention of 90.2% after 200 cycles, while the cell with pure Li metal decreased to 80.5%. Keywords: Lithium metal; Battery; Anode; MXene; Doping

Anode-free lithium (Li) metal batteries (AFLBs) featured high energy density are viewed as the viable future energy storage technology. However, the irregular Li deposition and unstable solid electrolyte interphase (SEI) on anode current collectors reduce their cycling performance. Here, we propose a concept of anion-recognition electrodes enabled by anion-π interactions to regulate the inner Helmholtz plane (IHP) and electrolyte solvation chemistry for high-performance AFLBs. By engineering the electrodes with electron-deficient aromatic-π systems that possess high permanent quadrupole moment (Qzz), the anion-π interactions can be generated to concentrate the anions on the electrode surface and tune the IHP structure to construct a stable anion-derived SEI layer, thus achieving highly reversible Li plating/stripping process. Through designing various current collectors with different Qzz values, the intimate correlations among the surface charge of the electrode, competitive adsorption of the IHP, and SEI structures are demonstrated. Particularly, the modified carbon cloth current collector with a high Qzz value (+35.1) delivers a high average Li stripping/plating Coulombic efficiency of 99.1 % over 230 cycles in the carbonated electrolyte, enabling a long lifespan and high capacity retention of LiNi0.8Co0.1Mn0.1O2-based AFLBs with a commercial-level areal capacity (4.1 mAh cm-2).

Lithium-metal batteries suffer from sluggish charge-transfer kinetics and unstable solid electrolyte interphase (SEI) layers under low temperatures, invariably leading to significant performance degradation. Herein, we propose a complementary “push and pull” electrolyte design strategy to controllably regulate the Li+ solvation structure. The pull factor is designed to enhance the interaction between Li+ and weakly solvating solvents, considering the electrostatic potential (ESP), Li+–solvent binding energy, solvent–solvent interactions, and F-donating ability. Furthermore, inorganic Li salt with a high Li+–anion binding energy is designed as a push factor to lower the Li+ desolvation barrier and weaken the destructive effects of the pull factor on the SEI, forming a high-ionic-conductive and stable SEI. As a result, stable Li plating/stripping with high Coulombic efficiencies of 99.4% and 98.5% are achieved under −20 and −40 °C, respectively, and the Li/LiFePO4 full cell can retain 73% of room-temperature capacity under −20 °C. These results demonstrate an effective electrolyte strategy for low-temperature Li-metal batteries.