A Successive Conversion-Deintercalation Delithiation Mechanism for Practical Composite Lithium Anodes

LiC6@Li as a Promising Substitution of Li Metal Counter Electrode for Low-Temperature Battery Evaluation

Li metal, as a counter electrode, is widely used for electrode materials evaluation in coin type half-cells. However, whether this configuration is suitable for different working conditions has often been neglected. Herein, the large resistance and high cathodic/anodic over-potential of Li metal at low temperature are highlighted, revealing its incompetence as counter electrode on cryogenic condition. In view of this, a novel LiC6@Li composite electrode is developed as a promising substitution for electrode materials evaluation. In the LiC6@Li electrode, Li+ de-intercalated from LiC6 preferentially due to the low interface resistance of LiC6, presenting a cathodic/anodic over-potential of 0.05 V (67 µA cm-2) at -20 °C, which is ten times lower than that of Li metal. Moreover, the rapid lithium replenishment into LiC6 from Li metal enables a stable potential of LiC6@Li. Consequently, the LiC6@Li-based half-cells enabled more precise evaluation of the Li+ storage potential and specific capacities of a series of electrode materials at low temperature. As an extension, KC8@K is also successfully prepared as a superior counter electrode to K metal. This work proposes a suitable counter electrode for more accurately evaluating electrode materials at subfreezing scenarios, demonstrating the necessity of specialized electrode evaluation systems for particular operating conditions.

Transition metal phosphide/ molybdenum disulfide heterostructures towards advanced electrochemical energy storage: recent progress and challenges

Transition metal phosphide @ molybdenum disulfide (TMP@MoS2) heterostructures, consisting of TMP as the core main catalytic body and MoS2 as the outer shell, can solve the three major problems in the field of renewable energy storage and catalysis, such as lack of resources, cost factors, and low cycling stability. The heterostructures synergistically combine the excellent conductivity and electrochemical performance of transition metal phosphides with the structural robustness and catalytic activity of molybdenum disulfide, which holds great promise for clean energy. This review addresses the advantages of TMP@MoS2 materials and their synthesis methods-e.g., hydrothermal routes and chemical vapor deposition regarding scalability and cost. Their electrochemical energy storage and catalytic functions e.g., hydrogen and oxygen evolution reactions (HER and OER) are also extensively explored. Their potential within battery and supercapacitor technologies is also assessed against leading performance metrics. Challenges toward industry-scale scalability, longevity, and environmental sustainability are also addressed, as are optimization and large-scale deployment strategies.

A Bifunctional Shear-Thickened Composite Electrolyte Toward High-Safety Lithium Metal Batteries

Lithium metal batteries (LMBs) are limited in practical applications due to safety issues resulting from uncontrolled dendrite growth and mechanical abuse. Herein, a bifunctional gel shear-thickened electrolyte (STE) is developed to simultaneously prevent lithium dendrite growth and improve impact protection by dispersing hydroxyl-rich fumed silica in a conventional liquid electrolyte (LE). STE in Li||Cu cells enabled a lower overpotential for Li deposition compared to that using LE. Li|STE|Li cells stably cycled 1200 h, while Li|LE|Li cells only survived for 200 h, which is attributed to STE promoting the formation of the stable inorganic-rich SEI. Li|STE|LFP full cells achieved capacity retention of 77% after 200 cycles, much higher than LE-containing cells (54%@200 cycles). In addition, the superior protection performance of STE-containing pouch cells is verified by in-situ monitoring with digital image correlation technology and theoretical analysis with finite element simulation. Compared with the pouch cell without STE, the maximum principal strain and plastic strain of the STE-containing pouch cell are reduced by 80% and 62.5%, respectively, which benefits from the non-Newtonian fluid behavior of STE under impact loading. This work confirmed the great potential of the bifunctional gel electrolyte for enhancing the electrochemical performance and safety of LMBs.

Regulation of Extra Li Inventory in Anode-Free Lithium Metal Batteries by Li-Rich Layered Oxide Cathode Materials

Li-rich layered oxide (LRO) cathode material is utilized in anode-free Li metal batteries to provide extra Li inventory, compensating for the constant Li loss during cycling. The Li compensation mechanism of LRO in the anode-free system is elucidated by exploring the reversible/irreversible Li consumption behaviors. Moreover, the relationship between cathode areal capacity, Li inventory, and the cycling performance of the Cu||LRO cell is quantitatively analyzed. The well-designed Cu||LRO anode-free cell demonstrates 51% capacity retention after 60 cycles at a practical areal capacity of 5.0 mAh cm-2, overwhelming the 0.6% capacity retention for Cu||NCM523. Further optimization with an artificial anode protection layer and a fully fluorinated electrolyte enhances the capacity retention of Cu||LRO to 61.4% and 71.5% after 60 cycles, respectively. Combining its low initial Coulombic efficiency and high specific energy, the LRO cathode shows great prospects in the future development of high energy and long lifespan anode-free Li metal batteries.

Highly Reversible Anode-Free Lithium Metal Batteries Enabled by Porous Organic Cages with Subnano Lithiophilic Triangular Windows

The widespread application of anode-free lithium metal batteries (AFLMBs) is hindered by the severe dendrite growth and side reactions due to the poor reversibility of Li plating/stripping. Herein, our study introduces an ultrathin interphase layer of covalent cage 3 (CC3) for highly reversible AFLMBs. The subnano triangular windows in CC3 serve as a Li+ sieve to accelerate Li+ desolvation and transport kinetics, inhibit electrolyte decomposition, and form LiF- and Li3N-rich solid-electrolyte interphases. Moreover, the lithiophilic backbone of CC3 homogenizes Li+ distribution and deposition with mitigated dendrite growth. Thus, CC3 promotes Li plating/stripping kinetics and reversibility, achieving an ultralong stability over 8000 h of the Cu@CC3 electrode. Furthermore, practical Cu@CC3/LiFePO4 AFLMBs deliver a capacity retention (66%) over 600 cycles. This work emphasizes the effectiveness of CC3 to regulate the Li plating/stripping behavior, demonstrating the application potential of porous organic cages for enhancing the cycle life of AFLMBs.

Hubbard Gap Closure-Induced Dual-Redox Li-Storage Mechanism as the Origin of Anomalously High Capacity and Fast Ion Diffusivity in MOFs-Like Polyoxometalates

MOFs-like polyoxometalate (POMs) electrodes, harvesting combined advantages of interlocking porosity and multi-electron transfer reaction, have already emerged as promising candidates for lithium-ion batteries (LIBs), yet the origins of the underlying redox mechanism in such materials remain a matter of uncertainty. Of critical challenges are the anomalously high storage capacities beyond their theoretical values and the fast ion diffusivity that cannot be satisfactorily comprehended in the theory of crystal lattice. Herein, for the first time we decode t2g electron occupation-regulated dual-redox Li-storage mechanism as the true origin of extra capacity in POMs electrodes. The lattice and electronic transition of active centers and reaction intermediates were systematically decoupled through density functional theory (DFT) and a suite of structural spectroscopic investigations, such as X-ray absorption near-edge spectroscopy (XANES), soft X-ray absorption spectroscopy (sXAS) and 7Li solid-state nuclear magnetic resonance (NMR). Enhanced V-t2g orbital occupation by Li coordination significantly triggers the Hubbard gap closure and reversible Li deposition/dissolution at surface region. Conjugated V-O-Li configuration at interlayers endow Li+ ion pathways along pore walls as the dominant contribution to the low migration barrier and fast diffusivity. As a result, remarkable cycle stability (~100 % capacity retention after 2000 cycles at 1 A g-1), extremely high specific capacity (1200 mAh g-1 at 100 mA g-1) and excellent rate performance (404 mAh g-1 at 8 A g-1) were achieved, providing new understandings on the underlying mechanism of POMs electrodes and pivotal guidance for dual-storage materials.

Revealing the overlithiation effect on cycling and calendar aging of a silicon/graphite electrode for high-energy lithium-ion batteries

Lithium (Li) plating, triggered by fast charging and low temperature, will cause performance degradation and safety concerns for lithium-ion batteries (LIBs). However, strategically limited and controlled Li deposition might be advantageous for enhancing energy density. The detailed mechanism and regulation for performance improvement are yet to be fully explored. This study meticulously modulates the overlithiation capacity to regulate Li plating and probes its effects on the stability of high-capacity silicon/graphite (Si/Gr) electrodes through consecutive cycling and over the calendar aging period. The Si/Gr electrode (20 wt% Si) with a 20% overlithiation degree exhibits enhanced reversible capacity in comparison to the pristine Si/Gr electrode. This improvement is attributed to precision-controlled Li deposition, the increased electrochemical utilization of Si and Gr above 0 V, and the additional intercalation/alloying reactions below 0 V, which decelerate the progression of capacity degradation and significantly boost the electrochemical performance of Si/Gr electrodes. Moreover, this tailored Si/Gr electrode with a 20% overlithiation degree attenuates the deterioration associated with calendar aging. This research not only elucidates the intricate interplay and mechanisms of Li plating on Si/Gr electrodes during overlithiation but also presents a new understanding and approach to advance the performance of LIBs and extend their service lifespan.

Direct lithium extraction from spent batteries for efficient lithium recycling

The flourishing expansion of the lithium-ion batteries (LIBs) market has led to a surge in the demand for lithium resources. Developing efficient recycling technologies for imminent large-scale retired LIBs can significantly facilitate the sustainable utilization of lithium resources. Here, we successfully extract active lithium from spent LIBs through a simple, efficient, and low-energy-consumption chemical leaching process at room temperature, using a solution comprised of polycyclic aromatic hydrocarbons and ether solvents. The mechanism of lithium extraction is elucidated by clarifying the relationship between the redox potential and extraction efficiency. More importantly, the reclaimed active lithium is directly employed to fabricate LiFePO4 cathode with performance comparable to commercial materials. When implemented in 56 Ah prismatic cells, the cells deliver stable cycling properties with a capacity retention of ∼90% after 1200 cycles. Compared with the other strategies, this technical approach shows superior economic benefits and practical promise. It is anticipated that this method may redefine the recycling paradigm for retired LIBs and drive the sustainable development of industries.

Liquid Metal Loaded Molecular Sieve: Specialized Lithium Dendrite Blocking Filler for Polymeric Solid-State Electrolyte

All-solid-state lithium metal batteries (LMBs) are currently one of the best candidates for realizing the yearning high-energy-density batteries with high safety. However, even polyethylene oxide (PEO), the most popular polymeric solid-state electrolyte (SSE) with the largest ionic conductivity in the category so far, has significant challenges due to the safety issues of lithium dendrites, and the insufficient ionic conductivity. Herein, molecular sieve (MS) is integrated into the PEO as an inert filler with the liquid metal (LM) as a functional module, forming an "LM-MS-PEO" composite as both SSE with enhanced ionic conductivity, and protection layer against lithium dendrites. As demonstrated by theoretical and experimental investigations, LM released from MS can be uniformly and efficiently distributed in PEO, which could avoid agglomeration, enable the effective blocking of lithium dendrites, and regulate the mass transport of Li ions, thus achieving even deposition of lithium during charge/discharge. Moreover, MS could reduce the crystallinity of PEO, improve lithium-ion conductivity, and reduce operating temperature. Benefiting from the introduction of the functional MS/LM, the LM-MS-PEO electrolyte exhibits fourfold higher lithium ionic conductivity than the pristine PEO at 40 °C, while the as-assembled all-solid-state LMBs have four to five times longer stable cycle life.

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.

Realizing Low-Temperature Graphite-based Rechargeable Potassium-Ion Full Battery

Graphite (Gr) has been considered as the most promising anode material for potassium-ion batteries (PIBs) commercialization due to its high theoretical specific capacity and low cost. However, Gr-based PIBs remain unfeasible at low temperature (LT), suffering from either poor kinetics based on conventional carbonate electrolytes or K+ -solvent co-intercalation issue based on typical ether electrolytes. Herein, a high-performance Gr-based LT rechargeable PIB is realized for the first time by electrolyte chemistry. Applying unidentate-ether-based molecule as the solvent dramatically weakens the K+ -solvent interactions and lowers corresponding K+ de-solvation kinetic barrier. Meanwhile, introduction of steric hindrance suppresses co-intercalation of K+ -solvent into Gr, greatly elevating operating voltage and cyclability of the full battery. Consequently, the as-prepared Gr||prepotassiated 3,4,9,10-perylene-tetracarboxylicacid-dianhydride (KPTCDA) full PIB can reversibly charge/discharge between -30 and 45 °C with a considerable energy density up to 197 Wh kgcathode -1 at -20 °C, hopefully facilitating the development of LT PIBs.

Insight into Dendrites Issue in All Solid-State Batteries with Inorganic Electrolyte: Mechanism, Detection and Suppression Strategies

All solid-state batteries (ASSBs) are regarded as one of the promising next-generation energy storage devices due to their expected high energy density and capacity. However, failures due to unrestricted growth of lithium dendrites (LDs) have been a critical problem. Moreover, the understanding of dendrite growth inside solid-state electrolytes is limited. Since the dendrite process is a multi-physical field coupled process, including electrical, chemical, and mechanical factors, no definitive conclusion can summarize the root cause of LDs growth in ASSBs till now. Herein, the existing works on mechanism, identification, and solution strategies of LD in ASSBs with inorganic electrolyte are reviewed in detail. The primary triggers are thought to originate mainly at the interface and within the electrolyte, involving mechanical imperfections, inhomogeneous ion transport, inhomogeneous electronic structure, and poor interfacial contact. Finally, some of the representative works and present an outlook are comprehensively summarized, providing a basis and guidance for further research to realize efficient ASSBs for practical applications.

Li, Na, K, Mg, Zn, Al, and Ca Anode Interface Chemistries Developed by Solid-State Electrolytes

Solid-state batteries (SSBs) have received significant attention due to their high energy density, reversible cycle life, and safe operations relative to commercial Li-ion batteries using flammable liquid electrolytes. This review presents the fundamentals, structures, thermodynamics, chemistries, and electrochemical kinetics of desirable solid electrolyte interphase (SEI) required to meet the practical requirements of reversible anodes. Theoretical and experimental insights for metal nucleation, deposition, and stripping for the reversible cycling of metal anodes are provided. Ion transport mechanisms and state-of-the-art solid-state electrolytes (SEs) are discussed for realizing high-performance cells. The interface challenges and strategies are also concerned with the integration of SEs, anodes, and cathodes for large-scale SSBs in terms of physical/chemical contacts, space-charge layer, interdiffusion, lattice-mismatch, dendritic growth, chemical reactivity of SEI, current collectors, and thermal instability. The recent innovations for anode interface chemistries developed by SEs are highlighted with monovalent (lithium (Li+ ), sodium (Na+ ), potassium (K+ )) and multivalent (magnesium (Mg2+ ), zinc (Zn2+ ), aluminum (Al3+ ), calcium (Ca2+ )) cation carriers (i.e., lithium-metal, lithium-sulfur, sodium-metal, potassium-ion, magnesium-ion, zinc-metal, aluminum-ion, and calcium-ion batteries) compared to those of liquid counterparts.

In Situ Formed Tribofilms as Efficient Organic/Inorganic Hybrid Interlayers for Stabilizing Lithium Metal Anodes

The practical application of Li metal anodes (LMAs) is limited by uncontrolled dendrite growth and side reactions. Herein, we propose a new friction-induced strategy to produce high-performance thin Li anode (Li@CFO). By virtue of the in situ friction reaction between fluoropolymer grease and Li strips during rolling, a robust organic/inorganic hybrid interlayer (lithiophilic LiF/LiC6 framework hybridized -CF2-O-CF2- chains) was formed atop Li metal. The derived interface contributes to reversible Li plating/stripping behaviors by mitigating side reactions and decreasing the solvation degree at the interface. The Li@CFO||Li@CFO symmetrical cell exhibits a remarkable lifespan for 5,600 h (1.0 mA cm-2 and 1.0 mAh cm-2) and 1,350 cycles even at a harsh condition (18.0 mA cm-2 and 3.0 mAh cm-2). When paired with high-loading LiFePO4 cathodes, the full cell lasts over 450 cycles at 1C with a high-capacity retention of 99.9%. This work provides a new friction-induced strategy for producing high-performance thin LMAs.

Gradient Lithium Metal Infusion in Ag-Decorated Carbon Fibers for High-Capacity Lithium Metal Battery Anodes

Lithium (Li) metal is a promising anode material for high-energy-density Li batteries due to its high specific capacity. However, the uneven deposition of Li metal causes significant volume expansion and safety concerns. Here, we investigate the impact of a gradient-infused Li-metal anode using silver (Ag)-decorated carbonized cellulose fibers (Ag@CC) as a three-dimensional (3D) current collector. The loading level of the gradient-infused Li-metal anode is controlled by the thermal infusion time of molten Li. In particular, a 5 s infusion time in the Ag@CC current collector creates an appropriate space with a lithiophilic surface, resulting in improved cycling stability and a reduced volume expansion rate. Moreover, integrating a 5 s Ag@CC anode with a high-capacity cathode demonstrates superior electrochemical performance with minimal volume expansion. This suggests that a gradient-infused Li-metal anode using Ag@CC as a 3D current collector represents a novel design strategy for Li-metal-based high-capacity Li-ion batteries.

Quantifying the Influence of Li Plating on a Graphite Anode by Mass Spectrometry

The prominent problem with graphite anodes in practical applications is the detrimental Li plating, resulting in rapid capacity fade and safety hazards. Herein, secondary gas evolution behavior during the Li-plating process was monitored by online electrochemical mass spectrometry (OEMS), and the onset of local microscale Li plating on the graphite anode was precisely/explicitly detected in situ/operando for early safety warnings. The distribution of irreversible capacity loss (e.g., primary and secondary solid electrolyte interface (SEI), dead Li, etc.) under Li-plating conditions was accurately quantified by titration mass spectroscopy (TMS). Based on OEMS/TMS results, the effect of typical VC/FEC additives was recognized at the level of Li plating. The nature of vinylene carbonate (VC)/fluoroethylene carbonate (FEC) additive modification is to enhance the elasticity of primary and secondary SEI by adjusting organic carbonates and/or LiF components, leading to less "dead Li" capacity loss. Though VC-containing electrolyte greatly suppresses the H₂/C₂H₄ (flammable/explosive) evolution during Li plating, more H₂ is released from the reductive decomposition of FEC.

Building K-C Anode with Ultrahigh Self-Diffusion Coefficient for Solid State Potassium Metal Batteries Operating at -20 to 120 °C

Solid state potassium (K) metal batteries are intriguing in grid-scale energy storage, benefiting from the low cost, safety, and high energy density. However, their practical applications are impeded by poor K/solid electrolyte (SE) interfacial contact and limited capacity caused by the low K self-diffusion coefficient, dendrite growth, and intrinsically low melting point/soft features of metallic K. Herein, a fused-modeling strategy using potassiophilic carbon allotropes molted with K is demonstrated that can enhance the electrochemical performance/stability of the system via promoting K diffusion kinetics (2.37 × 10^-8 cm² s^-1 ), creating a low interfacial resistance (≈1.3 Ω cm² ), suppressing dendrite growth, and maintaining mechanical/thermal stability at 200 °C. A homogeneous/stable K stripping/plating is consequently implemented with a high current density of 2.8 mA cm^-2 (at 25 °C) and a record-high areal capacity of 11.86 mAh cm^-2 (at 0.2 mA cm^-2 ). The enhanced K diffusion kinetics contribute to sustaining intimate interfacial contact, stabilizing the stripping/plating at high current densities. Full cells coupling ultrathin K-C composite anodes (≈50 µm) with Prussian blue cathodes and β/β″-Al₂ O₃ SEs deliver a high energy density of 389 Wh kg^-1 with a retention of 94.4% after 150 cycles and fantastic performances at -20 to 120 °C.

Interfacial Anchored Sesame Ball-like Ag/C To Guide Lithium Even Plating and Stripping Behavior

Lithium (Li) metal is a candidate anode for the next generation of high-energy density secondary batteries. Unfortunately, Li metal anodes (LMAs) are extremely reactive with electrolytes to accumulate uncontrolled dendrites and to generate unwanted parasitic electrochemical reactions. Much attention has been focused on carbon materials to address these issues. Ulteriorly, the failure mechanism investigation of lithiophilic sites on carbon materials has been not taken seriously. Herein, we design a new type of sesame ball-like carbon sphere (AgNPs@CS, an average diameter of ∼700 nm) with uniformly interfacial anchored silver nanoparticles (AgNPs), which is used as the dendrite-free Li metal anode host. This anchored structure significantly enhances reversible and chemical affinity of Li, effectively inhibiting "dead Li". In addition, the protective effect of the carbon layer can avoid the damage of lithiophilic AgNPs in the carbon matrix. With a plating/striping capacity of 2 mA h cm^-2, the AgNPs@CS electrode can be cycled over 2400 h at 0.5 mA cm^-2. When the stripping voltage increases to 1 V, the AgNPs@CS electrode also enables excellent cycling stability to achieve over 260 cycles (1 mA cm^-2, 1 mA h cm^-2) and 130 cycles (2 mA cm^-2, 1 mA h cm^-2). This material by electrochemical characterization highlights the efficacy of this facile method for developing dendrite-free LMAs.

Thermally Stable Polymer-Rich Solid Electrolyte Interphase for Safe Lithium Metal Pouch Cells

Serious safety risks caused by the high reactivity of lithium metal against electrolytes severely hamper the practicability of lithium metal batteries. By introducing unique polymerization site and more fluoride substitution, we built an in situ formed polymer-rich solid electrolyte interphase upon lithium anode to improve battery safety. The fluorine-rich and hydrogen-free polymer exhibits high thermal stability, which effectively reduces the continuous exothermic reaction between electrolyte and anode/cathode. As a result, the critical temperature for thermal safety of 1.0 Ah lithium-LiNi_0.5 Co_0.2 Mn_0.3 O₂ pouch cell can be increased from 143.2 °C to 174.2 °C. The more dangerous "ignition" point of lithium metal batteries, the starting temperature of battery thermal runaway, has been dramatically raised from 240.0 °C to 338.0 °C. This work affords novel strategies upon electrolyte design, aiming to pave the way for high-energy-density and thermally safe lithium metal batteries.

Advances in the Emerging Gradient Designs of Li Metal Hosts

Developing host has been recognized a potential countermeasure to circumvent the intrinsic drawbacks of Li metal anode (LMA), such as uncontrolled dendrite growth, unstable solid electrolyte interface, and infinite volume fluctuations. To realize proper Li accommodation, particularly bottom-up deposition of Li metal, gradient designs of host materials including lithiophilicity and/or conductivity have attracted a great deal of attention in recent years. However, a critical and specialized review on this quickly evolving topic is still absent. In this review, we attempt to comprehensively summarize and update the related advances in guiding Li nucleation and deposition. First, the fundamentals regarding Li deposition are discussed, with particular attention to the gradient design principles of host materials. Correspondingly, the progress of creating different gradients in terms of lithiophilicity, conductivity, and their hybrid is systematically reviewed. Finally, future challenges and perspective on the gradient design of advanced hosts towards practical LMAs are provided, which would provide a useful guidance for future studies.

Commercially Viable Hybrid Li-Ion/Metal Batteries with High Energy Density Realized by Symbiotic Anode and Prelithiated Cathode

The energy density of commercial lithium (Li) ion batteries with graphite anode is reaching the limit. It is believed that directly utilizing Li metal as anode without a host could enhance the battery's energy density to the maximum extent. However, the poor reversibility and infinite volume change of Li metal hinder the realistic implementation of Li metal in battery community. Herein, a commercially viable hybrid Li-ion/metal battery is realized by a coordinated strategy of symbiotic anode and prelithiated cathode. To be specific, a scalable template-removal method is developed to fabricate the porous graphite layer (PGL), which acts as a symbiotic host for Li ion intercalation and subsequent Li metal deposition due to the enhanced lithiophilicity and sufficient ion-conducting pathways. A continuous dissolution-deintercalation mechanism during delithiation process further ensures the elimination of dead Li. As a result, when the excess plating Li reaches 30%, the PGL could deliver an ultrahigh average Coulombic efficiency of 99.5% for 180 cycles with a capacity of 2.48 mAh cm^-2 in traditional carbonate electrolyte. Meanwhile, an air-stable recrystallized lithium oxalate with high specific capacity (514.3 mAh g^-1) and moderate operating potential (4.7-5.0 V) is introduced as a sacrificial cathode to compensate the initial loss and provide Li source for subsequent cycles. Based on the prelithiated cathode and initial Li-free symbiotic anode, under a practical-level 3 mAh capacity, the assembled hybrid Li-ion/metal full cell with a P/N ratio (capacity ratio of LiNi_0.8Co_0.1Mn_0.1O₂ to graphite) of 1.3 exhibits significantly improved capacity retention after 300 cycles, indicating its great potential for high-energy-density Li batteries.

Fluorinating the Solid Electrolyte Interphase by Rational Molecular Design for Practical Lithium-Metal Batteries

The lifespan of practical lithium (Li)-metal batteries is severely hindered by the instability of Li-metal anodes. Fluorinated solid electrolyte interphase (SEI) emerges as a promising strategy to improve the stability of Li-metal anodes. The rational design of fluorinated molecules is pivotal to construct fluorinated SEI. Herein, design principles of fluorinated molecules are proposed. Fluoroalkyl (-CF₂ CF₂ -) is selected as an enriched F reservoir and the defluorination of the C-F bond is driven by leaving groups on β-sites. An activated fluoroalkyl molecule (AFA), 2,2,3,3-tetrafluorobutane-1,4-diol dinitrate is unprecedentedly proposed to render fast and complete defluorination and generate uniform fluorinated SEI on Li-metal anodes. In Li-sulfur (Li-S) batteries under practical conditions, the fluorinated SEI constructed by AFA undergoes 183 cycles, which is three times the SEI formed by LiNO₃ . Furthermore, a Li-S pouch cell of 360 Wh kg^-1 delivers 25 cycles with AFA. This work demonstrates rational molecular design principles of fluorinated molecules to construct fluorinated SEI for practical Li-metal batteries.

Stable Solvent-Derived Inorganic-Rich Solid Electrolyte Interphase (SEI) for High-Voltage Lithium-Metal Batteries

The inorganic-rich solid electrolyte interphase (SEI) has attracted wide attention due to its good compatibility with the lithium (Li) metal anode. Herein, a stable solvent-derived inorganic-rich SEI is constructed from a hydrofluoroether-diluted low-concentration electrolyte, which simultaneously possesses the merits of nonflammability and low cost (0.5 M LiPF₆). The addition of hydrofluoroether enhances the coordination strength between Li⁺ and solvents, altering the decomposition path of solvents to yield more Li₂O. The abundant Li₂O crystals endow the SEI with improved passivating ability and ion conductivity. The 30 μm Li|NCM523 (3.8 mAh cm^-2) batteries with solvent-derived Li₂O-rich SEI deliver 96.1% capacity retention after 200 cycles. Notably, a 1.1 Ah Li|NCA pouch cell delivers an energy density of 374 Wh kg^-1 and achieves 45 stable cycles. This study points out that tuning the decomposition of solvents provides a new approach to construct stable inorganic-rich SEI for practical Li-metal batteries.

Anion Concentration Gradient-Assisted Construction of a Solid-Electrolyte Interphase for a Stable Zinc Metal Anode at High Rates

Coulombic efficiency (CE) and cycle life of metal anodes (lithium, sodium, zinc) are limited by dendritic growth and side reactions in rechargeable metal batteries. Here, we proposed a concept for constructing an anion concentration gradient (ACG)-assisted solid-electrolyte interphase (SEI) for ultrahigh ionic conductivity on metal anodes, in which the SEI layer is fabricated through an in situ chemical reaction of the sulfonic acid polymer and zinc (Zn) metal. Owing to the driving force of the sulfonate concentration gradient and high bulky sulfonate concentration, a promoted Zn²⁺ ionic conductivity and inhibited anion diffusion in the SEI layer are realized, resulting in a significant suppression of dendrite growth and side reaction. The presence of ACG-SEI on the Zn metal enables stable Zn plating/stripping over 2000 h at a high current density of 20 mA cm^-2 and a capacity of 5 mAh cm^-2 in Zn/Zn symmetric cells, and moreover an improved cycling stability is also observed in Zn/MnO₂ full cells and Zn/AC supercapacitors. The SEI layer containing anion concentration gradients for stable cycling of a metal anode sheds a new light on the fundamental understanding of cation plating/stripping on metal electrodes and technical advances of rechargeable metal batteries with remarkable performance under practical conditions.

Modification of Nitrate Ion Enables Stable Solid Electrolyte Interphase in Lithium Metal Batteries

The lifespan of high-energy-density lithium metal batteries (LMBs) is hindered by heterogeneous solid electrolyte interphase (SEI). The rational design of electrolytes is strongly considered to obtain uniform SEI in working batteries. Herein, a modification of nitrate ion (NO₃ ^- ) is proposed and validated to improve the homogeneity of the SEI in practical LMBs. NO₃ ^- is connected to an ether-based moiety to form isosorbide dinitrate (ISDN) to break the resonance structure of NO₃ ^- and improve the reducibility. The decomposition of non-resonant -NO₃ in ISDN enriches SEI with abundant LiN_x O_y and induces uniform lithium deposition. Lithium-sulfur batteries with ISDN additives deliver a capacity retention of 83.7 % for 100 cycles compared with rapid decay with LiNO₃ after 55 cycles. Moreover, lithium-sulfur pouch cells with ISDN additives provide a specific energy of 319 Wh kg^-1 and undergo 20 cycles. This work provides a realistic reference in designing additives to modify the SEI for stabilizing LMBs.

Revisiting the Roles of Natural Graphite in Ongoing Lithium-Ion Batteries

Graphite, commonly including artificial graphite and natural graphite (NG), possesses a relatively high theoretical capacity of 372 mA h g^-1 and appropriate lithiation/de-lithiation potential, and has been extensively used as the anode of lithium-ion batteries (LIBs). With the requirements of reducing CO₂ emission to achieve carbon neutral, the market share of NG anode will continue to grow due to its excellent processability and low production energy consumption. NG, which is abundant in China, can be divided into flake graphite (FG) and microcrystalline graphite (MG). In the past 30 years, many researchers have focused on developing modified NG and its derivatives with superior electrochemical performance, promoting their wide applications in LIBs. Here, a comprehensive overview of the origin, roles, and research progress of NG-based materials in ongoing LIBs is provided, including their structure, properties, electrochemical performance, modification methods, derivatives, composites, and applications, especially the strategies to improve their high-rate and low-temperature charging performance. Prospects regarding the development orientation as well as future applications of NG-based materials are also considered, which will provide significant guidance for the current and future research of high-energy-density LIBs.

Toward Practical High-Energy and High-Power Lithium Battery Anodes: Present and Future

Lithium batteries are key components of portable devices and electric vehicles due to their high energy density and long cycle life. To meet the increasing requirements of electric devices, however, energy density of Li batteries needs to be further improved. Anode materials, as a key component of the Li batteries, have a remarkable effect on the increase of the overall energy density. At present, various anode materials including Li anodes, high-capacity alloy-type anode materials, phosphorus-based anodes, and silicon anodes have shown great potential for Li batteries. Composite-structure anode materials will be further developed to cater to the growing demands for electrochemical storage devices with high-energy-density and high-power-density. In this review, the latest progress in the development of high-energy Li batteries focusing on high-energy-capacity anode materials has been summarized in detail. In addition, the challenges for the rational design of current Li battery anodes and the future trends are also presented.

Strategies and challenges of carbon materials in the practical applications of lithium metal anode: a review

Lithium (Li) metal is strongly considered to be the ultimate anode for next-generation high-energy-density rechargeable batteries. Carbon materials and their composites with excellent structure tunability and properties have shown great potential applications in Li metal anodes.