Li Half-cells Research Articles

Electronic effect tuned ion-dipole interactions for low-temperature electrolyte design of LiFePO4-based lithium-ion batteries

Poor low-temperature performance is one of the major challenges hindering the widespread use of lithium-ion batteries. Modulation of Li+ solvation structure to facilitate desolvation process is an important strategy in electrolyte engineering under low temperature. Herein, different electronic effect groups including electron-withdrawing groups (CH2Cl) and electron-donating groups (CH3), are introduced in the weakly solvated solvent tetrahydrofuran (THF), respectively, to compare their effects on the ion-dipole interaction in the electrolyte and thus the regulation of Li+ solvation structure. Theoretical calculations combined with characterization demonstrates that the introduction of electron-withdrawing groups CH2Cl in the solvent can reduce the electron cloud density of oxygen in the THF solvent molecule, weaken the binding energy between Li+ and the solvent, and lead to more anions participating in solvation shell of Li+ and coordinating with Li+, thus accelerating the desolvation kinetics of Li+. This electrolyte-design strategy based on electronic effect tuned ion-dipole interactions has notably increased the cycling stability of the LiFePO4||Li half-cell at −20 °C, that is, it not only increases the capacity by about 10 mAh g−1 at the rate of 0.2 C, but also maintains the capacity retention rate at 97.4 % after 100 cycles. This study reveals an important electrolyte design strategy at the molecular level.

Li-Fe-Cl Families as Novel Solid Electrolytes for All-Solid-State Batteries.

The halides have attracted much attention as novel solid electrolytes because of their easy synthesis, high electrochemical stability, and high ionic conductivities. However, the reported halides for solid electrolytes are still understudied compared with the oxides and sulfides. Here, we studied the Li-Fe-Cl phases that include Li2FeCl4 and Li6FeCl8. Using the self-doping approach, a maximum ionic conductivity of 2.0 × 10-4 S cm-1 at 50 °C was achieved for Li1.8Fe1.1Cl4. It was improved by 3 orders of magnitude compared with that of Li2FeCl4 (8.27 × 10-7 S cm-1 at 50 °C). For the Li|Li1.8Fe1.1Cl4|Li half-cell, it cycled for 2000 h at 50 °C under a current density of 0.01 mA cm-2, indicating an acceptable compatibility between Li2FeCl4 and Li. Finally, an all-solid-state battery was successfully assembled with Li1.8Fe1.1Cl4@LFP as the cathode, Li1.8Fe1.1Cl4 as the electrolyte, and a Li sheet as the anode. The initial specific charge capacity of the battery was 76.36 mAh g-1 at 0.1C and 50 °C. The initial Coulombic efficiency was 73.06%. This study suggests Li2FeCl4 as a new solid electrolyte, and the introduction of Li vacancies into the Li site is an efficient way to improve the electrochemical properties of halides.

Lamellar COF solid-state electrolytes for robust ambient-temperature lithium-ion transfer enhanced by PEI-driven channel alignment

Ionic covalent organic framework (COF) lamellar membranes are the alternative materials as promising Li+ conductors for all-solid-state lithium batteries. However, COF lamellar membrane suffers from poor structural stability and inevitable cross-layer transfer resistance due to the weak interaction at interface of adjacent nanosheets. Herein, a lamellar polymer-threaded ionic COF (PEI@TpPa-SO3Li) composite electrolyte with single Li+ conduction was prepared by assembling lithium sulfonated COF (TpPa-SO3Li) nanosheets and then threading them with polyethyleneimine (PEI) chains. It reveals that the threaded PEI chains induce the oriented permutation of pore channel of PEI@TpPa-SO3Li electrolyte through electrostatic interaction between –NH2/−NH− and –SO3Li groups. This enables the construction of continuous and aligned –SO3− … Li+ … −NH2/−NH− pairs along pore channels, which act as efficient Li+ conducting sites and afford high Li+ hopping conduction (1.4 × 10−4 S cm−1 at 30 °C) with a high Young's modulus of 408.7 MP and wide electrochemical stability window of 0∼4.7 V. The assembled LiFePO4||Li and LiNi0.8Mn0.1Co0.1O2||Li half-cells achieve high discharge capacities of 155.0 mAh g−1 and 167.2 mAh g−1 at 30 °C under 0.2 C, respectively, with high capacity retention of 98% after 300 cycles. This study provides an alternative route to highly ion-conductive lamellar porous electrolytes for high-performance energy devices.

Overlooked challenges of interfacial chemistry upon developing high energy density silicon anodes for lithium-ion batteries

Evaluation of silicon (Si) anode performance by the assembled Si||Li half-cells is the primary approach in the development of high-energy-density lithium-ion batteries (LIBs). However, most studies focus solely on the variations of Si anode, the stability of electrolyte on the lithium (Li)-metal counter electrode has been overlooked. Herein, we discovered that the acquired cell performance not only depends on the Li+ (de-)solvation behaviors on the Si anode surface but also was affected significantly by the lithiation overpotential caused by the side reactions on the Li electrode. It is significant to identify this point, as these influences of electrolyte decomposition on the Li electrode have been previously regarded as an integral part of side reactions on the Si anode. We proposed a new perspective of the electrolyte solvation structure and electrode interfacial model to unravel the interfacial behaviors on the Si and Li electrodes respectively. The identified differences in the Li+ solvation and (de-)solvation behaviors not only provide reasons for the varied electrolyte stability in different electrolytes but also interpret the superior performance in tetrahydrofuran (THF)-based electrolytes. This study underscores the importance of understanding electrolyte behavior at the interfaces of individual electrodes to discern the reliability of electrode performance and also introduce a novel principle for designing superior electrolytes for high-energy-density LIBs.

Inhibition of silicon-based anode interfacial volume expansion behavior by 1,3,6-hexane trinitrile additive via induced interfacial solvation effect

Silicon(Si)-based anodes exhibit higher energy density than traditional graphite anodes but suffer from significant volume changes during lithiation/delithiation, destabilizing the solid electrolyte interface (SEI) and reducing cycle stability. This study explores the effect of 1,3,6-hexane trinitrile (HTCN) on mitigating Si@C electrode expansion. The inclusion of HTCN modifies the original solvation structure of Li+, and the HTCN additive undergoes preferential coordination with Li+ because its binding energy with Li+ is larger than that of ethylene carbonate (EC). This lowers the lowest unoccupied molecular orbital (LUMO) of the HTCN-containing solvation structure, promoting preferential reduction decomposition on the anode surface. This process increases inorganic Li3N formation and produces a rich carbon-organic SEI film, effectively reducing electrolyte decomposition and Si@C anode expansion from 72.98 % to 4.46 %. Adding 1 % HTCN to Si@C/Li half-cells enhances capacity retention to 72.4 % after 100 cycles at 0.2C, significantly outperforming cells without HTCN (50.9 %). This study provides a new idea for constructing high-performance SEI films to inhibit electrode expansion by adjusting the solvation structure of Li+.

Engineering High-Performance Li Metal Batteries through Dual-Gradient Porous Cu-CuZn Host.

Porous copper (Cu) current collectors show promise in stabilizing Li metal anodes (LMAs). However, insufficient lithiophilicity of pure Cu and limited porosity in three-dimensional (3D) porous Cu structures led to an inefficient Li-Cu composite preparation and poor electrochemical performance of Li-Cu composite anodes. Herein, we propose a porous Cu-CuZn (DG-CCZ) host for Li composite anodes to tackle these issues. This architecture features a pore size distribution and lithiophilic-lithiophobic characteristics designed in a gradient distribution from the inside to the outside of the anode structure. This dual-gradient porous Cu-CuZn exhibits exceptional capillary wettability to molten Li and provides a high porosity of up to 66.05%. This design promotes preferential Li deposition in the interior of the porous structure during battery operation, effectively inhibiting Li dendrite formation. Consequently, all cell systems achieve significantly improved cycling stability, including Li half-cells, Li-Li symmetric cells, and Li-LFP full cells. When paired synergistically with the double-coated LiFePO4 cathode, the pouch cell configured with multiple electrodes demonstrates an impressive discharge capacity of 159.3 mAh g-1 at 1C. We believe this study can inspire the design of future 3D Li anodes with enhanced Li utilization efficiency and facilitate the development of future high-energy Li metal batteries.

Regulation of fiber surface nucleation kinetics via ordered nitrogen-rich carbon dots

Three dimensional (3D) carbon-based current collectors have attracted much attentions as host for Li metal anodes (LMAs) owing to their lightweight, flexible, and wide sources etc. However, the lithiophobic nature of carbon makes it difficult to achieve low nucleation overpotential and dendrite-free Li deposition. Herein, carbon dots (CDs) with nitrogen (N)-rich were introduced to modify carbonized cotton fiber (CCF) coated by reduced graphene oxide (CD@RGCCF). Coating graphene oxide (GO) increases the active site of cotton fiber (CF), which facilitates the growth of CDs on the surface of CF fiber. The introduction of ordered structure CDs drives fast migration of Li+ in the “highway-like” channels and induces the uniform nucleation of Li in the initial stage. As a result, the obtained CD@RGCCF decreases the nucleation overpotential of Li, and achieves dendrite-free Li deposition. the CD@RGCCF|Li half cells exhibit extending cycling life over 5000 h with a voltage hysteresis of 10.5 mV at 2 mA cm−2. As coupled with the LiFePO4 (LFP), the Li@CD@RGCCF||LFP composite anode enables a high reversible specific capacity and improved cycle stability. This work provides a low-cost modification method for carbon substrate to realize dendritic-free LMAs.

Diphenylphosphoryl Azide as a Multifunctional Flame Retardant Electrolyte Additive for Lithium-Ion Batteries

Graphite anode materials and carbonate electrolyte have been the top choices for commercial lithium-ion batteries (LIBS) for a long time. However, the uneven deposition and stripping of lithium cause irreversible damage to the graphite structure, and the low flash point and high flammability of the carbonate electrolyte pose a significant fire safety risk. Here, we proposed a multifunctional electrolyte additive diphenylphosphoryl azide (DPPA), which can construct a solid electrolyte interphase (SEI) with high ionic conductivity lithium nitride (Li3N) to ensure efficient transport of Li+. This not only protects the artificial graphite (AG) electrode but also inhibits lithium dendrites to achieve excellent electrochemical performance. Meanwhile, the LIBS with DPPA offers satisfactory flame retardancy performance. The AG//Li half cells with DPPA-0.5M can still maintain a specific capacity of about 350 mAh/g after 200 cycles at 0.2 C. Its cycle performance and rate performance were better than commercial electrolyte (EC/DMC). After cycling, the microstructure surface of the AG electrode was complete and flat, and the surface of the lithium metal electrode had fewer lithium dendrites. Importantly, we found that the pouch cell with DPPA-0.5M had low peak heat release rate. When exposed to external conditions of continuous heating, DPPA significantly improved the fire safety of the LIBS. The research of DPPA in lithium electrolyte is a step towards the development of safe and efficient lithium batteries.

Formulating compatible non-flammable electrolyte for lithium-ion batteries with ethoxy (pentafluoro) cyclotriphosphazene.

Lithium (Li) ion batteries have played a great role in modern society as being extensively used in commercial electronic products, electric vehicles, and energy storage systems. However, battery safety issues have gained growing concerns as there might be thermal runaway, fire or even explosion under external abuse. To tackle these safety issues, developing non-flammable electrolytes is a promising strategy. However, the balance between the flame-retarding effect and the electrochemical performance of electrolytes remains a great challenge. Herein, we evaluate the function of ethoxy (pentafluoro) cyclotriphosphazene (PFPN) as an effective flame-retarding additive for lithium-ion batteries. The flammability of electrolytes is greatly suppressed with the introduction of a small amount of PFPN. Moreover, PFPN exhibited excellent compatibility with LiFePO4 (LFP) cathode and graphite (Gr) anode, the electrochemical performances of LFP|Li and Gr|Li half cells are virtually unaffected. Scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) reveal the stable interphase between PFPN-containing electrolyte and LFP and Gr electrodes. Fourier transform infrared spectroscopy (FT-IR), Raman and nuclear magnetic resonance (NMR) spectra demonstrate the introduction of PFPN only exhibits negligible influence on the solvation structure of electrolyte. Benefiting from these merits of PFPN, the LFP|Gr cell shows desirable long-term cycling performance, which demonstrates great potential for practical application.

Reversible multielectron redox activity of the anti-NASICON-type phosphate LiNbV(PO4)3 towards lithium and sodium intercalation.

The LiNbV(PO4)3 phosphate with the anti-NASICON structure (a = 12.126(1) Å, b = 8.6158(4) Å, c = 8.6959(6) Å, V = 908.5(1) Å3, S.G. Pbcn) has been synthesized using a Pechini sol-gel process. It exhibits reversible multielectron transitions versus Li and Na anodes. In a Li half-cell, it supports a 4e- transfer due to the activation of the Nb5+/Nb3+ and V4+/V2+ redox couples, being the first example of 4d metal redox transitions within the anti-NASICON framework confirmed by XANES measurements. X-ray diffraction performed in ex situ and operando regimes disclosed a single-phase mechanism of lithium (de)intercalation. In a Na half-cell, the material demonstrates reversible uptake of 2.77 Na+ ions. Density functional theory calculations revealed percolation barriers of ∼0.5-0.7 eV for Na+ hopping, thus supporting the activation of Na+ ion diffusion in the NbV(PO4)3 framework. This study introduces a new approach to improve anti-NASICON-structured electrode materials by utilizing redox transitions of 4d elements for energy storage.

Synthesis, Structural and Electrochemical Investigation of Disordered Rock Salt Compounds Based on Ni and Ti

Li-ion batteries achieved in the last 3 decades extremely high energy densities, making them the energy storage devices of choice for the electrification of our society. Despite this improvement, their energy density is still low as compared to gasoline, motivating further research towards materials with better performances. State of the art positive electrodes are nowadays layered materials with a ratio Li:M of 1:1, with M being one or multiple transition metals. Disordered rock salt (DRX) materials without a layered structure were thought to be electrochemically inactive. With the development of the percolation theory, 1(Urban, Lee, and Ceder) it was demonstrated that lithium-rich materials (Li:M>1) with a cation disordered rock-salt structure (DRX) can achieve high reversible specific capacities. The general formula of these lithium-rich compounds can be written Li1+y(MM′)1−yO2 where the Li content ranges usually from 1.05 to 1.33, essential to promote Li percolation pathways. With M is indicated a redox active specie (Mn, Ni, Fe, Cr, V) and M’ is typically a d0 element, which is redox inactive during charge and discharge and therefore stabilizes the disordered structure and acting as charge compensator.2 (Chen, Ahn, and Chen)In this work a class of Li-rich compounds with the chemical composition Li2yNiyTi2-3yO2 has been investigated (y = 0.50, 0.55, 0.60, 0.67). These samples were prepared via solid-state reaction at three different temperatures (700 °C, 800 °C, 900 °C). X-ray diffraction has been used to determine the crystal structure of the samples, revealing a predominant rock salt-type phase. However, by decreasing the synthesis temperature and increasing the Li content, phase separation occurs into a rock salt-type and a Li2TiO3 phase. The synthesis has been also verified by DFT and by in situ X-ray diffraction. Neutron diffraction experiment have been carried out to fully understand the cationic distribution in the samples. Finally, the electrochemical performances of the samples have been investigated in Li half cells, revealing a strong voltage hysteresis between charge and discharge.3 (Li et al.) Bibliography Urban, Alexander, Jinhyuk Lee, and Gerbrand Ceder. “The Configurational Space of Rocksalt-Type Oxides for High-Capacity Lithium Battery Electrodes.” Advanced Energy Materials 4, no. 13 (September 2014): 1400478. https://doi.org/10.1002/aenm.201400478.Chen, Dongchang, Juhyeon Ahn, and Guoying Chen. “An Overview of Cation-Disordered Lithium-Excess Rocksalt Cathodes.” ACS Energy Letters, March 17, 2021, 1358–76. https://doi.org/10.1021/acsenergylett.1c00203.Li, Biao, Khagesh Kumar, Indrani Roy, Anatolii V. Morozov, Olga V. Emelyanova, Leiting Zhang, Tuncay Koç, et al. “Capturing Dynamic Ligand-to-Metal Charge Transfer with a Long-Lived Cationic Intermediate for Anionic Redox.” Nature Materials 21, no. 10 (October 2022): 1165–74. https://doi.org/10.1038/s41563-022-01278-2

Uniform Li-metal growth on renewable lignin with lithiophilic functional groups derived from wood for high-performance Li-metal batteries

Lithium metal batteries (LMBs) are promising energy storage devices with high energy density owing to their high theoretical capacity (3860 mAh g−1) and low reduction potential of lithium (Li)-metal anodes. However, their practical application is limited by poor Coulombic efficiency (CE) and safety issues due to Li dendrite growth during Li plating/stripping. Herein, a three-dimensional (3D) structure of lignin with a lithiophilic functional group derived from waste wood is suggested as an additional functional layer of LMBs, i.e., a lignosulfonic acid sodium salt (LASS) with a negatively charged sulfonate group (SO3−) in its chemical structure. The SO3− group enhances the Li-ion (Li+) affinity and enables Li+-flux control, supplying homogeneous Li growth sites. It induces stable electrochemical dendrite-free Li growth. Consequently, in the LASS-Cu||Li half-cell, a high CE of 96.7 % at 210 cycles and stable operation is achieved without a short circuit and, symmetric-cell with LASS layers shows stable cycling over 2000 h. Moreover, full-cells with LiFePO4 (LFP) and LiNi0.8Co0.1Mn0.1O2 (NCM 811) cathodes exhibit enhanced electrochemical performance. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) reveal that the LASS layer suppressed dendritic Li growth and stimulated densely packed Li growth. This work suggests an effective strategy for improving the performance of LMBs using renewable lignin materials.

Building a Flexible and Highly Ionic Conductive Solid Electrolyte Interphase on the Surface of Si@C Anodes by Binary Electrolyte Additives.

Si@C as a high specific capacity anode material for lithium batteries (LIBs) has attracted a lot of attention. However, the severe volume change during lithium de-embedding causes repeated rupture/reconstruction of the solid electrolyte interphase (SEI), resulting in poor cycling stability of the Si-based battery system and thus hindering its application in commercial batteries. Using electrolyte additives to form an excellent SEI is considered to be a cost-effective method to meet this challenge. Here, the classical film-forming additive vinyl carbonate (VC), and the newly emerging lithium salt additive lithium difluorophosphate (LiDFP), are chosen as synergistic additives to improve the electrode-electrolyte interface properties. Final results show that the VC additive generates flexible polycarbonate components at the electrode/electrolyte interface, preventing the fragmentation of Si particles. However, the organic components show high impedance, inhibiting the fast transport of Li+. This defect can be supplemented from the decomposition substances of the LiDFP additive. The derived inorganic products, such as LiF and Li3PO4, can strengthen the reaction kinetics of the electrode, reduce the interfacial impedance, and promote the Li+ transport. Thus, the synergistic effect of VC and LiDFP additives builds an effective SEI with good flexibility and high ionic conductivity and then significantly improves the cycling and rate stability of Si@C anodes. The experimental results show that the utilization of LiDFP and VC additives to modify the Si@C anode interface enhances the capacity retention of the Si@C/Li half-cell after 100 cycles from 68.2% to 85.1%. Besides, the possible mechanism of action between VC and LiDFP is proposed by using the spectral characterization technique and density functional theory (DFT) calculations. This research opens up a new possibility for improvement of SEI, and provides a simple way to achieve high-performance Si-based LIBs.

Gel electrolyte and anode material derived from electro-spun polyacrylonitrile/polysilsesquioxane composite and application in advanced lithium-ion batteries

The aim of this work is to improve the comprehensive performance of Lithium-ion batteries (LIBs) by designing and fabricating novel polymer electrolyte. A flexible film composed of electro-spun polyacrylonitrile/1,2-ethylidene-bridged polysilsesquioxane composite nanofibers (PAN@ee-PSiO) was synthesized via a sol–gel method, and then used as scaffold to absorb organic electrolyte to make gel electrolyte membrane (PAN@ee-PSiO-GE). It presents high electrolyte uptake (472 wt%), thermal stability (up to ∼300 °C), high ionic conductivity (∼7.2 mS cm−1 at room temperature) and excellent interfacial contact with Li metal electrodes. Meanwhile, Si/SiC/C composite nanofibers (SSCNFs) were also produced from PAN/ee-PSiO film by magnesiothermic reduction and could act as anode material. The assembled SSCNFs|PAN@ee-PSiO-GE|Li half-cell exhibits excellent rate capability and good cycling stability, indicating a new way for designing and fabricating safer high-performance LIBs.

Enabling high rate capability and stability all-solid-state batteries via cationic surfactant modification of composite electrolyte

The garnet-type solid electrolyte Li6.4La3Zr1.4Ta0.6O12 (LLZTO) was modified with a cationic surfactant Cetyltrimethylammonium Bromide (CTAB) to improve the dispersion of LLZTO inorganic particles in Poly (ethylene oxide) (PEO) electrolyte (PEO-LLZTO@CTAB) by a liquid phase casting method. During fabrication, the cationic modifier CTAB is uniformly adsorbed on the surface of LLZTO particles, which can effectively reduce their surface energy and lead to a thin CTAB surface coating layer. This fabricated PEO-LLZTO@CTAB can avoid the aggregation of LLZTO particles in the composite solid-state electrolyte (CSSE) and improve the interfacial contact at the PEO/LLZTO interface, thus reducing the overall resistance of PEO-LLZTO@CTAB/Li half-cell and inhibiting the dendrite growth during cycling. The all-solid-state batteries (ASSBs) with LiFePO4 (LFP) as the cathode, PEO-LLZTO@CTAB as the electrolyte and Li as the anode exhibit a high initial discharge capacity of 146.6 mAh-g−1, excellent rate performance and high-capacity retention of 91.0 % after 300 cycles at 0.2 C multiplier and 60 °C within the voltage range of 2.7–4.0 V.

Fabrication of Composite Gel Electrolyte and F-Doping Carbon/Silica Anode from Electro-Spun P(VDF-HFP)/Silica Composite Nanofiber Film for Advanced Lithium-Ion Batteries.

The aim of this work is to effectively combine the advantages of polymer and ceramic nanoparticles and improve the comprehensive performance of lithium-ion batteries (LIBs) diaphragm. A flexible film composed of electro-spun P(VDF-HFP) nanofibers covered by a layer of mesoporous silica (P(VDF-HFP)@SiO2) was synthesized via a sol-gel transcription method, then used as a scaffold to absorb organic electrolyte to make gel a electrolyte membrane (P(VDF-HFP)@SiO2-GE) for LIBs. The P(VDF-HFP)@SiO2-GE presents high electrolyte uptake (~1000 wt%), thermal stability (up to ~350 °C), ionic conductivity (~2.6 mS cm-1 at room temperature), and excellent compatibility with an active Li metal anode. Meanwhile, F-doping carbon/silica composite nanofibers (F-C@SiO2) were also produced by carbonizing the P(VDF-HFP)@SiO2 film under Ar and used to make an electrode. The assembled F-C@SiO2|P(VDF-HFP)@SiO2-GE|Li half-cell showed long-cycle stability and a higher discharge specific capacity (340 mAh g-1) than F-C@SiO2|Celgard 2325|Li half-cell (175 mAh g-1) at a current density of 0.2 A g-1 after 300 cycles, indicating a new way for designing and fabricating safer high-performance LIBs.

Catalytic Chemistry Derived Artificial Solid Electrolyte Interphase for Stable Lithium Metal Anodes Working at 20 mA cm-2 and 20 mAh cm-2.

A stable solid electrolyte interphase (SEI) layer is crucial for lithium metal anode (LMA) to survive in long-term cycling. However, chaotic structures and chemical inhomogeneity of natural SEI make LMA suffering from exasperating dendrite growth and severe electrode pulverization, which hinder the practical application of LMAs. Here, we design a catalyst-derived artificial SEI layer with an ordered polyamide-lithium hydroxide (PA-LiOH) bi-phase structure to modulate ion transport and enable dendrite-free Li deposition. The PA-LiOH layer can substantially suppress the volume changes of LMA during Li plating/stripping cycles, as well as alleviate the parasitic reactions between LMA and electrolyte. The optimized LMAs demonstrate excellent stability in Li plating/stripping cycles for over 1000 hours at an ultra-high current density of 20 mA cm-2 in Li||Li symmetric cells. A high coulombic efficiency up to 99.2 % in Li half cells in additive-free electrolytes is achieved even after 500 cycles at a current density of 1 mA cm-2 with a capacity of 1 mAh cm-2 .

Catalytic Chemistry Derived Artificial Solid Electrolyte Interphase for Stable Lithium Metal Anodes Working at 20 mA cm−2 and 20 mAh cm−2

AbstractA stable solid electrolyte interphase (SEI) layer is crucial for lithium metal anode (LMA) to survive in long‐term cycling. However, chaotic structures and chemical inhomogeneity of natural SEI make LMA suffering from exasperating dendrite growth and severe electrode pulverization, which hinder the practical application of LMAs. Here, we design a catalyst‐derived artificial SEI layer with an ordered polyamide‐lithium hydroxide (PA‐LiOH) bi‐phase structure to modulate ion transport and enable dendrite‐free Li deposition. The PA‐LiOH layer can substantially suppress the volume changes of LMA during Li plating/stripping cycles, as well as alleviate the parasitic reactions between LMA and electrolyte. The optimized LMAs demonstrate excellent stability in Li plating/stripping cycles for over 1000 hours at an ultra‐high current density of 20 mA cm−2 in Li||Li symmetric cells. A high coulombic efficiency up to 99.2 % in Li half cells in additive‐free electrolytes is achieved even after 500 cycles at a current density of 1 mA cm−2 with a capacity of 1 mAh cm−2.

Binder-free boron-doped Si nanowires toward the enhancement of lithium-ion capacitor

Lithium-ion capacitors (LICs) are next-generation electrochemical storage devices that combine the benefits of both supercapacitors and lithium-ion batteries. Silicon materials have attracted attention for the development of high-performance LICs owing to their high theoretical capacity and low delithiation potential (∼0.5 V versus Li/Li+). However, sluggish ion diffusion has severely restricted the development of LICs. Herein, a binder-free anode of boron-doped silicon nanowires (B-doped SiNWs) on a copper substrate was reported as an anode for LICs. B-doping could significantly improve the conductivity of the SiNW anode, which could enhance electron/ion transfer in LICs. As expected, the B-doped SiNWs//Li half-cell delivered a higher initial discharge capacity of 454 mAh g−1 with excellent cycle stability (capacity retention of 96% after 100 cycles). Furthermore, the near-lithium reaction plateau of Si endows the LICs with a high voltage window (1.5–4.2 V), and the as-fabricated B-doped SiNWs//AC LIC possesses the maximum energy density value of 155.8 Wh kg−1 at a battery-inaccessible power density of 275 W kg−1. This study provides a new strategy for using Si-based composites to develop high-performance LIC.

High-performance honeycombed FeF3@C cathodes enabling practical lithium pouch cells and silicon−metal fluoride batteries

Metal fluoride cathodes are promising candidates for next-generation rechargeable lithium metal batteries (LMBs). However, the sluggish reaction kinetics limits their electrochemical applications, especially at high mass loadings. Moreover, current designs on fluoride cathodes hardly achieve the related practical pouch cells and full cells. A honeycombed FeF3@C nanocomposite with high specific surface area (SSA) of 191.6 m2 g−1, is successfully synthesized herein, where the nanosized FeF3 particles (less than 40 nm) are uniformly embedded in the honeycombed carbon matrix. Benefiting from the unique configuration, it can provide an efficient mixed Li+/e− conduction networks then enable excellent lithium storage performance under three-electron transfer reaction even at high mass loadings. The high-loading honeycombed FeF3@C (∼3.5 mg cm−2) cathode offers a reversible specific capacity of 369.9 mAh g−1 after 500 cycles in a Li half-cell, corresponding to noticeable areal capacity of ∼1.25 mAh cm−2. In order to further investigate their practical applications, as-produced FeF3@C−Li pouch cell is constructed, delivering average nominal capacity of ∼50 mAh per cycle. Furthermore, the FeF3−prelithiated Si (PLSi) full cell is produced for the first time, demonstrating cycle life over 200 cycles and rate capability up to 5C. Notably, the as-produced cathodes show partially reversible phase transition during discharge/charge, which offers abundant fresh phase interface, contributing to growing pseudocapacitance and Li+ migration ability as the cycle proceeds. The pseudocapacitance compensates for lost capacity caused by incompletely reversible phase transition, and enables superior electrochemical properties.