Enhanced Cycling Stability of Rechargeable Li–O2 Batteries Using High‐Concentration Electrolytes

The stability of electrolytes against highly reactive, reduced oxygen species is crucial for the development of rechargeable Li–O₂ batteries. In this work, the effect of lithium salt concentration in 1,2‐dimethoxyethane (DME)‐based electrolytes on the cycling stability of Li–O₂ batteries is investigated systematically. Cells with highly concentrated electrolyte demonstrate greatly enhanced cycling stability under both full discharge/charge (2.0–4.5 V vs Li/Li⁺) and the capacity‐limited (at 1000 mAh g^?1) conditions. These cells also exhibit much less reaction residue on the charged air‐electrode surface and much less corrosion of the Li‐metal anode. Density functional theory calculations are used to calculate molecular orbital energies of the electrolyte components and Gibbs activation energy barriers for the superoxide radical anion in the DME solvent and Li⁺–(DME) _n solvates. In a highly concentrated electrolyte, all DME molecules are coordinated with salt cations, and the C–H bond scission of the DME molecule becomes more difficult. Therefore, the decomposition of the highly concentrated electrolyte can be mitigated, and both air cathodes and Li‐metal anodes exhibit much better reversibility, resulting in improved cyclability of Li–O₂ batteries.     

Enabling Stable Cycling of 4.2 V High‐Voltage All‐Solid‐State Batteries with PEO‐Based Solid Electrolyte

Poly(ethylene oxide) (PEO)‐based solid electrolytes are expected to be exploited in solid‐state batteries with high safety. Its narrow electrochemical window, however, limits the potential for high voltage and high energy density applications. Herein the electrochemical oxidation behavior of PEO and the failure mechanisms of LiCoO₂‐PEO solid‐state batteries are studied. It is found that although for pure PEO it starts to oxidize at a voltage of above 3.9 V versus Li/Li⁺, the decomposition products have appropriate Li⁺ conductivity that unexpectedly form a relatively stable cathode electrolyte interphase (CEI) layer at the PEO and electrode interface. The performance degradation of the LiCoO₂‐PEO battery originates from the strong oxidizing ability of LiCoO₂ after delithiation at high voltages, which accelerates the decomposition of PEO and drives the self‐oxygen‐release of LiCoO₂, leading to the unceasing growth of CEI and the destruction of the LiCoO₂ surface. When LiCoO₂ is well coated or a stable cathode LiMn_0.7Fe_0.3PO₄ is used, a substantially improved electrochemical performance can be achieved, with 88.6% capacity retention after 50 cycles for Li_1.4Al_0.4Ti_1.6(PO₄)₃ coated LiCoO₂ and 90.3% capacity retention after 100 cycles for LiMn_0.7Fe_0.3PO₄. The results suggest that, when paired with stable cathodes, the PEO‐based solid polymer electrolytes could be compatible with high voltage operation.     

High‐Power Lithium Metal Batteries Enabled by High‐Concentration Acetonitrile‐Based Electrolytes with Vinylene Carbonate Additive

To enable next‐generation high‐power, high‐energy‐density lithium (Li) metal batteries (LMBs), an electrolyte possessing both high Li Coulombic efficiency (CE) at a high rate and good anodic stability on cathodes is critical. Acetonitrile (AN) is a well‐known organic solvent for high anodic stability and high ionic conductivity, yet its application in LMBs is limited due to its poor compatibility with Li metal anodes even at high salt concentration conditions. Here, a highly concentrated AN‐based electrolyte is developed with a vinylene carbonate (VC) additive to suppress Li⁺ depletion at high current densities. Addition of VC to the AN‐based electrolyte leads to the formation of a polycarbonate‐based solid electrolyte interphase, which minimizes Li corrosion and leads to a very high Li CE of up to 99.2% at a current density of 0.2 mA cm^‐2. Using such an electrolyte, fast charging of Li||NMC333 cells is realized at a high current density of 3.6 mA cm^‐2, and stable cycling of Li||NMC622 cells with a high cathode loading of 4 mAh cm^‐2 is also demonstrated.     

Enhanced Interfacial Stability of Hybrid‐Electrolyte Lithium‐Sulfur Batteries with a Layer of Multifunctional Polymer with Intrinsic Nanoporosity

The use of lithium‐ion conductive solid electrolytes offers a promising approach to address the polysulfide shuttle and the lithium‐dendrite problems in lithium‐sulfur (Li‐S) batteries. One critical issue with the development of solid‐electrolyte Li‐S batteries is the electrode–electrolyte interfaces. Herein, a strategic approach is presented by employing a thin layer of a polymer with intrinsic nanoporosity (PIN) on a Li⁺‐ion conductive solid electrolyte, which significantly enhances the ionic interfaces between the electrodes and the solid electrolyte. Among the various types of Li⁺‐ion solid electrolytes, NASICON‐type Li_1+xAl_xTi_2‐x(PO₄)₃ (LATP) offers advantages in terms of Li⁺‐ion conductivity, stability in ambient environment, and practical viability. However, LATP is susceptible to reaction with both the Li‐metal anode and polysulfides in Li‐S batteries due to the presence of easily reducible Ti⁴⁺ ions in it. The coating with a thin layer of PIN presented in this study overcomes the above issues. At the negative‐electrode side, the PIN layer prevents the direct contact of Li‐metal with the LATP solid electrolyte, circumventing the reduction of LATP by Li metal. At the positive electrode side, the PIN layer prevents the migration of polysulfides to the surface of LATP, preventing the reduction of LATP by polysulfides.     

Metal Organic Framework Derivative Improving Lithium Metal Anode Cycling

This work demonstrates a new approach in using metal organic framework (MOF) materials to improve Li metal batteries, a burgeoning rechargeable battery technology. Instead of using the MIL‐125‐Ti MOF structure directly, the material is decomposed into intimately‐mixed amorphous titanium dioxide and crystalline terephthalic acid. The resulting composite material outperforms the oxide alone, the organic component alone, and the parent MOF in suppressing Li dendrite growth and extending cycle life of Li metal electrodes. Coated on a commercial polypropylene separator, this material induces the formation of a desirable solid electrolyte interphase layer comprising mechanically flexible organic species and ionically conductive lithium nitride species, which in turn leads to Li||Cu and Li||Li cells that can stably operate for hundreds of charging–discharging cycles. In addition, this material strongly adsorbs lithium polysulfides and can also benefit the cathode of lithium–sulfur batteries.     

Constructing a High‐Strength Solid Electrolyte Layer by In Vivo Alloying with Aluminum for an Ultrahigh‐Rate Lithium Metal Anode

The serious safety issues caused by uncontrollable lithium (Li) dendrite growth, especially at high current densities, seriously hamper the rapid charging of Li metal‐based batteries. Here, the construction of Al–Li alloy/LiCl‐based Li anode (ALA/Li anode) is reported by displacement and alloying reaction between an AlCl₃‐ionic liquid and a Li foil. This layer not only has high ion‐conductivity and good electron resistivity but also much improved mechanical strength (776 MPa) as well as good flexibility compared to a common solid electrolyte interphase layer (585 MPa). The high mechanical strength of the Al–Li alloy interlayer effectively eliminates volume expansion and dendrite growth in Li metal batteries, so that the ALA/Li anode achieves superior cycling for 1600 h (2.0 mA cm^?2) and 1000 cycles at an ultrahigh current density (20 mA cm^?2) without dendrite formation in symmetric batteries. In lithium–sulfur batteries, the dense alloy layer prevents direct contact between polysulfides and Li metal, inhibiting the shuttle effect and electrolyte decomposition. Long cycling performance is achieved even at a high current density (4 C) and a low electrolyte/sulfur (6.0 µL mg^?1). This easy fabrication process provides a strategy to realize reliable safety during the rapid charging of Li‐metal batteries.     

Electro–Chemo–Mechanical Issues at the Interfaces in Solid‐State Lithium Metal Batteries

Effective solid‐state interfacial contact of both the cathode and lithium metal anode with the solid electrolyte (SE) are required to improve the performance of solid‐state lithium metal batteries (SSBs). Electro–chemo–mechanical coupling (ECMC) strongly affects the interfacial stability of SSBs. On one hand, mechanical stress strongly influences interfacial contact and causes side reactions. On the other hand, electrochemical reactions such as lithium deposition cause mechanical deformation and stress at electrode/SE interfaces. To solve the degradation/failure problems of interfaces and provide guidelines to construct high‐performance SSBs, the ECMC at electrode/SE interfaces should be comprehensively investigated. In this review, the problems associated with ECMC at electrode/SE interfaces are summarized. The interfacial degradation/failure mechanisms, including the contact and electrochemical stability of interfaces, are introduced. Mechanical factors affecting interfacial contact and lithium deposition are highlighted. Experimental observation and computational analysis methods for electrode/SE interfaces are then summarized. Strategies to construct stable electrode/SE interfaces, such as assembling stress and wetting layers to improve interfacial contact, 3D SE structure, and plating stress relief to suppress lithium dendrite formation, are reviewed. The remaining challenges to better understanding ECMC and related solutions to aid SSB development are discussed.     

High Lithium Ion Conductivity LiF/GO Solid Electrolyte Interphase Inhibiting the Shuttle of Lithium Polysulfides in Long‐Life Li–S Batteries

The “shuttle effect” that stems from the dissolution of polysulfides is the most fatal issue affecting the cycle life of lithium‐sulfur (Li–S) batteries. In order to suppress the “shuttle effect,” a new strategy of using a highly lithium ion conductive lithium fluoride/graphene oxide (LiF/GO) solid electrolyte interphase (SEI) to mechanically prevent the lithium dendrite breakthrough is reported. When utilized in Li–S batteries, the LiF/GO SEI coated separator demonstrates significant feature in mitigating the polysulfide shuttling as observed by in situ UV–vis spectroscopy. Moreover, the restrained “shuttle effect” can also be confirmed by analysis of electrochemical impedance spectroscopy and characterization of lithium dendrites, which indicates that no insulating layer of solid Li₂S₂/Li₂S is found on lithium anode surface. Furthermore, the LiF/GO SEI layer puts out good lithium ion conductivity as its lithium ion diffusion coefficient reaches a high value of 1.5 × 10^?7 cm² s^?1. These features enable a remarkable cyclic property of 0.043% of capacity decay per cycle during 400 cycles.     

3D Carbonaceous Current Collectors: The Origin of Enhanced Cycling Stability for High‐Sulfur‐Loading Lithium–Sulfur Batteries

The cycling stability of high‐sulfur‐loading lithium–sulfur (Li–S) batteries remains a great challenge owing to the exaggerated shuttle problem and interface instability. Despite enormous efforts on design of advanced electrodes and electrolytes, the stability issue raised from current collectors has been rarely concerned. This study demonstrates that rationally designing a 3D carbonaceous macroporous current collector is an efficient and effective “two‐in‐one” strategy to improve the cycling stability of high‐sulfur‐loading Li–S batteries, which is highly versatile to enable various composite cathodes with sulfur loading >3.7 mAh cm^?2. The best cycling performance can be achieved upon 950 cycles with a very low decay rate of 0.029%. Moreover, the origin of such a huge enhancement in cycling stability is ascribed to (1) the inhibition of electrochemical corrosion, which severely occurs on the typical Al foil and disables its long‐term sustainability for charge transfer, and (2) the passivation of cathode surface. The role of the chemical resistivity against corrosion and favorable macroscopic porous structure is highlighted for exploiting novel current collectors toward exceptional cycling stability of high‐sulfur‐loading Li–S batteries.     

A LiF Nanoparticle‐Modified Graphene Electrode for High‐Power and High‐Energy Lithium Ion Batteries

Surface modification of carbon materials plays an important role in tailoring carbon surface chemistry to specify their electrochemical performance. Here, a surface modification strategy for graphene is proposed to produce LiF‐nanoparticle‐modified graphene as a high‐rate, large‐capacity pre‐lithiated electrode for high‐power and high‐energy lithium ion batteries. The LiF nanoparticles covering the active sites of the graphene surface provide an extra Li source and act as an effective solid electrolyte interphase (SEI) inhibiter to suppress LiFP₆ electrolyte decomposition reactions, affect SEI components, and reduce their thickness. Consequently, the Li‐ion diffusion is greatly sped up and the thermodynamic stability of the electrode is significantly improved. This modified graphene electrode shows excellent rate capability and improved first‐cycle coulombic efficiency, cycling stability, and ultrahigh power and energy densities accessible during fast charge/discharge processes.     

Facile Solid‐State Growth of 3D Well‐Interconnected Nitrogen‐Rich Carbon Nanotube–Graphene Hybrid Architectures for Lithium–Sulfur Batteries

Constructing 3D carbon structures built from carbon nanotubes (CNTs) and graphene has been considered as an effective approach to achieve superior properties in energy conversion and storage because of the synergistic combination of the advantages of each building block. Herein, a facile solid‐state growth strategy is reported for the first time to fabricate highly nitrogen doped CNT–graphene 3D nanostructures without the necessity to use chemical vapor deposition. As cathode hosts for lithium–sulfur batteries, the hybrid architectures exhibit reversible capacities of 1314 and 922 mAh g^?1 at 0.2 and 1 C, respectively, and a capacity retention of 97% after 200 cycles at a high rate of 2 C, revealing their great potential for energy storage application.     

Copper‐Stabilized Sulfur‐Microporous Carbon Cathodes for Li–S Batteries

A copper‐stabilized sulfur‐microporous carbon ( MC‐Cu‐S) composite is synthesized by uniformly dispersing 10% highly electronically conductive Cu nanoparticles into microporous carbon (MC), followed by wet‐impregnating S. In the MC‐Cu‐S composite, the MC host that physically confines S/polysulfides provides free space to accommodate volumetric expansion of S during lithiation, while the Cu nanoparticles that are anchored in the MC further chemically interact with S/polysulfides through bonding between Cu and S/polysulfides. The Cu loading allows the S content to increase from 30 to 50% in the carbon‐S cathode material without scarifying the electrochemical performance in a low‐cost carbonate electrolyte. At a current density of 100 mA g^‐1, the MC‐Cu‐S cathode shows that Coulumbic efficiency is close to 100% and capacity maintains more than 600 mAh g^‐1 with progressive cycling up to more than 500 cycles. In addition, the Cu nano‐inclusins also enhance the electronic conductivity of the MC‐Cu‐S composite, remarkably increasing the rate capabilities. Even the current density increases 10.0 A g^‐1, the MC‐Cu‐S cathode can still deliver a capacity of 200 mAh g^‐1. This strategy of stabilization of S with small amount of metal nanoparticles anchored in MC provides an effective approach to improve the cycling stability, Coulumbic efficiency, and S loading for Li–S batteries.     

Surface Reconstruction Limited Conductivity in Block‐Copolymer Li Battery Electrolytes

Solid polymer electrolytes for lithium batteries promise improvements in safety and energy density if their conductivity can be increased. Nanostructured block‐copolymer electrolytes specifically have the potential to provide both good ionic conductivity and good mechanical properties. This study shows that the previously neglected nanoscale composition of the polymer electrolyte close to the electrode surface has an important effect on impedance measurements, despite its negligible extent compared to the bulk electrolyte. Using standard stainless steel blocking electrodes, the impedance of lithium salt‐doped poly(isoprene‐b‐styrene‐b‐ethylene oxide) (ISO) exhibits a marked decrease upon thermal processing of the electrolyte. In contrast, covering the electrode surface with a low molecular weight poly(ethylene oxide) (PEO) brush results in higher and more reproducible conductivity values, which are insensitive to the thermal history of the device. A qualitative model of this effect is based on the hypothesis that ISO surface reconstruction at the different electrode surfaces leads to a change in the electrostatic double layer, affecting electrochemical impedance spectroscopy measurements. As a main result, PEO‐brush modification of electrode surfaces is beneficial for the robust electrolyte performance of PEO‐containing block‐copolymers and may be crucial for their accurate characterization and use in Li‐ion batteries.     

A High‐Performance Li–B–H Electrolyte for All‐Solid‐State Li Batteries

Highly Li‐ion conductive Li₄(BH₄)₃I@SBA‐15 is synthesized by confining the LiI doped LiBH₄ into mesoporous silica SBA‐15. Uniform nanoconfinement of P6₃ mc phase Li₄(BH₄)₃I in SBA‐15 mesopores leads to a significantly enhanced conductivity of 2.5 × 10^?4 S cm^?1 with a Li‐ion transference number of 0.97 at 35 °C. The super Li‐ion mobility in the interface layer with a thickness of 1.2 nm between Li₄(BH₄)₃I and SBA‐15 is believed to be responsible for the fast Li‐ion conduction in Li₄(BH₄)₃I@SBA‐15. Additionally, Li₄(BH₄)₃I@SBA‐15 also exhibits a wide apparent electrochemical stability window (0 to 5 V vs Li/Li⁺) and a superior Li dendrite suppression capability (critical current density 2.6 mA cm^?2 at 55 °C) due to the formation of stable interphases. More importantly, Li₄(BH₄)₃I@SBA‐15‐based Li batteries using either high‐capacity sulfur cathode or high‐voltage oxide cathode show excellent electrochemical performances, making Li₄(BH₄)₃I@SBA‐15 a very attractive electrolyte for next‐generation all‐solid‐state Li batteries.     

Bimetal–Organic Framework: One‐Step Homogenous Formation and its Derived Mesoporous Ternary Metal Oxide Nanorod for High‐Capacity,High‐Rate,and Long‐Cycle‐Life Lithium Storage

Metal–organic frameworks (MOFs) and relative structures with uniform micro/mesoporous structures have shown important applications in various fields. This paper reports the synthesis of unprecedented mesoporous Ni_xCo_3?xO₄ nanorods with tuned composition from the Co/Ni bimetallic MOF precursor. The Co/Ni‐MOFs are prepared by a one‐step facile microwave‐assisted solvothermal method rather than surface metallic cation exchange on the preformed one‐metal MOF template, therefore displaying very uniform distribution of two species and high structural integrity. The obtained mesoporous Ni_0.3Co_2.7O₄ nanorod delivers a larger‐than‐theoretical reversible capacity of 1410 mAh g^?1 after 200 repetitive cycles at a small current of 100 mA g^?1 with an excellent high‐rate capability for lithium‐ion batteries. Large reversible capacities of 812 and 656 mAh g^?1 can also be retained after 500 cycles at large currents of 2 and 5 A g^?1, respectively. These outstanding electrochemical performances of the ternary metal oxide have been mainly attributed to its interconnected nanoparticle‐integrated mesoporous nanorod structure and the synergistic effect of two active metal oxide components.     

Solid‐State Plastic Crystal Electrolytes: Effective Protection Interlayers for Sulfide‐Based All‐Solid‐State Lithium Metal Batteries

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.     

Solid‐State Lithium–Sulfur Battery Enabled by Thio‐LiSICON/Polymer Composite Electrolyte and Sulfurized Polyacrylonitrile Cathode

Solid‐state lithium–sulfur battery (SSLSB) is attractive due to its potential for providing high energy density. However, the cell chemistry of SSLSB still faces challenges such as sluggish electrochemical kinetics and prominent “chemomechanical” failure. Herein, a high‐performance SSLSB is demonstrated by using the thio‐LiSICON/polymer composite electrolyte in combination with sulfurized polyacrylonitrile (S/PAN) cathode. Thio‐LiSICON/polymer composite electrolyte, which processes high ionic conductivity and wettability, is fabricated to enhance the interfacial contact and the performance of lithium metal anodes. S/PAN is utilized due to its unique electrochemical characteristics: electrochemical and structural studies combined with nuclear magnetic resonance spectroscopy and electron paramagnetic resonance characterizations reveal the charge/discharge mechanism of S/PAN, which is the radical‐mediated redox reaction within the sulfur grafted conjugated polymer framework. This characteristic of S/PAN can support alleviating the volume change in the cathode and maintaining fast redox kinetics. The assembled SSLSB full cell exhibits excellent rate performance with 1183 mAh g^?1 at 0.2 C and 719 mAh g^?1 at 0.5 C, respectively, and can accomplish 50 cycles at 0.1 C with the capacity retention of 588 mAh g^?1. The superior performance of the SSLSB cell rationalizes the construction concept and leads to considerations for the innovative design of SSLSB.     

In Batteria Electrochemical Polymerization to Form a Protective Conducting Layer on Se/C Cathodes for High‐Performance Li–Se Batteries

The lithium–selenium (Li–Se) battery is a promising energy storage system for portable devices owing to its high energy density (2528 Wh L^?1) and electrical conductivity (10^?3 S m^?1). The main issue with Li–Se batteries is their poor stability originating from the dissolution of Se‐containing compounds. Hence, many studies have focused on the immobilization of Se using protective layers prepared via ex situ or in situ approaches. However, these strategies are too complicated and costly for practical use. Herein, a facile in batteria electrochemical treatment to form a protective conductive layer on a Se‐based cathode is introduced. Specifically, aniline monomers added to an assembled Li–Se cell are polymerized into electrically conductive polyaniline. The treated Li–Se cell exhibits 40% higher capacity retention compared to untreated one. Moreover, at a high rate (4 C), the treated cell maintains a capacity of 1538 mAh cm^?3, whereas the untreated cell exhibits no capacity. The enhanced cyclic stability and rate capability are attributed to the electrochemical formation of a uniform, ultrathin (≤10 nm) polyaniline layer, to confine lithium polyselenides with its C?N bonds, and improve ionic conductivity by self‐doping with lithium salts to form delocalized polaron lattice in the polyaniline.