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The formation of H2O molecules competitively solvating Mg-ion solvation structures and their decomposition in electrochemical and/or chemical reaction pathways with inherent H2O ligands result in dendritic and passivated electrodeposition.

For dilute electrolyte, more solvent decomposition during Li+ stripping process leads to inferior interface. Whereas the concentrated electrolyte possesses preferable interfacial stability due to relatively stable Li+–solvent interaction evolution.

As a promising component for next-generation high energy lithium-ion batteries, silicon based electrode has attracted increasing attention by virtue of ultrahigh theoretical specific capacities. Nevertheless, fast capacity fade posed by tremendous volume changes during the lithiation and delithiation process remains a huge challenge before large-scale applications. Inspired by spidroin, we herein develop a tenacious hierarchical structure binder for tolerating huge volume change of silicon-based anode, which is prepared through simply mixing aqueous poly(acrylic acid) solution, and oily N-methyl pyrrolidone solution containing a tetrazole groups based copolymer (PPB) of polyacrylonitrile and poly(ethylene glycol) bisazide. Such an aqueous-oil binary solution based blend (AOB) binder exhibits a spidroin-like hierarchical structure. In the AOB binder, hydrophobic PPB polymer condensates in the mixture solution to form crystalline region within submicron-sized irregular spherical domains as the rigid node of the molecular chain segment similar to β-sheet of spidroin; while water-souble, amorphous poly(acrylic acid) mimicks the α-helix structure of spidroin, and builds up a network structure by linking with PPB via ionic bonding similar to the interactions between repetitive amino acid sequence segment in the primary structure of spidroin. Benefited by these, AOB binder enables both high tensile strength and elasticity, and superior adhesion of electrodes, therefore apparently stabilizing silicon-based anode structure and rendering prolonged electrode cycle life. This work marks a milestone in developing state-of-the-art silicon-based electrodes towards high energy density lithium battery applications.

Investigation of lithium-oxygen cells on discharge using a mixture of16O16O and18O18O gases, showed that O–O bond cleavage occurs during disproportionation of LiO2to O2and Li2O2, detected by the presence of isotopic16O18O. The formation of singlet oxygen,1O2, was also monitored during disproportionation. While only 4.5% of oxygen was found to undergo bond cleavage and scrambling of oxygen atoms, more than 40% of the singlet oxygen produced during disproportionation came from the scrambling pathway, making it a major source of singlet oxygen generation in lithium-oxygen batteries. Our results demonstrate that Li2O2formation occurs predominantly by disproportionation, and by controlling the pathway of this step, it may be possible to suppress1O2formation, a species that has been implicated in the degradation of lithium-oxygen batteries.

The only way for commercial application of Li−air batteries with open structure is to receive O2 from ambient air. Nevertheless, H2O-containing ambient air easily induces Li passivation/dendrites and electrolyte decomposition. Apart from above issues, volatilization and leakage of organic liquid electrolytes and relatively infinite dimension variation of metallic Li also seriously discount performance of Li−air batteries. Herein, Li coating polythiophene-derived (S-doped) carbon fiber-based electrode (Li/SC) is prepared by simple rolling method and then in situ coated with deep eutectic solvent-based polymer electrolyte (DES-PE), which are further applied as anode and electrolyte of Li−air battery, respectively. Theoretical/experimental data suggest that SC skeleton possess excellent lithiophilicity/stability which restrain dendritic Li formation and reduce electrode structure damage over cycles. Furthermore, DES-PE not only possesses high ionic conductivity (1.19*10−3 S cm−1, 30 °C), wide electrochemical window (5.0 V), no-leakage and excellent interfacial compatibility, but also combine with SC framework to greatly reduce Li passivation induced by ambient air. Hence, DES-PE@Li/SC based Li−air battery could exhibit extra-large capacity of 15,310 mAh g−1 at 100 mA g−1, high-capacity retention even under high current (11,896 mAh g−1 at 500 mA g−1) and extra-long cycling life up to 300 cycles under fixed capacity. This result provides enlightment for the advancement of Li−air batteries.

Our strategy of polymerizing lithium salt as a polymer electrolyte (3D-SIPE-LiFPA) simultaneously enhances the cycle life and safety characteristics of ultrahigh-energy-density lithium metal batteries (437 W h kg−1).

For layered transition metal oxides cathode-based lithium batteries, the chemical degradation of electrolytes leads to fast battery capacity decay, severely challenging their practical applications. This kind of chemical degradation of electrolytes is caused by the oxidation of reactive oxygen (e.g., singlet oxygen) and the attack of free radicals during cycling. To address this, we first report a biologically inspired antiaging strategy of developing the photostabilizer with singlet oxygen- and free radicals-scavenging abilities as a cathode binder additive. It is fully evidenced that this binder system consisting of the binder additive and a commercially available polyvinylidene difluoride can scavenge singlet oxygen and free radicals generated during high-voltage cycling, thus significantly restraining electrolyte decomposition. As a result, high-voltage layered transition metal oxides-based lithium batteries with reproducibly superior electrochemical performance, even under elevated temperatures, can be achieved. This bioinspired strategy to scavenge reactive oxygen and free radicals heralds a new paradigm for manipulating the cathode/electrolyte interphase chemistry of various rechargeable batteries involving layered transition metal oxides-based cathodes.

As a next-generation electrochemical energy storage technology, rechargeable magnesium (Mg)-based batteries have attracted wide attention because they possess a high volumetric energy density, low safety concern, and abundant sources in the earth's crust. While a few reviews have summarized and discussed the advances in both cathode and anode materials, a comprehensive and profound review focusing on the material design strategies that are both representative of and peculiar to the performance improvement of rechargeable Mg-based batteries is rare. In this mini-review, all nine of the material design strategies and approaches to improve Mg-ion storage properties of cathode materials have been comprehensively examined from both internal and external aspects. Material design concepts are especially highlighted, focusing on designing "soft" anion-based materials, intercalating solvated or complex ions, expanding the interlayer of layered cathode materials, doping heteroatoms into crystal lattice, size tailoring, designing metastable-phase materials, and developing organic materials. To achieve a better anode, strategies based on the artificial interlayer design, efficient electrolyte screening, and alternative anodes exploration are also accumulated and analyzed. The strategy advances toward Mg-S and Mg-Se batteries are summarized. The advantages and disadvantages of all-collected material design strategies and approaches are critically discussed from practical application perspectives. This mini-review is expected to provide a clear research clue on how to rationally improve the reliability and feasibility of rechargeable Mg-based batteries and give some insights for the future research of Mg-based batteries as well as other multivalent-ion battery chemistries.

Electrolyte leakage is a severe safety concern in lithium batteries. With highly volatile 1,2-dimethoxyethane as solvent, the leakage related hazards are more pronounced in lithium-sulfur (Li-S) batteries. To address this concern, a leakage-proof electrolyte is delicately designed through functionalizing the commercial electrolyte by Li6 PS5 Cl-grafted poly(ethyl cyanoacrylate), which can interact readily with the aluminum-plastic packing through hydrogen bond to immobilize the electrolyte. The moisture from ambient can also catalyze a further polymerization of the macromolecules to seal the leaking points and thereby to solve the leakage issue, endowing Li-S batteries superior safety even in an artificial cut pouch cell. With a bare S loading of 4.9 mg cm-2 , the battery can deliver good endurance owing to the suppressed polysulfide shuttle by its polar groups. This work enlightens the design of leakage-proof electrolyte and makes a milestone for high performance Li-S batteries.

Discovering the underlying reason for Li anode failure is a critical step towards applications of lithium metal batteries (LMBs). In this work, we conduct deuterium-oxide (D2 O) titration experiments in a novel on-line gas analysis mass spectrometry (MS) system, to determine the content of metallic Li and lithium hydride (LiH) in cycled Li anodes disassembled from practical LiCoO2 /Li LMBs. The practical cell is comprised of ultrathin Li anode (50 μm), high loading LiCoO2 (17 mg cm-2 , 2.805 mAh cm-2 ) and different formulated electrolytes. Our results suggest that the amount of LiH accumulation is negatively correlated with cyclability of practical LMBs. More importantly, we reveal a temperature sensitive equilibrium (Li + 1/2 H2 ⇌ LiH) governing formation and decomposition process of LiH at Li anode. We believe that the unusual understanding provided by this study will draw forth more insightful efforts to realize efficient Li protection and the ultimate applications of "holy grail" LMBs.

Robust bismuth-based interphases, comprised of bismuth and bismuth oxides, were developed using galvanic replacement reactions. Facilitated Mg atom adsorption and distinct interfacial Mg atom migration were demonstrated, greatly lowering the electrochemical energy penalty (23 mV for the nucleation process and 69 mV for the growth process at 1.0 mA cm-2).

In situ polymerization system can provide a compact and compatible interface with minimum polymer electrolyte, which is imperative to address the bottleneck of notorious solid–solid interface issue...

Magnesium (Mg) metal anode pairing with Sulfur (S) cathode has been regarded as a promising contender for next-generation battery technology holding the characteristics of safety in use, low cost and high energy density. However, the sluggish kinetic and the inferior reversibility of Mg–S electrochemical reaction are two main challenges impeding the development of practical Mg–S batteries. Herein, SeS2 is proposed as a superior cathode for Mg batteries based on the complementary features of S (high specific capacity) and Se (high electronic conductivity). In this designed Mg–SeS2 battery with a Cu foam interlayer between cathode and separator, SeS2 compositing with ordered mesoporous carbon (SeS2/CMK3) exhibits impressive electrochemical performance. Various characterizations towards the electrochemical evolution on cathode side reveal that Cu foam interlayer not only acts as the trapping layer by the rapid chemical immobilization of polysulfide (polyselenide) species on Cu foam, but also serves as a “promoter” to propel the overall charge-discharge kinetics by the reversible displacement reaction between copper sulfide (copper selenide) and Mg2+. Benefiting from the unique advantages of SeS2/CMK3 and the rationally designed Cu interlayer, this novel Mg–SeS2 system demonstrates a feasible strategy to exploit the rechargeable Mg batteries with low cost, high areal capacity and large current capability.

In general, solid polymer electrolyte suffers from relatively low ionic conductivity and inferior oxidation stability. Herein, these issues can be effectively addressed by a supramolecular strategy based on the intermolecular interaction between a novel amorphous comb polymer of poly[propylene oxide-co-2-(2-methoxyethoxy)ethyl glycidyl ether] [P(PO/EM)] and highly fluorinated anion based lithium salt of lithium trifluoro(perfluoro-tert-butyloxyl)borate (LiTFPFB). The supramolecular solid state polymer electrolyte exhibits superior lithium ion transference number (0.59). It is noted that this polymer electrolyte presents enlarged electrochemical window up to 4.6 V (vs. Li/Li+ at 70 °C), which is resulted from the powerful supramolecular interaction between polymer skeleton and lithium salt. The supramolecular interaction was confirmed by Fourier transform infrared spectroscopy (FT-IR) analysis, solid state nuclear magnetic resonance (NMR) spectroscopy, stripping and self-healing tests. More bracingly, high voltage LiFe0.2Mn0.8PO4/Li cell based on this polymer electrolyte exhibits improved cycling performance (capacity retention is 88.7% after 100 cycles at 0.1C). Meanwhile, this well-designed electrolyte endows LiFe0.2Mn0.8PO4/Li cell pouch cell excellent safety characteristic even under deformation and truncation procedures. This supramolecular strategy paves a new way for boosting high energy density all solid state lithium metal batteries.

Robust bismuth-based interphases, comprised of bismuth and bismuth oxides, were developed using galvanic replacement reactions. Facilitated Mg atom adsorption and distinct interfacial Mg atom migration were demonstrated, greatly lowering the electrochemical energy penalty (23 mV for the nucleation process and 69 mV for the growth process at 1.0 mA cm

Achieving non-dendritic Li deposition is generally believed to be a prerequisite for the successful commercialization of lithium metal batteries (LMBs). However, it is discussed here that eliminating the growth of the dendritic Li structure seems not to be sufficient to propel the LMB technology from laboratory research to practical applications. Other types of the electrochemically generated Li structure, besides the dendritic structure, must be further studied. It is suggested that considerable research effort be focused on studying the electrochemical nature of generated Li structures, in addition to finding novel strategies to eradicate them.

Nonflammable functional electrolytes with remarkably interfacial compatibility toward both lithium anodes and high-voltage cathodes are considered as the ultimate pursuit for rechargeable lithium m...

Blended-salt electrolytes showing synergistic effects have been formulated by simply mixing several lithium salts in an electrolyte. In the burgeoning field of next-generation lithium batteries, blended-salt electrolytes have enabled great progress to be made. In this Review, the development of such blended-salt electrolytes is examined in detail. The reasons for formulating blended-salt electrolytes for lithium batteries include improvement of thermal stability (safety), inhibition of aluminum-foil corrosion of the cathode current collector, enhancement of performance over a wide temperature range (or at a high or low temperature), formation of favorable interfacial layers on both electrodes, protection of the lithium metal anode, and attainment of high ionic conductivity. Herein, we highlight key scientific issues related to the formulation of blended-salt electrolytes for lithium batteries.

N, P dual-doped carbon nanosheets was prepared by an in-situ foaming technology. The crude lecithin extracted from egg yolk was explored to prepare this novel carbon material. In the synthesis process, the crude lecithin molecular is as the Gemini surfactant and the graphitic carbon nitride (g-C3N4) plays the role of self-sacrificing template. At the high temperature, the sandwich-mixture “lecithin/C3N4/lecithin” expanded and carbonized with the decomposition of g-C3N4. This induces the formation of many multi-wrinkled nanosheets and synchronously constitute a multi-doped carbon foam. This unique carbon material exhibits a super-efficient catalytic activity towards oxygen reduction reaction, with the limited current density of 6.7 mA cm−2 tested at 1600 rpm in 0.1 M KOH solution, which is far larger than that of Pt/C (20%) catalyst (5.5 mA cm−2). It was demonstrated that this novel catalyst also possesses great catalytic stability. After about 9 h continuous test, the current density of this catalyst remained above 91%. These results demonstrate that the N, P dual-doped multi-wrinkled carbon nanosheets can be used as the high-efficient metal-free electrocatalyst towards oxygen reduction reaction.

Batteries, as highly concerned energy conversion system, have a great development prospect in various fields, especially in the field of energy powered vehicles. Multivalent ion batteries are getting more attention due to their low cost, high abundance in earth crust, high capacity and safety compared with Lithium batteries. Despite above advantages, several problems still need to be solved before multivalent ion batteries achieve large-scale application, such as interfacial parasitic reaction, anode passivation, and dendrites. The replacement of liquid electrolytes with gel polymer electrolytes (GPEs) which pose high safety, high mechanical strength and simplified battery system, is an effective strategy to inhibit dendrite growth and improve electrochemical performance. This review mainly discusses the advantages and challenges of multivalent ion batteries including zinc, magnesium, calcium and aluminum batteries. Meanwhile, the major targets of this review are introducing the recent developments and making a summary of the future trends of GPEs in the multivalent ion batteries.

The continuous energy density increase of lithium ion batteries (LIBs) inevitably accompanies with the rising of safety concerns. Here, the thermal runaway characteristics of a high‐energy 5 Ah LiNi0.5Co0.2Mn0.3O2/graphite pouch cell using a thermally stable dual‐salt electrolyte are analyzed. The existence of LiH in the graphite anode side is innovatively identified in this study, and the LiH/electrolyte exothermic reactions and H2 migration from anode to cathode side are proved to contribute on triggering the thermal runaway of the pouch cell, while the phase transformation of lithiated graphite anode and the O2‐releasing from cathode are just accelerating factors for thermal runaway. In addition, heat determination during cycling at two boundary scenarios of adiabatic and isothermal environment clearly states the necessity of designing an efficient and smart battery thermal management system for avoiding heat accumulation. These findings will shed promising lights on thermal runaway route map depiction and thermal runaway prevention, as well as formulation of electrolyte for high energy safer LIBs.

Solid‐state lithium battery promises highly safe electrochemical energy storage. Conductivity of solid electrolyte and compatibility of electrolyte/electrode interface are two keys to dominate the electrochemical performance of all solid‐state battery. By in situ polymerizing poly(ethylene glycol) methyl ether acrylate within self‐supported three‐dimensional porous Li1.3Al0.3Ti1.7(PO4)3 framework, the as‐assembled solid‐state battery employing 4.5 V LiNi0.8Mn0.1Co0.1O2 cathode and Li metal anode demonstrates a high Coulombic efficiency exceeding 99% at room temperature. Solid‐state nuclear magnetic resonance results reveal that Li+ migrates fast along the continuous Li1.3Al0.3Ti1.7(PO4)3 phase and Li1.3Al0.3Ti1.7(PO4)3/polymer interfacial phase to generate a fantastic conductivity of 2.0 × 10−4 S cm−1 at room temperature, which is 56 times higher than that of pristine poly(ethylene glycol) methyl ether acrylate. Meanwhile, the in situ polymerized poly(ethylene glycol) methyl ether acrylate can not only integrate the loose interfacial contact but also protect Li1.3Al0.3Ti1.7(PO4)3 from being reduced by lithium metal. As a consequence of the compatible solid‐solid contact, the interfacial resistance decreases significantly by a factor of 40 times, resolving the notorious interfacial issue effectively. The integrated strategy proposed by this work can thereby guide both the preparation of highly conductive solid electrolyte and compatible interface design to boost practical high energy density all solid‐state lithium metal battery.

Unevenly distributed magnesium (Mg) electrodeposits have emerged as a major obstacle for Mg-metal batteries. A comprehensive design matrix is reported for 3D magnesiophilic hosts, which regulate the uniform Mg electrodeposition through a synergistic coupling of homogenizing current distribution, geometric confinement, and chemisorptive interaction. Vertically aligned nitrogen- and oxygen-doped carbon nanofiber arrays on carbon cloth (denoted as "VNCA@C") are developed as a proof of concept. The evenly arranged short nanoarray architecture helps to homogenize the surface current density and the microchannels built in this 3D host allow the preferential nucleation of Mg due to their geometrical confinement effect. Besides, the nitrogen-/oxygen-doped carbon species exhibit strong chemisorptive interaction toward Mg atoms, providing preferential nucleation sites as demonstrated by first-principle calculation results. Electrochemical analysis reveals a peculiar yet highly reversible microchannel-filling growth behavior of Mg metals, which empowers the delicately designed VNCA@C host with the ability to deliver a reduced nucleation overpotential of 429 mV at 10.0 mA cm-2 and an elongated Mg plating/stripping cycle life (110 cycles) under high current density of 10.0 mA cm-2 . The proposed design matrix can be extended to other metal anodes (such as lithium and zinc) for high-energy-density batteries.

Uniform magnesium (Mg) plating/stripping under high areal capacity utilization is critical for the practical application of Mg-metal anodes in rechargeable Mg batteries. However, the failure of the Mg-metal anode when cycling under a practical areal capacity (4 mA h cm

The continuous energy density increase of lithium ion batteries (LIBs) inevitably accompanies with the rising of safety concerns. Here, the thermal characteristics of a high-energy 5 Ah LiNi0.5Co0.2Mn0.3O2/graphite pouch cell using a thermally stable dual-salt electrolyte were analyzed. Heat determination during cycling at two boundary scenarios of adiabatic and isothermal environment clearly states the necessity of designing an efficient and smart battery thermal management system. More importantly, it is innovatively proposed that the hydrogen anion (H−) induced H2 releasing at anode side and H2 migration to cathode side is the rooted thermal runaway trigger of the pouch cell, while the phase transformation of lithiated graphite anode and the O2-releasing by delithiated cathode are just accelerating factors for thermal runaway. These findings will shed promising lights on thermal runaway route map depiction and thermal runaway prevention, as well as formulation of electrolyte for high energy safer LIBs.

It is demonstrated that a novel eutectic solution including 1,3,5‐trioxane (TXE) and succinonitrile (SN) can be converted into solid‐state polymer electrolyte (SPE) via in situ polymerization triggered by lithium difluoro(oxalato)borate (LiDFOB). It is worth noting that all the precursors (LiDFOB, TXE, and SN) of this novel SPE are totally solid and nonvolatile at room temperature, where, LiDFOB works as a lithium salt and an initiator simultaneously to avoid the introduction of impurity. It is noted that such SPE presents a considerable ionic conductivity of 1.14 × 10−4 S cm−1 and a sufficiently wide electrochemical window of 4.5 V, which is significant for supporting the high‐energy lithium batteries. In addition, this dedicatedly designed in situ polymerization is powerful to build kinetically favorable polymer‐based protective layers on LiCoO2 cathode and Li metal anode simultaneously, guaranteeing outstanding cycling stability (capacity retention of 88% after 200 cycles) of 4.3 V LiCoO2/lithium metal batteries at room temperature. More intriguingly, soft packed LiCoO2/SPE/Li metal batteries can still light a blue light emitting diode (LED) under the harsh conditions of being bent, cut, and stroked by a hammer, demonstrating excellent safety characteristics., A new type of solid‐state polymer electrolyte (SPE) free of additional initiators and flammable precursors is dedicatedly designed through an in situ polymerization of novel eutectic solution by LiDFOB. Such SPE can build kinetically favorable protective layers on LiCoO2 and Li simultaneously, guaranteeing outstanding cycling stability of 4.3 V LiCoO2/Li metal battery.

Solid‐state lithium battery promises highly safe electrochemical energy storage. Conductivity of solid electrolyte and compatibility of electrolyte/electrode interface are two keys to dominate the electrochemical performance of all solid‐state battery. By in situ polymerizing poly(ethylene glycol) methyl ether acrylate within self‐supported three‐dimensional porous Li1.3Al0.3Ti1.7(PO4)3 framework, the as‐assembled solid‐state battery employing 4.5 V LiNi0.8Mn0.1Co0.1O2 cathode and Li metal anode demonstrates a high Coulombic efficiency exceeding 99% at room temperature. Solid‐state nuclear magnetic resonance results reveal that Li+ migrates fast along the continuous Li1.3Al0.3Ti1.7(PO4)3 phase and Li1.3Al0.3Ti1.7(PO4)3/polymer interfacial phase to generate a fantastic conductivity of 2.0 × 10−4 S cm−1 at room temperature, which is 56 times higher than that of pristine poly(ethylene glycol) methyl ether acrylate. Meanwhile, the in situ polymerized poly(ethylene glycol) methyl ether acrylate can not only integrate the loose interfacial contact but also protect Li1.3Al0.3Ti1.7(PO4)3 from being reduced by lithium metal. As a consequence of the compatible solid‐solid contact, the interfacial resistance decreases significantly by a factor of 40 times, resolving the notorious interfacial issue effectively. The integrated strategy proposed by this work can thereby guide both the preparation of highly conductive solid electrolyte and compatible interface design to boost practical high energy density all solid‐state lithium metal battery., The poor room‐temperature ionic conductivity of solid electrolyte and incompatibility of solid–solid electrolyte/electrode interface are resolved simultaneously by in situ polymerizing electrode compatible polymer within a highly conductive, three‐dimensional self‐supported porous oxide framework. The composite solid electrolyte guided by this strategy is exploited to achieve excellent cycling performance for high‐voltage solid‐state lithium battery.