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Highlights: The introduction of self-healing mechanism into flexible energy storage devices is expected to solve the problems of mechanical and electrochemical performance degradation caused by mechanical deformation. Applications of different healing mechanisms and advanced characterization techniques in energy storage devices are summarized. The key challenges of self-healing in the field of flexible energy storage are pointed out, and the future research direction is prospected. The booming wearable/portable electronic devices industry has stimulated the progress of supporting flexible energy storage devices. Excellent performance of flexible devices not only requires the component units of each device to maintain the original performance under external forces, but also demands the overall device to be flexible in response to external fields. However, flexible energy storage devices inevitably occur mechanical damages (extrusion, impact, vibration)/electrical damages (overcharge, over-discharge, external short circuit) during long-term complex deformation conditions, causing serious performance degradation and safety risks. Inspired by the healing phenomenon of nature, endowing energy storage devices with self-healing capability has become a promising strategy to effectively improve the durability and functionality of devices. Herein, this review systematically summarizes the latest progress in intrinsic self-healing chemistry for energy storage devices. Firstly, the main intrinsic self-healing mechanism is introduced. Then, the research situation of electrodes, electrolytes, artificial interface layers and integrated devices based on intrinsic self-healing and advanced characterization technology is reviewed. Finally, the current challenges and perspective are provided. We believe this critical review will contribute to the development of intrinsic self-healing chemistry in the flexible energy storage field. [ABSTRACT FROM AUTHOR]

A stable interface between silicon anodes and electrolytes is vital to realizing reversible electrochemistry cycling for lithium‐ion batteries. Herein, a zincone polymer coating is controllably deposited on a silicon electrode using the molecular layer deposition to serve as an artificial solid electrolyte interphase (SEI). Enhanced electrochemical cycling depends on the thickness of zincone coating. The optimal zincone coating of ≈3 nm markedly improves the lithium storage performance of silicon anodes, resulting in a high reversible capacity (1741 mA h g−1 after 100 cycles at 200 mA g−1), outstanding cycling stability (1011 mA h g−1 after 500 cycles), and superior rate capability (1580 mA h g−1 at 2 A g−1). Such remarkable electrochemical reversibility stems from the in situ conversion of the zincone coating and a zincone‐driven thin lithium fluoride (LiF)‐rich SEI, which endow the silicon electrode with superior electron/ion transport and structural stability. Meanwhile, the zincone coating demonstrates good compatibility with ether‐based electrolytes (893 mA h g−1 after 200 cycles, 970 mA h g−1 at 5 A g−1). Additionally, in situ conversion of artificial zincone coating also opens a door for constructing a functional interface on other electrode surfaces, such as lithium/sodium metal. [ABSTRACT FROM AUTHOR]

Silicon-carbon composite is recognized as one of the most promising next-generation anodes for high-energy lithium-ion batteries, especially silicon-graphite composites. Herein, cost-efficient and scalable submicron/micron silicon particles are stabilized in a robust graphite-carbon architecture by solid-phase ball milling and liquid-phase coating methods. The obtained silicon-graphite-carbon composite with a stable encapsulated sandwich-like architecture exhibits impressive lithium storage performance, including high initial Coulombic efficiency of 83.7%, outstanding cycle stability and remarkable rate capability. Even at high loadings of 4 mg cm−2, it still exhibits great reversible capacity with 620 mA h g−1 after 100 cycles at 0.2 C. Furthermore, 8 wt% silicon-graphite-carbon composites as additives are applied into the full cell with a designed capacity of 1000 mA h, and the full cell displays superior cycle stability with high capacity retention of 85% after 100 cycles. In addition, the scalable and low-cost preparation makes it enormous application value and huge commercial prospect. [ABSTRACT FROM AUTHOR]

Si-based anode materials have been widely accepted as one of the most potential candidates for lithium ion batteries due to their abundance and high theoretical specific capacity. However, their practical application is seriously restricted by huge volume change and low intrinsic electric conductivity. Herein, a sandwich structured mesocarbon microbeads/nano-Si/amorphous carbon (MSC) composite was successfully fabricated through simple solution process and magnesiothermic reduction. The MCMB core acts as perfect materials support for nano-Si and conductive network for high electrochemical lithiation stability. Nano-Si provides high lithium storage capacity for enhanced energy density, and the amorphous carbon layer can effectively buffer the volume change from the nano-Si. As a result, the obtained MSC composite with optimal design displays high reversible capacity of 648 mA h g−1 at a current density of 100 mA g−1, along with a satisfactory capacity retention ratio of 90.3% after 100 cycles. To sum up, we develop a simple approach for large-scale preparation of silicon-based composites with high capacity and long-term cycle stability, which shows great potential for applications in the next-generation lithium ion batteries. Image 1 [ABSTRACT FROM AUTHOR]

Abstract The three-dimensional conductive skeleton plays an important role for silicon-based anode materials to achieve good electrochemical performance in lithium ion batteries with high energy density. Here, we prepared a three-dimensional silicon/N-doped graphitized carbon composite (3D Si/NGC) from ZIF-67 precursor by magnesiothermic reduction reaction. The N-doped and graphitized conductive carbon acts as a robust three-dimensional configuration for the silicon nanoparticles, not only improving the conductivity of electrode, but also buffering the volume expansion of silicon nanoparticles. The 3D Si/NGC electrode exhibits good long-term cycle stability and impressive rate performance, delivering reversible capacity of 900 mA h g−1 at 0.2 A g−1 after 300 cycles with a capacity retention of 85.5% and a high discharge capacity of 880 mA h g−1 at 1 A g−1. The 3D Si/NGC with good electrochemical performance shows great potential as the next generation anode material for lithium ion batteries. Graphical abstract Image 1 Highlights • 3D Si/NGC composite derived from ZIF-67 is prepared by the magnesiothermic reduction. • Si/NGC composite displays a robust porous three-dimensional structure. • The N-doping and the graphitization enhance the electronic conductivity of composite. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • NRC/Si composite is prepared through a facile self-assembly process. • NRC/Si composite possesses a two-dimensional structure. • Rich-nitrogen doping improves the electronic conductivity of the composites. • NRC/Si anode exhibits high reversible capacity and excellent rate capability. Abstract The two-dimensional (2D) carbon material shows great superiority in improving the electrochemical performance of silicon-based anode for lithium ion batteries. We synthesize a nitrogen-rich carbon/silicon composite (NRC/Si) with a graphene-like structure by an amino-carboxyl self-assembly of the citric acid, melamine and Si-NH 2. The NRC/Si composite with a two-dimensional structure can effectively buffer the volume change of silicon material during cycling. Moreover, the rich-nitrogen doping improves the electronic conductivity and facilitates the charge transfer during charge and discharge process. The NRC/Si as anode material for lithium ion batteries shows good cycle stability and rate capability, delivering a reversible capacity of 1000 mA h g−1 after 300 cycles at 2 A g−1 and 572 mA h g−1 even at 5 A g−1, respectively. In addition, the synthesis method of the NRC/Si composite is cost-effective, environmentally friendly and industrially scalable, which makes it very promising to obtain the high-performance anode materials in lithium ion batteries. [ABSTRACT FROM AUTHOR]

• An artificial protective layer with interface defects is proposed; • Interface defect chemistry promotes the lithium ions diffusion kinetics; • Interface oxygen defect achieve the ultra-long electrochemical plating/stripping stability; • The electrochemical performance of full cells has been significantly improved. Lithium dendrite can cause battery failure and safety risks, which is a major obstacle for the commercial application of lithium metal anodes. Herein, an artificial protective layer with interface defects is proposed to promote the interfacial electrochemical kinetics and achieve the ultra-long electrochemical plating/stripping stability. Taking titanium oxide (TiO 2) as a research object, the interfacial oxygen-deficient TiO 2 coating (H-TiO 2) shows the faster lithium ion diffusion kinetics compared to the pristine TiO 2 layer and fresh lithium metal anode, and this interfacial defect chemistry can facilitate homogenous lithium ion flux and regulate lithium metal dendrite-free electrodeposition. Specifically, the H-TiO 2 protective layer endows lithium metal anodes ultra-long cycling stability up to 1990 h at 2.0 mA cm−2 with a low overpotential of 27.5 mV. Remarkably, the artificial H-TiO 2 coating improves the cycling stability (97.5 mAh g−1 after 350cycles) and rate performance (68.5 mAh g−1 at 4.0C) of full cells paired with LiFePO 4 cathode. More importantly, this work opens a door for regulating lithium metal reversible electrodeposition by interface defect chemistry. [ABSTRACT FROM AUTHOR]

• MP-Si is obtained through magnesiothermic reduction reaction driven from waste glass. • Micron-sized MP-Si is composed of numerous interconnected 2D nanoplates. • MP-Si possesses abundant mesoporous structure. • MP-Si anode exhibits high reversible capacity and excellent rate capability. Constructing micro-nano hierarchical porous structure is an effective strategy to solve key issues arising from the large volume change of silicon-based materials during cycling. Herein, we successfully obtain the mesoporous silicon microparticles composed of nanoplates driven from waste glass by the magnesiothermic reduction reaction. The two-dimensional nanoplates and abundant mesoporous structure in the microparticles not only effectively mitigate the mechanical strains caused by volume changes but also promote lithium ion diffusion. The silicon microparticles display outstanding lithium storage performance including extremely high first Coulombic efficiency (85.1%), remarkable reversible specific and volumetric capacities (1793 mAh g−1 and 747 mAh cm−3 after 120 cycles at 200 mA g−1, 1000 mAh g−1 after 360 cycles at 500 mA g−1) and impressive rate performance (1183.7 mA h g−1 at 1 A g−1). Simultaneously, the corresponding electrode exhibits significantly less impedance build-up and smaller electrode thickness increase than that of commercial silicon nanoparticles. Furthermore, the scalable and cost-effective method makes it an attractive candidate for next generation lithium ion batteries anode materials. [ABSTRACT FROM AUTHOR]

The inhomogeneous nature of SiO x anode material on the atomic scale directly affects its electrochemical performance. A large irreversible capacity loss at the first cycle severely hinders the applications of SiO x materials in lithium ion batteries. The modification of SiO x by means of high-energy ball-milling and wet alkali chemical reaction can tune the ordering of amorphous silicon and silicon dioxide in SiO x materials, which is beneficial to the activation of nano silicon region and the surficial composition optimization of the lithiated products of SiO x during the first discharge process, and the formed Li 2 SiO 3 phase and the increased O/Si ratio in the surface of SiO x contribute to the improved cyclic performance. This surface regulation approach is quite simple, efficient and suitable for large-scale applications of high-performance SiO x anode material. [Display omitted] • The SiO x was modified via high-energy ball milling and wet-alkali chemical reaction. • The Li + ions as network modifier contributes the surface structural recombination of SiO x. • The changes in SiO x surface chemistry optimize the lithiated products of SiO x. • The increased O/Si ratio of SiO x improves the cycling performance. [ABSTRACT FROM AUTHOR]

The micro-sized SiO-based composite anode material (d-SiO/G/C) for lithium-ion batteries (LIBs) is achieved via the disproportionation reaction of SiO followed by a pitch pyrolysis reaction. The d-SiO/G/C composite exhibits an initial reversible capacity of 905 mAh g −1 and excellent cycling stability. The initial Coulombic efficiency of the d-SiO/G/C composite can be significantly improved from 68.1% to 98.5% by the prelithiation of the composite anode using stabilized lithium metal powders (SLMP), which counteracts the irreversible capacity loss caused by the solid electrolyte interphase (SEI) formation and irreversible conversion reaction during the first lithiation. The micro-sized d-SiO/G/C composite anode with SLMP prelithiation maintains an excellent cycling stability, suggesting its great potential in practical application for high specific energy lithium ion batteries. [ABSTRACT FROM AUTHOR]

SiOx/C composites with a void‐reserving structure are promising anodes for lithium‐ion batteries. However, the facile and controllable synthesis of uniformly dispersed SiOx and carbon components, simultaneously incorporating ample voids, still remains a great challenge. Herein, a molecular polymerization strategy is devised to construct SiOx/C hollow particles for lithium‐ion batteries. 3‐aminopropyltriethoxysilane and dialdehyde molecules are judiciously engineered as silicon and carbon precursors to produce the polymer hollow spheres (PHSs) through a one‐step aldimine condensation without any template and additive. A range of PHSs is obtained using terephthalaldehyde, glutaraldehyde, and glyoxal as the crosslinkers, demonstrating the high tunability of the strategy. Importantly, in situ pyrolysis of the PHSs warrants the homogeneous incorporation of SiOx (<5 nm) in carbon hollow capsids at a nanocluster scale. The obtained SiOx/C hollow spheres exhibit excellent Li+‐ion storage behaviors, including cycling lifespan, coulombic efficiency, and rate performance. The superior performance is attributed to the well‐dispersed SiOx nanoclusters in carbon substrate and the hollow structure. This molecular polymerization approach not only enables Si‐based hollow composites effective and scalable anode materials but also opens up a new avenue for the controllable synthesis of template‐free hollow architectures. [ABSTRACT FROM AUTHOR]

Seeking free volume around nanostructures for silicon-based anodes has been a crucial strategy to improve cycling and rate performance in the next generation Li-ion batteries. Herein, through a simple pyrolysis and in-situ polymerization approach, the low cost commercially available melamine foam as a soft template converts carbon nanotubes into highly dispersed and three-dimensionally interconnected framework with encapsulated silicon/polyaniline hierarchical nanoarchitecture. This unique core-sheath structure based on carbon nanotubes foam integrates a large number of mesoporous, thus providing well-accessible space for electrolyte wetting, whereas the carbon nanotubes matrix serves as conductive thoroughfares for electron transport. Meanwhile, the outer polyaniline coated on silicon nanoparticles provides effective space for volume expansion of silicon, further inhibiting the active material escape from the current collector. As expected, the PANI-Si@CNTs foam exhibits a high initial specific capacity of 1954 mAh g −1 and retains 727 mAh g −1 after 100 cycles at 100 mA g −1 , which can be attributed to highly electrical conductivity of carbon nanotubes and protective layer of polyaniline sheath, together with three-dimensionally interconnected porous skeleton. This facile structure can pave a way for large scale synthesis of high durable silicon-based anodes or other electrode materials with huge volume expansion. [ABSTRACT FROM AUTHOR]

The micro-sized silicon@carbon@graphene spherical composite (Si@C@RGO) has been prepared by an industrially scalable spray drying approach and a subsequent calcination process. The obtained Si@C@RGO anode exhibits a high initial reversible specific capacity of 1599 mAh g −1 at a current density of 100 mA g −1 with a good capacity retention of 94.9% of the original charge capacity at a higher current density of 200 mA g −1 . Moreover, the Si@C@RGO anode shows a high reversible specific capacity of 951 mAh g −1 even at a high current density of 2000 mA g −1 . The excellent cycling stability and superior rate capability are attributed to the unique structural design of carbon coating and wrapped by highly conductive graphene. The combination of carbon shells and flexible graphene can effectively enhance the electrical conductivity of the composite and accommodate significant volume changes of silicon during cycling. The presented spray drying strategy is adaptable for large-scale industrial production of Si-based composite, and it can be extended to the design of other promising micro-sized electrode materials. [ABSTRACT FROM AUTHOR]

• An artificial interphase composed of Zn/MgZn 2 /MgCl 2 was pre-constructed by replacement reaction of ZnCl 2 and Mg. • The Mg plating/stripping overpotential of the modified Mg electrode can be reduced 0.2 V at 0.1 mA/cm2. • The reversibility of cathode can be improved by serving Cu powders as additive in cathode. • The change of redox couple from S/S2− to Cu 2 S/Cu0 is completed during the cycle. The Mg-S battery has great development potential benefiting from its high volume energy density and high-safety. However, it also confronts with two key issues especially when using the Mg(TFSI) 2 -based electrolyte. One is the poor compatibility between electrolyte and Mg anode, and the other is the poor reversibility of cathode. In this work, an artificial interphase including Zn/ZnCl 2 /MgZn 2 /MgCl 2 was firstly pre-constructed by replacement reaction of ZnCl 2 and Mg, which can reduce Mg plating/stripping overpotential to 0.2 V at 0.1 mA/cm2. Meanwhile, the reversibility of cathode can be improved by using copper powders as additive in sulfur/carbon composite cathode, and the improvement effect is directly related to the addition amount and particle size of copper powders. In addition, it is also revealed that the chemical reaction can occur between copper and intermediates MgS 8 at the initial stage of discharge process. The reaction product of Cu 2 S continues to participate in the electrochemical reduction reaction to regenerate copper, which can be reoxidized to Cu 2 S during the charging process. The conversion of redox couple from S/S2− to Cu 2 S/Cu0 in cathode improves the cycling stability of the battery in comparison with the conversional Mg-S battery. [ABSTRACT FROM AUTHOR]

[Display omitted] • An artificial interphase on the Mg-metal surface was pre-constructed successfully. • Such interphase enables the application of TFSI-based electrolytes in RMMBs with low Mg plating/stripping overpotential. • The Mg/Li hybird batteries were designed to improve the reaction kinetics of cathode by influencing the intercalation mechanism. • The superior cycling stability and rate performance can be obtained for the Mg-Mo 6 S 8 full cells. The Mg-metal batteries (MMBs) as a forceful competitor for Li-metal batteries (LMBs) have the advantages of high-safety and high-volume energy density. Whereas, the MMBs still confronts two vital issues to be addressed, including the incompatibility of conventional TFSI-based electrolytes with the Mg electrode and the poor reversibility of the cathode. In this work, to satisfyingly settle the incompatibility, an artificial interphase was first pre-constructed by high-temperature displacement reaction of CuCl 2 and Mg metal, responsible for the faster charge-transfer rate and the lower Mg plating/stripping overpotential (∼0.2 V) in Mg symmetric cells. Regarding the Mg-Mo 6 S 8 full cells, to enhance the reversibility and rate performance, Mg/Li hybrid batteries were designed. Consequently, the Mg-Mo 6 S 8 battery can achieve excellent cycle stability and deliver a desirable capacity. Even as the current density increases to 1C, the battery still shows a desirable capacity of 92 mAh g−1 over 500 cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • Layered sieve-like porous Si microparticle is firstly used as the anode for LIBs. • Even-distributed pore structure alleviates volume change and stress concentration. • The intertwined CNT layer constructs a robust structural and conductive network. • LSP-Si@CNT micro-material exhibits stable cyclability and Coulombic efficiency. Despite the tremendous efforts in developing Si-based anode materials, the instable structure and electrode/electrolyte interphase caused by the severe volumetric expansion/contraction still remain quite challenging for their application in Li-ion batteries (LIBs). Here we firstly propose and synthesize a micron-sized layered sieve-like porous silicon (LSP-Si) anode material by a facile etching and magnesiothermic reduction strategy. This LSP-Si material possesses special layered porous structure with evenly distributed pores in the layers, forming the interconnected nanonetwork like a sieve. Concomitant with this hierarchal layered porous structure, the LSP-Si microparticle can effectively accommodate the severe volume expansion and mitigate the stress concentration due to the mutual extrusion upon lithiation, and thus stable solid electrolyte interphase (SEI) films can be well maintained. Meanwhile, a large number of mesopores provide well-accessible space for electrolyte penetration, facilitating faster transport and better intercalation kinetics of Li+ ions. Further, the LSP-Si microparticle are encapsulated within the CNT cage through the electrostatic adsorption to achieve high mechanical integrity and good electrical contact. Accordingly, the LSP-Si@CNT material delivers a high reversible capacity (1862 mAh g−1 at 100 mA g−1), superior cycling stability (91.9% capacity retention after 500 cycles) and excellent rate capability (1546.8 mAh g−1 at 200 mA g−1 and 719.3 mAh g−1 at 5000 mA g−1). Our work provides a design strategy for high-capacity Si-based micron material viable in the next-generation high-energy LIBs. [ABSTRACT FROM AUTHOR]

Silicon-based anode for lithium-ion batteries (LIBs) has attracted much attention due to its high theoretical capacity, low operating potential and abundant resources. However, the large volume expansion/shrink during the lithiation/delithiation process induces extreme damage to the electrode microstructure. The resulting failure of electrical contact between silicon and current collector will severely deteriorate the cycling stability. Herein, a three-dimensional nano-Si/N-doped carbon network was obtained by a facile approach with NaCl templates. The N-doped carbon network not only significantly improves the electronic conductivity, but also ensures a valid electrode microstructure through a highly elastic carbon framework. Additionally, a two-dimensional nano-Si/N-doped carbon sheet was prepared without NaCl templates, revealing the boosting action of NaCl templates in the microstructure adjustment from low dimension to spatial crosslinking. The optimal three-dimensional nano-Si/N-doped carbon composite can deliver a high specific capacity of 1396 mAh g−1 with a capacity retention of 84.3% after 100 cycles at 200 mA g−1. This study provides effective guidance for novel Si-based anode design to achieve high-energy LIBs with excellent cycling stability. Image 1 [ABSTRACT FROM AUTHOR]