ILs unique properties such as ionic conductivity, low volatility, noninflammability, high chemical and electrochemical stability, and so on. [3] These properties coupled with adjustable structure and functionality allow ILs to evolve from unique liquid mediums to the solvents/electrolytes widely used across multiple disciplines in science and engineering. [4][5][6][7][8][9] The incorporation of ILs and advanced energy storage and conversion technology seems to be a nice strategy to meet the increasing demand for clean and sustainable energy. [10] However, traditional ILs based on ammonium, alkylpyridinium, dialkylimidazolium, and phosphonium cations, are generally expensive, nonbiodegradable, and toxicities, which are unfavorable to achieving the aforementioned goals. [11] Thus, numerous efforts have been devoted to exploring the advanced ILsderived materials, which retain most of the characteristics of ILs and are endowed with new features. Novel ILs, including deep eutectic solvents (DESs), [12,13] poly(ionic liquid)s (PILs), [14][15][16] ionic liquid crystals (ILCs), [17,18] and redox-active ionic liquids (RAILs), [19,20] have been synthesized and have been proved to be promising materials to compensate for the inadequacies of the traditional ILs.In general, those four types of novel ILs exhibit unique features and advantages in the fields of energy storage and conversion, respectively. For example, DESs are inexpensive, biodegradable, and nontoxic, they have great advantages in building environmental-friendliness energy storage devices. [21,22] The PILs have a polymeric structure while maintaining ionic conductivity. This means they are excellent potential materials for preparing binder, membranes, and solid-state electrolyte. [23] They are also a kind of building blocks for self-assembly. ILCs with enhanced ordered structure and unique phase behavior are able to achieve the efficient and directional conduction of species, which are excellent properties to construct high-performance energy storage devices. [24] Besides, RAILs are a liquid material with ionic conductivity and redox centers and have exhibited promising potentiality for use as redox additives and electroactive electrolytes. [25] In this review, we focus on the intrinsic properties of novel ILs and their related self-assembly behavior for constructing highperformance energy storage and conversion devices. In the following four chapters, we discuss the unique properties,
The ever-growing demands of rechargeable portable devices, electric vehicles, and large-scale grid energy storage have greatly accelerated the research of high-energy-density batteries. [1] Due to its high theoretical specific capacity (3860 mAh g À1 ) and low electrochemical potential (À3.04 V versus the standard hydrogen electrode), [2] lithium (Li) metal is regarded to be an important choice for battery system with high energy density. [3] However, there are some obstacles the Li anode has to remove before its application, including dendritic lithium formation, [4] unlimited volume change, [5] and unstable solid-electrolyte interface (SEI) layer. [6] Various strategies have been explored to achieve the Li anode protection, such as in situ protection by optimizing electrolyte, [7] ex situ protection by introducing an artificial SEI layer, [8] reasonable design of Li metal anode structure, [9] construction of novel solid electrolyte, [10] etc. Among these strategies, the construction of 3D current collectors or Li hosts seems to be a comprehensive solution. Researchers have chosen a series of metal elements, metal oxides, and heteroatoms as lithiophilic sites decorated on traditional 3D current collectors including copper foam, [11] nickel foam, [12] copper mesh, [13] etc. However, these current collectors are all metal based, and the large density makes them occupy too much weight of the whole battery.In view of this, 3D carbon skeletons with lightweight and high specific surface area would be ideal hosting materials for high-energy-density Li metal battery systems. [14] However, the common methods of lithiophilic layer construction for 3D carbon current collector are difficult for large-scale application, like chemical vapor deposition (CVD) [15] or atomic layer deposition (ALD). [16] Thus, developing feasible strategy of fabricating lithiophilic carbon framework is vital for the practical application of Li metal anode.Electrospinning is one of the most scalable techniques that produce nanofibrous membranes with highly porous structure, abundant active sites, and excellent mechanical properties. [17] If lithiophilic active sites and carbon precursor could be eletrospun simultaneously into uniformly hybrid membrane, then a 3D lithiophilic carbon Li host would be obtained. As a source of lithiophilic elemental Zn, [18] Zeolitic imidazolate framework-8 (ZIF-8) has been used to facilitate the Li-ion flow at the Li anode side for dendrite-free Li deposition. [19] As for the carbon source, polyacrylonitrile (PAN) is one of the most widely used polymers for electrospinning, [20] and it has been applied in Li batteries due
In this work, the effects of the coexistence of Ni−Nx sites and Ni metal nanoparticles of Ni−N−C (nickel‐nitrogen‐carbon) materials on the thermodynamic Li nucleation overpotential (η) and kinetic exchange current density (j0) are systematically studied. Ni‐Nx sites guarantee reduced nucleation resistance on the hollow carbon sphere (HCS) host, while the low amount residual of Ni nanoparticles plays an adverse role. The Li nucleation overpotential was down to 10.6 mV and the exchange current density increased from 1.139 to 2.325 mA cm−2 when the residual Ni nanoparticles in the prepared Ni−N−C composite were removed. As a result, pure Ni‐Nx sites displayed an average CE of 98.4 % over 300 cycles and a stable Li plating/stripping behavior for over 800 h.
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