Hard carbons, an important category of amorphous carbons, are non‐graphitizable and are widely accepted as the most promising anode materials for emerging sodium‐ion batteries (SIBs)， because of ...their changeable low‐potential charge/discharge plateaus. However, their microstructures are not fixed and are difficult to accurately demonstrate as graphites do. The successful use of hard carbons in SIBs revives the interest to clearly picture their complicated microstructures that are in close relevance to sodium storage. In this review, the past definitions and structural models of hard carbons are revisited first, and a renewed understanding of their sodium storage is presented. Three critical structural features are highlighted for hard carbons, namely crystallites, defects, and nanopores, which are directly responsible for the presence of the low‐potential plateaus and their reversible extension. The impact of these structural features upon the sodium storage is then deeply discussed and sieving carbons is finally proposed as an ideal configuration of carbon anode for superhigh sodium storage. This review is expected to offer a clear picture of hard carbons, and help realize a truly rational design of high‐capacity carbon anodes, driving the industrialization of SIBs, and more promisingly open up a window for exploring their possible new uses.
This review highlights three critical structural features of hard carbons for practical use in sodium‐ion batteries, namely crystallites, defects, and nanopores. The impact of these structural features upon sodium storage is systematically discussed and an ideal configuration, namely sieving carbons with tightened pore entrance and enlarged pore body, is finally proposed for superior sodium storage.
Rechargeable aqueous zinc (Zn) ion‐based energy storage systems have been reviving recently because of their low cost and high safety merits; however, they still suffer from the problems of corrosion ...and dendrite growth on Zn metal anodes that cause gas generation and early battery failure. Unfortunately, the corrosion problem has not received sufficient attention until now. Here, it is pioneeringly demonstrated that decorating the Zn surface with a dual‐functional metallic indium (In) layer, acting as both a corrosion inhibitor and a nucleating agent, is a facile but effective strategy to suppress both drastic corrosion and dendrite growth. Symmetric cells assembled with the treated Zn electrodes can sustain up to 1500 h of plating/stripping cycles with an ultralow voltage hysteresis (54 mV), and a 5000 cycle‐life is achieved for a prototype full cell. This work will instigate the further development of aqueous metal‐based energy storage systems.
A dual‐functional metallic In layer is in situ decorated on the Zn anode surface, acting as both a corrosion inhibitor and a nucleating agent, to suppress both drastic corrosion and dendrite growth. Symmetric cells assembled with the treated Zn electrodes can sustain up to 1500 h of plating/stripping cycles with an ultralow voltage hysteresis (54 mV).
Gelation is an effective way to realize the self‐assembly of nanomaterials into different macrostructures, and in a typical use, the gelation of graphene oxide (GO) produces various graphene‐based ...carbon materials with different applications. However, the gelation of MXenes, another important type of 2D materials that have different surface chemistry from GO, is difficult to achieve. Here, the first gelation of MXenes in an aqueous dispersion that is initiated by divalent metal ions is reported, where the strong interaction between these ions and OH groups on the MXene surface plays a key role. Typically, Fe2+ ions are introduced in the MXene dispersion which destroys the electrostatic repulsion force between the MXene nanosheets in the dispersion and acts as linkers to bond the nanosheets together, forming a 3D MXene network. The obtained hydrogel effectively avoids the restacking of the MXene nanosheets and greatly improves their surface utilization, resulting in a high rate performance when used as a supercapacitor electrode (≈226 F g−1 at 1 V s−1). It is believed that the gelation of MXenes indicates a new way to build various tunable MXene‐based structures and develop different applications.
Fast gelation of Ti3C2Tx MXenes is initiated by divalent metal ions in aquesous solution. Typically, Fe2+ ions eliminate the electrostatic repulsion, networking MXene nanosheets into a 3D structured hydrogel. The wet hydrogel avoids nanosheet restacking and is ideal for applications highlighting the surface utilization, especially as freestanding electrodes for high‐rate supercapacitors.
Carbon materials show their importance in electrochemical energy storage (EES) devices as key components of electrodes, such as active materials, conductive additives and buffering frameworks. To ...meet the requirements of vastly developing markets related to EES, especially for electric vehicles and large scale energy storage, the rational design of functional carbon materials with the basis of a deep understanding of the structure‐property relationships is demanded, in which dimensionality variations and hybridizations of the carbon materials play critical roles in improving electrochemical performances of EES devices. This review focuses on the dimensionality manipulation in functional carbon materials, including transition, matching and integration, to optimize the reaction space, interface and framework in electrodes, respectively. This review gives a comprehensive review on how the dimensionality manipulation improves performance of the carbon‐based electrodes in kinetics optimization, electron transfer acceleration, mechanical stabilization and thermal dissipation upon charging/discharging. The report ends with a critical perspective on the future challenges facing carbon‐based electrodes with dimensionality dependence. The progress highlighted here is expected to provide a guidance for the precise design and targeted synthesis of dimensionality varied carbon‐based electrode materials towards safe and high performance EES devices and the resulting optimized energy deployments.
The dimensionality design of functional carbon materials towards high‐energy and high‐power electrochemical energy storage (EES) devices is summarized as dimensionality transition, matching and integration. Rational dimensionality manipulations show great potential to effectively tune the carbon functions to enhance the ion/electron conduction, stress and thermal‐transfer efficiencies, finally building up high performance EES devices.
Low‐cost and scalable sodium ion (Na‐ion) batteries serve as an ideal alternative to the current lithium‐ion batteries. To compensate for the shortage of energy density, the most accessible solution ...is developing a high‐voltage anode‐free configuration comprising a lightweight Al current collector on the anode and a high‐voltage sodiumized cathode. However, it imposes stringent Na reversibility and high‐voltage stability requirements on the electrolyte. A 3A zeolite molecular sieve film is rationally designed, and a highly aggregated solvation structure is constructed through the size effect. It suppresses the trace but continuous oxidative decomposition and extends the oxidative stability to 4.5 V without sacrificing the Na reversibility of the anode (99.91 %). Thus, we can make anode‐free cells with high energy density of 369 and 372 W h kg−1 for 4.0 and 4.25 V class cells, respectively. Furthermore, this strategy enables a long lifespan (250 cycles) for 4.0 V‐class anode‐free cells.
A highly aggregated ether electrolyte is rationally constructed by introducing a 3A zeolite molecular sieve film. Benefitting from the highly aggregated electrolyte configuration, it enables a dramatically improved oxidative stability. Under the extremely harsh anode‐free conditions, the high‐voltage anode‐free Na battery configuration has an ultrahigh energy density of 369 W h kg−1 for 4.0 V class cathodes.
The development of lithium (Li) metal anodes Li metal batteries faces huge challenges such as uncontrolled Li dendrite growth and large volume change during Li plating/stripping, resulting in severe ...capacity decay and high safety hazards. A 3D porous copper (Cu) current collector as a host for Li deposition can effectively settle these problems. However, constructing a uniform and compact 3D porous Cu structure is still an enormous challenge. Herein, an electrochemical etching method for Cu–Zinc (Zn) alloy is reported to precisely engrave a 3D Cu structure with uniform, smooth, and compact porous network. Such a continuous structure endows 3D Cu excellent mechanical properties and high electrical conductivity. The uniform and smooth pores with a large internal surface area ensures well dispersed current density for homogeneous Li metal deposition and accommodation. A smooth and stable solid electrolyte interphase is formed and meanwhile Li dendrites and dead Li are effectively suppressed. The Li metal anode conceived 3D Cu current collector can stably cycle for 400 h under an Li plating/stripping capacity of 1 mA h cm−2 and a current density of 1 mA cm−2. The Li@3D Cu||LiFePO4 full cells present excellent cycling and rate performances. The electrochemical dealloying is a robust method to construct 3D Cu current collectors for dendrite‐free Li metal anodes.
The electrochemical etching method is presented to prepare 3D Cu with a uniform and compact porous network. As current collector of Li metal anode, the 3D Cu with large internal surface area and enhanced mechanical properties can effectively accommodate Li metal and suppress Li dendrite growth to achieve a high performance in a Li–metal battery.
All‐solid‐state lithium metal battery is the most promising next‐generation energy storage device. However, the low ionic conductivity of solid electrolytes and high interfacial impedance with ...electrode are the main factors to limit the development of all‐solid‐state batteries. In this work, a low resistance–integrated all‐solid‐state battery is designed with excellent electrochemical performance that applies the polyethylene oxide (PEO) with lithium bis(trifluoromethylsulphonyl)imide as both binder of cathode and matrix of composite electrolyte embedded with Li7La3Zr2O12 (LLZO) nanowires (PLLN). The PEO in cathode and PLLN are fused at high temperature to form an integrated all‐solid‐state battery structure, which effectively strengthens the interface compatibility and stability between cathode and PLLN to guarantee high efficient ion transportation during long cycling. The LLZO nanowires uniformly distributed in PLLN can increase the ionic conductivity and mechanical strength of composite electrolyte efficiently, which induces the uniform deposition of lithium metal, thereby suppressing the lithium dendrite growth. The Li symmetric cells using PLLN can stably cycle for 1000 h without short circuit at 60 °C. The integrated LiFePO4/PLLN/Li batteries show excellent cycling stability at both 60 and 45 °C. The study proposed a novel and robust battery structure with outstanding electrochemical properties.
A low resistance–integrated all‐solid‐state Li metal battery with excellent electrochemical performance is designed. The structure not only guarantees high ionic conductivity and good mechanical properties to suppress lithium dendrite growth by using polyethylene oxide (PEO)/lithium bis(trifluoromethylsulphonyl)imide embedded with Li7La3Zr2O12 nanowire composite electrolyte, but also decreases the interfacial impedance by applying PEO in both electrolyte and cathode that can fuse during operation.
Due to its amphiphilic property, graphene oxide (GO) can achieve a variety of nanostructures with different morphologies (for example membranes, hydrogel, crumpled particles, hollow spheres, ...sack‐cargo particles, Pickering emulsions, and so on) by self‐assembly. The self‐assembly is mostly derived from the self‐concentration of GO sheets at various interfaces, including liquid‐air, liquid‐liquid and liquid‐solid interfaces. This paper gives a comprehensive review of these assembly phenomena of GO at the three types of interfaces, the derived interfacial self‐assembly techniques, and the as‐obtained assembled materials and their properties. The interfacial self‐assembly of GO, enabled by its fantastic features including the amphiphilicity, the negatively charged nature, abundant oxygen‐containing groups and two‐dimensional flexibility, is highlighted as an easy and well‐controlled strategy for the design and preparation of functionalized carbon materials, and the use of self‐assembly for uniform hybridization is addressed for preparing hybrid carbon materials with various functions. A number of new exciting and potential applications are also presented for the assembled GO‐based materials. This contribution concludes with some personal perspectives on future challenges before interfacial self‐assembly may become a major strategy for the application‐targeted design and preparation of functionalized carbon materials.
With its amphiphilic nature, graphene oxide as a 2D soft molecule is characterized by many self‐concentration phenomena at interfaces, and these interesting interfacial properties, together with developed self‐assembly techniques, indicate a simple and effective strategy for producing a variety of novel carbon nanostructures and final bulk materials with designed functions.
A macroscopic 3D porous graphitic carbon nitride (g‐CN) monolith is prepared by the one‐step thermal polymerization of urea inside the framework of a commercial melamine sponge and exhibits improved ...photocatalytic water‐splitting performance for hydrogen evolution compared to g‐CN powder due to the 3D porous interconnected network, larger specific surface area, better visible light capture, and superior charge‐separation efficiency.
Accelerated conversion by catalysis is a promising way to inhibit shuttling of soluble polysulfides in lithium–sulfur (Li–S) batteries, but most of the reported catalysts work only for one direction ...sulfur reaction (reduction or oxidation), which is still not a root solution since fast cycled use of sulfur species is not finally realized. A bidirectional catalyst design, oxide–sulfide heterostructure, is proposed to accelerate both reduction of soluble polysulfides and oxidation of insoluble discharge products (e.g., Li2S), indicating a fundamental way for improving both the cycling stability and sulfur utilization. Typically, a TiO2–Ni3S2 heterostructure is prepared by in situ growing TiO2 nanoparticles on Ni3S2 surface and the intimately bonded interfaces are the key for bidirectional catalysis. For reduction, TiO2 traps while Ni3S2 catalytically converts polysulfides. For oxidation, TiO2 and Ni3S2 both show catalytic activity for Li2S dissolution, refreshing the catalyst surface. The produced sulfur cathode with TiO2–Ni3S2 delivers a low capacity decay of 0.038% per cycle for 900 cycles at 0.5C and specially, with a sulfur loading of 3.9 mg cm−2, achieves a high capacity retention of 65% over 500 cycles at 0.3C. This work unlocks how a bidirectional catalyst works for boosting Li–S batteries approaching practical uses.
A lithium–sulfur battery with long cycling stability is assembled with a specially designed bidirectional catalyst. The TiO2–Ni3S2 heterostructured catalyst realizes the smooth trapping–diffusion–conversion of polysulfides in the reduction process. The two components show catalytic activity toward the oxidation of Li2S. Thus, the shuttle effect and the formation of dead sulfides are effectively suppressed.
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