Guoqiang Zou

Graphene‐Rich Wrapped Petal‐Like Rutile TiO2 tuned by Carbon Dots for High‐Performance Sodium Storage

Carbon dots inducing petal-like rutile TiO2 wrapped by ultrathin graphene-rich layers are proposed to fabricate superior anodes for sodium-ion batteries, featuring high-rate capabilities and long-term cyclelife, benefiting from promoted electron transport and a shortened Na+ diffusion length. High capacities of 144.4 mA h g-1 (at 837.5 mA g-1 ) after 1100 cycles and 74.6 mA h g-1 (at 3350 mA g-1 ) after 4000 cycles are delivered outstandingly.

Large-Area Carbon Nanosheets Doped with Phosphorus: A High-Performance Anode Material for Sodium-Ion Batteries

Large‐area phosphorus‐doped carbon nanosheets (P‐CNSs) are first obtained from carbon dots (CDs) through self‐assembly driving from thermal treatment with Na catalysis. This is the first time to realize the conversion from 0D CDs to 2D nanosheets doped with phosphorus. The sodium storage behavior of phosphorus‐doped carbon material is also investigated for the first time. As anode material for sodium‐ion batteries (SIBs), P‐CNSs exhibit superb performances for electrochemical storage of sodium. When cycled at 0.1 A g−1, the P‐CNSs electrode delivers a high reversible capacity of 328 mAh g−1, even at a high current density of 20 A g−1, a considerable capacity of 108 mAh g−1 can still be maintained. Besides, this material also shows excellent cycling stability, at a current density of 5 A g−1, the reversible capacity can still reach 149 mAh g−1 after 5000 cycles. This work will provide significant value for the development of both carbon materials and SIBs anode materials.

Black Anatase Titania with Ultrafast Sodium-Storage Performances Stimulated by Oxygen Vacancies.

Nanostructured black anatase titania with oxygen vacancies (OVs) is efficiently obtained and employed as an anode in sodium-ion batteries (SIBs) for the first time. The incorporation of OVs into TiO2 is demonstrated to render considerably enhanced-rate performances, higher initial capacities, and an accelerated electrochemical activation process during cycling, derived from the boosted intrinsic electric conductivity and improved kinetics of Na uptake. Bestowed with the integrated merits of OVs and shortened Na ion diffusion length in the nanostructure, black titania delivers a reversible specific capacity of 207.6 mAh g(-1) at 0.2 C, retains 99.1% over 500 cycles at 1 C stably, and still maintains 91.2 mAh g(-1) even at the high rate of 20 C. Density functional theory (DFT) calculations suggest that the lower sodiation energy barrier of anatase with OVs enables a more favorable Na intercalation into black anatase. Thus, it is of great significance to introduce OVs into TiO2 to stimulate ultrafast and durable sodium-storage properties, which also offers a potential strategy to project more superior electrodes, utilizing internal defects.

Size‐Tunable Olive‐Like Anatase Tio2 Coated with Carbon as Superior Anode for Sodium‐Ion Batteries

Olive-shaped anatase TiO2 with tunable sizes in nanoscale are designed employing polyvinyl alcohol (PVA) as structure directing agents to exert dramatic impacts on structure shaping and size manipulation. Notably, the introduced PVA simultaneously serves as carbon sources, bringing about a homogenous carbon layer with intimate coupling interfaces for boosted electronic conductivity. Constructed from tiny crystalline grains, the uniformly dispersed carbon-coated TiO2 nano-olives (TOC) possess subtle loose structure internally for prompt Na+ transportations. When utilized for sodium-ion storage, the size effects are increasingly significant at high charge-discharge rates, leading to the much superior rate performances of TOC with the smallest size. Bestowed by the improved Na+ adsorption and diffusion kinetics together with the promoted electron transfer, it delivers a high specific capacity of 267 mAh g-1 at 0.1 C (33.6 mA g-1 ) and sustains 110 mAh g-1 at a rather high rate of 20 C. Even after cycled at 10 C over 1000 cycles, a considerable capacity of 125 mAh g-1 with a retention of 94.6% is still obtained, highlighting its marvelous long-term cyclability and high-rate capabilities.

Controllable Interlayer Spacing of Sulfur‐Doped Graphitic Carbon Nanosheets for Fast Sodium‐Ion Batteries

The electrochemical behaviors of current graphitic carbons are seriously restricted by its low surface area and insufficient interlayer spacing for sodium-ion batteries. Here, sulfur-doped graphitic carbon nanosheets are reported by utilizing sodium dodecyl sulfate as sulfur resource and graphitization additive, showing a controllable interlayer spacing range from 0.38 to 0.41 nm and a high specific surface area up to 898.8 m2 g-1 . The obtained carbon exhibits an extraordinary electrochemical activity for sodium-ion storage with a large reversible capacity of 321.8 mAh g-1 at 100 mA g-1 , which can be mainly attributed to the expanded interlayer spacing of the carbon materials resulted from the S-doping. Impressively, superior rate capability of 161.8 mAh g-1 is reserved at a high current density of 5 A g-1 within 5000 cycles, which should be ascribed to the fast surface-induced capacitive behavior derived from its high surface area. Furthermore, the storage processes are also quantitatively evaluated, confirming a mixed storage mechanism of diffusion-controlled intercalation behavior and surface-induced capacitive behavior. This study provides a novel route for rationally designing various carbon-based anodes with enhanced rate capability.

Pinecone-like hierarchical anatase TiO2 bonded with carbon enabling ultrahigh cycling rates for sodium storage

Hierarchical anatase TiO2 homogeneously tuned by using carbon through Ti–C bonds has been designed, exploiting carbon quantum dots as uniform carbon additives and functionalization inducers for structure tailoring and surface modification. The fabricated pinecone-like structure constructed by ultrafine subunits presents a highly increased surface area (202.4 m2 g−1) and abundant mesopores. Surface bonded carbon significantly boosts its electronic conductivity derived from both the conductive carbon and accompanied oxygen vacancies. When utilized in sodium-ion batteries, it delivers a high reversible specific capacity of 264.1 mA h g−1 at a rate of 0.1C (33.6 mA g−1) and still maintains 108.2 mA h g−1 even after 2000 cycles at 10C with a retention of 94.7% outstandingly. Notably, its Na+ intercalation pseudocapacitive behavior is enhanced by the modulated TiO2/carbon interfaces, facilitating a fast (de-)sodiation process. Combining the elaborate hierarchical structure with the unique surface composition, synergetic merits are noticed when the promoted kinetics, improved electronic conductivity, increased electrolyte penetration areas and shortened Na+ diffusion length are achieved simultaneously, giving rise to remarkable high-rate capabilities and long-term cyclability.

Metal-Organic Framework-Derived Materials for Sodium Energy Storage

Recently, sodium-ion batteries (SIBs) are extensively explored and are regarded as one of the most promising alternatives to lithium-ion batteries for electrochemical energy conversion and storage, owing to the abundant raw material resources, low cost, and similar electrochemical behavior of elemental sodium compared to lithium. Metal-organic frameworks (MOFs) have attracted enormous attention due to their high surface areas, tunable structures, and diverse applications in drug delivery, gas storage, and catalysis. Recently, there has been an escalating interest in exploiting MOF-derived materials as anodes for sodium energy storage due to their fast mass transport resulting from their highly porous structures and relatively simple preparation methods originating from in situ thermal treatment processes. In this Review, the recent progress of the sodium-ion storage performances of MOF-derived materials, including MOF-derived porous carbons, metal oxides, metal oxide/carbon nanocomposites, and other materials (e.g., metal phosphides, metal sulfides, and metal selenides), as SIB anodes is systematically and completely presented and discussed. Moreover, the current challenges and perspectives of MOF-derived materials in electrochemical energy storage are discussed.

Preparation of S/N-codoped carbon nanosheets with tunable interlayer distance for high-rate sodium-ion batteries

The conventional strategies for obtaining S/N-codoped carbon materials suffer from a series of problems caused by their complicated experimental procedures. Here, S,N-codoped carbon nanosheets were firstly prepared by a solvent-free one-pot method, displaying an ultra-thin sheet-like structure, a tunable interlayer distance ranging from 0.37 nm to 0.41 nm, and a large surface area up to 809 m2 g−1. When they were used as an anode for sodium-ion batteries (SIBs), an outstanding sodium-ion storage performance of 380 mA h g−1 was acquired at 100 mA g−1, which can be attributed to the expanded interlayer distance caused by the introduction of the large covalent radius-sulfur. The initial coulombic efficiency improved to 60.9%, which may benefit from N-doping. Most importantly, an excellent rate capability of ∼178 mA h g−1 was observed at a current density of 5 A g−1 after 5000 cycles, which is among best of the state-of-the-art carbon-based SIBs. Interestingly, the morphology of the obtained carbon materials can be tuned from bulk to flake by adjusting the sulfur content or temperature. Given this, this work provides a new method to construct co-doped carbon (especially tri-doped and multi-doped carbon) and shows that the strategy of co-doping of heteroatoms can effectively optimize the nano/microstructure and enhance the rate capability of the carbon materials.

N-rich carbon coated CoSnO3 derived from in situ construction of a Co–MOF with enhanced sodium storage performance

In this study, N-rich carbon coated interconnected CoSnO3 nanoboxes (CoSnO3–NCs) with controllable amounts of N-rich carbon ranging from 7.5% to 24.6% were firstly prepared by the carbonization of CoSnO3–MOFs. Impressively, the preparation of CoSnO3–MOFs has been realized for the first time by directly utilizing CoSnO3 as the precursor under solvent-free conditions, bridging between the cobalt(II) ion in the skeleton of CoSnO3 and the 2-methylimidazole. Interestingly, the growth of these CoSnO3–MOFs can be manipulated by changing the amount of 2-methylimidazole used, resulting in a tunable N-rich carbon content. Furthermore, the electrochemical storage behavior of these materials for SIBs was initially explored. Compared with the pure CoSnO3, the as-resulted CoSnO3–NC materials showed largely enhanced sodium storage performance with a reversible capacity of 493.9 mA h g−1 at a current density of 0.1 A g−1 after 100 cycles. Moreover, the as-prepared materials showed an excellent high rate storage performance with a remarkable capacity of 273.8 mA h g−1 at 1 A g−1 after 1000 cycles. This work provides a new approach for constructing Co–MOFs as well as providing an efficient N-rich carbon-coating route, which may be expanded to other Co-based oxides and can greatly expand the development of new species of Co-based MOFs.

Sulfur-doped carbon employing biomass-activated carbon as a carrier with enhanced sodium storage behavior

Restricted by their high specific surface area and porous structures, activated carbon (AC) materials display poor performances, such as a low initial coulombic efficiency in sodium-ion batteries (SIBs). Nevertheless, it is an ideal choice for carriers, where the high specific surface area is indispensable. Herein, a novel strategy to design S-doped carbon employing durian shell-based AC (DSAC) as the template is proposed and the effect of the amount of DSAC additive was investigated in detail. Impressively, an optimized amount of DSAC additive would contribute to the good dispersion of poly-2-thiophenemethanol (sulfur source) as well as an increased number of active sites for Na storage, thus resulting in excellent electrochemical performance. A high reversible specific capacity of 345 mA h g−1 was attained and the specific capacity of 264 mA h g−1 was retained after 200 cycles. In particular, a high initial coulombic efficiency of 56.02% and remarkable rate capability of 100.02 mA h g−1 were achieved at 5 A g−1 even after 4500 cycles. Meaningfully, the proposed route used to prepare carbon materials for SIBs can effectively facilitate the further application of AC and the construction of high-performance electrode materials for SIBs.