Xianlong Zhou

S‐Doped N‐Rich Carbon Nanosheets with Expanded Interlayer Distance as Anode Materials for Sodium‐Ion Batteries

2D composites with S doping into N-rich carbon nanosheets are fabricated, whose interlayer distance becomes large enough for Na+ insertion and diffusion. The large surface area and stable structure also provide more sites for Na+ adsorption, leading to high Na-storage capacity and excellent rate performance. Moreover, Faradaic reactions between Na+ and tightly bound S is beneficial for further improvement of Na-storage capacity.

Orderly Packed Anodes for High-Power Lithium-Ion Batteries with Super-Long Cycle Life: Rational Design of MnCO3/Large-Area Graphene Composites

MnCO3 particles uniformly distributed on large-area graphene form 2D composites whose large-area character enables them to self-assemble face-to-face into orderly packed electrodes. Such regular structures form continuous and efficient transport networks, leading to outstanding lithium storage with high capacity, ultralong cycle life, and excellent rate capability--all characteristics that are required for high-power lithium-ion batteries.

The First Introduction of Graphene to Rechargeable Li–CO2 Batteries

The utilization of the greenhouse gas CO2 in energy-storage systems is highly desirable. It is now shown that the introduction of graphene as a cathode material significantly improves the performance of Li-CO2 batteries. Such batteries display a superior discharge capacity and enhanced cycle stability. Therefore, graphene can act as an efficient cathode in Li-CO2 batteries, and it provides a novel approach for simultaneously capturing CO2 and storing energy.

Achieving battery-level energy density by constructing aqueous carbonaceous supercapacitors with hierarchical porous N-rich carbon materials

Pseudocapacitive materials hold great promise for achieving battery-level energy density integrated with power-related preponderance of electrostatic capacitors. However, it still remains a great challenge to find suitable capacitive material pairs to provide high operating voltage and high-level capacitance with good rate capability. Here, a three-dimensional hierarchical porous N-rich graphitic carbon (HNGC) material was prepared to construct novel symmetric aqueous carbonaceous supercapacitors (ACSCs). With ultrathin slice units, highly graphitic texture, and copious heteroatom functionalities, HNGC significantly promoted the faradic pseudo-capacitance, demonstrating an extremely high single-electrode capacitance of over 710 F g−1 in 1 M H2SO4 aqueous solution. First-principles computations revealed that copious N-induced defects tremendously boost the electrochemical performance of HNGC in acidic electrolytes by accommodating more protons, facilitating ion mobility and interfacial charge transport. Due to the co-existence of both electrical double-layer capacitance and pseudo-capacitance, the novel symmetric ACSCs with both structural and elemental advantages provide high operating voltage and a further high-level energy density of over 75 W h kg−1electrodes at a large power density of 1500 W kg−1, achieving battery-level energy density while retaining capacitor-level power delivery ability (30 kW kg−1) and cycling stability (ultra-long 8000 cycles). The proof-of-concept design of ACSCs outclasses the generally known high-voltage asymmetric counterparts under the same power and represents an advance towards battery-level energy density in supercapacitors.

Structural design for anodes of lithium-ion batteries: emerging horizons from materials to electrodes

High performance anodes are of great significance to high energy-power lithium ion batteries (LIBs); however, challenges are still pervasive in advancing new materials beyond commercial graphite. In this review, we outline the subsistent concerns on these adolescent anodes and systematically summarize the representative problem-solving designs, which are classified into two major categories totally including seven types, namely low-dimensional, inter-spatial, and composite design on materials; and ordered-array, cross-aligned, alternating-layer, and 3D porous design on electrodes. After generalizing advantageous features, we further highlight the burgeoning design horizon from materials to electrodes as well as their competences and perspectives to push the energy storage of LIBs to the next-generation level. These designing rationales represent general models of advanced LIB anodes and can illuminate the material and electrode innovations in other energy storage realms.

MOF-Derived Porous Co3O4 Hollow Tetrahedra with Excellent Performance as Anode Materials for Lithium-Ion Batteries

Porous Co3O4 hollow tetrahedra were prepared through the thermolysis of metal-organic frameworks and presented reversible capacities of 1196 and 1052 mAh g(-1) at 50 and 200 mA g(-1) after 60 charge/discharge cycles, respectively. Such excellent performances stem from the well-defined hollow structure of Co3O4 tetrahedra.

Stable layered P3/P2 Na0.66Co0.5Mn0.5O2 cathode materials for sodium-ion batteries

Rechargeable sodium-ion batteries are promising next-generation energy storage devices due to the low cost and rich natural abundance of Na. However, it is still a great challenge to suppress phase changes of cathode materials in the high-voltage region. Unlike P-type single-phase composites, herein we present a facile strategy for preparing P3/P2-type biphasic layered Na0.66Co0.5Mn0.5O2, namely, integrating P2 into P3-layered materials. The crystalline structure of Na0.66Co0.5Mn0.5O2, which was investigated by ex situ X-ray diffraction, was well maintained over long cycling in a high-voltage range. Taking advantage of their structural stabilization, Na0.66Co0.5Mn0.5O2 cathode materials displayed remarkably steady discharge capacity at high rates. With outstanding structural flexibility and electrochemical performance, Na0.66Co0.5Mn0.5O2 would stimulate the development of sodium-ion batteries.

Co2(OH)2CO3 Nanosheets and CoO Nanonets with Tailored Pore Sizes as Anodes for Lithium Ion Batteries

Co2(OH)2CO3 nanosheets were prepared and initially tested as anode materials for Li ion batteries. Benefiting from hydroxide and carbonate, the as-prepared sample delivered a high reversible capacity of 800 mAh g(-1) after 200 cycles at 200 mA g(-1) and long-cycling capability of 400 mAh g(-1) even at 1 A g(-1). Annealed in Ar, monoclinic Co2(OH)2CO3 nanosheets were transformed into cubic CoO nanonets with rich pores. The pore size had apparent influence on the high-rate performances of CoO. CoO with appropriate pore sizes exhibited greatly enhanced Li storage performances, stable capacity of 637 mAh g(-1) until 200 cycles at 1 A g(-1). More importantly, after many fast charge-discharge cycles, the highly porous nanonets were still maintained. Our results indicate that Co2(OH)2CO3 nanosheets and highly porous CoO nanonets are both promising candidate anode materials for high-performance Li ion batteries.

Ultrasmall MnO@N-rich carbon nanosheets for high-power asymmetric supercapacitors

Manganese monoxide (MnO) holds great potential for high-performance supercapacitors; however, it is highly desirable to establish a feasible structure to address common concerns of MnO materials. Herein, we have inserted ultrasmall MnO nanoparticles into N-rich carbon nanosheets (MnO@NCs) via a facile and scalable method. By integrating copious nitrogen species (over 13 wt%), flexible but robust carbon nanosheets offer powerful support for dispersing large amounts of MnO nanoparticles, creatively avoiding the inherent deficiencies of MnO such as poor electrical conductivity, low mechanical stability and severe electrochemical dissolution. Consequently, the MnO@NC electrode exhibited a striking capacitance of 570 F g−1 at 2 A g−1 within a wide operation voltage of 1 V, which spurs the low capacitance of MnO materials (generally 200–350 F g−1) to a higher level. Furthermore, initial attempts at fabricating asymmetric supercapacitors based on MnO@NCs demonstrated an energy density superior to its well-studied MnO2 counterpart. The introduction of N-rich species is of great significance for releasing restricted properties and fully exerting positive effects on the supercapacitors. Particularly, the impressive capacitance retention of ∼99% over 6000 cycles also propels a new direction for transition metal oxide/NC composites towards high-performance energy storage devices.

A P2-Na0.67Co0.5Mn0.5O2 cathode material with excellent rate capability and cycling stability for sodium ion batteries

Sodium ion batteries are considered as next-generation energy storage devices; however, stable cathode materials are highly desirable and challenging for sodium ion batteries. Herein, we report the preparation of a layered cathode material, P2-Na0.67Co0.5Mn0.5O2, with a hierarchical architecture, through a facile and simple sol–gel route. X-ray diffraction (XRD) and high resolution transmission electron microscopy elucidated a well-defined P2-type phase structure, and in situ XRD measurements provided further evidence about the structural stability during desodiation/sodiation. Benefiting from the structural stability, the cathode material delivered a high discharge capacity of 147 mA h g−1 at 0.1C rate, and excellent cyclic stability with nearly 100% capacity retention over at least 100 cycles at 1C. More importantly, 88 mA h g−1 was maintained when the electrode was cycled at a very high rate of 30C, and almost half of its capacity was retained over 2000 cycles, which outperforms all the reported P2-type cathode materials. With outstanding electrochemical performance and structural flexibility, the P2-Na0.67Co0.5Mn0.5O2 cathode material will promote the practical applications of sodium ion batteries.