Shaohua Guo

A Layered P2‐ and O3‐Type Composite as a High‐Energy Cathode for Rechargeable Sodium‐Ion Batteries

A layered composite with P2 and O3 integration is proposed toward a sodium-ion battery with high energy density and long cycle life. The integration of P2 and O3 structures in this layered oxide is clearly characterized by XRD refinement, SAED and HAADF and ABF-STEM at atomic resolution. The biphase synergy in this layered P2+O3 composite is well established during the electrochemical reaction. This layered composite can deliver a high reversible capacity with the largest energy density of 640 mAh g(-1), and it also presents good capacity retention over 150 times of sodium extraction and insertion.

High-performance symmetric sodium-ion batteries using a new, bipolar O3-type material, Na0.8Ni0.4Ti0.6O2

Based on low-cost and rich resources, sodium-ion batteries have been regarded as a promising candidate for next-generation energy storage batteries in the large-scale energy applications of renewable energy and smart grids. However, there are some critical drawbacks limiting its application, such as safety and stability problems. In this work, a stable symmetric sodium-ion battery based on the bipolar, active O3-type material, Na0.8Ni0.4Ti0.6O2, is developed. This bipolar material shows a typical O3-type layered structure, containing two electrochemically active transition metals with redox couples of Ni4+/Ni2+ and Ti4+/Ti3+, respectively. This Na0.8Ni0.4Ti0.6O2-based symmetric cell exhibits a high average voltage of 2.8 V, a reversible discharge capacity of 85 mA h g−1, 75% capacity retention after 150 cycles and good rate capability. This full symmetric cell will greatly contribute to the development of room-temperature sodium-ion batteries with a view towards safety, low cost and long life, and it will stimulate further research on symmetric cells using the same active materials as both cathode and anode.

A High-Voltage and Ultralong-Life Sodium Full Cell for Stationary Energy Storage.

Recently, there has been great interest in developing advanced sodium-ion batteries for large-scale application. Most efforts have concentrated on the search for high-performance electrode materials only in sodium half-cells. Research on sodium full cells for practical application has encountered many problems, such as insufficient cycles with rapid capacity decay, low safety, and low operating voltage. Herein, we present a layered P2-Na0.66 Ni0.17 Co0.17 Ti0.66 O2 , as both an anode (ca. 0.69 V versus Na(+) /Na) and as a high-voltage cathode (ca. 3.74 V versus Na(+) /Na). The full cell based on this bipolar electrode exhibits well-defined voltage plateaus near 3.10 V, which is the highest average voltage in the symmetric cells. It also shows the longest cycle life (75.9 % capacity retention after 1000 cycles) in all sodium full cells, a usable capacity of 92 mAh g(-1) , and superior rate capability (65 mAh g(-1) at a high rate of 2C).

A High-Capacity, Low-Cost Layered Sodium Manganese Oxide Material as Cathode for Sodium-Ion Batteries

A layered sodium manganese oxide material (NaMn3 O5 ) is introduced as a novel cathode materials for sodium-ion batteries. Structural characterizations reveal a typical Birnessite structure with lamellar stacking of the synthetic nanosheets. Electrochemical tests reveal a particularly large discharge capacity of 219 mAh g(-1) in the voltage rang of 1.5-4.7 V vs. Na/Na(+) . With an average potential of 2.75 V versus sodium metal, layered NaMn3 O5 exhibits a high energy density of 602 Wh kg(-1) , and also presents good rate capability. Furthermore, the diffusion coefficient of sodium ions in the layered NaMn3 O5 electrode is investigated by using the galvanostatic intermittent titration technique. The results greatly contribute to the development of room-temperature sodium-ion batteries based on earth-abundant elements.

Surface coating of lithium–manganese-rich layered oxides with delaminated MnO2 nanosheets as cathode materials for Li-ion batteries

Lithium–manganese-rich layered oxides are of great importance as cathode materials for rechargeable lithium batteries. In this article, Li1.2Mn0.567Ni0.167Co0.066O2 is prepared by a co-precipitation method, and the delaminated MnO2 nanosheets with different amounts, 1 wt%, 3 wt% and 5 wt%, are introduced for coating this material for the first time. The structure and morphology of these materials have been investigated via X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterizations. The results clearly demonstrate that the surface of lithium–manganese-rich layered oxides is covered by continuous delaminated MnO2 nanosheets. The electrochemical properties including the discharge capacity, initial coulombic efficiency, rate capability and cycle stability of these coated materials have been greatly enhanced, which are obviously related to the delaminated MnO2 nanosheet coating with good electrochemical activity and low charge transfer resistance. Moreover, the lithium–manganese-rich layered oxide coated with 3 wt% delaminated MnO2 nanosheets presents the best comprehensive electrochemical properties as well as improves the initial discharge capacity and coulombic efficiency by 299 mA h g−1 and 88% respectively; the capacity retention after 50 cycles also reaches 93%, and the discharge capacity can be 157 mA h g−1 even at a 5 C discharge rate.

Novel Stable Gel Polymer Electrolyte: Toward a High Safety and Long Life Li–Air Battery

Nonaqueous Li-air battery, as a promising electrochemical energy storage device, has attracted substantial interest, while the safety issues derived from the intrinsic instability of organic liquid electrolytes may become a possible bottleneck for the future application of Li-air battery. Herein, through elaborate design, a novel stable composite gel polymer electrolyte is first proposed and explored for Li-air battery. By use of the composite gel polymer electrolyte, the Li-air polymer batteries composed of a lithium foil anode and Super P cathode are assembled and operated in ambient air and their cycling performance is evaluated. The batteries exhibit enhanced cycling stability and safety, where 100 cycles are achieved in ambient air at room temperature. The feasibility study demonstrates that the gel polymer electrolyte-based polymer Li-air battery is highly advantageous and could be used as a useful alternative strategy for the development of Li-air battery upon further application.

Status and prospects of polymer electrolytes for solid-state Li–O2 (air) batteries

Li–air batteries have drawn considerable attention due to their high energy density and promising implementation in long-range electric vehicle and wearable electronic devices. Nevertheless, safety concerns, mainly derived from the use of flammable organic liquid electrolytes, have become a major bottleneck to the strategically crucial applications of Li–air batteries. Polymer electrolytes with non-toxicity, low vapor pressure, and non-flammable properties provide a feasible solution to safety issues through the replacement of organic liquid electrolytes, although fundamental understanding of polymer electrolytes for Li–air batteries is still insufficient. Accordingly, substantial research efforts have been devoted to achieving next-generation solid-state Li–air batteries with polymer electrolytes. Herein, we provide a specific review on the development of polymer electrolytes for Li–O2 (air) batteries, from comprehensive insight to emerging horizons, especially in understanding the underpinning chemistry and electrochemistry that govern the properties of polymer electrolytes for the solid-state lithium–air batteries. The discussion will highlight the recent progress in and challenges associated with polymer electrolytes for Li–O2 (air) batteries, as well as corresponding strategic perspectives.

From O2− to HO2−: Reducing By-Products and Overpotential in Li-O2 Batteries by Water Addition

The development of aprotic Li-O2 batteries, which are promising candidates for high gravimetric energy storage devices, is severely limited by superoxide-related parasitic reactions and large voltage hysteresis. The fundamental reaction pathway of the aprotic Li-O2 battery can be altered by the addition of water, which changes the discharge intermediate from superoxide (O2- ) to hydroperoxide (HO2- ). The new mechanism involving HO2- intermediate realizes the two-electron transfer through a single step, which significantly suppresses the superoxide-related side reactions. Moreover, addition of water also triggers a solution-based pathway that effectively reduces the voltage hysteresis. These discoveries offer a possible solution for desirable Li-O2 batteries free of aggressive superoxide species, highlighting the design strategy of modifying the reaction pathway for Li-O2 electrochemistry.

Synthesis of alkylidene pyrrolo[3,4-b]pyridin-7-one derivatives via RhIII-catalyzed cascade oxidative alkenylation/annulation of picolinamides

A novel tunnel Na(0.61)Ti(0.48)Mn(0.52)O2 material is explored as a cathode for sodium-ion batteries for the first time. It can deliver a reversible discharge capacity of 86 mA h g(-1) with an average voltage of 2.9 V at 0.2 C rate in a sodium half cell, exhibiting good rate capability and capacity retention at a cut-off voltage of 1.5-4 V. These results indicate that tunnel Na(0.61)Ti(0.48)Mn(0.52)O2 has a great potential application in large scale energy storage.

Environmentally stable interface of layered oxide cathodes for sodium-ion batteries

Sodium-ion batteries are strategically pivotal to achieving large-scale energy storage. Layered oxides, especially manganese-based oxides, are the most popular cathodes due to their high reversible capacity and use of earth-abundant elements. However, less noticed is the fact that the interface of layered cathodes always suffers from atmospheric and electrochemical corrosion, leading to severely diminished electrochemical properties. Herein, we demonstrate an environmentally stable interface via the superficial concentration of titanium, which not only overcomes the above limitations, but also presents unique surface chemical/electrochemical properties. The results show that the atomic-scale interface is composed of spinel-like titanium (III) oxides, enhancing the structural/electrochemical stability and electronic/ionic conductivity. Consequently, the interface-engineered electrode shows excellent cycling performance among all layered manganese-based cathodes, as well as high-energy density. Our findings highlight the significance of a stable interface and, moreover, open opportunities for the design of well-tailored cathode materials for sodium storage.The interface of layered cathodes for sodium ion batteries is subject to atmospheric and electrochemical corrosions. Here, the authors demonstrate an environmentally stable interface via titanium enriched surface reconstruction in a layered manganese-based oxide.