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LiNi0.8Co0.1Mn0.1O2 cathodes suffer from severe bulk structural and interfacial degradation during battery operation. To address these issues, a three in one strategy using ZrB2 as the dopant is proposed for constructing a stable Ni‐rich cathode. In this strategy, Zr and B are doped into the bulk of LiNi0.8Co0.1Mn0.1O2, respectively, which is beneficial to stabilize the crystal structure and mitigate the microcracks. Meanwhile, during the high‐temperature calcination, some of the remaining Zr at the surface combined with the surface lithium source to form lithium zirconium coatings, which physically protect the surface and suppress the interfacial phase transition upon cycling. Thus, the 0.2 mol% ZrB2‐LiNi0.8Co0.1Mn0.1O2 cathode delivers a discharge capacity of 183.1 mAh g−1 after 100 cycles at 50 °C (1C, 3.0–4.3 V), with an outstanding capacity retention of 88.1%. The cycling stability improvement is more obvious when the cut‐off voltage increased to 4.4 V. Density functional theory confirms that the superior structural stability and excellent thermal stability are attributed to the higher exchange energy of Li/Ni exchange and the higher formation energy of oxygen vacancies by ZrB2 doping. The present work offers a three in one strategy to simultaneously stabilize the crystal structure and surface for the Ni‐rich cathode via a facile preparation process. [ABSTRACT FROM AUTHOR]

Demand for energy in day to day life is increasing exponentially. However, existing energy storage technologies like lithium ion batteries cannot stand alone to fulfill future needs. In this regard, potassium ion batteries (KIBs) that utilize K ions in their charge storage mechanism have attracted considerable attention due to their unique properties and are therefore established as one of the future battery systems of interest among the scientific community. Nevertheless, the development and identification of appropriate electrode materials is very essential for practical applications. This review features the current development in KIBs electrode and electrolyte materials, the present challenges facing this technology (in the commercial aspect), and future aspects to develop fully functional KIBs. The potassium storage mechanisms, evolution of the KIBs, and the advantages and disadvantages of each category of materials are included. Additionally, various approaches to enhance the electrochemical performances of KIBs are also discussed. This review is not only an amalgamation of different viewpoints in literature, but also contains concise perspectives and strategies. Moreover, the potential emergence of a novel class of K‐based dual ion batteries is also analyzed for the first time. [ABSTRACT FROM AUTHOR]

Current energy crises are inspiring researchers to focus intensively on development of feasible ways to produce high performing composite electrode materials for increasing energy demands. The present work addresses this objective by developing a novel structure of NiFe2O4 (NFO) nanoparticles coated on graphene capsules (GCs) by a simple hydrothermal technique. This NFO–GCs electrode material was subjected to different types of electrochemical performance evaluations to investigate its feasibility as a supercapacitor electrode. The as-prepared NFO–GCs nanocomposite electrode exhibits high specific capacitance of 1028 F g−1 at a current density of 2 A g−1 and 94% capacitance retention at the end of 10 000 charge–discharge cycles, whereas pristine NFO electrode shows 720 F g−1 specific capacitance with 88% capacitance retention. The high specific capacitance, good rate capability, and excellent cycling stability of NFO–GCs composite can be attributed to effective synergism between the GCs and NFO. The superior electrochemical performance of NFO–GCs nanocomposite demonstrates possible application of this material as a working electrode for fully functional supercapacitor devices. [ABSTRACT FROM AUTHOR]

Current trends in battery research are promoting the development of feasible methods to prepare electrode materials with new architectures that can meet the requirements of high energy density associated with sodium ion batteries (SIB). It is logical to use solid-state processing techniques to fabricate SIB electrode materials due to its ease of handling and capability for large-scale production. From the SIB standpoint, the sulfate based polyanionic system is well known for its high operating voltage. The present study utilizes a hitherto-unknown solid-state process with an entirely new composition to develop an electrode comprising earth abundant carbon, sodium, sulfur, fluorine, and iron materials. This new NaFeSO 4 F-CNT system, where CNT is carbon nanotube, obtained by the solid-state technique, exhibits a highly stable Fe 2+ /Fe 3+ redox couple and achieves a capacity of ∼110 mAg −1 at 0.1C with capacity retention of >91% after 200 cycles (1C). This is the best-ever reversible, high potential sulfate based cathode for sodium ion batteries reported to date. This study also provides an in-depth understanding of the outstanding electrochemical performance of this novel electrode. These findings can make it possible to achieve maximum performance from potential electrodes, when the operating temperature is limited to 350 °C or below. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of MnCo 2 O 4 nanoflake/graphene nanoplatelets composite is reported here for high performance supercapacitor electrode applications. The MnCo 2 O 4 nanoflakes with different morphologies were synthesized successfully via a hydrothermal technique by changing the amount of NH 4 F. The MnCo 2 O 4 nanoflakes in combination with the graphene nanoplatelets was deposited on Ni foam using an electrophoretic deposition technique. The as prepared composite electrode showed superior performance in terms of specific capacitance and cycling stability, as compared to the pristine MnCo 2 O 4 system, due to the enhanced electronic conductivity resulted from bond formation between carbon and MnCo 2 O 4. A high specific capacitance of ∼1268 F g −1 was observed at 1 mV s −1 scan rate. Noteworthy cycling stability was observed even at the end of 10,000 cycles of consecutive charging and discharging at a current density of 7.81Ag −1 . [ABSTRACT FROM AUTHOR]

A yolk-shell-structured carbon@void@silicon (CVS) anode material in which a void space is created between the inside silicon nanoparticle and the outer carbon shell is considered as a promising candidate for Li-ion cells. Untill now, all the previous yolk-shell composites were fabricated through a templating method, wherein the SiO2 layer acts as a sacrificial layer and creates a void by a selective etching method using toxic hydrofluoric acid. However, this method is complex and toxic. Here, a green and facile synthesis of granadilla-like outer carbon coating encapsulated silicon/carbon microspheres which are composed of interconnected carbon framework supported CVS nanobeads is reported. The silicon granadillas are prepared via a modified templating method in which calcium carbonate was selected as a sacrificial layer and acetylene as a carbon precursor. Therefore, the void space inside and among these CVS nanobeads can be formed by removing CaCO3 with diluted hydrochloric acid. As prepared, silicon granadillas having 30% silicon content deliver a reversible capacity of around 1100 mAh g−1 at a current density of 250 mA g−1 after 200 cycles. Besides, this composite exhibits an excellent rate performance of about 830 and 700 mAh g−1 at the current densities of 1000 and 2000 mA g−1, respectively. [ABSTRACT FROM AUTHOR]

3D lithium vanadium phosphate/reduced graphene oxide porous structures are prepared using a facile lyophilization process. The 3D porous nature of these lyophilized electrodes along with their high surface area lead to high rate capability and specific capacity. A high specific discharge capacity of ≈192 mAh g−1 is observed at 0.5 C. The cycling performance is noteworthy, as these lyophilized samples at 0.5 and 1 C do not show any fading, even after 1000 and 5000 cycles, respectively. Capacity retention of ≈96.2% is observed at the end of 10 000 cycles at 20 C. This remarkable cycling performance is attributed to the structural stability of the 3D porous network and is confirmed using scanning electron microscopy and selected area electron diffraction after 10 000 cycles of consecutive charging and discharging at 20 C. [ABSTRACT FROM AUTHOR]

The present study demonstrates a low temperature hydrothermal route for the synthesis of α-cobalt hydroxide comprising of randomly arrayed nano strands in a three dimensional plane. These micro/nano hybrid structures were used as building blocks for processing high surface area supercapacitor electrodes. Surface area of these structures was measured to be ∼100 m 2 g −1 . The influence of surface morphology in three different electrolytes namely lithium hydroxide, sodium hydroxide and potassium hydroxide was analyzed. The influence of surface morphology on capacitance and internal resistance was also determined and explained on the basis of redox reactions in these electrolytes. Capacitance values as high as 1024 F g −1 was attained for these structures when employed as thin film electrodes with life extending to more than 5000 cycles. Inductively coupled plasma-atomic emission spectroscopy was used to determine the electrode dissolution in the given electrolyte and the observations were co-related with the cycling stability. Low self-discharge, high rate capability along with low cost makes them promising systems for supercapacitor applications. [ABSTRACT FROM AUTHOR]

A new type of high-capacity sacrificial additive (Na4C6O6) is proposed to replenish the sodium loss in sodium ion full-cells. The HC//Na3V2(PO4)2F3 full-cells demonstrate significantly enhanced energy density after introducing an appropriate amount of additive. [ABSTRACT FROM AUTHOR]

• A multifunctional hybrid coating layer was proposed to modify the NCM811. • The modified sample demonstrated much enhanced electrochemical properties. • The capacity retention mechanisms were investigated in detail. Irreversible phase transition and surface residual lithium, which cause the fast capacity fading of LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), are the main obstacles that hinder their commercial application. Herein, to modify the surface/interphase properties of NCM811, we elaborately propose a hybrid Li 3 PO 4 -AlPO 4 -Al(PO 3) 3 coating layer that combines the advantages of ionic conductor (Li 3 PO 4) and thermal stable compound (AlPO 4) via reacting aluminum metaphosphate (Al(PO 3) 3) precursor with the surface residual lithium (Li 2 CO 3 or/and LiOH) during the coating process. When used as cathode for lithium-ion battery, the optimized NCM811 delivers a high initial discharge capacity of 201.8 mAh g−1 and 218.9 mAh g−1 at 0.1C under the temperature of 30 °C and 50 °C, with capacity retention of 85.4% and 78.89% after 50 cycles, respectively, which are much higher than that of uncoated sample (73.93% and 57.98%). Moreover, when it is coupled with graphite anode to form a lithium-ion full cell, it delivers an impressively high energy density of 467.5 Wh kg−1 (based on mass of positive and negative material), and retains 71.8% of its initial energy density after 100 cycles. The significantly enhanced electrochemical properties should be attributed to the multifunctional hybrid nano-coating layer that could efficiently reduce the surface residual lithium, suppress the irreversible phase transition, and prevent the active materials from the erosion of HF as verified by the ex-situ X-ray diffractometry, Raman spectroscopy and transmission electron microscopy. This work provides new insights into the surface/interphase design strategies to improve the structural stability of Ni-rich cathode, which will promote the development of high capacity cathode materials. [ABSTRACT FROM AUTHOR]

Abstract The application of Na 3·32 Fe 2·34 (P 2 O 7) 2 sodium cathodes with abundant resources and robust structure is severely hindered by the poor electronic conductivity. A multiple-dimensional carbon matrix could provide a satisfactory electronic conductivity as well as facilitate structural stability via wrapping and bridging of the active material. With an analysis of the raw materials and their respective reactions, Na 3·32 Fe 2·34 (P 2 O 7) 2 @C (NFP Cs) composites with a hybrid carbon matrix have been synthesized. The reactions in the system result in versatile N-doped carbon structures, including thin carbon layers, carbon rods, carbon nanosheets and carbon scaffolds. This integrated carbon architecture wraps and bridges the Na 3·32 Fe 2·34 (P 2 O 7) 2 particles, not only promoting electronic conductivity, but also serving as a buffer to minimize volume changes and stabilize the structural integrity of the composite. Furthermore, the nitrogen doping could generate more defects and active sites, which provide improved conductivity and better redox activity. Finally, the synthesized composite material has demonstrated impressive rate capabilities (100 mAh g−1 at 0.1 C and 66 mAh g−1 at 20 C), and outstanding cycling stability (90.5% at 1 C after 1000 cycles, 89.9% at 5 C after 2000 cycles). This study takes the utmost advantage of the synthesis, which is also easily scaled-up for mass production. Highlights • Na 3.32 Fe 2.34 (P 2 O 7) 2 @C composites are prepared via solid-state route. • Na 3.32 Fe 2.34 (P 2 O 7) 2 with a hybrid carbon matrix is investigated. • The multiple-dimensional N-doped carbon improves electronic conductivity. • Na 3.32 Fe 2.34 (P 2 O 7) 2 @C exhibits excellent electrochemical performance. [ABSTRACT FROM AUTHOR]

On page 440, S. Dou, H. Liu, and co‐workers present yolk‐shell‐structured carbon@void@silicon (CVS) anode material as a promising candidate for Li‐ion cells. The anode material is composed of an interior carbon network supporting the CVS yolk–shell silicon nanobeads. Fabrication of the anode material is achieved via a simple and green templating method. [ABSTRACT FROM AUTHOR]

• Etching of KMnO 4 could well tune the pyridinic-N content and defects of N-CNT. • Etching of KMnO 4 significantly improved the ORR performance of N-CNT. • This catalyst even outperformed the commercial Pt/C in Zn-air battery. • The second nearest carbon atom to the pyridinic-N at the edge was the real active site. Increasing the number of active sites is critical for developing N-doped carbon electrocatalysts towards oxygen reduction reaction (ORR) in fuel cells and metal-air batteries applications. Herein, we prepared N-doped carbon nanotubes (N-CNT) with enriched pyridinic N and abundant defects resulted from the etching of KMnO 4 of the precursor (polypyrrole). It was observed that the content of pyridinic N could be well controlled by regulating the etching time. The resultant catalyst displayed a superior ORR activity compared commercial Pt/C in an alkaline solution, which was further confirmed by home-made Zn-air batteries. Density functional theory (DFT) computations showed that the superior catalytic activity originated from the second nearest carbon atom to the pyridinic-N at the edge. This work provides a simple etching approach to alter the N configuration and the amount of defects in N-doped CNT, which can be extended to many other energy conversion materials. [ABSTRACT FROM AUTHOR]