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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]

Benefiting from the high theoretic capacity, structural designability, low cost, abundant resources and sustainability, oxocarbons materials have attracted extensive attention as a promising candidate to replace inorganic electrode materials for alkali ion batteries (AIBs). This review focuses on the in‐depth evaluation of the electrochemical properties of oxocarbons for lithium, sodium and potassium ion batteries. Further, we summarize the evolution, challenges and opportunities of oxocarbon compounds based on our current understanding. In addition, we identified two main aspects that limit their applications as electrode materials: 1) inferior conductivity and 2) fast capacity decay. Hence, in this review we also integrate different strategies to improve these two aspects, e. g. compositing with carbon, grafting conductive polymers, nanostructuring, optimizing electrolytes, designing interface, and selecting appropriate binders. This review can be useful to understand the practical application and commercial feasibility of such materials for different AIBs applications. [ABSTRACT FROM AUTHOR]

The development of lithium-ion batteries (LIBs) is facing a huge challenge due to high cost and insufficient lithium resources. With the large-scale application of electric vehicles and portable electronics, the demand for LIBs is growing rapidly. In this connection, it is urgent to find a new secondary battery technology to make up for the shortcomings of LIBs. Potassium-ion batteries (PIBs) with low cost and high efficiency have drawn much attention. Particularly, layered transition metal oxides (LTMOs) with large interlayer distance and diffusion paths have been intensively investigated as cathode materials for PIBs. However, LTMO cathode materials often exhibit unsatisfactory electrochemical performance caused by the large potassium ion radius. To this end, this review mainly summarizes the progress of the research on LTMO cathode materials in PIBs. Meanwhile, the potassium storage mechanism and structural transformation are also analyzed for different metal-based LTMO cathode materials (single metal materials, dual-metal-based materials and multi-metal-based materials). What's more, the key technical issues and scientific challenges faced by LTMO cathode materials in PIBs are analyzed. This review provides constructive insights into the development of PIBs based on LTMOs. [ABSTRACT FROM AUTHOR]

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]

Even though NiCo2O4 is considered to be one of the most promising materials for supercapacitor applications, its unsatisfactory rate performance and cycling stability, due to inherently low electrical conductivity, have limited its further growth as a supercapacitor electrode. The present study tries to profitably exploit reduced graphene oxide (rGO) nanosheets as a conducting unit to enhance the electronic conductivity, by a simple hydrothermal technique assisted by ammonia hydroxide, to improve the overall electrochemical performance of NiCo2O4 in supercapacitors. The as-prepared NiCo2O4–rGO nanocomposite consists of NiCo2O4 hexagons wrapped in conducting rGO sheets, which ensure a short ion diffusion distance, percolating electron conducting pathways, and stable structural integrity. Such a feasible design provides good synergism between the rGO and the NiCo2O4, resulting in better electrochemical performance. As a result, this nanocomposite displays impressive overall electrochemical performance, in aspects such as promising capacitance (1185 F g−1 at a current density of 2 A g−1) and remarkable cycling stability (98% capacitance retention after 10 000 charge–discharge cycles at 2 A g−1). This facile method could be beneficial for preparing similar materials that require high electronic conductivity. [ABSTRACT FROM AUTHOR]

Even though Na3V2(PO4)3 (NVP) is regarded as one of the next-generation cathode materials in sodium-ion batteries (SIBs), its undesirable rate performance due to its inherently low electrical conductivity has limited its application in demanding fields such as electric vehicles. Motivated by this fact, the present study profitably employed a conductive carbon grown in situ to obtain an NVP@C composite with a pomegranate-like structure by a simple sol–gel assisted hydrothermal technique. The as-prepared NVP@C composite consists of small carbon-coated NVP particles (∼200 nm) embedded in a conductive carbon matrix, which ensures short ion diffusion distances, percolating electron/ion conduction pathways and stable structural integrity. As a result, the pomegranate-structured NVP@C composite displayed remarkable overall electrochemical performance: a high discharge capacity (110 mA h g−1 at 1C), excellent rate capability (92 mA h g−1 even at 50C) and impressive cycling stability (capacity retention of 91.3% over 2000 cycles at 10C). Such a feasible and beneficial design provides a good strategy for other materials that require both size reduction and high electronic/ionic conductivity. [ABSTRACT FROM AUTHOR]

Even though significant improvements have been made in sodium ion batteries, battery management mandates that all batteries in a pack are kept at an acceptable level of more than 80% capacity retention after a long cycle when it is tested for emergencies. Based on these realistic facts, the present study profitably exploits in situ grown reduced graphene oxide on 3D Na3V2 (PO4)3 matrices exhibiting a high rate performance and a specific discharge capacity of 117 mAh g-1. Unlike the earlier literature reports, it is demonstrated that the fabricated electrode shows >85% capacity retention after 6000 cycles at 10 C, the longest cycle life reported till date. The work also reasons in-depth the outstanding sodiation/desodiation capabilities to the low hysteresis voltage and how these electrodes can be used for deep discharges by extending the potential window to 1.3-3.8 V (vs Na/Na+) resulting in a noteworthy specific capacity of ≈165.4 mAh g-1 at 1 C. [ABSTRACT FROM AUTHOR]

Silicon and hematite, both important functional materials with high theoretical capacity, have been intensively investigated separately for application as anode materials in lithium ion batteries (LIBs). The main challenges associated with these anode materials are their low electronic conductivity and structural degradation caused by large volume expansion during cycling, which are not tolerable for future LIBs with high energy density and large power output. Active particles anchored on a porous conductive skeleton are widely used for improving the electrochemical performance of silicon as well as that of hematite. Herein, we develop a novel-structured carbon–silicon–hematite anode material via a single-step technique that addresses these problems. In the resultant architecture, silicon nanoparticles are sandwiched between the iron-oxide-embedded porous carbon sheets. The flexible and conductive carbon sheets improve the conductivity and accommodate the volume changes of the embedded hematite and silicon nanoparticles, and thus maintain the structural and electrical integrity. Meanwhile, the void space between the carbon layers leaves enough room for the expansion and contraction of silicon during the lithiation and delithiation processes. High capacity (∼1980 mA h g−1 at 750 mA g−1) and long cycle life (250 cycles) have been achieved for this sandwich-like carbon–silicon–hematite electrode. [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]

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]

Single-crystalline LiNi 0.6 Co 0.2 Mn 0.2 O 2 cathodes have received great attention due to their high discharge capacity and better electrochemical performance. However, the single-crystal materials are suffering from severe lattice distortion and electrode/electrolyte interface side reactions when cycling at high voltage. Herein, a unique single-crystal LiNi 0.6 Co 0.2 Mn 0.2 O 2 with Al and Zr doping in the bulk and a self-formed coating layer of Li 2 ZrO 3 in the surface has been constructed by a facile strategy. The optimized cathode material exhibits excellent structural stability and cycling performance at room/elevated temperatures after long-term cycling. Specifically, even after 100 cycles (1C, 3.0-4.4 V) at 50 °C, the capacity retention for the Al and Zr co-doped sample reaches 92.1%, which is much higher than those of the single Al-doped (85.4%), single Zr-doped (87.1%), and bare samples (76.3%). The characterization results and first-principles calculations reveal that the excellent electrochemical properties are attributed to the stable structure and interface, in which the Al and Zr co-doping hinders cation mixing and suppresses detrimental phase transformations to reduce internal stress and mitigate microcracks, and the coating layer of Li 2 ZrO 3 can protect the surface and suppress interfacial parasitic reactions. Overall, this work provides important insights into how to simultaneously build a stable bulk structure and interface for the single-crystal NCM cathode via a facile preparation process.

LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathodes suffer from severe bulk structural and interfacial degradation during battery operation. To address these issues, a three in one strategy using ZrB 2 as the dopant is proposed for constructing a stable Ni-rich cathode. In this strategy, Zr and B are doped into the bulk of LiNi 0.8 Co 0.1 Mn 0.1 O 2 , 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% ZrB 2 -LiNi 0.8 Co 0.1 Mn 0.1 O 2 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 ZrB 2 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., Competing Interests: The authors declare no conflict of interest., (© 2020 The Authors. Advanced Science published by Wiley‐VCH GmbH.)

Si-based anode materials have attracted considerable attention because of their ultrahigh reversible capacity. However, poor cycling stability caused by the large volume change during cycling prevented the commercial application of Si anodes for lithium-ion batteries (LIBs). To overcome these challenges, in the present study, we designed a nitrogen plasma-treated core-bishell nanostructure where the Si nanoparticle was encapsulated into a SiO x shell and N-doped TiO 2-δ shell. Here, the SiO x inside the shell and the TiO 2 outside the shell act as binary buffer matrices to accommodate the large volume change and also help to stabilize the solid electrolyte interphase films on the shell surface. More importantly, the plasma-induced N-doped TiO 2-δ shell with many Ti 3+ species and oxygen vacancies plays a key role in improving the electrical conductivity of Si anodes. Owing to the synergistic effects of SiO x and N-doped TiO 2-δ bishells, the cycling stability and rate performance of Si anodes are significantly enhanced. The as-obtained sample exhibits superior cycling stability with a capacity retention of 650 mA h g -1 at 200 mA g -1 after 300 cycles. This strategy is favorable for improving the electrochemical performances of Si-based anodes to employ in practical LIBs.

The capacity fluctuation phenomenon during cycling, which is closely related with solid electrolyte interphase and plays a key role for the design for advanced electrode, could be frequently observed in the titanium-based anode. However, the underlying reason for capacity fluctuation still remains unclear with rare related reports. Here, the origin of capacity fluctuation is verified with a long-life Na 2 Ti 6 O 13 anode. The reaction mechanism, structural evolution and reaction kinetics during the reported sodiation/desodiation processes were carefully investigated. The gradually enhanced diffusion controlled contribution resulted in the capacity increasing. And the capacity decay could be ascribed to the irreversible reaction of metallic titanium formation and the increasing potential polarization. It is worth noting that sodium ions seem to partially reduce NTO to metallic state, which is irreversible. The present study can provide more information for the design of advanced Na 2 Ti 6 O 13 anode.

The methodology employed here utilizes the sodium super ion conductor type sodium iron phosphate wrapped with conducting carbon network to generate a stable Fe 3+ /Fe 4+ redox   couple, thereby exhibiting higher operating voltage and energy density of sodium-ion batteries. This new class of sodium iron phosphate wrapped by carbon also displays a cycling stability with >96% capacity retention after 200 cycles., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)