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Sodium‐on batteries (SIBs) are promising alternatives to lithium‐ion batteries (LIBs) because of the low cost, abundance, and high sustainability of sodium resources. Analogous to LIBs, the high‐capacity electrodes in SIBs always suffer from rapid capacity decay upon long‐term cycling due to the particle pulverization induced by a large volume change. Circumventing particle pulverization plays a critical role in developing high‐energy and long‐life SIBs. Herein, tetrahydroxy‐1,4‐benzoquinone disodium salt (TBDS) that can self‐heal the cracks by hydrogen bonding between hydroxyl group and carbonyl group is employed as a cathode for sustainable and stable SIBs. The self‐healing TBDS exhibits long cycle life of 1000 cycles with a high rate capability up to 2 A g−1 due to the fast Na‐ion diffusion reaction in the TBDS cathode. The intermolecular hydrogen bonding has been comprehensively characterized to understand the self‐healing mechanism. The hydrogen bonding‐enabled self‐healing organic materials are promising for developing high‐energy and long‐cycle‐life SIBs. [ABSTRACT FROM AUTHOR]

A single-crystalline Ni-rich (SCNR) cathode with a large particle size can achieve higher energy density, and is safer, than polycrystalline counterparts. However, synthesizing large SCNR cathodes (>5 μm) without compromising electrochemical performance is very challenging due to the incompatibility between Ni-rich cathodes and high temperature calcination. Herein, we introduce Vegard's Slope as a guide for rationally selecting sintering aids, and we successfully synthesize size-controlled SCNR cathodes, the largest of which can be up to 10 μm. Comprehensive theoretical calculation and experimental characterization show that sintering aids continuously migrate to the particle surface, suppress sublattice oxygen release and reduce the surface energy of the typically exposed facets, which promotes grain boundary migration and elevates calcination critical temperature. The dense SCNR cathodes, fabricated by packing of different-sized SCNR cathode particles, achieve a highest electrode press density of 3.9 g cm−3 and a highest volumetric energy density of 3000 Wh L−1. The pouch cell demonstrates a high energy density of 303 Wh kg−1, 730 Wh L−1 and 76% capacity retention after 1200 cycles. SCNR cathodes with an optimized particle size distribution can meet the requirements for both electric vehicles and portable devices. Furthermore, the principle for controlling the growth of SCNR particles can be widely applied when synthesizing other materials for Li-ion, Na-ion and K-ion batteries. [ABSTRACT FROM AUTHOR]

The capacity of transition metal oxide cathode for Li‐ion batteries can be further enhanced by increasing the charging potential. However, these high voltage cathodes suffer from fast capacity decay because the large volume change of cathode breaks the active materials and cathode‐electrolyte interphase (CEI), resulting in electrolyte penetration into broken active materials and continuous side reactions between cathode and electrolytes. Herein, a robust LiF‐rich CEI was formed by potentiostatic reduction of fluorinated electrolyte at a low potential of 1.7 V. By taking LiCoO2 as a model cathode, we demonstrate that the LiF‐rich CEI maintains the structural integrity and suppresses electrolyte penetration at a high cut‐off potential of 4.6 V. The LiCoO2 with LiF‐rich CEI exhibited a capacity of 198 mAh g−1 at 0.5C and an enhanced capacity retention of 63.5 % over 400 cycles as compared to the LiF‐free LiCoO2 with only 17.4 % of capacity retention. [ABSTRACT FROM AUTHOR]

Aqueous rechargeable nickel‐zinc batteries (NZBs) have the advantages of economical cost and reliable safety. Despite reports of success in achieving high‐utilization and stable Zn anodes, the practical application of NZBs has been plagued by the restrictive capacity density and degradation of the Ni‐based cathode. Herein, it is reported that nickel‐ligand coordination grids (NCGs) with a high theoretical capacity of 128.12 mAh g−1 offer a fast faradic reaction while maintaining good reversibility due to the abundant open metal sites and flexible network structures. In situ and ex situ characterizations demonstrate that the graphene nanosheet (GN) modification of NCGs supramolecular substantially boosts surface charge and reducing the work function of supramolecular compounds. A Ni//Zn battery using such a graphene organic‐inorganic material (G‐NCGs) achieve a high gravimetric capacity of 113.8 mAh g−1 at 0.5 A g−1 with 50% of its initial capacitance retained after 2000 cycles and an exceptional rate capacity of 43.3 mAh g−1 even at the current density of 5.0 A g−1. [ABSTRACT FROM AUTHOR]

P2‐type layered oxides suffer from an ordered Na+/vacancy arrangement and P2→O2/OP4 phase transitions, leading them to exhibit multiple voltage plateaus upon Na+ extraction/insertion. The deficient sodium in the P2‐type cathode easily induces the bad structural stability at deep desodiation states and limited reversible capacity during Na+ de/insertion. These drawbacks cause poor rate capability and fast capacity decay in most P2‐type layered oxides. To address these challenges, a novel high sodium content (0.85) and plateau‐free P2‐type cathode‐Na0.85Li0.12Ni0.22Mn0.66O2 (P2‐NLNMO) was developed. The complete solid‐solution reaction over a wide voltage range ensures both fast Na+ mobility (10−11 to 10−10 cm2 s−1) and small volume variation (1.7 %). The high sodium content P2‐NLNMO exhibits a higher reversible capacity of 123.4 mA h g−1, superior rate capability of 79.3 mA h g−1 at 20 C, and 85.4 % capacity retention after 500 cycles at 5 C. The sufficient Na and complete solid‐solution reaction are critical to realizing high‐performance P2‐type cathodes for sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

Residual Li compounds are inevitably present in the form of Li2O, LiOH, and Li2CO3 on the surface of layered cathode materials, which not only causes slurry gelation in the cathode‐coating process but also degrades liquid electrolyte in the batteries. Owing to their strong alkaline nature, the residual Li compounds can react with acidic LiPF6 to form Li3PO4 and LiF, two of the main components of robust solid electrolyte interphases. By demonstrating LiNi0.80Co0.10Mn0.10O2 (NCM811) as an example in this work, we simply dissolved a small amount of LiPF6 into the cathode‐coating slurry, finding that as the amount of LiPF6 is controlled in the 0.5–1.0 wt % range versus the mass of NCM811, the LiPF6 additive not only improves the cycling stability but also enhances rate capability of the Li/NCM811 cells. The former is because the strongly alkaline residual Li compounds react with acidic LiPF6 to form stable Li3PO4 and LiF. The latter is attributed to a reduction in the surface layer resistance on the cathode, as suggested by the results of surface chemistry and impedance analyses. Added value: Dissolving a small amount of LiPF6 into the cathode slurry effectively removes residual Li compounds, which consequently improves the cycling stability and rate capability of layered cathode materials. [ABSTRACT FROM AUTHOR]

Benefiting from a higher volumetric capacity (3833 mA h cm−3 for Mg vs. 2046 mA h cm−3 for Li) and dendrite-free Mg metal anode, reversible Mg batteries (RMBs) are a promising chemistry for applications beyond Li ion batteries. However, RMBs are still severely restricted by the absence of high performance cathodes for any practical application. In this review, we provide a critical and rigorous review of Mg battery cathode materials, mainly reported since 2013, focusing on the impact of structure and composition on magnesiation kinetics. We discuss cathode materials, including intercalation compounds, conversion materials (O2, S, organic compounds), water co-intercalation cathodes (V2O5, MnO2etc.), as well as hybrid systems using Mg metal anode. Among them, intercalation cathodes are further categorized by 3D (Chevrel phase, spinel structure etc.), 2D (layered structure), and 1D materials (polyanion: phosphate and silicate), according to the diffusion pathway of Mg2+ in the framework. Instead of discussing every published work in detail, this review selects the most representative works and highlights the merits and challenges of each class of cathodes. Advances in theoretical analysis are also reviewed and compared with experimental results. This critical review will provide comprehensive knowledge of Mg cathodes and guidelines for exploring new cathodes for rechargeable magnesium batteries. [ABSTRACT FROM AUTHOR]

Abstract: Potassium‐ion batteries have been regarded as the potential alternatives to lithium‐ion batteries (LIBs) due to the low cost, earth abundance, and low potential of K (−2.936 vs standard hydrogen electrode (SHE)). However, the lack of low‐cost cathodes with high energy density and long cycle life always limits its application. In this work, high‐energy layered P2‐type hierarchical K0.65Fe0.5Mn0.5O2 (P2‐KFMO) microspheres, assembled by the primary nanoparticles, are fabricated via a modified solvent‐thermal method. Benefiting from the unique microspheres with primary nanoparticles, the K+ intercalation/deintercalation kinetics of P2‐KFMO is greatly enhanced with a stabilized cathodic electrolyte interphase on the cathode. The P2‐KFMO microsphere presents a highly reversible potassium storage capacity of 151 mAh g−1 at 20 mA g−1, fast rate capability of 103 mAh g−1 at 100 mA g−1, and long cycling stability with 78% capacity retention after 350 cycles. A full cell with P2‐KFMO microspheres as cathode and hard carbon as anode is constructed, which exhibits long‐term cycling stability (>80% of retention after 100 cycles). The present high‐performance P2‐KFMO microsphere cathode synthesized using earth‐abundant elements provides a new cost‐effective alternative to LIBs for large‐scale energy storage. [ABSTRACT FROM AUTHOR]

Abstract: Low‐cost multivalent battery chemistries (Mg2+, Al3+) have been extensively investigated for large‐scale energy storage applications. However, their commercialization is plagued by the poor power density and cycle life of cathodes. A universal polyimides@CNT (PI@CNT) cathode is now presented that can reversibly store various cations with different valences (Li+, Mg2+, Al3+) at an extremely fast rate. The ion‐coordination charge storage mechanism of PI@CNT is systemically investigated. Full cells using PI@CNT cathodes and corresponding metal anodes exhibit long cycle life (>10000 cycles), fast kinetics (>20 C), and wide operating temperature range (−40 to 50 °C), making the low‐cost industrial polyimides universal cathodes for different multivalent metal batteries. The stable ion‐coordinated mechanism opens a new foundation for the development of high‐energy and high‐power multivalent batteries. [ABSTRACT FROM AUTHOR]

Safety and the polysulfide shuttle reaction are two major challenges for liquid electrolyte lithium-sulfur (Li-S) batteries. Although use of solid-state electrolytes can overcome these two challenges, it also brings new challenges by increasing the interface resistance and stress/strain. In this work, the interface resistance and stress/strain of sulfur cathodes are significantly reduced by conformal coating ≈2 nm sulfur (S) onto reduced graphene oxide (rGO). An Li-S full cell consisting of an rGO@S-Li10GeP2S12-acetylene black (AB) composite cathode is evaluated. At 60 °C, the all-solid-state Li-S cell demonstrates a similar electrochemical performance as in liquid organic electrolyte, with high rate capacities of 1525.6, 1384.5, 1336.3, 903.2, 502.6, and 204.7 mA h g−1 at 0.05, 0.1, 0.5, 1.0, 2.0, and 5.0 C, respectively. It can maintain a high and reversible capacity of 830 mA h g−1 at 1.0 C for 750 cycles. The uniform distribution of the rGO@S nanocomposite in the Li10GeP2S12-AB matrix generates uniform volume changes during lithiation/delithiation, significantly reducing the stress/strain, thus extending the cycle life. Minimization of the stress/strain of solid cells is the key for a long cycle life of all-solid-state Li-S batteries. [ABSTRACT FROM AUTHOR]

Bipolar materials, which work as both the cathode and anode material in aqueous sodium-ion batteries, have advantages over aqueous electrolytes such as the low cost of sodium and high convenience of the material processing. However, the available materials are greatly limited. Herein, Prussian blue FeFe(CN)6 nanocubes were successfully synthesized by using a modified co-precipitation method. Owing to the well-separated redox reactions, fair cycling stability and rate capability of FeFe(CN)6, it could be developed as a bipolar material in an aqueous sodium-ion battery. The as-obtained full battery exhibits good cycling stability and rate capability. It was able to deliver a capacity of 32 mAhg-1 at 20 C, 76% of the capacity at 2 C. After 200 cycles at 2 C, 97% of the initial capacity was maintained for this battery, which suggests good cycling stability. [ABSTRACT FROM AUTHOR]

The polysulfide shuttle reaction has severely limited practical applications of Li-S batteries. Recently, functional materials that can chemically adsorb polysulfide show significant enhancement in cycling stability and Coulombic efficiency. However, the mechanism of the chemisorption and the control factors governing the chemisorption are still not fully understood. Here, it is demonstrated for the first time that the surface acidity of the host material plays a crucial role in the chemisorption of polysulfide. By tailoring the surface acidity of TiO2 via heteroatom doping, the polysulfide-TiO2 interaction can be fortified and thus significantly the capacity fading be reduced to 0.04% per cycle. The discovery presented here sheds light on the mechanism of this interfacial phenomenon, and opens a new avenue that can lead to a practical sulfur/host composite cathode. [ABSTRACT FROM AUTHOR]

A new super-concentrated aqueous electrolyte is proposed by introducing a second lithium salt. The resultant ultra-high concentration of 28 m led to more effective formation of a protective interphase on the anode along with further suppression of water activities at both anode and cathode surfaces. The improved electrochemical stability allows the use of TiO2 as the anode material, and a 2.5 V aqueous Li-ion cell based on LiMn2O4 and carbon-coated TiO2 delivered the unprecedented energy density of 100 Wh kg−1 for rechargeable aqueous Li-ion cells, along with excellent cycling stability and high coulombic efficiency. It has been demonstrated that the introduction of a second salts into the 'water-in-salt' electrolyte further pushed the energy densities of aqueous Li-ion cells closer to those of the state-of-the-art Li-ion batteries. [ABSTRACT FROM AUTHOR]

The sulfur-based cathode materials suffer severely from poor cycling stability and low utilization, incurred by their stepwise reaction mechanism that generates polysulfide intermediates and the subsequent irreversible losses. In this work, those issues are significantly relieved by entrapping sulfur species in carbon host rich in oxygen functionalities. Sulfur species in such C/S composite are highly stabilized by their interaction with oxygen, and can deliver a reversible capacity of 508 mAh/(g of S) for 2000 cycles when coupled with Li, representing the best cycling stability up to date. More interestingly, extra capacity can be accessed by simply prelithiating the oxygen-stabilized C/S composites down to 0.6 V for a few cycles, which enables a high capacity of 1621 mAh/(g of S) that eventually stabilizes at 820 mAh/(g of S) for 600 cycles. The mechanism for this electrochemical activation process is investigated with both spectroscopic and electrochemical techniques, which reveal that the inactive sulfur bonded to oxygen is liberated in the initial deep lithiation precycles and becomes electrochemically active. The oxygen-stabilized sulfur can also be coupled with Na anode to form Na/S cell, confirming that the formation of S−O interaction in C/S composite generates promising sulfur-based cathode materials for Li-S and Na-S batteries. [ABSTRACT FROM AUTHOR]

A facile synthesis of selenium sulfide (SeSx)/carbonized polyacrylonitrile (CPAN) composites is achieved by annealing the mixture of SeS2 and polyacrylonitrile (PAN) at 600 °C under vacuum. The SeSx molecules are confined by N-containing carbon (ring) structures in the carbonized PAN to mitigate the dissolution of polysulfide and polyselenide intermediates in carbonate-based electrolyte. In addition, formation of solid electrolyte interphase (SEI) on the surface of SeSx/CPAN electrode in the first cycle further prevents polysulfide and polyselenide intermediates from dissolution. The synergic restriction of SeSx by both CPAN matrix and SEI layer allows SeSx/CPAN composites to be charged and discharged in a low-cost carbonate-based electrolyte (LiPF6 in EC/DEC) with long cycling stability and high rate capability. At a current density of 600 mA g−1, it maintains a reversible capacity of 780 mAh g−1 for 1200 cycles. Moreover, it retains 50% of the capacity at 60 mA g−1 even when the current density increases to 6 A g−1. The superior electrochemical performance of SeSx/CPAN composite demonstrates that it is a promising cathode material for long cycle life and high power density lithium ion batteries. This is the first report on long cycling stability and high rate capability of selenium sulfide-based cathode material. [ABSTRACT FROM AUTHOR]

Abstract: Equilibrium potential hysteresis of electrode materials refers to the phenomenon that discharge equilibrium potential is lower than charge equilibrium potential. It is induced by the strain accommodation energy of phase transformation. Taking LiFePO4 as an example, the equilibrium potential hysteresis and accommodation energy of two LiFePO4 with different particle sizes were characterized using galvanostatic intermittent titration technique (GITT), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) methods. The LiFePO4 sample with 40nm particle size has lower accommodation energy than that of 100nm LiFePO4, which is due to a narrower miscibility gap and smaller potential hysteresis of 40nm LiFePO4 comparing to 100nm LiFePO4. The phase transformation of LiFePO4 occurs only at potential levels above delithiation (charge) equilibrium potential and below lithiation (discharge) equilibrium potential. No phase transformation occurs when charge/discharge is limited in the potential hysteresis range, i.e. LiFePO4 behaves like a solid solution in the potential hysteresis range. A reliable EIS can only be obtained when it is performed at the center of potential hysteresis and the potential amplitude does not exceed the range of equilibrium potential hysteresis. The analysis on strain accommodation and potential hysteresis of LiFePO4 cathodes during Li ion insertion/extraction is also suitable for other phase transformation electrodes. [ABSTRACT FROM AUTHOR]

Sodium ion batteries (SIBs) are promising candidatesfor the applicationsof large-scale energy storage due to their cost-effective and environmental-friendlycharacteristics. Nevertheless, it remains a practical challenge tofind a cathode material of SIBs showing ideal performance (capacity,reversibility, etc.). We report here a nanocomposite material of amorphous,porous FePO4nanoparticles electrically wired by single-wallcarbon nanotubes as a potential cathode material for SIBs. The hydrothermallysynthesized nanocomposite shows excellent cell performance with unprecedentedcycling stability and reversibility. The discharge capacity of ashigh as 120 mAh/g is delivered at a 0.1 C rate (10 mA/g). The capacityretentions are about 70 mAh/g, 60 mAh/g, and 55 mAh/g at higher currentsof 20 mA/g, 40 mA/g, and 60 mA/g, respectively. Even at a 1 C rate(100 mA/g), a capacity of about 50 mAh/g is still retained after 300cycles. With a simple synthetic procedure, cost-effective chemicals,and desirable cell performance, this method offers a highly promisingcandidate for commercialized cathode materials of SIBs. [ABSTRACT FROM AUTHOR]

• LLZNO nanoparticles coated LiCoO 2 cathodes are synthesized by a sol-gel method. • 3D ionic/electronic conducting networks inside the cathodes are constructed. • A reactive intermediate layer of PP13-TFSI is introduced in cathode/garnet interface. • A solid electrolyte interphase composed of LiF, Li 3 N, Li 2 S and Li 2 O is in situ formed. The garnet solid electrolyte battery confronts crucial challenges of electronic/ionic conduction inside the cathode and interfacial contact between the cathode and the electrolyte. In this report, a super ion/electron conductive LiCoO 2 (LCO) material is fabricated by partially coating nano Li 6.375 La 3 Zr 1.375 Nb 0.625 O 12 (LLZNO) electrolyte on LCO and then filling Super P carbons into the uncoated space. This configuration offers continuous ionically and electronically conducting networks inside the LCO cathode. In addition, an intermediate layer of N-Methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (PP13-TFSI) is introduced in between the composite cathode and the garnet electrolyte to form a solid-state ionically conducting interphase during charge/discharge cycles. Through the above interfacial engineering, the solid garnet batteries based on LiCoO 2 run as long as 400 cycles with the capacity retention of 80.2% at 0.2 C and 60 °C. [ABSTRACT FROM AUTHOR]