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Abstract Despite advances in traditional lithium-ion batteries in the past decades, its high cost has always been a bottleneck for large-scale applications. In this work, we demonstrate it is possible to replace expensive cathodes such as LiCoO 2 with inexpensive stainless steel to store energy via a stripping/deposition mechanism: during charging, the stainless-steel cathode removes charges by releasing metal ions into the electrolyte, and during discharge, the metal ions re-deposit on the electrode reversibly. An anion exchange membrane allows passage of anions to balance the charge and prevents cross-over of cations. We show here a battery with a stainless-steel cathode and a lithium metal anode with a high discharge voltage of 2.5 V and good reversibility. We also study the mechanism at the stainless-steel electrode, as well as the kinetics of the battery system. Our work can potentially reduce the cost of energy storage by turning common construction materials into cathode materials. In addition, a metal cathode undergoing stripping/deposition gives a theoretical energy density comparable to lithium-sulfur batteries and provides a new exciting direction for future energy storage development. [ABSTRACT FROM AUTHOR]

P2-type Na 0.7 MnO 2 , with high capacity and excellent Na ion conductivity, is a promising cathode material for Na-ion batteries. However, its rapid capacity decay upon repeated cycles restricts its practical application. In this study, we demonstrate a facile method to surface coat and dope P2-Na 0.7 MnO 2 with a P2-Na 0.7 Ni 0.33 Mn 0.67 O 2 layer in a single step to enhance its cycle stability. The coating suppresses the dissolution of Mn ions into electrolyte, and the Ni dopant suppresses orthorhombic distortion, inhibits Na + /vacancy ordering and improves structural stability upon cycling. As a consequence, the coating enhances capacity retention from 62.2% (Na 0.7 MnO 2 ) to 87.7% (Na 0.7 MnO 2 /20 wt% Na 0.7 Ni 0.33 Mn 0.67 O 2 ) over 50 cycles, and from 20.7% (Na 0.7 MnO 2 ) to 68.9% (Na 0.7 MnO 2 /20 wt% Na 0.7 Ni 0.33 Mn 0.67 O 2 ) over 100 cycles without sacrificing the initial discharge capacity. In addition, the air-stable Na 0.7 Ni 0.33 Mn 0.67 O 2 surface layer protects Na 0.7 MnO 2 against air exposure. [ABSTRACT FROM AUTHOR]

[Display omitted] Layered oxides based on manganese (Mn), rich in lithium (Li), and free of cobalt (Co) are the most promising cathode candidates used for lithium-ion batteries due to their high capacity, high voltage and low cost. These types of material can be written as xLi 2 MnO 3 ·(1 − x) LiTMO 2 (TM = Ni,Mn,etc.). Though, Li 2 MnO 3 is known to have poor cycling stability and low capacity, which hinder its industrial application commercially. In this work, Li 1.2 Ni 0.2 Mn 0.6 O 2 materials with different amounts of structural defects was successfully synthesized using powder metallurgy followed by different cooling processes in order to improve its electrochemical properties. Microstructural analyses and electrochemical measurements were carried out on the study samples synthesized by a combination of X-ray diffraction, transmission electron microscopy, and cyclic voltammetry. It is found that the disorder of the transition metal layer in Li 2 MnO 3 promotes its electrochemical activity, whereas the Li/Ni antisites of the Li layer maintain the stability of its local structure. The material with optimal amount of structural defects had an initial capacity of 188.2 mAh g−1, while maintaining an excellent specific capacity of 144.2 mAh g−1 after 500 cycles at 1C. In comparison, Li 1.2 Ni 0.2 Mn 0.6 O 2 without structural defect only gives a capacity of 40.8 mAh g−1 after cycling. This microstructural control strategy provides a simple and effective route to develop high-performance Co-free, Li-rich Mn-based cathode materials and scale-up manufacturing. [ABSTRACT FROM AUTHOR]

High-Ni materials LiNiO 2 or LiNi 1-x M x O 2 (x < 0.1), whose energy density is over 800 Wh kg−1 (discharge capacity >220 mAh g−1, average discharge voltage ∼3.8 V), are promising candidates as cathode for next-generation electric vehicle batteries. However, commercial applications of high-Ni cathodes have been hindered by their fast capacity fading with cycling. Herein, we synthesized a series of high-Ni materials (LiNiO 2 , LiNi 0.95 Co 0.05 O 2 and LiNi 0.9 Co 0.1 O 2) by adopting nanosheet hydroxide precursors. The obtained high-Ni materials with micro-spheres made up of nanorod grains can sustain the large volume deformation and eliminates cracking during charge-discharge. Owing to the hierarchical structure, our as-synthesized high-Ni cathodes exhibit excellent cycling stability up to 4.7 V and under high temperatures, and the corresponding full cells show superior long cycling stability suitable for practical applications, such as 94% and 83% capacity retention after 300 and 500 cycles, respectively for a LiNi 0.95 Co 0.05 O 2 ||graphite cell. Overall, this study offers a facile approach to address the poor cycling stability of high-Ni materials. Nanosizing the primary crystals of high-Ni cathode materials (LiNi 1-x M x O 2 , x < 0.1) can eliminate particle pulverization, and nanorods are more effective than ultra-fine nanocrystals in suppressing cracking. The nanorods in pure or Co-doped LiNiO 2 can be directly synthesized from nanosheet hydroxide precursors. [Display omitted] • High Ni nanosheet hydroxide precursors were synthesized. • Corresponding LiNiO 2 and LiNi 0.95 Co 0.05 O 2 adopt spherical particles with nanorods. • Nanorods LiNiO 2 and LiNi 0.95 Co 0.05 O 2 cathodes exhibit excellent cycle stability. • Cycle stability maintained at high voltage and high temperature. • Nanorod grains accommodate lattice stress and suppress particle cracking. [ABSTRACT FROM AUTHOR]

Abstract Traditional sodium-ion battery cathodes utilize the change in oxidation state of the transition metal(s) in the structure to accommodate the electron transfer during charge and discharge. Recent researches on sodium-rich compounds such as Na 2 RuO 3 and Na 2 IrO 3 suggest that anionic reaction with oxygen can be an additional source of electrons during electrochemical reactions. Here we demonstrate for the first time that stoichiometric NaVO 3 , despite the valence of vanadium of 5+, delivers a reversible capacity by activating it beyond 4.5 V. Elemental analysis confirms Na removal and insertion from/into NaVO 3 during charge/discharge. X-ray photoelectron spectroscopy and X-ray absorption near-edge spectroscopy results show that the oxidation state of vanadium remains unchanged, while oxygen is likely to compensate for the charge transfer during charge/discharge. Theoretical calculation on spin density of electrons in the lattice also supports the involvement of oxygen during sodium removal. Our demonstration of the unique behaviors of NaVO 3 provides a new exciting direction for research in sodium-ion battery cathodes. Highlights • NaVO 3 can be charged despite vanadium in its highest oxidation state. • Capacity of NaVO 3 depends strongly on particle size and electrical conductivity. • NaVO 3 undergoes reversible charge-discharge after activation. • NaVO 3 maintains its crystal structure upon charge and discharge. • Theoretical calculation suggests the involvement of oxygen during sodium removal. [ABSTRACT FROM AUTHOR]

Thermal stability of a lithium-rich layered oxide cathode material with composition 0.5Li 4/3 Mn 2/3 O 2 –0.5LiNi 1/3 Co 1/3 Mn 1/3 O 2 (LMO–NCM) is investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Investigated material shows higher thermal stability (higher onset temperature) than LiCoO 2 . The state of charge and previous cycling history of LMO–NCM, particularly activation of lithium manganese oxide (LMO) “component” during first charge, affect its thermal stability. Activation of LMO has an ambivalent effect on cathode thermal stability: on the one hand, the onset temperature of cathode decomposition is increased, probably due to the change in oxidation states of Ni, Co and Mn after the first cycle. On the other hand, the enthalpy of decomposition increases, presumably due to formation of unstable oxygen in the lattice. X-ray diffraction (XRD) analyses of cathodes before and after thermal decomposition at 600 °C indicate differences in decomposition reactions of charged cathodes, depending on state of charge and cycling history. [ABSTRACT FROM AUTHOR]

[Display omitted] • NASICON-structured Na 3 MnTi(PO 4) 2.83 F 0.5 cathode was first synthesized. • The introduction of F regulates the microstructure. • The incorporation of F- significantly enhances sodium storage performance. • The reversible solid-solution structural evolution in NMTPF-0.5 was revealed. NASICON-structured materials with high ionic conductivity, robust structure, and high operation potential have aroused extensive attentions as cathode for sodium-ion batteries (SIBs). However, the poor intrinsic electronic conductivity and low specific capacity are crucial obstacles for practical application of NASICON materials. Herein, a new NASICON-structured Na 3 MnTi(PO 4) 2.83 F 0.5 (NMTPF-0.5) with the hierarchical and porous structure is synthesized by a simple sol–gel method. The Rietveld refinements and Inductively Coupled Plasma (ICP) chemical analysis confirms the NASICON structure of NMTPF-0.5. The unique structural design significantly enhances rate performance. Meanwhile, the introduction of F- stimulates electrochemical activities of Mn, and stabilizes crystal structure compared with traditional Na 3 MnTi(PO 4) 3. Consequently, the NMTPF-0.5 achieves the high energy density of 511 Wh kg−1 at 0.1C, an outstanding rate performance (364 Wh kg−1 at 10C), and the desirable cycling stabilities exceeding 500 cycles at 10C. The ex-situ XRD reveals the insertion/extraction of Na+ through the reversible solid-solution mechanism. Moreover, we statistically analyze how the electrochemical properties and microstructure affected by various F- substitution amounts. This study explored a novel strategy for designing high capacity and high power-density cathode materials for SIBs via the microstructure and crystal structure optimization. [ABSTRACT FROM AUTHOR]

Silicon monoxide (SiO) is a promising anode material for Li-ion batteries because of its high capacity. Though, its low first Coulombic efficiency (FCE) due to the formation of inactive Li–Si–O compounds during lithiation hinders its practical application. Herein, we report a facile pre-sodiation technique by annealing SiO with a small amount of Na 2 CO 3 (≤ 5 wt%) under 850 °C, which improves FCE of pristine SiO from 61.4% to 86.0% without the use of lithium metal, solvent and disassembling and re-assembling of cells. Transmission electron microscopy, X-ray photoelectron spectroscopy, and nuclear magnetic resonance demonstrate that the incorporation of Na facilitates the disproportionation of SiO into crystalline Si and SiO 2 through nucleophilic substitution, and reduces the reactivity of the oxygen atoms with lithium and thereby suppresses the irreversible capacity during initial lithiation. The pre-sodiation process also improves thermal stability of SiO. Since the Na-containing SiO material is not sensitive to moisture in ambient condition, special handling of the material is not necessary. Combining with a LiFePO 4 cathode, the full cell shows a FCE of 85.8% with good cycle stability. The energy density of lithium-ion battery can even reach 900 Wh L−1 based on a theoretical calculation with high-capacity Ni-based metal-oxide cathode. • First Coulombic efficiency of SiO is increased to 86% by heat-treating with Na 2 CO 3. • Na 2 CO 3 facilitates disproportionation of SiO to SiO 2 , inactivating the oxygen atoms in the lattice. • Thermal stability of pre-treated SiO is enhanced with less heat generation. • The treated material is stable in air and exhibits remarkable water compatibility. • A LIB with volumetric energy density of 900 Wh L−1 can be achieved with optimization. [ABSTRACT FROM AUTHOR]

Capacity and operating voltage are critical parameters of cathode materials that dictate the energy density of lithium-ion batteries. Traditionally, redox reaction of the transition metal in the cathode limits the operating voltage and capacity during charge/discharge. Here, we simultaneously increase the capacity and operating voltage of LiVO 3 by utilizing the anionic redox reaction of oxygen in the lattice. While LiVO 3 gives a capacity of 235 mAh g−1 with an average potential of 2.18 V vs. Li/Li+ between 1.5 and 3.0 V from the vanadium redox reaction, they increase to 358 mAh g−1 and 2.55 V vs. Li/Li+, respectively, between 1.5 and 4.8 V. The higher capacity and operating voltage are due to the extraction of 0.56 mol of Li from its lattice when charging it to 4.8 V, despite vanadium originally in its highest oxidation state of 5+. The additional charge transfer derives from oxygen in the material, as X-ray spectroscopies and density functional theory calculation demonstrate the presence of peroxide species in the material and spin density around oxygen atoms, respectively, upon lithium extraction. Structural and gas analyses further reveal the stability of the anionic reaction, with only 0.21% volume change during lithium extraction with no O 2 gas release. • Monoclinic LiVO 3 exhibits anionic redox reaction (ARR) by charging it to 4.8 V. • 0.56 mol of Li is extracted from LiVO 3 upon charging despite valence of V is 5+. • Structural change of LiVO 3 is negligible with ARR between 2.4 and 4.8 V. • LiVO 3 gives discharge capacity of 358 mAh g−1 between 1.5 and 4.8 V. • Effect of voltage range on electrochemical performance of LiVO 3 studied. [ABSTRACT FROM AUTHOR]

Metal chalcogenides undergoing alloying and conversion mechanism can give high capacity as anode for lithium-ion batteries. However, large volume change and phase segregation lead to poor cycle performance. In this study, we focus on Sb 2 Se 3 and develop methods to enhance its long-term stability and reversibility. In particular, we find that carbon encapsulation reduces volume change during lithiation/delithiation and facilitates the recombination process of Sb and Se even after long cycling. With an addition of 20 wt% acetylene black, the Sb 2 Se 3 /C nanocomposite material exhibits an excellent cycle performance with a charge capacity of 545 mAh g−1 at 250 mA g−1 after 1000 cycles, corresponding to a capacity retention of 99.3%. We also demonstrate a full cell with LiFePO 4 cathode and Sb 2 Se 3 /C anode that is capable of delivering a stable capacity of 340 mAh g−1 at 1 A g−1 (about 3 C rate) after 300 cycles. • Sb 2 Se 3 nanoparticles encapsulated with carbon matrix is synthesized via mechanical ball-milling. • Carbon matrix enhances the mechanical stability of the electrode and suppresses phase segregation. • Sb 2 Se 3 @20%AB delivers a stable capacity of 545 mAh g−1 over 1000 cycles. • Sb 2 Se 3 @20%AB/LiFeO 4 full cell shows good rate capability and cycle stability. [ABSTRACT FROM AUTHOR]

The origins of low reversibility for Cu–Al battery were revealed. Components modifications solve irreversibility issues for Cu–Al battery. The polyacrylonitrile coating on Cu cathode reduces self-discharge. Polyvinylpyrrolidone modified 3M LiTFSI FEC inhibits the dendrite growth. The graphene oxide layer on Al anode suppresses side reaction between FEC and anode. 3 V rechargeable Cu–Al batteries are highly desirable for large-scale energy storage owing to the low cost and excellent scalability of the two metal electrodes. However, they still undergo irreversible processes such as the crossover of Cu ions, dendrite growth during alloy reaction at Al anode, and side reaction between AlLi and the electrolyte. In this work, we solve the poor reversibility of the battery by modifying the cathode, anode and electrolyte. Specifically, a polyacrylonitrile coating on the copper cathode anchors the dissolved Cu ions, polyvinylpyrrolidone additive in the electrolyte enables dendrite-free AlLi alloy formation and a graphene oxide layer on the Al anode suppresses reductive decomposition of the electrolyte, thereby improving average Coulombic efficiency. Our work overcomes some of the critical challenges in Cu–Al batteries and opens new opportunities for the development of low-cost, high-performance rechargeable metal-metal batteries. [Display omitted] [ABSTRACT FROM AUTHOR]

Aqueous rechargeable Zn-ion batteries (ARZIBs) are attractive due to their low cost, high safety and environmental friendliness. However, the development of ARZIBs still faces many challenges. One of the biggest challenges is to find suitable cathode materials for reversible Zn2+ ions insertion/extraction. In this work, we synthesize a Prussian blue analogue (PBA) with a new chemical composition, vanadium hexacyanoferrate (VHCF), via a simple co-precipitation method and study its performance as a cathode material for an aqueous rechargeable Zn-ion battery. The VHCF with two electrochemical redox active sites, V and Fe, delivers a three-electron redox reaction with a capacity of 187 mA h g−1 at current density of 0.5 A g−1. Even at a current rate of 5 A g−1, VHCF can still deliver a large capacity of 122 mA h g−1. The Zn//VHCF battery also exhibits a long cycle life of 1000 cycles with excellent capacity retention of 87.8% and a high Coulombic efficiency close to 100%. During the first charging process, the cubic structure of VHCF changes to a rhombohedral phase, a structure where the Zn2+ ions can be reversibly inserted into and extracted from in subsequent cycles. The promising performances make VHCF an attractive candidate as cathode material for ARZIBs system. Image 1 • A new kind of Prussian blue, vanadium hexacyanoferrate, is synthesized. • The vanadium hexacyanoferrate was tested as cathode in aqueous Zn-ion battery. • Two redox active sites, V and Fe, together contribute to the capacity. • The material exhibits excellent rate capability and long-term cyclability. • Structural evolution during the charge-discharge process is investigated. [ABSTRACT FROM AUTHOR]

Dual-ion battery (DIB) can potentially provide higher power, lower cost and faster charging capability than traditional lithium-ion batteries. Even though graphite can effectively accommodate anions as a cathode for DIB, the high working voltage of around 5 V vs. Li/Li+ leads to continuous side reactions, yielding to low Coulombic efficiency (CE < 90%) and poor cycle life. Here, we demonstrate that fluoroethylene carbonate (FEC) additive can induce a protective cathode electrolyte interface (CEI) on the graphite cathode, effectively suppressing electrolyte decomposition and stabilizing the graphite surface. This CEI enables a high CE (~99.0%) and an excellent cycle stability of 5000 cycles with capacity retention of 85.1% at the cutoff voltage of 5.1 V. The CEI layer can also reduce the self-discharge of the battery. Furthermore, the DIB exhibits a high-rate capability with 93.3% utilization at 30C (3000 mA g−1), enabling an ultrafast charging time within two minutes. This work sheds light on the features of CEI on graphite cathodes and provides a facile and economically effective strategy to achieve highly reversible/stable cycling of DIBs with high power capability. Image 1 • A protective cathode electrolyte interface is constructed on the graphite cathode. • The graphite surface is effectively stabilized for PF 6 − de-/intercalation process. • The cathode electrolyte interface significantly suppresses electrolyte decomposition. • The graphite-based dual-ion batteries with FEC additive exhibits low self-discharge. • Highly reversible/stable cycling and ultrahigh power capability are achieved. [ABSTRACT FROM AUTHOR]

• The surface of Cu 2+1 O is found to be wettable to molten Li for the first time. • The lithiophilicity origin of Cu 2+1 O surface was investigated. • The lithiophilicity is a key to fabricate and stabilize Li metal anodes. • An approach for mass production was proposed to obtain stable Li composite anodes. • The fabricated composite anodes showed excellent electrochemical performance. The carbon-based materials are promising hosts for metallic Li owing to their merits of excellent chemical stability, high porosity and electrical conductivity, as well as lightweight. Nevertheless, homogeneously pre-depositing Li into the carbon hosts remains a challenge owing to the inherited lithiophobic surface of carbon materials. In this contribution, we found that the Cu 2+1 O was lithiophilic and the origin of the lithiophilicity of Cu 2+1 O was investigated. Furthermore, a facile approach was presented to uniformly coat a thin Cu 2+1 O layer onto commercial carbon papers (CPs) to modify the surfaces of CPs into lithiophilic and after molten Li infusion, the Li-Cu 2+1 O-CP composite anode was fabricated. The CP could accommodate the huge volume change of Li and suppress the Li dendrite growth during cycling. As a result, the Li-Cu 2+1 O-CP composite anode delivered a stable repeating Li plating and stripping behavior (500 cycles at 10 mA cm−2 with 3 mAh cm−2Li) based on symmetric cell, as well as enhanced rate capability and cycling stability (97% capacity retention after 500 cycles) in full cells integrated with a commercial LiFePO 4 cathode. [ABSTRACT FROM AUTHOR]