ABSTRACT
This study explores the impact of introducing vacancy in the transition metal layer of rationally designed Na0.6[Ni0.3Ru0.3Mn0.4]O2 (NRM) cathode material. The incorporation of Ru, Ni, and vacancy enhances the structural stability during extensive cycling, increases the operation voltage, and induces a capacity increase while also activating oxygen redox, respectively, in Na0.7[Ni0.2VNi0.1Ru0.3Mn0.4]O2 (V-NRM) compound. Various analytical techniques including transmission electron microscopy, X-ray absorption near edge spectroscopy, operando X-ray diffraction, and operando differential electrochemical mass spectrometry are employed to assess changes in the average oxidation states and structural distortions. The results demonstrate that V-NRM exhibits higher capacity than NRM and maintains a moderate capacity retention of 81% after 100 cycles. Furthermore, the formation of additional lone-pair electrons in the O 2p orbital enables V-NRM to utilize more capacity from the oxygen redox validated by density functional calculation, leading to a widened dominance of the OP4 phase without releasing O2 gas. These findings offer valuable insights for the design of advanced high-capacity cathode materials with improved performance and sustainability in sodium-ion batteries.
ABSTRACT
In this work, the effects of dopant size and oxidation state on the structure and electrochemical performance of LiNi0.8Co0.1Mn0.1O2 (NCM811) are investigated. It is shown that doping with boron (B) which has a small ionic radius and an oxidation state of 3+, leads to the formation of a boron oxide-containing surface coating (probably Li3BO3), mainly on the outer surface of the secondary particles. Due to this effect, boron only slightly affects the size of the primary particle and the initial capacity, but significantly improves the capacity retention. On the other hand, the dopant ruthenium (Ru) with a larger ionic radius and a higher oxidation state of 5+ can be stabilized within the secondary particles and does not experience a segregation to the outer agglomerate surface. However, the Ru dopant preferentially occupies incoherent grain boundary sites, resulting in smaller primary particle size and initial capacity than for the B-doped and pristine NCM811. This work demonstrates that a small percentage of dopant (2 mol%) cannot significantly affect bulk properties, but it can strongly influence the surface and/or grain boundary properties of microstructure and thus the overall performance of cathode materials.
ABSTRACT
Herein, an Au-coating layer adjusted on the surface of a Zn metal electrode that effectively suppresses the dendrite growth as well as the mechanisms underlying the dendrite suppression as a result of the zincophilic character of Au is introduced. For the Au-coated Zn metal symmetric cell, uniform deposition of Zn-derived compounds was revealed by operando synchrotron tomography. Microscopic studies demonstrate that the Au-coating layer is induced to form a new Zn-Au alloy during the initial Zn deposition, resulting in stabilized long-term stripping/plating of Zn via the 'embracing effect' that intimately accommodates Zn deposition for further cycles. This property supports the successful operation of symmetrical cells up to 50 mA cm-2 . According to Zn electrodeposition simulation, it is verified that the suppression of dendrite growth is responsible for the electro-conducting Au nanolayer that uniformly distributes the electric field and protects the Zn electrode from corrosion, ultimately promoting uniform Zn growth. The compatibility of the Au-coating layer for full cell configuration is verified using NaV3 O8 as a cathode material over 1 000 cycles. This finding provides a new pathway for the enhancement of the electrochemical performance of ZIBs by suppressing the dendritic growth of Zn by means of a zincophilic Au nanolayer.
ABSTRACT
Rechargeable zinc aqueous batteries are key alternatives for replacing toxic, flammable, and expensive lithium-ion batteries in grid energy storage systems. However, these systems possess critical weaknesses, including the short electrochemical stability window of water and intrinsic fast zinc dendrite growth. Hydrogel electrolytes provide a possible solution, especially cross-linked zwitterionic polymers that possess strong water retention ability and high ionic conductivity. Herein, an in situ prepared fiberglass-incorporated dual-ion zwitterionic hydrogel electrolyte with an ionic conductivity of 24.32 mS cm-1 , electrochemical stability window up to 2.56 V, and high thermal stability is presented. By incorporating this hydrogel electrolyte of zinc and lithium triflate salts, a zinc//LiMn0.6 Fe0.4 PO4 pouch cell delivers a reversible capacity of 130 mAh g-1 in the range of 1.0-2.2 V at 0.1C, and the test at 2C provides an initial capacity of 82.4 mAh g-1 with 71.8% capacity retention after 1000 cycles with a coulombic efficiency of 97%. Additionally, the pouch cell is fire resistant and remains safe after cutting and piercing.
ABSTRACT
Since Ni-rich cathode material is very sensitive to moisture and easily forms residual lithium compounds that degrade cell performance, it is very important to pay attention to the selection of the surface modifying media. Accordingly, hydroxyapatite (Ca5 (PO4 )3 (OH)), a tooth-derived material showing excellent mechanical and thermodynamic stabilities, is selected. To verify the availability of hydroxyapatite as a surface protection material, lithium-doped hydroxyapatite, Ca4.67 Li0.33 (PO4 )3 (OH), is formed with ≈10-nm layer after reacting with residual lithium compounds on Li[Ni0.8 Co0.15 Al0.05 ]O2 , which spontaneously results in dramatic reduction of surface lithium residues to 2879 ppm from 22364 ppm. The Ca4.67 Li0.33 (PO4 )3 (OH)-modified Li[Ni0.8 Co0.15 Al0.05 ]O2 electrode provides ultra-long term cycling stability, enabling 1000 cycles retaining 66.3% of its initial capacity. Also, morphological degradations such as micro-cracking or amorphization of surface are significantly suppressed by the presence of Ca4.67 Li0.33 (PO4 )3 (OH) layer on the Li[Ni0.8 Co0.15 Al0.05 ]O2 , of which the Ca4.67 Li0.33 (PO4 )3 (OH) is transformed to CaF2 via Ca4.67 Li0.33 (PO4 )3 F during the long term cycles reacting with HF in electrolyte. In addition, the authors' density function theory (DFT) results explain the reason of instability of NCA and why CaF2 layers can delay the micro-cracking during electrochemical reaction. Therefore, the stable Ca4.67 Li0.33 (PO4 )3 F and CaF2 layers play a pivotal role to protect the Li[Ni0.8 Co0.15 Al0.05 ]O2 with ultra-long cycling stability.
Subject(s)
Electric Power Supplies , Lithium , Electrodes , IonsABSTRACT
Materials in nature have evolved to the most efficient forms and have adapted to various environmental conditions over tens of thousands of years. Because of their versatile functionalities and environmental friendliness, numerous attempts have been made to use bio-inspired materials for industrial applications, establishing the importance of biomimetics. Biomimetics have become pivotal to the search for technological breakthroughs in the area of rechargeable secondary batteries. Here, the characteristics of bio-inspired materials that are useful for secondary batteries as well as their benefits for application as the main components of batteries (e.g., electrodes, separators, and binders) are discussed. The use of bio-inspired materials for the synthesis of nanomaterials with complex structures, low-cost electrode materials prepared from biomass, and biomolecular organic electrodes for lithium-ion batteries are also introduced. In addition, nature-derived separators and binders are discussed, including their effects on enhancing battery performance and safety. Recent developments toward next-generation secondary batteries including sodium-ion batteries, zinc-ion batteries, and flexible batteries are also mentioned to understand the feasibility of using bio-inspired materials in these new battery systems. Finally, current research trends are covered and future directions are proposed to provide important insights into scientific and practical issues in the development of biomimetics technologies for secondary batteries.
ABSTRACT
We developed a new nanowire for enhancing the performance of lithium-sulfur batteries. In this study, we synthesized WO3 nanowires (WNWs) via a simple hydrothermal method. WNWs and one-dimensional materials are easily mixed with carbon nanotubes (CNTs) to form interlayers. The WNW interacts with lithium polysulfides through a thiosulfate mediator, retaining the lithium polysulfide near the cathode to increase the reaction kinetics. The lithium-sulfur cell achieves a very high initial discharge capacity of 1558 and 656 mAh g-1 at 0.1 and 3 C, respectively. Moreover, a cell with a high sulfur mass loading of 4.2 mg cm-2 still delivers a high capacity of 1136 mAh g-1 at a current density of 0.2 C and it showed a capacity of 939 mAh g-1 even after 100 cycles. The WNW/CNT interlayer maintains structural stability even after electrochemical testing. This excellent performance and structural stability are due to the chemical adsorption and catalytic effects of the thiosulfate mediator on WNW.
Subject(s)
Electric Power Supplies , Lithium/chemistry , Nanotubes, Carbon/chemistry , Nanowires/chemistry , Oxides/chemistry , Sulfur/chemistry , Tungsten/chemistry , Adsorption , Particle Size , Surface PropertiesABSTRACT
Cu, Al, and 316L stainless steel are the main components of the current collectors and coin-type cells used in the characterization of potassium-ion battery (KIB) materials and are expected to be electrochemically inactive. Herein, their electrochemical stabilities in a nonaqueous potassium-bis(fluorosulfonyl)imide (KFSI)-based electrolyte are investigated. In dynamic- and transient-mode polarization, passivation of each metal is observed to occur below 3.9, 3.8, and 4.05 V versus K+/K for Cu, Al, and 316L stainless steel, respectively, which are considered the threshold potentials. The composition of the passive layers of each metal is determined using time-of-flight secondary-ion mass spectrometry. The passive layers of Cu and Al consist of Cu-O (CuO or Cu2O) and Al-O (Al2O3), respectively, and 316L stainless steel is passivated with an outermost Cr-F (CrF3) layer and an inner Cr-O (Cr2O3) layer. Above the threshold potentials, however, severe corrosion of each metal occurs accompanied by the dissolution of metal ions, which could affect the reliability of experimental results for KIBs using KFSI-based electrolytes.
ABSTRACT
In this work, rhombohedral KTi2 (PO4 )3 is introduced to investigate the related theoretical, structural, and electrochemical properties in K cells. The suggested KTi2 (PO4 )3 modified by electro-conducting carbon brings about a flat voltage profile at ≈1.6 V, providing a large capacity of 126 mAh (g-phosphate)-1 , corresponding to 98.5% of the theoretical capacity, with 89% capacity retention for 500 cycles. Structural analyses using electrochemical performance measurements, first-principles calculations, ex situ X-ray absorption spectroscopy, and operando X-ray diffraction provide new insights into the reaction mechanism controlling the (de)intercalation of potassium ions into the host KTi2 (PO4 )3 structure. It is observed that a biphasic redox process by Ti4+/3+ occurs upon discharge, whereas a single-phase reaction followed by a biphasic process occurs upon charge. Along with the structural refinement of the electrochemically reduced K3 Ti2 (PO4 )3 phase, these new findings provide insight into the reaction mechanism in Na superionic conductor (NASICON)-type KTi2 (PO4 )3 . The present approach can also be extended to the investigation of other NASICON-type materials for potassium-ion batteries.
ABSTRACT
Sodium-ion batteries (SIBs) are emerging power sources for the replacement of lithium-ion batteries. Recent studies have focused on the development of electrodes and electrolytes, with thick glass fiber separators (~380 µm) generally adopted. In this work, we introduce a new thin (~50 µm) cellulose-polyacrylonitrile-alumina composite as a separator for SIBs. The separator exhibits excellent thermal stability with no shrinkage up to 300°C and electrolyte uptake with a contact angle of 0°. The sodium ion transference number, t Na + , of the separator is measured to be 0.78, which is higher than that of bare cellulose ( t Na + : 0.31). These outstanding physical properties of the separator enable the long-term operation of NaCrO2 cathode/hard carbon anode full cells in a conventional carbonate electrolyte, with capacity retention of 82% for 500 cycles. Time-of-flight secondary-ion mass spectroscopy analysis reveals the additional role of the Al2O3 coating, which is transformed into AlF3 upon long-term cycling owing to HF scavenging. Our findings will open the door to the use of cellulose-based functional separators for high-performance SIBs.
ABSTRACT
Herein, the Cu2P2O7/carbon-nanotube nanocomposite is reported as a cathode material based on a conversion reaction for rechargeable sodium batteries (RSBs). The nanocomposite electrode exhibits the large capacity of 355 mAh g-1, which is consistent with the 4 mol Na+ storage per formula unit determined by first-principles calculation. Its average operation voltage is approximately 2.4 V (vs Na+/Na). Even at 1800 mA g-1, a capacity of 223 mAh g-1 is maintained. Moreover, the composite electrode exhibits acceptable capacity retention of over 75% of the initial capacity for 300 cycles at 360 mA g-1. The overall conversion reaction mechanism on the Cu2P2O7/carbon-nanotube nanocomposite is determined to be Cu2P2O7 + 4Na+ + 4e- â 2Cu + Na4P2O7 based on operando/ex situ structural and physicochemical analyses. The high energy density of the Cu2P2O7/carbon-nanotube nanocomposite (720 Wh kg-1) supported by this conversion chemistry indicates a high possibility of application of this material as a promising cathode candidate for RSBs.
ABSTRACT
Here, we present K0.28MnO2·0.15H2O, which has a two-dimensional open framework, as an intercalation host for potassium ions. K0.28MnO2·0.15H2O has a layered structure consisting of edge-sharing MnO6 octahedra with a large basal spacing of â¼7.3 Å, which facilitates K+-ion mobility. Water molecules in the interlayers between the MnO2 layers play an important role as a pillar to support the structure during repetitive de/potassiation cycles, as confirmed by an operando X-ray diffraction study. As a result, the large K+ ions readily migrate into the crystal structure, resulting in satisfactory electrochemical performance in K-cells. With the aid of the structural pillar, the K0.28MnO2·0.15H2O cathode delivers a high reversible capacity of 150 mA h g-1 over 100 cycles at a rate of 0.1 C (15 mA g-1), with acceptable power capability up to 5 C-rates.
ABSTRACT
The P2-Na2/3MnO2 compound is one of the attractive cathodes for sodium-ion batteries due to its high initial capacity and abundance of Na and Mn elements in nature. The existence of Mn3+ Jahn-Teller ion, however, impedes electrode performance for long term. Here, we challenge to minimize the effect of the Jahn-Teller distortion caused by Mn3+ in the structure, via substitution of Mn3+ by Co3+ in P2-Na2/3[Mn1-xCox]O2 (x = 0-0.3). The P2-Na2/3[Mn0.8Co0.2]O2 compound substantializes the electrochemical performance with a capacity of about 175 mAh g-1 (26 mA g-1) and retained over 90% of its initial capacity for 300 cycles at 0.1 C (26 mA g-1) and 10 C (2.6 A g-1). The operando X-ray diffraction study indicates that a single-phase reaction is associated with the insertion of sodium ions into the structure, accompanied by a small volume change of approximately 3%. Furthermore, ex situ X-ray diffraction and high-resolution transmission electron microscopy results show that the crystal structure remained after 300 continuous cycles. It is believed that such good electrode performances attribute to the structural stabilization assisted by the presence of Co3+ in the crystal structure. Our finding provides a way to take advantage of low-cost Mn-rich cathode materials for sodium-ion batteries.
ABSTRACT
Potassium-ion batteries have emerged as an alternative to lithium-ion batteries as energy storage systems. In particular, KxMnO2 has attracted considerable attention as a cathode material because of its high theoretical capacity and low cost. In this study, partial substitution of Mn in P3-type K0.5MnO2 with divalent Ni is performed, resulting in a first discharge capacity of approximately 121 mAh (g-oxide)-1 with 82% retention for 100 cycles. Operando synchrotron X-ray diffraction analysis reveals the occurrence of phase transition from P3 to O3 on charge and O3-P3-P'3 transition on discharge at the first cycle, where P'3 is a new distorted form of the P3 phase, accompanied by reversible Mn4+/3+ and Ni3+/2+ redox pairs, as evidenced by X-ray absorption spectroscopy. The reduced variation in the lattice parameters during de/potassiation for P3-K0.5[Ni0.1Mn0.9]O2 relative to P3-K0.5MnO2 is suggested as a possible reason for the enhanced electrochemical performance of K0.5[Ni0.1Mn0.9]O2. These results open the possibility of using inexpensive and high-capacity Mn-based cathode active materials for potassium-ion batteries.
ABSTRACT
Sacrificing sodium supply sources is needed for sodium-deficient cathode materials to achieve commercialization of sodium-ion full cells using sodium-ion intercalation anode materials. Herein, the potential of ethylenediaminetetraacetic acid tetrasodium salt (EDTA-4Na) as a sacrificing sodium supply source was investigated by intimately blending it with sodium-deficient P2-type Na0.67[Al0.05Mn0.95]O2. The EDTA-4Na/Na0.67[Al0.05Mn0.95]O2 composite electrode unexpectedly exhibited an improved charge capacity of 177 mA h (g-oxide)-1 compared with the low charge capacity of 83 mA h (g-oxide)-1 for bare Na0.67[Al0.05Mn0.95]O2. The reversible capacity of an EDTA-4Na/Na0.67[Al0.05Mn0.95]O2//hard carbon full-cell system increased to 152 mA h (g-oxide)-1 at the first discharge with a Coulombic efficiency of 89%, whereas the Na0.67[Al0.05Mn0.95]O2 without EDTA-4Na delivered a discharge capacity 51 mA h g-1 because of the small charge capacity. The EDTA-4Na sacrificed itself to generate Na+ ions via oxidative decomposition by releasing four sodium ions and producing C3N as a decomposition resultant on charge. It is thought that the slight increase in discharge capacity is associated with the electroconducting nature of the C3N deposits formed on the surface of the Na0.67[Al0.05Mn0.95]O2 electrode. We elucidated the reaction mechanism and sacrificial activity of EDTA-4Na, and our findings suggest that the addition of EDTA-4Na is beneficial as an additional source of Na+ ions that contribute to the charge capacity.
ABSTRACT
Layered Na2/3MnO2 suffers from capacity loss due to Jahn-Teller (J-T) distortion by Mn3+ ions. Herein, density functional theory calculations suggest Na2/3[Fe xMn1- x]O2 suppresses the J-T effect. The Fe substitution results in a decreased oxygen-metal-oxygen length, leading to decreases in the b and c lattice parameters but an increase in the a lattice constant. As a result, the capacity retention and rate capability are enhanced with an additional redox pair associated with Fe4+/3+. Finally, the thermal properties are improved, with the Fe substitution delaying the exothermic reaction and reducing exothermic heat.
ABSTRACT
Conversion electrodes, which can realize high capacities by employing the wider valence states of transition metals, are investigated for sodium storage and applied for rechargeable sodium-ion batteries (SIBs). Importantly, this work is a first report for the sodium storage ability and related storage mechanism in oxalate compounds, specifically cobalt oxalate (CoC2O4) nanorods. The nanorods are intimately blended with acetylene black powders to achieve sufficient electrical conductivity (â¼10-3 S cm-1). The resulting C-CoC2O4 electrode delivers an initial capacity of about 330 mA h (g-CoC2O4)-1 at a rate of 0.2 C (60 mA g-1) and preserves 75% of the initial capacity over 200 cycles. A high charge (oxidation) capacity, â¼111 mA h g-1, was achieved even at 30 C (9000 mA g-1). This remarkable electrode performance is reported for the first time for metal oxalate compounds tested for Na cells, to the best of our knowledge. X-ray diffraction, transmission electron microscopy, and time-of-flight secondary-ion mass spectroscopy analyses lead to the proposal of a new sodium storage mechanism. For this mechanism, CoC2O4 is converted into Co metal involving with the creation of Na2C2O4 on discharge (reduction), and the Co metal is recovered to CoC2O4 on charge. The employed electroconducting carbon is likely to provide good electron conduction paths, which enables fast conversion on both discharge and charge. A full cell comprised of the C-CoC2O4 anode and carbon-coated NaCrO2 cathode exhibits good retention capacity over prolonged cycling, with retention of about 84.7% of the first capacity [107 mA h (g-NaCrO2)-1] for 300 cycles, and is active at a rate of 5 C (550 mA g-1), with a capacity of 79.5 mA h g-1. This result demonstrates the potential of applying C-CoC2O4 as an anode material for rechargeable SIBs.
ABSTRACT
Li3V2-xMnx(PO4)3 (x = 0, 0.05) cathode materials, which allow extraction of 3 mol of Li from the formula unit, were investigated to achieve a high energy density utilizing multielectron reactions, activated by the V3+/5+ redox reaction. Structural investigation demonstrates that V3+ was replaced by equivalent Mn3+, as confirmed by Rietveld refinement of the X-ray diffraction data and X-ray absorption near edge spectroscopy. The substitution simultaneously lowered the band gap energy from 3.4 to 3.2 eV, according to a density functional theory calculation. In addition to the effect of Mn doping, surface carbonization of Li3V2-xMnx(PO4)3 (x = 0, 0.05) dramatically increased the electric conductivity up to 10-3 S cm-1. As a result, the carbon-coated Li3V2-xMnx(PO4)3 (x = 0.05) delivered a high discharge (reduction) capacity of approximately 180 mAh g-1 at a current of 20 mA g-1 (0.1 C rate) with excellent retention, delivering approximately 163 mAh g-1 at the 200th cycle. Even at 50 C (10 A g-1), the electrode afforded a discharge capacity of 68 mAh g-1 and delivered approximately 104 mAh g-1 (1 C) at -10 °C with the help of Mn doping and carbon coating. The synergetic effects such as a lowered band gap energy by Mn doping and high electric conductivity associated with carbon coating are responsible for the superior electrode performances, including thermal properties with extremely low exothermic heat generation (<0.4 J g-1 for Li0.02V1.95Mn0.05(PO4)3), which is compatible with the layered high energy density of LiNi0.8Co0.15Al0.05O2 and LiNi0.8Co0.1Mn0.1O2 materials.
ABSTRACT
Unlike for SnO2, few studies have reported on the use of SnC2O4 as an anode material for rechargeable lithium batteries. Here, we first introduce a SnC2O4-reduced graphene oxide composite produced via hydrothermal reactions followed by a layer-by-layer self-assembly process. The addition of rGO increased the electric conductivity up to â¼10-3 S cm-1. As a result, the SnC2O4-reduced graphene oxide electrode exhibited a high charge (oxidation) capacity of â¼1166 mAh g-1 at a current of 100 mA g-1 (0.1 C-rate) with a good retention delivering approximately 620 mAh g-1 at the 200th cycle. Even at a rate of 10 C (10 A g-1), the composite electrode was able to obtain a charge capacity of 467 mAh g-1. In contrast, the bare SnC2O4 had inferior electrochemical properties relative to those of the SnC2O4-reduced graphene oxide composite: â¼643 mAh g-1 at the first charge, retaining 192 mAh g-1 at the 200th cycle and 289 mAh g-1 at 10 C. This improvement in electrochemical properties is most likely due to the improvement in electric conductivity, which enables facile electron transfer via simultaneous conversion above 0.75 V and de/alloy reactions below 0.75 V: SnC2O4 + 2Li+ + 2e- â Sn + Li2C2O4 + xLi+ + xe- â LixSn on discharge (reduction) and vice versa on charge. This was confirmed by systematic studies of ex situ X-ray diffraction, transmission electron microscopy, and time-of-flight secondary-ion mass spectroscopy.
ABSTRACT
We report a highly performing anode material for sodium-ion batteries (SIBs) composed of graphene decorated by indium sulfide (In2S3). The composite is synthesized by a facile hydrothermal pathway with subsequent annealing and is characterized by defined structure and well-tailored morphology, as is indeed demonstrated by X-ray diffraction and spectroscopy as well as high-resolution microscopy. These optimal characteristics allow the electrode to perform remarkably in sodium cell by achieving a maximum specific capacity as high as 620 mAh g-1 and the still-relevant value of 335 mAh g-1 at an extremely high current (i.e., 5 A g-1). The high storage capacity, the long cycle life, and the impressive rate capability of the composite may be attributed to the synergetic effect between uniform In2S3 nanoparticles and the graphene matrix. These features suggest that the In2S3-graphene is a viable choice for application as an anode material in high-performance SIBs.