Discharge Platforms Research Articles

Solvent Polarity‐Induced Regulation of Cation Solvation Sheaths for High‐Voltage Zinc‐Based Batteries with a 1.94 V Discharge Platform

To address the challenge of low discharge platforms (<1.5 V) in aqueous zinc‐based batteries, highly concentrated salts have been explored due to their wide electrochemical window (~3 V). However, these electrolytes mainly prevent hydrogen evolution and dendrite growth at the anode without significantly enhancing voltage performance. Herein we introduce an approach by adjusting solvent polarity to regulate cation solvation sheaths in hybrid electrolytes, reducing Zn/Zn2+ oxidation potential and water activity. Through strong cation‐water coordination and hydrogen bonding between dimethylsulfoxide and water, the designed electrolyte, at a low concentration, achieves a broader electrochemical window (4 V) than conventional concentrated electrolytes. Using this electrolyte, a Zn/Zn battery showed an impressive cycle life of 4340 cycles, while a Zn/lithium manganate battery delivered a high discharge platform of over 1.9 V with exceptional cycling stability. A Zn‐based micro‐battery with a polyvinyl alcohol‐based hybrid electrolyte also achieved a record‐high discharge platform of 1.94 V. This work presents a promising strategy for developing low‐concentration electrolytes for high‐performance sustainable energy storage.

Solvent Polarity-Induced Regulation of Cation Solvation Sheaths for High-Voltage Zinc-Based Batteries with a 1.94 V Discharge Platform.

To address the challenge of low discharge platforms (<1.5 V) in aqueous zinc-based batteries, highly concentrated salts have been explored due to their wide electrochemical window (~3 V). However, these electrolytes mainly prevent hydrogen evolution and dendrite growth at the anode without significantly enhancing voltage performance. Herein we introduce an approach by adjusting solvent polarity to regulate cation solvation sheaths in hybrid electrolytes, reducing Zn/Zn2+ oxidation potential and water activity. Through strong cation-water coordination and hydrogen bonding between dimethylsulfoxide and water, the designed electrolyte, at a low concentration, achieves a broader electrochemical window (4 V) than conventional concentrated electrolytes. Using this electrolyte, a Zn/Zn battery showed an impressive cycle life of 4340 cycles, while a Zn/lithium manganate battery delivered a high discharge platform of over 1.9 V with exceptional cycling stability. A Zn-based micro-battery with a polyvinyl alcohol-based hybrid electrolyte also achieved a record-high discharge platform of 1.94 V. This work presents a promising strategy for developing low-concentration electrolytes for high-performance sustainable energy storage.

Triphenylamine‐Supported Benzoquinone Polymer as High Performance Cathode for Lithium‐Ion Batteries

AbstractBenzoquinone (BQ) electrode is regarded as next generation energy storage material for lithium ion batteries (LIBs) because of its advantages of high theoretical specific capacity, abundant source, environmental friendliness. However, the two key challenges, the dissolution of BQ in organic electrolyte and the low discharge plateaus, impede practical application of BQ as cathode. Here, triphenylamine (TPA) with high working voltage and BQ with high theoretical capacity are used to synthesize triphenylamine‐benzoquinone monomer (TPA‐BQ) and its polymer (poly triphenylamine‐benzoquinone (PTPA‐BQ)) as cathodes for LIBs. The charge/discharge results reveal that the discharge plateaus of TPA‐BQ and PTPA‐BQ increase from ~2.5 V to ~3.5 V, and PTPA‐BQ exhibits high discharge capacity and remarkable cyclic stability compared with TPA‐BQ. The electrochemical mechanism shows that the redox peak potential of ~2.3 V/~2.2 V are assigned to the insertion/extraction of lithium ion in C=O groups of BQ, while at high potential of ~3.6 V/~3.5 V corresponds to the de‐dope/dope of the PF6− anion in TPA unit. The results demonstrate TPA was introduced BQ into small molecule to form PTPA‐BQ polymer that can improve discharge plateaus and charge/discharge performance of BQ small molecule, which provide guides for solving the dissolution and discharge platforms of the other organic electrode materials.

Study on high voltage (5 V) spinel lithium manganese oxide LiNi0.5Mn1.5O4 by doping niobium

AbstractThe effect of niobium ions with high‐valence doping on high‐voltage LiNi0.5Mn1.5O4 (LNMO) materials was investigated. LiNi0.5Mn1.5−xNbxO4 was prepared by doping high‐valent niobium ions into LiNi0.5Mn1.5O4 material using the organic assisted combustion method. The experimental samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), electrochemical impedance (EI), and cyclic voltammetry (CV) analysis. The experimental results show that ‐doping with high‐valence niobium ions changes the orientation of the crystal plane growth of spinel particles, and the morphology of these particles changes from the octahedral shape before doping to the spherical shape after doping. With the increase in doping amount, the crystal structure changes gradually, resulting in the Li0.96Nb1.01O3 impurity phase. The doping of high valence‐niobium ions increases the content of Mn3+ in the material, resulting in the appearance of a 4 V discharge platform and the formation of a 4.7 and 4 V discharge platforms. The doping of Nb can improve the cycling stability of LiNi0.5Mn1.5O4 material, but the specific capacity of the material is reduced.

A novel chlorine-zinc dual-ion battery

The development of new rechargeable safe batteries featuring high discharge platforms, low cost and environmental protection is one of the most ideal goals to achieve energy storage. Here we develop a novel chlorine-zinc dual-ion battery (C-ZDIB) that uses graphite paper as cathode, zinc as cathode, and (CH3)4NCl + Na2CO3 salt in water as electrolyte. The battery operates by redox reaction between Zn with Zn(OH)42− on the anode side and between ClO− and Cl− on the cathode side. The battery exhibits high discharge platform (about 2.6 V), high discharge capacity (226.2 mAh/g at 0.5 A/g), and long cycle life.

In situ three-dimensional cross-linked carbon nanotube-interspersed SnSb@CNF as freestanding anode for long-term cycling sodium-ion batteries

Alloying-based material has achieved tremendous appealing being anode used in sodium‑ion batteries (SIBs) by virtue of its relatively giant sodium storage specific capacity along with low discharge platforms. Nevertheless, the sluggish ion transmission dynamics and the huge volume change during cycling induced irreparable particle pulverization and agglomeration result in collapse of electrode structure and deterioration of cycling properties. In this work, three-dimensional cross-linked carbon nanotube-interspersed SnSb@CNF integrated structure (SnSb@CNF/CNT) is designed and synthesized. In this ingenious nanostructure, CNTs interspersed between CNF frames play the role of electron transport and diffusion “bridges” for enhancing the electrical conductivity of anode materials and relieve aggregation of SnSb alloy particles, the N doped-CNFs serve as external frame could efficiently mitigate dramatic volume effect to maintain system integrity. Based on these constructive advantages, the elastic conductive system can be directly available as anode for SIBs, showing ultralong cycling performance of 210 mAh g−1 over 700 sodiation/desodiation processes with a current density of 0.5 A g−1, even 161 mAh g−1 following 1000 cycling under a high current density of 1 A g−1 accompanied by an almost 100% superb capacity retention ratio, as well as distinguished high rate performance (470 mAh g−1 with a returned current density of 0.05 A g−1). This work shed distinctive insight to construct in situ three-dimensional cross-linked freestanding alloying-based anode materials used in alternative electrochemical grid-scale application.

A high-performance direct carbon solid oxide fuel cell powered by barium-based catalyst-loaded biochar derived from sunflower seed shell

Direct carbon solid oxide fuel cell (DC-SOFC) is one of the most attractive thesises for clean and efficient utilization of solid carbon to produce electricity. According to the operating principle, DC-SOFC performance is closely associated with the carbon sources and catalysts of the reverse Boudouard reaction. Here, we report a high-performance DC-SOFC powered by the biochar derived from sunflower seed shell (SSS) with barium-based catalyst loaded. The physicochemical properties of the SSS biochar are characterized and analyzed detailly. The electrolyte-supported symmetrical SOFC fueled with the SSS biochar gives an output of 216 mW cm−2 at 850 °C, indicating a great potential of the SSS biochar for DC-SOFCs. More importantly, the best output of 265 mW cm−2 and open circuit voltage of 1.03 V are obtained from DC-SOFC operated on 5 wt% barium-loaded SSS biochar, which is comparable to the output of 273 mW cm−2 from the hydrogen-fueled SOFC at 850 °C with the identical configuration. The superiorities of the SSS biochar and barium-based catalyst are also reflected in the operation stability and fuel utilization of DC-SOFCs. The discharge platforms are stable and the longest lifetime is up to 28.0 h under 50 mA with the fuel utilization of 31.3%, which is very excellent and competitive. This work provides a new idea for the effective utilization of the SSS biochar and other biomass for DC-SOFCs.

Mechanical Insights into the Electrochemical Properties of Thornlike Micro-/Nanostructures of PDA@MnO2@NMC Composites in Aqueous Zn Ion Batteries.

As emerging energy storage devices, aqueous zinc ion batteries (AZIBs) with outstanding advantages of high safety, high energy density, and environmental friendliness have attracted much research interest. Herein, the favorable thornlike MnO2 micro-/nanostructures (PDA@MnO2@NMC) are rationally constructed by the incorporation of both carbon substrates (NMC) and polydopamine (PDA) surface modifications. Ex situ X-ray diffraction and Raman characteristics show the formation of MnOOH and ZnMn2O4 products, corresponding to H+ and Zn2+ insertions in two discharge platforms. Density functional theory (DFT) calculations also demonstrate that PDA can firmly anchor onto MnO2 surfaces and prevent the dissolution of MnOOH. In addition, PDA with more hydrophilic groups can capture more H+ together with the increased surface capacitance and the extension of the first discharge platform, while the NMC carbon substrate can provide abundant active sites for the overgrown MnO2 nanowires, improve the conductivity, and promote fast ion and electron transportations. Further, electrochemical impedance spectroscopy (EIS) and GITT results show that the ohmic resistance of PDA@MnO2@NMC decreases to almost half and, in particular, the ion diffusion coefficient increases more than 30 times of pure MnO2. As such, PDA@MnO2@NMC in the AZIB cathode exhibits excellent electrochemical performance compared to the pure MnO2, which is expected to have favorable competitiveness in energy storage devices.

Modeling of a non-aqueous Li-O2 battery incorporating synergistic reaction mechanisms, microstructure, and species transport in the porous electrode

Li-O2 batteries are considered to be the next generation of new energy storage technology due to the extremely high theoretical energy density. The microstructure of the porous electrode takes an important role in the battery performance since the solid discharge product Li2O2 occupies the surface and void volume, increasing the transfer resistance. The product morphology and reaction mechanisms are affected by the electrode catalytic activity, electrolyte, and operating conditions. To systematically portray the microscopic processes in non-aqueous Li-O2 batteries, a model by coupling the above multiple factors is developed in this work. Unlike previous models where a single surface pathway or pore size distribution is considered alone, the present model focus on the interdependence of the reaction mechanisms and the electrode microstructure evolution, in which the reaction pathways are controlled by dynamic pore size. Moreover, the effective species transport relationship is modified, and the volume fraction and the corresponding active area of the products with different morphologies are calculated. The simulation results demonstrate the significant effects of microstructure on performance and explain the phenomenon of two discharge platforms, which comes from the tortuous variation of the electrode active area and are further influenced by current density and oxygen diffusion coefficient. This work is expected to guide the design of electrode structures and operating conditions for achieving improved performance.

Halogenated Ti3C2 MXenes with Electrochemically Active Terminals for High-Performance Zinc Ion Batteries.

The class of two-dimensional metal carbides and nitrides known as MXenes offer a distinct manner of property tailoring for a wide range of applications. The ability to tune the surface chemistry for expanding the property space of MXenes is thus an important topic, although experimental exploration of surface terminals remains a challenge. Here, we synthesized Ti3C2 MXene with unitary, binary, and ternary halogen terminals, e.g., -Cl, -Br, -I, -BrI, and -ClBrI, to investigate the effect of surface chemistry on the properties of MXenes. The electrochemical activity of Br and I elements results in the extraordinary electrochemical performance of the MXenes as cathodes for aqueous zinc ion batteries. The -Br- and -I-containing MXenes, e.g., Ti3C2Br2 and Ti3C2I2, exhibit distinct discharge platforms with considerable capacities of 97.6 and 135 mAh·g-1. Ti3C2(BrI) and Ti3C2(ClBrI) exhibit dual discharge platforms with capacities of 117.2 and 106.7 mAh·g-1. In contrast, the previously discovered MXenes Ti3C2Cl2 and Ti3C2(OF) exhibit no discharge platforms and only ∼50% of capacities and energy densities of Ti3C2Br2. These results emphasize the effectiveness of the Lewis-acidic-melt etching route for tuning the surface chemistry of MXenes and also show promise for expanding the MXene family toward various applications.

A Ni-doping-induced phase transition and electron evolution in cobalt hexacyanoferrate as a stable cathode for sodium-ion batteries.

Prussian blue analogues are potential competitive energy storage materials due to their diverse metal combinations and wide three-dimensional ion channels. Here, we prepared a new highly crystalline monoclinic nickel-doped cobalt hexacyanoferrate via a feasible and simple one-step co-precipitation method. In the process of sodium-ion de-intercalation, three stable charge and discharge platforms, which are consistent with the cyclic voltammetry performance, are seen for the first time, showing the function of nickel ions in Prussian blue. Furthermore, the charge transfer and structural evolution caused by the transmission of sodium ions were well revealed via ex situ XRD, ex situ XPS, and in situ EIS studies. Simulation calculations are performed relating to the energy band structure and the highest-occupied bonding orbitals of the system in different charge states, revealing the charge and discharge mechanism of the nickel-doped material and the reason for the emergence of the new platform at low voltages. In addition, NaNi0.17Co0.83Fe(CN)6 also delivers a striking capacity of 146 mA h g-1 and superior cyclability, with 93% capacity retention over 100 cycles; it can be considered as a promising alternative cathode material for use in sodium-ion batteries.

Hydrometallurgical Regeneration of LiMn2O4 Cathode Scrap Material and Its Electrochemical Properties

AbstractThe main researches focus on the recovery of metal elements in lithium manganate and not consider regenerating the cathode scrap materials. In this study, first, the polyvinylidene fluoride (PVDF) binder is removed by a combination of solvent dissolution and heat treatment. PVDF is easily separated by dissolving in an N‐methyl‐2‐pyrrolidone solution at a heating temperature of 60 °C, stirring time of 50 min, and solid solution ratio of 80 g⋅L−1. The dissolution rate of the scrap material achieves 86.70 % under optimal conditions. Further, using inductively coupled plasma spectroscopy to define the Li and Mn metal contents, and the LiMn2O4 cathode material is regenerated by a hydrometallurgical method. At the optimum calcination conditions of 500 °C for 12 h, electrochemical performance show that there are obvious charge and discharge platforms in the charge/discharge curves, and high first‐cycle discharge capacity is 123.7 mAh g−1 (3.0–4.3 V and 0.1 C), after 50 cycles, it decrease to 83.2 mAh g−1.

Pyrometallurgically regenerated LiMn2O4 cathode scrap material and its electrochemical properties

Recycling cathode materials from lithium-ion battery scraps can play a significant role in reducing environmental contamination and resource depletion. In this study, we employed pyrometallurgical techniques to regenerate LiMn2O4 cathode materials from recovered cathode scraps. First, the binder was removed under optimal conditions by a heating and stirring method to maximize the dissolution rate of the cathode scrap materials. Next, inductively coupled plasma spectroscopy was used to define the Li and Mn contents, and finally, the LiMn2O4 cathode material was regenerated by a pyrometallurgical method. After calcination under the optimum conditions of 500 °C for 12 h, electrochemical performance testing revealed obvious charge and discharge platforms in the charge/discharge curves; further, a high first-cycle discharge capacity was observed at 136.6 mAh·g-1 (3.0–4.3 V and 0.1 C), which decreased to 93 mAh·g-1 after 50 cycles. This process is low-cost and environmentally friendly, with the potential for recovering other cathode scrap materials.

Self‐Assembled Fe, N‐Doped Chrysanthemum‐Like Carbon Microspheres for Efficient Oxygen Reduction Reaction and Zn–Air Battery

Developing low‐cost, high‐activity, and stable carbon catalysts for electrochemical oxygen reduction reaction (ORR) has become the focus for the commercialization of Zn–air batteries. Herein, the 3D stereo ferrocene is introduced for constructing a novel structure with Fe, N‐doped chrysanthemum‐like carbon microspheres. This structure consists of open nanotubes with abundant cavities, which can facilitate the exposure of active sites. Ferrocene, with a unique sandwich structure, not only plays a pivotal role in inducing the chrysanthemum‐like structure but is also involved as iron‐related active species after pyrolysis. Eventually, FCN@F‐1 exhibits outstanding ORR performance with an onset potential of 1.03 V and a half‐wave potential of 0.87 V in alkaline media, which is superior to commercial Pt/C. The durability and methanol tolerance of FCN@F‐1 also outperform those of Pt/C. In addition, the Zn–air battery assembled by FCN@F‐1 air cathode manifests an open‐circuit voltage of 1.48 V, a prominent peak power density of 132 mW cm−2, and excellent discharge platforms at different current densities, which can provide wide prospects for the development of Zn–air batteries.

Study on discharge voltage and discharge capacity of LiFe1−xMnxPO4 with high Mn content

Rod-like LiFe1−xMnxPO4/C cathode with particle size of about 300–500 nm was fabricated successfully via simple hydrothermal method. By means of adjusting the manganese content of LiFe1−xMnxPO4, the electrochemical property was studied to clarify the effect of manganese content. LiFe1−xMnxPO4/C sample with x = 0.70 showed the superior specific discharge capacity of 153.1 mAh g−1 at a rate of 0.1 C, and the electrochemical mechanism analyzed by electrochemical impedance spectra demonstrated that the LiFe0.30Mn0.70PO4/C exhibited the smallest charge transfer impedance and the largest lithium-ion diffusion coefficient. With the increase of manganese content, the reduction of discharge capacity is attributed to the linear decrease of Mn2+/Mn3+ reduction reaction. When x = 0.80, the two discharge platforms located at 3.5 and 3.9 V, respectively, reach a maximum, which result from the reduction electromotive force of Fe2+/Fe3+ affected by the addition of manganese ions since the discharge platform of LiMnPO4 is higher than that of LiFePO4.

Highly dispersed ultra-small nano Sn-SnSb nanoparticles anchored on N-doped graphene sheets as high performance anode for sodium ion batteries

High theoretical capacity and low discharge platforms of Sn and Sb-based materials are an auspicious anode material for sodium ion batteries. Although, their large volume change before and after sodium insertion during cycling leads to unstable electrode structure and poor cycle performance. In view of the above, a thermo chemical strategy by a simple one-pot for producing 3–6 nm diameter homogeneously dispersed Sn/SnSb nanoparticles on a nitrogen-doped graphene sheet with a large-scale and low-cost feature for high performance sodium ion battery is reported. Highly dispersed nano Sn-SnSb alloy/graphene composite electrode not only had good stress adaptability and good integrity protection to prevent agglomeration and polarization during cycling, and also provided the rapid Na+ diffusion and electronic transfer channels, thus showing high rate and ultra-stable cycle performance. The as-prepared electrode could maintain the super stable reversible capacities of 251.8, 146.2 and 60.2 mAh g−1 at 1, 4 and 10 A g−1 over 1000 cycles, respectively.

A High Capacity Aluminum‐Ion Battery Based on Imidazole Hydrochloride Electrolyte

AbstractAluminum‐ion batteries (Al‐ion batteries) have become a potential energy storage system, owing to their excellent cycling performance, three‐electron‐redox properties, and safety performance. Until now, great progress has been made in Al‐ion batteries. However, the Al‐ion battery system still encounters various problems, such as high electrolyte price, harsh working environment, low discharge platforms, and inferior capacity. Here, we prepared a novel Al‐ion battery with AlCl3/Imidazole hydrochloride (ImidazoleHCl) as the electrolyte, aluminum as the negative electrode, and commercial graphite as the positive electrode. The battery achieves a high specific discharge capacity of 129 mA h g−1 at a current density of 0.5 A g−1 and 105 mA h g−1 with a high coulombic efficiency of 99 % at the current density of 4 A g−1 after 1000 cycles. The mechanism of AlCl4− intercalation/de‐intercalation is proved by Raman, XRD and EDS studies. ImidazoleHCl is a promising electrolyte and this work provides a new insight for the Al‐ion battery system.

A bridge between battery and supercapacitor for power/energy gap by using dual redox-active ions electrolyte

Capacitor-like and battery-like energy storage characteristics can be incorporated into a single cell to achieve optimal performance metrics through adding dual redox-active ions Bi3+/Br− to electrolyte. By adding dual redox-active ions to traditional electrolyte of carbon-based supercapacitor, redox reactions occur at each electrolyte/electrode interface simultaneously to store energy, exhibiting significant charge and discharge platforms which are battery-like energy storage characteristics. Moreover, a specific capacitance of 1150 F/g and an energy density of 61.8 Wh/kg are achieved at 2 A/g, surpassing most of the state-of-the-art work.

The facile in situ preparation and characterization of C/FeOF/FeF3 nanocomposites as LIB cathode materials

C/FeOF/FeF3 nanocomposite was synthesized by a facile in situ partial oxidation method. High-resolution transmission electron microscopy (HR-TEM) showed a special texture comprised of interpenetrating nanodomains of FeOF and FeF3. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements revealed that the introduction of nanodomain FeOF enhanced both the electronic and ionic conductivity of the composite material. Therefore, the improvement of electron and lithium-ion dynamics resulted in the significant enhancement of the electrochemical performances of the material at ambient temperature. At a current density of 20 mA g−1 within potential range 1.5–4.5 V, the specific capacities of the first ten circles were maintained at about 400 mAh g−1 . This material also exhibited excellent cycling capacity retention capability especially for high C rates. When the current density further increased to 100 and 200 mA g−1, a steady capacity of 80 and 60 mAh g−1 was observed, respectively. Furthermore, nearly no capacity loss was observed for the followed cycles. The discharge platforms based on intercalation and conversion reaction were also heightened by about 0.4 V, which increased the contribution of high voltage capacities. Compared to C/FeF3, C/FeOF/FeF3 is showing more of capacitive behavior, which also contributes to the high specific capacity delivered and is believed to be closely related to the enlarged nanodomain interfaces between two electrochemical active materials. An expansion-cracking-oxidation mechanism was proposed to explain the formation of this interpenetrating nanodomains of FeOF and FeF3.

Potassium salts of para-aromatic dicarboxylates as the highly efficient organic anodes for low-cost K-ion batteries

Two small organic molecules, namely potassium terephthalate (K2TP) and potassium 2,5-pyridinedicarboxylate (K2PC), were newly exploited as the highly efficient organic anodes in K-ion batteries. Both K2TP and K2PC exhibited the clear and reversible discharge and charge platforms in K-ion half cells, which were resulted from the redox behavior of organic para-aromatic dicarboxylates. The satisfactory and reversible specific capacities were realized in the K2TP- and K2PC-based K-ion cells, with average values of 181 and 190mAhg−1 for 100 cycles, respectively. The currently-obtained achievement of organic anodes could make a forward step for the further development of rocking-chair K-ion batteries.