Application In Rechargeable Batteries Research Articles

Lithium Storage Performance Boosted via Delocalizing Charge in ZnxCo1−xPS3/CoS2 of 2D/3D Heterostructure

AbstractA promising anode material consisting of bimetallic thiophosphate ZnxCo1−xPS3 and CoS2 with 2D/3D heterostructure is designed and prepared by an effective chemical transformation. Density functional theory calculations illustrate that the Zn2+ can effectively modulate the electrical ordering of ZnxCo1−xPS3 on the nanoscale: the reduced charge distribution emerging around the Zn ions can enhance the local built‐in electric field, which will accelerate the ions migration rate by Coulomb forces and provide tempting opportunities for manipulating Li+ storage behavior. Moreover, the merits of the large planar size enable ZnxCo1–xPS3 to provide abundant anchoring sites for metallic CoS2 nanocubes, generating a 2D/3D heterostructure with a strong electric field. The resultant ZnxCo1−xPS3/CoS2 can offer the combined advantages of bimetallic alloying and heterostructure in lithium storage applications, leading to outstanding performance as an anode material for lithium‐ion batteries. Consequently, a high capacity of 794 mA h g−1 can be retained after 100 cycles at 0.2 A g−1. Even at 3.0 A g−1, a satisfactory capacity of 465 mA h g−1 can be delivered. The appealing alloying‐heterostructure and electrochemical performance of this bimetallic thiophosphate demonstrate its great promise for applications in practical rechargeable batteries.

Nitrogen doped CuCo2O4 nanoparticles anchored on beaded-like carbon nanofibers as an efficient bifunctional oxygen catalyst toward zinc-air battery

The elaborative design and construction of first-rank bifunctional oxygen electrocatalysts featuring low price, high activity and strong stability is critical for the large-scale applications of rechargeable Zn-air batteries. Here, a resultful strategy is proposed for fabricating nitrogen-doped 1D beaded-like structure carbon nanofibers uniformly decorated with nitrogen-doped CuCo2O4 nanoparticles (N-CuCo2O4@CNFs) toward boosting oxygen evolution reaction/oxygen reduction reaction (OER/ORR) catalysis. Taking advantage of the synergistic effect between interconnected 1D hierarchical porous carbon nanofiber structure and high catalytic activity of N-doped CuCo2O4 nanoparticles derived from bimetallic MOFs, the N-CuCo2O4@CNFs catalysts possess enhanced reaction kinetics and preferable charge transfer ability. Impressively, the obtained catalysts exhibit prominent electrocatalytic ability and superior stability for OER/ORR, even surpass the commercial RuO2 and Pt/C. More significantly, the Zn-air batteries employing the N-CuCo2O4@CNFs-800 as cathode display a higher power density of 175.6 mW cm−2, a lower charge-discharge voltage gap of 0.82 V at 10 mA cm−2, as well as a better cycling stability with respect to those of Pt/C + RuO2 mixture, demonstrating the great potential of N-CuCo2O4@CNF as a high-efficiency catalyst for clean energy devices.

Unravel SEI Formation on Li Metal Interfaces By Mechanistic Multi-Scale Modelling

Nowadays, lithium metal anodes are often referred to as the ‘holy grail’ of next-generation battery technology. Compared to graphite anodes used in state-of-the-art lithium-ion batteries they promise several times higher energy densities [1]. However, Li metal shows a high reactivity with liquid electrolytes and uncontrolled dendrite growth which hinders a safe and efficient cyclability and therefore the commercial application in rechargeable batteries. Thus, stabilization of the solid-electrolyte interphase (SEI) between liquid electrolyte and the lithium surface is the key challenge to be solved before bringing this promising battery technology to market. In order to suppress unwanted effects such as dendrite formation, persistent loss of active material and high kinetic losses, this layer of electrolyte decomposition products needs to be electrically insulating and should prevent direct contact of metal with electrolyte while ensuring a good ionic conductivity and mechanical stability.Such a beneficial SEI design requires detailed understanding of the fundamental formation mechanism and the resulting chemical SEI composition and structure depending on electrolyte composition. In literature, a large range of experimental methods are applied to characterize the SEI under various conditions [2]. These approaches are mainly descriptive and struggle to identify and understand the underlying mechanisms. Theoretical approaches like density functional theory (DFT), ab-initio molecular dynamics (MD) or classical MD are well suited to determine reaction mechanisms and to model the very beginning of SEI formation in the ns-range. However, they are too computationally expensive to model technical relevant length- and time scales [3].Therefore, this work focuses on overcoming these restrictions by developing an efficient multiscale-model with input from ab-initio calculations. The acceleration originates from focusing on rare events such as reaction or diffusion processes in a 3-dimensional kinetic Monte Carlo instead of considering the vibrational motions of single atoms like in molecular dynamics. Thereby, every process is represented by a probability derived from ab-initio calculations to ensure physical correctness. An additional coupling with efficient ordinary differential equations as shown in [4] ensures electroneutrality in the simulation box.Implementation of the degradation reactions for a 1.2M LiPF6/EC electrolyte obtained from molecular simulations (see Figure 1, appendix), allows to unravel the initial SEI formation, the emerging structure and its composition within the first µs. The simulation suggests an almost instantaneous formation of SEI species on the pristine Li metal within the first nanoseconds after immersion. Due to this early passivation layer the formation process slows down continuously until electron tunneling is blocked by SEI species and a first passivation of the lithium surface is reached. Interestingly, the formed passivation layer mainly consists of inorganic species such as LiF close to the lithium metal surface and Li2CO3 throughout the whole layer but only of minor organic (CH2OCO2Li)2-molecules, suggesting that organic species are mainly formed at larger time scales which is the reason for the typical layering structure of the SEI.In summary this novel approach allows unprecedented insight of initial SEI-formation and thereby extends the accessible insight, time- and length-scales compared to molecular simulations.

Zn Metal Anodes for Zn-Ion Batteries in Mild Aqueous Electrolytes: Challenges and Strategies.

Over the past few years, rechargeable aqueous Zn-ion batteries have garnered significant interest as potential alternatives for lithium-ion batteries because of their low cost, high theoretical capacity, low redox potential, and environmentally friendliness. However, several constraints associated with Zn metal anodes, such as the growth of Zn dendrites, occurrence of side reactions, and hydrogen evolution during repeated stripping/plating processes result in poor cycling life and low Coulombic efficiency, which severely impede further advancements in this technology. Despite recent efforts and impressive breakthroughs, the origin of these fundamental obstacles remains unclear and no successful strategy that can address these issues has been developed yet to realize the practical applications of rechargeable aqueous Zn-ion batteries. In this review, we have discussed various issues associated with the use of Zn metal anodes in mildly acidic aqueous electrolytes. Various strategies, including the shielding of the Zn surface, regulating the Zn deposition behavior, creating a uniform electric field, and controlling the surface energy of Zn metal anodes to repress the growth of Zn dendrites and the occurrence of side reactions, proposed to overcome the limitations of Zn metal anodes have also been discussed. Finally, the future perspectives of Zn anodes and possible design strategies for developing highly stable Zn anodes in mildly acidic aqueous environments have been discussed.

Design of a LiF-Rich Solid Electrolyte Interphase Layer through Highly Concentrated LiFSI-THF Electrolyte for Stable Lithium Metal Batteries.

Lithium metal is a promising anode material for lithium metal batteries (LMBs). However, dendrite growth and limited Coulombic efficiency (CE) during cycling have prevented its practical application in rechargeable batteries. Herein, a highly concentrated electrolyte composed of an ether solvent and lithium bis(fluorosulfonyl)imide (LiFSI) salt is introduced, which enables the cycling of a lithium metal anode at a high CE (up to ≈99%) without dendrite growth, even at high current densities. Using 3.85 m LiFSI in tetrahydrofuran (THF) as the electrolyte, a Li||Li symmetric cell can be cycled at 1.0 mA cm-2 for more than 1000 h with stable polarization of ≈0.1 V, and Li||LFP cells can be cycled at 2 C (1 C = 170 mA g-1 ) for more than 1000 cycles with a capacity retention of 94.5%. These excellent performances are observed to be attributed to the increased cation-anion associated complexes, such as contact ion pairs and aggregate in the highly concentrated electrolyte; revealed by Raman spectroscopy and theoretical calculations. These results demonstrate the benefits of a high-concentration LiFSI-THF electrolyte system, generating new possibilities for high-energy-density rechargeable LMBs.

Long cycle life aqueous rechargeable battery Zn/Vanadium hexacyanoferrate with H+/Zn2+ coinsertion for high capacity

Aqueous rechargeable ion batteries have drawn considerable interest owing to their high safety, low cost, and outstanding ionic conductivity. Herein, the vanadium hexacyanoferrate Prussian blue analogs (VO-PBAs) nanoparticles are prepared by a facile co-precipitation way to fully make use of the merits of VO2+/VO2+ and Fe(CN)6]4−/[Fe(CN)6]3− redox actives. Specifically, the as-fabricated Zn/VO-PBAs aqueous rechargeable battery achieves a high capacity of 209.6 mAh g−1 at 0.1 A g−1 due to the introduction of V = O bonds and obtains an excellent rate performance (129.0 mAh g−1 at 2 A g−1) due to the high proportion of pseudocapacitive contribution. Moreover, the conversion of the VO-PBAs nanoparticles to nanosheets during the initial activation process increases the electrochemical reaction active sites and promotes the fast electrolyte ions transport of the electrode materials. Meanwhile, the VO-PBAs cathode presents excellent cycle stability, which can retain 95.5% capacity after 2000 cycles at 1 A g−1. Besides, the electrochemical energy storage mechanism is involved with the co-insertion/extraction of the Zn2+/H+, and the VO-PBAs keeps the cubic phase during the charge/discharge process revealed by the in situ XRD. The synergistic effect of the Zn2+/H+ ions makes the excellent electrochemical performance of the Zn/VO-PBAs system and thus promotes the application of aqueous rechargeable ion batteries.

A Novel Filler for Gel Polymer Electrolyte with a High Lithium-Ion Transference Number toward Stable Cycling for Lithium-Metal Anodes in Lithium-Sulfur Batteries.

Although the lithium metal is considered as the most promising anode for high energy density batteries, uncontrolled lithium dendrite growth and continuous side reactions with electrolyte hinder its practical applications for rechargeable batteries. Herein, we prepared a gel polymer electrolyte by synthesizing a novel 250 nm filler (KMgF3), which is greatly beneficial to the formation of a uniformly deposited lithium-metal anode. This is due to the regulation effect of KMgF3 that double the lithium-ion transference number up to 0.63 and adjust the solid electrolyte interphase layer full of dense LiF and flexible polycarbonates, which greatly reduces the side reactions on the lithium-metal surface and inhibits the growth of lithium dendrites. Consequently, the composite gel polymer electrolyte guarantees a stable long cycle performance of more than 1400 h with 1 mA h cm-2 for symmetric cells. Moreover, the composite gel polymer electrolyte demonstrates high compatibility and great promise for rechargeable lithium-sulfur (Li-S) batteries.

Interfacial interaction between molybdenum phosphide and N, P co-doped hollow carbon fibers boosting the oxygen electrode reactions in zinc-air batteries

The development of highly efficient electrocatalysts with excellent stability and electrocatalytic activity for oxygen electrode reactions is important for facilitating the application of rechargeable zinc-air batteries. The interface interaction between components is one of the most important factors that affects the catalytic activity of electrode materials. Herein, N and P co-doped hollow carbon fibers embedded with molybdenum phosphide nanoparticles (MoP@N, P-HCF) are elaborately fabricated as novel bifunctional electrocatalysts to study the influence of interface interaction on oxygen redox reactions in zinc-air batteries. As evidenced, a strong electron transfer is realized at the interface between N, P-HCF and MoP NPs due to their remarkable interfacial interaction, enabling the uniform combination of the nanoparticles with the doped carbonaceous matrix. More importantly, the rearrangement of electrons along the heterogeneous interface in MoP@N, P-HCF endows the electrode with abundant active sites and excellent catalytic activity, thus promoting the kinetics of the oxygen electrode reactions. Based on the above merits, MoP@N, P-HCF based rechargeable zinc-air batteries demonstrate improved power density of 93.8 mW cm−2 and superior cyclability of over 600 cycles. Our work emphasizes the significant role of interface chemistry between conductive carbon matrix and transition metal compounds in regulating the catalytic activity and provides a profound insight for the development of highly active and stable oxygen electrode materials.

Aramid nanofiber-based porous membrane for suppressing dendrite growth of metal-ion batteries with enhanced electrochemistry performance

Huge volume changes, uncontrolled side-reactions with electrolytes and irregular dendrite induced short-circuits have impeded practical application in rechargeable batteries based on metallic electrodes including lithium (Li), sodium (Na) and aluminum (Al). Separator with superior mechanical strength represent attractive alternatives to inhibit metal-dendrite growth while preventing capacity fading by stabilizing the solid electrolyte interphase (SEI). However, the challenge of simultaneous retaining high thermal resistance and good electrolyte wettability still have been not overcome in commonly used separators. Here we show that these key properties can be acquired in a porous membrane fabricated from Kevlar microfiber-derived aramid nanofibers (ANFs) prepared in a facile and scalable vacuum filtration method. The obtained ANFs membrane (ANFM), which yields mechanically strong that are markedly effective in inhibit dendrite growth as well as provides good electrolyte wettability to ensure excellent electrochemistry performance. Benefitting from these merits, ANFM guarantee stable cycling of Li-ion or Na-ion rechargeable batteries paired with conventional intercalating cathodes (LiCoO4 and Na2Ti3O7) even at a high operated temperature (150 ℃ for Li-ion battery). Replacing polyolefins-based separator with an ANFM appear to offer a major step towards dendrite-free Li /Na batteries and potentially other metal-ion batteries.

Controlled defective engineering of MoS2 nanosheets for rechargeable Mg batteries

Developing high energy density and high stability rechargeable battery for higher power output devices is urgent but challenging. Rechargeable Mg batteries are justified in raising high hopes for grid-scale energy storage. However, the practical application of rechargeable Mg batteries is severely limited by electrolytes and anode materials, especially cathode materials. One of the inherent challenges with rechargeable Mg batteries is how to accelerate the diffusion of Mg2+ in cathode materials. Various approaches are currently in their infancy. Herein, 2D (2 dimension) MoS2 nanosheets of controlled defective degree prepared via hydrothermal method have been investigated for assembled battery systems. The defective structures have been characterized by XRD (X-ray diffraction), FESEM (field emission scanning electron microscopy) and HRTEM (high-resolution transmission electron microscopy), and the cathode performance also been evaluated by cyclic voltammetry, galvanostatic charge/discharge, rate performance and cycling performance tests and electrochemical impedance spectra. The results show that the introduction of defects into MoS2 nanosheets improves the diffusion of Mg2+, resulting an excellent electrochemical performances in rechargeable Mg batteries. The discharge specific capacity reaches up to 152 mAh g−1 while the charge-transfer resistance (Rct) only for 2000 Ω, when assembling defective MoS2 as cathode at Mo:S = 1:4. This work highlights the potential applications of defective structure in rechargeable Mg batteries.

Amino Acid‐Induced Interface Charge Engineering Enables Highly Reversible Zn Anode

AbstractDespite the impressive merits of low‐cost and high‐safety electrochemical energy storage for aqueous zinc ion batteries, researchers have long struggled against the unresolved issues of dendrite growth and the side reactions of zinc metal anodes. Herein, a new strategy of zinc‐electrolyte interface charge engineering induced by amino acid additives is demonstrated for highly reversible zinc plating/stripping. Through electrostatic preferential absorption of positively charged arginine molecules on the surface of the zinc metal anode, a self‐adaptive zinc‐electrolyte interface is established for the inhibition of water adsorption/hydrogen evolution and the guidance of uniform zinc deposition. Consequently, an ultra‐long stable cycling up to 2200 h at a high current density of 5 mA cm−2 is achieved under an areal capacity of 4 mAh cm−2. Even cycled at an ultra‐high current density of 10 mA cm−2, 900 h‐long stable cycling is still demonstrated, demonstrating the reliable self‐adaptive feature of the zinc‐electrolyte interface. This work provides a new perspective of interface charge engineering in realizing highly reversible bulk zinc anode that can prompt its practical application in aqueous rechargeable zinc batteries.

Ultrahigh density nucleation leading to extraordinary long-cycle dendrite-free Li metal deposition

Li metal is the prospective candidate of next generation anode materials. However, the growth of dendritic Li during electrochemical cycling has severely hindered the practical application of rechargeable Li-metal batteries. Herein, “seaweed” graphene paper (SGP) is designed for 3D matrix of Li metal anode to address the growth of dendrites. SGP has abundantly exposed edges of graphene sheets and realizes ultrahigh density nucleation. Compared with nonuniform lithium deposition on parallelly stacked GP which has been observed by in-situ scanning electron microscopy, electrochemical deposition behavior of Li in SGP manifests as uniformly distributed granular lithium. Significant decrease of nucleation barrier can be observed during the dendrite-free deposition. With the elimination of dendritic Li growth and excellent stability of SGP host, the lithium anode based on SGP can run over 2500 cycles without short circuit and exhibits low voltage hysteresis. When matched with cathode LiCoO2, the full battery also presents stable cycling. There is no trace of lithium dendrite even after 1200 cycles which proves continuously regulating effect on lithium dendrites by SGP host. This work further develops potential application of graphene materials in the Li anode with high reversibility for stable cycling Li metal batteries.

Dendrite-Suppressing Polymer Materials for Safe Rechargeable Metal Battery Applications: From the Electro-Chemo-Mechanical Viewpoint of Macromolecular Design.

Metal batteries have been emerging as next-generation battery systems by virtue of ultrahigh theoretical specific capacities and low reduction potentials of metallic anodes. However, significant concerns regarding the uncontrolled metallic dendrite growth accompanied by safety hazards and short lifespan have impeded practical applications of metal batteries. Although a great deal of effort has been pursued to highlight the thermodynamic origin of dendrite growth and a variety of experimental methodologies for dendrite suppression, the roles of polymer materials in suppressing the dendrite growth have been underestimated. This review aims to give a state-of-the-art overview of contemporary dendrite-suppressing polymer materials from the electro-chemo-mechanical viewpoint of macromolecular design, including i) homogeneous distribution of metal ion flux, ii) mechanical blocking of metal dendrites, iii) tailoring polymer structures, and iv) modulating the physical configuration of polymer membranes. Judiciously tailoring electro-chemo-mechanical properties of polymer materials provides virtually unlimited opportunities to afford safe and high-performance metal battery systems by resolving problematic dendrite issues. Transforming these rational design strategies into building dendrite-suppressing polymer materials and exploiting them towards polymer electrolytes, separators, and coating materials hold the key to realizing safe, dendrite-free, and long-lasting metal battery systems.

Defect engineering on three-dimensionally ordered macroporous phosphorus doped Co3O4–δ microspheres as an efficient bifunctional electrocatalyst for Zn-air batteries

Developing low-cost and high-efficiency bifunctional electrocatalysts for both oxygen evolution and reduction reactions is urgent to fulfill the practical application of rechargeable Zn-air batteries (ZABs). However, to explore the high catalytic performance of air electrocatalysts still remains a challenge. In response, a three-dimensionally ordered macroporous (3DOM) Co3O4 electrocatalyst is designed and synthesized through a nanocasting strategy. A well-controlled phosphorization treatment is further conducted to induce defect engineering on the resulting P-doped Co3O4–δ (3DOM P-Co3O4–δ). With the oxygen vacancy (Vo) tailoring, partial reduction from Co3+ to Co2+ is verified as the key to improving the intrinsic electrocatalytic bifunctionality. By incorporating the geometric and electronic merits, 3DOM P-Co3O4–δ possesses an ORR half-wave potential of 0.82 V and an OER overpotential of 366 mV to achieve 10 mA cm–2, which is comparable to noble-metal benchmarks. Particularly, under galvanostatic cycling measurements, ZABs using 3DOM P-Co3O4–δ containing air cathode showcase a potential gap of 0.84 V with negligible voltage fading over 250 h at 10 mA cm–2.

Electrochemical Corrosion Behavior of Iron in Lithium-ion Battery Electrolyte

The element iron (Fe) is affordable and abundantly available, and thus, it finds use in a wide range of applications. As regards its application in rechargeable lithium-ion batteries (LIBs), the electrochemical reactions of Fe must be clearly understood during battery charging and discharging with the LIB electrolyte. In this study, we conducted systematic electrochemical analyses under various voltage conditions to determine the voltage at which Fe corrosion begins in general lithium salts and organic solvents used in LIBs. During cyclic voltammetry (CV) experiments, we observed a large corrosion current above 4.0 V (vs. Li/Li+). When a constant voltage of 3.7 V (vs. Li/Li+), was applied, the current did not increase significantly at the beginning, similar to the CV scenario; on the other hand, at a voltage of 3.8 V (vs. Li/Li+), the current increased rapidly. The impact of this difference was visually confirmed via scanning electron microscopy and optical microscopy. Our X-ray photoelectron spectroscopy measurements showed that at 3.7 V, a thick organic solid electrolyte interphase (SEI) was formed atop a thin fluoride SEI, which means that at ≥3.8 V, the SEI cannot prevent Fe corrosion. This result confirms that Fe corrosion begins at 3.7 V, beyond which Fe is easily corrodible.

Sowing Silver Seeds within Patterned Ditches for Dendrite-Free Lithium Metal Batteries.

The interfacial instability of lithium (Li) metal is one of the critical challenges, which hinders the application of rechargeable Li metal batteries (LMBs). Designing facile and effective surface/interface is extremely important for practical LMBs manufacturing. Here, a highly stable Li anode with silver nanowires sowed in the patterned ditches via a simple calendaring process is developed. The remarkably increased electroactive surface area and the superior lithiophilic Ag seeds enable Li stripping/plating mainly inside the ditches. Benefitting from such unique structural design, the ditches‐patterned and Ag‐modified composite Li anode (D‐Ag@Li) achieves excellent cyclability under 2 mA cm−2 / 4 mAh cm−2 over 360 h cycling with low nucleation overpotential of 16 mV. Pairing with the D‐Ag@Li anode, the full cells with LiNi0.8Mn0.1Co0.1O2 and LiFePO4 (LFP) cathodes achieve long cycle life with 94.2% retention after 2000 cycles and 74.2% after 4000 cycles, respectively. Moreover, ultrasonic transmission mapping shows no gas generation for the LFP pouch full cell pouch cell based on D‐Ag@Li over prolonged cycling, demonstrating the feasibility and effectiveness of the authors' strategy for LMBs.

ZIF-derived two-dimensional Co@Carbon hybrid: Toward highly efficient trifunctional electrocatalysts

Hybrid electrocatalysts with stable two-dimensional (2D) framework and fine sub-structures are of great interest for enhancing the mass/electron transport and accessibility of maximized active sites. Here, we report a facile 2D-ZIF transformation strategy for fabricating highly efficient hybrid catalysts composed of highly dispersed Co quantum dots (~4.57 nm in diameter) embedded in ultrathin N-doped carbon layers (~3 nm in thickness), denoted as Co@NCL. The as-fabricated hybrids have excellent overall trifunctional electrocatalytic activities toward oxygen reduction (half-wave potential (E1/2) = 0.84 V), oxygen evolution (potential at 10 mA cm−2 (Ej10) = 1.63 V), and hydrogen evolution (Ej10 = −0.22 V) reactions in alkaline media. Notably, its reversible oxygen electrode index (ΔE = Ej10 − E1/2 = 0.79 V) is comparable with that of benchmarked noble-metal catalysts (0.80 V for Pt/C-RuO2) and superior to ZIF polyhedrons-derived counterpart (0.90 V) as well as most Co-based bifunctional catalysts ever reported. The as-constructed Zn–air battery and overall water splitting electrolyzer based on Co@NCL delivered a high peak power density of 170 mW cm−2 and a small voltage of 1.70 V that affords a current density of 10 mA cm−2 along with robust long-term stability, respectively, which demonstrates its promising applications in rechargeable metal-air batteries and water splitting.

Hierarchical cobalt-nitrogen-doped carbon composite as efficiently bifunctional oxygen electrocatalyst for rechargeable Zn-air batteries

Developing cost-effective bifunctional oxygen electrocatalysts with superior catalytic performance is essential for the large-scale application of rechargeable Zn-air batteries. Herein, a cobalt-nitrogen-doped carbon catalyst Co-UA-OCB with heavy nitrogen content has been synthesized. The N-doped graphene sheets from carbonized uric acid wrapped on the particles of carbon black to construct a hierarchical microstructure. Benefiting from the higher electrochemical active surface area and well dispersed cobalt particles, the catalyst exhibits a remarkable bifunctional activity toward oxygen reduction (ORR) and evolution reactions (OER) with 0.834 V of half-wave potential for ORR and 1.621 V of OER potential at 10 mA cm2. The rechargeable Zn-air battery fabricated with Co-UA-OCB as the air electrode, delivers 142 mW cm−2 of maximum power density, 799 mAh g−1 of specific capacity, 1000 mWh g−1 of energy density and 1.24–1.29 V of running voltage at 10 mA cm2 of current density. The battery exhibits excellent durability and rechargeability, indicating the Co-UA-OCB is a promising candidate to replace the precious metal-based electrocatalyst for rechargeable Zn-air batteries.

Synthesis, Characterization and Electrochemical Evaluation of Layered Vanadium Phosphates as Cathode Material for Aqueous Rechargeable Zn-ion Batteries

The potential application of rechargeable multivalent ion batteries in portable devices and renewable energy grid integration have gained substantial research interest in aqueous Zn-ion batteries (ZIBs). Compared to Li-based batteries, ZIBs offer lower costs, higher energy density, and safety that make them more attractive for energy storage in grid integration applications. Currently, more research is required to find a suitable cathode material for ZIBs with high capacity and structural stability during charge/discharge cycling. Vanadium phosphate (VOP) compounds as cathode material for ZIBs have been of particular interest, owing to vanadium’s diverse oxidation states. In this present work, two VOP compounds, [H0.6(VO)3(PO4)3(H2O)3].4H2O and VOPO4.2H2O, were synthesized from phosphoric acid and different sources of vanadium via a simple hydrothermal method. Various characterization techniques were carried out, revealing the layered structure of both products and high purity of [H0.6(VO)3(PO4)3(H2O)3].4H2O. Zn/VOP batteries were prepared using Zn metal as counter and reference electrode and 3 M ZnSO4.7H2O as electrolyte. Electrochemical tests were conducted to evaluate the cycling performance of VOPs as cathode material for aqueous Zn-ion batteries. Based on the results, both compounds have shown highly reversible Zn-ion intercalation and deintercalation. VOPO4.2H2O achieved a higher specific capacity of up to 85 mAh/g during discharging, as opposed to 65 mAh/g for the hydrated VOP complex. However, [H0.6(VO)3(PO4)3(H2O)3].4H2O is more stable with higher reproducibility than VOPO4.2H2O during cycling. Nevertheless, more research is still required to enhance the specific capacity and improve the cycling performance of VOP-based cathodes for their prospective use in aqueous ZIBs.

Isotopic Depth Profiling of Discharge Products Identifies Reactive Interfaces in an Aprotic Li-O2 Battery with a Redox Mediator.

Prior to the practical application of rechargeable aprotic Li-O2 batteries, the high charging overpotentials of these devices (which inevitably cause irreversible parasitic reactions) must be addressed. The use of redox mediators (RMs) that oxidatively decompose the discharge product, Li2O2, is one promising solution to this problem. However, the mitigating effect of RMs is currently insufficient, and so it would be beneficial to clarify the Li2O2 reductive growth and oxidative decomposition mechanisms. In the present work, Nanoscale secondary ion mass spectrometry (Nano-SIMS) isotopic three-dimensional imaging and differential electrochemical mass spectrometry (DEMS) analyses of individual Li2O2 particles established that both growth and decomposition proceeded at the Li2O2/electrolyte interface in a system containing the Br-/Br3- redox couple as the RM. The results of this study also indicated that the degree of oxidative decomposition of Li2O2 was highly dependent on the cell voltage. These data show that increasing the RM reaction rate at the Li2O2/electrolyte interface is critical to improve the cycle life of Li-O2 batteries.