Excellent Electrochemical Performance Research Articles

Regulating the “core-shell” microstructure of hard carbon through sodium hydroxide activation for achieving high-capacity SIBs anode

Pore structure engineering has been acknowledged as suitable approach to creating active sites and enhancing ion transport capabilities of hard carbon anodes. However, conventional porous carbon materials exhibit high BET and surface defects. Additionally, the sodium storage mechanism predominantly occurs in the slope region. This contradicts practical application requirements because the capacity of the plateau region is crucial for determining the actual capacity of batteries. In our work, we prepared a novel “core-shell” carbon framework (CNA1200). Introducing closed pores and carboxyl groups into coal-based carbon materials to enhance its sodium storage performance. The closed pore structure dominates in the “core” structure, which is attributed to the timely removal of sodium hydroxide (NaOH) to prevent further formation of active carbon structure. The presence of closed pores is beneficial for increasing sodium ion storage in the low-voltage plateau region. And the “shell” structure originates from coal tar pitch, it not only uniformly connects hard carbon particles together to improve cycling stability, but is also rich in carboxyl groups to enhance the reversible sodium storage performance in slope region. CNA1200 has excellent electrochemical performance, it exhibits a specific capacity of 335.2 mAh g−1 at a current density of 20 mA g−1 with ICE = 51.53 %. In addition, CNA1200 has outstanding cycling stability with a capacity retention of 91.8 % even when cycling over 200 times. When CNA1200 is used as anode paired with Na3V2(PO4)3 cathode, it demonstrates a capacity of 109.54 mAh g−1 at 0.1 C and capacity retention of 94.64 % at 0.5 C. This work provides valuable methods for regulating the structure of sodium-ion battery (SIBs) anode and enhances the potential for commercialization.

Effective recovery of Ni and Cu from low-grade nickel sulfide concentrate: Process kinetics and preparation of Ni80Cu20O material

In this work, NaCl was used to synchronously extract metal from a low-grade nickel sulfide concentrate. Optimized process parameters were determined as follows: particle size 80–96 μm, temperature 400 °C, time 100 min, and NaCl dosage 100 %. The transformation mechanism of mineral phase was clarified using the means of XRD, SEM and EDS. The roasting process contained solid–solid and gas–solid reactions, and the valuable metal was effectively extracted by the combined action of sulfation of sodium sulfate and chlorination of chlorine gas. The kinetic study of the roasting process showed that the transformation of metals depends on the diffusion control between solid and solid phases. The reaction activation energies of valuable metal were calculated to be 9.15 kJ/mol for Ni, 11.14 kJ/mol for Cu, and 12.72 kJ/mol for Co. Nickel and copper were recovered from the leaching solution by purification and solvent extraction process to prepare Ni80Cu20O material. The Ni80Cu20O electrode material prepared at calcination temperature of 400 °C has excellent electrochemical performance. A new process of recovering metals from minerals to prepare Ni80Cu20O cathode material was established, which was proved to be a clean and promising technology.

Upgrading Gel Electrolytes Through Electrostatic-Induced Dual-Salt Paradigm for Superior Zn-Ion Battery Performance.

Gel electrolytes are gaining attention for rechargeable Zn-ion batteries because of their high safety, high flexibility, and excellent comprehensive electrochemical performances. However, current gel electrolytes still perform at mediocre levels due to incomplete Zn salts dissociation and side reactions. Herein, an electrostatic-induced dual-salt strategy is proposed to upgrade gel electrolytes to tackle intrinsic issues of Zn metal anodes. The competitive coordination mechanism driven by electrostatic repulsion and steric hindrance of dual anions promotes zinc salt dissociation at low lithium salt addition levels, improving ion transport and mechanical properties of gel electrolytes. Li+ ions and gel components coordinate with H2O, reducing active H2O molecules and inhibiting associated side reactions. The dual-salt gel electrolyte enables excellent reversibility of Zn anodes at both room and low temperatures. Zn||Polyaniline cells using the dual-salt gel electrolyte exhibit a high discharge capacity of 180mAhg-1 and long-term cycling stability over 180 cycles at -20°C. The dual-salt strategy offers a cost-effective approach to improving gel electrolytes for high-performance flexible Zn-ion batteries.

Pre-introducing Li4NiWO6 defect phase by tungsten modification enables highly stabilized Ni-rich cathode

Tungsten (W) has attracted considerable attention as a promising dopant capable of enhancing the structural stability of Ni-rich cathode materials. However, investigations into W modification remain highly debated due to the elusive mechanisms involved, particularly in determining whether W is doped into the lattice structure or exists as a distinct phase on the surface of the particles. In this work, we systematically observe the effects induced by the introduction of W into LiNi0.9Co0.05Mn0.05O2 (NCM). We discovered that during high-temperature solid-state reactions, W-containing substances tend to react preferentially with surface Li, creating a lithium-deficient state on the NCM surface, resulting in the generation of Li4NiWO6. Molecular dynamics simulations tracking Li, W, and Ni elemental changes at the interface confirm the initial creation of Li6WO6, succeeded by diffusion of Ni to replace Li, forming Li4NiWO6. The pre-introducing Li4NiWO6 defect phase can effectively absorb anisotropic lattice strain, preserving the mechanical integrity of the secondary particles. Furthermore, the Li4NiWO6 phase, combined with the amorphous LixWyOz coating layer, effectively acts as a guard against undesirable interfacial side reactions, ultimately imparting excellent electrochemical performance to NCM. Understanding the dynamic processes of interfacial reactions is crucial for tailoring surface properties of Ni-rich cathodes towards long-life lithium-ion batteries.

A nickel-based dendritic electrode matrix with high surface efficiency mass transfer for highly efficient overall water splitting

Electrodes are key components in water splitting. Owing to their porous structures, commercial foam metal electrode matrices can provide numerous active sites. However, the complex and disordered surface structure impedes the release of the generated gas bubbles, and sluggish mass transfer usually becomes a bottleneck in the electrochemical reaction kinetics. For this purpose, this study proposes a pulse-jet electrodeposition method for the preparation of nickel-based dendritic electrode matrices (NDEM). This research shows that the electrode matrix prepared under the conditions of V = 26 V, PW = 10 μs, and PI = 35 μs has a unique surface structure, which can quickly release bubbles, effectively attract ions, and accelerate mass transfer on the electrode surface, resulting in excellent electrochemical performance. After loading the catalyst, the NDEM requires only 1.552 V to reach a current density of 10 mA cm−2. At an electrolysis voltage of 2.5 V, the hydrogen production was 45% higher than that of the NF electrode, and it had excellent stability. This study opens a new avenue for the design of highly efficient and low-cost electrodes for water splitting.

Rationally Regulating Closed Pore Structures by Pitch Coating to Boost Sodium Storage Performance of Hard Carbon in Low‐voltage Platforms

AbstractHard carbon (HC) materials with rich closed pore structures and nano‐scaled soft carbon coating layer have emerged as promising anode in sodium‐ion batteries (SIBs). However, it still remains a tremendous challenge to precisely regulate closed pore structures and soft carbon coating thicknesses for achieving excellent electrochemical performance in SIBs at low‐voltage platforms. Herein, PCHC‐10 with abundant and suitable‐sized closed pore size (0.45 nm) and nano‐scaled soft carbon coating layer has been accurately designed by chemical crosslink reaction between the pre‐oxidized phenolic resin and a small addition of pitch to form ester‐based bond. As anode, PCHC‐10 delivered large reversible capacity of 359.8 mAh g−1 within 0.001–2.5 V, and high capacity of 242.8 mAh g−1 in low voltage platforms (≤0.15 V). Besides, PCHC‐10 anode exhibits 91.4% capacity retention for 100 cycles, and Na3V2(PO4)3//PCHC‐10 full cell has superior rate performance and high energy density of 231.2 Wh kg−1. Furthermore, the detailed electrochemical storage behaviors and theoretical calculations revealed that the HC owning closed pore‐size of 0.45 nm has the strongest Na+ storage abilities in low‐voltage platforms. This work presents a novel insight for constructing HC with suitable‐sized closed pore structures and soft coating layer to boost Na+ storage capability in low‐voltage platforms.

Construction of Monolayer Ti3C2Tx MXene on Nickel Foam under High Electrostatic Fields for High-Performance Supercapacitors

Ti3C2Tx MXene, as a common two-dimensional material, has a wide range of applications in electrochemical energy storage. However, the surface forces of few-layer or monolayer Ti3C2Tx MXene lead to easy agglomeration, which hinders the demonstration of its performance due to the characteristics of layered materials. Herein, we report a facile method for preparing monolayer Ti3C2Tx MXene on nickel foam to achieve a self-supporting structure for supercapacitor electrodes under high electrostatic fields. Moreover, the specific capacitance varies with the deposition of different-concentration monolayer Ti3C2Tx MXene on nickel foam. As a result, Ti3C2Tx/NF has a high specific capacitance of 319 mF cm−2 at 2 mA cm−2 and an excellent long-term cycling stability of 94.4% after 7000 cycles. It was observed that the areal specific capacitance increases, whereas the mass specific capacitance decreases with the increasing loading mass. Attributable to the effect of the high electrostatic field, the self-supporting structure of the Ti3C2Tx/NF becomes denser as the concentration of the monolayer Ti3C2Tx MXene ink increases, ultimately affecting its electrochemical performance. This work provides a simple way to overcome the agglomeration problem of few-layer or monolayer MXene, then form a self-supporting electrode exhibiting excellent electrochemical performance.

Fabrication of Fe/KB Composite as Sulfur Host for Li-S Battery.

Lithium sulfur battery is a novel kind of secondary battery which has high energy density, however its application is greatly affected by the shuttle effect of polysulfides generated in the redox reaction of cathode electrode. Metal active sites are supposed as effective catalysts which can absorb and accelerate the conversion efficiency of lithium polysulfides, thus the shuttle effect will be alleviated. In this work, we conducted a simple way to prepare a metal Fe doped ketjen black to serve as the sulfur host of lithium sulfur battery. Ketjen black has a large specific surface area and rich porous structure, while Fe nanodot is an excellent catalyst for lithium polysulfides. Because of these advantages, the Fe/KB host can effectively confine a large amount of active material and accelerate its, therefore the Fe/KB-S cathode electrode show an excellent electrochemical performance.

Preparation of biomass-derived activated carbon from golden needle mushroom roots for supercapacitor electrodes

Herein, an original activated carbon (AC) is prepared using golden needle mushroom roots and potassium hydroxide. After carbonization under 500 °C, AC-5 exhibits good graphitization degree, appropriate nitrogen and oxygen elements, large specific surface area, and micro-meso porous structures. Notably, AC-5 as electrodes in supercapacitors has excellent electrochemical performances, e. g. high specific capacitance (360.4 F/g), impressive rate capability (77 %, from 10 mV/s to 200 mV/s), and outstanding cycling durability (99.56 %, after 10,000 cycles).

Guanine-derived core-shell FeCo alloy confined in graphene-like N-doped carbon as efficient bifunctional oxygen electrocatalysts for rechargeable Zn-air batteries

Maximization the synergistic effect of each component in transition metal-carbon complexes is expected to improve the bifunctional oxygen electrocatalysis for rechargeable Zn-air batteries but is still challenging. Herein, nucleobase guanine is employed as a supramolecular precursor to generate the core (FeCo alloy)-shell (carbon) structure embedded in ultrathin graphene-like nitrogen-doped carbon nanosheets (FeCo@NCNSs) via a confinement pyrolysis strategy. Thanks to the generated core-shell structure and bimetallic synergistic effect, the as-prepared FeCo@NCNSs exhibits excellent electrochemical performance in both oxygen reduction reaction and oxygen evolution reaction. As a result, when served as the bifunctional air electrode for a practical Zn-air battery, FeCo@NCNSs exhibits a higher open-circuit voltage (1.553 V) and peak power density (197.30 mW cm−2), as well as the greatly improved long-term cyclic stability compared to the noble metal benchmarks. This work provides a promising approach to integrate various active sites for bifunctional oxygen electrocatalysis and inspires the exploration of simple but efficient electrocatalysts for energy storage and conversion.

An ultrasensitive electrochemical sensor based on boron-doped porous graphene for efficient detection of nitrite in food

Boron (B) doping plays a critical role in adjusting the electronic properties of carbon materials. In this work, B-doped porous graphene (B-PG) was successfully prepared by a simple strategy and used as an advanced electrode material for the detection of nitrite (NO-2) in food. The scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed to characterize this B-PG. Due to the ideal doping of boron atoms, the material has good conductivity and exhibits excellent electrochemical catalytic performance. NO-2 was used as the representative analytes to demonstrate the sensing performance of B-PG. It is found that the B-PG modified GCE exhibited a linear response over the concentration range from 3 μM – 3 mM and 3 mM – 15 mM, with a detection limit of 1.1 μM. The designed electrochemical sensor has good analytical performance, such as high sensitivity, good reproducibility and acceptable accuracy, and can be successfully applied to the accurate and precise detection of residual NO-2 in food.

Pyrolysis of spent coffee grounds dispersed clay in N2: Production of type-II conductive ceramics with electrochemical performance

Pyrolysis of spent coffee grounds dispersed clay in N2 produces type-II conductive ceramics with electrochemical performance. Protective atmosphere and surface screening play important roles in converting spent coffee grounds into carbon coatings on ceramic surfaces; the former prevents oxidation of organic ingredients and confinement of pyrolysis in clay for the latter. Selective-area electrical measurements indicate resultant ceramics to be conductive and interconnected carbon coatings are further verified by SEM inspections and consistency between thermal conductivity and diffusivity. Conductive ceramics show a high usage of surface area by electric double layer charging mechanism thus giving an excellent electrochemical performance.

Ni-rich LiNi0.905Co0.043Al0.052O2 cathode material for high-energy density Li-ion cells: Tuning lithium content, structural evolution, and full-cell performance

Ni-rich LiNi0.905Co0.043Al0.052O2 oxides with the Li excess (x) up to 7 mol.% used in the synthesis are prepared by a facile dry-mixing method. It is shown that the Li/Ni mixing level and crystallite size are dependent on the Li amount, while Al from the precursor acts as a scavenger of the excessive Li. Operando X-ray diffraction (XRD) studies enable explaining differences in the structural evolution of materials exhibiting high and low Li/Ni mixing, especially in the H2↔H3 transition region. Soft X-ray absorption spectroscopy (XAS) studies show differences in the charge state evolution of the surface and bulk Ni. The optimized oxide with the Li excess x = 2 mol.% delivers excellent electrochemical performance, with an initial discharge capacity of 205.5 mAh g−1 at 0.1C, and 91.4 % capacity retention after 100 cycles at 1C. The unmodified in any other way cathode material allows achieving the discharge capacity of 178.5 mAh g−1 at the high rate of 5C, and works well in the full-cells.

Dendrite-free Zn anode enabled by combining carbon nanoparticles hydrophobic layer with crystal face reconstruction toward high-performance Zn-ion battery

Aqueous zinc ion batteries (ZIBs) have been considered promising energy storage systems due to their excellent electrochemical performance, environmental toxicity, high safety and low cost. However, uncontrolled dendrite growth and side reactions at the zinc anode have seriously hindered the development of ZIBs. Herein, we prepared the carbon nanoparticles layer coated zinc anode with (103) crystal plane preferential oriented crystal structure (denoted as C@RZn) by a facile one-step vapor deposition method. The preferential crystallographic orientation of (103) crystal plane promotes zinc deposition at a slight angle, effectively preventing the formation of Zn dendrites on the surface. In addition, the hydrophobic layer of carbon layer used as an inert physical barrier to prevent corrosion reaction and a buffer during volume changes, thus improving the reversibility of the zinc anode. As a result. the C@RZn anode achieves a stable cycle performance of more than 3000 h at 1 mA cm−2 with CE of 99.77 % at 5 mA cm−2. The full battery with C@RZn anode and Mn-doped V6O13 (MVO) cathode show stability for 5000 cycles at the current density of 5 A g−1. This work provides a new approach for the design of multifunctional interfaces for Zn anode.

The role of nanoporous carbon materials for thiophosphate-based all solid state lithium sulfur battery performance

Due to their high theoretical energy density, all solid state lithium sulfur batteries (LS-SSB) represent one of the most promising candidates for next-generation energy storage systems. Whilst high sulfur utilizations have been published for several cathode compositions and preparation methods in recent years, there is still a lack of clarity regarding the influence of the used carbon. Furthermore, LS-SSBs face challenges in up-scaling as the common preparation methods including high energy ball milling are time consuming, batch-wise and need high energy impact. In this study, high sulfur utilization >1600 mAh gS−1 and reversibility with 80 % of initial discharge capacity after 60 cycles is achieved, using a more time-efficient preparation method with drastically lowered energy impact by selecting a suitable carbon. Additionally, the influence of the carbon nanostructure on the electrochemical performance is discussed. This study provides guidance in selecting nanostructured carbon materials to enable cost-efficient, up-scalable preparation methods for LS-SSBs without compromising on the excellent electrochemical performance.

Anion trapping-coupling strategy driven asymmetric nonflammable gel electrolyte for high performance sodium batteries

Gel polymer electrolytes, promising electrolyte candidates for advanced sodium metal batteries (SMBs), suffer from the great challenges of combustion risk and inferior interfacial stability caused by poor mechanical properties and low Na+ selectivity. Herein, we proposed a rational anion trapping-coupling strategy to build a mechanically robust asymmetric nonflammable composite gel electrolyte (AS-NFCGE) by introducing in-situ coupled boron nitride nanosheets (BNNs) on glass fiber matrix embedded with synchronous polymerized flame-retardant polymer. Theoretical calculations, finite-element simulations, and experimental tests prove that the high coupling BNNs with anion trapping effect constructed asymmetric structure can significantly accelerate selective Na+ migration kinetics, enhance mechanical properties of AS-NFCGE and endow a similar single-ion conducting behavior to homogenize ion-distribution at the anode side, thus improving interfacial stability and suppressing dendrite growth to achieve ultra-stable SMBs. Specifically, the AS-NFGE delivers high ionic conductivity and Na+ transference number (0.73) together with excellent flam-retardant. Consequently, the dendrite-free Na/Na symmetric cell exhibits considerable cycling life for over 3000 h at 0.1 mA cm−2 with low overvoltage. Applications of the AS-NFCGE in SMBs further demonstrate the excellent electrochemical performances, and no thermal runaway and no electrolyte leakage occur for pouch cells using AS-NFCGE. This strategy provides new insight into the development of safe and high-energy SMBs and the beyond.

Guiding lithium growth direction by Au coated separator for improving lithium metal anode

Lithium metal is the most promising anode for next-generation batteries due to its highest theoretical capacity and lowest electrochemical potential. However, its dendritic growth hinders its practical use due to the consequent poor reversibility, potential short-circuit, and safety concerns. Suppressing lithium dendrite is difficult since dendritic growth is thermodynamically and kinetically favorable. Herein, we guide lithium to uniformly deposit along the opposite direction to normal by a nanolayer Au coating on a commercial polypropylene separator. It prevents lithium dendrites from piercing the separator, instead of inhibiting dendrites growth only. Au is lithiophilic, and lithium is calculated to be more attracted to Au and is confirmed to uniformly deposit on Au at the separator side rather than on the current collector side. Furthermore, Au also regulates the morphology of deposited lithium from a mossy state to a bulky state. In this work, the symmetric cell with the designed structure achieves excellent electrochemical performances of a long-life cycle over 2,000 h at 1 C for 1 mA h cm-2. Pairing with LiFePO4 cathode as a full cell, lithium metal anode with Au-modified polypropylene separator exhibits extraordinary performance with a high Coulombic efficiency of 99.23% over 800 cycles at 1 C.

Thiocarbamide conversion-based nitrogen-rich covalent organic framework coatings for electro-enhanced solid-phase microextraction of bisphenols

Design and preparation of fiber coatings with excellent electrochemical performance and high polarity is significant for efficient extraction of polar targets in electro-enhanced solid-phase microextraction (EE-SPME). In this work, a combination strategy for structure regulation of covalent organic framework (COF) was proposed to fabricate a nitrogen-rich thiocarbamide linked COF coating (Thiocarbamide-TZ-DHTP) via molecular design and post-synthetic thiocarbamide conversion. The prepared COF coating possesses a large number of O, N, and S functional groups, which not only endow the coating with higher polarity but also significantly enhance its electrochemical performance. The COF coating was used for EE-SPME of polar bisphenols (BPs), demonstrating excellent enrichment efficiency and durability. Subsequently, coupled with gas chromatography-tandem mass spectrometry (GC-MS/MS), a sensitive method was developed for determination of trace BPs. The established method possess wide linear ranges (2.0–800.0 ng L−1), good correlation coefficients (0.9985–0.9994) and low detection limits (0.1–2.0 ng L−1). Moreover, the established method had been successfully applied to detection of trace BPs in tea beverage with satisfactory recoveries (81.6 % to 118.6 %). This research provides a feasible pathway for preparing COF coating with excellent electrochemical performance and high polarity for EE-SPME.

Synthesis and Catalytic Performance of Mo2C/MoS2 Composite Heterojunction Catalysts.

Hydrogen, as a clean, safe, and efficient energy carrier, is one of the hot energy sources that have attracted much attention. Mo2C, due to the introduction of C atoms, makes the atomic spacing of the Mo lattice decrease and changes the width of the d-band, which makes the electronic properties of Mo2C similar to that of Pt noble metals, exhibiting excellent electrochemical hydrogen precipitation performance. MoS2, due to its special crystal structure and tunable electronic structure, has been widely studied. In this paper, Mo2C nanoparticles were prepared by high-temperature carbonization, and then two-dimensional layered MoS2 were be loaded on Mo2C nanoparticles by the hydrothermal method to synthesize Mo2C/MoS2 composite catalysts. Their electrochemical hydrogen precipitation (HER) performance under acidic conditions was tested. The above catalysts were also characterized by modern material testing methods such as XRD, SEM, TEM, and XPS. The results showed that the composite catalysts exhibited the most excellent electrochemical hydrogen precipitation performance at Mo2C/MoS2-3, with the lowest overpotential at a current density of 10 mA cm-2, Tafel slope, and electrochemical impedance. At the same time, the electrochemically active area was dramatically enhanced, with good stability under prolonged testing. The catalytic activity was significantly improved compared with that of Mo2C and MoS2. The characterization and experimental results indicate that the heterogeneous structure of Mo2C and MoS2 formed a built-in electric field between the two, which accelerated the electron transfer efficiency and provided more active sites. The Mo2C/MoS2 composite catalyst is a low-cost, easy-to-prepare, and high-efficiency electrochemical hydrogen precipitation catalyst, providing a new idea for developing green and clean energy.

In-situ conversion method for Co9S8 embedded in N-doped carbon derived from resin waste induced ultra-stable Li-S batteries

The effective suppression of the shuttle effect in lithium-sulfur batteries require the development of efficient electrocatalysts. Transition metal sulfides show great potential as S cathode electrocatalysts. However, the conventional secondary sulfidation or heat-treatment process used in their synthesis limits their catalytic performance. In this study, we propose an efficient and scalable “exchange-constriction-in-situ conversion” strategy to prepare Co9S8@NC electrocatalysts using CoSO4 and waste resins as sources. No additional sulfur source is required in this process. The resulting Co9S8@NC catalyst demonstrates outstanding long-cycle performance, with a slight decay of only 0.028 % per cycle after 500 cycles at a current density of 2 C. Moreover, it exhibits excellent electrochemical performance even at high surface loading and low electrolyte dosage (E/S). The combination of theoretical calculations and electrochemical analyses demonstrates that Co9S8 possesses strong adsorption, superior catalytic capacity and lower energy barrier of decomposition towards lithium polysulfide, consequently leads to an enhancement in reaction kinetics. This study presents a novel approach for synthesizing high-performance sulfide electrocatalysts.