Charge Transfer Kinetics Research Articles

Withdrawal: Steering Sulfur Reduction Pathways via Cisplatin Enables High Performance in Lithium-Sulfur Batteries.

The sulfur reduction reaction (SRR) is an attractive 16-electron transfer process that endows Li-S batteries with a theoretical capacity of 1,672 mAh g-1. However, the slow kinetics and complex pathways of the SRR cause the shuttling of soluble polysulfides (PSs), thus fast capacity fading. Here, we report using cisplatin (cis-Pt) as a novel mediator to improve the SRR kinetics and a molecular probe to identify the SRR pathways. We show that cis-Pt with a reductive Pt2+ center can directly slice the S-S bonds of PSs, leading to enhanced charge transfer kinetics, guided SRR pathways, and depth conversion of PSs to Li2S. With cis-Pt added, Li-S coin cells deliver a maximum specific capacity of 1,437 mAh g-1 and a capacity decay of 0.017% per cycle after 1000 cycles, while a pouch cell with a practical electrolyte-sulfur ratio (2.5 μl mg-1) exhibits a high energy density of 318.8 Wh kg-1. Our mechanistic studies reveal that cis-Pt steers the cathodic SRR pathways by generating redox active cis-Pt/PSs complexes, enabling the replacement of the sluggish SRR with a faster redox cycling of Pt4+/Pt2+ pairs. These findings provide insights into the rational design of functional mediators for tackling the cathodic challenges inside Li-S batteries.

N-doped carbon dots-modulated interfacial charge transfer and surface structure in FeNbO4 photocatalysts for enhanced CO2 conversion selectivity to CH4

The photocatalytic carbon dioxide reduction reaction (CO2RR) is an innovative and reliable technology to address the issues of energy shortage and climate change simultaneously. However, issues such as insufficient light absorption, rapid electron-hole recombination and low surface activity during CO2RR severely limit the catalysts’ efficiency for photocatalysis. In this study, we present nanohybrid N-CDs/FeNbO4 catalysts to overcome these challenges and achieve high-efficient photocatalytic conversion of CO2 to CH4. The enhancement process starts with the introduction of modified N-CDs, which have a broad light absorption capability. These N-CDs also help to modulate the interfacial charge transfer kinetics, leading to improved charge separation and transfer. This, in turn, enhances the multielectron transfer conversion selectivity of CO2 to CH4. Meanwhile, CO2 adsorption on the photocatalysts is increased due to the creation of oxygen vacancies and lattice stresses resulting from the introduction of N-CDs. This work presents a new approach for improving the photocatalytic performance by adjusting surface structure and interfacial behaviors.

Phase-Induced Strain Effect to Synthesize an Iron-Doped Orthogonal Cobalt Selenide Electrocatalyst for the Oxygen Evolution Reaction.

The etching effect has the capability to control atom doping and trigger phase transformation, thereby enhancing the electrocatalytic reaction. Herein, iron-doped cobalt selenide (Fe-CoSe2) nanoparticle-decorated carbon nanofibers (Fe-CoSe2/CNFs) are synthesized by assembling an FeCo-Prussian blue analogue (FeCo-PBA) cube precursor with polyacrylonitrile fibers and then treating with hydrochloric acid, followed by gas phase selenization. The Fe-CoSe2/CNFs catalyst exhibits a large surface area and a porous structure, facilitating the permeation of electrolytes. Moreover, orthorhombic CoSe2 is obtained, which is in favor of improving the oxygen evolution reaction (OER). By modulating the etching time, the ideal crystal phase and the optimal amount of the dopant (Fe) can be achieved, thus showing favorable OER activity. Specifically, the Fe-CoSe2/CNFs electrocatalyst enables high electrocatalytic activity for the OER with a low overpotential of 263 mV to drive a current density of 10 mA cm-2 in 1 M KOH. A small Tafel slope of 51 mV dec-1 shows fast charge transfer kinetics. Density functional theory (DFT) calculations reveal that Fe-doped orthorhombic CoSe2(111) can modulate the electron structure, contributing to OH- adsorption ability. Given this, a strategy for phase transformation induced by etching technology is proposed to improve the intrinsic activity of the catalyst.

Unlocking the electrochemical performance of glassy carbon electrodes by surface engineered, sustainable chitosan membranes

Chitosan coatings, derived from crustacean shell waste, possess inherent biocompatibility and biodegradability, rendering them suitable for various biomedical and environmental applications, including electrochemical biosensing. Its amine and hydroxyl functional groups offer abundant sites for chemical modifications to boost the charge transfer kinetics and provide excellent adhesion, enabling the construction of robust electrode-coating interfaces for electroanalysis. This study explores the role of electrostatically-driven chemical interactions and crosslinking density originating from different chitosan (Cs) and glutaraldehyde (Ga) concentrations in this aspect. Studying anionic ([Fe(CN)6]3−/4−), neutral (FcDM0/+), and cationic ([Ru(NH3)6]2+/3+) redox probes highlights the influence of Coulombic interactions with chitosan chains containing positively-charged pathways, calculated by DFT analysis. Our study reveals how a proper Ch-to-Ga ratio has a superior influence on the cross-linking efficacy and resultant charge transfer kinetics, which is primarily boosted by up to 20× analyte preconcentration increase, due to electrostatically-driven migration of negatively charged ferrocyanide ions toward positively charged chitosan hydrogel. Notably the surface engineering approach allows for a two-orders of magnitude enhancement in [Fe(CN)6]4− limit of detection, from 0.1 µM for bare GCE down to even 0.2 nM upon an adequate hydrogel modification.

Dipole field as charge-transfer bridge between Cu atomic clusters/PtCu alloy nanocubes and nitrogen-rich C3N5 for superior photocatalytic hydrogen evolution

Utilizing spontaneous polarization field to harness charge transfer kinetics is a promising strategy to boost photocatalytic performance. Herein, a novel Cu atom clusters/PtCu alloy nanocubes coloaded on nitrogen-rich triazole-based C3N5 (PtCu-C3N5) with dipole field was constructed through facile photo-deposition and impregnation method. The dipole field-drive spontaneous polarization in C3N5 acts as a charge-transfer bridge to promote directional electron migration from C3N5 to Cu atom clusters/PtCu alloy. Through the synergistic effects between Cu atom clusters, PtCu alloy and dipole field in C3N5, the optimized Pt2Cu3-C3N5 achieved a record-high performance with H2 formation rate of 4090.4 μmol g−1 h−1 under visible light, about 154.4-fold increase compared with pristine C3N5 (26.5 μmol g−1 h−1). Moreover, the apparent quantum efficiency was up to 25.33 % at 320 nm, which is greatly superior than most previous related-works. The directional charge transfer mechanism was analyzed in detail through various characterizations and DFT calculations. This work offers a novel pathway to construct high-efficiency multi-metal photocatalysts for solar energy conversion.

Radiation Chemistry as a Tool to Accelerate and Predict Calendar Ageing in Lithium-Ion Batteries

Electrochemical energy storage systems such as batteries are in a resting mode most of the time. Even when no current is passing through them, they undergo ageing phenomena, more or less detrimental to their lifespan, known as calendar ageing. Limiting these ageing processes requires a better understanding of them, but studies on calendar ageing are generally time-consuming. Here, we show that radiolysis, i.e. chemistry induced by ionizing radiation, generates similar degradation compounds and can significantly accelerate calendar ageing phenomena (by a factor of 30 under our experimental conditions). Using electrochemical impedance spectroscopy (EIS), we studied symmetrical coin cells containing an electrolyte between two identical electrodes, with or without various additives commonly used in batteries. EIS makes it possible to monitor the change in resistance in the device over time and therefore the formation of the electrode/electrolyte interphase and the charge transfer kinetics. Among the various additives tested (vinylene carbonate, fluoroethylene carbonate and ethyl acetate), the first two proved to be those with the best properties for the cell as a whole. In all cases, just a few hours of irradiation were sufficient to simulate the equivalence of several weeks of calendar ageing.

In Situ Construction of Bimetallic Selenides Heterogeneous Interface on Oxidation-Stable Ti3C2Tx MXene Toward Lithium Storage with Ultrafast Charge Transfer Kinetics.

Ti3C2Tx (MXene) is widely acknowledged as an excellent substrate for constructing heterogeneous structures with transition metal chalcogenides (TMCs) for boosting the electrochemical performance of lithium-ion storage. However, conventional synthesis strategies inevitably lead to poor electrochemical charge transfer due to Ti3C2Tx-derived TiO2 at the heterogeneous interface between Ti3C2Tx and TMCs. Here, an innovative in situ selenization strategy is proposed to replace the originally generated TiO2 on Ti3C2Tx with metallic TiSe2 interphase, clearing the bottleneck of slow charge transfer barrier caused by MXene oxidation. The construction of bimetallic selenide formed by CoSe2 and TiSe2 generates intrinsic electric fields to guide the fast ion diffusion kinetics in a heterogeneous interface. Additionally, the CoSe2/TiSe2/Ti3C2Tx heterogeneous structure with enhanced structural stability and improved rate performance is confirmed by both experiments and theoretical calculations. The engineered heterogeneous structure exhibits an ultra-high pseudocapacitance contribution (73.1% at 0.1mVs-1), rendering it well-suited to offset the kinetics differences between double-layer materials. The assembled lithium-ion capacitor based on CoSe2/TiSe2/Ti3C2Tx possesses a high energy density and an ultralong life span (89.5% after 10000 times at 2Ag-1). This devised strategy provides a feasible solution for utilizing the performance advantages of MXene substrates in lithium storage with ultrafast charge transfer kinetics.

Collagen‐Mediated Solvent Sheathing and Derived Interfacial Manipulation Toward Ultrahigh‐Rate Zn Anodes

AbstractThe zinc (Zn) anode in zinc‐ion batteries suffers from potential defects such as wild dendrite growth, severe Zn corrosion, and violent hydrogen evolution reaction, inducing erratic interfacial charge transfer kinetics, which eventually leads to electrochemical failure. Here, collagen, a biomacromolecule, is added to achieve the reconstruction of the electrolyte hydrogen‐bonding network and the modification of the derived Zn interface. Benefiting from the electronegativity advantage of amino groups (‐NH2) in collagen, the Zn (002) crystal plane is preferentially exposed and the solid electrolyte interface (SEI) rich in ZnF2 and Zn3N2 promotes the rapid charge transfer of Zn anode. Thence, an impressive cumulative capacity of 7,500 mAh cm−2 at 30 mA cm−2 is achieved and the assembled Zn|VO2 cell exhibited robust cycle reversibility even when subject to a maximum current of 100 A g−1 and an ultra‐long cycle life of 20,000 cycles at 50 A g−1, with a single‐cycle capacity loss as low as 0.0021%. Such a convenient strategy of solvent sheathing regulation and derived interfacial manipulation opening up a promising universal approach toward long‐life and high‐rate Zn anodes.

Tethering Cobalt Ions to BiVO4 Surface via Robust Organic Bifunctional Linker for Efficient Photoelectrochemical Water Splitting.

In the quest for efficient and stable oxygen evolution catalysts (OECs) for photoelectrochemical water splitting, the surface modification of BiVO4 is a crucial step. In this study, a novel and robust OEC, based on 3-(bis(pyridin-2-ylmethyl) amino) propanoic acid bifunctional linker known as dipicolyl alanine acid (DPAA) and cobalt ions, is prepared and fully characterized. The DPAA is anchored to the surface of BiVO4 and utilized to tether cobalt ions. The Co-DPAA/BiVO4 photoanode exhibits remarkable stability and efficiency toward photoelectrochemical water oxidation. Specifically, it showed anodic photocurrent increase of 7.1, 5.0, 3.0, and 1.3-fold at 1.23VRHE as compared to pristine BiVO4, DPAA/BiVO4, Co-BiVO4, and Co-Pi/BiVO4 photoanodes, respectively. The photoelectrochemical and IMPS studies revealed that the Co-DPAA/BiVO4 photoanode exhibits a longer transient decay time for surface-trapped holes, higher charge transfer kinetics, and charge separation efficiency compared to Co-Pi/BiVO4 and pristine BiVO4 photoelectrodes. This indicates that the Co-DPAA effectively reduces surface recombination and facilitates charge transfer. Moreover, at 1.23VRHE, the Co-DPAA/BiVO4 photoanode achieved a faradic efficiency of 92% for oxygen evolution reaction and could retain a turnover frequency of 3.65s-1. The- exhibited effeciency is higher than most of the efficient molecular oxygen evolution catalyst based on Ru.

Plasmonic tandem heterojunctions enable high-efficiency charge transfer for broad spectrum photocatalytic hydrogen production

Rational engineering of semiconductor photocatalysts for efficient hydrogen production is of great significance but still challenging, primarily due to the limitations in charge transfer kinetics. Herein, a fascinating plasmonic tandem heterojunction with the hc-CdS/Mo2C@C heterostructure is aimfully prepared for effectively promoting the charge separation kinetics of the CdS photocatalyst via the synergistic strategy of phase junction, Schottky junction, and photothermal effect. The difference in atomic configuration between cubic-CdS (c-CdS) and hexagonal-CdS (h-CdS) leads to effective charge separation through a typical II charge transfer mechanism, and plasmonic Schottky junction further extracts the electrons in the hc-CdS phase junction to realize gradient charge transfer. Besides, the photothermal effect of Mo2C@C helps to expand the light absorption, accelerate charge transfer kinetics, and reduce the hydrogen evolution energy barrier. The carbon layer provides a fast channel for charge transfer and protects the photocatalyst from photocorrosion. As a result, the optimized hc-CMC photocatalyst exhibits a significantly high photocatalytic H2 production activity of 28.63 mmol/g/h and apparent quantum efficiency of 61.8%, surpassing most of the reported photocatalysts. This study provides a feasible strategy to enhance the charge transfer kinetics and photocatalytic activity of CdS by constructing plasmonic tandem heterogeneous junctions.

Hydrothermally grown copper cobalt phosphate hydrate nanostars for supercapacitors: Investigation of their charge transfer kinetics

The transition bimetal phosphates are optimistic materials for supercapacitors. In this study, copper cobalt phosphate hydrate ((Cu0.35Co0.65)3(PO4)2·H2O) (CCPH) was deposited on Nickel foam using a hydrothermal method at different reaction temperatures as 120, 150, and 180 °C. X-ray diffraction analysis results in the monoclinic crystal structure of CCPH. The Raman study confirms the presence of the phosphate group. The scanning electron microscopy (SEM) study reveals that the reaction temperature-dependent morphological evolution takes place from nanostars to three dimensional (3D)-porous spongy balls-like structure. The elevating reaction temperature has changed the morphology from nanostars to 3D-porous spongy balls. The electrochemical analysis of the CCPH12 electrode resulted in a specific capacitance of 3390.73 mF/cm2 (518.02 µAh/cm2) at 10 mA/cm2 current density. The charge storage dynamics of the CCPH electrodes were analyzed using power law. The CCPH12 electrode delivered the energy density and power density as 0.142 mWh/cm2 and 2.75 mW/cm2, respectively.

Physical reservoir computing with visible-light signals using dye-sensitized solar cells

Physical reservoir computing (PRC) with visible-light signals was demonstrated using dye-sensitized solar cells. The short-term memory required for PRC was confirmed using light pulse inputs. Waveform learning was demonstrated for nonlinear autoregressive moving-average time series level 2 (NARMA2) signals with normalized mean square error of 0.027. The relatively slow (milliseconds to seconds) and complex charge transfer dynamics in the TiO2 porous layer with redox reactions in the solution phase provided the characteristics required for PRC.

In-situ Fe–O co-doped carbon nitride heterogenous catalyst for enhanced photo-Fenton oxidation performance towards recalcitrant organic pollutants

One-step and in-situ FeCl3-participated molten urea thermal polymerization strategy is designed to prepare Fe–O co-doped carbon nitride photo-Fenton catalyst (Fe/OCN). Fe/OCN exhibits remarkable photo-Fenton catalytic oxidation capacity towards recalcitrant organic pollutants, in which 0.31 wt% Fe/OCN with optimal Fe-doping level exhibits significantly 60 and 6.3 times higher pseudo-first-order kinetic constant than single photocatalysis and Fenton system in the degradation of methyl orange. The enhancement of photo-Fenton catalytic performance is mainly ascribed to the realization of ideal Fe–O and Fe–N coordination structure in the framework of polymeric carbon nitride, which can not only serve as prime sites for the adsorption of target pollutants molecules and transfer channels for directed migration of photogenerated charges, but also well-modulate electronic structure and band structure of Fe/OCN. Accordingly, the resulting boosted charge carriers separation and transfer dynamics and increased electron density around Fe active centers facilitate ≡Fe(II) regeneration and H2O2 activation, leading to the significant production of plentiful reactive species responsible for degradation and mineralization of organic pollutants. The present work provides new insight into the optimized design and precise regulation of carbon nitride-based photo-Fenton system for advanced wastewater treatment.

Cation-induced interface electric field redistribution and molecular orbital coupling in Co-FeS/MoS2 for boosting electrocatalytic overall water splitting

A green hydrogen economy requires efficient bifunctional electrocatalysts for simultaneous hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). In this study, a mild sulfuration strategy was used to create a Co-FeS/MoS2 catalyst from metal-organic frameworks (MOFs) on foam nickel. This catalyst exhibits exceptional activity in 1 M KOH, only requiring ultralow overpotentials of 63 mV and 230 mV to achieve current densities of 10 mA cm−2 and 100 mA cm−2 for the HER and OER processes. Additionally, it achieves a low cell voltage of 1.45 V at 10 mA cm−2, surpassing reported catalysts. DFT calculations and XPS tests show that Co introduction induces high-valence Fe active sites and facilitates interface electric field redistribution. Crystal orbital Hamilton population (COHP) calculations reveal d-p orbital hybridization, enhancing conductivity and charge transfer kinetics. This research sheds light on the catalytic impacts of metal cations on transition metal sulfides to design high efficient electrocatalysts.

Optimizing sodium storage mechanisms and electrochemical performance of high Nitrogen-Doped hard carbon anode materials Derived from waste plastics for Sodium-Ion batteries

The development of high-performance hard-carbon (HC) anode materials for sodium-ion batteries was constrained by slow charge-transfer kinetics and sodium-storage mechanisms. In this paper, high nitrogen-doped (12.24 %) HC with an efficient interworking structure was synthesized in situ using waste plastics as precursors by utilizing the strong 2-D self-template effect of guanine. Elucidating the mechanism of sodium storage in heteroatom-doped carbon with coexisting heterocyclic and graphitic nitrogen, which synergistically enhances electrochemical activity, utilizing a range of in-situ and ex-situ characterization methods. Based on density functional theory (DFT), it has been discovered that the doping of pyrrole nitrogen (N5) and pyridinium nitrogen (N6) can effectively expand the interlayer spacing during the Na+ sodiated/de-sodiated process, thereby enhancing electrochemical activity. The optimized HC has increased the Na+ diffusion coefficient by 1.5 orders of magnitude (10-8.2 cm2 s−1 vs 10-9.76 cm2 s−1) and exhibits high reversible capacity (452 mAh/g@20 mA g−1), high rate performance (388mAh/g@500 mA g−1), superior cycling stability (87.6 % @500 mA g−1 after 2,000 cycles). The full cell exhibits good cyclic stability (91.87 %@100 mA g−1 after 2,00 cycles), while the designed pouch cell also demonstrates favorable cycle life (90.78 %@200 mA g−1 after 100 cycles).

Photoredox phase engineering of transition metal dichalcogenides

Crystallographic phase engineering plays an important part in the precise control of the physical and electronic properties of materials. In two-dimensional transition metal dichalcogenides (2D TMDs), phase engineering using chemical lithiation with the organometallization agent n-butyllithium (n-BuLi), to convert the semiconducting 2H (trigonal) to the metallic 1T (octahedral) phase, has been widely explored for applications in areas such as transistors, catalysis and batteries1–15. Although this chemical phase engineering can be performed at ambient temperatures and pressures, the underlying mechanisms are poorly understood, and the use of n-BuLi raises notable safety concerns. Here we optically visualize the archetypical phase transition from the 2H to the 1T phase in mono- and bilayer 2D TMDs and discover that this reaction can be accelerated by up to six orders of magnitude using low-power illumination at 455 nm. We identify that the above-gap illumination improves the rate-limiting charge-transfer kinetics through a photoredox process. We use this method to achieve rapid and high-quality phase engineering of TMDs and demonstrate that this methodology can be harnessed to inscribe arbitrary phase patterns with diffraction-limited edge resolution into few-layer TMDs. Finally, we replace pyrophoric n-BuLi with safer polycyclic aromatic organolithiation agents and show that their performance exceeds that of n-BuLi as a phase transition agent. Our work opens opportunities for exploring the in situ characterization of electrochemical processes and paves the way for sustainably scaling up materials and devices by photoredox phase engineering.

Unlocking a Fast Track for Magnesium Migration in Cu1.8S1-xSex via Anion-Tuning Chemistry.

Rechargeable magnesium batteries (rMBs) are promising candidates for next-generation batteries in which sulfides are widely used as cathode materials. The slow kinetics, low redox reversibility, and poor magnesium storage stability induced by the large Coulombic resistance and ionic polarization of Mg2+ ions have obstructed the development of high-performance rMBs. Herein, a Cu1.8S1-xSex cathode material with a two-dimensional sheet structure has been prepared by an anion-tuning strategy, achieving improved magnesium storage capacity and cycling stability. Element-specific synchrotron radiation analysis is evidence that selenium incorporation has indeed changed the chemical state of Cu species. Density functional theory calculations combined with kinetics analysis reveal that the anionic substitution endows the Cu1.8S1-xSex electrode with favorable charge-transfer kinetics and low ion diffusion barrier. The principal magnesium storage mechanisms and structural evolution process have been revealed in details based on a series of ex situ investigations. Our findings provide an effective heteroatom-tuning tactic of optimizing electrode structure toward advanced energy storage devices.

Inhibited Passivation by Bioinspired Cell Membrane Zn Interface for Zn-Air Batteries with Extended Temperature Adaptability.

Due to the slow dynamics of mass and charge transfer at Zn|electrolyte interface, the stable operation of Zn-air batteries (ZABs) is challenging, especially at low temperature. Herein, inspired by cell membrane, a hydrophilic-hydrophobic dual modulated Zn|electrolyte interface is constructed. This amphiphilic design enables the quasi-solid-state (QSS) ZABs to display a long-term cyclability of 180 h@50mAcm-2 at 25°C. Moreover, a record-long time of 173 h@4mAcm-2 at -60°C is also achieved, which is almost threefolds of untreated QSS ZABs. Control experiments and (in situ) characterization reveal that the growth of insulating ZnO passivation layers is largely inhibited by tuned hydrophilic-hydrophobic behavior. Thus, the enhanced transfer dynamic of Zn2+ at Zn|electrolyte interface from 25 to -60°C is attained. As an extension, the QSS Al-air batteries (AABs) with bioinspired interface also show unprecedented discharge stability of 420 h@1mAcm-2 at -40°C, which is about two times of untreated QSS AABs. This bioinspired-hydrophilic-hydrophobic dual modulation strategy may provide a reference for energy transform and storage devices with broad temperature adaptability.

Strong Covalent Metal-Ligand Interaction Enables a Fast Kinetic and Structurally Stable Na-Ion Layered Cathode.

Anionic redox chemistry has attracted increasing attention for the improvement in the reversible capacity and energy density of cathode materials in Li/Na-ion batteries. However, adverse electrochemical behaviors, such as voltage hysteresis and sluggish kinetics resulting from weak metal-ligand interactions, commonly occur with anionic redox reactions. Currently, the mechanistic investigation driving these issues still remains foggy. Here, we chemically designed Na0.8Fe0.4Ti0.6S2 and Na0.8Fe0.4Ti0.6O2 as model cathodes to explore the covalency effects on metal-ligand interactions during anionic redox process. Na0.8Fe0.4Ti0.6S2 with strengthened covalent interaction of metal-ligand bonds exhibits smaller voltage hysteresis and faster kinetics than Na0.8Fe0.4Ti0.6O2 during (de)sodiation process. Theoretical calculations suggest that Fe is the dominant redox-active center in Na0.8Fe0.4Ti0.6S2, whereas the redox-active center moves from Fe to O with the removal of Na+ in Na0.8Fe0.4Ti0.6O2. We attribute the above different redox behaviors between Na0.8Fe0.4Ti0.6S2 and Na0.8Fe0.4Ti0.6O2 to the charge transfer kinetics from ligand to metal. Moreover, the structural stability of Na0.8Fe0.4Ti0.6S2 is enhanced by increasing the cation migration barriers through strong metal-ligand bonds during desodiation. These insights into the originality of metal-ligand interactions provide guidance for the design of high-capacity and structurally stable cathode materials for Li/Na-ion batteries.

Cost‐Effective Layered Oxide – Olivine Blend Cathodes for High‐Rate Pulse Power Lithium‐Ion Batteries

AbstractSustainability and supply‐chain concerns require lithium‐ion batteries (LIBs) free from critical minerals, such as nickel and cobalt. While recent advances provide encouraging signs that cobalt can be removed, the question remains how much Ni can be removed from Co‐free layered oxide cathodes before sacrificing critical performance metrics. This study highlights the effect of reducing Ni by benchmarking several Co‐free cathodes with decreasing Ni content. Keeping the energy density the same by increasing the charge voltage, cathodes below 80% Ni content exhibit worsened capacity fade due to increasing oxygen release and electrolyte decomposition. Charge transfer and diffusion kinetics are also hindered with increasing Mn content and exacerbated by resistive surface phases formed at high voltages, rendering lower‐Ni, Co‐free cathodes less competitive than high‐Ni cathodes for high energy and power applications. It is demonstrated blending layered oxide with olivine as an effective alternative to deliver energy density and cycling stability comparable to lower‐Ni cathodes with moderate charging voltages. Blending with 30 wt% olivine LiMn0.5Fe0.5PO4 (LMFP) virtually eliminates the diffusion limitation of layered oxides at low state‐of‐charge, with enhanced pulse power characteristics rivaling the high‐Ni counterparts. Cathode blending can further reduce the overall Ni content and cost without the performance limitations of lower‐Ni, Co‐free cathodes.