Sodium Ion Diffusion Research Articles

Silicone oil-based selective SiOC coating onto hydrophobic rGO-MoS2 composite materials to achieve ultra-stable composite anodes in sodium-ion batteries

Molybdenum sulfide (MoS2) has a 2-D open framework structure and provide delocalized sodium ion diffusion and intercalation within the MoS2 structure. The structure exhibits a high theoretical capacity due to its wide interlayer spacing (∼6.2 Å). Therefore, MoS2 has recently been used as an anode material in sodium-ion batteries (SIBs). However, it exhibits inferior cycle performance and rate characteristics due to its low electronic conductivity and volume change during continuous operation, which restrict its use as an anode material in SIBs. Herein, a MoS2 surface modified with hydrophobic reduced graphene oxide (rGO-MoS2) was dispersed in silicone oil, which is the starting material for silicon oxycarbide (SiOC), and subsequently used to prepare a MoS2 composite with a SiOC coating-layer surface modified with rGO (rGO-MoS2@SiOC) via single pyrolysis reaction. rGO expands the interlayer spacing of MoS2, improving the electronic conductivity, and the SiOC layer capable of accommodating the volume expansion of MoS2 supports the insufficient buffer layer provided by rGO alone to form a conductive pathway that suppressed any adverse reactions at the electrode and electrolyte interface. The rGO-MoS2@SiOC composite exhibits a high reversible capacity of ∼532.5 mAh g−1, no capacity fading even after 100 cycles, and superior rate characteristics.

Structural regulation of Mn-based Prussian blue induced by zinc-substitution for enhanced sodium storage performance

Mn-based Prussian blue (NMF) is a prospective choice for sodium-ion battery cathode materials because of its high theoretical specific capacity, high charge/discharge voltage plateau, cheap raw materials and eco-friendly. However, it undergoes serious capacity fading during cycling owing to the unstable Jahn-Teller distortion caused by the oxidation of Mn2+ to Mn3+. In this work, the structural regulation of NMF is achieved through zinc substitution, and the effect of structural adjustment caused by zinc substitution on the sodium storage properties of NMF is studied in detail. The experimental results verify that NZMF still maintain cubic structure with high content of sodium, less [Fe(CN)6] vacancies and low level of crystal water. Moreover, the four coordination of Zn-N is lower than six coordination of Mn-N, confining the nucleus growth, thereby reducing the powders size of NZMF. The smaller powder size of NZMF with higher surface area results in shortened sodium ion diffusion path and accelerated the charge transfer. In addition, the electrochemically inactive zinc plays a pillar role in maintaining its structural stability. Consequently, NZMF reveals better rate capacity and cycling stability than original NMF. In particular, its capacity can be maintained at 68.6 mAh g−1 under a high current density of 1600 mA/g, and the capacity retention is 76.5% at 800 mA/g after 1000 cycles. This work provides a new insight to improve the structural stability of Prussian blue.

Controlled growth of Co9S8 nanoparticle-embedded carbon nanosheets/carbon nanofibers toward high-performance sodium storage

Transition metal sulfides (TMSs) are considered as promising anodes for sodium-ion batteries (SIBs) due to their high theoretical capacity and low cost. However, TMSs suffer from massive volume expansion, slow sodium-ion diffusion kinetics, and poor electrical conductivity, which severely restrict their practical application. Herein, we design self-supporting Co9S8 nanoparticles embedded carbon nanosheets/carbon nanofibers (Co9S8@CNSs/CNFs) as anode materials for SIBs. The electrospun carbon nanofibers (CNFs) provide continuous conductive networks to accelerate the ion and electron diffusion/transport kinetics, while MOFs-derived carbon nanosheets (CNSs) buffer the volume variation of Co9S8, consequently improving the cycle stability. Benefitting from the unique design and pseudocapacitive features, Co9S8@CNSs/CNFs deliver a stable capacity of 516 mAh g−1 at 200 mA g−1 and a reversible capacity of 313 mAh g−1 after 1500 cycles at 2 A g−1. Note that, it also displays excellent sodium storage performance when assembled into a full cell. The rational design and excellent electrochemical properties endow Co9S8@CNSs/CNFs with the potential stepping into commercial SIBs.

Ultra-fine SnO2 nanocrystals anchored on reduced graphene oxide as a high-performance anode material for sodium-ion batteries

SnO2 has attracted extensive research attentions as a promising anode material for sodium-ion batteries (SIBs) due to its high theoretical capacity. However, its application is largely hindered by sluggish sodium ion diffusion and drastic volume change during the conversion reaction and alloying process. Herein, ultra-fine SnO2 nanocrystals (3–5 nm) anchored on reduced graphene oxide (rGO) is demonstrated as a promising anode material for SIBs. Ultra-fine SnO2 nanocrystals are uniformly grown on rGO sheets by a facile one-step hydrothermal process. Nano-scaled SnO2 grains tolerate volume expansion and provide shortened diffusion pathway for sodium ions, and meanwhile rGO acts as an excellent conductive matrix, thus endowing the composite electrode with excellent electrochemical performance. More importantly, the ratio of SnO2 to rGO in the composite is optimized. The optimized sample delivers an initial charge capacity of 518 mAh g−1 at a current density of 50 mA g−1, and 504 mAh g−1 after 300 cycles at a current density of 100 mA g−1. Furthermore, a capacity of 287 mAh g−1 can be maintained after 1000 cycles at a current density of 1000 mA g−1.

Iron-based Prussian blue coupled with polydopamine film for advanced sodium-ion batteries

In this study, high-performance polydopamine (PDA) coated Na1.33FeFe(CN)6·1·16H2O (PBA) cathode materials for sodium-ion batteries (SIBs) are successfully synthesized by using a single source method with Na4Fe(CN)6 as sole iron source. The PDA coating does not alter the structure or morphology of the PBA sample, but greatly improves its conductivity and Na ion diffusion ability because of the good conductivity. Consequently, we observe enhanced reversible capacity, rate capability and cycle stability during cycling. Our results indicate that PBA-2 has the best electrochemical performance and sodium ion diffusion coefficient among all samples. Even at 1 C rate, PBA-2 has a high initial discharge capacity of 145 mAh g−1 with a capacity retention of 90% over 100 cycles. The introduction of a suitable amount of PDA represents an effective strategy for enhancing the electrochemical activity of PBA for advanced SIBs. Such design strategies can be also used to modify other cathode materials for SIBs.

Rationally designed NASICON-type Na3.75V1.25Mn0.75(PO4)3 cathode towards long life-span sodium ion batteries

Owning to non-toxic and high working potential, Mn-substituted NASICON-type Na3+xMnxV2-x(PO4)3 cathodes have promising application in sodium ion batteries (SIBs). However, the poor cycling stability limits their further practical applications. Herein, a succession of carbon coated Na3.75Mn0.75V1.25(PO4)3 cathodes are constructed via a sol–gel combining with heating treatment. The effects of carbon content on the structure, electrochemical properties and sodium ion diffusion kinetics are investigated. The optimal composition, Na3.75Mn0.75V1.25(PO4)3/2VitC, displays an outstanding specific capacity and long-cycling stability. It releases a discharge capacity of 105.6 mAh g-1 with a high initial Coulombic efficiency of 97.5% at 0.2C. It can also deliver a high capacity of 92.6 mAh g-1 with a capacity retention of 88.3% at 5C over 2000 cycling, and the reversible capacity can achieve to 79.1 mAh g-1 with 78% capacity retention after 4000 cycles at high rate of 10C. Ex-situ X-ray diffraction and X-ray photoelectron spectroscopy reveal a biphasic reaction process and high structural reversibility during sodium ion insertion/extraction. The good multiplicity performances, excellent long cycle stability and low cost of the optimized Na3.75Mn0.75V1.25(PO4)3 composite indicate that it is a promising cathode material for SIBs.

Engineering CSFe Bond Confinement Effect to Stabilize Metallic-Phase Sulfide for High Power Density Sodium-Ion Batteries.

Metallic-phase iron sulfide (e.g., Fe7 S8 ) is a promising candidate for high power density sodium storage anode due to the inherent metal electronic conductivity and unhindered sodium-ion diffusion kinetics. Nevertheless, long-cycle stability can not be achieved simultaneously while designing a fast-charging Fe7 S8 -based anode. Herein, Fe7 S8 encapsulated in carbon-sulfur bonds doped hollow carbon fibers (NHCFs-S-Fe7 S8 ) is designed and synthesized for sodium-ion storage. The NHCFs-S-Fe7 S8 including metallic-phase Fe7 S8 embrace higher electron specific conductivity, electrochemical reversibility, and fast sodium-ion diffusion. Moreover, the carbonaceous fibers with polar CSFe bonds of NHCFs-S-Fe7 S8 exhibit a fixed confinement effect for electrochemical conversion intermediates contributing to long cycle life. In conclusion, combined with theoretical study and experimental analysis, the multinomial optimized NHCFs-S-Fe7 S8 is demonstrated to integrate a suitable structure for higher capacity, fast charging, and longer cycle life. The full cell shows a power density of 1639.6Wkg-1 and an energy density of 204.5Whkg-1 , respectively, over 120 long cycles of stability at 1.1Ag-1 . The underlying mechanism of metal sulfide structure engineering is revealed by in-depth analysis, which provides constructive guidance for designing the next generation of durable high-power density sodium storage anodes.

Sodium Dynamics in the Cellular Environment.

Sodium ions are essential for the functions of biological cells, and they are maintained at the balance between intra- and extracellular environments. The quantitative assessment of intra- and extracellular sodium as well as its dynamics can provide crucial physiological information on a living system. 23Na nuclear magnetic resonance (NMR) is a powerful and noninvasive technique to probe the local environment and dynamics of sodium ions. However, due to the complex relaxation behavior of the quadrupolar nucleus in the intermediate-motion regime and because of the heterogeneous compartments and diverse molecular interactions in the cellular environment, the understanding of the 23Na NMR signal in biological systems is still at the early stage. In this work, we characterize the relaxation and diffusion of sodium ions in the solutions of proteins and polysaccharides, as well as in the in vitro samples of living cells. The multi-exponential behavior of 23Na transverse relaxation has been analyzed according to the relaxation theory to derive the crucial information related to the ionic dynamics and molecular binding in the solutions. The bi-compartment model of transverse relaxation and diffusion measurements can corroborate each other to quantify the fractions of intra- and extracellular sodium. We show that 23Na relaxation and diffusion can be used to monitor the viability of human cells, which offers versatile NMR metrics for in vivo studies.

Exploiting the Coordination Effect in Fe-Phenanthroline Complex for the Catalytic Carbonization of Phenanthroline toward the High Capacity Anode Grade Carbon

Aromatic organic molecules (AOMs) present an appealing precursor option for anode-grade hard carbon for sodium-ion batteries (SIBs) because of their prevalence, diverse chemical functionalities, and huge scope for nanostructure engineering at the molecular level. However, most small organic molecules decompose before actual carbonization is initiated unless reactions are carried out under high pressures or in the presence of catalysts. Herein, we report a facile carbonization of aromatic monomeric phenanthroline (phen) by exploiting the strong molecule-level coordination effect of the Fe-phen complex and in situ catalysis affected by Fe. With this carbonization strategy, we achieve better scalability with appreciable carbon yield, while carbonization of simple phen molecule returns zero carbon yields. The as-prepared N-doped microporous carbon (NMC) possesses desirable microstructural features with optimum nitrogen content to be employed as an anode for SIB. As an anode, the NMC delivers a high reversible capacity of 271 mAh g–1 at 100 mA g–1, an ultrahigh rate capability of 101 mAh g–1 at 1 A g–1, and a stable cycle life. The galvanostatic intermittent titration technique (GITT) depicts sodium ion diffusion coefficients of the order of ∼10–13 (cm2 s–1) in the intercalation region, which implies a faster sodium ion diffusion rate compared to most of the reported hard carbons. Given the vast diversity of AOMs, this work encourages new research interests to produce advanced carbon materials with nanostructure engineering at the molecular level for sodium-ion battery applications.

Sodium-ion diffusion coefficients in tin phosphide determined with advanced electrochemical techniques

Sodium ion insertion plays a critical role in developing robust sodium-ion technologies (batteries and hybrid supercapacitors). Diffusion coefficient values of sodium (DNa+) in tin phosphide between 0.1 V and 2.0 V vs. Na/Na+ are systematically determined by galvanostatic intermittent titration technique (GITT), electrochemical impedance spectroscopy (EIS), and potentiostatic intermittent titration technique (PITT). These values range between 4.55 × 10−12 cm2 s−1 and 1.94 × 10−8 cm2 s−1 and depend on the insertion/de-insertion current and the thickness of the electrode materials. Additionally, DNa+ values differ between the first and second cation insertion because of the solid electrolyte interface (SEI) formation. DNa+ vs. insertion potential alters non-linearly in a “W” form due to the strong interactions of Na+ with tin phosphide particles. The results reveal that GITT is a more appropriate electrochemical technique than PITT and EIS for evaluating DNa+ in tin phosphide.

Dual metal (Fe and Mg) substituted layered titanium-based P2 and O3-type negative electrodes for rechargeable sodium batteries

A first attempt was made to enhance the electrochemical performances, using the binary metal (Fe and Mg) substitution on the layered Titanium-based P2-type Na0.5Ni0.2Ti0.6O2 (P2-NNTFMO) and O3-type NaNi0.2Ti0.6O2 (O3-NNTFMO) anode materials, via traditional solid state reaction for sodium ion batteries (SIBs). The XPS analysis of the O3-NNTFMO negative material exhibit the presence of Ti, Ni, Fe and Mg ions happens in +4, +2, +3 and +1 valance states respectively. The discharge and charge curves reveal the P2-NNTFMO and O3-NNTFMO anode materials have the charge capacities of 117.60 and 128.48 mAh/g respectively. The limited amount of co-substitution (Fe and Mg) in transition metal oxide layers would enlarge the sodium ion diffusion layers during cycling for O3 and P2-type anodes, due to the shrinkage of TMO6 octahedrons and decrease of TM-O bond lengths.

INCREASING OF THE CORROSION RESISTANCE OF FIBERGLASS PLASTIC REINFORCEMENT THROUGH MODIFICATION OF THE POLYMER BINDER

The issue of increasing the corrosion resistance of composite reinforcement, based on glass fiber and epoxy anhydride binder, is considered. The proposed samples of composite reinforcement were manufactured by needle extrusion technology. Glass fibers were evenly distributed in the channels and impregnated with a polymer binder based on epoxy resin. The amount of phenolic modifier in the polymer binder, according to the technological mode of obtaining composite reinforcement, was brought up to 5%. With a further increase in the content of the modifier, the degree of conversion of epoxy groups was no more than 70%, which sharply reduced the operational characteristics of the material. The overall ratio of polymer binder and glass reinforcement in the composite was ~ 60÷40. It was established that at low concentrations of the polymer modifier (up to 5 wt. parts), the processes of ordering and chemical grafting lead to compaction of the molecular grouping in the system, which in our case is characteristic of phenolic resins of the novolach and resol types. At the same time, under the conditions of the production technology, internal stresses in materials of this type increase sharply, which leads to the formation of surface defects (microcracks). At the tip of a crack or defect, sodium ions or other cations under the action of water undergo hydrolysis to form metal hydroxide, which, in turn, causes hydrolysis of siloxane bonds, thus weakening the mesh structure of silicon dioxide. The experimental activation energy was identified with the activation energy of sodium ion diffusion in the glass mass. But the plastic deformation of the glass in the region before the crack is very small, and instead of a uniform distribution of stress, the material cracks along the weakened centers The obtained data indicate that the action of the alkaline environment causes an increased loss of mass of the composite, both for the unmodified and for those modified with traditional phenolic resins. In turn, this ensures a high degree of penetration of alkalis into the volume of the material, access to reinforced fibers with their subsequent damage. To increase the corrosion resistance of composite reinforcement based on an epoxy anhydride binder, it is advisable to use a reactive sulfur-containing phenolic modifier. Its action is based on the ability to maintain the permissible monolithicity of fiberglass in the alkaline environment of concrete, the modulus of elasticity and necessary strength. Keywords: composite polymer reinforcement, fiberglass, alkaline environment, phenolic modifier.

Petroleum-Pitch-Based Carbon Nanocages Encapsulated Few-Layer MoS2 with S Vacancies for a High-Performance Sodium-Ion Battery

Molybdenum disulfide (MoS2), one of the promising anode materials for high-energy-density sodium-ion batteries (SIBs), is subjected to poor electronic conductivity and severe volume expansion during the charge–discharge cycle. Herein, cage-like carbon was prepared from petroleum pitch to composite with few-layer MoS2 as MoS2/C anodes for SIBs, giving an excellent capacitive performance (89.18% at 1.4 mV s–1) and nearly 100% capacity retention after 300 cycles at 1 A g–1. The unique cage-like structures relieve the volume expansion of MoS2 during the charge–discharge cycles. Meanwhile, MoS2 has an expanded interlayer distance (0.685 nm) and abundant S vacancies, affording rich active sites for the adsorption diffusion of sodium ions. This work provides a convenient method to solve the inherent defects of MoS2 by introducing cage-like carbon from petroleum pitch.

Molybdenum disulfide/phosphorus-doped carbon nanosheet composites as anode materials for sodium ion batteries

In this paper, the phosphorus-doped carbon nanosheet and molybdenum disulfide (P-CNSs-MoS2) composites was synthesized by a hydrothermal method, and the P-CNSs-MoS2 composites could be applied as anode material for Na+ battery. The morphology and structure of the composites were characterized by X-ray diffractometer (XRD) and scanning electron microscopy (SEM). And the electrochemical properties of the composite were also measured. The results showed that the size of MoS2 material became significantly larger by the attachment and derivation of phosphorus-doped carbon nanosheets, which could also further promote the diffusion of electrons and sodium ions. As the current density was 0.1 A g−1, the first cycle specific discharge capacity of P-CNSs-MoS2 composite could reach 1059.2 mA·h/g and its reversible specific capacity could still maintain at 446.2mA·h/g after 20 cycles.

Tunnel‐Type Na2Ti6O13@Carbon Nanowires as Anode Materials for Low‐Temperature Sodium‐Ion Batteries

AbstractEconomical efficient anode materials play an important role in low‐temperature sodium‐ion batteries (SIBs). Tunnel‐type structured Na2Ti6O13@C nanowires were synthesized and utilized as anode material for low‐temperature SIBs. The appropriate interlayer spacing for sodium ion insertion and short diffusion pathway can accelerate the sodium ion kinetics and decrease the apparent activation energy at low temperature. The diffusion apparent activation energy and activation energy for Na2Ti6O13@C were calculated to be 42.0 kJ mol−1 and 15.3 kJ mol−1 with the sodium ion diffusion coefficients about 10−12 cm2 s−1. The Na2Ti6O13@C nanowires exhibit a high reversible capacity of 100 mAh g−1 at 0 °C with 99.6 % retention after 200 cycles at 0.5 C. Coupling with the sodium vanadium phosphate as cathode, the assembled Na2Ti6O13@C||NVP full‐cell can keep a 65 % capacity retention after 175 cycles at 0 °C. This work presents that Na2Ti6O13@C nanowires can be an ideal type of anode active materials for low‐temperature SIBs.

Pore Perforation of Graphene Coupled with In Situ Growth of Co3 Se4 for High-Performance Na-Ion Battery.

Graphene-based nanomaterials have sprung up as promising anode materials for sodium-ion batteries due to the intriguing properties of graphene itself and the synergic effect between graphene and active materials. However, the 2Dgraphene sheet only allows the rapid diffusion of sodium ions along the parallel direction while that of the vertical direction is difficult, limiting the rate capability of graphene-based electrode materials. To tackle this problem, pore-forming engineering has been employed to perforate graphene and concurrently achieve the in situ growth of Co3 Se4 nanoparticles. The generation of in-plane nanohole breaks through the physical barriers of the graphene nanosheets, enabling the fast diffusion of electrolyte ions in the longitudinal direction. In addition, this design limits the aggregation of Co3 Se4 nanoparticles because of the high affinity of Co3 Se4 on graphene. Benefiting from the high conductivity and fast ion transport bestowed by the ingenious architecture, the Co3 Se4 /holey graphene exhibits a remarkable rate performance of 519.5 mAh g-1 at 5.0 A g-1 and desirable cycle stability. Conclusions drawn from this investigation are that the transport of sodium inside the graphene-based composites is crucial for rate performance enhancement and this method is effective in modifying graphene-based nanomaterials as potential anode materials.

Dopant-enhanced sodium and potassium-ion adsorption and diffusion in two-dimensional titanium disulfide

Two-dimensional (2D) titanium disulfide (TiS2) is the lightest transition-metal dichalcogenide (TMD). It exhibits relatively better adsorption and diffusion of sodium (Na) and potassium (K) ions than other TMDs, such as MoS2 (molybdenum disulfide) and ReS2 (rhenium disulfide), making it a promising anode material for alkali-ion batteries. Previous studies have found that doping significantly enhances the adsorption and diffusion capabilities of 2D TMDs. For the first time, this work reports the adsorption of Na and K ions on doped TiS2 monolayers using first-principles calculations, where the Ti atom is substituted by 3d-transition metals, including iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu). Metal-atom doping induces remarkably stronger binding of alkali ions on the surface of TiS2, with adsorption energies ranging from −2.07 to −2.48 eV for Na and −2.59 to −3.00 eV for K. The diffusion barrier energies for alkali ions decrease in the proximity of the doping site and increase as the ions travel away from the doping site for Fe-, Co-, and Ni-doped TiS2. The average open circuit voltage increases dramatically when Na ions are adsorbed on Fe-doped TiS2 (by 62%) and Co-doped TiS2 (by 61%), while K ions result in a moderate improvement of 9% and 8%, respectively. These findings suggest that metal-atom doping considerably improves the electrochemical properties of 2D TiS2, potentially enabling its use as anode materials in Na- and K-ion batteries.

Phase separation-hydrogen etching-derived Cu-decorated Cu-Mn bimetallic oxides with oxygen vacancies boosting superior sodium-ion storage kinetics

Understanding the crystal phase evolution of bimetallic oxide anodes is the main concern to profoundly reveal the conversion reaction kinetics and sodium-ion storage mechanisms. Herein, an integrated self-supporting anode of the Cu-decorated Cu-Mn bimetallic oxides with oxygen vacancies (Ov-BMO-Cu) are in-situ generated by phase separation and hydrogen etching using nanoporous Cu-Mn alloy as self-sacrificial templates. On this basis, we have elucidated the relationship between the phase evolution, oxygen vacancies and sodium-ion storage mechanisms, further demonstrating the evolution of oxygen vacancies and the inhibition effect of manganese oxides as an “anchor” on grain aggregation of copper oxides. The kinetic analyses confirm that the expanded lattice space and increased oxygen vacancies of cycled Ov-BMO-Cu synergistically guarantee effective sodium-ion diffusion and storage mechanisms. Therefore, the Ov-BMO-Cu electrode exhibits higher reversible capacities of 4.04 mA h cm−2 at 0.2 mA cm−2 after 100 cycles and 2.20 mA h cm−2 at 1.0 mA cm−2 after 500 cycles. Besides, the pre-sodiated Ov-BMO-Cu anode delivers a considerable reversible capacity of 0.79 mA h cm−2 at 1.0 mA cm−2 after 60 cycles in full cells with Na3V2(PO4)3 cathode, confirming its outstanding practicality. Thus, this work is expected to provide enlightenment for designing high-capacity bimetallic oxide anodes.

High-Voltage Layered Manganese-Based Oxide Cathode with Excellent Rate Capability Enabled by K/F Co-doping

P-type layered manganese-based materials are prone to undergo lattice oxygen oxidation accompanied by oxygen layer slipping and even unfavorable phase transitions at around 4.2 V, giving rise to rapid discharge capacity decline and inferior structural stability, which restricts their operating voltage and energy density. Here we propose a modification strategy for layered Na0.67MnO2 material with K/F co-doping so as to reach the optimization of lattice oxygen oxidation behavior and structural stability at a high cut-off voltage of 4.4 V. Combining X-ray powder diffraction refinement results, ex situ X-ray photoelectron spectrometry analysis, high-resolution transmission electron microscopy, and electrochemical characterization, our work demonstrates that an appropriate amount of K/F co-doping has a favorable effect on the formation of well-reversible lattice oxygen oxidation behavior and the improvement of Na layer spacing. Owing to the synergetic effect of potassium and fluorine atoms, the initial discharge capacity is up to 210.2 mA h g–1 at 0.1 C and 140.2 mA h g–1 at 1 C with 73% capacity retention after 100 cycles and high discharge capacity of 115.0 mA h g–1 at 5 C, with 68.1 mA h g–1 retained after 200 cycles. The kinetic analysis shows that the optimal K0.05Na0.62MnO1.95F0.05 sample exhibits the largest sodium ion diffusion coefficient and the smallest electrochemical polarization, which paves a novel path for the application of layered manganese-based oxides in high-voltage cathode materials for sodium-ion batteries.

Magnetic Nanoparticle Thermometry via Controlled Diffusion

The process of magnetic nanoparticle heating releases enormous amounts of thermal energy. Through typical calorimetric analyses, the total thermal energy released can be easily quantified; however, knowledge of nanoscale temperature is necessary. Herein, a novel method of nanoscale thermometry by analyzing intra-particle diffusion in core–shell nanoparticles is proposed. Heating the iron cores with an alternating magnetic field in a saline suspension encourages the diffusion of sodium ions into the silica shells of the particles, which is modeled numerically; however, experimental measurements are needed in order to provide accurate diffusivity estimations. After determining the diffusion characteristics from X-ray photoelectron spectroscopy) depth profiling of silica films, energy dispersive analysis with high-resolution transmission electron microscopy measures the sodium ion gradient within single particles before and after heating. When compared directly to the numerical simulations, the results indicate that the temperature gradient between particles and saline suspension reaches significantly higher temperatures than the macro-scale temperature of the solution. By accurately knowing the thermal gradient between nanoparticles and the surrounding medium, nanoparticles can be engineered to limit surface resistances as much as possible and promote high rates of thermal energy transfer.