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The solid-electrolyte interphase (SEI) in lithium-based batteries has been extensively studied regarding its composition, structure, and formation mechanisms. However, an understanding of the ion transport through the SEI remains incomplete. Revealing the underlying ion diffusion processes across the SEI holds great potential for enhancing battery performance and improving safety. In this study, we present the outcomes of first-principles density functional theory (DFT) calculations based on cryogenic high-resolution transmission electron microscopy (cryo-HRTEM) imaging, which elucidate the dominant diffusion pathways, energetics, and diffusion coefficients associated with lithium (Li) diffusion through the polycrystalline SEI. Specifically, we focus on Li diffusion through the grain boundaries (GBs) formed by the three primary inorganic components of the SEI, namely, Li2O, LiF, and Li2CO3. Our findings reveal that Li diffusion primarily occurs through numerous open channels created by the GBs. The energetics and potential barriers reveal significant variations depending upon the structural characteristics of these channels, with a distinguished trend being faster Li diffusion within the GB compared to neighboring crystalline regions within the grain interiors. The analysis of the charge density in GBs revealed that Li dendrite formation occurs in GBs with less Li diffusion kinetics.

Multi-principal element nanoparticles are an emerging class of materials with potential applications in medicine and biology. However, it is not known how such nanoparticles interact with bacteria at nanoscale. In the present work, we evaluated the interaction of multi-principal elemental alloy (FeNiCu) nanoparticles with Escherichia coli(E. coli) bacteria using the in situgraphene liquid cell (GLC) scanning transmission electron microscopy (STEM) approach. The imaging revealed the details of bacteria wall damage in the vicinity of nanoparticles. The chemical mappings of S, P, O, N, C, and Cl elements confirmed the cytoplasmic leakage of the bacteria. Our results show that there is selective release of metal ions from the nanoparticles. The release of copper ions was much higher than that for nickel while the iron release was the lowest. In addition, the binding affinity of bacterial cell membrane protein functional groups with Cu, Ni, and Fe cations is found to be the driving force behind the selective metal cations’ release from the multi-principal element nanoparticles. The protein functional groups driven dissolution of multielement nanoparticles was evaluated using the density functional theory (DFT) computational method, which confirmed that the energy required to remove Cu atoms from the nanoparticle surface was the least in comparison with those for Ni and Fe atoms. The DFT results support the experimental data, indicating that the energy to dissolve metal atoms exposed to oxidation and/or the to presence of oxygen atoms at the surface of the nanoparticle catalyzes metal removal from the multielement nanoparticle. The study shows the potential of compositional design of multi-principal element nanoparticles for the controlled release of metal ions to develop antibacterial strategies. In addition, GLC-STEM is a promising approach for understanding the nanoscale interaction of metallic nanoparticles with biological structures.

Over the past two decades, numerous studies have investigated and characterized the transient and amorphous phases in early stages of mineralization as well as their transition mechanisms to apatite crystals in buffered solutions. Recently more attention has been drawn to the identification and characterization of collagen structure and how it can affect mineralization in contact with non-collagenous protein and calcium phosphate clusters. This review highlights some of the pathways and mechanisms through which amorphous calcium phosphate clusters form. The conversion of these clusters into hydroxyapatite crystals is also reviewed. The thermodynamic aspects of nucleation and growth processes based on classical and non-classical nucleation theories related to hydroxyapatite are discussed. In addition, this paper is written to address the significant progress on mechanisms and pathways engaged in mineralization of collagen fibrils. Finally, it addresses some of the breakthroughs and limitations in the field of collagen biomineralization studies and new challenges in this field of study.

Understanding the behavior of high-entropy alloy (HEA) materials under hydrogen (H2) environment is of utmost importance for their promising applications in structural materials, catalysis, and energy-related reactions. Herein, the reduction behavior of oxidized FeCoNiCuPt HEA nanoparticles (NPs) in atmospheric pressure H2environment was investigated by in situgas-cell transmission electron microscopy (TEM). The reduction reaction front was maintained at the external surface of the oxide. During reduction, the oxide layer expanded and transformed into porous structures where oxidized Cu was fully reduced to Cu NPs while Fe, Co, and Ni remained in the oxidized form. In situchemical analysis showed that the expansion of the oxide layer resulted from the outward diffusion flux of all transition metals (Fe, Co, Ni, Cu). Revealing the H2reduction behavior of HEA NPs facilitates the development of advanced multicomponent alloys for applications targeting H2formation and storage, catalytic hydrogenation, and corrosion removal.

Although high-entropy alloys (HEAs) have shown tremendous potential for elevated temperature, anticorrosion, and catalysis applications, little is known on how HEA materials behave under complex service environments. Herein, we studied the high-temperature oxidation behavior of Fe0.28Co0.21Ni0.20Cu0.08Pt0.23HEA nanoparticles (NPs) in an atmospheric pressure dry air environment by in situgas-cell transmission electron microscopy. It is found that the oxidation of HEA NPs is governed by Kirkendall effects with logarithmic oxidation rates rather than parabolic as predicted by Wagner’s theory. Further, the HEA NPs are found to oxidize at a significantly slower rate compared to monometallic NPs. The outward diffusion of transition metals and formation of disordered oxide layer are observed in real time and confirmed through analytical energy dispersive spectroscopy, and electron energy loss spectroscopy characterizations. Localized ordered lattices are identified in the oxide, suggesting the formation of Fe2O3, CoO, NiO, and CuO crystallites in an overall disordered matrix. Hybrid Monte Carlo and molecular dynamics simulations based on first-principles energies and forces support these findings and show that the oxidation drives surface segregation of Fe, Co, Ni, and Cu, while Pt stays in the core region. The present work offers key insights into how HEA NPs behave under high-temperature oxidizing environment and sheds light on future design of highly stable alloys under complex service conditions.

Materials storing energy viaan alloying reaction are promising anode candidates in rechargeable lithium-ion batteries (LIBs) due to their much higher energy density than the current graphite anode. Until now, the volumetric expansion of such electrode particles during lithiation has been considered as solely responsible for cycling-induced structural failure. In this work, we report different structural failure mechanisms using single-crystalline bismuth nanowires as the alloying-based anode. The Li–Bi alloying process exhibits a two-step transition, that is, Bi–Li1Bi and Li1Bi–Li3Bi. Interestingly, the Bi–Li1Bi phase transition occurs not only in the bulk Bi nanowire but also on the particle surface showing its characteristic behavior. The bulk alloying kinetics favors a Bi-(012)-facilitated anisotropic lithiation, whose mechanism and energetics are further studied using the density functional theory calculations. More importantly, the protrusion of Li1Bi nanograins as a result of anisotropic Li–Bi alloying is found to dominate the surface morphology of Bi particles. The growth kinetics of Li1Bi protrusions is understood atomically with the identification of two different controlling mechanisms, that is, the dislocation-assisted strain relaxation at the Bi/Li1Bi interface and the short-range migration of Bi supporting the off-Bi growth of Li1Bi. As loosely rooted to the bulk substrate and easily peeled off and detached into the electrolyte, these nanoscale protrusions developed during battery cycling are believed to be an important factor responsible for the capacity decay of such alloying-based anodes at the electrode level.

Zinc (Zn) deposition and dissolution are very important processes during the charge and discharge cycles of rechargeable Zn aqueous batteries (ZBs). During this process, an interfacial ZnO layer is formed on the surface of Zn electrode that can have profound effects on the formation and growth of Zn dendrites and ZB performance and stability. The present work seeks to understand the structure and stability of the ZnO interfacial layer and mechanisms of Zn diffusion through this layer. The density functional theory (DFT) calculations supported by the aberration-corrected scanning transmission electron microscopy (AC-STEM) are employed to understand the ZnO atomic structure and its chemo-mechanical properties. Owing to the polycrystalline nature of the ZnO layer, the Zn diffusion through the two subsystems, namely, ZnO grain and ZnO grain boundary (GB) are studied. The activation energy of Zn diffusion varies significantly depending upon the modeled structure and the number of Zn adatoms. The calculated elastic properties show the decrease of Young’s modulus with an increase of Zn adatoms. Our findings provide insights into developing mitigation strategies toward the suppression of Zn dendrites during electrodeposition.

Metal–air batteries have attracted extensive research interests due to their high theoretical energy density. However, most of the previous studies were limited by applying pure oxygen in the cathode, sacrificing the gravimetric and volumetric energy density. Here, we develop a real sodium–“air” battery, in which the rechargeability of the battery relies on the reversible reaction of the formation of sodium peroxide dihydrate (Na2O2·2H2O). After an oxygen evolution reaction catalyst is applied, the charge overpotential is largely reduced to achieve a high energy efficiency. The sodium–air batteries deliver high areal capacity of 4.2 mAh·cm–2and have a decent cycle life of 100 cycles. The oxygen crossover effect is largely suppressed by replacing the oxygen with air, whereas the dense solid electrolyte interphase formed on the sodium anode further prolongs the cycle life.

Ferritin biomineralization is essential to regulate the toxic Fe2+iron ions in the human body. Unravelling the mechanism of biomineralization in ferritin facilitates our understanding of the causes underlying many iron disorder-related diseases. Until now, no report of in situ visualization of ferritin biomineralization events at nanoscale exists due to the requirement for high-resolution imaging of nanometer-sized ferritin proteins in their hydrated states. Herein, for the first time, we show that the biomineralization processes within individual ferritin proteins can be visualized by means of graphene liquid cell-transmission electron microscopy (GLC-TEM). The increase in the ratio of Fe3+/Fe2+ions over time monitored via electron energy loss spectroscopy (EELS) reveals the change in oxidation state of iron oxide phases with time. This study lays a foundation for future investigations on iron regulation mechanisms in healthy and dysfunctional ferritins.

The decoration of two-dimensional (2D) substrates with nanoparticles (NPs) serve as heterostructures for various catalysis applications. Deep understanding of catalyst degradation mechanisms during service conditions is crucial to improve the catalyst durability. Herein, we studied the sintering behavior of Pt and bimetallic Au-core Pt-shell (Au@Pt core–shell) NPs on MoS2supports at high temperatures under vacuum, nitrogen (N2), hydrogen (H2), and air environments by in situgas-cell transmission electron microscopy (TEM). The key observations are summarized as effect of environment:while particle migration and coalescence (PMC) was the main mechanism that led to Pt and Au@Pt NPs degradation under vacuum, N2, and H2environments, the degradation of MoS2substrate was prominent under exposure to air at high temperatures. Pt NPs were less stable in H2environment when compared with the Pt NPs under vacuum or N2, due to Pt–H interactions that weakened the adhesion of Pt on MoS2. Effect of NP composition:under H2, the stability of Au@Pt NPs was higher in comparison to Pt NPs. This is because H2promotes the alloying of Pt–Au, thus reducing the number of Pt at the surface (reducing H2interactions) and increasing Pt atoms in contact with MoS2. Effect of NP size:The alloying effect promoted by H2was more pronounced in small size Au@Pt NPs resulting in their higher sintering resistance in comparison to large size Au@Pt NPs and similar size Pt NPs. The present work provides key insights into the parameters affecting the catalyst degradation mechanisms on 2D supports.

Despite the ever-growing demand in safe and high power/energy density of Li+ion and Li metal rechargeable batteries (LIBs), materials-related challenges are responsible for the majority of performance degradation in such batteries. These challenges include electrochemically induced phase transformations, repeated volume expansion and stress concentrations at interfaces, poor electrical and mechanical properties, low ionic conductivity, dendritic growth of Li, oxygen release and transition metal dissolution of cathodes, polysulfide shuttling in Li–sulfur batteries, and poor reversibility of lithium peroxide/superoxide products in Li–O2batteries. Owing to compelling physicochemical and structural properties, in recent years two-dimensional (2D) materials have emerged as promising candidates to address the challenges in LIBs. This Review highlights the cutting-edge advances of LIBs by using 2D materials as cathodes, anodes, separators, catalysts, current collectors, and electrolytes. It is shown that 2D materials can protect the electrode materials from pulverization, improve the synergy of Li+ion deposition, facilitate Li+ion flux through electrolyte and electrode/electrolyte interfaces, enhance thermal stability, block the lithium polysulfide species, and facilitate the formation/decomposition of Li–O2discharge products. This work facilitates the design of safe Li batteries with high energy and power density by using 2D materials.

Homogeneously mixing multiple metal elements within a single particle may offer new material property functionalities. High entropy alloys (HEAs), nominally defined as structures containing five or more well-mixed metal elements, are being explored at the nanoscale, but the scale-up to enable their industrial application is an extremely challenging problem. Here, we report an aerosol droplet-mediated technique toward scalable synthesis of HEA nanoparticles with atomic-level mixing of immiscible metal elements. An aqueous solution of metal salts is nebulized to generate ∼1 μm aerosol droplets, which when subjected to fast heating/quenching result in decomposition of the precursors and freezing-in of the zero-valent metal atoms. Atomic-level resolution scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy analysis reveals that all metal elements in the nanoparticles are homogeneously mixed at the atomic level. We believe that this approach offers a facile and flexible aerosol droplet-mediated synthesis technique that will ultimately enable bulk processing starting from a particulate HEA.

Proton batteries are emerging as a promising solution for energy storage; however, their development has been hindered by the lack of suitable cathode materials. Herein, a hydrous Turnbull’s blue analogue (TBA) of Ni[Fe(CN)6]2/3·4H2O has been investigated as a viable proton cathode. Particularly, it shows an extremely high rate performance up to 6000 C (390 A g–1) at room temperature and delivers good capacity values at a low temperature of −40 °C in an aqueous electrolyte. The excellent rate capability is also amenable to high mass loadings of 10 mg cm–2. Such fast and low-temperature rate behavior likely stems from the fast proton conduction that is afforded by the Grotthuss mechanism inside the TBA structure. Furthermore, advanced characterization, including in operando synchrotron X-ray diffraction (XRD), and X-ray absorption near-edge structure (XANES) were employed to understand the changes of crystal structures and the oxidation-states of metal elements of the electrodes.

Solar conversion of carbon dioxide (CO2) into hydrocarbon fuels offers a promising approach to fulfill the world’s ever-increasing energy demands in a sustainable way. However, a highly active catalyst that can also tune the selectivity toward desired products must be developed for an effective process. Here, we present oxygen functionalized copper (OFn-Cu) nanoparticles as a highly active and methane (CH4) selective catalyst for the electrocatalytic CO2reduction reaction. Our electrochemical results indicate that OFn-Cu (5 nm) nanoparticles with an oxidized layer at the surface reach a maximum CH4formation current density and turnover frequency of 36.24 mA/cm2and of 0.17 s–1at the potential of −1.05 V vsRHE, respectively, exceeding the performance of existing Cu and Cu-based catalysts. Characterization results indicate that the surface of the OFn-Cu nanoparticles consists of an oxygen functionalized layer in the form of Cu2+(CuO) separated from the underneath elemental Cu by a Cu+(Cu2O) sublayer. Density functional theory calculations also confirm that presence of the O site at the CuO (101) surface is the main reason for the enhanced activity and selectivity. Using this catalyst, we have demonstrated a flow cell with an active area of 25 cm2that utilizes solar energy to produce 7.24 L of CH4after 10 h of continuous process at a cell power density of 30 mW/cm2.

Despite their high energy densities, Li- and Mn-rich, layered–layered, xLi2MnO3·(1 – x)LiTMO2(TM = Ni, Mn, Co) (LMR-NMC) cathodes require further development in order to overcome issues related to bulk and surface instabilities such as Mn dissolution, impedance rise, and voltage fade. One promising strategy to modify LMR-NMC properties has been the incorporation of spinel-type, local domains to create “layered–layered–spinel” cathodes. However, precise control of local structure and composition, as well as subsequent characterization of such materials, is challenging and elucidating structure–property relationships is not trivial. Therefore, detailed studies of atomic structures within these materials are still critical to their development. Herein, aberration corrected-scanning transmission electron microscopy (AC-STEM) is utilized to study atomic structures, prior to and subsequent to electrochemical cycling, of LMR-NMC materials having integrated spinel-type components. The results demonstrate that strained grain boundaries with various atomic configurations, including spinel-type structures, can exist. These high energy boundaries appear to induce cracking and promote dissolution of Mn by increasing the contact surface area to electrolyte as well as migration of Ni during cycling, thereby accelerating performance degradation. These results present insights into the important role that local structures can play in the macroscopic degradation of the cathode structures and reiterate the complexity of how synthesis and composition affect structure–electrochemical property relationships of advanced cathode designs.

Low-cost, highly efficient catalysts for hydrogen evolution reaction (HER) are very important to advance energy economy based on clean hydrogen gas. Intensive studies on two-dimensional molybdenum disulfides (2D MoS2) have been conducted due to their remarkable catalytic properties. However, most of the reported syntheses are time consuming, complicated and less efficient. The present work demonstrates the production of MoS2/graphene catalyst viaan ultra-fast (60 s) microwave-initiated approach. High specific surface area and conductivity of graphene delivers a favorable conductive network for the growth of MoS2nanosheets, along with rapid charge transfer kinetics. As-produced MoS2/graphene nanocomposites exhibit superior electrocatalytic activity for the HER in acidic medium, with a low onset potential of 62 mV, high cathodic currents and a Tafel slope of 43.3 mV/decade. Beyond excellent catalytic activity, MoS2/graphene reveals long cycling stability with a very high cathodic current density of around 1000 mA cm−2at an overpotential of 250 mV. Moreover, the MoS2/graphene-catalyst exhibits outstanding HER activities in a temperature range of 30 to 120°C with low activation energy of 36.51 kJ mol−1, providing the opportunity of practical scalable processing.

Rechargeable zinc (Zn) batteries suffer from poor cycling performance that can be attributed to dendrite growth and surface-originated side reactions. Herein, we report that cycling performance of Zn metal anode can be improved significantly by utilizing monolayer graphene (Gr) as the electrodeposition substrate. Utilizing microscopy and X-ray diffraction techniques, we demonstrate that electrodeposited Zn on Gr substrate has a compact, uniform, and nondendritic character. The Gr layer, due to its high lattice compatibility with Zn, provides low nucleation overpotential sites for Zn electrodeposition. Atomistic calculations indicate that Gr has strong affinity to Zn (binding energy of 4.41 eV for Gr with four defect sites), leading to uniform distribution of Zinc adatoms all over the Gr surface. This synergistic compatibility between Gr and Zn promotes subsequent homogeneous and planar Zn deposits with low interfacial energy (0.212 J/m2) conformal with the current collector surface.

Here we demonstrate a thermal shock synthesis method triggered by microwave irradiation for the rapid synthesis of nanoparticles on reduced graphene oxide (RGO) substrate. With properly controlled reduction, RGO has high electrical conductivity while maintaining functional groups, leading to an extremely efficient microwave absorption of ∼70%. The high utilization of microwaves results in the ability to raise the temperature to 1,600 K in just 100 ms, which is followed by rapid quenching to room temperature. The defects on the RGO are crucial for achieving this record-high microwave-induced temperature as these defects play a fundamental role in absorbing the radiation as well as the self-quenching mechanism. By loading precursors onto RGO, we can utilize rapid temperature change to synthesize nanoparticles. The nanoparticles are ∼10 nm with uniform distribution. This facile, rapid, and universal synthesis technique has the potential to be employed in large-scale production of nanomaterials and suggests a new direction for nanosynthesis.

The stability of single-atom catalysts is critical for their practical applications. Although a high temperature can promote the bond formation between metal atoms and the substrate with an enhanced stability, it often causes atom agglomeration and is incompatible with many temperature-sensitive substrates. Here, we report using controllable high-temperature shockwaves to synthesize and stabilize single atoms at very high temperatures (1,500–2,000 K), achieved by a periodic on–off heating that features a short on state (55 ms) and a ten-times longer off state. The high temperature provides the activation energy for atom dispersion by forming thermodynamically favourable metal–defect bonds and the off-state critically ensures the overall stability, especially for the substrate. The resultant high-temperature single atoms exhibit a superior thermal stability as durable catalysts. The reported shockwave method is facile, ultrafast and universal (for example, Pt, Ru and Co single atoms, and carbon, C3N4and TiO2substrates), which opens a general route for single-atom manufacturing that is conventionally challenging. A repeated on–off high-temperature shockwave is shown to be a generalizable way of efficiently synthesizing and stabilizing single atoms at high temperatures.

Supported metallic nanoclusters (NCs, < 2 nm) are of great interests in various catalytic reactions with enhanced activities and selectivities, yet it is still challenging to efficiently and controllably synthesize ultrasmall NCs with a high-dispersal density. Here we report the in situ synthesis of surfactant-free, ultrasmall, and uniform NCs via a rapid thermal shock on defective substrates. This is achieved by using high-temperature synthesis with extremely fast kinetics while limiting the synthesis time down to milliseconds (e.g., ∼1800 K for 55 ms) to avoid aggregation. Through defect engineering and optimized loading, the particle size can be robustly tuned from >50 nm nanoparticles to <1 nm uniform NCs with a high-dispersal density. We demonstrate that the ultrasmall NCs exhibit drastically improved activities for catalytic CO oxidation as compared to their nanoparticulated counterparts. In addition, the reported method shows generality in synthesizing most metallic NCs (e.g., Pt, Ru, Ir, Ni) in an extremely facile and efficient manner. The ultrafast and controllable synthesis of uniform, high-density, and size-controllable NCs paves the way for the utilization and nanomanufacturing of NCs for a range of catalytic reactions.

In lithium–oxygen batteries, the solubility of LiO2intermediates in the electrolyte regulates the formation routes of the Li2O2discharge product. High-donor-number electrolytes with a high solubility of LiO2tend to promote the formation of Li2O2large particles following the solution route, which eventually benefits the cell capacity and cycle life. Here, we propose that facet engineering of cathode catalysts could be another direction in tuning the formation routes of Li2O2. In this work, β-MnO2crystals with high occupancies of {111} or {100} facets were adopted as cathode catalysts in Li–O2batteries with a tetra(ethylene)glycol dimethyl ether electrolyte. The {111}-dominated β-MnO2catalyzed the formation of the Li2O2discharge product into large toroids following the solution routes, while {100}-dominated β-MnO2facilitated the formation of Li2O2thin films through the surface routes. Further computational studies indicate that the different formation routes of Li2O2could be related to different adsorption energies of LiO2on the two facets of β-MnO2. Our results demonstrate that facet engineering of cathode catalysts could be a new way to tune the formation route of Li2O2in a low-donor-number electrolyte. We anticipate that this new finding would offer more choices for the design of lithium–oxygen batteries with high capacities and ultimately a long cycle life.

Nanostructured catalysts often face an important challenge: poor stability. Many factors contribute to catalytic degradation, including parasitic chemical reactions, phase separation, agglomeration, and dissolution, leading to activity loss especially during long-term catalytic reactions. This challenge is shared by a new family of catalysts, multimetallic nanoparticles, which have emerged owing to their broad tunability and high activity. While significant synthesis-based advances have been made, the stability of these nanostructured catalysts, especially during catalytic reactions, has not been well addressed. In this study, we reveal the critical influence of a synthetic method on the stability of nanostructured catalysts through aprotic oxygen catalysis (Li-O2battery) demonstrations. In comparison to the conventional wet impregnation (WI) method, we show that the carbothermal shock (CTS) method dramatically improves the overall structural and chemical stability of the catalyst with the same elemental compositions. For multimetallic compositions (4- and 8-elements), the overall stability of the electrocatalysts as well as the battery lifetime can be further improved by incorporating additional noncatalytically active elements into the individual nanoparticles via CTS. The results offer a new synthetic path toward the stabilization of nanostructured catalysts, where additional reaction schemes beyond oxygen electrocatalysis are foreseeable.

Ni-rich LiNi1–x–yMnxCoyO2(NMC) cathode materials are being aggressively developed for high-voltage applications such as electric vehicles. These materials are desirable because of their high volumetric energy and power densities. However, degradation phenomena related to surface instabilities of highly charged Ni-rich cathodes have been, and remain, a major concern with respect to cycle life and safety of Li-ion cells. Although many reports exist on the properties and behavior of such materials, sufficient advances have yet to be made with respect to the stabilization of cathode surfaces. Herein, we report on an investigation aimed at probing the inherent stability of electrochemically active Niδ+species at the surface of NMC-type, layered-oxide cathode particles. A model system is developed that allows for studies of both surface and bulk species using hard X-ray absorption and electron energy loss spectroscopies. Spectroscopy data collected on cathode electrodes, coated with Al2O3via atomic layer deposition, reveals that the coating does not enhance the ability to attain, or maintain, fully oxidized Ni (Ni4+) in the near-surface regions of charged cathode particles. The results suggest an inherent instability of Niδ+near the surfaces of cathode particles and imply that the strategy of using Al2O3as a physical barrier coating is not sufficient to overcome these instabilities in layered nickel-rich oxides. Furthermore, the system developed for this work can be used as a tool to probe, in working cells, the efficacy of other strategies such as electrolytes, additives, and coatings in stabilizing surface Niδ+species in NMC-type cathodes.

Battery materials, which store energy by combining mechanisms of intercalation, conversion, and alloying, provide promisingly high energy density but usually suffer from fast capacity decay due to the drastic volume change upon cycling. Particularly, the significant volume shrinkage upon mass (Li+, Na+, etc.) extraction inevitably leads to the formation of pores in materials and their final pulverization after cycling. It is necessary to explore the failure mechanism of such battery materials from the microscopic level in order to understand the evolution of porous structures. Here, prototyped Sb2Se3nanowires are targeted to understand the structural failures during repetitive (de)sodiation, which exhibits mainly alloying and conversion mechanisms. The fast growing nanosized pores embedded in the nanowire during desodiation are identified to be the key factor that weakens the mechanical strength of the material and thus cause a rapid capacity decrease. To suppress the pore development, we further limit the cutoff charge voltage in a half-cell against Na below a critical value where the conversion reaction of such a material system is yet happening, the result of which demonstrates significantly improved battery performance with well-maintained structural integrity. These findings may shed some light on electrode failure investigation and rational design of advanced electrode materials with long cycling life.

The composition, structure, and the formation mechanism of the solid–electrolyte interphase (SEI) in lithium-based (e.g., Li-ion and Li metal) batteries have been widely explored in the literature. However, very little is known about the ion transport through the SEI. Understanding the underlying ion diffusion processes across the SEI could lead to a significant progress, enabling the performance increase and improving safety aspects of batteries. Herein, we report the results of first-principles density functional theory calculations on the dominant diffusion pathways, energetics, and the corresponding diffusion coefficients associated with Li diffusion through the polycrystalline SEI. This paper is particularly concerned with the Li diffusion through the grain boundary (GB) formed between the three major inorganic components of the SEI, such as Li2O, LiF, and Li2CO3. It is found that Li diffusion occurs through the numerous open channels formed by the GB. The energetics and potential barriers vary significantly depending upon the structure of these channels, with the general trend being that Li diffusion in the GB is generally faster than in the neighboring crystalline regions within the grain interiors. In addition, the elastic properties of the GB are calculated allowing for more profound understanding of the SEI stability and formation.

Water is ubiquitous in natural systems, ranging from the vast oceans to the nanocapillaries in the earth crust or cellular organelles. In bulk or in intimate contact with solid surfaces, water molecules arrange themselves according to their hydrogen (H) bonding, which critically affects their short- and long-range molecular structures. Formation of H-bonds among water molecules designates the energy levels of certain nonbonding molecular orbitals of water, which are quantifiable by spectroscopic techniques. While the molecular architecture of water in nanoenclosures is of particular interest to both science and industry, it requires fine spectroscopic probes with nanometer spatial resolution and sub-eV energy sensitivity. Graphene liquid cells (GLCs), which feature opposing closely spaced sheets of hydrophobic graphene, facilitate high-resolution transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS) measurements of attoliter water volumes encapsulated tightly in the GLC nanovessels. We perform in situTEM and EELS analysis of water encased in thin GLCs exposed to room and cryogenic temperatures to examine the nanoscale arrangement of the contained water molecules. Simultaneous quantification of GLC thickness leads to the conclusion that H-bonding strengthens under increased water confinement. The present results demonstrate the feasibility of nanoscale chemical characterization of aqueous fluids trapped in GLC nanovessels and offer insights on water molecule arrangement under high-confinement conditions.

[MnO6] octahedra are the structural units for a large family of manganese dioxides (MnO2) possessing one-dimensional tunnel structures with extensive applications in catalysis and energy storage. Despite the long-range [MnO6] ordering confirmed by conventional diffraction tools, surprisingly, the functional properties of a specific MnO2tunnel phase still vary significantly in literature with unclear structural origins. Here, we demonstrate the existence of tunnel heterogeneity featuring localized tunnel intergrowths within single MnO2nanoparticles via atomically resolved imaging. The degree of tunnel heterogeneity increases with the size increase of tunnels from β-MnO2(1 × 1 tunnel) to α-MnO2(2 × 2 tunnel), and to todorokite MnO2(3 × 3 tunnel). Furthermore, the tunnel heterogeneity within one MnO2nanoparticle significantly affects the energy storage kinetics even down to sub-nanometer scale. These findings are expected to call for renewed attention to the controlled synthesis of homogeneous tunnel-specific phases with predictable properties and to yield a more precise structure-property relationship in polymorphic materials.

Sodium-ion batteries (SIBs) are increasingly on demand owning to their prospect as an inexpensive alternative to Li-ion batteries. However, designing electrode materials with satisfactory rate capacity performance requires high electron transport and Na+conductivity, which is extremely challenging. Herein, we report a hexadecylamine (HDA)-mediated synthesis of NaTi2(PO4)3(NTP) electrodes via one-step solvothermal process. The addition of HDA material (1) enables the formation of a carbon coating that improves the electron conductivity and (2) importantly serves as a structure-directing agent reducing the NTP-impurity phases in which the transport of Na+ions are sluggish. As a result, the synthesized NTP anode delivers superior rate of capacity retention of 77.8% under the 100-fold increase in current densities. Moreover, outstanding specific capacity of 117.9 mAh g–1at 0.5 C and capacity retention of 88.6% after 1500 cycles at 1 C can be obtained. The findings of this work provide new opportunity to design SIBs electrodes with superior electrical and ionic conductivity.

Solid state electrolytes (SSEs) offer great potential to enable high-performance and safe lithium (Li) batteries. However, the scale-up synthesis and processing of SSEs is a major challenge. In this work, three-dimensional networks of lithium lanthanum titanite (LLTO) nanofibers are produced through a scale-up technique based on solution blowing. Compared with the conventional electrospinning method, the solution blowing technique enables high-speed fabrication of SSEs (e.g., 15 times faster) with superior productivity and quality. Additionally, the room-temperature ionic conductivity of composite polymer electrolytes (CPEs) formed from solution-blown LLTO fibers is 70% higher than the ones formed from electrospun fibers (1.9 × 10 –4vs 1.1 × 10–4S cm–1for 10 wt % LLTO fibers). Furthermore, the cyclability of the CPEs made from solution-blown fibers in the symmetric Li cell is more than 2.5 times that of the CPEs made from electrospun fibers. These comparisons show that solution-blown ion-conductive fibers hold great promise for applications in Li metal batteries.

The global lithium-ion batteries (LIBs) market has grown substantially, particularly in the automotive, smartphone, and aerospace sectors. This expansion aims to significantly reduce the environmental carbon footprint caused by human activities. However, the development of lithium-ion batteries has been accompanied by extensive research focused on enhancing thermal performance and ensuring safe operation under various conditions. Consequently, a significant number of researchers in this field are dedicated to achieving precise temperature control in LIBs as a long-term objective. Yet, to accurately define and quantify uniform or non-uniform temperature distribution within LIBs, it is imperative to create and assess coupled electrochemical-thermal models of the battery cells. These models must effectively integrate both temperature-related aspects. In this study, we offer a comprehensive overview of electrochemical modeling in LIBs, including an in-depth description of the governing electrochemical model that dictates the internal reactions of the batteries. Furthermore, we summarize critical thermal models for LIBs and their applicability in analyses spanning zero, one, two, and three dimensions. The battery thermal energy balance, Lumped Battery Analysis, and Simplified Heat Generation models are thoroughly examined. Moreover, we delve into the methodologies employed during the construction of these models and the intricate process of coupling electrochemical and thermal models to attain precise temperature predictions and management for LIB applications. This comprehensive approach enhances our understanding of the pivotal link between lithium-ion batteries' thermal and electrochemical behaviors, enabling the quantification and prediction of safer operational parameters for these systems.

Solid polymer electrolytes (SPE) have attracted considerable attention as electrolytes for solid-state batteries due to their toughness, high safety, and ionic conductivities that can be comparable with liquid electrolytes, especially at higher temperatures. However, polymers have low elastic moduli, which decrease at higher temperatures, limiting their ability to reduce dendrite formation. Mechanical blocking is one method of improving the interfacial layer and reducing dendritic growth but requires the elastic modulus of the polymer to be high enough to suppress lithium dendrites growth. Previous studies have focused on using unary metal oxides, which are limited by the percent of additives that can be included in the polymer before causing negative effects on electrochemical properties. In this study, we demonstrate a new strategy for improving the performance of polymers by synthesizing a multielement oxide (MEO) filler, AlTiMgLiO, to create a composite SPE with enhanced electrochemical performance. The synthesized AlTiMgLiO-containing SPE resulted in a voltage window of 0–6.18 V and a lithium transference number of 0.42. The overpotential voltage during galvanostatic cycling was reduced due to the improvements made to the morphology. The improvement of the interfacial layer reduced Li dendritic growth, resulting in a capacity of 99.68 mAh g−1after 500 cycles, and a capacity retention of 78.69 %. The possible reasons for the improvement are discussed, providing a direction for future studies on the use of multielement materials as fillers in solid polymers electrolytes.

Surface degradation of lithium-ion cathodes at high voltages represents a significant barrier to increasing the useable energy of conventional cathodes. Though much work has been focused on mitigating the detrimental effects of such phenomena, the complex and correlated mechanisms involved have made progress difficult. Herein, the effect of electrolyte identity on surface degradation is examined. LiNi0.5Mn0.3Co0.2O2(NMC532)/Li4Ti5O12(LTO) full cells were constructed using three different electrolytes: a baseline organic carbonate electrolyte, a baseline organic carbonate electrolyte with an oxidizable additive, and a fluorinated carbonate electrolyte. Each system was subjected to a 60 h potentiostatic hold at 3.05 V (4.6 V vs. Li+/Li) and subsequently deconstructed for characterization via transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). Molecular simulations were carried out on each distinct component of the three electrolytes in contact with crystal surfaces of an NMC532 particle. Results indicate an affinity for the additive-containing electrolyte to extract atomic oxygen from the cathode surface, whereas the fluorinated electrolyte components have negligible interactions. Hydrogen abstraction from the baseline electrolyte is facilitated by the NMC532 surface. TEM analysis of cathode surfaces, after the potentiostatic holds, revealed that the NMC532 particles cycled with the additive-containing electrolyte underwent significant surface degradation, including changes to local crystal structure in a region penetrating 20–40 nm from the surface; consistent with oxygen and lithium loss from the cathode material. However, the NMC532 in contact with the fluorinated electrolyte showed a disordered layer of just a few nm in thickness, similar to the depth of crystal disorder observed in pristine NMC532 primary particles. EELS data of the oxygen K-edge also indicated transition metal (TM) reduction, consistent with oxygen loss and changes in crystal structure extending into the cathode surface for each of the electrolytes surveyed. These surface reactions, including oxygen loss, are shown to correlate well with elevated oxidation currents and surface reconstructions of cathode particles.

Abstract

Lithium metal anodes can largely enhance the energy density of rechargeable batteries because of the high theoretical capacity and the high negative potential. However, the problem of lithium dendrite formation and low Coulombic efficiency (CE) during electrochemical cycling must be solved before lithium anodes can be widely deployed. Herein, a new atomic layer deposition (ALD) chemistry to realize the low-temperature synthesis of homogeneous and stoichiometric lithium fluoride (LiF) is reported, which then for the first time, as far as we know, is deposited directly onto lithium metal. The LiF preparation is performed at 150 °C yielding 0.8 Å/cycle. The LiF films are found to be crystalline, highly conformal, and stoichiometric with purity levels >99%. Nanoindentation measurements demonstrate the LiF achieving a shear modulus of 58 GPa, 7 times higher than the sufficient value to resist lithium dendrites. When used as the protective coating on lithium, it enables a stable Coulombic efficiency as high as 99.5% for over 170 cycles, about 4 times longer than that of bare lithium anodes. The remarkable battery performance is attributed to the nanosized LiF that serves two critical functions simultaneously: (1) the high dielectric value creates a uniform current distribution for excellent lithium stripping/plating and ultrahigh mechanical strength to suppress lithium dendrites; (2) the great stability and electrolyte isolation by the pure LiF on lithium prevents parasitic reactions for a much improved CE. This new ALD chemistry for conformal LiF not only offers a promising avenue to implement lithium metal anodes for high-capacity batteries but also paves the way for future studies to investigate failure and evolution mechanisms of solid electrolyte interphase (SEI) using our LiF on anodes such as graphite, silicon, and lithium.

Despite the promising future of lithium-oxygen (Li-O2) battery in replacing conventional lithium ion battery for high-energy applications, the complicated reaction mechanisms determining the sluggish discharge-charge kinetics have not been fully understood. Here, utilizing in situliquid transmission electron microscopy, the (electro)chemical fundamentals in a working Li-O2battery is explored. During discharge, the nucleation of Li2O2is observed at the carbon electrode/electrolyte interface, and the following growth process exhibits Li+diffusion-limited kinetics. Nucleation and growth of Li2O2are also observed within the electrolyte, where there is no direct contact with the carbon electrode indicating the existence of non-Faradaic disproportionation reaction of intermediate LiO2into Li2O2. The growth of Li2O2isolated in the electrolyte exhibits O2-diffusion-limited kinetics. Li2O2at the carbon electrode surface and isolated in the electrolyte are both active upon charging and gradually decomposed. For Li2O2particles rooted at the carbon electrode surface, the decomposition starts at the electrode/Li2O2interface indicating electron-conduction limited charge kinetics. For Li2O2isolated within the electrolyte, surprisingly, a side-to-side decomposition mode is identified indicating the non-Faradaic formation of dissolvable O2-, whose diffusion in the electrolyte controls the overall charge kinetics. This work reveals further details of underlying mechanisms in a working Li-O2battery and identifies various limiting factors controlling the discharge and charge processes.

Engineering crystal facets to enhance their functionalities often require complex processing routes to suppress the growth of surfaces with the lowest thermodynamic energies. Herein, we report a unique method to control the morphologies of β-MnO2crystals with different occupancy of {100}/{111} facets through the effect of K+cations. Combining aberration-corrected scanning transmission electron microscopy (STEM), ultramicrotomy, and dynamic functional theory (DFT) simulation, we clarified that the β-MnO2crystals were formed through a direct solid-state phase transition process. Increasing the concentration of K+cations in the precursor gradually changed the morphology of β-MnO2from bipyramid prism ({100}+{111} facets) to an octahedron structure ({111} facets). The K+cations controlled the morphology of β-MnO2by affecting the formation of α-K0.5Mn4O8intermediate phase and the subsequent phase transition. Utilizing the β-MnO2crystals as the cathode for Li-ion batteries showed that highly exposed {111} facets offered β-MnO2crystal better rate performance, with ~70% capacity retention when the charge-discharge rate increased from 20 mA/g to 200 mA/g. Our work revealed a new mechanism to tune the morphology of this earth-abundant metal oxide crystal, which could be used to adjust its electrochemical performance for different applications, such as supercapacitors and catalysts for metal-air batteries and fuel cells.

Lithium metal is considered the “holy grail” of next-generation battery anodes. However, severe parasitic reactions at the lithium–electrolyte interface deplete the liquid electrolyte and the uncontrolled formation of high surface area and dendritic lithium during cycling causes rapid capacity fading and battery failure. Engineering a dendrite-free lithium metal anode is therefore critical for the development of long-life batteries using lithium anodes. In this study, we deposit a conformal, organic/inorganic hybrid coating, for the first time, directly on lithium metal using molecular layer deposition (MLD) to alleviate these problems. This hybrid organic/inorganic film with high cross-linking structure can stabilize lithium against dendrite growth and minimize side reactions, as indicated by scanning electron microscopy. We discovered that the alucone coating yielded several times longer cycle life at high current rates compared to the uncoated lithium and achieved a steady Coulombic efficiency of 99.5%, demonstrating that the highly cross-linking structured material with great mechanical properties and good flexibility can effectively suppress dendrite formation. The protected Li was further evaluated in lithium–sulfur (Li–S) batteries with a high sulfur mass loading of ∼5 mg/cm2. After 140 cycles at a high current rate of ∼1 mA/cm2, alucone-coated Li–S batteries delivered a capacity of 657.7 mAh/g, 39.5% better than that of a bare lithium–sulfur battery. These findings suggest that flexible coating with high cross-linking structure by MLD is effective to enable lithium protection and offers a very promising avenue for improved performance in the real applications of Li–S batteries.

Wrinkle structures are commonly seen on graphene grown by the chemical vapor deposition (CVD) method due to the different thermal expansion coefficient between graphene and its substrate. Despite the intensive investigations focusing on the electrical properties, the nanotribological properties of wrinkles and the influence of wrinkle structures on the wrinkle-free graphene remain less understood. Here, we report the observation of anisotropic nanoscale frictional characteristics depending on the orientation of wrinkles in CVD-grown graphene. Using friction force microscopy, we found that the coefficient of friction perpendicular to the wrinkle direction was ∼194% compare to that of the parallel direction. Our systematic investigation shows that the ripples and “puckering” mechanism, which dominates the friction of exfoliated graphene, plays even a more significant role in the friction of wrinkled graphene grown by CVD. The anisotropic friction of wrinkled graphene suggests a new way to tune the graphene friction property by nano/microstructure engineering such as introducing wrinkles.

Nanoparticles (NPs) dispersed within a conductive host are essential for a range of applications including electrochemical energy storage, catalysis, and energetic devices. However, manufacturing high quality NPs in an efficient manner remains a challenge, especially due to agglomeration during assembly processes. Here we report a rapid thermal shock method to in situsynthesize well-dispersed NPs on a conductive fiber matrix using metal precursor salts. The temperature of the carbon nanofibers (CNFs) coated with metal salts was ramped from room temperature to ∼2000 K in 5 ms, which corresponds to a rate of 400,000 K/s. Metal salts decompose rapidly at such high temperatures and nucleate into metallic nanoparticles during the rapid cooling step (cooling rate of ∼100,000 K/s). The high temperature duration plays a critical role in the size and distribution of the nanoparticles: the faster the process is, the smaller the nanoparticles are, and the narrower the size distribution is. We also demonstrated that the peak temperature of thermal shock can reach ∼3000 K, much higher than the decomposition temperature of many salts, which ensures the possibility of synthesizing various types of nanoparticles. This universal, in situ, high temperature thermal shock method offers considerable potential for the bulk synthesis of unagglomerated nanoparticles stabilized within a matrix.

As a potential multi-electron electrode material for next generation lithium ion batteries, iron fluoride (FeF3) and its analogues are attracting much more attentions. Their microstructures are the key to achieve good electrochemical performances. In this work, FeF3·3H2O nano-flakes precursor with high crystallinity and flower-like morphology is synthesized successfully, by a liquid precipitation method using Fe(NO3)3·9H2O and NH4HF2as raw materials. The formation and the crystal growth mechanisms of the FeF3·3H2O precursors are investigated and discussed. After different temperature heat-treatment and followed by ball-milling with Super P, the as-prepared FeF3.0·33H2O/C and FeF3/C nanocomposites are used as cathode materials for lithium ion batteries. The FeF3.0·33H2O/C nanocomposite exhibits a noticeable initial specific capacity of 187.1 mAh g−1and reversible specific capacity of 172.3mAhg−1at .1C within a potential range of 2.0–4.5V. The capacity retention is as high as 97.33% after 50 cycles. Combined with HRTEM test, it confirms that the hydration water is not harmful but useful, namely, the tunnel phase formed with the hydration water is crucial to unobstructed Li+diffusion, and therefore leading to excellent electrochemical performances.

Electrocatalytic conversion of carbon dioxide (CO2) into energy-rich fuels is considered to be the most efficient approach to achieve a carbon neutral cycle. Transition-metal dichalcogenides (TMDCs) have recently shown a very promising catalytic performance for CO2reduction reaction in an ionic liquid electrolyte. Here, we report that the catalytic performance of molybdenum disulfide (MoS2), a member of TMDCs, can be significantly improved by using an appropriate dopant. Our electrochemical results indicate that 5% niobium (Nb)-doped vertically aligned MoS2in ionic liquid exhibits 1 order of magnitude higher CO formation turnover frequency (TOF) than pristine MoS2at an overpotential range of 50–150 mV. The TOF of this catalyst is also 2 orders of magnitude higher than that of Ag nanoparticles over the entire range of studied overpotentials (100–650 mV). Moreover, the in situdifferential electrochemical mass spectrometry experiment shows the onset overpotential of 31 mV for this catalyst, which is the lowest onset potential for CO2reduction reaction reported so far. Our density functional theory calculations reveal that low concentrations of Nb near the Mo edge atoms can enhance the TOF of CO formation by modifying the binding energies of intermediates to MoS2edge atoms.

Controlling the transport of ions within electrodes is highly desirable for the operation of rechargeable ion batteries. Here, for the first time, we report the role of mechanical stress in controlling the redistribution of lithium ions in a layered LiCoO2electrode at a resolution of ∼100 nm. Under a higher stress field, more active redistribution of lithium ions was observed along the grain boundaries than the interiors of the layered LiCoO2. The dynamic force ramping test proved the external stress field (<100 nN) is capable of inducing the resistive-switching effect of the layered LiCoO2. The comparison test on the highly ordered pyrolytic graphite (HOPG) substrate further demonstrated the improved current responses from the layered LiCoO2resulted from the deficiency of lithium ions, rather than the increase of tip–sample contact area. Our findings will pave the road for a full understanding of how mechanical stimulus can affect the distribution of ions in the layered electrodes of rechargeable ion batteries.

Phosphorus in water eutrophication has become a serious problem threatening the environment. However, the development of efficient adsorbents for phosphate removal from water is lagging. In this work, we recovered the waste material, graphitized carbon, from spent lithium ion batteries and modified it with nanostructured Mg(OH)2on the surface to treat excess phosphate. This phosphate adsorbent shows one of the highest phosphate adsorption capacities to date, 588.4 mg/g (1 order of magnitude higher than previously reported carbon-based adsorbents), and exhibits decent stability. A heterogeneous multilayer adsorption mechanism was proposed on the basis of multiple adsorption results. This highly efficient adsorbent from spent Li-ion batteries displays great potential to be utilized in industry, and the mechanism study paved a way for further design of the adsorbent for phosphate adsorption.

Line defects, including grain boundaries and wrinkles, are commonly seen in graphene grown by chemical vapor deposition. These one-dimensional defects are believed to alter the electrical and mechanical properties of graphene. Unfortunately, it is very tedious to directly distinguish grain boundaries from wrinkles due to their similar morphologies. In this report, high-resolution Kelvin potential force microscopy (KPFM) is employed to measure the work function distribution of graphene line defects. The characteristic work function variations of grain boundaries, standing-collapsed wrinkles, and folded wrinkles could be clearly identified. Classical and quantum molecular dynamics simulations reveal that the unique work function distribution of each type of line defects is originated from the doping effect induced by the SiO2substrate. Our results suggest that KPFM can be an easy-to-use and accurate method to detect graphene line defects, and also propose the possibility to tune the graphene work function by defect engineering.

Thin-film batteries that can be folded, bent, and even repeatedly creased with minimal or no loss in electrochemical performance have been demonstrated and systematically evaluated using two dynamic mechanical testing approaches for either controlled bending or creasing of flexible devices. The results show that mechanically robust and flexible Li-ion batteries (Li4Ti5O12//LiFePO4) based on the use of a nonwoven multiwalled carbon nanotube (MWNT) mat as a current collector (CC) exhibited a 14-fold decrease in voltage fluctuation at a bending strain of 4.2%, as compared to cells using traditional metal foil CCs. More importantly, MWNT-based full-cells exhibited excellent mechanical integrity through 288 crease cycles, whereas the foil full-cell exhibited continuously degraded performance with each fold and catastrophic fracture after only 94 folds. The enhancements due to MWNT CCs can be attributed to excellent interfacial properties as well as high mechanical strength coupled with compliancy, which allow the batteries to easily conform during mechanical abuse. These results quantitatively demonstrate the substantial enhancement offered in both mechanical and electrochemical stability which can be realized with traditional processing approaches when an appropriate choice of a flexible and robust CC is utilized.

Calcium oxalate (CaOx) is a ubiquitous biomineral with applications in geological, botanical, and environmental processes. The pathological biomineralization of CaOx is of interest due to its role in kidney stone formation. While the dissolution–reprecipitation events of CaOx mineralization resulting in specific architecture with clinical outcomes have been studied on the macroscale, there is a dearth of understanding of how these processes influence the stability of CaOx on the nanoscale. In this study, liquid cell transmission electron microscopy was used to observe in situ transformations of CaOx. The results revealed the development of multistructural core–shell CaOx nanoparticles and the pathways leading to growth, stabilization, or dissolution. The data suggest that partial dissolution of the shell may lead to localized structural defects and buckling, resulting in the dissolution of the nanoparticle. Moreover, the results uncovered the dynamic nature of these nanoparticles due to the continuous precipitation–dissolution–reprecipitation in both the core and the shell. This study connected the formation of boundary layers, porosity, and reactive surface area on the nanoscale to the resulting complex nanoarchitecture and particle stability. Together, these insights may serve as a gateway to the investigation of potential therapeutic approaches that address the pathological biomineralization of CaOx on the nanoscale.

The ability to have precise control over the designed structure and properties of molecular self-assemblies is critical for tailoring the quality and efficacy of their functionality, yet the underlying mechanisms governing the evolution from molecules into self-assembled structures are not fully resolved. Here, we employed the graphene liquid cell (GLC) transmission electron microscopy (TEM) approach to observe nucleation and evolution of individual nanoscale micelles during polymerization-induced self-assembly. We speculate that the electron beam induces radical formation by homolytic cleavage of the poly(glycerol methacrylate)–thiocarbonylthio (PolyGMA–thiocarbonylthio) macro-chain-transfer agent (macroCTA), at which it initiates the polymerization of HPMA monomer in aqueous solution. Chain growth of the hydrophobic block, PolyHPMA, and subsequent instability of the resulting block copolymer in the solution trigger the formation of the nanoscale polymer self-assemblies. The spinodal decomposing mechanism is proposed here for the formation and evolution of the polymer assemblies. Such in-situ visualization of polymeric micelle formation, devoid of metal-ion labeling, provides new insights into understanding the complex mechanism of the self-assembly process in amphiphilic molecules.