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Perovskite solar cells have drawn much attention recently owing to their world-record-setting photovoltaic performances, whereas their practicality is still limited by the structural instability that often arises from ion migration and defect formation. Despite the general understanding that ion instability is a primary cause for degradation, there is no observation of structural transformation at the atomistic scale. Such observation is crucial to understand how instabilities are induced by external perturbations such as illumination or electrical bias, allowing researchers to devise effective strategies to mitigate them. Here, we designed an in situ transmission electron microscopy setup to enable real-time observation of amorphization in perovskite materials under electrical biasing. To reverse the device performance degradation due to such structural changes, the samples were heated at 50 °C and were found to recrystallize, effectively regaining their performance losses. This work presents vital insights on understanding ion-migration phenomena and addressing instability challenges of perovskite optoelectronics.

Lithium metal has been an attractive candidate as a next-generation anode material. Despite its popularity, stability issues of lithium in the liquid electrolyte and the formation of lithium whiskers have kept it from practical use. Three-dimensional (3D) current collectors have been proposed as an effective method to mitigate whisker growth. Although extensive research has been done, the effects of three key parameters of the 3D current collectors, namely, the surface area, the tortuosity factor, and the surface chemistry, on the performance of lithium metal batteries remain elusive. Herein, we quantitatively studied the role of these three parameters by synthesizing four types of porous copper networks with different sizes of well-structured microchannels. X-ray microscale computed tomography (micro-CT) allowed us to assess the surface area, the pore size, and the tortuosity factor of the porous copper materials. A metallic Zn coating was also applied to study the influence of surface chemistry on the performance of the 3D current collectors. The effects of these parameters on the performance were studied in detail through scanning electron microscopy (SEM) and titration gas chromatography (TGC). Stochastic simulations further allowed us to interpret the role of the tortuosity factor in lithiation. The optimal range of the key parameters is thereby found for the porous coppers and their performance is predicted. Using these parameters to inform the design of porous copper anodes for Li deposition, Coulombic efficiencies (CEs) of up to 99.63% are achieved, thus paving the way for the design of effective 3D current collector systems.

Interest in alkali-rich oxide cathodes has grown in an effort to identify systems that provide high energy densities through reversible oxygen redox. However, some of the most promising compositions such as those based solely on earth abundant elements, e. g., iron and manganese, suffer from poor capacity retention and large hysteresis. Here, we use the disordered rocksalt cathode, Li1.3Fe0.4Nb0.3O2, as a model system to identify the underlying origin for the poor performance of Li-rich iron-based cathodes. Using elementally specific spectroscopic probes, we find the first charge is primarily accounted for by iron oxidation to 4+ below 4.25 V and O2 gas release beyond 4.25 V with no evidence of bulk oxygen redox. Although the Li1.3Fe0.4Nb0.3O2 is not a viable oxygen redox cathode, the iron 3+/4+ redox couple can be used reversibly during cycling.

Lithium-rich NMC (LR-NMC) compounds exhibit high capacities beyond the traditional redox, but it remains unclear whether the anomalous charge compensation mechanism is due to oxidized lattice oxygen or migration-assisted Mn oxidation. We compare LR-NMC with a model Mn7+ system (KMnO4) using a combination of resonant inelastic X-ray scattering (RIXS) irradiation studies and operando X-ray absorption spectroscopy/X-ray diffraction (XAS/XRD) to quantify transition metal (TM) migration, Mn oxidization, and beam-induced effects. We reveal how for KMnO4 it is possible to observe beam-induced Mn reduction resulting in trapped molecular oxygen. For LR-NMC, we observe negligible evidence for Mn oxidation while stabilized tetrahedral sites correlate more with a reduced TM environment. Finally, the additional spectroscopic structures observed in oxidized oxygen RIXS for LR-NMC are absent for gas-phase molecular oxygen.

Li metal anode coupled with solid-state electrolyte is regarded as an important step for next-generation high-energy batteries to boost the performance of electric vehicles. However, commercialization of Li metal anode in all-solid-state batteries have faced challenges, one of which is the interfacial instability originated during battery operation. To overcome the difficulties in characterizing such interfaces due to their sensitivity to beam and ambient air, we applied cryogenic electron microscopy to unravel the stable nature of Li metal/LiPON interface that has exhibited remarkable electrochemical cyclability. An 80-nm-thick interphase with concentration gradients of N and P was observed, with decomposition products embedded in an amorphous matrix and exhibiting a multilayer-mosaic structure. The findings and methodology in this work give rise to a mechanistic understanding of the stability of Li metal/LiPON interface and can then be extended to study other solid-solid interfaces.

The rapidly growing technological demand for lithium-ion batteries has prompted the development of novel cathode materials with high energy density, low cost, and improved safety. High voltage spinel, LiNi0.5Mn1.5O4 (LNMO), is one of the most promising candidates yet to be commercialized. The two primary obstacles for this material are the inferior electronic conductivity and fast capacity degradation in full cells due to the high operating voltage. By systematically addressing these limitations, we successfully develop a thick LNMO electrode with areal capacity loadings up to 3 mAh·cm−2. The optimized thick electrode is paired with a commercial graphite anode at both the coin cell and pouch cell level, achieving a full cell capacity retention as high as 72% and 78%, respectively, after 300 cycles. We attribute this superior cycling stability to careful optimizations of cell components and testing conditions, with a specific focus improving electronic conductivity and high voltage compatibility. These results suggest precise control of materials quality, electrode architecture and electrolyte optimization can soon support the development of a cobalt-free battery system based on a thick LNMO cathode (>4 mAh·cm2), which will eventually meet the needs of next-generation Li-ion batteries with reduced cost, improved safety, and assured sustainability.

To achieve high-energy all-solid-state batteries (ASSBs), solid-state electrolytes (SE) must be thin, mechanically robust, and possess the ability to form low resistance interfaces with electrode materials. Embedding an inorganic SE into an organic polymer combines the merits of high conductivity and flexibility. However, the performance of such an SE-in-polymer matrix (SEPM) is highly dependent on the microstructure and interactions between the organic and inorganic components. We report on the synthesis of a free-standing, ultrathin (60 μm) SEPM from a solution of lithium polysulfide, phosphorus sulfide, and ethylene sulfide (ES), where the polysulfide triggers the in situ polymerization of ES and the formation of Li3PS4. Reactant ratios were optimized to achieve a room-temperature conductivity of 2 × 10-5 S cm-1. Cryogenic electron microscopy confirmed a uniform nanoscopic distribution of β-Li3PS4 and PES (polyethylene sulfide). This work presents a facile route to the scalable fabrication of ASSBs with promising cycling performance and low electrolyte loading.

Stable lattice oxygen redox (l-OR) is the key enabler for achieving attainable high energy density in Li-rich layered oxide cathode materials for Li-ion batteries. However, the unique local structure response to oxygen redox in these materials, resulting in energy inefficiency and hysteresis, still remains elusive, preventing their potential applications. By combining the state-of-the-art neutron pair distribution function with crystal orbital overlap analysis, we directly observe the distinct local structure adaption originated from the potential O–O chemical bonds. The structure adaptability is optimized based on the nature of multi transition metals in our model compound Li1.2Ni0.13Mn0.54Co0.13O2, which accommodates the oxygen redox and at the same time preserves the global layered structure. These findings not only advance the understanding of l-OR, but also provide new perspectives in the rational design of high-energy-density cathode materials with reversible and stable l-OR.

All solid-state batteries (ASSBs) have the potential to deliver higher energy densities, wider operating temperature range, and improved safety compared with today's liquid-electrolyte-based batteries. However, of the various solid-state electrolyte (SSE) classes - polymers, sulfides, or oxides - none alone can deliver the combined properties of ionic conductivity, mechanical, and chemical stability needed to address scalability and commercialization challenges. While promising strategies to overcome these include the use of polymer/oxide or sulfide composites, there is still a lack of fundamental understanding between different SSE-polymer-solvent systems and its selection criteria. Here, we isolate various SSE-polymer-solvent systems and study their molecular level interactions by combining various characterization tools. With these findings, we introduce a suitable Li7P3S11SSE-SEBS polymer-xylene solvent combination that significantly reduces SSE thickness (∼50 μm). The SSE-polymer composite displays high room temperature conductivity (0.7 mS cm-1) and good stability with lithium metal by plating and stripping over 2000 h at 1.1 mAh cm-2. This study suggests the importance of understanding fundamental SSE-polymer-solvent interactions and provides a design strategy for scalable production of ASSBs.

This work reports a comprehensive study of a novel polyol method that can successfully synthesize layered LiNi0.4Mn0.4Co0.2O2, spinel LiNi0.5Mn1.5O4, and olivine LiCoPO4 cathode materials. When properly designed, polyol method offers many advantages such as low cost, ease of use, and proven scalability for industrial applications. Most importantly, the unique properties of polyol solvent allow for greater morphology control as shown by all the resulting materials exhibiting monodispersed nanoparticles morphology. This morphology contributes to improved lithium ion transport due to short diffusion lengths. Polyol-synthesized LiNi0.4Mn0.4Co0.2O2 delivers a reversible capacity of 101 and 82 mAh·g−1 using high current rate of 5C and 10C, respectively. It also displays surprisingly high surface structure stability after charge-discharge processes. Each step of the reaction was investigated to understand the underlying polyol synthesis mechanism. A combination of in situ and ex situ studies reveal the structural and chemical transformation of Ni-Co alloy nanocrystals overwrapped by a Mn- and Li-embedded organic matrix to a series of intermediate phases, and then eventually to the desired layered oxide phase with a homogeneous distribution of Ni, Co, and Mn. We envisage that this type of analysis will promote the development of optimized synthesis protocols by establishing links between experimental factors and important structural and chemical properties of the desired product. The insights can open a new direction of research to synthesize high-performance intercalation compounds by allowing unprecedented control of intermediate phases using experimental parameters. [Figure not available: see fulltext.]

Resonant inelastic X-ray scattering (RIXS) at the O K-edge is considered a prime technique to identify bulk oxidized oxygen formation, but its fundamental interpretation is not straightforward. In this study, we intentionally induce RIXS signatures of oxidized oxygen upon beam exposure in LiAlO2 polymorphs that are easily distinguished because of their wide band gaps. After careful consideration of beam exposure effects on Li[Li0.144Ni0.136Mn0.544Co0.136]O2 (LR-NMC), we conclude that oxidized oxygen features are inherent at high states of charge and are lost upon aggressive beam exposure. The extracted oxidized oxygen line shapes from our X-ray irradiation studies for both LiAlO2 (induced) and LR-NMC (inherent) are found to have an additional oxidized oxygen RIXS feature not observed in O2 gas studies. This study highlights the unique insight of O K-edge RIXS into determining the nature and stability of oxidized oxygen states.

State-of-the-art lithium (Li)-ion batteries are approaching their specific energy limits yet are challenged by the ever-increasing demand of today’s energy storage and power applications, especially for electric vehicles. Li metal is considered an ultimate anode material for future high-energy rechargeable batteries when combined with existing or emerging high-capacity cathode materials. However, much current research focuses on the battery materials level, and there have been very few accounts of cell design principles. Here we discuss crucial conditions needed to achieve a specific energy higher than 350 Wh kg −1 , up to 500 Wh kg −1 , for rechargeable Li metal batteries using high-nickel-content lithium nickel manganese cobalt oxides as cathode materials. We also provide an analysis of key factors such as cathode loading, electrolyte amount and Li foil thickness that impact the cell-level cycle life. Furthermore, we identify several important strategies to reduce electrolyte-Li reaction, protect Li surfaces and stabilize anode architectures for long-cycling high-specific-energy cells.

Lithium metal is viewed as the ultimate battery anode because of its high theoretical capacity and low electrode potential, but its implementation has been limited by low Coulombic efficiency and dendrite formation above a critical current density. Determining the fundamental properties dictating lithium metal plating-stripping behavior is challenging because characterization techniques are limited by the sensitivity of lithium metal to damage by external probes, which regularly results in altered morphology and chemistry. Motivated by recent application of cryogenic transmission electron microscopy (cryo-TEM) to characterize lithium metal at the atomic scale, we explore the cryogenic focused ion beam (cryo-FIB) method as a quantitative tool for characterizing the bulk morphology of electrochemically deposited lithium and as a technique that enables TEM observation of Li-metal/solid-state electrolyte interfaces. This work highlights the importance of cryo-FIB methodology for preparing sensitive battery materials and elucidates the impact of electrolyte selection on the density and morphology of plated lithium.

The electrochemical performance and mechanistic effects of incorporating two salts in an ether electrolyte in Li-metal cells were investigated experimentally and via molecular scale modeling. Improvements in efficiency and cycling stability over baseline electrolytes in lithium (Li) versus copper (Cu) cells were directly correlated to the initial Li-nucleation process, as observed via cryogenic-focused ion beam (cryo-FIB) prepared cross sections, which revealed that Li films deposited with the bisalt electrolyte were significantly thinner and denser than those from the baseline. This behavior was further traced back to the initial nucleation process via cryogenic transmission electron microscopy (cryo-TEM), which shows stark differences in the morphology and conformality of deposited Li as a function of electrolyte chemistry. X-ray photoelectron spectroscopy (XPS) indicated that the solid electrolyte interphase (SEI) formed from the bisalt electrolyte primarily consists of larger anion fragments, suggesting that the anion chemistry strongly influences the extent of reduction and resulting surface chemistry. Ab initio DFT-based and force field-based molecular dynamics calculations revealed the complex interplay (positioning, orientation, reactivity, kinetics) between the FSI - and TFSI - anions in the double layer at both electrode-electrolyte interfaces and the ramifications for stabilizing these interfaces. As a result of the unique interphasial chemistry brought by this bisalt system, this electrolyte supports an unprecedented (for an ether-based electrolyte) capacity retention (>88%) after 300 cycles (∼2 months of cycling) in a 4.4 V NMC622-Li cell, and a >30% improvement in capacity retention over baseline after 50 cycles in 4.4 V NMC622-Cu "anode-free" cells. Altogether, these results provide new insight into how the bisalt effect can be leveraged for regulating the timescale, chemistry, and extent of interfacial reactions. When balanced properly, this promotes efficient plating/deplating of Li, and potentially supports widespread implementation of high nickel content NMC cell configurations with limited or no excess lithium.

Rechargeable lithium metal batteries based on organic electrolytes face challenges of both lithium metal cycling stability and the associated safety issues. Herein, we demonstrate an in situ formed polymer gel electrolyte which enables dendrite-free lithium metal cycling. Moreover, the gel electrolyte goes through further polymerization at elevated temperatures and loses its ionic conductivity, effectively shutting down the battery. When lithium iodide (LiI) is dissolved in vinylene carbonate (VC), LiI induces the polymerization of VC to form poly(vinylene carbonate) (polyVC). The electrolyte then transforms into a polymer gel electrolyte containing VC as the solvent and LiI as the salt. At room temperature, the gel electrolyte enables dendrite-free lithium metal cycling at current densities as high as 5 mA cm-2 for 500 cycles. Furthermore, a Li/Li4Ti5O12 (LTO) cell retains 50% of the initial capacity at the 700th cycle. When the cell is heated to 80 °C, the ionic resistance of the electrolyte increases by a factor of 103, resulting in the shutdown of the cell due to the complete polymerization of VC. The approach of using in situ polymerization to enable stable lithium cycling and to serve as a thermally triggered shutdown mechanism provides a new pathway for fabricating safer lithium metal batteries.

To obtain high-energy density Li-ion batteries for the next-generation storage devices, silicon anodes provide a viable option because of their high theoretical capacity, low operating potential versus lithium (Li), and environmental abundance. However, the silicon electrode suffers from large volume expansion (?300%) that leads to mechanical failure, cracks in the SEI (solid electrolyte interphase), and loss of contact with the current collector, all of which severely impede the capacity retention. In this respect, the choice of binders, carbon, electrolyte, and the morphology of the silicon itself plays a critical role in improving capacity retention. Of specific mention is the role of binders where a carboxylic acid-heavy group, PAA (polyacrylic acid), has been demonstrated to have better cycling capacity retention as compared to CMC (carboxy methyl cellulose). Traditionally, the role of binders has been proposed as a soft matrix backbone that allows volume expansion of the anode while preserving its morphology. However, the effect of the binder on both the rate of formation of SEI species across cycles and its distribution around the silicon nanoparticles has not been completely investigated. Herein, we use two different binders (PAA and CMC) coupled with LiFSI (lithium bis(fluorosulfonyl)imide)/EMI-FSI (1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide) ionic liquid as the electrolyte to understand the effect of binder on the SEI. Using STEM-EDX (scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy), EELS (electron energy loss spectroscopy), and XPS (X-ray photoelectron spectroscopy), we discuss the evolution of the SEI on the Si electrode for both binders. Our results indicate that a faster decomposition of FSI - with a PAA binder leads to LiF (lithium fluoride) formation, making F - unavailable for subsequent SEI formation cycles. This allows further decomposition of the LiFSI salt to sulfates and sulfides which form a crucial component of the SEI around silicon nanoparticles after 100 cycles in the PAA binder-based system. The dual effects of faster consumption of F - to form LiF together with the distribution of passivating sulfides in the SEI could allow for better capacity retention in the PAA binder system as compared to that with CMC.

Solid-state electrolytes can offer improved lithium-ion battery safety while potentially increasing the energy density by enabling alkali metal anodes. There have been significant research efforts to improve the ionic conductivity of solid-state electrolytes and the electrochemical performance of all-solid-state batteries; however, the root causes of their poor performance - interfacial reaction and subsequent impedance growth - are poorly understood. This is due to the dearth of effective characterization techniques for probing these buried interfaces. In situ and operando methodologies are currently under development for solid-state interfaces, and they offer the potential to describe the dynamic interfacial processes that serve as performance bottlenecks. This article highlights state-of-the-art solid-solid interface probing methodologies, describes practical limitations, and describes a future for dynamic interfacial characterization.

To enable next-generation high-energy-density lithium (Li)-metal batteries (LMBs), an electrolyte that has simultaneous high Li-metal Coulombic efficiency (CE) and high anodic stability on cathodes is of significant importance. Sulfones are known for strong resistance against oxidation, yet their application in LMBs is restricted because of their poor compatibility with Li-metal anodes, high viscosity, and poor wettability. Here, we demonstrate that a high Li CE over 98% can be achieved in concentrated sulfone-based electrolytes. Furthermore, the viscosity and wettability issues of sulfones are resolved by the addition of a fluorinated ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, to form a localized high-concentration electrolyte (LHCE), which not only provides further improvement in Li CE (98.8%) but also remains anodically stable with high-voltage cathodes, suppresses Al corrosion, and enables LMBs to operate in a wide temperature range. As a result, significantly improved cycling performance of LMBs has been realized with sulfone-based LHCE. For high-voltage rechargeable lithium (Li)-metal batteries (LMBs), electrolytes with good stabilities on both the highly oxidative cathodes and the highly reductive Li-metal anodes are urgently desired. Sulfones have excellent oxidative stability, yet their high viscosity, poor wettability, and, in particular, incompatibility with Li anodes greatly hinder their applications in LMBs. Here, we demonstrate that a high Li Coulombic efficiency (CE) of 98.2% during repeated Li plating and stripping cycles can be realized in concentrated lithium bis(fluorosulfonyl)imide (LiFSI)-tetramethylene sulfone electrolyte. More importantly, the localized high-concentration electrolyte, formed by the dilution of the high-concentration electrolyte with a non-solvating fluorinated ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, solves the viscosity and wettability issues, further improves Li CE (98.8%), and improves the high-voltage (4.9 V) performance of LMBs with effective Al protection. High-voltage batteries with Li-metal anodes can offer desirable high energy densities. Despite their excellent oxidative stability, sulfones have various limitations to be useful in Li-metal batteries, in particular their instability with Li metal. Here, we achieved a high Li Coulombic efficiency of nearly 99% in a sulfone-based localized high-concentration electrolyte (LHCE) with the addition of a non-solvating co-solvent. In addition, this co-solvent is highly beneficial for realizing stable battery cycling up to 4.9 V.

Defects and their interactions in crystalline solids often underpin materialproperties and functionality as they are decisive for stability, result inenhanced diffusion, and act as a reservoir of vacancies. Recently, lithium-richlayered oxides have emerged among the leading candidates for thenext-generation energy storage cathode material, delivering 50 % excesscapacity over commercially used compounds. Oxygen-redox reactions are believedto be responsible for the excess capacity, however, voltage fading hasprevented commercialization of these new materials. Despite extensive researchthe understanding of the mechanisms underpinning oxygen-redox reactions andvoltage fade remain incomplete. Here, using operando three-dimensional Braggcoherent diffractive imaging, we directly observe nucleation of a mobiledislocation network in nanoparticles of lithium-rich layered oxide material.Surprisingly, we find that dislocations form more readily in the lithium-richlayered oxide material as compared with a conventional layered oxide material,suggesting a link between the defects and the anomalously high capacity inlithium-rich layered oxides. The formation of a network of partial dislocationsdramatically alters the local lithium environment and contributes to thevoltage fade. Based on our findings we design and demonstrate a method torecover the original high voltage functionality. Our findings reveal that thevoltage fade in lithium-rich layered oxides is reversible and call for newparadigms for improved design of oxygen-redox active materials.

Lithium methyl carbonate (LMC) is synthesized in a single step and investigated as a coating material for Li protection. The LMC layer can be formed in situ during Li plating on Cu foil. The chemical and crystal structure of the ∼1 μm thick coating is confirmed, which remains intact during lithium cycling. SEM also confirms the dissolution of the LMC layer after being transferred into the commercial LiPF6-carbonate electrolyte. Presaturating the electrolyte with LMC powder prevents the dissolution of the LMC coating layer, which improves the Li plating/stripping Coulombic efficiency from 90.5% (bare Cu in commercial electrolyte) to 96.1% at 0.5 mA cm-2 and 1 mAh cm-2.

Practical implementation of next-generation Li-ion battery chemistries is to a large extent obstructed by the absence of an electrolyte that is capable of simultaneously supporting reversible electrochemical reactions at two extreme electrochemical potentials—above 4.5 V at the positive electrode and near 0 V vs. Li at the negative electrode. Electrolytes based on carbonate esters have been reliable in satisfying state-of-the-art Li-ion battery (LIB) chemistries below 4.4 V), releasing CO2. In this work, we explore a carbonate-free electrolyte system based on a single sulfone solvent, in which a newly discovered synergy between solvent and salt simultaneously addresses the interfacial requirements of both graphitic anode and high-voltage cathode (LiNi0.5Mn1.5O4 (LNMO)). Experimental measurements, quantum chemistry (QC) calculations, and molecular dynamics simulations reveal the system's fast ion conduction, stability over a wide temperature range, and non-flammability. At the anode, a LiF-rich interphase generated by early-onset reduction of the salt anion effectively suppresses solvent co-intercalation and subsequent graphite exfoliation, enabling unprecedented and highly reversible graphite cycling in a pure sulfone system. Under oxidative conditions, QC calculations predict that high salt concentration promotes complex/aggregate formation which slow the decomposition of sulfolane and leads to polymerizable rather than gaseous products—a fundamental improvement over carbonate solvents. These predictions are corroborated by X-ray photoelectron spectroscopy (XPS), cryogenic-transmission electron microscopy (TEM), and electron energy loss spectroscopy (EELS) experiments, which revealed the presence of a thin, conformal, sulfur-based cathode electrolyte interphase (CEI). Together, the functional interphases (SEI/CEI) generated by this electrolyte system supported long term operation of a high-voltage (4.85 V) LNMO/graphite full cell, which retained ∼70% of its original first-cycle discharge capacity after the 1000th cycle. Based on these results, this new carbonate-free electrolyte system, supported by the mechanistic understanding of its behavior, presents a promising new direction toward unlocking the potential of next generation Li-ion battery electrodes.

Metal-ion doping can improve the electrochemical performance of Na3V2(PO4)3. However, the reason for the enhanced electrochemical performance and the effects of cation doping on the structure of Na3V2(PO4)3 have yet been probed. Herein, Mg2+ is doped into Na3V2(PO4)3/C according to the first-principles calculation. The results indicate that Mg2+ prefers to reside in the V site and an extra electrochemical active Na+ is introduced to the Na3V2(PO4)3/C crystal to maintain the charge balance. The distribution of Mg2+ in the particle of Na3V2(PO4)3/C is further studied by electrochemical impedance spectroscopy. We find that the highest distribution of Mg2+ on the surface of the particles leads to facile surface electrochemical reactions for Mg2+-doped samples, especially at high rates.

While several stretchable batteries utilizing either deterministic or random composite architectures have been described, none have been fabricated using inexpensive printing technologies. In this study, the authors printed a highly stretchable, zinc-silver oxide (Zn-Ag2O) battery by incorporating polystyrene-block-polyisoprene-block-polystyrene (SIS) as a hyperelastic binder for custom-made printable inks. The remarkable mechanical properties of the SIS binder lead to an all-printed, stretchable Zn-Ag2O rechargeable battery with a ≈2.5 mA h cm−2 reversible capacity density even after multiple iterations of 100% stretching. This battery offers the highest reversible capacity and discharge current density for intrinsically stretchable batteries reported to date. The electrochemical and mechanical properties are characterized under different strain conditions. The new stress-enduring printable inks pave ways for further developing stretchable electronics for the wide range of wearable applications.

Structural processes occurring upon electrochemical cycling in P2-Nax[LiyNizMn1-y-z]O2 (x, y, z ≤ 1) cathode materials are investigated using 23Na and 7Li solid-state nuclear magnetic resonance (ssNMR). The interpretation of the complex paramagnetic NMR data obtained for various electrochemically-cycled NaxNi1/3Mn2/3O2 and NaxLi0.12Ni0.22Mn0.66O2 samples is assisted by state-of-the-art hybrid Hartree-Fock/density functional theory calculations. Two Na crystallographic environments are present in P2-Nax[LiyNizMn1-y-z]O2 compounds, yet a single 23Na NMR signal is observed with a shift in-between those computed for edge- and face-centered prismatic sites, indicating that Na-ion motion between sites in the P2 layers results in an average signal. This is the first time that experimental and theoretical evidence are provided for fast Na-ion motion (on the timescale of the NMR experiments) in the interlayer space in P2-type NaxTMO2 materials. A full assignment of the 7Li NMR data confirms that Li substitution delays the P2 to O2 phase transformation taking place in NaxNi1/3Mn2/3O2 over the range 1/3 ≥ xNa ≥ 0. 23Na ssNMR data demonstrate that NaxNi1/3Mn2/3O2 samples charged to ≥3.7 V are extremely moisture sensitive once they are removed from the cell, water molecules being readily intercalated within the P2 layers leading to an additional Na signal between 400 and 250 ppm. By contrast, the lithiated material NaxLi0.12Ni0.22Mn0.66O2 shows no sign of hydration until it is charged to ≥4.4 V. Since both TMO2 layer glides and water intercalation become increasingly favorable as more vacancies are present in the Na layers, the higher stability of the Li-doped P2 phase at high voltage can be accounted for by its higher Na content at all stages of cycling.

Despite the extensive research on MnO2 as a pseudocapacitor electrode material, there has been no report on heterostructures of multiple phase MnO2. Here we report the combination of two high-capacitance phases of MnO2, namely, α-MnO2 nanowires and δ-MnO2 ultrathin nanoflakes, to form a core-branch heterostructure nanoarray. This material and structure design not only increases the mass loading of active materials (from 1.86 to 3.37 mg cm2), but also results in evident pseudocapacitance enhancement (from 28 F g-1 for pure nanowires to 178 F g-1 for heterostructures at 5 mV s-1). The areal capacitance is up to 783 mF cm-2 at 1 mV s-1. Upon 20 000 cycles, the heterostructure array electrode still delivers a reversible capacitance above 100 F g-1 at 4.5 A g-1. Kinetic analysis reveals that capacitances due to both capacitive and diffusion controlled processes have been enlarged for the self-branched heterostructure array. This work presents a new route to improve the electrochemical performance of MnO2 as a binder-free supercapacitor electrode.

Structural processes occurring upon electrochemical cycling in P2-Nax[LiyNizMn1-y-z]O2 (x, y, z ≤ 1) cathode materials are investigated using 23Na and 7Li solid-state nuclear magnetic resonance (ssNMR). The interpretation of the complex paramagnetic NMR data obtained for various electrochemically-cycled NaxNi1/3Mn2/3O2 and NaxLi0.12Ni0.22Mn0.66O2 samples is assisted by state-of-the-art hybrid Hartree-Fock/density functional theory calculations. Two Na crystallographic environments are present in P2-Nax[LiyNizMn1-y-z]O2 compounds, yet a single 23Na NMR signal is observed with a shift in-between those computed for edge- and face-centered prismatic sites, indicating that Na-ion motion between sites in the P2 layers results in an average signal. This is the first time that experimental and theoretical evidence are provided for fast Na-ion motion (on the timescale of the NMR experiments) in the interlayer space in P2-type NaxTMO2 materials. A full assignment of the 7Li NMR data confirms that Li substitution delays the P2 to O2 phase transformation taking place in NaxNi1/3Mn2/3O2 over the range 1/3 ≥ xNa ≥ 0. 23Na ssNMR data demonstrate that NaxNi1/3Mn2/3O2 samples charged to ≥3.7 V are extremely moisture sensitive once they are removed from the cell, water molecules being readily intercalated within the P2 layers leading to an additional Na signal between 400 and 250 ppm. By contrast, the lithiated material NaxLi0.12Ni0.22Mn0.66O2 shows no sign of hydration until it is charged to ≥4.4 V. Since both TMO2 layer glides and water intercalation become increasingly favorable as more vacancies are present in the Na layers, the higher stability of the Li-doped P2 phase at high voltage can be accounted for by its higher Na content at all stages of cycling.

Lithium lanthanum titanate (LLTO) is a promising solid state electrolyte for solid state batteries due to its demonstrated high bulk ionic conductivity. However, crystalline LLTO has a relatively low grain boundary conductivity, limiting the overall material conductivity. In this work, we investigate amorphous LLTO (a-LLTO) thin films grown by pulsed laser deposition (PLD). By controlling the background pressure and temperature we are able to optimize the ionic conductivity to 3 × 10-4 S/cm and electronic conductivity to 5 × 10-11 S/cm. XRD, TEM, and STEM/EELS analysis confirm that the films are amorphous and indicate that oxygen background gas is necessary during the PLD process to decrease the oxygen vacancy concentration, decreasing the electrical conductivity. Amorphous LLTO is deposited onto high voltage LiNi0.5Mn1.5O4 (LNMO) spinel cathode thin films and cycled up to 4.8 V vs. Li showing excellent capacity retention. These results demonstrate that a-LLTO has the potential to be integrated into high voltage thin film batteries.

NASICON is one of the most promising sodium solid electrolytes that can enable the assembly of cheaper and safer sodium all-solid-state batteries. In this study, we perform a combined experimental and computational investigation into the effects of aliovalent doping in NASICON on both bulk and grain boundary (secondary phase) ionic conductivity. Our results show that the dopants with low solid solubility limits in NASICON lead to the formation of a conducting (less insulating) secondary phase, thereby improving the grain boundary conductivity measured by electrochemical impedance spectroscopy (including grain-boundary, secondary-phase, and other microstructural contributions) that is otherwise hindered by the poorly-conducting secondary phases in undoped NASICON. This is accompanied by a change in the Si/P ratio in the primary NASICON bulk phase, thereby transforming monoclinic NASICON to rhombohedral NASICON. Consequently, we have synthesized NASICON chemistries with significantly improved and optimized total ionic conductivity of 2.7 mS/cm. More importantly, this study has achieved an understanding of the underlying mechanisms of improved conductivities via doping (differing from the common wisdom) and further suggests a new general direction to improve the ionic conductivity of solid electrolytes via simultaneously optimizing the primary bulk phase and the microstructure (including grain boundary segregation and secondary phases).

An ionic liquid (IL) electrolyte with 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIFSI) is applied to a silicon (Si) composite anode for Lithium-ion batteries (LIB). Si is one of the most promising anode materials for LIBs and fluoroethylene carbonate (FEC) has been widely used as an electrolyte additive with Si anodes to enhance electrochemical performance. However, the effect of FEC only lasts for a limited number of cycles. To overcome this issue, a bis(fluorosulfonyl)imide (FSI)-based IL is studied as a potential electrolyte candidate for a Si composite anode. Its effects on the electrochemical performance and the corresponding solid electrolyte interphase (SEI) formation on the Si composite anode are not well understood. This work addresses the correlation between the electrochemical performance and SEI formation to probe the surface chemistry on the Si composite anode. We find that the FSI-based electrolyte provides a stable and reversible capacity in long term cycling tests. This electrolyte has excellent rate capability compared to that of carbonate-based electrolytes. The decomposition products of these electrolytes on Si anodes are investigated by X-ray photoelectron spectroscopy. These results show that the chemical composition on the surface of the Si anode is largely different when using the FSI-based electrolyte than it is when using carbonate type electrolytes. The decomposition products of the IL lead to a large number of inorganic species such as LiOH and Li2O, which yield superior rate capability for the IL electrolyte. The FSI-based IL offers promising applicability for a practical Si composite anode.

In this study we experimentally investigated the effects of two processing techniques on the sodium-rich anti-perovskite, Na3OBr; namely, conventional cold pressing (CP) and spark plasma sintering (SPS). We demonstrated that the electrolyte can be synthesized via a single-step solid state reaction. We compared the CP and SPS processed samples using XRD, SEM, and EIS. From these analyses it was found that SPS reduced Na3OBr's interfacial impedance by three orders of magnitude, which translated into an increase in the overall ionic conductivity and a reduction in the activation energy, from 1.142 eV to 0.837 eV. DFT was used to probe the mechanisms for ionic transport in Na-rich Na3OBr. The formation energies of ion diffusion-facilitating defects in Na3OBr were found to be much higher compared to the lithium-rich anti-perovskites (LiRAP), which can explain the difference in overall ionic conductivity between the two.

The energy density of current batteries is limited by the practical capacity of the positive electrode, which is determined by the properties of the active material and its concentration in the composite electrode architecture. The observation in dynamic conditions of electrochemical transformations creates the opportunity of identifying design rules toward reaching the theoretical limits of battery electrodes. But these observations must occur during operation and at multiple scales. They are particularly critical at the single-particle level, where incomplete reactions and failure are prone to occur. Here, operando full-field transmission X-ray microscopy is coupled with X-ray spectroscopy to follow the chemical and microstructural evolution at the nanoscale of single crystals of Li1+xMn2-xO4, a technologically relevant Li-ion battery electrode material. The onset and crystallographic directionality of a series of complex phase transitions are followed and correlated with particle fracture. The dynamic character of this study reveals the existence of nonequilibrium pathways where phases at substantially different potentials can coexist at short length scales. The results can be used to inform the engineering of particle morphologies and electrode architectures that bypass the issues observed here and lead to optimized battery electrode properties. Compositional and morphological transitions during the electrochemical reaction of a single Li1+xMn2-xO4 microcrystal are successfully probed at the nanoscale using operando full-field transmission X-ray microscopy coupled with X-ray spectroscopy. It is possible to visualize the directionality of the transitions and correlate them with fracture. The approach reveals nonequilibrium pathways where phases at different potentials can coexist within a microcrystal.

We report experimental studies to understand the reaction mechanism of the intermetallic anode Cu2Sb with Na and demonstrate that it is capable of retaining about 250 mAh g-1 over 200 cycles when using fluoroethylene carbonate additive. X-ray diffraction data indicate during the first discharge the reaction leads to the formation of crystalline Na 3Sb via an intermediate amorphous phase. Upon desodiation the Na 3Sb reverts to an amorphous phase, which then recrystallizes into Cu2Sb at full charge, indicating a high degree of structural reversibility. The structure after charging to 1 V is different from that of Cu2Sb, as indicated by X-ray absorption spectroscopy and 121Sb Mössbauer spectroscopy, and is due to the formation of an amorphous Na-Cu-Sb phase. At full discharge, an isomer shift of -8.10 mm s -1 is measured, which is close to that of a Na3Sb reference powder (-7.95 mm s-1) and in agreement with the formation of Na3Sb domains. During charge, the isomer shift at 1 V (-9.29 mm s-1) is closer to that of the pristine material (-9.67 mm s -1), but the lower value is consistent with the lack of full desodiation, as expected from the potential profile and the XAS data. © 2014 American Chemical Society.

Coherent x-ray diffraction imaging is used to map the local three dimensional strain inhomogeneity and electron density distribution of two individual LiNi0.5Mn1.5O4-δ cathode nanoparticles in both ex-situ and in-situ environments. Our reconstructed images revealed a maximum strain of 0.4%. We observed different variations in strain inhomogeneity due to multiple competing effects. The compressive/tensile component of the strain is connected to the local lithium content and, on the surface, interpreted in terms of a local Jahn-Teller distortion of Mn 3+. Finally, the measured strain distributions are discussed in terms of their impact on competing theoretical models of the lithiation process. © 2014 AIP Publishing LLC.

Bing-Lei Ma,1,2,* Lin Yao,1,2,* Yu Fan,1,2 Yu Wang,1,2 Yi-Sen Meng,1,2 Qian Zhang,1,2 Zhi-Song He,1,2 Jie Jin,1,2 Li-Qun Zhou1,21Department of Urology, Peking University First Hospital, Institute of Urology, Peking University, Beijing, People’s Republic of China; 2Beijing Key Laboratory of Urogenital Diseases (male), Molecular Diagnosis and Treatment Center, Beijing, People’s Republic of China*These authors contributed equally to this workPurpose: Radical surgery is the preferred method for local high-risk and limited progressive prostate cancer in the routine clinical setting. However, current guidelines do not recommend neoadjuvant hormone therapy (NHT). Opinions regarding NHT vary among individual clinicians. According to the experience gained at our center, we explored the benefits of NHT for patients with prostate cancer during the perioperative period in this study.Methods: In this retrospective study, we explored the perioperative benefits of NHT among 189 patients with local high-risk or limited progressive prostate cancer who underwent radical prostatectomy and divided them into two groups: the NHT group and the non-NHT group. The NHT regimens were a gonadotropin-releasing hormone (GnRH) agonist alone (3.75/11.25 mg of leuprolide or 3.6/10.8 mg of goserelin acetate), an androgen receptor antagonist (ARA) alone, or a combination of the two. The duration of treatment was 6 months.Results: We found that NHT could reduce the surgery time and intraoperative hemorrhage, thus reducing the difficulty of surgery; NHT could also improve the postoperative recovery of patients. However, it did not reduce the stage of prostate cancer or positive surgical margin rate.Conclusions: Neoadjuvant therapy is optional for some patients. We believe that NHT will improve the overall prognosis of patients as progress continues in the medical field in the future.Keywords: localized high-risk, limited advanced, prostate cancer, neoadjuvant hormone therapy, short-term benefit

Li-substituted layered P2-Na0.80[Li0.12Ni 0.22Mn0.66]O2 is investigated as an advanced cathode material for Na-ion batteries. Both neutron diffraction and nuclear magnetic resonance (NMR) spectroscopy are used to elucidate the local structure, and they reveal that most of the Li ions are located in transition metal (TM) sites, preferably surrounded by Mn ions. To characterize structural changes occurring upon electrochemical cycling, in situ synchrotron X-ray diffraction is conducted. It is clearly demonstrated that no significant phase transformation is observed up to 4.4 V charge for this material, unlike Li-free P2-type Na cathodes. The presence of monovalent Li ions in the TM layers allows more Na ions to reside in the prismatic sites, stabilizing the overall charge balance of the compound. Consequently, more Na ions remain in the compound upon charge, the P2 structure is retained in the high voltage region, and the phase transformation is delayed. Ex situ NMR is conducted on samples at different states of charge/discharge to track Li-ion site occupation changes. Surprisingly, Li is found to be mobile, some Li ions migrate from the TM layer to the Na layer at high voltage, and yet this process is highly reversible. Novel design principles for Na cathode materials are proposed on the basis of an atomistic level understanding of the underlying electrochemical processes. These principles enable us to devise an optimized, high capacity, and structurally stable compound as a potential cathode material for high-energy Na-ion batteries. © 2014 American Chemical Society.

X-ray microscopy is powerful in that it can probe large volumes of material at high spatial resolution with exquisite chemical, electronic and bond orientation contrast. The development of diffraction-based methods such as ptychography has, in principle, removed the resolution limit imposed by the characteristics of the X-ray optics. Here, using soft X-ray ptychography, we demonstrate the highest-resolution X-ray microscopy ever achieved by imaging 5â €..nm structures. We quantify the performance of our microscope and apply the method to the study of delithiation in a nanoplate of LiFePO 4, a material of broad interest in electrochemical energy storage. We calculate chemical component distributions using the full complex refractive index and demonstrate enhanced contrast, which elucidates a strong correlation between structural defects and chemical phase propagation. The ability to visualize the coupling of the kinetics of a phase transformation with the mechanical consequences is critical to designing materials with ultimate durability.

This work reports a physical mixture aswell as an integrated composite structure (ICS) of lithium-excess layered oxides and high voltage spinel oxides. With respect to physical mixture (PM), the improvement has shown in cycling retention. Different synthesis routes would result in drastically different properties in the composite case. The optimized composite, in comparison with the non-optimized one, both energy density and the power density have increased. The optimized composite could deliver 125 mAh/g capacity after 200 cycles at a rate of 1.2 C. Thework here provides some new insights into how to design better cathode materials for lithium ion batteries. © The Author(s) 2014. Published by ECS.

Improved methods for the flux growth of single crystals of the important battery material LiFePO4 have been developed, allowing the facile preparation of single crystals up to 1 cm across with well-developed facets at relatively low temperatures. The structural characterization of these samples by both powder X-ray diffraction and single crystal diffraction (X-ray and neutron) indicates that the samples are typically stoichiometric with a very low concentration of Fe defects on the Li site, though crystals with larger concentrations of defects can be specifically grown using Fe-rich fluxes. These defects occur through the formation of a Fe-rich (Li1-2xFe x)FePO4 partial solid solution, in contrast to the antisite defects more commonly discussed in the literature which would preserve the ideal LiFePO4 stoichiometry. The LiFePO4 defects are shown to be sarcopside-like (2 Li+ → Fe2+ + vacancy) based on compositions refined from single crystal diffraction data, the observed dependence of unit cell parameters on defect concentration, and their observed phase behavior (defects only appear in growths from fluxes which are Fe-rich relative to stoichiometric LiFePO4). The distribution of defects has been studied by aberration corrected scanning transmission electron microscopy and was found to be highly inhomogenous, suggesting that defect-containing crystals may consist of endotaxial intergrowths of olivine LiFePO4 and sarcopside Fe3(PO4)2 in a manner that minimizes the detrimental influence of FeLi defects on the rate of Li-ion transport within crystallites. © 2013 American Chemical Society.

CuO is an attractive anode material for Li-ion batteries because of its high specific capacity. However, conventional CuO powders suffer from a large volume expansion during the Li insertion-extraction process, resulting in contact loss between the active material and the current collector. In this work, a nano-architecture made of metallic Cu core-CuO shell nanocable arrays is fabricated directly on a metallic collector by partial oxidation of three-dimensional Cu nanowire arrays. This type of binder/additive free electrode achieves a high specific capacity (840 mA h g-1 at 0.1 C) and excellent capacity retention ability (∼600 mA h g-1 after 200 cycles at 0.5 C). The improved cyclic stability is attributed to its excellent adhesion of the active material on the current collector and short ionic/electronic transport pathways during cycling. © The Royal Society of Chemistry 2013.

The layered oxide compounds xLi2MnO3·(1 - x)LiMO2 (M=Ni, Mn, Co) are of great interest as positive electrode materials for high energy density lithium-ion batteries. In-situ neutron diffraction was carried out to compare the structural changes between the classical layered compound Li[Ni1/3Mn1/3Co1/3]O2 (x=0) and lithium-excess layered compound Li[Li0.2Ni0.18Mn0.53Co0.1]O2 (x=0.5) during electrochemical cycling. In this work, lab made pouch cells were built for the in-situ study and graphite was used as the anode material. Irreversible structural change of Li[Li0.2Ni0.18Mn0.53Co0.1]O2 during first charge (4.7 V)/discharge cycle (2.0 V) was indicated by dynamic changes in lattice d-spacing, while the Li[Ni1/3Mn1/3Co1/3]O2 showed completely reversible structural evolution between 4.4 V and 2.5 V. Ex-situ neutron powder diffraction was performed on both pristine and chemically delithiated lithium-excess layered compounds to better understand the irreversible structure change. © 2013 Published by Elsevier B.V.

Donghua Zou,1,* Chunbin Liu,1,* Qian Zhang,1 Xianfeng Li,1 Gang Qin,1 Qi Huang,1 Youshi Meng,1 Li Chen,2 Jinru Wei1 1Department of Stroke Center, The Fifth Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi, People’s Republic of China; 2Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi, People’s Republic of China *These authors contributed equally to this work Background: Polymorphisms in miR-146a (rs2910164), miR-196a2 (rs11614913), miR-149 (rs2292832) and miR-499 (rs3746444) have been associated with ischemic stroke (IS), but studies have given inconsistent results. Methods: This meta-analysis investigated the possible association between IS risk and the four polymorphisms. A total of 14 case-control studies from Asian populations involving 6,083 cases and 7,248 controls for the four polymorphisms were included.Results: Results showed that the GG genotype of miR-146a (rs2910164) may be associated with increased IS risk according to the recessive model (OR=1.20, 95% CI=1.02-1.42, P=0.03). Similarly, the CC genotype of miR-149 (rs2292832) may be associated with increased IS risk according to the recessive model (OR=1.28, 95% CI=1.08-1.52, P=0.005) and the homozygous model (OR=1.31, 95% CI=1.09-1.58, P=0.004). In contrast, miR-196a2 (rs11614913) and miR-499 (rs3746444) polymorphisms did not show significant association with IS risk in any of the five genetic models.Conclusion: These results indicate that the GG genotype of miR-146a (rs2910164) and CC genotype of miR-149 (rs2292832) may confer increased susceptibility to IS, while miR-196a2 (rs11614913) and miR-499 (rs3746444) polymorphisms may not be associated with IS risk in Asian populations. These conclusions should be verified in large and well-designed studies. Keywords: miRNAs, polymorphism, ischemic stroke, meta-analysis

Graphitic carbon is currently considered the state-of-the-art material for the negative electrode in lithium ion cells, mainly due to its high reversibility and low operating potential. However, carbon anodes exhibit mediocre charge/discharge rate performance, which contributes to severe transport-induced surface structural damage upon prolonged cycling and limits the lifetime of the cell. Lithium bulk diffusion in graphitic carbon is not yet completely understood, partly due to the complexity of measuring bulk transport properties in finite-sized nonisotropic particles. To solve this problem for graphite, we use the Devanathan-Stachurski electrochemical methodology combined with ab initio computations to deconvolute and quantify the mechanism of lithium ion diffusion in highly oriented pyrolytic graphite (HOPG). The results reveal inherent high lithium ion diffusivity in the direction parallel to the graphene plane (∼10-7-10-6 cm2 s-1), as compared to sluggish lithium ion transport along grain boundaries (∼10 -11 cm2 s-1), indicating the possibility of rational design of carbonaceous materials and composite electrodes with very high rate capability. © 2010 American Chemical Society.