Materials Science & Engineering Theses and Dissertations

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    Improving the performance of solid polymer electrolytes for lithium batteries via plasticization with aqueous salt or ionic liquid
    (2019) Widstrom, Matthew; Kofinas, Peter; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The goal of this dissertation is to investigate and enable polyethylene oxide (PEO)-based solid polymer electrolytes (SPEs) for lithium batteries. Specifically, two different strategies to plasticize the PEO matrix for improving ion transport are explored. PEO has a propensity to crystallize below 60C, rendering ion motion too slow to be commercially competitive and constituting one of the main challenges of utilizing PEO SPEs as an alternative to organic liquid electrolytes. ILSPEs incorporating ionic liquids (ILs) were fabricated by blending PEO, IL, and corresponding lithium salt followed by hot-pressing the mixture into a homogenous film. Aqueous SPEs (ASPEs) were fabricated by blending a highly concentrated solution of lithium salt in water (aqueous salt) with PEO followed by hot-pressing in a similar manner. Thermal analysis and electrochemical characterization were carried out for both classes of SPEs to assess their suitability as electrolytes and to optimize their composition for performance. Additionally, engineering the interface between the SPE and electrodes remains challenging and is critical for achieving good cycling performance. Multiple approaches for quality interface creation are proposed and carried out. Optimized ILSPE compositions show resistance to oxidation and were able to achieve room temperature conductivity of 0.96 mS/cm at room temperature, a value suitable for commercial application, as well as good rate performance at room temperature cycling in Li/ ILSPE/ lithium iron phosphate configuration. ASPE compositions exhibit conductivities between 0.68 and 1.75mS/cm at room temperature, with proof-of-concept cycling in a LTO/ ASPE/ LMO configuration.
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    NEXT GENERATION ANODES FOR LITHIUM ION AND LITHIUM METAL BATTERIES
    (2019) Pastel, Glenn; Hu, Liangbing; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Engineering of specific battery components can yield incremental gains in performance, but sustained advancements are derived from an understanding of charge transfer, interphase formation, and ion storage in the system. In this dissertation, the next generation of lithium-ion and alkali metal anodes are integrated with promising flame retardant electrolyte systems for safe and energy-dense portable storage devices. The intent of this research is to bring safe lithium ion batteries to the market without compromising performance and, more specifically, volumetric energy density. The first part of this dissertation describes the invention and optimization of a silicon-based additive which employs a solution-based process to functionalize silicon nanoparticle precursors. The additive is thoroughly characterized by chemical and electrochemical methods and the electrolyte interphase is improved by the attachment of partially reduced graphene oxide and sacrificial additive species. The design principles developed for the silicon-based system deviate significantly from those used for other conventional intercalation and host electrodes. As a result, in the second part of this dissertation, three chemically separable electrolyte systems, selected for their flame retardant properties, are individually investigated and tailored for energy-dense pouch cells. The bulk transport and interfacial properties of each electrolyte system are adapted to meet the industry standards of portable electronic devices. Insights into the preferred species for stable solid electrolyte interphase formation are discussed with an emphasis on the impact of fluorinated solvents and sacrificial additives. In the last part of this dissertation, alkali metal hosts are also proposed for chemistries beyond lithium ion. Novel synthesis methods including rapid joule heating are explored to form the innovative host architectures which greatly mitigate the coulombic inefficiency of metal stripping and plating in half and full cell configurations. The design principles outlined in this dissertation reveal how to successfully engineer the charge transfer, interphase formation, and ion storage of high capacity electrodes with safe electrolyte for state-of-the-art portable energy storage devices.
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    MULTI-LAYERED, VARIABLE POROSITY SOLID- STATE LITHIUM-ION ELECTROLYTES: RELATIONSHIP BETWEEN MICROSTRUCTURE AND LITHIUM-ION BATTERY PERFORMANCE
    (2019) Hamann, Tanner; Wachsman, Eric; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The global drive to create safer, higher capacity energy storage devices is increasingly focused on the relationship between the microstructures of electrochemically- active materials and overall battery performance. The advent of solid-state electrolytes with multi-layered, variable porosity microstructures opens new avenues to creating the next generation of rechargeable batteries, while creating new challenges for device integration and operation. In this dissertation, microstructures of solid-state Li-ion conducting electrolytes were characterized to identify the primary limiting factors on electrolyte performance and identify structural changes to improve porous electrolyte performance in dense-porous bilayer systems. LLZO-based garnet electrolytes were fabricated with varied porosity and characterized using 3D Focused Ion Beam (FIB) Tomography, enabling digital reconstructions of the underlying 3D microstructures. Ion transport through the microstructures was analyzed using M-factors, which identified garnet volume fraction and bottlenecks as primary limiters on effective conductivity, followed by geometric tortuosity. Notably, a template-based porous microstructure displayed a low tortuosity plane and a high tortuosity direction, as opposed to the more homogenous tape-cast porous microstructures. To evaluate the performance of these microstructures in Li symmetric cells, dense-porous bilayers were digitally constructed using the FIB Tomography microstructures as porous layers with fully infiltrated Li-metal electrodes, and equilibrium electric potentials were simulated. The bilayers had area-specific resistance (ASR) values similar to the ASR value of the dense layer alone. The bilayer ASR also decreased as porous layer porosity increased, due to ion transport occurring primarily through the dense layer-electrode interface and higher porosity creating higher interfacial area. Artificial bilayers were created with porous layers composed of columns for a range of column diameters/particle sizes, porous layer porosities, and porous layer thicknesses. The bilayer ASR decreased with increasing porosity and decreasing column diameter, similar to the FIB Tomography bilayers. However, bilayer ASR dramatically increased when only partially infiltrated with electrodes, and instead increased with increasing porosity and decreasing column diameter. The simulation results showed that fabricating solid-state bilayer symmetric cells with low ASR required high porosity porous microstructures with small particle sizes, and electrodes completely infiltrated to the dense layer.
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    CHARACTERIZATION OF MECHANICAL PROPERTIES AND DEFECTS OF SOLID-OXIDE FUEL CELL MATERIALS
    (2018) Stanley, Patrick; Wachsman, Eric D; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Solid-oxide fuel cells (SOFCs) have the potential to help meet global energy demands by efficiently converting fuel to electricity. The technology currently requires high temperatures and has reliability limitations. A critical concern is the structural integrity of the cell after redox cycling at operating temperatures. As new materials are developed to reduce operating temperatures and improve redox stability, the effect of the environment on the mechanical properties must be studied. Ceria-based systems have allowed the operating temperature to be decreased to the 600℃ range. For this reason, a three-point bend apparatus was developed which could test materials up to 650℃ in reducing environments. Using this apparatus, it was shown how pore geometry and amount affected strength of porous gadolinium doped ceria (GDC) at 650℃ with lower aspect ratio pores, leading to higher fracture strength due to crack tip blunting. The strength of Ni-GDC/GDC half-cell coupons showed no dependence on loading orientation at elevated temperatures in air, but were 47% weaker when the electrolyte was placed in tension under H2 as compared to when the electrolyte was placed in compression. It was also determined that a reduced Ni-GDC/GDC coupon could be exposed to air for an extended period of time and reheated under H2 with no effect to the strength, allowing for more options when processing and preparing cells. A new anode material, SrFe0.2Co0.4Mo0.4O3-δ (SFCM), was investigated for chemical expansion, oxygen non-stoichiometry, and mechanical properties. SFCM maintains phase purity under reducing conditions, with little changes to lattice parameter between oxidation and reduction, but under oxidation, SFCM forms Sr2Co1.2Mo0.8O6 impurities. SFCM supports a large degree of non-stoichiometry, up to δ = 0.176 at 600℃, due to a low enthalpy of formation for oxygen vacancies of 44.3 kJ mol−1. Fracture toughness of SFCM was determined to be (0.124 ± 0.023) MPa√m in air at room temperature and (0.286 ± 0.038) MPa√m at 600℃. The strength of SFCM-GDC half-cells increased by 31% upon heating to 600℃, after which reduction decreased strength by 29%. Reduction and redox cycling were shown to only decrease the characteristic strength, not alter the structural flaw distribution, as microcracks uniformly grew.
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    Atomistic Modeling of Solid Interfaces in All-solid-state Li-ion Batteries
    (2018) Zhu, Yizhou; Mo, Yifei; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    All-solid-state Li-ion battery based on solid electrolyte is a promising next-generation battery technology, providing intrinsic safety and higher energy density. Despite the development of solid electrolyte materials with high ionic conductivity, the high interfacial resistance and interfacial degradation at the solid electrolyte–electrode interfaces limit the electrochemical performance of the all-solid-state batteries. Fundamental understanding about the solid-solid interfaces is essential to improve the performance of all-solid-state batteries. In this dissertation, I perform first principles computation to bring new understanding about these solid interfaces. Using our developed computation approach based on large materials database, I calculated the intrinsic electrochemical stability window of solid electrolytes and predicted interphase decomposition products. I revealed the effects of different types of interphase layers on the interface stability and battery performance, and also provided interfacial engineering strategies to improve interface compatibility. Lithium metal anode can provide significantly higher energy density of Li-ion batteries. However, only a limited number of materials are known to be stable against lithium metal due to its strong reducing nature. Using first-principles calculations and large materials database, I revealed the general trend of lithium reduction behavior in different material chemistry. Different from oxides, sulfides, and halides, nitride anion chemistry exhibits unique stability against lithium metal, which is either thermodynamically intrinsic or a result of stable passivation. Therefore, many nitrides materials are promising candidate materials for lithium metal anode protection. Since solid electrolytes in all-solid-state batteries are often polycrystalline, the grain boundaries can have an important impact on the ion diffusion in solid electrolytes. I performed molecular dynamics simulations to study the ion diffusion at grain boundaries in solid electrolyte materials, and showed the distinct diffusion behavior at grain boundaries different from the facile ion transport in the bulk. In addition, I studied the order-disorder transition induced by mechanical strain in lithium garnet. Such transition can lead to orders of magnitude change in ionic diffusivity. This series of work demonstrated that computational modeling techniques can help to gain critical fundamental understandings of the solid interfaces in all-solid-state Li-ion battery, and to provide practical engineering strategies to improve the battery performance.
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    Nanomaterials for Garnet Based Solid State Energy Storage
    (2018) Dai, Jiaqi; Hu, Liangbing; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Solid state energy storage devices with solid state electrolytes (SSEs) can potentially address Li dendrite-dominated issues, enabling the application of metallic lithium anodes to achieve high energy density with improved safety. In the past several decades, many outstanding SSE materials (including conductive oxides, phosphates, hydrides, halides, sulfides, and polymer-based composites) have been developed for solid-state batteries. Among various SSEs, garnet-type Li7La3Zr2O12 (LLZO) is one of the most important and appealing candidates for its high ionic conductivity (10-4~10-3 S/cm) at room temperature, wide voltage window (0.0-6.0V), and exceptional chemical stability against Li metal. However, its applications in current solid state energy storage devices are still facing various critical challenges. Therefore, in this quadripartite thesis I focus on developing nanomaterials and corresponding processing techniques to improve the comprehensive performance of solid state batteries from the perspectives of electrolyte design, interface engineering, cathode improvement, and full cell construction. The first part of the thesis provides two novel designs of garnet-based SSE with outstanding performance enabled by engineered nanostructures: a 3D garnet nanofiber network and a multi-level aligned garnet nanostructure. The second part of the thesis focuses on negating the anode|electrolyte interfacial impedance. It consists of several processing techniques and a comprehensive understanding, through systematic experimental analysis, of the governing factors for the interfacial impedance in solid state batteries using metallic anodes. The third part of the thesis reports several processing techniques that can raise the working voltage of Li2FeMn3O8 (LFMO) cathodes and enable the self-formation of a core-shell structure on the cathode to achieve higher ionic conductivity and better electrochemical stability. The development and characterization of a solid state energy storage device with a battery-capacitor hybrid design is included in the last part of the thesis.
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    Functional imaging of photovoltaic materials at the nanoscale
    (2018) Tennyson, Elizabeth; Leite, Marina S; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The ideal photovoltaic technology for global deployment must exhibit two key attributes: (i) high power-conversion efficiency, enabling a solar panel with a large power output per area and, (ii) low-cost/W, due to either being derived from earth-abundant materials and/or ease of fabrication. For the past two decades, extensive efforts have been made to boost the efficiency of some of the most promising high performance and low-cost photovoltaic materials, such as CdTe, Cu(In,Ga)Se2 (CIGS), and hybrid organic-inorganic perovskites, to achieve higher efficiency devices. However, improvement in the overall performance is still limited by the open-circuit voltage (Voc). All of the solar cell materials listed above are composed of grains and grain boundaries on the order of micro- and nanometers, respectively, and their nanoscale interfaces can cause electrical charge carriers to become trapped and recombine non-radiatively, reducing the Voc. Therefore, in this thesis, I implement high spatial resolution functional imaging techniques to resolve the local voltage variations in the thin-lm polycrystalline and hybrid perovskites materials for photovoltaic applications. First, I spectrally and spatially resolve the local photovoltage of CIGS solar cells through confocal optical microscopy to build a qualitative voltage tomography. From these photovoltage results, I discover variations in the electrical response of >20% that are also on the same length scale as the grains composing the CIGS material. Therefore, by enhancing the spatial resolution beyond the diffraction limit, the electronic properties of individual grains and the interfaces between the grains can be fully resolved. For this, I implement Kelvin probe force microscopy (KPFM), and demonstrate a universal method to directly map the Voc of any photovoltaic material with nanoscale spatial resolution. Next, we extend this ability of KPFM to rapidly image (16 sec/map) the real-time dynamics of perovskite solar cells, which are notorious for their slow and unstable electrical output. Through fast-KPFM imaging, we discover regions within a single grain that show a residual Voc response which pervades for ~9 min, likely caused by a slow ion migration process. Finally, to understand how dierent perovskite compositions influence the behavior of the nanoscale electrical response, I utilize KPFM to realize both irreversible and reversible Voc signals. Compiling all these results discussed above, throughout my Ph.D. I have yielded the following contributions: (i) evidence that the photovoltage of polycrystalline solar cell materials varies at the same length scale as the grains composing them, (ii) a nanoscale imaging platform to directly map the Voc with unprecedented spatial resolution, and (iii) a technique to map the real-time voltage response of many perovskite compositions, ultimately indicating that the elements constituting the perovskite cation and halide positions are both directly related to their reversible vs. irreversible electrical nature. From these contributions, I foresee the functional imaging methods developed in this thesis to be widely implemented as a diagnostic tool for the rational design of photovoltaics with enhanced electrical performance and lower cost.
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    DEVELOPMENT OF VAPOR-PHASE DEPOSITED THREE DIMENSIONAL ALL-SOLID-STATE BATTERIES
    (2017) Pearse, Alexander John; Rubloff, Gary; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Thin film solid state batteries (SSBs) are an attractive energy storage technology due to their intrinsic safety, stability, and tailorable form factor. However, as thin film SSBs are typically fabricated only on planar substrates by line-of-sight deposition techniques (e.g. RF sputtering or evaporation), their areal energy storage capacity (< 1 mWh/cm2) and application space is highly limited. Moving to three dimensional architectures provides fundamentally new opportunities in power/energy areal density scaling, but requires a new fabrication process. In this thesis, we describe the development of the first solid state battery chemistry which is grown entirely by atomic layer deposition (ALD), a conformal, vapor-phase deposition technique. We first show the importance of full self-alignment of the active battery layers by measuring and modelling the effects of nonuniform architectures (i.e. does not reduce to a one-dimensional system) on the internal reaction current distribution. By fabricating electrochemical test structures for which generated electrochemical gradients are parallel to the surface, we directly quantify the insertion of lithium into a model cathode material (V2O5) using spatially-resolved x-ray photoelectron spectroscopy (XPS). Using this new technique, we show that poorly electrically contacted high aspect ratio structures show highly nonuniform reaction current distributions, which we describe using an analytical mathematical model incorporating nonlinear Tafel kinetics. A finite-element model incorporating the effects of Li-doping on the local electrical conductivity of V2O5, which was found to be important in describing the observed distributions, is also described. Next, we describe the development of a novel solid state electrolyte, lithium polyphosphazene (LPZ), grown by ALD. We explore the thermal ALD reaction between lithium tert-butoxide and diethyl phosphoramidate, which exhibits self-limiting half-reactions and a growth rate of 0.09 nm/cycle at 300C. The resulting films are primarily characterized by in-situ XPS, AFM, cyclic voltammetry, and impedance spectroscopy. The ALD reaction forms the amorphous product Li2PO2N along with residual hydrocarbon contamination, which is determined to be a promising solid electrolyte with an ionic conductivity of 6.5 × 10-7 S/cm at 35C and wide electrochemical stability window of 0-5.3 V vs. Li/Li+ . The ALD LPZ is integrated into a variety of solid state batteries to test its compatibility with common electrode materials, including LiCoO2 and LiV2O5, as well as flexible substrates. We demonstrate solid state batteries with extraordinarily thin solid state electrolytes, mitigating the moderate ionic conductivity (< 40 nm). Finally, we describe the successful integration of the ALD LPZ into the first all-ALD solid state battery stack, which is conformally deposited onto 3D micromachined silicon substrates and is fabricated entirely at or below 250C. The battery includes ALD current collectors (Ru and TiN), an electrochemically formed LiV2O5 cathode, and a novel ALD tin nitride conversion-type anode. The full cell exhibits a reversible capacity of ~35 μAh cm-2 μmLVO -1 with an average discharge voltage of ~2V. We also describe a novel fabrication process for forming all-ALD battery cells, which is challenging due to ALD’s incompatibility with conventional lithography. By growing the batteries into 3D arrays of varying aspect ratios, we demonstrate upscaling the areal capacity of the battery by approximately one order of magnitude while simultaneously improving the rate performance and round-trip efficiency.
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    Nano-Engineering of Densely Packed Electrochemical Energy Storage Architectures by Atomic Layer Deposition
    (2016) Liu, Chanyuan Liu; Rubloff, Gary W; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Nanostructures are highly attractive for future electrical energy storage devices because they enable large surface area and short ion transport time through thin electrode layers for high power devices. Significant enhancement in power density of batteries has been achieved by nano-engineered structures, particularly anode and cathode nanostructures spatially separated far apart by a porous membrane and/or a defined electrolyte region. A self-aligned nanostructured battery fully confined within a single nanopore presents a powerful platform to determine the rate performance and cyclability limits of nanostructured storage devices. Atomic layer deposition (ALD) has enabled us to create and evaluate such structures, comprised of nanotubular electrodes and electrolyte confined within anodic aluminum oxide (AAO) nanopores. The V2O5- V2O5 symmetric nanopore battery displays exceptional power-energy performance and cyclability when tested as a massively parallel device (~2billion/cm2), each with ~1m3 volume (~1fL). Cycled between 0.2V and 1.8V, this full cell has capacity retention of 95% at 5C rate and 46% at 150C, with more than 1000 charge/discharge cycles. These results demonstrate the promise of ultrasmall, self-aligned/regular, densely packed nanobattery structures as a testbed to study ionics and electrodics at the nanoscale with various geometrical modifications and as a building block for high performance energy storage systems[1, 2]. Further increase of full cell output potential is also demonstrated in asymmetric full cell configurations with various low voltage anode materials. The asymmetric full cell nanopore batteries, comprised of V2O5 as cathode and prelithiated SnO2 or anatase phase TiO2 as anode, with integrated nanotubular metal current collectors underneath each nanotubular storage electrode, also enabled by ALD. By controlling the amount of lithium ion prelithiated into SnO2 anode, we can tune full cell output voltage in the range of 0.3V and 3V. This asymmetric nanopore battery array displays exceptional rate performance and cyclability. When cycled between 1V and 3V, it has capacity retention of approximately 73% at 200C rate compared to 1C, with only 2% capacity loss after more than 500 charge/discharge cycles. With increased full cell output potential, the asymmetric V2O5-SnO2 nanopore battery shows significantly improved energy and power density. This configuration presents a more realistic test - through its asymmetric (vs symmetric) configuration – of performance and cyclability in nanoconfined environment. This dissertation covers (1) Ultra small electrochemical storage platform design and fabrication, (2) Electron and ion transport in nanostructured electrodes inside a half cell configuration, (3) Ion transport between anode and cathode in confined nanochannels in symmetric full cells, (4) Scale up energy and power density with geometry optimization and low voltage anode materials in asymmetric full cell configurations. As a supplement, selective growth of ALD to improve graphene conductance will also be discussed[3]. References: 1. Liu, C., et al., (Invited) A Rational Design for Batteries at Nanoscale by Atomic Layer Deposition. ECS Transactions, 2015. 69(7): p. 23-30. 2. Liu, C.Y., et al., An all-in-one nanopore battery array. Nature Nanotechnology, 2014. 9(12): p. 1031-1039. 3. Liu, C., et al., Improving Graphene Conductivity through Selective Atomic Layer Deposition. ECS Transactions, 2015. 69(7): p. 133-138.
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    MANIPULATION OF IONS, ELECTRONS, AND PHOTONS IN 2D MATERIALS BY ION INTERCALATION
    (2016) Wan, Jiayu Wan; Hu, Liangbing; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    2D materials have attracted tremendous attention due to their unique physical and chemical properties since the discovery of graphene. Despite these intrinsic properties, various modification methods have been applied to 2D materials that yield even more exciting results. Among all modification methods, the intercalation of 2D materials provides the highest possible doping and/or phase change to the pristine 2D materials. This doping effect highly modifies 2D materials, with extraordinary electrical transport as well as optical, thermal, magnetic, and catalytic properties, which are advantageous for optoelectronics, superconductors, thermoelectronics, catalysis and energy storage applications. To study the property changes of 2D materials, we designed and built a planar nanobattery that allows electrochemical ion intercalation in 2D materials. More importantly, this planar nanobattery enables characterization of electrical, optical and structural properties of 2D materials in situ and real time upon ion intercalation. With this device, we successfully intercalated Li-ions into few layer graphene (FLG) and ultrathin graphite, heavily dopes the graphene to 0.6 x 10^15 /cm2, which simultaneously increased its conductivity and transmittance in the visible range. The intercalated LiC6 single crystallite achieved extraordinary optoelectronic properties, in which an eight-layered Li intercalated FLG achieved transmittance of 91.7% (at 550 nm) and sheet resistance of 3 ohm/sq. We extend the research to obtain scalable, printable graphene based transparent conductors with ion intercalation. Surfactant free, printed reduced graphene oxide transparent conductor thin film with Na-ion intercalation is obtained with transmittance of 79% and sheet resistance of 300 ohm/sq (at 550 nm). The figure of merit is calculated as the best pure rGO based transparent conductors. We further improved the tunability of the reduced graphene oxide film by using two layers of CNT films to sandwich it. The tunable range of rGO film is demonstrated from 0.9 um to 10 um in wavelength. Other ions such as K-ion is also studied of its intercalation chemistry and optical properties in graphitic materials. We also used the in situ characterization tools to understand the fundamental properties and improve the performance of battery electrode materials. We investigated the Na-ion interaction with rGO by in situ Transmission electron microscopy (TEM). For the first time, we observed reversible Na metal cluster (with diameter larger than 10 nm) deposition on rGO surface, which we evidenced with atom-resolved HRTEM image of Na metal and electron diffraction pattern. This discovery leads to a porous reduced graphene oxide sodium ion battery anode with record high reversible specific capacity around 450 mAh/g at 25mA/g, a high rate performance of 200 mAh/g at 250 mA/g, and stable cycling performance up to 750 cycles. In addition, direct observation of irreversible formation of Na2O on rGO unveils the origin of commonly observed low 1st Columbic Efficiency of rGO containing electrodes. Another example for in situ characterization for battery electrode is using the planar nanobattery for 2D MoS2 crystallite. Planar nanobattery allows the intrinsic electrical conductivity measurement with single crystalline 2D battery electrode upon ion intercalation and deintercalation process, which is lacking in conventional battery characterization techniques. We discovered that with a “rapid-charging” process at the first cycle, the lithiated MoS2 undergoes a drastic resistance decrease, which in a regular lithiation process, the resistance always increases after lithiation at its final stage. This discovery leads to a 2- fold increase in specific capacity with with rapid first lithiated MoS2 composite electrode material, compare with the regular first lithiated MoS2 composite electrode material, at current density of 250 mA/g.