Yun Jung Lee

Fabricating Genetically Engineered High-Power Lithium Ion Batteries Using Multiple Virus Genes

Viral Battery In developing materials for batteries, there is a trade-off between charge capacity, conductivity, and chemical stability. Nanostructured materials improve the conductivity for some resistive materials, but fabricating stable materials at nanometer-length scales is difficult. Harnessing their knowledge of viruses as toolkits for materials fabrication, Lee et al. (p. 1051; published online 2 April) modified two genes in the filamentous bacteriophage M13 to produce a virus with an affinity for nucleating amorphous iron phosphate along its length and for attaching carbon nanotubes at one of the ends. In nanostructured form, the amorphous iron phosphate produced a useful cathode material, while the carbon nanotubes formed a percolating network that significantly enhanced conductivity. A genetically modified virus is used to form an efficient cathodic battery material. Development of materials that deliver more energy at high rates is important for high-power applications, including portable electronic devices and hybrid electric vehicles. For lithium-ion (Li+) batteries, reducing material dimensions can boost Li+ ion and electron transfer in nanostructured electrodes. By manipulating two genes, we equipped viruses with peptide groups having affinity for single-walled carbon nanotubes (SWNTs) on one end and peptides capable of nucleating amorphous iron phosphate(a-FePO4) fused to the viral major coat protein. The virus clone with the greatest affinity toward SWNTs enabled power performance of a-FePO4 comparable to that of crystalline lithium iron phosphate (c-LiFePO4) and showed excellent capacity retention upon cycling at 1C. This environmentally benign low-temperature biological scaffold could facilitate fabrication of electrodes from materials previously excluded because of extremely low electronic conductivity.

Peptide-mediated reduction of silver ions on engineered biological scaffolds.

Herein we report the spontaneous reduction of silver ions into nanostructures by yeast surface-displayed glutamic acid (E(6)) and aspartic acid (D(6)) peptides. Light spectroscopy and electron microscopy reveal that silver ions are photoreduced in the presence of the polycarboxylic acid-containing peptides and ambient light, with an increase in reduction capability of E(6) expressing yeast over D(6) yeast. The importance of tethering peptides to a biological scaffold was inferred by observing the reduced particle forming capacity of soluble peptides with respect to corresponding yeast-displayed peptides. This principle was further extended to the M13 virus for fabrication of crystalline silver nanowires. These insights into the spontaneous reduction of metal ions on biological scaffolds should help further the formation of novel nanomaterials in biological systems.

Stamped microbattery electrodes based on self-assembled M13 viruses.

The fabrication and spatial positioning of electrodes are becoming central issues in battery technology because of emerging needs for small scale power sources, including those embedded in flexible substrates and textiles. More generally, novel electrode positioning methods could enable the use of nanostructured electrodes and multidimensional architectures in new battery designs having improved electrochemical performance. Here, we demonstrate the synergistic use of biological and nonbiological assembly methods for fabricating and positioning small battery components that may enable high performance microbatteries with complex architectures. A self-assembled layer of virus-templated cobalt oxide nanowires serving as the active anode material in the battery anode was formed on top of microscale islands of polyelectrolyte multilayers serving as the battery electrolyte, and this assembly was stamped onto platinum microband current collectors. The resulting electrode arrays exhibit full electrochemical functionality. This versatile approach for fabricating and positioning electrodes may provide greater flexibility for implementing advanced battery designs such as those with interdigitated microelectrodes or 3D architectures.

Biologically Activated Noble Metal Alloys at the Nanoscale: For Lithium Ion Battery Anodes

We report the synthesis and electrochemical activity of gold and silver noble metals and their alloy nanowires using multiple virus clones as anode materials for lithium ion batteries. Using two clones, one for specificity (p8#9 virus) and one versatility (E4 virus), noble metal nanowires of high-aspect ratio with diameters below 50 nm were successfully synthesized with control over particle sizes, morphologies, and compositions. The biologically derived noble metal alloy nanowires showed electrochemical activities toward lithium even when the electrodes were prepared from bulk powder forms. The improvement in capacity retention was accomplished by alloy formation and surface stabilization. Although the cost of noble metals renders them a less ideal choice for lithium ion batteries, these noble metal/alloy nanowires serve as great model systems to study electrochemically induced transformation at the nanoscale. Given the demonstration of the electrochemical activity of noble metal alloy nanowires with various compositions, the M13 biological toolkit extended its utility for the study on the basic electrochemical property of materials.

Graphene sheets stabilized on genetically engineered M13 viral templates as conducting frameworks for hybrid energy-storage materials.

Utilization of the material-specific peptide-substrate interactions of M13 virus broadens colloidal stability window of graphene. The homogeneous distribution of graphene is maintained in weak acids and increased ionic strengths by complexing with virus. This graphene/virus conducting template is utilized in the synthesis of energy-storage materials to increase the conductivity of the composite electrode. Successful formation of the hybrid biological template is demonstrated by the mineralization of bismuth oxyfluoride as a cathode material for lithium-ion batteries, with increased loading and improved electronic conductivity.

Protein/peptide based nanomaterials for energy application.

Biological systems have developed unique capabilities to generate, harness and store energy in efficient ways. In recent years, biologically inspired approaches have been introduced as a new approach to find breakthroughs for next generation energy devices and storage. Of particular interest are efforts to translate biological principles directly into synthetic energy systems. In this review, we focus on the use of proteins and protein mimicry for energy applications. We highlight the major advances and results achieved with proteins as new concept energy devices.

Bimetallic Metal–Organic Frameworks as Efficient Cathode Catalysts for Li–O2 Batteries

Metal-organic frameworks (MOFs) have the potential to improve the electrochemical performance of Li-O2 batteries with high O2 accessibility and catalytic activity of the open metal sites. Here, we explored bimetallic MnCo-MOF-74 as a cathode catalyst in Li-O2 batteries. MnCo-MOF-74 was synthesized with the Mn to Co ratio of 1:4 by a simple hydrothermal reaction. Compared to monometallic Mn-MOF-74 and Co-MOF-74 with only single catalytic activity for LiOH formation or oxygen evolution reactions, bimetallic MnCo-MOF-74 demonstrated a capability to facilitate improved reversibility and efficiency during both discharge and charge cycles. Benefitting from the porous structure of the MOF as well as the complementary contribution from both Mn- and Co-metal clusters, MnCo-MOF-74 outperformed Mn-MOF-74 and Co-MOF-74. A high full discharge capacity of 11 150 mAh g-1 at 200 mA g-1 was achieved in MnCo-MOF-74. During the cycling test, MnCo-MOF-74 stably delivered a limited discharge capacity of 1000 mAh g-1 for 44 cycles at 200 mA g-1, which is remarkably longer than those of carbon black, Mn-MOF-74, and Co-MOF-74 with cycle lives of 8, 22, and 18 cycles, respectively.

Fibrous all-in-one monolith electrodes with a biological gluing layer and a membrane shell for weavable lithium-ion batteries

The increasing demand for wearable devices ultimately requires the development of energy storage devices with wide structural versatility, lightweight and high energy density. Although various flexible batteries have been developed based on two-dimensional and one-dimensional platforms, truly weavable batteries with high capacity and elongation capability have not been materialized yet. Herein, we report weavable lithium ion batteries (LIBs) with high capacity by developing fibrous all-in-one electrode threads based on nanosized hybrid active layers with a biological gluing inner layer and a membrane shell. The thread consists of four distinct concentric structures, a carbon fiber core as a current collector, a conductive biological gluing layer, nanohybrid active materials, and a porous membrane layer. Nanosized LiFePO4/C-rGO and Li4Ti5O12/rGO are used for cathode and anode threads, respectively. This unique all-in-one structure combined with an inline coating approach ensures flexibility and mechanical stability with a high linear capacity of 1.6 mA h cm−1. These features all together allow for various assembly schemes such as twisting and hierarchical weaving, enabling fabric LIBs to show 50% elongation via encoded structural deformation.

Flexible Lithium-Ion Batteries with High Areal Capacity Enabled by Smart Conductive Textiles

Increasing demand for flexible devices in various applications, such as smart watches, healthcare, and military applications, requires the development of flexible energy-storage devices, such as lithium-ion batteries (LIBs) with high flexibility and capacity. However, it is difficult to ensure high capacity and high flexibility simultaneously through conventional electrode preparation processes. Herein, smart conductive textiles are employed as current collectors for flexible LIBs owing to their inherent flexibility, fibrous network, rough surface for better adhesion, and electrical conductivity. Conductivity and flexibility are further enhanced by nanosizing lithium titanate oxide (LTO) and lithium iron phosphate (LFP) active materials, and hybridizing them with a flexible 2D graphene template. The resulting LTO/LFP full cells demonstrate high areal capacity and flexibility with tolerance to mechanical fatigue. The battery achieves a capacity of 1.2 mA h cm-2 while showing excellent flexibility. The cells demonstrate stable open circuit voltage retention under repeated flexing for 1000 times at a bending radius of 10 mm. The discharge capacity of the unflexed battery is retained in cells subjected to bending for 100 times at bending radii of 30, 20, and 10 mm, respectively, confirming that the suggested electrode configuration successfully prevents structural damage (delamination or cracking) upon repeated deformation.

Graphene Oxide Sieving Membrane for Improved Cycle Life in High-Efficiency Redox-Mediated Li-O2 batteries

As soluble catalysts, redox-mediators (RMs) endow mobility to catalysts for unconstrained access to tethered solid discharge products, lowering the energy barrier for Li2 O2 formation/decomposition; however, this desired mobility is accompanied by the undesirable side effect of RM migration to the Li metal anode. The reaction between RMs and Li metal degrades both the Li metal and the RMs, leading to cell deterioration within a few cycles. To extend the cycle life of redox-mediated Li-O2 batteries, herein graphene oxide (GO) membranes are reported as RM-blocking separators. It is revealed that the size of GO nanochannels is narrow enough to reject 5,10-dihydro-5,10-dimethylphenazine (DMPZ) while selectively allowing the transport of smaller Li+ ions. The negative surface charges of GO further repel negative ions via Donnan exclusion, greatly improving the lithium ion transference number. The Li-O2 cells with GO membranes efficiently harness the redox-mediation activity of DMPZ for improved performance, achieving energy efficiency of above 80% for more than 25 cycles, and 90% for 78 cycles when the capacity limits were 0.75 and 0.5 mAh cm-2 , respectively. Considering the facile preparation of GO membranes, RM-sieving GO membranes can be cost-effective and processable functional separators in Li-O2 batteries.