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Li, Yiju

Publications and source records attributed to Li, Yiju.

13 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

3D Wettable Framework for Dendrite-Free Alkali Metal Anodes

The infinite volume change and dendritic behavior in alkali metal anodes lead to low Coulombic efficiency and short-circuit issues that significantly hamper renewed efforts at commercialization. In this study, a dendrite-free alkali metal anode, made by thermally preloading molten Li or Na into a 3D framework with high alkali wettability, is reported. In the mechanically robust 3D framework, carbon fiber (CF) serves as an electrical highway that provides fast charge transfer for the redox reaction. Through a facile solution-based process, a SnO 2 coating is introduced to modify the poor wetting behavior of the carbon framework and drastically improve both the electrochemical performance and reliability. The kinetic barrier to adhesion of molten alkali metals on the CF framework is eliminated by the mixed reaction with SnO 2 . The growth of dendrites is effectively repressed under the decreased local current density of the 3D framework. In full-cell configurations with LiFePO 4 cathodes, the Li–CF electrode shows reduced polarization and 90% capacity retention after 500 cycles in traditional carbonate electrolyte. Comparable improvements are also observed in 3D electrodes for Na metal batteries. These findings on a stable 3D carbon framework with improved wetting behavior provide significant practical implications for achieving safe and commercially viable alkali metal anodes.

25 ENERGY STORAGE↗
DOE OSTI2017

Textile Inspired Lithium-Oxygen Battery Cathode with Decoupled Oxygen and Electrolyte Pathways

The lithium–air (Li–O 2 ) battery has been deemed one of the most promising next–generation energy–storage devices due to its ultrahigh energy density. However, in conventional porous carbon–air cathodes, the oxygen gas and electrolyte often compete for transport pathways, which limit battery performance. Here, a novel textile–based air cathode is developed with a triple–phase structure to improve overall battery performance. The hierarchical structure of the conductive textile network leads to decoupled pathways for oxygen gas and electrolyte: oxygen flows through the woven mesh while the electrolyte diffuses along the textile fibers. Due to noncompetitive transport, the textile–based Li–O 2 cathode exhibits a high discharge capacity of 8.6 mAh cm –2 , a low overpotential of 1.15 V, and stable operation exceeding 50 cycles. The textile–based structure can be applied to a range of applications (fuel cells, water splitting, and redox flow batteries) that involve multiple phase reactions. In conclusion, the reported decoupled transport pathway design also spurs potential toward flexible/wearable Li–O 2 batteries.

25 ENERGY STORAGE↗
DOE OSTI2017

Hierarchically Porous, Ultrathick, “Breathable” Wood-Derived Cathode for Lithium-Oxygen Batteries

Here, a hierarchically porous and ultrathick “breathable” wood-based cathode for high-performance Li-O 2 batteries is developed. The 3D carbon matrix obtained from the carbonized and activated wood (denoted as CA-wood) serves as a superconductive current collector and an ideal porous host for accommodating catalysts. The ruthenium (Ru) nanoparticles are uniformly anchored on the porous wall of the aligned microchannels (denoted as CA-wood/Ru). The aligned open microchannels inside the carbon matrix contribute to unimpeded oxygen gas diffusion. Furthermore, the hierarchical pores on the microchannel walls can be facilely impregnated by electrolyte, forming a continuous supply of electrolyte. As a result, numerous ideal triphase active sites are formed where electrolyte, oxygen, and catalyst accumulate on the porous walls of microchannels. Benefiting from the numerous well-balanced triple-phase active sites, the assembled Li-O 2 battery with the CA-wood/Ru cathode (thickness: ≈700 µm) shows a high specific area capacity of 8.58 mA h cm -2 at 0.1 mA cm -2 . Also, the areal capacity can be further increased to 56.0 mA h cm -2 by using an ultrathick CA-wood/Ru cathode with a thickness of ≈3.4 mm. The facile ultrathick wood-based cathodes can be applied to other cathodes to achieve a super high areal capacity without sacrificing the electrochemical performance.

25 ENERGY STORAGE↗
DOE OSTI2017

Stabilizing the Garnet Solid-Electrolyte/Polysulfide Interface in Li–S Batteries

Chemical and physical short circuits are the main challenges faced by lithium batteries which compromise battery performance and safety. At the cathode, solvation of active cathode materials and shuttling of unwanted chemical species in the liquid electrolyte result in “chemical short circuits”, which deteriorate the Li metal electrode and limit the deployment of new cathode materials, such as high voltage cathodes, sulfur, and air/O 2 . In Li–S batteries, the repeated shuttling of polysulfides between electrodes constantly corrodes the Li metal anode and the loss of active material will result in low Coulombic efficiency. At the anode, Li dendrite penetration through the separator causes internal electronic, or “physical”, short circuits. Finally, several strategies have been reported to prevent chemical and physical short circuits by using a cathode host, small sulfur molecules, modified separators, or electrolyte additives to alleviate sulfur materials diffusion and shuttling, and finding ways to delay, confine, or block Li dendrites to extend the cycling lifetime and avoid thermal runaway in lithium metal batteries.

25 ENERGY STORAGE↗
DOE OSTI2017

Highly Conductive, Lightweight, Low-Tortuosity Carbon Frameworks as Ultrathick 3D Current Collectors

The growing demand for advanced energy storage techniques and devices has driven the energy storage market to strive for higher performance, longer cycling life, and better safety. Thick electrode design enabling more electroactive materials has the potential to significantly improve the energy density on device level yet faces major challenges of slow ion transport and high deformability. In this work, inspired by natural wood materials with aligned channels along the tree growth direction, a highly conductive, lightweight, and low-tortuosity carbon framework (CF) directly carbonized from natural wood as an ultrathick 3D current collector is demonstrated. Benefiting from the uniqueness of the multichanneled CF, an ultrathick 3D electrode of lithium iron phosphate filled carbon framework with a large thickness of 800 µm and active material mass loading of 60 mg cm -2 delivers a rational capacity of 7.6 mAh cm -2 (95 Ah L -1 based on volume), long cycling life, and lower deformability with enhanced mechanical properties. This work presents a design concept for thick electrode toward high performance energy storage devices that are not limited to lithium-ion batteries.

09 BIOMASS FUELS↗
DOE OSTI2017

Three-dimensional bilayer garnet solid electrolyte based high energy density lithium metal–sulfur batteries

To simultaneously address the challenges of chemical/physical short circuits and electrode volume variation, we demonstrate in this paper a three-dimensional (3D) bilayer garnet solid-state electrolyte framework for advanced Li metal batteries. The dense layer is reduced in thickness to a few microns and still retains good mechanical stability, thereby enabling the safe use of Li metal anodes. The thick porous layer acts as a mechanical support for the thin dense layer which serves as a host for high loading of cathode materials and provides pathways for continuous ion transport. Results show that the integrated sulfur cathode loading can reach >7 mg cm -2 while the proposed hybrid Li–S battery exhibits a high initial coulombic efficiency (>99.8%) and high average coulombic efficiency (>99%) during the subsequent cycles. Finally, this electrolyte framework represents a promising strategy to revolutionize Li-metal batteries by transitioning to all-solid-state batteries and can be extended to other cathode materials.

25 ENERGY STORAGE↗
DOE OSTI2017

Encapsulation of Metallic Na in an Electrically Conductive Host with Porous Channels as a Highly Stable Na Metal Anode

Room-temperature Na ion batteries (NIBs) have attracted great attention because of the widely available, abundant sodium resources and potentially low cost. Currently, the challenge of the NIB development is due primarily to the lack of a high-performance anode, while the Na metal anode holds great promise considering its highest specific capacity of 1165 mA h/g and lowest anodic potential. However, an uneven deposit, relatively infinite volume change, and dendritic growth upon plating/stripping cycles cause a low Coulombic efficiency, poor cycling performance, and severe safety concerns. In this study, a stable Na carbonized wood (Na–wood) composite anode was fabricated via a rapid melt infusion (about 5 s) into channels of carbonized wood by capillary action. The channels function as a high-surface-area, conductive, mechanically stable skeleton, which lowers the effective current density, ensures a uniform Na nucleation, and restricts the volume change over cycles. As a result, the Na–wood composite anode exhibited flat plating/stripping profiles with smaller overpotentials and stable cycling performance over 500 h at 1.0 mA/cm 2 in a common carbonate electrolyte system. Finally, in sharp comparison, the planar Na metal electrode showed a much shorter cycle life of 100 h under the same test conditions.

09 BIOMASS FUELS↗
DOE OSTI2017

Reducing Interfacial Resistance between Garnet-Structured Solid-State Electrolyte and Li-Metal Anode by a Germanium Layer

Substantial efforts are underway to develop all–solid–state Li batteries (SSLiBs) toward high safety, high power density, and high energy density. Garnet–structured solid–state electrolyte exhibits great promise for SSLiBs owing to its high Li–ion conductivity, wide potential window, and sufficient thermal/chemical stability. A major challenge of garnet is that the contact between the garnet and the Li–metal anodes is poor due to the rigidity of the garnet, which leads to limited active sites and large interfacial resistance. Furthermore, this study proposes a new methodology for reducing the garnet/Li–metal interfacial resistance by depositing a thin germanium (Ge) (20 nm) layer on garnet. By applying this approach, the garnet/Li–metal interfacial resistance decreases from ≈900 to ≈115 Ω cm 2 due to an alloying reaction between the Li metal and the Ge. In agreement with experiments, first–principles calculation confirms the good stability and improved wetting at the interface between the lithiated Ge layer and garnet. In this way, this unique Ge modification technique enables a stable cycling performance of a full cell of lithium metal, garnet electrolyte, and LiFePO 4 cathode at room temperature.

25 ENERGY STORAGE↗
DOE OSTI2016

Flexible, solid-state, ion-conducting membrane with 3D garnet nanofiber networks for lithium batteries

Beyond state-of-the-art lithium-ion battery (LIB) technology with metallic lithium anodes to replace conventional ion intercalation anode materials is highly desirable because of lithium’s highest specific capacity (3,860 mA/g) and lowest negative electrochemical potential (~3.040 V vs. the standard hydrogen electrode). In this work, we report for the first time, to our knowledge, a 3D lithium-ion–conducting ceramic network based on garnet-type Li 6.4 La 3 Zr 2 Al 0.2 O 12 (LLZO) lithium-ion conductor to provide continuous Li + transfer channels in a polyethylene oxide (PEO)-based composite. This composite structure further provides structural reinforcement to enhance the mechanical properties of the polymer matrix. The flexible solid-state electrolyte composite membrane exhibited an ionic conductivity of 2.5 × 10 -4 S/cm at room temperature. The membrane can effectively block dendrites in a symmetric Li | electrolyte | Li cell during repeated lithium stripping/plating at room temperature, with a current density of 0.2 mA/cm 2 for around 500 h and a current density of 0.5 mA/cm 2 for over 300 h. Finally, these results provide an all solid ion-conducting membrane that can be applied to flexible LIBs and other electrochemical energy storage systems, such as lithium–sulfur batteries.

25 ENERGY STORAGE↗