Mun Sek Kim

Stanford University | SU · Department of Chemical Engineering

Designing a stable solid–electrolyte interphase on a Li anode is imperative to developing reliable Li metal batteries. Herein, we report a suspension electrolyte design that modifies the Li+ solvation environment in liquid electrolytes and creates inorganic-rich solid–electrolyte interphases on Li. Li2O nanoparticles suspended in liquid electrolyte...

Inorganic-rich solid-electrolyte interphases (SEIs) on Li metal anodes improve the electrochemical performance of Li metal batteries (LMBs). Therefore, a fundamental understanding of the roles played by essential inorganic compounds in SEIs is critical to realizing and developing high-performance LMBs. Among the prevalent SEI inorganic compounds ob...

Practical lithium metal batteries require full and reversible utilization of thin metallic Li anodes. This introduces a fundamental challenge concerning how to create solid-electrolyte interphases (SEIs) that are able to regulate interfacial transport and protect the reactive metal, without adding appreciably to the cell mass. Here, we report on ph...

Rechargeable electrochemical cells with metallic anodes are of increasing scientific and technological interest. The complex composition, poorly defined morphology, heterogeneous chemistry, and unpredictable mechanics of interphases formed spontaneously on the anodes are often examined but rarely controlled. Here, we couple computational studies wi...

Zn/MnO2 batteries, driven by a dual deposition reaction, are a prominent avenue for achieving high energy density in aqueous systems. Introducing an initially dual-electrode-free (anode/cathode) configuration can further boost energy density to over 200 Wh kg⁻¹, but with limited cycle life due to the poor reversibility of Zn/MnO2 deposition and str...

The Li-S battery is a promising next-generation battery chemistry that offers high energy density and low cost. The Li-S battery has a unique chemistry with intermediate sulphur species readily solvated in electrolytes, and understanding their implications is important from both practical and fundamental perspectives. In this study, we utilise the...

Rechargeable Li-metal batteries have the potential to more than double the specific energy of the state-of-the-art rechargeable Li-ion batteries, making Li-metal batteries a prime candidate for next-generation high-energy battery technology1–3. However, current Li-metal batteries suffer from fast cycle degradation compared with their Li-ion battery...

The composition of the solid electrolyte interphase (SEI) plays an important role in controlling Li-electrolyte reactions, but the underlying cause of SEI composition differences between electrolytes remains unclear. Many studies correlate SEI composition with the bulk solvation of Li ions in the electrolyte, but this correlation does not fully cap...

Electrolyte engineering is crucial for improving battery performance, particularly for lithium metal batteries. Recent advances in electrolytes have greatly improved cyclability by enhancing electrochemical stability at the electrode interfaces, but concurrently achieving high ionic conductivity has remained challenging. Here we report an electroly...

At >95% Coulombic efficiencies, most of the capacity loss for Li metal anodes (LMAs) is through the formation and growth of the solid electrolyte interphase (SEI). However, the mechanism through which this happens remains unclear. One property of the SEI that directly affects its formation and growth is the SEI's solubility in the electrolyte. Here...

Electrolyte engineering is crucial for improving battery performance, particularly for lithium metal batteries. Recent advances in electrolytes have greatly improved cyclability by enhancing electrochemical stability at the electrode interfaces, but concurrently achieving high ionic conductivity has remained challenging. Here we report an electroly...

Improving Coulombic efficiency (CE) is key to the adoption of high energy density lithium metal batteries. Liquid electrolyte engineering has emerged as a promising strategy for improving the CE of lithium metal batteries, but its complexity renders the performance prediction and design of electrolytes challenging. Here, we develop machine learning...

Poor fast-charge capabilities limit the usage of rechargeable Li metal anodes. Understanding the connection between charging rate, electroplating mechanism, and Li morphology could enable fast-charging solutions. Here, we develop a combined electroanalytical and nanoscale characterization approach to resolve the current-dependent regimes of Li plat...

Electrolyte engineering is a critical approach to improve battery performance, particularly for lithium metal batteries. In this work, we introduce the concept of high entropy electrolytes (HEEs) that achieve improved ionic conductivity while maintaining excellent electrochemical stability. We find that increasing the molecular diversity and concom...

Electrolyte engineering improved cycling of Li metal batteries and anode-free cells at low current densities; however, high-rate capability and tuning of ionic conduction in electrolytes are desirable yet less-studied. Here, we design and synthesize a family of fluorinated-1,2-diethoxyethanes as electrolyte solvents. The position and amount of F at...

Lithium metal (Li) have received growing attention for use in rechargeable electrochemical cells with various types of cathodes owing to their potential as high-capacity anodes. However, continuous electrochemical reactions and...

Rational approaches for achieving fine control of the electrodeposition morphology of Li are required to create commercially-relevant rechargeable Li metal batteries.

Lithium-sulfur battery is garnering much of attention due to its high energy densities, low-cost active material of sulfur and variety of applications in portable electronics. High integrity and consistent qualities of the large-scale sulfur cathode with high energy have to be ensured to construct reliable and practical lithium-sulfur batteries tha...

Lithium-sulfur (Li–S) batteries are attracting substantial attention because of their high energy densities and potential applications in portable electronics. However, an intrinsic property of Li–S systems, i.e., the solubility of lithium polysulfides (LiPS), hinders the commercialization of Li–S batteries. Herein, a new material, i.e., carbon nit...

The α-Fe2O3@nitrogen doped carbon (as donated α-Fe2O3@NC) composites derived from green microalgae was synthesized using one-pot spray pyrolysis, which showed a high discharge capacity of 1281.5 mAh g⁻¹ at 100 mA g⁻¹ as anode materials for lithium ion storage. They also provided good rate performance in a range of 200 mA g⁻¹–1000 mA g⁻¹, and mainta...

Lithium metal is among the most sought-after anode chemistries for next-generation electrical energy storage due to its high theoretical capacity (3860 mAh g⁻¹) and low reduction potential (− 3.04 V vs S.H.E.). To realize its promise, reactive Li anodes must be paired with high-energy conversion cathodes, such as sulfur or oxygen. Chemical and phys...

Multifunctional nanoparticle coatings created in a new Langmuir-Blodgett-like process are used to design high-performance membranes for regulating transport of ions and molecules. In article 1600450, the effectiveness of such membranes in Lithium-sulfur batteries is demonstrated by Lynden A. Archer and co-workers, where coatings based on metal oxid...

A facile and binder-free coating method, termed Langmuir–Blodgett–Scooping, is reported. The method takes advantage of Marangoni stresses and self-assembly to rapidly create functional coating films of various nanomaterials, with single-particle thickness resolution, at an air–water interface (left). Transfer of the film to a conventional separator...

A rechargeable lithium metal battery (LMB), which uses metallic lithium at the anode, is among the most promising technologies for next generation electrochemical energy storage devices due to its high energy density, particularly when Li is paired with energetic conversion cathodes such as sulfur, oxygen/air, and carbon dioxide. Practical LMBs in...

The Langmuir-Blodgett (LB) technique is a powerful, widely used method for preparing coatings of amphiphilic molecules at air/water interfaces with thickness control down to a single molecule. Here we report two new LB techniques designed to create ordered, multifunctional nanoparticle films on any non-reactive support. The methods utilize Marangon...

The rechargeable Lithium-Sulfur (Li-S) battery is an attractive platform for high-energy, low-cost electrochemical energy storage. Practical Li-S cells are limited by several fundamental issues, such as the low conductivity of sulfur and its reduction compounds with Li and the dissolution of long-chain lithium polysulfides (LiPS) into the electroly...

Three-dimensional ultrathin graphitic foams are grown via chemical vapor deposition on templated Ni scaffolds, which are electrodeposited on a close-packed array of polystyrene microspheres. After removal of the Ni, free-standing foams composed of conjoined hollow ultrathin graphite spheres are obtained. Control over the pore size and foam thicknes...

This paper reports a simple and scalable technique for the fabrication of flexible micro-supercapacitors. The supercapacitor electrodes are synthesized via the pyrolysis of patterned photoresist on a SiO2/Si substrate. The electrodes can then be moved to flexible substrates through a simple transfer process. The fabricated devices show excellent en...

Carbon-based supercapacitors typically have low energy density but high cycle lifetime relative to batteries. Surface functionalization can significantly increase charge storage through reversible faradaic reactions at the electrode/electrolyte interface, a phenomenon known as pseudocapacitance. However, pseudocapacitive reactions, if not completel...

All solid-state micro-supercapacitors are an attractive solution for integrated, on-chip energy storage. Photoresist-derived porous carbon, which has a high specific capacitance and good conductivity, is used as an electrode material in conjunction with an ionogel electrolyte to fabricate a high energy density supercapacitor. Fabricated devices yie...

The effectiveness of silicon carbide (SiC) nanowires (NW) as electrode material for micro-supercapacitors has been investigated. SiC NWs are grown on a SiC thin film coated with a thin Ni catalyst layer via a chemical vapor deposition route at 950 °C. A specific capacitance in the range of ∼240 μF cm−2 is demonstrated, which is comparable to the va...

Supercapacitors have attracted much attention for energy storage applications, owing to their long cycle life and high power densities. We report on the growth of silicon carbide (SiC) nanowires (NW) and the evaluation of their performance as electrode material for micro-supercapacitors. Their specific capacitance has been studied as a function of...