Interface Engineering with Nonsacrificial Perfluorinated-Anion Additives for Boosting the Kinetics of Lithium-Ion Batteries.

Though lithium-ion batteries (LIBs) have seen a meteoric rise in worldwide deployment over the last decade, they should be further advanced in constant demand of higher rate capability and wider temperature adaptability. A solid electrolyte interphase (SEI) is the essential part of LIBs, determining the charge-discharge performance and degradation behavior. Herein, improvement of the SEI properties is achieved by regulating the electrochemical double layer structure with a nonsacrificial electrolyte additive, that is, lithium nonafluoro-1-butanesulfonate. The anion adsorption of the additive affects the decomposition behavior of other additive and solvent species, and the generated SEI at the graphite electrode becomes thinner and more uniform, leading to decreased impedance and finally resulting in improved energy efficiency, power capability, and fast charging performance of the graphite/NCM811 cell. Furthermore, the low-temperature cycleability at -20 °C is considerably enhanced with no dendritic Li metal deposition at the negative electrode surface. A mechanistic study on the interfacial phenomena and the effect is carried out by using various theoretical and experimental methods, such as density functional theory calculations, electrochemical quartz crystal microbalance, and transmission electron microscopy. Consequently, the approach of SEI modification with the nonsacrificial electrolyte additive can be one of the effective ways to advance LIB technology in future.

Interphasial Engineering via Individual Moiety Functionalized Organosilane Single-Molecule for Extreme Quick Rechargeable SiO/NCM811 Lithium-Ion Batteries.

The individual moiety-functionalized organosilane single molecule, that is, 1,1,1,5,5,5-hexamethyl-3-[(trimethylsilyl)oxy]-3-vinyltrisiloxane (TMSV), is investigated as an electrolyte additive for a less charge-consuming and viscoelastic solid electrolyte interphase (SEI) forming agent, finally accomplishing extremely quick (6 min) rechargeable SiO/NCM811 lithium-ion batteries. The moiety of the vinyl group serves with a poly(ethylene oxide)-like viscoelastic SEI film on the SiO electrode, which provides a physicochemically stable interphase during long-term cycling. The increase of DC-iR due to electrolyte decomposition on the continuously exposed SiO surface with cycling is inhibited by the alternated SEI composition. Degradation of bulk electrolyte solution caused by thermal decomposition of the LiPF6 salt is also suppressed by the trimethylsilyl moiety in the TMSV additive, which scavenges HF. Owing to the multifunctionality of TMSV, the cycle performance of laminated pouch full cells comprising high-nickel-contented NCM811 positive electrode and SiO-enriched negative electrode is significantly improved at both room and elevated temperatures. Furthermore, the 6 min quick recharging cycle performance is also enhanced by the TMSV additive.

Self-Formulated Na-Based Dual-Ion Battery Using Nonflammable SO2 -Based Inorganic Liquid Electrolyte.

Sodium secondary batteries have gained much attention as alternative power sources to replace lithium secondary batteries. However, some technical issues must be solved to ensure their success. Here, a highly safe and cost-effective Na-based dual-ion battery system employing self-formulated CuCl cathode material starting from a mixture of Cu and NaCl in conjunction with a nonflammable NaAlCl4 ·2SO2 inorganic liquid electrolyte is demonstrated. It is found that CuCl is spontaneously formed by redox coupling of Cu/Cu(I) and SO2 /SO2 - anion radical. In the proposed battery, Na+ and Cl- are employed as energy carriers for the anode and cathode, respectively, and it is further demonstrated that the Na-metal-free battery configuration is possible using a hard carbon anode. Owing to the use of cheap electrode materials and a highly conductive and safe electrolyte, the proposed batteries deserve to be regarded as a promising approach for next-generation Na rechargeable batteries.

Sulfide-Compatible Conductive and Adhesive Glue-Like Interphase Engineering for Sheet-Type All-Solid-State Battery.

An all-solid-state lithium battery based on a sulfide electrolyte is one of the most promising next-generation energy storage systems. However, the high interfacial impedance, particularly due to the internal pores in the electrode or electrolyte layers, is the major limiting factor to the development of sheet-type all-solid-state batteries. In this study, a low-resistance integrated all-solid composite electrode is developed using a hybrid of a pyrrolidinium-based ionic liquid and a polyethylene oxide polymer with lithium salt as a multifunctional interphase material, which is engineered to be compatible with the sulfide electrolyte as well as the fabrication process of sheet-type composite electrode. The interphase material fills the pore in the composite sheet while binding the components together, which effectively increases the interfacial contact area and strengthens the physical network between the components, thereby enabling enhanced ion transport throughout the electrode. The interphase-engineered sheet-type LiNi0.8 Co0.1 Mn0.1 O2 /Li10 GeP2 S12 electrode shows a high reversible capacity of 166 mAh g-1 at 25 °C, corresponding to 92% of the observed capacity in a current liquid-based cathode system, as well as enhanced cycle and rate performances. This study proposes a novel and practical method for the development of high-performance sheet-type all-solid-state lithium batteries.

Wet-Chemical Tuning of Li3-x PS4 (0≤x≤0.3) Enabled by Dual Solvents for All-Solid-State Lithium-Ion Batteries.

All-solid-state lithium-ion batteries (ASLBs) employing sulfide solid electrolytes are attractive next-generation rechargeable batteries that could offer improved safety and energy density. Recently, wet syntheses or processes for sulfide solid electrolyte materials have opened opportunities to explore new materials and practical fabrication methods for ASLBs. A new wet-chemical route for the synthesis of Li-deficient Li3-x PS4 (0≤x≤0.3) has been developed, which is enabled by dual solvents. Owing to its miscibility with tetrahydrofuran and ability to dissolve elemental sulfur, o-xylene as a cosolvent facilitates the wet-chemical synthesis of Li3-x PS4 . Li3-x PS4 (0≤x≤0.15) derived by using dual solvents shows Li+ conductivity of approximately 0.2 mS cm-1 at 30 °C, in contrast to 0.034 mS cm-1 for a sample obtained by using a conventional single solvent (tetrahydrofuran, x=0.15). The evolution of the structure for Li3-x PS4 is also investigated by complementary analysis using X-ray diffraction, Raman, and X-ray photoelectron spectroscopy measurements. LiCoO2 /Li-In ASLBs employing Li2.85 PS4 obtained by using dual solvents exhibit a reversible capacity of 130 mA h g-1 with good cycle retention at 30 °C, outperforming cells with Li2.85 PS4 obtained by using a conventional single solvent.

Rational Design of a Composite Electrode to Realize a High-Performance All-Solid-State Battery.

A potential solid electrolyte for realizing all-solid-state battery (ASB) technology has been discovered in the form of Li10 GeP2 S12 (LGPS), a lithium superionic conductor with a high ionic conductivity (≈12 mS cm-1 ). Unfortunately, the achievable Li+ conductivity of LGPS is limited in a sheet-type composite electrode owing to the porosity of this electrode structure. For the practical implementation of LGPS, it is crucial to control the pore structures of the composite electrode, as well as the interfaces between the active materials and solid- electrolyte particles. Herein, the addition of an ionic liquid, N-methyl-N-butylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([Py14 ][TFSI]), is proposed as a pore filler for constructing a highly reliable electrode structure using LGPS. [Py14 ][TFSI] is coated onto the surface of LGPS powder through a wet process and a sheet-type composite electrode is prepared using a conventional casting procedure. The [Py14 ][TFSI]-embedded composite electrode exhibits significantly improved reversible capacity and power characteristics. It is suggested that pore-filling with [Py14 ][TFSI] is effective for increasing contact areas and building robust interfaces between the active materials and solid-electrolyte particles, leading to the generation of additional Li+ pathways in the composite electrode of ASBs.

Lithium-Ion Intercalation into Graphite in SO2-Based Inorganic Electrolyte toward High-Rate-Capable and Safe Lithium-Ion Batteries.

Herein, we have identified that lithium ions in an SO2-based inorganic electrolyte reversibly intercalate and deintercalate into/out of graphite electrode using ex situ X-ray diffraction and various electrochemical methods. X-ray photoelectron spectroscopy shows that the solid electrolyte interphase on the graphite electrode is mainly composed of inorganic compounds, such as LiCl and lithium sulfur-oxy compounds. Graphite electrode in SO2-based inorganic electrolyte has stable capacity retention up to 100 cycles and outstanding rate capability performance. This can be attributed to low interfacial impedance and high ionic conductivity of SO2-based inorganic electrolyte, which are superior to those of conventional organic electrolytes. Considering the remarkable rate capability and intrinsically nonflammable properties of the electrolyte, use of graphite and an SO2 electrolyte will likely facilitate the development of advanced lithium-ion batteries.

Dendrite-Free Li Metal Anode for Rechargeable Li-SO2 Batteries Employing Surface Modification with a NaAlCl4-2SO2 Electrolyte.

Dendritic growth of a Li metal anode during cycling is one of major issues to be addressed for practical application of Li metal rechargeable batteries. Herein, we demonstrate that surface modification of Li metal with a Na-containing SO2 electrolyte can be an effective way to prevent dendritic Li growth during cell operation. The surface-modified Li metal anode exhibited no dendritic deposits even under a high areal capacity (5 mA h cm-2) and a high current density (3 mA cm-2), whereas the unmodified anode showed typical filamentary Li deposition. The surface-modified Li metal anode also demonstrated significantly enhanced electrochemical performance, which could be attributed to the newly formed Na-containing inorganic surface layer that exhibits uniform and dense properties. Consequently, surface modification with a Na-containing SO2 inorganic electrolyte is suggested as one of the most effective ways to realize a highly stable Li metal anode with dendrite-free Li deposition for Li metal-based rechargeable batteries.

A joint experimental and theoretical determination of the structure of discharge products in Na-SO2 batteries.

Na-SO2 batteries are promising power sources for energy storage systems. However, it is unclear what happens on the cathode surface at the molecular level during the discharge process. Here, we provide the working mechanism of Na-SO2 batteries through a combination of nuclear magnetic resonance (NMR) spectroscopy and first-principles NMR calculations.

Dendrite-Free Polygonal Sodium Deposition with Excellent Interfacial Stability in a NaAlCl4-2SO2 Inorganic Electrolyte.

Room-temperature Na-metal-based rechargeable batteries, including Na-O2 and Na-S systems, have attracted attention due to their high energy density and the abundance of sodium resources. Although these systems show considerable promise, concerns regarding the use of Na metal should be addressed for their success. Here, we report dendrite-free Na-metal electrode for a Na rechargeable battery, engineered by employing nonflammable and highly Na(+)-conductive NaAlCl4·2SO2 inorganic electrolyte, as a result, showing superior electrochemical performances to those in conventional organic electrolytes. We have achieved a hard-to-acquire combination of nondendritic Na electrodeposition and highly stable solid electrolyte interphase at the Na-metal electrode, enabled by inducing polygonal growth of Na deposit using a highly concentrated Na(+)-conducting inorganic electrolyte and also creating highly dense passivation film mainly composed of NaCl on the surface of Na-metal electrode. These results are highly encouraging in the development of room-temperature Na rechargeable battery and provide another strategy for highly reliable Na-metal-based rechargeable batteries.

A room-temperature sodium rechargeable battery using an SO2-based nonflammable inorganic liquid catholyte.

Sodium rechargeable batteries can be excellent alternatives to replace lithium rechargeable ones because of the high abundance and low cost of sodium; however, there is a need to further improve the battery performance, cost-effectiveness, and safety for practical use. Here we demonstrate a new type of room-temperature and high-energy density sodium rechargeable battery using an SO2-based inorganic molten complex catholyte, which showed a discharge capacity of 153 mAh g(-1) based on the mass of catholyte and carbon electrode with an operating voltage of 3 V, good rate capability and excellent cycle performance over 300 cycles. In particular, non-flammability and intrinsic self-regeneration mechanism of the inorganic liquid electrolyte presented here can accelerate the realization of commercialized Na rechargeable battery system with outstanding reliability. Given that high performance and unique properties of Na-SO2 rechargeable battery, it can be another promising candidate for next generation energy storage system.

A highly resilient mesoporous SiOx lithium storage material engineered by oil-water templating.

Mesoporous silicon-based materials gained considerable attention as high-capacity lithium-storage materials. However, the practical use is still limited by the complexity and limited number of available synthetic routes. Here, we report carbon-coated porous SiOx as high capacity lithium storage material prepared by using a sol-gel reaction of hydrogen silsesquioxane and oil-water templating. A hydrophobic oil is employed as a pore former inside the SiOx matrix and a precursor for carbon coating on the SiOx . The anode exhibits a high capacity of 730 mAh g(-1) and outstanding cycling performance over 100 cycles without significant dimensional changes. Carbon-coated porous SiOx also showed highly stable thermal reliability comparable to that of graphite. These promising properties come from the mesopores in the SiOx matrix, which ensures reliable operation of lithium storage in SiOx . The scalable sol-gel process presented here can open up a new avenue for the versatile preparation of porous SiOx lithium storage materials.

Hydrogen silsequioxane-derived Si/SiO(x) nanospheres for high-capacity lithium storage materials.

Si/SiOx composite materials have been explored for their commercial possibility as high-performance anode materials for lithium ion batteries, but suffer from the complexity of and limited synthetic routes for their preparation. In this study, Si/SiOx nanospheres were developed using a nontoxic and precious-metal-free preparation method based on hydrogen silsesquioxane obtained from sol-gel reaction of triethoxysilane. The resulting Si/SiOx nanospheres with a uniform carbon coating layer show excellent cycle performance and rate capability with high-dimensional stability. This approach based on a scalable sol-gel reaction enables not only the development of Si/SiOx with various nanostructured forms, but also reduced production cost for mass production of nanostructured Si/SiOx.

Zr4+ doping in Li4Ti5O12 anode for lithium-ion batteries: open Li+ diffusion paths through structural imperfection.

One-dimensional nanomaterials have short Li(+) diffusion paths and promising structural stability, which results in a long cycle life during Li(+) insertion and extraction processes in lithium rechargeable batteries. In this study, we fabricated one-dimensional spinel Li4Ti5O12 (LTO) nanofibers using an electrospinning technique and studied the Zr(4+) doping effect on the lattice, electronic structure, and resultant electrochemical properties of Li-ion batteries (LIBs). Accommodating a small fraction of Zr(4+) ions in the Ti(4+) sites of the LTO structure gave rise to enhanced LIB performance, which was due to structural distortion through an increase in the average lattice constant and thereby enlarged Li(+) diffusion paths rather than changes to the electronic structure. Insulating ZrO2 nanoparticles present between the LTO grains due to the low Zr(4+) solubility had a negative effect on the Li(+) extraction capacity, however. These results could provide key design elements for LTO anodes based on atomic level insights that can pave the way to an optimal protocol to achieve particular functionalities.

Core-shell structured silicon nanoparticles@TiO2-x/carbon mesoporous microfiber composite as a safe and high-performance lithium-ion battery anode.

A core-shell structured Si nanoparticles@TiO2-x/C mesoporous microfiber composite has been synthesized by an electrospinning method. The core-shell composite exhibits high reversible capacity, excellent rate capability, and improved cycle performance as an anode material for Li-ion batteries. Furthermore, it shows remarkable suppression of exothermic behavior, which can prevent possible thermal runaway and safety problems of the cells. The improved electrochemical and thermal properties are ascribed to the mechanically, electrically, and thermally robust shell structure of the TiO2-x/C nanocomposite encapsulating the Si nanoparticles, which is suggested as a promising material architecture for a safe and reliable Si-based Li-ion battery of high energy density.

Metallic anodes for next generation secondary batteries.

Li-air(O2) and Li-S batteries have gained much attention recently and most relevant research has aimed to improve the electrochemical performance of air(O2) or sulfur cathode materials. However, many technical problems associated with the Li metal anode have yet to be overcome. This review mainly focuses on the electrochemical behaviors and technical issues related to metallic Li anode materials as well as other metallic anode materials such as alkali (Na) and alkaline earth (Mg) metals, including Zn and Al when these metal anodes were employed for various types of secondary batteries.

Post oxygen treatment characteristics of coke as an anode material for Li-ion batteries.

The effect of a oxygen treatment on the electrochemical characteristics of a soft carbon anode material for Li-ion batteries was investigated. After a coke carbonization process at 1000 degrees C in an argon atmosphere, the samples were treated under a flow of oxygen gas to obtain a mild oxidation effect. After this oxygen treatment, the coke samples exhibited an improved initial coulombic efficiency and cycle performance as compared to the carbonized sample. High-resolution transmission electron microscopy revealed that the carbonized cokes consisted of disordered and nanosized graphene layers and the surface of the modified carbon was significantly changed after the treatment. The chemical state of the cokes was analyzed using X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The enhanced electrochemical properties of the surface modified cokes could be attributed to the mild oxidation effect induced by the oxygen treatment. The mild oxidation process could have led to the elimination of surface imperfections and the reinforcement of a solid electrolyte interphase film, which resulted in the improved electrochemical characteristics.

Morphological modification of alpha-MnO2 catalyst for use in Li/air batteries.

Single crystal alpha-MnO2 nanowires and nanopowders have been successfully synthesized in order to facilitate a comparison of their catalytic activity for use in Li-air batteries. The importance of the morphological modification of the alpha-MnO2 catalyst for facilitating electrochemical reactions between Li and O2 is addressed. Distinctive catalytic activity of alpha-MnO2 is observed, which is in line with its different morphologies. The catalytic activity significantly affects the reversible capacity of Li-air batteries. A high aspect ratio, large surface area and good dispersibility of alpha-MnO2 in the nanowire form are advantageous providing larger active surfaces for promoting the fundamental reactions in Li-air batteries. We also introduce a robustly designed air-electrode composed of highly porous carbon and nanostructured alpha-MnO2 catalysts, with employs a metal foam current collector to ensure sufficient air-permeability and to maximize electronic conduction during cycles. Our suggestions should prove helpful in forming a basis for further investigations in developing advanced Li-air batteries.

Novel catalytic effects of Mn3O4 for all vanadium redox flow batteries.

A new approach for enhancing the electrochemical performance of carbon felt electrodes by employing non-precious metal oxides is designed. The outstanding electro-catalytic activity and mechanical stability of Mn(3)O(4) are advantageous in facilitating the redox reaction of vanadium ions, leading to efficient operation of a vanadium redox flow battery.

One-step synthesis of a sulfur-impregnated graphene cathode for lithium-sulfur batteries.

A practical route is introduced for synthesizing a sulfur-impregnated graphene composite as a promising cathode material for lithium-sulfur batteries. Sulfur particles with a size of a few microns are successfully grown in the interior spaces between randomly dispersed graphene sheets through a heterogeneous crystal growth mechanism. The proposed route not only enables the control of the particle size of active sulfur but also affords quantitative yields of composite powder in large quantities. We investigate the potential use of the sulfur-impregnated graphene composite as a cathode material owing to its advantages of confining active sulfur, preventing the dissolution of soluble polysulfides, and providing sufficient electrical conduction. A high discharge capacity of 1237 mA h g(-1) during the first cycle and a good cyclic retention of 67% after 50 cycles are attained in a voltage range of 1.8-2.6 V vs. Li/Li(+). These results emphasize the importance of tailoring cathode materials for improving the electrochemical properties of lithium-sulfur batteries. Our results provide a basis for further investigations on advanced lithium batteries.