20 Search Results

The practical applications of lithium (Li) metal batteries (LMBs) are limited by challenges such as dendrite formation and unstable solid electrolyte interphase (SEI), especially at higher C-rates. Here, this study introduces melamine-coated Li metal anodes (LMAs), forming a Li₃N-rich SEI layer that improves ionic conductivity and mechanical stability. The optimized melamine-coated LMA demonstrated uniform coverage resulting in denser Li deposition, nearly doubled cycle life (~148 cycles at 0.5 C, 1C = 4.1 mA cm^-2), compared to Bare-Li. These findings emphasize that coating materials-induced beneficial SEI components could lead to improvement of LMB performance.

Achieving long-term stability and consistent capacity in lithium (Li) metal batteries with sulfurized polyacrylonitrile (SPAN) cathodes requires precisely engineered electrolytes to optimize interphase formation and redox reversibility. Here, this study presents 1,1-difluoro-2-(2-methoxyethoxy)ethane (DFE)-based localized high-concentration electrolytes (LHCEs), incorporating fluorinated components such as salt, solvating solvent, and diluent for improved electrode stability. Molecular dynamics simulations and surface analyses reveal that the DFE-LHCE with 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane (BTFEE) diluent produces uniform and robust interphase layers on both cathode and anode, enriched with inorganic species like LiF and Li₂O. These properties lead to prolonged redox reversibility of the SPAN cathode, suppressed side reactions, and extendedmore » cycle life for Li||SPAN cells. Remarkably, DFE-BTFEE-LHCE enables Li||SPAN coin cells with an areal capacity of ∼7 mAh cm^-2 for SPAN to retain 81.3% capacity after 200 cycles and pouch cells of 0.12 Ah with 8 mAh cm^-2 of SPAN and lean electrolyte to maintain 96.4% capacity over 80 cycles. These findings pave the way for advancing Li||SPAN battery technologies.« less

Silicon (Si) is a promising anode for the next generation of lithium-ion batteries, but its large volume changes (~300 %) during cycling hindered its practical applications. One method to improve its stability is to etch micron sized Si/SiO₂ particles to form porous Si (p-Si) and accommodate volume changes internally. However, the conventional HF etching method generates excess gas/heat and is difficult to scale up. Herein, we developed an organic-solvent-assisted HF etching process (O-HF) using a mixture of benzene and saturated HF aqueous solution. The organic solvent can be preferentially absorbed on the surface of Si/SiO₂ powder so etching rate ofmore » SiO₂ can be controlled to avoid rapid gas/heat generation. This method can also prevent over-etching of Si by minimizing direct contact/react between water and newly exposed Si. Si||NMC622 cells using carbon coated p-Si particles prepared by optimized O-HF etching process demonstrate a capacity retention of 82.0 % after 500 cycles, which is much better than those prepared by conventional HF etching (73.7 %). The thickness of Si anode increases only ~10 % during the initial lithiation, which is comparable with those of graphite anode. In conclusion, the O-HF etching strategy developed in this work can also be applied to the etching of a broad range of materials.« less

Lithium (Li) metal batteries (LMBs) are one of the most promising high energy density batteries to meet the demands of electric transportation. However, the practical applications of LMBs are hindered by short cycle life and safety concern, mainly associated with side reactions between Li metal anode and liquid electrolyte and the growth of Li dendrites during cycling. In this study, we develop a stable artificial solid electrolyte interphase (aSEI), which consists of a surface-treated (S_T) PEO–Li_6.4Ga_0.2La₃Zr₂O₁₂ composite polymer coating layer (CPL) on Li metal anode. The developed aSEI is stable against selected electrolyte and enables a uniform electrodeposition of Li.more » Therefore, S_TCPL@Li||LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) cells exhibit improved cycling stability compared with bare Li||NMC811 cells at moderate to high current densities. Notably, using a 50 µm thick Li and a practical NMC811 cathode (~4.8 mAh cm^-2), a capacity retention of 85% is obtained for S_TCPL@Li||NMC811 cells at a current density of 2.4 mAcm^-2 after 300 cycles compared with 24% for bare Li||NMC811 cells. Furthermore, S_TCPL@Li||NMC811 cells demonstrate higher capacities at charge current densities of 2.4, 4.8 and 7.2 mAcm^-2 compared with bare Li||NMC811 cells. Further, these findings suggest that S_TCPL is promising for high current density practical LMBs.« less

Abstract The energy storage density of Li‐ion batteries can be improved by replacing graphite anodes with high‐capacity Si‐based materials, though instabilities have limited their implementation. Performance degradation mechanisms that occur in Si anodes can be divided into cycling stability (capacity retention after repeated battery cycles) and calendar aging (shelf life). While cycling instabilities and improvement strategies have been researched intensively, there is little known about the underlying mechanisms that cause calendar aging. In this work, multiple electron microscope techniques are used to explore the mechanism that governs calendar aging from the sub‐nanometer‐to‐electrode scale. Plasma focused ion beam tomography is usedmore » to create 3D reconstructions of calendar aged electrodes and revealed the growth of a LiF‐rich layer at the interface between the copper current collector and the silicon material, which can lead to delamination and increased interfacial impendence. The LiF layer appeared to derive from the fluoro‐ethylene‐carbonate electrolyte additive, which is commonly used to improve cycling stability in Si‐based systems. The results reveal that additives necessary to improve cycling stability can cause performance degradation over the long‐term during calendar aging. The results show that high performing, stable systems require careful design to simultaneously mitigate both cycling and calendar aging instabilities.« less

The high energy density advantage of lithium (Li) metal batteries (LMBs) makes them increasingly desirable; however, problems such as strong reactivity and dendrite growth of Li metal anode limit their practical uses. In this work, a novel Li‐containing glycerol (LiGL) or lithicone protection layer on a 50 μm thick Li metal anode is employed for improving the performance of LMBs. This LiGL layer was accurately deposited via a molecular layer deposition (MLD) process at 150 °C, using lithium tert‐butoxide and glycerol as precursors. The as‐formed LiGL coating layer is highly tunable in its thickness by simply adjusting MLD cycles and shows amore » good stability and outstanding ionic transport properties. The LiGL layer is found to effectively mitigate side reactions and enhance cycling stability in both symmetric cells and full cells. Specifically, the LMBs with LiGL@Li anode of 400 MLD cycles and LiNi _0.6 Mn _0.2 Co _0.2 O ₂ cathode enable a capacity retention of ≈87%, much higher than ≈35% of the cells with bare Li after 200 cycles at a charge/discharge current density of 2.1 mA cm ⁻² . This work paves a feasible way for practical LMBs with improved capacity and stability through applying an innovative protection layer on Li metal anodes.« less

Silicon (Si) is one of the most promising anode materials for the next generation lithium-ion batteries (LIBs). Although significant progresses have been made on the cycle life of Si-based LIBs, their calendar-life is still far less than those required for electrical vehicle applications. Here, in this work, the fundamental mechanisms behind the limited calendar life of Si-LIBs have been investigated. It is found that the unstable interphase layers formed on electrodes during the formation/cycling of batteries using conventional electrolyte with fluoroethylene carbonate (FEC) additive are responsible for the rapid impedance-increase of Si-LIBs during storage at elevated temperature (55°C). By usingmore » an FEC-free localized high concentration electrolyte (lithium bis(fluorosulfonyl)imide:ethyl propionate:ethylene carbonate:1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (1:2.8:0.2:1 by mol.) with 1 wt.% lithium difluorophosphate), stable interphase layers formed on electrodes can effectively block the crosstalk between cathode and anode, minimize the impedance increase of Si||LiNi_0.6Mn_0.2Co_0.2 (NMC622) batteries during storage at elevated temperature (55°C), therefore largely improve their calendar life. Si||NMC622 batteries using this electrolyte also demonstrated a high-capacity retention of ~92.4% after 500 cycles at 45°C with well-preserved electrode structure. Hence, this novel electrolyte is a good candidate to extend the cycling life and calendar life of Si-LIBs.« less

Sulfurized polyacrylonitrile (SPAN) is a promising cathode material for lithium-sulfur (Li-S) batteries due to its significantly reduced polysulfide (PS) dissolution compared to the elemental S cathode. Although conventional carbonate-based electrolytes is stable with SPAN electrodes, it is less stable with Li metal anode (LMA). Recently, localized high-concentration electrolytes (LHCEs) have been developed to improve the stability of LMA. Here, we report a new strategy to further improve the performance of LI||SPAN batteries by replacing the conventional solvating solvent 1,2-dimethoxyethane (DME) in the LHCE with a new solvating solvent, 1,2-diethoxyethane (DEE), the new LHCEs exhibits less reactivity against Li₂S₂, alleviates PSmore » dissolution, forms a better cathode-electrolyte interphase layer on the SPAN, and enhances structure reversibility even at elevated temperature (ET, 45°C). With the same salt and diluent as in other LHCEs, the LHCE with DEE leads to better performance in Li||SPAN batteries (with 82.9% capacity retention after 300 cycles at ET), preservation of SPAN cathode structure, and suppression of the volume change of LMA. The similar strategy on tailoring the solvating solvents in LHCEs can also be used in other rechargeable batteries to improve their performances.« less

Here, the practical applications of high-energy-density rechargeable lithium (Li) metal batteries (LMBs) have been impeded by the intrinsic issues of the Li metal anode (LMA) including high reactivity with electrolyte and dendritic formation. Conventional LMAs, which have the "hostless" feature consisting of a Li layer on a two-dimensional copper (Cu) foil as a current collector, led to additional loss in specific energy density, since Cu is a nonfaradaic heavy metal, bringing formidable areal capacity loss. To address these problems, a heat-treated three-dimensional-structured Cu-coated polyimide (HT-Cu@PI) membrane is designed and fabricated as a current collector. Benefiting from this unique material/structure, itmore » enables not only better electrochemically deposited Li by a uniform/continuous Li-ion transport pathway but also a significant increase in the gravimetric/volumetric energy densities of LMBs by allowing more Li deposition in a fixed weight/volume. Therefore, this new LMA structure will accelerate the practical application of high-energy-density LMBs.« less

X‐ray photoelectron spectroscopy (XPS) has become a highly important tool for the analysis of battery materials and components. However, both anecdotal and detailed analysis of selected parts of the literature indicate that many reports of XPS on battery electrodes have significant analysis or data flaws. In this paper, we highlight several of the common challenges that analysts face when using XPS for battery materials, pointing to recent literature that addresses many of the critical issues associated with sample preparation as well as data collection and analysis. A common error for battery materials (and other materials) involves ignoring peak overlaps andmore » interferences. Specifically, when a “minor” peak associated with a component in relatively high concentration overlaps or contributes to the primary peak (or one recommended for quantitative analysis) from a different element in the material. Overlap issues apply to many battery electrodes composed of many elements with complex photoelectron peak structures, as well as those involving peaks with seemingly simpler spectral envelopes such as Li and F. Examples of issues associated with battery systems are highlighted by a discussion of challenges associated with XPS analysis of Li and nickel–manganese–cobalt (NMC) electrodes in battery systems. Lithium analysis has challenges associated with the preparation and an often‐unrecognized peak overlap with F. In our laboratory and in the literature, NMC electrodes are often examined and new XPS users do not always recognize interference of the Auger signal from F _KLL (in or on the electrode) with Ni 2p photoelectron spectrum when generated with Al Kα X‐rays. The use of simulated spectra involving both F and NiO demonstrates the extent of F Auger contributions to the Ni 2p signal strength as a function of the F/Ni atom ratio in the material and suggests spectra information that can be used to identify how significant effects will be on the resultant spectra. Our analysis demonstrates that in many cases overlap issues are significant for real electrode materials.« less