Weikang Li

High voltage spinel cathode LiNi_0.5Mn_1.5O₄ (LNMO) offers higher energy density and competitive cost compared to traditional cathodes in lithium-ion batteries, making it a promising option for high-performance battery applications. However, the fast capacity decay in full cells hinders further commercialization. The Li inventory evolution upon cycling in the LNMO–graphite pouch cell is systematically studied by developing lithium quantification methods on the cathode, anode, and electrolyte. The findings reveal that active Li loss is a primary factor contributing to capacity decay, stemming from an unstable anode interphase caused by crosstalk. This crosstalk primarily originates from electrolyte degradation on the cathode under high-voltage operation, leading to increased moisture and acidity, subsequently corroding the anode interphase. In response, two approaches including an aluminum oxide (Al₂O₃) surface coating layer on the cathode and lithium difluoro(oxalato)borate (LiDFOB) electrolyte additives are evaluated systematically, resulting in cycling stability enhancement. This study offers a quantitative approach to understanding the Li inventory loss in the LNMO–Gr system, providing unique insights and guidance into identifying critical bottlenecks for developing high voltage (>4.4 V) lithium battery technology.

Battery technology is pivotal in addressing energy efficiency and environmental sustainability challenges. Lithium-sulfur (Li-S) batteries feature promising high energy density and sustainability, but are hindered by a short cycle life under lean lithium and electrolyte conditions. A critical hurdle for Li-S batteries is the selection of an optimal electrolyte solution, crucial for controlling effective polysulfide electrochemical reactions. The conventional ether- based Li-S electrolyte, consisting of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium nitrate (LiNO3), frequently suffers from LiNO3 depletion in high-energy-density applications. To address the capacity decay in Li-S batteries caused by LiNO3 depletion, this investigation introduces 2-nitrophenol lithium (NPL) as an alternative. By incorporating 25 1 mM NPL and 1 M LiTFSI in a 1,3-dioxolane/1,2-dimethoxyethane (DOL/DME) solvent, NPL mediates polysulfide oxidation during charging and prevents polysulfide corrosion, therefore improving Li retention and plating behavior. This results in Li-S batteries with NPL achieving 310 cycles, significantly surpassing the 75 cycles observed with traditional LiNO3-containing electrolytes using lean lithium anode. Pouch cells incorporating NPL exhibit stable cycling over 80 cycles, maintaining 75% of their capacity. The molecular structure of NPL prevents decomposition and facilitates interaction with polysulfides to minimize corrosion, positioning it as a strong substitute for LiNO3. This highlights NPL as a promising solution for extending the lifespan of Li-S batteries.

Sodium-ion batteries exhibit significant promise as a viable alternative to current lithium-ion technologies owing to their sustainability, low cost per energy density, reliability, and safety. Despite recent advancements in cathode materials for this category of energy storage systems, the primary challenge in realizing practical applications of sodium-ion systems is the absence of an anode system with high energy density and durability. Although Na metal is the ultimate anode that can facilitate high-energy sodium-ion batteries, its use remains limited due to safety concerns and the high-capacity loss associated with the high reactivity of Na metal. In this study, titration gas chromatography is employed to accurately quantify the sodium inventory loss in ether- and carbonate-based electrolytes. Uniaxial pressure is developed as a powerful tool to control the deposition of sodium metal with dense morphology, thereby enabling high initial coulombic efficiencies. In ether-based electrolytes, the Na metal surface exhibits the presence of a uniform solid electrolyte interphase layer, primarily characterized by favorable inorganic chemical components with close-packed structures. The full cell, utilizing a controlled electroplated sodium metal in ether-based electrolyte, provides capacity retention of 91.84% after 500 cycles at 2C current rate and delivers 86 mA h g⁻¹ discharge capacity at 45C current rate, suggesting the potential to enable Na metal in the next generation of sodium-ion technologies with specifications close to practical requirements.

Lithium phosphorus oxynitride (LiPON) is an amorphous solid electrolyte that has been extensively studied over the last three decades. Despite the promise of pairing it with various electrode materials, LiPON’s rigidity and air sensitivity set limitations to understanding its intrinsic properties. Here we report a methodology to synthesize LiPON in a free-standing form that manifests remarkable flexibility and a Young’s modulus of ∼33 GPa. We use solid-state nuclear magnetic resonance and differential scanning calorimetry to quantitatively reveal the chemistry of the Li/LiPON interface and the presence of a well-defined LiPON glass-transition temperature of 207 °C. Combining interfacial stress and a gold seeding layer, our free-standing LiPON shows a uniformly dense deposition of lithium metal without the aid of external pressure. This free-standing LiPON film offers opportunities to study fundamental properties of LiPON for interface engineering for solid-state batteries.

“Thick electrode using high voltage cathode” can be considered, since this research focuses on high voltage cathode materials.

Silicon anode solid-state batteries: Research on solid-state batteries has focused on lithium metal anodes. Alloy-based anodes have received less attention in part due to their lower specific capacity even though they should be safer. Tan et al . developed a slurry-based approach to create films from micrometer-scale silicon particles that can be used in anodes with carbon binders. When incorporated into solid-state batteries, they showed good performance across a range of temperatures and excellent cycle life in full cells. —MSL