Search for: All records

Metal negative electrodes that alloy with lithium have high theoretical charge storage capacity and are ideal candidates for developing high-energy rechargeable batteries. However, such electrode materials show limited reversibility in Li-ion batteries with standard non-aqueous liquid electrolyte solutions. To circumvent this issue, here we report the use of non-pre-lithiated aluminum-foil-based negative electrodes with engineered microstructures in an all-solid-state Li-ion cell configuration. When a 30-μm-thick Al_94.5In_5.5negative electrode is combined with a Li₆PS₅Cl solid-state electrolyte and a LiNi_0.6Mn_0.2Co_0.2O₂-based positive electrode, lab-scale cells deliver hundreds of stable cycles with practically relevant areal capacities at high current densities (6.5 mA cm⁻²). We also demonstrate that the multiphase Al-In microstructure enables improved rate behavior and enhanced reversibility due to the distributed LiIn network within the aluminum matrix. These results demonstrate the possibility of improved all-solid-state batteries via metallurgical design of negative electrodes while simplifying manufacturing processes.

Operation of lithium‐based batteries at low temperatures (<0 °C) is challenging due to transport limitations as well as sluggish Li⁺kinetics at the electrode interface. The complicated relationships among desolvation, charge transfer, and transport through the solid electrolyte interphase (SEI) at low temperatures are not well understood, hindering electrolyte development. Here, an ether/hydrofluoroether and fluoroethylene carbonate (FEC)‐based ternary solvent electrolyte is developed to improve Li cycling at low temperatures (Coulombic efficiency of 93.3% at ‐40 °C), and the influence of the local solvation structure on interfacial Li⁺kinetics and SEI chemistry is further revealed. The hydrofluoroether cosolvent allows for modulation of the solvation structure, thereby enabling facile Li⁺desolvation while forming an inorganic‐rich SEI, which are both beneficial for lowering Li⁺kinetic barriers at the interface. This cosolvent also increases the oxidative stability of the electrolyte to over 4.0 V versus Li/Li⁺, thereby enabling cycling of NMC‐based full cells at −40 °C. This study advances the understanding of the influence of Li⁺solvation structure, SEI chemistry, and interfacial Li⁺kinetics on Li electrochemistry at low temperatures, providing new design considerations for creating effective low‐temperature electrolyte systems.

Lithium‐ion batteries (LIBs) show poor performance at temperatures below 0 °C due to sluggish reaction kinetics, hindered diffusion, and electrolyte freezing. Materials that alloy with lithium offer higher specific capacity than graphite anodes and are studied extensively at room temperature, but their low‐temperature behavior is not well understood. Here, the electrochemical and transformation behavior of three alloy materials (antimony, silicon, and tin) are investigated. It is shown that antimony is particularly well suited for low‐temperature applications due to its relatively high electrode potential and promising electrochemical stability at low temperatures. It is found that lithium‐antimony alloys can be cycled down to −40 °C with ten times higher specific capacity than graphite on the first cycle. The galvanostatic intermittent titration technique is used to understand the kinetic and thermodynamic limitations of these electrode materials at low temperatures, and X‐ray diffraction shows that electrochemical phase transformation behavior is also altered at low temperatures. Finally, it is found that the use of reference electrodes is necessary at low temperatures to avoid counter electrode effects. This investigative study provides new understanding of the behavior of alloy anodes at low temperatures and reveals the need for electrode/electrolyte optimization to enable low‐temperature LIBs.

“Anode‐free” solid‐state batteries (SSBs), which have no anode active material, can exhibit extremely high energy density (≈1500 Wh L⁻¹). However, there is a lack of understanding of the lithium plating/stripping mechanisms at initially lithium‐free solid‐state electrolyte (SSE) interfaces because excess lithium metal is often used. Here, it is demonstrated that commercially relevant quantities of lithium (>5 mAh cm⁻²) can be reliably plated at moderate current densities (1 mA cm⁻²) using the sulfide SSE Li₆PS₅Cl. Investigations of lithium plating/stripping mechanisms, in conjunction with cryo‐focused ion beam (FIB) imaging, synchrotron tomography, and phase‐field modeling, reveal that the cycling stability of these cells is fundamentally limited by the nonuniform presence of lithium during stripping. Local lithium depletion causes isolated lithium regions toward the end of stripping, decreasing electrochemically active area and resulting in high local current densities and void formation. This accelerates subsequent filament growth and short circuiting compared to lithium‐excess cells. Despite this degradation mode, it is shown that anode‐free cells exhibit comparable Coulombic efficiency to lithium‐excess cells, and improved resistance to short circuiting is achieved by avoiding local lithium depletion through retention of thicker lithium at the interface. These new insights provide a foundation for engineering future high‐energy anode‐free SSBs.