Enhancing the Electrochemical Performance of High Voltage LiNi0.5Mn1.5O4 Cathode Materials by Surface Modification with Li1.3Al0.3Ti1.7(PO4)3/C

A novel method for surface modification of LiNi_0.5Mn_1.5O₄ (LNMO) was proposed, in which a hybrid layer combined by Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) and carbon (C) composite on LNMO material were connected by lithium iodide. Structure and morphology analyses illustrated that a higher contact area of active substances was achieved by the LATP/C composite layer without changing the original crystal structure of LNMO. XPS analysis proved that I^- promoted the reduction of trace Mn⁴⁺, resulting in a higher ion conductivity. Galvanostatic charge-discharge tests exhibited the capacity of the LNMO with 5% LATP/C improved with 35.83% at 25 °C and 95.77% at 50 °C, respectively, compared with the bare after 100 cycles, implying the modification of high-temperature deterioration. EIS results demonstrated that one order of magnitude of improvement of the lithium-ion diffusion coefficient of LATP/C-LNMO was achieved (3.04 × 10^-11 S cm^-1). In conclusion, the effective low-temperature modification strategy improved the ionic and electronic conductivities of the cathode and suppressed the side reactions of high-temperature treatment.

In Situ Formed LiI Interfacial Layer for All-Solid-State Lithium Batteries with Li6PS5Cl Solid Electrolyte Membranes

Sulfide-based solid electrolytes are considered ideal materials for all-solid-state Li metal batteries owing to their high ion conductivity and satisfactory mechanical stiffness. However, the interfacial reaction between the sulfide electrolyte membrane and Li anode severely limits the commercial application of such membranes. Herein, a lithium iodide (LiI) layer is synthesized at the Li metal-sulfide electrolyte membrane interface via chemical vapor deposition. The synthesized LiI layer exhibits satisfactory ionic conductivity and high interfacial energy, as confirmed via density functional theory calculations. Consequently, the LiI@Li/Li₆PS₅Cl membrane/LiI@Li symmetric cell can cycle for >150 h at 0.1 mA cm^-2. The as-prepared all-solid-state batteries exhibit a high discharge capacity of 107 mA h g^-1 and an excellent capacity retention of 76% after 800 cycles at 1 C. This work offers a simple and effective method to improve the interface between the Li anode and sulfide electrolyte membranes that facilitates the mass production and practical application of high-energy-density sulfide-based all-solid-state batteries.

Selective Csp3-F Bond Functionalization with Lithium Iodide

A highly efficient method for C-F bond functionalization of a broad variety of activated and unactivated aliphatic substrates with inexpensive lithium iodide is presented. Primary, secondary, tertiary, benzylic, propargylic and α-functionalized alkyl fluorides react in chlorinated or aromatic solvents at room temperature or upon heating to the corresponding iodides which are isolated in 91-99% yield. The reaction is selective for aliphatic monofluorides and can be coupled with in situ nucleophilic iodide replacements to install carbon-carbon, carbon-nitrogen and carbon-sulfur bonds with high yields. Alkyl difluorides, trifluorides, even in activated benzylic positions, are inert under the same conditions and aryl fluoride bonds are also tolerated.

Understanding the Role of Lithium Iodide in Lithium-Oxygen Batteries

Lithium-oxygen (Li-O₂ ) batteries possess a high theoretical energy density, which means they could become a potential alternative to lithium-ion batteries. Nevertheless, the charging process of Li-O₂ batteries requires much higher energy, due to the insulating nature of the discharge product. It has been revealed that the anion additive, lithium iodide (LiI), can tune the cell chemistry to form lithium hydroxide (LiOH) as the product and facilitate the kinetics during the charging process. Although numerous studies have been reported, the role of this additive is still under investigation. Herein, the recent advances focusing on the use of LiI in Li-O₂ batteries are reviewed, its catalytic behavior on discharge and charge is discussed, and its synergistic effect with water is understood. The ambiguity existing among the studies are also revealed, and solutions to the current issues are introduced.

LiI-Doped Sulfide Solid Electrolyte: Enabling a High-Capacity Slurry-Cast Electrode by Low-Temperature Post-Sintering for Practical All-Solid-State Lithium Batteries

All-solid-state lithium batteries (ASSLBs) based on sulfide solid electrolytes (SEs) have received great attention because of the high ionic conductivity of the SEs, intrinsic thermal safety, and higher energy density achievable with a Li metal anode. However, studies on practical slurry-cast composite electrodes show an extremely limited battery performance than the binder-free pelletized electrodes because of the poor interfacial robustness between the active materials and SEs by the presence of a polymeric binder. Here, we employ a low-temperature post-sintering process for the slurry-cast composite electrodes in order to overcome the binder-induced detrimental effects on the electrochemical performance. The LiI-doped Li₃PS₄ SEs are chosen because the addition of iodine not only improves the Li-ion conductivity and Li metal compatibility but also lowers the glass-transition and crystallization temperatures. Low-temperature post-sintering of composite cathodes consisting of a LiNi_0.6Co_0.2Mn_0.2O₂-active material, LiI-doped Li₃PS₄ SE, polymeric binder, and conducting agent shows a significantly improved electrochemical performance as compared to a conventional slurry-cast electrode containing pre-annealed SEs. Detailed analyses by electrochemical impedance spectroscopy and galvanostatic intermittent titration technique confirm that post-sintering effectively reduces the interfacial resistance and enhances the chemomechanical robustness at solid-solid interfaces, which enables the development of practical slurry-cast ASSLBs with sulfide SEs.

Reduced Graphene Oxide/LiI Composite Lithium Ion Battery Cathodes

Li-iodine chemistry is of interest for electrochemical energy storage because it has been shown to provide both high power and high energy density. However, Li-iodine batteries are typically formed using Li metal and elemental iodine, which presents safety and fabrication challenges (e.g., the high vapor pressure of iodine). These disadvantages could be circumvented by using LiI as a starting cathode. Here, we present fabrication of a reduced graphene oxide (rGO)/LiI composite cathode, enabling for the first time the use of LiI as the Li-ion battery cathode. LiI was coated on rGO by infiltration of an ethanolic solution of LiI into a compressed rGO aerogel followed by drying. The free-standing rGO/LiI electrodes show stable long-term cycling and good rate performance with high specific capacity (200 mAh g^-1 at 0.5 C after 100 cycles) and small hysteresis (0.056 V at 1 C). Shuttling was suppressed significantly. We speculate the improved electrochemical performance is due to strong interactions between the active materials and rGO, and the reduced ion and electron transport distances provided by the three-dimensional structured cathode.

Lithium iodide as a promising electrolyte additive for lithium-sulfur batteries: mechanisms of performance enhancement

Lithium Iodide (LiI) is reported as a promising electrolyte additive for lithium-sulfur batteries. It induces formation of Li-ion-permeable protective coatings on both positive and negative electrodes, which prevent the dissolution of polysulfides on the cathode and reduction of polysulfides on the anode. In addition to enhancing the cell cycle stability, LiI addition also decreases the cell overpotential and voltage hysteresis.