Microwave-Assisted Synthesis of High-Voltage Nanostructured LiMn_1.5Ni_0.5O₄ Spinel: Tuning the Mn³⁺ Content and Electrochemical Performance

The LiMn_1.5Ni_0.5O₄ spinel is an important lithium ion battery cathode material that has continued to receive major research attention because of its high operating voltage (∼4.8 V). This study interrogates the impact of microwave irradiation on the Mn³⁺ concentration and electrochemistry of the LiMn_1.5Ni_0.5O₄ spinel. It is shown that microwave is capable of tuning the Mn³⁺ content of the spinel for enhanced electrochemical performance (high capacity, high capacity retention, excellent rate capability, and fast Li⁺ insertion/extraction kinetics). This finding promises to revolutionize the application of microwave irradiation for improved performance of the LiMn_1.5Ni_0.5O₄ spinel, especially in high rate applications

Improving Contact Impedance via Electrochemical Pulses Applied to Lithium–Solid Electrolyte Interface in Solid-State Batteries

Stabilizing interfaces in solid-state batteries (SSBs) is crucial for development of high energy density batteries. In this work, we report a facile electrochemical protocol to improve the interfacial impedance and contact at the interface of Li | Li6.25Al0.25La3Zr2O12 (LALZO). Application of short duration, high-voltage pulses to poorly formed interfaces leads to lower contact impedance. It is found that the local high current density that results from these pulses at the vicinity of the interfacial pores can lead to a better contact between Li and LALZO because of local Joule heating, as supported by theoretical simulations. The pulse technique, which has also been applied to a Li | Li6.4La3Zr1.4Ta0.6O12 (LLZTO) | LiNi0.6Mn0.2Co0.2O2 (NMC622) cell, results in remarkable reduction of the charge-transfer resistance. Ex situ characterizations, which include X-ray photoelectron spectroscopy and scanning electron microscopy techniques, reveal that there is no detrimental effects of the pulse on cathode and solid electrolyte bulks and interfaces. This electrochemical pulse technique sheds light on a facile, nondestructive method that has the potential to significantly improve the interfacial contacts in a solid-state battery configuration

Tailoring of the Anti-Perovskite Solid Electrolytes at the Grain-Scale

The development of thin, dense, defect-free solid electrolyte films is key for achieving practical and commercially viable solid-state batteries. Herein, we showcase a facile processing pathway for antiperovskite (Li2OHCl) solid electrolyte materials that can yield films/pellets with very high densities (∼100%) and higher conductivities compared with conventional uniaxially pressed pellets. We have also achieved close to 50% improvement in the critical current density of the material and an improved lithiophilicity due to the surface nitrogen enrichment of the processed pellets. Distribution of relaxation time analysis supports the contributions from “faster” transport mechanisms for the antiperovskite films/pellets developed using the new protocol. Overall, the results highlight the feasibility of our new processing pathway for engineering antiperovskite solid electrolytes at the grain scale as a highly desirable approach for practical all-solid-state batteries

Operando Analysis of Gas Evolution in TiNb₂O₇ (TNO)-Based Anodes for Advanced High-Energy Lithium-Ion Batteries under Fast Charging

TiNb2O7 (TNO) is regarded as one of the promising next-generation anode materials for lithium-ion batteries (LIBs) due to its high rate capabilities, higher theoretical capacity, and higher lithiation voltage. This enables the cycling of TNO-based anodes under extreme fast charging (XFC) conditions with a minimal risk of lithium plating compared to that of graphite anodes. Here, the gas evolution in real time with TNO-based pouch cells is first reported via operando mass spectrometry. The main gases are identified to be CO2, C2H4, and O2. A solid–electrolyte interphase is detected on TNO, which continues evolving, forming, and dissolving with the lithiation and delithiation of TNO. The gas evolution can be significantly reduced when a protective coating is applied on the TNO particles, reducing the CO2 and C2H4 evolution by ∼2 and 5 times, respectively, at 0.1C in a half-cell configuration. The reduction on gas generation in full cells is even more pronounced. The surface coating also enables 20% improvement in capacity under XFC conditions

Nanoscale Ion Transport Enhances Conductivity in Solid Polymer-Ceramic Lithium Electrolytes

The predictive design of flexible and solvent-free polymer electrolytes for solid-state batteries requires an understanding of the fundamental principles governing the ion transport. In this work, we establish a correlation among the composite structures, polymer segmental dynamics, and lithium ion (Li+) transport in a ceramic-polymer composite. Elucidating this structure–property relationship will allow tailoring of the Li+ conductivity by optimizing the macroscopic electrochemical stability of the electrolyte. The ion dissociation from the slow polymer segmental dynamics was found to be enhanced by controlling the morphology and functionality of the polymer/ceramic interface. The chemical structure of the Li+ salt in the composite electrolyte was correlated with the size of the ionic cluster domains, the conductivity mechanism, and the electrochemical stability of the electrolyte. Polyethylene oxide (PEO) filled with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) or lithium bis(fluorosulfonyl) imide (LiFSI) salts was used as a matrix. A garnet electrolyte, aluminum substituted lithium lanthanum zirconium oxide (Al-LLZO) with a planar geometry, was used for the ceramic nanoparticle moieties. The dynamics of the strongly bound and highly mobile Li+ were investigated using dielectric relaxation spectroscopy. The incorporation of the Al-LLZO platelets increased the number density of more mobile Li+. The structure of the nanoscale ion-agglomeration was investigated by small-angle X-ray scattering, while molecular dynamics (MD) simulation studies were conducted to obtain the fundamental mechanism of the decorrelation of the Li+ in the LiTFSI and LiFSI salts from the long PEO chain