Crystal structure of dilithium biphenyl-4,4'-di-sulfonate dihydrate

The asymmetric unit of the title compound, μ-biphenyl-4,4'-di-sulfonato-bis-(aqua-lithium), [Li2(C12H8O6S2)(H2O)2] or Li2[Bph(SO3)2](H2O)2, consists of an Li ion, half of the diphenyl-4,4'-di-sulfonate [Bph(SO3 -)2] ligand, and a water mol-ecule. The Li ion exhibits a four-coordinate tetra-hedral geometry with three oxygen atoms of the Bph(SO3 -)2 ligands and a water mol-ecule. The tetra-hedral LiO4 units, which are inter-connected by biphenyl moieties, form a layer structure parallel to (100). These layers are further connected by hydrogen-bonding inter-actions to yield a three-dimensional network.

Operando Bragg Coherent Diffraction Imaging of LiNi0.8Mn0.1Co0.1O2 Primary Particles within Commercially Printed NMC811 Electrode Sheets

Due to complex degradation mechanisms, disparities between the theoretical and practical capacities of lithium-ion battery cathode materials persist. Specifically, Ni-rich chemistries such as LiNi_0.8Mn_0.1Co_0.1O₂ (or NMC811) are one of the most promising choices for automotive applications; however, they continue to suffer severe degradation during operation that is poorly understood, thus challenging to mitigate. Here we use operando Bragg coherent diffraction imaging for 4D analysis of these mechanisms by inspecting the individual crystals within primary particles at various states of charge (SoC). Although some crystals were relatively homogeneous, we consistently observed non-uniform distributions of inter- and intracrystal strain at all measured SoC. Pristine structures may already possess heterogeneities capable of triggering crystal splitting and subsequently particle cracking. During low-voltage charging (2.7-3.5 V), crystal splitting may still occur even during minimal bulk deintercalation activity; and during discharging, rotational effects within parallel domains appear to be the precursor for the nucleation of screw dislocations at the crystal core. Ultimately, this discovery of the central role of crystal grain splitting in the charge/discharge dynamics may have ramifications across length scales that affect macroscopic performance loss during real-world battery operation.

Joint-Linker Type Ionic Gels Using Polymerizable Ionic Liquid as a Crosslinker via Thiol-Ene Click Reactions

In this work, we report the synthesis of ion-conductive gels, or ionic gels, via thiol-ene click reactions. The novel gel systems consist of the multifunctional thiol monomers tris[(3-mercaptopropionyloxy)-ethyl]-isocyanurate (TEMPIC), pentaerythritol tetrakis(3-mercaptopropionate) (PEMP), and dipentaerythritol hexakis(3-mercaptopionate) (DPMP) as joint molecules and bifunctional allyl ionic liquid (IL) as a crosslinker. The thiol-ene reaction was carried out in lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) in a propylene carbonate (PC) (1 M) solvent system via a photopolymerization process. The chemical structure and mechanical, thermal, and conductive properties of the gels were investigated using Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), compression tests, and impedance spectroscopy, respectively. The mechanical and conductive properties of the ionic gels were found to be largely dependent on the monomer content and functionalities of the joint molecules. TGA revealed good thermal stability of the gels up to 100 °C. An ionic conductivity of 4.89 mS cm-1 was realized at room temperature (298 K) for low-functional thiol monomers, and a further increase in ionic conductivity was observed with an increase in Li+ ion content and temperature.

Surface-Dependent Performance of Ultrathin TiN Films as an Electrically Conducting Li Diffusion Barrier for Li-Ion-Based Devices

An in-depth understanding of lithium (Li) diffusion barriers is a crucial factor for enabling Li-ion-based devices such as three-dimensional (3D) thin-film batteries and synaptic redox transistors integrated on silicon substrates. Diffusion of Li ions into silicon can damage the surrounding components, detach the device itself, lead to battery capacity loss, and cause an uncontrolled change of the transistor channel conductance. In this study, we analyze for the first time ultrathin 10 nm titanium nitride (TiN) films as a bifunctional Li-ion diffusion barrier and current collector. Thermal atomic layer deposition (ALD) and pulsed chemical vapor deposition (pCVD) are employed for manufacturing ultrathin films. The 10 nm ALD films demonstrate excellent blocking capability with an insertion of only 0.03 Li per TiN formula unit exceeding 200 galvanostatic cycles at 3 μA/cm² between 0.05 and 3 V versus Li/Li⁺. An ultralow electrical resistivity of 115 μΩ cm is obtained. In contrast, a partial barrier breakdown is observed for 10 nm pCVD films. High surface quality with low contamination is identified as a key factor for the excellent performance of ALD TiN. Conformal deposition of 10 nm ALD TiN in 3D structures with high aspect ratios of up to 20:1 is demonstrated. The measured capacities of the surface area-enhanced samples are in good agreement with the expected values. High-temperature blocking capability is proven for a typical electrode crystallization step. Ultrathin ALD TiN is an ideal candidate for an electrically conducting Li-ion diffusion barrier for Si-integrated devices.

Rational Design of a Composite Electrode to Realize a High-Performance All-Solid-State Battery

A potential solid electrolyte for realizing all-solid-state battery (ASB) technology has been discovered in the form of Li₁₀ GeP₂ S₁₂ (LGPS), a lithium superionic conductor with a high ionic conductivity (≈12 mS cm^-1 ). Unfortunately, the achievable Li⁺ conductivity of LGPS is limited in a sheet-type composite electrode owing to the porosity of this electrode structure. For the practical implementation of LGPS, it is crucial to control the pore structures of the composite electrode, as well as the interfaces between the active materials and solid- electrolyte particles. Herein, the addition of an ionic liquid, N-methyl-N-butylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([Py₁₄ ][TFSI]), is proposed as a pore filler for constructing a highly reliable electrode structure using LGPS. [Py₁₄ ][TFSI] is coated onto the surface of LGPS powder through a wet process and a sheet-type composite electrode is prepared using a conventional casting procedure. The [Py₁₄ ][TFSI]-embedded composite electrode exhibits significantly improved reversible capacity and power characteristics. It is suggested that pore-filling with [Py₁₄ ][TFSI] is effective for increasing contact areas and building robust interfaces between the active materials and solid-electrolyte particles, leading to the generation of additional Li⁺ pathways in the composite electrode of ASBs.

Computational and Experimental Investigation of Ti Substitution in Li1(NixMnxCo1-2x-yTiy)O2 for Lithium Ion Batteries

Aliovalent substitutions in layered transition-metal cathode materials has been demonstrated to improve the energy densities of lithium ion batteries, with the mechanisms underlying such effects incompletely understood. Performance enhancement associated with Ti substitution of Co in the cathode material Li1(NixMnxCo1-2x)O2 were investigated using density functional theory calculations, including Hubbard-U corrections. An examination of the structural and electronic modifications revealed that Ti substitution reduces the structural distortions occurring during delithiation due to the larger cation radius of Ti(4+) relative to Co(3+) and the presence of an electron polaron on Mn cations induced by aliovalent Ti substitution. The structural differences were found to correlate with a decrease in the lithium intercalation voltage at lower lithium concentrations, which is consistent with quasi-equilibrium voltages obtained by integrating data from stepped potential experiments. Further, Ti is found to suppress the formation of a secondary rock salt phase at high voltage. Our results provide insights into how selective substitutions can enhance the performance of cathodes, maximizing the energy density and lifetime of current Li ion batteries.

3D printing of interdigitated Li-ion microbattery architectures

3D interdigitated microbattery architectures (3D-IMA) are fabricated by printing concentrated lithium oxide-based inks. The microbatteries are composed of interdigitated, high-aspect ratio cathode and anode structures. Our 3D-IMA, which exhibit high areal energy and power densities, may find potential application in autonomously powered microdevices.