Lithium-Battery Anode Gains Additional Functionality for Neuromorphic Computing through Metal-Insulator Phase Separation

Specialized hardware for neural networks requires materials with tunable symmetry, retention, and speed at low power consumption. The study proposes lithium titanates, originally developed as Li-ion battery anode materials, as promising candidates for memristive-based neuromorphic computing hardware. By using ex- and in operando spectroscopy to monitor the lithium filling and emptying of structural positions during electrochemical measurements, the study also investigates the controlled formation of a metallic phase (Li₇ Ti₅ O₁₂ ) percolating through an insulating medium (Li₄ Ti₅ O₁₂ ) with no volume changes under voltage bias, thereby controlling the spatially averaged conductivity of the film device. A theoretical model to explain the observed hysteretic switching behavior based on electrochemical nonequilibrium thermodynamics is presented, in which the metal-insulator transition results from electrically driven phase separation of Li₄ Ti₅ O₁₂ and Li₇ Ti₅ O₁₂ . Ability of highly lithiated phase of Li₇ Ti₅ O₁₂ for Deep Neural Network applications is reported, given the large retentions and symmetry, and opportunity for the low lithiated phase of Li₄ Ti₅ O₁₂ toward Spiking Neural Network applications, due to the shorter retention and large resistance changes. The findings pave the way for lithium oxides to enable thin-film memristive devices with adjustable symmetry and retention.

Epitaxial Thin Films as a Model System for Li-Ion Conductivity in Li4Ti5O12

Using an epitaxial thin-film model system deposited by pulsed laser deposition (PLD), we study the Li-ion conductivity in Li₄Ti₅O₁₂, a common anode material for Li-ion batteries. Epitaxy, phase purity, and film composition across the film thickness are verified employing out-of-plane and in-plane X-ray diffraction, transmission electron microscopy, time-of-flight mass spectrometry, and elastic recoil detection analysis. We find that epitaxial Li₄Ti₅O₁₂ behaves like an ideal ionic conductor that is well described by a parallel RC equivalent circuit, with an ionic conductivity of 2.5 × 10^-5 S/cm at 230 °C and an activation energy of 0.79 eV in the measured temperature range of 205 to 350 °C. Differently, in a co-deposited polycrystalline Li₄Ti₅O₁₂ thin film with an average in-plane grain size of <10 nm, a more complex behavior with contributions from two distinct processes is observed. Ultimately, epitaxial Li₄Ti₅O₁₂ thin films can be grown by PLD and reveal suitable transport properties for further implementation as zero-strain and grain boundary free anodes in future solid-state microbattery designs.

A Simple and Fast Electrochemical CO2 Sensor Based on Li7 La3 Zr2 O12 for Environmental Monitoring

In the goal of a sustainable energy future, either the energy efficiency of renewable energy sources is increased, day-to-day energy consumption by smart electronic feedback loops is managed in a more efficient way, or contribution to atmospheric CO₂ is reduced. By defining a next generation of fast-response electrochemical CO₂ sensors and materials, one can contribute to local monitoring of CO₂ flows from industrial plants and processes, for energy management and building control or to track climate alterations. Electrochemical Li⁺ -garnet-based sensors with Li₇ La₃ Zr₂ O₁₂ solid electrolytes can reach notable 1 min response time at lowered operation temperatures to track 400-4000 ppm levels of CO₂ when compared with state-of-the-art NASICON-based sensors. By using principles of redefining the electrode electrochemistry, it is demonstrated that Li_6.75 La₃ Zr_1.75 Ta_0.25 O₁₂ can be used to alter its classic use as energy-storage function to gain additional functions such as CO₂ tracking.

Designing Strained Interface Heterostructures for Memristive Devices

Ionic heterostructures are used as a strain-modulated memristive device based on the model system Gd_0.1 Ce_0.9 O_2-δ /Er₂ O₃ to set and tune the property of "memristance." The modulation of interfacial strain and the interface count is used to engineer the R_off /R_on ratio and the persistence of the system. A model describing the variation of mixed ionic-electronic mobilities and defect concentrations is presented.

[One-stage urethra repair with end-to-end anastomosis]

The direct anastomosis in one session is the method of choice for the treatment of urethral strictures (< 2.5 cm length) when at least three internal urethrotomies have failed. If certain important details are kept in mind about the operative technique (wide anastomosis without tension), suitable suture materials used, and the urinary diversion is done without placing a burden on the anastomosis, the long-term results are good. The direct anastomosis and operative approach can be varied according to the special situation in individual cases. The analysis of 47 patients operated on with direct anastomosis for strictures in the posterior urethra (28 post-traumatic, 9 iatrogenic, 10 postinflammatory) revealed that 83% of the patients had good or satisfactory results, while in 8 patients (17%) the results were poor. The poorist long-term results occurred in post-traumatic strictures in the bulbomembranous part of the urethra connected with complicated pelvic fractures.