From protonation & Li-rich contamination to grain-boundary segregation: Evaluations of solvent-free vs. wet routes on preparing Li_(7)La_(3)Zr_(2)O_(12) solid electrolyte

Garnet-type Li_(7)La_(3)Zr_(2)O_(12)(LLZO) has been recognized as a candidate solid electrolyte for high-safety Lianode based solid-state batteries because of its electro-chemical stability against Li-metal and high ionic conductivity. Solvent(e.g., isopropanol(IPA)) has been commonly applied for preparing LLZO powders and ceramics. However, the deterioration of the proton-exchange between LLZO and IPA/absorbed moisture during the mixing and tailoring route has aroused less attention. In this study, a solvent-free dry milling route was developed for preparing the LLZO powders and ceramics. For orthogonal four categories of samples prepared using solvent-free and IPA-assisted routes in the mixing and tailoring processes, the critical evaluation was conducted on the crystallinity, surficial morphology, and contamination of ascalcinated and as-tailored particles, the cross-sectional microstructure of green and sintered pellets,the morphology and electro-chemical properties of grain boundaries in ceramics, as well as the interfacial resistance and performance of Li anode based symmetric batteries. The wet route introduced Li-rich contaminations(e.g., Li OH·H)_(2)O and Li)_(2)CO)_(3)) onto the surfaces of LLZO particles and Li-Ta-O segregations at the adjacent and triangular grain boundaries. The LLZO solid electrolytes prepared through dry mixing in combination with the dry tailoring route without the use of any solvent were found to the optimal performance. The fundamental material properties in the whole LLZO preparation process were found, which are of guiding significance to the development of LLZO powder and ceramic production craft.

Constructing stable Li-solid electrolyte interphase to achieve dendrites-free solid-state battery:A nano-interlayer/Li prereduction strategy

Solid-state batteries based on Li and nonflammable solid-state electrolytes(SSEs)have aroused the attention of numerous researchers because of their absolute safety and potentially high energy density.Most SSEs after coming into contact with Li are reduced,which leads to high interfacial charge-transfer impedance and dendrites formation.In this study,an“interlayer-Li pre-reduction strategy”was proposed to solve the above problem of reduction.An intermediate layer was introduced between solid electrolyte and Li,and it reacted with Li to produce a stable and ion-conductive interphase.Cubic garnet-type Nb-doped Li_(7)La_(3)Zr_(2)O_(12)(Nb-LLZO)was selected as an example solid electrolyte since it is characterized by high ionic conductivity,feasible preparation under ambient conditions,as well as low cost.The high impedance arising from the reduction at the Nb-LLZO|Li interface has limited its application.In this paper,a nano-scale Li phosphorus oxynitride(LiPON)layer was deposited on the Nb-LLZO pellets through radio frequency(RF)magnetron sputtering,which pre-reacted with Li in-situ to produce a lithiophilic,electronically insulating,and ionic conductive interphase.The produced interphase significantly inhibited the reduction of Nb5+against Li and the formation and propagation of Li dendrites.It is noteworthy that Li|LiPON|Nb-LLZO|LiPON|Li cells stably cycled for over 2,000 h without any short circuit.This study emphasizes and demonstrates the significance of the pre-conversion of modification layer between unstable SSE and Li metal to improve interfacial stability.

Off-axis three-mirror reflective zoom system based on freeform surface

A reflective optical system is not affected by chromatic aberration, so it has a wide range of applications. Based on the design theory of reflective zoom system with three mirrors, this paper presents the simulation, optimiza- tion, and image quality evaluation of the traditional off- axis three-mirror zoom system and freeform off-axis three- mirror reflective zoom system.. In these systems, the optical design was aided by software CODEV. Through the analysis of aberrations and structural performance for the traditional aspherical off-axis three-mirror system, the freeform surface was introduced to the tertiary mirror to improve the balance capacity for optical aberrations. This off-axis three-mirror reflective zoom system based on freeform surface could provide technical reference to the study of such systems.

Design and demonstration of a foveated imaging system with reflective spatial light modulator

In this paper, a foveated imaging system using a reflective liquid crystal spatial light modulator （SLM） was designed. To demonstrate the concept of foveated imaging, we simulated with software Code V and established a laboratory prototype. The result of the experiment shows that an SLM can be used to correct the aberration of region of interest （ROI） while the resolution of other area was still very low. The vary- resolution system was relative simple compared to the traditional high resolution system and obviously can reduce the amount of data transmission. Such systems will have wide application prospect in various fields.