Chloride solid electrolytes (SEs) have attracted widespread attention due to their high room-temperature ionic conductivity and excellent cathode compatibility. However, the conventionally selected central metal elements (e.g., In, Y and Ta) are usually rare and heavy, inevitably causing the high cost and high density of the obtained chloride SEs. Here, by choosing abundant and light Mg and Al as central metal elements, we develop a cheap and low density Li1.2Mg0.95Al0.3Cl4 SE for high active material ratio in all solid state cathode. Partial replacement of Mg2+ by Al3+ in the framework yields vacancies and lowers the non-lithium metal ions occupancy at Mg/Li co-occupied 16d site, effectively relieving the blocking effects by Mg2+ in the pristine spinel Li2−2xMg1+xCl4. Thus, a significantly improved room-temperature conductivity of 3.08 × 10−4 S·cm−1 is achieved, two orders of magnitude higher than that of Li1.2Mg1.4Cl4. More attractively, its low density of only 1.98 g·cm−3 enables low SE mass ratio in cathodes (only 16 wt.%) with still effective electrolyte/cathode contact and lithium-ion conduction inside. When charged to potential of 4.30 V, the as-fabricated Li1.2Mg0.95Al0.3Cl4-based solid lithium battery with uncoated NCM523 cathode can be cycled for over 100 cycles with a capacity retention of 86.68% at room temperature.

Horizontally aligned carbon nanotube (HACNT) arrays hold significant potential for various applications in nanoelectronics and material science. However, their high-throughput characterization remains challenging due to the lack of methods with both high efficiency and high accuracy. Here, we present a novel technique, Calibrated Absolute Optical Contrast (CAOC), achieved through the implementation of differential principles to filter out stray signals and high-resolution calibration to endow optical contrast with physical significance. CAOC offers major advantages over previous characterization techniques, providing consistent and reliable measurements of HACNT array density with high throughput and non-destructive assessment. To validate its utility, we demonstrate wafer-scale uniformity assessment by rapid density mapping. This technique not only facilitates the practical evaluation of HACNT arrays but also provides insights into balancing high throughput and high resolution in nanomaterial characterization.