Broadband electrochromism from visible to infrared wavelengths is attractive for applications like smart windows, thermal camouflage, and temperature control. In this work, the broadband electrochromic properties of Li 4 Ti 5 O 12 (LTO) and its suitability for infrared camouflage and thermoregulation are investigated. Upon Li + intercalation, LTO changes from a wide bandgap semiconductor to a metal, causing LTO nanoparticles on metal to transition from a super-broadband optical reflector to a solar absorber and thermal emitter. Large tunabilities of 0.74, 0.68, and 0.30 are observed for the solar reflectance, mid-wave infrared (MWIR) emittance, and long-wave infrared (LWIR) emittance, respectively, with a tunability of 0.43 observed for a wavelength of 10 µm. The values exceed, or are comparable to notable performances in the literature. A promising cycling stability is also observed. MWIR and LWIR thermography reveal that the emittance of LTO-based electrodes can be electrochemically tuned to conceal them amidst their environment. Moreover, under different sky conditions, LTO shows promising solar heating and subambient radiative cooling capabilities depending on the degree of lithiation and device design. The demonstrated capabilities of LTO make electrochromic devices based on LTO highly promising for infrared-camouflage applications in the defense sector, and for thermoregulation in space and terrestrial environments.The large tunability, along with its excellent cycle-life, [9] makes LTO attractive for infrared camouflage and radiative thermoregulation.

An important requirement of battery anodes is the processing step involving the formation of the solid electrolyte interphase (SEI) in the initial cycle, which consumes a significant portion of active lithium ions. This step is more critical in nanostructured anodes with high specific capacity, such as Si and Sn, due to their high surface area and large volume change. Prelithiation presents a viable approach to address such loss. However, the stability of prelithiation reagents is a big issue due to their low potential and high chemical reactivity toward O and moisture. Very limited amount of prelithiation agents survive in ambient air. In this research, we describe the development of a trilayer structure of active material/polymer/lithium anode, which is stable in ambient air (10-30% relative humidity) for a period that is sufficient to manufacture anode materials. The polymer layer protects lithium against O and moisture, and it is stable in coating active materials. The polymer layer is gradually dissolved in the battery electrolyte, and active materials contact with lithium to form lithiated anode. This trilayer-structure not only renders electrodes stable in ambient air but also leads to uniform lithiation. Moreover, the degree of prelithiation could vary from compensating SEI to fully lithiated anode. With this strategy, we have achieved high initial Coulombic efficiency of 99.7% in graphite anodes, and over 100% in silicon nanoparticles anodes. The cycling performance of lithiated anodes is comparable or better than those not lithiated. We also demonstrate a LiTiO/lithiated graphite cell with stable cycling performance. The trilayer structure represents a new prelithiation method to enhance performance of Li-ion batteries.

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