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It has been reported that introducing Ag interlayer at the Cu/Bi 2 Te 3 interface can achieve ultra-low electrical contact resistivity. However, there is no consensus on the influence of Ag diffusion induced by Ag interlayer on electrical contact. Thus, the impact of Ag diffusion on electrical contact conductivity for Cu/Ag/Bi 2 Te 3 multilayers was investigated. The generation of interfacial compounds induced by Ag diffusion was analyzed and the contact resistivity was measured in Cu/Ag/Bi 2 Te 3 multilayers with different Ag interlayer thickness before and after annealing. It was found that Ag diffusion induced interfacial compounds Cu 4 Ag 3 Te 4 at the Cu/Ag interface before annealing, which could decrease contact resistivity to 3.728×10−12 Ω∙m2. After annealing, the relative amount of Cu 4 Ag 3 Te 4 at the Cu/Ag interface slightly decreased, and the Ag 2 Te was found to appear at the Ag/Bi 2 Te 3 interface, which could further decrease contact resistivity to 3.187×10−12 Ω∙m2. With Ag interlayer thickness increasing from 50 nm to 300 nm, the contact resistivity decreased from 3.726×10−10 Ω∙m2 to 3.728×10−12 Ω∙m2 before annealing because the relative amount of Cu 4 Ag 3 Te 4 increased about 5 times, after annealing the contact resistivity further decreased by 10.27∼41.7 % because the relative amount of Ag 2 Te increased about 1.1 times. In addition, we had optimized the ultra-low contact resistivity test method by redesigning the structure of test samples and modifying the formula of contact resistivity to eliminate two errors. One is caused by Cu electrode short-circuit resistance due to the test current being short-circuited by the middle electrode between two test electrodes. The other is caused by the increased electrical resistance of Bi 2 Te 3 thin film due to Te atom volatilization after annealing. The results showed that the errors of the test results were reduced by at least 21.50 %. Our work provides guidance for further optimizing electrical contact of thin-film thermoelectric devices. [Display omitted] • The influence of Ag diffusion on contact resistivity is investigated. • The variation of contact resistivity with Ag interlayer thickness is studied. • Interfacial compounds induced by Ag diffusion is semi-quantitatively analyzed. • Ultra-low contact resistivity test method is optimized by eliminating two errors. [ABSTRACT FROM AUTHOR]

The development of lithium-oxygen battery was an effective way to alleviate energy crisis, save energy and protect environment. The design of cathode catalyst with high catalytic performance can effectively promote the performance of lithium-oxygen battery. To research the influence of oxygen vacancies on the electrochemical catalytic performance, a novel and effective method was proposed to introduce more oxygen vacancies into MoO 3. The h-MoO 3 with oxygen-rich vacancies (named MoO 3 -HTP) was synthesized by using original MoO 3 to heat together with NaH 2 PO 4. As the cathode catalyst of lithium-oxygen batteries, MoO 3 -HTP had a smaller first cycle overpotential of 0.76 V and showed 137 stable cycles under a limited capacity of 500 mAh g−1 at 200 mA g−1 from the comparison of the MoO 3 and MoO 3 -HT. And MoO 3 -HTP-based batteries had the lower overpotential of 1.58 V under the first full charge-discharge curves at 200 mA g−1 and 400 mA g−1. The excellent conductivity and electrocatalytic performance of MoO 3 -HTP were put down to the abundance of oxygen vacancies. [Display omitted] • The h-MoO 3 with oxygen vacancies was synthesized by calcining with NaH 2 PO 4. • Oxygen vacancies increased conductivity and electrochemical surface areas. • The enhanced conductivity and ECSAs resulted in better cyclic stability. [ABSTRACT FROM AUTHOR]

Cathode materials based on zLi 2 SiO 3 @LiNi 0.6 Co 0.2 Mn 0.2 O 2 (z = 0, 0.03, 0.05, 0.08) (where “@” denotes “coated on the surface of”) have been successfully prepared via a syn-lithiation strategy. The cycling performance of LiNi 0.6 Co 0.2 Mn 0.2 O 2 has been effectively enhanced by coating a Li 2 SiO 3 thin film. Compared to the 81 mAh/g discharge capacity of the pristine materials, the 5 mol% Li 2 SiO 3 -coated LiNi 0.6 Co 0.2 Mn 0.2 O 2 electrode exhibits 31% higher discharge capacity between 2.5 V and 4.5 V at a rate of 5 C. The reason for the improved cycling performance of LiNi 0.6 Co 0.2 Mn 0.2 O 2 is Li 2 SiO 3 coating and Si 4+ doping, which stabilizes the structure, suppresses the direct contact between the active materials and electrolytes, enhances lithium ion diffusion at the electrode/electrolyte interface, and prevents the pulverization of active materials during repeated charging/discharging. [ABSTRACT FROM AUTHOR]

• Honeycomb-like NiCo 2 O 4 nanoflakes are successfully synthesized by electrochemical deposition and subsequent heat treatment. • NiCo 2 O 4 /CC benefits from a vital synergistic effect of Co and Ni and has abundant oxygen vacancies. • The NiCo 2 O 4 /CC electrode delivers a long lifetime of 102 cycles. • The NiCo 2 O 4 /CC electrodes deliver high discharge capacities of 8388 and 5238 mA h g−1 at 200 and 400 mA g−1, respectively. The development of high energy density Li-O 2 batteries is restricted by the sluggish kinetics of both the oxygen reduction reaction and the oxygen evolution reaction, and developing an efficient cathode catalyst is the key to resolving this issue. In present study, interconnected honeycomb-like NiCo 2 O 4 nanoflakes are synthesized by facile electrochemical deposition on carbon cloth (CC) and subsequent heat treatment. Compared with NiO and Co 3 O 4 , suitably sized NiCo 2 O 4 nanoflakes benefit from a vital synergistic effect of components Co and Ni and are expected to show superior OER/ORR performance. The presence of redox couples Co3+/Co2+ and Ni2+/Ni3+ and abundant oxygen vacancies in NiCo 2 O 4 allow Li-O 2 batteries deliver satisfactory cycle durability and high discharge/recharge capacities. Li-O 2 batteries that use the NiCo 2 O 4 /CC cathodes exhibit high specific discharge capacities of 8388 mA h g−1 and 5238 mA h g−1 at 200 mA g−1 and 400 mA g−1, respectively, and deliver a long lifetime of 102 cycles with a capacity limit of 500 mA h g−1 at 340 mA g−1, thereby suggesting that honeycomb-like NiCo 2 O 4 nanoflakes are a promising cathode catalyst. [ABSTRACT FROM AUTHOR]