Ni/Mn-based layered oxides have been widely studied for sodium ion battery cathode because of high capacity and simple preparation. However, its application has been restricted owing to unstable structure and poor cycling performance. Herein, the multi-element doped hexagonal sheet Ni/Mn-based layered oxide with ZrO 2 surface modification O3-NaNi 0.3 Mn 0.5-x Fe 0.1 Cu 0.1 Zr x O 2 @ZrO 2 (NFMCZ-x) cathode materials have been successfully synthesize by high temperature calcination method accompanied by ball milling activation. XRD refinement results show Zr 4+ substitution of Mn 3+ can increase interlayer distance of sodium layer. Benefiting from the synergetic effect of multi-element doping and ZrO 2 surface modification, the optimized NFMCZ-0.03 sample exhibits a higher discharge capacity of 178 mAh/g at 0.1C and good capacity retention (77 % after 50 cycles at 2C). Furthermore, NFMCZ-0.03 has an excellent air stability with a capacity retention rate of 86 % during 50 cycles at 1C after being exposed in the air for 20 days. The ex-situ XRD results of NMFC at different charge/discharge voltages show Zr 4+ doping can suppress O3 + P3′'–O3′-O3 + P3′' phase transition during charge/discharge process. These results confirm that synergistic effect of multi-doping combined with surface modification can improve electrochemical performance of layered oxides cathodes, which provides a research idea for development of Ni/Mn-based layered oxides cathodes for sodium-ion batteries.
Lei Meng,Bin Yao,Yongfeng Li,Zhanhui Ding,Zhenyu Xiao,Kaisi Liu,Gang Wang
The back contact adhesion is the important factor of the microstructural performance which can determine the optoelectronic properties of the kesterite-based solar cells. Here, we present a rational and effective strategy to significantly enhance the back contact adhesion of Cu 2 (Zn,Cd)Sn(S,Se) 4 (CZCTSSe) absorber layers by insetting the appropriate thickness carbon-doping CZCTS thin films . We chose the oleylamine as the carbon-doping reagent which can generate a small amount of carbon in the annealing process . The suitable thickness carbon-doping CZCTS films can significantly change the crystal growth mechanism of CZCTSSe absorber layers, and eliminate the holes in the back contact. The efficiency of CZCTSSe solar cells fabricated by insetting the appropriate thickness carbon-doping CZCTS films is above 7%, and shows the excellent repeatability and long-term air stability compared with the control devices.
Sulfide solid state electrolytes capture much attention owing to their high conductivity and decent mechanical property. Nevertheless, the moisture instability and poor interfacial compatibility against lithium metal anode remain challenging and hinder the practical application. Herein, we report a novel indium (In) doping strategy based on the hard-soft-acid-base theory to tackle these issues. Optimized Li 7 P 2.9 S 10.9 In 0.1 electrolyte exhibits a high ionic conductivity of 4.1 × 10 −3 S cm −1 and achieves an enhanced interfacial compatibility. Importantly, as In partially replaces the phosphorus (P), the amount of released hydrogen sulfide can be significantly decreased and the air stability is improved. The all-solid-state battery assembled with the Li 7 P 2.9 S 10.9 In 0.1 electrolyte demonstrates a high discharge capacity and a good cycling stability under a high current density of 1.0 C. This work provides a practical and effective method to design sulfide-based solid-state electrolyte with high ionic conductivity and enhanced air stability for all-solid-state battery applications.
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