| Lithium ion battery as a green power source is widely used in various portableelectronic devices and Electric/Hybrid Electric vehicles. However, the performance oflithium-ion battery cannot fully meet the current consumer demands. Researchersremain committed to the study of new electrode materials and electrolyte. NiO anodematerial is extensive concerned by researchers, with the advantages of simplepreparation, abundant of raw materials, environmentally friendly, high theoreticalcapacity and good safety performance. But the high irreversible capacity in the firstdischarge process and the poor cycle stability, hinder the practical application of NiO.In order to get better electrochemical performance of NiO materials, several methodsincluding metal ion doping, compositing with the other oxide, nickel foam loading ofactive material are investigated.To lower the irreversible capacity and improve the cycle stability, based on theconversion mechanism of NiO in the process of charge-discharge, Ni dopingflower-like NiO material is synthesized by hydrothermal and followed calcinedmethods. Ni nanoparticles are uniformly embedded in the NiO body. The results showthat the glucose concentration has an important impact on the morphology, structureand electrochemical performance of the products. The electrochemical testsdemonstrate that Ni nanoparticles can significantly improve the initial coulombefficiency and cycle stability. When cycling at the current density of100mA/g, theproduct obtained from the glucose concentration18.5mmol/Lhas the bestelectrochemical performance. Its initial discharge capacity is1165.7mAh/g, thereversible capacity can still maitain536.4mAh/g even after40cycles. Compared to thedischarge capacity of the second cycle, after40cycles the reversible capacity retentionis70.8%. During the cycles, the coulomb efficiency is maintained above95%. Rateperformance test shows that after cycling at0.14C,0.28C,0.7C and1.4C each for10times, when the current density returned to0.14C and cycled for10times again, thedischarge capacity can still maintain314.2mAh/g.To improve the cycle stability of NiO material, CoO-NiO-C composite materialswith3CoO5NiO crystal structure are prepared by co-precipitation and followedcalcined methods based on the conversion mechanism of transitional metal oxides inthe process of charge-discharge. Ni and Co nanoparticles produced in the dischargeprocess are used to increase the conductivity and catalyse the decomposition of the SEIto reduce the irreversible capacity loss. When cycling at the current density of100mA/g, sample obtained at600℃has the best electrochemical performance. Its initialdischarge capacity is1125.4mAh/g, even after60cycles the reversible capacity can still maintain562.6mAh/g. Compared to the discharge capacityofthe second cycle, thereversible capacity retention is76.7%after60cycles. During the cycles, the coulombefficiency is maintained above97%. Rate performance test shows that after cycling at0.28C,0.7C,1.4C,2.1C each for10times, when the current density returned to0.1Cand cycled for10times again, the discharge capacity can still maintain528mAh/g.To significantly increase the capacity of CoO-NiO composite materialand improvethe cycle stability under high current density, a nickel foam loading dimensionalelectrode is synthesized by hydrothermaland followed caicined methods. The results ofTEM demonstrate that nanoparticles are uniformly surrounded by the amorphouscarbon. The results of electrochemical test show that the reversible capacity of thethree-dimensional electrode is much higher than the corresponding powder material,and the cycle stability under high current density is also excellent. When cycling at thecurrent density of100mA/g, the initial discharge capacity is884.9mAh/g, after100cycles the reversible capacity can maintian815mAh/g. When cycling at the currentdensity of1,3,6A/g, the reversible capacity are540.6,387.2and122.5mAh/g, after250cycles with the reversible capacity retention81%,98.6%and30%, respectively. |
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