Research On NiZn Battery Construction, Performance Research And Its Recovery

In this thesis, the main research contents include the development, electrochemical performances and recycle of nickel zinc battery. According to the mechanism and existing problems of NiZn battery, we proposed the solution. The ideas of the subject is that Ni（OH）₂ directly grows on the surface of carbon nanomaterials to prepare Ni（OH）₂/nano-carbon hybrid by altering the traditional preparation methods of Ni（OH）₂ positive electrode of commercial NiZn battery. NiZn battery is assembled by using Ni（OH）₂/nano-carbon hybrid as cathode and Zn as anode. According to characteristics of the positive and negative electrode materials and the electrolyte of NiZn battery, the waste Ni Zn battery was disassembled and recycled. First of all, the carbon nanomaterials were modified in controlled way. After that, the oxygen functional groups were introduced in the surface of carbon nanomaterials and the inner kept high electrical conductivity. Electrons could rapidly transfer in charge/discharge stage, which solved the problems of effective usage of active materials and effective transformation of electrons. The thesis reported the oxidized conditions of carbon nanotube and nanofiber and process conditions of Ni（OH）₂/carbon nanotubes and Ni（OH）₂/carbon nanofibers in various reaction systems. Electronic properties and cycle life of NiZn battery were characterized. The relationships among reaction condition, structure and property were explored and the optimize synthesis conditions were obtained. The crystal phase, shape, size, and electronic properties of products were characterized by SEM, XRD, CV, and battery test system. The detailed content is as followed:（1） The surface modification of carbon nanotubes or nanofibers: The impurities were first deleted from carbon nanotubes or carbon nanofibers by acid treatment; and then oxidized carbon nanomaterials containing oxygen functional group were obtained by hydrothermal treatment.（2） Using oxidized carbon nanotubes as substances, Ni（OH）₂/multi-wall carbon nanotube（MWNT） hybrids were prepared in two-step methods by using NH3·H2O as the precipitant. XRD patterns, TEM and SEM images confirmed β-Ni（OH）₂ nanoparticles with high crystalline degree growth on the MWNT surfaces. CV testing results demonstrated the specific capacity was 159.1 mAh·g^-1 at 2 mV·s^-1 scanning rate. The cycle mumbles was 1000 times at 100 mV·s^-1 scanning rate and the specific capacity does not almost decay. NiZn battery were assembled with Ni（OH）₂/MWNT hybrid and zinc foil in KOH gel electrolyte. The measuring results displayed that the energy density still retained 190 Wh·kg^-1 after 1100 cycles.（3） Using oxidized carbon nanofibles as substances, Ni（OH）₂/carbon nanofible（CNF） hybrids were prepared in DMF-H2 O solvent system. CV testing results demonstrated the specific capacity was 208.4 mAh·g^-1 at 5 m V·s^-1 scanning rate. The cycle mumbles was up to 1000 times at 100 mV·s^-1 scanning rate and the specific capacity did not almost decay. The NiZn battery assembled with Ni（OH）₂/CNF hybrid and zinc foil had 1000 cycle times and its energy density was 145 Wh·kg^-1 at a charge current density 2.35 A·g^-1 and charge time 3 min and discharge current density 2.54 A·g^-1. It displayed that the pouch-cell with high energy density, power density, and cycle stability was obtained.（4） Using oxidized carbon nanofibles as substances, Ni（OH）₂/CNF hybrids were prepared by using NaOH solution as the precipitant. The specific capacities at 5 mV·s^-1 and 40 mV·s^-1 scanning rates were 250.6 mAh·g^-1 and 205.5 m Ah·g^-1 separately. The Ni（OH）₂/CNF hybrids exhibited long cycling stability over 1100 times with little capacitance decay. The battery’s columbic efficiency was over 98% and its energy density could keep 170 Wh·kg^-1 with over 1100 cycles at a charge current density 2.35 A·g^-1 and charge time 3 min and discharge current density 2.54 A·g^-1.（5） Recycle of waste NiZn battery: Considering the feature of Ni Zn battery, we designed the recovery process and carried out the recycle experiments. Ultimately, main parts of waste NiZn battery were recovered effectively.