| Bipolar lead-acid battery has the characteristics of high specific energy, high specific power and long life. The key to prepare bipolar lead-acid battery is its bipolar plate. In this thesis, compound titanium substrate, active material additive and porous array active material electrode were studied for high specific energy, high specific power and long life bipolar lead-acid battery.Titanium foils surface were coated with a layer of non-stoichiometric titanium oxide(Ti O2-x) film employing the Sol-gel carbothermic reduction method and direct oxidation carbon thermal reduction method. Both of modified titanium substrates sintered at 800 ℃ for 2 h using the abovementioned two methods had excellent electronic conductivity. The XPS analysis confirmed t he average calence state of titanium in the surface film is all 3.74. The lead-acid battery used the titanium substrate prepared through Sol-gel carbon thermal reduction method displayed the specific capacities of 90 m Ah·g-1, 80 m Ah·g-1, 65 m Ah·g-1 and 60 m Ah·g-1 at 0.25 C, 0.5 C, 1 C and 2 C respectively.w While, the lead-acid battery used the titanium substrate prepared via the direct oxidation carbon thermal reduction method presented the specific capacities of 100 m Ah·g-1, 90 m Ah·g-1, 80 m Ah·g-1 and 65 m Ah·g-1 at same test conditions. Both of them exhibited high specific capacity. Moreover, compared with the unmodified titanium foil, the treated titanium substrate effectively improved the chemical stability of the titanium foil in bipolar lead-acid battery during the charge and discharge processes.The compound titanium substrate was soaked with the 50 wt% fluoboric acid to form a uniform corrosion interface, which was beneficial for improving the bonding strength between the lead paste and the lead layer in the curing process, and thus enhanced the capacity and cycling life of the acitive material.Tetrabasic lead sulfate(4BS)/ superfine Si O2 compound additive was synthesized using the high speed milling method. In the preparing process, 6 wt% gas phase Si O2 was added to inhibit the aggregation of nanosised 4BS. XRD results confirmed that the purity of the prepared nano 4BS was close to 100%. SEM images found that the morphology of the milled 4BS is grainy, which is different from the traditional rod-like 4BS. HRTEM analysis showed that nano 4BS is a type of polycrystalline consisting of 4BS crystals. 4BS/Si O2 has very high activity, which displayed discharge specific capacities of 183 m Ah.g-1 at 40 m A.g-1 and 150 m Ah.g-1 at 160 m A.g-1, respectively.After adding nano 4BS/Si O2 compound additive to the positive acitive material, a cross-linked net skeleton can be observed from the SEM images. TEM found that 4BS had both rod and grainy morphlolgy. HRTEM analysis showed that rod 4BS was a type of single crystal, and grainy 4BS was polycrystalline. XRD results suggested that 4BS grow with preferentially crystal facet during the curing process. Charge-discharge test results showed that positive active material with 1 wt% nano 4BS had higher discharge specific capacity, because of no obviously capacity decay after 300 cycles, which indicated that nano 4BS/Si O2 compound additive can improve positive active material cycle life without reducing its specific capacity.Design and fabrication of porous array active material electrode improved bipolar lead-acid battery capacity per unit area. The porous array active material can effectively improve active material utilization and cycle life. Specific capacity at 1 C can reach 50.08 m Ah·g-1. A mathematical model of the porous array active material electrode was setup to derive the relationship between the whole porosity of active material and array pore size and quantity in the unit area for explaining the high utilization of acitive material in the high rate using acid storage mechanism. Finally, a 12 V experimental bipolar lead-acid batteries was prepared and the specific energy reached more than 40 Wh·kg1. |
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