Study On Carbon-Based Composite Seawater Dissolved Oxygen Battery And Its Discharge Performance

With the development of society,the value of the ocean has been paid more and more attention by human beings.Countries all over the world have gradually strengthened the exploration and exploitation of marine resources,and various marine equipment emerge one after another.However,the traditional land power supply mode is difficult to meet the working conditions of marine equipment,so it is extremely urgent to develop new power supply technology suitable for marine equipment.Seawater dissolved oxygen battery uses seawater as electrolyte,which has the characteristics of high energy density,good safety performance and long service life.The open structure does not consider the pressure problem caused by the increase of seawater depth,and has a bright future in supplying power for marine equipment.In this dissertation,carbon brush-graphene-platinum（Pt-G@CFB）and carbon cloth-polypyrrole-platinum（Pt-PPy@CC）modified electrodes were prepared with carbon fiber brush and carbon cloth as matrix,graphene or polypyrrole as carrier and Pt nanoparticles as catalyst.Al-Si-In-Ga-Sn alloy was doped and smelted for negative electrode of battery,and the materials were characterized by SEM,TEM and XPS.The electrode performance was evaluated by cyclic voltammetry curve,potentiodynamic polarization curve and galvanostatic polarization.The effects of dissolved oxygen concentration,temperature,salinity and simulated deep sea environment on the discharge performance of cathode materials and batteries composed of Al-Si-In-Ga-Sn alloy were studied by galvanostatic polarization.The influence of current on the discharge performance of electrode and battery is studied and the battery power is calculated The voltage change law of electrical appliances for battery cell or parallel load is explored The discharge performance of the battery in static and dynamic seawater system was investigated by means of constant resistance discharge,and the composition and distribution of reaction by-products on the positive electrode surface were analyzed.The main results are as follows:（1）The specific surface area of Pt-G@CFB electrode prepared by growing graphene and Pt particles on carbon brush is increased to 29.4508 m/g,and the porous structure is easy to absorb oxygen.Pt particles are uniform Ly dispersed on graphene surface,and the grain size is about 3.1 nm.The Pt-G@CFB electrode showed an obvious oxygen reduction peak at-0.3V,the limiting diffusion current density at 2025r was 4.91 mA/cm,the oxygen reduction reaction was a 4-electron process,and the positive shift of the potential value was 0.15V,showing good catalytic activity.On the surface of Pt-PPy@CC electrode,Pt particles are clustered to some extent,and the CV curve has obvious oxygen reduction peak,which is also a 4-electron reaction process.The limiting diffusion current density reaches 5.5 mA/cm,the potential value shifts 0.22 V,and the potential value still reaches 0.14 V when discharging for 1.5 h at 0.1 mA/cm current density.（2）The elements in Al-Si-In-Ga-Sn alloy are dispersed uniform Ly,and the activity of the alloy is improved after doping with elements,which makes it easy to corrode in seawater.The open-circuit potential of Al-Si-In-Ga-Sn alloy is as low as-1.6 V,which is less than-1.43 V of Mg-Mn alloy and-1.18 V of Al-Zn-In-Sn-Mg alloy.The discharge potential is negative 0.51 V than that of Al-Zn-In-Sn-Mg alloy at 0.1 ma/cm,and is-1.33V at 10 mA/cm current density.The open circuit voltage of the battery formed with Pt-G@CFB electrode is as high as 1.86 V.（3）The Pt-G@CFB electrode is less affected by low dissolved oxygen concentration,low temperature and low salinity.After being composed of seawater battery,the voltage of Pt-G@CFB electrode is still 1.77 V and the voltage drop is only 0.07 V when it is discharged at a current density of 0.1 mA/cm for 1 hour at 5℃and 3 mg/L dissolved oxygen.The influence of environmental factors on the discharge of Pt-PPy@CC electrode is more serious than that of Pt-G@CFB electrode,but it still has a stable voltage of 1.2 V at 20℃and saturated oxygen.The maximum output power of Pt-G@CFB battery and Pt-G@CC battery is 55.1 mW and 50.4 mW,respectively.（4）Material modification can obviously improve the application performance of batteries.Both Pt-G@CFB and Pt-PPy@CC batteries can supply power to electrical appliances with different working voltages.Under 87 mA current,Pt-G@CFB batteries can supply power to LED displays for 17 minutes,which is as high as 105 minutes after series connection,and Pt-PPy@CC batteries also have 87 minutes.The higher the current through the battery,the more serious the deposit on the positive electrode surface,which is mainly composed of Mg（OH）₂,Al₂O₃and CaCO₃.Pt-G@CFB battery has a 50-day average voltage of 1.78 V and a maximum energy density of 653.44 Wh/kg.The energy density of Pt-PPy@CC battery at 500Ωwas 183.2 Wh/kg,which was twice that of the control group.