Studies Of Novel Secondary Batteries Based On Alkaline Aqueous Electrolyte

Batteries based on aqueous electrolyte,which is represented by silver-zinc batteries are promising energy conversion devices.In which,silver-zinc batteries as a mature type of alkaline system zinc-based batteries,have been widely used in different fields.Compared to lithium-ion batteries which are seen as the most promising candidates,silver-zinc batteries have decent specific energy.What is more,aqueous electrolyte can help avoid flamming and bombing problems that bothers lithium-ion batteries for a long time.The use of non-toxic elements make such batteries environmentally-friendly.However,aqueous batteries using KOH as electrolyte still face many problems.An unavoidable problem is that the electrode materials and battery components can be easily corroded and dissolved due to the strong basicity of KOH electrolyte,hence deceasing the utility and cyclability of electrode materials,which make it impossible for aqueous system batteries to match lithium-ion batteries.To address these issues,this thesis is focus on improving the cyclability of silverzinc batteries and searching for substitutes of KOH electrolyte.The major progress is summarized as follows:1.Due to its non-toxic and has good solubility in water,PEG-200 has been used as an effective additive to increase the cycleability of the silver-zinc batteries.By adding proper amount of PEG-200 into the KOH electrolyte,the cycle life of the silverzinc battery has been significantly improved to 100 cycles without obvious decay in capacity.In 100 cycles,the capacity remains 70 m Ah/g and the energy density keeps at 110 Wh/kg.Series characterizations show that PEG-200 as electrolyte additive can maintain the morphology of the zinc electrode,and inhibit the formation of zinc dendrites.2.KOH/Na OH of high concentration as electrolyte owns high p H values,which promote dissolution of the electrode materials,hence decreasing its utility in capacity and cycleability.However,K₂CO₃ of the same p H value as KOH?p H=13.0? is much more concentrated?3.6 M?and owns high ionic conductivity.Meanwhile,the solubility of Mn,Pb,Zn,etc.is much lower in 3.6 M K₂CO₃ than that in 0.1 M KOH.CV shows Mn,Pb,Zn,etc.have good cycle performance in 3.6 M K₂CO₃ electrolyte.3.For the first time,lead carbonate as electrode materials in 3.6 M K₂CO₃ have been investigated.It is discovered that:?1?Two-electron transfer reaction is take place for lead carbonate as both positive and negative electrode materials.As negative material,lead carbonate?Pb₃C₂O₇,JCPDS#17-0730?is the charged state,and lead is the discharged state.As positive material,lead dioxide?Pb O2,JCPDS#41-1492?is the charged state,and lead carbonate?Pb₃C₂O₇,JCPDS#17-0730?is the discharged state.?2?Lead carbonate as both positive and negative electrodes show good cycling performance.?3?The full battery,which used lead carbonate as positive and negative electrodes respectively,3.6 M K₂CO₃ as electrolyte,can be cycled for 200 cycles without obvious decay in capacity.The full battery has the discharge plateau of 1.04 V,the capacity of 70.0 m Ah/g and energy density of 70.0 Wh/kg.4.For the first time,manganese carbonate as electrode materials in 3.6 M K₂CO₃ electrolyte has been demonstrated.It is discovered that:?1?Two-electron transfer reaction is take place for manganese carbonate as positive electrode material.Manganese carbonate?Mn CO3,JCPDS#44-1472?is the discharged state,and manganese dioxide?Mn O2,JCPDS#44-0141?is the charged state.The theoretical capacity reaches 466.3 m Ah/g.?2?Manganese carbonate as positive electrode shows good cycling performance.?3?The full battery,which used manganese carbonate as positive electrode and lead carbonate as negative electrode,3.6 M K₂CO₃ as electrolyte,can be cycled for 200 cycles without obvious decay in capacity.The full battery has the steady capacity of over 60.0 m Ah/g and energy density of 35.5 Wh/kg.