【作者】 魏春光；

【导师】 康飞宇；

【作者基本信息】 清华大学 ， 材料科学与工程， 2013， 博士

【摘要】 二氧化锰是一种重要的功能材料，由于具有多种晶体结构和锰的多变价态，已广泛应用于电化学储能领域。二氧化锰晶体结构的基础单元为MnO6八面体，由其可构成一维、二维或三维的特殊隧道结构，这些隧道中常含有水分子或者阳离子（如Li+、K+或NH4+等）。二氧化锰电化学储能原理是利用其隧道存储一价或二价离子（如Na+或Zn2+）来存储能量，因此其隧道结构和隧道中的阳离子决定了其电化学储能行为，本论文系统地研究了二氧化锰隧道结构和隧道中阳离子的种类和浓度对其电化学储存Na+或Zn2+行为的影响。首先本论文利用液相中锰的氧化还原反应，通过控制氧化剂和还原剂的比例、合成条件和合成方法制备了不同隧道结构的α-MnO2、δ-MnO2、γ-MnO2、β-MnO2和其它锰氧化合物MnOOH、Mn2O3和Mn3O4，对二氧化锰隧道结构转变的机理进行了探讨，并对其存储一价Na+和二价Zn2+的行为进行了研究。研究发现不同隧道结构的二氧化锰都能存储一价Na+，但在所有隧道结构中大隧道的α-MnO2能够快速存储大量的Na+，因此其具有最高的存储容量。本论文对制备的具有不同隧道结构的二氧化锰存储二价Zn2+的电池行为进行研究，发现不同隧道结构的二氧化锰在含Zn2+的水溶液中也能储存二价的Zn2+。二氧化锰通过Mn4+和Mn3+之间的变价来存储Zn2+。研究发现在ZnSO4电解液中加入Mn2+可以抑制Mn3+歧化反应生成Mn2+，减少了锰溶解引起的活性物质二氧化锰的减少，改善了充放电过程中循环容量的衰减。而由于二氧化锰的隧道结构，Zn2+能够快速的嵌入和脱出，放电时间可以从数十秒到数小时，说明其可以应用于新型的同时具有高功率密度和能量密度的锌离子电池中。本文系统研究了不同阳离子（Li+、Na+、K+或NH4+）对α-MnO2隧道结构稳定性和其存储一价Na+和二价Zn2+行为的影响，发现K+由于具有和O2-以及OH-近似的离子半径，对无定形态的α-MnO2有最好的稳定效果，K+的出现促使由MnO6八面体组成的二氧化锰链进行更多的无序搭接，提供了更多的大隧道结构，使其能存储更多的Na+和Zn2+，表现出更高的储存容量。此外，研究发现K+的引入极大的改变了α-MnO2的比表面、孔结构，提供了一种得到不同密度非晶态α-MnO2的新方法。更多还原

【Abstract】 Manganese dioxides are important functional materials. Since having a variety ofcrystal structures and manganese changeable valence, manganese oxides are widelyused as electrode materials in electrochemical storage energy devices. The basic crystalstructure of manganese dioxide consists of MnO6octahedral units, which form1D,2Dand3D tunnel structures, it possesses H2O or cations such as Li+, K+, NH4+in the tunnelstructures. The electrochemical energy storage mechanism of MnO2is using the tunnelas host and monovalent or divalent ion (Na+or Zn2+) as media to store energy, thereforethe tunnel structures and cations in tunnel determine its electrochemical energy storagebehavior. The influence of cation species and concentration on electrochemical energystorage of Na+or Zn2+performances of MnO2was studied systematically in this work.First, a common liquid co-precipitation method based on the redox reactions of Mnwas used to synthesize α-MnO2, δ-MnO2, γ-MnO2, β-MnO2, MnOOH, Mn2O3andMn3O4by controlling the proportion of the oxidant and reductant, the synthesiscondition and synthesis method in this dissertation,. The transformation mechanism oftunnel structure of MnO2and its storage of Na+or Zn2+performances were discussed.The results indicated that all types MnO2with tunnel structure could store Na+, sinceα-MnO2with large tunnel old store large amounts of Na+, it had the highest storagecapacity of all manganese dioxides..The battery behavior of zinc ions stored by manganese dioxides with differenttunnel structures was study, the result showed that of Zn2+could be stored bymanganese dioxide with different tunnel structure in an aqueous solution. Manganesedioxide storage Zn2+by the redox reaction between Mn4+and Mn3+. Further studyindicated that adding Mn2+in aqueous ZnSO4electrolyte inhibited thedisproportionation reaction of Mn3+changing to Mn2+, which caused manganesedissolved. Through reducing the dissolution the active materials of manganese dioxideto improve the capacity during the charging and discharging cycle. Since Zn2+couldinsertion/extraction into the positive MnO2tunnel rapidly, the discharge time could befrom several tens of seconds to several hours, which made it can be used in the newtype zinc ion battery having a high power density and energy density at the same time.The effect of different ions such as Li+, Na+, K+or NH4+on the stability of tunnel structure of α-MnO2and storage performances of Na+or Zn2+was studied systematicallyin this dissertation. It was found that K ion has the best stabilizing effect of α-MnO2tunnel with approximate ionic radius of O2-and OH-. Since the MnO6octahedral chaindisorder lap provides more space, amorphous α-MnO2can store more Na+and Zn+,exhibit better capacitor performance. In addition, introducing K ions in the tunnel ofα-MnO2changed its specific surface area and pore structure greatly, which provided anew method for getting amorphous α-MnO2with different density.更多还原