【作者】 符显珠；

【导师】 廖代伟；

【作者基本信息】 厦门大学 ， 物理化学， 2007， 博士

【摘要】 碱性锌锰原电池和镍系列蓄电池广泛应用在便携式电子产品中,具有高性能价格比。近年来以球形β-NiOOH替代碱性锌锰电池中全部或部分MnO₂正极材料的高功率新型原电池首先在日本被开发出来。NiOOH是生产这种新电池的关键材料。球形β-NiOOH在碱性电解质中储存性能差且Zn-NiOOH原电池因一次性用价格较贵的NiOOH而成本高。MH-Ni蓄电池与其它高能电池相比具有非常好的安全性能,很适合大规模开发用作电动车动力电池。然而普通球形β-Ni（OH）₂正极材料不能很好地满足MH-Ni动力电池的高温、大电池充放电等要求。锂离子电池在目前大规模商品化的电池中综合性能最好、发展最快。但锂离子电池主要使用的正极材料LiCoO₂不仅价格高而且对环境有污染。开发性优价廉的锂离子电池正极材料对于锂离子电池更大规模的使用和更大范围的应用很是迫切和重要。LiNiO₂系列材料具有容量高、功率大、价格适中等优点被研究用来替代LiCoO₂,但LiNiO₂系列材料也存在合成困难、容量衰减快、热稳定性差、储存性能不佳等缺点,从而影响其实用化。低温燃料电池比能量高于锂离子电池、镍氢电池等普通电池,是目前研究开发最活跃的电池体系。贵金属Pt是氢等燃料氧化和氧气还原电催化活性最高的单质金属催化剂。但纯Pt等贵金属Pt资源储量有限,价格昂贵,使低温燃料电池成本居高不下,严重阻碍其商品化推广使用。本论文就是为了解决上述这些问题而展开,有关结果如下:1、碱性电池NiOOH和Ni（OH）₂正极材料以球形β-Ni（OH）₂为前驱体在KOH溶液中通过K₂S₂O₈化学氧化制备NiOOH并考察了制备条件对产物的影响。低浓度KOH溶液（1-3M）只能够得到低氧化值的产物,高浓度KOH溶液（6-9M）中可以得到高氧化值的产物且其氧化值随K₂S₂O8与β-Ni（OH）₂的反应当量比增大而升高。控制反应条件可以得到氧化值从₂.95（纯β-NiOOH相）到3.55（纯γ-NiOOH相）的一系列NiOOH产物。NiOOH氧化值越高,产物中γ相NiOOH含量越大,密度越小,球形颗粒碎裂得越严重,比表面积越大,K含量越大,Ni含量越小,质量比放电容量越小,在KOH溶液中的储存稳定性越好,热分解行为越接近γ-NiOOH。γ-NiOOH的热分解行为比β-NiOOH复杂,在加热过程会失去层间嵌合水,发生层间距收缩,经过二步热分解层状结构成氧化物。从放电比容量、储存稳定性、振实密度等因素考虑,采用氧化值为3.04的NiOOH作为碱性Zn-NiOOH原电池的正极材料既可以获得较大的体积比放电容量又可具有较佳的储存稳定性。以Al取代球形α-Ni（OH）₂为前驱体在6M的KOH溶液中与过量K₂S₂O8反应制备了Al取代球形γ-NiOOH。用XRD、SEM、FTIR、TGA-DTG、TPD-MS和HT-XRD等对Al取代球形α-Ni（OH）₂和γ-NiOOH进行了表征。发现Al取代球形α-Ni（OH）₂氧化生成Al取代球形γ-NiOOH时层间距变小,层间嵌合物变少,振实密度变大。Al取代γ-NiOOH的热分解行为与Al取代α-Ni（OH）₂类似但热稳定性不及Al取代α-Ni（OH）₂好。与球形β-NiOOH相比, Al取代球形γ-NiOOH不仅具有较高的质量比放电容量（353mAhg-1）而且在碱性电解液中还具有良好的储存稳定性。Al取代γ-NiOOH与球形β-NiOOH都具有良好充放循环性能。Al取代球形γ-NiOOH振实密度（1.51 gcm-3）虽大于非规则碎片状γ-NiOOH（1.01 gcm-3）,但还是小于球形β-NiOOH的振实密度（₂.45 gcm-3）。以球形β-Ni（OH）₂颗粒为种子通过受控结晶在其表面沉积β-Co（OH）₂制备了β-Co（OH）₂包覆球形β-Ni（OH）₂。在制备β-Co（OH）₂包覆球形β-Ni（OH）₂过程中加入K₂S₂O8则可制得β-CoOOH包覆球形β-NiOOH。β-Co（OH）₂包覆球形β-Ni（OH）₂和β-CoOOH包覆球形β-NiOOH比未包覆的样品具有更好的充电氧化、放电还原及充放电循环性能。β-CoOOH包覆球形β-NiOOH在碱性电解液中比未包覆的球形β-NiOOH具有更好的储存稳定性。以β-Co（OH）₂包覆球形β-Ni（OH）₂制成的MH-Ni蓄电池比未包覆的球形β-Ni（OH）₂制成的MH-Ni蓄电池具有更好的高倍率充放电特性、活性物质利用率、高温充电效率及充放电循环性能。以β-CoOOH包覆球形β-NiOOH为正极材料制成的Zn-NiOOH成品电池不仅具有原电池的方便而且具有蓄电池的经济环保。Zn-NiOOH电池1000mA大电流放电至1.1V的持续时间可达56min,是碱锰电池五倍以上,工作电压平台比碱锰电池也约高0.3V左右。而以包覆的球形β-NiOOH和MnO₂混合作为正极材料的Zn-NiOOH/MnO₂原电池既保持Zn-NiOOH原电池的方便与大功率放电性能又具有较低的成本,而且其储存稳定性比用未包覆的球形β-NiOOH制成的Zn-NiOOH/MnO₂原电池得到很大改善。₂、锂离子电池LiNiO₂@LiCoO₂正极材料以球形核壳结构β-NiOOH@CoOOH为前驱体与LiOH在空气气氛下烧结反应合成LiNiO₂-LiCoO₂复合正极材料并考察了反应温度和时间对产物结构的影响。反应温度低或时间短,产物层状结构和结晶程度差;反应温度高或时间长,产物结晶程度增高但层状结构变差而且Ni与Co发生迁移形成各处Ni与Co浓度相同的LiNi1-xCoxO₂固溶体,得不到具有核壳结构的产物。在600oC下反应24小时可以得到XRD衍射峰003与104强度比高达1.79的具有良好层状结构的球形核壳结构LiNiO₂@LiCoO₂复合材料。以球形β-NiOOH@CoOOH为前驱体合成得到产物的层状结构特征比以球形β-NiOOH和β-Ni（OH）₂为前驱体在相同情况条件下合成得到的产物都要好。I003/I104比为1.79的球形核壳结构LiNiO₂@LiCoO₂复合材料壳层主要为LiCoO₂,核主要为LiNiO₂。LiNiO₂@LiCoO₂首次放电容量为181.41mAhg-1,充放电循环₂0次以后容量保持率还可达97%而LiNiO₂只有88%。LiNiO₂@LiCoO₂储存性能也要优于没有LiCoO₂壳层包覆的LiNiO₂。以球形β-NiOOH@CoOOH作为前驱体制备LiNiO₂@LiCoO₂不需要氧气氛和很高的合成温度,有利于材料的大规模工业化生产,且产物性能良好。3、低温燃料电池核壳结构Ni@Pt电催化剂以NiCl₂和H₂PtC_l6为金属盐,乙二醇为溶剂,水合肼为还原剂,采用逐步还原法制备了不同Ni Pt比值的Pt为壳层Ni为核的核壳结构Ni@Pt复合粒子电催化剂。用TEM、XRD、XPS等表征方法测试了所合成电催化剂的粒径大小、物相结构及表面组成。作为核的Ni粒子平均粒径为8.6nm,随Pt比例的增高,核壳复合粒子的粒径逐渐增加,当Pt与Ni比值为2时的粒子达12.1nm。Ni@Pt复合粒子的核壳界面可能为NiPt合金层,壳层主要为Pt。纳米核壳结构Ni@Pt复合粒子的甲醇氧化电催化性能和抗类CO中间产物中毒性能比纯Pt都要好得多。在合成的NiPt01、NiPt02、NiPt05、NiPt10、NiPt20等5个纳米核壳结构Ni@Pt电催化剂中,NiPt01（即Pt与Ni的摩尔比为1:10）的电催化性能最高（甲醇催化氧化电流密度为₂90.3 mAmg-1Pt）抗类CO中间产物中毒能力也最强。即使在酸性电解质中纳米核壳结构Ni@Pt电催化剂因Ni核被外面富Pt壳层所包覆而具有良好的耐腐蚀稳定性。纳米核壳结构Ni@Pt复合粒子同样具有比纯Pt更好的氧还原电催化性能。纳米核壳结构Ni@Pt电催化剂因Pt充分分布在纳米电催化剂颗粒的表面,且富Pt壳层还含有Ni起到协同催化作用,因此不论是对甲醇的电催化氧化还是对氧的电催化还原的催化性能都比纳米纯Pt电催化剂要高得多,贵金属Pt得到充分地利用,从而能够降低燃料电池成本。更多还原

【Abstract】 Alkaline Zn-MnO₂ primary batteries and nickel-based rechargeable batteries are widely applied in portable electronics, which have high ratio of performance and cost. A new type of high powder primary battery with sphericalβ-NiOOH positive electrode material has been developed in Japan recent years. However, the storage stability ofβ-NiOOH is very poor in electrolyte. The synthetic method and performance improvement of NiOOH are keys for the production of this new type of battery. MH-Ni rechargeable battery has better safe performance compared to other high energy batteries, which is more suitably used in electric vehicle. However, the common sphericalβ-Ni（OH）₂ can not well meet the demand in electric vehicle battery such as high temperature and current charge and discharge, etc.Lithium ion rechargeable battery has the best comprehensive performance and most fast development among the large scale commercial batteries. But the commonly used LCoO₂ positive electrode material in the battery is high cost and harmful to the environment. The low cost and high performance positive electrode material substituting for LCoO₂ is very important and urgent for the extend application of lithium ion rechargeable battery. The LiNiO₂ serial positive electrode materials have advantages such as high specific capacity, specific power and moderate cost, etc. However, the disadvantages of LiNiO₂ such as hard preparation, fast capacity decay, bad storage stability, etc have hampered its practical application.The specific energy of low temperature fuel cells is higher than that of common batteries such as lithium ion and MH-Ni rechargeable batteries. The research of fuel cells is the most active among all electrochemical power sources at present. Pt has the highest electrocatalytic activity than other elements in the fuel cell oxidation and oxygen reduction reactions. But the catalytic activity of pure Pt is not satisfied for the application of direct methanol fuel cells, etc. Furthermore, the cost of Pt is very high, which seriously hinders the commercial use of low temperature fuel cells.This thesis is in order to solve the above problems and the results are following: 1. NiOOH and Ni（OH）₂ as positive electrode materials for alkaline batteriesThe NiOOH products were prepared by chemical oxidation of sphericalβ-Ni（OH）₂ with K₂S₂O8 in KOH solution and the effects of preparation conditions were investigated. The NiOOH with low nickel oxidation state was obtained only in low concentration of KOH solution （1-3M）. The NiOOH with high nickel oxidation state was got in high concentration KOH solution （6-9M）. The nickel oxidation state of products increased with the ratio of K₂S₂O8 andβ-Ni（OH）₂ increased or the KOH solution increased from 3M to 6M. The NiOOH with nickel oxidation state from ₂.95 （pureβ-NiOOH phase） to 3.55 （pureγ-NiOOH phase） can be obtained by controlled the synthetic conditions. As the nickel oxidation state of NiOOH increased, theγ-NiOOH phase content increased, tap density decreased, spherical particles broke more seriously, specific surface increased, K content increased, Ni content decreased, specific discharge capacity decreased, storage stability in KOH electrolyte increased and the thermal behavior was more similar to pureγ-NiOOH. The NiOOH with nickel oxidation state of 3.04 was suitable as positive electrode material for alkaline Zn-NiOOH primary battery for comprehensive concern.The spherical Al substitutedγ-NiOOH was synthesized by oxidation of spherical Al substitutedα-Ni（OH）₂ with K₂S₂O₈ in 6M KOH solution. The samples were characterized by XRD, SEM, FTIR, TGA-DTG, TPD-MS and HT-XRD. The results indicated that the interlayer distance and the intercalated species decreased while the tap density increased when the Al substitutedα-Ni（OH）₂ was oxidized to Al substitutedγ-NiOOH. And the Al substitutedγ-NiOOH has similar thermal behavior to Al substitutedα-Ni（OH）₂ but the thermal stability of Al substitutedγ-NiOOH was inferior to that of Al substitutedα-Ni（OH）₂. The spherical Al substitutedγ-NiOOH has higher specific discharge capacity of 353mAhg-1 and better storage stability in KOH electrolyte than sphericalβ-NiOOH. Both of spherical Al substitutedγ-NiOOH andβ-NiOOH have good charge-discharge cycleability. The spherical Al substitutedγ-NiOOH has higher tap density （1.53gcm-3） than un-sphericalγ-NiOOH （1.01 gcm-3） but it is lower compared to sphericalβ-NiOOH （2.45 gcm-3）.β-Co（OH）₂ coated sphericalβ-Ni（OH）₂ was prepared by the precipitation of β-Co（OH）₂ on the surface of sphericalβ-Ni（OH）₂ particles. Theβ-CoOOH coated sphericalβ-NiOOH was obtained by adding K₂S₂O8 following the product ofβ-Co（OH）₂ coated sphericalβ-Ni（OH）₂. Cyclic voltammetry measurement demonstrated that the coated sphericalβ-Ni（OH）₂ andβ-NiOOH.have better electrochemical performance in charge-discharge and cyclability than uncoated ones, respectively. The sphericalβ-NiOOH also has better storage stability in alkaline electrolyte than uncoated one. The MH-Ni rechargeable battery withβ-Co（OH）₂ coated sphericalβ-Ni（OH）₂ as electrode material has better specific charge-discharge performance, higher active material utilization, charge efficiency at elevate temperature and cycleability than the MH-Ni rechargeable battery with uncoated sphericalβ-Ni（OH）₂ as positive electrode material. The Zn-NiOOH battery withβ-CoOOH coated sphericalβ-NiOOH as positive electrode material can be used not only conveniently as primary battery but also repeatedly as rechargeable battery. The 1000 mA discharge time of Zn-NiOOH battery to 1.1 V is 56 min, which is more than five times and about 0.3 V higher of discharge voltage than conventional alkaline Zn-MnO₂ primary battery. The alkaline Zn-NiOOH/MnO₂ primary battery then has both lower cost compared to Zn-NiOOH battery and higher power compared to alkaline Zn-MnO₂ battery.₂. LiNiO₂@LiCoO₂ as positive electrode material for lithium ion battery The spherical LiNiO₂-LiCoO₂ composite positive electrode material was prepared by sintering sphericalβ-NiOOH@CoOOH with LiOH in air atmosphere. The product with bad stoichiometry and low crystallinity was obtained at too low temperature or short time. The reaction temperature was too high or the reaction time was too long, resulting in production without core-shell structure with bad stoichiometry and high crystallinity. The LiNiO₂@LiCoO₂ with the highest XRD peak intensity ratio of 003 and 004 of 1.79 and the best stoichiometry was obtained from sphericalβ-NiOOH@CoOOH at 600oC and ₂4 h, which also has the best layered structure than ones from sphericalβ-NiOOH orβ-Ni（OH）₂. The first discharge capacity of this LiNiO₂@LiCoO₂ with core-shell structure is 181.41mAhg-1. The LiNiO₂@LiCoO₂ also has better cycleability and storage stability than LiNiO₂. The synthesis of LiNiO₂@LiCoO₂ from sphericalβ-NiOOH@CoOOH can be carried out in air amphorae and at low temperature, which is very facile in large scale produce.3. Ni@Pt core-shell nanoparticle as electrocatalyst for low temperature fuel cells The Ni@Pt nanoparticles with Ni core and Pt shell as electrocatalysts were prepared by successive reduction of nickel and Pt ions with hydrazine in glycol solution. The mean particle size of core-shell nanoparticles increased with the ratio of Pt and Ni increased. The interface of Ni core and Pt shell might be NiPt alloy and the shell was main Pt. The Ni@Pt core-shell nanoparticles have higher catalytic efficiency of methanol oxidation and CO tolerance than pure Pt, especially the NiPt01 sample （01 donate the molar ratio of Pt and Ni is 1:10）. The NiPt01 also had good stability in acid electrolyte because the Ni core was coated by Pt. The Ni@Pt core-shell nanoparticles also had better electrochemical oxygen reduction catalytic efficiency than pure Pt by rotating disc electrode tests. The noble metal of Pt was most efficiently dispersed on the un-noble metal of Ni core surface, and the nickel underlay the Pt had co-catalytic effect. Therefore the catalytic efficiency of Ni@Pt core-shell nanoparticles was very high and the noble metal of Pt was most utilized, the cost of fuel cells could be decreased.更多还原