Hydrothermal synthesis of spindle-like Li_2FeSiO_4-C composite as cathode materials for lithium-ion batteries

In this paper,we report on the preparation of Li2FeSiO4,sintered Li2FeSiO4,and Li2FeSiO4-C composite with spindle-like morphologies and their application as cathode materials of lithium-ion batteries.Spindle-like Li2FeSi04 was synthesized by a facile hydrothermal method with（NH4）2Fe（SO4）2 as the iron source.The spindle-like Li2FeSiO4 was sintered at 600 ℃ for 6 h in Ar atmosphere.Li2FeSiO4-C composite was obtained by the hydrothermal treatment of spindle-like Li2FeSiO4 in glucose solution at 190 ℃ for 3 h.Electrochemical measurements show that after carbon coating,the electrode performances such as discharge capacity and high-rate capability are greatly enhanced.In particular.Li2FeSiO4-C with carbon content of 7.21 wt%delivers the discharge capacities of 160.9 mAh·g-1 at room temperature and 213 mAh·g-1 at45℃（0.1 C）,revealing the potential application in lithium-ion batteries.

Effect of TiB_2 content on resistance to sodium penetration of TiB_2/C cathode composites for aluminium electrolysis

TiB2/C cathode composites with various contents of TiB2 were prepared and their characterizations were observed and compared. The expansion of samples due to sodium and bath penetration was tested with a modified laboratory Rapoport apparatus and the appearances of the cut sections of specimens after electrolysis were studied. The results show that the mass of TiB2/C cathode composites with mass fraction of TiB2 less than 70% appreciably increases, but that of the composites with mass fraction of TiB2 more than 70% decreases slightly after being baked. The resistance to sodium and bath penetration of TiB2/C cathode composites increases with the increase of TiB2 content, especially in the composites with high TiB2 content. TiB2/C cathode composites have high resistance to the penetration of sodium and bath as well as good wettability by molten aluminum, and keep integrality and have little change of appearance after electrolysis, which indicates that TiB2/C cathode composites can be used as inert wettable cathode for aluminum electrolysis.

Nb和TiB_(2)对ZrB_(2)基复合陶瓷材料组织及性能的影响

利用气压辅助烧结法制备ZrB_(2)基复合陶瓷材料,借助力学性能测试、XRD、SEM等探究了添加Nb与TiB_(2)对所制材料烧结行为、力学性能及抗氧化能力的影响。结果表明,金属Nb在烧结过程中发生塑性形变促使ZrB_(2)颗粒重排,同时破坏B—B共价键促进物质扩散,改善了材料的烧结及力学性能,但也造成材料高温抗氧化性能下降。进一步引入TiB_(2)能提高陶瓷材料的力学性能,且反应生成的ZrTiO4有利于形成抗氧化保护层以提高材料的高温抗氧化能力。

C/C复合材料表面ZrB_(2)基陶瓷涂层改性及抗氧化性能研究

为了提升碳/碳(C/C)复合材料的抗氧化性能,通过大气等离子喷涂技术在C/C-SiC复合材料表面制备了添加剂改性的ZrB_(2)陶瓷涂层,分别为ZrB_(2)-SiC、ZrB_(2)-TiB_(2)涂层,对涂层样品进行1200℃的氧化性能测试。结果表明,氧化5 h后,ZrB_(2)-SiC涂层仍有2.62 wt.%增重量,与ZrB_(2)涂层相比(氧化失重率为10.76 wt.%),ZrB_(2)-SiC涂层抗氧化性能大幅度提升,主要由于SiC的添加降低了涂层热膨胀系数,缓解热失配,提升了涂层结合强度,而且氧化后形成致密的硼硅酸盐熔融玻璃表面,填充了涂层裂缝、孔洞,为基材提供更为优异的抗氧化防护。而ZrB_(2)-TiB_(2)涂层表现出较差的抗氧化性,氧化5 h后,失重量达到18.76 wt.%,ZrB_(2)-TiB_(2)涂层极差的抗氧化性是因为TiB_(2)的引入改变了涂层的形貌,氧化后形成疏松多孔的组织结构,无法有效隔绝氧气。

TiB_(2)的分散行为对铝电解惰性阴极材料性能的影响

为了解TiB_(2)对铝电解阴极材料性能的影响,在实验室通过热压烧结制备TiB_(2)-C复合阴极材料,并对制备的阴极试样进行在线钠膨胀测试。结合XRD,SEM和TEM等微观分析手段,研究钠元素对阴极的渗透、TiB_(2)-C复合阴极材料与基体之间的界面行为和TiC对阴极材料性能的影响。结果表明,在电解过程中,TiC通过溶解-析出方式提高了阴极材料石墨化度,改善了阴极材料的性能。在相同电流密度情况下,TiB_(2)-C复合阴极材料能够有效降低阴极压降。通过在功能层与基体之间插入一层过渡层,改善了TiB_(2)-C复合阴极材料与基体之间的黏合,能够有效减少钠元素对阴极的侵蚀。该研究对延长电解槽阴极的使用寿命以及降低铝电解的生产能耗具有理论指导意义。