| In view of the safety issue and graphite’s low-capacity feature of liquid-state electrolyte lithium-ion batteries(LIBs),research and development on inorganic solid-state electrolytes and on high-capacity anode materials have been hot topics in recent years.As one of the most promising inorganic solid-state electrolytes,the fast-ion Li-conducting garnet of cubic Li6.4La3Zr1.4Ta0.6O12(LLZTO)is popular in solving the safety problem,owing to its good electrochemical and chemical stability when in contact with lithium metal,its high ionic conductivity at room temperture,and its high mechanical strength in an assembled cell.Insofar as the wide preparation and practical application of LLZTO ceramic pellets are concerned,both the involved grain boundary resistance and the pellet/electrode interfacical problems should be effectively suppressed.Therefore,solving these key issues of all-solid-state LIBs,as well as developing a new-typed anode material of iron oxychloride for liquid-state electrolyte LIBs,is of foundamentally importance.By focusing on the above-mentioned problems,preparation and electrochemical properties of garnet-typed LLZTO ceramic pellet and of anodic electrode material iron oxychloride are carried out.That is,this dissertation deals with two parts,being shown as below.(1)The garnet-type Li fast ion conductor of cubic Li6.4La3Zr1.4Ta0.6O12(LLZTO)is one of the most promising solid-state electrolytes for safety-critical lithium-ion batteries,and the involved interfacial problems of LLZTO ceramic pellet must be alleviated prior to practical application.In this part,the low-melting-point Li-ion conductor of LiCl is chosen as a sintering additive of LLZTO crystallites to address its positive effect on the structural properties of 1140℃-sintered LLZTO-x wt%LiCl(x=0,2,4,6 and/or 8).Through the physically filling into inter-particle gaps and chemically anchoring onto LLZTO particles’ surface,an optimal mass fraction of LiCl(4 wt%)makes the resulting ceramic pellet to acquire a room-temperature ionic conductivity of 3.66×10-4 S cm-1,and the corresponding Li-C|LLZTO-4 wt%LiCl|Li-C or Li-C|LLZTO-4 wt%LiCl|LiCoO2 cell is endowed with a high critical current density(2.00 mA cm-2)or a good cycling stability at 20 mA g-1 within 2.54.2 V(e.g.,discharge capacity-124.4/91.1 mAh g-1,the 1st/100th cycle).Aside from these,a plausible mechanism of the agglutinant’s actions suggests an effective approach to the further development of LLZTO-based all-solid-state lithium-ion batteries in future.(2)FeOCl powder is prepared by partial pyrolysis method at 250℃,and then is combined with commercial graphite(G)to prepare FeOCI:G(100:0,75:25,50:50,25:75,0:100)composite anodes.Layered structure of FeOCl is confirmed by a series of structural characterization.And the electrochemical tests within 0.01-2.50 V show poor cyclic stability(at 100 mA g-1 of current density:1270.7 mAh g-1,1st;114.5 mAh g-1,100th;119.5 mAh g-1,200th)and rate performance of FeOCl anode in lithium-ion batteries.Compared with the electrochemical performance of single-component FeOCl,when FeOCl:G is combined used as active substance of anode,its cycling and rate performance improved to some extent owing to the synergy between two components,and the optimal compounding ratio is 50:50.Taking capacity retention rate as an example,at 100 mA g-1 of current density,the FeOCI:G(50:50)anode exhibits discharge capacity values of 1064.5,456.6 and 799.5 mAh g-1 at initial,100th and 200th cycle,respectively.In addition,XPS and GITT analysis show that the poor electrochemical performance of single-component FeOCl is due to the low lithium ion diffusion coefficient and irreversible formation and accumulation of metal Fe during cycling;the synergistic effect of the FeOCl and low-therotical-capacity G can better suppress above problems. |
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