|Place of Conferral||北京
（1）研究了B掺杂改性磷酸盐电极材料Na3V2P3-xBxO12 (0 ≤ x ≤ 1) 作为钠离子电池正极材料的电化学性能。采用实验和计算相结合的方法揭示了不同B掺杂量样品的晶体结构和电子结构的演化以及Na+储存性能。Na3V2P3-xBxO12 (0 ≤ x ≤ 1/3)呈现略微扭曲的六方晶系Na3V2(PO4)3的结构。精细结构解析和理论计算表明掺杂后材料V-O键长的缩短引起局域结构的改变，带隙变窄，离子迁移势垒降低。电化学性能研究发现，Na3V2P3-1/6B1/6O12样品具有最佳的结构稳定性和电化学性能。
（2）开发了一种新型的V-系磷酸盐钠离子电池负极材料。电化学性能测试发现，在0.05 V- 3.0 V之间循环1 C 可逆容量为146 mAh g-1，通过碳包覆改性后，循环和倍率性能大幅度提高，20 C倍率下可以发挥107 mAh g-1比容量。采用Na3V2(PO4)3/G作为正极组成的全电池表现出优异的循环稳定性，1000 次循环后容量保持80 % 以上。原位XRD测试研究了材料充放电过程中结构演化和反应机制，发现NaV3(PO4)3脱嵌钠的反应过程结构可逆性好、稳定，体积变化率小于10 %。利用Zn2+和Mg2+取代NaV3(PO4)3/C中V2+合成了一系列NaMV2(PO4)3/C (M= Zn, Mg) 复合材料，虽然Zn2+取代的NaZnV2(PO4)3/C样品可逆容量比NaV3(PO4)3/C低，但循环长循环容量保持率明显提高，说明通过离子掺杂可以一定程度上提高材料结构的稳定性。
|Other Abstract||With the rapid development of new energy resources and renewable energytechnology, rechargeable electrochemical devices for energy storage have been received growing attention. In this thesis, application of phosphate-based materials in rechargeable batteries, including Na-ion batteries, Li-ion batteries, Zn-based batteries, was evaluated. The concrete research contents are summarized as follows:
(1)The electrochemical performance of B substitutedNa3V2P3-xBxO12 (0 ≤ x ≤ 1) as stable cathode materials for Na-ion batterywas investigated. A combined experimental and theoreticalinvestigations on Na3V2P3-xBxO12 (0 ≤ x ≤ 1) were undertaken to reveal the evolution of crystalline and electronic structures and Na storage properties associated with various concentration of B. The crystal structure of Na3V2P3-xBxO12 (0 ≤ x ≤ 1/3) consisted of rhombohedralNa3V2(PO4)3with tiny shrinkage of crystal lattice. Fine structure analysis and the calculated crystal structures suggested that the detailed local structural distortion of substituted materials originated from the slight reduction of V-O distances, the narrow band gap and reduced the lower Na+ diffusion energy barriers.Electrochemical testing demonstrate that Na3V2P3-1/6B1/6O12 significantly enhances the structural stability and electrochemical performance.
(2) A vanadium-based orthophosphate, NaV3(PO4)3 has been exploited as a novel anode material for Na-ion batteries. Electrochemical investigation showed that it delivered a high reversible capacity of 146 mAhg-1 at potential range of 0.05 – 3.0 V. A Na-ion full battery with long term cycle life based on NaV3(PO4)3/C anode and Na3V2(PO4)3/C cathode, retaining 80 % of initial capacity after 1000 cycles. The structural revolution and reaction mechanism of NaV3(PO4)3 was evaluated by in-situ XRD, revealing the excellent structural reversibility and stability with small volume expansion (< 10%). A series ofNaMV2(PO4)3/C (M= Zn, Mg) composites were synthesized by replacememt of V2+ with Zn2+ and Mg2+. The substituted materials showed a lower capacity compared to pristine NaV3(PO4)3/C, but exhibited an obviously better capacity retention after long term cycling, demonstrating structural stability could be enhanced by ion doping.
(3) Anovel Na+/Zn2+ dual salt aqueous hybrid battery was constructed by using Na3V2(PO4)3 as cathode and metal Zn as anode. It could be found that the battery using sodium acetate and zinc acetate solution as electrolyte exhibited the best electrochemical performance by optimizing the electrolyte composition. The charge/discharge profiles were compared in the electrolyte with various Na+/Zn2+ ratio. NaV2(PO4)3 presents reversible intercalation/deintercation of Zn2+ in Na+ free solution. Thus a prototype of Zn-ion battery was proposed on the bases of NaV2(PO4)3 as cathode and Zn as anode. The cycling stability and rate capability of battery in Na+/Zn2+ dual salt electrolyte were better than that in Zn2+ single salt electrolyte, because the Zn anode was more satble in hybrid electrolyte, effectively inhibiting the dendrite growth.
(3) Phosphates, NASICON structured NaSn2(PO4)3were exploited as a novel anode material for Li-ion batteries. Nanoscale Sn was uniformly dispersed in the lithium phosphate matrix during the first discharge. The enhanced properties are attributed to the “in-situ” formation of the ionic conductor as protective matrix, which prevents the aggregation of nanoparticles during the cycling and provides Li+ diffusion channels in the electrode for fast electrochemical reaction. The initial irreversible capacity loss could be eliminated by prelithiation. The obtained material exhibits excellent cycling performance and high rate capabilityfor full cell using LiFePO4 and LiNi0.5Mn1.5O4 as cathode, suggeating the feasibility of practical application.|
胡朴. 高性能磷酸盐二次电池电极材料构效关系的研究[D]. 北京. 中国科学院研究生院,2016.
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