Investigations Of A PVDF-HFP Based Solid State Porous Polymer Electrolytes

All solid state ion battery with high energy density, battery safety, no electrolytes leakage phenomenon, etc.,is in the same development trend with chemical power sources. And PVDF-HFP based porous polymer electrolytes is the most investigated one. The current common problems for ion battery including poor low-temperature performance, fire hazard, low room-temperature ionic conductivity, low interface stability, are still to be solved.In this dissertation, two polymer electrolytes salts Polymeric Sodium Tartaric acid Borate(PSTB)and Polymeric Lithium Tartaric acid Borate(PLTB)were synthesized, and they were separately mixed with PVDF-HFP to form the electrolytes membranes PSTB@ PVDF-HFP and PLTB@ PVDF-HFP Respectively. The structure and electrochemical property of thus obtained two electrolytes salts and their membranes were characterized by a variety of techniques such as IR, XRD, SEM, AC Impedance, Liquid NMR, Solid 7Li NMR, Solid 23 Na NMR, 13 C CP/MAS NMR, 11 B MAS NMR, ~1H MAS NMR and so on.In this paper, the major results are summarized as follows:(1) Two polymer electrolytes salts were synthesized via a condensation reaction, and then were characterized by DSC, IR, XRD and liquid NMNR. It is found that the two polymer electrolytes salts are of similar structure and low degree of crystallinity. The two polymer electrolytes salts exhibit excellent thermal stability, with decomposition temperatures TPSTB =352 ? and TPLTB =320 ?.(2) Two porous electrolytes films PSTB@ PVDF-HFP and PLTB@ PVDF-HFP were prepared by spin coating. The thermal performance of two electrolytes membranes is excellent, and the decomposition peaks of PLTB @ PVDF-HFP and PSTB @ PVDF-HFP film determined by DSC are both close to 350 ?. The ionic conductivity of the two electrolyte membranes at room temperature is relatively high, with ?(PSTB@PVDF-HFP film) =0.013 m S/cm and ?(PLTB@PVDF-HFP film) = 0.042 m S/cm.The structure of the two electrolytes salts at room temperature was futher investigated by ~1H,11 B MAS NMR and 13 C CP/MAS NMR. It is found that the two electrolyte salts are of high degree of similarity in the structure of the polymer chains, i.e. four-coordinate complex of B atoms in the polymer chain. The 11 B NMR spectra of two solids PSTB and PLTB show that all B atoms are approximately in similar environment(four coordinates with oxygens of Tartaric acid) and both PSTB and PLTB appear in form of the six-member ring complex.(4) Using a variety of methods related to variable temperature NMR(HW-T, T1-T, T1?-T,etc) to study the two electrolytes salts and the two porous membranes soaked in PC solution for 2 hours. Multi-time scale ion motion was studied, and some very important information were got. 1) In the porous electrolytes film PSTB@PVDF-HFP,the motion of Na+ is stronger significantly than that in pure electrolyte salt PSTB; the motion of Li+ in the porous electrolytes films PLTB@PVDF-HFP is much faster than electrolytes salt PLTB;3) The motion rate of Li+ in the sample porous electrolytes films PLTB@PVDF-HFP at 40? was close to estimated to be 2×10~5/s.