Quasi-solid-state polymer plastic crystal electrolyte for subzero lithium-ion batteries

Succinonitrile(SN)-based polymer plastic crystal electrolytes(PPCEs)have attracted considerable attention as solid-state electrolytes owing to their high ionic conductivities similar to those of liquid electrolytes,excellent contacts with the electrodes,and good mechanic properties.As a crucial property of a solid-state electrolyte,the ionic conductivity of the PPCE directly depends on the interactions between the constituent parts including the polymer,lithium salt,and SN.A few studies have focused on the effects of polymer–lithium–salt and polymer–SN interactions on the PPCE ionic conductivity.Nevertheless,the impact of the lithium–salt–SN combination on the PPCE ionic conductivity has not been analyzed.In particular,tuning of the lithium-salt–SN interaction to fabricate a subzero PPCE with a high low-temperature ionic conductivity has not been reported.In this study,we design and fabricate five PPCE membranes with different weight ratios of Li N(SO2 CF3)2(Li TFSI)and SN to investigate the effect of the Li TFSI–SN interaction on the PPCE ionic conductivity.The ionic conductivities of the five PPCEs are investigated in the temperature range of–20 to 60°C by electro-chemical impedance spectroscopy.The interaction is analyzed by Fourier-transform infrared spectroscopy,Raman spectroscopy,and differential scanning calorimetry.The Li TFSI–SN interaction significantly influences the melting point of the PPCE,dissociation of the Li TFSI salt,and thus the PPCE ionic conductivity.By tuning the Li TFSI–SN interaction,a subzero workable PPCE membrane having an excellent low-temperature ionic conductivity(6×10-4 S cm–1 at 0°C)is obtained.The electro-chemical performance of the optimal PPCE is evaluated by using a Li Co O2/PPCE/Li4 Ti5 O12 cell,which confirms the application feasibility of the proposed quasisolid-state electrolyte in subzero workable lithium-ion batteries.

A Survey of Output Feedback Robust MPC for Linear Parameter Varying Systems

For constrained linear parameter varying(LPV)systems,this survey comprehensively reviews the literatures on output feedback robust model predictive control(OFRMPC)over the past two decades from the aspects on motivations,main contributions,and the related techniques.According to the types of state observer systems and scheduling parameters of LPV systems,different kinds of OFRMPC approaches are summarized and compared.The extensions of OFRMPC for LPV systems to other related uncertain systems are also investigated.The methods of dealing with system uncertainties and constraints in different kinds of OFRMPC optimizations are given.Key issues on OFRMPC optimizations for LPV systems are discussed.Furthermore,the future research directions on OFRMPC for LPV systems are suggested.

Wide-temperature range and high safety electrolytes for highvoltage Li-metal batteries

Along with the keeping growing demand for high-energy-density energy storage system,high-voltage Li-metal batteries(LMBs)have attracted many attentions.In view of many defects of the commercial electrolytes,such as flammability,limited operation temperature range,and severe Li dendrite growth,non-flammable phosphate-based localized highly concentrated electrolytes(LHCE)have been explored as one of the safe electrolytes for LMBs.But until now there is rare report on wide-temperature range LMBs using phosphate-based electrolytes.Here,we prepare a wide-temperature LHCE,which is composed of lithium difluoro(oxalato)borate(LiDFOB),triethyl phosphate(TEP),and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether(HFE),and explore the applicability in wide-temperature LMBs from−40 to 70℃.In the LHCE,both TEP and HFE are non-flammable,and Li^(+) is highly coordinated with TEP and DFOB^(−),which can effectively inhibit the TEP decomposition on anode,and facilitate the preferential reduction of DFOB^(−),thus obtain a robust solid electrolyte interphase(SEI)to suppress Li dendrite growth and side reactions.Therefore,this LHCE can not only endow Li/Cu and Li/Li cells with high Coulombic efficiency(CE)and long cycling lifespan,but also be applied to LiFePO_(4)(LFP)/Li and LiNi_(0.5)Co_(0.2)Mn_(0.3)O_(2)(NCM523)/Li LMBs.Most importantly,the NCM523/Li LMBs with LHCE can deliver stable cycling performance at 4.5 V high-voltage and high-temperature(70℃),as well as excellent low-temperature capacity retention even though both charging and discharging process were carried out at−40℃.