Development Of Zeolite-based Solid Electrolyte And Study Of Solid-state Lithium Batteries

Reversible batteries with high energy density and safety are facing the urgently increasing demands for clean energy storage systems.Although the batteries with liquid electrolytes have achieved successful commercialization,the risks of leakage,combustion,volatilization and decomposition of liquid electrolytes remain challenging the safe and stable operation of batteries.Solid electrolytes are promising candidates for developing safe battery systems with high specific energy.Since the high mechanical strength of solid electrolytes,they are expected to inhibit metal dendrite growth and short circuits,and reduce the proportion of combustible materials in the battery,constructing highly safe solid-state batteries.However,the ionic conductive capability chemical/electrochemical stability,as well as interfacial compatibility of traditional solid electrolytes are limited,and it is difficult to construct an ideal interface structure.Even worse,the high electronic conductivities of solid electrolytes and incompatible contact between their uneven surfaces and Li anode generate Li nucleation inside the electrolytes,thereby resulting in short circuits in the batteries.In addition,the large-scale production of solid electrolytes with low cost remains difficult,and the nonflexible nature of common inorganic solid electrolytes restricts their application in wearable devices.Meanwhile,poor electrochemical performance of solid-state batteries assembled with existing solid electrolytes seriously restrict the application and development of solid-state energy storage devices.Herein,zeolite-based solid electrolytes are introduced into solid-state lithium batteries,which largely overcomes the problems associated with conventional solid electrolytes.And a new type of solid electrolyte based on zeolite-solvated ion structure is developed,which significantly boosts a highly efficient conduction of ion carriers.Besides,integrated cathode/anode-zeolite membrane solid electrolyte structure with extremely high interfacial compatibility and novel in-situ battery assembly strategy are also provided,constructing a series of high-performance solid-state lithium batteries with high safety,high energy density and low cost.The main contents of this thesis are listed as follow.1.An Li X zeolite membrane（Li XZM）is developed as a solid electrolyte,overcoming the core issues including constructing low-resistance interfaces between solid particles,the instability against Li metal,and the formation of interior Li dendrites.As a new solid electrolyte,based on the easy in-situ membrane growth process of Li XZM under mild hydrothermal reaction conditions,the above interfacial issue is effectively solved.Homogeneous ultrathin Li XZM shows a sufficiently high ionic conductivity owing to the regular porous structure and the remarkable ionic exchange capability of the zeolite.And we present a breakthrough in stability and interface construction by designing an integrated solid-state Li–air battery based on Li XZM as the sole solid electrolyte.This electrolyte is integrated with casted Li as an anode and carbon nanotubes as a cathode via an in-situ assembly strategy.The intrinsic high chemical stability of the zeolite membrane effectively suppresses electrolyte degeneration resulting from Li/air attack.As a result,the battery delivers a high specific capacity and a record cycling life（149 cycles）at 500 m A g^-1and 1000m Ah g^-1.This cycling life is much higher than those of highly stable NASICON-type Li_1.5Al_0.5Ge_1.5P₃O₁₂（LAGP）-based batteries（max.27 cycles）and is even superior to those of batteries with organic electrolytes（102 cycles）under the same conditions.In addition,the superior flexibility,shape-tailoring capability,and abuse tolerance of the zeolite-based Li–air batteries endow them with practical applicability that extends to other energy storage systems.2.We present a new design concept to use zeolite as a solid solvent to disperse ionic species,constructing a zeolite-solvated ion structured electrolyte（ZISE）with highly efficient ionic conduction.In this zeolite-solvated ion structure（ZIS）,the framework-associated Li ions can be activated by oxygen atoms of the encapsulated TFSI^-anion of ion species to achieve high mobility as shown by experiments and Car–Parrinello molecular dynamics simulations.According to the calculated radial distribution functions and coordination numbers,the first-shell integration shows that the Li⁺（SIII）of ZIS is coordinated with 3 adjacent oxygen atoms（two from zeolite and one from TFSI^-as mentioned above）,which is different from the coordination number of 2 for Li⁺（SIII）in the pristine zeolite.Also,the average atomic distance between Li⁺（SIII）and O changes from 1.89?to 1.95?after the solvation of ionic carriers in zeolite.These results indicate there are more loosely bound Li ions in ZIS,which is beneficial for a more facile ionic mobility than that in the pristine zeolite.In virtue of the facile conduction of zeolite-solvated ion carriers,the ZISE-based all-solid-state Li–air battery exhibits remarkable electrochemical performance with a cycle life of 909 cycles at 500 m A g^-1,far beyond that based on zeolite solid electrolyte and liquid electrolytes.It is the best cycling stability reported to date in solid-state Li–air batteries,delivering a great scientific impact on practical all-solid-state energy storage devices.3.The integrated anode-zeolite-solvated ion structure solid electrolyte（ZISE）structure Graphite-ZISE is constructed to assemble high-performance integrated all-solid-state lithium-ion batteries,and the application of ZISE-based solid electrolyte is also extended in the solid-state sodium-ion battery system,verifying that ZISE-based solid electrolyte can be used as a promising solid electrolyte for a variety of solid-state energy storage devices.Thanks to the well-solvated ionic structure of the zeolite,ZISE can be a single ion conductor solid electrolyte with an ultra-high Li⁺transference number up to 0.97.Molecular dynamics simulations show that the ionic conductivity is mainly derived from the contribution of Li ions.At the same time,ZISE possesses excellent chemical and electrochemical stability and a wide electrochemical window of 0～5.0 V.The broadened electrochemical voltage window of ZISE renders high adaptability in various battery systems.The ZISE-based integrated all-solid-state lithium-ion batteries exhibit a stable cycle time of over 1000cycles at 1C and a capacity retention of 96.4%,greatly expanding the application prospects of zeolite-based all-solid-state batteries.Furthermore,the application of the zeolite membrane as solid electrolytes can be extended to other energy storage devices.As sodium ions have been identified as cationic species with low ion conduction activation energy in some zeolites and skeleton structures,the integrated structure proposed in this work is expected to be a promising alternative for solid-state Na–air batteries and solid-state K-ion batteries.As for divalent cations,although each divalent cation needs to be associated with two negatively charged sites,it is unreasonable to consider that the activation energy of divalent ion conduction is twice that of monovalent ion conduction merely from the aspect of electrostatics.The fact that a divalent cation must reside between two relatively more dispersed negative charges greatly reduces the bonding strength and thus the activation energy.Therefore,solid electrolytes based on zeolite membranes are expected to be applied in Ca-ion and Mg-ion batteries.Besides,as for ultra-thin solid-state thin film devices,bipolar stacking of the anode of one battery and the cathode of the next one on the same current collector can be implemented to obtain higher voltage and energy density.This fabrication strategy is expected to expand the practical application,especially in some battery systems with industrialized cathodes and anodes.