Preparation And Properties Of Ppo/ZrO₂ Composite Solid Electrolyte Thin Films

Solid-state electrolytes are a promising alternative to traditional flammable and explosive organic liquid electrolyte and have become a hot topic in battery research.Organic-inorganic composite solid-state electrolytes（CSE）can combine the strengths of polymer and inorganic electrolytes,which are expected to be the first to be used.However,the comprehensive performance of existing solid electrolytes,such as mechanical,thermal and electrochemical properties,is far from the requirements for commercial applications.Therefore,the development of new organic/inorganic composite electrolyte systems to improve the mechanical,thermal and electrochemical performance of electrolytes is currently a hot spot and a difficult area in this field.In this paper,PPO/ZrO₂ composite solid electrolyte thin films were prepared by two methods based on polypropylene oxide（PPO）as polymer matrix and zirconia（ZrO₂）as inorganic filler,and their comprehensive properties were studied.PPO/ZrO₂composite solid electrolyte thin films were prepared by flow-delaying method with porous cellulose membrane as the framework,and the properties of CSE films were improved by plasticizer modification and modified PPO monomer.A simple and controllable film preparation method is formed.The specific contents and results are as follows:（1）PPO/ZrO₂ composite solid electrolyte thin films were prepared by combining the thermal cross-linking method and flow-delaying method using polyetheramine-T403,adipic acid and polyetheramine-D400 as precursors,porous cellulose film as the backbone,and modified by plasticizer peg400 and inorganic filler ZrO₂.The properties of PPO based solid electrolytes were improved.We studied the effects of ZrO₂ and peg400 on the physical and electrochemical properties of the CSE.It was found that ZrO₂ can effectively improve the mechanical properties of electrolyte,promote the dissociation of lithium salt in CSE and the movement of polymer chain segment,and greatly improve the ionic conductivity,migration number and electrochemical stability window.And the introduction of plasticizer significantly improved the flexibility and electrochemical property of the CSE.When the content of ZrO₂ was 10 wt%and the content of peg400 was 20 wt%,the CSE films showed no change in dimensions after heating at 200°C for 1 h.The tensile strength of CSE reached 60 MPa,the strain reached 73%.The room temperature ionic conductivity of the CSE reached 6.67×10^-4S cm^-1,with an electrochemical stability window of 4.6 V and an ion mobility number of 0.67.The excellent mechanical,thermal and electrochemical properties of the electrolyte films enhance the cycling stability of the solid-state batteries.When the Li Fe PO₄/PPO-10 wt%ZrO₂-20 wt%peg400 CSE/Li cell cycled at 0.1 C,the initial discharge specific capacity was 135.8 m Ah g^-1.After 600 cycles,the specific capacity of cell remained 76%of the initial specific.（2）The BSPPO/ZrO₂ composite solid-state electrolyte films were innovatively prepared at room temperature using silicone methoxy capped poly（propylene oxide）（BSPPO）as the precursor,porous cellulose film as the backbone,ZrO₂ as the inorganic filler and succinonitrile（SN）as the plasticizer.We studied the relationship between different contents of ZrO₂ and SN and thermal,dynamics and electrochemical properties of the electrolyte films.It was found that electrolyte films with thickness below 78μm could be prepared by this method,which is about 50%lower than that of the thermal cross-linking method.And the method is especially simple and suitable for scale up.The composite electrolyte showed excellent comprehensive performance when the contents of ZrO₂ and peg400 reached 15 wt%and 30 wt%,respectively.The films were heated continuously at 120°C for 2 h without significant changes in shape and appearance,showed excellent thermal stability.The ionic conductivity of CSE reached 9.62×10^-4 S cm^-1 at room temperature and 2.60×10^-3 S cm^-1 at 100°C,and the electrochemical window of it reached 5 V,which is suitable for high voltage cathode materials.The initial discharge specific capacity of NCM622/BSPPO-15 wt%ZrO₂-30wt%SN CSE/Li cell reached 145.1 m Ah g^-1 at a current density of 0.5 C.After 140cycles,the specific capacity of cell was still 63%of the initial specific.The Li/BSPPO-15 wt%ZrO₂-30 wt%SN CSE/Li cell showed good stability to lithium,which cycled for 600 hours at 0.1 m A cm^-2 current.In conclusion,the above results show that the PPO/ZrO₂ composite solid electrolyte thin films prepared in the two methods have good mechanical,thermal and electrochemical properties,especially the room temperature flow-delay method is simple and practical,which provides a reference for the preparation of excellent comprehensive performance solid electrolyte films and high specific energy solid lithium batteries in the future.