Lithium-ion batteries (LIBs) are a vital energy storage for electric automobiles and portable electronics due to their extended cycle life and high energy density. However, traditional LIBs that use organic liquid electrolytes are prone to safety issues like fires, spills, and ruptures because of their flammability and interactions with electrodes
[1, 2]. These problems necessitate the development of safer electrolytes with a wider electrochemical range and higher energy density. Solid-state composite polymer electrolytes (SSCPEs) have recently gained popularity as a potential replacement for liquid electrolyte LIBs [3]. The all-solid-state lithium-ion batteries (ASSLIBs) are becoming increasingly important for powering portable electronic devices due to their high energy efficiency and extended durability [4]. The solid electrolytes usage in these batteries makes them more compatible with lithium-ion and helps to avoid the formation of Li dendrites, a common issue in other types of lithium-ion batteries. This compatibility also means that ASSLIBs can use Lithium cobalt oxide (LiCoO2) as a cathode and Li metal as an anode. Solid state composite polymer electrolytes provide excellent stability to ASSLIBs, making them a perfect option for enhancing battery performance by preventing the growth of Li dendrites [5, 6]. Therefore, ASSLIBs with SSCPEs are among the most promising lithium batteries for the future generation.
Solid electrolytes are separated into two major groups: polymeric and inorganic. Inorganic solid electrolytes are further classified into different types such as NASICON type LiTi2(PO4)3, garnet-type Li7La3Zr2O12 (LLZO), perovskite-type Li0.33La0.56TiO3, and
sulphuride-type Li2S–P2S5. These types of solid electrolytes are known for their excellent thermal and electrochemical stability [7]. Among them, LLZO has shown great promise because of its broad window for electrochemistry, large Li+ ion conductivity, and high chemical stability against Li metal. However, due to its ceramic nature, the material is fragile and challenging to manufacture into thin membranes [8, 9]. When compared to inorganic solid electrolytes, polymeric solid electrolytes, such as (PEO), offer several advantages including high mechanical strength, good electrochemical stability and interface compatibility [10]. However, Polymeric solid electrolytes based on PEO have low ionic conductivity, weak thermostability, and limited mechanical strength, which may restrict their use in lithium-ion batteries [11]. The solution to this problem is the creation of composite solid polymer electrolyte (CSPE) by combining both inorganic and polymeric solid electrolytes. CSPE integrate the best qualities of both components.
Till now, ASSLIBs have used lithium-based salts that are easily available as an electrolyte. The most commonly used electrolytes are LiFSI−, LiClO4−, and LiTFSI− due to their good stability, excellent ionic conductivity, and high energy density [12–14]. However, in this work, we are planning to use Lithium perborate (LiBO3) as an electrolyte. LiBO3 is a widely used industrial chemical that is inexpensive, safe for the environment, and nontoxic. A low-cost and highly flexible composite solid polymer electrolyte has been successfully synthesized by using PEO polymer, LiBO3, and LLZO filler as a reinforcing phase to decrease the formation of Li dendrites [15, 16]. The efficiency of the CSPE (PEO − LiBO3 − LLZO) with Li metal anode and LiCoO2 cathode has been tested in this study.