All-solid-state lithium batteries (ASSLB) are very promising for the future development of next generation lithium battery systems due to their increased energy density and improved safety. ASSLB employing Solid Polymer Electrolytes (SPE) and Solid Composite Electrolytes (SCE) in particular have attracted significant attention. Among the several expected requirements for a battery system (high ionic conductivity, safety, mechanical stability), increasing the energy density and the cycle life relies on the electrochemical stability window of the SPE or SCE. Most published works target the importance of ionic conductivity (undoubtedly a crucial parameter) and often identify the Electrochemical Stability Window (ESW) of the electrolyte as a secondary parameter. In this review, we first present a summary of recent publications on SPE and SCE with a particular focus on the analysis of their electrochemical stability. The goal of the second part is to propose a review of optimized and improved electrochemical methods, leading to a better understanding and a better evaluation of the ESW of the SPE and the SCE which is, once again, a critical parameter for high stability and high performance ASSLB applications.

Herein, we propose a fast and simple deposition method of a highly robust pseudocapacitive material based on a straightforward drop-cast of a commercial PEDOT:PSS solution onto 3 nm alumina-coated silicon nanowires. The composite material produced (PPSS-A@ SiNWs) displays, remarkable capacitive behavior with a specific capacitance of 3.4 mF•cm −2 at a current density of 2 A•g −1 in aqueous Na 2 SO 4 electrolyte. Moreover microsupercapacitor (MSC) devices based on this material exhibits outstanding lifetime capacity retaining 95% of its initial capacitance after more than 500 000 cycles at a current density of 0.5 A•g −1 , a specification which exceeds by far most of the stability of conducting polymers previously reported in the literature. In term of pure energy storage performances, the system is able to reach excellent specific energy and power values of 8.2 mJ•cm −2 and of 4.1 mW•cm −2 , respectively, at a high current density of 2 A•g −1 . Results are systematically compared to both the state-of-the-art silicon based aqueous on-chip supercapacitors and to that of the pristine alumina-coated silicon nanowires (A@SiNWs) to highlight the contribution of the conductive PEDOT:PSS polymer (PPSS in this study). Hence, the aforementioned one-step deposition represents a simple, cheap and scalable method to thoroughly increase the cycling stability of a well-known conductive polymer, PEDOT−PSS, while drastically increasing the electrochemical performances of an existing technology, the Si NW-based MSCs using aqueous electrolytes.