Résumé
Driven by the growing need for efficient and high-performance power sources, microenergy storage systems have emerged as a key area in modern technology [1]. Among various electrochemical devices, LiPON-based microsupercapacitors become a valuable candidate for addressing several energy storage challenges [2]. As an efficient solid-state electrolyte, LiPON has garnered significant attention and has been extensively studied through material science and film growth approaches to unlock new pathways for performance enhancement [3]. Therefore, incorporating complementary oxides such as Alumina into LiPON offers a promising pathway to rearrange the intrinsic structure and particularly improve lithium-ion mobility within the film [3]. Moreover, employing precise techniques such as ALD for film growth allows a controlled insertion of doping agents while finely adjusting composition, thickness and electrochemical behavior. In this study, we aim to provide a comprehensive approach to establish the ALD process and explore the interplay between the physico-chemistry and electrochemical performances of both LiPON and LiPON-doped films.LiPON ultra-thin films (<50nm) were primary deposited using Li-Bistrimethylsilylamide (LiHMDS) and Diethylphosphoramidate (DEPA), at Tdeposition=330°C. To further optimize LiPON’s electrochemical performance, Trimethyl Aluminium (TMA) and H2O were pulsed using a super-cycle approach to inject Al2O3 traces. Meanwhile, physico-chemical characterization provided valuable insights into composition variations. TOF-SIMS depth profiling highlighted the effectiveness of the supercycle approach in ensuring a homogeneous distribution of Al atoms across the LiPON-doped film. Moreover, FTIR analysis revealed an increase in (PO3) peak intensity, suggesting that the oxygen environments were favorably modified by Al2O3 insertion. Further XPS analysis revealed changes in the atomic environments, particularly around oxygen and nitrogen, showing a simultaneous increase in the Nd/Nt and Ob/Onb ratios with increasing Al₂O₃ doping. These findings indicate significant rearrangements in the pristine LiPON network and unveiled potential factors that can either facilitate or hinder lithium-ion transport within the films. LiPON-based films were then integrated within a (TiN/LiPON/Pt) MIM structure for electrochemical assessment. From EIS measurements, Nyquist plots revealed a gradual improvement in ionic conductivity up to an optimal doping ratio, beyond which the ionic conductivity decreased, potentially due to excess Al. Thanks to its excellent insulating properties, Al2O3 did not alter the pristine characteristics of LiPON, effectively preventing leakage currents (I leakage < 10 nA.cm⁻²) in the LiPON(Al2O3) film. Additionally, LiPON-doped films displayed a wide potential window (0V to 5V).Throughout this work, we aimed to conduct a multidisciplinary study on LiPON enhancements, covering ALD process development, electrochemical analysis and material science. The ALD technique demonstrated promising potential to fine-tune doping ratios and improve electrochemical performances (i.e., Li+ mobility, areal capacitance, etc.) of LiPON thin films. Hence, this approach may extend to other ALD-enabled thin films, paving the way for wide applications in lithium-based systems, such as micro-batteries and synaptic transistors. [1] Y. Duan et al., ‘Advances in wearable textile-based micro energy storage devices: structuring, application and perspective’, Nanoscale Adv., vol. 3, no. 22, pp. 6271–6293, 2021, doi: 10.1039/D1NA00511A. [2] V. Sallaz et al., ‘Dual Storage Mechanism in Nanoscale Solid-State Lithium-Ion Supercapacitors’, ACS Electrochem., p. acselectrochem.4c00022, Oct. 2024, doi: 10.1021/acselectrochem.4c00022. [3] ‘Adv Funct Materials - 2024 - Zou - Lithium Phosphorous Oxynitride as an Advanced Solid‐State Electrolyte to Boost.