Tuning the Cation Ordering with the Deposition Pressure in Sputtered LiMn_1.5Ni_0.5O₄ Thin Film Deposited on Functional Current Collectors for Li-Ion Microbattery Applications

Abstract

The development of high voltage spinel LiMn 1.5 Ni 0.5 O 4 (LMNO) sputtered thin films on functional current collector was reported within the framework of this study. We have first solved the technological issue due to the PtSi phase which originates from the interdiffusion between silicon wafer and chromium/platinum current collector to form PtSi phase under annealing treatment. By substituting the Cr layer with a very dense and pinhole free Al 2 O 3 thin film deposited by ALD acting as a barrier diffusion between the silicon substrate and the LMNO layer, the synthesis process (sputtered thin films annealed under air at 700°C) has been validated. In the second part of this study, the behavior of the sputtered LMNO thin films as a function of the deposition pressure and the film thickness has been investigated. The deposition pressure has been found to play a key role on the Mn−Ni cations ordering in spinel-like structures (P4 3 32 ordered vs Fd3̅ m disordered spinel) and consequently on the electrochemical performance. We have thus shown that LMNO thin films deposited at 10 −2 mbar and annealed at 700°C deliver a normalized capacity of 65 μAh•cm −2 •μm −1 with good capacity retention upon cycling thanks to its disordered spinel structure. Moreover, the Coulombic efficiency has been shown to be highly dependent on the film thickness for high voltage LMNO thin film electrodes. To the best of the authors' knowledge, this work is one of the most complete study combining structural and electrochemical characterizations of the LMNO thin film obtained by sputtering deposition on Si/Al 2 O 3 /Pt functional current collectors.

Synthesis of T-Nb2O5 thin-films deposited by Atomic Layer Deposition for miniaturized electrochemical energy storage devices

“…!Os polymorph was achieved by thermal annealing at 750 °C during 2 h under air atmosphere. During the annealing process, the presence of the Al2Üs thin film avoids interdiffusion between Si and Pt so that PtSi alloy cannot form [27). The crystal structure of the T ~Os is descnbed in Fig.…”

“…There is then intere.sting opportunities for designing thin films of Nb:!O 5 for micro devices applications. Thin film electrode for MB [27,28] or MSC [5,11) applications can be prepared by using magnetron sputtering technique or, alternatively, by Atomic Layer Deposition (ALD) which has also been found as a suitable deposition tool, compatible with CMOS facilities, to grow thin films on large scale substrate with high uniformity and homogeneity [29 35).…”

Precise Surface Engineering of Cathode Materials for Improved Stability of Lithium‐Ion Batteries

“…Inspired by the extraordinary capability in surface control, ALD has been applied to different cathode materials to have a systematic investigation on the coating effect of high‐energy materials . For example, Li et al employed the ALD technique to systematically study the effects of both composition and thickness on the performance of LiCoO 2 cathode.…”

Interfacial Incompatibility and Internal Stresses in All‐Solid‐State Lithium Ion Batteries

“…The high‐voltage plateau of LNMO (≈4.7 V vs Li/Li + ) makes its energy density 20–30% higher than the energy density of commercial LiCoO 2 and LiFePO 4 . However, successful commercialization of the LNMO is restricted in high‐energy LIBs due to electrolyte decomposition and side reaction of the cathodes and liquid electrolytes when operating at high voltages . The other way to improve the energy/power density is to replace the conventional graphite anode with Li metal.…”

“…However, they suffer from flammability, poor electrochemical stability, limited temperature range of operation, and low power density. [7,8] The other way to improve the energy/power density is to replace the conventional graphite anode with Li metal. [5] To improve the energy/power density of LIBs, one way is to adopt high-potential cathode materials such as LiNi 0.5 Mn 1.5 O 4 (LNMO).…”