Tunnel Intergrowth Li_xMnO₂ Nanosheet Arrays as 3D Cathode for High‐Performance All‐Solid‐State Thin Film Lithium Microbatteries

Abstract

All‐solid‐state thin film lithium batteries (TFBs) are proposed as the ideal power sources for microelectronic devices. However, the high‐temperature (>500 °C) annealing process of cathode films, such as LiCoO2 and LiMn2O4, restricts the on‐chip integration and potential applications of TFBs. Herein, tunnel structured LixMnO2 nanosheet arrays are fabricated as 3D cathode for TFBs by a facile electrolyte Li+ ion infusion method at very low temperature of 180 °C. Featuring an interesting tunnel intergrowth structure consisting of alternating 1 × 3 and 1 × 2 tunnels, the LixMnO2 cathode shows high specific capacity with good structural stability between 2.0 and 4.3 V (vs. Li+/Li). By utilizing the 3D LixMnO2 cathode, all‐solid‐state LixMnO2/LiPON/Li TFB (3DLMO‐TFB) has been successfully constructed with prominent advantages of greatly enriched cathode/electrolyte interface and shortened Li+ diffusion length in the 3D structure. Consequently, the 3DLMO‐TFB device exhibits large specific capacity (185 mAh g−1 at 50 mA g−1), good rate performance, and excellent cycle performance (81.3% capacity retention after 1000 cycles), outperforming the TFBs using spinel LiMn2O4 thin film cathodes fabricated at high temperature. Importantly, the low‐temperature preparation of high‐performance cathode film enables the fabrication of TFBs on various rigid and flexible substrates, which could greatly expand their potential applications in microelectronics.

Low Temperature Deposition of Highly Cyclable Porous Prussian Blue Cathode for Lithium‐Ion Microbattery

“…The electrode (PBA-5) exhibited reversible gravimetric capacity of ≈110 mAh g −1 (at 0.1 mA cm −2 ), consistent with previous reports with the iron hexacyanoferrate based materials [31,33,34] and a huge areal capacity of ≈650 µAh cm −2 (≈5.41 µAh cm −2 µm −1 ) as compared to other cathodic materials for microbattery applications. [17,[35][36][37][38][39][40][41][42] Indeed, the size and the compactness being the primary selection criteria, it is imperative to consider all reported properties normalized to the footprint area on the chip. The different porous Li-Fe-PBA electrodes show good rate stability with excellent capacity retention upon reverting to slower rates (Figure S4, Supporting Information).…”

“…Moreover, the low temperature deposition techniques developed here are fully compatible with the existing microfabrication facilities of the microelectronic industry and will help to accelerate the development on-chip energy storage systems for the IoT. [17,[35][36][37][38][39][40][41][42] In green: low temperature synthesis compatible with microfabrication process.…”

Physical Vapor Deposition of Cathode Materials for All Solid-State Li Ion Batteries: A Review

“…The 3D LiMn 2 O 4 /Lipon/Li ASTB had an initial capacity of 24.2 µAh cm −2 and showed 90% capacity retention after 500 cycles at 1°C, while the capacity retentions of 2D counterparts were ≤73%. Later, the same group fabricated 3D tunnel intergrowth Li x MnO 2 nanosheet arrays using low-temperature processing (180°C) with the assistance of electrolyte Li + ion infusion (Xia et al, 2020). The Li x MnO 2 /LiPON/Li ASTB showed an initial capacity of 32.8 μAh cm −2 at a current density of 20 μAh cm −2 and retained 81.3% after 1000 cycles.…”

“…Moreover, thin-film cathodes of α-MoO 3-x that have vertically aligned nanoflakes of about 40-60 nm thickness show superior electrochemical performance, maximizing the cathode-electrolyte interface while retaining the short Li + diffusion length (Sun et al, 2019). The 3D nanowall architecture of LiMn 2 O 4 and Li x MnO 2 has also shown greater performance than the 2D counterparts (Xia et al, 2018;Xia et al, 2020). A significant increase in the cathode-electrolyte interface area and improved accommodation capability for volume change provide fast ion transport and enhanced structural and mechanical stability.…”

Designing Polymer‐in‐Salt Electrolyte and Fully Infiltrated 3D Electrode for Integrated Solid‐State Lithium Batteries

“…[18,36] With electrochemically stable interface guaranteed, building an integrated electrode-electrolyte structure is of extreme importance to enhance interface affinity. [37] To this end, several previous studies have made attempts through directly casting SPEs onto the electrode surface or their mixed slurry, and fusing electrodes and electrolytes via heating or hot pressing. [36,[38][39][40][41] Although the interfacial adhesion is reinforced, there remains critical challenges.…”