Unraveling the Stable Cathode Electrolyte Interface in all Solid‐State Thin‐Film Battery Operating at 5 V

Abstract

Spinel‐type LiNi0.5Mn1.5O4 (LNMO) is one of the most promising 5 V‐class cathode materials for Li‐ion batteries that can achieve high energy density and low production costs. However, in liquid electrolyte cells, the high voltage causes continuous cell degradation through the oxidative decomposition of carbonate‐based liquid electrolytes. In contrast, some solid‐state electrolytes have a wide electrochemical stability range and can withstand the required oxidative potential. In this work, a thin‐film battery consisting of an LNMO cathode with a solid lithium phosphorus oxynitride (LiPON) electrolyte is tested and their interface before and after cycling is characterized. With Li metal as the anode, this system can deliver stable performance for 600 cycles with an average Coulombic efficiency >99%. Neutron depth profiling indicates a slight overlithiated layer at the interface prior to cycling, a result that is consistent with the excess charge capacity measured during the first cycle. Cryogenic electron microscopy further reveals intimate contact between LNMO and LiPON without noticeable structure and chemical composition evolution after extended cycling, demonstrating the superior stability of LiPON against a high voltage cathode. Consequently, design guidelines are proposed for interface engineering that can accelerate the commercialization of a high voltage cell with solid or liquid electrolytes.

Monolithic All-Solid-State High-Voltage Li-Metal Thin-Film Rechargeable Battery

“…During the revision process of this work, another report on thin-film LNMO/LiPON/Li cells grown by pulsed laser deposition (PLD) on Pt-coated Al 2 O 3 substrates was published. 56 This work presented a cell that delivered 99.6% Coulombic efficiency after 600 cycles; however, the reported capacity values of the cell were not very high: ∼18 μAh cm −2 μm −1 as normalized to the cathode thickness, three times lower than the capacity of our cathode (65 μAh cm −2 μm −1 ). 57 In any case, it is worth mentioning that those two reports on thin-film LNMO/LiPON/Li cells present results of batteries that have been grown on Pt-coated Al 2 O 3 substrates, with the Pt cost at $28,000 kg −1 , using evaporation techniques, namely, RF magnetron sputtering and PLD, which involve a much higher production cost than the ones used in this work.…”

“…In this case, the cell delivered a first cycle capacity of 122 mAh g –1 at C/10 and a 90.6% capacity retention after 10,000 cycles and a 99.98% Coulombic efficiency. During the revision process of this work, another report on thin-film LNMO/LiPON/Li cells grown by pulsed laser deposition (PLD) on Pt-coated Al 2 O 3 substrates was published . This work presented a cell that delivered 99.6% Coulombic efficiency after 600 cycles; however, the reported capacity values of the cell were not very high: ∼18 μAh cm –2 μm –1 as normalized to the cathode thickness, three times lower than the capacity of our cathode (65 μAh cm –2 μm –1 ) .…”

A review of all-solid-state electrolytes for lithium batteries: high-voltage cathode materials, solid-state electrolytes and electrode–electrolyte interfaces

“…6e and f). Shimizu 116 used LNMO cathode materials and a lithium phosphorus oxide nitride (LiPON) solid electrolyte to form a thin-film battery. The battery was still stable after 600 cycles at 5 V-class high voltage, and the average coulomb efficiency was greater than 99%.…”

Na–K Alloy Anode for High-Performance Solid-State Sodium Metal Batteries

“…Given the XRD results, we were specifically hoping to capture the crystalline patterns that emerge in the ZNSE after cycling. Cryo-TEM is the most suitable technique for SEI characterization because it perfectly maintains the interfaces; unfortunately, cryo-TEM sample preparation is extremely difficult and relatively time-consuming, and detailed SEI structure is rarely reported in literature. , …”

“…Cryo-TEM is the most suitable technique for SEI characterization because it perfectly maintains the interfaces; unfortunately, cryo-TEM sample preparation is extremely difficult and relatively time-consuming, and detailed SEI structure is rarely reported in literature. 23,24 When ZNSE is characterized using normal TEM, no crystalline phase can be observed for either the Na||ZNSE or Na−K||ZNSE, most likely because ZNSE is highly susceptible to beam irradiation (Figure S2). However, we were able to successfully use cryo-TEM to probe the crystallography of ZNSE.…”