An All-Solid-State Battery with a Tailored Electrode–Electrolyte Interface Using Surface Chemistry and Interlayer-Based Approaches

Abstract

Major challenges in the development of solid-state batteries using garnet-type solid-state electrolytes (SSEs) include suppressing dendrite growth, improving moisture stability, and reducing interfacial resistance. Prior attempts to remove surface impurities of SSEs through dry polishing caused high interfacial resistance that proves this method to be unviable. Further, several efforts on depositing thin-film protective layers on SSEs without understanding surface chemistry failed to demonstrate improved electrochemical performance. Here, we report the simultaneous removal of the surface impurities and protection of the SSE against air and moisture by regulating its surface chemistry. In situ X-ray photoelectron spectroscopy (XPS) studies revealed that primary surface contaminants such as lithium carbonate (Li 2 CO 3 ) and lithium hydroxide on the SSE, Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZT), could be removed by either argon-ion sputtering at 227 °C or annealing at 777 °C in ultrahigh vacuum conditions. To protect the cleaned LLZT surface from further ambient contamination, in situ atomic layer deposition was used to deposit ∼3 nm-thick h-BN using tris(dimethylamino)borane and ammonia precursors at 450 °C. Intermittent XPS analysis confirmed the absence of Li 2 CO 3 formation and the stability of h-BN-coated LLZT pellets for over 2 months of exposure to atmospheric air and moisture. Electrochemical impedance spectroscopy studies revealed that an ultrathin layer of ∼3 nm h-BN drastically reduced the interfacial resistance from 1145 to 18 Ω cm 2 (∼65× reduction). Li plating/stripping studies revealed a constant polarization of 27 mV at a 0.5 mA cm −2 current density over prolonged cycling and a high critical current density of 0.9 mA cm −2 . An all-solid-state battery using a LiFePO 4 cathode exhibited a stable capacity of 130 mAh g −1 for over 100 cycles and a negligible capacity fade-off of 0.11 mAh g −1 per cycle at an average Coulombic efficiency of 98.4%.

Role of Electronic Structure in Li Ordering and Chemical Strain in the Fast Charging Wadsley–Roth Phase PNb9O25

“…Secondary lithium-ion batteries have become a standard for portable electronics and electric vehicles due to their reliability, high cycle lives, and high efficiencies . Despite their widespread use, Li-ion batteries continue to face challenges in high-power applications, where they have a propensity for thermal runaway reactions due to the formation of lithium dendrites on the anode during fast charging. − The Li dendrites can pierce the separator and lead to direct contact between the anode and the cathode, thereby increasing explosion risks. These safety concerns put constraints on the charging times of Li-ion batteries, which limit their use in mobile applications, including electric and hybrid electric vehicles.…”

Coordination-Assisted Precise Construction of Metal Oxide Nanofilms for High-Performance Solid-State Batteries

“…Cross-sectional SEM of the Li/LLZT interface (Figure d) shows the existence of gaps at the interface. This Li/LLZT interface is only a point-to-point contact, as illustrated in the upper portion of Figure e, which is caused by the superlithiophobicity of contaminants on the LLZT surface and the rigid nature of LLZT and Li . Depositing a 6 nm Al 2 O 3 nanofilm on the LLZT surface (sample denoted as LLZT-Al) drastically changes its ability to form good interfacial contact with molten lithium metal (Figure e lower portion); the molten Li easily spreads over the entirety of the LLZT-Al pellet surface (Figure f inset).…”

“…This Li/LLZT interface is only a point-to-point contact, as illustrated in the upper portion of Figure 3e, which is caused by the superlithiophobicity of contaminants on the LLZT surface and the rigid nature of LLZT and Li. 36 Depositing a 6 nm Al 2 O 3 nanofilm on the LLZT surface (sample denoted as LLZT-Al) drastically changes its ability to form good interfacial contact with molten lithium metal (Figure 3e lower portion); the molten Li easily spreads over the entirety of the LLZT-Al pellet surface (Figure 3f inset). SEM imaging of a crosssectioned Li/LLZT-Al interface shows the intimate contact between the Al 2 O 3 surface layer on the LLZT and the Li metal (Figure 3f).…”

Interface Engineering of a Ceramic Electrolyte by Ta2O5 Nanofilms for Ultrastable Lithium Metal Batteries

“…The Nyquist plots show two distinct arcs for each sample ascribed to bulk resistant and grain boundary resistant + interfacial resistant, respectively. [37,38] Interfacial ASR is determined by the interface resistance on each side of the symmetric cells through subtracting the electrolyte resistance from the total cell resistance, dividing by two, and then normalizing the pellet surface area. As shown in Figures 3j, the interfacial ASRs have a drastic decrease from 1258 Ω cm 2 for Li/LLZT to 9 Ω cm 2 for Li/LLZT-Ta at 25 °C.…”