Synthesis and Postprocessing of Single-Crystalline LiNi_0.8Co_0.15Al_0.05O₂ for Solid-State Lithium-Ion Batteries with High Capacity and Long Cycling Stability

Abstract

The application of nickel-rich LiNi x Co y Al z O 2 (NCA) cathode materials in solid-state lithium-ion batteries (SSBs) promises significant improvements in energy density, stability, and safety over traditional lithium-ion batteries with liquid electrolytes. However, low active mass utilization and strong capacity fading associated with degradation of the cathode often limit SSB applicability. The use of single-crystalline cathode active materials (CAMs) instead of spherical polycrystalline materials optimized for performance in lithium-ion batteries recently emerged as a promising approach in the field of SSBs to overcome this issue. In this work, single-crystalline LiNi 0.8 Co 0.15 Al 0.05 O 2 (SC-NCA) is investigated as cathode active material for SSBs. It is shown that appropriate postprocessing of assynthesized materials, which consists of washing steps with either water or ethanol followed by postannealing at different temperatures, is key to achieve high-performance cathodes. X-ray powder diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and scanning transmission electron microscopy are employed to characterize the effect of postprocessing on structure and morphology. The postprocessing procedure was tailored to mitigate detrimental side reactions that result in structural damage of the SC-NCA, while retaining the beneficial effects of deagglomeration and control of surface impurities. Washing with ethanol and subsequent postannealing at 750 °C allowed us to obtain SC-NCA materials that perform well in SSB cells with Li 6 PS 5 Cl as solid electrolyte, enabling a high initial discharge capacity of 174 mAh g −1 , good rate performance, and high capacity retention (94% after 200 cycles) at 25 °C.

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

“…The open structure of PNb 9 O 25 allows for rapid lithium diffusion while operating in a potential window between 2 and 1 V and accommodates approximately 11. 5 Li when cycled at a C/20 rate against Li. The higher operating voltage window of PNb 9 O 25 makes it possible to discharge at higher current densities than graphite-based anodes that operate at an average potential of 0.1 V. 28 Our systematic study of the electrochemical properties of PNb 9 O 25 as a function of Li concentration reveals a complex site filling sequence that is strongly influenced by the chemical strain induced by changes in the electronic structure that accompany Li insertion.…”

“…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.…”

Constructing a High-Energy and Durable Single-Crystal NCM811 Cathode for All-Solid-State Batteries by a Surface Engineering Strategy

“…In particular, the initial capacity of the 400-ALDNCM electrode is comparable to that of LIBs. Moreover, the initial CE of the 400-ALDNCM (80.6%) electrode is significantly higher than that of ALDNCM (72.1%) and bare NCM (69.8%), indicating that the nano-LNO layer effectively relieves severe irreversible capacity during the first cycle, which is in line with the results of the decrease of the peak intensity below 3.5 V in d Q /d V curves after ALD especially after post-annealing treatment (Figure f–h) . Notably, the average discharge voltage of 400-ALDNCM (3.79 V) is also higher than that of ALDNCM (3.75 V) and much higher than that of bare NCM (3.65 V), which is well underpinned by the negligible polarization of the 400-ALDNCM electrode in the d Q /d V curves (Figure f–h).…”

Challenges, interface engineering, and processing strategies toward practical sulfide‐based all‐solid‐state lithium batteries

“…[222][223][224][225] Recently, single-crystalline cathode materials gained close attention in the solid-state system due to their favorable mechanical properties. 85,213,214,[226][227][228] In the liquid LiBs, upon the secondary CAM particles cracking during cycling, the flowing liquid electrolyte can penetrate into the pores of polycrystalline CAMs, promoting the electrochemical reaction kinetics to a certain extent. 110 In sharp contrast, the ionic transport and electrochemical reaction in the composite cathode of ASSLBs can only occur at the surface region of secondary CAM particles, and SEs are difficult to penetrate into the voids or cracks of secondary CAM particles, indicating that the insufficient utilization of CAMs when the structural collapse of polycrystalline materials occur during pressing electrode process and electrochemical cycling.…”

“…The single crystalline structure is considered to have better thermal, high voltage, and mechanical tolerance than typical polycrystalline materials in liquid LiBs 222–225 . Recently, single‐crystalline cathode materials gained close attention in the solid‐state system due to their favorable mechanical properties 85,213,214,226–228 . In the liquid LiBs, upon the secondary CAM particles cracking during cycling, the flowing liquid electrolyte can penetrate into the pores of polycrystalline CAMs, promoting the electrochemical reaction kinetics to a certain extent 110 .…”