Amorphous Ni‐Rich Li(Ni_1−x−yMn_xCo_y)O₂–Li₂SO₄ Positive Electrode Materials for Bulk‐Type All‐Oxide Solid‐State Batteries

Abstract

typical organic liquid electrolytes. [1][2][3] Although the safety and reliability of batteries can be potentially improved by utilizing solid electrolytes instead of liquid electrolytes, there are still several challenges in sulfide-type all-solidstate batteries, such as H 2 S generation and chemical reaction with active materials. [4][5][6][7] On the other hand, oxide-type all-solid-state batteries have been regarded as one of the leading candidates to overcome these problems owing to the high chemical and electrochemical stabilities of oxide electrolytes. Despite the merits, the construction of all-oxide solid-state batteries is quite difficult owing to the lack of deformability of the typical crystalline oxide electrolytes, which leads to a poor contact between the active material and solid electrolyte particles. [8] Therefore, high-temperature sintering is required to achieve a good contact. Even if a good contact is achieved, unfavorable chemical reactions between the active material and solid electrolyte might proceed at the high temperature, leading to generation of a highly resistive layer. [9,10] Therefore, formation of an excellent electrode/ electrolyte interface without high-temperature sintering is important for the operation of all-oxide solid-state batteries. In order to achieve a good formability in oxide electrolytes, we have focused on materials with lower melting points such as Li 3 BO 3 . [11] A mechanochemically prepared Li 3 BO 3 glass electrolyte exhibited a relatively high conductivity of 10 −7 S cm −1 at room temperature and good formability. In addition, we previously developed ductile oxide glass-ceramic electrolytes of the pseudobinary system Li 3 BO 3 -Li 2 SO 4 . The Li 2.9 B 0.9 S 0.1 O 3.1 (90Li 3 BO 3 ·10Li 2 SO 4 (mol%)) glass-ceramic electrolyte exhibited a high conductivity of ≈10 −5 S cm −1 at room temperature. [12,13] A good contact with electrode active materials was successfully achieved simply by pressing at room temperature, which was enabled by the excellent formability of the electrolyte.Crystalline materials such as layered, [14,15] spinel, [16] and olivine [17] structures have been utilized as positive electrode materials in typical lithium-ion and all-solid-state batteries. Amorphous materials are also candidates for electrode materials, which generally exhibit higher conductivities than those of the All-solid-state batteries attract significant attention owing to their potential to realize an energy storage system with high safety and energy density. In this paper, a mechanochemical synthesis of novel amorphous positive electrode materials of the Ni-rich LiNi 1−x−y Mn x Co y O 2 (NMC)-Li 2 SO 4 system suitable for oxide-type all-solid-state batteries is reported. Through the mechanochemical treatment with Li 2 SO 4 , excellent formabilities of the electrode materials as those of ductile solid electrolytes are obtained. Owing to the deformability of the active material, a good electrode/electrolyte interface is provided simply by pressing at room temperature. In all...

Highly Stable Li/Li3BO3–Li2SO4 Interface and Application to Bulk-Type All-Solid-State Lithium Metal Batteries

“…Figure S3 shows the charge−discharge performance of the cold-pressed all-solid-state cells at 100 °C. The cell with the amorphous 80LiNi 0.5 Mn 0.3 Co 0.2 O 2 •20Li 2 SO 4 gave the charge−discharge curves with a gentle slope, 23 which is somewhat different with the behavior of typical crystalline LiNi 0.5 Mn 0.3 Co 0.2 O 2 having a layered rock-salt structure. The operation of the cold-pressed cell was stable at lower current densities, with a capacity of ∼160 mAh g −1 .…”

“…Amorphous 80LiNi 0.5 Mn 0.3 Co 0.2 O 2 •20Li 2 SO 4 was used as a positive electrode active material due to its high ductility and mixed conductivity. 23 The all-solid-state cells were fabricated by coldpressing or hot-pressing the constituent powders. Figure S3 shows the charge−discharge performance of the cold-pressed all-solid-state cells at 100 °C.…”

“…Meanwhile, some voids and grain boundaries existed in the cold-pressed composite electrode layer. 23 However, these voids and grain boundaries were hardly observed in the composite electrode layer when a hot-pressing technique was used. Hence, a favorable electrode−electrolyte interface with large contact area was obtained as shown in Figure 4c.…”

“…20−22 Furthermore, we demonstrated the stable operation of bulktype all-oxide-solid-state batteries using the Li 3 BO 3 -based glass-ceramic electrolytes. 23 Previously, Li−In alloy has been used as a model negative electrode model in all-solid-state batteries. Utilization of Li metal enhances the energy density of the battery, but the electrochemical stability of Li 3 BO 3 -based glass-ceramic electrolytes has not been investigated in detail.…”

Low‐Resistive LiCoO2/Li1.3Al0.3Ti2(PO4)3 Interface Formation by Low‐Temperature Annealing Using Aerosol Deposition

“…Several approaches have been reported from materials innovation aspects such as lower melting-point solid electrolyte [8] and ductile materials. [9,10] From process engineering aspects, spark plasma sintering, [11,12] cold sintering, [13] low-temperature sintering triggered by ion exchange, [14] and aerosol deposition (AD) [15][16][17][18][19][20][21] have been reported.…”