Drastic Reduction of the Solid Electrolyte–Electrode Interface Resistance via Annealing in Battery Form

Abstract

The origin of electrical resistance at the interface between the positive electrode and solid electrolyte of an all-solid-state Li battery has not been fully determined. It is well known that the interface resistance increases when the electrode surface is exposed to air. However, an effective method of reducing this resistance has not been developed. This report demonstrates that drastic reduction of the resistance is achievable by annealing the entire battery cell. Exposing the LiCoO2 positive electrode surface to H2O vapor increases the resistance by more than 10 times (to greater than 136 Ω cm2). The magnitude can be reduced to the initial value (10.3 Ω cm2) by annealing the sample in a battery form. First-principles calculations reveal that the protons incorporated into the LiCoO2 structure are spontaneously deintercalated during annealing to restore the low-resistance interface. These results provide fundamental insights into the fabrication of high-performance all-solid-state Li batteries.

Modifying the Interface between the Solvated Ionic Liquid Electrolyte and Positive Electrode to Boost Lithium-Ion Battery Performance

“…Because the arc only appears in the charging state, the origin should be the charge-transfer reaction at the Li 3 PO 4 –LiCoO 2 (001) interface. The resistance at this interface is evaluated to be 1.5 × 10 1 Ω cm 2 (Table S2); the value is in good agreement with the Li 3 PO 4 –LiCoO 2 (001) charge-transfer resistance in our previous reports (∼10 Ω cm 2 ). ,, …”

“…At the Li 3 PO 4 –LiCoO 2 (001) interface, Li ions transport smoothly across the interface because the interface is clean and atomically well-ordered, leading to an extremely low interface resistance. , These results confirm that the Li 3 PO 4 buffer layer is chemically and electrochemically stable in the presence of the solvated ionic liquid electrolyte, indicating that this layer is responsible for improving the battery performance. The buffer layer counteracts the deterioration in the battery operation, suppressing the formation of an SEI layer at the [LiG4]­[TFSA]–LiCoO 2 (001) interface.…”

Sputter-Deposited Amorphous Li3PO4 Solid Electrolyte Films

“…It should be noted that other resistances, e.g., the interface resistance between the Li anode and Li 3 PO 4 , or Li 3 PO 4 and the LiCoO 2 cathode, are not clearly observed, which is different from previously reported results. 7,14 Most recently, the reduced interface resistance was reported to be 10.3 Ω cm 2 between LiCoO 2 and RF-sputtered Li 3 PO 4 , 29 and also a further reduced resistance of 8.6 Ω cm 2 was reported between LiCoO 2 and LiPON. 7 As the active area of our battery was 0.567 cm 2 (8.5 mm-diameter Li anode), at least 15 Ω of interface resistance should appear in the Nyquist plots, if such a resistance exists; however, it cannot be seen in Figure 8 (bottom).…”

Immense Reduction in Interfacial Resistance between Sulfide Electrolyte and Positive Electrode

“…Thin-film model systems are a good representation of typical solid-state batteries. Moreover, thin-film model systems are sensitive to changes to the interfaces because of the large ratio of contacting interfacial area to electrode volume . If the thickness of the positive electrode is increased, thin-film model systems exhibit typical battery performance.…”

“…Moreover, thin-film model systems are sensitive to changes to the interfaces because of the large ratio of contacting interfacial area to electrode volume. 22 If the thickness of the positive electrode is increased, thin-film model systems exhibit typical battery performance. Indeed, we have observed stable cycling in a thin-film battery with thick positive electrodes when the degradation of the interfaces is limited to a thin layer.…”