First two charge-discharge voltage profiles of the a) LiTiS2/Li-In (LTS/Li-In) and b) Li4Ti5O12/Li-In (LTO/Li-In) all solid state cells at 30 oC. First two charge-discharge voltage profiles of the a) LiCoO2/Li-In (LCO/Li-In) and b) Li4Ti5O12/Li-In (LTO/Li-In) all solid state cells at 30 oC. First-cycle discharge-charge voltage profiles for Sn/Li-In all solid state cells with two different electrode mass charges.
Comparison of the discharge-charge voltage profiles of each electrode for Sn/Li-In all-solid-state three-electrode cells using Li0.5In or Li metal as REs. Transient charge–discharge voltage profiles of each electrode for NCM/Gr solid-state three-electrode cells at different current densities. Charge-discharge voltage profiles for a, c) NCM electrodes, b) Gr electrode and d) Si-C electrode for NCM/Gr or NCM/Si-C solid-state three-electrode cells during discharge to 0 V.
Cycling performance of NCM/Gr and NCM/Si-C all-solid cells during discharge to 0 V. The corresponding charge-discharge voltage profiles are shown in Figures 55, 57 and 58.
Background
Principle of Lithium Secondary Batteries
Overview of Bulk-Type Inorganic All-Solid-State Lithium Batteries
- Conductivity of Solid Electrolytes
- Electrochemical Stability of Solid Electrolytes
- Interface Compatibility between Active Materials and Solid Electrolytes
- Electrochemical test protocol for All-Solid-State Lithium Batteries
In this regard, the electrochemical stability of sulfide SEs is also important for the development of high-performance ASLBs. Unfortunately, since the understanding of the decomposition of sulfide SEs at the interface is in its infancy, they have limited electrochemical windows from theoretical calculation.44-45, 54 Ceder and co-workers investigated the phase stability, electrochemical stability and Li-ion conductivity of the family of highly conductive Li10±1MP2X12 (where is M=Ge, Si, Sn, Al or P and X=O, S or Se) using first-principles calculations. 79–82 Although the narrow electrochemical window of sulfide SEs may degrade ASLB performance, it provides new insight into the design of interfacial engineering and the understanding of the passivation phenomenon.
Thus, understanding phenomena at the interface between active materials and SEs is one of the crucial factors for achieving high performance of ASLBs. 97-99 In this regard, the protective layer for suppressing dendritic growth of Li metal and reaction with sulfide SEs is essential for practical full-fledged Li metal batteries. Furthermore, since solid-state lithium batteries (ASLBs) have been operated under high external pressure, volume changes of active materials and/or dissolution of sulfide SEs are not critical for weakening interfacial layer in terms of their ionic and electronic conduction pathways during cycling so far.66-67 From a practical perspective, since the operating conditions of large-scale ASLBs should be milder than the current ones, tracking volume changes at the interface between active materials and sulfide SEs is an essential prerequisite.
In this regard, understanding and controlling the interfacial reactions such as the decomposition of SE with Li metal or oxide cathode materials and volume changes of active materials should be required for the development of high performance of ASLBs.
Experimental
Preparation of materials
Materials characterization
FESEM images of the cross section were obtained using a Quanta 3D FEG (FEI, SE mode); the sample was prepared completely in a dry room. For the HRTEM and EDS analyzes of the pNW film, a 30 keV Ga + ion beam was used for sectioning. Cross-sectional surfaces of the electrodes were prepared by polishing at 5 kV for 13 h with an Ar ion beam (JEOL, SM-0910).
The FESEM images and corresponding EDXS element maps of sectioned electrodes were acquired using a JSM-7000F (JEOL). For the For the results of fault mode diagnosis of ASLBs using three-electrode cells, the cross-sectional surfaces of the samples were prepared by polishing with an Ar ion beam (HITACHI, IM4000) at 1.5 kV for 4 h.
The base pressure of the analytical chamber was maintained at < Pa during all analyses.
Electrochemical characterization
Bag-shaped NCM622/graphite full cells were fabricated by sealing an assembly of wet slurry fabricated electrodes and SE layers (positive electrodes: 80 60 mm2, negative electrodes and SE layers: 83 63 mm2) in a bag, and then subsequently compression at 492 MPa. All electrode and cell fabrication procedures were performed in an Ar-filled dry box in which H2O was controlled to < 1 ppm. Sn electrodes for all semiconductor half-cells were obtained by manually mixing Sn (99%, 10 m, Sigma-Aldrich) and SE powders (Li6PS5Cl) in a mass ratio of 70:30.
The np ratios (ratio of surface area capacity of negative and positive electrodes) for NCM/Gr and NCM/Si-C full cells were approx. All semiconductor cell fabrication procedures were performed in a dry box filled with Ar. NCM622/graphite semiconductor cells were fabricated from 15 mg of a mixture of NCM622, LPSCl and super C65 with a mass ratio of 70:30:3 and 8.8 mg of a mixture of graphite, LPSCl (and/or LGPS) with a mass ratio of 6:4 were used as positive and negative composite electrodes.
The np ratios (ratio of surface area capacity of negative and positive electrodes) for NCM/Gr full cells were approx.
Results and Discussion
Sheet-Type Electrodes & Solid Electrolyte Films
- Solid Electrolyte Films
- Properties of Solid Electrolyte Films
- Sheet-Type All-Solid-State Lithium-Ion Batteries using Solid Electrolyte Films
- Sheet-Type Electrodes
- Comparison of Electrodes Fabricated by Dry-mixing and Wet-slurry processes
- Electrodes Fabricated by Premixing Process
- Practical All-Solid-State NCM622/Gr Full-Cells
Two different configurations (“SE- NW-SE” and “NW-SE-NW”) of the NW-SE films were prepared using this 'transfer' method. However, note that the conductivity values of the NW-SE films (37 mS for LPS-NW-LPS and 29 mS for NW-LPS-NW) are higher than those of the conventional SE film (14 mS). It should be emphasized that the free-standing feature or flexibility of the NW-SE films can provide a viable option to allow roll-to-roll processes.
This increased rate performance is attributed to the higher ionic conductivity of the latter (37 mS) compared to that of the former (14 mS) (Table 1). However, the speed capability of the NW-SE-NW film cell is slightly lower than that of the conventional cell. This indicates that the cell containing NW-SE-NW has a higher charge transfer resistance compared to that of the other two cells.
By combining a heat-treated LCO with a SE-NW-SE (or NW-SE-NW) film and a nickel-coated NW (acting as a flexible current collector), the free-standing LCO/LTO is entirely solid-state. the cell was made. The free-standing (NW-SE) feature of the embedded ASLB also facilitates single-cell stacking. First charge-discharge voltage profiles of a prototype self-standing LTS/LTO flat panel battery at 89 A cm-2 at 30 oC.
The first charge and discharge voltage profiles of free-standing LCO/LTO semiconductor monocells with differently structured SE films (SE-NW-SE, NW-SE-NW, pNW-SE-pNW) and a free-standing bipolar cell fabricated by stacking two free-standing monocells ( LCO/(SE-NW-SE)/LTO) at 14 mA gLCO-1 (= 0.11 mA cm-2) at 30 oC. A controlled premixing process for active materials and SE is introduced as a scalable method to improve the use of active materials in fully semiconductor cells. The presence of insulating polymer binders that partially block the contacts between the active materials and the SE (shown in Fig. 20e) may be responsible for the poorer performance of the slurry-blend electrodes than the dry-blend electrodes.
27 In the cross-sectional FESEM images of dry (D85) and powder-mixed (W85) electrodes and their corresponding elemental maps of Ni, sulfur, and nitrogen (Figure 26), the regions for Ni match that for nitrogen. . Top-view FESEM images of dry and slurry mixed electrodes and their corresponding energy dispersive X-ray spectroscopy (EDXS) maps for sulfur are shown in Figure 29. Nyquist plots of mixed electrodes with dry and mixed with sludge in Fig. 30 show a depressed semicircle followed by a Warburg tail.
The safety performance of the bag-type NCM622/graphite full cell was evaluated by simple tests.
Diagnostic Study for Sheet-Type All-Solid-State Lithium-Ion Batteries
- All-Solid-State Three-Electrode Cells
The unique durability of all-solid-state full cells when discharging to 0 V is also analyzed. Discharge-charge voltage profiles for each electrode for Sn/Li-In all-solid-state three-electrode with different CEs using three different weight ratios of Li0.5In/SE. The other test vehicle for three-electrode solid-state cells is wet slurry-manufactured NCM/Gr full cells with thin SE layers.
Cross-sectional FESEM images and the corresponding EDXS element maps for NCM/Gr fully solid cells using a thin SE layer (50-60 m). Electrochemical performance of all-solid state cells NCM/Li-In, Gr/Li-In-SE and Si-C/Li-In-SE. Schematic representation of the ISC induced by Li metal penetration for NCM/Gr all-solid-state cells during charging at high C rates.
Cycling performances of NCM/Gr and NCM/Si-C solid state cells during discharge to 0 V. Since the solid NCM/Gr solid cells are terminated by termination of NCM electrode, the volume expansion of graphite electrode is slightly prevented. Sakuda, A.; Hayashi, A.; Tatsumisago, M., Sulfide solid electrolyte with favorable mechanical property for all solid state lithium battery.
G.; Janek, J., Degradation Mechanisms at the Li10GeP2S12/LiCoO2 Cathode Interface in an All-Solid-State Lithium-Ion Battery. SEM analysis between Li/Li3PS4 interface with Au thin film for solid-state lithium batteries. H.; Lee, S.-H., Tin network electrode providing improved volumetric capacity and pressureless operation for all-solid-state Li-ion batteries.
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