Solid-state Electrolytes Testing Method for Electrochemical Properties

1. Preface

The performance of solid-state electrolytes—especially their ionic conductivity and cycling stability—is highly dependent on physical characteristics such as density, surface roughness, and structural integrity. Achieving consistent and accurate electrolyte measurement is essential for advancing the development of all-solid-state batteries. Reliable solid state test systems must provide stable and quantifiable pressure application throughout testing to ensure reproducible and meaningful results. This underscores the importance of integrated manufacturing and testing platforms capable of delivering standardized mechanical conditions.

Figure 1. Solid state battery electrolyte diagram — schematic of the solid-state electrolyte testing configuration

2. Testing Instrument

The Solid-State Electrolyte Test System model SEMS1100, co-developed by IEST and Xiamen University, is an advanced multi-functional platform designed specifically for solid-state electrolyte evaluation. This integrated system combines several key modules:

• Pressurization unit

• Electrochemical testing station

• Density measurement cell

• Ceramic pellet compression and clamping fixtures

It supports a wide range of solid electrolyte materials, including oxide-based, sulfide-based, and polymer electrolytes. The SEMS1100 enables high-precision electrolyte measurement under controlled pressure, making it ideal for R&D and quality control applications spanning both solid-state electrolyte characterization and full solid state battery testing.

Figure 2. IEST SEMS1100 solid-state electrolyte test system — integrated pressurization, electrochemical testing, and density measurement modules

3. Application Cases

3.1 Powder Production & Screening Equipment Considerations

Solid electrolyte pellet quality begins upstream of the pressing step itself, with powder handling and screening equipment that determines particle size distribution and packing behavior before compaction. Manual, uninstrumented pressing of solid electrolyte powders into pellets is difficult to standardize: applied force varies from operator to operator and from batch to batch, which is one of the practical reasons laboratories evaluating solid-state battery and EV-grade powder processing lines look for screening and pressing equipment with quantifiable, repeatable force control rather than manual hydraulic presses. To perform accurate electrolyte measurement, solid electrolyte powders must be compressed into uniform pellets, and inconsistent pressure during this process often results in cracked or uneven samples. As shown in Figure 3, the SEMS1100 system produces pellets with superior structural integrity and surface uniformity across varying pressure ranges. This improves manufacturing yield and ensures more reliable solid state test outcomes.

Figure 3. Solid electrolyte pellet production comparison — IEST SEMS1100 vs. conventional pressing equipment

3.2 Ion Electrical Conductivity & Sulfide Electrolyte Performance Testing

The ionic conductivity of solid electrolytes such as LATP and LLZO is highly sensitive to applied pressure. Using the SEMS1100, electrochemical impedance spectra (EIS) can be captured under precise mechanical conditions — a capability equally applicable to sulfide electrolyte performance testing, where the ductile, pressure-sensitive nature of sulfide materials makes standardized load control especially important for reproducible results. Figure 4 illustrates how quantified pressure application significantly influences ionic conductivity, highlighting the necessity of standardized solid state test protocols for meaningful electrolyte measurement and, by extension, for ensuring lithium-ion battery electrolyte quality through improved conductivity measurement.

Figure 4. EIS of two solid-state electrolytes and their ionic conductivity vs. pressure — conductivity measurement for electrolyte quality evaluation

3.3 Electron Conductivity & Compaction Density

With SEMS1100, both electronic conductivity and compaction density of LATP powder can be measured simultaneously. Results show compaction density increases from 1.7 g/cm³ to 2.1 g/cm³ with rising pressure, while electronic conductivity stabilizes around 50 MPa (see Figure 5).

This demonstrates that density and electronic conductivity trends of solid state electrolytes do not always align, emphasizing the need for comprehensive electrolyte measurement under different test conditions rather than relying on a single pressure point.

Figure 5. LATP electronic conductivity and compaction density vs. pressure — compaction density measurement from 1.7 to 2.1 g/cm³

3.4 Cycling Performance of Solid-State Lithium Metal Batteries

Using a Li-SE-Li symmetric cell configuration, the influence of pressure on lithium deposition stability was evaluated as part of solid state battery testing. A decrease in applied pressure from 120 MPa to 110 MPa resulted in a noticeable increase in overpotential (Figure 6), confirming that interfacial stability is strongly pressure-dependent. This type of solid state test is essential for evaluating long-term battery performance.

Figure 6. Li-SE-Li symmetric cell cycling test — overpotential vs. applied pressure for solid state battery testing

3.5 Electrochemical Stabilization Window

The electrochemical window of a Li-SE-stainless steel battery was evaluated using cyclic voltammetry. Results indicate that the solid state electrolyte remains stable within a voltage window of 0–3V, as oxidative current density remains low (≈1.2 A cm⁻² at 3V).

This confirms SEMS1100’s capability for solid state tests, enabling pressurization and sealing for comprehensive evaluation of electrolyte measurement and electrochemical stability in lithium-metal batteries.

Figure 7. Electrochemical stability window test of solid-state electrolytes — 0–3V cyclic voltammetry

4. Summary

Using the integrated solid state electrolyte test system SEMS1100, researchers can accurately measure:

• Ionic conductivity

• Electronic conductivity

• Compaction density

• Electrochemical stability window

• Lithium-metal battery interface stability & cycle performance

These measurements, conducted under controlled pressure conditions, provide reliable insights into the design and development of next-generation solid state electrolytes and solid-state batteries. The system’s co-development with Xiamen University reflects academic-grade validation of its pressure-controlled electrolyte measurement methodology, supporting its use in both fundamental research and industrial quality control settings.

By offering standardized and repeatable solid state test procedures, SEMS1100 accelerates electrolyte material research and promotes breakthroughs in battery technology.

5. References

[1] Huang Xiao, Wu Linbin, Huang Zhen, et al. Characterization and testing of key electrical and electrochemical properties of lithium-ion solid electrolytes, Energy Storage Science and Technology, 2020,9 (2): 479-500.

[2] Yong-Gun Lee, Satoshi Fujiki, Changhoon Jung, et al.High-energy long -cycling all-solid-state lithium metal batteries enabled by silver–carbon composite anodes.2020, 4(5): 299-308.

[3] Nicholas Williard a, Chris Hendricks a, Jaesik Chung, et al. Effects of external pressure on phase stability and diffusion rate in lithium-ion cells.Journal of Electroanalytical Chemistry, 2021, 895, 115400.

[4] T / SPSTS 019- -2021; Performance Requirements and Test Methods of Solid State Electrolytes for Solid State Lithium Battery; Inorganic oxide; Solid State Electrolytes for Solid State Electrolytes.

6. FAQs