R&D PULSE
Batteries Under Pressure
New research demonstrates how pressure significantly impacts the performance of all-solid-state lithium-sulfur batteries.
Written by Mark Crawford
WITH THE PRESSING NEED TO REDUCE the impacts of climate change and fossil fuel dependency, the push to develop high-energy-density battery cells is yet another key to advancing energy-saving initiatives. In the battery market, all-solid-state lithium-sulfur batteries (ASLSBs) offer a superior advantage to traditional lithium-ion batteries, given their potential for higher energy densities and enhanced safety.
However, ASLSBs have a drawback in that they’re considered pressure sensitive. Both fabrication and operational or stack pressure have profound effects on cell performance.
To understand this relationship further, Timothy P. Cleary, a researcher at the Department of Mechanical Engineering at Pennsylvania State University, decided to study ASLSBs under controlled stress and constant-strain scenarios, hoping to develop data-driven models that predict cell voltage based on input current.
Research Basics
Cleary’s work, “Modeling the Effects of Pressure on Solid-State Lithium–Sulfur Batteries,” was published in the January 2026 issue of ASME Letters in Dynamic Systems and Control. The work investigated how lithium-sulfur cells, made using a lithium metal alloy anode, respond to cell pressure or stresses of less than 0.5 megapascals (MPa) with an 80 percent active material volume change.
“The ASLSB data, collected under various operational pressure conditions, will be used to perform system identification of equivalent circuit model [ECM] parameters that account for variations in the externally applied force resulting from dynamic operational pressure,” Cleary said. “We also investigate the correlation between variations in battery stress versus time in constant-volume operation and state of charge [SOC].”
The ASLSB used for the test had a lithium–indium (Li0.7In) anode, a lithium phosphorus sulfur chloride (Li6PS5Cl) separator, and a sulfur, carbon black, lithium phosphorus sulfide (75Li2S25P2S5) cathode, at a ratio of 40:20:40.
According to the team, ASLSBs typically exceed hundreds of megapascals, while operation pressures range in the tens of megapascals. For this study, the cells were fabricated with forces up to 3.5 tons or 437 MPa and were exercised over an operational pressure range from five to 60 MPa.
The researchers used two operational or stack pressure scenarios. First, controlled pressure or stress, and second, constant volume or strain. The same relationship between force and pressure was observed at the cell, as both use a 10-millimeter diameter split-cell holder and series strain gauge, assuming zero radial deflection.
Holding each battery’s cells were 10-millimeter diameter stainless steel push rods or plungers at the top and bottom, along with a thick polyether ether ketone (PEEK) sleeve on the outside. Each test scenario required a unique test fixture to meet the mechanical loading requirements.
“Cell performance evaluation under controlled pressure or cell stress utilized a large air cylinder with a digital pressure regulator,” Cleary said. “In contrast, constant volume or cell strain testing relied on a single screw press. Load cells are placed in series with the battery cells and the force applied to each fixture, which were also housed in a small chamber, with the air temperature controlled at a constant temperature of 0 °C.”
The research team used a pneumatic press (left) and single screw press (right) for these experiments. Image: Cleary, et al.
A snapshot of the team’s experimental results. First, (a) test case 1’s pressure and capacity, (b) test case 1’s voltage response, and (c) a controlled-pressure test of case 2’s incremental capacity. Additionally, (d) test case 2’s pressure and capacity, (e) test case 2’s voltage response, and (f) a section of fixed-strain in test case 2’s incremental capacity. Image: Cleary, et al.
Future Work
This experiment confirmed pressure’s critical role in optimizing the performance of lithium-sulfur solid-state batteries.
Perhaps the most significant result is that, in a controlled-pressure scenario, usable capacity decreases with stack pressure. “However, this damage can be repaired early in cell life, and capacity can be restored when the cell is returned to higher pressures,” Cleary noted.
“We can achieve a harmonious balance between mechanical stability and electrochemical efficiency, paving the way for the practical implementation of lithium-sulfur solid-state batteries in next-generation energy storage applications,” he added. One way to do that is by fine-tuning the equivalent circuit model parameter identification and modeling results—for example, an open circuit voltage map as a function of external pressure.
The study also found a clear relationship between cell pressure and SOC exists in a constant-strain scenario. “Future research will focus on the long-term stability of these batteries under cyclic pressure conditions and the scalability of the pressure application techniques for commercial production,” Cleary said.
Mark Crawford is a technology writer in Corrales, N.M.
© 2026 The American Society of Mechanical Engineers. All rights reserved.