The solid-state battery Maxell wants factories to stop thinking about

Ask a maintenance engineer to name their least favourite job and few will mention anything as dramatic as a bearing failure or a controller fault. More often it is something smaller: tracking down which of several hundred robots has a backup battery nearing end of life, scheduling a pause to reach it, and having to repeat the exercise a few years later. Not difficult work, by any means, just relentless, exhaustive, and entirely dependent on someone being available to do it.

That dependency is the starting point for Maxell's pitch to automotive manufacturers. The Japanese electronics group, whose battery business traces back through decades of coating and moulding expertise developed for cassette tape and videotape production, has built a ceramic-packaged all-solid-state battery designed to run for the working life of the equipment it powers, with no scheduled replacement required at all.

The solution lands at a moment when the labour needed to keep swapping those batteries is becoming harder to find.

Where the maintenance burden actually lives

The scale of the problem becomes clearer once you count the parts involved. Robot encoders track the precise angle of a joint and need backup power to hold that position data through any interruption; Programmable Logic Controllers (PLCs) rely on similar backup power to protect memory, and a single production plant can run hundreds of each.

Mr. Tatsuya Ishikawa, circuit engineer and design department manager, (and co-inventor of Maxell's battery technologies) has watched that process play out on customer sites. "In automotive manufacturing plants in particular, a large number of robots and PLCs are installed, and each robot is equipped with multiple encoders.

“As a result,” he says, “a considerable number of backup batteries are used throughout a single automotive factory's production equipment. We believe that customers face challenges related to unexpected downtime caused by battery failures, maintenance costs associated with battery replacement, and the need to reduce the number of batteries disposed of during operation."

Solving the chemistry, not just the schedule

Getting a battery to last that long meant rethinking what is inside it. Conventional cells rely on a liquid electrolyte to carry ions between electrodes, a solution that works well until temperatures climb. Mr. Atsushi Hatakeyama, battery engineer and technology marketing manager, (as well as researcher and co-inventor of Maxell's solid-state battery technology,) explains the trade-off his team had to solve. "In conventional batteries, the liquid electrolyte tends to become chemically unstable at high temperatures. By replacing this liquid electrolyte with a solid electrolyte that remains stable at high temperatures, all-solid-state batteries can operate at temperatures beyond the range of conventional batteries."

Swapping liquid for solid does, however, bring its own complication. A liquid naturally seeps into the gaps between electrode materials and forms its own conductive pathways; a solid cannot do that, which makes ion movement harder to sustain, particularly in the cold.

Maxell's answer draws on manufacturing skills the company has refined since its earliest days making magnetic tape, where uniform coating and precise material contact were just as critical. "Maxell addresses this challenge by combining materials expertise developed through decades of battery development with manufacturing technologies for uniform material mixing and precise electrode formation," Hatakeyama says. "By carefully controlling the contact between solid materials, Maxell has achieved a wide discharge temperature range from -50°C to +125°C."

Building safety into the case, not the checklist

Wide temperature tolerance answers one industrial concern; fire risk answers another, and here Maxell leans on the same shift in chemistry. Removing the liquid electrolyte removes most of what makes a conventional battery flammable, and the company pairs that with a hermetically welded ceramic case rather than the crimped seal used in a standard coin cell.

"Using a flame-resistant solid electrolyte instead of a flammable liquid electrolyte helps improve the inherent safety of Maxell's all-solid-state battery," Hatakeyama says. "In addition, the ceramic package is hermetically sealed by welding, helping to prevent moisture from entering the battery and reducing the possibility of undesirable internal reactions."

That combination gives Maxell a case worth making to compliance teams as well as engineers. Fire-safety rules governing industrial and automotive components have been tightening across both the EU and the US, and a cell built with no flammable liquid sidesteps a category of risk that regulators are increasingly focused on, rather than merely managing it through containment or ventilation.

The welded seal does double-duty on longevity too. Maxell's own moisture-ingress testing - comparing crimped coin cells against the welded ceramic package under prolonged storage at 120°C and 100% relative humidity - shows the crimped cases absorbing moisture steadily over time while the welded package absorbs almost none.

"By welding and hermetically sealing the ceramic package, we can minimise moisture ingress, which is one of the causes of battery degradation," Hatakeyama says. "Compared with conventional crimp-sealed structures, this construction provides higher resistance to moisture, particularly under high-temperature and high-humidity conditions."

Put those properties together, and Maxell points to batteries rated for roughly ten years of service at 105°C deployed inside equipment that Hatakeyama describes as being used "in locations that are difficult to inspect frequently, and in industrial systems where fire or leakage could lead to equipment downtime or damage to surrounding components."

From backup power to a design decision

And for the skeptical of mind, none of this is theoretical and is tried and tested - and active across significant deployments. In late 2023, Nikon selected Maxell's PSB401010H cell for the MAR-M700MFA, a multi-turn absolute encoder built to hold position data through power interruptions on industrial robots. The battery's ability to survive reflow soldering, mounting directly onto a circuit board and passing through the same high-temperature process used to solder every other component, together with its tolerance for operation up to 105°C, was central to why Nikon chose it.

Ishikawa argues that this reflow compatibility changes more than just where the battery sits. "When an all-solid-state battery is adopted in a new design, its reflow-compatible characteristics eliminate the need for wiring dedicated to battery replacement," he says.

"Because a compact backup battery can be mounted directly onto the circuit board, designers gain greater flexibility in system and product design. The battery is no longer treated as a replaceable component. As a result, designers can eliminate the need to consider battery replacement throughout the product lifecycle, simplifying equipment design and reducing long-term maintenance requirements."

For equipment already on the factory floor, retrofitting is not always so straightforward, which is why Maxell is also developing standalone backup battery modules built around the same cells. "While the level of awareness varies among equipment manufacturers, some have already recognised the issue of what we call ‘hidden maintenance dependency’ and are taking steps to address it," Ishikawa says. 

"We are also developing backup battery modules based on all-solid-state battery technology, enabling maintenance-free operation for existing equipment currently in service."

Counting the benefit beyond the battery

Ishikawa is careful not to reduce Maxell’s positioning to a simple swap-one-part-for-another calculation. The direct savings, he says, come from "reduced maintenance workload, lower losses caused by unexpected production downtime, and improved environmental sustainability through the reduction of waste batteries." But the larger gain, in his view, is what happens to the people freed up by removing the task altogether.

"By reducing the time and effort required for battery maintenance and replacement, equipment engineers and maintenance personnel can focus on more value-added and mission-critical activities. As labour shortages continue to become a growing challenge across the manufacturing industry, we believe this advantage is particularly significant."

This is where the technology's implications expand and reach beyond the factory gate. Encoders, PLCs and equipment-monitoring sensors remain the clearest use case, but those same properties - wide temperature range, long unattended life, and a chemistry with nothing to leak or ignite, apply equally to robotics deployed outside a controlled plant and to automotive components that spend their working life under a bonnet rather than on an assembly line.

Where the roadmap goes from here

Yet Maxell is not treating its current line-up as a finished job. The 8mAh PSB401010H is already in mass production, with a larger 16mAh PSB401515H currently under development, and the company's roadmap points toward cells approaching 500mAh by 2027 and roughly 5,000mAh by 2030. This is a trajectory that would take the technology from a backup role into serving as a primary power source for sensors in its own right.

Hatakeyama ties that ambition to the same demographic pressure that a recent Maxell whitepaper on labour shortages in industrial manufacturing describes. "As the working population declines and factory automation continues to advance,” he says, “we expect manufacturing to move progressively toward factories that require minimal human intervention. AMS concurs.

"We believe long-life all-solid-state batteries can make an important contribution to this shift toward maintenance-free operation." Getting there, he says, means solving unglamorous production problems first, chiefly "increasing capacity by developing larger battery cells" while reducing the industry's reliance on the tightly controlled dry environments that solid-state battery manufacturing currently demands.

Ishikawa frames the destination in similarly broad terms. "We expect maintenance-free power solutions to become a fundamental enabling technology for a wide range of new equipment and applications by eliminating the constraints associated with battery replacement," he says. "Looking ahead, we believe maintenance-free power sources will help unlock new possibilities not only in factory automation but also across various industrial and infrastructure applications."

How that process unfolds will depend on industry-wide manufacturing scale-up as much as on chemistry. But the underlying argument - that a factory's reliability should not hinge on someone remembering to change a battery - is one that plant managers watching their maintenance rosters thin-out are unlikely to dismiss. And so Maxell moves into a production area burgeoning ripe for the harvest, with its solutions set to further branch out and bear fruit for the automotive industry and beyond.