Li-Metal batteries

SES AI’s Li-Metal batteries will enable a new era of aerial electric transportation

In 1991, Sony commercialized the first Li-ion battery and kicked off an era of portable electronics. More than 30 years later, SES AI is developing and commercializing the first Li-Metal battery and will kick off an era of electric transportation in air.

SES AI Hermes Li-Metal battery cell


Platform for new material development
Hermes is our internal new material R&D platform, where we have world’s best human scientists and best-trained machine that work on fundamental breakthroughs in materials to improve Li-Metal performance and safety. Some research areas include electrolyte, anode, anode coating, separator, cathode, cycling protocol, and other aspects.
SES AI Apollo large-format Li-Metal cell


Engineering capability for large automotive cells

Apollo is large format EV and eVTOL cells that combine the latest material development from Hermes and the best Li-Metal cell engineering and manufacturing. These can be customized for different OEM requests. Currently, we are developing and manufacturing (pilot-scale) 50Ah to >100Ah Li-Metal cells for EV and eVTOL applications with GM, Hyundai, and Honda in our Shanghai China and Chungju Korea lines. In 2021, we introduced the world’s first 100Ah Li-Metal cell.

SES AI Avatar artificial intelligence


AI-powered safety and health-monitoring software

Avatar is an AI-powered “digital twin” equivalent of physical Li-Metal batteries. Battery health is like human health, which depends on genetic inheritance, nutrition during pregnancy, and  lifestyle. These three sets of data are mapped to battery Avatar as material information, manufacturing quality data, and real-world vehicle data. Avatar is a new fundamental breakthrough in integrating Hermes material information, Apollo cell design and manufacturing information, quality management, and actual vehicle mission profile, to precisely monitor battery health and predict failures and incidents.

SES AI’s approach versus other approaches

SES AI is pioneering a hybrid battery approach
Indicator for the anode, separator, cathode

Conventional Li-ion

Conventional Li-ion battery approach

Solid-state Li-Metal

All-solid-state Li-Metal battery approach

SES AI hybrid Li-Metal

SES hybrid Li-Metal approach
Scientists in SES AI's R&D in its Woburn headquarters just outside Boston
SES AI's Shanghai Giga facility

SES AI’s innovative hybrid Li-Metal approach

SES AI’s original approach was a solid-state Li-Metal battery. However, through our research and development efforts, we realized the limitations of all-solid-state batteries: they require high temperature to be operational and are very difficult to scale up. We then pivoted to a solution that would meet EV and eVTOL requirements while allowing us to manufacture batteries at scale using existing infrastructure and processes. 



Today, SES uses a hybrid Li-Metal approach that involves several key technologies, including:


SES AI is also layering in an AI-powered battery health monitoring algorithm, large format Li-Metal cell engineering and manufacturing capability, and other technological advancements to create a first-of-its-kind battery that will power a new era in electric transportation.

Key breakthrough: our proprietary and patented liquid electrolyte

SES electrolyte uses a high concentration solvent-in-salt approach. A conventional liquid electrolyte is low concentration, where the salt is coordinated by solvent and there are free solvent molecules, the overall electrolyte stability on Li-Metal is poor. In SES’s high concentration electrolyte, the solvent is coordinated by the salt and there are no free solvent molecules. This allows the electrolyte to achieve unprecedented Coulombic efficiency of >99.6% on Li-Metal. Without this high concentration approach, it was thought liquid electrolyte could never achieve such high stability on Li-Metal and high voltage cathode at the same time.

Electrolyte composition


  • Salt: A single or multiple salt(s) with purity profile and trade secret purification process
  • Solvent: Proprietary and patented solvent that SES designed and synthesized not commercially available
  • Additives: Proprietary/trade secret
SES AI's innovative and proprietary electrolyte composition
SES AI's innovative and proprietary high concentration solvent-in-salt electrolyte composition
Patents granted
Patents pending
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Trade secrets
Issued trademarks
All stats current as of June 16, 2023
SES AI bunker where SES safely tests thousands of 100Ah Li-Metal battery cells
SES AI bunker where SES safely tests thousands of 100Ah Li-Metal battery cells

A safe place to innovate and test

Pioneering a first-of-its-kind Li-Metal battery requires the ability to safely try new things. SES AI’s state-of-the-art facilities are equipped with several bunkers, a place where we can safely innovate, test, fail, learn, and repeat. Here we test hundreds and thousands of 100Ah Li-Metal cells.

SES AI believes in full transparency and regularly publishes our cell test data and results on our website. We will continue to publish data reports regularly to keep the industry updated as we improve everything from materials to engineering to manufacturing quality.


+ View cell data reports here

Watch how our Li-Metal batteries are made

SES AI Li-Metal battery cell production
SES AI battery development timeline of an automotive Li-Metal battery

Introducing the world's first large-format 100Ah Li-Metal cells

Introducing the world's first large-format 100Ah Li-Metal cells

SES AI’s Li-Metal Battery

SES AI Li-Metal battery explained

SES AI is the first company in the world to enter into A sample JDAs with three major automotive OEMs

General Motors logo
Yoshiya Josh Fujiwara of Honda R&D talks about working with SES AI

“Let's communicate closely in the common language of technology and be the first in the world to bring the Li-Metal battery to the automobile market."

Expert engineer, Honda R&D

Honda logo