Quartz today reported that Bosch has agreed to acquire Berkeley Lab solid-state Li-ion battery spinoff Seeo. Seeo’s cell design couples a solid lithium metal anode with a conventional porous lithium iron phosphate cathode and Seeo’s nanostructured solid polymer electrolyte (“DryLite”). The electrolyte is entirely solid-state with no flammable or volatile components.
In January 2015, Seeo was awarded a contract for technology assessment from the United States Advanced Battery Consortium LLC (USABC), a collaborative organization of FCA US LLC, Ford Motor Company and General Motors. Under the contract, Seeo will deliver its DryLyte battery modules to USABC for testing under a 9-month assessment program. These modules are based on Seeo’s current cell technology, which provides an energy density of 220 Wh/kg. (Earlier post.)
Bosch won’t be releasing the terms of the deal, according to the Quartz report. Bosch has acquired all of Seeo’s intellectual property plus its research staff.
Lithium metal is an ideal anode material for rechargeable Li batteries. It offers an extremely high theoretical specific capacity (3,860 mAh g−1); low density (0.534 g cm−3); and the lowest negative electrochemical potential (−3.040 vs standard hydrogen electrode). Unfortunately, using Li as an anode in rechargeable Li batteries faces severe challenges, including dendriticLi growth and limited Columbic efficiency (CE) during repeated Li deposition/stripping processes. (Earlier post.)
One potential solution for addressing the problems facing Li metal anodes in rechargeable batteries is the use of a solid-state electrolyte rather than a liquid electrolyte. Solid-state electrolytes offer excellent electrochemical stability, favorable mechanical properties, and operation over a wide temperature window. They preclude the safety and performance issues associated with dendritic growth. However, ionic conductivity can be significantly lower than that of a liquid electrolyte. As a result, a great deal of research is investigating the development of high ionic conductivity solid-state electrolytes for next-generation rechargeable Li batteries. (Earlier post.)
One approach to a solid-state electrolyte is the use of a solid polymer. This can also be problematic, as the core requirements of a solid-state electrolyte for use with a Li metal anode—i.e., high ionic conductivity and mechanical ruggedness—tend to call for different types of polymers. The property of conductivity calls for a softer material, while strength calls for a harder material. Unfortunately, hard polymers tend to be nonconductive.
Researchers at Berkeley Lab developed copolymers comprising both hard and soft blocks—in other words, using block copolymers to combine mechanical stability with ionic conductivity.
Founded in 2007 by Berkeley Lab researchers Nitash Balsara, Hany Eitouni, and Mohit Singh, Seeo has an exclusive license to the solid-state electrolyte technology developed at the Lab.
The basic material featured 50-nanometer channels composed of a softer polymer laced with lithium salts encased in a hard polymer matrix. Lithium dendrites that spawn from the Li metal anode are some 20 times as large as the soft polymer channels; i.e., the dendrites are too large to force their way into the material.
The weakest link in terms of safety and stability of Li-ion batteries is the organic liquid electrolyte that facilitates ionic transport between the electrodes. The continuous electrochemical degradation of the electrolyte at the electrodes causes poor cycle life of the batteries, and in some cases, runaway reactions that lead to explosions.
Dry polymer electrolytes coupled to Li-metal anodes had been considered a high energy alternative to liquid-based systems, as the solid-solid interface promised to alleviate the stability problems of the liquid electrolyte. However, repeated cycling of Li metal anodes leads to dendrite formation, reducing battery life and compromising safety. Recent theoretical work indicates that dendrite growth can be stopped if the shear modulus of current polymer electrolytes can be increased by three orders of magnitude without a significant decrease in ionic conductivity. Thus, the mechanical properties of polymer electrolytes are particularly important in rechargeable solid-state lithium batteries.
Because ion transport in polymers is coupled to the motion of the molecules that are solvating the ions, the presence of mobile molecules is essential to allow for a conductive medium. However, the same mobility of molecules is detrimental to the polymer’s structural integrity. There is, thus, a clear need to develop methodologies for decoupling the conductive and mechanical properties of polymer electrolytes. Electrolytes comprised of self-assembled block-copolymer nanostructures overcome this principal constraint.—Eitouni (2011)
Seeo now has Seeo has more than 40 issued, exclusively licensed and pending patent applications on the technology. Seeo currently offers a range of products based on its technology, including:
DryLyte Battery 1.6 kWh Modules. Constructed from the Seeo DryLyte 10Ah cell (220 Wh/kg at the cell level), the DryLyte Battery 1.6 kWh Module is available in a 160V/10Ah configuration.
DryLyte Automotive Pack. Employing the 1.6 kWh modules as the basic building block, the automotive pack is scalable in voltage and capacity, and can be configured to meet a variety of requirements. Pack level energy density is 130 Wh/kg.
In December 2014, Seeo closed its largest funding round up to that time, adding Samsung Ventures Investment Corporation to its investor roster. (Earlier post.) At that time, Seeo said that it had cells in development cycling with an energy density of 350 Wh/kg, with a future target of 400 Wh/kg.
Hany Eitouni (2011) “Block-Copolymer Lithium Battery Electrolytes ” 11 AIChE