researchers at the empa (federal laboratories for materials science and technology) in dubendorf, switzerland have announced the development of novel, next generation solid-state electrolytes to replace liquid, lithium-ion electrolytes and make battery technology safer, avoiding concern about thermal runaway.

empa has announced two options for safer electrolytes in batteries. (empa)

in a report in may, empa announced the potential for sodium and magnesium as alternative materials for electrolytes. to allow for the displacement of ions, which brings about the battery’s charge, the researchers created crystalline structures for the solid-state materials.

the researchers developed a solid electrolyte that allowed the displacement of sodium ions at 20°c, was non-flammable, and remained stable up to °c, was non-flammable, and remained stable up to 300°c. sodium is also widely available, unlike lithium.

in addition, the researchers created a solid-state electrolyte from magnesium, another abundant material. magnesium ions contain two positive charges, which empa explained, allows for nearly double the energy storage per volume compared to lithium. the magnesium electrolyte worked at 70°c, which is not close enough to room temperature, but far lower than previous attempts that only worked at more than 400°c.

this research was published in chemical communications (among other journals). the abstract read:

“na₂(b₁₂h₁₂)_0.5(b₁₀h₁₀)_0.5, a new solid-state sodium electrolyte is shown to offer high na⁺ conductivity of 0.9 ms cm⁻¹ at 20 °c, excellent thermal stability up to 300 °c, and a large electrochemical stability window of 3 v including stability towards sodium metal anodes, all essential prerequisites for a stable room-temperature 3 v all-solid-state sodium-ion battery.”

in june, empa made another announcement that the research team had succeeded in developing a solid-state electrolyte with the same electrical conductivity as liquid using amide-borohydride as the material. this new material is used in sold-state electrolytes with oxides and thiophosphates.

according to empa, “this means that the conductivity of the solid-state electrolyte developed at empa is comparable to a liquid electrolyte at room temperature. the innovative solid-state electrolyte is also stable at temperatures of up to 150°c, whereas liquid electrolytes pose a safety risk at such high temperatures.”

this research is still at the early stages and far from producing a commercially viable battery. the researchers continue to explore options, including the use of other boron compounds.

this research was published in advanced energy materials. the abstract stated:

“high ionic conductivity of up to 6.4 × 10⁻³ s cm⁻¹ near room temperature (40 °c) in lithium amide-borohydrides is reported, comparable to values of liquid organic electrolytes commonly employed in lithium-ion batteries.

“density functional theory is applied coupled with x-ray diffraction, calorimetry, and nuclear magnetic resonance experiments to shed light on the conduction mechanism. a li₄ti₅o₁₂ half-cell battery incorporating the lithium amide-borohydride electrolyte exhibits good rate performance up to 3.5 ma cm⁻² (5 c) and stable cycling over 400 cycles at 1 c at 40 °c, indicating high bulk and interfacial stability.

“the results demonstrate the potential of lithium amide-borohydrides as solid-state electrolytes for high-power lithium-ion batteries.”