Sodium-Ion Conducting Solid Electrolyte Membrane and Battery thereof

Technology: Solid Electrolyte Film ;

Industry & Application: Automobile & Transportation

Market: The global Solid Electrolyte Film market is projected to grow at a CAGR of 15% during 2024-2030.

In the Present era, both the Electric Vehicle (EV) & renewable energy sectors are heavily affected on the safety issues due to the use of Li-ion and Na- ion batteries.
The problem can be resolved by using solid electrolyte film in such batteries.
There are a few prior art solutions disclosed for Na-ion battery, however, could not resolve the issues related to poor mechanical stability, lower ionic conductive issues.
Hence, there is a need to address said issues in efficient matter.

The present invention describes a room temperature rechargeable sodium-sulphur battery configured with a novel solid electrolyte film.
The battery includes an anode comprising sodium metal, a solid electrolyte film comprising sintered Na3Zr2Si2PO12(NZSP) infiltrated with poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) polymer.
The polymer comprises 12-20% of the weight of the film.
The polymer is configured to absorb a solution of 1.5M NaClO4 in tetraethylene glycol dimethyl ether (TEGDME) to produce a gel conductive of Na+ ions, the electrolyte film is placed in contact with the anode, the solid electrolyte film has a ionic conductivity of ~0.4 mS/cm2.
The battery further includes a cathode, said cathode comprises of carbon in contact with a catholyte prepared by dissolving stoichiometric amounts of sodium sulfide (Na2S) & sulpher in 1.5M NaClO4/TEGDME.
The sulphur content is configured to be 0.1 mg µL-1 or lower;
The sodium sulphide battery further includes a current collector, coated with 95% acetylene black & 5% PVDF-HFP on a carbon fiber fabric laminated on the NSZP electrolyte film configured to enhance interfacial contact between cathode & the electrolyte.
Further, a method of making a solid electrolyte film for sodium ion batteries is disclosed in Fig. 2.

Said method comprising following steps :

1st step states that synthesizing Na₃Zr₃Si₃PO₃₃ (NZSP) powder by a sol-gel method comprising formation of a sol & a gel;
2nd step states that dispersing the Na3Zr2Si2PO12(NZSP) powder in water with 5wt% polyvinyl alcohol to form a NZSP slurry;
3rd step states that tape casting the NZSP slurry over a sacrificial layer on a carbon fiber fabric substrate to form a NZSP sheet;
4th step states that heating the NZSP sheet to about 600°C to separate the sheet from the substrate;
5th step states that sintering the sheet at about 1000°C; & finally, infiltrating a sodium ion conducting polymer on to the sheet to obtain the polymer infiltrated solid electrolyte film.

Technical Perspective:

The Sodium sulphide battery includes a current collector, coated with 95% acetylene black & 5% PVDF-HFP on a carbon fiber fabric laminated on the NSZP electrolyte film configured to enhance interfacial contact between cathode & the electrolyte, thereby ionic conductivity increases.
The infiltration of the polymer into the pores of the NZSP sheet provides mechanical stability, enhances ionic conductivity & reduces surface contact resistance of the solid electrolyte.
The solid electrolyte has a thickness of 0.25 mm or less & ionic conductivity 0.4 mScm⁻2 or more.

Industrial Perspective:

The solid electrolyte film finds many application, used as carbon fiber cloth, gel electrolyte & etc.
The process of making a solid electrolyte film is cost-effective, safe, required less energy for manufacturing sodium-sulphur battery applicable in India & globally.

Prof. Ramaprabhu S

Department of Physics

TRL-4

Proof of Concept ready, tested in lab.

Technology Transfer