Research Projects

India’s surging energy demand and its commitment to net-zero emissions necessitate the development of sustainable, scalable, and domestically sourced energy storage technologies. The projected terawatt-hour-scale storage demand for renewable grid integration, electric mobility, and load balancing cannot be met with current lithium-based batteries alone, given India’s limited lithium reserves and import-dependent battery supply chain. In this context, sodium-ion batteries (SIBs) offer a viable alternative, leveraging India’s abundant sodium resources. Among the emerging battery architectures, All-Solid-State Sodium Batteries (ASSBs) stand out due to their inherent safety, non-flammable nature, and improved electrochemical and thermal stability. Yet, ASSBs face critical material challenges, especially regarding the development of chemically stable and ionically conductive solid electrolytes and sodium-compatible interfaces. NASICON-type (Na1+xZr2SixP3-xO12) solid electrolytes offer a promising platform due to their open three-dimensional framework that facilitates fast Na+ transport, excellent air/moisture stability, and tunable properties via aliovalent and isovalent doping. However, NASICON synthesis remains plagued by impurity formation (e.g., ZrO₂), grain boundary resistance, and interfacial degradation with sodium. To overcome these challenges, our project proposes a multi-ion doping strategy combined with entropy engineering and rapid sintering (Joule heating) to stabilize phase composition, enhance ionic conductivity, and improve mechanical integrity. These dopants will be carefully selected using DFT calculations and refined through AI-assisted models that predict Na⁺ migration pathways and defect chemistries across compositional spaces. At the same time, metallic Na anodes, while theoretically optimal, present major safety and cycling issues due to dendritic growth and unstable interfaces with NASICON. To overcome this, we propose anode-free ASSBs (AF-ASSBs) where the only source of Na⁺ is the cathode, eliminating metallic sodium and related failure modes. As part of this effort, our group has developed and demonstrated a fluorine-doped Na₃.₁₂Fe₂.₄₄(P₂O₇)₂ (NFP) cathode via a solid-state chemo-mechanical approach. This cathode exhibits high sodium content, robust structural integrity, and excellent cycle life, making it ideal for Na⁺ sourcing in AF-ASSBs. Additionally, dual substitution of Mn²⁺ and F⁻ in the NFP framework effectively tunes the electronic structure by mitigating Jahn–Teller distortion, narrowing the band gap, and improving both structural stability and electrochemical performance. The project objectives are to: 1. Synthesize and optimize multi-ion doped NASICON-type solid electrolytes using mechano-chemical processing and rapid Joule sintering. 2. Characterize and evaluate the electrochemical performance and stability of NASICON SEs using EIS, DC polarization, and critical current density testing. 3. Integrate our in-house Mn and F-doped NFP cathode into full-cell anode-free ASSB architectures. 4. Elucidate structure–property–performance correlations using in situ and ex situ techniques such as XRD, ssNMR, EPR, SEM/TEM, and impedance spectroscopy. 5. Employ DFT and machine learning to screen dopant chemistries and predict ion migration and interface compatibility. 6. Investigate degradation and failure mechanisms in AF-ASSBs through operando diagnostics and post-mortem characterizations. If successful, this research will not only establish an integrated in-house solution for high-performance AF-ASSBs but also provide a materials-by-design framework for next-generation energy storage based on India’s abundant resources. The outcomes will significantly elevate India’s position in the global battery innovation landscape and support long-term goals of energy sovereignty and decarbonization.