Research Projects

The current Lithium-ion batteries (LIBs) deliver practical energy density of 150-296 Wh/kg (Tesla’s 4680) [1] However, challenges, high cost due to Cobalt, Nickel scarcity and safety concerns restrict high-performance applications. In this regard, lithium–sulfur (Li–S) batteries attracted due to its theoretical energy density of 2600 Wh/kg, 1675 mAh/g as theoretical specific capacity. The practical energy density falls between 400-600 Wh/kg, which gives hope in extending EVs automotive industry range to 500 km and the natural abundance, low cost and environmental benignity of S make it as an alternate to LIB [2] However, LiSBs are possessing hurdles such as low conductivity, shuttle effect, volume expansion are major concerns. To address these issues, many strategies were implemented such as designing suitable cathode host materials [3] interlayer [4] modifying binders [5] new separator [6] anode modifications [7] but still exhibiting poor performances, low capacity and shuttle effect issues. In this aspect, solid state Li-S batteries (SSLiSBs) attracted due superior nature over the liquid state, no polysulfide shuttle, low self-discharge, no leakage and size compactness. [8] Nevertheless, issues like poor contact between solid electrolyte and solid S, solid Li₂S, no clear reaction mechanism to prove whether Li₂S₂ is present in SSLiSB. Next, slow solid –solid (Li₂S → Li₂S₂ → S₈) conversion, which yields lower S utilization, unreacted Li2S and inactive S, low electronic conductivity, 80% volume expansion, contact loss, mechanical degradation are major concerns [9]. Hence, cathode engineering to improve Li₂S → Li₂S₂ → S₈ conversion reaction, electronic conductivity of S, interface issues are mandatory area to upscale SSLiSB technology. In this aspect, this proposal takes an effort towards developing an asymmetric material loaded carbon-sulfur catholyte. The use of catholytes in Li-SB will enhance S utilization, reduce internal resistance, mechanical stress, increase energy density. [10] However, to make the less electrochemically inactive, insulating Li₂S₂, Li₂S to be active, there is a need of an additive, which is the best way to advance catholytes. Thus, we introduce the concept of incorporating asymmetric materials (ASM) to catholyte. ASM consists of two separate entities which are compartmentalized into a single object, anisotropic in nature, offers different physicochemical properties when measured in different direction. Integrating asymmetric material [titanium carbide(TiC)–iron phosphide (FeP)] to carbon -sulfur catholyte offers a multifunctional platform, where FeP boosts redox kinetics, improve Li₂S → Li₂S₂ → S₈ conversion, TiC enhances electron transport and structural integrity, together they stabilize active material, improve S utilization, rate performance, enable high-capacity and energy density with long-life SSLiSB. Overall, this proposal develops advanced feasible SSLiSB with high energy density.

Asymmetric material, TiC-FeP, Catholyte, Kinetics, Polysulfides, SSLiSB