Sivaraj Pazhaniswamy

Abstract:

Composite solid‐state electrolytes (CPEs) offer great potential for advancing quasi‐solid‐state lithium metal batteries (QSLMBs) due to their high ionic conductivity, electrochemical performance, and thermal stability. However, conventional CPEs, formed by incorporating ceramic particles into polymer matrices, often fail to significantly improve critical current density and rate performance. This study presents a green synthesis of NASICON‐type Li1.4Al0.4Ti1.6(PO4)3 ceramic nanofibers (LATP‐NFs) via electrospinning. It optimizes parameters such as solvent type, polymer and LATP precursor concentrations, heating rates, and calcination temperatures to control LATP‐NF microstructures. Embedding 30 wt.% LATP‐NF (LATP‐30) into a poly(vinylidene fluoride)‐lithium bis(trifluoromethanesulfonyl)imide (PVDF‐LiTFSI) matrix yields a CPE with reasonable ionic conductivity of 0.21 mS cm−1 at room temperature (RT), good thermal and electrochemical stability (>5 V), and enhanced mechanical strength. LATP‐30 effectively suppresses lithium dendrite growth, achieving a high critical current density of 10 mA cm−2. The LFP|LATP‐30|Li cell delivers 169 mAh g−1 at 0.1 C and maintains capacities of 122, 111, and 101 mAh g−1 at 3, 5, and 10 C, respectively. It retains 153 mAh g−1 after 300 cycles, with 97% capacity retention at 0.5C. This work demonstrates a sustainable and non‐toxic strategy for synthesizing LATP‐NFs for high‐performance QSLMBs.

Abstract:

Long-term electrochemical cycle life of the LiNi0.5Mn1.5O4 (LNMO) cathode with liquid electrolytes (LEs) and the inadequate knowledge of the cell failure mechanism are the eloquent Achilles’ heel to practical applications despite their large promise to lower the cost of lithium-ion batteries (LIBs). Herein, a strategy for engineering the cathode–LE interface is presented to enhance the cycle life of LIBs. The direct contact between cathode-active particles and LE is controlled by encasing sol–gel-synthesized truncated octahedron-shaped LNMO particles by an ion–electron-conductive (ambipolar) hybrid ceramic–polymer electrolyte (IECHP) via a simple slot-die coating. The IECHP-coated LNMO cathode demonstrated negligible capacity fading in 250 cycles and a capacity retention of ∼90% after 1000 charge–discharge cycles, significantly exceeding that of the uncoated LNMO cathode (a capacity retention of ∼57% after 980 cycles) in 1 M LiPF6 in EC:DMC at 1 C rate. The difference in stability between the two types of cathodes after cycling is examined by focused ion beam scanning electron microscopy and time-of-flight secondary ion mass spectrometry. These studies revealed that the pristine LNMO produces an inactive layer on the cathode surface, reducing ionic transport between the cathode and the electrolyte and increasing the interface resistance. The IECHP coating successfully overcomes these limitations. Therefore, the present work underlines the adaptability of IECHP-coated LNMO as a high-voltage cathode material in a 1 M LiPF6 electrolyte for prolonged use. The proposed strategy is simple and affordable for commercial applications.