Aqueous and non-aqueous Li+/H+ ion exchange in Li0.44La0.52TiO3 perovskite

Review of the Developments and Difficulties in Inorganic Solid-State Electrolytes

All-solid-state lithium-ion batteries (ASSLIBs), with their exceptional attributes, have captured the attention of researchers. They offer a viable solution to the inherent flaws of traditional lithium-ion batteries. The crux of an ASSLB lies in its solid-state electrolyte (SSE) which shows higher stability and safety compared to liquid electrolyte. Additionally, it holds the promise of being compatible with Li metal anode, thereby realizing higher capacity. Inorganic SSEs have undergone tremendous developments in the last few decades; however, their practical applications still face difficulties such as the electrode-electrolyte interface, air stability, and so on. The structural composition of inorganic electrolytes is inherently linked to the advantages and difficulties they present. This article provides a comprehensive explanation of the development, structure, and Li-ion transport mechanism of representative inorganic SSEs. Moreover, corresponding difficulties such as interface issues and air stability as well as possible solutions are also discussed.

Influence of Cation Vacancies on Li Conductivity of La1/2Li1/2-2x Sr x TiO3 Perovskites (0 < x ≤ 0.25): The Role of Nominal and Effective Vacancies

The Li_1/2-2x Sr _x La_1/2TiO₃ series (0 ≤ x ≤ 0.25) is investigated with X-ray diffraction, nuclear magnetic resonance, and impedance spectroscopy techniques. The substitution of two Li⁺ by one Sr²⁺ in Li_1/2La_1/2TiO₃ perovskite generates cation vacancies that, when ordered in alternating planes along the c-axis, confer a two-dimensional character to Li mobility. In previous works, it was shown that Li⁺ ions partially occupy the center of the six faces of the cubic perovskite, resulting in the associated A-sites to participate like a vacancy in the definition of the percolation vacancy threshold. The results obtained in the Li_1/2-2x Sr _x La_1/2TiO₃ series are compared with those obtained in the Li_3x La_2/3-x TiO₃ series, and other Sr-doped solid solutions (Li_1/2-x Sr_2x La_1/2-x TiO₃ and Li _x Sr _x La_2/3-x TiO₃), to highlight the importance of the effective vacancies with respect to the nominal ones in conductivity. The analysis of four series, belonging to the ternary SrTiO₃-La_2/3TiO₃-Li₂TiO₃ phase diagram, permits a better understanding of the ionic conduction mechanism in perovskites. The results show that the vacancy percolation model is more adequate to explain Li conductivity than the conventional hopping probability model. In the analyzed series, Li conductivity is maximum when a small amount of Sr is incorporated into the pseudo-cubic La_1/2Li_1/2TiO₃ end member, while it decreases as the amount of strontium increases.

Recent Advances in Stability Issues of Inorganic Solid Electrolytes and Composite Solid Electrolytes for All-Solid-State Batteries

The development of solid-state batteries has become one of the most promising directions in rechargeable secondary batteries due to their considerable energy densities and favorable safety. However, solid-state batteries with higher energy density and more durable and stable cycle life should be developed for large-scale energy storage and adaption to the rapidly increasing lithium battery production and sales market. Although inorganic solid electrolytes (ISEs) and composite solid electrolytes (CSEs) are relatively advantageous solid-state electrolytes, they also face severe challenges. This review summarizes the main stability issues related to chemical, mechanical, thermal, and electrochemical aspects faced by ISEs and CSEs. The corresponding state-of-the-art improvement strategies have been proposed, including filling of modified particles, electrolyte pore adjustment, electrolyte internal structure arrangement, and interface modification.