Insight into the Key Factors in High Li⁺ Transference Number Composite Electrolytes for Solid Lithium Batteries

Abstract

Solid lithium batteries (SLBs) have received much attention due to their potential to achieve secondary batteries with high energy density and high safety. The solid electrolyte (SE) is believed to be the essential material for SLBs. Among the recent SEs, composite electrolytes have good interfacial compatibility and customizability, which have been broadly investigated as promising contenders for commercial SLBs. The high Li+ transference number (t Li+ ${{_{{\rm Li}{^{+}}}}}$ ) of composite electrolytes is critically important concerning the power/energy density and cycling life of SLBs, however, which is often overlooked. This Review presents a current opinion on the key factors in high t Li+ ${{_{{\rm Li}{^{+}}}}}$ composite electrolytes, including polymers, Li‐salts, inorganic fillers, and additives. Various strategies concerning providing a continuous pathway for Li‐ions and immobilizing anions via component interaction are discussed. This Review highlights the major obstacles hindering the development of high t Li+ ${{_{{\rm Li}{^{+}}}}}$ composite electrolytes and proposes future research directions for developing composite electrolytes with high t Li+ ${{_{{\rm Li}{^{+}}}}}$ .

LLZTO Nanoparticle- and Cellulose Mesh-Coreinforced Flexible Composite Electrolyte for Stable Li Metal Batteries

“…According to the equation for calculation in the Section , the t Li+ of the LZEC composite electrolyte is approximately 0.71. The LZEC composite electrolyte contains many LLZTO nanoparticles, and the Lewis acid–base interactions between ceramics nanoparticles and mobile anions (PF 6 – ) are responsible for this high value, as previous research studies revealed. , The LZEC composite electrolyte with high t Li+ is expected to reduce polarization and facilitate uniform Li deposition, as it can alleviate the space charge layer at the electrolyte/electrode interface caused by free migration and accumulation of anions . More importantly, t Li+ represents the ratio of Li + to all mobile ions in composite electrolytes.…”

“…37,38 The LZEC composite electrolyte with high t Li+ is expected to reduce polarization and facilitate uniform Li deposition, as it can alleviate the space charge layer at the electrolyte/electrode interface caused by free migration and accumulation of anions. 46 More importantly, t Li+ represents the ratio of Li + to all mobile ions in composite electrolytes. So high t Li+ further demonstrates the superior ability of the LZEC composite electrolyte in conducting Li + , which may help to improve the rate performance of batteries.…”

Evaluation of solid electrolytes: Development of conventional and interdisciplinary approaches

“…Moreover, charge transfer, that is, electrons or ions, occurs at the solid-solid contact point between the SE and electrodes due to electrochemical reactions, such as Limetal deposition. [14,108,109] Consequently, mechanical alteration happens along the electrochemical reaction, leading to local lattice deformation of the SEs. [110] The extension of such alteration is normally restricted to the very surface layers of solid materials, triggering the local stress.…”

Spontaneous In Situ Formation of Lithium Metal Nitride in the Interface of Garnet-Type Solid-State Electrolyte by Tuning of Molten Lithium

“…Therefore, long-term cycling will lead to lithium dendrite growth at the solid electrolyte grain boundaries and cause electrolyte failure and short-circuit the battery. The most direct way to solve wettability is to use artificial SEI layers or alloys of lithium metal with different metal elements , or composites with polymers to the solid composite electrolyte to change the mechanical properties of the electrolyte. − Most of the artificial SEI layers are modified with Li 3 N, LiCl, LiF, , and other materials for interface layer modification, which improves the wettability between the electrolyte and lithium metal layer. The alloy part is quite broad.…”