Capacity Loss Mechanism of the Li₄Ti₅O₁₂ Microsphere Anode of Lithium-Ion Batteries at High Temperature and Rate Cycling Conditions

Abstract

Li4Ti5O12 (LTO) as the anode of lithium (Li) ion batteries has high interfacial side reactivity with the electrolyte, which leads to severe gassing behavior and poor cycling stability. Herein, the capacity loss mechanism of the high-tap density LTO microsphere anode under different temperatures (25, 45, and 60 °C) and charge/discharge rates (1 and 5 C) is systematically investigated. The capacity retentions of the LTO/Li cell after 500 cycles at 1 C are 95.6, 90.0, and 87.1% under three temperatures, which drop to 91.9, 58.3, and 20.9% when cycling at 5 C, respectively. Results show that the high temperature and rate almost do not damage the structure of LTO, but greatly affect the thickness and components of the solid electrolyte interface (SEI), and consequently reduce the performance of the LTO/Li cells. An SEI mainly consisting of inorganic species forms on LTO after 500 cycles at 1 C, while organic compounds are observed after 500 cycles at 5 C. The capacity of cycled LTO cannot recover again because of the thick SEI although using new Li metal anodes, separators, and electrolytes. This work demonstrates that it is of great significance for LTO to construct a stable SEI for achieving excellent cycling performance at a high rate and temperature.

Controlling Interfacial Reduction Kinetics and Suppressing Electrochemical Oscillations in Li4Ti5O12 Thin‐Film Anodes

“…This high‐temperature cycling performance degradation seen for these LTO films is similar to that observed previously for LTO composite electrodes due to electrolyte decomposition. [ 19 ] As shown in Figure 2d, comparing AZO(90)–LTO with the bare LTO samples reveals that their capacities are similar at low rates, but at high rates, AZO(90)–LTO delivers higher capacity. This indicates that uniform coating of the LTO surface with too thick an AZO layer may still resist the electrolyte decomposition at elevated temperature.…”

“…The AZO(90)–LTO film had an even higher initial capacity of over 33.4 μAh cm −2 , and then gradually decayed to ≈16.7 μAh cm −2 after 300 cycles. This high initial capacity derives from the electrochemically active AZO coating layer and the irreversible SEI formation, [ 19 ] as well as the surface lithium storage [ 20 ] that contributes to the extra initial Faraday capacity. However, a thicker AZO coating layer may not be able to be fully and uniformly reduced into the highly conductive Li–Zn/Li 2 O/AlF 3 protection layer.…”

“…The electrochemical performances of the bare LTO and AZO decorated LTO was also studied in a high‐temperature environment, in which lithium diffusion is activated and more serious electrolyte decompositions is commonly observed. [ 19 ] Figure 2c,d shows their cycling and rate performances between 0.1 and 3.0 V at 60 °C. The AZO(60)–LTO film shows good cycle stability at high temperature and high rate (5C).…”

Recent Developments of Nanomaterials and Nanostructures for High‐Rate Lithium Ion Batteries

“…In addition to graphitic materials, there is a number of studies focusing on other anode materials with nanostructures. For example, lithium titanate (Li 4 Ti 5 O 12 , LTO), as an alternative to graphite, has been widely studied because it (i) provides outstanding reversibility of ion intercalation and deintercalation at high charge rates (above 10 C), (ii) effectively avoids side reactions, including the decomposition of electrolyte and plating issue, (iii) exhibits limited volume expansion (less than 1 %) during the redox process, and (iv) has excellent thermal stability . However, the lithium ion diffusion coefficient (10 −9 –10 −13 ) in LTO is not high enough to achieve high rate capabilities…”

Lithium-Ion Capacitor Lifetime Extension through an Optimal Thermal Management System for Smart Grid Applications

“…They have shown that the cell's capacity retention would decrease at elevated temperatures; LTO could deliver up to 87.1% capacity retention in low C-rates (1 C, 60 • C, 500 Cycles). However, with raising the C-rate, the capacity retention had drastically dropped to 20.9% (5 C, 60 • C, 500 Cycles) [14]. Considering that high C-rates are in the interest of LiC applications, it is expected that controlling the temperature and keeping that in lower values could cause the LiC lifetime's amelioration.…”