Additive Effects on Li‖CF_xand Li‖CF_x-MnO₂Primary Cells at Low Temperature

Abstract

The effect of additives and electrolyte composition was investigated for Li CF x and Li CF x -MnO 2 cells operated at low (ca. −40 • C) temperature. Electrochemical impedance spectroscopy (EIS) and Tafel measurements indicated that the anode is far more resistive than the cathode at low temperatures. Adding a small amount of fluoroethylene carbonate (FEC) to a propylene carbonate (PC) + 1,2-dimethoxyethane (DME) + tetrahydrofuran (THF) ternary blend was found to have a beneficial effect on the anode of a cell when using 0.5 M LiClO 4 as the electrolyte salt. Although the cathode impedance did increase with the addition of FEC, the overall cell impedance dropped dramatically, particularly at −40 • C. Capacity at low temperature was not significantly improved with FEC addition, however, indicating that static (i.e. EIS) measurements may not be the best tool to understand the cell under dynamic (discharge) conditions. 15-crown-5 (as an additive) proved to have severe negative effects on specific capacity.

Study on Crystal Growth Kinetics and Preferred Orientation for LiF Crystal in Dimethyl Sulfoxide/1,3-Dioxolane-based Electrolyte

“…To enhance the performance of the Li/CF x battery, many efforts have been devoted to overcoming these drawbacks. These efforts may be divided into three categories: (1) the improvement of the CF x cathode conductivity, which includes a new material, hybrid cathode, preparation method, conductive additive, and surface modification; − (2) the exploration of a novel electrolyte, which includes a low-temperature electrolyte, a high-temperature electrolyte, and a solid-state electrolyte; − and (3) the geometry modification of the discharge product layer, which comprises the electrolyte additive and a selection of different CF x materials. − …”

Beyond Transition Metal Oxide Cathodes for Electric Aviation: The Case of Rechargeable CFx

“…One approach to addressing these needs is to look at primary batteries. The Li-CF x chemistry, which has been studied in the context of primary batteries for space exploration, , possesses one of the highest specific energies (∼800 Wh/kg) because of the high specific capacity of the CF x cathode (864 mAh/g) . However, this chemistry suffers from issues such as low discharge voltage, poor rate capability, excess heat generation during discharge, and nonrechargeability .…”

Low‐Temperature Electrolyte Design for Lithium‐Ion Batteries: Prospect and Challenges

“…Besides, the electrolyte of 0.8 M LiTFSI, 0.2 M LiNO 3 , 10 % FEC in DOL/DME exhibited higher CE from ∼85 % to ∼50 % over 50 cycles in the Li|Cu asymmetric cell and a lower voltage polarization of 770 mV in the Li|Li symmetric cell at −60 °C [75e] . The other kinds of additives, such as lithium oxalate, [75b] vinylene carbonate (VC), [75b] LiBOB, [75b] and 15‐crown‐5, [75d] can be also used to improve the low‐temperature performance. For example, 76.4 % or 76.5 % of the room temperature capacity can be delivered in the MCMB|Li x Ni y Co 1−y O 2 full‐cell at −40 °C under the current density of 0.25 mA cm −2 when the blank electrolyte (i. e., 1.0 M LiPF 6 in EC/EMC/MB) was modified by 2 % VC or 0.1 M LiBOB, respectively (Figure 6d) [75b] …”