Electrochemical Analysis for Enhancing Interface Layer of Spinel LiNi0.5Mn1.5O4 Using p-Toluenesulfonyl Isocyanate as Electrolyte Additive

Abstract

LiNi 0. 5Mn 1.5 O 4 (LNMO) is a potential cathode material for lithium-ion batteries with outstanding energy density and high voltage plateau (>4.7 V). However, the interfacial side reaction between LNMO and the liquid electrolyte seriously causes capacity fading during cycling at the high voltage. Here, p-toluenesulfonyl isocyanate (PTSI) is used as the electrolyte additive to overcome the above problem of LNMO. The results show that the specific capacity of LNMO/Li cell with 0.5 wt.% PTSI at the first cycle is effectively enhanced by 36.0 mAh/g and has better cycling performance than that without PTSI at 4.98 V. Also, a stable solid electrolyte interface (SEI) film derived from PTSI is generated on the electrode surface, which could alleviate the strike of hydrofluoric acid (HF) caused by electrolyte decomposition. These results are explained by the molecular structure of PTSI, which contains SO 3 . The S=O groups can delocalize the nitrogen nucleus to block the reactivity of PF 5 .

Sulfur‐containing compounds as electrolyte additives for lithium‐ion batteries

“…Along with the development of electrolytes containing above four representative sulfur-containing CEI builders, there has been extensive effort on searching other potential sulfur-containing molecules, including PTSI, 68,144,145,[151][152][153] MSM, 154 DPDS, 74 dihydro-1,3,2-dioxathiolo [1,3,2]dioxathiole-2,2,5,5-tetraoxide (D-DTD), 64 lithium-cyclodifluoromethane-1,1-bis(sulfonyl)imide (LiDMSI), 78 methyl benzenesulfonate (MBS), 78 methyl 2,2-difluoro-2-(fluorosulfonyl) acetate (MDFA), 72 N,N,N,N-tetraethylsulfamide (NTESA), 71 1,2,6-oxadithiane 2,2,6,6-tetraoxide (ODTO), 155 2,3,4,5,6-pentafluorophenyl methanesulfonate (PFPMS), 60 phenyl trifluoromethane sulfonate (PTM), 61 phenyl transstyryl sulfone (PTSS), 70 and so on. For example, it has been confirmed that PTSI is able to form a functional stable CEI film on the positive electrode, consisting of Li 2 SO 3 , Li 2 S, and ROSO 2 Li, particularly in high-voltage systems (>4.2 V).…”

“…As result, transition metal ions dissolution is effectively suppressed, and cycle performance together with calendar life are also improved (Figure 12(B)). 68,144,145,[151][152][153] For instance, Li et al 152 revealed that LijjLiMn 2 O 4 cells (4.35 V) at 55 C, containing 0.5 wt% PTSI in 1.0 M LiPF 6 -EC/DEC/EMC (1:1:1, wt%) deliver 81% capacity retention after 100 cycles at 55 C, better than that without PTSI (with capacity retention 76% after 100 cycles). Wang et al 145 reported that, when 0.5 wt% PTSI included in 2 M LiPF 6 -EC/DEC (1:1, by wt), the high-voltage graphitejjLiNi 0.5 Co 0.2 Mn 0.3 O 2 cells (4.8 V) stably operates for 640 cycles with capacity retention increasing from 29% to 66% at 1 C (Figure 12(C)), and Mn 3 + dissolution into electrolyte is effectively suppressed therein.…”

Improving the Cyclic Stability of LiNi0.5Mn1.5O4 at High Cutoff Voltage by Using Pyrene as a Novel Additive

“…[ 8 ] Compared with surface modification, electrolyte additive is a more economical and effective method to improve the interface stability of LiNi 0.5 Mn 1.5 O 4 cathode. [ 9 ] At present, different film‐forming additives including trifluoromethyl sulfide (PTS), [9d] 1,1‐sulfonyldiimidazole (SDM), [ 10 ] allyloxytrimethylsilsilane (AMSL), [ 11 ] tris(pentafluorophenyl)silane (TPFPS), [ 12 ] (pentafluorophenyl)diphenylphosphine (PFPDPP), [ 13 ] p‐toluenesulfonyl isocyanate (PTSI), [ 14 ] tris(pentafluorophenyl)borane (TPFPB), [ 15 ] 3‐(trimethylsilyl)‐2‐oxazolidinone (TMS‐ON), [ 16 ] and so on have been used to improve the interface stability of the LiNi 0.5 Mn 1.5 O 4 , but it finds that some film‐forming additives also increase the interface resistance, which is harmful to the rate performance of the cells. [ 10,17 ] To compare with aforementioned film‐forming additives, using a monomer of a conductive polymer as a film‐forming additive is a more effective method to improve the interface stability because it can not only effectively protect the surface of cathode, but also improve the rate performance of cells by its excellent conductivity.…”

Machine learning approach in exploring the electrolyte additives effect on cycling performance of LiNi 0 . 5 Mn 1 . 5 O 4 cathode and graphite anode‐based lithium‐ion cell

“…To minimize electrolyte decomposition as well as the formation of stable electrode/electrolyte interface, several studies have been reported on optimizing the half‐cells like LNMO/Li 14,15 and graphite/Li 16,17 prior to the assembly of LNMO/graphite full‐cell. In these studies, the electrolytes mainly composed of lithium salts such as LiPF 6 , LiPF 6 , LiClO 4 , and LiTFSI in either various combinations of ethylene carbonate (EC)‐based conventional electrolyte with some solvents such as propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), 18 or in other organic solvent groups such as tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), and sulfolane (SL) 19,20 . Incorporating small amounts of additives effectively prevented the baseline electrolyte from the electrochemical decomposition during the charge/discharge process 21‐23 .…”

“…19,20 Incorporating small amounts of additives effectively prevented the baseline electrolyte from the electrochemical decomposition during the charge/discharge process. [21][22][23] Vinylene carbonate (VC) [24][25][26] and lithium bis(oxalate) borate (LiBOB) [27][28][29][30][31] are among the most common additives which have received great interest due to strong enhancement of cycling performance through the formation of stable solid electrolyte interface (SEI), 32 decrease of Mn and Ni dissociation, inhibition of the electrochemical decomposition at high voltage, increase of high-temperature stability, and suppression of the graphitic exfoliation issue. 16 Furthermore, the combination of two additives (dual-additive) also showed a significant efficiency in combining their advantages.…”