Towards a High‐Performance Lithium‐Metal Battery with Glyme Solution and an Olivine Cathode

Abstract

High‐performance lithium‐metal batteries are achieved by using a glyme‐based electrolyte enhanced with a LiNO3 additive and a LiFePO4 cathode. An optimal electrolyte formulation is selected upon detailed analysis of the electrochemical properties of various solutions formed by dissolving respectively lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium bis(pentafluoroethanesulfonyl)imide (LiBETI) either in diethylene glycol dimethyl ether or in triethylene glycol dimethyl ether and by adding LiNO3. A thorough investigation shows evidence of efficient ionic transport, a wide stability window, low reactivity with lithium metal, and cathode/electrolyte interphase characteristics that are strongly dependent on the glyme chain length. The best Li/LiFePO4 battery delivers 154 mAh g−1 at C/3 (1 C=170 mA g−1) without any decay after 200 cycles. Tests at 1 C and 5 C show initial capacities of about 150 and 140 mAh g−1, a retention exceeding 70 % after 500 cycles, and suitable electrode/electrolyte interphases evolution.

Electrochemical behavior of nanostructured NiO@C anode in a lithium-ion battery using LiNi⅓Co⅓Mn⅓O2 cathode

“…Based on these observations, we can attribute the (R(lf)Q(lf)) sub-circuit (large low-frequency semicircle in Figure 6g-j) to the cathode charge transfer resistance and double layer capacitance. Besides, we ascribe the (R(hf)iQ(hf)i) sub-circuit (i = 1, 2) mostly to the passivation layers over the electrodes [59][60][61]. Negligible contribution of the anode charge transfer, and double layer capacitance in the low-frequency region is expected, considering the relatively small semicircles observed in the Nyquist plots of Figure 4.…”

“…In detail, the (R(hf)iQ(hf)i) sub-circuit (i = 1, 2) reflects the response of the cell at high-medium frequency (herein briefly indicated as high-frequency region), occurring as a small semicircle in the Nyquist plots of Figure 6g-j, while the (R(lf)Q(lf)) sub-circuit describes the large semicircle at medium-low frequency (herein briefly indicated as low-frequency region). Further spectra of the NiO@C and NCM electrodes performed employing the additional lithium reference probe (Figure S3a, c, e, g, and i for Li/NiO@C side and Figure S3b, d, f, h, and j for Li/NMC side) suggest a characteristic low-frequency response for NiO@C and NCM, that is, a Warburg-type diffusion for the former and a slow charge transfer for the latter after the 1 st cycle, as well as an high-frequency region mostly reflecting the lithium passivation [59][60][61]. It is noteworthy that such a high charge transfer resistance at the cathode is in full agreement with the expected low Li + content in the NCM lattice in charged condition [59].…”

Synthesis of a High-Capacity α-Fe2O3@C Conversion Anode and a High-Voltage LiNi0.5Mn1.5O4 Spinel Cathode and Their Combination in a Li-Ion Battery

“… 58 Furthermore, a capacity excess at high voltages during the first cycle suggests the partial occurrence of the electrolyte decomposition with the deposition of a suitable SEI film, which protects the electrode surface. 59 Accordingly, the subsequent cycles reveal only the typical high voltage signature of the Ni 4+ /Ni 2+ redox pair, that is, around 4.7–4.8 V. 60 …”

Lithium–Metal Batteries Using Sustainable Electrolyte Media and Various Cathode Chemistries

“…The decrease of cell capacity and the appearance of the slope at the end of the (de)insertion processes of LiFePO 4 may be associated with an excessive growth of the SEI layer at the electrodes surface and possibly with gradual changes in cathode crystallite size distribution and surface free energies of the lithiated and delithiated phases, which lead to a change of the biphasic potential. 11 Instead, the cell employing TREGDME_HCE shows a capacity retention increasing from 94% of the previous test ( Figure 4 d) up to 97% ( Figure 5 d), while the corresponding voltage profiles reveal only a slight slope after 50 cycles without any sign of polarization increase or deterioration ( Figure 5 c). Therefore, we may suggest the additional reduction step at low voltage during the first cycle as an actual strategy to improve the performance of the lithium–metal cell using concentrated glyme-based electrolytes with the LFP electrode, particularly those having a longer ether chain such as TREGDME.…”