Patent Application
20250219157
This disclosure relates to electrolyte additives used in lithium-ion batteries.
Lithium-manganese rich (LMR) cathodes have a higher specific capacity and gravimetric energy density compared to other lithium-ion battery cathode materials such as lithium iron phosphate (LFP) and lithium nickel manganese cobalt oxide (NCM). However, a lithium-ion battery with an LMR cathode may show diminished capacity retention over successive cycles which may be caused by interaction between the LMR cathode and an electrolyte.
A battery cell comprising a negative electrode, a lithium-manganese rich positive electrode, and an electrolyte is disclosed. This electrolyte includes a methylene methanedisulfonate additive, and saturates both the negative and lithium-manganese rich positive electrodes. The cycling of the battery cell, at an upper cut-off voltage of 4.45 volts, leads to the formation of a positive electrolyte interface on the surface of the lithium-manganese rich positive electrode. This interface reduces the direct current impedance of the battery cell for a given state of charge, as compared to a similar battery cell without the additive. The positive electrolyte interface contributes to a capacity retention of the battery cell at 45 degrees Celsius and after 100 cycles of charge and discharge being greater than a capacity retention of a comparable battery cell lacking the methylene methanedisulfonate additive. Additionally, the electrolyte saturates the negative electrode as previously mentioned, resulting in the formation of a solid electrolyte interface on a surface of the negative electrode, which faces the positive electrolyte interface.
The methylene methanedisulfonate additive's weight percentage in the electrolyte ranges from 0.1 wt % to 5 wt %. The electrolyte itself comprises the methylene methanedisulfonate additive, a lithium salt, and a solvent, wherein the lithium salt may be lithium hexafluorophosphate. The solvent used in this electrolyte may be a carbonate-based solvent. The lithium-manganese rich positive electrode in the battery cell includes a metal current collector and a lithium-manganese rich active material layer on the metal current collector. The negative electrode may be graphite-based. Additionally, the battery cell may incorporate a separator, which is also saturated by the electrolyte.
An electrode assembly comprising a current collector and a lithium-manganese rich active material layer on the current collector is presented. The electrolyte includes methylene methanedisulfonate additive and saturates the lithium-manganese rich active material layer. During cycling of the electrode, a solid electrolyte interface forms on the surface of the lithium-manganese rich active material layer. The weight percentage of the methylene methanedisulfonate additive in the electrolyte is between 0.1 wt % to 5 wt %. The electrode assembly may further include a separator saturated by the electrolyte.
Another battery cell, comprising a negative electrode, a lithium-manganese rich positive electrode, and an electrolyte is presented. The electrolyte includes a methylene methanedisulfonate additive, and saturates both the negative and lithium-manganese rich positive electrodes. During cycling of the battery, the formation of a positive electrolyte interface occurs on a surface of the lithium-manganese rich positive electrode. This interface contributes to a capacity retention of the battery cell better than that of a similar battery cell without the methylene methanedisulfonate additive. The positive electrolyte interface also contributes to a reduction in the direct current impedance of the battery cell, for a given state of charge when compared to a similar battery cell without the additive.
The weight percentage of the methylene methanedisulfonate additive in the electrolyte is between 0.1 wt % to 5 wt %. The electrolyte may be made by dissolving a lithium salt in a solvent and adding the methylene methanedisulfonate additive. The lithium salt used may be lithium hexafluorophosphate, and the solvent may be carbonate-based. The lithium-manganese rich positive electrode of the battery cell includes a metal current collector with a lithium-manganese rich active material layer on it. The negative electrode of the battery cell may be made of a graphite-based material. The battery cell may include a separator also saturated by the electrolyte.
Embodiments are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments may take various and alternative forms. The figures are not necessarily to scale. Some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art.
Various features illustrated and described with reference to any one of the figures may be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations.
A technical challenge with lithium-manganese rich (LMR) cathode-based lithium-ion batteries (LiBs) is that they may show diminished capacity retention over time. This may be caused by the interaction between the LMR cathode and a cathode electrolyte interface at voltages above 4.40V. Experimental investigations into electrolyte additives that perform well in the necessary high-voltage (HV) conditions have yielded mixed results. Electrolyte additives that are known to perform well with cathode materials in LiBs, such as lithium cobalt oxide (LCO), lithium ion manganese oxide battery (LMO), lithium iron phosphate (LFP) and lithium nickel manganese cobalt oxide (NCM), generally do not perform similarly when paired with a LiB that has a LMR cathode. Such additives include ethylene sulfate (ESA), 1,3-propanediol cyclic sulfate (PCS), lithium bis(oxalate) borate (LiBOB), and 1,3,6-hexanetricarbonitrile (HTN). 1.9 Ah pouch cell samples with the LMR cathodes and the respective electrolyte additives were prepared. The experimental results for capacity retention over cycles at an upper control voltage (UCV) of 4.45V for the respective additives in an electrolyte of a battery cell with an LMR-based cathode have been documented. For comparison purposes, the same baseline lithium salt electrolyte was utilized across all samples. Additionally, each additive was incorporated into this lithium salt electrolyte.
Referring now to the figures,
Methylene methanedisulfonate (MMDS) was also evaluated as a bi-functional additive to form a stable and ionic conductive solid electrolyte interface (SEI) on an anode and a cathode electrolyte interface (CEI) on an LMR cathode. A 1.9 Ah pouch cell was prepared with an electrolyte having 3.0 wt % of MMDS additive. It was unexpectedly observed that the LMR cathode-based LiB with 3.0 wt % MMDS additive in the electrolyte showed reduced cell impedance at beginning of life, had greater capacity retention over cycles at HV and elevated temperatures, and had reduced cell impedance growth over cycles at HV and elevated temperatures.
During cycling of the battery cell 10, at an upper cut-off voltage of 4.45 volts, the MMDS additive 20 in the electrolyte 18 facilitates the formation of a positive electrolyte interface 26 on a surface of the LMR active material layer 24. The positive electrolyte interface 26 contributes to the resulting battery cell 10 having a lower direct current impedance for a given state of charge compared to a similar battery cell without the MMDS additive 20. The positive electrolyte interface 26 further results in a capacity retention of the battery cell 10, at 45 degrees C. temperature after 100 cycles of charge and discharge, being greater than a capacity retention of an otherwise same battery cell without the MMDS additive 20. Additionally, the MMDS additive 20 in the electrolyte 18 may also contribute to the formation of a solid electrolyte interface 28 on a surface of the negative electrode 14 facing the positive electrolyte interface 26. This may also contribute to the overall electrochemical stability and performance of the battery cell 10.
While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of these disclosed materials.
As previously described, the features of various embodiments may be combined to form further embodiments of the disclosure that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics may be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes may include, but are not limited to strength, durability, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and may be desirable for particular applications.
