TECHNICAL FIELD

The present application relates to passivation techniques. More specifically, the present application provides for systems, devices, and methods for creating a battery having a passivation layer to protect its electrodes.

BACKGROUND

There is a growing awareness that current lithium ion battery technologies are reaching their limits in terms of storage and energy capabilities. However, there is still increasing demand for higher energy storage and longer lasting devices. This has challenged the research community to search for next-generation battery systems. Some of the current systems being researched include lithium-air (Li—O2) and lithium-sulfur (Li—S) batteries.

Lithium (Li) metal has been known as the “hostless” material to store Li ions (Li+) without the need for using intercalating and/or conducting scaffold techniques. For this reason, Li metal electrodes exhibit high theoretical specific capacity (3860 mAh g−1) and low redox potential (−3.04 V); thus, they are often regarded as the best choice to use for manufacturing/fabricating anodes for next-generation rechargeable Li batteries. However, Li metal anodes exhibit properties that cause multiple practical issues which inhibit their use. These properties are often associated with uncontrollable dendrite formation during repeated Li deposition/dissolution processes, which can lead to short circuiting the battery and potential overheating and fire.

Several techniques have been implemented to suppress Li dendrite growth and/or to enhance stability of Li metal. For example, methods have sought to do this through: controlling the dendrite growth/deposition of Li through liquid electrolyte modification with additives; adopting Li+ conducting polymer or solid state electrolytes; and applying a layer of alumina (Al2O3) upon the surface of Li metal. A thin layer of Al2O3is a ceramic-based material that lacks the electron conductivity of 2D materials, thus increasing internal resistance of the battery electrode. However, none of the approaches has been shown to be effective in the context of rechargeable batteries.

While the low cost and abundance of sulfur make the concept of Li—S batteries alluring, there are several issues that generally prevent the widespread development of Li—S batteries. For example, sulfur is an insulating material, which provides for poor utilization of the active material and hinders electron transfer during the charge/discharge process. In addition, during the discharge process, Li may react with sulfur to form higher-order soluble polysulfides at the cathode, which creates shuttling of polysulfide between the anode and cathode during the cycling process. The shuttle effect may increase the internal resistance of the battery and contribute to capacity fading. Further, the formation of uncontrolled dendrites resulting from uneven deposition of Li metal may cause safety problems at higher C-rates as well as continuous evolution of a porous Li metal structure, which may lead to corrosion of Li metal. While some approaches have been developed, issues of decreased cell efficiency and increased capacity fading still affect the performance of Li—S batteries when used with a Li anode.

SUMMARY

The present application is directed to systems, methods and devices which passivate Li metal with thin layers of 2D materials (e.g., MoS2, WS2, MoTe2, MoSe2, WSe2, BN, BN—C composite, and the like). Two-dimensional (2D) materials, one atomic thickness film, exhibit low impedance due to their unique interlayer structure that readily intercalates Li ions with minimum energy to substantially increase Li-ion diffusivity and electric conductivity while acting as a passivation layer for Li dendrite growth. Such methods may utilize sputtering or evaporation deposition to create the passivation layer. These methods may form a new phase between Li metal and electrolyte where large amounts of Li atoms may be intercalated in order to facilitate homogenous flow of Li+into and out of bulk Li metal. Unlike other carbon/polymer/ceramic-based protective layers, the unique structural aspects and phase-changing characteristics (e.g., semiconductor and/or metallic traits) of 2D materials such as MoS2, WS2, MoTe2, MoSe2, WSe2, have allowed embodiments of the application to circumvent high impedance and/or poor interfacial-contact related issues. For example, in one embodiment MoS2-coated Li electrodes have demonstrated no Li dendrite growth at a challenging current density over 10 mA cm−2and high capacity retention for over 1000 cycles. The fabricated 2D materials coated Li metal exhibits stable adhesion to the substrate, and yields high cycling stability in 2D materials coated Li metal over bare Li electrode counterparts in rechargeable batteries. Accordingly, embodiments of the present application provide for significant performance improvements in rechargeable batteries.

In an embodiment, a method for passivating lithium metal includes providing a lithium electrode, depositing at least one layer of a two-dimensional material on the lithium electrode, and intercalating the at least one layer of the two-dimensional material with a plurality of lithium ions. In another embodiment, a rechargeable lithium battery includes a first electrode, an electrolyte, and a second electrode, wherein the second electrode comprises a lithium metal having at least one layer of a two-dimensional material deposited thereon.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.

