摘要:
Electrochemical cells containing nanostructured negative active materials and composite positive active materials and methods of fabricating such electrochemical cells are provided. Positive active materials may have inactive components and active components. Inactive components may be activated and release additional lithium ions, which may offset some irreversible capacity losses in the electrochemical cells. In certain embodiments, the activation releases lithium ion having a columbic content of at least about 400 mAh/g based on the weight of the activated material.
摘要:
Provided are novel electrodes for use in lithium ion batteries. An electrode includes one or more intermediate layers positioned between a substrate and an electrochemically active material. Intermediate layers may be made from chromium, titanium, tantalum, tungsten, nickel, molybdenum, lithium, as well as other materials and their combinations. An intermediate layer may protect the substrate, help to redistribute catalyst during deposition of the electrochemically active material, improve adhesion between the active material and substrate, and other purposes. In certain embodiments, an active material includes one or more high capacity active materials, such as silicon, tin, and germanium. These materials tend to swell during cycling and may loose mechanical and/or electrical connection to the substrate. A flexible intermediate layer may compensate for swelling and provide a robust adhesion interface. Provided also are novel methods of fabricating electrodes containing one or more intermediate layers.
摘要:
Provided are novel methods of fabricating electrochemical cells containing high capacity active materials that form multilayered solid electrolyte interphase (SEI) structures on the active material surface during cell fabrication. Combining multiple different SEI layers on one surface can substantially improve cell performance by providing each layer with different properties. For example, an outer layer having a high electronic resistance may be combined with an inner layer having a high ionic permeability. To form such multilayered SEI structures, formation may involve changing electrolyte composition, functionalizing surfaces, and/or varying formation conditions. For example, formation may start with a boron containing electrolyte. This initial electrolyte is then replaced with an electrolyte that does not contain boron and instead may contain fluorine additives. In certain embodiments, cell's temperature is changed during formation to initiate different chemical reactions during SEI formation. Variations in multilayered SEI structures may be also achieved by varying current rates.
摘要:
Provided are novel negative electrodes for use in lithium ion cells. The negative electrodes include one or more high capacity active materials, such as silicon, tin, and germanium, and a lithium containing material prior to the first cycle of the cell. In other words, the cells are fabricated with some, but not all, lithium present on the negative electrode. This additional lithium may be used to mitigate lithium losses, for example, due to Solid Electrolyte Interphase (SEI) layer formation, to maintain the negative electrode in a partially charged state at the end of the cell discharge cycle, and other reasons. In certain embodiments, a negative electrode includes between about 5% and 25% of lithium based on a theoretical capacity of the negative active material. In the same or other embodiments, a total amount of lithium available in the cell exceeds the theoretical capacity of the negative electrode active material.
摘要:
Provided are conductive substrates having open structures and fractional void volumes of at least about 25% or, more specifically, or at least about 50% for use in lithium ion batteries. Nanostructured active materials are deposited over such substrates to form battery electrodes. The fractional void volume may help to accommodate swelling of some active materials during cycling. In certain embodiments, overall outer dimensions of the electrode remain substantially the same during cycling, while internal open spaces of the conductive substrate provide space for any volumetric changes in the nanostructured active materials. In specific embodiments, a nanoscale layer of silicon is deposited over a metallic mesh to form a negative electrode. In another embodiment, a conductive substrate is a perforated sheet with multiple openings, such that a nanostructured active material is deposited into the openings but not on the external surfaces of the sheet.
摘要:
Provided are conductive substrates having open structures and fractional void volumes of at least about 25% or, more specifically, or at least about 50% for use in lithium ion batteries. Nanostructured active materials are deposited over such substrates to form battery electrodes. The fractional void volume may help to accommodate swelling of some active materials during cycling. In certain embodiments, overall outer dimensions of the electrode remain substantially the same during cycling, while internal open spaces of the conductive substrate provide space for any volumetric changes in the nanostructured active materials. In specific embodiments, a nanoscale layer of silicon is deposited over a metallic mesh to form a negative electrode. In another embodiment, a conductive substrate is a perforated sheet with multiple openings, such that a nanostructured active material is deposited into the openings but not on the external surfaces of the sheet.
摘要:
A lithium ion battery electrode includes silicon nanowires used for insertion of lithium ions and including a conductivity enhancement, the nanowires growth-rooted to the conductive substrate.
摘要:
A lithium ion battery electrode includes silicon nanowires used for insertion of lithium ions and including a conductivity enhancement, the nanowires growth-rooted to the conductive substrate.
摘要:
Provided are nanostructures containing electrochemically active materials, battery electrodes containing these nanostructures for use in electrochemical batteries, such as lithium ion batteries, and methods of forming the nanostructures and battery electrodes. The nanostructures include conductive cores, inner shells containing active materials, and outer shells partially coating the inner shells. The high capacity active materials having a stable capacity of at least about 1000 mAh/g can be used. Some examples include silicon, tin, and/or germanium. The outer shells may be configured to substantially prevent formation of Solid Electrolyte lnterphase (SEI) layers directly on the inner shells. The conductive cores and/or outer shells may include carbon containing materials. The nanostructures are used to form battery electrodes, in which the nanostructures that are in electronic communication with conductive substrates of the electrodes.
摘要:
Provided are methods of preparing a lithium ion cell including forming the cell by charging the lithium ion cell to at least about 5% or, more specifically, to at least about 20% of the theoretical capacity of the negative electrode electrochemically active material, holding the lithium ion cell in a charged state for at least about 0.5 hours, and discharging the lithium ion cell. Holding the lithium ion cell in a partially charged state is believed to significantly improve its Coulombic efficiency during subsequent cycling.