Fade-resistant high capacity electrodes for a lithium-ion battery

A method of applying a layer for inhibiting diffusion of lithium to portions of a plurality of spaced-apart, nanowires of a lithium-accepting composition attached to, and extending outwardly from, a current collector, the nanowires having a length;

• the current collector and lithium-accepting nanowires comprising a negative electrode for a lithium-ion battery, the diffusion-inhibiting layer being selectively applied over only a portion of the length of the nanowires extending from the surface of the current collector part-way along the length of the nanowires and serving to manage the diffusion of lithium into the nanowires during charging of the battery, the method comprising:
• applying a removable coating to the current collector surface to encase a first portion of each nanowire proximate the current collector while leaving a second portion of each nanowire accessible for further reaction, the removable coating having a thickness, the thickness being generally equal to the preferred length of the diffusion-inhibiting layer;
• applying a thin layer of aluminum to the accessible portion of each nanowire;
• anodizing the aluminum coating to render an electrically non-conducting coating of alumina on the accessible portion of each nanowire;
• removing the removable coating;
• applying, to the first portion of each nanowire, a diffusion-inhibiting layer of a material which will restrict access of lithium to each nanowire;
• and
• removing the alumina coating.

A method of fabricating a negative electrode for a lithium-ion battery, the electrode comprising a plurality of upstanding nanowires of a lithium-accepting composition comprising silicon or tin, the nanowires having a length and being coated over a portion of the length with a layer of material for inhibiting diffusion of lithium into the nanowires, the nanowires being embedded, at an end portion, in a metal current collector, the structure of the electrode serving to reduce the stresses resulting from the expansion of the nanowires during diffusion of lithium into the lithium-accepting composition during charging of the battery, the method comprising the steps of:

• preparing a surface of the metal current collector to accommodate end portions of a preselected density of nanowires of the lithium-accepting composition by masking the surface of the current collector with a removable mask adapted to bar access to the metal collector surface except at a plurality generally circular openings in the mask, the density of the mask openings being equal to, or greater than, the preselected nanowire density;
• then
• etching the surface of the current collector with a suitable etchant for a predetermined time through the openings in the removable mask, the etchant and mask cooperating to create, at each mask opening, a cavity of suitable depth for the end portions of the nanowires, each cavity extending part-way through the current collector to produce, on the surface of the current collector, a plurality of such cavities;
• depositing a metal catalyst within the cavities by chemical or physical vapor deposition, the catalyst being a particle or a nanometer cluster, the catalyst being selected and adapted to promote growth of the nanowires of the lithium-accepting composition;
• removing the mask and growing nanowires of the lithium-accepting negative electrode composition from the catalyst particles by physical or vapor deposition, an end of the nanowires being anchored in the cavity and embedded in the current collector;
• continuing to grow the nanowires until they extend above the surface of the current collector and achieve a predetermined length above the surface of the current collector;
• then,
• applying a removable coating to the current collector surface to encase a first portion of each nanowire proximate the current collector while leaving a second portion of each nanowire accessible for further reaction, the removable coating having a thickness, the thickness being generally equal to the preferred length of the diffusion-inhibiting layer;
• applying a thin layer of aluminum to the accessible portion of each nanowire;
• anodizing the aluminum coating to render an electrically non-conducting coating of alumina on the accessible portion of each nanowire;
• removing the removable coating;
• applying, to the first portion of each nanowire, a layer of a diffusion-inhibiting material which will restrict access of lithium to each nanowire, the layer of diffusion-inhibiting material extending from the current collector part-way along the length of the nanowires;
• and
• removing the alumina coating.