Porous Sintered Superstructure with Interstitial Silicon for Use in Anodes for Lithium Batteries

Abstract

Anodes for the lithium secondary batteries include a strong, electrically conductive, porous superstructure filled with a milled or melted interstitial material, such as nano-scaled silicon; the milled or melted interstitial material provides high lithiation capacity, and the superstructure provides durability and controls the anode's electromechanical expansion and contraction during the lithiation and de-lithiation cycle. Embodiments include porous superstructures comprised of silicon carbide, tungsten, and other materials, many of which offer capability of lithiating.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]Not ApplicableSTATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT[0002]Not ApplicableBACKGROUND OF THE INVENTION[0003]1. Field of Invention[0004]The present general inventive concept relates to components for batteries and more particularly to sintered anodes for lithium batteries and to methods and processes to fabricate such anodes.[0005]2. Description of the Related Art[0006]A secondary battery differs from a primary battery in that unlike a primary battery which is a single use non-rechargeable device, a secondary battery can be recharged many times. It value is established by a number of factors, for instance its power factors and cost, and of course its ability to be recycled quickly and reliably with steady power is a main factor in its value.[0007]Lithium ion secondary batteries are today limited by the low function of current electrodes, particularly the anode. Lithium can function at levels as high as 3840 mAh / g, so ...

AI Technical Summary

Benefits of technology

[0016]Disclosed herein are anodes for the lithium secondary battery which include a porous superstructure filled with a milled interstitial material, such as nano-scaled silicon; the milled interstitial material provides high lithiation capacity, and if the silicon is small enough the lithiation will not cause mechanical failure in the silicon. Alternatively one can fill the porosity of the superstructure post superstructure fabrication though melting of silicon in contact with the superstructure and “wicking” the silicon into the superstructure through the capillary forces. The superstructure provides durability and can control the anode's electromechanical expansion and contraction during the lithiation and de-lithiation cycle. Embodiments include porous superstructures comprised of silicon carbide, tungsten, and other materials. The alternatives of filling the porosity with the nano milled silicon or wicking the silicon in post superstructure through melting and using capillary forces to “wick” the silicon to fill the superstructure is determined by the processing temperature and atmosphere used for the fabrication of the superstructure. Silicon melts at about 1414 centigrade.

[0017]One object of the present general inventive concept is to provide electrodes for a lithium secondary battery for an automobile or similar vehicle, where those electrodes enable that lithium secondary battery to be charged quickly; to be light weight; to allow the vehicle to travel on the order of 300 miles on one charge; to be charged very quickly—close to the time required to fill a gas tank and use the rest room on the highway—and to be reusable / rechargeable over a long use life of 10,000 cycles or more. To that end, present general inventive concept, in some of its many embodiments, includes electrodes for the lithium secondary battery that feature a porous superstructure filled with an interstitial material, generally milled silicon; the milled silicon provides high lithiation capacity, and the superstructure provides durability and decreases the electrode's electromechanical expansion and contraction during the lithiation and de-lithiation cycle. Thus, such electrodes sacrifice some capacity (compared to pure silicon) for the sake of durability and long usable life, while still achieving appreciably higher capacities than graphite anodes and other anodes known in the art. However, it should be noted that a superstructure can be selected that also lithiates. For instance, silicon carbide, properly constructed, can lithiate at 700 mAh / gram or higher, thus creating a composite anode where the proportional contributions of the materials provide a much higher total capacity.

[0025]In some embodiments, said anode is fabricated by sintering the silicon carbide with the interstitial material including silicon derived from milled silicon particulates. Very fine graphite can be co-milled in ethanol with the silicon carbide and silicon and form a nano size carbon coating on the silicon carbide and silicon which when sintered in a 10−5 or 10−6 torr vacuum at 1,400 centigrade will form a graphene coating on the silicon and silicon carbide, said coating not be converted to silicon carbide. This coating precludes oxidation on the surface of the particle, increases electrical conductivity of the surface of the particle, enhances the Schottky effect and increases both the rate and total amount of lithiation.

Problems solved by technology

Thus, such electrodes sacrifice some capacity (compared to pure silicon) for the sake of durability and long usable life, while still achieving appreciably higher capacities than graphite anodes and other anodes known in the art.

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