United States Patent and Trademark Office
Patent for germanium-containing lithium-ion devices granted to StoreDot
Lithium ion batteries, also known as Li-ion Batteries or LIBs, are widely used in consumer electronics, for example in mobile telephones, tablets and laptops. LIBs are also used in other fields, such as military uses, electric vehicles, and aerospace applications.
During discharge of the battery, lithium ions (Li-ions) travel from a high-energy anode material through an electrolyte and a separator to a low-energy cathode material. During charging, energy is used to transfer the Li-ions back to the high-energy anode assembly. The charge and discharge processes in batteries are slow processes and can degrade the chemical compounds inside the battery over time. Rapid charging causes accelerated degradation of the battery constituents, as well as a potential fire hazard due to a localized, over-potential build-up and increased heat generation, which can ignite the internal components, and lead to explosion.
This patent relates to a lithium ion device comprising: an anode having an active material comprising germanium nano-particles having a particle size of 20 to 100 nm, boron carbide nano-particles having a particle size of 20 to 100 nm, and tungsten carbide nano-particles having a particle size of 20 to 60 nm, wherein the weight percentage of the germanium is between 5 to 80 weight % of the total weight of the anode, the weight percentage of boron in the anode is between 2 to 20 weight % of the total weight of the anode and the weight percentage of tungsten in the anode is between 5 to 20 weight % of the total weight of the anode; a cathode; and an electrolyte.
The presence of boron and/or tungsten may facilitate the electrochemical utilization of the germanium (and the silicon in a Si—Ge anode material), and substantially may reduce the migration of germanium into the electrode substrate. Moreover, boron carbide may enhance the binding energy of Li atoms, (boron's binding energy is greater than the cohesive energy of lithium metal) and may prevent lithium from clustering at high lithium doping concentrations.
Tungsten carbide with naturally occurring germanium oxide-carbon composites may improve the electrochemical behavior of the anode. The tungsten-carbide may act as hydron (H+) ion barrier. Tungsten carbide is highly conductive and inert substance, therefore, may further stabilize the conductivity of the electrode over the life cycle and therefore, may stabilize the conductivity of the electrode.