Multi-stage magnesiothermic reduction for production of silicon oxides with reduced silicon grain size

A method of making a composition of matter useful as an electrode in an electrochemical cell, comprising:

• providing a precursor comprising silicon oxide;
• and
• reducing the precursor using a multi-stage magnesiothermic reduction reaction so as to form a composite comprising silicon and oxygen;
• and
• wherein:
• the composite comprises a reduced compound comprising a plurality of particles,
• each of the particles comprise a grain embedded in silicon dioxide,
• the grain comprises silicon,
• the grain has a largest dimension D,
• 3 nanometers≤D≤30 nanometers, and
• the multi-stage magnesiothermic reduction reaction forms the particles comprising grain sizes that are more uniform as compared to the grain sizes formed by a one step magnesiothermic reduction process and the largest dimensions of the grains in the plurality of particles are all within 5% of each other.