Anode compositions and alkali metal batteries comprising same

A process of preparing a composition-of-matter comprising a plurality of particles, said particles comprising a substance selected from the group consisting of:

• a) a compound which forms an alloy with an alkali metal;
• and
• b) said alloy of said alkali metal with said compound,
• said alloy reversibly releasing said alkali metal while decreasing in volume and absorbing said alkali metal while increasing in volume, wherein each of said particles is encapsulated within a volume enclosed by a shell or matrix which conducts cations of said alkali metal, the process comprising:
• i) providing particles comprising said alloy of an alkali metal with said compound, wherein said alloy is saturated with said alkali metal;
• and
• ii) coating said particles with a conductor of cations of said alkali metal, thereby forming said shell or matrix, wherein said coating comprises:
• mixing said particles comprising said alloy with particles of said conductor of cations of said alkali metal, and optionally with additional particles of an electron conductor, to obtain a mixture;
• and subjecting said mixture to a heat treatment, said heat treatment effecting sintering of particles in said mixture by heating for at least 1 hour at a temperature of no more than 10° C. lower than a melting point of said conductor of cations of said alkali metal, to thereby form said shell or matrix.