NOVELTY - An array of nanowires (n1) comprises: transition metal core surrounded by a shell comprising at least one Group IV metal selected from silicon, germanium, and tin.    USE - As anode in a lithium ion battery (claimed) e.g. electric vehicles.    ADVANTAGE - The arrays of nanowires that possess a greater charge transport efficiency and resistance to wire distortions, stresses, and wire fractures. Thus, nanowires exhibit a greater resistance to capacity loss (i.e. better capacity retention on cycling). The nanowire arrays has a high theoretical capacity, fast charging, and increased power density; exhibit a suitable or improved durability e.g. as compared to graphite or aluminum.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) an array of nanowires (n2) comprising at least one Group IV metal selected from silicon, germanium, and tin, where each nanowire is surrounded by a metal oxide shell, and where a space separates the nanowire and metal oxide shell to prevent the nanowire from contacting the metal oxide shell;    (2) an array of nanowires (n3) comprising at least one Group IV metal selected from silicon, germanium, and tin, and where the nanowires are embedded within periodic nanochannels of a metal oxide-ionic liquid ordered host material;    (3) a lithium ion battery containing an anode comprising the nanowire array (n1)-(n3);    (4) producing (M1) the array of nanowires (n1) involving: either depositing a transition metal into channels of a nanoporous template, removing the template to produce exposed transition metal nanowires and depositing a metal comprised of at least one Group IV metal selected from silicon, germanium, and tin, onto the transition metal nanowires to produce an array of transition metal core and Group IV metal shell nanowires; or depositing a coating of an etchable material into pores of a porous substrate provided that a nanochannel having a width remains in each coated pore, depositing a transition metal into the nanochannels to produce transition metal nanowires of the width, removing the coating of etchable material to provide a spacing between each transition metal nanowire and inner walls of the pores of the porous substrate, and depositing a metal comprised of at least one Group IV metal selected from silicon, germanium, and tin, into the spacings to produce an array of transition metal core and Group IV metal shell nanowires;    (5) producing (M2) the array of nanowires (n2) involving: depositing a coating of an etchable material into pores of a porous metal oxide substrate provided that a nanochannel having a width remains in each coated pore, depositing a metal comprised of at least one Group IV metal selected from silicon, germanium, and tin into the nanochannels to produce Group IV metal nanowires of the width and removing the coating of etchable material to provide a spacing between each Group IV metal nanowire and inner walls of the pores of the porous metal oxide substrate; and    (6) producing (M3) the array of nanowires (n3) involving: depositing a metal comprised of at least one Group IV metal selected from silicon, germanium, and tin, into periodic nanochannels of a metal oxide-ionic liquid ordered host material.