Vapor deposition method for preparing an amorphous lithium borosilicate

A method of making a surface-modified electrode by a vapour deposition process, the electrode comprising an electrode active material, wherein a surface of said electrode is modified by an amorphous lithium borosilicate compound or doped lithium borosilicate compound, wherein the method comprises:

• (a) providing a vapour source of each component element of the amorphous compound, wherein the vapour sources comprise at least a source of lithium, a source of oxygen, a source of boron and a source of silicon, and, optionally, a source of at least one dopant element;
• wherein the vapour source of oxygen is a vapour source of atomic oxygen;
• (b) providing an electrode;
• (c) delivering a flow of said lithium, said oxygen, said boron and said silicon, and, optionally, said dopant element, wherein the rate of flow of said oxygen is at least about 8×10−8 m3/s;
• and
• (d) co-depositing the component elements from the vapour sources onto the electrode, wherein:
• the component elements react on the electrode to form the amorphous compound;
• and
• the electrode is provided at a temperature of 110° C. when the component elements from the vapour sources are co-deposited onto the electrode, the temperature the substrate resulting in a relative dominance of silicate and orthosilicate from the co-deposition of the component elements.