Non-aqueous electrolyte secondary battery negative electrode material, making method, and lithium ion secondary battery
A non-aqueous electrolyte secondary battery negative electrode material is provided wherein a negative electrode active material containing a lithium ion-occluding and releasing material which has been treated with an organosilicon base surface treating agent is surface coated with a conductive coating. Using the negative electrode material, a lithium ion secondary battery having a high capacity and improved cycle performance is obtainable.
1. A negative electrode material for non-aqueous electrolyte secondary batteries, comprising:
a negative electrode active material containing a lithium ion-occluding and releasing material selected from the group consisting of (1) silicon particles having an average particle size of about 0.01 to 50 μm, (2) silicon oxide particles represented by the general formula SiO x wherein 1.0≦x<1.6 and having an average particle size of about 0.01 to 50 μm, (3) composite dispersion particles having an average particle size of about 0.01 to 50 μm where metallic silicon crystallites having an average particle size of about 1 to 500 nm are dispersed in a crystalline or amorphous silicon dioxide, and (4) mixtures thereof, wherein
the lithium ion-occluding and releasing material has been treated with an organosilicon base surface treating agent, and
the negative electrode active material is surface-coated with a conductive coating.
2. The negative electrode material of claim 1 wherein said organosilicon base surface treating agent is at least one member selected from the group consisting of a silane coupling agent or a (partial) hydrolytic condensate thereof, a silylating agent, and a silicone resin.
3. The negative electrode material of claim 1 wherein said conductive coating is a carbon coating.
4. The negative electrode material of claim 3 wherein the amount of carbon coating is 5 to 70% by weight of said negative electrode active material.
5. The negative electrode material of claim 1 , wherein
said lithium ion-occluding and releasing material is metallic silicon particles having an average particle size of 3.5 μm and a BET specific surface area of 4 m 2 /g or a silicon oxide particles SiO 1.02 having an average particle size of 1.1 μm and a BET specific surface area of 10.3 m 2 /g, and
said surface treating agent is vinyltrimethoxysilane, γ-methacryloxypropyl-trimethoxysilane, or hexamethyldisilazane.
6. A negative electrode material for non-aqueous electrolyte secondary batteries, comprising:
a negative electrode active material containing a lithium ion-occluding and releasing material which has been treated with an organosilicon base surface treating agent is at least one member selected from the group consisting of a silane coupling agent of the general formula (1) or a (partial) hydrolytic condensate thereof, a silylating agent of the general formula (2), and a silicone resin of the general formula (3),
R (4-n) Si(Y) n (1)
(R m Si) L (Y) p (2)
wherein R is a monovalent organic group, Y is a hydrolyzable group or hydroxyl group, n is an integer of 1 to 4, p is an integer of 1 to 3, L is an integer of 2 to 4, and m is an integer of 1 to 3,
R 1 q (R 2 O) r SiO (4-q-r)/2 (3)
wherein R 1 is hydrogen or a substituted or unsubstituted monovalent hydrocarbon group of 1 to 10 carbon atoms, R 2 is hydrogen or a substituted or unsubstituted monovalent hydrocarbon group of 1 to 6 carbon atoms, q and r each are 0 or a positive number satisfying 0≦q≦2.5, 0.01≦r≦3, and 0.5≦q+r≦3,
wherein the negative electrode active material is surface-coated with a conductive coating.
7. A lithium ion secondary battery comprising the negative electrode material of claim 1 or 6 as a negative electrode active material.