Modified natural graphite material used in lithium ion battery negative electrodes, and preparation method thereof

The invention discloses a modified natural graphite material used in lithium ion battery negative electrodes. With a core-shell structure, the material comprises an inner core and a shell coated on the inner-core. The inner-core is composed of natural graphite, and the shell coated on the core is composed of an inner shell and an outer shell. The inner shell is a boron-containing hard carbon layer, and the outer shell is a soft carbon layer. The boron-containing hard carbon layer is coated on natural graphite, and the soft carbon layer is coated on the boron-containing hard layer. The method has advantages of simple technology, suitability for mass production, low graphitization processing temperature, and low cost. With advantages of small specific surface area, high tap density, high first efficiency, high specific capacity, excellent cycling performance, and good rate performance, the modified natural graphite material can be applied in power batteries.