Method for preparing porous silicon cathode material by polyvinyl alcohol freezing-unfreezing crosslinked carbonization

The invention relates to an environmental friendly method for preparing a cathode piece of a lithium ion battery, and more specifically, relates to a method for preparing a porous silicon cathode material by polyvinyl alcohol freezing-unfreezing crosslinked carbonization. The method comprises the following steps: coating a silicon material by polyvinyl alcohol macromolecules, generating a cross-linked network by a freezing-unfreezing process, and partially carbonizing an organic matter. When the conductivity of a silicon electrode is effectively improved, a pore structure effectively increases the contact area of the silicon material and the electrolyte, which is more beneficial for the transmission of lithium ions. A constant current charge-discharge test is carried out on a lithium ion button cell prepared from the porous silicon cathode piece, after a cycle of 50 weeks under a condition of 0.1C (400Ma.g-1), the charge-discharge specific capacity can be maintained at about 800 mAh.g-1.