Spinel　Co3O4,　as　conversion-type　transitional　metal　oxide,　has　attracted　extensive　interest　for　LIBs　anode　due　to　its　high　theoretical　capacity.　The　application　of　transitional　metal　oxide　including　Co3O4　anode　has　been　proved　challenging　due　to　voltage　hysteresis,　bad　rate　capability,　extremely　low　initial　Coulombic　efficiency　(typically　65　similar　to　70%),　and　volume　change　induced　mechanical　failure.　Among　the　facing　problems,　the　fundamental　understanding　of　severe　capacity　fading　at　high　C-rate　is　clearly　needed　to　be　unveiled.　In　this　paper,　we　utilized　in　situ　transmission　electron　microscopy　(TEM)　to　study　the　electrochemical　reaction　process　of　spinel　Co3O4　anode　and　firstly　unveiled　the　rate-dependent　morphological　and　structural　evolution　process.　It　has　been　demonstrated　that　the　structural　evolution　from　pristine　Co3O4　phase　to　the　formation　of　Co/Li2O　composites　during　lithiation　(bias　=similar　to　3　V).　Impressively,　the　Co/Li2O　composites　could　fully　delithiated　into　pure　tightly-contacted　CoO　crystals　(similar　to　1.45　nm)　at　lower　delithiated　bias　(+3　V);　while　the　lithiated　products　partially　transformed　into　the　CoO　crystals,　and　further　suffered　a　severe　aggregation　(similar　to　6　nm)　at　higher　delithiated　bias　(+8　V).　These　findings　advance　the　understanding　of　the　mechanism　of　capacity　fading　at　high　current　density　(C-rate)　in　conversion-type　spinel　Co3O4　anode　for　lithium　ion　batteries.　(C)　2018　Elsevier　B.V.　All　rights　reserved.