Low　electronic　and　ionic　transport,　limited　cathode　active　material　utilization,　and　significant　volume　change　have　pledged　the　practical　application　of　all-solid-state　Li/S　batteries　(ASSLSBs).　Herein,　an　unprecedented　Li2S-LixIn2S3　cathode　is　designed　whereby　In(2)S(3)reacts　with　Li2S　under　high-energy　ball　milling.　In　situ　electron　diffraction　and　ex　situ　XPS　are　implanted　to　probe　the　reaction　mechanism　of　Li2S-LixIn2S3　in　ASSLSBs.　The　results　indicate　that　LixIn(2)S(3)　serves　as　a　mobility　mediator　for　both　charge-carriers　(Li+　and　e(-))　and　redox　mediator　for　Li2S　activation,　ensuring　efficient　electronic　and　ionic　transportation　at　the　cathode　interface　and　inhibiting　approximate　to　70%　relative　volumetric　change　in　the　cathode,　as　confirmed　by　in　situ　TEM.　Thus,　the　Li2S-LixIn2S3　cathode　delivers　an　initial　areal　capacity　of　3.47　mAh　cm(-2)　at　4.0　mgLi(2)S　cm(-2)　with　78%　utilization　of　Li2S.　A　solid-state　cell　with　Li2S-LixIn2S3　cathode　carries　82.35%　capacity　retention　over　200　cycles　at　0.192　mA　cm(-2　)and　a　remarkable　rate　capability　up　to　0.64　mA　cm(-2　)at　RT.　Besides,　Li2S-LixIn2S3　exhibits　the　highest　initial　areal　capacity　of　4.08　mAh　cm(-2)　with　approximate　to　74.01%　capacity　retention　over　50　cycles　versus　6.6　mgLi(2)S　cm(-2)　at　0.192　mA　cm(-2)　at　RT.　The　proposed　strategy　of　the　redox　mediator　minimized　volumetric　change　and　realized　outstanding　electrochemical　performance　for　ASSLSBs.