Solid-state　lithium　metal　batteries　(SSLMBs)　are　now　under　intensive　research　for　their　high　energy　density　and　excellent　safety.　However,　the　Li　transport　limitation　in　Li　metal　anode　(LMA)　leads　to　mass/stress　accumulation,　dendrite　initiation　and　void　formation　at　the　interface,　which　seriously　hinders　the　development　of　SSLMBs.　Herein,　it　is　demonstrated　through　in　situ　electron　microscopies　that　a　mixed　ionic-electronic　conducting　(MIEC)　3D　host　can　promote　the　Li　transport　in　LMA　by　increasing　the　diffusion　pathways　along　the　carbonaceous　framework,　carbon/Li　interface　and　Li　metal　surface,　enabling　a　fast　and　long-distance　(nearly　100　mu　m)　diffusion　of　Li　atoms　in　LMA.　Consequently,　the　spatio-temporal　sequence　of　Li　plating/stripping　can　be　fundamentally　changed.　Specifically,　both　deposition　and　dissolution　can　occur　far　away　from　the　interface,　thereby　mitigating　the　dendrite　and　void　issues.　Impressively,　the　resulting　cells　with　carbonaceous　hosts　can　achieve　excellent　cyclability　and　the　highest　capacity　(28.8　mAh　cm(-2))　so　far.　This　work　provides　valuable　insight　for　understanding　Li　transport　and　deposition/dissolution　mechanisms　in　MIEC　host-based　LMAs,　and　a　feasible　solution　for　tackling　the　interface　issues　without　involving　stack　pressure　in　SSLMBs.