For　energy　storage　technologies,　secondary　batteries　have　the　merits　of　environmental　friendliness,　long　cyclic　life,　high　energy　conversion　efficiency　and　so　on,　which　are　considered　to　be　hopeful　large-scale　energy　storage　technologies.　Among　them,　rechargeable　lithium-ion　batteries　(LIBs)　have　been　commercialized　and　occupied　an　important　position　as　secondary　batteries　due　to　their　high　energy　density　and　long　cyclic　life.　Nevertheless,　the　uneven　distribution　of　lithium　resources　and　a　large　number　of　continuous　consumptions　result　in　a　price　increase　for　lithium.　So,　it　is　very　crucial　to　seek　and　develop　alternative　batteries　with　abundant　reserves　and　low　cost.　As　one　of　the　best　substitutes　for　widely　commercialized　LIBs,　sodium-ion　batteries　(SIBs)　display　gorgeous　application　prospects.　However,　further　improvements　in　SIB　performance　are　still　needed　in　the　aspects　of　energy/power　densities,　fast-charging　capability　and　cyclic　stability.　Electrode　materials　locate　at　a　central　position　of　SIBs.　In　addition　to　electrode　materials,　electrolytes,　conductive　agents,　binders　and　separators　are　imperative　for　practical　SIBs.　In　this　review,　the　latest　progress　and　challenges　of　applications　of　SIBs　are　reviewed.　Firstly,　the　anode　and　cathode　materials　for　SIBs　are　symmetrically　summarized　from　aspects　of　the　design　strategies　and　synthesis,　electrochemical　active　sites,　surrounding　environments　of　active　sites,　reaction　mechanisms　and　characterization　methods.　Secondly,　the　influences　of　electrolytes,　conductive　agents,　binders　and　separators　on　the　electrochemical　performance　are　elucidated.　Finally,　the　technical　challenges　are　summarized,　and　the　possible　future　research　directions　for　overcoming　the　challenges　are　proposed　for　developing　high　performance　SIBs　for　practical　applications.