The　resourceful　and　inexpensive　red　phosphorus　has　emerged　as　a　promising　anode　material　of　potassium-ion　batteries　(PIBs)　for　its　large　theoretical　capacities　and　low　redox　potentials　in　the　multi-electron　alloying/dealloying　reactions,　yet　chronically　suffering　from　the　huge　volume　expansion/shrinkage　with　a　sluggish　reaction　kinetics　and　an　unsatisfactory　interfacial　stability　against　volatile　electrolytes.　Herein,　we　systematically　developed　a　series　of　localized　high-concentration　electrolytes　(LHCE)　through　diluting　high-concentration　ether　electrolytes　with　a　non-solvating　fluorinated　ether　to　regulate　the　formation/evolution　of　solid　electrolyte　interphases　(SEI)　on　phosphorus/carbon　(P/C)　anodes　for　PIBs.　Benefitting　from　the　improved　mechanical　strength　and　structural　stability　of　a　robust/uniform　SEI　thin　layer　derived　from　a　composition-optimized　LHCE　featured　with　a　unique　solvation　structure　and　a　superior　K+　migration　capability,　the　P/C　anode　with　noticeable　pseudocapacitive　behaviors　could　achieve　a　large　reversible　capacity　of　760　mA　h　g−1　at　100　mA　g−1,　a　remarkable　capacity　retention　rate　of　92.6%　over　200　cycles　at　800　mA　g−1,　and　an　exceptional　rate　capability　of　334　mA　h　g−1　at　8000　mA　g−1.　Critically,　a　suppressed　reduction　of　ether　solvents　with　a　preferential　decomposition　of　potassium　salts　in　anion-derived　interfacial　reactions　on　P/C　anode　for　LHCE　could　enable　a　rational　construction　of　an　outer　organic-rich　and　inner　inorganic-dominant　SEI　thin　film　with　remarkable　mechanical　strength/flexibility　to　buffer　huge　volume　variations　and　abundant　K+　diffusion　channels　to　accelerate　reaction　kinetics.　Additionally,　the　highly　reversible/durable　full　PIBs　coupling　P/C　anodes　with　annealed　organic　cathodes　further　verified　an　excellent　practical　applicability　of　LHCE.　This　encouraging　work　on　electrolytes　regulating　SEI　formation/evolution　would　advance　the　development　of　P/C　anodes　for　high-performance　PIBs.　©　2023　Science　Press　and　Dalian　Institute　of　Chemical　Physics,　Chinese　Academy　of　Sciences