Flexible　lithium-ion　batteries　(LIBs)　with　high　energy　density　are　highly　desirable　for　wearable　electronics.　However,　difficult　to　achieve　excellent　flexibility　and　high　energy　density　simultaneously　via　the　current　approaches　for　designing　flexible　LIBs.　To　mitigate　the　mismatch,　mechano-graded　electrodes　with　gradient-distributed　maximum　allowable　strain　are　proposed　to　endow　high-loading-mass　slurry-coating　electrodes　with　brilliant　intrinsic　flexibility　without　sacrificing　energy　density.　As　a　proof-of-concept,　the　up-graded　LiNi1/3Mn1/3Co1/3O2　cathodes　(≈15 mg　cm−2,　≈70 µm)　and　graphite　anodes　(≈8 mg　cm−2,　≈105 µm)　can　tolerate　an　extremely　low　bending　radius　of　400　and　600 µm,　respectively.　Finite　element　analysis　(FEA)　reveals　that,　compared　with　conventionally　homogeneous　electrodes,　the　flexibility　of　the　up-graded　electrodes　is　enhanced　by　specifically　strengthening　the　upper　layer　and　avoiding　crack　initiation.　Benefiting　from　this,　the　foldable　pouch　cell　(required　bending　radius　of　≈600 µm)　successfully　realizes　a　remarkable　figure　of　merit　(FOM,　energy　density　vs　bending　radius)　of　121.3　mWh　cm−3.　Moreover,　the　up-graded-electrodes-based　pouch　cells　can　deliver　a　stable　power　supply,　even　under　various　deformation　modes,　such　as　twisting,　folding,　and　knotting.　This　work　proposes　new　insights　for　harmonizing　the　mechanics　and　electrochemistry　of　energy　storage　devices　to　achieve　high　energy　density　under　flexible　extremes.　©　2022　Wiley-VCH　GmbH.