Li8ZrO6　is　a　pseudolamellar　compound　with　high　lithium　content.　Even　though　it　is　intrinsically　a　poor　conductor　and　does　not　contain　a　transition　metal　with　easily　variable　oxidation　states,　a　new　synthetic　approach　to　preparing　it　in　nanocomposite　form　with　intimate　contact　to　a　conductive　carbon　by　mechanical　delamination　enabled　galvanostatic　cycling　of　coin　half-cells　containing　Li8ZrO6/C　as　the　cathode　and　Li　metal　as　the　anode　at　221　mAh/g　(which　corresponds　to　extracting　2　Li　per　formula　unit)　over　at　least　140　cycles.　With　a　higher　capacity　limit,　a　discharge　capacity　of　331　mAh/g　(which　corresponds　to　extracting　3　Li　per　formula　unit)　was　maintained　over　15-20　cycles.　Ex　situ　and　operando　X-ray　diffraction　(XRD)　studies　of　galvanostatically　cycled　cells　showed　that　at　these　levels　of　charge,　delithiation　follows　a　reversible,　topotactic　path　with　only　small　distortions　around　Zr　atoms.　During　this　process,　crystalline　grain　sizes　decrease　continuously,　shortening　diffusion　lengths　within　grains　but　increasing　the　number　of　grain　boundaries　and　electrode/electrolyte　interfaces.　Charge　storage　in　Li8ZrO6　appears　to　involve　partial　oxidation　of　oxygen　atoms　and　production　of　small-polaron　holes,　as　supported　by　XRD,　X-ray　photoelectron　spectroscopy,　and　pair-distribution　function　studies　and　predicted　by　quantum　mechanical　calculations.　At　higher　depths　of　charge,　delithiation　results　in　amorphization　of　the　active　electrode　material.　The　charge　storage　mechanism　in　Li8ZrO6　is　unusual　among　lithium-ion　battery　electrode　materials　and　involves　a　combination　of　mechanisms　that　resemble　intercalation　and　conversion　reactions.　With　further　refinement,　Li8ZrO6/C　based　materials　open　up　opportunities　to　develop　new　cathode　materials　for　lithium-ion　batteries　that　may　improve　on　currently　existing　capacity　barriers.　©　Copyright　2019　American　Chemical　Society.