Organic electrode materials are promising alternatives to transition-metal based intercalation compounds for the next generation of high-performance and sustainable batteries. Herein, a novel quinone-based organic, lithium salt of poly(2,5-dihydroxy-p-benzoquinonyl sulfide) (Li 2 PDHBQS), was successfully synthesized through a simple one-step polycondensation reaction, and applied as a cathode for Li-organic batteries. As an oligomeric lithium salt with average polymerization degree of 7, Li 2 PDHBQS combines the advantages of the O/Li/O coordination bond and increased molecular weight, thus solves absolutely the dissolution problem of active material in non-aqueous electrolytes, which has seriously hindered development of organic electrode materials. Benefiting from the high theoretical capacity, intrinsic insolubility, fast reaction kinetics of the quinone group, accelerated Li-ion transport and uniform blending with conductive carbon, as well as the stable amorphous structure, Li 2 PDHBQS shows superior comprehensive electrochemical performance including high reversible capacity (268 mA h g À1 ), high cycling stability (1500 cycles, 90%), high rate capability (5000 mA g À1 , 83%) andhigh Coulombic efficiency (99.9-100.1%). Investigation of the structure-property relationship of Li 2 PDHBQS and its analogues also gives new insights into developing novel quinone-based organic electrode materials, for building better Li-organic or Na-organic batteries beyond traditional Li-ion batteries. Broader contextAll electroactive organics or polymers involving reversible redox reactions have the potential to be applied as organic electrode materials for rechargeable batteries. Aer nearly half a century's exploration, conjugated carbonyl compounds are recognized as one of the most promising types among various electroactive materials, as only they have the potential to achieve simultaneously high energy density, high cycling stability and high power density. The conjugated carbonyl compounds can be divided into small organic molecules, organic polymers and organic salts according to the molecular structure, or quinones, dianhydrides, carboxylates, diketones and so on according to the electroactive group. Usually the redox potential of conjugated carbonyl compounds is between 1.5 and 3.0 V vs. Li + /Li, but carboxylates show relatively low redox potential below 1.0 V vs. Li + /Li, so they have the potential to be applied as either cathode or anode. As the theoretical specic capacity is up to 600 mA h g À1 , it is possible to achieve high energy density, although the redox potential is much lower than that of conventional inorganic cathodes. Research on this topic mainly focuses on solving the dissolution problem of active materials to improve the cycling stability, as well as developing new organic electrode materials with higher energy density.

A layered composite with P2 and O3 integration is proposed toward a sodium-ion battery with high energy density and long cycle life. The integration of P2 and O3 structures in this layered oxide is clearly characterized by XRD refinement, SAED and HAADF and ABF-STEM at atomic resolution. The biphase synergy in this layered P2+O3 composite is well established during the electrochemical reaction. This layered composite can deliver a high reversible capacity with the largest energy density of 640 mAh g(-1), and it also presents good capacity retention over 150 times of sodium extraction and insertion.

O3-type NaTi(0.5)Ni(0.5)O2 is explored as a titanium-based cathode material for sodium ion batteries. It delivers a reversible capacity of 121 mA h g(-1) at 0.2 C with smooth charge-discharge curves, and exhibits excellent cycling stability and good rate capability, indicating its superiority as a promising candidate electrode material for sodium ion batteries.

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Al ayered composite with P2 and O3 integration is proposed towardasodium-ion battery with high energy density and long cycle life.The integration of P2 and O3 structures in this layered oxide is clearly characterized by XRD refinement, SAED and HAADF and ABF-STEM at atomic resolution. The biphase synergy in this layered P2 + O3 composite is well established during the electrochemical reaction. This layered composite can deliver ahigh reversible capacity with the largest energy density of 640 mAh g À1 ,a nd it also presents good capacity retention over 150 times of sodium extraction and insertion.