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Highly conductive electrochemically active materials are required for developing a new generation of ultrafast lithium-ion batteries (LIBs). Recently, a novel family of transition metal coordination polymers derived from arylamines exhibited conductivities of over 1 S cm–1. Low molecular weight analogues of these materials show rich and reversible electrochemical behavior. However, there are just very few reports on the application of such materials in LIBs. In this paper, linear nickel(II) and copper(II) coordination polymers derived from 1,2,4,5-tetraaminobenzene are reported and investigated as anode and cathode materials for LIBs. In the anode mode, both materials show ultrafast cycling behavior with impressive stability. Particularly, for the nickel-based material, a specific capacity of 83 mA h g–1is reached at 20 A g–1current density, and 79% of this capacity is retained after 20 000 cycles. Moreover, the copper-based polymer used as a cathode component shows a specific capacity of up to 262 mA h g–1in the voltage range of 1.5–4.1 V vs Li/Li+, which corresponds to the energy density of 616 W h kg–1.

Lithium iron phosphate LiFePO4triphylite is now one of the core positive electrode (cathode) materials enabling the Li-ion battery technology for stationary energy storage applications, which are important for broad implementation of the renewable energy sources. Despite the apparent simplicity of its crystal structure and chemical composition, LiFePO4is prone to off-stoichiometry and demonstrates rich defect chemistry owing to variations in the cation content and iron oxidation state, and to the redistribution of the cations and vacancies over two crystallographically distinct octahedral sites. The importance of the defects stems from their impact on the electrochemical performance, particularly on limiting the capacity and rate capability through blocking the Li-ion diffusion along the channels of the olivine-type LiFePO4structure. Up to now, the polyanionic (i.e., phosphate) sublattice has been considered idle in this case. Here, we demonstrate that under hydrothermal conditions up to 16% of the phosphate groups can be replaced with hydroxyl groups yielding the Li1–xFe1+x(PO4)1–y(OH)4ysolid solutions, which we term “hydrotriphylites”. This substitution has a tremendous effect on the chemical composition and crystal structure of the lithium iron phosphate causing abundant population of the Li-ion diffusion channels with the iron cations and off-center Li displacements due to their tighter bonding to oxygens. These perturbations trigger the formation of an acentric structure and increase the activation barriers for the Li-ion diffusion. The hydrotriphylite-type substitution also affects the magnetic properties by progressively lowering the Néel temperature. The off-stoichiometry caused by this substitution critically depends on the overall concentration of the precursors and reducing agents in the hydrothermal solutions, placing it among the most important parameters to control the chemical composition and defect concentration of the LiFePO4-based cathodes.