LiNiPO4

LiNiPO4 is an inorganic compound in the lithium metal phosphate family that has been studied as a cathode material for lithium-ion batteries. It adopts the olivine-type structure, with Li+ occupying one channel and a framework built from PO4 tetrahedra linked to Ni2+ centers. The material crystallizes in an orthorhombic lattice, typically described as an olivine structure similar to LiFePO4, with a space group that supports one-dimensional Li+ diffusion pathways along the crystal framework.

In electrochemical terms, LiNiPO4 operates via the Ni2+/Ni3+ redox couple, enabling Li+ extraction and insertion during charge and discharge. The theoretical capacity is about 170 mAh/g (one electron per formula unit), reflecting the single-Li per formula unit stoichiometry. The average operating voltage is high, commonly reported around 4.8–5.0 V versus Li+/Li, which implies high theoretical energy density but also imposes strict requirements on electrolyte stability and cell design.

Synthesis and material engineering efforts often employ solid-state routes from precursors such as Li2CO3, NiO, and NH4H2PO4, as well as hydrothermal or solvothermal methods to produce nanoscale particles. To address inherently poor electronic conductivity and relatively slow Li+ diffusion, researchers explore carbon coatings, dopants (for example Mg or Al), nanosizing, and conductive composite architectures.

Despite its attractive theoretical energy density, LiNiPO4 faces practical limitations, including sluggish ionic and electronic transport, high-voltage electrolyte oxidation, and capacity fade during cycling. As a result, it remains primarily the subject of academic research rather than a widely adopted commercial cathode material. Ongoing work focuses on stabilizing high-voltage operation and improving rate capability through advanced synthesis and cell chemistry.