Numerous materials are required in the actual production of lithium batteries, including cathode and anode materials, separators, electrolytes, N-methylpyrrolidone (NMP), polyvinylidene fluoride (PVDF), aluminum foil, copper foil, aluminum strips, nickel strips, and vacuum-formed parts. Among these, cathode materials, anode materials, separators, and electrolytes are considered critical components, as the performance of lithium-ion batteries primarily depends on these key materials. In the material cost of lithium battery manufacturing, cathode materials account for the largest proportion, exceeding 30%. Therefore, researching high-quality, low-cost cathode materials is one of the key tasks in the development of lithium-ion batteries.
Since the inception of lithium-ion batteries, their development has been a winding journey. Although numerous cathode materials have emerged over time, only a handful have achieved commercialization. An ideal cathode material for lithium-ion batteries must exhibit the following electrochemical properties:
- Possess a layered or tunnel-like crystal structure to facilitate lithium ion insertion and extraction. The structure must be robust and exhibit excellent stability across the charge-discharge voltage range, ensuring good charge-discharge reversibility and guaranteeing the battery’s cycle life;
- Enable the maximum possible number of lithium ions to be inserted and extracted during charging and discharging, resulting in high electrochemical capacity;
- The free energy change of electrode reactions during lithium ion insertion/extraction should be minimal, enabling stable charge/discharge voltage profiles and facilitating widespread application of lithium-ion batteries;
- Possess a high diffusion coefficient to minimize energy loss from polarization, ensuring superior fast-charge/discharge performance;
- Feature low molecular weight to enhance weight energy density; exhibit low molar volume to improve volumetric energy density.
Additionally, from a practical standpoint, cathode materials should feature abundant raw material sources, low cost, ease of industrialization, and environmental sustainability.
Currently researched cathode materials fall into two categories: pure-phase and modified types. Pure-phase materials include cobalt oxides, nickel oxides, manganese oxides, vanadium oxides, polyatomic anion cathode materials, and other cathode materials.
