Cell Design and Materials: Li-Ion

Cathode Introduction Across rechargeable battery systems, the cathode is the positive electrode that primarily impacts a batteryʼs operating voltage, energy density, power capability, thermal behavior, and lifetime. Cathode materials vary widely by battery chemistry and may include metal oxides, phosphates, sulfides, or conversion-type compounds, each offering different trade-offs between performance, cost, safety, and durability. In lithium-ion batteries, cathodes are most commonly based on transition-metal compounds, such as lithium cobalt oxide LCO, lithium manganese oxide LMO, lithium nickel manganese cobalt oxide NMC, lithium nickel cobalt aluminum oxide NCA, and lithium iron phosphate LFP. The specific metal composition and crystal structure strongly influence voltage, energy density, rate capability, and long-term stability. Function of the cathode: During discharge, ions migrate from the anode through the electrolyte and are accepted and stored in the cathode while electrons flow through the external circuit to provide power. During charge, this process is reversed, with ions released from the cathode and transported back to the anode. The cathodeʼs structure and chemistry govern how efficiently ions can be stored and transported under different operating conditions.. Factors influencing cathode choice:

Energy density: How much energy the battery can store per unit mass or volume, driven by cathode capacity and operating voltage.

Power density: How quickly ions and electrons can move within the cathode structure to deliver high power.

Cycle life: The ability of the cathode to maintain capacity and voltage over repeated charge-discharge cycles.

Thermal Stability & Safety: Resistance to thermal runaway, oxygen release, or structural degradation under abuse or high temperature.

Cost & Supply Chain: Raw material availability, processing complexity, and exposure to critical or constrained elements.

Source: Redwood, ANL, Nature-lithium-ion battery cathode chemistry, Battery Report 20232024, Battery Talk: Battery Application Break Down 12/31/2025 Version 3.0

Extracted from the PDF; charts and images may read imperfectly.