Cell Chemistry & Components

Battery cells are the core of an EV battery pack. While each cell contains several important components, the choice of chemistry has the biggest impact on cost, energy density, charging performance, durability, and safety.

This article explains the main parts of a lithium-ion battery cell and the most important chemistries used in EVs today.

Anode

The anode is one of the two electrodes in a lithium-ion battery, the other being the cathode. During discharge, lithium ions leave the anode and move through the electrolyte toward the cathode, while electrons flow through the external circuit to power the vehicle. During charging, the process is reversed, and lithium ions move back to the anode.

In most EV batteries, the anode is primarily made of graphite. Graphite has a layered structure that allows lithium ions to be stored between its layers during charging and released again during discharge.

The anode has a major influence on charging performance, energy density, efficiency, and battery life. A good anode material needs high lithium storage capacity, good conductivity, structural stability, and long cycle life.

Graphite remains the dominant anode material in EV batteries, but manufacturers are gradually adding silicon to improve energy density. Silicon can store more lithium than graphite, but it also expands significantly during charging, which makes durability and long-term stability more difficult.

Cathode

The cathode is the other main electrode in the battery cell. During discharge, it receives lithium ions from the electrolyte and electrons from the external circuit. During charging, lithium ions leave the cathode and move back toward the anode.

In most discussions about EV battery chemistry, the cathode chemistry is the main focus. That is because the cathode has the largest influence on cell cost, voltage, energy density, thermal behavior, and material supply chain requirements.

Most EV batteries today are lithium-ion, with NMC, NCA, and LFP as the dominant chemistries. LMFP and sodium-ion are newer alternatives that may expand in the coming years.

Lithium Nickel Manganese Cobalt Oxides (NMC)

NMC is one of the most widely used cathode families in EV batteries. It offers a strong balance between energy density, performance, and durability, which makes it suitable for many types of electric vehicles.

Different NMC variants are named according to the ratio of nickel, manganese, and cobalt, such as NMC111, NMC532, NMC622, and NMC811. In general, higher nickel content can increase energy density, but it can also make thermal management, durability, and material stability more challenging.

NMC is commonly used in EVs where higher range and strong overall performance are priorities.

Lithium Nickel Cobalt Aluminum Oxides (NCA)

NCA is another nickel-rich cathode chemistry designed for high energy density. It has been used in EV batteries where long driving range and strong performance are important.

Compared with many other chemistries, NCA offers high specific energy, but it also places high demands on thermal management and battery control systems. It is less common across the wider EV market than NMC and LFP, but it remains an important chemistry in some applications.

Lithium Iron Phosphate (LFP)

LFP is a cathode chemistry known for strong thermal stability, long cycle life, and relatively low cost. Compared with nickel-based chemistries such as NMC and NCA, LFP usually has lower energy density, but it offers important advantages in safety, durability, and affordability.

These characteristics have made LFP increasingly important in EVs, especially in models where cost, long life, and robust daily use matter more than maximizing range from a given battery size.

Advantages of LFP

• High thermal stability
• Long cycle life
• Lower cost than most nickel-based chemistries
• Lower dependence on nickel and cobalt

Disadvantages of LFP

• Lower energy density than NMC and NCA
• Typically weaker cold-weather performance
• Larger and heavier packs for the same energy content

Lithium Manganese Iron Phosphate (LMFP)

LMFP is an emerging cathode chemistry based on LFP, but with manganese added to increase voltage and improve energy density.

The goal of LMFP is to retain many of LFP's strengths, such as good safety, long cycle life, and relatively low cost, while narrowing the energy-density gap to nickel-based chemistries. This makes LMFP attractive for future EV applications, but it is still less established than LFP, NMC, and NCA.

Potential advantages of LMFP

• Higher energy density than LFP
• High thermal stability
• Good cycle life
• Lower cost than many nickel-rich chemistries

Challenges of LMFP

• Lower conductivity than some competing chemistries
• More demanding material and cell engineering
• Less mature large-scale adoption than LFP and NMC

Sodium-ion

Sodium-ion batteries work in a broadly similar way to lithium-ion batteries, but use sodium instead of lithium as the charge carrier. Their main appeal is lower dependence on lithium and the potential for lower material costs.

For EVs, sodium-ion is generally seen as most promising in lower-cost vehicles and applications where energy density is less critical than cost, durability, and temperature robustness. However, sodium-ion is still less established than LFP, NMC, and NCA, and is expected to remain a minority chemistry in EVs for the next several years.

Potential advantages of sodium-ion

• Lower dependence on lithium
• Potential for lower material cost
• Good low-temperature performance
• Attractive for cost-focused applications

Challenges of sodium-ion

• Lower energy density than leading lithium-ion chemistries
• Less mature supply chain and manufacturing scale
• Limited use in long-range EVs today

Summary of Cathode Materials

Separator

The separator is a thin porous membrane placed between the anode and cathode. Its job is to keep the two electrodes physically apart to prevent an internal short circuit while still allowing lithium ions to move between them through the electrolyte.

A separator must combine mechanical strength, chemical stability, and good ion permeability. It also plays an important role in battery safety.

Common separator materials include polyethylene (PE), polypropylene (PP), and more advanced coated or ceramic-reinforced designs.

Electrolyte

The electrolyte is the medium that allows lithium ions to move between the anode and cathode. In most lithium-ion batteries used in EVs today, the electrolyte is a liquid made from lithium salts dissolved in organic solvents.

The electrolyte is critical for conductivity, charging behavior, temperature performance, and safety. It must transport ions efficiently while remaining stable across the battery's operating voltage and temperature range.

Future battery designs may use semi-solid or solid electrolytes to improve safety and potentially enable higher energy density. However, these technologies are still more complex and less mature than conventional liquid-electrolyte lithium-ion cells.

Current Collectors

Current collectors carry electrons between the active electrode materials and the external circuit. In lithium-ion cells, they are usually thin metal foils.

The anode side typically uses copper, while the cathode side typically uses aluminum. These materials are chosen because they combine good conductivity, low weight, and compatibility with the electrochemical environment inside the cell.

Although current collectors are simple compared with the active materials, they still affect resistance, efficiency, durability, and cell weight.

The next step is to look at how battery cells are packaged, as cell format and housing also affect cost, cooling, durability, and energy density.