ONYX Battery Chemistry Guide: NMC, NCA, LFP, LTO and Solid-State

This page is part of the ONYX Battery Guide

This guide explains the battery chemistries and emerging battery technologies relevant to ONYX RCR and CTY2 builds, including their effects on energy density, power capability, cycle life, thermal stability, weight, and battery packaging.

Battery chemistry is only one part of battery performance. Cell construction, internal resistance, series and parallel configuration, BMS capability, bus bars, wiring, connectors, temperature, and controller demand also determine how a complete ONYX battery performs.

For specific 21700 cell recommendations and tabless cell technology, see the ONYX Battery Cells: Tabless 21700 Performance Guide.

For complete AMORGE battery configurations, capacities, current ratings, fitment, and pricing, see ONYX AMORGE Batteries: RCR and CTY2 Options.

Battery Chemistry and ONYX Performance

Battery chemistry affects several important characteristics of a battery pack:

• Energy density
• Power capability
• Cycle life
• Thermal stability
• Temperature performance
• Battery weight
• Battery volume
• Cost

For an ONYX RCR or CTY2, energy density and power capability are especially important because battery space is limited while performance builds can place substantial current demands on the pack.

There is no single battery chemistry that is best for every application. Higher energy density, longer cycle life, greater thermal stability, lower weight, and higher power capability involve different engineering tradeoffs.

These characteristics are general comparisons rather than fixed specifications. Actual battery performance depends on the specific cell design, operating temperature, charge voltage, depth of discharge, current, and complete pack construction.

NMC: The Practical ONYX Performance Chemistry

Lithium nickel manganese cobalt oxide (NMC) is a family of layered-oxide cathode materials used extensively in lithium-ion batteries.

NMC provides a useful combination of:

• High energy density
• Strong power capability
• Reasonable cycle life
• Compact battery packaging

This combination is particularly useful for performance-oriented electric vehicles where both battery volume and weight are limited.

For an ONYX RCR or CTY2, packaging efficiency matters because increasing battery size is constrained by the physical space available in the frame. A chemistry that stores more energy within a given volume can provide more usable battery energy without requiring the much larger pack that lower-energy-density technologies may require.

NMC-family cells therefore provide a practical balance for ONYX applications where range, power, weight, and physical battery size all matter.

Cycle life should not be treated as a fixed property of NMC chemistry. Temperature, maximum charge voltage, depth of discharge, discharge current, charging rate, and individual cell design can substantially affect how long an NMC battery lasts.

NCA

Lithium nickel cobalt aluminum oxide (NCA) is another high-energy layered-oxide cathode chemistry.

NCA is associated with:

• Very high energy density
• Strong power capability
• Low battery weight for a given amount of stored energy
• Greater thermal-management considerations than more thermally stable chemistries such as LFP

NCA has historically been important in cylindrical lithium-ion cells and electric vehicle applications where maximizing energy density is a major design objective.

For an ONYX battery, the primary attraction would be packaging efficiency. High energy density can allow more stored energy without substantially increasing battery volume or weight.

However, the exact performance and thermal behavior of an NCA cell still depend on the individual cell design and battery management system. NCA should therefore be evaluated at the cell and pack level rather than selected based on chemistry alone.

LFP

Lithium iron phosphate (LFP) prioritizes thermal stability, longevity, and durability over maximum energy density.

Its primary advantages include:

• Very high thermal stability
• Long cycle life
• Strong durability
• Good power capability
• No nickel or cobalt in the cathode

The primary tradeoff for an ONYX application is energy density.

Compared with higher-energy-density nickel-based lithium-ion cells, an LFP battery generally requires more mass and/or physical volume to store a comparable amount of energy in watt-hours.

This distinction is important. Comparing batteries only by amp-hour capacity can be misleading because battery voltage also determines stored energy.

For an ONYX RCR or CTY2, where battery compartment volume is limited, the additional size required for comparable stored energy can make LFP less practical for builds focused on maximum range and performance within the available space.

LFP can still make sense when cycle life, thermal stability, and durability are more important than maximum energy density or minimum battery size.

LTO

Lithium titanate (LTO) is somewhat different from NMC, NCA, LFP, and LMO because LTO normally refers to the anode material, not the cathode chemistry.

Conventional lithium-ion cells commonly use graphite-based anodes. LTO cells instead use lithium titanate as the anode material.

LTO is known for:

• Extremely long cycle life
• Very high charge capability
• Strong power capability
• Excellent low-temperature performance
• Very high thermal stability

The major disadvantage is low energy density.

For an ONYX battery, this creates a substantial packaging problem. Storing comparable energy would generally require considerably more battery mass and volume than a high-energy lithium-ion configuration.

The combination of low energy density, different cell-voltage characteristics, physical size requirements, and cost makes LTO generally impractical for conventional ONYX RCR and CTY2 battery upgrades despite its exceptional longevity.

LMO

Lithium manganese oxide (LMO) is a manganese-based lithium-ion cathode chemistry known for relatively strong power capability and good thermal characteristics.

LMO generally provides:

• Moderate energy density
• High power capability
• Good thermal stability
• Lower material cost
• Shorter cycle life than chemistries optimized primarily for longevity

LMO has been used independently and in blended cathode systems where manufacturers can balance power capability, energy density, cost, and durability.

For current ONYX battery selection, LMO is less important as a standalone recommendation than NMC-family high-energy cells, but it remains useful for understanding the development and design of lithium-ion battery chemistry.

Chemistry Does Not Determine Battery Performance Alone

Two batteries using the same general chemistry can perform very differently.

Complete battery performance also depends on:

• Cell construction
• Internal resistance
• Cell capacity
• Series configuration
• Parallel configuration
• BMS current limits
• Bus bar and cell interconnection design
• Wiring gauge
• Discharge connectors
• State of charge
• Battery temperature
• Controller current demand
• Pack thermal design

A high-power chemistry does not automatically produce a high-power battery.

For example, a battery using high-performance cells can still be limited by its BMS, bus bars, wiring, connectors, or thermal design. Likewise, increasing the number of parallel cells can reduce the electrical load placed on each individual cell.

Cell construction also matters independently of chemistry. Tabless 21700 cells can reduce internal resistance and improve current distribution without changing the fundamental cathode chemistry category.

For specific cell construction, current ratings, and recommendations, see the ONYX Battery Cells: Tabless 21700 Performance Guide.

Cathode Chemistry vs Battery Architecture

Terms such as NMC, NCA, LFP, LMO, lithium metal, and solid-state are sometimes grouped together even though they describe different parts of a battery.

This distinction becomes particularly important when discussing next-generation batteries.

A solid-state battery, for example, can still use an NMC-family cathode. “Solid-state” describes the electrolyte architecture and does not by itself identify the cathode chemistry.

Emerging Battery Technologies

Several next-generation battery technologies are being developed to improve energy density, safety, cycle life, charging performance, and manufacturing efficiency.

These technologies are important to future electric vehicles, but they should not currently be treated as practical replacements for established lithium-ion cells in an ONYX battery build.

Solid-State and Semi-Solid-State Batteries

Traditional lithium-ion batteries use a liquid electrolyte to transport lithium ions between the electrodes.

Solid-state batteries replace some or all of that liquid electrolyte with a solid electrolyte. Depending on the design, the electrolyte may use ceramic, sulfide, polymer, halide, or other solid materials.

Semi-solid and hybrid systems retain some liquid or gel-like electrolyte components while incorporating technologies intended to reduce the amount of conventional liquid electrolyte or change how active materials are structured.

Potential advantages include:

• Higher energy-density potential
• Reduced reliance on flammable liquid electrolyte
• Compatibility with lithium-metal anodes
• Potential improvements in thermal stability

However, solid-state batteries still face major engineering challenges, including:

• Electrode-electrolyte interface resistance
• Maintaining physical contact between solid layers
• Lithium dendrite formation
• Material cracking and mechanical stress
• Manufacturing complexity
• Production cost
• Scaling to high-volume manufacturing

Solid electrolytes do not automatically eliminate lithium dendrites. Lithium can still penetrate or propagate through solid electrolyte materials under certain operating conditions, potentially causing internal short circuits.

Likewise, replacing a flammable liquid electrolyte can potentially improve safety, but the safety of the complete battery still depends on electrode materials, interfaces, cell construction, manufacturing quality, mechanical damage, and pack design.

Lithium-Metal Anodes

Conventional lithium-ion batteries generally store lithium within a host material such as graphite at the anode.

A lithium-metal anode instead uses metallic lithium.

Lithium metal has extremely high theoretical specific capacity, making it attractive for batteries designed to achieve substantially higher energy density.

The major challenges include:

• Dendrite formation
• Unstable interfaces
• Loss of active lithium
• Reduced cycling efficiency
• Mechanical changes during cycling

Lithium-metal anodes are frequently discussed alongside solid-state batteries because solid electrolytes are being investigated as one way to enable practical lithium-metal cells.

However, lithium metal and solid-state are separate concepts. A battery can use a solid electrolyte without necessarily using a lithium-metal anode.

Lithium-Sulfur

Lithium-sulfur (Li-S) batteries use sulfur-based cathode chemistry and commonly pair it with a lithium-metal anode.

Sulfur offers very high theoretical specific energy and is abundant compared with nickel- and cobalt-containing cathode materials.

Potential advantages include:

• Very high theoretical specific energy
• Lightweight active materials
• Reduced reliance on nickel and cobalt
• Abundant sulfur feedstock

The theoretical energy potential should not be confused with the energy density of a complete practical battery cell.

Real lithium-sulfur cells must include electrolyte, current collectors, separators, packaging, conductive materials, and other inactive components. These substantially reduce practical cell-level energy density compared with theoretical calculations based primarily on active materials.

Current engineering challenges include:

• Polysulfide shuttle
• Sulfur and lithium sulfide conductivity
• Lithium-metal anode stability
• Dendrite formation
• Electrolyte requirements
• Capacity degradation
• Cycle life

Recent lithium-sulfur research continues to demonstrate high practical energy-density potential, but maintaining that energy density while achieving long cycle life remains a major challenge.

What Chemistry Makes Sense for an ONYX?

For an ONYX RCR or CTY2, the battery must fit within a relatively constrained physical space while supplying substantial energy and, in performance builds, very high current.

That combination favors lithium-ion cells with high energy density and strong power capability.

NMC-family and related high-energy lithium-ion cells currently provide a practical balance of:

• Energy density
• Power capability
• Battery weight
• Battery volume
• Availability
• Pack design flexibility

LFP offers excellent thermal stability and longevity, but storing comparable energy generally requires additional battery mass and/or volume.

LTO pushes longevity and power capability even further but carries a much larger energy-density and packaging penalty.

Solid-state, lithium-metal, and lithium-sulfur technologies have the potential to change these tradeoffs in the future, but they are not currently the technologies around which I would design a conventional ONYX RCR or CTY2 battery upgrade.

For the specific 21700 cells I currently recommend for ONYX builds, see the ONYX Battery Cells: Tabless 21700 Performance Guide.

For current battery sizes, voltage configurations, capacities, current ratings, fitment, and pricing, see ONYX AMORGE Batteries: RCR and CTY2 Options.