1. What Are the Primary Constituents of Lithium Batteries?
Lithium batteries are composed of four essential components: the cathode material, anode material, electrolyte, and separator. Each of these elements plays a crucial role in the battery’s performance and efficiency.
The electrolyte serves as a conduit for the transfer of lithium ions between the positive and negative electrodes. It is typically composed of organic solvents and lithium salts.
One commonly used lithium salt is lithium hexafluorophosphate, which is essential for facilitating ion transfer within the battery.
Positioned between the positive and negative electrodes, the separator’s primary function is to prevent internal short circuits. Additionally, it enables the passage of lithium ions while creating a conductive pathway, essential for the battery’s operation.
● Cathode Materials
Cathode materials come in various types, including ternary materials（NCM,NCA）, lithium iron phosphate, lithium manganese oxide, and lithium cobalt oxide.
These materials define the battery’s characteristics and performance, making them a critical factor in battery technology.
Understanding the components of lithium batteries, including their electrolytes, separators, and cathode materials, is crucial for developing more efficient and sustainable lithium-ion battery solutions. This knowledge is essential in the pursuit of cleaner and more advanced energy technologies.
Lithium carbonate plays a pivotal role as a primary source of lithium for the production of various cathode materials. When combined with other compounds, it serves as the foundation for synthesizing critical materials such as lithium iron phosphate (LiFePO4), ternary nickel cobalt manganese (NCM), lithium manganese oxide, and lithium cobalt oxide. Among these, LiFePO4 and NCM materials stand out as the most widely utilized cathode materials in battery technology.
2. What Are the Roles of Different Elements in NCM/NCA Lithium Materials?
Ternary elements, commonly recognized as nickel, cobalt, and manganese (NCM), as well as nickel, cobalt, and aluminum (NCA). The numbers following NCM denote the relative proportions of these three elements, as illustrated in the figure below.
Each of these elements has distinct responsibilities within the positive electrode material, contributing to the overall performance of the battery:
● Nickel (Ni)
Nickel is primarily employed to boost energy density, resulting in increased battery capacity.
This enhancement in energy density enables batteries to store and deliver more power, making them ideal for high-performance applications.
● Cobalt (Co)
Cobalt plays a crucial role in stabilizing the layered structure of the positive electrode material.
This structural stability enhances material magnification and cycling performance, contributing to longer-lasting and more reliable batteries.
● Manganese (Mn) or Aluminum (Al)
Manganese or aluminum is incorporated into the mix to enhance battery stability and safety.
These elements contribute to the overall durability and reliability of batteries, ensuring they perform consistently over their lifespan.
3. Which Battery Technology Will Lead the Market: NCM or LiFePO4?
Let’s review them in three aspects.
The raw material cost of lithium iron phosphate mainly includes lithium, phosphorus, and iron
1T LiFePO4 cathode material=0.25T Lithium Carbonate +0.87T Iron phosphate
1GWh LiFePo4 battery request 2200-2500 tons of Lithium Iron phosphate
The NCM cathode materials generally uses nickel cobalt ore, manganese oxide, and lithium hydroxide (the main synthetic material is lithium carbonate), while lithium hydroxide is commonly used (taking 532 as an example)
In today’s market, NCM (Nickel-Cobalt-Manganese) lithium batteries demand a higher lithium input compared to LiFePO4 (Lithium Iron Phosphate) batteries. Approximately 681 tons of lithium carbonate are required to produce 1 GWh of NCM lithium batteries, while 1 GWh of LiFePO4 batteries necessitates around 645 tons of lithium carbonate (taking the intermediate value).
NCM lithium batteries rely on two precious metals, nickel and cobalt, both of which tend to be relatively costly. Cobalt, in particular, presents a unique challenge due to its limited availability. Roughly 66% of the world’s cobalt supply originates from the Democratic Republic of Congo in Africa, leading to price volatility.
When assessing the cost breakdown, it’s important to note that the cathode material of an NCM battery constitutes approximately 60% of the total battery cost, while lithium iron phosphate accounts for roughly 30%.
NCM Material Safety:
NCM materials start to decompose at temperatures exceeding 200 degrees Celsius. This decomposition results in the release of a significant number of oxygen atoms, triggering intense chemical reactions with the battery’s solvent. This process generates a substantial amount of gas and heat. If this gas and heat cannot be dissipated promptly, it may lead to deflagration or rapid combustion.
LiFePO4 Material Safety:
In contrast, LiFePO4 exhibits remarkable stability, with an upper temperature limit of around 700 degrees Celsius. Its olivine microstructure contributes to this stability, making it highly resistant to thermal runaway and decomposition.
However, it’s essential to approach safety dialectically, considering not only the properties of the battery cells but also the design of the entire battery pack (PACK). Under normal operating conditions, a power battery’s working environment rarely exceeds 60 degrees Celsius. Even during extreme weather conditions, a robust thermal management system ensures that the PACK remains within safe temperature ranges. In the unlikely event of a thermal management system failure, safety measures, including circuit breakers, are in place to prevent temperatures from reaching critical levels.
It’s crucial to recognize that safety is a multifaceted and systematic concept, and it cannot be solely defined by the positive electrode materials. Instead, a comprehensive approach to battery design, monitoring, and control is necessary to ensure the highest level of safety.
The performance of the battery is the ultimate determinant of its trajectory.
Why does lithium iron phosphate (LiFePO4) have good cycling performance?
Olivine Structure Stability:
LiFePO4’s positive electrode boasts an olivine crystal structure, renowned for its remarkable stability. This stability ensures a secure molecular framework that remains intact throughout the battery’s lifecycle. As a result, it maintains a one-dimensional channel for ion movement, effectively limiting their diffusion and migration efficiency.
Enhanced Cycling Longevity:
The restricted ion migration allows for rapid ion movement along a single plane, albeit with limited electron conductivity due to the closely packed lattice structure. However, this inherent stability and consistent molecular arrangement contribute to LiFePO4’s impressive cycling life, which can extend up to an astonishing 3000-4000 cycles.
Because of this, the low-temperature performance of iron phosphate is poor. Originally, the migration of lithium ions is slow, and the impedance increases at low temperatures. The viscosity of the electrolyte further hinders the performance. Therefore, the capacity retention rate of iron phosphate at -20 degrees Celsius is only about 60%, while the ternary structure can achieve more than 70%. But objectively speaking, the difference between the two at room temperature is not significant.
4. Why does NCM lithium have high energy density?
● Lattice Structure:
Examining the lattice structure, lithium predominantly occupies 3A positions within the lattice. Simultaneously, nickel, cobalt, and manganese are scattered in a disordered fashion at 3B positions, with oxygen filling 6C positions. This arrangement creates the MO6 octahedral structure, with ‘M’ representing the transition metal. Consequently, the ternary positive electrode consists of lithium ions and transition metal oxides.
● Interlayer Advantage:
The lattice can be visualized as a layered assembly of MO6 octahedral and Li06 octahedral layers. This arrangement is exceptionally conducive to the insertion and extraction of lithium ions. In essence, the interlayer structure of ternary materials is more open, facilitating the seamless movement of lithium ions between the MO6 layers.
Additionally, when it comes to coating positive electrode materials, NCM materials boast a higher compaction density (up to 3.5g/cm3) compared to iron phosphate (2.3 to 2.4g/cm3). This difference further elevates the energy density of NCM materials.
5. NCM vs. LiFePO4 – Which Battery Technology Will Prevail?
From the current technology and market situation, the market share of iron phosphate will be very high for a long period of time. Firstly, the cost of iron phosphate is relatively small, does not involve precious metals, is rich in minerals, and has a simple industrial structure.
Secondly, iron phosphate can improve the migration efficiency of electrons and ions to a certain extent without sacrificing stability through methods such as carbon coated nanoparticle doping process.
Thirdly, advancements in battery pack design, such as the implementation of CTP (Cell-to-Pack) structures, have the potential to substantially boost the overall energy performance of LiFePO4 batteries at the PACK level.
These factors collectively suggest that LiFePO4 technology is well-positioned to continue its dominance in the battery market. If you’re seeking further insights or guidance on choosing the optimal battery technology for your specific requirements, please don’t hesitate to reach out to Bonnen team. We’re here to help you make informed decisions and elevate your lithium battery solutions.
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