Lithium plating is the deposition of metallic lithium on the surface of the anode in a lithium-ion battery. The process is considered one of the most severe aging mechanisms in these types of batteries, and it can shorten the battery’s life and rapidly reduce its capacity.
This article will discuss how anode design, anode materials, and battery management system (BMS) can minimize lithium plating in EV batteries.
Anode structure designs for battery capacity retention
Anode’s contribution to minimizing lithium plating can be seen from the perspective of design structure and material composition. Both factors have an independent effect on lithium plating.
Anode design can minimize lithium plating by engineering the anode’s physical structure to enhance lithium-ion transport. A multi-layered porous structure can be useful in retaining the capacity of EV batteries.
Figure 1. The effect of 1-layered and 3-layered anode design on specific capacity as charging cycles increase. (Image: Energies, MDPI)
For example, Figure 1 illustrates the impact of a multi-layered anode design on capacity retention during fast charging. The figure indicates that a three-layered porous structure across the graphite anode leads to a notable increase in capacity retention during fast charging cycles.
This improved capacity retention suggests that the engineered porous anode is more effective at mitigating degradation mechanisms that occur during fast charging, with lithium plating being a primary concern.
By creating a more porous structure with multiple layers, this design facilitates better and more uniform lithium-ion transport within the anode. Enhanced ion transport can prevent the accumulation of lithium ions at the anode surface, which is a precursor to lithium plating.
Anode materials that minimize lithium plating
The choice of anode material is crucial in minimizing lithium plating during charging, particularly under extreme conditions such as low temperatures or high current rates. Traditional graphite anodes are widely used due to their high theoretical capacity (~372 mAh/g), affordability, and long cycle life.
However, graphite operates close to the lithium plating potential, especially when overpotentials arise during fast charging or at low temperatures. This behavior makes it likely for lithium metal to build up on the surface, which can cause dendrite growth and eventually lead to short-circuiting, as shown in Figure 2.
To counteract this, researchers have explored alternative materials and modified graphite structures that can offer safer electrochemical profiles. One promising material is graphdiyne, a carbon allotrope with a naturally porous structure.
Figure 2. The presence of dendrites leading to a short-circuit path in Li-ion batteries. (Image: MSE Supplies)
Graphdiyne exhibits self-expanding lithium-ion transport channels, which enhance the rate of Li⁺ diffusion. This results in reduced lithium accumulation on the surface and promotes more uniform intercalation within the anode structure.
Another commonly discussed alternative is lithium titanate (Li₄Ti₅O₁₂, also known as LTO). This material operates at a much higher potential (~1.55 V vs. Li⁺/Li), well above the threshold for lithium plating. While it has a lower specific capacity (~175 mAh/g) than graphite, its zero-strain property and high thermal stability make it a suitable option for applications prioritizing safety over energy density.
There’s also ongoing research into composite anode materials, such as silicon-graphite blends. While silicon can theoretically store much more lithium (~4,200 mAh/g), it also suffers from volume expansion and unstable solid electrolyte interphase formation.
These challenges with silicon can indirectly contribute to non-uniform lithium deposition. So, careful formulation and surface engineering are required to make silicon-based anodes viable without increasing the risk of plating.
How BMS affects lithium plating, especially during fast charging
A sophisticated BMS is an often-overlooked phenomenon in minimizing lithium plating in EV batteries, especially during fast charging. By integrating real-time detection methods, such as differential pressure sensing, a BMS can monitor conditions indicative of lithium plating, as shown in Figure 3.
When the BMS detects the onset of lithium plating (e.g., through exceeding a dP/dQ threshold), it can implement adaptive charging protocols by dynamically regulating the charging current.
This change, as shown in Figure 3d, reduces the current to prevent more lithium from accumulating, as demonstrated by the successful avoidance of plating at low temperatures where regular charging was ineffective (Figure 3e). This change highlights the crucial effect of an advanced BMS in enhancing battery safety and longevity.
Figure 3. A flowchart of a Battery Management System integrating differential pressure sensing to detect lithium plating and dynamically regulate charging current. (Image: Nature Communications)
Recent advances use in situ electrochemical signatures to identify the early onset of plating. These include shifts in voltage profiles, coulombic efficiency, and open-circuit voltage relaxation behavior.
Machine learning models are also increasingly employed to detect patterns in large datasets generated during charge-discharge cycles. These models analyze features such as charge rate, temperature, and voltage-time curves to predict when and where lithium plating may occur.
Integrating these data-driven insights into BMS helps trigger preemptive responses such as reducing charge current or adjusting thermal conditions, thereby suppressing further plating.
Summary
A multi-layered, porous anode enhances lithium-ion transport, resulting in improved capacity retention during fast charging. While graphite is common, its proximity to the lithium plating potential makes it susceptible, prompting the exploration of alternatives like graphdiyne.
By using real-time detection methods, such as differential pressure sensing, the BMS can identify lithium plating and implement adaptive charging protocols to dynamically regulate the charging current dynamically, preventing further lithium buildup, especially during EV fast charging.
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