Lithium plating and stripping inefficiencies represent critical failure modes in lithium-ion batteries, particularly affecting cells with graphite anodes operated under aggressive charging conditions or low temperatures. These phenomena lead to capacity fade, increased impedance, and potential safety risks through distinct but interrelated mechanisms.

Lithium plating occurs when lithium ions arriving at the anode surface during charging cannot intercalate into graphite quickly enough, instead reducing to metallic lithium on the surface. This process competes with intercalation and becomes dominant under conditions that slow intercalation kinetics or increase lithium-ion flux. Three primary morphological outcomes emerge: smooth lithium films, mossy lithium, and dendritic growth. Smooth films typically form at low current densities, while mossy structures develop at moderate rates, characterized by porous, filamentous deposits. Dendrites, needle-like protrusions, grow under high current densities and pose the highest risk of separator penetration.

Dead lithium formation represents a key degradation pathway. During discharge, plated lithium undergoes stripping, but incomplete reactions leave isolated metallic lithium fragments electronically disconnected from the current collector. This inactive material accumulates over cycles, directly reducing reversible capacity. Studies show dead lithium content can reach 15-30% of total plated lithium after just 50 cycles under plating conditions. Concurrently, continuous electrolyte decomposition at fresh lithium surfaces consumes cyclable lithium and generates resistive solid-electrolyte interphase (SEI) layers.

Capacity fade manifests through multiple mechanisms. Dead lithium constitutes direct active material loss, while SEI growth consumes lithium inventory and increases impedance. Plated lithium also exacerbates particle cracking in graphite anodes through localized stress, exposing new surfaces for further SEI formation. Post-mortem analysis reveals that cells cycled with plating exhibit 20-40% higher thickness swelling compared to non-plating conditions due to these combined effects.

Charging protocols critically influence plating severity. The C-rate directly determines lithium-ion flux to the anode surface. At 1C charging, graphite anodes typically maintain sufficient intercalation kinetics to avoid plating above 15°C, while 2C charging induces plating even at 25°C. Constant-current constant-voltage (CCCV) protocols mitigate plating by allowing redistribution during the voltage hold phase, with optimal hold times depending on temperature and cell design. Pulse charging strategies can reduce plating by providing relaxation periods for lithium concentration gradients to equalize.

Temperature dependence follows Arrhenius kinetics, with intercalation barriers becoming prohibitive below approximately 10°C. At -10°C, even 0.5C charging can induce severe plating due to the 10x decrease in graphite intercalation kinetics compared to 25°C. Thermal gradients within cells further exacerbate inhomogeneous plating, with colder regions accumulating more deposits.

Plating morphology depends on overpotential conditions. Low overpotentials favor compact deposits, while higher overpotentials produce mossy or dendritic structures. The transition typically occurs around 50-80 mV overpotential relative to lithium intercalation potential. Cycling history also affects morphology - cells with prior plating episodes exhibit more dendritic growth in subsequent cycles due to preferential deposition on existing nuclei.

Voltage hysteresis analysis serves as a key diagnostic tool. The difference between charge and discharge voltage curves (ΔV) increases with lithium plating due to the additional overpotential required for stripping compared to intercalation. A hysteresis increase of 20-30 mV often indicates plating onset. Differential voltage analysis (dV/dQ) provides higher sensitivity, showing distinct features when plating begins.

Electrochemical impedance spectroscopy (EIS) reveals plating through low-frequency impedance changes. Plated cells show a 2-3x increase in the 0.1-1 Hz range corresponding to lithium stripping kinetics. The impedance arc associated with SEI also grows due to increased surface area from mossy deposits.

Advanced techniques include coulombic efficiency (CE) measurements, where values below 99.8% often indicate lithium plating losses. Isothermal microcalorimetry detects the exothermic signature of lithium deposition, while pressure measurements track gas evolution from electrolyte reduction at lithium surfaces. Post-mortem analysis using scanning electron microscopy clearly distinguishes between different plating morphologies and their penetration depths.

Mitigation strategies focus on operational boundaries rather than material solutions (covered in G39). Temperature management maintains anode kinetics, with minimum operating temperatures of 10-15°C recommended for fast charging. Current limits should scale with temperature, reducing maximum C-rate by 50% for every 10°C below 25°C. Voltage control proves critical - charging above 80% state of charge (SOC) at low temperatures significantly increases plating risk due to decreased graphite intercalation potential.

Cycling protocols can recover some capacity lost to dead lithium through deliberate overdischarge strategies that reconnect isolated lithium, though this risks lithium deposition on the cathode. Calendar aging studies show that plated lithium continues reacting with electrolyte during rest periods, suggesting that immediate diagnostic testing after cycling provides the most accurate plating assessment.

Quantitative relationships emerge between plating severity and performance loss. Each 1% of cyclable lithium lost to dead lithium typically corresponds to a 1.2-1.5% capacity fade due to accompanying SEI growth. Impedance increases follow a power-law relationship with plating extent, with 10% surface coverage causing approximately 25% rise in DC resistance.

Safety implications arise from both dendritic penetration risk and the high reactivity of plated lithium. Cells with extensive plating exhibit thermal runaway onset temperatures 20-30°C lower than unaffected cells due to the additional exothermic lithium-electrolyte reactions. Gas generation rates scale linearly with plated lithium surface area, creating internal pressure risks.

Operational detection remains challenging due to the subtle initial signatures of plating. Voltage plateau analysis during constant-voltage charging provides early indicators - extended plateaus suggest lithium deposition competing with intercalation. Advanced battery management systems incorporate these features alongside impedance tracking for real-time plating detection.

The cumulative effects of cycling with lithium plating typically reduce cell lifespan by 40-60% compared to non-plating operation under equivalent conditions. This accelerated degradation underscores the importance of charging protocols tailored to environmental conditions and cell state. Future developments in operando diagnostics may enable dynamic adjustment of charging parameters to avoid plating while maintaining performance.