Solid-State Batteries: Dendrite Formation and Key Solutions

A 2026 review published in eScience argues that dendrite formation in all-solid-state lithium-metal batteries is best understood as an interconnected chain of microscopic processes rather than as a single materials failure. Researchers from Forschungszentrum Jülich, RWTH Aachen University and Stanford University identify low lithium self-diffusion, interfacial inhomogeneities, defects, void formation, electronic leakage and mechanical damage as mutually reinforcing factors.

• Core finding: lithium atoms in the metal anode can replenish the electrolyte interface too slowly during stripping, promoting voids that subsequently concentrate current and facilitate filament growth.
• Interface remains decisive: grain boundaries, pores, cracks, impurities and chemically unstable interphases can create preferred locations for non-uniform lithium deposition.
• Pressure is a trade-off: higher stack pressure can improve contact and promote lithium creep, but excessive pressure can also encourage lithium penetration into the electrolyte or damage the solid electrolyte.
• Commercial implication: the pathway to durable solid-state batteries is likely to depend on coordinated control of materials, interfaces, pressure and cycling conditions rather than on a single breakthrough material.

Why Dendrites Remain a Commercial Barrier

All-solid-state lithium-metal batteries continue to attract attention because replacing the conventional liquid electrolyte and graphite anode with a solid electrolyte and lithium metal could enable higher energy density while reducing some safety risks associated with flammable liquid electrolytes. Yet the technology has not consistently translated those theoretical advantages into competitive operating performance.

The principal problem examined in the new review is the formation and propagation of lithium filaments, commonly referred to as dendrites. During charging, lithium can deposit unevenly and penetrate the solid electrolyte. Under sufficiently severe conditions, these filaments can establish an electronic connection between the electrodes, producing a short circuit and compromising cell operation.

The review notes that oxide-class electrolytes such as lithium lanthanum zirconium oxide (LLZO) and sulfide-class electrolytes such as lithium thiophosphate systems can exhibit dendrite-related failure at current densities below 1 mA cm⁻², while liquid-electrolyte cells can operate in the range of approximately 4–10 mA cm⁻² at room temperature. Polymer solid electrolytes provide greater mechanical compliance and can maintain conformal contact, but their room-temperature ionic conductivity can remain substantially lower, with representative values in the 10⁻⁴–10⁻⁶ S cm⁻¹ range in systems without plasticizers.

The Microscopic Origin: An Interface Under Stress

The review, titled A microscopic view of diffusion and failure mechanisms of lithium anodes in solid-state batteries, was published in eScience in 2026. It compares inorganic, polymer and hybrid solid electrolytes and focuses on how microscopic transport, interfacial structure and mechanical processes evolve during electrochemical cycling.

At the solid electrolyte/lithium interface, the physical contact is fundamentally different from that in a liquid-electrolyte battery. Instead of a liquid phase naturally filling microscopic gaps, the solid materials must maintain intimate contact while lithium is repeatedly removed from and deposited onto the interface. Small imperfections can therefore have disproportionately large effects on local current distribution.

In inorganic solid electrolytes, lithium-ion transport occurs through crystal structures and is strongly affected by microstructural features. Grain boundaries can impede ion transport; the review notes that their ionic conductivity can be as much as three orders of magnitude lower than that of the corresponding bulk material. Grain boundaries containing impurities or other defects may consequently become favorable sites for non-uniform lithium nucleation.

“Low lithium self-diffusion, coupled with interfacial inhomogeneities, is identified as a key driver for dendrite formation.”

The review's central message is therefore broader than the familiar question of whether a solid electrolyte is mechanically strong enough to block a lithium filament. Dendrite growth can emerge from the interaction of ionic transport, lithium-metal deformation, interfacial defects, chemical reactions and electronic conduction.

Lithium Self-Diffusion and the Formation of Voids

One of the review's most consequential observations concerns lithium itself. During stripping, lithium atoms must move toward the solid electrolyte interface so that the physical contact between the metal anode and electrolyte is maintained. If lithium cannot replenish the interface rapidly enough, microscopic voids can develop.

The review reports that the lithium self-diffusion coefficient is commonly observed at approximately 10⁻¹¹ cm² s⁻¹. At demanding current densities, this relatively slow atomic transport can become a limiting process. Once voids appear, the remaining contact area carries a larger share of the current, producing local current-density concentrations. Subsequent lithium deposition can then become increasingly non-uniform, creating conditions favorable to filament formation.

This relationship also explains why dendrite formation cannot be considered solely a charging problem. Severe stripping can alter the interface first, creating the voids and morphological changes that later promote unstable plating. In this sense, the failure sequence can begin during one electrochemical process and become visible during another.

Stack Pressure: Necessary, but Not Without Risk

Stack pressure has consequently become a central engineering variable in solid-state battery research. Applying pressure can improve interfacial contact and promote lithium creep, helping compensate for the slow self-diffusion of lithium and reducing void formation during stripping.

However, the review emphasizes that pressure does not provide a simple solution. Lithium is mechanically soft and can creep under sustained stress. The authors cite reported lithium creep deformation rates on the order of a few micrometers per hour under pressures of approximately 0.6–3.6 MPa at ambient temperatures. Over long storage periods or extended cycling, such deformation can alter the interface and potentially drive lithium into regions of the solid electrolyte where it can contribute to short-circuit formation.

The relationship between pressure and performance is therefore non-linear. Insufficient pressure can produce contact loss and voids, while excessive pressure can promote creep, mechanical damage or other forms of interfacial instability. The relevant engineering objective is not simply to maximize pressure, but to establish an operating window that preserves contact without accelerating competing degradation mechanisms.

Electronic Leakage Creates Another Route for Internal Plating

A second mechanism highlighted by the review is electronic conductivity within materials that are expected to function primarily as ionic conductors. Defects, impurities and decomposition products can create pathways through which electrons move into the solid electrolyte.

When electrons enter the electrolyte, lithium ions can be reduced and metallic lithium can plate within the solid rather than exclusively at the intended lithium-metal interface. Once metallic lithium has formed inside the electrolyte, it can itself provide an electronic pathway that facilitates further deposition, creating a reinforcing cycle of internal filament growth.

The review cites evidence suggesting that the electronic conductivity required to avoid dendrite formation becomes extremely restrictive at higher current densities. For example, reported criteria indicate electronic conductivity below approximately 10⁻¹⁰ S cm⁻¹ at 1 mA cm⁻² and below approximately 10⁻¹² S cm⁻¹ at 10 mA cm⁻² for certain solid-electrolyte systems. These figures illustrate why chemical purity, defect control and long-term interphase stability are relevant to dendrite suppression alongside ionic conductivity.

Mechanical Strength Alone Does Not Explain Dendrite Penetration

Mechanical resistance has traditionally been viewed as another potential barrier to dendrites, particularly in ceramic solid electrolytes. Yet the review indicates that the relationship is more complicated than a simple “harder electrolyte equals dendrite-free battery” rule.

Lithium deposition can generate stress inside the electrolyte, while pre-existing cracks, pores and other defects can provide pathways for penetration. The review notes that the stress associated with dendrite growth can be substantially lower than the fracture stress of LLZO, suggesting that mechanical fracture alone cannot explain all observations of lithium penetration. Insufficient lithium replenishment and resulting loss of contact can concentrate pressure locally, potentially pushing stresses beyond the effective fracture resistance of the material.

This distinction is important for materials development. A solid electrolyte must simultaneously provide sufficient ionic transport, chemical compatibility, appropriate mechanical behavior and extremely low electronic conductivity. Optimizing one property in isolation can therefore produce limited gains if another failure mechanism becomes dominant.

Different Electrolyte Classes Require Different Engineering Responses

The review divides its analysis across inorganic, polymer and hybrid solid electrolytes, reflecting the fact that no single failure mechanism dominates every architecture.

• Inorganic electrolytes: attention centers on grain-boundary chemistry, impurities, defects, electronic conductivity, interfacial contact and pressure management. Ceramic strength can provide mechanical advantages, but cracks and localized stresses remain important failure pathways.
• Polymer electrolytes: mechanical compliance can improve contact with lithium, while ion transport is closely linked to polymer-chain segmental motion. Dynamic and dynamically crosslinked polymer networks are being investigated for their ability to reorganize and potentially repair microscopic interfacial damage.
• Hybrid electrolytes: incorporating inorganic fillers into polymers can improve mechanical strength and introduce barriers to filament propagation. However, excessive filler loading can increase transport tortuosity and interfere with lithium-ion movement, making composition optimization essential.

The review therefore points toward a systems-engineering approach in which ionic transport, interfacial chemistry, mechanical properties and operating pressure are optimized together rather than sequentially.

From Laboratory Metrics to Commercial Cycling

The commercial relevance of the findings extends beyond the commonly cited theoretical energy-density advantage of lithium metal. A lithium-metal anode can provide substantially greater gravimetric capacity than graphite, but the practical value of that advantage depends on whether the cell can repeatedly strip and plate lithium without accumulating voids, dead lithium, internal filaments or interfacial resistance.

The review consequently places considerable emphasis on realistic cycling conditions. Current density alone does not capture the full severity of an operating condition; areal capacity, pressure, temperature, interface morphology and the history of previous plating and stripping events can all influence failure. A material that performs well under a short laboratory pulse may therefore behave differently under prolonged cycling with substantial lithium inventory movement.

This distinction is particularly important as the solid-state battery sector moves from material demonstrations toward cells intended to operate for thousands of cycles. Long-duration testing must account for slow processes such as lithium creep, interphase evolution, crack propagation and accumulation of electronically conductive degradation products.

GuideView Insight

GuideView observes that the significance of the new review lies less in identifying another isolated dendrite mechanism than in connecting mechanisms that are often evaluated separately. The evidence points to a feedback system: slow lithium self-diffusion can create voids; voids can concentrate current; concentrated current can promote non-uniform deposition; deposition can generate mechanical stress; and defects or electronic pathways can subsequently accelerate penetration of the solid electrolyte.

For the industry, this shifts the development question from “Which solid electrolyte can block dendrites?” toward a broader engineering problem: which combination of electrolyte chemistry, interface architecture, lithium morphology, pressure and operating conditions can maintain uniform transport over commercially relevant time scales?

GuideView also notes that the findings place greater importance on manufacturing consistency. Grain-boundary chemistry, surface roughness, microscopic pores, cracks and contamination are not merely laboratory characterization details when each can influence local current distribution. As a result, scalable interface preparation and quality control may become as consequential to commercialization as improvements in bulk ionic conductivity.

The review does not suggest that solid-state batteries have reached a dead end. Instead, it provides a more detailed framework for understanding why promising laboratory materials can struggle under realistic conditions. For the global battery industry, the practical implication is that progress will likely depend on simultaneously controlling transport, mechanics and interfacial chemistry—and validating those controls under sustained cycling rather than relying solely on short-duration demonstrations.

Research Reference

The underlying review is A microscopic view of diffusion and failure mechanisms of lithium anodes in solid-state batteries, authored by Luca Weckelmann, Hao Lyu, Han Yang, Chih-Long Tsai, Krzysztof Dzieciol, Shicheng Yu, Anna Windmüller, Hans Kungl, Zhenan Bao and Rüdiger-A. Eichel. It was published in eScience, Volume 6, Issue 5, Article 100589, in September 2026, with DOI 10.1016/j.esci.2026.100589.

The review synthesizes evidence across inorganic, polymer and hybrid solid electrolytes and identifies low lithium self-diffusion together with interfacial inhomogeneities as key contributors to dendrite formation.