Voltage fade has quietly limited some of the most promising lithium-ion cathodes, eroding the energy they can deliver long before the rest of the cell wears out. A new wave of research suggests that trace amounts of tungsten, inserted at the atomic scale, can stabilize these materials and sharply cut that voltage loss. If the approach scales, it could unlock higher energy batteries for electric vehicles and grid storage without sacrificing safety or lifespan.
Instead of redesigning the entire cell, scientists are re‑engineering the cathode crystal itself, using single-atom dopants to pin its structure in place as lithium shuttles in and out. By targeting lithium-rich layered oxides and high-nickel compositions, they are going after the chemistries that promise the biggest jump in range and capacity, but that have so far been held back by rapid performance decay.
Why voltage fade is the quiet battery killer
When people talk about battery degradation, they usually focus on capacity loss, the shrinking number of kilowatt-hours a pack can hold. Voltage fade is more insidious. In lithium-rich layered oxides, the average discharge voltage gradually drops with each cycle, so even if the cathode still stores a similar amount of charge, the usable energy falls because energy equals charge multiplied by voltage. For drivers, that translates into a car that seems to lose highway range faster than the state-of-health numbers suggest.
At the materials level, this fading voltage is tied to structural changes in the cathode as it is repeatedly charged to high voltages. Oxygen can be pushed to participate in the redox reactions alongside transition metals, which initially boosts capacity but also destabilizes the lattice. Over time, that instability leads to oxygen vacancy formation, phase transitions and even O₂ release, all of which drag the working voltage downward and make it harder to justify using lithium-rich layered oxides in commercial cells.
How lithium-rich layered oxides went from promise to problem
Lithium-rich layered oxides, often abbreviated as LRL, were hailed as next-generation cathodes because they can deliver capacities well above conventional nickel manganese cobalt materials. By activating both cationic and anionic redox, they squeeze more energy out of the same mass of material, which is exactly what electric vehicle makers want. The catch has been that this extra capacity comes with severe voltage decay and structural degradation, especially when cells are charged to the high voltages needed to access that performance.
Researchers working on LRL have documented how repeated cycling triggers oxygen vacancy formation, detrimental phase transitions and O₂ release, a trio of failure modes that show up clearly in advanced measurements such as EELS. Those signatures are the fingerprints of a cathode that is slowly rearranging itself into less favorable structures, which in turn lowers the average operating voltage. Without a way to stabilize the lattice at the atomic scale, the most energy-dense LRL formulations have remained stuck in the lab.
Dec researchers turn to single-atom tungsten
A team of Dec researchers has now shown that trace tungsten dopants can directly attack the root causes of voltage fade in lithium-rich cathodes. Instead of relying on bulk coatings or large compositional changes, they insert individual tungsten atoms into specific sites in the lattice, effectively acting as atomic anchors. Because tungsten has a high valence and strong bonding characteristics, even a small concentration can significantly stiffen the local structure and resist the distortions that lead to oxygen loss.
In their work on lithium-rich layered cathodes, the Dec researchers report that this atomic-scale tungsten doping curbs voltage fade when the materials are charged to high voltages, precisely the regime where LRL usually deteriorates fastest. By stabilizing the oxygen framework and suppressing the cascade of structural changes, the doped cathodes maintain a higher average discharge voltage over extended cycling, which directly translates into more consistent energy output from the same cell footprint according to trace tungsten dopants.
What single-atom engineering actually changes inside the cathode
At first glance, adding a tiny amount of tungsten might sound like a cosmetic tweak, but single-atom engineering fundamentally reshapes how the cathode behaves during cycling. By occupying carefully chosen lattice sites, tungsten can block the migration pathways that lead to cation mixing and phase transitions, keeping the layered structure intact. It also helps maintain charge balance in a way that reduces the driving force for oxygen to leave its position, which is crucial for preventing vacancy formation and gas evolution.
Detailed characterization backs up this picture. EELS measurements confirm that oxygen vacancy formation, detrimental phase transition and O₂ release, all hallmarks of LRL degradation, are suppressed when tungsten is introduced through tetrahedral-site dopant engineering. That atomic-scale stabilization mechanism, described in eScience as a new way to protect lithium-rich layered cathodes, relies on placing the dopant in positions that are not typical of octahedral-site dopants, a distinction highlighted in single-atom engineering. By locking in the desired structure at the level of individual atoms, the cathode can sustain high-voltage operation with far less drift in its electrochemical profile.
High-Ni and Co-free cathodes get a tungsten upgrade
The benefits of tungsten doping are not limited to lithium-rich layered oxides. High-Ni and Co-free oxides have emerged as some of the most prospective cathodes for lithium-ion batteries because of their high energy density and lower reliance on cobalt, a metal with both cost and ethical sourcing concerns. These Ni-rich materials, however, are also prone to structural instability and surface degradation, especially under the aggressive cycling conditions demanded by fast-charging electric vehicles.
Recent work on a tungsten-doped Ni-rich LiNi0.8Mn0.18Al0.02O2 cathode shows that carefully introducing tungsten can improve both structural and electrochemical performance. In that study, the high-Ni and Co-free oxides are identified as leading candidates for next-generation cathodes, and tungsten is used to enhance their stability and rate capability. The doped LiNi0.8Mn0.18Al0.02O2 composition demonstrates that Ni and Co free designs can still deliver strong performance when supported by targeted dopants, as detailed in the tungsten-doped Ni-rich work.
Bulk versus surface W-doping and the role of LixWOy layers
One of the key questions for any dopant strategy is where to put the foreign atoms. A comparative study of bulk and surface W-doped high-Ni cathodes tackles this directly, exploring how tungsten placement affects both structure and cycling behavior. Bulk doping integrates tungsten throughout the lattice, which can strengthen the entire crystal but may be harder to control precisely. Surface doping, by contrast, concentrates tungsten near the particle exterior, where it can directly interact with the electrolyte and the most reactive sites.
According to the Abstract of that comparative work, tungsten doping influences the structural and electrochemical performance of high-Ni cathodes in distinct ways depending on whether it is in the bulk or on the surface. Surface W-doping can lead to the formation of a protective LixWOy layer, which acts as a barrier against electrolyte attack and transition metal dissolution while still allowing lithium ions to move. The study notes that this LixWOy layer is a central feature of the improved stability, a point underscored in the comparative study of bulk and surface W-doped high-Ni materials.
How tungsten reshapes the cathode surface at the nanoscale
Zooming in further, nanoscale investigations show that tungsten does more than just sit passively in the lattice. A detailed study published in Mar explores the influence of tungsten doping on the structural and electrochemical performance of high-Ni cathodes, with a particular focus on how it modifies the surface. At this scale, even subtle changes in composition can dramatically alter how the cathode interacts with the electrolyte, which in turn affects both capacity retention and voltage stability.
The Mar work finds that tungsten doping promotes the formation of a protective LixWOy layer at the particle surface, which helps suppress parasitic reactions and mechanical degradation. This LixWOy layer effectively passivates the most vulnerable regions while still supporting fast lithium transport, a balance that is essential for high-rate applications. By tying the improved cycling behavior directly to this nanoscale architecture, the study provides a mechanistic explanation for why W-doped high-Ni cathodes outperform their undoped counterparts, as detailed in the nanoscale tungsten analysis.
Lessons from Zn/Ti dual-gradient doping on stabilizing surfaces
Tungsten is not the only element being used to tame unstable cathodes, and the broader doping landscape offers useful comparisons. Work on Zn/Ti dual concentration-gradients surface doping for Li-rich layered oxides shows that carefully engineered surface chemistry can significantly improve both stability and kinetics. By creating gradients of zinc and titanium near the surface, researchers can tailor the local structure to better withstand repeated cycling and high-voltage operation.
Moreover, the voltage decay of the doped samples in that Zn/Ti system is also suppressed, a result attributed to the stable surface structure that mitigates structural degradation. The study notes that this improved stability is directly linked to how the dopants reshape the outer layers of the cathode particles, reinforcing the idea that surface engineering is a powerful lever for controlling voltage behavior. Those findings, summarized around Fig. S5, provide a useful benchmark for what tungsten-based strategies need to achieve, and they are documented in the Zn/Ti dual surface doping work.
From lab-scale voltage stability to real-world batteries
For all the promise of tungsten doping, the real test will be how these materials behave in full cells that resemble commercial products. Lithium-rich layered oxides and high-Ni cathodes must not only hold their voltage in coin cells but also survive the thermal, mechanical and electrical stresses of large-format packs in electric vehicles or stationary storage. That means integrating W-doped cathodes with realistic anodes, electrolytes and formation protocols, then tracking voltage fade over hundreds or thousands of cycles.
The early evidence is encouraging. By directly addressing oxygen vacancy formation, phase transitions and O₂ release in LRL, and by building protective LixWOy layers on high-Ni surfaces, tungsten doping targets the same mechanisms that have historically undermined voltage stability. If those gains translate into pack-level performance, drivers could see electric cars that maintain their original range for longer, and grid operators could deploy storage systems that deliver more consistent energy over their service life. The next phase of work will need to connect the atomic-scale engineering demonstrated by Dec researchers and their peers to the manufacturing realities of gigafactories, where even trace dopants must be controlled with industrial precision.
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