🔬 materials science

NASICON solid-electrolyte modification and analysis using ion and neutron beams

This study synthesizes NASICON pellets via solid-state methods, converts them into nanofilms using ion sputtering, and investigates the impact of 1.1 MeV Ni ion implantation on their electrical properties through electrochemical impedance spectroscopy.

Original authors: Giovanni Ceccio, Jiri Vacik, Mykhailo Drozdenko, Romana Miksova, Ivan Mastronardo, Dejan Prokop, Benedetta Brancato, Eva Stepanovska, Claudia D'Urso, Leone Frusteri

Published 2026-01-23

📖 4 min read☕ Coffee break read

CC BY 4.0

Original authors: Giovanni Ceccio, Jiri Vacik, Mykhailo Drozdenko, Romana Miksova, Ivan Mastronardo, Dejan Prokop, Benedetta Brancato, Eva Stepanovska, Claudia D'Urso, Leone Frusteri

Original paper licensed under CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine you are trying to build a super-efficient battery for your phone or electric car, but instead of using liquid juice that can leak, you want to use a solid block of material. This is the world of "All-Solid-State Batteries."

The scientists in this paper are working with a special type of solid material called NASICON. Think of NASICON as a busy highway system designed specifically for sodium ions (tiny charged particles) to zip through, powering the battery.

Here is the story of what they did, explained simply:

1. The Problem: Thick Roads vs. Thin Paths

Usually, these solid highways are made as thick, heavy blocks (pellets). The problem is that the thicker the road, the harder it is for the ions to get through, kind of like how it takes longer to walk through a crowded, deep tunnel than a short hallway.

The team wanted to make these highways super thin—like a sheet of paper or even thinner (nanofilms). If you make the road thinner, the ions can move much faster, making the battery more efficient.

2. Making the Thin Film: The "Sandblasting" Trick

To make these tiny films, they didn't just pour the material out. They used a clever trick called Ion Beam Sputtering.

The Setup: They first made a solid block of NASICON (like a brick).
The Action: They fired a high-speed beam of Argon gas ions at this brick.
The Result: Imagine a powerful wind hitting a sandcastle; the wind knocks tiny grains of sand off the castle. In this case, the ion beam knocked tiny grains of NASICON off the brick. These grains flew through the air and landed on a silicon chip, building up a very thin, continuous layer.

3. The Surprise: The "Amorphous" Highway

When they looked at these new thin films under a microscope, they found something interesting. Because they made the films at room temperature (not hot enough to bake them into a perfect crystal), the material wasn't a neat, organized crystal. It was amorphous.

The Analogy: Think of a crystalline material like a perfectly organized grid of train tracks. The ions know exactly which way to go.
The Reality: Their thin film was more like a disorganized pile of gravel. There were no clear tracks. The ions had to "hop" from one loose stone to another. Usually, this makes it harder for them to move, resulting in higher resistance (slower battery).

4. The Twist: The "Ni" Bombardment

Here is where the experiment got really cool. The scientists decided to shoot Nickel (Ni) ions at these gravel-pile films to see if they could fix the traffic jam. They shot the ions at three different strengths (low, medium, and high).

Low Strength (The First Hit): When they hit the film with a small amount of Nickel, the traffic got worse. The ions got stuck. It was like throwing a few rocks onto the gravel path, creating more bumps and blocking the way.
Medium Strength (The Sweet Spot): When they increased the dose to a medium level, something magical happened. The traffic started to flow better than before! The Nickel ions created tiny holes and rearranged the gravel just enough to create new, easier paths for the sodium ions to hop through. It was like clearing a path through a dense forest by knocking down just the right trees.
High Strength (Too Much): If they hit it too hard, the path might get damaged again, but for most samples, the "medium" dose was the sweet spot.

5. The Conclusion

The team proved two main things:

You can make these solid electrolytes incredibly thin using their "sandblasting" (ion beam) technique.
Even though the thin films were messy (amorphous) and usually bad at conducting electricity, they could tune them to work better by shooting them with Nickel ions.

The Big Picture:
They found that by carefully controlling how hard they "hit" the material with ions, they could turn a messy, slow highway into a fast, efficient one. This suggests that in the future, we might be able to engineer these tiny, solid battery parts to be super-efficient just by tweaking how we shoot ions at them, without needing to melt or bake them into perfect crystals.

What they didn't do:
They did not build a working battery yet, nor did they test it in a car or phone. They only made the material and measured how well electricity moved through it in a lab setting. They also didn't test other types of ions or materials yet; they focused strictly on this specific NASICON film and Nickel.

Technical Summary: NASICON Solid-Electrolyte Modification and Analysis Using Ion and Neutron Beams

Problem Statement
While lithium-ion batteries (LIBs) dominate the current energy storage market, the scarcity and rising cost of lithium necessitate the development of alternative technologies, particularly sodium-based systems. Sodium metal offers high specific capacity and abundance, but safety concerns regarding liquid electrolytes drive the need for "all-solid-state" solutions using solid electrolytes (SEs). Sodium-based superionic conductors (NaSICON), such as NZSP (Na₃Zr₂Si₂PO₁₂), are recognized for their excellent ionic conductivity. However, a significant bottleneck exists: while bulk NaSICON is well-established, the fabrication of thin-film NaSICON for all-solid-state batteries (ASSBs) remains challenging. Thin films are desirable because reducing SE thickness to the nanometer scale significantly lowers electrical resistance and enhances ionic conductivity. Furthermore, there is a need to understand how ion beam modification can tune the electrochemical properties of these nanofilms, potentially by introducing specific defects or doping.

Methodology
The study employed a multi-step approach involving synthesis, deposition, modification, and characterization:

Synthesis of Bulk Targets: NASICON pellets were prepared using a mixed oxide solid-state method. Precursors (Ammonium Phosphate monobasic, Zirconium Dioxide, Sodium Carbonate, and Silicon Dioxide) were ball-milled, pressed, and calcined at 1150 °C, followed by a second milling and final sintering at 1250 °C. Both lab-synthesized pellets (with and without a second milling step) and commercial NZSP powder were used to create distinct targets (labeled Pellet 2, 4, and 5).
Thin Film Deposition: Continuous and uniform NASICON nanofilms were produced using Ion Beam Sputtering (IBS) at the Low Energy Ion Facility (LEIF) at the Nuclear Physics Institute (NPI) Řež. The synthesized pellets served as sputtering targets. An Ar ion beam (20 keV) irradiated the targets at a 45° angle, depositing material onto <100> Silicon substrates held at room temperature.
Ion Beam Modification: The deposited films were modified via ion implantation using 1.1 MeV Ni ions at the Tandetron accelerator. Three fluences were applied: $1 \times 10^{14}$ , $5 \times 10^{14}$ , and $1 \times 10^{15}$ Ni/cm². The energy was selected to ensure ions passed through the coating and interacted primarily with the substrate, modifying the film via electronic stopping (ionization and bond disruption) rather than significant atomic displacement.
Characterization:
- Morphology: Scanning Electron Microscopy (SEM) in backscattered electron mode was used to observe surface structures.
- Structure: X-ray Diffraction (XRD) was performed in an asymmetric 2θ-ω scan to exclude substrate peaks and identify crystalline phases.
- Electrical Properties: Electrochemical Impedance Spectroscopy (EIS) was conducted at room temperature (25°C) using a two-electrode setup to measure ionic conductivity and impedance.

Key Results

Structural State: XRD analysis revealed that the deposited films are predominantly amorphous. Unlike bulk NaSICON, which requires high-temperature sintering to form a long-range crystalline framework, the room-temperature deposition resulted in a disordered network. A small broad peak between 18° and 39° 2θ indicated the presence of amorphous NaSICON.
Surface Morphology: Pristine films exhibited flat, uniform surfaces. Post-irradiation, films produced from commercial NaSICON (NASICON 2) developed nanostructures, with density increasing with fluence. Lab-made films showed varied responses: NASICON 4 formed large clusters at high doses, while NASICON 5 remained relatively homogeneous.
Electrochemical Behavior: EIS measurements demonstrated a non-linear, fluence-dependent response to Ni implantation:
- Low Fluence ( $1 \times 10^{14}$ Ni/cm²): All samples showed an increase in impedance. This is attributed to initial structural damage disrupting ionic transport pathways in the amorphous matrix.
- High Fluence ( $5 \times 10^{14}$ and $1 \times 10^{15}$ Ni/cm²): A reduction in impedance was observed for most samples, indicating improved ionic conductivity. The authors suggest that at higher fluences, the accumulation of irradiation-induced defects (vacancies and locally disordered regions) creates new hopping sites for sodium ions within the amorphous network.
- Optimal Fluence: Most samples exhibited a minimum impedance (maximum conductivity) at a fluence of approximately $5 \times 10^{14}$ Ni/cm². NASICON 4 showed a slightly different trend, with its minimum at the highest fluence tested.

Significance and Claims
The paper presents a pioneering investigation into the fabrication and functional tuning of ultrathin NaSICON electrolytes. The authors claim that:

Feasibility of Nanofilms: Ion beam sputtering using bulk pellets as targets is a viable method for producing continuous, uniform NaSICON nanofilms, despite the resulting amorphous structure.
Defect Engineering: Ion implantation serves as an effective tool for tuning the electrical properties of these amorphous films. The study demonstrates that while low-dose irradiation degrades performance, controlled high-dose irradiation can enhance ionic conductivity by introducing beneficial defects (vacancies) that facilitate ion hopping in the absence of crystalline channels.
Strategic Potential: The combination of low-energy ion beam sputtering and controlled ion implantation offers a promising strategy for engineering solid electrolytes at the nanoscale. This approach allows for the deliberate exploitation of disorder and defect chemistry to enhance transport mechanisms, providing a pathway for developing next-generation sodium-based all-solid-state batteries.

The authors conclude that future work should focus on inducing crystallinity through annealing (during or after deposition) and correlating specific structural changes with transport mechanisms, as well as extending this methodology to other dopants and electrolyte systems.