Advanced Powder Materials: IEST SPFT2000 Enable B/Zr Co‑Doping for Lattice Regulation and Internal Stress Relief in Ultra‑High‑Nickel Single‑Crystal Cathodes

Academic Application, Single Particle Mechanics

Updated on 2026/08/26

Abstract

B/Zr co-doping is a lattice-bulk regulation strategy for stabilizing ultra-high-nickel single-crystal cathodes by coordinating bulk lattice reinforcement with surface structural protection. Reported by Wei Shu, Zhou-Shuang Fan, An-Qiang Pan, Yun Liu, Wen-Xing Zhang and co-authors in Advanced Powder Materials (DOI: 10.1016/j.apmate.2026.100412), the study investigates single-crystalline $LiNi_{0.92}Co_{0.04}Mn_{0.04}O_2$ (SNCM) and develops SCNCM@0.5%Zr/B to mitigate internal stress, lattice collapse, Li/Ni cation mixing, interfacial degradation, limited Li⁺ transport, and intragranular cracking during cycling. By distributing B within the particle and enriching Zr near the surface, the co-doping strategy reduces the calculated Li⁺ migration barrier from 0.6 to 0.4 eV and improves structural stability. The IEST SPFT2000 Single-Particle Mechanical Testing System was used to quantify particle compressive strength after 500 and 1,000 cycles, providing direct mechanical evidence that the B/Zr-modified cathode better preserves particle integrity during long-term cycling.

📄 Source Paper

Wei Shu, Zhou-Shuang Fan, An-Qiang Pan, Yun Liu, Wen-Xing Zhang, et al.

Lattice-bulk regulation enables internal stress mitigation toward ultra-stable nickel-rich layered cathodes

DOI: 10.1016/j.apmate.2026.100412
| Journal: Advanced Powder Materials
| Institutions: Nanoyang Group, Tianjin University of Advanced Carbon and Energy Materials Laboratory, Tsinghua University,

✓ IEST SPFT2000 Single Particle Mechanical Properties Test System used in this research

1. Degradation Challenges in Ultra-High-Nickel Single-Crystal Cathodes

Ultra-high-nickel NCM cathodes offer high specific capacity and reduced cobalt dependence, but their structural stability becomes increasingly difficult to maintain as the nickel content and upper cutoff voltage increase. During charge and discharge, unstable Ni⁴⁺ can promote irreversible phase transitions and interfacial side reactions. The nickel-rich composition also undergoes anisotropic lattice and volume changes that generate internal stress during deep cycling.

The source study identifies a coupled degradation sequence rather than a single isolated failure mode:

Ni-rich layered lattices undergo non-uniform structural evolution at high states of charge.
Internal stress accumulates as the lattice contracts or distorts.
Intragranular cracks can initiate and propagate inside otherwise single-crystalline particles.
Cracking exposes fresh surfaces to the electrolyte and accelerates side reactions.
Particle pulverization, phase transformation, impedance growth, and electrochemical-mechanical performance loss can then reinforce one another.

Single-crystal architecture reduces grain-boundary-driven fracture compared with conventional polycrystalline particles, but it does not eliminate intragranular cracking. The remaining problem is therefore a coupled lattice–interface–mechanics problem.

2. B/Zr Co-Doping for Lattice-Bulk Regulation

Lattice regulation refers to deliberate modification of a cathode crystal structure to control lattice distortion, phase evolution, ion transport, and mechanical stability during electrochemical cycling.

B/Zr co-doping refers to coordinated modification using boron and zirconium so that bulk lattice stability and near-surface structural stability are regulated within the same cathode particle.

The study proposes a lattice-bulk regulation strategy instead of treating doping as a uniform bulk substitution problem. The two dopants are assigned complementary structural functions:

B: more uniformly distributed in the crystal interior, where it reinforces the lattice framework and helps relieve internal strain.
Zr: more strongly enriched near the particle surface, where it suppresses Li/Ni cation mixing during high-cutoff-voltage cycling and helps stabilize the interface.
B/Zr synergy: links bulk lattice reinforcement with surface stabilization, improving structural integrity, Li⁺ transport, and interfacial resistance to electrolyte attack.

This division of function is central to the paper. The strategy does not attempt to solve every degradation pathway with one dopant; instead, it uses different dopant locations to regulate different parts of the degradation chain.

Table 1. Degradation mechanisms in Ni-rich single-crystal cathodes and corresponding lattice-bulk regulation strategies.
Degradation problem in Ni-rich single-crystal cathodes	Conventional approach	Remaining limitation	B/Zr lattice-bulk regulation	Scientific implication
Internal lattice strain and local structural distortion	Single-crystal architecture or conventional bulk doping	Single-crystal particles can still develop intragranular stress and cracking	B is incorporated through the lattice to reinforce the crystal framework and mitigate internal strain	Addresses the crystal-scale mechanical origin of particle damage
Surface instability and Li/Ni cation mixing	Surface coating	Surface protection does not directly reinforce the bulk lattice	Zr preferentially enriches the surface layer	Connects surface stabilization with suppression of high-voltage structural disorder
Li⁺ transport degradation	Structural modification without coordinated bulk/surface control	Improved structural stability does not automatically guarantee efficient ion transport	B/Zr regulation modifies the local lattice environment and reported Li⁺ migration barrier	Links lattice design with transport kinetics
Particle cracking after long cycling	Post-cycling morphology observation alone	Microscopy confirms damage but does not directly quantify particle fracture resistance	Particle mechanics are measured directly after cycling with single-particle compression	Adds a quantitative mechanical evidence layer to cathode qualification

3. Spatial Distribution of B and Zr in the Single-Crystal Cathode

SCNCM@0.5%Zr/B was synthesized using a co-precipitation route. TOF-SIMS depth profiling showed that the B signal remained relatively consistent as the etching depth increased, indicating a relatively uniform distribution of B through the particle. In contrast, Zr showed a stronger signal near the surface, indicating preferential surface enrichment.

HRTEM and HAADF-STEM further reveal the structural consequences of the modification. The supplied research source reports that the observed (101) lattice spacing changes from 0.242 nm to 0.482 nm after 0.5% Zr/B modification, while the (003) lattice spacing increases from 0.472 nm to 0.477 nm. Along the [100] zone axis, the layered structure remains intact within approximately 10 nm from the surface.

These observations support the paper’s central interpretation: bulk B incorporation and surface-enriched Zr are not redundant modifications. Their different spatial distributions enable the crystal interior and surface region to be stabilized through complementary mechanisms.

Figure 1. TEM, HRTEM, TOF-SIMS, and HAADF-STEM characterization before cycling, showing uniform B distribution, surface-enriched Zr, preserved near-surface layered structure, and the reported changes in (101) and (003) lattice spacing.

4. B/Zr Co-Doping and Li⁺ Transport Kinetics

The lattice modification is not only mechanical. By changing the local crystal environment, B/Zr co-doping also affects lithium-ion transport. The study reports that the calculated Li⁺ migration barrier decreases from 0.60 eV in the original SCNCM to 0.40 eV after B/Zr co-doping.

The source attributes the improved transport behavior to the combined structural effects of the two dopants. The altered lattice environment provides more favorable conditions for Li⁺ migration, while the preserved layered structure near the particle surface helps maintain a continuous diffusion pathway.

For high-nickel single-crystal cathodes, this relationship is important because mechanical stabilization and transport kinetics can interact. A structural modification that suppresses cracking but significantly impedes lithium transport would introduce a different bottleneck. The study instead targets both properties through coordinated lattice regulation.

Figure 2. Electrochemical evaluation of SCNCM and SCNCM@0.5%Zr/B pouch full cells across 2.75–4.2 V at 25°C and 50°C, demonstrating the reported electrochemical stability of the B/Zr-modified cathode.

5. DFT Insights into Lattice Stabilization and Li⁺ Migration

The DFT analysis distinguishes the effects of Zr-only doping from B/Zr co-doping. Zr-only modification produces relatively weak lattice distortion, whereas B/Zr co-doping produces controlled local distortion and a more thermodynamically stable layered framework.

The source describes four interconnected effects:

B occupies oxygen tetrahedral interstitial positions and reinforces the lattice framework, helping release internal stress.
Zr preferentially accumulates near the surface and suppresses cation mixing.
Electronic density shifts toward oxygen, corresponding to stronger metal–oxygen interactions.
Zr 2p and B 1s states modify the electronic distribution around the Fermi level and are associated with improved intrinsic electronic conductivity.

The calculated Li⁺ migration barrier decreases from 0.60 eV to 0.40 eV, while the co-doping formation energy is lower than that of Zr-only doping. The calculation therefore provides a mechanistic basis for the experimentally observed combination of lattice stability and improved lithium-ion transport.

Figure 3. DFT calculations linking B/Zr co-doping with controlled lattice distortion, thermodynamic stabilization, stronger metal–oxygen interactions, electronic redistribution, and the reported reduction in Li+ migration barrier.

6. Internal Stress Relief and Lattice Stability During Cycling

Internal strain refers to mechanical strain generated inside a cathode particle when lithium extraction/insertion produces non-uniform lattice distortion or volume change.

Deep delithiation can drive large changes in the layered lattice of Ni-rich cathodes. When different regions of a particle respond differently, local strain can accumulate instead of being relaxed uniformly. The resulting stress concentration provides favorable sites for crack initiation and phase transformation.

In the reported strategy, B acts as a structural reinforcement in the bulk lattice, while Zr stabilizes the near-surface region. The paper describes B and Zr as electrochemically inactive under the evaluated conditions, allowing them to function as structural pillars rather than redox-active species.

This mechanism is supported by in-situ XRD, which tracks lattice evolution during electrochemical operation, and by post-cycling GPA strain analysis. The combination is more informative than either technique alone: XRD identifies average crystal-structure evolution, while strain mapping visualizes localized mechanical heterogeneity.

Table 2. Multi-scale characterization evidence and design implications for single-crystal NCM cathodes.
Evidence layer	Measured or calculated variable	Reported result	Mechanistic interpretation	Design implication for single-crystal NCM
HRTEM / HAADF-STEM	(003) lattice spacing	0.472 nm → 0.477 nm	Modified interlayer environment and preserved near-surface layered structure	Maintain a structurally favorable pathway for Li⁺ transport
DFT	Li⁺ migration barrier	0.60 eV → 0.40 eV	More favorable calculated Li⁺ transport in the co-doped lattice	Reduce the transport penalty associated with structural stabilization
In-situ electrochemical XRD	Lattice evolution during cycling	Reduced lattice strain and contraction	More controlled structural response during electrochemical operation	Reduce the structural driving force for crack initiation
GPA analysis	Local strain concentration	Less severe stress concentration in the modified sample	Reduced localization of deformation associated with phase evolution	Improve particle-level mechanical integrity

7. Electrochemical Performance

The prepared cathodes were paired with conventional graphite negative electrodes to assemble pouch full cells. The electrochemical evaluation used a 2.75–4.2 V voltage window and included testing at both 25°C and 50°C.

The source reports favorable electrochemical performance for SCNCM@0.5%Zr/B under both temperature conditions. The published paper further reports that a 1.8 Ah pouch cell based on the optimized material delivered 164.2 mAh g⁻¹ after 1,500 cycles, corresponding to 82.3% capacity retention. This long-cycle result is important because the paper does not present lattice modification as a short-term electrochemical optimization; it connects the structural strategy with extended full-cell durability.

At the material level, the electrochemical results need to be interpreted together with structural and mechanical measurements. Capacity retention alone cannot identify whether degradation originates from lattice collapse, interfacial side reactions, lithium transport limitations, or particle fracture.

8. IEST SPFT2000 Single-Particle Mechanical Testing

The IEST SPFT2000 was used in the study to perform single-particle compression testing on the cathode material. This is a critical part of the paper’s evidence chain because B/Zr co-doping is designed to stabilize the crystal lattice, while the mechanical test asks whether that structural stabilization remains meaningful at the level of an individual particle after electrochemical aging.

The study compares particles after 500 and 1,000 cycles. The modified SCNCM@0.5%Zr/B particles exhibit higher compressive strength than the original SCNCM particles at both aging stages. The result complements the microscopy data: instead of showing only whether cracks are visible, the SPFT2000 measurement quantifies the particle’s resistance to controlled compression and fracture.

From a battery-engineering perspective, this creates a useful particle-to-cell linkage:

Crystal engineering: B/Zr co-doping changes lattice structure and local strain.
Particle mechanics: SPFT2000 measures how the aged particle responds to controlled compression.
Electrode robustness: higher particle strength can reduce crack-driven degradation and help maintain particle integrity under electrode processing and cycling stresses.
Cell durability: particle-level integrity contributes to maintaining electrochemical contact and limiting exposure of fresh surfaces to the electrolyte.

IEST SPFT2000 — what the instrument measuresThe published SPFT system measures particle displacement and pressure during controlled single-particle compression and records the stress–displacement response. The published product specifications include a 0–80 μm displacement range, 0–100 mN pressure range, 1 nm displacement resolution, and 0.1 mN pressure resolution. The system supports particle-image observation, automatic displacement/pressure control, and testing of battery-material particles in the approximately 5–50 μm size range. These capabilities make it suitable for linking particle crushing behavior with electrochemical aging and material modification. See IEST SPFT product specifications.

Figure 4. In-situ XRD, COMSOL simulation, and single-particle mechanical testing after long-term cycling, showing reduced lattice strain, a more uniform Li+ concentration distribution, and higher particle compressive strength after 500 and 1000 cycles.

9. Interfacial Stability Revealed by TOF-SIMS and XPS

TOF-SIMS and XPS provide complementary information about chemical degradation. TOF-SIMS resolves depth-dependent elemental or molecular signals, whereas XPS characterizes surface composition and chemical states.

The study reports that B/Zr modification reduces electrolyte decomposition products both within and near the surface region of the particles. This is consistent with a reduction in harmful interfacial reactions and supports the proposed role of surface-enriched Zr in stabilizing the cathode–electrolyte interface.

For Ni-rich cathodes, interfacial stabilization is particularly important because particle cracking and surface reactions are coupled. Once cracks expose fresh active material, electrolyte penetration can accelerate transition-metal dissolution, HF-related attack, and further structural damage. The paper’s chemical analysis therefore supports the mechanical and structural results rather than standing as an isolated surface characterization.

Figure 5. TOF-SIMS depth profiling and XPS characterization showing reduced electrolyte decomposition products and improved interfacial chemical stability after B/Zr co-doping.

10. Suppression of H₂–H₃ Phase Transition and Intragranular Cracking

The H₂–H₃ transition is particularly important in high-nickel layered cathodes because abrupt lattice changes during high-voltage charging can amplify local stress. The supplied study describes B/Zr regulation as a means of reducing lattice strain, preventing local structural collapse, and suppressing phase-transition-driven stress concentration.

After 1,000 cycles, the original SCNCM develops abundant intragranular nanocracks and particle pulverization. The layered structure also undergoes transformation toward spinel and rock-salt phases. GPA strain analysis identifies severe local stress concentration associated with these structural changes.

In contrast, SCNCM@0.5%Zr/B retains a more intact particle morphology with no obvious extensive cracking. The R-3m layered structure is better preserved, cation mixing is suppressed, and the stress concentration associated with phase transformation is substantially reduced.

Figure 6. Post-cycling morphology and GPA strain analysis after 1000 cycles, comparing nanocracking, pulverization, phase transformation, and stress concentration in SCNCM with the more intact R-3m layered structure of SCNCM@0.5%Zr/B.

🔬 Quantify Single-Particle Mechanical Stability with IEST SPFT2000

When high-nickel cathode development focuses on lattice regulation, long-term cycling, or crack suppression, single-particle mechanics can provide the missing quantitative link between crystal structure and particle failure. The IEST SPFT2000 measures controlled single-particle compression, records force–displacement behavior, and supports particle-image observation for direct evaluation of crushing strength and mechanical integrity.

Learn More About SPFT2000 →

Also explore our comprehensive Solid-State Battery Testing Solutions for multi-dimensional characterization.

11. Conclusion

The study demonstrates that B/Zr co-doping can stabilize an ultra-high-nickel single-crystal NCM cathode through coordinated bulk and surface regulation. B is distributed more uniformly through the crystal and helps reinforce the lattice and relieve internal stress. Zr preferentially enriches the surface and helps suppress cation mixing and interfacial degradation.

The resulting material shows a lower calculated Li⁺ migration barrier, more stable lattice evolution, higher single-particle compressive strength after 500 and 1,000 cycles, reduced electrolyte-derived degradation products, and substantially less intragranular cracking after long-term cycling. The paper therefore presents lattice regulation as a coupled solution to structural, transport, interfacial, and mechanical failure modes rather than as a single-parameter optimization.

For engineers and researchers developing single-crystal NCM cathodes, the practical implication is equally important: particle mechanical characterization should be treated as a complementary metric alongside electrochemical cycling, structural analysis, and interfacial chemistry. The SPFT2000 plays a specific role in this evidence chain by converting the abstract concept of particle stability into a measurable force–displacement response after electrochemical aging.

12. FAQs

What is B/Zr co-doping for ultra-high-nickel single-crystal cathodes?

B/Zr co-doping is a lattice-bulk regulation strategy in which B is more uniformly incorporated into the cathode interior while Zr preferentially enriches the particle surface. The study links this spatially differentiated modification with internal-strain relief, suppressed cation mixing, improved Li⁺ transport, and stronger particle integrity.

How does lattice regulation relieve internal stress in Ni-rich cathodes?

Lattice regulation modifies the crystal environment so that structural distortion and phase evolution are better controlled during lithium extraction and insertion. In this study, B reinforces the bulk lattice while Zr stabilizes the surface region, and in-situ XRD shows reduced lattice strain and contraction.

What does single-particle crushing strength after long-term cycling reveal?

Single-particle crushing strength provides a quantitative measure of how well an individual cathode particle resists controlled compression and fracture after electrochemical aging. The IEST SPFT2000 was used to compare particles after 500 and 1,000 cycles, showing higher compressive strength for SCNCM@0.5%Zr/B.

How can TOF-SIMS depth profiling help evaluate cathode interfacial degradation?

TOF-SIMS depth profiling maps chemical signals as a function of depth and can distinguish bulk distribution from surface enrichment. In the study, TOF-SIMS showed relatively uniform B distribution and stronger surface Zr enrichment, while combined TOF-SIMS/XPS evidence indicated fewer electrolyte-derived degradation products after B/Zr modification.

What is the industry significance of this Advanced Powder Materials study for single-crystal NCM cathodes?

The study suggests that single-crystal cathode development should move beyond capacity retention alone and evaluate lattice stability, Li⁺ transport, interfacial chemistry, and particle mechanics as a connected system. For industry, the key implication is a more complete qualification framework in which single-particle crushing strength complements 4.2 V cycling, structural characterization, and post-cycle failure analysis.

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