Electrode Damage Research Articles

Favored Amorphous LixSi Process with Restrained Volume Change Enabling Long Cycling Quasi-Solid-State SiOx anode.

Silicon-based anodes are becoming promising materials due to their high specific capacity. However, the intrinsically large volume change brought about by the alloying reaction results in the crushing of the active particles and destruction of the electrode structure, which severely limits its practical application. Various structured and modified silica-based anodes exhibit improved cycling stability and the demonstrated ability to mitigate their volume changes through interfacial and binder strategies. However, the issue of large volume changes in silicon-based anodes remains. Herein, we report a gel polymer electrolyte (GPE) prepared through an in situ thermal polymerization process that is suitable for SiOx anode materials and achieving long-term cycling stability. GPE-based cells essentially mitigate the volume change of SiOx anodes by guiding the unique lithiation/delithiation mechanism that tends to favor the formation and delithiation of amorphous-LixSi (a-LixSi) with smaller volume change, thereby mitigating electrode damage and cracking, and achieving the significant improvement in cycling performance. The prepared GPE-SiOx cells retained 693.80 mAh g-1 reversible capacity after 450 cycles at 500 mA g-1. In addition, the prelithiation process was incorporated to mitigate capacity fluctuations and improve the Initial Coulombic Efficiency (ICE), and a reversible capacity of 641.90 mAh g-1 was retained after 480 cycles.

Compensating effect of self-assembled capsule towards enhanced structural stability of prussian blue cathodes for sodium-ion batteries

The Prussian Blue analog (PBA) is a promising sodium-ion cathode material with high theoretical capacity and relatively easy to synthesize. One of the Prussian Blue analogs, sodium manganese hexacyanoferrate (NaxMn[Fe(CN)6], MnHCF), experiences significant initial capacity decrease due to Jahn–Teller distortion depending on the sodium content. In contrast, Sodium copper hexacyanoferrate (NaxCu[Fe(CN)6], CuHCF) exhibits lower reversible sodium-ion content compared to MnHCF and exhibits excellent cycling stability. We designed direct-strike coprecipitation process to synthesize nanocomposite of PBAs. The proposed encapsulated composite has been successfully synthesized by encapsulating MnHCF with self-assembled CuHCF, leading to substantial improvement in the cycling performance of MnHCF. The encapsulated composite demonstrated a capacity of 106.2 mAh g−1 even at high current rate. Regarding cycle stability, it retained over 68 % of its initial capacity even after 500 cycles. The ion conductivity was calculated through the Galvanostatic intermittent titration test (GITT), and the encapsulated composite exhibited higher ion conductivity than pristine MnHCF. Ex-situ post-analysis was conducted to confirm structural evolution of samples. The severe structural collapse of MnHCF led to electrode damage, whereas the encapsulated composite demonstrated excellent electrode condition. The encapsulated composite exhibited superior performance in full-cell tests as well.

Electro-Chemo-Mechanical Model for the Damage in Porous Electrodes of Lithium-Ion Batteries

An electro-chemo-mechanical model is developed for lithium-ion battery (LIB) considering the damage of active material (AM) particles. The established model is used to evaluate the effect of stress and the effect of damage on the electro-chemo-mechanical behavior of cathode. The cathode is generated with a random distribution method. Computational results show that moderate stress is beneficial for the battery performance, while damage generated by high stress can considerably degrade the battery capacity. The impact of several structural factors on the electro-chemo-mechanical behaviors of LIB are investigated. Smaller particles are found beneficial for the battery performance. Furthermore, the computational results also suggest that an increasing particle size from the separator to the current collector leads to higher capacity. The presented model helps to understand the electro-chemo-mechanical coupling mechanism of LIB.

Rate-dependent damage and failure behavior of lithium-ion battery electrodes

The mechanical properties and failure behavior of composite electrodes are critical to understanding the internal short circuits and ensuring the crush safety of lithium-ion batteries used in electric transportation. This study provides a comprehensive experimental investigation into the strain rate–dependent tensile/compressive behavior and failure mechanism of both anode and cathode, covering a range from quasi-static to dynamic conditions. A universal testing machine equipped with an industrial camera was used to assess the mechanical properties and observe the deformation process of the electrodes under quasi-static conditions. Additionally, a split Hopkinson bar system, coupled with a high-speed camera, was utilized to evaluate the mechanical properties and capture the deformation process of the electrodes under dynamic loading. The detailed deformation and failure modes of the electrodes were revealed by a combination of post-mortem characterization and images from high-speed cameras. The experimental results demonstrate a significant strain rate effect on the tensile and compressive mechanical behavior and failure mechanism of both anode and cathode. The rate dependence of tensile/compressive strength and failure strain were discussed, and the underlying mechanism for strain rate sensitivity was analyzed. The results and conclusions from this study provide an important foundation for the detailed modeling and failure prediction of lithium-ion batteries under impact loading. Further, these findings facilitate the safety design of electric vehicles by informing to enhance crash safety.

Perspective of material evolution Induced by sinusoidal reflex charging in lithium-ion batteries

BackgroundLithium-ion batteries are globally prominent and extensively employed alternative energy sources with decisive applications. In depth understanding of influences of various charging and discharging cycles on electrode materials and life span of these batteries is critical as cycle-life and safety of lithium-ion batteries are closely related crystallinity of electrode materials. This study is a detailed investigation endeavor in observing the degree of damage to electrode materials under multiple charging and discharging cycles. Methodology: A constant current-sinusoidal reflex charging method (CC-Sinusoidal) was implemented to charge commercial cathode Lithium cobalt oxide (LiCoO2) electrodes and anode graphite electrodes in comparison to the conventional charging method of constant current-constant voltage (CC-CV). After 100, 300, and 500 cycles of charging and discharging, EIS, SEM, XRD, and Raman spectroscopies were used to compare the degree of electrode damage caused by different charging methods. Significant outcomesThe structure of positive LiCoO2 electrode of the battery was observed to be stable, with no significant change in both the charging methods after 500 cycles. The use of CC-CV charging method had caused severe damages to graphite electrode with generation of solid electrolyte interface (SEI) films. The CC-Sinusoidal charging method had maintained the electrode material in a relatively ideal state.

Quantifying the mechanical degradation of solid oxide cells based on 3D reconstructions of the real microstructure using a unified multiphysics coupling numerical framework

In this work, a multiphysics coupling numerical framework is developed to quantitatively investigate the initial performances of solid oxide cells (SOCs) based on the thermodynamically consistent integration of the finite element method (FEM) and the phase field method (PFM) to reveal the interaction between species-defect transport, electrochemical reaction kinetics, stress and mechanical damage in SOC electrodes. The modeling framework is validated by comparing the simulation results based on real 3D microstructure reconstructions of specific SOCs with the experimental measurements in electrolysis and fuel cell modes. The phenomena of internal microstructure fracture and delamination observed in the experiment thus can be numerically modeled to quantify the effects of thermal and chemical stresses on the mechanical degradation of heterogeneous electrodes. The framework is also applied in the cross-scale quantification of the possible mechanical damage in SOCs subjected to different mechanical boundary conditions. The framework proposed in this work is flexible, can be superimposed with other fields, and incorporates input from cross-scale simulations. It provides a great potential platform for the optimization of future energy devices considering actual operating conditions and fills the gap in theoretical multiphysics modeling in the field of SOCs.

A Comprehensive Review of In Situ Measurement Techniques for Evaluating the Electro-Chemo-Mechanical Behaviors of Battery Electrodes.

The global production landscape exhibits a substantial need for efficient and clean energy. Enhancing and advancing energy storage systems are a crucial avenue to optimize energy utilization and mitigate costs. Lithium batteries are the most effective and impressive energy utilization system at present, with good safety, high energy density, excellent cycle performance, and other advantages, occupying most of the market. However, due to the defects in the electrode material of the battery itself, the electrode will undergo the process of expansion, stress evolution, and electrode damage during electro-chemical cycling, which will degrade battery performance. Therefore, the detection of property changes in the electrode during electro-chemical cycling, such as the evolution of stress and the modulus change, are useful for preventing the degradation of lithium-ion batteries. This review presents a current overview of measurement systems applied to the performance detection of batteries' electrodes, including the multi-beam optical stress sensor (MOSS) measurement system, the digital image correlation (DIC) measurement system, and the bending curvature measurement system (BCMS), which aims to highlight the measurement principles and advantages of the different systems, summarizes a part of the research methods by using each system, and discusses an effective way to improve the battery performance.

Phenomenological modelling of cycling-induced damage in the metal-ion battery electrode

This work addresses a pivotal challenge in metal-ion batteries, namely the structural degradation and damage of electrodes, which profoundly impacts the operational performance and overall longevity of metal-ion batteries. A chemo-mechanical model is introduced, including the interaction between the degradation/damage induced by chemical reaction and the damage-dependent mechanical stress/strain during electrochemical cycling. A visco-plastic constitutive relationship is developed that explicitly considers the effects of both the mechanical and chemical damages. The contributions of the mechanical and chemical damages are incorporated in the model, employing scalar damage variables to depict the damage states. We numerically analyze the dynamic evolution of stress, plastic strain, and damages throughout multiple lithiation and de-lithiation cycles and illustrate the effects of electrochemical cycling on surface damage and stress distribution. The experimental results support the developed model, with the numerical results closely matching the experimental results for the retaining of the capacity of a graphite-based lithium-ion half-cell. The numerical results reveal the importance of the damage parameters in describing the evolution of the structural damage in electrodes during electrochemical cycling. This study enriches our understanding of the structural damage in electrodes during electrochemical cycling and has great potential to improve the design of metal-ion batteries.

Alkali-Ion Intercalation Chemistry and Phase Evolution of Sn4P3.

Despite its high theoretical capacities, Sn4P3 anodes in alkali-ion batteries (AIBs) have been plagued by electrode damage and capacity decay during cycling, mainly rooted in the huge volume changes and irreversible phase segregation. However, few reports endeavor to ascertain whether these causes bear relevance to phase evolution upon cycling. Moreover, the phase evolution mechanism for alkali-ion intercalation remains imprecise. Herein, the structural transformations and detailed mechanisms upon various alkali-ion intercalation processes are systematically revealed, utilizing both experimental techniques and theoretical simulations. The results reveal that the energy storage of Sn4P3 occurs in a two-stage process, starting from an insertion process, followed by a transition process. As the cycle proceeds, the final delithiated/desodiated/depotassiated components gradually trap alkali ions (Li+, Na+, and K+), which is attributed to the incomplete electrochemical transition and difficulty in Sn4P3 regeneration due to the kinetic limitations in removing M (M = Li, Na, and K). Furthermore, Sn4P3 anode obeys the "shrinking core mechanism" in potassium-ion batteries (KIBs), wherein a minor fraction of Sn4P3 in the outer layer of the particles is initially involved in the potassiation/depotassiation processes, followed by a gradual participation of the inner parts until the entire particle is involved. It is worth mentioning that K-Sn alloys are not found to exist during the transition process of KIBs; instead, K-Sn-P phases are found, which makes it differ from that in lithium-ion batteries (LIBs) and sodium-ion batteries (NIBs). These findings are expected to deepen the understanding of the reaction mechanism of Sn4P3 and enlighten the material designs for improved performance.

In vitro biocompatibility evaluation of functional electrically stimulating microelectrodes on primary glia.

Neural interfacing devices interact with the central nervous system to alleviate functional deficits arising from disease or injury. This often entails the use of invasive microelectrode implants that elicit inflammatory responses from glial cells and leads to loss of device function. Previous work focused on improving implant biocompatibility by modifying electrode composition; here, we investigated the direct effects of electrical stimulation on glial cells at the electrode interface. A high-throughput in vitro system that assesses primary glial cell response to biphasic stimulation waveforms at 0mA, 0.15mA, and 1.5mA was developed and optimized. Primary mixed glial cell cultures were generated from heterozygous CX3CR-1+/EGFP mice, electrically stimulated for 4h/day over 3days using 75μm platinum-iridium microelectrodes, and biomarker immunofluorescence was measured. Electrodes were then imaged on a scanning electron microscope to assess sustained electrode damage. Fluorescence and electron microscopy analyses suggest varying degrees of localized responses for each biomarker assayed (Hoescht, EGFP, GFAP, and IL-1β), a result that expands on comparable in vivo models. This system allows for the comparison of a breadth of electrical stimulation parameters, and opens another avenue through which neural interfacing device developers can improve biocompatibility and longevity of electrodes in tissue.

Computational modeling of coupled mechanical damage and electrochemistry in ternary oxide composite electrodes

Performance degradation of ternary layered oxide cathodes largely originates from their loss of structural integrity in cyclic usage. Mechanical damage, such as intergranular fracture of the active particles, is not only a mechanical cleavage process but also interferes with electrochemical kinetics such as infiltration of liquid electrolyte, surface corrosion of the constituent primary particles, and may eventually isolate the primary grains from the electron conducting network. Here we develop a computational framework that integrates electrochemistry of a LiNixMnyCo1−x−yO2 (NMC) composite cathode with mechanical damage of the active particles. To fully examine the intricate chemomechanical behavior of the electrode, we evaluate the effects of the anisotropic material properties, the influence of mechanical potential on Li transport, and the concurrent intergranular fracture and electrolyte penetration along the grain boundaries upon multiple cycles. Electrolyte infiltration benefits capacity retention but aggravates further mechanical damage by corrosion. Structural failure mostly occurs in the first charging due to the anisotropic mechanical strain between the primary grains, while the resulting damage remains stable in the later few cycles. The results are consistent with experimental observations and the integration of electrochemistry and mechanical failure enables a step further understanding of the complex mechanism of battery degradation.

Maskless fabrication of quasi-omnidirectional V-groove solar cells using an alkaline solution-based method

Silicon passivated emitter and rear contact (PERC) solar cells with V-groove texture were fabricated using maskless alkaline solution etching with in-house developed additive. Compared with the traditional pyramid texture, the V-groove texture possesses superior effective minority carrier lifetime, enhanced p–n junction quality and better applied filling factor (FF). In addition, a V-groove texture can greatly reduce the shading area and edge damage of front Ag electrodes when the V-groove direction is parallel to the gridline electrodes. Due to these factors, the V-groove solar cells have a higher efficiency (21.78%) than pyramid solar cells (21.62%). Interestingly, external quantum efficiency (EQE) and reflectance of the V-groove solar cells exhibit a slight decrease when the incident light angle (θ) is increased from 0° to 75°, which confirms the excellent quasi omnidirectionality of the V-groove solar cells. The proposed V-groove solar cell design shows a 2.84% relative enhancement of energy output over traditional pyramid solar cells.

Temperature-Triggered Adhesive Bioelectric Electrodes with Long-Term Dynamic Stability and Reusability.

Bioelectric electrodes with low modulus and high adhesion have been intensively pursued, as they afford conformal and strong bonding at skin-electrode interface to improve the fidelity and stability of electrophysiological signals. However, during detachment, tough adhesion can cause pain or skin allergy; worse still, the soft electrodes can suffer damage due to excessive stretch/torsion, hampering long-term, dynamic, and multiple uses. Herein, a bioelectric electrode is proposed by transferring silver nanowires (AgNWs) network to the surface of bistable adhesive polymer (BAP). The phase transition temperature of BAP is tuned to be slightly below skin temperature at 30 °C. Triggered by skin heat, the BAP electrode achieves low modulus and high adhesion within seconds, allowing robust skin-electrode interface under dry, wet, and body-moving conditions. Ice bag treatment can dramatically stiffen the electrode and reduce the adhesion, which allows painless detachment and avoids electrode damage. Meanwhile, the AgNWs network with biaxial wrinkled microstructure remarkably promotes the electro-mechanical stability of the BAP electrode. The BAP electrode successfully combines long-term (7 days) and dynamic (body movements, sweat, underwater) stability, reusability (at least ten times), and minimized skin irritation during electrophysiological monitoring. The high signal-to-noise ratio and dynamic stability are demonstrated in the application of piano-playing training.

Photolithographic Structuring of Ordered Silicon Micropillar Electrodes for Lithium-Ion Batteries and Electrochemical Performance

Ordered and vertically oriented silicon (Si) micropillar structures, when optimally designed, can accommodate the lithiation-induced volumetric expansion that is limiting the implementation of Si as negative electrodes in Li-ion batteries. As there is not much work in this area, this study is focused on evaluating systematically the potential of Si micropillar electrodes prepared by photolithographic structuring of Si. The specific objective is to determine the effect of micropillar length and the free space around the pillars on the electrochemical performance of the electrode. The Si micropillar electrode with the pillar length of 14 μm showed a high specific capacity (2600 mAh/g) and a high areal capacity (3 mAh/cm2), which were stable for over 100 cycles. However, there was significant capacity degradation in 32 and 48 μm-long Si pillar electrodes due to cracking and electrode damage during cycling. In the 32 μm Si micropillar electrode, a small change in porosity from 69 to 86% caused a substantial increase in specific capacity from 1400 to 2000 mAh/g over 100 cycles, with the areal capacity decreasing from 3 to 2 mAh/cm2. The findings also show the directions for further work for the optimization of Si micropillar electrodes.

Rod Insertion TDR for Detecting Corrosion Damage in Vertical Grounding Electrodes

Faults in a grounding network pose a serious threat to power system equipment protection and worker safety. A large number of vertical electrodes are used in a grounding network and break-points in these due to soil induced corrosion is one of the prime reasons for faults. We present a rod insertion time domain reflectometry (TDR) technique for vertical grounding electrode break-point detection. A secondary bare rod is inserted adjacent to the grounding electrode while a fast risetime pulse is continuously applied to excite a transverse electromagnetic (TEM) wave that propagates along the rods and reflects back from the break-point. The reflected signals for different depths of the secondary rod are analyzed to identify the location and severity of the break-point. We show that fault detection is possible without prior knowledge of soil electrical parameters. To show the feasibility of the proposed technique, a full wave simulation approach is used to evaluate the wideband input impedance of the grounding and inserted rod system and then FFT is applied to obtain TDR responses. The results show the method is capable of detecting faults for a wide range of soil conductivity for a system bandwidth of 300MHz.

Transitions between field emission and vacuum breakdown in nanoscale gaps

The continuing reduction in device size motivates a more fundamental understanding of breakdown and electron emission for nanoscale gaps. While prior experiments have separately studied breakdown and electron emission in vacuum gaps, no study has comprehensively examined the transitions between these mechanisms. In this study, we measure the current-voltage (I−V) curves for electrodes with different emitter widths for 20–800 nm gaps at vacuum (∼1 μTorr) to measure breakdown voltage and assess electron emission behavior. The breakdown voltage Vb increases linearly with increasing gap distance from ∼15 V at 20 nm to ∼220 V at 300 nm and remains nearly constant for larger gaps; Vb does not depend strongly on the emitter width. Breakdown can proceed directly from the field emission regime. Nexus theory, which predicts transitions between space-charge limited current (SCLC) and field emission (FE), shows that the experimental conditions are in the Fowler–Nordheim regime and within a factor of 0.7 to the FE-SCLC transition. We also present the results of electrode damage by emission current-induced heating to explain the flattening of Vb at larger gaps that was absent in previous experiments for similar gap distances at atmospheric pressure.

Machining characteristics of various powder-based additives, dielectrics, and electrodes during EDM of micro-impressions: a comparative study

Electric discharge machining (EDM) has great acceptance in different application sectors to wipe out intrinsic problems, like product miniaturizing and tight tolerances, during the fabrication of micro-size products. Many researchers have worked well in the micro-cutting of various alloys through the EDM process. However, limited work has been reported on the EDM of SS 316 for micro-impression fabrication using EDM. The selection of the best dielectric, electrode material, and powder-based additives has never been targeted so far to have dimensionally accurate micro-impression at an appreciable cutting rate with no/less electrode damage in the EDM of the said alloy. Therefore, in this research, the collective influence of various dielectrics (kerosene oil, transformer oil, and canola oil), powders (alumina, graphite, and silicon carbide), and electrodes (copper, brass, and aluminum) have been comprehensively examined for the fabrication of micro-impressions in AISI 316 using EDM. Taguchi L9 orthogonal technique was applied to study the effect of four input parameters on material removal rate, overcut, and tool wear rate. Results were statistically explored using main effect plots and supplemented by scanning electron microscopy, surface profilometry, and optical microscopy. The results show that material removal and tool wear rates notably improved from the mean value by 29% and 89.4%, respectively, when the machining is carried out under silicon carbide mixed kerosene dielectric against silicon carbide the aluminum tool at a pulse time ratio of 1.5. Furthermore, for dimensional overcut, 5.3 times lesser value is observed from the average magnitude of 0.189 mm when the proposed EDM setup is employed for cutting AISI 316. An optimized setting has also been proposed by grey relational analysis and then validated through a confirmation experiment.

In Situ measurements of Stress and Potential Evolution during Self Discharge of a Lithiated Silicon Electrode

In this work, we report direct/in situ measurements of stress and potential evolution during self-discharge of a fully lithiated silicon electrode. Parasitic reactions, typically attributed to the formation of the solid-electrolyte-interphase (SEI) layer on the surface of the silicon electrode, cause the self-discharge leading to the loss of cyclable lithium ions from the electrode and irreversible capacity loss. These parasitic reactions continuously occur when the electrode potential is below the equilibrium potential (typically 0.8V vs. Li/Li+) for SEI formation, and when the surface is electronically conductive. We previously reported on coupled electrochemical-mechanical measurements in the Li-Si binary system between pure Si and Li15Si4 with the following key observations: the system undergoes cyclic compressive (up to -2GPa) and tensile stresses (up to +2GPa) during electrochemical lithiation and delithiation, respectively, with extensive plastic flow and associated mechanical dissipation1; the biaxial stress and the electrode potential are strongly coupled2; the electrode softens upon lithiation and toughens upon delithiation3; and the energy losses due to mechanical dissipation are comparable to the sum of kinetic/polarization, and ohmic losses4. Using the substrate-curvature measurement technique, we measured the stress and potential evolution during self-discharge (due to parasitic reactions) of a fully lithiated thin-film silicon electrode, and compare it to same measurements made during galvanostatic delithiation. Upon self-discharge, the stress of a fully lithiated electrode evolves from -1.2 GPa (compressive) towards a state of zero stress, and continues to become tensile (+0.5 GPa). The evolution from -1.2 GPa towards zero stress and continual increase in the tensile direction is caused by the removal of lithium ions from the electrode driven by the parasitic reactions5, and tensile stresses typically cause cracking and damage in electrodes. Figure 1 shows (a) the current density, (b) potential vs. Li/Li+, and (c) the electrode stress during a galvanostatic lithiation/delithiation cycle (in red), and during galvanostatic lithiation followed by self-discharge and galvanostatic delithiation (in blue).We also quantified the rates at which the parasitic reactions occur by measuring both potential and stress evolution during self-discharge at various states of charge, SOCs (i.e., by varying the concentration of lithium in the silicon electrode via galvanostatic lithiation, followed by open-circuit measurements). We show that the resulting parameters are useful in predicting changes in electrode stress and its evolution during the self discharge at various SOCs. We will discuss why these measurements are useful in the context of storing fully charged lithium-ion batteries on the shelf for long periods of time. Because of self-discharge-induced mechanical damage, for batteries made with a large-volume-expansion electrodes, it is better to store them at or near a state of zero stress than at a higher SOC.Acknowledgements:This work was supported at the Indian Institute of Science - Bangalore, by XII Plan grant (#12-0509-0457-01), and at Faraday Laboratory LLC by financial support from Unify Inc. (04UNIFY04302018 onward). PG gratefully acknowledges financial support through the Kishore Vaigyanik Protsahan Yojana Scholarship (KVPY, 2012-2017).

Spatial Quantification of Microstructural Degradation during Fast Charge in 18650 Lithium-Ion Batteries through Operando X-ray Microtomography and Euclidean Distance Mapping

Fast charging at rates above 1C aggressively accelerates structural degradation induced by increases in local temperature and inhomogeneous transport of charge. At the micron scale, the first indication of damage is irreversible expansion of the electrode layers. Electrode damage often involves void formation between the active material and conductive binder matrix. Quantification of this evolution must be carried out in real time and, thus, nondestructively. We report operando X-ray microtomography of cylindrical cells under fast-charge cycling. Two 18650 batteries were measured during cycling after antecedent fast charging cycles to track morphological damage at different points of battery life. A method of deep learning segmentation was used to objectively quantify the electrode degradation. Using Euclidean distance mapping, electrode dilation and voids were spatially resolved. Highly reversible trends in dilation were quantified during charge/discharge in the anode layers with irreversible increases in electrode voids. Anode voids showed clear localization within the first 10 μm near the current collectors, indicating delamination that spread upon further cycling. The cathode dilation trended opposite to the anode with higher fluctuations and an overall decrease in cathode voids. Insight into how fast charging induces structural damage better informs research into fast-charge protocols and battery chemistries.

Phase Transformations and Phase Segregation during Potassiation of Sn x P y Anodes.

K-ion batteries (KIBs) have the potential to offer a cheaper alternative to Li-ion batteries (LIBs) using widely abundant materials. Conversion/alloying anodes have high theoretical capacities in KIBs, but it is believed that electrode damage from volume expansion and phase segregation by the accommodation of large K-ions leads to capacity loss during electrochemical cycling. To date, the exact phase transformations that occur during potassiation and depotassiation of conversion/alloying anodes are relatively unexplored. In this work, we synthesize two distinct compositions of tin phosphides, Sn4P3 and SnP3, and compare their conversion/alloying mechanisms with solid-state nuclear magnetic resonance (SSNMR) spectroscopy, powder X-ray diffraction (XRD), and density functional theory (DFT) calculations. Ex situ31P and 119Sn SSNMR analyses reveal that while both Sn4P3 and SnP3 exhibit phase separation of elemental P and the formation of KSnP-type environments (which are predicted to be stable based on DFT calculations) during potassiation, only Sn4P3 produces metallic Sn as a byproduct. In both anode materials, K reacts with elemental P to form K-rich compounds containing isolated P sites that resemble K3P but K does not alloy with Sn during potassiation of Sn4P3. During charge, K is only fully removed from the K3P-type structures, suggesting that the formation of ternary regions in the anode and phase separation contribute to capacity loss upon reaction of K with tin phosphides.