Date: 2025-05-20 hits: 121
A. Introduction
The presence of metal particles is an important factor affecting the performance and safety of lithium batteries. In-depth research on its mechanism of action and corresponding inhibition strategies has important theoretical and practical significance. It is pointed out in "Quality Management of Positive Electrode Materials for Lithium-ion Batteries" that the performance of lithium-ion batteries is related to the quality of positive and negative electrode materials. Metal impurities can cause battery self-discharge, failure, and even thermal runaway. It is important to detect foreign matter in raw materials.
B. Negative impact of metal particles on lithium batteries
(I) Inducing internal micro-short circuits and accelerating self-discharge
1. After metal particles enter the battery as conductive foreign matter, they may pierce the diaphragm or form a conductive bridge between the positive and negative electrodes, causing local micro-short circuits.
2. During the battery formation stage, metal impurities undergo redox reactions in the electrolyte. The metal in the positive electrode is oxidized and migrates to the negative electrode to be reduced to a single metal. Repeated deposition forms a spike-like structure, which further pierces the diaphragm, causing more serious self-discharge and energy loss. Enter the "Lithium Battery Technology Knowledge Platform" video account and "Follow the video account". There is knowledge that interests you. Thank you for your support!
(II) Catalytic side reactions and electrolyte decomposition
1. HF produced by electrolyte decomposition reacts with metallic iron to produce compounds with poor conductivity, destroying the stability of the SEI film.
2. Metal ions shuttle between the positive and negative electrodes, continuously consuming active lithium ions, resulting in capacity decay.
3. Metal catalyzes the decomposition of electrolyte to produce gas, increase internal pressure, and release heat, which may trigger a thermal runaway chain reaction.
(III) Promote dendrite growth and structural damage
1. Metal particles act as heterogeneous nucleation sites, exacerbating the growth of lithium/copper dendrites. Lithium dendrites pierce the diaphragm to cause malignant short circuits, and copper dendrites have a higher risk of piercing.
2. Dendrite growth causes volume expansion of electrode materials, resulting in pulverization and shedding of active materials, accelerating capacity decay.
(IV) Deterioration of electrochemical performance
1. Metal reaction products block electrode pores, hinder lithium ion transmission, degrade the electronic conductive network, and increase internal resistance.
2. Local current density unevenness leads to increased overpotential, increased polarization, and reduced energy efficiency.
3. Side reactions caused by metal impurities irreversibly consume electrolyte and active lithium, shortening cycle life.
(V) Manufacturing process-related impacts
1. Metal particles are introduced by burrs generated by electrode slitting, metal chips from welding spatter, or environmental dust pollution.
2. Burrs on the cutting edge of the electrode may penetrate conventional diaphragms.
3. Metal debris generated by the welding process contaminates the lug area, causing the shell to short-circuit.
4. Metal particles reduce the diaphragm breakdown voltage and increase the local electric field strength.
C. Strategies to inhibit the negative impact of metal particles
1. Material purification: Control the metal impurity content of electrode materials to <50ppm, and the silicon content should generally be controlled below 10ppm; use pretreatment methods such as magnetic separation and pickling.
2. Diaphragm enhancement: Use ceramic coating diaphragms (such as AlzO: coating) to improve puncture resistance.
3. Structural design: Use three-dimensional porous current collectors (such as copper mesh) to disperse current density and inhibit dendrite growth.
4. Electrolyte optimization: Add film-forming agents such as LiPOzF2 to form a more stable SEI layer.
5. Process control: Ensure that the cleanliness of the production environment reaches 1S07 level or above, and use laser cutting instead of traditional slitting to reduce burrs.
IV. Conclusion
The impact of metal particles on lithium batteries runs through the entire process of their electrochemical cycle, and there is a significant correlation from microscopic reactions to macroscopic failures. Through in-depth research on its mechanism of action and the adoption of effective inhibition strategies, it is expected to achieve safer and higher-performance lithium battery design.
