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A common failure mechanism for batteries is mechanical shock,which can damage the electrodes or system container,resulting in poor conductivity and electrolyte leakage.However,the mechanical properties of electrodes are of relevance beyond collision resistance due to their environment.During standard operation, the incorporation of ions into the electrodes causes a change in volume.A good example is the silicon electrode in a Li-ion battery,which expands by about 300% during lithiation.This change can lead to deformation of the crystal lattice, which leads to stress in the material.The source of the stress could be due to geometrical constraints in the electrodes or uneven plating of ions.This phenomenon is very worrying because it can lead to electrode fracture and performance loss.Therefore,mechanical properties are crucial for developing new electrodes for long-lasting batteries.One possible strategy to measure the mechanical behavior of electrodes during operation is to use nanoindentation.
The method enables analysis of how stress evolves during electrochemical reactions and is a valuable tool for evaluating possible pathways for coupling mechanical behavior and electrochemistry.Stress not only affects the morphology of electrodes but also affects electrochemical reactions.While the magnitude of chemical driving force is usually higher than mechanical energy,this is not the case for Li-ion batteries.A study by Dr. Larché established a direct relationship between the applied stress and the chemical potential of the electrode.Although it ignores multiple variables,such as changes in elastic constraints,it subtracts the elastic energy due to stress from the total chemical potential.In this equation,μ represents the chemical potential and μ° is its reference value.T stands for temperature and k stands for Boltzmann's constant.The term γ in the logarithm is the activity and x is the ratio of ions to the total composition of the electrode.The new term Ω is the partial molar volume of the ion in the host, and σ corresponds to the average stress experienced by the system.A consequence of this equation is that diffusion that depends on the chemical potential can be affected by additional stress,changing the performance of the cell.In addition, mechanical stress may also affect the solid electrolyte interfacial layer of the electrode.Interfaces that regulate ion and charge transfer can be degraded by stress.Therefore, more ions in the solution will be consumed to recombine them, reducing the overall efficiency of the system.
Other anodes and cathodes
In vacuum tubes or polarized semiconductors (diodes, electrolytic capacitors), the anode is the positive (+) electrode and the cathode is the negative (-). Electrons enter the device through the cathode and leave the device through the anode. Many devices have other electrodes to control operation such as base,gate,control gate.In a three-electrode cell, the counter electrode (also known as the auxiliary electrode) is only used to connect the electrolyte so that current can be applied to the working electrode.The counter electrode is usually made of an inert material, such as a noble metal or graphite, to prevent it from dissolving.
Welding electrodes
In arc welding,electrodes are used to conduct electrical current through the workpieces to fuse the two workpieces together. Depending on the process,electrodes are either consumable,such as gas metal arc welding or shielded metal arc welding, or non-consumable,such as gas tungsten arc welding. For DC systems,the electrode or electrode can be the cathode for filler type welding or the anode for other welding processes.For AC arc welders, the welding electrode is not considered an anode or cathode.
Alternating current electrodes
For electrical systems using alternating current,an electrode is the connection between the circuit and the object to which the current flows,but is not designated as an anode or cathode because the direction of flow of electrons changes periodically,usually many times per second.
Chemically modified electrodes
A chemically modified electrode is an electrode whose surface is chemically modified to change the physical,chemical, electrochemical,optical,electrical, and transport properties of the electrode.These electrodes are used for advanced purposes in research and investigation
