An electrolyte is a substance that produces an electrically conducting solution when dissolved in a polar solvent, such as water. The dissolved electrolyte separates into cations and anions, which disperse uniformly through the solvent. Electrically, such a solution is neutral. If an electric potential is applied to such a solution, the cations of the solution are drawn to the electrode that has an abundance of electrons, while the anions are drawn to the electrode that has a deficit of electrons. The movement of anions and cations in opposite directions within the solution amounts to a current. This includes most soluble salts, acids, and bases. Some gases, such as hydrogen chloride, under conditions of high temperature or low pressure can also function as electrolytes. Electrolyte solutions can also result from the dissolution of some biological (e.g., DNA, polypeptides) and synthetic polymers (e.g., polystyrene sulfonate), termed "polyelectrolytes", which contain charged functional groups. A substance that dissociates into ions in solution acquires the capacity to conduct electricity. Sodium, potassium, chloride, calcium, magnesium, and phosphate are examples of electrolytes, informally known as "lytes".

In medicine, electrolyte replacement is needed when a person has prolonged vomiting or diarrhea, and as a response to strenuous athletic activity. Commercial electrolyte solutions are available, particularly for sick children (such as oral rehydration solution, Suero Oral, or Pedialyte) and athletes (sports drinks). Electrolyte monitoring is important in the treatment of anorexia and bulimia.


The word electrolyte derives from the Greek lytós, meaning "able to be untied or loosened".


Svante Arrhenius put forth, in his 1884 dissertation, his explanation of the fact that solid crystalline salts disassociate into paired charged particles when dissolved, for which he won the 1903 Nobel Prize in Chemistry.[1][2][3][4]

Arrhenius's explanation was that in forming a solution, the salt dissociates into charged particles, to which Michael Faraday had given the name "ions" many years earlier. Faraday's belief had been that ions were produced in the process of electrolysis. Arrhenius proposed that, even in the absence of an electric current, solutions of salts contained ions. He thus proposed that chemical reactions in solution were reactions between ions.[2][3][4]


Electrolyte solutions are normally formed when a salt is placed into a solvent such as water and the individual components dissociate due to the thermodynamic interactions between solvent and solute molecules, in a process called "solvation". For example, when table salt (sodium chloride), NaCl, is placed in water, the salt (a solid) dissolves into its component ions, according to the dissociation reaction



Molten salts can also be electrolytes as, for example, when sodium chloride is molten, the liquid conducts electricity. In particular, ionic liquids, which are molten salts with melting points below 100 °C,[5] are a type of highly conductive non-aqueous electrolytes and thus have found more and more applications in fuel cells and batteries.[6]

An electrolyte in a solution may be described as "concentrated" if it has a high concentration of ions, or "diluted" if it has a low concentration. If a high proportion of the solute dissociates to form free ions, the electrolyte is strong; if most of the solute does not dissociate, the electrolyte is weak. The properties of electrolytes may be exploited using electrolysis to extract constituent elements and compounds contained within the solution.

Alkaline earth metals form hydroxides that are strong electrolytes with limited solubility in water, due to the strong attraction between their constituent ions. This limits their application to situations where high solubility is not required.[7]

Physiological importance


All known higher lifeforms require a subtle and complex electrolyte balance between the intracellular and extracellular environments. In particular, the maintenance of precise osmotic gradients of electrolytes is important. Such gradients affect and regulate the hydration of the body as well as blood pH, and are critical for nerve and muscle function. Various mechanisms exist in living species that keep the concentrations of different electrolytes under tight control.


Electrolyte balance is maintained by oral, or in emergencies, intravenous (IV) intake of electrolyte-containing substances, and is regulated by hormones, in general with the kidneys flushing out excess levels. In humans, electrolyte homeostasis is regulated by hormones such as antidiuretic hormones, aldosterone and parathyroid hormones. Serious electrolyte disturbances, such as dehydration and overhydration, may lead to cardiac and neurological complications and, unless they are rapidly resolved, will result in a medical emergency.


Measurement of electrolytes is a commonly performed diagnostic procedure, performed via blood testing with ion-selective electrodes or urinalysis by medical technologists. The interpretation of these values is somewhat meaningless without analysis of the clinical history and is often impossible without parallel measurements of renal function. The electrolytes measured most often are sodium and potassium. Chloride levels are rarely measured except for arterial blood gas interpretations, since they are inherently linked to sodium levels. One important test conducted on urine is the specific gravity test to determine the occurrence of an electrolyte imbalance.


In oral rehydration therapy, electrolyte drinks containing sodium and potassium salts replenish the body's water and electrolyte concentrations after dehydration caused by exercise, excessive alcohol consumption, diaphoresis (heavy sweating), diarrhea, vomiting, intoxication or starvation. Athletes exercising in extreme conditions (for three or more hours continuously, e.g. a marathon or triathlon) who do not consume electrolytes risk dehydration (or hyponatremia).[10]

A home-made electrolyte drink can be made by using water, sugar and salt in precise proportions.[11] Pre-made preparations are also available commercially,[12] and also for veterinary use.

Electrolytes are commonly found in fruit juices, sports drinks, milk, nuts, and many fruits and vegetables (whole or in juice form) (e.g., potatoes, avocados).


When electrodes are placed in an electrolyte and a voltage is applied, the electrolyte will conduct electricity. Lone electrons normally cannot pass through the electrolyte; instead, a chemical reaction occurs at the cathode, providing electrons to the electrolyte. Another reaction occurs at the anode, consuming electrons from the electrolyte. As a result, a negative charge cloud develops in the electrolyte around the cathode, and a positive charge develops around the anode. The ions in the electrolyte neutralize these charges, enabling the electrons to keep flowing and the reactions to continue.


2H2O + 2e → 2OH + H2

and hydrogen gas will bubble up; the anode reaction is

2NaCl → 2 Na+ + Cl2 + 2e



Electrolytic conductors are used in electronic devices where the chemical reaction at a metal-electrolyte interface yields useful effects.

  • In electrolytic capacitors the chemical effect is used to produce an extremely thin dielectric or insulating coating, while the electrolyte layer behaves as one capacitor plate.

Solid electrolytes

Solid electrolytes can be mostly divided into four groups:

  • Gel electrolytes - closely resemble liquid electrolytes. In essence, they are liquids in a flexible lattice framework. Various additives are often applied to increase the conductivity of such systems.[13][15]
  • Organic ionic plastic crystals - are a type organic salts exhibiting mesophases (i.e. a state of matter intermediate between liquid and solid), in which mobile ions are orientationally or rotationally disordered while their centers are located at the ordered sites in the crystal structure.[14] They have various forms of disorder due to one or more solid–solid phase transitions below the melting point and have therefore plastic properties and good mechanical flexibility as well as improved electrode|electrolyte interfacial contact. In particular, protic organic ionic plastic crystals (POIPCs),[14] which are solid protic organic salts formed by proton transfer from a Brønsted acid to a Brønsted base and in essence are protic ionic liquids in the molten state, have found to be promising solid-state proton conductors for fuel cells. Examples include 1,2,4-triazolium perfluorobutanesulfonate[14] and imidazolium methanesulfonate.[19]

See also


  1. "The Nobel Prize in Chemistry 1903". Retrieved 5 January 2017.
  2. 1 2 Harris, William; Levey, Judith, eds. (1975). The New Columbia Encyclopedia (4th ed.). New York City: Columbia University. p. 155. ISBN 0-231035-721.
  4. 1 2 Cillispie, Charles, ed. (1970). Dictionary of Scientific Biography (1 ed.). New York City: Charles Scribner's Sons. pp. 296–302. ISBN 0-684101-122.
  5. 石家华; 孙逊; 杨春和; 高青雨; 李永舫 (2002). "离子液体研究进展" (PDF). 化学通报 (in 中文). 北京 (4): 243. ISSN 0441-3776. Retrieved 2017-03-01.
  6. Jiangshui Luo; Jin Hu; Wolfgang Saak; Rüdiger Beckhaus; Gunther Wittstock; Ivo F. J. Vankelecom; Carsten Agert; Olaf Conrad (2011). "Protic ionic liquid and ionic melts prepared from methanesulfonic acid and 1H-1,2,4-triazole as high temperature PEMFC electrolytes". Journal of Materials Chemistry. 21: 10426–10436. doi:10.1039/C0JM04306K.
  7. Brown, Chemistry: The Central Science, 14th edition, pg. 680.
  8. 叶胜龙; 汤钊猷 (1986). "细胞膜钠泵及其临床意义". 上海医学 (in 中文) (1): 1.
  9. 涂志全 (2004). 张定昌. "电解质紊乱对晚期肿瘤的治疗影响". 中华中西医杂志 (in 中文) (10). 在正常人体内，钠离子占细胞外液阳离子总量的92%，钾离子占细胞内液阳离子总量的98%左右。钠、钾离子的相对平衡，维持着整个细胞的功能和结构的完整。钠、钾是人体内最主要的电解质成分...
  10. J, Estevez E; Baquero E; Mora-Rodriguez R (2008). "Anaerobic performance when rehydrating with water or commercially available sports drinks during prolonged exercise in the heat". Applied Physiology, Nutrition, and Metabolism. 33 (2): 290–298. doi:10.1139/H07-188. PMID 18347684.
  11. "Rehydration drinks". Webmd.com. 2008-04-28. Retrieved 2010-08-20.
  12. "Oral Rehydration Salt Suppliers". Rehydrate.org. 2014-10-07. Retrieved 2014-12-04.
  13. 1 2 Kamil Perzyna; Regina Borkowska; Jaroslaw Syzdek; Aldona Zalewska; Wladyslaw Wieczorek (2011). "The effect of additive of Lewis acid type on lithium–gel electrolyte characteristics". Electrochimica Acta. 57: 58–65. doi:10.1016/j.electacta.2011.06.014.
  14. 1 2 3 4 Jiangshui Luo; Annemette H. Jensen; Neil R. Brooks; Jeroen Sniekers; Martin Knipper; David Aili; Qingfeng Li; Bram Vanroy; Michael Wübbenhorst; Feng Yan; Luc Van Meervelt; Zhigang Shao; Jianhua Fang; Zheng-Hong Luo; Dirk E. De Vos; Koen Binnemans; Jan Fransaer (2015). "1,2,4-Triazolium perfluorobutanesulfonate as an archetypal pure protic organic ionic plastic crystal electrolyte for all-solid-state fuel cells". Energy & Environmental Science. 8. doi:10.1039/C4EE02280G.
  16. Syzdek J, Borkowska R, Perzyna K, Tarascon JM, Wieczorek W (2007). "Novel composite polymeric electrolytes with surface-modified inorganic fillers". Journal of Power Sources. 173 (2): 712–720. Bibcode:2007JPS...173..712S. doi:10.1016/j.jpowsour.2007.05.061. ISSN 0378-7753.
  17. Syzdek J, Armand M, Marcinek M, Zalewska A, Żukowska G, Wieczorek W (2010). "Detailed studies on the fillers modification and their influence on composite, poly(oxyethylene)-based polymeric electrolytes". Electrochimica Acta. 55 (4): 1314–1322. doi:10.1016/j.electacta.2009.04.025. ISSN 0013-4686.
  18. Syzdek J, Armand M, Gizowska M, Marcinek M, Sasim E, Szafran M, Wieczorek W (2009). "Ceramic-in-polymer versus polymer-in-ceramic polymeric electrolytes—A novel approach". Journal of Power Sources. 194 (1): 66–72. Bibcode:2009JPS...194...66S. doi:10.1016/j.jpowsour.2009.01.070. ISSN 0378-7753.
  19. Jiangshui Luo; Olaf Conrad; Ivo F. J. Vankelecom (2013). "Imidazolium methanesulfonate as a high temperature proton conductor". Journal of Materials Chemistry A. 1. doi:10.1039/C2TA00713D.
