New nano­lithia cath­ode bat­tery does not ‘breathe’ oxy­gen

The Witness - Wheels - - MOTORING -

A NEW bat­tery con­cept, called a nano­lithia cath­ode bat­tery, is de­scribed in the jour­nal Na­ture

En­ergy in a pa­per by Ju Li, the Bat­telle En­ergy Al­liance Pro­fes­sor of Nu­clear Sci­ence and En­gi­neer­ing at MIT; post­doc Zhi Zhu; and five oth­ers at MIT, Ar­gonne Na­tional Lab­o­ra­tory, and Pek­ing Uni­ver­sity in China.

In the pa­per Li ex­plains a ma­jor short­com­ing of lithi­u­mair bat­ter­ies is dif­fer­ence in volt­ages be­tween charg­ing and dis­charg­ing, with the out­put volt­age 1,2 or more volts lower than the charg­ing volt­age.

This means 30% of the elec­tri­cal en­ergy is lost as heat dur­ing charg­ing, said Li. Con­ven­tional lithium-air bat­ter­ies draw in oxy­gen to drive a chem­i­cal re­ac­tion with the bat­tery’s lithium dur­ing the dis­charge cy­cle, and re­lease the oxy­gen dur­ing the charg­ing cy­cle. In the new bat­tery, the same elec­tro­chem­i­cal re­ac­tions be­tween lithium and oxy­gen take place dur­ing charg­ing and dis­charg­ing, but the oxy­gen stays in­side the bat­tery and trans­forms di­rectly be­tween its three re­dox states, while bound in the form of three dif­fer­ent solid chem­i­cal com­pounds, Li2O, Li2O2, and LiO2, which are mixed to­gether in the form of a glass. Li said the new bat­tery loses only eight per­cent of the elec­tri­cal en­ergy as heat. “This means faster charg­ing for cars, as heat re­moval from the bat­tery pack is less of a safety con­cern, as well as en­ergy ef­fi­ciency ben­e­fits,” Li said.

The new bat­tery is also in­her­ently pro­tected from over­charg­ing, as the chem­i­cal re­ac­tion is self-lim­it­ing. “With a typ­i­cal bat­tery, if you over­charge it, it can cause ir­re­versible struc­tural dam­age or even ex­plode,” Li said, adding they over­charged the bat­tery for 15 days, to a hun­dred times its ca­pac­ity, but there was no dam­age at all.

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