Lokacin hunturu yana zuwa, kalli yanayin binciken ƙananan zafin jiki na baturan lithium-ion

Ayyukan batura lithium-ion yana da tasiri sosai saboda halayen motsin su. Domin Li+ yana buƙatar rushewa da farko lokacin da aka saka shi a cikin kayan graphite, yana buƙatar cinye wani adadin kuzari kuma ya hana yaduwar Li+ a cikin graphite. Akasin haka, lokacin da aka saki Li + daga kayan graphite a cikin bayani, tsarin warwarewa zai fara faruwa, kuma tsarin warwarewa baya buƙatar amfani da makamashi. Li+ na iya cire graphite da sauri, wanda ke haifar da ƙarancin cajin karɓar kayan graphite. A cikin yarda da fitarwa .

A ƙananan yanayin zafi, halayen motsin motsi na lantarki na graphite mara kyau sun inganta kuma sun zama mafi muni. Saboda haka, electrochemical polarization na korau electrode yana da muhimmanci a lokacin da caji tsari, wanda zai iya sauƙi kai ga hazo na karfe lithium a saman da korau electrode. Wani bincike da Christian von Lüders na Jami’ar Fasaha ta Munich ta Jamus ya yi ya nuna cewa a -2°C, yawan cajin ya zarce C/2, kuma yawan hazo na karfen lithium yana karuwa sosai. Misali, a ƙimar C/2, adadin lithium plating akan farfajiyar wutar lantarki mai gaba ɗaya shine game da duka cajin. 5.5% na iya aiki amma zai kai 9% a ƙarƙashin girman 1C. Lithium da aka haɗe da ƙarfe na iya haɓaka gaba kuma a ƙarshe ya zama lithium dendrites, yana huda ta diaphragm kuma yana haifar da gajeriyar kewayawa na ingantattun na'urorin lantarki. Don haka, ya zama dole a guji yin cajin baturin lithium-ion a ƙananan zafin jiki gwargwadon yiwuwa. Lokacin da dole ne ya yi cajin baturi a ƙananan zafin jiki, yana da mahimmanci don zaɓar ƙaramin halin yanzu don cajin baturin lithium-ion gwargwadon yuwuwa kuma a adana cikakken baturin lithium-ion bayan ya yi caji don tabbatar da cewa lithium na ƙarfe ya haye daga gurɓataccen lantarki. na iya mayar da martani tare da graphite kuma a sake sakawa a cikin gurɓataccen lantarki na graphite.

Veronika Zinth da wasu na Jami'ar Fasaha ta Munich sun yi amfani da diffraction na Neutron da sauran hanyoyin don nazarin yanayin juyin halittar lithium na baturan lithium-ion a ƙananan zafin jiki na -20 ° C. Neutron diffraction ya kasance sabuwar hanyar ganowa a cikin 'yan shekarun nan. Idan aka kwatanta da XRD, diffraction neutron ya fi kula da abubuwa masu haske (Li, O, N, da dai sauransu), don haka ya dace sosai don gwajin rashin lalacewa na batir lithium-ion.

A cikin gwajin, VeronikaZinth yayi amfani da batirin NMC111/graphite 18650 don nazarin yanayin juyin halittar lithium na baturan lithium-ion a ƙananan yanayin zafi. Ana cajin baturi kuma ana fitar da shi yayin gwajin bisa ga tsarin da aka nuna a hoton da ke ƙasa.

Hoton da ke gaba yana nuna canjin lokaci na mummunan lantarki a ƙarƙashin SoCs daban-daban yayin zagayowar caji na biyu a cajin ƙimar C/30. Yana iya zama alama cewa a 30.9% SoC, matakai na mummunan electrode sun fi LiC12, Li1-XC18, da ƙananan adadin LiC6 Composition; bayan SoC ya wuce 46%, rarrabuwar ƙarfi na LiC12 yana ci gaba da raguwa, yayin da ƙarfin LiC6 ke ci gaba da ƙaruwa. Duk da haka, ko da bayan an kammala cajin ƙarshe, tun da kawai 1503mAh ana cajin shi a ƙananan zafin jiki (ikon shine 1950mAh a dakin da zafin jiki), LiC12 yana wanzu a cikin wutar lantarki mara kyau. A ce an rage cajin halin yanzu zuwa C/100. A wannan yanayin, har yanzu baturin zai iya samun ƙarfin 1950mAh a ƙananan zafin jiki, wanda ke nuna cewa raguwar ƙarfin baturan lithium-ion a ƙananan yanayin zafi ya fi girma saboda lalacewar yanayin motsi.

Hoton da ke ƙasa yana nuna canjin lokaci na graphite a cikin gurɓataccen lantarki yayin caji gwargwadon ƙimar C/5 a ƙananan zafin jiki na -20°C. Yana iya ganin cewa canjin lokaci na graphite ya bambanta sosai idan aka kwatanta da cajin ƙimar C/30. Ana iya gani daga adadi cewa lokacin da SoC> 40%, ƙarfin lokaci na baturi LiC12 a ƙarƙashin ƙimar cajin C/5 yana raguwa sosai a hankali, kuma haɓaka ƙarfin lokaci na LiC6 shima ya yi rauni sosai fiye da na C/30. kudin caji. Ya nuna cewa a ƙaramin adadin C/5, ƙasa da LiC12 yana ci gaba da daidaita lithium kuma an canza shi zuwa LiC6.

Hoton da ke ƙasa yana kwatanta sauye-sauyen lokaci na lantarki na graphite mara kyau lokacin caji a ƙimar C/30 da C/5, bi da bi. Adadin ya nuna cewa ga farashin caji guda biyu daban-daban, matakin lithium-malauci na Li1-XC18 yayi kama da juna. Bambancin yana nunawa a cikin matakai biyu na LiC12 da LiC6. Ana iya gani daga adadi cewa yanayin canjin lokaci a cikin gurɓataccen lantarki yana kusa da matakin farko na caji ƙarƙashin ƙimar caji biyu. Don lokacin LiC12, lokacin da ƙarfin caji ya kai 950mAh (49% SoC), yanayin canzawa ya fara bayyana daban. Lokacin da yazo 1100mAh (56.4% SoC), lokacin LiC12 a ƙarƙashin manyan ma'auni biyu ya fara nuna babban gibi. Lokacin yin caji a ƙananan ƙimar C / 30, raguwar matakin LiC12 yana da sauri sosai, amma raguwar lokaci na LiC12 a ƙimar C / 5 yana da hankali sosai; wato, yanayin motsin motsa jiki na shigar lithium a cikin gurɓataccen lantarki yana lalacewa a ƙananan zafin jiki. , Don haka LiC12 ya ƙara haɗa lithium don samar da saurin lokaci na LiC6 ya ragu. Hakazalika, lokacin LiC6 yana ƙaruwa da sauri a ƙananan ƙimar C/30 amma yana da hankali sosai a ƙimar C/5. Wannan yana nuna cewa a cikin ƙimar C / 5, ƙarin ƙaramin Li yana cikin tsarin kristal na graphite, amma abin ban sha'awa shine ƙarfin cajin baturi (1520.5mAh) a ƙimar cajin C / 5 ya fi wancan a C. /30 kudin caji. Ikon (1503.5mAh) ya fi girma. Ƙarin Li wanda ba a haɗa shi a cikin na'urar lantarki mai graphite mara kyau ba zai yiwu a haɗe shi a saman graphite a cikin nau'in lithium na ƙarfe. Tsarin tsaye bayan ƙarshen caji kuma yana tabbatar da hakan daga gefe-kadan.

Hoto mai zuwa yana nuna tsarin lokaci na lantarki mai graphite mara kyau bayan caji da kuma bayan an bar shi na awanni 20. A ƙarshen caji, lokacin da madaidaicin graphite electrode ya bambanta sosai a ƙarƙashin ƙimar caji guda biyu. A C/5, rabon LiC12 a cikin graphite anode ya fi girma, kuma adadin LiC6 ya ragu, amma bayan tsayawa na sa'o'i 20, bambanci tsakanin su biyu ya zama kaɗan.

Hoton da ke ƙasa yana nuna canjin lokaci na lantarki mai hoto mara kyau yayin aikin ajiya na 20h. Ana iya gani daga adadi cewa ko da yake sassan biyu masu adawa da wutar lantarki har yanzu sun bambanta sosai a farkon, yayin da lokacin ajiya ya karu, nau'i biyu na caji Matsayin graphite anode a ƙarƙashin girman girman ya canza sosai. LiC12 na iya ci gaba da canzawa zuwa LiC6 yayin aiwatar da tanadin, yana nuna cewa Li za ta ci gaba da sanyawa a cikin graphite yayin aikin tanadin. Wannan ɓangaren Li yana yiwuwa ya zama ƙarfe na ƙarfe lithium wanda ya hado saman madaidaicin graphite lantarki a ƙananan zafin jiki. Ci gaba da bincike ya nuna cewa a ƙarshen caji a ƙimar C/30, ƙimar lithium intercalation na graphite mara kyau shine 68%. Duk da haka, matakin intercalation na lithium ya karu zuwa 71% bayan adanawa, karuwa na 3%. A ƙarshen caji a ƙimar C/5, matakin shigar lithium na lantarki mai graphite mara kyau shine 58%, amma bayan an bar shi na awanni 20, ya ƙaru zuwa 70%, jimlar karuwar 12%.

Binciken da aka yi a sama ya nuna cewa lokacin yin caji a ƙananan zafin jiki, ƙarfin baturi zai ragu saboda lalacewar yanayin motsi. Hakanan zai haifar da ƙarfe na lithium akan saman madaidaicin lantarki saboda raguwar ƙimar shigar lithium graphite. Koyaya, bayan ɗan lokaci na ajiya, Wannan ɓangaren na lithium na ƙarfe yana iya sake sakawa a cikin graphite; a ainihin amfani, lokacin shiryayye sau da yawa gajere ne, kuma babu tabbacin cewa za a iya sake shigar da duk wani ƙarfe na lithium a cikin graphite, don haka yana iya haifar da wani ƙarfe na ƙarfe ya ci gaba da wanzuwa a cikin gurɓataccen lantarki. Fuskar baturin lithium-ion zai shafi ƙarfin baturin lithium-ion kuma yana iya haifar da lithium dendrites waɗanda ke yin haɗari ga amincin baturin lithium-ion. Don haka, yi ƙoƙarin guje wa cajin baturin lithium-ion a ƙananan zafin jiki. Ƙananan halin yanzu, kuma bayan saiti, tabbatar da isasshen lokacin shiryayye don kawar da lithium na ƙarfe a cikin lantarki mai hoto mara kyau.

Wannan labarin yana magana ne akan takardu masu zuwa. Ana amfani da rahoton ne kawai don gabatarwa da duba ayyukan kimiyya masu alaƙa, koyarwar aji, da binciken kimiyya. Ba don amfanin kasuwanci ba. Idan kuna da wasu batutuwan haƙƙin mallaka, da fatan za a ji daɗin tuntuɓar mu.

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