Synthesis and electrochemical performance of an imidazolium based Li salt as electrolyte with Li fluorinated sulfonylimides as additives for Li-Ion batteries

Ahmed, Faiz,Rahman, Md. Mahbubur,Sutradhar, Sabuj Chandra,Lopa, Nasrin Siraj,Ryu, Taewook,Yoon, Sujin,Choi, Inhwan,Lee, Yonghoon,Kim, Whangi Elsevier 2019 ELECTROCHIMICA ACTA Vol.302 No.-

<P><B>Abstract</B></P> <P>Herein, we report the synthesis of a novel imidazolium-based ionic salt, lithium (fluorosulfonyl) ((3-(1-methyl-1H-imidazol-3-ium-3-yl)propyl)sulfonyl) bis(fluorosulfonyl)imide (LiFSMIPFSI) as an electrolyte for the application in lithium-ion battery (LIB). The as-synthesized LiFSMIPFSI exhibited high purity and yield, which was characterized by various spectroscopic techniques. The LiFSMIPFSI electrolyte with a mixed solvent of ethylene carbonate (EC) and dimethyl sulfoxide (DMSO) (75:25 v/v) showed a wide electrochemical stability (ca. 4.5 V <I>vs.</I> Li/Li<SUP>+</SUP>) and high thermal stability (300 °C), good Li<SUP>+</SUP> conductivity (ca. 8.02 mS/cm at 30 °C), and low intrinsic viscosity, which concurrently delivered a specific discharge capacity of ca. 125 mAhg<SUP>−1</SUP> at 0.1 C with the full LIB configuration of LiFePO<SUB>4</SUB>/electrolytes/graphite. The performance of this LiFSMIPFSI electrolyte was enhanced further by the addition of conventional lithium bis(fluoro-sulfonyl)imide (LiFSI) and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) ionic salts (20% each) as additives with the specific discharge capacity of ca. 147 and 139 mAhg<SUP>−1</SUP>, respectively, at 0.1 C. This is mainly due to the additional enhancement of Li<SUP>+</SUP> conductivity and its concentrations in the electrolytes induced by the additives. The LiFSMIPFSI electrolyte with LiFSI additive based LIB showed the highest cycling stability (capacity retention ca. 97%) among the electrolytes after 500 charge-discharge cycles. Thus, the present work contributes to the development of new ionic salts and its effects upon the addition of additives on LIB performance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Imidazolium-based ionic salt (LiFSMIPFSI) was prepared as an electrolyte for LIBs. </LI> <LI> LiFSMIPFSI electrolyte showed good ionic conductivity and LIB performance. </LI> <LI> LiFSI and LiTFSI were added as additives to enhance the performance of LiFSMIPFSI. </LI> <LI> LiFSMIPFSI with LiFSI additive delivered a maximum capacity of 147 mAhg<SUP>−1</SUP>. </LI> <LI> The electrolyte without/with additives showed good capacity retention. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

마음의 理氣와 자연의 理氣 정약용의 四端七情論爭 평가에 대한 재평가

김형찬 계명대학교 한국학연구원 2010 한국학논집 Vol.0 No.40

Yi Hwang classified sadan (the Four Beginnings) and chiljeong (the Seven Emotions) on the basis that li issues or gi issues, and presented the propositions like ‘li issues’, ‘li moves’, and ‘li approaches by itself’. It is meaningful in the respects that it made the direction which people should follow clearer by distinctively dividing the ethical emotions, judgments, and actions on the criteria of goodness or badness, and showed in words the fact that the ethical norms of li should be always able to exercise its governing power over the ethical emotions, judgments, and actions. Naturally it caused some criticisms because he used the words which were usually used on physical actions as the predicates of li. However it can be said that he intentionally made good use of the equivocalness. By using the words with the meanings of physical actions, he could reveal in language that li have the meanings of the ethical norms as well as the meanings of the physical laws, and the ethical norms are or must be carried out on the action of gi as the working rules like the physical laws. On this point of view, if the concepts of li and gi were confined in the realm of the human mind-heart like Jeong Yak-yong's explanation, the meanings that Yi Hwang tried to reveal are not showed well. In fact, this problem had begun from the moment that Yi Ik tried to defend Yi Hwang's theory in the dimension of the universal li-gi theory against Yi I's one-way theory that gi issues first and li follows. Jeong Yak-yong's explanation that succeeded Yi Ik's method of concepts classification looks like putting the debate in order clearly on the surface. Jeong Yak-yong considered Yi Hwang's li-gi as the special li-gi in the human mind-heart and Yi I's li-gi as the universal li-gi in the nature, and confined Yi Hwang's li-gi in the realm of the human mind-heart and nature. But Jeong lost the solid foundation of the ontology for the theory of mind-heart and nature taken from Yi Hwang who Jeong had respected and adored in his heart because he understood Yi Hwang's li-gi in this restrictive meaning. 이황이 사단·칠정을 理發·氣發로 구분하고, 理動·理發·理自到라는 명제를 제기한 것은 善惡의 기준으로 도덕적 감성·판단·행위를 선명하게 구분함으로써 지향해야 할 바를 명확히 하고, 그러한 도덕적 감성·판단·행위에 理의 도덕규범이 기준으로서 언제나 지배력을 행사할 수 있도록 해야 한다는 것을 언어로 드러냈다는 점에서 의미가 있다. 물론 이는 일반적으로 물리적 작용을 의미하는 용어들을 理의 술어로 사용함으로써 논란을 야기하였다. 하지만 오히려 그러한 물리적 작용을 의미하는 용어를 사용함으로써 理가 도덕규범의 의미와 동시에 물리법칙의 의미를 가지고 있으며, 도덕규범이 물리법칙과 동시에 물리법칙처럼 준칙으로서 氣의 작용에 관철되거나 혹은 관철되어야 함을 언어상으로 드러낼 수 있었다는 점에서, 이황은 理氣 개념의 다의성을 의도적으로 이용하였다고 하겠다. 이렇게 볼 때, 정약용처럼 이황의 理氣 개념을 人心의 영역으로 한정할 경우에는 이황이 드러내고자 하였던 뜻을 온전히 드러내기 어렵다. 사실상 이러한 문제점은 이익이 이이의 氣發理乘一途說에 맞서서 이황의 설을 보편적인 理氣論 차원에서 옹호하려 하면서부터 비롯된 것이었다. 정약용은 이익의 개념 구분 방식을 이어받아 이황의 理氣와 이이의 理氣를 각각 人心의 특수한 理氣와 자연의 보편적 理氣로 구분하고, 이황의 理氣를 인간 心性의 영역으로 한정함으로써 표면상 논의를 명쾌하게 정리한 듯이 보인다. 그러나 정약용은 이황의 理氣를 이렇게 한정적인 의미로 이해하였기 때문에, 그가 존경하며 사숙했던 이황으로부터 받아들인 理氣論은 견고한 존재론적 기반을 상실한 것이 되었다.

Non-volatile, Li-doped ion gel electrolytes for flexible WO₃-based electrochromic devices

Yun, Tae Yong,Li, Xinlin,Bae, Jaehyun,Kim, Se Hyun,Moon, Hong Chul Elsevier 2019 Materials & Design Vol.162 No.-

<P><B>Abstract</B></P> <P>Flexible electrochromic devices (ECDs) based on Li-doped ion gels and tungsten trioxide (WO<SUB>3</SUB>) are demonstrated. Colored ECDs cannot be produced using conventional ion gels comprised of copolymers and room temperature ionic liquids (RTILs) due to a lack of cations that can be inserted into WO<SUB>3</SUB>. Based on considerations of the coloration mechanism, we developed Li-doped ion gels and applied these to devices. The effects of Li salt concentration are systematically examined, with respect to device dynamics, coloration efficiency, and transmittance contrast. In addition, the coloration/bleaching switching stability of the ECD produced using optimal Li salt content is investigated. The ECD exhibits distinct colored and bleached states even after 24 h operation in air. Using the described Li-doped ion gel electrolytes, flexible WO<SUB>3</SUB> ECDs were successfully demonstrated with good bending stability and no electrolyte leakage.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Non-volatile, Li-doped ion gel electrolytes are designed for flexible WO<SUB>3</SUB>-based ECDs. </LI> <LI> ECDs exhibit low voltage operation (–0.9 V) and large transmittance contrast (~85%) between colored and bleached states. </LI> <LI> Electrolyte leakage is not observed in flexible ECDs containing Li-doped gel electrolyte when bending deformation is applied. </LI> <LI> Flexible ECDs maintain ~90.3 and ~84.5% of initial optical transmittance and coloration efficiency after 1000 bending tests. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Li_0.5La_0.5TiO₃와 Si박막을 갖는 구리 집전체의 Li free 음극으로써의 전기화학적 특성

이재준,김수호,이종민,윤영수,Lee Jae-Jun,Kim Soo-Ho,Lee Jong-Min,Yoon Young-Soo 한국전기화학회 2006 한국전기화학회지 Vol.9 No.1

Electrochemical properties of Cu foil current collector with a $Li_{0.5}La_{0.5}TiO_3$ Cu a Si thin film deposited by r.f sputtering as an anode for Li free battery were evaluated. The Cu foil current collectors were lied in and out of plasma during sputtering process. The X-ray diffraction results indicated that the as-deposited Si and $Li_{0.5}La_{0.5}TiO_3$ thin films in and out of plasma did not show any crystalline difference. The $Li_{0.5}La_{0.5}TiO_3$ film in plasma and Si film out of plasma showed better cyclability since crystalline $Li_{0.5}La_{0.5}TiO_3$ has much higher ionic conductivity and crystalline Si film is much sensitive far volume change during charge-discharge process. These results suggested that the deposition of amorphous Si on Cu foil current collector is much better for fabrication of Li free battery and it can be useful for the unique battery with a cycling number constraint of below 10. Li free 음극으로써 구리 foil 집전체에 $Li_{0.5}La_{0.5}TiO_3$ 및 Si 박막을 r.f, 스퍼터링법을 이용하여 증착하고 양극 물질로는 $Li[Co_{0.1}Ni_{0.15}Li_{0.2}Mn_{0.55}]O_2$를 이용하여 전기화학적 특성을 평가하였다. 박막 증착시 플라즈마 내(in-plasma)와 밖(out of plasma)에 구리 foil을 각각 위치시켰다. X-ray 회절 분석의 경우 각각의 조건에서 $Li_{0.5}La_{0.5}TiO_3$ 및 Si 모두 결정 특성의 차이를 발견할 수 없었다. $Li_{0.5}La_{0.5}TiO_3$의 경우 플라즈마 내에서 증착된 경우 그리고 Si 경우는 플라즈마 밖에서 증착된 경우 각각 싸이클 특성이 우수한 것으로 나타났다. 이는 $Li_{0.5}La_{0.5}TiO_3$ 경우 결정성이 존재할 경우 이온전도 특성이 우수하며 Si 경우 플라즈마 내에서 성장된 박막이 더욱 치밀하여 충방전 중 부피변화에 더욱 민감하였기 때문으로 판단된다. 이상의 결과로부터 (1)전지 용량을 갖는 5게 의한 표면 개질의 경우 구조적으로 안정할 수 있는 비정질 상의 Si이 보다 더 바람직하며 (2) 이온전도 특성을 보이는 $Li_{0.5}La_{0.5}TiO_3$와 같은 소재를 이용하여 표면 개질을 할 경우 Li의 확산이 더욱 용이한 구조가 바람직할 것으로 판단된다.

LiFePO₄와 Li₄P₂O₇의 ⁷Li MAS NMR 특성 연구

한덕영,박남신,이상혁,이학만,김창삼,Han, Doug-Young,Park, Nam-Sin,Lee, Sang-Hyuk,Lee, Hak-Man,Kim, Chang-Sam 한국결정성장학회 2011 한국결정성장학회지 Vol.21 No.1

[ $^7Li$ ]Magic Angle Spinning(MAS) NMR Spectroscopy를 활용하여 $Li_4P_2O_7$와 $LiFePO_4$ 물질에서 $^7Li$ 핵의 NMR 특성 및 화합물 분자내의 국부적 구조 연구를 수행하였다. $Li_4P_2O_7$와 $LiFePO_4$ 물질 연구는 리튬이온전지에서 고체-전해질 경계상(SEI, solid-electrolyte interphase) 물질 연구를 위한 것이다. $Li_4P_2O_7$와 $LiFePO_4$ 분말은 고상합성법으로 제조하였다.$^7Li$MAS NMR 실험은 $27^{\circ}C$에서 $97^{\circ}C$의 영역에서 변온 실험을 수행하였으며 이는 주변 온도 변화 환경에서 $Li_4P_2O_7$ 물질 내의 Li 핵의 구조 변화를 관찰하기 위한 것이다. $^7Li$ MAS NMR 측정 결과 시료 온도가 $27^{\circ}C$에서 $97^{\circ}C$의 온도 분포 영역에서는 $Li_4P_2O_7$ 물질 내부의 Li 핵은 구조적으로 변화하지 않는 것이 확인되었다. 금번 실험을 통하여 $LiFePO_4$ 분말에 5.0 wt%이내로 포함되어있는 $Li_4P_2O_7$ 물질의 $^7Li$ MAS NMR 신호를 측정할 수 있는 측정 조건을 알았다. [ $^7Li$ ]Magic Angle Spinning (MAS) NMR spectroscopy has been used to study the lithium local environments in $Li_4P_2O_7$ and$LiFePO_4$ materials. The purpose of this study was to know the structure of the solid electrolyte interphase (SEI) in lithium ion cells composed of $LiFePO_4$ as cathode material. $Li_4P_2O_7$ and $LiFePO_4$ were prepared by a solid-state reaction. The $^7Li$ MAS NMR experiments were carried out at variable temperatures in order to observe the local structure changes at the temperatures in $Li_4P_2O_7$ system. The $^7Li$ MAS NMR spectra of in $Li_4P_2O_7$ indicate that the lithium local environments in $Li_4P_2O_7$ were not changed in the temperature range between $27^{\circ}C$ and $97^{\circ}C$ Through this work, we confirmed that the small amount of $Li_4P_2O_7$ less than 5.0 wt% in $LiFePO_4$ could be clearly measured by the $^7Li$ MAS NMR spectroscopy at high spinning rate over than 11 kHz.

Reactivity of Li14P6S22 as a Potential Solid Electrolyte for All-Solid-State Lithium-Ion Batteries

도칠훈,하윤철,이유진,유지현 대한화학회 2018 Bulletin of the Korean Chemical Society Vol.39 No.10

The electrochemical reactivity of Li14P6S22 (Li7P3S11) as a sulfur-based solid electrolyte for Li+ conduction was evaluated by electrochemical cell tests and ab initio calculations to determine its utility for all-solid-state lithium secondary batteries. Reversible removal and incorporation of lithium into Li14P6S22 with a gradient of lithium concentration was confirmed as thermodynamically unfavorable. Otherwise, reductive/oxidative decomposition of Li14P6S22 by the addition/removal of lithium was thermodynamically favorable. The electrochemical stability window (ESW) of Li14P6S22 was 0.429?V between 1.860 and 2.289?V (Li/Li+). The lowest potential of Li elimination was 2.289?V and occurred as oxidative decomposition. The highest potential of lithium addition was 1.860?V as reductive decomposition. Formation of Li14+xP6S22 and Li14?xP6S22 could be simultaneously achieved with reductive and oxidative decomposition by applying negative and positive over-potentials. The exposure of Li14P6S22 electrodes to positive and negative electric fields generated a large amount of irreversible specific capacity, which confirmed the oxidative and reductive decomposition. Considering the results of ab initio calculations on ESW and electrochemical cell tests, Li14P6S22 material should be protected from direct contact to the potential of cathode and anode so that it can appropriately serve as a solid electrolyte. The high Li+ conductivity of Li14P6S22 might originate from temporal (kinetic) and endurable formation of Frenkel defects resulting in a Li-deficient/excess composition of Li14P6S22.

Li₂O-LiCl 용융염을 이용한 ZrO₂의 전기화학적 환원과정에서 발생하는 Li₂O의 손실

박우신,허진목,최은영,김종국,Park, Wooshin,Hur, Jin-Mok,Choi, Eun-Young,Kim, Jong-Kook 한국방사성폐기물학회 2012 방사성폐기물학회지 Vol.10 No.4

$Li_2O$-LiCl 용융염을 이용한 전해환원기술은 사용후핵연료로부터 우라늄 금속을 회수하기 위해 연구되고 있다. 이 전해환원기술에서는 $Li_2O$가 촉매로 이용되기 때문에 그 농도를 유지하는 것은 매우 중요한 운전인자이다. $ZrO_2$는 피복관의 주성분이 Zr이기 때문에 사용후핵연료에 불가피하게 함유되며, 본 연구에서는 $Li_2O$를 촉매로 이용하는 전해환원공정에서 $ZrO_2$의 거동을 살펴보았다. $Li_2O$와 $ZrO_2$의 화학반응과 전해환원공정 중에서의 생성물을 분석한 결과, $Li_2ZrO_3$와 $Li_4ZrO_4$가 주요하게 관찰되었고, 이는 $Li_2O$의 손실을 가져오는 원인이 된다. 즉, $ZrO_2$는 $Li_2O$를 소모하는 역할을 하며, 반응생성물은 전기화학적으로 안정하기 때문에 $Li_2O$의 손실이 불가피하게 된다. A molten salt technology using $Li_2O$-LiCl has been extensively investigated to recover uranium metal from spent fuels in the field of nuclear energy. In the reduction process, it is an important point to maintain the concentration of $Li_2O$. $ZrO_2$ is inevitably contained in the spent fuels because Zr is one of the main components of fuel rod hulls. Therefore, the fate of $ZrO_2$ in $Li_2O$-LiCl molten salt has been investigated. It was found that $Li_2ZrO_3$ and $Li_4ZrO_4$ were formed chemically and electrochemically and they were not reduced to Zr. The recycling of $Li_2O$ is the key mechanism ruling the total reaction in the electrolytic reduction process. However, $ZrO_2$ will have a role as a $Li_2O$ sink.

Loss of Li2O Caused by ZrO2 During the Electrochemical Reduction of ZrO2 in Li2O-LiCl Molten Salt

Wooshin Park,Jin-Mok Hur,Eun-Young Choi,Jong-Kook Kim 한국방사성폐기물학회 2012 방사성폐기물학회지 Vol.10 No.4

Li2O-LiCl 용융염을 이용한 전해환원기술은 사용후핵연료로부터 우라늄 금속을 회수하기 위해 연구되고 있다. 이 전해환원기술에서는 Li2O가 촉매로 이용되기 때문에 그 농도를 유지하는 것은 매우 중요한 운전인자이다. ZrO2는 피복관의 주성분이 Zr이기 때문에 사용후핵연료에 불가피하게 함유되며, 본 연구에서는 Li2O를 촉매로 이용하는 전해환원공정에서 ZrO2의 거동을 살펴보았다. Li2O와 ZrO2의 화학반응과 전해환원공정 중에서의 생성물을 분석한 결과, Li2ZrO3와 Li4ZrO4가 주요하게 관찰되었고, 이는 Li2O의 손실을 가져오는 원인이 된다. 즉, ZrO2는 Li2O를 소모하는 역할을 하며, 반응생성물은 전기화학적으로 안정하기 때문에 Li2O의 손실이 불가피하게 된다.

Co/Ti co-substituted layered LiNiO₂ prepared using a concentration gradient method as an effective cathode material for Li-ion batteries

Ko, Hyoung Shin,Kim, Jea Han,Wang, Juan,Lee, Jong Dae Elsevier Sequoia 2017 Journal of Power Sources Vol. No.

<P><B>Abstract</B></P> <P>The design of Li-ion batteries with high energy storage capacities and efficiencies is a subject of increased research interest, being of key importance for their large-scale applications and further commercialization. However, conventional Li-ion batteries are expensive and have stability-related concerns, which limit their practical applications. In our search for cheaper and safer Li-ion batteries, we use a concentration gradient method to prepare LiNi<SUB>0.9</SUB>Co<SUB>0.1–<I>x</I> </SUB>Ti<SUB> <I>x</I> </SUB>O<SUB>2</SUB> (0.02 ≤ <I>x</I> ≤ 0.05) cathode materials surface-enriched with Co and Ti that exhibit decreased oxygen loss and improved structural stability. The corresponding crystal structures and morphologies are analyzed by X-ray diffraction and field emission scanning electron microscopy, with the Ni, Co, and Ti concentration distributions determined by energy-dispersive X-ray spectroscopy. The material with the best performance (<I>x</I> = 0.04) exhibits a discharge capacity of 214 mAh g<SUP>−1</SUP> in a charge/discharge voltage range of 3.0–4.3 V (vs. Li/Li<SUP>+</SUP>), and possesses an excellent 50-cycle capacity retention of 98.7%. Thermogravimetric analysis shows that partial substitution of Ni with the strongly oxophilic Ti solves the problem of oxygen loss observed in Ni-rich cathode materials such as LiNiO<SUB>2</SUB>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Concentration-gradient LiNi<SUB>0.9</SUB>Co<SUB>0.1–<I>x</I> </SUB>Ti<SUB> <I>x</I> </SUB>O<SUB>2</SUB> cathode materials were prepared. </LI> <LI> These materials exhibit decreased oxygen loss and improved structural stability. </LI> <LI> Best performance observed for <I>x</I> = 0.04. </LI> <LI> LiNi<SUB>0.9</SUB>Co<SUB>0.06</SUB>Ti<SUB>0.04</SUB>O<SUB>2</SUB> exhibits a discharge capacity of 214 mAh g<SUP>−1</SUP>. </LI> <LI> LiNi<SUB>0.9</SUB>Co<SUB>0.06</SUB>Ti<SUB>0.04</SUB>O<SUB>2</SUB> exhibits an excellent 50-cycle capacity retention of 98.7%. </LI> </UL> </P>

Hierarchical hollow microspheres grafted with Co nanoparticle-embedded bamboo-like N-doped carbon nanotube bundles as ultrahigh rate and long-life cathodes for rechargeable lithium-oxygen batteries

Kim, Jung Hyun,Park, Seung-Keun,Oh, Yeon Jong,Kang, Yun Chan Elsevier 2018 Chemical engineering journal Vol.334 No.-

<P><B>Abstract</B></P> <P>Rational design of efficient, affordable, and durable electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is essential for rechargeable lithium-oxygen (Li–O<SUB>2</SUB>) batteries. We present for the first time hierarchical hollow microspheres grafted with metallic Co-embedded bamboo-like N-doped carbon nanotube bundles (Co-b-NCNTs hollow microspheres) as oxygen electrodes for Li-air batteries. Hierarchical composite microspheres are prepared <I>via</I> a facile two-step process involving synthesis of Co<SUB>3</SUB>O<SUB>4</SUB>-MgO hollow microspheres by spray pyrolysis, followed by internal and external growth of bamboo-like NCNTs in the shells. During post-treatment, metallic Co and MgO nanoparticles play key respective roles in catalyzing <I>in-situ</I> growth of NCNTs and maintaining structural integrity of the composites. The hierarchical composite structure with Co and N doping not only provides ample active sites for the OER and ORR, but also sufficient space for storing produced Li<SUB>2</SUB>O<SUB>2</SUB>. Thus, Co-b-NCNTs hollow microspheres exhibit high initial round-trip efficiency, long-term cycling and ultrahigh rate performances when applied as oxygen electrodes for Li–O<SUB>2</SUB> batteries. The initial discharge capacity and round-trip efficiency at a current density of 200 mA g<SUP>−1</SUP> are 28,968 mA h g<SUP>−1</SUP> and 78.2%, respectively. Specific capacities at cutoff capacities of 500 and 1000 mA h g<SUP>−1</SUP> are stable for 201 and 157 cycles, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Co-embedded bamboo-like N-doped carbon nanotube bundles are studied as cathode for Li-air batteries. </LI> <LI> Hierarchical structure provides active sites for the OER and ORR and sufficient space for storing Li<SUB>2</SUB>O<SUB>2</SUB>. </LI> <LI> Hierarchical composite exhibit high initial round-trip efficiency, long-term cycling and ultrahigh rate performance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Hierarchical hollow microspheres grafted with Co nanoparticle-embedded bamboo-like N-doped CNT bundles were first introduced as efficient cathodes for Li-O<SUB>2</SUB> batteries. The synergetic effect of the presence of the N-doped CNTs and the hierarchical structure enabling uniform deposition of the Li<SUB>2</SUB>O<SUB>2</SUB> product were responsible for the superior performances of Co-b-NCNTs hollow microspheres as the cathode material for Li-O<SUB>2</SUB> batteries.</P> <P>[DISPLAY OMISSION]</P>