논문에서 리튬이온전지용 양극 소재의 개발 동향과 함께 앞으로 필요한 양극 소재의 연구 방향을 제시한다. 현재 리튬이온 전지는 지구 환경 개선을 위한 친환경 에너지로 주목받고 있으며, 전기차와 에너지저장 시스템 등에서의 다양한 활용으로 고용량 및 고안정성 소재 개발에 초점을 맞추어 연구가 진행되고 있다. 특히, 리튬이온전지 양극 소재의 경우 전지의 가격 및 성능을 결정하기 때문에 활발한 연구가 이루어지며, 그중 높은 이론 용량을 가지는 Ni-rich 계 layered 구조의 양극 소재에 대한 연구가 집중되고 있다. 그러나, 고용량 특성을 달성하기 위한 Ni-rich 계 양극 소재는 높은 Ni 조성에 의해 비용량이 증가함에 따라 전기화학적 불안정성 또한 증가하는 문제를 가지기 때문에 활용에 한계를 가진다. 이를 해결하기 위한 방법으로 본 논문에서는 양극 소재의 표면 개질 방법 과 원소치환 방법에 대해 언급하며, 이에 진일보하여 리튬이온전지의 가격 경쟁력을 확보하기 위한 양극 소재의 연구 방향을 제안한다.

Numerous studies have addressed the commercial viability of lithium–air batteries (LABs). However, the high reactivity of Li with air moisture and CO2 has hindered the broad applicability of LABs. In this study, lithium-protective hybrid lithium–air batteries (HLABs) were fabricated with Super P (SP) and composites of fluorinated carbon ( CFx), MoS2, and WS2 as the cathodes. Subsequently, their potential use as a power source for the next generation of defense technologies was investigated. It was observed that a single cell HLAB with the SP-CFx composite cathode exhibited a specific capacity of 893 mAhg− 1 cathode. In comparison, a Tomcell with the SP cathode demonstrated a specific capacity of 465 mAhg− 1 cathode when discharged. The cells with SP-MoS2 and SP-WS2 cathode yielded specific capacities of 357 and 386 mAhg− 1 cathode, respectively. The improved performance of the SP-CFx cell can be attributed to synergistic effects of lithium–air cell and lithium battery reactions between CFx and SP. To assess all functionalities of the SP-CFx HLAB, lithium-protective HLABs were fabricated and discharged in air. To operate the lithium–air battery in air, pure lithium metal was sealed with solid electrodes (lithium-ion conducting glass–ceramics (LICGC)) and a buffer electrolyte (1 M LiFTSI in TEGDME) was applied. The SP-CFx cell was discharged for 25 days in air, greatly exceeding the 72 h requirement for the next-generation soldier power systems. These results demonstrate significant potential for HLABs to be used as a pioneering power source in nextgeneration energy-independent tactical defense units.

Nanostructured ZnO materials have been studied extensively because of their functional properties. This paper presents a composite material of zinc oxide quantum dots (ZnO QDs) and porous carbon using a one-step carbonization process. The direct carbonization of a metal–organic complex generates mesostructured porous carbon with a homogeneous distribution of ZnO QDs. The structural and morphological properties are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The resulting ZnO QDs@porous carbon composite delivers a high specific capacity of 990 mAh g−1 at 100 mA g−1, 357 mAh g−1 at 2 A g−1, and high reversibility when evaluated as an anode for lithium ion batteries.

Morphology control of a graphene nanosheet (GNS) is important for graphene-based battery electrodes to exhibit the increased practical surface area and the enhanced ion diffusion into the nanosheets. Nevertheless, it is very difficult to minutely control the shape of graphene nanosheets based on the conventional GNS suspension methods. In this work, we fabricated wrinkle textures of free-standing GNS for large area using Langmuir–Schaefer technique. The wrinkles are oriented vertically to the direction of the monolayer compression. The textured structure of GNS was obtained by cross-deposition of each layer with controlling the orientation of the wrinkle direction. These wrinkles can cause Li-ion to diffuse into the voids created by them and raise the specific surface area between the GNSs. Consequently, as a prospective anode for Li-ion battery, the wrinkled GNS multilayer, exhibits the high specific capacity of ~ 740 mAh g− 1 at 100 mA g−1 and the great power capability with ~ 404 mAh g− 1 being delivered even at 2 A g− 1. Furthermore, outstanding cycle performance of the wrinkled GNS multilayer is achieved over 200 cycles at 300 mA g−1 with high Coulombic efficiency of ~ 96%.

In this study, soybean oil, which is used in a large variety of processed foods, is used as a carbon source. Soybean oil is successfully coated onto the surface of LiNi1/ 3Co1/3Mn1/3O2 (NCM) by a simple method. The physical and electrochemical properties of NCM/C hybrid materials are determined. As a result, a 5 nm thickness carbon coating layer is formed on the surface of the NCM, resulting in improved capability and cyclic performance in the battery. The NCM/C battery shows an initial discharge capacity of 159 mAh g−1 and 95% capacity retention after 100 cycles (a discharge capacity of 120 mAh g−1 and 94% retention are observed after 100 cycles for the NCM cathode).

The effect of flow direction on heat transfer in water cooling channel of lithium-ion battery is numerically investigated. Battery Design StudioⓇ software is used for modeling electro-chemical heat generation in the battery and the conjugated heat transfer is analyzed with the commercial package STAR-CCM+. The result shows that the maximum temperature and temperature difference of battery with Type 1 are the lowest because the heat transfer in the entrance region near the electrode is enhanced. As the inlet velocity is increased, the maximum temperature and temperature difference of battery decreases but the pressure loss increases. The pressure loss in Type 2 channel is the lowest due to the shortest channel length, while the pressure loss with Type 3 or 4 channel is the highest because of the longest channel length. Considering heat transfer performance and pressure loss, Type 1 is the best cooling channel.

The carbon anode material for lithium-ion battery was prepared by pyrolysis fuel oil and waste polyethylene terephthalate (PET) additive. The pitch was synthesized as a medium material for carbon anode by heat treatment. The waste PET additive improved the softening point and thermal stability of the pitch. La and Lc of the anode material (heat-treated pitch) increased at higher treatment temperature but decreased by waste PET additive. The electric capacity was evaluated based on effects of defective cavity and developed graphite interlayer, respectively. When the La and Lc of the anode material decreased, the electric capacity by cavity increased based on defective graphite structure. Therefore, the addition of waste PET causes the improved capacity by the cavity. The anode material which has a high efficiency (over 95%) and C-rate (95%, 2 C/0.1 C) was obtained by controlling the process of heat treatment and PET addition. The mechanism of lithium-ion insertion was discussed based on effects of defective cavity and developed graphite interlayer.

We reported the synthesis of dendrite-like carbon nanotube-confined polymeric sulfur composite by modifying the surface of carbon nanotubes (CNTs) with trithiocyanuric acid (TTCA) and then copolymerizing with sulfur. DSC results show the successfully formation of robust chemical bonds between sulfur and TTCA modified CNTs, which effectively avoid the dissolution of polysulfide when used as cathodes for lithium–sulfur batteries. The composite with a high sulfur content of 78 wt% exhibits an initial charge capacity of 698 mAh g− 1 and the residual capacity of 553 mAh g− 1 after 1000 cycles at a rate of 1 C.

Giant miscanthus (GM) is an Asian grass that can produce biomass in high yields per land area. It can be used as a cathode material in lithium sulfur (Li/S) batteries. Giant-miscanthus-derived activated carbon (GMAC) is prepared via carbonization of GM followed by KOH activation. It is prepared with a large amount of KOH, and thus contained more defects but had a highly porous structure and graphitic cluster lattice. GMAC has a large specific surface area of 3327 m2/g and a large total pore volume of 1.86 cm3/g. The pore volume served as a storage space for the retention of polysulfides, thereby inhibiting the shuttle effect. When a GMAC–sulfur composite cathode is tested in a Li/S battery, an initial discharge capacity of 1148 mAh/g can be attained at 0.1 C. In a cyclic charge–discharge experiment at 1 C, discharge capacities of 529 mAh/g and 248 mAh/g are observed in the first and 200th cycles, respectively.

리튬 이온 전지의 양극과 음극 사이에 물리적인 층을 만들어주는 분리막은 분리막의 품질에 따라 리튬 이온 전지의 성능을 결정함에 따라 많은 관심을 받고 있다. 일반적으로 전기화학적 안정성과 적절한 역학적 강도를 갖고 있는 폴리에 틸렌과 폴리프로필렌으로 구성된 다공성 막이 리튬 이온 전지의 분리막으로 사용된다. 하지만 폴리에틸렌과 폴리프로필렌의 낮은 열 저항성과 젖음성으로 인해 리튬 이온 전지의 잠재력을 충분히 끌어내지 못한다. 녹는점 이상의 온도에 도달하게 되면 분리막의 구조가 변형되고 리튬 이온 전지는 단락된다. 분리막의 낮은 젖음성은 낮은 이온전도도와 부합하고, 이는 전지의 저항을 상승시킨다. 이러한 폴리에틸렌과 폴리프로필렌 분리막의 단점을 극복하고자 이중 전기방사방법, 코팅 층 도포 방법, 코어 셸 구조 형성 방법, 제지법 등 여러 가지 방법들이 연구되었다. 언급된 방법들로 합성된 분리막들은 열 저항성과 젖음성이 크게 향상되었고 유연성과 인장 강도 같은 역학적 특성도 향상되었다. 본 리뷰 논문에는 각기 다른 방법으로 형성된 리튬 이온 전지의 분리막에 대해서 다루고 있다.

The improvement of heat transfer in water cooling passage of lithium-ion battery is numerically studied by employing trapezoidal vortex generators. Battery Design StudioⓇ software is used for modeling electro-chemical heat generation in the battery. The conjugated heat transfer is analyzed with the commercial package STAR-CCM+ in terms of inlet flow velocities. The result shows that vortex generator enhances the convective heat transfer by developing thermal boundary layers and secondary flows in downstream, which results in reducing the average temperature of the battery by about 1℃. The heat transfer is enhanced for the whole inlet velocity, while the pressure loss sharply increases at more than inlet velocity of 0.1m/s. The optimum inlet velocity is around 0.1m/s for in terms of the heat transfer and pressure loss.

리튬금속전지(LMB)는 매우 큰 이론 용량을 갖지만 단락(short circuit), 수명 감소 등을 야기하는 덴드라이트(dendrite) 가 형성되는 큰 문제점을 갖고 있다. 본 연구에서는 poly(dimethylsiloxane) (PDMS)에 graphene oxide (GO) nanosheet를 고르게 분산시킨 PDMS/GO 복합체를 합성하였고 이를 박막 형태로 코팅하여 덴드라이트의 형성을 물리적으로 억제할 수 있는 막의 효과를 이끌어내었다. PDMS의 경우, 그 자체로는 이온 전도체가 아니기 때문에 리튬 이온의 통로를 형성시켜 리튬 이온의 이동을 원활하게 하기 위하여 5wt% 불산(HF)으로 에칭하여 PDMS/GO 박막이 이온전도성을 가질 수 있도록 하였다. 주사전자현미경(scanning electron microscopy, SEM)을 통해 전면 및 단면을 관찰하여 PDMS/GO 박막의 형상을 확인하였다. 그리고 PDMS/GO 박막을 리튬금속전지에 적용하여 실시한 배터리 테스트 결과, 100번째 사이클까지 쿨롱 효율(columbic efficiency) 이 평균 87.4%로 유지되었고, 박막이 코팅되지 않은 구리 전극보다 과전압이 감소되었음을 전압 구배(voltage profile) 를 통해 확인하였다.

리튬 덴드라이트의 효과적인 억제를 위해 유/무기 복합체를 리튬메탈 전극의 보호층으로 사용하였다. 유기물로는 PVDF-HFP가 사용되었으며 무기물로는 TiO2가 사용되었다. 유기물로 사용된 PVDF-HFP는 높은 유연성을 가지는 고분자로서 무기물의 matrix 역할을 하며, 무기물로 사용된 TiO2 나노입자는 보호막의 기계적 강도와 이온전도성을 향상시켜주는 역할을 하였다. 합성된 보호막은 SEM, AFM, XRD를 통하여 PVDF-HFP matrix에 TiO2가 잘 분산되어 있는 형태인 것을 확인할 수 있 었다. 또한 전기화학적 분석 결과, 향상된 기계적 물성과 이온전도성으로 인해 polymer-inorganic composite은 비교 샘플(untreated 와 PVDF-HFP 보호층) 대비 100번째 사이클까지 80%의 높은 쿨롱 효율 및 20 mV 미만의 낮은 과전압을 나타내었다.

Amine-functionalized graphene was synthesized via a one-step solvothermal method and used as a metal-free cathode for non-aqueous lithium–oxygen batteries. The material delivered an outstanding specific capacity of 19,789 mAh/g at a current density of 200 mA/g as well as better cycling stability than graphene without the amine functional group. This improvement was attributed to the electron-donating effect of the amine groups and appropriate mesopore volume, which can promote the penetration of oxygen, electrons, and lithium ions, as well as accommodate more discharge products, Li2O2 in Li–O2 batteries. Amine-functionalized graphene has an amine functional group on the carbon surface, which improves the electrical conductivity of carbon and provides electrochemical active sites for oxygen absorption reactions.

Due to the rapid development of electricity, electronics, information communication, and biotechnology in recent years, studies are actively being conducted on nanopowders as it is required not only for high strengthening but also for high-function powder with electric, magnetic, and optical properties. Nonetheless, studies on nickel nanopowders are rare. In this study of the synthesis of nickel nanoparticles from LiNiO2 (LNO), which is a cathode active material, we have synthesized the nanosized nickel powder by the liquid reduction process of NiSO4 obtained through the leaching and purification of LNO. Moreover, we have studied the reduction reaction rate according to the temperature change of liquid phase reduction and the change of particle size as a function of NaOH addition amount using hydrazine monohydrate (N2H4·H2O) and NaOH.